RU2196352C2 - Element of liquid-crystal display - Google Patents

Abstract

FIELD: electronics. SUBSTANCE: element of liquid-crystal display includes layer of liquid crystal confined between two transparent substrates with clear electrodes. Electrodes on both substrates come in the form of combs with mutually penetrating teeth. Periods of teeth on one substrate match up via fractional correlation. In points of potential superimposition of teeth of combs electrodes in register are split. Periods of combs on second substrate are equal. With supply of controlling voltage to comb electrodes phase diffraction grating emerges in layer of liquid crystal which disintegrates passing light into several diffraction spectra. EFFECT: increased brightness and stability under unstable conditions of operation. 3 dwg

Description

 The invention relates to indicator technology, in particular to color liquid crystal displays, in which the selection of colors is carried out along the plane with light filters with three primary colors (triads), and the modulation of each of the colors is carried out by means of a liquid crystal (LCD).

 A known element of the LCD display containing a layer of an LCD placed between two substrates with transparent electrodes and orienting coatings on the inside, and a triad of filters that transmit light from one of the three primary wavelengths: R - red, G - green, B - blue [1 ]. The filters of the triad are made of polymer, and a dye of one of the primary colors is introduced in each of them. A section of the LCD is located opposite each of the filters, which, with the use of polaroids, regulates the amount of light passing through each of the filters through the application of voltage, which creates a color image.

 The disadvantages of the known display are the low luminosity (a large fraction of the light is absorbed by the light filter) and the high cost due to technological difficulties in manufacturing: usually low-melting polymer must be applied alignment and orientation coatings, transparent electrodes, and these processes are usually high-temperature. The durability of the element is limited, since the LCD can chemically react with the polymer of the light filter and / or with the dye. This can lead to its degradation and loss of performance.

 The closest in technical essence to the invention is an element of a liquid crystal display containing a layer of liquid crystal enclosed between two substrates with transparent electrodes, one of which is solid, and the other is made in the form of two combs with mutually penetrating teeth [2]. The period of the teeth of one comb 2 d, the total period of two combs d. The element is equipped with input and output masks with slots. The mutual position of the slots of the masks is coordinated in such a way that in the absence of control voltage, the light does not pass through the masks. When a control voltage is applied to a continuous common electrode and one of the combs, the LC is reoriented in the parts under the teeth. The LC layer with regions with the initial orientation and reoriented is a phase diffraction grating. The white light beams passing through the slits of the input mask are diffracted on the resulting phase diffraction grating, forming a system of diffraction spectra in the plane of the output mask. In those places of the output mask to which certain wavelengths fall, for example, λ, slots are provided through which light of this wavelength passes. When a voltage is applied to a common and two comb electrodes, a diffraction grating with a half time period appears in the LC layer and light with a double wavelength will pass through the same slits. Thus, the element provides three optically distinguishable states: DARK, COLOR 1, COLOR 2, and the wavelengths of colors differ strictly twice. The element has high performance properties, such as: stable colors, independent of temperature or thickness variations, there are no layers chemically interacting with the layer in contact with the layer, and therefore its durability is increased.

 A disadvantage of the known element is a limited set of colors (only two) and therefore the inability to create a full-color display. In addition, the element has a significant loss of light, because of the entire incident intensity on the element, only light rays parallel to the optical axis that fall on the slits of the input mask are used.

 The possibility of realizing a full-color display is carried out only if there are three independent colors and sufficient brightness. The provision of such an opportunity is the aim of the invention.

 This goal is achieved by the fact that in the known element containing a layer of liquid crystal enclosed between two transparent substrates with transparent electrodes, one of which is made in the form of two combs with mutually penetrating teeth, the input and output masks with slots, the mutual position of which is coordinated, are introduced lens raster-condenser between the input mask and the first substrate, lens raster-lens between the second substrate and the output mask, the second electrode is made in the form of two combs with penetrating teeth, the periods of the combs on the first substrate differ by a fraction of the number of times and do not coincide with the period of the combs of the second substrate, at the points of coincidence of the teeth of the first and second combs of the first substrate, cuts are provided to exclude the electrical closure of the combs.

 According to claim 1, certain relations are established between the periods of the combs on the first and second substrates, in particular: the period of one comb of the first substrate is d, the period of the second comb is 1.2 d, the period of the comb on the second substrate is 1.5 d.

 Due to this design, phase gratings can be formed in the LC layer in three different, independent periods: 1.5 d, 1.2 d and d, pass the color of three wavelengths through the slits of the output mask and provide 4 optically distinguishable states: DARK, COLOR 1 (λ ), COLOR 2 (1.2 λ) and COLOR 3 (1.5 λ).

 It is this ratio of periods that allows us to provide color coordinates in the display that exactly correspond to accepted international standards (CIE system).

 The presence of lens rasters can increase the efficiency of the use of light and increase the brightness of images in the display by providing the possibility of using paraxial rays from the light source.

The drawing shows:
a - element design (for ease of presentation, three elements are depicted),
b - the shape of the electrodes on the first of the substrates,
in - the shape of the electrodes on the second of the substrates.

The liquid crystal display element (see a) contains a layer of liquid crystal 1, enclosed between two transparent substrates 2 and 3, on the inner sides of which transparent electrodes 4 and 5 are applied. The transparent electrode 4 is made in the form of two combs 4a, 4b with mutually penetrating teeth. The period of the teeth of one of the combs d _B = d, the period of the second comb d _G = 1,2 d. Since the periods of the combs 4a and 4b are related to each other by a fractional ratio, for any of the values of d, a situation will arise in which the teeth of the combs must overlap each other. In order to eliminate this possibility, in the places of possible overlapping of the teeth, cuts of each of the matching teeth are provided, for example, in the middle of each of the teeth (see b).

The transparent electrode 5 is made in the form of two combs, the period of the teeth of which d _R is 1.5 d.

 On the outer side of the substrate 2, a lens raster-condenser 6 and an input mask 7 with slots are placed. On the outer side of the substrate 3 there is a lens raster lens 8 and an output mask 9.

 The rays of white unpolarized light 10 (axial and paraxial) illuminate the input mask 7 and narrow beams of light pass through the slits of the input mask. The slots of the input mask are located in the foci of the lens raster-condenser 6, therefore, an almost parallel beam of light is formed at the output of the condenser 6, uniformly illuminating the area of the LCD cell with a comb electrode.

 The lens raster lens 8 forms an image of a light source (slits of the input mask 7) in its focal plane, i.e. on the output mask 9.

 In the initial state in the axial direction (O-O), a bright white image of the slit will be formed on the output mask. Since in these places of the output mask 9 there are opaque portions, all the transmitted radiation will be absorbed and, thus, the first of the optical states of the element will be realized: DARK.

 Three other optical states: COLOR 1, COLOR 2, COLOR 3 can be obtained by applying control voltages to comb electrodes 4 and 5 in various combinations.

We accept for the system of primary colors that comply with the International Standard CIE:
B - blue 0.440 μm,
G - green 0.528 μm = (0.440 • 1.2) μm,
R - red 0.660 microns = (0.440 • 1.5) microns.

 If the control voltage is applied to the electrode 4a and the electrically connected electrodes 5a, 5b (in this case they are used as a common, almost continuous electrode), then a periodic system with a reoriented LCD and LCD with the initial orientation will appear in the LC layer. The system of sections with different LC orientations is a phase diffraction grating with a period of d (in this case, the application of stresses).

 The light transmitted through the phase diffraction grating, using a lens raster-lens 8, will form a system of diffraction spectra of ± m orders in the plane of the output mask 9.

The angles with respect to the zero maximum (O-O axial direction) at which certain wavelengths are observed are determined by the expression
sinφ = ± mλ / 2d,
where φ is the angle at which light with a wavelength λ propagates, m is the number of the diffraction maximum (takes integer values), d is the comb period.

At an angle φ _B in the plane of the output mask 9, the blue color B will be focused, at an angle φ _{G the} green color G will be focused, at an angle φ _{R the} red color _R will be focused.

In places of focusing of blue color (distance l at an angle φ _B for period d), transparent sections are provided in the output mask 9 — slots that transmit light only at a given wavelength.

 Thus, with the combination of voltage application options described above, COLOR 1 — blue color B — will pass through the slots of the output mask (the situation is shown on the right of three elements).

 When voltages are applied to the electrode 4b and the electrically connected electrodes 5a, 5b, a phase grating with a period of 1.2 d will appear in the LC layer and light with a wavelength 1.2 times longer will pass through the same slots of the output mask, i.e. COLOR 2 - green color G (the situation is depicted on an average of three elements).

 When a control voltage is applied between the electrodes 5a and 5b (no voltage is applied to the electrodes 4a, 4b at all), a periodic system with a reoriented LCD (in the gap between the teeth) and an LCD with the initial orientation (above the teeth) will appear in the LC layer. The resulting phase lattice has a period of 1.5 d. Through these slots of the output mask, light will pass with a wavelength of 1.5 times greater than with period d (the left of the elements shown). Thus, the fourth optical state will be realized: COLOR 3 - red color R.

 The periods of the comb electrodes 4a and 4b differ in a fractional number of times (in the specific case, 1.2 times). Therefore, regardless of the magnitude of the periods and the width of the teeth and the gaps between them with a sufficiently large number of teeth, a situation will arise when the teeth of one comb should overlap with the teeth of another comb. In order to eliminate possible electrical shorting of the combs, overlapping teeth are cut, for example, in the middle. The periods of the combs from the cut of the teeth do not change and, therefore, their ability to function as diffraction gratings is not lost. A certain number of shortened teeth of the lattice leads to a slight decrease in efficiency.

 Thus, the execution of both electrodes in the form of combs with mutually penetrating teeth, the periods of which correspond to a fractional number of times, and the introduction of lens rasters into the element make it possible to obtain three independent bright colors in the element, which allows creating full-color displays on its basis.

Sources of information
1. Patent PCT (WO) 85/04962, MKI 6 G 02 F 1/133, published 04/19/1985.

 2. Auth. testimonial. USSR 488177, MKI 2 G 02 B 5/24, published on 10.06.1976.

Claims (2)

 1. The element of the liquid crystal display containing a layer of liquid crystal enclosed between two transparent substrates with transparent electrodes, one of which is made in the form of two combs with mutually penetrating teeth, the input and output masks with slots, the mutual position of which according to, characterized in that a lens raster-capacitor is inserted into it between the input mask and the first substrate, a lens raster-lens is between the second substrate and the output mask, the second electrode is made in the form of two combed with mutually penetrating prongs periods combs on the first substrate differ in fractional number of times and do not coincide with the period of the combs of the second substrate, at locations where the teeth of the first and second combs first substrate provided slits excluding the electric circuit combs.  2. The element according to claim 1, characterized in that the ratio of the periods of the gratings is chosen as follows: the period of one comb of the first substrate is d, the period of the second comb is 1.2 d, the period of the comb on the second substrate is 1.5 d.

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