JPH08179303A - Color liquid crystal display device - Google Patents

Abstract

PURPOSE: To display a bright and sharp picture and to simplify the production process of a liquid crystal display element by using a hologram which is thin and selectively transmits a light in a specified wavelength area. CONSTITUTION: A hologram plate 5 is constituted of three kinds of holograms 15R, 15G and 15B corresponding to the pixel of the liquid crystal display element 6. The hologram 15R transmitting a light in red is obtained by laminating a hologram 21G reflecting a light in green and a hologram 21B reflecting a light in blue. The hologram 15G transmitting a light in green is obtained by laminating a hologram 22B reflecting a light in blue and a hologram 22R reflecting a light in red. The hologram 15B transmitting a light in blue is obtained by laminating a hologram 23R reflecting a light in red and a hologram 23B reflecting a light in blue. A microlens 7 condenses color light emitted from the hologram plate 5 on the pixel of the liquid crystal display element 6.

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 for displaying a color image using a hologram.

[0002]

2. Description of the Related Art In recent years, color liquid crystal display devices have been widely used as display devices for personal computers and the like. Since this color liquid crystal display device constitutes one display pixel with three pixels, it is an effective display pixel as compared with a black and white liquid crystal display device due to the space between adjacent electrodes and the arrangement of TFTs and the like. Area tends to be small. In addition, because the color is produced by the color filter, compared to monochrome liquid crystal display devices,
Originally, the light transmittance is considerably low.

Therefore, it is necessary to brighten the light source,
There is a problem that power consumption increases. In order to solve this problem, it has been proposed to use holograms instead of color filters. This is, for example,
As disclosed in Japanese Patent Laid-Open No. 05-249318, it has been proposed to provide a microlens and a hologram plate on which a group of holograms for separating RGB are arranged behind a liquid crystal display element.

[0004]

[Problems to be Solved by the Invention] This hologram plate 35
As shown in FIG. 4, the incident light from the back is divided into RGB color lights and emitted at different emission angles, and the microlens 37 is passed through the RGB pixel portions of the liquid crystal display element 36. It is configured to be condensed by.
This hologram plate 35 is a uniform hologram as a whole, and the white light incident as parallel rays passes through the hologram so that no matter which part of the hologram it passes through, RG
The B color lights are emitted at the same emission angle. 31A, 31
B is the substrate of the liquid crystal display element 36, and 32A and 32B are its electrodes.

For example, if the green light goes straight, the red light goes left, and the blue light goes right, as shown in the figure, the red lights 38R and 39R turn left and the green light goes. The light of 38G,
39G straight, blue light 38B, 39B turn right,
The respective colored lights are condensed by the microlenses to the pixels corresponding to the colored lights.

If such a structure is adopted, it is difficult to design the microlens, and the colored light is not sufficiently separated,
There was a problem that the color became cloudy. Also,
Even if the incident light is input as parallel rays, there is also a problem that each color light becomes light of various angles.

Further, as shown in FIG. 5, the hologram plate 45
As another example, it has been proposed that three types of holograms having different RGB refraction angles are arranged behind the liquid crystal display element 46. 41A and 41B are liquid crystal display elements.
46 substrates, 42A and 42B indicate the electrodes. This uses three types of holograms that emit a specific color in the vertical direction and inject the other colors by tilting them to the right and left.

As shown in the figure, the blue light 48 is emitted from the hologram 47R.
B is emitted to the left, red light 48R is emitted vertically, and green light 48G is emitted to the right. In the adjacent hologram 47G, the blue light 49B is emitted to the right side to the adjacent blue pixel, the red light 49R is emitted to the left side to the same red pixel that the red light 48R reaches, and the green light is emitted. 49G exits vertically and reaches the same red pixel that green light 48G reaches. Similarly, the adjacent hologram 47B is also divided into different colors and emitted, and light of the same color reaches pixels of the same color.

However, the angle at which this is also inclined and emitted is usually
Since the angle is about 5 °, there is a problem that a slight inclination of incident light causes color mixing, resulting in color turbidity. Further, even if the incident light is incident as parallel rays, there is a problem that each color light becomes light of various angles. The present invention aims to solve these problems and to provide the following.

[0010]

The present invention has been made to solve the above-mentioned problems, and has a light source and a hologram plate for separating the light from the light source behind the liquid crystal display element. In a color liquid crystal display device, a hologram plate is composed of a plurality of holograms that transmit light in a specific wavelength range and reflect light in other wavelength ranges, and the plurality of holograms have different wavelength ranges of transmitted light. At least 2
Divided into different types of hologram groups, each hologram is made to correspond to a pixel of the liquid crystal display element, and the colored light emitted from the hologram plate is condensed on the pixel of the liquid crystal display element between the liquid crystal display element and the hologram plate. The present invention provides a color liquid crystal display device characterized by being provided with a microlens for performing the above.

Further, the liquid crystal display element forms one display pixel by three pixels for controlling the respective color lights of three colors of RGB, and as a hologram plate, one display pixel is provided corresponding to each pixel of the liquid crystal display element. It is intended to provide a color liquid crystal display device characterized in that individual holograms are arranged so that the corresponding colored lights of three colors are transmitted to the respective portions.

Further, the hologram plate having the holograms of the three colors has a two-layer structure, and the portion transmitting the first color has a structure in which the hologram reflecting the second color and the hologram reflecting the third color are laminated. And has a structure in which a hologram that transmits the second color and a hologram that reflects the first color and a hologram that reflects the third color are stacked, and the portion that transmits the third color reflects the first color. And a hologram for reflecting the second color, which is laminated, to provide a color liquid crystal display device.

In the color liquid crystal display device of the present invention, the hologram plate is used for spectral separation, and the hologram plate is composed of a plurality of holograms that transmit light in a specific wavelength range and reflect light in other wavelength ranges. Has been done. The plurality of holograms are divided into at least two types of hologram groups in which the wavelength range of light that passes through is different, and each hologram corresponds to a pixel of the liquid crystal display element. Thus, when light is made incident on the hologram in a direction perpendicular to the hologram, the emitted light is emitted from the hologram in the direction perpendicular to the hologram.

Therefore, it is possible to display a bright and sharp image, which is an effect peculiar to the color filter by the hologram plate. Furthermore, in the present invention, the characteristics of the emitted light can be maintained as substantially parallel rays, but in order to widen the viewing angle of the color liquid crystal display device and improve color separation between pixels, the liquid crystal display element and the hologram plate are used. A microlens is placed between and to collect light.

FIG. 1 is a typical example of a color liquid crystal display device of the present invention, which includes a light source 1 such as a cold cathode discharge tube and a condenser mirror.
2, a backlight consisting of a condenser lens 3 and a reflector 4,
Hologram plate 5 in front of it, micro lens
7 and a liquid crystal display element 6.

This backlight is constructed so that the light emitted from a linear light source is condensed by an elliptical mirror or the like, converted into parallel rays by a condenser lens, and is incident on a hologram almost perpendicularly by a reflector. There is. This backlight structure is suitable for a thin type. Further, when the depth can be obtained, the light may be incident on the hologram almost vertically with another structure.

The reflector of this backlight is shown in FIG.
It has a micro prism shape as shown in 14 of
The light 13 from the light source is reflected and is incident on the hologram plate 5 almost vertically. This reflector is usually made of plastic or glass coated with a metal film having a high reflectance such as aluminum or silver. The reflector having such a micro-prism shape can be manufactured by the following manufacturing method.

When a plastic such as polymethylmethacrylate is extruded into a film, the shape of a desired prism-shaped roll is transferred to the film to produce the original prism array. Further, light irradiation is carried out with a relatively low-viscosity unpolymerized photopolymerizable composition sandwiched between a film serving as a base material and a roll having a desired prism shape, and after polymerization, peeled off from the roll together with the base material to produce. May be. Further, it may be manufactured by hot pressing using a thermoplastic, or may be cast by molding. Then, aluminum or silver is deposited on the surface by vapor deposition or plating.

The hologram plate 5 is composed of three kinds of holograms 15R, 15G and 15B corresponding to the pixels of the liquid crystal display element. Hologram 15R transmits only red light and reflects green and blue. Hologram 15G transmits only green light and reflects red and blue.
15B Only blue light is transmitted, and green and red are reflected.

When the transmitted light is almost parallel light,
It can be seen from the front without the microlens 7, but the viewing angle is narrowed. A micro lens 7 is arranged to widen the viewing angle. The transmitted light split into RGB is the electrodes 12A provided on the substrates 11A and 11B of the liquid crystal display element 6,
The light enters the pixel determined by 12B and is turned on / off for each color to form a color image. The liquid crystal display element of this example is RG
One display pixel is formed by three pixels in order to control the three color lights of B respectively. However, by controlling the colored light of two colors of RG instead of the three colors of RGB, three colors of red, yellow and green are controlled.
It can be said that it is displayed in color.

This hologram plate preferably has a two-layer structure. That is, the portion that transmits the first color has a structure in which a hologram that reflects the second color and a hologram that reflects the third color are stacked. Similarly, a portion that transmits the second color has a structure in which a hologram that reflects the first color and a hologram that reflects the third color are laminated, and a portion that transmits the third color has a hologram that reflects the first color and the second The structure is such that holograms that reflect colors are stacked.

Specifically, as shown in FIG. 3, the hologram plate 5 includes a hologram 15R that transmits red light, a hologram 21G that reflects green light, and a hologram 21B that reflects blue light.
The hologram 15G that transmits green is laminated with the hologram 22B that reflects blue and the hologram 22R that reflects red is laminated, and the hologram 15B that transmits blue is the hologram 23R that reflects red and the hologram 23B that reflects blue. To do.

As a result, for example, in the hologram 15R that transmits red, the green light 24G is reflected by the hologram 21G that reflects green in the first layer. The blue light 24B is reflected by the hologram 21B that reflects blue in the second layer. As a result, only the red light 24R reaches the liquid crystal display element through the two-layer hologram. Hologram 15G that transmits green
Similarly, only green light passes through, and similarly, only blue light passes through the hologram 15B that transmits blue.

For such a hologram, if it is desired to transmit red light, a refractive index distribution parallel to the hologram surface may be provided so as to selectively reflect green and blue light. This hologram is generally preferably mounted on a glass or plastic film for reinforcement.

As described above, this hologram has a diffraction grating plane parallel to the hologram surface, that is, a simple reflection type, and the manufacturing method may follow the Lippmann-Denischuk reflection type hologram exposure method. In other words, spread the hologram photosensitive film such as photopolymer on the mirror surface,
Collimated and coherent laser light is applied perpendicularly to the surface of the hologram photosensitive material film, for example, from the surface opposite to the mirror-side surface of the hologram.

As a result, the laser light (reference light) incident on the photosensitive material and the return light (object light) which is transmitted through the photosensitive material and reflected by the mirror interfere with each other in the photosensitive material to form interference fringes. The fringes form a diffraction grating parallel to the hologram surface. For a full-color liquid crystal display device, RGB color filters are required. Therefore, it is necessary to divide the exposure into three sets of pixel regions corresponding to the respective colors of RGB. Divide into three groups of pixel areas corresponding to the window RGB corresponding to each group,
Expose. Normally, there are 3 windows with windows for each group.
It suffices to perform exposure by using different types of exposure mask.

In this case, the size of each window is the size of the pixel area of the hologram. For example, in the case of a red filter, windows are provided at all locations corresponding to red. In order to make the hologram have a two-layer structure, two hologram photosensitive films such as a photopolymer film are used in a stacked manner. When creating a hologram that allows the transmission of red light, one of the two films should have a diffraction grating that reflects green in the red pixel area of one film and the corresponding area of the other film. A diffraction grating that reflects blue may be created.

Specifically, first, one hologram photosensitive film is adhered to a mirror, a red mask is overlaid on the photosensitive material side, and collimated green laser light is irradiated from the mask side. Next, another unexposed film was overlaid and adhered to the laser-irradiated film, and the red mask was again installed on the same side as the previous one so as to overlap with the window region, and this time. Irradiates a blue laser beam in the same manner as above.

As an actual procedure, three masks are used on the first film to form diffraction gratings for green, blue and red in regions corresponding to red, green and blue filters. Next, a grating for diffracting blue, red, and green is formed in each filter corresponding region of the second film, as in the case of the first film. In addition, in order to widen the band width of the spectrum which is reflected and diffracted, the thickness of the film is preferably thin.

In the above description, an example in which two hologram photosensitive films are used has been described, but three films can also be used. That is, the diffraction grating for one specific color is recorded on one film. In this case as well, three types of exposure masks are required, but one film has one
A type of exposure mask may be used. Alternatively, three unexposed hologram photosensitive films (sensitized to each color) may be preliminarily overlapped with each other and adhered to a mirror, and exposure may be sequentially performed while changing the laser light exposure masks of three colors.

The microlens may be made of plastic, glass or the like, but it is usually made of plastic because of its advantages such as light weight, resistance to breakage and easy formation. As a manufacturing method thereof, for example, when a plastic such as polymethylmethacrylate is extruded to form a film, a desired microlens-shaped roll shape may be transferred to the film.

As another production method, a relatively low-viscosity unpolymerized photopolymerizable composition is sandwiched between a film as a base material and a roll having a desired microlens shape, and light irradiation is carried out to conduct polymerization. Alternatively, it may be manufactured by peeling it off from the roll together with the substrate. Further, it may be manufactured by hot pressing using a thermoplastic, or may be cast by molding.
When the hologram has a stripe shape, the microlens may be a stripe lens or may be a dot shape corresponding to each pixel. When the hologram has a dot shape, it is preferable to make it a dot shape.

As the liquid crystal display element used in the present invention, various known liquid crystal display elements can be used. Typical liquid crystal display elements include, but are not limited to, TN type liquid crystal display elements, STN type liquid crystal display elements, and ferroelectric liquid crystal display elements. Of course, it can also be used for a transmission / scattering type liquid crystal display device in which liquid crystal, which has recently been drawing attention, is dispersed in a resin matrix.

Typical liquid crystal display elements include TN type liquid crystal display elements and STN type liquid crystal display elements. This can be placed on a plastic, glass or other substrate,
An undercoat layer of SiO ₂ , Al ₂ O _3, etc. is formed, and In ₂ O ₃ -Sn
After providing electrodes such as O ₂ (ITO) and SnO ₂ and patterning, if necessary, polyimide, polyamide, SiO ₂ , Al ₂ O
An overcoat layer such as ₃ is formed, an orientation treatment is performed, a sealing material is printed on this, sealing is performed so that the electrode surfaces face each other, the periphery is sealed, and the sealing material is cured to form an empty cell.

A liquid crystal composition is injected into this empty cell, and the injection port is sealed with a sealant to form a liquid crystal cell. If necessary, a polarizing plate, a color polarizing plate, an ultraviolet ray cut filter and the like are laminated on this liquid crystal cell, characters and figures are printed, and non-glare processing is performed to obtain a liquid crystal display element.

In addition to these, for example, a substrate using a two-layer electrode, a two-layer liquid crystal cell in which two liquid crystal layers are formed, TF
Various configurations such as an active matrix element using an active matrix substrate on which active elements such as T and MIM are formed can be used.

The color liquid crystal display device of the present invention can be applied to a liquid crystal display element for displaying a segment of, for example, a "day" shape by dividing a segment for color display. However, it is suitable for a liquid crystal display element that displays arbitrary characters and figures with a large number of dots. Specifically, 640
It is suitable for high-definition display such as × 480 dots, 800 × 600 dots, 1024 × 768 dots.

Example 1 A color liquid crystal display device as shown in FIGS. 1 to 3 was manufactured. A cold cathode discharge tube with a diameter of 3 mm is used as the light source 1,
It was arranged so as to be perpendicular to the paper surface of FIG. An elliptic lens barrel was installed as the focusing mirror 2 so that this cold cathode discharge tube was the first focal point. Furthermore, as the condenser lens 3,
A 3 cm long convex lens barrel having the second focal point of this elliptic lens barrel as a focal point was arranged. Further, as the reflector 4, a prism array having a reflection surface of aluminum was arranged to form a backlight.

The prism surface of this prism array was adjusted in angle so that the white light from the cold cathode discharge tube was reflected so that the white light would enter the surface of the liquid crystal display element perpendicularly.

One hologram photosensitive film was adhered to a plane mirror, a red mask was overlaid on the photosensitive material side, and collimated green laser light was irradiated from the mask side. Next, a green mask is overlapped, blue laser light is irradiated from the mask side, a blue mask is further overlapped, and red laser light is irradiated from the mask side to form a hologram for three colors. A 5 mm thick first film was prepared.

Next, another unexposed film is laminated and adhered on the laser-irradiated film, and the red mask is again installed on the same side as the above so as to overlap with the window region. Then, the blue laser light was irradiated in the same manner as the previous time. Hereinafter, similarly, the mask for green is overlapped, the red laser light is irradiated from the mask side, the mask for blue is further overlapped, and the green laser light is irradiated from the mask side,
A hologram plate was formed.

As a liquid crystal display element, a 6-inch panel having a diagonal length of 9 inches is used.
A 240 ° twisted FSTN type liquid crystal display device was prepared by laminating 40 × 480 dot retardation films. Behind this liquid crystal display element, the hologram plate described above, a microlens for converging light of different specific wavelength ranges transmitted from respective regions of the hologram to each pixel of the liquid crystal display element, and a backlight are arranged. did.

As the hologram plate for STN as this hologram, the hologram was formed in a stripe shape. Therefore, the microlens was formed in a stripe shape, and the cross section of the stripe was one for each pixel. The focal length was the distance to the pixel of the liquid crystal display element. With this color liquid crystal display device, bright and clear color display was obtained.

Example 2 As a liquid crystal display element, an active matrix liquid crystal display element using a 640 × 480 dot TFT was prepared. As the hologram plate, a hologram plate having dots formed therein (pixels of different colors arranged in the vertical direction and the horizontal direction) was used. Behind this liquid crystal display element, the hologram plate, the microlens and the backlight were arranged.

This microlens has a dot shape (rectangle)
And one pixel per pixel. The focal length was the distance to the pixel of the liquid crystal display element. With this color liquid crystal display device, bright and clear color display was obtained.

[0046]

Since the color liquid crystal display device of the present invention uses a hologram which is thin and selectively transmits a specific wavelength range, a bright and sharp image can be displayed. Further, the manufacturing process of the liquid crystal display element is simplified as compared with the conventional color liquid crystal display device in which the color filter is installed inside the liquid crystal display element.

Further, since the light is condensed by the microlens, the viewing angle is widened and the color separation between pixels can be improved. The present invention can be applied in various ways within a range that does not impair the effects of the present invention.

[Brief description of drawings]

FIG. 1 is a front view of a representative example of the present invention.

FIG. 2 is an enlarged explanatory diagram of a main part of the example of FIG.

FIG. 3 is an enlarged explanatory view of a main part of a preferable example of the hologram plate of the example of FIG.

FIG. 4 is an explanatory diagram of a conventional example.

FIG. 5 is an explanatory diagram of another conventional example.

[Explanation of symbols]

 1: Light source 2: Condensing mirror 3: Condensing lens 4: Reflector 5: Hologram plate 6: Liquid crystal display element 7: Micro lens

Claims (3)

[Claims] 1. A color liquid crystal display device having a light source behind a liquid crystal display element and a hologram plate for dispersing light from the light source, wherein the hologram plate transmits light in a specific wavelength range and other wavelengths. It is composed of a plurality of holograms that reflect the light in the range, and the plurality of holograms are divided into at least two types of hologram groups in which the wavelength range of the transmitted light is different, and each hologram corresponds to a pixel of the liquid crystal display element. A color liquid crystal display device comprising a liquid crystal display element and a hologram plate, and a microlens for condensing colored light emitted from the hologram plate to a pixel of the liquid crystal display element. 2. The liquid crystal display device according to claim 1, wherein the liquid crystal display device is RGB.
One display pixel is formed by three pixels for controlling the respective three color lights, and the three color lights corresponding to the respective pixels behind the liquid crystal display element are transmitted as a hologram plate corresponding to each pixel. A color liquid crystal display device in which individual holograms as described above are arranged. 3. The hologram plate according to claim 1 or 2, wherein the hologram plate having a three-color hologram has a two-layer structure, and a portion that transmits the first color reflects a hologram that reflects the second color and a hologram that reflects the third color. It has a structure in which holograms are stacked, and the portion that transmits the second color has a structure in which a hologram that reflects the first color and a hologram that reflects the third color are stacked, and the portion that transmits the third color is the first A color liquid crystal display device having a structure in which a hologram that reflects a color and a hologram that reflects a second color are stacked.