JP3880640B2 - Color liquid crystal display - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a liquid crystal display device for displaying a color image using a hologram.
[0002]
[Prior art]
In recent years, color liquid crystal display devices have begun to be widely used as display devices such as personal computers. Since this color liquid crystal display device constitutes one display pixel with three pixels, the display pixel is more effective than a monochrome liquid crystal display device because of the space between adjacent electrodes and the arrangement of TFTs. The area tends to be small. Furthermore, since the color filter is used to produce colors, the light transmittance is originally considerably lower than that of a monochrome liquid crystal display device.
[0003]
For this reason, there is a problem that the light source needs to be brightened and power consumption increases. In order to solve this problem, it has been proposed to use a hologram instead of a color filter. For example, as disclosed in Japanese Patent Application Laid-Open No. 05-249318, it is proposed that a microlens and a hologram plate in which hologram groups for separating RGB are arranged are arranged behind a liquid crystal display element.
[0004]
[Problems to be solved by the invention]
As shown in FIG. 4, the hologram plate 35 divides incident light from the back into RGB color lights and emits them at different emission angles, and each of the RGB pixels of the liquid crystal display element 36 has a micro lens. The light is condensed by passing through 37. This hologram plate 35 is a uniform hologram as a whole, and white light incident as parallel rays passes through the hologram, and is emitted at the same emission angle for each RGB color light regardless of which part of the hologram passes. The 31A and 31B indicate substrates of the liquid crystal display element 36, and 32A and 32B indicate electrodes thereof.
[0005]
For example, if the green light is straight, the red light turns to the left and the blue light turns to the right, the red lights 38R and 39R turn to the left and the green light 38G as shown in the figure. , 39G is straight, blue light 38B, 39B is bent to the right, and each color light is condensed by the microlens onto a pixel corresponding to the color light.
[0006]
When such a configuration is adopted, there is a problem in that it is difficult to design a microlens, color light is not sufficiently separated, and the color becomes cloudy. In addition, there is a problem that even if incident light is entered as parallel light, each color light becomes light at various angles.
[0007]
In addition, as shown in FIG. 5, it has also been proposed that a hologram plate 45 in which three types of holograms having different RGB refraction angles are arranged behind the liquid crystal display element 46. 41A and 41B denote substrates of the liquid crystal display element 46, and 42A and 42B denote electrodes thereof. This uses three types of holograms that emit specific colors in the vertical direction and emit other colors tilted to the right and left.
[0008]
As shown, in the hologram 47R, the blue light 48B is emitted to the left, the red light 48R is emitted vertically, and the 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, and the red light 48R reaches the same red pixel that reaches the green light. 49G is a green light 48G is emitted vertically to reach the same green pixel and to reach. Similarly, the adjacent hologram 47B is divided and emitted, and the same color light reaches the same color pixel.
[0009]
However, since the angle at which the light is inclined and emitted is usually about 5 °, there is a problem that a slight inclination of the incident light causes color mixture and the color becomes cloudy. In addition, there is a problem that even if incident light is entered as parallel light, each color light becomes light at various angles. It is an object of the present invention to provide a color liquid crystal display device that solves these problems.
[0010]
[Means for Solving the Problems]
The present invention has been made to solve the above-described problems. A linear light source, a hologram plate for dispersing light from the light source, and a hologram plate by reflecting the light source are reflected behind the liquid crystal display element. In a color liquid crystal display device having a reflector that receives light from a light source, the hologram plate is composed of three hologram films, and each hologram film is formed using one type of exposure mask. There, the reflector is intended to incident light perpendicularly to the hologram plate, the hologram plate reflects three color lights of the transmitted and the other two wavelength regions of one particular light in the wavelength range of the wavelength range of to that diffraction grating surface it is composed of a plurality of holograms are parallel to the hologram surface, the plurality of holograms divided into three types of hologram groups wavelength range different light transmitted, Contact Each hologram group corresponds to a pixel of the liquid crystal display element, and a microlens for condensing the color light emitted from the hologram plate on the pixel of the liquid crystal display element between the liquid crystal display element and the hologram plate A color liquid crystal display device is provided.
[0011]
Further, the liquid crystal display element forms one display pixel with three pixels for controlling color light of three colors of RGB, and corresponds to each pixel of the liquid crystal display element as a hologram plate, and corresponding to each part behind it. There is provided the above-mentioned color liquid crystal display device in which individual holograms that transmit three colors of light are arranged.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
The color liquid crystal display device of the present invention has a reflector that vertically reflects light from a light source to the hologram plate by reflection, and uses the hologram plate to split the light, and the hologram plate has a specific wavelength range. The diffraction grating surface is made up of a plurality of holograms that transmit light and reflect light in other wavelength ranges perpendicularly to the hologram plate , parallel to the hologram surface . The plurality of holograms are divided into at least two types of hologram groups having different wavelength ranges of transmitted light, and each hologram corresponds to a pixel of a liquid crystal display element. Thus, when light is incident on the hologram from a vertical direction, the emitted light is emitted from the hologram in the vertical direction.
[0014]
For this reason, a bright and sharp image which is an effect peculiar to the color filter by the hologram plate can be displayed. Furthermore, in the present invention, although the characteristics of the emitted light can be maintained as substantially parallel rays, 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 A microlens is placed on and condensed.
[0015]
FIG. 1 is a typical example of a color liquid crystal display device according to the present invention. A backlight comprising a light source 1 such as a cold cathode discharge tube, a condensing mirror 2, a condensing lens 3 and a reflector 4, and a front surface thereof. The hologram plate 5, the microlens 7, and the liquid crystal display element 6 are arranged.
[0016]
This backlight is configured such that light emitted from a linear light source is collected by an elliptical mirror or the like, converted into parallel rays by a condenser lens, and incident on the hologram almost perpendicularly by a reflector. This backlight configuration is suitable for a thin type. In addition, when the depth can be taken, light may be incident on the hologram almost vertically with another structure.
[0017]
The reflector of the backlight has a microprism shape as shown by 14 in FIG. 2, for example, and reflects the light 13 from the light source so as to enter the hologram plate 5 almost vertically. This reflector is usually made of plastic or glass coated with a highly reflective metal film such as aluminum or silver. The reflector having such a microprism shape can be manufactured by the following manufacturing method.
[0018]
When a plastic such as polymethyl methacrylate is formed into a film by extrusion, the shape of a desired prism-shaped roll is transferred to the film to produce the original prism array. In addition, light is irradiated with a relatively low-viscosity unpolymerized photopolymerized composition sandwiched between a film serving as a base and a desired prism-shaped roll, and after polymerization, it is peeled off from the roll together with the base. May be. Moreover, it may be manufactured by hot pressing using a thermoplastic plastic, or may be cast. Next, aluminum or silver is deposited on the surface by vapor deposition or plating.
[0019]
The hologram plate 5 includes three types of holograms 15R, 15G, and 15B corresponding to the pixels of the liquid crystal display element. The hologram 15R transmits only red light and reflects green and blue, the hologram 15G transmits only green light, the red and blue reflect, and the hologram 15B transmits only blue light. Green and red reflect.
[0020]
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. Transmitted light split into the RGB, the substrate 11A of the liquid crystal display element 6, 11B and the provided et the electrodes 12A, is incident on the pixel defined by the 12B, it is turned on and off to form a color image for each color. In the liquid crystal display element of this example, one display pixel is formed by three pixels in order to control the three color lights of RGB. Of course, instead of the three RGB colors, RG two-color light can be controlled to display three colors, red, yellow, and green.
[0021]
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 hologram that reflects the first color. A structure in which holograms reflecting two colors are stacked.
[0022]
Specifically, as shown in FIG. 3, the hologram plate 5R that transmits red has a hologram 21G that reflects green and a hologram 21B that reflects blue, and the hologram 15G that transmits green is blue. The hologram 22B reflecting red and the hologram 22R reflecting red are stacked, and the hologram 15B transmitting blue transmits the hologram 23R reflecting red and the hologram 23G reflecting green.
[0023]
Thereby, 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 the blue color of the second layer. As a result, only the red light 24R passes through the two-layer hologram and reaches the liquid crystal display element. Similarly, only green light passes through the hologram 15G that transmits green, and only blue light passes through the hologram 15B that transmits blue.
[0024]
In order to transmit red light, such a hologram may be provided with a refractive index distribution parallel to the hologram surface so as to selectively reflect green and blue light. This hologram is generally preferably placed on a reinforcing glass or plastic film.
[0025]
As described above, this hologram has a diffraction grating surface parallel to the hologram surface, that is, a simple reflection type, and the production method may be in accordance with the Lippmann Denishku reflection type hologram exposure method. In other words, a hologram photosensitive film such as a photopolymer is spread on the mirror surface, and collimated coherent laser light is irradiated perpendicularly to the hologram photosensitive material film surface, for example, from the surface opposite to the mirror side surface of the hologram. To do.
[0026]
As a result, the laser light (reference light) incident on the photosensitive material and the return light (object light) transmitted through the photosensitive material and reflected by the mirror interfere with each other in the photosensitive material, and an interference fringe is formed. A diffraction grating parallel to the surface is formed. For a full-color liquid crystal display device, RGB color filters are required. For this reason, exposure divided into three sets of pixel areas corresponding to RGB colors is required. Exposure is performed by dividing into three sets of pixel regions corresponding to the window RGB corresponding to each set. Usually, exposure may be performed using three types of exposure masks each having a window corresponding to each set.
[0027]
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 an overlapping manner. When creating a hologram that wants to transmit red light, one of the two films has a diffraction grating that reflects green in the red pixel area of one film, and a corresponding area in the other film. A diffraction grating that reflects blue light may be created.
[0028]
Specifically, first, a hologram photosensitive film is bonded to a mirror, a red mask is superimposed on the photosensitive material side, and collimated green laser light is irradiated from the mask side. Next, another unexposed film is laminated on this laser irradiated film, and the red mask is again installed on the same side as the previous window so as to overlap the window area. Irradiates with blue laser light in the same manner as before.
[0029]
As an actual procedure, three masks are used for the first film, and diffraction gratings for green, blue, and red are created in regions corresponding to the 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 in the same manner as the first film. In order to widen the bandwidth of the spectrum that is reflected and diffracted, the film should be thinner.
[0030]
In the above description, an example using two hologram photosensitive films has been described, but three films can also be used. That is, a diffraction grating for one specific color is recorded on one film. In this case, three types of exposure masks are required, but one type of exposure mask may be used for one film. Alternatively, three unexposed holographic photosensitive films (photosensitive to each color) can be preliminarily stacked and adhered to a mirror, and exposure can be performed while sequentially changing the three-color laser light exposure masks.
[0031]
The microlens may be made of plastic, glass, or the like, but is usually made of plastic from the advantages of being lightweight, difficult to break, and easy to form. As a manufacturing method thereof, for example, when a plastic such as polymethyl methacrylate is formed into a film by extrusion, a desired microlens-shaped roll shape may be transferred to the film.
[0032]
As another manufacturing method, light irradiation is performed with a relatively low-viscosity unpolymerized photopolymerization composition sandwiched between a film serving as a base and a desired microlens-shaped roll, and after polymerization, You may peel and manufacture from a roll with material. Moreover, it may be manufactured by hot pressing using a thermoplastic plastic, or may be cast. The microlenses, when holograms of the stripe may be as a lens stripe may be in the form of dots corresponding to each pixel. When the hologram has a dot shape, it is preferably a dot shape.
[0033]
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 element in which liquid crystal which has recently been attracting attention is dispersed in a resin matrix.
[0034]
As a typical liquid crystal display element, there is a TN liquid crystal display element or an STN liquid crystal display element.
For this, an undercoat layer such as SiO ₂ or Al ₂ O ₃ is formed on a substrate such as plastic or glass as necessary, and an electrode such as In ₂ O ₃ —SnO ₂ (ITO) or SnO ₂ is provided. After patterning, if necessary, an overcoat layer of polyimide, polyamide, SiO ₂ , Al ₂ O ₃ or the like is formed, oriented, and a sealing material is printed thereon, so that the electrode surfaces are opposed to each other. Then, the periphery is sealed, and the sealing material is cured to form an empty cell.
[0035]
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. A liquid crystal display element is formed by laminating a polarizing plate, a color polarizing plate, an ultraviolet cut filter, or the like on this liquid crystal cell as necessary, printing characters or figures, or non-glare processing.
[0036]
In addition to these, for example, a substrate using a two-layer electrode, a two-layer liquid crystal cell formed with two liquid crystal layers, an active matrix device using an active matrix substrate formed with an active element such as TFT, MIM, etc. Can be used.
[0037]
The color liquid crystal display device of the present invention can be applied, for example, to a liquid crystal display element that performs segment display of the “day” character type by dividing the segments and performing color display. However, it is suitable for a liquid crystal display element that displays an arbitrary character or figure with a large number of dots. Specifically, it is suitable for high-definition display such as 640 × 480 dots, 800 × 600 dots, 1024 × 768 dots.
[0038]
【Example】
"Example 1"
A color liquid crystal display device as shown in FIGS. 1 to 3 was manufactured.
As the light source 1, a cold cathode discharge tube having a diameter of 3 mm was used and arranged so as to be perpendicular to the paper surface of FIG. 1. An elliptic lens barrel was installed as the condensing mirror 2 so that this cold cathode discharge tube was the first focal point. Further, as the condensing lens 3, a convex lens cylinder having a length of 3 cm having the second focal point of the elliptical lens barrel as a focal point is disposed. Further, a prism array having an aluminum reflecting surface was disposed as the reflector 4 to constitute a backlight.
[0039]
The prism surface of this prism array was adjusted in angle so as to reflect white light from the cold cathode discharge tube so as to be perpendicularly incident on the surface of the liquid crystal display element.
[0040]
One hologram photosensitive film was bonded to a flat mirror, a red mask was superimposed on the photosensitive material side, and collimated green laser light was irradiated from the mask side. Then using a mask for green is irradiated with blue laser light from the mask side, further using a mask for blue, by irradiating a red laser beam from the mask side, the hologram is a diffraction grating surface of the three colors A first film having a thickness of 5 mm on which a hologram parallel to the surface was formed was prepared.
[0041]
Next, another unexposed film is laminated on this laser irradiated film, and the red mask is again installed on the same side as the previous window so as to overlap the window area. Was irradiated with blue laser light as before. Thereafter, similarly, a green mask is overlaid, a red laser beam is irradiated from the mask side, a blue mask is further overlaid, and a green laser beam is irradiated from the mask side to form a hologram plate. .
[0042]
As the liquid crystal display element, a 240 ° twist FSTN type liquid crystal display element in which a 640 × 480 dot retardation film having a diagonal length of 9 inches was laminated was prepared. Behind this liquid crystal display element, the above-mentioned hologram plate, a microlens for condensing light of different specific wavelength ranges transmitted from each area of the hologram to each pixel of the liquid crystal display element, and a backlight are arranged did.
[0043]
Since the hologram plate for STN was formed in a stripe shape as this hologram, the microlens was formed in a stripe shape so that one cross-section of the stripe is provided 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, a bright and clear color display was obtained.
[0044]
"Example 2"
As a liquid crystal display element, an active matrix liquid crystal display element using 640 × 480 dot TFTs was prepared. For this, a hologram plate in which a hologram is formed in a dot shape (pixels having different colors in both the vertical and horizontal directions) is used. The hologram plate, microlens, and backlight are arranged behind the liquid crystal display element.
[0045]
The microlenses are formed in a dot shape (rectangular shape), and one microlens is provided 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, a bright and clear color display was obtained.
[0046]
【The invention's effect】
Since the color liquid crystal display device of the present invention uses a thin hologram that selectively transmits a specific wavelength range, it can display a bright and sharp image. Furthermore, the manufacturing process of the liquid crystal display element is simplified as compared with a conventional color liquid crystal display device in which a color filter is installed inside the liquid crystal display element.
[0047]
Further, since the light is condensed by the microlens, the viewing angle is widened, and color separation between pixels can be improved.
The present invention can be applied in various ways as long as the effects of the present invention are not impaired.
[Brief description of the 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. 1;
FIG. 3 is an enlarged explanatory view of a main part of a preferable example of the hologram plate of the example of FIG. 1;
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: Microlens

Claims (2)

In a color liquid crystal display device having a linear light source behind the liquid crystal display element, a hologram plate that splits the light from the light source, and a reflector that reflects the light from the light source to the hologram plate by reflection, hologram plate will be composed of three holographic films, each hologram film has been formed by respectively using one kind of the exposure mask, the reflector is intended to incident light perpendicularly to the hologram plate, hologram plate is composed of three colors one specific wavelength range of transmitted light and the other two wavelength regions of the diffraction grating surface you reflecting light of a plurality of parallel to the hologram surface hologram of the wavelength range of and which, as the plurality of holograms which split into three hologram groups wavelength range different light transmitted, each of the hologram groups corresponding to the pixels of the liquid crystal display device It is, between the liquid crystal display element and the hologram plate, a color liquid crystal display device of the color light emitted from the hologram plate, characterized in that a microlens for condensing the pixels of the liquid crystal display device. The liquid crystal display element forms one display pixel with three pixels for controlling color light of three colors of RGB, and corresponds to each pixel of the liquid crystal display element as a hologram plate, and 3 corresponding to the back part thereof. 2. A color liquid crystal display device according to claim 1, wherein individual holograms that transmit colored light of colors are arranged .

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