JP3098334B2 - Multi-prism sheet for liquid crystal display device and liquid crystal display device - Google Patents

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 such as a liquid crystal television and a computer display , and a multi-prism sheet used therein . The present invention relates to a liquid crystal display device having luminance.

[0002]

2. Description of the Related Art Liquid crystal display devices have been widely used in OA equipment, personal computers, etc., due to their lighter weight and higher definition. However, since the liquid crystal itself does not emit light, the luminance is improved by using a back-lighting unit. On the other hand, recently, colorization of liquid crystal display devices such as color liquid crystal televisions has been progressing, and further improvement in luminance has been demanded. In such a color liquid crystal display element, it has become impossible to secure sufficient luminance with the conventional back lighting means for a single color liquid crystal display device. Therefore, attempts have been made to improve the brightness of the backlight unit.

[0003]

However, the method of improving the brightness of the backlight unit has new problems such as an increase in heat generation and an increase in cost. SUMMARY OF THE INVENTION It is an object of the present invention to provide a liquid crystal display device with improved brightness without problems such as an increase in the amount of heat generated by improving the brightness of the backlight unit.

[0004]

SUMMARY OF THE INVENTION In view of such a situation, the inventors of the present invention have a specific shape and are made of a specific material.
The present inventors have found that the brightness of a liquid crystal display device can be improved by using the multi-prism sheet described above, and have reached the present invention. That is, the liquid crystal display device of the present invention includes a multi-prism sheet was placed on top of the backlight unit, and a liquid crystal display device which is installed on the multi-pre-nozzle sheet, the prism surface of the multi prism sheet and liquid crystal and a liquid crystal display element is disposed so as to face
A display device, wherein the multi-prism sheet is
The surface has an apex angle of 60 to 95 ° and a pitch of 100 μm or less.
Is a series of elongated triangular prisms
Many are formed and the elastic modulus at 25 ° C. is 10,000 to 5000.
Molded with 0Kg / cm ² active energy ray-curable resin
It is characterized by having been done. In addition, the present invention
The multi-prism sheet has an elastic modulus of 10,000 at 25 ° C.
Active energy ray-curable tree of up to 50,000 kg / cm ²
It is formed from fat and has a vertex angle of 60-95 ° on its surface.
Series of elongated triangular cross-sections with a notch of 100 μm or less
Characterized in that a large number of prisms are continuously formed.
Things.

A liquid crystal display device of the present invention will be described with reference to FIG. FIG. 1 is a partial cross-sectional view showing an embodiment of the liquid crystal display device of the present invention. In FIG.
Is installed so that the prism surface of the lens faces upward. On the multi-prism sheet 1, a liquid crystal display element 2 is provided so as to face the prism surface.
The liquid crystal display element 2 is configured, for example, by filling a liquid crystal between two glass substrates provided at a predetermined interval by a spacer. Further, a polarizing plate is provided on each outer surface of the two upper and lower glass substrates,
A color filter layer is provided on the inner surface of the upper glass substrate, and internal electrodes are provided on the outer surface of the color filter layer. Internal electrodes are provided on the inner surface of the lower glass substrate.
The internal electrode is configured by arranging a large number of minute pixel electrodes vertically and horizontally. The color filter layers are red, green,
Three color filters of blue are arranged corresponding to the pixel electrodes to form each pixel.

[0006] As shown in FIG.
Plate-shaped light guide 5 having a light incident surface and a light exit surface, a fluorescent lamp, and the like
The linear light source 7 is provided. The light guide 5 is
One end face is a light incident surface, and light is emitted substantially perpendicular to the light incident surface.
Surface, and a reflective surface located on the opposite side.
A reflection film 6 is formed on the surface, and a light exit surface is provided as necessary.
Alternatively, a light amount adjustment pattern is formed on the reflection surface. Light guide
A linear light source 7 such as a fluorescent lamp is arranged opposite the light incident surface of the body 5.
Is placed. Then, incident light from the linear light source 7 incident from the light incident surface of the light guide plate 5 passes through the light guide plate 5, partially reflects on the reflection film 6 and exits from the light exit surface, and passes through the multi-prism sheet 1. Irradiation is uniformly performed on the back surface side of the liquid crystal display element 2. The backlight unit 3 is not limited to the one shown in FIG. 1, but may be any of various commonly used backlight units.

The multi-prism sheet 1 is formed from a resin plate, a sheet or a film, and a large number of a series of elongated prisms having a triangular cross section are continuously formed on one surface thereof. FIG. 2 shows a partial cross-sectional view of the multi-prism sheet 1. In the figure, reference numeral 8 denotes a transparent base made of a synthetic resin, and a prism portion 9 made of a synthetic resin having a prism shape formed on one surface of the transparent base 8 is integrally formed. The multi-prism sheet 1 of the present invention
May have a two-layer structure of a transparent base material and a lens portion as shown in FIG. 2, but may have no transparent base material, or may have a structure in which the transparent base material is peeled off and used. .

[0008] In the liquid crystal display device of the present invention, multiplexed
Prism portions formed on the surface of the prism sheet, it is important to set the angle θ of the prism apex angle in the range of 60 to 95 °. This is the angle θ is 60 ° Not <br/> Mitsurude prism apex angle, there Tamee screen becomes remarkably dark when viewed from the other front face directed it becomes significant, more than 95 ° in the opposite This is because the light condensing property is reduced and the effect of improving brightness cannot be obtained, or the brightness is reduced due to light absorption due to the thickness of the prism sheet.

The pitch a of the prism is preferably 100 μm or less, more preferably 70 to 90 μm.
Range. This is because the pitch of the color filter is becoming smaller with the colorization of the liquid crystal display device, and from the viewpoint of preventing the occurrence of moire patterns on the screen and improving the definition of the screen, the pitch a of the prism is also smaller. Is preferred. The height b of the irregularities of the prism is determined by the value of the angle θ of the prism apex angle and the pitch a of the prism, and is preferably in the range of 30 to 50 μm. Further, the thickness c of the prism sheet 1 is preferably thicker in terms of strength, and is preferably thinner optically to suppress light absorption. For this reason, an appropriate thickness is set depending on the size of the screen of the liquid crystal display device to be used, use conditions, etc. For example, a liquid crystal display device with a screen of about 4 to 10 inches has a thickness of about several hundred μm or less. Is preferably in the range of about 200 to 500 μm because the strength and the optical characteristics are balanced.

In the liquid crystal display device of the present invention having the above-described structure, the multi-prism sheet is set on the back-side illuminating means so that the orismal surface of the multi-prism sheet faces the liquid crystal display element. Since the light emitted from the device can be concentrated and emitted in the direction of the liquid crystal display element, a liquid crystal display device with high luminance and excellent directivity capable of effectively utilizing the light from the light source can be obtained. Furthermore, in the present invention, two or more multi-prism sheets can be used in a superposed state, and furthermore, the luminance can be further improved, and various directivities can be provided by combining the directions of the prisms. . However, in consideration of the loss of the light amount due to the multi-prism sheet, it is usually sufficient to use one multi-prism sheet.

The method of manufacturing the multi-prism sheet according to the present invention includes a method of injection molding a synthetic resin, a method of pressing a resin plate and a mold in contact with each other, and transferring the surface shape of the mold by heating and pressing. Any method can be used, such as a method of injecting an active energy ray-curable resin composition into a mold having surface irregularities, and then irradiating with an active energy ray to cure the composition, but from the viewpoint of optical characteristics and productivity, etc. The most preferred method is to use an active energy ray-curable resin composition.

Hereinafter, a method for manufacturing the multi-prism sheet of the present invention will be described. Examples of the active energy ray-curable resin composition include unsaturated polyester-styrene type, epoxy resin-Lewis acid type, polyene-thiol type, (meth) acrylate type and the like. Among them, a highly transparent (meth) acrylate ester type is particularly preferable. For example, a prepolymer such as polyester (meth) acrylate, epoxy (meth) acrylate, polyurethane (meth) acrylate and monofunctional or polyfunctional (meth) And acrylate monomers. These resins can be used alone or in combination, but it is preferable to select them in consideration of the elastic modulus of the obtained prism sheet. In particular, the elastic modulus at 25 ° C. of the active energy ray-curable resin after curing is 10%.
It is preferable to adjust so as to be in the range of 000 to 50,000 kg / cm ² . This is because the elastic modulus is 10,000k
If it is less than g / cm ² , the prism sheet becomes soft and the handling and workability when assembling into a liquid crystal display device are poor, and when the liquid crystal display element contacts the prism top, the prism top is crushed to cause a problem on the screen. This is because a shadow appears on the image. On the other hand, when the elastic modulus exceeds 50,000 kg / cm ² , the prism sheet is hard and brittle, and may be damaged by a slight impact.

After the active energy ray-curable resin composition as described above is applied to a mold and the surface of the resin composition is smoothed, the transparent substrates are overlapped and cured by irradiation with active energy rays. Here, as long as the transparent base material has high transparency, the thickness and the material are not particularly limited. Those having a thickness of 3 mm or less are preferable.
Further, as the material, for example, acrylic resin, polycarbonate resin, polyester resin, polystyrene resin,
Synthetic resins such as fluororesins, polyimide resins, mixtures of these resins, and the like, and glass are exemplified. Examples of usable active energy rays include particle beams such as electron beams and ion beams, electromagnetic rays such as γ-rays, X-rays, ultraviolet rays, visible rays, and infrared rays, and ultraviolet rays from the viewpoint of curing speed and production equipment. Is preferred.

The multi-prism sheet made of the resin composition cured on the transparent base material by the active energy ray can be used as it is.
The transparent substrate can be peeled off before use.

[0015]

The present invention will be specifically described below with reference to examples. Example 1 The following mixture was applied as a UV-curable resin composition to a mold previously designed such that the prism pitch after molding was 50 μm and the prism apex angle was 90 °, and the surface was smoothed. Thereafter, a polycarbonate film having a thickness of 500 μm was overlaid. Next, ultraviolet rays of 1000 mJ / cm ² were irradiated at an integrated irradiation amount of 320 to 390 nm to cure the ultraviolet-curable resin composition. afterwards,
The multi-prism sheet was obtained by peeling from the mold.

FANCRYL FA-321M 45 parts by weight (Ethylene oxide modified bisphenol A methacrylate manufactured by Hitachi Chemical Co., Ltd.) NK ester A-BPE-4 25 parts by weight (Shin Nakamura Chemical Co., Ltd. ethylene oxide modified bisphenol A diacrylate) Sartomer 285 30 parts by weight Part (tetrahydrofurfuryl acrylate manufactured by Sartomer Co., Ltd.) Darocure 1173 3 parts by weight (2-hydroxy-2-methyl-1-phenylpropan-1-one manufactured by Merck Japan Co., Ltd.) A back irradiation means having a surface luminance of 7000 cd / m ² Using the used liquid crystal display device, the obtained multi-prism sheet was placed on the back-side illuminating means so that the prism surface was opposed to the liquid crystal display element as shown in FIG. It was measured. As a result, it had a surface luminance of 290 cd / m ² . The surface luminance when the multi-prism sheet was not used was 200 cd / m ² . Using the above resin composition, a resin plate having a thickness of 2 mm was prepared by a glass cell casting method, and the obtained resin plate was formed to have a width of 1 mm.
The test piece was cut into 0 mm and 60 mm in length, and supported at two points placed at an interval of 32 mm to perform a three-point bending test. As a result, 25
It had a flexural modulus of 000 kg / cm ² .

Example 2 The same ultraviolet-curable resin composition as in Example 1 was used except that a mold was designed so that the prism pitch after molding was 50 μm and the prism apex angle was 75 °. A multi-prism sheet was obtained under the same manufacturing conditions. Using the obtained multi-prism sheet, the surface luminance was measured in the same manner as in Example 1. As a result, 300 cd /
It had a surface brightness of m ² .

Example 3 The same ultraviolet-curable resin composition as in Example 1 was used except that a mold designed so that the pitch of the prism after molding was 50 μm and the apex angle of the prism was 100 ° was used. A multi-prism sheet was obtained under the same manufacturing conditions. Using the obtained multi-prism sheet, the surface luminance was measured in the same manner as in Example 1. As a result, 220 cd /
It had a surface brightness of m ² .

Example 4 The same ultraviolet-curable resin composition as in Example 1 was used except that a mold designed in advance so that the prism pitch after molding was 50 μm and the prism apex angle was 60 ° was used. A multi-prism sheet was obtained under the same manufacturing conditions. Using the obtained multi-prism sheet, the surface luminance was measured in the same manner as in Example 1. As a result, 293 cd /
It had a surface brightness of m ² .

[0020]

Comparative Example 1 The same ultraviolet-curable resin composition as in Example 1 was used except that a mold designed in advance so that the prism pitch after molding was 50 μm and the prism apex angle was 100 ° was used. A multi-prism sheet was obtained under the same manufacturing conditions. Using the obtained multi-prism sheet, the surface luminance was measured in the same manner as in Example 1. As a result, 196 cd /
It had a surface brightness of m ² .

Comparative Example 2 The surface luminance was measured in the same manner as in Example 1 except that the same multi-prism sheet as in Example 1 was installed so that the prism face was directed toward the backside illuminating means. As a result, 19
It had a surface luminance of 5 cd / m ² .

[0023]

According to the liquid crystal display device of the present invention, a multi-prism sheet having a prism apex angle within a specific range is provided on a backside illuminating means so that the prism surface faces the liquid crystal display element. The light emitted from the back illuminating means can be concentrated and emitted in the direction of the liquid crystal display element, and the light from the light source can be effectively used. The color liquid crystal display device has a sufficient luminance without improving the brightness of the display.

[Brief description of the drawings]

FIG. 1 is a sectional view schematically showing a liquid crystal display device of the present invention.

FIG. 2 is a sectional view showing a part of the multi-prism sheet of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Multi-prism sheet 2 Liquid crystal display element 3 Back-lighting means 8 Transparent base material 9 Prism part

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masao Hamada 4-160, Sunadabashi, Higashi-ku, Nagoya-shi, Aichi Prefecture Inside Mitsubishi Rayon Co., Ltd. Product Development Laboratory (72) Inventor Makoto Okawa 4-chome, Sunadabashi, Higashi-ku, Nagoya-shi, Aichi Prefecture No. 1-60 Mitsubishi Rayon Co., Ltd. Product Development Laboratory (72) Inventor Takashi Takigawa 4-60 Sunadabashi, Higashi-ku, Nagoya-shi, Aichi Prefecture No. 1-60 Mitsubishi Rayon Co., Ltd. Product Development Laboratory (72) Inventor Kenichi Maezawa Aichi Prefecture 4-160, Sunadabashi, Higashi-ku, Nagoya-shi Mitsubishi Rayon Co., Ltd. Product Development Laboratory In-house panel Referee, Hidetomo Higashimori Referee, Yoshito Inazumi Referee, Shizuo Toyooka (56) References JP 3-16032 (JP, A) JP-A-4-67016 (JP, A) JP-A-4-212125 (JP, A) JP-A-3-9838 (JP, A) ) Patent Rights 2-248215 (JP, A) Patent Rights 4-196288 (JP, A) JitsuHiraku flat 4-107201 (JP, U)

Claims (4)

(57) [Claims] And multi-prism sheet as claimed in claim 1] was placed on top of the backlight unit, and a liquid crystal display device which is installed on the multi-pre-nozzle sheet, the prism surface of the multi prism sheet and the liquid crystal display device A liquid crystal display device installed to face , wherein the multi-prism
The surface has an apex angle of 60-95 ° and a pitch of 10
A series of elongated triangular prisms with a cross section of 0 μm or less
Are continuously formed, and the elastic modulus at 25 ° C. is 10,000.
Active energy ray-curable tree of up to 50,000 kg / cm ²
A liquid crystal display device characterized by being molded with fat . 2. The method according to claim 1, wherein the multi-prism sheet includes a transparent substrate and an active energy ray-curable resin formed on the transparent substrate.
The liquid crystal display device according to claim 1, characterized in that comprising a fat or Ranaru prism unit. 3. An elastic modulus at 25 ° C. of 10,000 to 5,000.
Formed from 0Kg / cm ² active energy ray-curable resin
The surface has an apex angle of 60 to 95 ° and a pitch of 10
A series of elongated triangular prisms with a cross section of 0 μm or less
Liquid crystal display characterized by being formed continuously in large numbers
Multi prism sheet for equipment. 4. A transparent substrate and an active material formed on the transparent substrate.
With a prism part made of reactive energy ray-curable resin.
2. The liquid crystal display device according to claim 1, wherein
Chiprism sheet.