JPH01301745A - Production of optically diffusive methacrylic resin molding - Google Patents

Abstract

PURPOSE:To provide the subject molding having a good balance between the lightness and maximum bending angle thereof and an excellent appearance, by subjecting specific crosslinked polymer beads to a polymerization process under a specified condition to form an optically diffusive polymer. CONSTITUTION:Crosslinked polymer beads having a difference of 0.02-0.15 between the refractive indexes of the crosslinked polymer beads and a substrate polymer and having an average particle size of 1-16mu are mixed and swollen with a monomer (mixture) which gives a polymer consisting mainly of methyl methacrylate when polymerized or a polymer compatible with the polymer consisting mainly of the methyl methacrylate or a monomer solution containing these polymers to give a swelling degree of the crosslinked polymer beads in an amount of 120-1,500%. The mixture containing the swollen crosslinked polymer beads are polymerized.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention is applicable to lighting covers, lighting signboards, various displays,
The present invention relates to a method for manufacturing a light-diffusing methacrylic resin molded product suitable for use in members for the purpose of light diffusion, such as glazing or transmission screens.

(Prior art) Light-diffusing members such as illuminated covers and transmissive screens that have been widely used in the past are generally molded from a material in which inorganic or organic transparent fine particles are dispersed in a transparent synthetic resin. ing.

In this case, the transparent synthetic resin used is methacrylic resin, styrene resin, or vinyl chloride resin.In order to obtain light diffusivity, resins with a refractive index different from that of the transparent synthetic resin of the base material, such as barium sulfate or carbonate, are used. Mixing inorganic transparent fine particles such as quartz, etc. with an average particle size of 10μ or less,
The method is obtained by applying a binder to the surface of these transparent synthetic resins (JP-A-54-155241, JP-B-46-43189, Utility Model Publication No. 29-744).
(See Publication No. 0). It is also known that instead of the above-mentioned fine particles, polymer beads made by copolymerizing styrene or substituted styrene with a polyfunctional monomer are mixed (
Special Publication No. 39-10515, Special Publication No. 46-1183
(See Publication No. 4 and Japanese Patent Publication No. 55-7471).

The resins disclosed in these prior art techniques are intended to improve diffusibility, and have exhibited corresponding effects. However, in recent years, due to the demand for energy conservation, it has become important to effectively utilize light in lighting covers, displays, and the like.

By the way, if the light emitted from the light source is constant, one of the desirable properties of a light diffusing material is to diffuse the light in the required direction without absorbing as much light as possible, that is, to perform directional diffusion. It is one. When a unidirectionally directional diffusive material is incorporated into a lighting cover, display, or other device, a shape suitable for the device is required. This shape includes a shape that surrounds a light source, a flat plate shape, and a regular shape such as a lenticular lens or a Fresnel lens with fine irregularities on the surface.

(Problems to be Solved by the Invention) Therefore, it is a material that not only improves diffusivity but also allows the above-mentioned shape to be easily imparted, and conventional materials cannot be said to have directional diffusivity. Even if it was directional, it had the flaw that the light source could be seen through it.

The present invention aims to efficiently produce a light-diffusing molded article that overcomes the deficiencies of the prior art.

(Means for Solving the Problems) The gist of the present invention is to use crosslinked polymer beads that satisfy the following (1) and (2) to meet the following (3).
A light-diffusing polymer obtained by polymerization under the following conditions is used, the light-diffusing polymer alone or b is mixed with a methacrylic resin, and a predetermined molded product is formed by extrusion molding, pressure molding, or injection molding. (1) The difference between the refractive index of the crosslinked polymer beads and the refractive index of the base polymer is 0.02 to 0.15, (2+) and the average particle size of the crosslinked polymer beads is 1 to 1. 16μ - (3) Monomers, monomer mixtures or monomers such that the polymer when polymerized becomes a polymer whose main component is methyl methacrylate or a polymer which is compatible with a polymer whose main component is methyl methacrylate. Cross-linked polymer beads are mixed and swollen in a monomer solution containing a polymer, and polymerized so that the degree of swelling of the cross-linked polymer beads at this time is 120 to 1.500 tI).

Until now, there has been a method of blending cross-linked polymer beads with a base material to make a light-diffusing resin, for example, in Japanese Patent Application Laid-Open No. 61-15944.
This is shown in Publication No. 0, etc. However, in this case, the crosslinked polymer beads are simply blended with the base resin and molded by extrusion molding or injection molding, and if you want to obtain a degree of diffusivity that does not cause see-through, the light transmittance is known to be significantly reduced. The cause is the problem of the interface between the cross-linked polymer beads and the base resin, and as in the present invention, the cross-linked polymer beads are swollen with a polymerizable monomer, this is polymerized to obtain a light-diffusing polymer, and other materials are added as necessary. By blending and molding the resin with the following resin, we have established a method for producing a light-diffusing methacrylic resin that is transparent even though it has a high light transmittance that could not be obtained conventionally.

The present invention will be explained in more detail below.

The light diffusive materials currently in practical use have very good diffusivity, with a maximum bending angle (β value) of 60° or more. In addition, when the maximum bending angle (β value) is set and the parallel light incident perpendicularly to the light diffusing material is viewed from the transmission side,
When the maximum gain on the incident optical axis is defined as the angle between the optical axis and the optical axis required for the gain to decrease by 1/3 ()o4, this is used for boat fishing.

The inventors of the present invention investigated light diffusing materials that can provide directivity and found the following facts. In other words, ■ As long as the light source etc. cannot be seen through, the maximum bending angle (β
Conventional light diffusing materials generally have a maximum bending angle (β value) of 20° or more. be. However, if the concentration of the light diffusing agent is lowered (that is, the light diffusing property is lowered) and the maximum bending angle (β value) is set to 10' or less, the light source will be visible through it, making it a limited material as a light diffusing material. , the present invention has a maximum bending angle (β value) of 100
Even if the light source is below, it is not possible to see through it, or even if it is, it can be seen through by providing a finely uneven surface or a lens surface such as a Fresnel lens or lenticular lens on the surface. The purpose is to provide a molded product with excellent light diffusing properties.

The light-diffusing methacrylic resin of the present invention is mainly composed of methyl methacrylate, and includes ethyl methacrylate, butyl methacrylate, cyclohexynope methacrylate, 2-ethylhexyl methacrylate, and phenyl methacrylate, which are copolymerizable with methyl methacrylate. , methacrylic acid esters such as benzyl methacrylate, 2-hydroxyethyl methacrylate, glycidyl methacrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, methyl acrylate, ethyl acrylate, butyl acrylate, cyclohexyl acrylate, acrylic Acrylic acid esters such as 2-ethylhexyl acrylate, phenyl acrylate, benzyl acrylate, 2-hydroxyethyl acrylate, glycidyl acrylate, dimethylaminoethyl acrylate, diethylaminoethyl acrylate, methacrylic acid, acrylic acid, etc. ) acrylic acids, diethylene glycol di(meth)acrylate, 1,3-butylene glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, allyl(meth)acrylate, neobentylglycol di(meth)acrylate, etc. Functional (meth)acrylate, styrene, α-
It is a polymer with methylstyrene, manic anhydride, etc., but is not limited to these.

Furthermore, the crosslinked polymer beads of the present invention include phenyl group-containing vinyl molybdenum such as styrene, vinyltoluene, α-methylstyrene, and halogenated styrene.
Methyl (meth)acrylate containing at least one type of phenyl group-containing (meth)acrylate such as acrylate and benzyl (meth)acrylate and copolymerizable with these;
(meth)ethyl acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, (meth)acrylic acid,
Maleic anhydride etc. are added as necessary, and diethylene glycol di(meth)acrylate, 1,3-butylene glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, allyl(meth)acrylate, etc., which are copolymerizable with these are added. ) Polyfunctional polymers such as acrylate, divinylbenzene, and triallyl cyanurate are suspension-polymerized at a weight concentration of 2 to 20 μm to form crosslinked polymer beads with an average particle size of 1 to 16 μm. is used. Note that the types of crosslinked polymers are not limited to those mentioned above.

The light-diffusing polymer of the present invention is composed of a polymer that can swell the crosslinked polymer beads.
Specifically, polymers containing methyl methacrylate as a main component, or monomers that can be compatible with polymers such as ethyl methacrylate, butyl methacrylate, cyclohexyl methacrylate, 2-ethylhexyl methacrylate, phenyl methacrylate, Benzyl methacrylate, 2-hydroxyethyl methacrylate, glinocyl methacrylate, dimethylaminoethyl methacrylate,
Methacrylic esters such as diethylaminoethyl methacrylate, methyl acrylate, ethyl acrylate, butyl acrylate, cyclohexyl acrylate, 2-ethylhexyl acrylate, phenyl acrylate, benzyl acrylate, 2-hydroxyethyl acrylate, acrylic acid The monomer contains as a main component acrylic esters such as glycidyl, dimethylaminoethyl acrylate, and diethylaminoethyl acrylate, (meth)acrylic acids such as methacrylic acid and acrylic acid, and preferably contains methyl methacrylate as a main component. YolA.

These monomers can be used alone or in combination of two or more, and can also be used as a partial polymer called Shiratsubu for boat fishing, that is, a monomer solution containing a polymer in the monomer. .

The present invention involves dispersing cross-linked polymer beads in the above monomer or monomer solution, and under swelling, adding a polymerization catalyst, a polymerization degree regulator, a colorant, an ultraviolet absorber, barium sulfate, barium carbonate, calcium carbonate as necessary. Inorganic transparent fine particles such as glue, aluminum hydroxide, titanium oxide, etc. are added, and light-diffusing polymer beads are obtained by a conventional suspension polymerization method, or by cell casting by a bulk polymerization method. The polymer is appropriately pulverized to obtain a light-diffusing polymer.

The light-diffusing polymer can be produced as it is or by mixing it with a methacrylic resin if necessary and extrusion molding, pressure molding or injection molding to obtain a predetermined molded product.

The composition and blending ratio of the cross-linked polymer beads and the light-diffusing polymer beads are first set so that the difference between the refractive index of the base polymer and the refractive index of the cross-linked polymer beads is 002 to α15, and then the degree of swelling of the cross-linked polymer beads is determined. is 120-1
500 (calculated as (volume after swelling/volume before swelling) x 100). At this time, the degree of swelling is 1
If it is less than 20mm, the maximum brightness that does not cause transmission is too low and too bright, which is not desirable.On the other hand, if it exceeds 1500%, when comparing at the same maximum brightness, it is not preferable to use diffused light with a large bending angle. This is an unfavorable factor because the ratio becomes too small.

It should be noted that if a large amount of crosslinked polymer beads having a particle size of less than 1 μm is included, it is more desirable that the transmitted light has a yellowish color due to selective scattering of short wavelength light. On the other hand, if a large number of particles with a diameter of 5 mm thicker than 30 μm are included, this is not desirable because it causes glare in transmitted light. Therefore, the average particle size of the crosslinked polymer beads is 1 to 16μ, more preferably an average particle size of 6μ.
~12μ is good. The weight concentration of Ushida multifunctional upper part is 5~
20% is good, but if it exceeds a factor of 20, the maximum gain of light diffusion performance that does not cause see-through will be low, which is bad. This is not preferable because the proportion of diffused light with large angles becomes too small.

The weight concentration of the crosslinked polymer beads in the light-diffusing methacrylic resin depends on the thickness in the light transmission direction and the desired diffusivity and directivity of the transmitted light, but is required to be 0.08 to 10.

(Examples) Examples will be described below, but the present invention is not limited to these examples.

〔Measuring method〕

The total light transmittance in the examples is as per ASTM Dl Go
It was measured according to 3-6if. Further, the maximum gain (Go) and maximum bending angle (β value) were determined as follows. In other words, the measurement equipment and sample were arranged as shown in Figure 1, and (1) in the figure is a collimator made by Nippon Kogaku Co., Ltd. that serves as a light source.
(2) is a sample, and (3) is a luminance meter "Auto Spot" manufactured by Minolta. Among these, the light source (1) was made to illuminate the sample (2) surface at right angles, and the brightness was adjusted so that the illuminance on the sample (2) surface was 10 ft-ca. 3) Light source (1
) and sample (2), and the brightness on the surface of sample (2) was measured and the maximum gain (Go) was determined from these values. Furthermore, this luminance meter (3
) was rotated about the sample (2) as an axis, and the maximum bending angle (β) at which the gain on the sample (2) surface reached 1/3 GO was measured. For the average particle size, a cumulative weight tz histogram of the particle size was prepared using an rTA-It model Coulter Counter J manufactured by Coulter Electronics, and the particle size corresponding to a weight of 50 inches was taken as the average particle size. Further, the transparency and appearance of the light source were determined by observing with the naked eye.

[Example of manufacturing cross-linked polymer beads]

90 parts of styrene, 10 parts of divinylbenzene, 2,2'-azobismo2,4-dimethylvaleronitrile (as a polymerization initiator) 0. 1 part, 100 parts of water, 70 parts as a dispersant
ql) 0.01 part of saponified potassium polyacrylate was charged into a polymerization vessel, and suspension polymerization was carried out at 80°C with stirring. After polymerization, it was washed, dried, and separated using an air micron separator to obtain crosslinked polymer beads with a desired particle size distribution.

Cross-linked polymer beads with symbol 1-1 shown in Table 1 were produced by the above method, but the composition was changed below, produced in the same manner, and classified to obtain a total of 18 types of cross-linked polymer beads shown in Table 1. is.

Table 1 Composition of crosslinked polymer beads PMA: Phenyl methacrylate MMA:
Methyl methacrylate EDMA: Ethylene glycol dimethacrylate AMA: Allyl methacrylate [Production example A of light-diffusing polymer] Pure water 1.050? , 70% saponified potassium polyacrylate as a dispersant, 12%, crosslinked polymer beads shown in Table 1 359 (symbol A-14), the same (2, s t (
symbol A-17) and the same <1.42 (symbol A-18)
, 72 for methyl acrylate, 69 for methyl methacrylate
No. 37 was charged into a polymerization container, and suspension polymerization was carried out at 80° C. with stirring. After polymerization, wash, dry, and prepare A in Table 2-1.
Six types of light-diffusing polymers, A-14, A-17 and A-18, were obtained.

[Production example B of light-diffusing polymer]

Partial polymer of methyl methacrylate (polymerization rate 2oo) 1
The cross-linked polymer beads shown in Table 1 were added to part oo in the proportions shown in Table 2 and sufficiently dispersed. To this mixture, 0.01 part of dioctyl sulfosuccinate sodium salt as a mold release agent and 0.04 part of 2,2'-azobis(2,4-dimethylvaleronitrile) as a polymerization initiator,
0.4 n-dodenlumerbutane as a polymerization degree regulator
After adding and melting the mixture, it is removed and poured into two inorganic glass molds whose thickness has been set in advance to be 2 mm.
The mold was immersed in a 65°C hot water bath for 180 minutes, then
Polymerization was completed by staying in an air bath at 20° C. for 120 minutes. After cooling, the resin plate was taken out of the mold and crushed into approximately 500 parts of particles using a crusher to obtain a light-diffusing polymer.

[Production example of light-diffusing methacrylic resin plate] Example (1) A light-diffusing polymer shown in Table 2-1 was added to 100 parts of a copolymer of methyl methacrylate and methyl acrylate (composition ratio 94:6). They were blended in the proportions shown in Table 1 and sufficiently dispersed. This mixture was extruded using an extruder set at 250° C. and molded using a vertical three-piece polygingerol molding at about 80° C. to obtain a light-diffusing methacrylic resin plate designated by symbol 1-14 having a thickness of 2 mm. The optical performance of this resin plate is shown in 3-1.
Shown in the table.

(2) Mitsubishi Rayon acrylic resin “Acrybella”
80 parts of VHJ and 20 parts of a copolymer of methyl methacrylate, methyl acrylate, butyl acrylate, and styrene (composition ratio 86:1:10:2), the light-diffusing polymer shown in Table 2-1 was added to the light-diffusing polymer shown in Table 3-1. The mixture was amalgamated in a proportionate manner and sufficiently dispersed. This mixture was extruded and shaped using an extruder set at 240° C. VC. Furthermore, this pellet was injection molded into a test piece (symbol 17) having a plate thickness of 2111 #l using an injection molding machine set at 250°C. The optical performance of this test piece was evaluated as
-1 Shown in Table.

(The pellet shaped by the method of 31(2) was extruded with an extruder set at 250°C, and molded with a vertical 6-piece polygingerol at about 80°C. A methacrylic resin plate was obtained. The optical performance of this resin plate is shown in Table 3-1.

(4) The pellet shaped by the method of (2) is
A test piece (symbol 18) with a thickness of 2 was obtained by putting 19V into a mold with a diameter of 100 m heated to 50°C and press-forming with ID Okg/c1n2. The optical performance of this test piece is shown in Table 3-1.

(5) The light-diffusing polymer obtained by the method of (1) was
Extruded with an extruder set at 50℃, molded with 3 vertical polygingerols at about 80℃, plate thickness 2m code 19~
A light-diffusing methacrylic resin plate shown in No. 22 was obtained. The optical performance of this resin plate is shown in Table 3-1.

(6) The light-diffusing polymer shown in Table 2-1 was blended with 100 parts of a copolymer of methyl methacrylate and styrene (composition ratio 60:40) in the proportions shown in Table 3-1, and thoroughly dispersed. This mixture was extruded using an extruder set at 240°C, and molded using 3 vertical polygingerols, with a plate thickness of 2++.
A light-diffusing methacrylic resin plate with the symbol 16 of lI++ was obtained. The optical performance of this resin plate is shown in Table 3-1.

Comparative Example (1) 100 parts of a copolymer of methyl methacrylate and methyl acrylate (composition ratio 94:6) was added with light-diffusing polymers (B-1 to B-4) shown in Table 2-2, respectively.
They were blended in the proportions shown in Table 2 and sufficiently dispersed. Add this mixture to 2
It was extruded with an extruder set at 50°C and molded with a vertical three-piece polygingerol at about 80°C to obtain a light-diffusing methacrylic resin plate with a thickness of 2 mm. When looking at the light sources through this resin plate, the light sources were clearly visible.

(2) A resin plate containing the light-diffusing polymer shown in Table 2-2 (B-6) was manufactured by the manufacturing method shown in Comparative Example (1). When I looked at the light source through the resin plate I had taken out, it was not transparent, but the light source appeared to be glaring.

(3) A resin plate containing the light-diffusing polymer shown in Table 2-2 (B-5) was manufactured by the manufacturing method shown in Comparative Example (1). When I looked at the light source through the resin plate I had taken out, I could see it through.

(4) A resin plate containing the light-diffusing polymer shown in Table 2-2 ('B-v) was produced by the manufacturing method shown in Comparative Example (1). When I looked at the light source through the resin board I had taken out, I could see it through.

(5) A resin plate containing the light-diffusing polymer shown in Table 2-2 (B-8) was manufactured by the manufacturing method shown in Comparative Example (1). When you look at the light source through the resin plate you took out, you can see the light source clearly.

As is clear from the table above, the examples of the present invention have a large GO, in particular, the light source does not pass through even when the β value is 10 degrees or less, and the appearance is excellent with no yellowish color or glare from transmitted light. It was something.

Although the embodiments of the present invention have been described above, the present invention is not limited to these examples. spherical,
Of course, it is also possible to use it by forming it into a dish shape or a box shape.

(Effects of the Invention) Since the present invention has the configuration as detailed above, it has a good balance between brightness and maximum bending angle, and has the ability to prevent the light source from passing through even when the maximum bending angle is 10° or less. ,
In addition to its excellent appearance, it also has features that have great practical effects, such as being able to be molded in the same way as general methacrylic resin.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing a method for measuring optical performance adopted in an embodiment of the present invention. (1)...Light source (2)...Sample (3)...Luminance meter

Claims (1)

[Claims] A light-diffusing polymer obtained by polymerizing crosslinked polymer beads satisfying the following (1) and (2) under the following conditions (3) is used, and the light-diffusing polymer alone or a methacrylic resin is used. A method for producing a light-diffusing methacrylic resin molded product, characterized in that the mixture is mixed with a predetermined molded product by extrusion molding, pressure molding, or injection molding (1) Refractive index of crosslinked polymer beads and base polymer (2) The average particle size of the crosslinked polymer beads is 1 to 16μ; (3) The polymer when polymerized is a polymer whose main component is methyl methacrylate. Alternatively, cross-linked polymer beads are mixed and swollen in a monomer, a monomer mixture, or a monomer solution containing a polymer that is compatible with a polymer containing methyl methacrylate as a main component, and the cross-linking at this time is performed. Polymerization is carried out so that the degree of swelling of the polymer beads is 120 to 1,500%.