RU2196353C2 - Element of liquid-crystal display - Google Patents

Abstract

FIELD: electronics. SUBSTANCE: element of liquid-crystal display has layer of liquid crystal embedded between two transparent substrates with clear electrodes. Element is divided into three subregions in which limits electrode comes in the form of combs with three different periods of teeth. Phase diffraction grating on which passing light disintegrates into several diffraction spectra emerges in layer of liquid crystal with supply of controlling voltage to comb electrodes. System of masks with slits and specular reflection sections and raster condenser and objective lens makes it feasible to extract three primary colors ensuring potential for operation of element under reflection mode. EFFECT: increased brightness and resistance to unfavorable conditions of operation. 1 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 proportion 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 and 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. In addition, the element cannot work in the reflective version in the mode with frontal illumination.

 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 combs with mutually penetrating teeth [2]. The period of the teeth of one comb 2d, 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 a 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. Another significant drawback is the rigid connection between wavelengths, namely: the wavelengths in the display are strictly twofold, which makes it difficult to obtain a gamut of mixed colors, which can only be realized if there are three independent colors and sufficient brightness. Another disadvantage is the inability to work in a reflective version with frontal illumination.

 Providing the possibility of obtaining a full color image and working in a reflective form 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 a comb, an input mask with slots, a lens raster-condenser is introduced into the gap between the input mask and the first substrate , an absorbing mask with specularly reflecting areas, a lens raster-lens in the gap between the second substrate and the absorbing mask, entrance and exit slots are provided in the input mask, the position of which is optical ki is consistent with the position of the mirror-reflecting sections of the absorbing mask, the area of the element is conditionally divided into three subregions, within which the period of the combs is different in each of the subregions, the location of the mirror-reflecting sections of the absorbing mask within each subregion is the same, and one of three different colors is reflected in within each of the subdomains, different in each of the subdomains.

 Thanks to this design, three independent phase gratings of the same period can be formed in the LC layer and, using a system of input and output slots in the input mask, absorbing masks with reflective sections, and a lens raster system, select three colors that are independent of one another, allowing to obtain a full gamut of colors in the display based on the proposed item. The element is designed to work in a reflective version.

 The drawing shows the design of the element and the path of the rays in it.

 The liquid crystal display element contains a layer of liquid crystal 1, enclosed between two transparent substrates 2 and 3, on the inner sides of which are deposited transparent electrodes 4 and 5. One of the transparent electrodes, for example, 5 is made in the form of a comb, for which it contains rectangular sections Windows removed the conductive layer. Window width a, window spacing b. Thus, the period of the comb structure is a + b = d and it is different on each of the three subdomains R, G, B, into which the element is conditionally divided. The electrode 4 is electrically divided into three subregions (4R, 4G, 4B) so that it is possible to independently supply control voltages to each of the three subregions of the element. On the outer side of the substrate 2 there is an input mask 6 with input slots 7 and output slots 8 and a lens raster-condenser 9.

 A lens raster-lens 10 and an absorbing substrate 11 with mirror portions 12 and 13 are placed on the outside of the substrate 3, the mirror portion 13 being located in the plane of the absorbing mask 11 and the portion 12 being located at a certain angle to the plane of the absorbing mask.

 The optical axis of the lens rasters 9 and 10 are the same. The entrance slots 7 of the input mask 6 are offset from the position of the optical axes of the lens rasters, but are located in the focal plane of the lens raster-condenser 9.

The rays of white non-polarized light 14 (axial and paraxial) illuminate the input 7 and output 8 slots of the input mask 6. The rays of light passing through the input slots in the absence of control voltages propagate along the offset axis O _i -О _i and through the raster optical system (condenser-lens ) form in the plane of the absorbing mask 11 (plot O _i ) the image of the entrance slit in white light. Since the absorbing sections of the mask 11 are located at the location of this image, all the light transmitted through the entrance slits will be absorbed. Thus, in the absence of control voltage, the first optical state of the element is realized: DARK.

The rays of white light 14, passing through the output slit 8 (spurious illumination) in the absence of control voltages, propagate in the direction of the axis O _about -O _about . (In order not to load the drawing, parasitic rays of light are not shown.) These rays form in the plane of the absorbing mask 11 (section O _about ) the image of the exit slit in white light. Since the absorbing sections of the mask 11 are located at the location of this image, all the light transmitted through the output slots will also be absorbed and the optical state of DARKNESS will not be disturbed by spurious light penetrating through the output slots 8 of the input mask 6.

 If a control voltage is applied to the electrode 5 and one or several subregions of the electrode 4R, 4G, 4B, then in the LC layer in these subregions a periodic system of sections with reoriented LCD and LCD with the initial orientation will appear. The system of sections with different orientations of the LC is a phase diffraction grating. The periods of diffraction gratings on each of the three subregions are different and are selected as follows.

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.

 The light transmitted through the phase diffraction grating, using a lens raster-lens 10, will form a system of diffraction spectra of ± m orders in the plane of the absorbing mask 11.

The angles relative to the zero maximum (direction O _i -O _i ), 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 the site In the lattice period, we take for d. Then, in sections G and R, the lattice period will be 1.2d and 1.5d, respectively.

At an angle φ _B in the plane of the absorbing mask 11, blue _B will be focused, at an angle φ _G, green _G will be focused, at an angle φ _R, red _R will be focused.

Since the periods of the lattices in each of the subdomains are different and equal to d, 1,2d and 1,5d, respectively, the angles φ _R , φ _G , φ _B , will also be different. Therefore, in each of the subdomains, the reflecting sections 12, 13 will have different strictly defined wavelengths, since the reflecting sections are located at the same distance l from the axis O _i -O _i . So, in the subregion B, the rays of blue color (B) will fall on the reflecting areas, in the subregion G - the rays of green color (G), in the subregion R - rays of red color (R). The rays of the same color, reflected from the flat 13 and inclined 12 sections, are collected using the lens raster-lens 10 at point K, additionally diffracted on the grating, get to the point L and are focused using the lens raster-condenser 9 on the inside of the input mask 6.

 At the places of focusing of reflected rays of the same color, exit slots 8 are located through which light of a certain wavelength leaves the element.

 Thus, four optical states are realized in the element: COLOR 1 (R red), COLOR 2 (G green), COLOR 3 (B blue) and the DARK state, which allows obtaining a full-color information display system.

 The spectral composition of the light emerging from the element is determined by the mutual position of the output slit 8 of the input mask 6 and the reflective sections 12 and 13 and the width of the slit of the output mask.

 These parameters are set constructively and independently for each of the colors, they can vary according to need. So, if cleaner colors are required, the width of the slots should be minimal. Then the intensity of the outgoing light will also be minimal. If high intensity is required and not very clear colors are acceptable, the width of the slots can be increased. There is no dependence of the spectral composition of the transmitted light on any LC parameters, for example, on the layer thickness, temperature, or viewing angles, since the light emerging through the exit slots is a point source with a wide and uniform scattering indicatrix. This property of the element is a very important operational parameter.

 The element implements four optical states: COLOR 1 (R red), COLOR 2 (G green), COLOR 3 (B blue) and the DARK state, which allows receiving a full-color information display system. Each of the colors can be modulated independently of one another.

 Thus, the introduction of an absorbing mask with mirror-reflecting elements, a lens raster-condenser, a lens raster-lens, the formation of three independent diffraction gratings on the field of an element allows to obtain an element that works on "reflection", with a full gamut of colors, with increased brightness images and higher efficiency of the use of light from the lighting system.

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

 2. Copyright certificate of the USSR 488177, MKI 2 G 02 B 5/25, publ. 06/10/1976.

Claims (1)

 An element of a 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 a comb, an input mask with slots, characterized in that a lens raster capacitor is inserted into it between the input mask and the first substrate , an absorbing mask with specularly reflecting areas, a lens raster-lens in the gap between the second substrate and the absorbing mask, entrance and exit slots are provided in the input mask, the position of which optically consistent with the position of the specularly reflecting sections of the absorbing mask, the area of the element is conditionally divided into three subregions, within which the periods of the combs are different, the location of the specularly reflecting sections of the absorbing mask within each subregion is the same, and one of three different colors is reflected within each of the subregions , different in each of the subdomains.

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