RU2196351C2 - Element of liquid-crystal display - Google Patents

Abstract

FIELD: electronics. SUBSTANCE: element of liquid-crystal display includes liquid-crystal cell and triad of light filters with primary colors. Triad of light filters comes in the form of input and output masks with slits, has passive diffraction grating, lens rasters, condenser and objective lens. 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 by filters with primary colors, 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 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, because LC 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 a liquid crystal display element consisting of a liquid crystal cell comprising two polaroids, a liquid crystal layer enclosed between two transparent substrates with transparent electrodes, and a triad of light filters transmitting light from one of the three primary wavelengths: R - red , G is green, B is blue [2]. The filters of the triad are located inside the LCD cell and are made of photopolymer. In each element of the triad, actinic light induced a different birefringence value, which, in the presence of polaroids, allows one of the three primary wavelengths to pass through each of the elements of the triad.

 The disadvantages of the known element are the strong angular dependence of the spectral composition of the light passing through the elements of the triad, and the low durability of the element, because LCD can chemically react with the polymer of the filter and this can lead to its degradation and loss of performance.

 The aim of the invention is to reduce the angular dependence of the spectral composition of transmitted light and increase the durability of the element.

 This goal is achieved by the fact that in the element of the liquid crystal display, consisting of a liquid crystal cell comprising two polaroids, a layer of liquid crystal enclosed between two transparent substrates with transparent electrodes, and a triad of light filters, a triad of light filters is made of an input mask with slots, a lens raster-condenser , diffraction grating, lens raster lens, output mask with slots, the position of which is consistent with the slots of the input mask, and the triad of light filters is located outside her side of the liquid crystal cell.

 Thanks to this design, a filter consisting of a diffraction grating, input and output masks, and lens rasters allows separation of primary colors, and the spectral composition of light after separation does not depend on the viewing angle. Placing the filter outside the LCD cell allows you to eliminate its possible chemical interaction with the LCD layer and thereby increase the durability of the element.

The drawing shows:
a is the design of the element and the path of the rays in it,
b - the relative position of the electrodes of the liquid crystal cell.

 The liquid crystal display element (see a) contains an LCD cell consisting of a liquid crystal layer 1, enclosed between two transparent substrates 2 and 3, on the inner sides of which are transparent electrodes 4 and 5. One of the transparent electrodes, for example, 4, is solid , the other electrode 5 is divided into three sections: 5R, 5G and 5V (see c). Polaroids 6 are placed on the outer sides of the substrates, which make it possible to use one of the field effects in the LC, for example, the twist effect, to modulate transmitted light.

 An input mask 7 with slots, a lens raster-condenser 8, a diffraction grating 9 on a solid transparent carrier, a lens raster-lens 10 and an output mask 11 are placed on the outer side of the substrate 2.

 The rays of white unpolarized light 12 (axial and paraxial) illuminate the input mask 7 and narrow beams of light pass through the slits of the input mask. The slits of the input mask are located in the foci of the lens raster-condenser 8, therefore, an almost parallel beam of light is formed at its output, uniformly illuminating the areas of the diffraction grating.

 The lens raster lens 10 forms an image of a light source (slits of the input mask 7) in its focal plane, i.e. on the output mask 11. If there is a diffraction grating in the path of the optical rays in the plane of the output mask, colored images of the slots of the input mask will be formed, placed at different angles relative to the O-O axial line, i.e. diffraction spectra of different orders.

We take for the primary color system the following:
B - blue 0.440 μm,
G - green 0.528 μm,
R - red 0.660 μm.

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 period of the comb.

At an angle φ _in the plane of the output mask 11 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.

At these angles, transparent windows 13 are provided in the output mask, which transmit light to the output of the filter. The plane of the mask is conditionally divided into three sections: 11R, 11G and 11B (see a). Within each of the sections, the position of the slits of the output mask relative to the O-O centerline is different (distances l _R , l _G , l _B ) and ensures the passage of only one of the given primary colors in each of the sections.

 The spectral composition of the light transmitted by the slit is determined by the position of the slit of the output mask relative to the center line, on which the slit of the input mask is located, and the width of the slit of the output mask and does not depend on the viewing angles.

 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 transmitted 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 up to 1/3 of the width of the entire spectrum.

 After the initial white light passed through the slits of the output mask and acquired the color of one of the primary colors in each of the sections, its intensity is modulated by means of an LCD cell divided into 3 sections: 5R, 5G, 5B, and polaroids 6. Applying control voltages to the electrode and any of the sections 5R, 5G and 5V, you can independently control the intensity of any color and create any color combinations, which is a necessary condition for building full-color displays.

 The diffraction grating 9 can be of any type, with any, preferably small, technologically accessible period and with maximum efficiency.

 Since the filters are outside the LCD cell, the problem of the chemical interaction of the LCD and the filter does not exist.

 Thus, the introduction of an optical filter based on a diffraction grating, lens rasters, and masks into the element made it possible to obtain angular independence of the spectral composition of the light modulated by the element, and the removal of the filter from the contact zone with the LC made it possible to increase the durability of the element and thereby achieve its goal.

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

 2. US patent 5389698, C 08 F 2/46, MKI 6 G 02 F 1/133 (NCI 522/2), published. 02/14/95

Claims (1)

 An element of a liquid crystal display consisting of a liquid crystal cell including two polaroids, a layer of a liquid crystal enclosed between two transparent substrates with transparent electrodes, and a triad of light filters, characterized in that the triad of light filters is made of an input mask with slots, a lens raster-condenser, a diffraction grating , a lens raster lens, an output mask with slots, the position of which is consistent with the slots of the input mask, a triad of light filters is located on the outside of the liquid crystal cal cell.

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