JPH0922005A - Liquid crystal display device formed by using hologram color filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a device using hologram color filters which do not degrade color purity and have good color reproducibility even if line light sources of metal halide lamps, etc., are used. SOLUTION: This device has a liquid crystal display element and the hologram color filters which are disposed on the incident side of the illumination light 3 thereof, consists of an array of element holograms 5' and spectrally split incident white light 3 by causing the wavelength dispersion of the light in a direction (y) approximately along the hologram recording surfaces. In such a case, the light source of the illumination light has the line light source 15 and an optical system 16 for converting the luminous flux radiated from the line light source 15 to approximately parallel luminous fluxes within the plane orthogonal with the line light source 1 and is so arranged that the direction of the line of the line light source 15 faces the direction (x) approximately orthogonal with the wavelength dispersion and diffraction direction (y) by the hologram color filters.

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 in particular, a hologram color filter having a color purity and a color reproducibility which greatly improve the utilization efficiency of illumination light. The present invention relates to a liquid crystal display device.

[0002]

2. Description of the Related Art Conventionally, in a color liquid crystal display device using an absorption color filter using a pigment, a dye or the like,
The backlight is indispensable for display.
However, if white light is simply irradiated from behind the color liquid crystal display device, its utilization efficiency is very low. The main reasons are as follows.

[0003] The area occupied by the black matrix other than the cells of each color is large, and the light hitting it is wasted. Among white light incident on each pixel, R (red), G (green),
Since the color components passing through the B (blue) color filter are limited, other complementary color components are wasted. There is a loss due to absorption in the color filter.

In order to solve such a problem, as shown in FIG. 6, for example, a microlens array 2 is installed in front of the color filter 1, and a white light backlight 3 is provided in each of the color filter cells R, G, B. Conventionally, a method of increasing the utilization efficiency of the backlight 3 by collecting the light is known. In FIG. 6, reference numeral 4 indicates a black matrix provided between the color filter cells R, G and B.

[0005] However, even with this method, it is not possible to irradiate the white light 3 to each of the color filter cells R, G, B in a spectral manner, so that the above-mentioned problem cannot be solved.

Further, a liquid crystal projector in which the use efficiency of light is improved by using three dichroic mirrors and a microlens array without using such a color filter has been proposed in Japanese Patent Application Laid-Open No. Hei 4-60538. In this case, the above-mentioned absorption color filters using pigments, dyes and the like become unnecessary, and the above-mentioned problems (1) to (5) are solved, and the luminance of a color image is improved. However, since three dichroic mirrors are required, optical The system and equipment become large and bulky. In addition, there is a problem that the cost becomes high.

In view of such a situation, the present applicant has proposed in Japanese Patent Application No. 5-12170, etc. a color filter using a hologram and a color filter using the hologram in order to significantly improve the utilization efficiency of a liquid crystal display backlight or the like. We have proposed a liquid crystal display device using.

Further, a liquid crystal projection display device which changes the liquid crystal display device using such a hologram color filter to a projection type and displays a bright color image on a screen is proposed in Japanese Patent Application No. 5-242292. did.

[0009]

By the way, the hologram color filter as described above has an R
Although the colors G and B are developed, a parallel light flux is required as a backlight in order to improve the color purity. However, a liquid crystal display device using the above hologram color filter, in particular, in the case of a projection type, a discharge lamp such as a metal halide lamp having a strong light amount is used as a backlight light source, but this is not a point light source but a line light source. Therefore, even if an optical system such as a parabolic mirror or a condensing lens is used, this results in a backlight with low parallelism, which causes a decrease in color purity.

The present invention has been made in view of such problems of the prior art, and an object thereof is to prevent the deterioration of color purity even if a linear light source such as a metal halide lamp is used.
A liquid crystal display device using a hologram color filter having good color reproducibility.

[0011]

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 including 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 light source of the illumination light includes a line light source and a light beam emitted from the line light source. An optical system for converting into a light flux which is substantially parallel in a plane orthogonal to the linear light source, and the line direction of the linear light source is oriented substantially orthogonal to the wavelength dispersion diffraction direction by the hologram color filter. It is characterized by being arranged.

In this case, a metal halide lamp or the like can be used as the linear light source.

Further, this liquid crystal display device can also be constructed as a projection type device having a projection optical system for projecting a display image on a screen.

[0014]

In the present invention, the light source of the illumination light includes a linear light source and an optical system for converting the luminous flux emitted from the linear light source into a luminous flux substantially parallel to the plane orthogonal to the linear light source, and
Since the line direction of the line light source is arranged to be substantially orthogonal to the wavelength dispersion diffraction direction by the hologram color filter, the wavelength component of each color of the light diffracted by the hologram color filter displays the corresponding color. Since the light does not enter the liquid crystal cells other than the liquid crystal cells that operate, the color purity and color reproducibility of the display are improved, and the utilization efficiency of the illumination light can be significantly improved.

[0015]

EXAMPLES A liquid crystal display device using the hologram color filter of the present invention will be described below based on examples. First, a liquid crystal display device using a hologram color filter of the first type, which is the object of the present invention, will be described with reference to the sectional view of FIG. In the figure, a hologram array 5 constituting a color filter is arranged at a distance from the backlight 3 incident side of a liquid crystal display element 6 which is regularly divided into liquid crystal cells 6 '(pixels). 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 provided on the incident side of the hologram array 5 and the liquid crystal display element 6.
It is placed on the injection side of. In addition, between the black matrix 4 and R, as in the conventional color liquid crystal display device,
An absorptive color filter that transmits light of colors corresponding to the G and B color separation pixels may be additionally arranged.

The hologram array 5 corresponds to a repeating cycle of R, G, and B color-separating pixels, that is, a set of three liquid crystal cells 6'adjacent to each other in the in-plane direction of the liquid crystal display element 6. It is composed of minute holograms 5'arranged in an array at the same pitch as the repeating pitch, and the minute holograms 5'are aligned in groups of three liquid crystal cells 6'adjacent to each other in the direction of the paper surface of the liquid crystal display element 6 to form one group. The micro holograms 5'are arranged one by one, and each micro hologram 5'corresponds to the micro hologram 5'the light of the green component in the backlight 3 which is incident at an angle θ with respect to the normal line of the hologram array 5. It is formed in a Fresnel zone plate shape so as to collect light on the liquid crystal cell G at the center of the three color-dividing 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 fact that there is no or little wavelength dependence of the diffraction efficiency is not a type that diffracts only a specific wavelength and does not diffract other wavelengths like a Lippman hologram,
Means that one diffraction grating diffracts any wavelength,
The diffraction grating having a small wavelength dependence of the diffraction efficiency diffracts at different diffraction angles according to the wavelength.

With such a structure, 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. The diffraction angles of the minute holograms 5'are different depending on the wavelengths, and the focusing positions for each wavelength are dispersed in the direction 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. The angle of incidence θ of the backlight 3 on the hologram array 5 depends on the hologram recording conditions, hologram array 5
Of the hologram array 5, the distance between the hologram array 5 and the liquid crystal display element 6, and the like.

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.

Next, the liquid crystal display device using the second type hologram color filter, which is the object of the present invention, will be described with reference to the sectional view of FIG. In the figure, the second type hologram color filter 1
0 is composed of a hologram 7 and a condensing microlens array 8, and a microlens 8 ′ forming the microlens array 8 has a repeating period of R, G, and B color separation pixels,
That is, the three adjacent liquid crystal display elements 6 in the direction of the paper surface
Corresponding to each set of two liquid crystal cells 6 ', they are arranged in an array at the same pitch as the repeating pitch. Also,
The hologram 7 is formed of parallel and uniform interference fringes acting as a diffraction grating, and is a relief type, phase type, amplitude type, or other transmission type hologram having no or little 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, the polarizing plate not shown is the liquid crystal display element 6.
Placed on both sides of. Black Matrix 4
In between, as in the conventional color liquid crystal display device, R,
An absorptive color filter that transmits light of colors corresponding to the G and B color separation pixels may be additionally arranged.

Due to this structure, 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 type hologram having uniform diffraction fringes having a small wavelength dependence of diffraction efficiency can be used as the hologram 7, so that the hologram 7 is made to be a microlens array 8. No need to be aligned with each microlens 8 ', and the pitch of the microlens array 8 depends on each liquid crystal cell 6'.
This is three times as large as that in the conventional case of FIG. 6 in which one microlens is arranged corresponding to each, and is characterized in that it is easy to make and aligns easily.

Further, the liquid crystal display device using the hologram color filter having the structure shown in FIGS. 3 and 4 is used as it is as a direct-view type liquid crystal display device, or
It can be used as a liquid crystal projection display device by utilizing it as a spatial light modulator for projection display. FIG. 5 is a sectional view when the liquid crystal display device of FIG. 3 is configured as a liquid crystal projection display device (similarly in the case of FIG. 4), in which the first polarizing plate 12 is provided close to or integrally with the incident side of the hologram array 5. , The second polarizing plate 1 close to or integrally with the exit side of the liquid crystal display element 6.
3 are arranged. The color liquid crystal display device 11 includes, for example, a metal halide lamp 15 and a parabolic mirror 1.
The display image illuminated by the white parallel backlight 3 from the illumination device 14 including the combination of 6 and modulated by the color liquid crystal display device 11 passes through the field lens 17 disposed near the liquid crystal display device 11, It is enlarged by the projection lens 18 and is enlarged and imaged on the screen 19, so that a bright projected image can be obtained.

By the way, as described above, the backlight light source such as the metal halide lamp 15 is not a point light source but a line light source. This is shown in FIG. Assuming that the light source 15 is a linear light source arranged parallel to the X direction, when the light source 15 is arranged at the focal point of the optical system (convex lens or parabolic mirror) 16, the backlight 3 emitted from the optical system 16 is
Although the luminous flux is parallel in the Y direction of the drawing orthogonal to the linear light source 16, the luminous flux is not parallel in the X direction to which the linear light source 16 is directed, and is distributed within an angle range of ± Δ with respect to the optical axis. The parallel light flux is a non-parallel light flux including a scattered component that is deviated to some extent. Therefore, assuming that this X direction coincides with the wavelength dispersion direction of the diffracted light of the hologram filters 5 and 10 of FIGS. 3 and 4, that is, the direction within the plane of the paper of FIGS. 3 and 4, Since the backlight 3 is not a parallel light flux but contains a scattering component to some extent, the red wavelength component of the light diffracted by the hologram filters 5 and 10 is not always located at the position of the liquid crystal cell R displaying red. Does not enter, some components will enter the positions of the liquid crystal cell G that displays green and the position of the liquid crystal cell B that displays blue adjacent to each other beyond the black matrix 4. Similarly, with respect to the green and blue wavelength components of the light diffracted by the hologram filters 5 and 10, some components are incident on the position of the liquid crystal cell that displays another adjacent color. This causes deterioration of the color purity of the display.

On the other hand, as shown in FIG. 1, the X direction in which the linear light source 16 faces is represented by a minute hologram 5 '(hereinafter, one spectroscopic element of the hologram filters 5, 10 is represented by a minute hologram 5'. However, regarding the hologram filter 10, the hologram 7 and the microlens 8 '
The combination of 2 corresponds to the minute hologram 5 '. When the backlight 3 is arranged in parallel with the direction x orthogonal to the wavelength dispersion diffraction direction y), the backlight 3 is incident on the minute hologram 5'as parallel light at the incident angle θ in the y direction as described above. All the wavelength components of each color of the light diffracted by 5'are incident on the position of the liquid crystal cell displaying the corresponding color. Therefore, the color purity of the display does not decrease at least within this range. In this case, the backlight 3 is
Since the x-direction contains not a parallel light beam but a scattering component to some extent, the wavelength components of the respective colors of the light diffracted by the minute hologram 5'are not collected at one point but distributed in the x-direction and collected. It will be. However, since each aperture of the black matrix 4 is usually formed in a rectangular shape which is long in the x direction orthogonal to the chromatic dispersion diffraction direction y, the x of the focusing position is
Due to the directional distribution, some components do not enter the positions of the liquid crystal cells adjacent in the x direction. Further, when the liquid crystal cells R, G, B for displaying the respective colors are arranged in a row as shown in FIG.
Even if some components are incident on the positions of the liquid crystal cells adjacent to each other in the x direction, since the liquid crystal cells display the same color, the display color purity is not deteriorated.

Therefore, according to the present invention, in the direct-view type and projection type liquid crystal display devices using the hologram color filters 5 and 10 as shown in FIGS. As shown in FIG. 1, the hologram color filters 5 and 10 are arranged so as to face the direction x orthogonal to the wavelength dispersion diffraction direction y. With such an arrangement, the color purity and color reproducibility of display can be improved, and the utilization efficiency of illumination light can be significantly improved.

The liquid crystal display device using the hologram color filter of the present invention has been described above based on the embodiments, but the present invention is not limited to these embodiments and various modifications can be made.

[0027]

As is apparent from the above description, according to the liquid crystal display device using the hologram color filter of the present invention, the light source of the illumination light is the line light source and the light flux emitted from the line light source is the line light source. Since it is provided with an optical system for converting a light beam into a parallel light beam in a plane orthogonal to, and is arranged so that the direction of the line of the line light source is substantially orthogonal to the wavelength dispersion diffraction direction by the hologram color filter. , Because the wavelength components of each color of the light diffracted by the hologram color filter do not enter the liquid crystal cells other than the liquid crystal cell displaying the corresponding color, the display color purity and color reproducibility are improved, and The utilization efficiency of illumination light can be greatly improved.

[Brief description of drawings]

FIG. 1 is a perspective view for explaining the arrangement of light sources in the present invention.

FIG. 2 is a front view showing a slide type arrangement of liquid crystal cells displaying each color.

FIG. 3 is a cross-sectional view of a liquid crystal display device using a hologram color filter of a first type, which is a target of the present invention.

FIG. 4 is a cross-sectional view of a liquid crystal display device using a second type hologram color filter which is an object of the present invention.

5 is a sectional view of a liquid crystal projection display device using the liquid crystal display device of FIG.

FIG. 6 is a diagram for explaining a conventional illumination method for a liquid crystal display device.

[Explanation of symbols]

 3 ... Backlight 4 ... Black matrix 5 ... Hologram array (hologram color filter) 6 ... Liquid crystal display element 5 '... Micro hologram 6' ... Liquid crystal cell 7 ... Hologram 8 ... Light collecting microlens array 8 '... Microlens 10 ... Hologram color filter 11 ... Color liquid crystal display device 12 ... First polarizing plate 13 ... Second polarizing plate 14 ... Illumination device 15 ... Metal halide lamp (line light source) 16 ... Parabolic mirror 17 ... Field lens 18 ... Projection lens 19 ... Screen

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification number Agency reference number FI Technical display location G03B 21/00 G03B 21/00 D

Claims (3)

[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 a liquid crystal display device comprising: a light source of the illumination light, a line light source, and an optical system for converting a light beam emitted from the line light source into a substantially parallel light beam in a plane orthogonal to the line light source, A liquid crystal display device using a hologram color filter, wherein the line of the line light source is arranged so as to face a direction substantially orthogonal to the wavelength dispersion diffraction direction of the hologram color filter. 2. A liquid crystal display device using a hologram color filter according to claim 1, wherein the linear light source is a metal halide lamp. 3. A liquid crystal display device using a hologram color filter according to claim 1, further comprising a projection optical system for projecting a display image on a screen.