JPH08171087A - Liquid crystal display - Google Patents

Abstract

(57) [Abstract] [PROBLEMS] To provide a simple and inexpensive liquid crystal display device that enhances the utilization efficiency of light emitted from a light source device, has high brightness, and maintains image clarity. [Structure] In a liquid crystal display device having a light source device, a rear polarizing plate, a liquid crystal cell, and a front polarizing plate as a basic structure, a lens sheet is further arranged between the light source device and the rear polarizing plate, and a light scattering plate is arranged between the liquid crystal cell and the front polarizing plate. A liquid crystal display device having the above structure. Further, in a liquid crystal display device having a light source device, a rear polarizing plate, a liquid crystal cell, and a front polarizing plate as a basic configuration, a lens sheet is further arranged between the light source device and the rear polarizing plate, and a light scattering plate is arranged in front of the front polarizing plate. A liquid crystal display device characterized by the following.

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 such as a liquid crystal display terminal of an office automation equipment such as a liquid crystal television and a computer.

[0002]

2. Description of the Related Art In recent years, liquid crystal display devices have the characteristics of thinness, light weight, and high image quality, and are used in liquid crystal televisions, computers, and the like.
It is widely used as a liquid crystal display terminal for device A. Currently, liquid crystal display devices are TN type, STN type,
There is a TFT method, etc., but basically these are all
A light source device, a polarizing plate, a liquid crystal cell, and a polarizing plate are arranged in this order, and an optical compensator and a color filter are further arranged if necessary. These liquid crystal display devices have a narrow viewing angle that can satisfy the image quality because the brightness and contrast of the image are significantly reduced when viewed from the vertical direction and / or the horizontal direction with respect to the display screen.

As a method of expanding the viewing angle of this liquid crystal display device, a method of improving the alignment of liquid crystal molecules in a liquid crystal cell has been proposed. Further, it has been proposed to dispose a light scattering plate on the front surface of the liquid crystal display device.

[0004]

As a method for expanding the viewing angle of a liquid crystal display device, it is said that a method for improving the liquid crystal molecule alignment of a liquid crystal cell has been established practically because the manufacturing process of the liquid crystal cell is complicated. It's hard. Further, by simply disposing the light scattering plate on the front surface of the liquid crystal display device, the light scattering plate scatters the light emitted from the surface of the liquid crystal cell in the normal direction to a wide angle range to thereby increase the viewing angle. Not only does the brightness significantly decrease due to the enlargement, but also the direct light and scattered light enter the eyes at the same time, and the sharpness of the image is lost.

Therefore, the present invention provides a liquid crystal display device which is relatively simple, improves the light utilization efficiency of the light source device, and has high brightness and sharpness despite a wide viewing angle.

[0006]

The present invention relates to a liquid crystal display device having a light source device, a back polarizing plate, a liquid crystal cell, and a front polarizing plate as a basic structure, further comprising a lens sheet between the light source device and the back polarizing plate. And a liquid crystal display device characterized in that a light scattering plate is arranged between the front polarizing plate, further in a liquid crystal display device having a light source device, a back polarizing plate, a liquid crystal cell, a front polarizing plate as a basic configuration, Further, the liquid crystal display device is characterized in that a lens sheet is arranged between the light source device and the rear polarizing plate, and a light scattering plate is arranged in front of the front polarizing plate.

In the present invention, the light source device, the rear polarizing plate,
A liquid crystal display device having a liquid crystal cell and a front polarizing plate as a basic configuration has various types depending on the mechanism of the liquid crystal cell,
At least a light source device, a polarizing plate, a liquid crystal cell, and a polarizing plate are formed of these four constituent elements in this order, and if necessary, other constituent elements such as an optical compensation plate and a color filter are arranged in these four constituent elements. It is installed between elements or before and after. Further, any constituent element may be a well-known and commonly used element, and is not particularly limited. In addition, in these configurations, since there are two polarizing plates, in the present invention, in order to distinguish them, the one between the light source device and the liquid crystal cell is placed on the front side of the display further than the rear polarizing plate and the liquid crystal cell. Was referred to as the front polarizing plate.

In the present invention, the lens sheet arranged between the light source device and the rear polarizing plate includes what is called a lens film or a prism sheet. The lens sheet of the present invention is for concentrating the light from the light source device in the direction perpendicular to the surface of the liquid crystal cell. In other words, it is desirable that the direction of the light from the light source device is originally concentrated in the direction perpendicular to the surface of the liquid crystal cell, but in reality, the light spreads widely and even the main direction of the light is not necessarily on the surface of the liquid crystal cell. Not oriented vertically. For example, in the one-lamp edge light light guide plate type light source device, about 40 ° to the normal line of the light emitting surface.
Generally, there is a peak of emitted light at an angle of 60 °.
Therefore, the lens sheet of the present invention has a characteristic in which the transmitted light of the lens sheet is concentrated in the direction perpendicular to the surface of the liquid crystal cell according to the light emission characteristics of the light source device used, and in particular, ± 80% of the total transmitted light in the range of 30 °
It is desirable that it has the characteristic of concentrating. Further, two or more lens sheets may be used to express this characteristic. The lens sheet shape includes a prism-shaped prism arrayed in a sheet shape, a plurality of pyramids or cones arrayed in a sheet shape, an elliptic cylinder plano-convex lens arrayed in a sheet shape, and an elliptic spherical plano-convex lens. Multiple sheets arranged in a sheet,
Sheet-shaped cylindrical plano-concave lenses, sheet-shaped spherical plano-concave lenses, prism sheet with flat top, prism pyramid or cone with flat top There are a plurality of those arranged side by side or those having a sinusoidal cross section, but the shape is not particularly limited.

The light-scattering plate used in the present invention has a function of spreading light from the liquid crystal cell mainly in a direction perpendicular to the surface thereof vertically and horizontally. Specifically, it is suitable that the half-width of the transmitted light intensity angular distribution is 20 ° to 90 ° when light is made incident perpendicularly to the surface of the light scattering plate. This light scattering plate expands the viewing angle of the liquid crystal display device.

The light-scattering plate may be a known one as long as it has the above-mentioned characteristics and is not particularly limited.
For example, glass or a transparent resin as a base material, in which a fine particle having a different refractive index is dispersed into a plate shape, specifically, acrylic resin, styrene resin, polycarbonate, silica, , Alumina, titanium oxide and the like, and fine particles of another kind of resin selected from acrylic resin, styrene resin, silicon resin and the like.

As the light scattering plate, a composition containing two or more kinds of photopolymerizable monomers or oligomers having a refractive index different from each other by 0.01 or more is formed into a film,
Then, a viewing angle widening filter composed of a light scattering plate obtained by irradiating ultraviolet rays can be used. The combination of the photopolymerizable monomer or oligomer may be two kinds selected from monomers, a combination of one kind of monomer and one kind of oligomer, two kinds selected from an oligomer, or one or more kinds of monomers in combination of these. Alternatively, an oligomer may be added. In these combinations, at least two of them have a refractive index of 0.01 or more. Further, at least one of them preferably has two or more photopolymerizable functional groups.

Specific examples of the photopolymerizable monomer or oligomer include 2,4,6-tribromophenyl acrylate, tribromophenoxyethyl acrylate,
Monoylphenoxyethyl acrylate, 2-hydroxy-3-phenoxypropyl acrylate, phenylcarbitol acrylate, phenoxyethyl acrylate, and other monomers, and one or more oligomers such as ethylene oxide-modified bisphenol A diepoxy acrylate, and triethylene glycol diacrylate, One or more combinations of monomers such as polyethylene glycol diacrylate, neopentyl glycol diacrylate, 1,6-hexanediol diacrylate and oligomers such as polyol polyacrylate, modified polyol polyacrylate, polybutadiene acrylate and polyether urethane acrylate can give. These monomers or oligomers are not limited to those described above, and at least 2 used in combination.
Refractive index difference of 0.01 kinds of monomers or oligomers is 0.01
It is also possible to use other photopolymerizable monomers or oligomers as long as they are above.

A photopolymerization initiator is preferably used in the composition containing the photopolymerizable monomer or oligomer in order to improve its curability. Examples of the photopolymerization initiator include benzophenone, benzyl, Michler's ketone, 2-chlorothioxanthone, 2,4-diethylthioxanthone, benzoin ethyl ether, diethoxyacetophenone, benzyl dimethyl ketal, 2-
Examples thereof include hydroxy-2-methylpiophenone and 1-hydroxycyclohexyl phenyl ketone.

The composition containing the photopolymerizable monomer or oligomer is applied to, for example, a substrate or
Alternatively, it is enclosed in a cell to form a film. Then, the film-shaped composition is irradiated with ultraviolet rays to be photopolymerized and cured to obtain a light-scattering plate used in the present invention.

The light scattering plate of the present invention may be placed in front of the liquid crystal cell. That is, it is arranged between the liquid crystal cell and the front polarizing plate or further in front of the front polarizing plate. Although the liquid crystal display device is provided with an optical compensator, a color filter, etc. in front of the liquid crystal cell depending on its method, the order of the light scattering plate of the present invention is not limited as long as it is in front of the liquid crystal cell. Absent.

[0016]

EXAMPLES The present invention will be described below with reference to examples.
A schematic diagram of the liquid crystal display device used in the examples is shown in FIG.
However, the present invention is not limited to these examples. The devices, parts, and measuring methods used in the examples are as follows. Liquid crystal display: Liquid crystal color TV 4E manufactured by Sharp Corporation
Based on the display unit of -L1, it was used after being modified for the example. Light source device: A one-lamp edge light light guide plate type (manufactured by Meitaku System Co., Ltd.) having the brightness distribution shown in FIG. 2 was used. Lens sheet: An elliptic cylinder plano-convex lens sheet (manufactured by Dai Nippon Printing Co., Ltd.) having a luminance distribution shown in FIG. 3 when light in the vertical direction is transmitted through the sheet. -Light scattering plate-1: 100 parts by weight of acrylic resin (Oroglass HFI-10 manufactured by Rohm & Haas Co.) was kneaded with 25 parts by weight of crosslinked polystyrene beads having an average particle size of 20 µ, and the thickness was 75 µ.
The light-scattering plate having the light-scattering characteristics shown in FIG.・ Light scattering plate-2: Refractive index different from each other by 0.01 or more 2
Polyether urethane acrylate having an average molecular weight of about 6000 obtained by reacting polypropylene glycol with hexamethylene diisocyanate and 2-hydroxyethyl acrylate as a resin composition for a light scattering plate containing one or more photopolymerizable monomers or oligomers (Refractive index 1.460) 30 parts by weight of 2,4,6-tribromophenyl acrylate (refractive index 1.576) 30 parts by weight
Parts by weight, 30 parts by weight of 2-hydroxy-3-phenoxypropyl acrylate (refractive index 1.526), and 1.5 parts by weight of 2-hydroxy-2-methylpropiophenone as a photopolymerization initiator were added and mixed. 188μ of the resin composition
A m-thick PET film was applied and photopolymerized and cured using a rod-shaped high-pressure mercury lamp to prepare a film having a scattering angle range defined by a haze value of 60% or more of -15 ° to -45 °. Then, the resin composition is applied onto the light-scattering plate, and similarly subjected to photopolymerization and curing using a rod-shaped high-pressure mercury lamp, so that the scattering angle range of the first layer is −15 ° to −45.
A laminated sheet having a second layer of 0 ° to 30 ° was prepared and used.・ White brightness, black brightness: A digital pattern generator (MTSG-1000 manufactured by Sony Corporation) displays white and black window patterns on the display screen of the liquid crystal display device, and a brightness meter (LS-manufactured by Minolta Camera Co., Ltd.) 100) in the range of visual angle ± 60 °. (Candela / m ² )

Comparative Example 1 The white brightness and the black brightness of a liquid crystal display device in which a light source device was combined with the above liquid crystal display portion were measured. Results are shown in FIG. White brightness has a viewing angle of −55 ° to + 45 °
Up to is a range with sufficient brightness, but from the viewpoint of the contrast of white and black brightness, which indicates the degree to which an image can be recognized,
The range is from −30 ° to + 20 °.

Comparative Example 2 Comparative Example 2 was carried out in the same manner as Comparative Example 1 except that a lens sheet was placed between the liquid crystal display section and the light source device to form a liquid crystal display device. FIG. 6 shows the results. Although the white brightness increased only in the vicinity of the viewing angle of 0 °, the contrast of sufficient white / black brightness was still in the range of −30 ° to + 20 ° and comparable to that of Comparative Example 1.

Comparative Example 3 The same procedure as in Comparative Example 1 was carried out except that the liquid crystal display was prepared by disposing the light scattering plate-1 on the front surface of the front polarizing plate in the liquid crystal display section. FIG. 7 shows the results. The sufficient white / black brightness contrast was −30 ° to + 15 °, and the viewing angle was narrower than that of Comparative Example 1.

Example 1 A comparison was made except that a lens sheet was placed between the liquid crystal display section and the light source device, and a light scattering plate-1 was placed in front of the front polarizing plate in the liquid crystal display section to form a liquid crystal display apparatus. The procedure was as in Example 1.
The results are shown in Fig. 8. White brightness is -30 ° to +30
Up to ° is a range having sufficient luminance, and the contrast of sufficient white / black luminance is −30 ° to + 25 °, and eventually the viewing angle is −30 ° to + 25 °, which is wider than that of Comparative Example 1.
Moreover, the brightness has increased.

Comparative Example 4 The procedure of Comparative Example 1 was repeated, except that a light scattering plate-2 was placed between the liquid crystal cell in the liquid crystal display section and the front polarizing plate to form a liquid crystal display device. The results are shown in Fig. 9. The sufficient white / black brightness contrast was −40 ° to + 25 °.

Example 2 A comparison was made except that a lens sheet was arranged between the liquid crystal display section and the light source device, and a light scattering plate-2 was arranged in front of the front polarizing plate in the liquid crystal display section to form a liquid crystal display apparatus. The procedure was as in Example 1.
The results are shown in Fig. 10. White brightness is -35 ° to +3
Up to 5 ° is a range with sufficient brightness, and the contrast of sufficient white / black brightness is −40 ° to + 35 °, and eventually the viewing angle is −35 ° to + 35 °, which is wider than that of Comparative Example 1. The brightness has also increased.

[0023]

According to the liquid crystal display device of the present invention, the utilization efficiency of the light emitted from the light source device can be increased and the viewing angle can be enlarged without losing the sharpness of the image by a simple and inexpensive method. .

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a configuration of a liquid crystal display device used in an example of the present invention.

FIG. 2 is a luminance distribution diagram of emitted light of a light source device used in an example of the present invention.

FIG. 3 is a diagram of a luminance distribution characteristic of a lens sheet used in an example of the present invention.

FIG. 4 is a diagram of light scattering characteristics of the light scattering plate-1 used in the examples of the present invention.

FIG. 5 is a diagram showing the relationship between the viewing angle and the white brightness and black brightness in Comparative Example 1 of the present invention.

FIG. 6 is a diagram showing a relationship between white luminance and black luminance with respect to a viewing angle in Comparative Example 2 of the present invention.

FIG. 7 is a diagram showing the relationship between the viewing angle and the white brightness and black brightness in Comparative Example 3 of the present invention.

FIG. 8 is a diagram showing the relationship between the white luminance and the black luminance with respect to the viewing angle in Example 1 of the present invention.

FIG. 9 is a diagram showing the relationship between the white luminance and the black luminance with respect to the viewing angle in Comparative Example 4 of the present invention.

FIG. 10 is a diagram showing a relationship between a white luminance and a black luminance with respect to a viewing angle in Example 2 of the present invention.

[Explanation of symbols]

 1. Light source device 2. Lens sheet 3. Rear polarizing plate 4. Liquid crystal cell 5. Color filter 6. Light scattering plate 7. Front polarizing plate

Claims (2)

[Claims] 1. A liquid crystal display device having a light source device, a back polarizing plate, a liquid crystal cell and a front polarizing plate as a basic structure, further comprising a lens sheet between the light source device and the back polarizing plate and a light scattering plate between the liquid crystal cell and the front polarizing plate. A liquid crystal display device having a structure in which a liquid crystal display device is arranged. 2. A liquid crystal display device having a light source device, a back polarizing plate, a liquid crystal cell and a front polarizing plate as a basic structure, further comprising a lens sheet between the light source device and the back polarizing plate and a light scattering plate in front of the front polarizing plate. A liquid crystal display device characterized by being arranged.