JPH03237133A - Scattering film - Google Patents

Abstract

PURPOSE:To obtain the title film useful for preventing reflection, having high transmittance and high scattering by polymerizing primarily crosslinked fine particles comprising a specific monomer in a specific monomer solution to give a secondarily crosslinked fine particles-containing polymer, blending the polymer with a multi-layer structure polymer and making the blend into a film. CONSTITUTION:5-30 pts.wt. primarily crosslinked fine particles prepared by copolymerizing one or more monomers selected from an aromatic vinyl compound and a (meth)acrylate with a polyfunctional monomer are blended with 100 pts.wt. monomer solution consisting essentially of 18-C alkyl (meth)acrylate, swollen and polymerized to give monomer in a specific monomer solution to give a secondarily crosslinked fine particles-containing polymer and 1-20 pts.wt. of the polymer is blended with 100 pts.wt. multi-layer structure polymer layer comprising four polymer layers such as an inner most polymer layer obtained by selecting from 1-8C alkyl acrylate, 1-4C alkyl methacrylate, copolymerizable double bond-containing monomer, polyfunctional monomer and graft crosslinking agent and blending and made into a film to give the objective film.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a diffusive film used for antireflection, or used for lighting covers, various displays, screens, etc.

[Prior Art 3] The most common method for obtaining a resin plate with good diffusivity is to mix an inorganic pigment into a resin material with good transparency.

Inorganic pigments include barium sulfate, titanium oxide, silicon oxide, aluminum hydroxide, calcium carbonate, and glass peas. Inorganic pigments are inexpensive and easy to use, but the total light transmittance of the resin plate tends to decrease, and the types and amounts that can be used tend to be limited.

As a method to improve this problem, there is a method of adding a crosslinked polymer having a refractive index different from that of the resin board base material to the synthetic resin serving as the base material.
No. 5-7471, No. 5B-11463, and Japanese Patent Applications No. 62-302D85 and No. 63-34862.

The techniques described in these documents have made it possible to manufacture methacrylic resin plates with high transmittance and high diffusivity.

[Problem to be solved by the invention]

However, all of the above techniques are for manufacturing resin plates with a certain degree of thickness;
In the case of a film, the resin plate obtained by the above technique is extremely fragile, and it has not been possible to obtain one that can withstand practical use.

The purpose of the present invention is high transmittance, high diffusivity,
Another object of the present invention is to provide a film that has excellent physical properties such as strength, flexibility, and elongation.

[Means to solve the problem]

In the present invention, primary crosslinked fine particles are obtained by copolymerizing at least one monomer selected from aromatic vinyl compounds and (meth)acrylates with a polyfunctional monomer. Primary crosslinked fine particles are mixed into a monomer liquid containing (meth)acrylate as the main component, and this is swollen and then polymerized to obtain a polymer containing secondary crosslinked fine particles. A diffusible film obtained by forming a film from a mixture obtained by mixing 1 to 20 parts by weight of a polymer containing fine lever particles, wherein the multilayer structure polymer contains 80 to 100 parts by weight of a carbon number 1. Alkyl acrylate having an alkyl group of ~8 and/or alkyl methacrylate having an alkyl group having 1 to 4 carbon atoms, 0 to 20
Parts by weight of a monomer having a copolymerizable double bond, 0 to 1
0 parts by weight of polyfunctional monomer, and their total amount 10
Innermost polymer layer formed by polymerizing 0.1 to 5 parts by weight of a grafting agent to 0 parts by weight: 80 to 100 parts by weight of alkyl acrylate having an alkyl group having 1 to 8 carbon atoms, 0 to 20 parts by weight 1 part of a monomer having a copolymerizable double bond, 0 to 10 parts by weight of a polyfunctional monomer, and 0.0 parts to 100 parts by weight of the total amount thereof.
A crosslinked elastic polymer layer formed by polymerizing 1 to 5 parts by weight of a grafting agent; and 51 to 100 parts by weight of an alkyl methacrylate having an alkyl group having 1 to 4 carbon atoms and 0 to 49 parts by weight of a copolymerizable The outermost polymer layer has a glass transition temperature of at least 60° C. and is formed by polymerizing a monomer having a double bond, and between the crosslinked elastic polymer layer and the outermost polymer layer, 10 to 90% by weight Alkyl acrylate having an alkyl group having 1 to 8 carbon atoms, 90 to 10 parts by weight of 1 to 1 carbon atoms
Alkyl methacrylate having 4 alkyl groups, 0-
20 parts by weight of monomers with copolymerizable double bonds, 0
~10 parts by weight of polyfunctional monomers, and their total amount 1
This is a diffusible film having an intermediate polymer layer formed by polymerizing 0.00 parts by weight with 0.1 to 5 parts by weight of a grafting agent.

In the present invention, first, at least one of an aromatic vinyl compound and a phenyl group-containing (meth)acrylate, and a polyfunctional monomer copolymerizable therewith are copolymerized to form primary crosslinked fine particles having a crosslinked structure. The refractive index of the above-mentioned primary crosslinked fine particles is relatively high (for example, the refractive index of styrene-based resin is about 158 to 1.59).
When these fine particles are mixed with a methacrylic resin (refractive index of about 1.49), diffuse reflection at the particle interface is strong, the film becomes whitish, and the total light transmittance is low even though the haze value is high.

In order to avoid such a situation, in the present invention, methyl methacrylate or a monomer whose main component polymer after polymerization forms a polymer compatible with polymethyl methacrylate, that is, an alkyl group having 1 carbon number, is used. After adding the primary crosslinked fine particles to a monomer liquid containing the alkyl (meth)acrylate monomer of 8 to 8 as a main component, this monomer liquid is polymerized. As a result, the crosslinked fine particles are swollen with the liquid, and monomers such as methyl methacrylate are polymerized while penetrating into the inside of the crosslinked fine particles.

Therefore, there is a gradient in the refractive index from the center of the crosslinked fine particles to the surface layer, and the refractive index near the surface layer approaches that of the methyl methacrylate polymer.Therefore, when formed into a film, diffuse reflection at the fine particle interface is reduced, and the transmittance of the film is It is possible to increase the haze value without lowering the value. Through this polymerization, a polymer containing secondary crosslinked fine particles with a gradient of refractive index (hereinafter referred to as a fine particle-containing polymer) is obtained.

Next, 1 to 20 parts by weight of the above fine particle-containing polymer is mixed with the multilayer structure polymer and formed into a film to obtain the film of the present invention.

As the aromatic vinyl compound which is the raw material for the primary crosslinked fine particles, for example, styrene or substituted styrene is used, and as the phenyl group-containing (meth)acrylate, for example, phenyl methacrylate, phenyl acrylate, etc. are used.

Further, as the polyfunctional monomer, for example, divinylbenzene, trivinylbenzene, alkylene glycol diacrylate, etc. are used alone or in a mixture of two or more, and this acts as a crosslinking agent.

-The concentration of the polyfunctional monomer in the second crosslinked fine particles is preferably 5 to 20% by weight, more preferably 5 to 10% by weight.

If the polyfunctional monomer is too small, the swelling of the crosslinked fine particles becomes excessive, and in some cases, the crosslinked fine particles may dissolve and may not retain their shape. If there is too much polyfunctional monomer, there will be little swelling and the effects of the present invention will not be obtained.

The average particle size of the primary crosslinked fine particles is preferably 5 to 20μ, 5
If there are too many particles of less than μ, especially 2 μ or less, the yellow tint of the light transmitted through the film becomes noticeable, and if the average particle size exceeds 20 μ, the diffusivity of the film decreases and the haze value decreases.

In order to obtain such crosslinked fine particles, conventionally known polymerization and crosslinking methods can be appropriately applied.

In addition to methyl methacrylate, the monomer solution to be polymerized with the crosslinked fine particles mixed therein may also contain alkyl acrylates such as methyl acrylate, ethyl acrylate, and 2-ethylhexyl acrylate. May contain. Furthermore, this liquid can contain a polymerization initiator and other components as appropriate.

The amount of the above-mentioned crosslinked fine particles is 5 parts per 100 parts by weight of the monomer liquid.
It is preferable to mix in a proportion of ~30 parts by weight. - If there are too many crosslinked fine particles, the viscosity of the mixture of the crosslinked fine particles and the above liquid will increase and the crosslinked fine particles will not swell sufficiently;
If it is too small, it will be necessary to use a large amount of pulverized powder, which will deteriorate the physical properties of the product.

The fine particle-containing polymer is mixed in an amount of 1 to 20 parts by weight with respect to 100 parts by weight of the multilayer structure polymer. Fine particle-containing polymer is 1
If it is less than 20 parts by weight, sufficient diffusibility cannot be obtained, and if it exceeds 20 parts by weight, the physical properties of the film will be insufficient.

Mixing of the fine particle-containing polymer and the multilayer structure polymer is not particularly limited, and may be carried out by appropriately selecting from known mixing methods.

In addition, the difference between the refractive index of the cross-linked fine particles (before soaking in the monomer solution) and the refractive index of the multilayer structure polymer is 0.02 to 0.15.
It is preferable that If this difference is too large, the whiteness will be strong and the total light transmittance will be reduced; if this difference is too small, the diffusion will be insufficient.

The multilayer structure polymer used in the present invention is a film resin composition having excellent transparency, weather resistance, solvent resistance, stress whitening resistance, processability, etc., and has a four-layer structure.

Examples of the alkyl acrylate (A+) having an alkyl group having 1 to 8 carbon atoms constituting the innermost layer polymer (A) include methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, and n-octyl acrylate. etc. can be used alone or in combination. As the alkyl methacrylate (A1) having an alkyl group having 1 to 4 carbon atoms, methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, etc. are used alone or in combination. Further, as the monomer (A2) having a copolymerizable double bond, acrylic monomers such as lower alkyl acrylate, lower alkoxy acrylate, cyanethyl acrylate, acrylamide, acrylic acid, and methacrylic acid can be used. Polyfunctional monomers (A) include alkylene glycol dimethacrylates such as ethylene glycol dimethacrylate, 1,3-butylene glycol dimethacrylate, 1,4-butylene glycol dimethacrylate and propylene glycol dimethacrylate. is preferred.

The graft cross agent (A4) refers to a compound having 2 to 3 unsaturated groups having addition polymerizability, and each unsaturated group has a large difference in polymerization reactivity, and is preferably a copolymerizable a, β −
Allyl, methallyl or crotyl esters of unsaturated carboxylic or dicarboxylic acids are used, more preferably their allyl esters of acrylic acid, methacrylic acid, maleic acid and fumaric acid. These may be used alone or in combination of two or more.

For A1, a total of 80 to 100 parts by weight of one or both of an alkyl acrylate having an alkyl group having 1 to 8 carbon atoms and an alkyl methacrylate having an alkyl group having 1 to 4 carbon atoms is used.

A2 is 0 to 20 parts by weight, A is o-io parts by weight, and A4 is 0.1 per 100 parts by weight of the total amount of AI”A s.
~5 parts by weight is used. If it is less than 0.1 parts by weight, there will be no grafting effect, and if it exceeds 5 parts by weight, the physical properties such as strength and elongation of the film will deteriorate.

In the crosslinked elastic polymer (B) formed in the second stage, B
+ is the alkyl acrylate shown in A1, B x
, B s and B 4 have Az and As, respectively.

The one shown in A4 is used. The same thing can be said about the amount of + Bl kB4 as in the cases of 81 to A4, respectively.

In the outermost layer polymer (C), C1 is the alkyl methacrylate shown in A1, and C2 is the monomer shown in A2, either alone or in combination. C3 is 51-100
C3 is used in an amount of 0 to 49 parts by weight. Outside this range, rigidity, heat resistance, strength, etc. will decrease.

In the intermediate polymer layer (D), Dr-Ds are B+, Cr, Aa, A3. A4
aD+, which is similar to that used for
0 parts by weight, D2 is 90 to 10 parts by weight, D3 is 0 to 20 parts by weight, D4 is 0 to 10 parts by weight, and Da is 0.1 to 5 parts by weight based on 100 parts by weight of the total amount of D1 to D4. It will be done.

If it is less than 0.1 parts by weight, there will be no grafting effect, and if it exceeds 5 parts by weight, the physical properties such as strength and elongation of the film will deteriorate.

In a multilayer structure polymer, A is transparency, B is flexibility, and C
is for imparting moldability, and D is for adjusting the refractive index with polymethyl methacrylate, and this structure greatly contributes to the excellent properties of the film of the present invention.

The thickness of the film is not particularly limited, but is 20 to 300μ.
s is preferred.

As a method for forming a film, conventional methods such as a T-die method, an inflation method, a calendar method, etc. can be applied without particular limitation. Furthermore, the obtained film can also be laminated to a resin substrate by a conventional lamination method, extrusion lamination method, hot melt lamination method, dry lamination method, wet lamination method, or the like.

〔Example〕

Examples 1 to 8 5 parts by weight of divinylbenzene were mixed with 100 parts by weight of styrene monomer and polymerized to obtain styrene fine particles (secondarily crosslinked fine particles) having an average particle size of 9 μm.

20 parts by weight of the styrene fine particles, 80 parts by weight of methyl methacrylate (monomer liquid), and azobisisobutyronitrile (polymerization initiator) are mixed and polymerized to obtain a plate-shaped polymer containing fine particles, which is crushed. It was made into a fine powder. The average particle size of the styrene fine particles at this stage is 1 l-
It had grown to 12p.

A multilayered polymer was made as follows.

In a polymerization vessel equipped with a cooler, 250 parts of ion-exchanged water (parts by weight, the same applies hereinafter), 2 parts of sulfosuccinic acid ester soda salt, and 0.05 part of Rongalit were charged, and after stirring under nitrogen, methyl methacrylate (MMA) was added. ) 1.6 parts,
From 8 parts of butyl acrylate (BuA), 0.4 parts of 1,3-butylene glycol dimethacrylate (BD), 0.1 part of allyl methacrylate (AMA) and 0.04 parts of cumene hydroperoxide (CHP). A mixture was prepared. After raising the temperature to 70°C, the reaction was continued for 60 minutes to complete polymerization of the innermost layer polymer (A). followed by MMAl, 5
A monomer mixture forming a crosslinked elastic polymer (B) consisting of 22.5 parts of BuA, 0 parts of BDl, and 025 parts of AMA was added over 60 minutes and polymerized to obtain a two-layer crosslinked rubber elastic body. In this case, the CHP used for the formation of the polymer (B)
The amount was 0.05% by weight based on the monomer mixture.

The degree of swelling and gel content of the obtained two-layer crosslinked rubber elastic body were determined to be 10.0.90%, respectively.

Subsequently, as an intermediate layer (D), a mixture of 5 parts of MMA, 5 parts of BuA, and 0.1 part of AMA was reacted, and finally, MMA
52.25 parts of MA and 2.75 parts of BuA were reacted to form an outermost layer polymer (C) with Tg=s6.6°C. The final particle size ranged from 1000 to 1500 particles. The obtained polymer emulsion was salted out using 5 parts of calcium chloride per 100 parts of the polymer, washed and dried, and after adding a stabilizer, it was shaped and various evaluations were performed. The residual amount of calcium in the final polymer was approximately 200 ppm, and the gel content was 67%.

Next, 100 parts by weight of this multilayer structure polymer was mixed with the fine powder of the above-mentioned fine particle-containing polymer in the amount shown in Table 1, pelletized with an extruder, and then extruded into a film. 100 or 150 as shown. created a film.

The total light transmittance and haze value of these films are determined according to JIS
- Measured based on -6714, gloss level is JIS-Z
-60 parts specular gloss was measured based on -8701.

We also evaluated whether the light source was visible or invisible when looking through it. The results are shown in Table 1.

Table 1: Total light transmittance As shown in Table 1, the total light transmittance was as high as 85% in all of the examples, and the haze value was also 65% or higher, indicating good diffusivity. Further, both sides of the film were matte, and the gloss level was 40 or less. It is empirically known that if the glossiness is 40 or less, surrounding light sources will not be visible in the image. Furthermore, due to the high haze value and the matte surface, the see-through was extremely good in all Examples.

If the amount of the fine particle-containing polymer added exceeds the range of the present invention, the spinnability during film extrusion would be poor and a thin film could not be obtained.

[Effects of the Invention] The present invention provides a diffusive film with high transmittance and high diffusion.The film of the present invention has a low surface gloss,
It also has a great anti-reflection effect.

This film is extremely effective in the field of films that require diffusivity, and is used in antireflection films, lighting covers laminated with transparent resin substrates, various displays, reflective or transmissive screens, and backlights for LCDs. It can be used very suitably for diffusion films, etc.

Claims (1)

[Scope of Claims] 1) Primary crosslinked fine particles are obtained by copolymerizing at least one monomer selected from aromatic vinyl compounds and (meth)acrylates with a polyfunctional monomer, and the alkyl group has 1 carbon atom. The primary crosslinked fine particles are mixed into a monomer liquid containing the alkyl (meth)acrylate of No. 8 as a main component, and this is swollen and then polymerized to obtain a polymer containing secondary crosslinked fine particles. A diffusible film obtained by forming a film from a mixture obtained by mixing 1 to 20 parts by weight of a polymer containing fine particles to parts by weight, wherein the multilayer structure polymer contains 80 to 100 parts by weight. , alkyl acrylate having an alkyl group having 1 to 8 carbon atoms and/or alkyl methacrylate having an alkyl group having 1 to 4 carbon atoms, 0 to 20
Parts by weight of a monomer having a copolymerizable double bond, 0 to 1
0 parts by weight of polyfunctional monomer, and their total amount 10
Innermost polymer layer formed by polymerizing 0.1 to 5 parts by weight of a grafting agent to 0 parts by weight; 80 to 100 parts by weight of alkyl acrylate having an alkyl group having 1 to 8 carbon atoms, 0 to 20 parts by weight 0.0 parts of a monomer having a copolymerizable double bond, 0 to 10 parts by weight of a polyfunctional monomer, and 0.0 parts to 100 parts by weight of the total amount thereof.
A crosslinked elastic polymer layer formed by polymerizing 1 to 5 parts by weight of a grafting agent; and 51 to 100 parts by weight of an alkyl methacrylate having an alkyl group having 1 to 4 carbon atoms and 0 to 49 parts by weight of a copolymerizable The outermost polymer layer has a glass transition temperature of at least 60° C. and is formed by polymerizing a monomer having a double bond, and between the crosslinked elastic polymer layer and the outermost polymer layer, 10 to 90% by weight 90 to 10 parts by weight of an alkyl acrylate having an alkyl group having 1 to 8 carbon atoms, 90 to 10 parts by weight of an alkyl group having 1 to 8 carbon atoms;
Alkyl methacrylate having 4 alkyl groups, 0-
20 parts by weight of monomers with copolymerizable double bonds, 0
~10 parts by weight of polyfunctional monomers, and their total amount 1
1. A diffusible film having an intermediate polymer layer formed by polymerizing 0.1 to 5 parts by weight of a grafting agent per 00 parts by weight.