JPH09179118A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal display device capable of realizing the thinning and the lightening of the device without lowering contrast. SOLUTION: A lower transparent base plate 16 is provided with a polarizing glass 17 and a transparent electrode 18 successively on its upper surface, and a reflection sheet 22 where a printing pattern 24 irregularly reflecting light S and emitting it from the upper surface is formed is provided on its lower surface. An upper transparaent base plate 20 is provided with the transparent electrode 18 on its lower surface, and an upper polarizing plate 21 on its upper surface. Then, a liquid crystal agent 19 is sealed in a space between the base plates 16 and 20, and a lamp 23 is set on the side surface of the base plate 16.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device, and more particularly to a liquid crystal display device having a flat light source device.

[0002]

2. Description of the Related Art FIG. 3 shows the structure of a conventional liquid crystal display device. In this liquid crystal display device 1, a liquid crystal agent 4 is put between an upper transparent substrate 2 and a lower transparent substrate 3 and sealed with a sealant 5, and an upper polarizing plate 6 and a lower polarizing plate 7 are provided on the front and back surfaces thereof. Each has a structure in which the flat light source device 8 is attached and the flat light source device 8 is arranged on the back side. The liquid crystal agent 4 is formed on the upper transparent substrate 2.
Pixels composed of a transparent electrode 9 for driving and electric circuits (not shown) are arranged in a matrix. Also,
The flat light source device 8 is configured so that the light S emitted from the lamp 10 is reflected by the reflection cover 11 and is incident on the end surface of the light guide plate 12. Then, the light S incident from the end face is radiated in a plane from the opposite side of the reflection sheet 13 due to diffused reflection inside the light guide plate 12 and reflection at the reflection sheet 13.

Next, the principle of display will be described. First, the light S incident from the flat light source device 8 is first reflected by the lower polarizing plate 7.
Results in linearly polarized light. Then, the polarized light is rotated by 90 ° by the action of the liquid crystal agent 4. On the other hand, since the polarization angle of the upper polarizing plate 6 is deviated by 90 ° with respect to the lower polarizing plate 7, the liquid crystal agent 4 causes 90 °.
The polarized light can pass through the upper polarizing plate 6. When this pixel is viewed from above in this state, the pixel appears to be lit. Next, when a part of the transparent electrodes 9 arranged in a matrix is electrically driven, the liquid crystal agent 4 of the pixel to which the electric field is applied loses the property of rotating the polarization angle, so that the light passing through the pixel is It cannot pass through the upper polarizing plate 6, and when this pixel is viewed from above, it looks as if the pixel is off. In this way, an image is formed and displayed by controlling the brightness of the pixels arranged in a matrix.

The first in the conventional liquid crystal display device of this type
However, it is difficult to reduce the thickness of the liquid crystal display device. The reason is that the light guide plate 12 is installed under the lower polarizing plate 7 for the purpose of making the light S of the lamp 10 planar, so that the total thickness of the liquid crystal display device 1 is equal to the thickness of the light guide plate 12. This is because the thickness becomes 4 to 6 mm). Next, the second
However, it is difficult to reduce the weight of the liquid crystal display device. The reason is that the light guide plate 12 generally uses an acrylic plate having a high light transmittance for the purpose, but the specific gravity of the acrylic plate is about 1.2, and the weight of a display device having a large display screen is large. Is difficult to reduce.

Now, three publicly known examples proposed as measures against these problems will be described below. First, in Japanese Utility Model Application Laid-Open No. 60-68281, a light source is provided in at least a part of a step portion formed by a front transparent substrate (front glass substrate) and a rear transparent substrate (rear glass substrate). A liquid crystal display device (known example 1) is disclosed in which a frame-shaped light guide plate made of resin or glass is arranged and illumination is performed from a transparent substrate on the front side. Further, Japanese Utility Model Laid-Open No. 62-91622 discloses a liquid crystal display device using a guest host effect or a DSM effect, in which a transparent substrate (lower substrate) on the back side has a light guide plate function ( Known example 2) is disclosed.

Further, in Japanese Unexamined Patent Publication No. 4-349428, a transparent substrate (rear glass plate) on the rear side is used as a light guide plate, and a polarizing plate is removed to provide a liquid crystal layer having a larger refractive index when transparent than the glass plate. Liquid crystal display device used (known example 3)
Is disclosed. In this liquid crystal display device, when displaying a dark pixel, liquid crystal molecules are driven by electrodes so that their major axis directions are parallel to the glass surface, and the light of the lamp is totally reflected on the glass surface to be opaque. In the case of displaying bright pixels, the liquid crystal molecules are driven by electrodes so as to be perpendicular to the glass surface so as to become transparent pixels. An image is formed using such a pixel brightness control method.

[0007]

However, the above-mentioned three known examples aiming to make the liquid crystal display device thinner have the following problems, respectively. In the case of the known example 1, nearly half of the light emitted from the frame-shaped light guide plate passes through the front transparent substrate (front glass substrate) side without passing through the pixels, so that the brightness near the light guide plate is high and the display center is dark. However, the brightness is not uniform. In addition, since there is no pixel, the brightness near the light guide plate is high but the contrast is low. In the case of the known example 2, since the transparent substrate (lower substrate) on the back side is simply used instead of the light guide plate, it can be applied only to the liquid crystal display device using the guest-host effect or the DMS effect. The liquid crystal display device of the guest-host effect cannot display a color in principle and is difficult to display a gradation due to its principle.
The liquid crystal display device using the effect has a defect that the contrast is low, and thus it is hardly used at present.

Further, in the case of the known example 3, since the difference in the refractive index between the glass and the liquid crystal agent is utilized, the light with a small incident angle of the light passing through the glass surface and the pixel is totally reflected. Light incident from other angles all passes through the pixel, so that the difference in luminance between the transparent pixel and the opaque pixel is small and the contrast is low.

The present invention has been made in order to solve the above problems, and an object of the present invention is to provide a liquid crystal display device which can be made thinner and lighter without deterioration in contrast. .

[0010]

In order to achieve the above object, a liquid crystal display device of the present invention comprises a lower transparent substrate having a polarizing glass and a transparent electrode sequentially provided on the upper surface thereof, and a side surface of the lower transparent substrate. A light source attached to the lower transparent substrate, a reflecting portion provided on the lower surface of the lower transparent substrate to diffusely reflect the light incident from the light source and emit the light from the upper surface of the lower transparent substrate, and a transparent electrode on the lower surface. It is characterized by having an upper transparent substrate provided with an upper polarizing plate, and a liquid crystal agent enclosed between the lower transparent substrate and the upper transparent substrate. Specifically, the reflecting portion may be formed of a reflecting sheet on which a pattern that diffusely reflects or absorbs light is printed, or a concavo-convex portion formed on the lower surface of the lower transparent substrate and a reflecting sheet.

In the liquid crystal display device of the present invention, the light from the light source is made incident on the side surface of the lower transparent substrate, then reflected by the reflecting portion and emitted from the upper surface of the lower transparent substrate.
Due to the configuration of illuminating the pixels, it is not necessary to use a conventional light guide plate. Further, in a liquid crystal display device that utilizes the polarization characteristics of a liquid crystal agent, such as the TFT system or STN system, which is the current mainstream of liquid crystal display devices, in principle, the light transmitted through pixels sandwiching the liquid crystal agent is previously It needs to be polarized. On the other hand, in the case of the present invention, the light incident on the lower transparent substrate is diffusely reflected by the reflecting portion, so that the lower transparent substrate functions like a surface emitting light source having uniform brightness and irradiates the pixels with light. To do. At that time, since the light from the light source is polarized by the polarizing glass provided on the upper surface of the lower transparent substrate, it is possible to display an image by electrically controlling the liquid crystal agent.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a first embodiment of the present invention will be described with reference to FIG. FIG. 1 is a diagram showing a liquid crystal display device 15 of the present embodiment, in which reference numeral 16 is a lower transparent substrate, 17 is polarizing glass, 18 is a transparent electrode, 19 is a liquid crystal agent, 20 is an upper transparent substrate, Reference numeral 21 is an upper polarizing plate, 22 is a reflection sheet (reflection portion), and 23 is a lamp (light source).

On the lower transparent substrate 16, a polarizing glass 17 and a transparent electrode 18 are sequentially provided on the upper surface thereof, and a reflection sheet 22 is provided on the lower surface thereof. A pattern 24 that diffuses or absorbs light is printed on the upper surface of the reflection sheet 22, and the printed pattern 24 side is fixed to the lower transparent substrate 16. On the other hand, the upper transparent substrate 20 is provided with an upper polarizing plate 21 on its upper surface and a transparent electrode 18 on its lower surface. A sealant 25 is provided between the lower transparent substrate 16 and the upper transparent substrate 20, and the lower transparent substrate 1
6, the liquid crystal agent 19 is enclosed in a space surrounded by the upper transparent substrate 20 and the sealant 25.

Further, one side of the lower transparent substrate 16 having a rectangular shape in plan view extends outwardly of the upper transparent substrate 20, and the liquid crystal display device 15 is provided on the side surface of the extended lower transparent substrate 16 at the end thereof. A lamp 23 that serves as a light source is installed. Further, the reflection cover 26 is fixed to the end of the lower transparent substrate 16 so as to cover the lamp 23 and the end of the lower transparent substrate 16.
The reflective cover 26 is for allowing the light of the lamp 23 to enter the end side surface of the lower transparent substrate 16 without waste.

The printed pattern 2 on the reflection sheet 22
In No. 4, the print density and the print distribution of the pattern are adjusted so that the light of the lamp 23 is uniformly diffused and reflected to the liquid crystal agent 19 side.

The operation of the liquid crystal display device 15 having the above structure will be described. First, the light S from the lamp 23 is incident from the side surface of the lower transparent substrate 16 directly or through the reflection cover 26. Then, the light S incident on the lower transparent substrate 16
Is a light of uniform brightness due to the action of the print pattern 24 located between the lower transparent substrate 16 and the reflection sheet 22,
The polarized glass 17 is radiated. Next, when the light S passes through the polarizing glass 17, the light S is polarized and the transparent electrode 1
8 is used to electrically change the polarization characteristic of the liquid crystal agent 19 to control the polarization angle of light. Then, the amount of light transmitted through the upper polarizing plate 21 changes depending on the controlled polarization angle of the light. In this way, an image is displayed by electrically controlling the brightness of the pixels.

According to the liquid crystal display device 15 of the present embodiment, after the light of the lamp 23 is made incident from the side surface of the lower transparent substrate 16, it is reflected by the reflecting sheet 22 and the lower transparent substrate 16 is made.
Since it is configured to illuminate the pixels by emitting light from the upper surface of the device, it is not necessary to use the light guide plate in the conventional liquid crystal display device. Usually, the acrylic light guide plate has a thickness of 4 to
6mm, diagonal size of the screen is 29cm, the weight is 20
Since the weight of the liquid crystal display device is about 0 to 250 g, the light guide plate is not required, so that the liquid crystal display device can be made thinner and lighter.

Further, since the polarizing glass 17 is arranged on the optical path between the pixel composed of the transparent electrode 18 and the liquid crystal agent 19 and the lamp 23, the TFT which is the mainstream of the present liquid crystal display device.
The present invention can be applied to a liquid crystal display device of the STN system or STN system, and the above effect can be obtained without lowering the contrast.

Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 2 is a diagram showing the liquid crystal display device 28 of the present embodiment, but the liquid crystal display device of the present embodiment is different from the device of the first embodiment only in the configuration of the reflecting portion of the lower transparent substrate. Therefore, common components are denoted by the same reference numerals as those in FIG. 1, and description thereof is omitted.

A reflection sheet 29 is provided on the lower surface of the lower transparent substrate 16.
However, there is no printing pattern on the reflection sheet 29 as in the first embodiment, and the lower transparent substrate 16 itself is provided with fine unevenness processing 30. The unevenness processing section 30 diffuses and reflects the light S incident on the lower transparent substrate 16 so that light having uniform brightness is emitted from the upper surface of the lower transparent substrate 16.

Also in the case of the liquid crystal display device 28 of the present embodiment, the device is made thin without lowering the contrast.
It is possible to obtain the same effect as that of the first embodiment that the weight can be reduced. Further, in the case of the present embodiment, since the lower transparent substrate 16 itself is processed to form the reflecting portion, it is possible to enhance the durability against changes in the temperature and humidity of the outside air as compared with the case of using a printing pattern. .

The technical scope of the present invention is not limited to the above-mentioned embodiment, and various modifications can be made without departing from the spirit of the present invention.

[0023]

As described above in detail, according to the liquid crystal display device of the present invention, the light is made incident on the side surface of the lower transparent substrate and then reflected by the reflecting portion so that the upper surface of the lower transparent substrate. Since it is configured to illuminate the pixels by emitting light from the liquid crystal display device, and the light guide plate in the conventional liquid crystal display device is not required, it is possible to reduce the thickness and weight of the entire liquid crystal display device.
Further, since the polarizing glass is arranged on the optical path between the light source and the pixel composed of the transparent electrode and the liquid crystal agent, the present invention can be applied to the TFT type or STN type liquid crystal display device which is the mainstream of the present liquid crystal display device. Therefore, it is possible to obtain the above-mentioned effects without causing a decrease in contrast.

[Brief description of the drawings]

FIG. 1 is a vertical sectional view of a liquid crystal display device according to a first embodiment of the present invention.

FIG. 2 is a vertical sectional view of a liquid crystal display device according to a second embodiment of the present invention.

FIG. 3 is a vertical cross-sectional view of a conventional liquid crystal display device.

[Explanation of symbols]

 15, 28 Liquid crystal display device 16 Lower transparent substrate 17 Polarizing glass 18 Transparent electrode 19 Liquid crystal agent 20 Upper transparent substrate 21 Upper polarizing plate 22, 29 Reflective sheet (reflective part) 23 Lamp (light source) 24 Printing pattern 25 Sealant 26 Reflective cover 30 Concavo-convex processed part (reflection part) S light

Claims (3)

[Claims] 1. A liquid crystal display device in which a liquid crystal agent is enclosed between two transparent substrates each provided with a transparent electrode, and a display is performed by utilizing the polarization characteristics of the liquid crystal agent. And a light source attached to the side surface of the lower transparent substrate, and a lower transparent substrate that is provided on the lower surface of the lower transparent substrate to diffusely reflect the light incident from the light source. A reflective part that is emitted from the upper surface of the substrate, an upper transparent substrate that is provided with a transparent electrode on the lower surface and an upper polarizing plate on the upper surface, and a liquid crystal agent enclosed between the lower transparent substrate and the upper transparent substrate. A liquid crystal display device having. 2. The liquid crystal display device according to claim 1, wherein the reflection portion is formed of a reflection sheet on which a pattern that diffuses or absorbs light is printed. 3. The liquid crystal display device according to claim 1, wherein the reflection portion includes an uneven processing portion formed on a lower surface of the lower transparent substrate and a reflection sheet.