Secrets of modern LCD monitors. Types of video adapters What does the LCD screen consist of?

There are three main options for implementing graphics cards:

    Expansion cards. In this case, it is assumed that separate expansion cards with a PCI Express, AGP or PCI interface will be used. This ensures the highest performance, large memory capacity, and support for the largest number of functions.

    Chipset with integrated graphics core. These are the most affordable solutions, but their performance is very low, especially when running 3D games and other graphics-intensive applications. This also provides lower resolutions and refresh rates than when using expansion cards. The most common integrated chipsets are found in budget laptop models, as well as in some of their mid-range models;

    Processor with integrated graphics core (Intel).

As a rule, desktop computers that use microATX, FlexATX, microBTX, PicoBTX or MiniITX motherboards are equipped with a graphics core integrated into the chipset manufactured by Intel, VIA Technology, SiS, etc.

Video card connectors

Video adapters MDA, Hercules, CGA and EGA were equipped with a 9-pin D-Sub connector. Occasionally, a coaxial Composite Video connector was also present, allowing a black-and-white image to be output to a television receiver or monitor equipped with a low-frequency video input.

Analog D-Sub connector

VGA and later video adapters typically had only one VGA connector (15-pin D-Sub). Occasionally, early versions of VGA adapters also had a previous generation connector (9-pin) for compatibility with older monitors. The choice of working output was set by switches on the video adapter board.

DVI is a relatively new standard interface most commonly used for digital video output. The DVI port comes in two varieties. DVI-I also includes analog signals that allow you to connect a VGA monitor via a D-SUB adapter. DVI-D does not allow this.

DVI connector (variations: DVI-I and DVI-D)

Recently, a new household interface has become widespread - High Definition Multimedia Interface. This standard provides simultaneous transmission of visual and audio information over a single cable, it is designed for television and cinema, but PC users can also use it to output video data using an HDMI connector. HDMI allows you to transmit copy-protected audio and video in digital format over a single cable; the first version of the standard was based on a bandwidth of 5 Gb/s, and HDMI 1.3 expanded this limit to 10.2 Gb/s.

HDMI connector

DisplayPort is a relatively new digital video interface, the first version of which was adopted by VESA (Video Electronics Standards Association) in the spring of 2006. It defines a new universal digital interface, license-free and royalty-free, designed to connect computers and monitors, as well as other multimedia equipment.

Dispay Port allows you to connect up to four devices, including speakers, USB hubs and other input/output devices. It supports up to four data lines, each of which can transmit 1.62 or 2.7 gigabits/s. Supports modes with color depths from 6 to 16 bits per color channel

DVI and HDMI ports are evolutionary stages in the development of the video signal transmission standard, so adapters can be used to connect devices with these types of ports.

The video card can also accommodate composite and S-Video inputs and outputs.

Composite connector

S-Video connectors 4 and 7 pin

Rice. 28 – Set of connectors for the Palit GeForce GTS 450 Sonic 1Gb DDR5 128bit PCI-E video card (2xDVI, 1 D-Sub, 1 miniHDMI)

It is customary to distinguish three states of matter: solid, liquid and gaseous. But some organic substances, when melted in a certain phase, exhibit properties inherent in both crystals and liquids. Having acquired the fluidity characteristic of liquids, in this phase they do not lose the order of molecules characteristic of solid crystals. This phase can well be called the fourth state of aggregation. True, we should not forget that only some substances have it and only in a certain temperature range.

The spatial orientation of liquid crystal molecules in the so-called resting position is called liquid crystal order. According to Friedel's classification, there are three main categories of FA order: smectic, nematic and cholesteric (Fig. 1).

Smectic LCs are the most ordered and are closer in structure to ordinary solid crystals. In addition to the simple mutual orientation of the molecules, they also have their division into planes.

The direction of preferential orientation of the long axes of molecules in liquid crystals is indicated by a vector of unit length, called the director.

The main interest is in materials with nematic order; they are used in modern liquid crystal panels of all types (TN, IPS and VA). In nematics, the normal state is the position of molecules with an ordered molecular orientation throughout the volume, characteristic of crystals, but with a chaotic position of their centers of gravity, characteristic of liquids. The molecules in them are oriented relatively parallel, and along the director axis they are shifted at different distances.

Liquid crystals with cholesteric order in structure resemble nematics, divided into layers. The molecules in each subsequent layer are rotated relative to the previous one by a certain small angle and the director smoothly twists in a spiral. This layered nature, formed by the optical activity of molecules, is the main feature of cholesteric order. Cholesterics are sometimes called "twisted nematics".

The boundary between the nematic and cholesteric orders is somewhat arbitrary. Cholesteric order can be obtained not only from cholesteric material in its pure form, but also by adding special additives containing chiral (optically active) molecules to the nematic material. Such molecules contain an asymmetric carbon atom and, unlike nematic molecules, are mirror-asymmetric.

The order in liquid crystals is determined by intermolecular forces, which create the elasticity of the LC material. Yes, here we can talk specifically about elastic properties, although their nature is different from the elastic properties of ordinary crystals, since liquid crystals still have fluidity. In the normal (or ground) state, molecules tend to return to their "resting position", for example in a nematic material to a position with the same director orientation.

The elasticity of LCs is several orders of magnitude lower than the elasticity of conventional crystals and provides a completely unique opportunity to control their position using external influences. Such an influence can be, for example, an electric field.

Now let's take a closer look at how this field can influence the orientation of molecules.

Let us take a sample consisting of two glass plates, the space between which is filled with a nematic material. The distance between the upper and lower plates and, accordingly, the thickness of the liquid crystal layer is several microns. To set the desired orientation of the director of molecules in the material, special treatment of the surface of the substrate is used. To do this, a thin layer of transparent polymer is applied to the surface, after which a relief is given to the surface by special rubbing (rubbing) - the finest grooves in one direction. Elongated crystal molecules in the layer in direct contact with the surface are oriented along the relief. Intermolecular forces force all other molecules to take the same orientation.

The ordered arrangement of liquid crystal molecules determines the anisotropy of some of their physical properties (let me remind you that anisotropy is the dependence of the properties of a medium on the direction in space). Liquids, with their random arrangement of molecules, are isotropic. But liquid crystals already have anisotropy, which is an important quality that allows them to influence the characteristics of light passing through them.

The anisotropy of the dielectric constant is used to control the position of the molecules. It represents the difference

Δε = ε || + ε ⊥ where ε || dielectric constant in the direction parallel to the director vector, ε ⊥ dielectric constant in the direction perpendicular to the director vector. The value of Δε can be either positive or negative.

Let's take a sample consisting of two glass plates with a distance of several microns between the plates, filled with a nematic material and sealed. To set the desired orientation of the director of molecules in the material, a special treatment of the surface of the substrate is used; for this, a thin layer of transparent polymer is applied to the surface, after which a relief is given to the surface by special rubbing - thin grooves in one direction. The elongated molecules of crystals in the layer in direct contact with the surface are oriented along the relief, and intermolecular forces force all other molecules to take the same orientation. If an electric field is created in the sample, the energy of the liquid crystals in this field will depend on the position of the molecules relative to the direction of the field. If the position of the molecules does not correspond to the minimum energy, they will rotate through the appropriate angle. In a material with a positive dielectric constant (positive dielectric anisotropy), the molecules will tend to turn along the direction of the electric field, in a material with a negative dielectric anisotropy - across the direction of the field. The angle of rotation will accordingly depend on the applied voltage.

Let the material in the sample have positive dielectric anisotropy, the direction of the electric field is perpendicular to the initial orientation of the molecules (Fig. 2). When voltage is applied, the molecules will tend to turn along the field. But they are initially oriented according to the relief of the internal surfaces of the sample, created by rubbing, and are connected to them by quite significant adhesion. As a consequence, when the director orientation changes, torques in the opposite direction will arise. As long as the field is weak enough, elastic forces keep the molecules in a constant position. As the voltage increases, starting from a certain value E c, the orientational forces of the electric field exceed the elastic forces, and rotation of the molecules begins to occur. This reorientation under the influence of the field is called the Fredericks transition. The Fredericks transition is fundamental to the organization of liquid crystal control; the operating principle of all LCD panels is based on it.

A workable mechanism is formed:

  • on the one hand, the electric field will force the liquid crystal molecules to rotate to the desired angle (depending on the value of the applied voltage);
  • on the other hand, elastic forces caused by intermolecular bonds will tend to return the original orientation of the director when the stress is released.

If the initial orientation of the director and the directions of the electric field are not strictly perpendicular, then the threshold field value E c decreases, making it possible to influence the position of molecules with a much smaller field.

At this point we will have to digress a little from liquid crystals in order to explain the concepts of “polarization of light” and “plane of polarization”; without them, further presentation will be impossible.

Light can be represented as a transverse electromagnetic wave, the electric and magnetic components of which oscillate in mutually perpendicular planes (Fig. 3).

Natural light (also called naturally polarized or unpolarized) contains vector oscillations E, equally probable in all directions perpendicular to the vector k(Fig. 4).

Partially polarized light has a preferential direction of vector oscillation E. For partially polarized light in the field of a light wave, the amplitude of the projection E to one of the mutually perpendicular directions is always greater than to the other. The relationship between these amplitudes determines the degree of polarization.

Linearly polarized light is light that has a single vector direction E for all waves. The concept of linearly polarized light is abstract. In practice, when we talk about linearly polarized light, we usually mean partially polarized light with a high degree of polarization.

The plane in which the vector lies E and wave direction vector k, is called the plane of polarization.

Now let's return to the LCD.

The second most important physical property of liquid crystals, after dielectric anisotropy, used to control the light flux through them, is optical anisotropy. Liquid crystals have different values ​​of the refractive index of light for the direction of propagation parallel and perpendicular to the director. That is, the speed of propagation of the light beam parallel or perpendicular to the director will be different; with a higher coefficient, it is known to be lower. Optical anisotropy or refractive index anisotropy is the difference between two coefficients:

Δ n= n|| + n⊥ Where n|| refractive index for the plane of polarization parallel to the director; n⊥ refractive index for the plane of polarization perpendicular to the director.

The presence in the material of two different meanings for n|| And n⊥ causes the effect of birefringence. When light hits a birefringent material, such as a nematic, the electric field component of the light wave splits into two vector components, vibrating in the fast axis and vibrating in the slow axis. These components are called ordinary and extraordinary rays, respectively. The polarization directions of the ordinary and extraordinary rays are mutually orthogonal. And the presence of “fast” and “slow” axes in the material is due to what was mentioned above - different refractive indices for rays propagating respectively parallel or perpendicular to the direction of the director.

Figure 5 shows the propagation of waves along the “fast” and “slow” axes. It must be emphasized that the axis in this case is not a fixed straight line, but the direction of the plane in which the wave oscillates.

Since the phase velocities of the ordinary and extraordinary beams are different, their phase difference will change as the wave propagates. Changing the phase difference of these orthogonal components causes a change in the polarization direction of the light wave. In the figure, for clarity, the sum of orthogonal components is represented by the resulting vector E r. It can be seen that as the wave propagates, the direction of the vector rotates E r. Thus, the addition of waves at the output of a birefringent material will produce a wave with a polarization direction changed relative to the original one.

The angle of rotation of the plane of polarization will depend on the orientation of the molecules in the material.

Panel design

There are several LCD panel technologies. To illustrate the design in this case, TN is shown as the most common (Fig. 6).

All liquid crystal panels for monitors are transmissive - the image in them is formed by converting the light flux from a source located behind it. Modulation of the light flux is carried out due to the optical activity of liquid crystals (their ability to rotate the plane of polarization of transmitted light). This is implemented as follows. When passing through the first polarizer, the light from the backlight lamps becomes linearly polarized. It then follows through a layer of liquid crystals contained in the space between two glasses. The position of the LC molecules in each cell of the panel is regulated by the electric field created by applying voltage to the electrodes. The rotation of the plane of polarization of transmitted light depends on the position of the molecules. Thus, by supplying the cells with the required voltage value, the rotation of the polarization plane is controlled.

To deliver voltage to the subpixel, vertical (data line) and horizontal (gate line) data lines are used, which are metal conductive tracks deposited on the internal (closest to the backlight module) glass substrate. The electric field, as already mentioned, is created by the voltage on the electrodes - general and pixel. The voltage used is variable, since the use of a constant voltage causes interaction of ions with the electrode material, disruption of the orderly arrangement of molecules of the LC material, and leads to cell degradation. The thin-film transistor plays the role of a switch that closes when the address of the required cell is selected on the scan line, allows the required voltage value to be “written” and opens again at the end of the scan cycle, allowing the charge to be retained for a certain period of time. Charging occurs over time T= Tf/n , Where Tf frame display time on the screen (for example, with a refresh rate of 60 Hz, frame display time is 1 s / 60 = 16.7 ms), n number of panel lines (for example, 1024 for panels with a physical resolution of 1280x1024). However, the inherent capacity of the liquid crystal material is not enough to maintain charge in the interval between refresh cycles, which should lead to a drop in voltage and, as a result, a decrease in contrast. Therefore, in addition to the transistor, each cell is equipped with a storage capacitor, which is also charged when the transistor is turned on and helps compensate for voltage losses before the start of the next scanning cycle.

Vertical and horizontal data lines, using glued flat flexible cables, are connected to the control chips of the panel - drivers, respectively columnar (source driver) and row (gate driver), which process the digital signal coming from the controller and generate a voltage corresponding to the received data for each cell.

After the layer of liquid crystals there are color filters applied to the inner surface of the glass panel and used to form a color image. The usual three-color additive synthesis is used: colors are formed as a result of optical mixing of radiation from three basic colors (red, green and blue). A cell (pixel) consists of three separate elements (subpixels), each of which is associated with a red, green or blue color filter located above it; combinations of 256 possible tone values ​​for each subpixel can produce up to 16.77 million pixel colors.

The panel structure (metallic vertical and horizontal data lines, thin film transistors) and the cell border regions where molecular orientation is disrupted must be hidden under an opaque material to avoid unwanted optical effects. For this, a so-called black matrix is ​​used, which resembles a thin mesh that fills the gaps between the individual color filters. The material used for the black matrix is ​​chromium or black resins.

The final role in image formation is played by the second polarizer, often called an analyzer. Its polarization direction is shifted relative to the first by 90 degrees. To imagine the purpose of the analyzer, you can conditionally remove it from the surface of the connected panel. In this case, we will see all subpixels maximally illuminated, that is, an even white fill of the screen, regardless of the image displayed on it. Because the light has become polarized, and the plane of its polarization is rotated by each cell differently, depending on the voltage applied to it, nothing has changed for our eyes yet. The function of the analyzer is precisely to cut off the necessary wave components, which allows you to see the required result at the output.

Now let's talk about how this cutting off of the necessary components occurs. Let's take as an example a polarizer with a vertical direction of polarization, i.e. transmitting waves oriented in a vertical plane.

Figure 7 shows a wave propagating in a plane lying at a certain angle relative to the vertical direction of polarization. The electric field vector of the incident wave can be decomposed into two mutually perpendicular components: parallel to the optical axis of the polarizer and perpendicular to it. The first component, parallel to the optical axis, passes, the second (perpendicular) is blocked.

Hence, two extreme positions are obvious:

  • a wave propagating in a strictly vertical plane will be transmitted without changes;
  • a wave propagating in a horizontal plane will be blocked as having no vertical component.

These two extreme positions correspond to the fully open and fully closed position of the cell. Let's summarize:

  • To block transmitted light as completely as possible by a cell (subpixel), it is required that the plane of polarization of this light be orthogonal to the plane of transmission of the analyzer (direction of polarization);
  • For maximum transmission of light by a cell, the plane of its polarization must coincide with the direction of polarization;
  • By smoothly regulating the voltage supplied to the cell electrodes, it is possible to control the position of liquid crystal molecules and, as a consequence, the rotation of the plane of polarization of transmitted light. And thereby change the amount of light transmitted by the cell.

Since the angle of rotation of the plane of polarization depends on the distance traveled by light in the liquid crystal layer, this layer must have a strictly consistent thickness throughout the entire panel. To maintain a uniform distance between the glasses (with the entire structure applied to them), special spacers are used.

The simplest option is the so-called ball spacers. They are transparent polymer or glass beads of a strictly defined diameter and are applied to the internal structure of the glass by spraying. Accordingly, they are located chaotically over the entire area of ​​the cell and their presence negatively affects its uniformity, since the spacer serves as the center for the defective area and the molecules are oriented incorrectly directly next to it.

Another technology is also used: column spacers (column spacer, photo spacer, post spacer). Such spacers are located with photographic precision under the black matrix (Fig. 8). The benefits of this technology are obvious: increased contrast due to the absence of light leaks near the spacers, more precise control of gap uniformity due to the ordered arrangement of spacers, increased panel rigidity and the absence of ripples when pressing on the surface.

The TN panel, the design of which was shown in Fig. 6, is the most inexpensive to produce, which determines its dominance in the market for mass monitors. In addition to it, there are several other technologies that differ in the location, configuration and material of the electrodes, the orientation of the polarizers, the LCD mixtures used, the initial orientation of the director in the liquid crystal material, etc. According to the director’s initial orientation, all existing technologies can be divided into two groups:

1. Planar orientation

This includes all IPS technologies (S-IPS, SA-SFT, etc.), as well as FFS (currently AFFS), developed and promoted by Boe HyDis. The molecules are aligned horizontally, parallel to the base of the substrates, in the direction specified by rubbing, the top and bottom substrates being rubbed in the same direction. All electrodes, both pixel and common, are on the same glass substrate of the panel - the inner one, along with the data lines and transistors. In IPS technologies, pixel and common electrodes are located in parallel, alternating with each other (Fig. 9). The field lines run horizontally, but at a certain angle relative to the direction of rubbing. Therefore, when a voltage is applied, the molecules, which in this case have positive dielectric anisotropy, tending to align in the direction of the applied field, rotate in the same plane by an angle depending on its (field) strength. In the case of FFS, the common electrode is located under the pixel with this design, the voltage applied to the electrodes generates an electric field that has both horizontal and vertical components. If for IPS in the coordinate axes shown in Fig. 9 the field can be characterized as E y, then for FFS the corresponding values ​​will look like E y And E z. This arrangement of field lines allows the use of LC materials with both positive and negative dielectric anisotropy. Molecular rotation, similar to IPS, occurs in the same plane in the direction of the horizontal field component, but due to fewer boundary zones, a significantly larger number of molecules are rotated, which makes it possible to narrow the width of the black matrix grating and achieve a higher panel aperture ratio.

One of the main advantages of technologies with planar director orientation is the extremely slight color shift of the palette when the viewing angle changes. This stability is explained by the configuration of the spiral formed by the molecules of the liquid crystal material under the influence of the field, which in this case has a symmetrical shape. Figure 9 schematically shows the position of LC molecules when voltage is applied to the electrodes; it is obvious that the maximum rotation angle is achieved in the middle layers. This heterogeneity is due to the fact that, as already mentioned, the orientation of the molecules in the desired direction parallel to the base of the substrates is obtained by pre-processing (wiping) their surfaces. Therefore, the mobility of molecules in the layer immediately adjacent to the substrate is limited by the topography of the substrate, and in subsequent nearby layers by intermolecular forces. As a result, under the influence of the field, the molecules form a spiral, reminiscent of a ribbon with the ends fixed in one plane and the central part rotated. There is the concept of an optical path, which depends on the refractive index of the medium in which the beam propagates and the resulting phase shift in the direction it travels. Light rays passing through a layer of liquid crystals have different optical path lengths depending on the angle of transmission. The symmetrical shape of the molecular spiral makes it possible to obtain for each gray level an exact addition to the length of the optical path in its upper and lower halves; the consequence is the almost complete absence of dependence of the displayed shades on viewing angles. Thanks to this property, IPS panels are used in the vast majority of monitors aimed at working with graphics.

When a light wave passes, the direction of rotation of the resulting vector (see Fig. 5) partially repeats the shape of the bend of the spiral formed by the molecules. Therefore, the rotation of the plane of polarization when a wave passes through the first part of the LC material occurs in one direction, and through the second in the opposite direction. The different phase lag of one of the wave components, depending on the applied voltage, leads to the fact that the direction of the resulting vector E r at the exit from the liquid crystal layer differs from the original one, this allows a certain part of the light flux to pass through the analyzer. The light-transmitting planes of the polarizer and analyzer, as in all other technologies, are shifted relative to each other by an angle of 90 degrees.

All currently produced variations (S-IPS, AFFS, SA-SFT) use a 2-domain cell design. For this purpose, zigzag-shaped electrodes are used, which cause the molecules to rotate in two directions. The initial versions, designated simply “IPS” and “FFS”, without the prefixes “Super” and “Advanced”, were mono-domain, therefore had a color shift and smaller viewing angles (from 140/140 in contrast drop to 10: 1 for the first IPS ).

Planar orientation usually includes twist orientation (or twisted orientation). In this case, the alignment of molecules along the base of the substrates is also achieved by wiping their surfaces, with the difference that the directions of wiping the upper and lower substrates are offset relative to each other. As a result of this alignment in the nematic material, the director forms a helix resembling a cholesteric one; for the correct formation of the helix, special additives containing chiral molecules are used in LC mixtures. Twist orientation is used in the most widely used TN (or TN+Film) technology. It makes no sense to describe and illustrate the TN design here; this has been done repeatedly in numerous materials on similar topics; we can say that it is well known.

2. Homeotropic orientation

MVA and PVA belong to this group. The director is oriented perpendicular to the base of the glass substrate; this is achieved by using surfactants in the coating of the substrate. General and pixel electrodes are located on opposite substrates, the field is oriented vertically. Here, liquid crystal materials with negative dielectric anisotropy are used, so the applied voltage causes the LC molecules to rotate against the field lines. MVA is characterized by the presence of microscopic longitudinal projections (protrusion) to pre-tilt the molecules on the top or both substrates, so the initial vertical alignment is not complete. Molecules, aligned along these protrusions, receive a slight pre-inclination, which makes it possible to set for each region (domain) of the cell a certain direction in which the molecules will rotate under the influence of the field. In PVA there are no such protrusions and in the absence of voltage the director is oriented strictly perpendicular to the surface, and the pixel and common electrodes are offset relative to each other so that the created field is not strictly vertical, but contains an inclined component (Fig. 10).

Technologies with homeotropic director orientation also include ASV, developed by Sharp. Within a subpixel, there are several pixel electrodes shaped like squares with rounded edges. The basic principles are the same: the common electrode is located on the opposite substrate, the molecules are oriented vertically in the absence of a field, and liquid crystalline materials with negative dielectric anisotropy are used. The created field has a pronounced oblique component and the molecules, turning against the direction of the field, create a structure in which the direction of the director resembles the shape of an umbrella centered in the middle of the pixel electrode.

There is also a division of LCD modules into types depending on the state of the cells in the absence of voltage. Normally white panels are those in which, at zero voltage on the cells, they are completely open; accordingly, white color is reproduced on the screen. All panels made using TN technology are normally white. Panels that block the passage of light in the absence of voltage are classified as normally black (normally black), all other technologies belong to this type.

Backlight module

...based on fluorescent lamps

Only a small part of the initial light flux from the backlight lamps passes through the body of the panel (polarizers, electrodes, color filters, etc.), no more than 3%. Therefore, the intrinsic brightness of the backlight module must be quite significant; as a rule, the lamps used have a brightness of over 30,000 cd/m2.

CCFL cold cathode fluorescent lamps (without cathode filaments) are used for illumination. A CCFL lamp is a sealed glass tube filled with an inert gas with a small admixture of mercury (Fig. 11). In this case, the cathodes are equal electrodes, since alternating current is used for power supply. Compared to lamps with incandescent (hot) cathode, CCFL electrodes have a different structure and are larger in size. The operating temperature of the cathode is significantly different: 80-150 o C versus approximately 900 o C for lamps with a hot cathode, with a similar temperature of the lamp itself - 30-75 o C and 40 o C, respectively. The operating voltage for CCFL is 600-900 V, the starting voltage is 900-1600 V (the numbers are quite arbitrary, since the range of lamps used is very wide). The formation of light occurs during gas ionization, and a necessary condition for its occurrence in a cold cathode lamp is a high voltage. Therefore, to start such a lamp, it is necessary to apply a voltage significantly higher than the operating voltage to the electrodes for several hundred microseconds. The applied high alternating voltage causes ionization of the gas and breakdown of the gap between the electrodes, and a discharge occurs.

Breakdown of the discharge gap occurs for the following reasons. Under normal conditions, the gas filling the lamp is a dielectric. When an electric field appears, a small number of ions and electrons, always present in the gas volume, begin to move. If a sufficiently high voltage is applied to the electrodes, the electric field imparts such a high speed to the ions that when they collide with neutral molecules, electrons are knocked out of them and ions are formed. Newly formed electrons and ions, moving under the influence of the field, also enter into the ionization process, the process takes on an avalanche-like character. Once the ions begin to receive sufficient energy to knock out electrons by striking the cathode, a self-discharge occurs. Unlike hot cathode lamps, where the discharge is arc, the type of discharge in CCFL is glow.

The discharge is maintained due to the so-called cathode potential drop. The main part of the potential (voltage) drop in the discharge occurs in the cathode region. The ions, passing through this gap with a high potential difference, acquire high kinetic energy, sufficient to knock electrons out of the cathode. The knocked-out electrons, due to the same potential difference, are accelerated back into the discharge, producing new pairs of ions and electrons there. The ions from these pairs return to the cathode, are accelerated by the voltage drop between the discharge and the cathode, and again knock out electrons.

The energy of the electric current causes the mercury in the lamp to transition from a liquid to a gaseous state. When electrons collide with mercury atoms, energy is released due to the return of atoms from an unstable state to a stable one. In this case, intense radiation occurs in the ultraviolet region; the share of ultraviolet radiation is about 60% of the total radiation.

Visible light is produced by a phosphor coating applied to the inner surface of the glass. The ultraviolet photons released by the mercury excite the atoms in the phosphor coating, increasing the energy level of the electrons. When the electrons return to their original energy level, the atoms in the coating produce energy in the form of photons of visible light. The phosphor is the most important component of the lamp; the characteristics of the emission spectrum depend on it. The CCFL spectrum is extremely uneven, containing pronounced narrow peaks. Even the use of a multilayer phosphor coating (at the expense of maximum brightness) does not allow you to “overtake” CRT monitors in terms of color gamut. Therefore, in the production of a panel, in order to achieve an acceptable color gamut, it is also necessary to accurately select color filters, the passbands of which must correspond as closely as possible to the peaks of the emission spectrum of the lamps.

The maximum color gamut could ideally be provided by a combination of monochromatic sources of primary colors and high-quality color filters. So-called laser LEDs can claim the role of “quasi-monochromatic” light sources, but production technology does not yet ensure the profitability of their use in backlight modules. Therefore, at the moment, the best color gamut can be achieved by backlight modules based on RGB LED packages (see below).

To generate a voltage of several hundred volts required for lamp operation, special converters and inverters are used. CCFL brightness can be adjusted in two ways. The first is to change the discharge current in the lamp. The discharge current value is 3-8 mA; a significant part of the lamps has an even narrower range. At a lower current, the uniformity of the glow suffers; at a higher current, the lamp service life is significantly reduced. The disadvantage of this adjustment method is that it allows you to change the brightness in a very small range, while it is impossible to significantly reduce it. Therefore, monitors with this adjustment, when working in low ambient lighting conditions, often turn out to be too bright, even at zero brightness. With the second method, pulse-width modulation (PWM) of the voltage supplying the lamp is generated (the width, i.e., pulse duration is controlled; by changing the width of a single pulse, the average voltage level is regulated.). The disadvantages of this method are sometimes attributed to the appearance of lamp flickering when PWM is implemented at a low frequency of 200 Hz and below, but in fact, adjustment using PWM is the most reasonable approach, since it allows you to change the brightness over a wide range.

To distribute the light of the lamps evenly, a system of light guides, diffusers and prisms is used. There are many options for organizing light distribution, one of them is shown in Fig. 12.

Solutions with lamps located on the upper and lower end sides of the panel are the most common; this arrangement can significantly reduce the overall thickness of the product. In 17- and 19-inch modules, as a rule, four lamps are installed: two on the top side and two on the bottom. There are special technological holes in the end part of the housing of such panels, so there is no need to disassemble the housing to remove the lamps (Fig. 13-b). Lamps with this arrangement are often combined into blocks of two pieces (Fig. 13-a).

Another option is to arrange the lamps over the entire area of ​​the back side of the module (Fig. 13-c) this solution is used in multi-lamp panels with eight or more lamps, as well as when using U-shaped CCFLs.

The minimum lamp life of panel manufacturers is now usually specified from forty to fifty thousand hours (life is defined as the time during which the luminosity of the lamps decreases by 50%).

...based on LEDs

In addition to fluorescent lamps, light emitting diodes (LEDs) can also be used as a light source. LED-based backlight modules are built either on “white” LEDs or on packages of primary-color LEDs (RGB-LEDs).

The largest color gamut is provided by RGB-LED packages. The fact is that a “white” LED is a blue LED with a yellow phosphor coating, or an ultraviolet LED with a combination of “red”, “green” and “blue” phosphor coating. The spectrum of “white” LEDs is not free from all the disadvantages of the spectrum of fluorescent lamps. In addition, unlike “white” LEDs, the RGB-LED package allows you to quickly adjust the color temperature of the backlight by separately controlling the glow intensity of each group of LEDs of primary colors.

As a result, two goals are achieved:

  • the color gamut is expanded due to a more ideal backlight spectrum,
  • color calibration capabilities are expanded: to the standard method based on color coordinate conversion tables for image pixels, the ability to adjust the color balance of the backlight is added.

The large slope of the current-voltage characteristic of LEDs does not allow smooth adjustment of the brightness of the radiation over wide ranges. But since the device allows operation in a pulsed mode, in practice, the pulse width modulation method is most often used to adjust the brightness of LEDs (as well as for fluorescent lamps).

Oleg Medvedev, Maxim Proskurnya

LCD(Liquid crystal display) or LCD(liquid crystal) TV, as they are popularly called, is a TV with an LCD display and lamp backlight. Liquid crystal, means that the display (monitor) itself is made on the basis liquid crystals

LCD TFT(English: Thin film transistor) - a type of liquid crystal display that uses an active matrix controlled thin film transistors. An amplifier for each subpixel (matrix element) is used to increase the speed, contrast and clarity of the display image

  • A little history:

    • Liquid crystals were first discovered by an Austrian botanist Reinitzer V 1888 g., but only in 1930 -researchers from a British corporation Marconi received a patent for their industrial use, however, the weakness of the technological base did not allow the active development of this area at that time.

    Scientists made the first real breakthrough Fergeson And Williams from an American corporation RCA. One of them created a thermal sensor based on liquid crystals, using their selective reflective effect, the other studied the effect of an electric field on nematic crystals. And so, at the end 1966 city, corporation RCA demonstrated a prototype of an LCD monitor - digital clock. The world's first calculator - CS10A was produced in 1964 corporation Sharp, aka, in October 1975 year, released the first compact digital watch with an LCD display. Unfortunately, I couldn’t find any photos, but many still remember this watch and calculator

    In the second half of the 70s, the transition began from eight-segment LCD indicators to the production of matrices with addressing (the ability to control) each point. So, in 1976 year, company Sharp released a black and white TV with a screen diagonal of 5.5 inches, based on an LCD matrix with a resolution of 160x120 pixels.

    The next stage in the development of LCD technology began in the 80s, when devices began to use STN elements with increased contrast. Then they were replaced by multilayer structures that eliminate errors when reproducing color images. Around the same time, active matrices based on technology appeared a-Si TFT. First monitor prototype a-Si TFT LCD was created in 1982 corporations Sanyo, Toshiba And Cannon, well, at that time we loved to play with toys like these with an LCD display

    Now LCD displays have almost completely replaced CRT TVs from the market, offering the buyer any size: from portable and small “kitchen” to huge ones, with diagonals of more than a meter. The price range is also very wide and allows everyone to choose a TV according to their needs and financial capabilities.

    The circuit design of LCD TVs is much more complex than that of simple CRT TVs: miniature parts, multilayer boards, expensive units... For those who are interested, a TV with an LCD panel without a back cover, and if you remove special protective screens, you can see other sections of the circuit, but it’s better not to do this, leave it to the masters

  • Design and principle of operation:

    • Job LCD display(LCD) is based on the phenomenon polarization of light flux. It is known that the so-called polaroid crystals are capable of transmitting only that component of light whose electromagnetic induction vector lies in a plane parallel to the optical plane of the polaroid. For the remainder of the light output, the Polaroid will be opaque. This effect is called polarization of light.

    Quite simply, imagine “light” in the form of small round balls, if you put a grid with longitudinal cuts (polarizer) in its path, then, after it, only flat “pancakes” (polarized light) will remain from the “balls”. Now, if the second mesh has the same longitudinal cuts, the pancakes will be able to “slip” through it and “shine” further, but if the second mesh has vertical slits, then the horizontal light “pancakes” will not be able to pass through it and will “get stuck”

    When liquid substances were studied, the long molecules of which are sensitive to electrostatic and electromagnetic fields and are capable of polarizing light, it became possible to control polarization. These amorphous substances were called liquid crystals

    Structurally, the display consists of LCD matrices(a glass plate, between the layers of which liquid crystals are located), light sources for lighting, contact harness and framing ( housing), usually plastic, with a metal frame of rigidity.

    Every pixel The LCD matrix consists of layer of molecules between two transparent electrodes, and two polarizing filters, the planes of polarization of which are (usually) perpendicular. In the absence of liquid crystals, the light transmitted by the first filter is almost completely blocked by the second.

    The surface of the electrodes in contact with the liquid crystals is specially treated to initially orient the molecules in one direction. In a TN matrix, these directions are mutually perpendicular, so the molecules, in the absence of tension, line up in a helical structure. This structure refracts light in such a way that the plane of its polarization rotates before the second filter and light passes through it without loss. Apart from the absorption of half of the unpolarized light by the first filter, the cell can be considered transparent, although the loss level is considerable.

    If voltage is applied to the electrodes, the molecules tend to line up in the direction of the electric field, which distorts the screw structure. In this case, elastic forces counteract this, and when the voltage is turned off, the molecules return to their original position. With a sufficient field strength, almost all molecules become parallel, which leads to an opaque structure; the degree of transparency can be controlled by changing the applied voltage.

    The light source (LCD matrix backlight) is cold cathode fluorescent lamps(they are called this because the electron-emitting cathode (negative electrode) inside the lamp does not need to be heated above the ambient temperature for the lamp to light.) This is what a lamp for an LCD TV might look like; in the right photo there is a “lamp assembly in operation” for a TV with a large diagonal LCD display:

    The lamps themselves (white bright glow) are located in special body clamps, behind them - reflector, to reduce luminous flux losses. In order for the LCD matrix to light up evenly (and not striped, as the lamps are installed), there is a diffuser, which evenly distributes the luminous flux over its entire area. Unfortunately, in this place there is also a considerable loss of “brightness” of the lamps.

    Modern LCD matrices have a fairly good viewing angle (about 160 degrees) without loss of image quality (colors, brightness), the most unpleasant thing you can see on them is these defective pixels, however, given that their size is very small, one or two such “burnt-out” pixels will not greatly interfere with watching movies and programs, but on a monitor screen this can already be quite unpleasant

  • Advantages and disadvantages:

    • Compared to CRT TVs, LCD panels have excellent focusing and clarity, there are no convergence errors or image geometry violations, the screen never flickers, they are lighter and take up less space. The disadvantages include weak (compared to CRT) brightness and contrast, the matrix is ​​not as durable as a kinescope screen, a set of digital brakes and glitches with an analog or weak signal, as well as poor processing of the source material

    The “heart” of any liquid crystal monitor is the LCD matrix (Liquid Cristall Display). The LCD panel is a complex multilayer structure. A simplified diagram of a color TFT LCD panel is shown in Fig. 2.

    The operating principle of any liquid crystal screen is based on the property of liquid crystals to change (rotate) the plane of polarization of light passing through them in proportion to the voltage applied to them. If a polarizing filter (polarizer) is placed in the path of polarized light passing through liquid crystals, then by changing the voltage applied to the liquid crystals, you can control the amount of light transmitted by the polarizing filter. If the angle between the planes of polarization of the light passing through the liquid crystals and the light filter is 0 degrees, then the light will pass through the polarizer without loss (maximum transparency), if it is 90 degrees, then the light filter will transmit a minimum amount of light (minimum transparency).

    Fig.1. LCD monitor. Operating principle of LCD technology.

    Thus, using liquid crystals, it is possible to produce optical elements with a variable degree of transparency. In this case, the level of light transmission of such an element depends on the voltage applied to it. Any LCD screen on a computer monitor, laptop, tablet or TV contains from several hundred thousand to several million of these cells, fractions of a millimeter in size. They are combined into an LCD matrix and with their help we can form an image on the surface of a liquid crystal screen.
    Liquid crystals were discovered at the end of the 19th century. However, the first display devices based on them appeared only in the late 60s of the 20th century. The first attempts to use LCD screens in computers were made in the eighties of the last century. The first liquid crystal monitors were monochrome and were much inferior in image quality to cathode ray tube (CRT) displays. The main disadvantages of the first generations of LCD monitors were:

    • - low performance and image inertia;
    • - “tails” and “shadows” in the image from the elements of the picture;
    • - poor image resolution;
    • - black and white or color image with low color depth;
    • - and so on.

    However, progress did not stand still and, over time, new materials and technologies were developed in the manufacture of liquid crystal monitors. Advances in microelectronics technology and the development of new substances with liquid crystal properties have significantly improved the performance of LCD monitors.

    Design and operation of TFT LCD matrix.

    One of the main achievements was the invention of LCD TFT matrix technology - liquid crystal matrix with thin film transistors (Thin Film Transistors). TFT monitors have dramatically increased pixel speed, increased image color depth, and managed to get rid of “tails” and “shadows.”
    The structure of the panel manufactured using TFT technology is shown in Fig. 2

    Fig.2. TFT LCD matrix structure diagram.
    A full-color image on an LCD matrix is ​​formed from individual dots (pixels), each of which usually consists of three elements (subpixels) responsible for the brightness of each of the main components of color - usually red (R), green (G) and blue (B) - RGB. The monitor's video system continuously scans all subpixels of the matrix, recording a charge level proportional to the brightness of each subpixel into the storage capacitors. Thin Film Transistors (Thin Film Trasistor (TFT) - in fact, that’s why the TFT matrix is ​​called that) connect storage capacitors to the data bus at the time information is written to a given subpixel and switch the storage capacitor to charge conservation mode for the rest of the time.
    The voltage stored in the memory capacitor of the TFT matrix acts on the liquid crystals of a given subpixel, rotating the plane of polarization of light passing through them from the backlight by an angle proportional to this voltage. Having passed through a cell with liquid crystals, the light enters a matrix light filter, on which a light filter of one of the primary colors (RGB) is formed for each subpixel. The pattern of the relative positions of dots of different colors is different for each type of LCD panel, but this is a separate topic. Next, the generated light flux of primary colors enters an external polarizing filter, the light transmittance of which depends on the polarization angle of the light wave incident on it. A polarizing filter is transparent to those light waves whose plane of polarization is parallel to its own plane of polarization. As this angle increases, the polarizing filter begins to transmit less and less light, up to a maximum attenuation at an angle of 90 degrees. Ideally, a polarizing filter should not transmit light polarized orthogonally to its own plane of polarization, but in real life, a small portion of the light does pass through. Therefore, all LCD displays have insufficient black depth, which is especially pronounced at high backlight brightness levels.
    As a result, in an LCD display, the light flux from some subpixels passes through a polarizing filter without loss, from other subpixels it is attenuated by a certain amount, and from some subpixels it is almost completely absorbed. Thus, by adjusting the level of each primary color in individual subpixels, it is possible to obtain a pixel of any color shade from them. And from many colored pixels, create a full-screen color image.
    The LCD monitor made it possible to make a major breakthrough in computer technology, making it accessible to a large number of people. Moreover, without an LCD screen it would be impossible to create portable computers such as laptops and netbooks, tablets and cell phones. But is everything so rosy with the use of liquid crystal displays?

    In addition to the well-proven LCD + TFT technology (thin-film transistors), there is an actively promoted OLED + TFT organic light-emitting diode technology, that is, AMOLED - active matrix OLED. The main difference between the latter is that the role of a polarizer, an LCD layer and light filters is played by organic LEDs of three colors.

    Essentially, these are molecules that are capable of emitting light when an electric current flows, and depending on the amount of current flowing, change the color intensity, similar to what happens in conventional LEDs. By removing the polarizers and LCD from the panel, we can potentially make it thinner, and most importantly, flexible!

    What types of touch panels are there?
    Since sensors are currently used more with LCD and OLED displays, I think it would be reasonable to talk about them right away.

    A very detailed description of touch screens or touch panels is given (the source once lived, but for some reason disappeared), so I will not describe all types of touch panels, I will focus only on the two main ones: resistive and capacitive.

    Let's start with the resistive sensor. It consists of 4 main components: a glass panel (1), as the carrier of the entire touch panel, two transparent polymer membranes with a resistive coating (2, 4), a layer of micro-insulators (3) separating these membranes, and 4, 5 or 8 wires, which are responsible for “reading” the touch.


    Resistive sensor device diagram

    When we press such a sensor with a certain force, the membranes come into contact, the electrical circuit is closed, as shown in the figure below, the resistance is measured, which is subsequently converted into coordinates:


    The principle of calculating coordinates for a 4-wire resistive display ()

    Everything is extremely simple.

    It is important to remember two things: a) the resistive sensors on many Chinese phones are not of high quality, this may be due precisely to the uneven distance between the membranes or poor-quality micro-insulators, that is, the “brain” of the phone cannot adequately convert the measured resistances into coordinates; b) such a sensor requires pressing, pushing one membrane to another.

    Capacitive sensors are somewhat different from resistive sensors. It’s worth mentioning right away that we will only talk about projective-capacitive sensors, which are now used in the iPhone and other portable devices.

    The operating principle of such a touchscreen is quite simple. A grid of electrodes is applied to the inside of the screen, and the outside is coated, for example, with ITO, a complex indium tin oxide. When we touch the glass, our finger forms a small capacitor with such an electrode, and the processing electronics measures the capacitance of this capacitor (supplies a current pulse and measures the voltage).

    Accordingly, the capacitive sensor reacts only to a firm touch and only with conductive objects, that is, such a screen will work every other time if touched by a nail, as well as by a hand soaked in acetone or dehydrated. Perhaps the main advantage of this touchscreen over a resistive one is the ability to make a fairly strong base - especially strong glass, such as Gorilla Glass.


    Scheme of operation of the surface capacitive sensor()

    How does an E-Ink display work?
    Perhaps E-Ink is much simpler compared to LCD. Once again, we are dealing with an active matrix responsible for image formation, but there are no traces of LCD crystals or backlight lamps here; instead, there are cones with two types of particles: negatively charged black and positively charged white. The image is formed by applying a certain potential difference and redistribution of particles inside such microcones, this is clearly demonstrated in the figure below:


    Above is a diagram of how an E-Ink display works, below are real microphotographs of such a working display ()

    If this is not enough for someone, the principle of operation of electronic paper is demonstrated in this video:

    In addition to E-Ink technology, there is SiPix technology, in which there is only one type of particles, and the “fill” itself is black:


    Scheme of operation of SiPix display ()

    For those who seriously want to get acquainted with “magnetic” electronic paper, please go here, there was once an excellent article in Perst.

    Practical part

    Chinaphone vs Korean smartphone (resistive sensor)
    After a “careful” screwdriver disassembly of the remaining board and display from the Chinese phone, I was very surprised to find a mention of one well-known Korean manufacturer on the phone’s motherboard:


    Samsung and Chinese phone are one!

    I disassembled the screen carefully and carefully - so that all the polarizers remained intact, so I simply could not help but play with them and with the working big brother of the object being dissected and remember the optics workshop:


    This is how 2 polarizing filters work: in one position the light flux practically does not pass through them, when rotated 90 degrees it passes completely

    Please note that all the lighting is based on just four tiny LEDs (I think their total power is no more than 1 W).

    Then I looked for a sensor for a long time, sincerely believing that it would be a rather thick socket. It turned out quite the opposite. In both Chinese and Korean phones, the sensor consists of several sheets of plastic, which are very well and tightly glued to the glass of the outer panel:


    On the left is the Chinese phone sensor, on the right is the Korean phone sensor

    The resistive sensor of the Chinese phone is made according to the “the simpler the better” scheme, unlike its more expensive counterpart from South Korea. If I'm wrong, correct me in the comments, but on the left in the picture is a typical 4-pin sensor, and on the right is an 8-pin sensor.

    Chinese phone LCD display
    Since the display of the Chinese phone was still broken, and the Korean one was only slightly damaged, I will try to talk about the LCD using the example of the first one. But for now we won’t break it completely, but let’s look under an optical microscope:


    Optical micrograph of the horizontal lines of the LCD display of a Chinese telephone. The upper left photograph has some deception of our vision due to the “wrong” colors: the white thin strip is the contact.

    One wire powers two lines of pixels at once, and the decoupling between them is arranged using a completely unusual “electric bug” (lower right photo). Behind this entire electrical circuit there are filter tracks, painted in the appropriate colors: red (R), green (G) and blue (B).

    At the opposite end of the matrix in relation to the place where the cable is attached, you can find a similar color breakdown, track numbers and the same switches (if someone could clarify in the comments how this works, it would be very cool!):


    Rooms-rooms-rooms...

    This is what a working LCD display looks like under a microscope:

    That’s all, now we won’t see this beauty anymore, I crushed it in the literal sense of the word, and after suffering a little, I “split” one such crumb into two separate pieces of glass, which make up the main part of the display...

    Now you can look at the individual filter tracks. I’ll talk about the dark “spots” on them a little later:


    Optical micrograph of filters with mysterious spots...

    And now a small methodological aspect regarding electron microscopy. The same color stripes, but under the beam of an electron microscope: the color has disappeared! As I said earlier (for example, in the very first article), it is completely “black and white” for an electron beam whether it interacts with a colored substance or not.


    It seems to be the same stripes, but without color...

    Let's take a look at the other side. Transistors are located on it:


    In an optical microscope - in color...


    And an electron microscope - black and white image!

    This is seen a little worse in an optical microscope, but the SEM allows you to see the fringing of each subpixel - this is quite important for the following conclusion.

    So, what are these strange dark areas?! I thought for a long time, racked my brains, read many sources (perhaps the most accessible was Wiki) and, by the way, for this reason I delayed the release of the article on Thursday, February 23. And this is the conclusion I came to (perhaps I’m wrong - correct me!).

    VA or MVA technology is one of the simplest, and I don’t think the Chinese have come up with anything new: every subpixel must be black. That is, light does not pass through it (an example of a working and non-working display is given), taking into account the fact that in the “normal” state (without external influence) the liquid crystal is misoriented and does not give the “necessary” polarization, it is logical to assume that each a separate subpixel has its own LCD film.

    Thus, the entire panel is assembled from single micro-LCD displays. The note about the edging of each individual subpixel fits in organically here. For me, this became a kind of unexpected discovery right as I was preparing the article!

    I regretted breaking the display of the Korean phone: after all, we need to show something to the children and those who come to our faculty for an excursion. I don't think there was anything else interesting to see.

    Further, for the sake of self-indulgence, I will give an example of the “organization” of pixels from two leading communicator manufacturers: HTC and Apple. The iPhone 3 was donated for a painless operation by a kind person, and the HTC Desire HD is actually mine:


    Photomicrographs of the HTC Desire HD display

    A small note about the HTC display: I didn’t look specifically, but could this stripe in the middle of the top two microphotos be part of that same capacitive sensor?!


    Microphotographs of the iPhone 3 display

    If my memory serves me correctly, then HTC has a superLCD display, while the iPhone 3 has a regular LCD. The so-called Retina Display, that is, an LCD in which both contacts for switching the liquid crystal lie in the same plane, In-Plane Switching - IPS, is already installed in the iPhone 4.

    I hope that an article will be published soon on the topic of comparing different display technologies with the support of 3DNews. For now, I just want to note the fact that the HTC display is truly unusual: the contacts on individual subpixels are placed in a non-standard way - somehow on top, unlike the iPhone 3.

    And finally, in this section, I’ll add that the dimensions of one subpixel for a Chinese phone are 50 by 200 micrometers, HTC is 25 by 100 micrometers, and the iPhone is 15-20 by 70 micrometers.

    E-Ink from a famous Ukrainian manufacturer
    Let's start, perhaps, with banal things - “pixels”, or rather the cells that are responsible for forming the image:


    Optical micrograph of the active matrix of an E-Ink display

    The size of such a cell is about 125 micrometers. Since we are looking at the matrix through the glass on which it is applied, I ask you to pay attention to the yellow layer in the “background” - this is gold plating, which we will subsequently have to get rid of.


    Forward to the embrasure!


    Comparison of horizontal (left) and vertical (right) “inputs”

    Among other things, many interesting things were discovered on the glass substrate. For example, positional marks and contacts, which, apparently, are intended for testing the display in production:


    Optical micrographs of marks and test pads

    Of course, this doesn't happen often and is usually an accident, but displays sometimes break. For example, this barely noticeable crack, less than a human hair thick, can forever deprive you of the joy of reading your favorite book about Foggy Albion in the stuffy Moscow metro:


    If the displays break, it means someone needs it... Me, for example!

    By the way, here it is, the gold I mentioned - a smooth area “bottom” of the cell for high-quality contact with the ink (more about them below). We remove the gold mechanically and here is the result:


    You"ve got a lot of guts. Let"s see what they look like! (With)

    Under a thin gold film are hidden the control components of the active matrix, if you can call it that.

    But the most interesting thing, of course, is the “ink” itself:


    SEM micrograph of ink on the surface of the active matrix.

    Of course, it is difficult to find at least one destroyed microcapsule to look inside and see “white” and “black” pigment particles:

    SEM micrograph of the surface of electronic “ink”


    Optical micrograph of "ink"

    Or is there still something inside?!


    Either a destroyed sphere, or torn out of the supporting polymer

    The size of individual balls, that is, some analogue of a subpixel in E-Ink, can be only 20-30 microns, which is significantly lower than the geometric dimensions of subpixels in LCD displays. Provided that such a capsule can operate at half its size, the image obtained on good, high-quality E-Ink displays is much more pleasant than on an LCD.

    And for dessert - a video about how E-Ink displays work under a microscope.