JP2011085886A - Dual layer holographic color filter and transmissive liquid crystal display using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a dual layer holographic color filter which achieves a liquid crystal display having low power consumption and capable of superior color reproduction, and to provide a transmissive liquid crystal display using the dual layer holographic color filter. <P>SOLUTION: The dual layer holographic color filter 100 includes a first hologram 110, which is provided between a light source 60 and the liquid crystal display 200 to spatially split white light from a substrate at the side of the light source, and a second hologram 120, which allows the split light to have the same direction as that of the light from the light source, to receive only light having a spectral bandwidth corresponding to colored cells of a color filter 210 so that the luminance of the liquid crystal display is enhanced. Light passing through the first hologram including hologram pieces 111 is diffracted at different angles according to wavelengths. The second hologram recovers the traveling direction of the white light spatially split in the first hologram to an original direction of light from the light source. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

The present invention relates to a two-layer holographic color filter and a transmissive LCD using the same, and in particular, adopts an optical device and a structure applicable to the LCD using the optical device, and is absorbed by the RGB color filter. The RGB color filter of the LCD only emits light having a wavelength band suitable for the RGB color filter so that the amount of light can be minimized and color reproduction can be improved by preventing the wavelengths from overlapping each other between the RGB color filters. The present invention relates to a two-layer holographic color filter that can improve light efficiency by being incident on the transmissive LCD and a transmissive LCD using the two-layer holographic color filter.

Generally, since 90% of the light supplied from the backlight is absorbed by the polarizing plate and the color filter, the light efficiency of the liquid crystal display (LCD) is very low. In particular, an RGB color filter manufactured using dyes or pigments selectively transmits only light having a wavelength of white light corresponding to the RGB color filter, so that the maximum efficiency is at most 33%. Furthermore, since the RGB color filter does not appropriately perform the filter function, the band is widened.

In order to solve this problem, the methods proposed in Patent Documents 1 and 2 prepare a hologram array having a unit pixel size for performing a lens function, and spatially convert wavelengths having RGB bands by chromatic dispersion. In this method, the light is divided and the wavelength is incident on the sub-pixel corresponding to the wavelength. Further, the method proposed in Patent Document 3 prepares two holograms and an array of lenses arranged between the holograms, and has light having a wavelength corresponding to each color cell and a pixel size. In this method, the light is condensed by a lens, and if white light is dispersed by one hologram, the optical path is corrected to the original state by the other hologram.

The method proposed in Patent Document 4 disperses color using a diffraction grating of one hologram, exercises a hologram serving as a three-layer lens, and collects light of RGB wavelength corresponding to RGB wavelength. As a result, the light is incident on each color cell.

As shown in FIG. 1, according to the method disclosed in Patent Document 1, white light from the backlight 3 is transferred to a Fresnel zone plate (a hologram 5 having a size of one pixel and functioning as a lens). After passing through, the light having RGB wavelengths selectively enters each RGB color cell 1 ′ of the color filter 1 of the liquid crystal 10. In this case, since a Fresnel zone plate is used, a circular focus is formed around each color cell 1 ′ of the color filter 1. Therefore, the liquid crystal 10 cannot rotate the polarization completely. A problem may occur in color synthesis due to color dispersion in which the divided RGB wavelengths are directed in different directions.

Patent Document 2 discloses the same structure as Patent Document 1 except that light rays are incident on the color filter obliquely rather than in the vertical direction. Specifically, according to Patent Document 2, an array of micro-holograms that carry a lens is used, and the focal point is formed around the liquid crystal. As a result, the polarization cannot be rotated perfectly, and problems still occur during color synthesis due to color dispersion after color division.

As shown in FIG. 2, according to the method disclosed in Patent Document 3, after white light from the light source 14 is divided by one typical diffraction grating 16 according to the wavelength, the RGB wavelength is the pixel size. By passing through the microlens 18, it is divided corresponding to the size of the pixel, and each wavelength is restored to its original direction before the diffraction grating 16 by passing through the other diffraction grating. Thereafter, the light enters the LCD 20. However, since this method is suitable for a transmissive LCD projector, a considerable distance is required between the diffraction gratings 16 and 22. Therefore, it is difficult to manufacture the microlens 18 interposed between the diffraction gratings 16 and 22, and it is difficult to arrange the three devices.

As shown in FIG. 3, according to the method disclosed in Patent Document 4, the white light F1 from the backlight passes through the first hologram 16, while the traveling direction of the wavelength of the white light F1 is due to light diffraction. Change. Thereafter, among the wavelengths arriving at the second hologram 14 serving as a lens, red, green, and blue wavelengths are focused on their respective target positions by the red, green, and blue holograms 14R, 14G, and 14B. According to this method, since the red, green, and blue wavelengths are focused in the same direction, the problem relating to color composition caused by chromatic dispersion is solved. However, with this method, the second hologram 14 that carries a lens and has three layers cannot be realized in units of pixels. Furthermore, as a hologram, the number of layers increases and the light absorption also increases.

US Patent No. 5,506,701 US Patent No. 6473144B1 US Patent No. 7046407B2 US Pat. No. 5,894,359

In order to solve the above problem, the method proposed in the present invention uses only red, green, and blue wavelengths for the red (R) and green colors of the transmissive liquid crystal display instead of white light including all wavelengths. (G) A method of improving the light efficiency by solving the problem that the color filter absorbs 2/3 of the light amount by exclusively entering the blue (B) color cell is proposed. To this end, a two-layer holographic color filter including a pair of holograms and a method for constructing a liquid crystal display using the two-layer holographic color filter are provided.

In order to achieve the object of the present invention, according to one aspect of the present invention, a first hologram that distributes the wavelength of white light in a space that is adjacent and has the size of a unit pixel, and supporting the first hologram And a second hologram for restoring the direction of the wavelength divided by the first hologram so that only the wavelength corresponding to each color cell is incident on the color cell. By providing the above, a two-layer holographic color filter is provided that prevents problems during color synthesis.

According to another aspect of the present invention, in a liquid crystal display including a color filter, the two-layer holographic color filter is interposed between the light source and the color filter.

According to still another aspect of the present invention, in a liquid crystal display without a color filter, the two-layer holographic color filter is interposed between a light source and the liquid crystal of the liquid crystal display.

As described above, according to the present invention, it is possible to realize a liquid crystal display capable of excellent color reproduction with low power consumption. This is because the light absorbed by the color filter can be completely used without causing overlapping of wavelengths. Furthermore, according to the present invention, the optical device includes an optical device that can be practically realized and that can solve the optical problem by correcting a problem that occurs in the conventional color separation type color filter. The present invention includes a two-layer holographic color filter and a transmissive LCD using the same. Since the present invention can be designed and manufactured appropriately for the type and characteristics of the light source, the brightness can be improved in all liquid crystal displays. Therefore, power consumption can be reduced. In addition, when replacing the color filter, the three processing steps for manufacturing the red, green, and blue color filters are replaced with two processing steps for manufacturing the first and second holograms. It can be simplified.

The above and other objects, features, and advantages of the present invention will become more apparent from the following detailed description of embodiments with reference to the drawings.

It is a figure which shows the reference figure of patent document 1 in order to demonstrate a prior art. It is a figure which shows the reference figure of patent document 2 in order to demonstrate a prior art. It is a figure which shows the reference figure of patent document 3 in order to demonstrate a prior art. 1 is a diagram showing a transmissive liquid crystal display using a two-layer holographic color filter according to the present invention. FIG. FIG. 5 is a diagram illustrating a method of manufacturing a surface relief hologram having multiple layers through a CGH scheme when manufacturing a holographic color filter according to the present invention. FIG. 5 is a diagram illustrating a method of manufacturing a surface relief hologram having multiple layers through a CGH scheme when manufacturing a holographic color filter according to the present invention. A method for directly recording a volume hologram on a recording material when a holographic color filter according to the present invention is manufactured will be described. In the two-layer holographic color filter according to the present invention, after the wavelength passes through the substrate by the first hologram piece, the position of the reconstructed image of each wavelength on the surface of the second hologram is shown. It is a figure which shows the operating characteristic of the 2nd hologram which corrects the advancing direction of the wavelength disperse | distributed by a 1st hologram in the two-layer holographic color filter by this invention. It is a figure which shows the two-layer type holographic color filter by embodiment of this invention. It is a figure which shows the two-layer type holographic color filter by embodiment of this invention. It is a figure which shows the two-layer type holographic color filter by embodiment of this invention. It is a figure which shows the two-layer type holographic color filter by embodiment of this invention. It is a figure which shows the arrangement | sequence of the 1st hologram of the two-layer type holographic color filter by this invention. The reconstructed image of the first hologram is suitable for a transmissive LCD including a color filter provided in a stripe shape. It is a figure which shows the arrangement | sequence of the 1st hologram of the two-layer type holographic color filter by this invention. The reconstructed image of the first hologram is suitable for a transmissive LCD having a color filter provided in a mosaic shape. It is a figure which shows the arrangement | sequence of the 1st hologram of the two-layer type holographic color filter by this invention. The reconstructed image of the first hologram is suitable for a transmissive LCD including a color filter provided in a delta shape. FIG. 3 is a view showing a liquid crystal display using a two-layer holographic color filter according to the present invention and including a color filter. FIG. 3 is a view showing a liquid crystal display using a two-layer holographic color filter according to the present invention and not including a color filter.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

According to this embodiment, the wavelengths are divided from each other corresponding to the spacing between the R, G, B color cells of the liquid crystal display (LCD). A holographic color filter is interposed between the backlight unit and the LCD. Here, since the holographic color filter includes two holograms, wavelengths having different optical paths are corrected. As a result, the wavelength travels in the same direction.

As shown in FIG. 4, the two-layer holographic color filter 100 according to the embodiment is interposed between the light source 60 and the LCD 200. The holographic color filter 100 includes a first hologram 110 provided on the light source 60 side, a second hologram 120 provided on the LCD 200 side, and glass or plastic between the first and second holograms 110 and 120. Including the substrate 130.

The color filter 210 connected to the LCD 200 includes unit pixels including red, green, and blue color cells 210R, 210G, and 210B. The red color cell 210R transmits only the red wavelength of the incident light. The green color cell 210G transmits only the green wavelength of the incident light, and the blue color cell 210B transmits only the blue wavelength of the incident light. Thereafter, after the incident light passes through the LCD 200, a color is realized through color synthesis.

The first hologram 110 includes a plurality of transparent transmissive first hologram pieces 111 (the size of which is the size of a unit pixel). The first hologram piece 111 is a multi-layer formed through a computer-generated hologram (CGH) scheme designed to exactly match the size of a unit pixel on the surface of the second hologram 120. A surface relief hologram having a volume hologram recorded directly on a holographic recording material according to the material and thickness of the substrate 130.

The first hologram 110 is located on the light source 60 side, but includes the first hologram piece 111 designed to reproduce a linear image. In addition, when designing the CGH scheme or using the green light used for recording the volume hologram as the recording light, the image is in the longitudinal direction on the lateral side of the green color cell 210B of the second hologram 120, It has a length shorter than the length of the green color cell 210G.

When compared to green recording light, red light having a longer wavelength diffracts at a larger angle so that a longer image is formed on the red subpixel 210R. Blue light having a smaller wavelength diffracts at a smaller angle so that a shorter image is formed on the blue color cell 210B. Accordingly, the white light having the RGB wavelength and having passed through the first hologram 110 is subjected to color separation by light diffraction so that only the wavelength corresponding to each RGB color cell is incident on the surface of the second hologram 120. .

The second hologram 120 includes a plurality of transparent transmission-type second hologram pieces 121, each piece 121 having a size of a unit pixel, and different after being color-separated by the first hologram 110. This is for correcting the direction of the RGB wavelength traveling in the selected direction. Therefore, after passing through the two-layer holographic color filter 100, the light enters the LCD 200 in the same direction as the original light of the light source 60. Accordingly, the problems related to color dispersion and color synthesis that occur when the two-layer holographic color filter 100 is inserted into the transmissive LCD can be solved. Similar to the first hologram piece 111, the second hologram piece 121 includes a surface relief hologram having multiple layers based on the CGH scheme or a volume hologram recorded directly on a holographic recording material.

The second hologram piece 121 is applied to the color filter 210 so that R, G, B light (its traveling direction is corrected through the second hologram piece 121) can enter the color cells 210R, 210G, 210B, respectively. On the other hand, it is necessary to arrange on the coaxial line. The first hologram piece 111 is arranged coaxially with respect to the second hologram piece 121 based on the diffraction angle of the RGB wavelength so that the diffracted wavelength reaches the corresponding second hologram piece 121. The The number of the first and second hologram pieces 111 and 121 may be a number corresponding to an integral multiple of the number of unit pixels according to the design and manufacturing scheme.

As shown in FIGS. 5A and 6, the first hologram piece 111 according to the present invention is manufactured using a surface relief hologram having multiple layers or a volume hologram directly recorded on a holographic recording material based on the CGH scheme. .

Hereinafter, a method of manufacturing a surface relief hologram having multiple layers based on the CGH scheme will be described in detail with reference to FIG. 5A.

The RGB center wavelengths (λR, λG, λB) are diffraction angles (θ including λR, λG, λB diffraction angles θr, θg, θb, respectively) with respect to the wavelength (λ) of all visible rays from the light source 60. (Diffractive equation), the size d of the minimum hologram pattern and the position of the reconstructed image 81 from the center of the target image 80 are θr and θb after the light passes through the substrate 130 having the thickness D. Is determined to be the distance between the central positions of the color cells 210R and 210B.

The size of the target image 80 including the reconstructed image 81 is set to the size of a single pixel, and “m” indicates the diffraction order having a value of “1” in multiple layers. As shown in FIG. 5B, the hologram pattern 91 is formed through the CGH scheme. In this case, the size of the target image 80, the size of the pattern, and the position of the reconstructed image 81 are taken into consideration. A typical surface relief hologram with multiple layers is then formed according to the height of each pixel.
Formula 1
dsin θ = mλ

FIG. 6 shows a method according to the invention for recording a volume hologram directly on a holographic recording material.

Referring to FIG. 6, if the recording light is a laser light having a green wavelength λG, the aperture is disposed on a substrate 130 coated with a holographic recording material 31 that reacts with the laser light. This takes into account the shadow region of the object beam 34 incident in an oblique direction. Here, the aperture has a transparent area slightly wider than the unit pixel, and light does not pass through the remaining area. Thereafter, after the laser light is divided into the object beam 34 and the reference beam 33, the hologram is recorded on the holographic recording material by traversing the reference beam 33 and the object beam 34. The reference beam 33 represents the traveling direction of the light of the light source 60 and generally advances straight. However, the reference beam 33 may have a divergent shape or a convergent shape according to the irradiation pattern of light. By determining the incident angle of the object beam 34, the object beam 34 can be directed toward a specific position with respect to the recording light. In this case, after the object beam 34 passes through the substrate 130 having the thickness D, the reconstructed images of the red and blue wavelengths λR and λB are arranged at the center positions of the virtual color cells 210R ′ and 210B ′ according to Equation 1. . Actually, the virtual color cells 210 </ b> R ′, 210 </ b> G ′, and 210 </ b> B ′ are provided at positions where the second hologram pieces 121 are disposed. The object beam 34 that diverges from the laser light combines a typical lens 35 for collecting light in all directions and a lenticular lens 36 for collecting light traveling in one direction, A linear focus is formed at the center of the virtual green color cell 210G ′. Therefore, if white light is incident on the hologram, the red and blue wavelengths are located above and below the green wavelength used for recording, respectively, with an interval corresponding to the size of one color cell.

The RGB central wavelengths of light used in the transmissive LCD have different wavelength intervals and intensities. Therefore, light that passes through the first hologram piece 111 and is spatially divided by diffraction and then incident on each color cell of the color filter 210 may have an intensity different from the decentered central wavelength. . The amount of light incident on each color cell may be adjusted according to the convenience of the user, but the adjustment is performed by adjusting the distance and position of the reconstructed image for the reference light used in the design of the first hologram piece 111. Can be adjusted. The adjustment is based on the band and intensity ratio of the RGB center wavelength of the light from the light source 60.

As shown in FIG. 7, since the white light that has passed through the first hologram 110 manufactured by the above method has a diffraction angle that changes according to the wavelength distance, the size of the entire reconstructed region 80 and the reconstructed image 81 The position changes. However, the ratio of the reconstructed image 81 to the entire reconstructed area 80 is constant regardless of the wavelength. Accordingly, the red reconstruction area 80R and the red reconstruction image 81R are formed for the red wavelength λR. The green reconstructed region 80G and the green reconstructed image 81G are formed for the green wavelength λG. The blue reconstruction area 80B and the blue reconstruction image 81B are formed for the blue wavelength λB. The reconstructed image 81 of the first hologram piece 111 is formed so that light passing through the unit pixel converges to one line regardless of the wavelength. Therefore, the absolute position of the reconstructed image 81 changes to a trapezoidal shape according to the wavelength. Here, the absolute position of the reconstructed image 81 changes corresponding to a short convergence line formed in the lower part by the short wavelength λMIN and a long convergence line formed in the upper part by the long wavelength λMAX. The distribution of the reconstructed image 81 is achieved by converting the spectral distribution of the visible light region of white light into a spatial spectrum. The distribution of the reconstructed image 81 represents the intensity distribution of all wavelengths of light from the light source 60, and here, the wavelengths do not overlap. In this case, the total light quantity does not change. The size of the reconstructed image 83 for all wavelengths represented by bold lines is designed to be the same as the size of the unit pixel.

Referring to FIG. 4, when light diffracted into a pixel unit by the first hologram 110 and then passed through the substrate 130 travels in different directions depending on the wavelength incident on the color filter 210 or the LCD 200, the color Dispersion may occur. Therefore, a problem may occur during color synthesis. In order to solve this problem, it is necessary to correct the traveling direction of each wavelength of light. Furthermore, in order to minimize the change in optical properties and the increase in brightness caused by the insertion of the holographic color filter 210, the light is preferably optically identical to the optical properties of the light from the light source 60. It is desirable to have specific characteristics. Such an operation is performed by the second hologram 120 including a plurality of second hologram pieces 121.

As shown in FIG. 8, the second hologram 120 includes a second hologram piece 121 having a unit pixel size. Therefore, the RGB center wavelengths λR, λG, and λB can travel in a direction perpendicular to the surface (xy plane) of the second hologram 120. The red, green, and blue wavelengths λR, λG, and λB divided by the first hologram piece 111 are diffracted upward, centrally, and downward, respectively. For example, when the second hologram piece 121 is constructed so that the green wavelength λG incident at the diffraction angle θg travels in a direction perpendicular to the surface of the second hologram piece 121, the second hologram 120 is in the same direction. The RGB central wavelengths incident at different angles are diffracted in the same direction, similar to the first hologram 110 diffracting the RGB central wavelengths at different angles. Accordingly, if the second hologram 120 including the second hologram piece 121 manufactured by the method shown in FIGS. 5 to 6 is formed on the opposite side of the first hologram 110 with respect to the substrate 130, color dispersion is prevented. be able to. Furthermore, since the traveling direction of the RGB central wavelengths is the same as that of the light from the light source 60, conventional color synthesis is possible.

The filtering operation performed by the two-layer holographic color filter 100 according to the present invention is based on the spatial spectrum distribution instead of the filtering operation of the dye layers R, G, and B of the color filter 210. Therefore, light is not absorbed by the color filter 210 and the RGB bands do not overlap each other. Thus, a transmissive LCD with improved brightness and excellent color reproduction is realized. The band and intensity of each wavelength passing through each pigment layer of the color filter 210 can be adjusted by changing the diffraction grating period of the first hologram 110 according to the spectral distribution of the wavelength from the light source 60. The wavelength diffracted from the corresponding dye layer is blocked by the adjacent dye layer so that a more uniform wavelength intensity distribution is obtained.

As described above, the first and second holograms 110 and 120 can be manufactured by using surface relief holograms and volume holograms. The two-layer holographic color filter 100 according to the present invention may exist in four types as shown in FIGS.

FIG. 9A is a diagram illustrating a case where both the first and second holograms 110 and 120 include surface relief holograms 111a and 121a, and FIG. 9B illustrates that the first hologram 110 includes a surface relief hologram 111a; It is a figure in case the said 2nd hologram 120 contains the volume hologram 121b. FIG. 9C is a diagram in the case where the first hologram 110 includes a volume hologram 111b and the second hologram 120 includes a surface relief hologram 121a. FIG. 9D is a diagram in the case where both the first and second holograms include volume holograms 111b and 121b. The two-layer holographic color filter 100 performs the same operation regardless of the above combination. However, in the case of a surface relief hologram, the efficiency decreases when the number of layers is small. Furthermore, when the number of layers is large, it becomes difficult to manufacture a surface relief hologram. Thus, volume holograms recorded directly on a recording material using a laser exhibit excellent properties in efficiency and stability.

Commercially sold LCDs have various color filter arrays for the purpose of color synthesis, and a manufacturing procedure of a two-layer holographic color filter suitable for the LCD is shown in FIGS. 10A to 10C. In the following description, the same reference numerals are given to components that perform the same operation, and the first and second hologram pieces 111 and 121 correspond to each other one-to-one on the coaxial outer line. Accordingly, the operational characteristics of the two-layer holographic color filter will be described using only the arrangement of the first hologram piece 111. In the reconstructed image 83 for all wavelengths, portions incident on the dye layer are expressed as R, G, and B, which is the same as the dye layer. Furthermore, the optical device for color separation is rotated 90 degrees according to the arrangement of the dye layer.

FIG. 10A shows a stripe-type first hologram 15 suitable for an LCD having a color filter provided in a stripe shape. The first hologram piece 111 is designed such that the reconstructed image 83 of all wavelengths of the first hologram piece 111 has the same size as the RGB dye layer, but has the same shape as the color filter. Provided in shape. FIG. 10B shows a mosaic-type first hologram 16 suitable for an LCD having color filters provided in a mosaic shape. The first hologram piece 111 is designed so that the reconstructed image 83 of all wavelengths of the first hologram piece 111 has the same size as the RGB dye layer, but is provided in a mosaic shape. In the same manner as the color filter, the line is shifted line by line corresponding to the width of one dye layer.

FIG. 10C shows a first delta hologram 17 suitable for an LCD having a color filter provided in a delta shape. The first hologram piece 111 is designed such that the reconstructed image 83 for all wavelengths of the first hologram piece 111 has the same size as the RGB dye layer. In the same manner as a color filter provided in a delta shape, each row is shifted by half the full width of the first hologram piece 111. Since the spacing between the RGB center wavelengths in the reconstructed image increases in the mosaic-type first hologram, the mosaic-type first hologram piece is designed so that the size d of the minimum pattern can be reduced, and is reproduced. The constructed image needs to be designed to be arranged in the outer region as much as possible.

Although the two-layer holographic color filter 100 according to the present invention is close to the LCD 200, the holographic color filter 100 is manufactured simultaneously with the LCD 200 so that the holographic color filter 100 and the LCD 200 are configured in a single module. Is done. 11 and 12 are cross-sectional views showing a transmissive LCD including a color filter 210 and a transmissive LCD that does not include the color filter 210 when the holographic color filter 100 is used for the LCD 200.

Referring to FIG. 11, according to the second embodiment of the present invention, the holographic color filter 100 is used for the LCD 200 including the color filter 210. After the first hologram 110 is provided on the light source 60 side of the substrate 130 and the second hologram 120 is provided on the LCD 200 side, the color filter 210 is placed between the second hologram 120 of the LCD 200 and the liquid crystal 250. Prepare for.

Referring to FIG. 12, according to a third embodiment of the present invention, a two-layer holographic color filter 100 is used for an LCD 200 that does not include a color filter 210. By providing the first hologram 110 on the side of the light source 60 on one side of the substrate 130 and the second hologram 120 on the opposite side of the substrate 130 adjacent to the liquid crystal 250, the two-layer holographic color filter 100 is provided. It plays the role of the color filter of LCD200.

As described above, the two-layer holographic color filter 100 according to the second and third embodiments of the present invention distributes the wavelength of white light. The light is incident on the first hologram 110. Note that the distribution extends over a space having the size of a unit pixel. The substrate has a diffraction space, and the second hologram restores the direction of the wavelength divided by the first hologram to the original direction. Therefore, there is no problem in color synthesis.

While exemplary embodiments of the present invention have been described for purposes of illustration, various other changes, additions and substitutions may be made without departing from the spirit and scope of the present invention. In view of this, it will be apparent to those skilled in the art.

Claims (18)

A first hologram including a plurality of first hologram pieces for distributing the wavelength of white light in a space adjacent to the light source and having a unit pixel size;
A substrate adjacent to the first hologram for supporting the first hologram and comprising a diffraction space;
A second hologram adjacent to the liquid crystal display for restoring the direction of the wavelength divided by the first hologram so that only the wavelength corresponding to each color cell is incident on the color cell. A two-layer holographic color filter characterized by preventing the problem of color synthesis. 2. The two-layer holographic color filter according to claim 1, wherein the first hologram includes a plurality of transparent transmissive hologram pieces having a unit pixel size.   In the first hologram piece constituting the first hologram, one of red, green, and blue wavelengths is used as reference light, and a wavelength longer than the reference light is diffracted at a larger angle and shorter than the reference light. The two-layer holographic color filter according to claim 1, wherein the two-layer holographic color filter is manufactured by a CGH design scheme or a volume hologram recording scheme so as to diffract at a small angle.   The second hologram is incident at different angles after passing through the first hologram, and the red, green, and blue center wavelengths diffracted on the substrate are diffracted in the same direction as the light from the light source. The two-layer holographic color filter according to claim 1, wherein the two-layer holographic color filter is manufactured.   2. The two-layer type according to claim 1, wherein the second hologram adjacent to the liquid crystal display includes an array of a plurality of transmissive and transparent second hologram pieces having a unit pixel size. Holographic color filter.   6. The two-layer holographic color filter according to claim 5, wherein the second hologram piece is located on a coaxial line with the pixel of the liquid crystal display.   The first hologram piece is positioned on the same axis as the second hologram piece based on a diffraction angle at which the diffracted wavelength reaches the second hologram piece corresponding to the wavelength. The two-layer holographic color filter according to 2 or 5.   6. The two-layer holographic color filter according to claim 2, wherein the first and second hologram pieces correspond to an integral multiple of a unit pixel.   2. The two-layer holographic color filter according to claim 1, wherein both the first and second hologram pieces include a surface relief hologram.   2. The two-layer holographic color filter according to claim 1, wherein the first hologram piece includes a surface relief hologram, and the second hologram piece includes a volume hologram.   2. The two-layer holographic color filter according to claim 1, wherein the first hologram piece includes a volume hologram, and the second hologram piece includes a surface relief hologram.   2. The two-layer holographic color filter according to claim 1, wherein both the first and second hologram pieces include volume holograms.   A two-layer holographic color filter having a color filter and having the structure according to claim 1 is interposed between a light source and a color filter.   The first hologram piece is provided in the same arrangement shape as the arrangement shape of the color filter, and the first hologram piece has a reconstructed image having the same size as the RGB dye layer for all wavelengths of the first hologram piece. The liquid crystal display according to claim 1, wherein the liquid crystal display is designed as described above.   The first hologram piece is provided by shifting the width of one dye layer for each line in the same manner as the color filter provided in a mosaic shape, and the first hologram piece is the same as that of the first hologram piece. 14. The liquid crystal display according to claim 1, wherein the reconstructed image for all wavelengths is designed to have the same size as that of the RGB dye layer.   The first hologram piece is provided in the same manner as the color filter provided in a delta shape, and is shifted for each line by a half of the entire width of the first hologram piece. 14. The liquid crystal display according to claim 1, wherein the reconstructed image for all wavelengths of the hologram piece is designed to have the same size as the RGB dye layer.   2. A liquid crystal display comprising a color filter, wherein the two-layer holographic color filter having the structure according to claim 1 is formed adjacent to the color filter of the liquid crystal display.   2. A liquid crystal display characterized in that the two-layer holographic color filter having no color filter and having the structure according to claim 1 is interposed between a light source and a liquid crystal of the liquid crystal display.

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