JPH09133916A - Liquid crystal display device formed by using hologram color filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve color reproducibility and contrast and to expand the visual field angle at which displayed images are observable by providing the device with a means for approximately shutting off zero order transmitted light passing a hologram color filter without being diffracted by this filter and arranging a light diffusing means on the projection side of a liquid crystal display element. SOLUTION: A louver 14 is arranged between the hologram color filter 5 consisting of a microhologram array and the liquid crystal display element 20. This louver 14 is formed by arranging thin absorption layers 13 of a planar form in black color in parallel at specified intervals within a transparent plate 12. The light above a specified incident angle and below the specified incident angle is absorbed by these absorption layers 13 by falling thereon and is no longer transmitted therethrough. Then, the zero order transmitted light 9 which is the cause for stray light is completely shut off without shutting off the diffracted light dispersed in the wavelength. Further, the diffusion layer 15 is arranged on the exit side of the liquid crystal display element 20. The display light is diffused to wide diffusion angles by the diffusion layer 15 and, therefore, the liquid crystal display element 30 may be viewed from the wide visual field angle direction facing the element 20.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device using a hologram color filter, and more particularly to a field of view capable of observing a display image while removing 0th order transmitted light to improve color reproducibility and contrast. The present invention relates to a color liquid crystal liquid crystal display device using a direct-view hologram color filter with widened corners.

[0002]

2. Description of the Related Art As a color filter for a color liquid crystal display device, each wavelength component of a backlight can be incident on each liquid crystal cell without waste and absorption, as compared with a conventional wavelength absorption type filter. The present applicant has proposed a hologram color filter in Japanese Patent Application No. 5-12170 or the like to significantly improve the hologram color filter. There are two types of configurations, the first type is composed of an eccentric Fresnel zone plate-shaped micro-hologram array. The second type consists of a hologram or diffraction grating composed of parallel and uniform interference fringes and a microlens array superimposed thereon. Hereinafter, these hologram color filters will be briefly described.

A liquid crystal display device using a hologram color filter of the first type will be described with reference to the sectional view of FIG. In this figure, the liquid crystal cell 6 'is regularly arranged.
Backlight 3 of liquid crystal display element 6 divided into (pixels)
A hologram array 5 constituting the hologram color filter is arranged at a distance from the incident side. On the back surface of the liquid crystal display element 6, a black matrix 4 provided between the liquid crystal cells 6 'is arranged. In addition to the above, polarizing plates (not shown) are arranged on both sides of the liquid crystal display element 6. An absorption type color filter that transmits light of colors corresponding to the R, G and B color separation pixels is additionally arranged between the black matrixes 4 as in the conventional color liquid crystal display device. You may do it.

The hologram array 5 has a repetition period of R, G, and B color separation pixels, that is, a set of three liquid crystal cells 6 ′ adjacent to each other in the direction of the liquid crystal display element 6 in the plane of the paper. The micro holograms 5 'are arranged in an array at the same pitch as the repetition pitch. The micro holograms 5' are aligned with each set of three liquid crystal cells 6 'adjacent to each other in the direction of the plane of the liquid crystal display element 6, and each hologram 5' Each of the micro holograms 5 ′ corresponds to the light of the green component in the backlight 3 that enters at an angle θ with respect to the normal to the hologram array 5 and corresponds to the micro hologram 5 ′. It is formed in a Fresnel zone plate shape so that light is condensed on the liquid crystal cell G at the center of the three color separation pixels R, G, and B. The micro hologram 5 ′ has a relief type, which has no or little wavelength dependence of the diffraction efficiency.
It consists of transmission holograms such as phase type and amplitude type. Here, the term "diffraction efficiency has no or little wavelength dependency" does not mean that it is a type that diffracts only a specific wavelength and hardly diffracts other wavelengths like a Lippmann hologram. Is also diffracted, and the diffraction grating whose diffraction efficiency has little wavelength dependence diffracts at different diffraction angles depending on the wavelength.

With such a configuration, when the white backlight 3 which is incident at an angle θ with respect to the normal line from the surface of the hologram array 5 on the side opposite to the liquid crystal display element 6 is incident, the wavelength is changed to the wavelength. The diffraction angles of the minute holograms 5'are different depending on each other, and the focal positions for each wavelength are dispersed in a direction substantially parallel to the surface of the hologram array 5. Among them, the red wavelength component is located at the position of the liquid crystal cell R displaying red, the green component is located at the position of the liquid crystal cell G displaying green, and the blue component is located at the position of the liquid crystal cell B displaying blue. By arranging the hologram array 5 so as to diffract and collect light, each color component passes through each liquid crystal cell 6 ′ with almost no attenuation in the black matrix 4 and the liquid crystal cell 6 ′ at the corresponding position. Color display can be performed according to the state.

As described above, by using the hologram array 5 as a color filter, each wavelength component of the conventional color filter backlight can be made incident to each liquid crystal cell 6'without being absorbed, and its utilization efficiency is improved. Can be significantly improved.

A liquid crystal display device using a hologram color filter of the second type will be described with reference to the sectional view of FIG. In the figure, a hologram color filter 10 of the second type comprises a hologram 7 and a condensing microlens array 8, and microlenses 8 'constituting the microlens array 8 are R, G, B color separation. The pixels are arranged in an array at the same pitch as the repetition cycle of the pixels, that is, each set of three liquid crystal cells 6 ′ adjacent to each other in the direction of the paper surface of the liquid crystal display element 6. The hologram 7 is composed of parallel and uniform interference fringes acting as a diffraction grating, and is formed of a transmission hologram such as a relief type, a phase type, and an amplitude type having little or no wavelength dependence of diffraction efficiency. On the back surface of the liquid crystal display element 6, a black matrix 4 provided between the liquid crystal cells 6 'is arranged. In addition to the above, polarizing plates (not shown) are arranged on both sides of the liquid crystal display element 6. An absorption type color filter that transmits light of colors corresponding to the R, G and B color separation pixels is additionally arranged between the black matrixes 4 as in the conventional color liquid crystal display device. You may do it.

With such a configuration, the hologram 7
When the backlight 3 is incident on the surface opposite to the liquid crystal display element 6 at an angle θ with respect to the normal line, the light is diffracted at different angles depending on the wavelength and dispersed on the exit side of the hologram 7. . Due to the microlenses 8 ′ arranged on the entrance side or the exit side of the hologram 7, this dispersed light
The light is separated and focused on the focal plane for each wavelength. Among them,
The red wavelength component is diffracted and condensed at the position of the liquid crystal cell R for displaying red, the green component is diffracted and condensed at the position of the liquid crystal cell G for displaying green, and the blue component is condensed at the position of the liquid crystal cell B for displaying blue. As described above, by arranging the color filter 10, each color component passes through each liquid crystal cell 6 'with little attenuation by the black matrix 4, and corresponds to the state of the liquid crystal cell 6' at the corresponding position. Color display can be performed.

In such an arrangement, as the hologram 7, a transmission hologram having uniform interference fringes and having a small wavelength dependency of diffraction efficiency, which is not a light-collecting property, can be used. And the pitch of the microlens array 8 is different from that of each liquid crystal cell 6 '.
It is three times as large as the conventional case where one microlens is arranged corresponding to each, and is characterized in that it is easy to manufacture and easy to align.

[0010]

By the way, there is a considerable component (zero-order diffracted light) that the backlight 3 transmits without being diffracted by the hologram color filters 5 and 10,
This becomes stray light, which is a major cause of color reproducibility and contrast deterioration of the color liquid crystal display device.

When the liquid crystal display device having the structure as shown in FIGS. 3 and 4 is used in a direct view type, each color component is once condensed in the opening of the black matrix 4 and then converted into a divergent light to display a liquid crystal display. The light is emitted from the liquid crystal display element 6 after being modulated by each color separation pixel of the element 6, but its divergence angle is narrow, and the viewing angle at which the image displayed on the liquid crystal display element 6 can be observed is relatively narrow.

The present invention has been made in view of such problems of the prior art, and an object thereof is to eliminate 0th-order transmitted light to improve color reproducibility and contrast and to observe a displayed image. It is an object of the present invention to provide a direct-view type color liquid crystal display device using a hologram color filter having a wide viewing angle.

[0013]

A liquid crystal display device using a hologram color filter of the present invention that achieves the above-mentioned object is provided with at least a liquid crystal display element and an illumination light incident side thereof, and is provided with an element condensing hologram. A hologram color filter consisting of an array, in which each element condensing hologram disperses white light incident at a predetermined angle with respect to the normal line of the hologram recording surface by wavelength dispersion in a direction substantially along the hologram recording surface. , Or a hologram or diffraction grating consisting of parallel and uniform interference fringes and an array of element condensing lenses arranged on the incident side or the exit side thereof,
The hologram or diffraction grating consisting of parallel and uniform interference fringes and the complex of the element condensing lens respectively emit white light incident at a predetermined angle with respect to the normal to the recording surface of the hologram or diffraction grating. In a liquid crystal display device comprising a hologram color filter that disperses wavelengths in a direction substantially along a recording surface of a hologram or a diffraction grating and disperses the light, a 0th order transmission that substantially blocks 0th order transmitted light that passes without being diffracted by the hologram color filter. The light blocking means is arranged between the hologram color filter and the liquid crystal display element or on the exit side of the liquid crystal display element, and the light diffusing means is arranged on the exit side of the liquid crystal display element. is there.

In this case, as the 0th order transmitted light blocking means,
It is realistic to use a louver.

A liquid crystal display device using another hologram color filter of the present invention comprises at least a liquid crystal display element and an array of element condensing holograms provided on the illumination light incident side thereof, and each element collection thereof. The optical hologram
A hologram color filter for wavelength-dispersing white light incident at a predetermined angle with respect to the normal line of the hologram recording surface in a direction substantially along the hologram recording surface, or a hologram composed of parallel and uniform interference fringes. Alternatively, a hologram or diffraction grating and an element condensing lens composite consisting of parallel and uniform interference fringes each consisting of a diffraction grating and an array of element condensing lenses arranged on the incident side or the exit side thereof are A liquid crystal composed of a hologram color filter for wavelength-dispersing white light incident at a predetermined angle with respect to the normal line of the recording surface of the hologram or diffraction grating in a direction substantially along the recording surface of the hologram or diffraction grating. In the display device, a lenticular lens screen is provided on the exit side of the liquid crystal display element, and the lenticular lens surface is provided on the liquid crystal display element. And a light-shielding portion is provided between the transmission apertures in the vicinity of the observer-side light-collecting portion by each cylindrical lens surface of the lenticular lens screen. is there.

In this case, it is desirable that the pitch of the lenticular lens surface of the lenticular lens screen is substantially the same as the pitch of the element converging hologram or the element condensing lens. Further, it is desirable that the transmission aperture of the lenticular lens screen has a scattering property.

In the present invention, a 0th-order transmitted light blocking means for substantially blocking 0th-order transmitted light that passes without being diffracted by the hologram color filter is provided between the hologram color filter and the liquid crystal display element or at the exit side of the liquid crystal display element. Or the light diffusing means is arranged on the exit side of the liquid crystal display element, or the lenticular lens screen is arranged on the exit side of the liquid crystal display element with its lenticular lens surface facing the liquid crystal display element side. Since a transmissive opening is provided in the vicinity of the condensing part on the observer side by each cylindrical lens surface of the screen and a light shielding part is provided between the transmissive openings, in a color liquid crystal display device using a hologram color filter, Color reproduction by removing transmitted light,
It is possible to improve the contrast and widen the viewing angle at which the display image can be observed.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a liquid crystal display using a hologram color filter according to the present invention will be described below. A first embodiment of the color liquid crystal display device according to the present invention will be described with reference to FIG. The hologram color filter 5 used in this figure is the hologram color filter 5 consisting of the minute hologram array of FIG. 3, but the hologram or diffraction grating consisting of parallel and uniform interference fringes of FIG. 4 and the microlens superposed on it. It will be apparent from the following description that the hologram color filter 10 made of an array can be similarly applied. In addition,
The same applies to the other examples.

In the sectional view of FIG. 1, a liquid crystal display element 20 is provided.
Is composed of, for example, a liquid crystal layer 24 such as twisted nematic sandwiched between two glass substrates 21 and 22, and a uniform transparent counter electrode (not shown) is provided on the inner surface of one of the glass substrates 22. On the inner surface of the other glass substrate 21, transparent display electrodes (not shown) are provided independently for each of the liquid crystal cells R, G, B, and between the transparent display electrodes, the liquid crystal cell R,
A black matrix 23 is arranged which separates G and B and prevents stray light from entering an adjacent liquid crystal cell. Therefore, by controlling the voltage applied between the transparent display electrodes for each cell to change the transmissive state, the display color of the pixel composed of a set of liquid crystal cells R, G, B can be controlled. It is possible to display in color. Glass substrate 21 on hologram color filter 5 side
A polarizing plate 25 is attached to the outer surface, and a polarizing plate 26 is attached to the outer surface of the glass substrate 22 on the observation side. For example, their transmission axes are arranged so as to be orthogonal to each other. Then, one of the color filters 5 (10) described with reference to FIGS. 3 and 4 is disposed on the incident side of the liquid crystal display element 20.

According to the present invention, the louver 14 is arranged between the color filter 5 and the liquid crystal display element 20. The louver 14 is formed by arranging a thin black planar absorption layer 13 in parallel in the transparent plate 12 at a constant interval, and light having a certain incident angle or more and a certain incident angle or less strikes the absorbing layer 13 and is transmitted. I can't do it,
Depending on the thickness of the transparent plate 12, the distance between the absorption layers 13 and the angle formed by the absorption layer 13 with respect to the plane of the transparent plate 12, only light having an incident angle within a predetermined range, for example, 24 ° ± 6 ° is transmitted.
Therefore, the incident angle θ of the backlight 3 is, for example, 40 °.
In the case of the hologram color filter 5 set to
This louver 14 can completely block the 0th-order transmitted light 9 that causes stray light without blocking the wavelength-dispersed diffracted light. The louver 14 may be arranged on the exit side (observer side) of the liquid crystal display element 20.

Further, in accordance with the present invention, the liquid crystal display element 20
The diffusion layer 15 is disposed on the exit side of the. Diffusion layer 15
As the layer, a layer obtained by diffusing fine particles having different refractive indexes in a transparent medium is used, but a diffusion plate such as frosted glass may be used instead.

With such an arrangement, the white backlight 3 is split into each color component by each minute hologram 5 ', and the non-split 0th-order transmitted light 9 strikes the absorption layer 13 of the louver 14 and is completely blocked, and the liquid crystal display is displayed. It does not reach the element 20. Each of the separated color components passes through the polarizing plate 25 to be linearly polarized light, in which the red component goes to the position of the liquid crystal cell R, the green component goes to the position of the liquid crystal cell G, and the blue component goes to the liquid crystal cell B.
Respectively, the respective color components are incident on the corresponding liquid crystal cells R, G, B, the polarization plane is rotated and passed according to the transmission state, and the state is changed by the other polarizing plate 26. It manifests as intensity-modulated light and reaches the eyes of the observer. A set of three liquid crystal cells R, G, and B is set as one pixel, and is displayed as a pixel of a different color depending on the ratio of the passing wavelength component therein. Since the display light is diffused by the diffusion plate 15 over a wide viewing angle, it can be viewed from a wide viewing angle direction facing the liquid crystal display element 20.

As described above, in this embodiment, the louver 14 can completely block the 0th-order transmitted light 9 and the diffuser plate 15 converts the modulated light emitted from the liquid crystal display element 6 having a narrow divergence angle into diffused light. Since the conversion is performed, the 0th-order transmitted light can be removed to improve the color reproducibility and the contrast, and the viewing angle at which the display image can be observed can be widened.

A second embodiment of the color liquid crystal display device according to the present invention will be described with reference to FIG. The difference from the embodiment of FIG. 1 is that, instead of using the louver 14 and the diffusion plate 15, a lenticular lens screen 19 is arranged on the exit side of the liquid crystal display element 20. The lenticular lens screen 19 is known as a transmissive screen and is composed of a transparent plate-like body having a refractive index of greater than 1, and has a pitch on the liquid crystal display element 20 side which is the same as the pitch of the minute hologram 5 '. , G, and B have the same lenticular lens surface as the repeating period of the color-separating pixels, that is, a cylindrical lens surface array 16, and a transmission aperture 17 is provided on the observer side near the condensing portion of the cylindrical lens surfaces. The surface between the transmission openings 17 is a black absorptive light-shielding portion 18 like the black matrix 23.
Then, each cylindrical lens surface of the lenticular lens surface 16 is aligned with each group of R, G, and B color separation pixels.

With such an arrangement, the white backlight 3 is not split by each minute hologram 5 '.
It is divided into the next transmitted light 9 and the respective color components dispersed therein, and the 0th-order transmitted light 9 which is not dispersed goes straight, the respective dispersed color components pass through the polarizing plate 25 to be linearly polarized light, and the red component therein is the liquid crystal. To the position of cell R, the green component to the position of liquid crystal cell G,
The blue component is condensed at the position of the liquid crystal cell B, and the respective color components are incident on the corresponding liquid crystal cells R, G, B, and the polarization plane is rotated and passed according to the transmission state thereof, and the other polarization The plate 26 reveals the state as intensity-modulated light and reaches the lenticular lens screen 19. By each cylindrical lens surface of the lenticular lens surface 16, each color component is re-focused on the transmission aperture 17, passes through the lenticular lens screen 19, and reaches the eyes of the observer. The emission surface of the transmission opening 17 is a diffusion surface, and a display image transmitted through the transmission opening 17 can be seen from a wide viewing angle direction facing the liquid crystal display element 20. On the other hand, the 0th-order transmitted light 9 that has proceeded straight is condensed on the light shielding portion 18, and thus is completely blocked.

As described above, in this embodiment, the 0th-order transmitted light 9 can be completely blocked by the light absorbing portion 18 of the lenticular lens screen 19, and the divergence angle expanding action by each cylindrical lens surface of the lenticular lens surface 16 can be achieved. Since the modulated light emitted from the liquid crystal display element 6 is converted into diffused light having a wide diffusion angle by the diffusing action of the diffusing surface of the transparent opening 17, the 0th-order transmitted light is removed to improve color reproducibility and contrast. It is possible to increase the viewing angle at which the display image can be observed. In this embodiment, instead of the exit surface of the transmission opening 17 being a diffusion surface, a diffusion layer or a diffusion plate may be separately provided as in the first embodiment.

The liquid crystal display device using the hologram color filter of the present invention has been described above based on some embodiments, but the present invention is not limited to these embodiments and various modifications can be made. It should be noted that the holograms 5 and 7 of the hologram color filter are not limited to those composed of a single layer or a single hologram, but Japanese Patent Application No. 7-2908.
No. 19, No. 7-290820, two or more layers or two layers in which the spatial wavelength distributions of wavelength dispersion are substantially the same and the peak wavelengths of diffraction efficiency are different from each other. The hologram may be composed of the above-mentioned superposed or multiple-recorded holograms.

[0028]

As is apparent from the above description, according to the liquid crystal display device using the hologram color filter of the present invention, the 0th-order transmitted light that substantially blocks the 0th-order transmitted light that passes without being diffracted by the hologram color filter. Between the hologram color filter and the liquid crystal display element, or arranged on the exit side of the liquid crystal display element, the blocking means, and arrange the light diffusing means on the exit side of the liquid crystal display element, or on the exit side of the liquid crystal display element, The lenticular lens screen is arranged with its lenticular lens surface facing the liquid crystal display element side, and a transmission aperture is provided in the vicinity of the converging portion on the observer side by each cylindrical lens surface of the lenticular lens screen, and a light blocking portion is provided between the transmission apertures. Therefore, in the color liquid crystal display device using the hologram color filter,
It is possible to improve the color reproducibility and the contrast by removing the 0th order transmitted light, and it is possible to widen the viewing angle at which the display image can be observed.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view for explaining the configuration and operation of a liquid crystal display device using a hologram color filter according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view for explaining the structure and operation of a liquid crystal display device using a hologram color filter according to a second embodiment of the present invention.

FIG. 3 is a cross-sectional view of a conventional liquid crystal display device using a first type of hologram color filter.

FIG. 4 is a cross-sectional view of a conventional liquid crystal display device using a second type of hologram color filter.

[Explanation of symbols]

 3 ... Backlight 5 ... Hologram color filter 5 '... Micro hologram 6 ... Liquid crystal display element 7 ... Hologram 8 ... Condensing microlens array 8' ... Microlens 9 ... Zero-order transmitted light 10 ... Hologram color filter 11 ... Transparent substrate 12 ... Transparent plate 13 ... Absorption layer 14 ... Louver 15 ... Diffusion layer 16 ... Lenticular lens surface 17 ... Transmissive opening 18 ... Shading part 19 ... Lenticular lens screen 20 ... Liquid crystal display element 21, 22 ... Glass substrate 23 ... Black matrix 24 ... Liquid crystal layer 25, 26 ... Polarizing plate

Claims (5)

[Claims] 1. A liquid crystal display element, and an array of element light converging holograms provided on the illumination light incident side thereof, each element light converging hologram having a predetermined distance from a normal line of a hologram recording surface. , A hologram color filter that disperses wavelengths of white light incident at an angle of approximately in the direction along the hologram recording surface, or a hologram or diffraction grating consisting of parallel and uniform interference fringes and its entrance side or exit side. And a composite of a hologram or diffraction grating and an element condensing lens, each of which is composed of an array of element condensing lenses arranged in parallel with each other, and is composed of parallel and uniform interference fringes, and A hologram color filter for wavelength-dispersing white light incident at a predetermined angle with respect to a line in a direction substantially along a recording surface of a hologram or a diffraction grating, and In the liquid crystal display device, a 0th-order transmitted light blocking unit that substantially blocks 0th-order transmitted light that passes without being diffracted by the hologram color filter is provided between the hologram color filter and the liquid crystal display element.
Alternatively, a liquid crystal display device using a hologram color filter, characterized in that the liquid crystal display device is arranged on the emission side and the light diffusion means is arranged on the emission side of the liquid crystal display device. 2. The liquid crystal display device using a hologram color filter according to claim 1, wherein said zero-order transmitted light blocking means comprises a louver. 3. An LCD comprising at least a liquid crystal display element and an array of element light converging holograms provided on the illumination light incident side, each element light converging hologram being predetermined with respect to a normal line of a hologram recording surface. , A hologram color filter that disperses wavelengths of white light incident at an angle of approximately in the direction along the hologram recording surface, or a hologram or diffraction grating consisting of parallel and uniform interference fringes and its entrance side or exit side. And a composite of a hologram or diffraction grating and an element condensing lens, each of which is composed of an array of element condensing lenses arranged in parallel with each other, and is composed of parallel and uniform interference fringes, and A hologram color filter for wavelength-dispersing white light incident at a predetermined angle with respect to a line in a direction substantially along a recording surface of a hologram or a diffraction grating, and In the liquid crystal display device consisting of, on the exit side of the liquid crystal display element, the lenticular lens screen is arranged with its lenticular lens surface facing the liquid crystal display element side, and the cylindrical lens surface of the lenticular lens screen on the viewer side. A liquid crystal display device using a hologram color filter, characterized in that a transmissive opening is provided in the vicinity of the condensing part, and a light shielding part is provided between the transmissive openings. 4. The hologram color filter according to claim 3, wherein the pitch of the lenticular lens surface of the lenticular lens screen is substantially the same as the pitch of the element converging hologram or the element condensing lens. Liquid crystal display device using. 5. The transmission opening of the lenticular lens screen has a scattering property.
Alternatively, a liquid crystal display device using the hologram color filter according to item 4.