JPH0736032A - Back light source - Google Patents

Abstract

PURPOSE:To obtain a direct view type back light source which has high luminance and superior uniformity of luminance by arranging a reflection plate which scatters light, a light emission body, a planar oriented cholesteric liquid crystal layer, and a 1/4-wavelength plate in this order. CONSTITUTION:The back light source consists of a diffusing reflection plate 21 which scatters light, a planar oriented cholesteric liquid crystal layer 40, a light emission body 10 which is arranged between the diffusing reflection plate 21 and liquid crystal layer 40, a light-transmissive diffusing plate 22 which is arranged between the light emission body 10 and liquid crystal layer 40, and the 1/4-wavelength plate 50 which is arranged on the light transmission side of the liquid crystal layer 40. A circular polarized light component 102 which is reflected by the CH liquid crystal layer 40 is irregularly reflected at the time of reflecting by the diffusing reflection plate 21 and partial polarization is eliminated; and its reflected light 103' is partially polarized light, but its polarized component 104 can be transmitted through the CH liquid crystal layer 40. Namely, 75% of the light emitted by the light emission body 10 is transmitted through the CH liquid crystal layer 40 and guided to a liquid crystal cell 70 to improve the luminance.

Description

Detailed Description of the Invention

[0001]

The present invention relates to TN (Twisted Nemati)
c), STN (Super Twisted Nematic), FLC (Ferr
liquid crystal display device such as oelectric liquid crystal), and a backlight light source for a direct-view liquid crystal display device that displays brightness and darkness by using polarized light.

[0002]

2. Description of the Related Art TN, STN, FLC as a display device for information equipment such as personal computers and word processors, and an operation panel for home electric appliances and industrial machines.
For example, liquid crystal display devices using polarized light are widely used. In the liquid crystal display device, in order to improve the visibility, a direct view type backlight light source is arranged on the back surface of the liquid crystal display panel.

The structures of a direct type backlight source and an end face light guide type backlight source which are relatively often used as a direct-view type backlight source are shown in FIGS. 4 and 5, respectively. The direct type backlight light source, as shown in FIG.
It is composed of a translucent diffusion plate 22, a reflection plate 30, and a light emitting body 10 arranged between the two. A liquid crystal display device is configured by arranging a liquid crystal display element including a polarizer 60, a liquid crystal cell 70, and a polarizer 80 on the light emission side.
The translucent diffusion plate 22 interposed in the optical path is arranged in order to obtain uniform brightness.

As shown in FIG. 5, the end face light guide type backlight light source includes a light emitter 10, a light guide plate 20 on which light emitted from the light emitter enters from an end face side, and one surface of the light guide plate 20. And a translucent diffuser plate 22 disposed on the other surface side of the light guide plate 20. The end face light guide type backlight light source is polarized to the light emission side. A liquid crystal display device is configured by sequentially arranging the child 60, the liquid crystal cell 70, and the polarizer 80. The light emitted from the light emitting body 10 propagates in the light guide plate 20 while repeating total reflection, but is scattered by the diffuse reflection plate 21 and is extracted to the outside of the light guide plate 20. The light emitted from the light guide plate 20 is transmitted through the translucent diffusion plate 22, is uniformized, and is guided to the polarizer 60 side.

In the liquid crystal display device having the backlight light source as described above, 80% or more of the power consumption is consumed by the backlight light source, so that the liquid crystal display device has high brightness and low power consumption. It is essential to improve the efficiency of the backlight source. However, since the backlight light source having the above structure is a non-polarized light source, 50% of the emitted light 100 from the light emitting body 10 is absorbed by the polarizer 60 of the liquid crystal display element, and the transmitted light 110 makes up 50% of the emitted light 100. It becomes the following.

Therefore, a cholesteric liquid crystal layer having a planar alignment (hereinafter referred to as a CH liquid crystal layer) and a reflector for reversing the rotation direction of circularly polarized light are used to effectively utilize the emitted light from the light emitting body to enhance the light emission. A backlight light source for improving efficiency has been proposed (see Japanese Patent Laid-Open No. 3-45906). As shown in FIG. 6, this backlight light source is used for the CH liquid crystal layer 4
0, the reflection plate 30, and the light-emitting body 10 arranged between them.
And a retardation plate having a retardation of λ / 4 (1/4 wavelength plate)
And 50. Since the CH liquid crystal layer 40 has a structure in which cholesteric (liquid crystal molecules) are arranged in a spiral shape, it exhibits selective reflection at a wavelength corresponding to the spiral pitch of the liquid crystal molecules. Therefore, by appropriately selecting the liquid crystal, the CH liquid crystal layer 40 can function as a circular polarization filter in the selective reflection wavelength range. That is, it reflects right-handed circularly polarized light or left-handed circularly polarized light, and transmits circularly polarized light in the opposite rotation direction. The direction of rotation when circularly polarized light is reflected is determined by the direction of rotation of the spiral of liquid crystal molecules.

In the above backlight light source, when the CH liquid crystal layer 40 transmits right circularly polarized light and reflects left circularly polarized light,
Right-handed circularly polarized light component 101 of light 100 emitted from light-emitting body 10
Is transmitted through the CH liquid crystal layer 40, and the left-handed circularly polarized component 102 is reflected. Since the light emitter 10 is a non-polarized light source, the intensity ratio of the right circularly polarized light component 101 and the left circularly polarized light component 102 is 1: 1. Left circularly polarized light component 102 reflected by the CH liquid crystal layer 40
Is left circularly polarized light without changing the polarization state after reflection. This left-handed circularly polarized light is then reflected by the reflecting plate 30, but the reflected light 103 becomes right-handed circularly polarized light 104 because the rotation direction of the polarized light is reversed at the time of reflection, so that it can be transmitted through the CH liquid crystal layer 40. Become. That is, all the light emitted from the light emitting body 10 is made into right circularly polarized light after passing through the CH liquid crystal layer 40. By converting this transmitted light into linearly polarized light 105 by the quarter-wave plate 50, it is possible to effectively use 50% of the emitted light which was conventionally absorbed by the polarizer 60 and wasted.

[0008]

However, the backlight source having the above structure has the following problems. That is, when the CH liquid crystal layer 40 is applied to the direct type backlight light source shown in FIG. 4, when the reflection plate 30 is a mirror surface, scattering due to reflection is eliminated, so that the brightness of the liquid crystal cell 70 arranged in front of the optical path is uniform. However, there is a problem that the property is significantly reduced.

Further, in order to reverse the rotation direction of the circularly polarized light reflected by the CH liquid crystal layer 40, the reflecting surface of the reflecting plate 30 needs to be a smooth mirror surface. However, in the end surface light guide type backlight light source shown in FIG.
When is a mirror surface, scattering due to reflection is eliminated, and almost no light can be extracted to the outside of the light guide plate 20. Therefore, the structure of the above-mentioned backlight light source using the CH liquid crystal layer 40 cannot be applied to the edge light guide type backlight light source having a feature that it can be thinned.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a direct-view type backlight light source having high brightness and excellent brightness uniformity.

[0011]

In order to solve the above-mentioned problems of the conventional example, a backlight light source according to claim 1 comprises a reflector having a light-scattering property, a light-emitting body, a cholesteric liquid crystal layer having a planar alignment, and The quarter-wave plate and the quarter-wave plate are arranged in this order.

According to another aspect of the present invention, there is provided a backlight light source, a light guide plate, a light emitting member arranged on an end face side of the light guide plate, and a light scattering property provided in optical contact with one surface of the light guide plate. A reflecting plate; a planar-oriented cholesteric liquid crystal layer arranged on the other surface side of the light guide plate; and a quarter-wave plate arranged on the side opposite to the light guide plate of the cholesteric liquid crystal layer. There is.

According to a third aspect of the present invention, there is provided a backlight light source having a light guide plate, a light emitting body disposed on the end face side of the light guide plate, and a light scattering property provided in optical contact with one surface of the light guide plate. A reflector, a light diffusing plate provided in close contact with the other surface of the light guide plate, a planar-oriented cholesteric liquid crystal layer arranged on the opposite side of the light diffusing plate from the reflecting plate, and a reflection of light from the cholesteric liquid crystal layer. And a quarter wavelength plate arranged on the side of the diffusion plate.

[0014]

According to the back light source of the first aspect, since the reflecting plate has a light-scattering property, the circularly polarized light reflected by the cholesteric liquid crystal layer (CH liquid crystal layer) is diffusely reflected when reflected by the reflecting plate. At the same time, some polarization is eliminated. The reflected light diffusely reflected by the reflector is partially polarized, but its right (or left) polarized component can be transmitted through the CH liquid crystal layer. Therefore,
If the polarization is completely depolarized by reflection on the reflection plate, half of the reflected light can be transmitted through the CH liquid crystal layer, and 75% of the light emitted from the light emitter is transmitted through the CH liquid crystal layer. Further, since the light reflected by the reflector is irregularly reflected, it is possible to achieve the uniformity of the brightness of the liquid crystal cell arranged in front of the optical path. The light transmitted through the CH liquid crystal layer is converted into linearly polarized light by the quarter-wave plate.

According to the backlight light source of the second aspect, the light guide plate which allows light to enter from the end face side is used, and the light reflector plate has a light scattering property so as to be in close optical contact with one surface of the light guide plate. Since the light from the light emitter is emitted to the outside of the light guide plate, the circularly polarized light reflected by the cholesteric liquid crystal layer (CH liquid crystal layer) is diffused and partially reflected when reflected by the reflector plate. Depolarize. The light reflected diffusely by the reflector is partially polarized, but its right (or left) polarized component can be transmitted through the CH liquid crystal layer. Therefore, if polarization is completely depolarized by reflection on the reflector, half of the reflected light is CH.
It becomes possible to pass through the liquid crystal layer, and 75% of the light emitted from the light emitter passes through the CH liquid crystal layer. Further, since the light reflected by the reflector is irregularly reflected, it is possible to achieve the uniformity of the brightness of the liquid crystal cell arranged in front of the optical path. The light transmitted through the CH liquid crystal layer is converted into linearly polarized light by the quarter-wave plate.

According to the backlight light source of the third aspect, in addition to the structure of the second aspect, the light diffusing plate is provided in optical contact with the other surface of the light guide plate. While reducing the reflection and improving the utilization efficiency without attenuating the light, it is possible to diffuse the light when the emitted light from the light emitting body and the reflected light from the reflecting plate pass through the light diffusing plate, Further excellent brightness uniformity can be achieved.

[0017]

Embodiments of the backlight light source according to the present invention will be described with reference to the drawings. FIG. 1 shows an embodiment of a direct type backlight light source, which is a diffuse reflection plate 21 having a light scattering property, a cholesteric liquid crystal layer 40 having a planar alignment, and light emission arranged between the diffusion reflection plate 21 and the liquid crystal layer 40. It comprises a body 10, a translucent diffusion plate 22 arranged between the light emitting body 10 and the liquid crystal layer 40, and a quarter-wave plate 50 arranged on the light transmission side of the liquid crystal layer 40.

A fluorescent tube, an LED, a halogen lamp, or the like can be used as the light-emitting body 10, but a fluorescent tube is suitable because it emits white light and is compact, high in luminous efficiency, and low in heat generation. As will be described later, since the selective reflection wavelength width of the CH liquid crystal cannot cover the entire visible light region, the spectrum of the light-emitting body 10 is assumed to be composed of bright lines, and the selective reflection wavelength of the CH liquid crystal is adjusted to the wavelength of the bright line. To As a fluorescent tube having a bright line spectrum, for example, a three-wavelength tube can be used.

The diffuse reflection plate 21 is made of metal such as stainless steel, white resin-formed product, metal surface coated with white paint, Al, Ag, and so on to reflect light on a substrate such as glass or resin. A material coated with a metal film such as Cr is used. The surface of the diffuse reflector 21 is a semi-ellipse, an inclined surface,
By processing these on a surface formed repeatedly, a light scattering property is imparted, and a decrease in brightness is reduced even when the light emitting body 10 is separated.

As the translucent diffuser plate 22, a material having a high transmittance is used, and for example, a sheet-like plate member having a surface made of a resin material such as acrylic, methacrylic, polycarbonate, polyester or the like or a glass surface having irregularities is used. Then, the transmitted light is diffused. Alternatively, a milky white material in which an inorganic or organic white pigment is dispersed in these translucent members may be used.

The CH liquid crystal layer 40 is a liquid crystal cell in which a low molecular weight CH liquid crystal is housed between two glass substrates subjected to a planar alignment treatment, and a polymer C formed on a glass substrate or a transparent resin substrate.
H liquid crystal layer. Since the CH liquid crystal layer 40 has a structure in which cholesteric (liquid crystal molecules) are arranged in a spiral shape, it exhibits selective reflection at a wavelength corresponding to the spiral pitch of the liquid crystal molecules, and as described above, by appropriately selecting the liquid crystal. In the selective reflection wavelength range, the CH liquid crystal layer 40 functions as a circular polarization filter. In addition, alignment defects in the liquid crystal layer cause light scattering and lower brightness, so it is necessary to prevent alignment defects from occurring.

When a liquid crystal cell containing a low molecular weight CH liquid crystal is used, the liquid crystal material is cholesteryl nonanoate,
A material having a cholesteric phase such as cholesteryl chloride alone or a mixed material obtained by adding a low molecular material having an asymmetric carbon (called a chiral agent) to a material having a nematic phase (N liquid crystal) can be used. The adjustment of the spiral pitch is performed by mixing two or more kinds of materials having different spiral pitches in an appropriate amount when a material having a cholesteric phase alone is used. When a mixed material obtained by adding a chiral agent to N liquid crystal is used, it is performed by controlling the concentration of the chiral agent.

As a specific example of the latter case, when a cyanobiphenyl-based mixed liquid crystal material and 2-methylbutyl-cyano-biphenyl are mixed at a ratio of 58:42 as the N liquid crystal, the central wavelength of the selective reflection region is It was possible to obtain a CH liquid crystal material having a green color reflection of 533 nm and a selective reflection width of 60 nm. Furthermore, a planarly aligned CH liquid crystal cell having a gap of 25 μm could be obtained by using two glass plates whose surfaces were covered with polyimide and rubbed.

As a material for the polymer CH liquid crystal layer, liquid crystalline polyester such as polyglutamate is used. As a method for forming a mono-domain thin film of these materials on a substrate, a polymer C is formed on a transparent substrate on which an alignment film is formed by a method such as spin coating, roll coating or screen printing.
An H liquid crystal material thin film is once formed, then heated to a glass transition temperature or higher to form a monodomain, and rapidly cooled to freeze the orientation (see Japanese Patent Laid-Open No. 3-291601). Since the polymer CH liquid crystal layer formed on the translucent substrate can be formed on one substrate, it is possible to make the light source thinner and lighter than a liquid crystal cell of a low molecular liquid crystal sandwiched between two substrates. Is preferred. Further, since the polymer CH liquid crystal is frozen in the room, the temperature dependence of the selective reflection wavelength is small, and it is suitable for preventing the characteristic change due to temperature.

If the thickness of the CH liquid crystal layer 40 is too thin, it is difficult to control the thickness, and unevenness is likely to occur. In addition, interference occurs and the hue changes. On the other hand, if the film thickness is too thick, alignment defects are likely to occur,
The phase change of the transmitted light becomes large at a wavelength outside the selective reflection wavelength range, and when laminated, the transmitted light is not circularly polarized in the selective reflection wavelength range of the lower CH liquid crystal layer. From the above, the thickness of the CH liquid crystal layer 40 is preferably about 2 to 10 μm.

The quarter-wave plate 50 is composed of a uniform uniaxial optical medium having a high transmittance and, for example, a uniaxially or biaxially stretched polymer film or the like can be used. Polycarbonate, polyester, polyvinyl alcohol or the like is used as the polymer film. In the above example,
Retardation R of quarter wave plate is λ = 550 nm
Corresponding to, R = 138 nm was set. However, in this setting, since a phase shift occurs for wavelengths other than λ = 550 nm and efficiency decreases, R = 100 nm for λ = 400 nm and R = 100 nm for λ = 600 nm.
It is desirable to use a quarter wave plate that is phase-compensated to be 150 nm. The phase-compensated quarter
The wave plate can be formed, for example, by bonding two types of uniaxial optical media having different refractive index dispersions so that their optical axes are orthogonal to each other.

According to the backlight light source of the embodiment shown in FIG. 1, the light 100 from the light emitting body 10 is diffused when passing through the translucent diffusion plate 22, is guided to the CH liquid crystal layer 40, and C
The right (or left) circularly polarized light component 101 is transmitted through the H liquid crystal layer 40. On the other hand, the left (or right) reflected by the CH liquid crystal layer 40
Since the circularly polarized light component 102 has the light-scattering property of the diffuse reflection plate 21, it is diffusely reflected when being reflected by the diffuse reflection plate 21 and partially polarized. The reflected light 103 ′ diffusely reflected by the diffuse reflection plate 21 is partially polarized light, but the right (or left) polarized light component 104 thereof can be transmitted through the CH liquid crystal layer 40. Then, the light transmitted through the CH liquid crystal layer 40 receives the quarter wave plate 50.
Is converted into linearly polarized light 105 and guided to the liquid crystal cell 70 of the liquid crystal display device. Therefore, if the polarization is completely depolarized by the reflection on the diffuse reflection plate 21, half of the reflected light 103 ′ can pass through the CH liquid crystal layer 40, and considering light that directly passes through the CH liquid crystal layer 40 from the light emitter 10. Therefore, 75% of the light emitted from the light emitter 10 is transmitted through the CH liquid crystal layer 40 and guided to the liquid crystal cell 70, and the conventional example of FIG. 4 (50% of the light emitted from the light emitter 10 is the liquid crystal cell 70). Led to)
It is possible to improve the brightness as compared with. Further, the light reflected by the diffuse reflection plate 21 is irregular reflection, and the translucent diffusion plate 2
Since light is diffused also in No. 2, it is possible to achieve uniform brightness in the liquid crystal cell 70.

FIG. 2 shows another embodiment of the present invention, in which the present invention is applied to an end surface light guide type backlight source.
The end surface light guide type backlight light source includes a light guide plate 20 that allows light to enter from the end surface side, a light emitting body 10 arranged on the end surface side of the light guide plate 20, and an optical member on one surface of the light guide plate 20. Diffuse reflector 21 provided in close contact with and having light scattering properties
A cholesteric liquid crystal layer 40 disposed on the other surface side of the light guide plate 20 and having a planar orientation, the light guide plate 20 and the liquid crystal layer 4
A transparent diffusion plate 22 disposed between the liquid crystal layer 4 and the liquid crystal layer 4;
¼ wavelength plate 5 arranged on the side opposite to the 0 light guide plate (light transmission side)
It is composed of 0 and. Light emitter 1 consisting of a fluorescent tube
The structures of 0, the translucent diffusion plate 22, the CH liquid crystal layer 40, and the quarter-wave plate 50 are the same as those in the embodiment of FIG.

The light guide plate 20 is preferably lightweight and has high transmittance, and is made of, for example, a resin material such as acrylic, methacrylic, or polycarbonate. If the thickness of the light guide plate 20 is too thin, the light guide efficiency from the fluorescent tube to the light guide plate 20 is reduced. Further, if the thickness of the light guide plate 20 is too thick, the weight and the volume are increased, so that the thickness is usually set to be about the same as the diameter d of the fluorescent tube.

The diffuse reflection plate 21 has only to have a high reflectance and a light scattering property, and for example, it is formed by printing a white paint on the light guide plate 20 to form a thin film. When the diffuse reflection plate 21 is formed by printing, the diffusion reflection plate 21 can be formed by using a pattern in which the area of the white paint increases as the distance from the light-emitting body 10 increases (away from the lower side of FIG. 2).
The uniformity of the brightness of the reflected light can be improved. Further, the diffuse reflection plate 21 does not necessarily need to be provided with another layer for the light guide plate 20 as long as the above conditions are satisfied. For example, micro cracks may be formed on the surface of the light guide plate 20 by a solvent treatment, or a mechanical crack may be formed. The light-scattering property may be obtained by engraving grooves to form irregularities.

When the luminous body 10 is a fluorescent tube, the brightness of the ends of the fluorescent tube is lower than that of the center, so that the length of the fluorescent tube (front and back direction in the figure) is made longer than the side surface of the light guide plate 20 to achieve brightness. It is desirable to aim for uniformity. Further, if the diameter of the fluorescent tube is made larger than the thickness of the light guide plate 20, the ratio of the light incident on the light guide plate 20 is reduced, and the efficiency is reduced. On the other hand, when the diameter of the fluorescent tube is small, the luminance of the end of the fluorescent tube becomes unstable, and the luminous efficiency and life of the fluorescent tube are reduced. Therefore, the diameter of the fluorescent tube is preferably 2 mm or more.

Further, in order to avoid that the light incident from the outside is sequentially transmitted through the translucent diffuser plate 22, the light guide plate 20, and the diffuse reflector plate 21, the back surface of the backlight source is not visible, so that the back surface of the diffuse reflector plate 21 is prevented. Another diffuse reflection plate (not shown) may be arranged on the side.

According to the backlight source of the embodiment shown in FIG. 2, the light guide plate 20 which allows light to enter from the end face side is used, and the light scattering property is such that the light guide plate 20 is optically closely attached to one surface of the light guide plate 20. Since the diffuse reflection plate 21 having the
The light guided from 0 to the light guide plate 20 is diffused inside by the diffuse reflection plate 21, emitted to the outside of the light guide plate 20, and transmitted light 100 diffused when passing through the translucent diffusion plate 22 is the CH liquid crystal layer. 40, and in this CH liquid crystal layer 40 right (or left)
The circularly polarized light component 101 is transmitted. On the other hand, the left (or right) circularly polarized light component 102 reflected by the CH liquid crystal layer 40 is diffusely reflected when the diffuse reflection plate 21 is reflected because the diffuse reflection plate 21 is made to have a light scattering property. To do. The reflected light 103 ′ diffusely reflected by the diffuse reflection plate 21 is a partially polarized light, but the right (or left) circularly polarized light component 104 thereof is the CH liquid crystal layer 4.
0 can be transmitted. Then, the light transmitted through the CH liquid crystal layer 40 is converted into linearly polarized light 105 by the quarter-wave plate 50 and guided to the liquid crystal cell 70 of the liquid crystal display device. Therefore, if the polarization is completely depolarized by the reflection on the diffuse reflection plate 21, half of the reflected light can be transmitted through the CH liquid crystal layer 40, and the CH liquid crystal layer 40 is not reflected by the CH liquid crystal layer 40.
Considering the light that passes through the
5% is transmitted through the CH liquid crystal layer 40 to be guided to the liquid crystal cell 70, and the luminance is higher than that in the conventional example of FIG. 5 (50% of the light emitted from the light emitting body 10 is guided to the liquid crystal cell 70). Can be improved. Further, the light reflected by the diffuse reflection plate 21 is irregular reflection, and the light is also diffused by the translucent diffusion plate 22, so that the uniformity of the brightness in the liquid crystal cell 70 can be achieved.

FIG. 3 shows another embodiment of the end surface light guide type backlight source, which is different from the embodiment of FIG. 2 in that the translucent diffusion plate 23 is in optical contact with the light guide plate 20. different. The other structure is the same as that of the embodiment of FIG. The translucent diffuser plate 23 only needs to be in optical contact with the light guide plate 20 and have a light-scattering property, and is composed of, for example, an innumerable minute prism group. In the case of the translucent diffuser plate 23, the apex of the prism is brought into optical contact with the light guide plate 20 to enable the extraction of light. Further, similar to the diffuse reflection plate 21, a microcrack is formed on the surface of the light guide plate 20 by a solvent treatment, or an unevenness is formed by mechanically carving a groove so as to obtain a light scattering property. The light diffusing plate 23 may be configured.

According to the embodiment of FIG. 3, the translucent diffuser plate 23
Since the light is provided in close contact with the light guide plate 20, the light is diffused when the light is emitted from the light guide plate 20 to the outside.
At this time, it is possible to prevent the light from being attenuated and to improve the light utilization efficiency.

[0036]

According to the present invention, since the CH liquid crystal layer and the reflector are provided, the light from the light emitting body is effectively utilized to improve the brightness and the reflector is made to have the light scattering property. It is possible to achieve uniform brightness. Further, by making the reflection plate light-scattering, the CH liquid crystal layer can be applied to the end face light guide type backlight light source, and it is possible to obtain a backlight light source that is thin and has high brightness and uniform brightness.

[Brief description of drawings]

FIG. 1 is a structural explanatory view showing an embodiment when the present invention is applied to a direct type backlight light source.

FIG. 2 is a structural explanatory view showing an embodiment in which the present invention is applied to an end surface light guide type backlight light source.

FIG. 3 is a structural explanatory view showing another embodiment when the present invention is applied to an end surface light guide type backlight light source.

FIG. 4 is a diagram illustrating a configuration of a conventional direct type backlight light source.

FIG. 5 is a structural explanatory view of a conventional end surface light guide type backlight light source.

FIG. 6 is a structural explanatory view of a conventional backlight light source using a CH liquid crystal layer.

[Explanation of symbols]

10 ... Light-emitting body, 20 ... Light guide plate, 21 ... Diffuse reflection plate (reflection plate), 22, 23 ... Translucent diffusion plate (light diffusion plate), 40 ... Cholesteric liquid crystal layer (CH liquid crystal layer),
50 ... Quarter wave plate, 70 ... Liquid crystal cell

Claims (3)

[Claims] 1. A light-scattering reflector and a light-emitting body,
A backlight light source comprising a planar-oriented cholesteric liquid crystal layer and a quarter-wave plate arranged in this order. 2. A light guide plate, a light-emitting body arranged on the end face side of the light guide plate, a light-scattering reflection plate provided in optical contact with one surface of the light guide plate, and the light guide plate. A back light source, comprising: a planar-oriented cholesteric liquid crystal layer disposed on the other surface side of the above, and a ¼ wavelength plate disposed on the side opposite to the light guide plate of the cholesteric liquid crystal layer. 3. A light guide plate, a light-emitting body arranged on the end face side of the light guide plate, a light-scattering reflection plate provided in optical contact with one surface of the light guide plate, and the light guide plate. A light diffusing plate provided in close contact with the other surface of the light diffusing plate, a planar-oriented cholesteric liquid crystal layer arranged on the side opposite to the reflecting plate of the light diffusing plate, and a light diffusing plate side opposite to the cholesteric liquid crystal layer. A quarter-wave plate, and a backlight light source.