JPH08334752A - Color liquid crystal display device formed by using hologram - Google Patents

Abstract

PURPOSE: To provide a color liquid crystal display device which is formed by using holograms and with which the color light components are made incident on respectively corresponding color filters of three primary colors and the remarkable improvement in the utilization efficiency of back light and the improvement in the brightness and contrast of pixel display are made possible by using a holographic mirror cell array of a volume phase type and reflection means having the apertures corresponding to pixels. CONSTITUTION: This color liquid crystal display device is provided with a hologram plate 4 formed with the holographic mirror cell array between the back light unit 2 and a liquid crystal display panel 5 provided with the color filters 6, and is further interposed with the reflection means 3 having the apertures and the reflection surface parts between the hologram plate 4 and the back light unit 2. Of the white light 19 from the back light unit 2, the light of only the colors respectively corresponding to the pixels on the liquid crystal display panel 5 side is made incident by the wavelength selective transmission and reflection of the reflection means 3 and the holographic mirror cell 15a, etc. All of the white light 19 are made incident on the liquid crystal display 5 side by repeating the wavelength selective transmission and reflection.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color liquid crystal display device, and more particularly to a color liquid crystal display device using a hologram for improving the utilization efficiency of a backlight.

[0002]

2. Description of the Related Art Conventionally, a backlight source for back lighting is used as a light source of a color liquid crystal display device using a color filter. The backlight is, for example, white light, but the utilization efficiency of the light quantity is very poor only by irradiating the white light from the back of the color liquid crystal display device. The reason is that, in addition to the colored cells divided into three colors, the black matrix that individually divides the color filter occupies a considerably large area in the color filter, and the light irradiated to this black matrix portion becomes the amount of lost light. Is. Also,
This is because, of the white light incident on the liquid crystal cell corresponding to each pixel, wavelength components other than the hue that passes through the colored cell are absorbed by the colored cell. In order to solve the above problems, for example, a method is adopted in which a microlens array is provided between a backlight and a liquid crystal cell, and light from the backlight is condensed on each colored cell of a color filter. However, this method can reduce the light loss due to the black matrix, but cannot remove the absorption loss of the light component having a complementary color relationship with the hue passing through the colored cell. Therefore, a hologram is conventionally interposed between the backlight and the color filter, and white light from the backlight is spectrally incident on each colored cell of the color filter by utilizing the function of the hologram as a spectral element. Things are adopted. As this known technique, for example, JP-A-6-222361 and JP-A-6-2819 are known.
There is one disclosed in Japanese Patent No. 32.

The "liquid crystal display device using hologram" disclosed in Japanese Patent Laid-Open No. 6-222361 discloses three primary colors R,
A hologram having no or little wavelength dependence of diffraction efficiency is provided between a color filter in which G and B colored cells are periodically arranged and a backlight, and light dispersed by the hologram is converted into its wavelength component. In this case, the light is made incident on the colored cell having the hue corresponding to. Further, in "Liquid crystal display device using hologram" of Japanese Patent Laid-Open No. 6-281932, a liquid crystal display device using a hologram is provided between a color filter and a backlight.
One or more holograms having a diffraction wavelength selectivity with respect to a specific wavelength are provided, and light of a specific wavelength component diffracted by the hologram is made incident on a coloring cell of a hue corresponding to the hologram and is subjected to diffraction. The configuration is such that the light of the remaining non-complementary hue is incident on the corresponding colored cell.

[0004]

[Problems to be Solved by the Invention] The former JP-A-6-22
In the liquid crystal display device of Japanese Patent No. 2361, since the hologram does not have wavelength selectivity, only the diffracted light on one side of (+) or (−) of the ± first-order diffracted light diffracted from the hologram becomes the hue of the diffracted light. It is only incident on the corresponding colored cell. That is, even if the (+) first-order diffracted light is incident on the R colored cell, for example, the colored cell of the color filter on which the (-) first-order diffracted light that is conjugate with the (+) first ordered diffracted light is different from the R colored cell. Is. As described above, there is a problem that the utilization efficiency of the light amount of the backlight does not improve so much. Further, in the latter case of the liquid crystal display device described in JP-A-6-281932, the hologram has wavelength selectivity, but in order to make diffracted light of that hue incident on the target colored cell. A high degree of positioning accuracy is required, and because there is a limit to the diffraction angle in hologram spectroscopy, a certain amount of space is required between the hologram and the liquid crystal cell or colored cell, which increases the size of the device in the thickness direction, resulting in a large device. There is a problem to be realized. In addition, since the light diffracted and reflected by the hologram cannot be effectively used, a light amount loss occurs.

The present invention solves the above-mentioned problems. All the light emitted from the backlight is made incident on the color filter side, and the utilization efficiency of light from the light source is greatly improved and the Further, it is an object of the present invention to provide a color liquid crystal display device using a hologram capable of displaying a color with high contrast and saving power consumption.

[0006]

In order to achieve the above object, the present invention is directed to a liquid crystal display panel having liquid crystal cells arranged in a matrix and divided into three primary colors corresponding to the individual liquid crystal cells. A color liquid crystal display device comprising: a color filter having a colored cell; a backlight unit for injecting white light into the liquid crystal display panel; and a hologram plate interposed between the backlight unit and the color filter. The hologram plate has volume phase type holographic mirror cells arranged corresponding to the individual colored cells, and the holographic mirror cells disperse white light incident from the backlight unit. Then, the necessary wavelength component that matches the hue of the corresponding colored cell is selectively transmitted and guided to the colored cell side, and the corresponding Serial and an unnecessary wavelength components that do not match the hue of the colored cells diffracted reflected constitute a color liquid crystal display device using a hologram returned to the backlight unit side. More specifically, a reflecting means is provided between the hologram plate and the backlight unit, and the reflecting means has openings corresponding to the central portion and the peripheral portion of each holographic mirror cell. It is characterized by having a reflective surface portion. Further, the reflecting means is formed on the back surface side of the hologram plate so as to face the backlight unit.
Alternatively, the reflecting means is formed on the front surface side of the backlight unit facing the hologram plate. Furthermore, the holographic mirror cell is
It has at least two types of volume phase interference fringes formed by multiple exposure, and at least two unnecessary wavelength components having a complementary color relationship with the hue of the corresponding colored cell are diffracted and reflected in a wavelength selective manner. It is a feature.

[0007]

The white light from the backlight is irradiated onto the hologram plate composed of the multiple-exposure volume phase type holographic mirror cell to be dispersed. The holographic mirror cell selectively transmits only the necessary wavelength component of the dispersed light that matches the hue of the colored cell corresponding to the holographic mirror cell and introduces it into the colored cell side. Unwanted wavelength components that do not match are diffracted and reflected back to the backlight side. However, the returned light is again made incident on the hologram plate side together with the white light from the backlight, and is made incident on the colored cell side of the corresponding hue via another holographic mirror cell that matches the wavelength. As described above, almost all of the white light from the backlight enters the color filter and can be effectively used. By providing a reflecting means having an opening at a position facing the holographic mirror cell between the hologram plate and the backlight unit, white light can be introduced into the hologram mirror cell without waste and reflection. The returning light is positively diffused in the horizontal direction, and the desired re-incident of white light is efficiently performed.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an enlarged cross-sectional view for explaining light transmission and reflection states in the color liquid crystal display device of this embodiment, FIG. 2 is a cross-sectional view showing the overall structure of this embodiment, and FIG. 3 is a hologram plate of this embodiment. FIG. 4 is an enlarged partial cross-sectional view for explaining the method, and FIG. 4 is a plan view of a patterned reflecting member used when manufacturing the hologram plate.

As shown in FIG. 2, the color liquid crystal display device 1 of this embodiment is roughly classified into a backlight unit 2, a reflecting means 3, a hologram plate 4, a liquid crystal display panel 5, and
It is composed of a laminated structure in which the color filters 6 and the like are stacked.

The backlight unit 2 comprises a white light source 7 such as a fluorescent lamp, a reflection surface 8 formed around the white light source 7, a diffuse reflection surface 9 and a diffusion surface 10. With the above structure, the diffused white light is emitted from the backlight unit 2 to the liquid crystal display panel 5.

The reflecting means 3 has an opening 11 and a reflecting surface portion 12.
Are formed alternately. In addition, in these, the opening 11 is formed corresponding to the central portion of the holographic mirror cell 15 which will be described later, and the reflecting surface portion 12 is formed in the portion corresponding to the peripheral portion of the holographic mirror cell 15. That is, the openings 11 are formed in the same number as the holographic mirror cells 15. The reflecting means 3 is provided between the hologram plate 4 and the backlight unit 2,
The film is formed on either the back surface side of the hologram plate or the front surface side of the backlight unit 2.

The hologram plate 4 is composed of a substrate 13 and a holographic mirror cell array 14 formed on the substrate 13, and the holographic mirror cell array 14 is composed of an assembly of holographic mirror cells 15 divided into pixel units. The holographic mirror cell 15 is
It has at least two types of volume phase type interference fringes formed by multiple exposure, and has three primary colors R (red) and G
Of the (green) and B (blue) hues, the necessary wavelength component is selectively transmitted, and other unnecessary wavelength components having a complementary color relationship with the transmitted hue are diffracted and reflected. That is, the holographic mirror cell 15a for R color (see FIG. 1) is formed so as to transmit only the R wavelength component, and diffractively reflect the G and B wavelength components having a complementary color relationship with the R wavelength component. The holographic mirror cell 15a for G, the holographic mirror cell 15b for G color, and the holographic mirror cell 15c for B color, which are adjacent to the holographic mirror cell 15a, transmit only the G wavelength component and the B wavelength component, respectively. Are formed so as to diffract and reflect the wavelength components of R and B and R and G that have a complementary color relationship with.

The liquid crystal display panel 5 is a liquid crystal cell 16 of three primary colors.
Are arranged in a matrix as pixels. The liquid crystal display panel 5 comprises a pair of glass substrates and a liquid crystal sandwiched therebetween as an electro-optical substance. There is an active matrix set in which a pixel electrode and a switching element are formed on one glass substrate, and a counter electrode is formed on the other substrate. Alternatively, it may be a simple matrix type in which row electrodes and column electrodes are formed on both substrates.

The color filter 6 is formed so as to overlap with the liquid crystal display panel 5, and a color cell 17 corresponding to a position facing the liquid crystal cell 16 is arranged. A black matrix 18 for pixel separation is formed between adjacent liquid crystal cells 16 and colored cells 17. For convenience of description, the liquid crystal cells 16 and the colored cells 17 corresponding to R, G, and B are referred to as liquid crystal cells 16a, 16b, and 16c and colored cells 17a, 17b, and 17c.

Next, the operation of the liquid crystal display device according to this embodiment will be described with reference to FIG. The white light 19 emitted from the backlight unit 2 is divided into reflected light 20 (shown by a chain double-dashed line) that is reflected by the reflection surface portion 12 of the reflection means 3 and transmitted light that is transmitted through the opening 11. The transmitted light is red light 21 (hereinafter referred to as R light 21) indicated by a dotted line, green light 22 (hereinafter referred to as G light) indicated by a chain line, and blue light 23 (hereinafter referred to as B light 23) indicated by a solid line. Is included. R light 2
The 1, G light 22 and B light 23 are incident on the hologram plate 4. R light 21 and G light 2 incident on the holographic mirror cell 15a to which the red color of the hologram plate 4 is assigned
2, the B light 23 transmits only the R light 21, and the other G light 22 and B light 23 are diffracted and reflected to become diffracted and reflected lights 22a and 23a. Similarly, a holographic mirror cell 1 for green
R light 21, G light 22, and B light 23 incident on 5b are G light 2
Only R 2 is transmitted, and the other R light 21 and B light 23 are diffracted and reflected to become diffracted reflected lights 21a and 23a. In addition, the R light 21 incident on the blue holographic mirror cell 15c,
The G light 22 and the B light 23 are transmitted only by the B light 23 and the other R light 2
1, G light 22 is diffracted and reflected to diffracted and reflected lights 21a and 22a.
Becomes R light 21 and G light 2 transmitted through the hologram plate 4
2, B light 23 is holographic mirror cell 15a, 1
5b and 15c are incident on liquid crystal cells 16a, 16b and 16c, which are arranged in correspondence with each other, where the intensity of each pixel is modulated, and then, the colored cells 17a, 17b and 1c, respectively.
7c is transmitted. From the above, the colored cells 17a, 17b,
An extremely bright and high-contrast image display in which only light of the corresponding hue is incident on 17c is performed.

On the other hand, the reflected light 20 reflected by the reflecting means 3 and the diffracted reflected lights 21a, 22 reflected by the hologram plate 4
a and 23a return to the backlight unit 2 and are reflected and scattered by the reflection surface 8, the irregular reflection surface 9 and the diffusion surface 10 which constitute the backlight unit 2, and again enter the hologram plate 4 side via the reflection means 3. The above-described reflection and transmission are repeated, and each dye component passes through the holographic mirror cell 15 and the liquid crystal cell 16 matching the hue thereof and enters the coloring cell 17 for display. As described above, all the white light 19 emitted from the backlight unit 2
By irradiating the pixels of the liquid crystal display panel 5 corresponding to the wavelength selective, the light amount loss is greatly reduced.

Next, a method of manufacturing the hologram plate 4 used in the present invention will be described with reference to FIGS. The hologram plate 4 is a holographic mirror cell 15a, 1 to which the three primary colors R, G, B are assigned in a matrix.
5b and 15c (FIG. 1) are arranged adjacent to each other. There are various methods for manufacturing the hologram plate 4, and a case of manufacturing by the contact copy method will be described. In the contact copy method, as shown in FIG. 4, a pattern reflecting member 25 is used in which a plurality of minute reflecting portions 24 for reflecting laser light corresponding to one color holographic mirror cell are formed in a matrix. This is brought into close contact with the photosensitive material for hologram 4a from the back side, and the minute reflecting portion 24
A single-wavelength laser beam is applied to the laser beam. That is, the laser light 26 having a predetermined wavelength is irradiated onto the minute reflecting portion 24 at an inclination angle θ, and the reflected light 27 is used as object light.
As a reference light, due to the interference between the two, a first type volume phase interference fringe is formed in the region of the hologram photosensitive material 4a corresponding to each minute reflection portion 24. By appropriately setting the wavelength and the inclination angle (incident angle) of the laser light, a volume phase type interference fringe (diffraction grating) that selectively diffracts and reflects only a desired wavelength component can be formed. Then, laser light of another wavelength and tilt angle is irradiated to form a second type of interference fringe. By the multiple exposure of these two types of interference fringes, R,
A holographic mirror cell is formed in which only R light of red wavelength of G and B is transmitted and other remaining G light and B light are not transmitted and are diffracted and reflected. Hereinafter, the same thing is performed by shifting the pattern reflecting member 25 by one pixel, respectively.
And B, the holographic mirror cells 15a, 1a corresponding to the R, G, B lights respectively.
5b and 15c can be manufactured. At this time, the pattern reflecting member (mask) shown in FIG. 4 can be shared for each color. More specifically, the peak wavelengths of R, G, and B lights are 610 nm, 545 nm, and 460 nm,
When only R light of 610 nm is transmitted and G light and B light are diffracted and reflected, the intervals of the interference fringes are 153 nm and 182.
The interference fringes of nm may be multiple-exposed. 45 for that
The laser beam 26 having a wavelength of 7.9 nm is tilted at an inclination angle θ = 8.2.
The laser beam 26 having a wavelength of 514.5 nm may be incident at θ = 29.65 degrees while being incident at 3 degrees. Also, 5
When only G light of 45 nm is transmitted, interference fringes having an interval of 153 nm and 203 nm may be subjected to multiple exposure. For that purpose, a laser beam 26 having a wavelength of 457.9 nm is used.
With an incident angle of θ = 8.23 degrees and 514.5
Laser light 26 having a wavelength of nm may be incident at θ = 53.69 degrees. Further, when only B light of 460 nm is transmitted, interference fringes having an interval of 182 nm and 203 nm may be multiple-exposed. 514.5 nm for that
Laser light 26 having a wavelength of 514.5 nm is incident at θ = 29.65 degrees, and laser light 26 having a wavelength of 514.5 nm is θ = 53.
It may be incident at 69 degrees. The wavelength of the laser light 26 and the value of the tilt angle θ are not limited to those described above, and the intervals of the three types of interference fringes described above are 153 nm and
Any combination that can realize 2 nm and 203 nm may be used.

[0018]

According to the present invention, the following remarkable effects are obtained. 1) Since the light from the backlight unit can be made incident on the color filter without waste, the utilization efficiency of the light from the light source is improved, and bright and high-contrast image display can be realized. 2) Since the utilization efficiency of the light from the light source is improved, the brightness of the white light from the backlight unit can be lowered as compared with the conventional one, and the power consumption can be saved accordingly.

[Brief description of drawings]

FIG. 1 is an enlarged partial cross-sectional view showing a detailed structure of each component of a color liquid crystal display device according to an embodiment of the present invention.

FIG. 2 is a sectional view showing the overall structure of an embodiment of the present invention.

FIG. 3 is a schematic cross-sectional view showing a method for manufacturing the holographic mirror cell array of this embodiment.

FIG. 4 is a plan view of a patterned reflecting member used in the manufacturing method of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Color liquid crystal display device 2 Backlight unit 3 Reflecting means 4 Hologram plate 4a Holographic photosensitive material 5 Liquid crystal display panel 6 Color filter 7 White light source 8 Reflecting surface 9 Diffuse reflecting surface 10 Diffusing surface 11 Opening 12 Reflecting surface 13 Substrate 14 Holographic Mirror cell array 15 Holographic mirror cell 15a Holographic mirror cell 15b Holographic mirror cell 15c Holographic mirror cell 16 Liquid crystal cell 16a Liquid crystal cell 16b Liquid crystal cell 16c Liquid crystal cell 17 Coloring cell 17a Coloring cell 17b Coloring cell 17c Coloring cell 18 Black matrix 19 White light 20 Reflected light 21 Red light (R light) 21a Diffracted reflected light 22 Green light (G light) 22a Diffracted reflected light 23 Blue light (B light) 23a Diffracted reflected light 24 Micro reflection part 25 pattern reflection member 26 laser light 27 reflected light

Claims (5)

[Claims] 1. A liquid crystal display panel having liquid crystal cells arranged in a matrix, and a color filter having colored cells divided into three primary colors corresponding to the individual liquid crystal cells,
A color liquid crystal display device comprising a backlight unit for injecting white light into the liquid crystal display panel, and a hologram plate interposed between the backlight unit and the color filter, wherein the hologram plate is It has a volume phase type holographic mirror cell arranged corresponding to the colored cell, and the holographic mirror cell disperses white light incident from the backlight unit, and the corresponding colored cell. The desired wavelength component that matches the hue of the above is selectively transmitted to lead to the colored cell side, and the unnecessary wavelength component that does not match the hue of the corresponding colored cell is diffracted and reflected back to the backlight unit side. Color liquid crystal display device using a hologram. 2. Reflecting means is provided between the hologram plate and the backlight unit, and the reflecting means comprises:
2. A color liquid crystal display device using a hologram according to claim 1, wherein each holographic mirror cell has an opening and a reflection surface corresponding to a central portion and a peripheral portion of the holographic mirror cell. 3. The color liquid crystal display device using a hologram according to claim 2, wherein the reflecting means is formed on the back surface side of the hologram plate so as to face the backlight unit. 4. The color liquid crystal display device using a hologram according to claim 2, wherein the reflecting means is formed on the front surface side of the backlight unit so as to face the hologram plate. 5. The holographic mirror cell has at least two types of volume phase interference fringes formed by multiple exposure, and at least two unnecessary wavelengths having a complementary color relationship with the hue of the corresponding colored cell. 2. A color liquid crystal display device using a hologram according to claim 1, wherein each component is wavelength-selectively diffracted and reflected.