JPH0931134A - Methacrylic resin for light guide - Google Patents

Abstract

(57) Abstract: 90-99% by weight of methyl methacrylate,
1 to 10% by weight of at least one alkyl acrylate ester whose alkyl group has 1 to 8 carbon atoms, and M
FR is 3 to 13 g / 10 minutes and the Vicat softening point is 1.
A methacrylic resin for light guides having an acid content of not less than 05 ° C. and not more than 50 ppm. [Effects] The methacrylic resin of the present invention has few impurities in the resin that cause light loss, has improved heat coloring property by injection molding at high temperature, and has adjusted fluidity, heat resistance, and mechanical strength. It is a methacrylic resin that provides a light guide having high brightness and high color temperature and sufficiently satisfies the higher performance requirements as a light guide for liquid crystals.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a methacrylic resin for a light guide, and more specifically, it has a small amount of impurities in the resin that cause light loss, and has improved heat tintability by injection molding at high temperature, and The present invention relates to a methacrylic resin having a high brightness and a high color temperature, in which fluidity, heat resistance and mechanical strength are adjusted, and which is suitable for an injection-molded light guide.

[0002]

2. Description of the Related Art Conventionally, as a resin for a light guide, a cast plate or an extruded methacrylic resin plate has been cut and used, but from the viewpoint of mass production, design shape and weight reduction, an injection molded body is used. Is moving to. However, with conventional methacrylic resin molding materials, transparency, hue, fluidity,
At present, there is no optimum one for a light guide in terms of adjusting heat resistance and mechanical strength.

[0003]

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a methacrylic resin for a light guide which has better colorless transparency and is suitable for injection molding with less light loss. More specifically, the present invention is directed to a light guide in which there are few impurities in the resin that cause light loss, heat coloring properties are improved by injection molding at high temperature, and fluidity, heat resistance, and mechanical strength are adjusted. An object is to provide a methacrylic resin for body.

[0004]

The present inventors have found that they have better colorless transparency, less light loss, improved heat colorability by injection molding at high temperature, and fluidity, heat resistance, As a result of earnest research on a methacrylic resin suitable for an injection-molded light guide whose mechanical strength is adjusted, the inventors have found that the desired methacrylic resin can be obtained, and have completed the present invention.

That is, the present invention relates to methyl methacrylate 90
% To 99% by weight, 1 to 10% by weight of at least one alkyl acrylate having an alkyl group having 1 to 8 carbon atoms, MFR of 3 to 13 g / 10 min, and Vicat softening point of 105 ° C. or higher. The methacrylic resin for a light guide is characterized by having an acid content of 50 ppm or less.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below.

In the methacrylic resin of the present invention, the methyl methacrylate unit is a monomer unit which is a main component of the polymer, and from the viewpoint of transparency, optical properties such as hue, heat resistance and mechanical properties. Its content is 90 to 99% by weight, preferably 92 to 97% by weight.

The other component, an alkyl acrylate unit, is used for the purpose of adjusting fluidity and thermal properties, and the content thereof is 1 to 10% by weight, more preferably 3% with respect to the polymer. ~ 8% by weight. If it is less than 1% by weight,
The thermal stability of the resin is lowered, and defects such as yellowing, generation of black dust due to burning, and flashing are likely to occur, and the optical performance as a light guide is deteriorated, which is not preferable. Also, 1
If it exceeds 0% by weight, heat resistance is lowered, deformation is caused by long-term use, and surface hardness is lowered so that it is easily scratched, which is not preferable. The alkyl acrylate is an alkyl acrylate whose alkyl group has 1 to 8 carbon atoms, and examples thereof include methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, and the like. Used in two or more kinds.

The methacrylic resin of the present invention must have an MFR of 3 to 13 g / 10 minutes, and an MFR of 3 g / min.
When the time is less than 10 minutes, the residual distortion of the molded product is large in the case of forming a light guide having a thinner and wedge shape, which causes a reduction in brightness, which is not preferable. If the MFR exceeds 13 g / 10 minutes, the strength of the thin-walled molded product decreases, which is not preferable.

The methacrylic resin of the present invention must have a Vicat softening point of 105 ° C. or higher.
When the Vicat softening point is less than 105 ° C, heat resistance is lowered, deformation occurs after long-term use, and surface hardness is lowered, which easily causes scratches.

Further, the methacrylic resin in the present invention is required to have an acid content of 50 ppm or less. If the acid content exceeds 50 ppm, the surface of the mold is roughened during the molding of the light guide, which may cause a reduction in the brightness of the light guide obtained, which is not preferable. Acid content is 50p
A methacrylic resin having a pm or less is produced by a continuous bulk polymerization method. The continuous bulk polymerization method is a polymerization method in which monomers are continuously polymerized and unreacted monomers, low molecular weight components, etc. are recovered from the obtained semipolymer by a degassing extruder or the like to obtain a polymer, and the viscosity of the semipolymer. A polymerization method in which a small amount of solvent is used for the purpose of decreasing The continuous bulk polymerization method is a method for producing other methacrylic resins, and it is possible to obtain a polymer in which transparency and hue are not significantly decreased due to additives such as an emulsifier in the emulsion polymerization method or a suspension dispersant in the suspension polymerization method. It is a polymerization method. Further, since the methacrylic resin obtained by continuous bulk polymerization takes out the polymer during the polymerization,
Compared with the polymers obtained by the emulsion polymerization method, the suspension polymerization method, the batch bulk polymerization method, and the like, the copolymer has a narrow copolymer composition distribution and a high light transmittance.

In the above continuous bulk polymerization, known polymerization initiators, chain transfer agents and the like are used, and lubricants, ultraviolet absorbers and the like can be used in balance with the optical properties.

[0013]

Next, the present invention will be described in detail with reference to examples, but the present invention is not limited to these examples.

The physical properties of the molded articles in the examples were measured by the following methods. (1) Spectral light transmittance, b value: ASTM-D1003 (2
(2) Luminance / color temperature: Measuring instrument Topcon BM-7 (3) MFR: ASTM-D1238 (condition: 230 ° C,
3.8Kg) (4) Vicat softening point / VSP: ASTM-D1525 (5) Quantification of acid content: 5 g of resin is dissolved in 100 g of acetone, and bromthymol blue is added as a target, N / 100Na
Titration with OH Example 1 A monomer mixture containing methyl methacrylate and methyl acrylate containing a predetermined amount of a polymerization initiator and a chain transfer agent was continuously charged into a polymerization reaction tank, and the mixture was allowed to stand at 150 ° C. for 2 hours and then the polymerization rate was 60. % Polymer / monomer mixture was obtained, unreacted monomers were recovered by a degassing extruder, and the target methacrylic resin was obtained in pellet form by the continuous bulk polymerization method. The basic composition, MFR and VSP of the obtained methacrylic resin are shown in Table 1.
Shown in

Cylinder temperature of 25
50 mm x 210 mm x under conditions of 0 ° C molding cycle for 60 seconds
A 5 mm mirror flat plate was injection molded, the measurement surface was cut, and mirror polishing was performed to obtain a molded product having a length of 200 mm. 2 of the obtained molded products
Table 1 shows the spectral light transmittance and b value of 00 mm length. Also, after injection molding a 10-inch wedge-shaped light guide (taper of 3 mm → 1 mm) under the condition of a cylinder temperature of 240 ° C., a dot pattern (a pattern in which large dots are sequentially arranged as the distance from the light source) is printed on the back surface. Then, the brightness and color temperature at the center of the light guide were measured by incorporating it into a one-light sidelight type backlight system equipped with a reflector and a diffuser. Table 1 shows the results.

Examples 2 to 4, Comparative Example 1 Methacrylic resin pellets were obtained by the continuous bulk polymerization method in the same manner as in Example 1 except that the copolymerization composition and MFR were changed. Using these pellets, a mirror flat plate molded product and a 10-inch wedge-shaped light guide were obtained and evaluated in the same manner as in Example 1.
The results are shown in Table 1.

Comparative Example 2 A methacrylic resin having a methyl methacrylate unit of 96% and an ethyl acrylate unit of 4% and an MFR of 7.8 g / 10 min was obtained by a suspension polymerization method and then melt-kneaded by an extruder. It was made into pellets. Example 1 using this pellet
In the same manner as in, a 10-inch wedge-shaped light guide was obtained and evaluated. The results are shown in Table 1.

[0018]

[Table 1]

[0019]

INDUSTRIAL APPLICABILITY The methacrylic resin of the present invention has a small amount of impurities in the resin which cause light loss, has improved heat coloring property by injection molding at high temperature, and has adjusted fluidity, heat resistance and mechanical strength. It is a methacrylic resin that can provide a light guide body having a high brightness and a high color temperature as described above and can sufficiently satisfy the higher required performance as a light guide body for liquid crystal.

Claims (1)

[Claims] 1. A methyl methacrylate unit of 90 to 99% by weight and at least one acrylic acid alkyl ester unit having an alkyl group having 1 to 8 carbon atoms in an amount of 1 to 10% by weight, and an MFR of 3 to 13 g / 10. And a Vicat softening point of 105 ° C. or higher and an acid content of 50 ppm or lower.