JPH05257002A - High transmissivity light diffusing plate of polycarbonate - Google Patents

Abstract

PURPOSE:To obtain a high transmissivity light diffusing plate of polycarbonate excellent in transparency and surface smoothness and giving a clear picture when used as the screen of the large-sized display of a projection television, etc. CONSTITUTION:This high transmissivity light diffusing plate of polycarbonate is made of a compsn. prepd., by blending 100 pts.wt. polycarbonate resin with 0.05-0.5 pts.wt. particles having <=50mum particle diameter and 5-20mum average particle diameter and has >=85% total light transmissivity and 10-30% luminous diffuse transmissivity.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light diffusing plate. More specifically, the present invention relates to a high-transmittance light diffuser plate made of a polycarbonate resin, which is suitable for a screen of a large-sized display such as a projection television.

[0002]

2. Description of the Related Art Conventionally, a high transmittance light diffusing plate is produced by sandwiching and pressing a thermoplastic resin with a roll having a mat pattern.
The method of transferring a matte pattern is industrially adopted. This method requires the production of a mat roll, which raises the production cost, and further has the drawbacks that the mat pattern is worn over a long period of use and the transmittance changes over time.

Also, a method of adding a diffusing agent to a thermoplastic resin is generally adopted. For example, a semitransparent polycarbonate resin containing 0.01 to 5 parts by weight of a fluorinated polyolefin (JP-A-55-94952), and a method of adding an inorganic filler to an olefin resin (JP-B-48-4088). , 48-4089), and a proposal to further contain an inorganic fine powder is a milky white half containing 0.1 to 5 parts by weight of calcium carbonate and 0.01 to 0.3 parts by weight of titanium oxide per 100 parts by weight of polycarbonate. Transparent polycarbonate resin (Japanese Patent Publication No. 50-14)
6646), a lighting equipment panel to which 1.0 to 2.5 parts by weight of calcium carbonate is added (Japanese Patent Publication No. 60-17530).
No. 3), and in the proposal of further containing organic fine powder, the crosslinked acrylic fine particles are added to the polycarbonate in an amount of 0.05 to 2
A method of adding 0 parts by weight (Japanese Patent Laid-Open No. 3-143950) has been proposed, but all of them are semitransparent or opaque and are mainly used as a light diffusing plate for lighting equipment. These materials have a low total light transmittance of 40 to 80%, and a high diffuse transmittance of 40 to 98%, and cannot be used for screens of large-sized display screens such as projection televisions. .

[0004]

OBJECT OF THE INVENTION The object of the present invention is a high transmittance light made of polycarbonate which is excellent in transparency and surface smoothness and has a clear image and no iridescence when used as a screen for a large display such as a projection television. The purpose is to provide a diffusion plate.

[0005]

The present invention comprises 100 parts by weight of a polycarbonate resin and 0.05 to 0.5 parts by weight of particles having an average particle size of 5 to 20 .mu.m and a total light transmittance of 85. The present invention relates to a polycarbonate high transmittance light diffusing plate having a diffuse transmittance of 10% to 30%.

The polycarbonate used in the present invention is produced by reacting a dihydric phenol with a carbonate precursor by a solution method or a melting method. As typical examples of the dihydric phenol, 2,2-bis (4-hydroxyphenyl) propane [bisphenol A], 1,1-bis (4-hydroxyphenyl) ethane, 1,1-bis (4
-Hydroxyphenyl) cyclohexane, 2,2-bis (4-hydroxy-3,5dimethylphenyl) propane, 2,2-bis (4-hydroxy-3-methylphenyl) propane, bis (4-hydroxylphenyl) Examples thereof include sulfide and bis (4-hydroxylphenyl) sulfone. The viscosity average molecular weight of the polycarbonate is generally 10,000 to 100,000, preferably 1500.
It is 0 to 35000. In producing such a polycarbonate, an appropriate molecular weight modifier, a branching agent for improving processability, a catalyst for accelerating the reaction and the like can be used as necessary.

The particles used in the present invention are generally used inorganic particles and organic particles, for example, silica-alumina clay minerals (hydrous aluminum silicates) represented by kaolin and silica-magnesium particles represented by talc. Clay minerals (hydrated magnesium silicates), calcium silicate,
Examples thereof include silica, alumina and calcium carbonate. In particular, talc, kaolin and calcium carbonate are preferable because they are excellent in dispersion in polycarbonate. Examples of the organic particles include crosslinked polyacrylate having a crosslinked structure, crosslinked polystyrene and the like. Especially crosslinked polyacrylate
Is preferred.

The particles used in the present invention have a particle size of 50 .mu.m or less, an average particle size of 5 to 20 .mu.m, and any particles may be used as long as they do not adversely affect the polycarbonate. If the particle size exceeds 50μ or the average particle size exceeds 20μ, the surface of the light diffusion plate becomes rough and the commercial value thereof is significantly reduced. When the amount of particles added is 0.05 parts by weight or less per 100 parts by weight of the polycarbonate resin, the diffuse transmittance is small and an rainbow pattern is generated in the image, which is not preferable. Also 0.5
If the amount is more than 1 part by weight, the total light transmittance is low and the brightness of the image is insufficient, which is not preferable.

The total light transmittance of the light diffusion plate thus obtained is preferably 85% or more. If it is less than 85%, the brightness of the image is insufficient, which is not preferable. Also, the diffuse transmittance is 10
30% is preferable. If the diffuse transmittance is 10% or less, flicker or rainbow pattern is generated in the image, which is not preferable. On the other hand, if it exceeds 30%, blurring occurs in the image and the image becomes difficult to see, which is not preferable.

In carrying out the present invention, for example, an ultraviolet absorber, a release agent, a colorant, a heat stabilizer, an anticoagulant and the like may be added to the polycarbonate in which inorganic and organic particles are dispersed. The thickness of the polycarbonate light diffusion plate is preferably 1.0 to 3.0 mm.

[0011]

EXAMPLES The present invention will be further described with reference to the following examples. In addition, the part in an Example means a weight part. The average particle size was determined by a microphotosizer manufactured by Seishin Enterprise Co., Ltd. The particle diameter obtained by this device is determined based on Stokes' law regarding the sedimentation velocity of particles in a liquid, and the average particle diameter is L related to the amount of light passing through a suspension of particles and the concentration of particles.
It is obtained as an average value of 50% by weight in the weight cumulative distribution of particles obtained by using the Ambert-Beer law. In the examples, water was used as the dispersion medium for measurement. The evaluation of other characteristics is as follows. (1) Total light transmittance (Tt) and diffuse transmittance (Td) In accordance with JIS K-6735, Nippon Denshoku Industries Co., Ltd.
Made, integrating sphere type light transmittance measuring device Σ-80 type (C light source)
It is the value measured by and is expressed in%. (2) Appearance The surface was visually evaluated and the sample was excellent in smoothness and the concavo-convex pattern was not conspicuous. (3) Rainbow pattern A polycarbonate board having a thickness of 1.5 mm cut into a size of 800 × 800 mm, coated with UV-curing acrylic resin on one side, and irradiated with UV to form a Fresnel lens. Was mounted on a projection TV and examined for the presence or absence of a rainbow pattern on the screen and its sharpness.

The case where the rainbow pattern did not occur and the image on the screen did not flicker was evaluated as ◯, and the case where the rainbow pattern occurred and the flicker of the screen image was noticeable was evaluated as x.

[0013]

Examples 1 to 7 and Comparative Examples 1 to 5 To 100 parts of a polycarbonate resin having a viscosity average molecular weight of 24500 produced from bisphenol A and phosgene, the particles shown in Table 1 were added in the amounts shown in Table 1 and mixed with a tumbler. A sheet having a width of 1000 mm was molded at 280 ° C. with a T-die extruder having a diameter of 120 mm. Table 1 shows the characteristic values of the obtained molded sheet and the polycarbonate sheet which was Fresnel-lensed using the sheet.

[0014]

[Table 1]

[0015]

The polycarbonate light diffusing plate obtained by the method of the present invention has excellent transparency and smoothness as shown in the examples, and when this is used for a screen of a projection television, an image is clear without a rainbow pattern. Is.

Claims (1)

[Claims] 1. Particles having a particle size of 50 μm or less and an average particle size of 5 to 20 μm in 0.05 part by weight of 100 parts by weight of a polycarbonate resin.
A total light transmittance of 8 consisting of a composition blended with 0.5 part by weight.
A high transmittance light diffusion plate made of polycarbonate having a diffuse transmittance of 10 to 30% at 5% or more.