JPH09304606A - Light diffusing prism sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the production cost and to improve the back light luminance of a liq. crystal display, etc., by the total reflection of incident light in the light diffusing sheet, by forming a fine projected line having a serrate section on at least one side of the sheet prepared by incorporating a specified amt. of a beady cross-linked acrylic resin having a specified particle diameter into a highly transparent resin. SOLUTION: Fine projected lines 11 having a serrate section are formed on at least one side of a light diffusing sheet prepared by incorporating 0.5-10 pts.wt. of beady cross-linked acrylic resin having 1-20μm average particle diameter into 100 pts.wt. of a highly transparent resin. Although any highly transparent resin having >=85% light transmittance can be used without any restriction, the polycarbonate, polysulfone, polyacrylate, polyether sulfone, etc., having >=100 deg.C glass transition temp. or secondary transition temp. are preferably used. Meanwhile, the material for the beady cross-linked acrylic resin is not specially limited, and methyl methacrylate is appropriately used.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light diffusing prism sheet, and more particularly, to a light which has both performances of a prism sheet and a light diffusing sheet to improve the brightness of a lighting cover and a liquid crystal backlight and to make the light uniform. The present invention relates to a diffusive prism sheet.

[0002]

2. Description of the Related Art Conventionally, in a liquid crystal display, in order to project light rays transmitted from a backlight unit onto the entire surface of the liquid crystal unit with high brightness, a prism film and a light film are provided between the backlight unit and the liquid crystal unit. At least one diffusive film is interposed between the two diffusive films. However, since the prism film and the light diffusing film must be set together in the process of assembling the liquid crystal backlight, there is a problem that the process is long and complicated.
Since it is inevitable to increase the thickness of the liquid crystal display by using a sheet of film together, there is an increasing demand for a thinner sheet having both the functions of the prism film and the light diffusing film.

[0003]

The present invention is to solve the above-mentioned problems, and the gist thereof is to provide a highly transparent resin 1
A fine cross-section serrated ridge is provided on at least one surface of a light diffusing sheet containing 0.5 to 10 parts by weight of a bead-shaped crosslinked acrylic resin having an average particle diameter of 1 to 20 μm per 100 parts by weight. A light diffusing prism sheet characterized by being formed.

[0004]

Embodiments of the present invention will be described below. FIG. 1 is a perspective view showing the light diffusing prism sheet of the present invention, and FIG. 2 is an enlarged side view showing the inside of the circle of FIG.

According to the present invention, at least one side of a light diffusing sheet comprising 0.5 to 10 parts by weight of a bead-like crosslinked acrylic resin having an average particle size of 1 to 20 μm with respect to 100 parts by weight of a highly transparent resin. In addition, the ridge 1 with a fine sawtooth cross section
1 is formed. The high transparency resin used in the present invention is not particularly limited as long as it has a light transmittance of 85% or more, but in view of heat resistance, the glass transition temperature or the second transition temperature is 100. ℃
The above-mentioned polycarbonate, polysulfone, polyarylate, polyether sulfone and the like are preferably used.

The bead-shaped crosslinked acrylic resin used in the present invention is not particularly limited in terms of material, but methylmethacrylate is preferred, and when the average particle size is less than the above range and less than 1 μm, In the kneading step, it is difficult to uniformly disperse the resin in the highly transparent resin, and when it exceeds 20 μm and exceeds the above range, the light diffusivity is not expressed. Therefore, the average particle size is set in the range of 1 to 20 μm. .

[0007]

【Example】

(Example 1) Polycarbonate resin (Novarex 7027 PUM manufactured by Mitsubishi Chemical Co., Ltd.) 100 parts by weight Cross-linked acrylic resin having an average particle diameter of 10 μm (MR8GSN manufactured by Soken Chemical Co., Ltd.) 5 parts by weight After mixing the above raw materials with a mixer, pellets granulated by a KCK continuous kneader are passed through a T-die forming die using a vent type extruder to extrude a 200 μm thick sheet while As shown in a perspective view in FIG. 1, transfer is performed by passing between nip rolls in which fine grooves having a serrated cross section are engraved.
The light diffusive prism sheet 1 of the present invention having the fine protrusions 11 having a serrated cross section on one surface was obtained.

The obtained light diffusing prism sheet 1 has a wall thickness (including the height of the ridge) t as shown in an enlarged side view of FIG.
Is 200 μm on the surface of the sheet 1, and the bottom width d is 100 μm
, The height h is 30 to 40 μm, and the convex apex angle θ is 90 to
A ridge 11 having a fine sawtooth cross section of 100 ° is formed. The results of measurement of the light transmittance, the degree of dispersion, and the intensity ratio of emitted light in the normal direction of the light diffusing prism sheet 1 are shown in Table 1 below.

Example 2 Polycarbonate resin (Novarex 7027 PUM manufactured by Mitsubishi Chemical Co., Ltd.) 100 parts by weight Crosslinked acrylic resin having an average particle size of 10 μm (MR8GSN manufactured by Soken Chemical Co., Ltd.) 10 parts by weight The above raw materials were mixed by a mixer and extruded in the same manner as in Example 1 to obtain a sheet having a thickness of 200 μm, and the sheet was formed into a fine groove having a serrated cross section. The sheet was passed through an engraved nip roll to obtain a light-diffusing prism sheet 1 of the present invention having fine protrusions 11 having a serrated cross section on one surface. The results of measuring the light transmittance, the degree of dispersion, and the intensity ratio of outgoing light in the normal direction of the obtained light diffusing prism sheet 1 are shown in Table 1 below.

Comparative Example 1 Polycarbonate resin (Novarex 7027 PUM manufactured by Mitsubishi Chemical Co., Ltd.) 100 parts by weight Crosslinked acrylic resin having an average particle diameter of 10 μm (MR8GSN manufactured by Soken Chemical Co., Ltd.) 5 parts by weight The above raw materials were mixed by a mixer and extruded in the same manner as in Example 1 to obtain a sheet having a smooth surface with a thickness of 200 μm. The results of measuring the light transmittance, the degree of dispersion, and the intensity ratio of light emitted in the normal direction of the obtained sheet are shown in Table 1 below.

[0011]

Table 1 Light transmittance (%) Dispersion degree (°) Normal direction outgoing light intensity ratio Example 1 70 40 1.0 Example 2 66 48 1.0 Comparative Example 1 70 40 0.2 Note) * Ray Transmittance (%) …… Measured using a reflection / transmission meter manufactured by Murakami Color Research Laboratory. * Dispersion (°) ………… When using the automatic goniophotometer manufactured by Murakami Color Research Laboratory and assuming that the transmitted light amount in the linear direction (0 °) is 100, the transmitted light amount becomes 50. angle. * Ratio of emitted light intensity in the normal direction: Emitted light intensity ratio when the light incident from the lateral direction is refracted at a right angle and the angle when the normal direction of the backlight surface is 0 ° is changed (emitted light intensity / Incident light intensity).

As shown in Table 1 above, Example 1 of the present invention
The sheet of Example 2 has a ratio of the intensity of emitted light in the normal direction of 0.2 in Comparative Example 1 (a sheet having a smooth surface on which no fine ridges are formed), which is 1.0, That is, it shows that the incident light is totally reflected in the sheet, and the effect of improving the brightness of the backlight of a liquid crystal display or the like is great.

[0013]

Since the present invention has the above-described structure, the following effects can be obtained. That is, the present invention is a thin single-layer sheet that has both the functions of a conventional prism film and a light diffusing film, so that the manufacturing cost is low and the incident light is totally reflected in the sheet so that the liquid crystal display etc. The effect of improving the brightness of the backlight is great.

[Brief description of drawings]

FIG. 1 is a perspective view showing a light diffusing prism sheet of the present invention.

2 is an enlarged side view showing the inside of the circle of FIG. 1. FIG.

[Explanation of symbols]

 1 Light-diffusing prism sheet 11 Fine ridges

Claims (1)

[Claims] 1. A light-diffusing sheet comprising 0.5 to 10 parts by weight of a bead-shaped cross-linked acrylic resin having an average particle diameter of 1 to 20 μm based on 100 parts by weight of a highly transparent resin, A light-diffusing prism sheet, which is characterized in that fine ridges having a serrated cross section are formed.