JPH0925387A - Methacrylic resin composition for molding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a methacrylic resin which is suitable for a photoconductor for an injection-molded liquid crystal and has excellent surface brightness by adding transparent crosslinked polymer particles having a specified particle diameter and refractive index to a polymer comprising mainly methyl methacrylate. SOLUTION: 100 pts.wt. polymer (A) consisting of 70-100wt.% methyl methacrylate, 0-30wt.% other methacrylic ester and 0-30wt.% acrylic ester is mixed with 0.03-1 pt.wt. transparent crosslinked polymer particles (B) having a particle diameter of 0.03-0.4μm and a refractive index (nB) in such a relation to that (nA) of the polymer A as shown by the formula to produce a methacrylic resin composition for molding. The component B is obtained by the emulsion polymerization of monomer(s) comprising (meth)acrylic ester(s), styrene(s), etc., in the presence of a crosslinking agent. Before molding this composition, it is desirable that the components A and B are uniformly mixed and pelletized through an extruder or that the component B is fed into an extruder after deaeration in the continuous polymerization of the component A.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a methacrylic resin composition for molding, and more specifically, a molding suitable for giving a light guide having higher and more uniform surface brightness by injection molding or extrusion molding. A methacrylic resin composition for use.

[0002]

BACKGROUND OF THE INVENTION Methacrylic resin is colorless and transparent and has good moldability, and is used for conventional louvers, tail lamps, tableware and other electrical parts, vehicle parts, decorations, sundries, signboards, as well as optical applications such as lenses and laser disks. It has become widely used. However, at present, even methacrylic resins for optical applications have not sufficiently met the market demand as a light guide for liquid crystal.

[0003]

SUMMARY OF THE INVENTION Therefore, the present invention provides a light guide having higher and more uniform in-plane brightness in injection molding and extrusion molding, and higher performance required as a light guide for liquid crystal. It is an object of the present invention to provide a methacrylic resin composition for molding which fully satisfies the above requirements.

[0004]

Means for Solving the Problems The inventors of the present invention have made earnest studies on a methacrylic resin composition which gives a light guide having higher and more uniform in-plane brightness by injection molding or the like.
By adding specific polymer fine particles to a methacrylic polymer, a methacrylic resin composition for molding which can sufficiently satisfy the higher required performance as a light guide for liquid crystal was found, and the present invention was completed.

That is, the present invention uses methyl methacrylate 70
~ 100% by weight, acrylic acid ester 0 to 30% by weight,
Methacrylic acid ester excluding methyl methacrylate 0-3
100 parts by weight of the methacrylic polymer (A) consisting of 0% by weight, a particle diameter of 0.03 to 0.40 μm, and a refractive index (nB) thereof is a refractive index (nA) of the methacrylic polymer (A). With respect to 0.01 ≦ | nA−nB | ≦ 0.09, the transparent crosslinked polymer fine particles (B) 0.03 to
It is achieved by a methacrylic resin composition for molding comprising 1 part by weight.

[0006]

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

In the methacrylic polymer (A) used in the present invention, methyl methacrylate is a monomer which is a main component of the polymer, and its methylation is advantageous in terms of optical properties such as transparency and mechanical properties. The content is 70% by weight or more.

The other component, acrylic acid ester, is used for the purpose of adjusting fluidity and thermal properties, and the content thereof is 0 to 30% by weight, preferably 1 to 30% by weight relative to the polymer.
It is 20% by weight. Examples of the acrylate ester include methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate and the like, and they may be used alone or in combination of two or more.

Methacrylic acid esters other than methyl methacrylate, which is another component, are used for the purpose of improving hygroscopicity, and the content thereof is 0 to 30% by weight, preferably 5 to 5% by weight relative to the polymer. It is 20% by weight. Examples of the methacrylic acid ester excluding methyl methacrylate include ethyl methacrylate, butyl methacrylate, cyclohexyl methacrylate, benzyl methacrylate, phenyl methacrylate, etc., which may be used alone or in combination of two or more.

The methacrylic polymer (A) can be produced by known polymerization methods such as bulk polymerization, continuous bulk polymerization, continuous solution polymerization and suspension polymerization. In these polymerizations, known polymerization initiators, A chain transfer agent or the like is used.

Examples of the monomer constituting the crosslinked polymer fine particles (B) used in the present invention include methyl methacrylate, ethyl methacrylate, butyl methacrylate, trifluoroethyl methacrylate, cyclohexyl methacrylate and benzyl methacrylate. , Methacrylic acid esters such as phenyl methacrylate, methyl acrylate, ethyl acrylate, butyl acrylate, acrylic acid esters such as 2-ethylhexyl acrylate, styrenes, etc. to obtain the desired refractive index. Are used alone or in combination of two or more.

The fine particles are substantially cross-linked, and examples of the cross-linking agent include ethylene glycol di (meth) acrylate, 1,3-butylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate and divinylbenzene. , Neopentyl glycol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, 1,9-nonanediol di (meth) acrylate, allyl methacrylate, allyl acrylate, allyl maleate, allyl fumarate, diallyl fuma Known materials such as rate and triallyl cyanurate are used.

The crosslinked polymer fine particles (B) have a particle diameter of 0.03 to 0.40 μm, preferably 0.5 to 0.
30 μm, and the refractive index (nB) is 0.01 ≦ | nA−nB | ≦ 0.09, preferably 0.03 ≦ | nA, with respect to the refractive index (nA) of the methacrylic polymer (A). It is necessary to satisfy the relationship of −nB | ≦ 0.07. The particle size is 0.
When it is less than 03 μm, the amount of the emulsifier used for producing the polymer fine particles is large, and as a result, the resin composition also contains a large amount of the emulsifier, which leads to a decrease in the brightness of the light guide and, conversely, a particle diameter Is more than 0.40 μm, the color temperature of the resin composition is lowered and the yellow tint is increased, which is not preferable.

In the relationship between the refractive index of the crosslinked polymer particles (B) and the refractive index of the methacrylic polymer (A), | nA-nB | <
At 0.01, there is almost no improvement in the brightness of the light guide, and there is no point in adding crosslinked polymer particles. Also, 0.09
In the case of <| nA-nB |, the effect of improving the brightness of the light guide is apparent, but the uniformity is low, and the decrease in brightness is not preferable as the distance from the light source increases.

The amount of the crosslinked polymer fine particles (B) added is 0.03 to 1 with respect to 100 parts by weight of the methacrylic polymer (A).
Parts by weight, more preferably 0.05 to 0.3 parts by weight. If it is less than 0.03 parts by weight, the brightness of the light guide does not improve,
On the other hand, if it exceeds 1 part by weight, the brightness is decreased, or the brightness is significantly decreased as the distance from the light source increases. The crosslinked polymer fine particles (B) may be used alone or in combination of two or more.

The crosslinked polymer fine particles (B) are produced by emulsion polymerization and a known polymerization initiator is used.

The methacrylic resin composition for molding of the present invention is
A methacrylic polymer (A) and a crosslinked polymer fine particle (B), which improve the brightness of the light guide by uniformly dispersing the crosslinked polymer fine particle (B) in the methacrylic polymer (A) which is a continuous phase. You can Therefore, it is preferable that the methacrylic polymer (A) and the crosslinked polymer fine particles (B) are uniformly mixed, then pelletized by an extruder and injection-molded or extrusion-molded. In the case of continuous bulk polymerization or continuous solution polymerization, it is preferable to feed the crosslinked polymer particles to the extruder after the degassing step and pelletize.

In the methacrylic resin composition for molding of the present invention, UV absorbers, lubricants, dyes and the like usually used for methacrylic resins are used as necessary within the range which does not hinder the achievement of the object of the present invention. Can be added.

[0019]

Next, the present invention will be described in detail with reference to examples, but the present invention is not limited to these examples. All "%" and "parts" in the examples are "wt%" and "parts by weight", and the abbreviations of the monomers used may be those in the following (). -Methyl methacrylate (MMA) -Butyl methacrylate (BMA) -Benzyl methacrylate (BzMA) -Trifluoroethyl methacrylate (TFEMA) -Methyl acrylate (MA) -Ethyl acrylate (EA) -Ethylene glycol dimethacrylate ( EGDMA) The physical properties of the molded articles in the examples were measured according to the following methods.

(1) Luminance measurement: Measuring instrument Topcon BM-7 Incorporating a light guide into the following backlight unit,
The luminance at three points (points a, b, and c) shown in 1 was measured.

(2) MFR: ASTM-D1238 (conditions: 230 ° C., 3.8 kg) Example 1 A pressure-resistant reaction vessel equipped with a reflux condenser was charged with ion-exchanged water 250.
Part, 1.0 part of sodium lauroyl sulfate were charged, the temperature was raised to 70 ° C. with stirring under a nitrogen atmosphere, and then 5 parts of MMA,
20 parts of TFEMA, 0.5 part of EGDMA, 2.5 parts of 1% KPS aqueous solution were charged and reacted for 60 minutes to polymerize.
Then, when 7.5 parts of a 1% KPS aqueous solution was charged, M
A monomer mixture consisting of 15 parts of MA, 60 parts of TFEMA and 1.5 parts of EGDMA was continuously added over 60 minutes, and then held for 60 minutes to complete the polymerization, and the particle diameter was 0.09 μm.
Obtained a latex. This latex was frozen at -30 ° C, melted at 80 ° C, dehydrated and dried to obtain crosslinked polymer fine particles (B-1).

98 MMA units obtained by suspension polymerization
%, MA unit 2%, and 100 parts of methacrylic polymer beads (A-1) having an MFR of 2.1 g / 10 min were mixed with 0.1 part of crosslinked polymer fine particles (B-1) and extruded at 40φ. Melt kneading with a machine to obtain pellets. The pellets were injection-molded under the condition of a cylinder temperature of 245 ° C., and
A 4-inch, wedge-shaped 4-1.5 mm specular light guide molded product was obtained. A dot pattern (a pattern in which large dots are sequentially arranged with increasing distance from the light source, the same applies hereinafter) was applied to the obtained molded product by screen printing, and the molded product was incorporated into a backlight system to measure the in-plane brightness. Table 1 shows the composition of the methacrylic polymer and the fine particles of the crosslinked polymer. The measurement results are shown in Table 2 and were good results.

Example 2 A pressure-resistant reaction vessel equipped with a reflux condenser was charged with ion-exchanged water 250.
Part, 1.0 part of sodium lauroyl sulfate were charged, the temperature was raised to 70 ° C. with stirring under a nitrogen atmosphere, and then 5 parts of MMA,
BzMA (20 parts), EGDMA (0.25 part) and 1% KPS aqueous solution (2.5 parts) were charged and reacted for 60 minutes to carry out polymerization.
Then, when 7.5 parts of a 1% KPS aqueous solution was charged, M
A monomer mixture consisting of 15 parts of MA, 60 parts of BzMA and 0.75 part of EGDMA was continuously added over 60 minutes, and then held for 60 minutes to complete the polymerization, and the particle diameter was 0.08 μm.
Obtained a latex. This latex was frozen at -30 ° C, melted at 80 ° C, dehydrated and dried to obtain crosslinked polymer fine particles (B-2).

At the stage of removing the monomer from the mixture of the polymer and the monomer obtained by continuous bulk polymerization at a polymerization temperature of 150 ° C. by an extruder having a degassing step, the MMA unit 92
%, EA unit 8%, 100 parts of methacrylic polymer (A-2) having an MFR of 20.3 g / 10 min, the crosslinked polymer fine particles (B-2) 0. 15
Parts were mixed to obtain pellets. Using this pellet, a 9.4-inch light guide molded product was obtained in the same manner as in Example 1, dot pattern printing was performed, and the product was incorporated into a backlight system to measure the in-plane brightness. The measurement results are as shown in Table 1 and were good results.

Examples 3 to 7 Implementation was carried out by changing the copolymerization composition and MFR of the methacrylic polymer (A) and changing the type, refractive index, particle size and addition amount of the copolymerization composition of the crosslinked polymer fine particles (B). Pellets were obtained by the same method as in Example 1 or Example 2. Using this pellet, a 9.4-inch light guide molded product was obtained in the same manner as in Example 1, dot pattern printing was performed, and the product was incorporated into a backlight system to measure the in-plane brightness. Table 2 shows the measurement results.

Example 8 100 parts of the methacrylic polymer (A-3) and 0.2 part of the crosslinked polymer fine particles (B-1) of Example 1 were uniformly mixed to obtain 5
Using a 0φ sheet extruder, a sheet with a width of 40 cm and a plate thickness of 4 mm was made as a prototype and was cut into a 9.4-inch flat plate light guide by an NS router. The obtained light guide was screen-printed to form a dot pattern, which was incorporated into a backlight system to measure the in-plane brightness. The measurement results are shown in Table 2 and were good results.

Comparative Example 1 The beads of the methacrylic polymer (A-1) according to Example 1 were melt-kneaded with a 40φ extruder to obtain pellets. The pellets were injection-molded at a cylinder temperature of 245 ° C. to obtain a mirror-shaped light guide molded product of 9.4 inches and a wedge shape of 4 to 1.5 mm. The obtained molded product was subjected to dot pattern printing by screen printing, incorporated into a backlight system, and the in-plane brightness was measured. The measurement results were as shown in Table 2.

Comparative Examples 2 to 5 The copolymerization composition and MFR of the methacrylic polymer (A) were changed, and the type, refractive index, particle size and addition amount of the crosslinked polymer fine particle (B) copolymerization composition were changed. Pellets were obtained by the same method as in Example 1 or Example 2. Using this pellet, a 9.4-inch light guide molded product was obtained in the same manner as in Example 1, dot pattern printing was performed, and the product was incorporated into a backlight system to measure the in-plane brightness. Table 1 shows the measurement results.

[0029]

[Table 1]

[0030]

[Table 2]

[0031]

INDUSTRIAL APPLICABILITY The methacrylic resin composition for molding of the present invention can be injection-molded or extruded to give a light guide having a higher and more uniform brightness on the surface, and a higher demand as a light-guide for liquid crystals. It is a methacrylic resin composition that can sufficiently satisfy the performance.

[Brief description of drawings]

FIG. 1 is a diagram showing a brightness measurement position of three points (a point, b point, and
It is a drawing showing point c).

Claims (1)

[Claims] 1. 100 parts by weight of methacrylic polymer (A) consisting of 70 to 100% by weight of methyl methacrylate, 0 to 30% by weight of acrylate ester, and 0 to 30% by weight of methacrylic acid ester excluding methyl methacrylate, and particles. The diameter is 0.03 to 0.40 μm, and the refractive index (n
B) has a relationship of 0.01 ≦ | nA−nB | ≦ 0.09 with respect to the refractive index (nA) of the methacrylic polymer (A). Transparent crosslinked polymer fine particles (B) 0.03 to
A methacrylic resin composition for molding comprising 1 part by weight.