JPH06160636A - Back light and liquid crystal display device - Google Patents

Abstract

(57) [Summary] [Construction] A lamp is built in the light guide, the shape of the reflector on the back of the light guide is changed according to the distance from the light source, and the reflector has a fine structure. Backlight. A liquid crystal display device in which a liquid crystal display element in which an optical path conversion element array is disposed on at least one of a pair of transparent substrates is disposed in front of the backlight. A liquid crystal display device in which the light guide of the backlight also serves as a substrate on one side of a liquid crystal display element. [Effect] By changing the shape of the reflection plate on the back surface of the light guide to have a fine structure, it is possible to efficiently and uniformly direct the light from the lamp from the front surface of the light guide. Further, the optical path conversion element array can narrow the light to the pixel portion to improve the substantial aperture ratio of the liquid crystal display element. Therefore, a thin liquid crystal display device with high light utilization efficiency can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin backlight with high light utilization efficiency and a liquid crystal display device using the same.

[0002]

2. Description of the Related Art As shown in FIG. 11, a structure of a backlight of a conventional liquid crystal display device includes a lamp 12 as a light source, a transparent light guide 11 for guiding light from the lamp 12 as a light source,
Diffusion films 15 arranged before and after the transparent conductor 11, a reflector 12 provided on the back surface of the lamp 12 and the light guide 11.
3,14.

With this structure, the diffusivity of the diffusion film 15 on the back surface of the light guide 11 is changed according to the distance from the lamp 12, so that the light from the lamp is made uniform in the screen. Although the light can be emitted, the light of the lamp cannot be efficiently used, and it is difficult to obtain a bright display with a thin backlight with low power consumption. Therefore, in order to improve the light utilization efficiency, the structure of a backlight in which a lamp is incorporated in a light guide body is described in JP-A-53-13395. Further, Japanese Patent Application Laid-Open Nos. 60-165621 to 165624 describe a structure in which a microlens or the like is used to increase the actual aperture ratio. Further, there is a configuration in which the light from the light guide is made uniform in the plane by changing the thickness of the light guide.
It is described in No. 4.

[0004]

However, since the above-mentioned conventional backlight does not consider the shape of the lamp even if the lamp is built in the light guide body, the launching efficiency to the light guide body is poor. Further, since the diffusion film is used, even if a reflection plate having a high reflectance is used, the efficiency is reduced due to light leakage and absorption loss.

Further, in the above-mentioned conventional liquid crystal display device, the backlight and the liquid crystal display device are not integrally designed by disposing a lens or the like on the glass substrate of the liquid crystal device itself.

Therefore, in order to solve the above problems, the present invention changes the shape of the reflecting plate without using a diffusing plate, and further uses a reflecting plate having a fine structure on its surface, It is to provide a thin, low power consumption and uniform in-plane backlight by efficiently coupling light into the light guide by changing the shape of the surface in contact with the lamp. Furthermore, by using the light guide itself provided with an optical path conversion element array that collects light on the front surface of the backlight as a substrate of a liquid crystal display element, the substantial aperture ratio is improved and the light utilization efficiency is high, thin and low. An object is to provide a liquid crystal display device with low power consumption.

[0007]

A backlight of the present invention is for a liquid crystal display device having a light source on the back surface of a liquid crystal display element, a light guide for guiding light from the light source, and a reflector on the back surface of the light guide. In a backlight, it is built in the light guide in order to efficiently launch the light flux of the lamp of the light source into the light guide, and the light coupled to the light guide from the lamp is uniformly emitted in the plane with directivity. In order to achieve this, the shape of the reflection plate on the back surface of the light guide changes in accordance with the distance from the light source, and the surface of the reflection plate has a fine structure.

Further, the liquid crystal display device of the present invention includes a liquid crystal display element, a light source on the back surface of the liquid crystal display element, a light guide for guiding light from the light source, and a back plate having a reflector on the back surface of the light guide. In a liquid crystal display device including a light, the lamp of the light source is built in the light guide, and the shape of the reflector on the back surface of the light guide changes according to the distance from the light source. Or the liquid crystal display element having the light path conversion element array on at least one of the transparent substrates on the front surface thereof or the liquid crystal display element having the light guide of the backlight. A liquid crystal display device used as one of the substrates.

[0009]

In the conventional backlight, since diffusion plates are used on both sides of the light guide to obtain in-plane uniformity, there are many absorption losses due to scattering, and many light components in useless directions exist. . That is, the viewing angle characteristic of the liquid crystal display element is about ± 50 degrees at most from the direction perpendicular to the substrate, and the light component emitted at an angle larger than that is not necessary. Also, in practice ± 50 to 6
It is said that there is no problem if the viewing angle is about 0 degree. Therefore, by making the shape of the reflector on the back surface of the light guide thin according to the distance from the lamp, the in-plane uniformity of the emitted light distribution is maintained, and by providing a fine structure on the surface of the reflector, The light that has entered the light guide is reflected with directivity and is emitted from the light guide. In this configuration, since a scattering plate is not used, a thin backlight with high absorption efficiency without absorption loss can be configured.

Further, by arranging an optical path conversion element array (for example, an optical fiber, a microlens, a Selfoc lens, etc.) for each pixel of the liquid crystal display element, light is transmitted only in the effective area of the pixel portion and the effective aperture ratio is increased. Improve.
Furthermore, by using the light guide as a substrate on one side of the liquid crystal display element, the liquid crystal display element and the backlight can be integrally designed, and the liquid crystal display device can be made thinner.

[0011]

Embodiments of the present invention will now be described with reference to the drawings.

Embodiment 1 FIG. 1 shows a schematic view of an embodiment of the present invention. FIG. 1 is a sectional view showing the structure of the backlight of the present invention. In the configuration of the present invention, the light source lamp 12 is built in the light guide body 11 that guides light, and the reflection plate 13 is provided on the back surface and the side surface of the light guide body 11. Further, a reflector 14 whose shape is changed linearly according to the distance from the lamp 12 is provided below the light guide 11. Further, on the front emission side of the light guide 11, an optical path conversion element array 10 for changing the optical path of the light emitted from the light guide 11 is arranged. The lamps 12 are arranged on both sides of the light guide body 11, but it is possible to arrange the lamps on only one side.

Light from the lamps arranged on both sides of the light guide is efficiently coupled into the light guide because the lamps are arranged inside the light guide. In addition, as shown in FIG. 9, a lens effect 17 is formed on the coupling portion of the light from the light guide 11 and the light from the lamp 12.
By making the shape spherical or elliptical so as to have the light, the light 53 from the lamp becomes light containing a lot of parallel light components. As shown in FIG. 1, the shape of the reflecting plate 14 is a flat surface so that the area of the reflecting surface with respect to the area of the emitting surface becomes wider and the inclination changes as the distance from the lamp increases. As shown in FIG. 10, the reflection plate 14 has a fine structure arranged with an inclination of about 45 degrees so as to efficiently reflect parallel light from the lamp perpendicularly to the emission surface. However, when the inclination angle of the fine structure is 45 degrees, the light from the lamp is all parallel light. In reality, since the light has a certain degree of angular distribution, the angle can be varied from 25 degrees to 65 degrees depending on the position. It is changing. At this time,
Its fine structure prevents interference colors from appearing, and
The pitch of the fine structure is 1 in order to reflect light efficiently.
It is preferably at least 00 μm. The shape and microstructure of the reflector need not be uniform.

Further, the shape of the light guide is set as shown in FIG. 9 in order to efficiently form parallel light. However, in order to make the light enter the light guide efficiently, it is preferable that the convex directions of the lenses are opposite. good. At this time, the emission direction of light from the light guide and the in-plane uniformity can be controlled by the inclination angle of the fine structure of the reflection plate below the light guide and the shape of the reflection plate.

Therefore, the light parallel to the exit surface of the light guide is efficiently reflected in-plane uniformly by the reflection plate 14 on the back surface of the light guide. The reflected light has a large amount of a component perpendicular to the light exit surface of the light guide, and since a diffuser plate is not used unlike the conventional backlight configuration, there is no backscattering and light absorption loss is small. Further, since light having a certain degree of angular distribution is emitted from the emission side surface of the light guide, it is preferable to include the optical path conversion element array 10 and convert it into a light component perpendicular to the emission surface. The optical path conversion element array may be an optical path plate, a microlens array, a prism array, a selfoc lens array, or any other optical path conversion element.

Further, TN (twist nematic) type and STM (super twist nematic) type liquid crystal display devices using nematic liquid crystal have a large viewing angle dependency and it is necessary to make the angle distribution characteristic of the backlight larger than that of the liquid crystal display device. Absent. When a liquid crystal display element having a narrow viewing angle is provided on the front surface of the backlight, the viewing angle characteristics of the liquid crystal display element in the widest direction are matched. In order to match the angular distribution of the light emitted from the backlight, an optical fiber, a microlens array, a prism array, etc. are used as an optical path conversion element array, and the light from the light guide is narrowed down to a component perpendicular to the light emission surface of the light guide. be able to.

In the above, in a liquid crystal display element in which active elements such as TFTs (thin film transistors) are arranged in a matrix, the electrodes are arranged in a matrix using STN and TN with a viewing angle in the range of contrast 10 or more. In a liquid crystal display element driven by time division by
The viewing angle is a range where the contrast is 3 or more. A liquid crystal display element using an active element has a high contrast ratio in the front, which is usually as high as 50 or more. Therefore, when the contrast ratio is 10 or less, humans feel that the image quality is deteriorated, and thus no further viewing angle is necessary. Furthermore, time-division driven TN, ST
Since the N liquid crystal display element has a contrast ratio of about 10 to 20 at the front, the contrast ratio of up to about 3 can be recognized as an image. Range.

Embodiment 2 A schematic diagram of one embodiment of the present invention is shown in FIG. FIG. 2 is a sectional view showing the structure of the backlight of the present invention. In the configuration of the present invention, the light source lamp 12 is built in the light guide body 11 that guides light, and the reflection plate 13 is provided on the back surface and the side surface of the light guide body 11. In addition, below the light guide 11, a reflector 1 having a curved shape depending on the distance from the lamp 12 is formed.
4 is equipped. Further, on the front emission side of the light guide 11, an optical path conversion element array 10 for changing the optical path of the light emitted from the light guide 11 is arranged. Lamp 1
Although 2 is arranged on both sides of the light guide 11, it is also possible to arrange it on only one side.

The structure is the same as that of the first embodiment except that the reflecting plate 14 is changed into a curved shape, and the same effect is obtained. In FIG. 1, a difference in brightness appears at the cuts of the reflection plate, but it can be made uniform in the plane by continuously changing the reflection plate into a curved shape.

Embodiment 3 FIG. 3 shows a schematic diagram of an embodiment of the present invention. FIG. 3 is a sectional view showing the structure of the backlight of the present invention. In the configuration of the present invention, the light source lamp 12 is built in the light guide body 11 that guides light, and the reflection plate 13 is provided on the back surface and the side surface of the light guide body 11. Further, by disposing a substance having a low refractive index, for example, a gas or a liquid, on the upper part of the light guide, the light from the lamp is refracted at the interface and is emitted to the front surface of the light guide. Further, on the front emission side of the light guide 11, an optical path conversion element array 10 for changing the optical path of the light emitted from the light guide 11 is arranged. The lamps 12 are arranged on both sides of the light guide body 11, but it is possible to arrange the lamps on only one side.

Light from the lamps arranged on both sides of the light guide is efficiently coupled into the light guide because the lamps are arranged inside the light guide. In addition, as shown in FIG. 9, a lens effect 17 is formed on the coupling portion of the light from the light guide 11 and the light from the lamp 12.
By making the shape spherical or elliptical so as to have the light, the light 53 from the lamp becomes light containing a lot of parallel light components. As shown in FIG. 3, the shape of the light guide body is configured so that it becomes thinner and the inclination changes as the distance from the lamp increases. As shown in FIG. 10, the slanted shape of the light guide body is such that the fine structure is arranged with an inclination of about 45 degrees so that parallel light from the lamp is efficiently reflected perpendicularly to the emission surface. It is preferable. However, when the inclination angle of the fine structure is 45 degrees, the light from the lamp is all parallel light. In reality, since the light has a certain degree of angular distribution, the angle can be varied from 25 degrees to 65 degrees depending on the position. It is changing. At this time, the pitch of the fine structure is preferably 100 μm or more so that the interference color does not appear due to the fine structure and the light is refracted efficiently.

The shape of the light guide is set as shown in FIG. 9 in order to make parallel light efficiently. However, in order to make the light enter the light guide efficiently, it is preferable that the convex directions of the lenses are opposite. good. At this time, the emission direction of light from the light guide and the in-plane uniformity can be controlled by the inclination angle of the fine structure of the reflection plate below the light guide and the shape of the reflection plate.

Except for the above description, the same effect can be obtained with the same configuration as the first embodiment.

Embodiment 4 FIG. 4 shows a schematic view of an embodiment of the present invention. FIG. 4 is a sectional view showing the structure of the backlight of the present invention. In the configuration of the present invention, the light source lamp 12 is built in the light guide body 11 that guides light, and the reflection plate 13 is provided on the back surface and the side surface of the light guide body 11. In addition, the light curtain 16 is arranged above the light guide body because the brightness right above the lamp becomes too high. This is a member having different transmittance and reflectance depending on the in-plane position where the portion where the light from the light guide is strong is reflected back, and the weak portion is transmitted backward with less back reflection. Further, on the front emission side of the light guide 11, an optical path conversion element array 10 for changing the optical path of the light emitted from the light guide 11 is arranged.

With the above structure, the light guide 11 can be hollow to reduce the weight of the backlight.

Conventionally, in such a direct type backlight, it has been difficult to reduce the thickness and make the in-plane distribution uniform. However, since the lamp of the light source is built in the light guide, it is efficiently incident on the light guide side, and a lamp with a small tube diameter (for example, 3
(mm) was able to achieve a thin backlight. Further, by arranging the light curtain and the optical path conversion element array on the front surface of the light guide, it was possible to obtain in-plane uniformity and directivity of emitted light, and match the viewing angle characteristics of the liquid crystal display element.

Embodiment 5 FIG. 5 shows a schematic view of an embodiment of the present invention. FIG. 5 is a sectional view showing the configuration of the liquid crystal display device of the present invention. The configuration of the present invention is a configuration in which the liquid crystal display element is arranged on the front surface of the backlight of Examples 1 to 4. One example of the liquid crystal display element has a structure as shown in FIG. 7, and has an optical path conversion element array on at least one of a pair of transparent substrates. An optical path changing element array 10 is provided on one of a pair of transparent substrates, a polarizing plate 31 is arranged inside thereof, and a transparent electrode 37 of an active element is arranged inside thereof, and an alignment film 35 for aligning liquid crystal in a certain direction. Liquid crystal is provided between the substrate coated with and rubbed, and the optical path conversion element array 10 arranged on the outside of the transparent substrate 38, and the polarizing film 32, the color filter 33, the electrodes 34, and the alignment film 35 deposited on the inside thereof in this order. The held liquid crystal display element 40 is the most suitable configuration for FIG. However, it can also be used in a conventional liquid crystal display device other than this structure.

As an example of the backlight, a light source lamp 12 is built in a light guide 11 for guiding light, and a reflection plate 13 is provided on the back and side surfaces of the light guide 11. Further, a reflector 14 whose shape is changed linearly according to the distance from the lamp 12 is provided below the light guide 11. Further, on the front emission side of the light guide 11, an optical path conversion element array 10 for changing the optical path of the light emitted from the light guide 11 is arranged. The lamps 12 are arranged on both sides of the light guide body 11, but it is possible to arrange the lamps on only one side. Further, when the liquid crystal display element is provided with the optical path conversion element array on the backlight side, the optical path conversion element array is not necessarily required on the light guide side of the backlight.

With the configuration as shown in FIG.
The light efficiently emitted perpendicularly to the exit surface of the light guide is focused by the optical path conversion element array 10 on the pixel portion of the liquid crystal display element. That is, in the liquid crystal display element using the active element, the ratio of the portion through which the current light is transmitted (aperture ratio)
Is about 30%, but by narrowing down to the pixel portion like the light 52, it is possible to increase the substantial aperture ratio and obtain a bright display. The backlight side optical path conversion element array of the liquid crystal display element is preferably arranged for each one minimum unit pixel, and the optical path conversion element on the front surface of the liquid crystal display element is shown in FIG.
When performing color display as described above, one optical path conversion element is arranged for every three pixels of RGB. By emitting light in units of 3 pixels, a beautiful RGB color mixture can be obtained.

The optical path conversion element array shown in FIG. 7 can use an optical fiber, a microlens array such as a concave lens and a convex lens, and a SELFOC lens array on both the back surface and the front surface. Preferably, the optical path conversion element array on the back surface is a microlens or a SELFOC lens in order to efficiently narrow the light, and the front surface is an optical fiber plate or a microlens array of concave lenses. It is also possible to reduce the viewing angle dependency by using an optical fiber plate or a microlens array of concave lenses.

Embodiment 6 A schematic diagram of an embodiment of the present invention is shown in FIG. FIG. 6 is a sectional view showing the configuration of the liquid crystal display device of the present invention. The configuration of the present invention is a configuration in which the front surface of the backlight of each of Examples 1 to 4 is used as one substrate of the liquid crystal display element. An embodiment of the liquid crystal display device has a structure as shown in FIG. 7, and a light guide of a backlight is used in place of at least one of the pair of transparent substrates.

As an example of the backlight, a light source lamp 12 is built in a light guide body 11 for guiding light, and a reflection plate 13 is provided on the back and side surfaces of the light guide body 11. In addition, a reflection plate 14 having a curved shape depending on the distance from the lamp 12 is provided below the light guide 11. Further, an optical path conversion element array 10 for converting the optical path of the light emitted from the light guide body 11 is arranged on the front emission side of the light guide body 11, and the light guide body is provided on one side of the liquid crystal display element. Also serves as the substrate. The lamp 12 is the light guide 1.
Although it is arranged on both sides of 1, it is possible to arrange it on only one side.

By adopting the configuration as shown in FIG.
The light efficiently emitted perpendicularly to the exit surface of the light guide is focused by the optical path conversion element array 10 on the pixel portion of the liquid crystal display element. That is, in the liquid crystal display element using the active element, the ratio of the portion through which the current light is transmitted (aperture ratio)
Is about 30%, but by narrowing down to the pixel portion like the light 52, it is possible to increase the substantial aperture ratio and obtain a bright display. Further, since one substrate of the liquid crystal display element also serves as a light guide, it is possible to minimize the deviation from the pixels when disposing the optical path conversion element array, and to improve the actual aperture ratio, Use efficiency can be improved.

Other configurations and the effects thereof are the same as those of the fifth embodiment.

Embodiment 7 FIG. 7 shows a schematic view of an embodiment of the present invention. FIG. 7 is a projection diagram showing a configuration of an application example of the liquid crystal display device of the present invention. The configuration of the present invention is an apparatus using the backlight and the liquid crystal display device of Examples 1 to 6. According to the present invention, a thin liquid crystal display device having high light utilization efficiency and brightness can be obtained. Therefore, as shown in FIG. 7, the liquid crystal display device can be used as a wall of a room or a surface of a table. By using it in this way, you can always get information in the house. Further, if the liquid crystal display device is provided with a sensing means such as a pen input and a touch sensor, information processing,
It can also be used as a home control device.

Furthermore, by using the backlight and the liquid crystal display device of the present invention as a display device of a personal computer or a television, a thin display with low power consumption can be obtained, and the work can be done without taking up space.

Particularly, when the liquid crystal display device of the present invention is used as a monitor for OA equipment, the screen size is 8 inches or more diagonally because of the ease of viewing and handling of the display screen.
It is preferable that the thickness is 7 mm or less. In particular, a liquid crystal display element using an active element is required to have a small aperture ratio and high brightness of a backlight. When the screen size is 8 inches or more, the surface brightness is evenly thin and bright. 2
It was difficult to produce a backlight of 000 nits or more. Therefore, the liquid crystal display device of the present invention has a screen size of
The effect is great when used in a liquid crystal display device having a diagonal of 8 inches or more and a thickness of 7 mm or less.

The shape of the light guide of the present invention is not limited to a manufacturing method such as a method in which a mold is made of metal and the material of the light guide is poured into the mold. There are various methods for the reflector, such as sputtering, vapor deposition, liquid coating, and attachment of the reflector, but the manufacturing method is not limited.

[0039]

EFFECTS OF THE INVENTION By making the shape of the reflection plate on the back surface of the light guide thin according to the distance from the lamp, the in-plane uniformity of the emitted light distribution is maintained, and the fine structure is provided on the surface of the reflection plate. The light entering the light guide from the lamp is reflected with directivity and emitted from the light guide. In this configuration, since a scattering plate is not used, a thin backlight with high absorption efficiency without absorption loss can be configured.

By disposing an optical path conversion element array (for example, an optical fiber, a microlens, a SELFOC lens, etc.) for each pixel of the liquid crystal display element, light is transmitted only in the effective area of the pixel portion, and the effective aperture ratio is increased. Can be improved. Furthermore, by using the light guide as a substrate on one side of the liquid crystal display element, the liquid crystal display element and the backlight can be integrally designed, and a thin and highly efficient liquid crystal display device can be obtained.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of a backlight of the present invention.

FIG. 2 is a diagram showing an embodiment of the backlight of the present invention.

FIG. 3 is a diagram showing an embodiment of the backlight of the present invention.

FIG. 4 is a diagram showing an embodiment of the backlight of the present invention.

FIG. 5 is a diagram showing an embodiment of a liquid crystal display device of the present invention.

FIG. 6 is a diagram showing an embodiment of a liquid crystal display device of the present invention.

FIG. 7 is a diagram showing an example of a liquid crystal display device of the present invention.

FIG. 8 is a diagram showing an application example of the liquid crystal display device of the present invention.

FIG. 9 is a diagram showing an embodiment of the backlight of the present invention.

FIG. 10 is a diagram showing an embodiment of the backlight of the present invention.

FIG. 11 is a diagram showing a conventional backlight configuration.

[Explanation of symbols]

10 ... Optical path changing element array, 11 ... Light guide, 12 ... Lamp, 13 ... Reflector, 14 ... Light guide reflector, 15 ... Diffuser, 16 ... Light curtain, 17 ... Condenser lens, 20 ...
Backlight, 30 ... Liquid crystal display element, 31 ... Lower polarizing plate, 32 ... Upper polarizing plate, 33 ... Color filter, 34 ...
Transparent electrode, 35 ... Alignment film, 36 ... Liquid crystal layer, 37 ... Transparent electrode of active element, 38 ... Upper transparent substrate, 40 ... Liquid crystal display element, 50 ... Incident light, 51 ... Outgoing light, 52 ... Transmissive liquid crystal element Light, 53 ... Incident light from the lamp to the light guide,
60 ... Liquid crystal display device of the present invention, 70 ... Room wall, 71 ...
Desk or table.

Claims (8)

[Claims] 1. A backlight for a liquid crystal display device, comprising a light source on the back surface of a liquid crystal display element, a light guide body for guiding light from the light source, and a reflector on the back surface of the light guide body, wherein the lamp of the light source is for guiding the light. A backlight having a fine structure, which is built in an optical body, wherein the shape of the reflection plate on the back surface of the light guide body changes according to the distance from the light source, and the surface of the reflection plate has a fine structure. 2. A liquid crystal display device comprising a liquid crystal display element, a light source on the back surface of the liquid crystal display element, a light guide body for guiding light from the light source, and a backlight having a reflection plate on the back surface of the light guide body. In, the lamp of the light source is built in the light guide, the shape of the reflection plate on the back surface of the light guide changes according to the distance from the light source, and the shape of the reflector changes depending on the distance from the lamp of the light source. A backlight characterized in that the light guide has a refractive index distribution and has a fine structure with an interface thereof. 3. A liquid crystal display device comprising a liquid crystal display element, a light source on the back surface of the liquid crystal display element, a light guide for guiding light from the light source, and a backlight having a reflector on the back surface of the light guide. In the liquid crystal display device, the light guide also serves as one of the transparent substrates of the liquid crystal display element. 4. A liquid crystal display device comprising a liquid crystal display element, a light source on the back surface of the liquid crystal display element, a light guide for guiding light from the light source, and a backlight having a reflector on the back surface of the light guide. In which the lamp of the light source is built in the light guide, the shape of the reflection plate on the back surface of the light guide changes according to the distance from the light source, and the surface of the reflection plate has a fine structure. A liquid crystal display device comprising: the backlight and the liquid crystal display element having an optical path conversion element array on at least one of a transparent substrate on the front surface thereof. 5. A liquid crystal display device comprising a liquid crystal display element, a light source on the back surface of the liquid crystal display element, a light guide for guiding light from the light source, and a reflector on the back surface of the light guide. The display element has a screen size of 8 inches or more diagonally,
A liquid crystal display device, which is a transmissive liquid crystal display device in which active elements are arranged in a matrix, and a thickness of a backlight provided on the back surface of the liquid crystal display element is 7 mm or less. 6. A liquid crystal display device comprising a liquid crystal display element, a light source on the back surface of the liquid crystal display element, a light guide body for guiding light from the light source, and a backlight having a reflection plate on the back surface of the light guide body. In which the lamp of the light source is built in the light guide, the shape of the reflection plate on the back surface of the light guide changes according to the distance from the light source, and the surface of the reflection plate has a fine structure. The liquid crystal display device, wherein the backlight and the liquid crystal display element arranged in front of the backlight have substantially the same viewing angle characteristics of light. 7. A liquid crystal display device, wherein the liquid crystal display backlight or liquid crystal display device according to claim 1 is used as a display device for electronic equipment such as a personal computer and a television. 8. A liquid crystal display device comprising the backlight for liquid crystal display or the liquid crystal display device according to any one of claims 1 to 6 for both interior and practical use such as a wall of a room or an upper portion of a desk.