JPH08198976A - Light-diffusive methacrylic resin plate - Google Patents

Abstract

PURPOSE: To obtain a light-diffusive methacrylic resin plate having uniformly delustered surface along with small decline in impact resistance even after subjected to highly oriented molding, by dispersing in a methacrylic resin an elastomer with multilayer structure, acrylic cross-linked polymer and light- diffusive particles. CONSTITUTION: This resin plate is obtained by dispersing in (A) 100 pts.wt. of a methacrylic resin 0.25-1.5dL/g in intrinsic viscosity [η] consisting mainly of ethyl methacrylate (B) 5-50 (pref. 10-40) pts.wt. of an elastomer with multilayer structure, (C) 5-20 (pref. 10-20) pts.wt. of an acrylic cross-linked polymer 10-50μm in weight-average particle diameter, and (D) 0.5-5 pts.wt. of light- diffusive particles 1-10μm in weight-average diameter. This resin plate satisfies the relationship: (WR/WP)<2> /DP>0.02 (WR is the weight of the component B; DP is the weight-average particle diameter of the component C; WP is the weight of the component C).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light diffusing methacrylic resin plate which diffuses and transmits incident light and has a uniform matte surface.

[0002]

2. Description of the Related Art Conventionally, as a light diffusing resin plate, an organic or inorganic light diffusing agent is dispersed in a transparent resin such as an acrylic resin, a styrene resin, a polycarbonate or a vinyl chloride resin to form a plate shape. Things are used. Recently, not only the performance of diffusing and transmitting light, but also the performance of diffusive reflection of light, so-called matting, has been emphasized from the viewpoint of high-class feeling and antireflection, and there are various proposals as a plate having such properties. For example, in JP-A-58-29622, 100 parts of a methyl methacrylate polymer is added to 1.
Disclosed is an acrylic resin plate having a matte surface and an excellent antiglare effect, which is obtained by mixing 0 to 5.0 parts and 0.1 to 1.0 part of barium sulfate fine powder and kneading and extruding. JP-A-61-78859 discloses that, based on 100 parts by weight of a methyl methacrylate polymer, an alkyl methacrylate having an alkyl group having 1 to 4 carbon atoms, an aromatic vinyl monomer, and an alkyl group having 1 to 8 carbon atoms. Non-crosslinkable monomer consisting of alkyl acrylate and 0.3-3% by weight of crosslinkable monomer
1 to 20 parts by weight of a cross-linked polymer having a particle diameter of 30 to 300 μm obtained by polymerizing
A light-scattering acrylic resin composition obtained by blending parts by weight is disclosed. The light-diffusing resin plate has conventionally been used for a transmissive display, a lighting plate, a lighting cover, and the like. For these purposes, the plate is further heated and subjected to a secondary molding process. is there. Examples of the secondary molding method include free blow molding, free vacuum molding, push-up molding, ridge molding, straight molding, drape molding, reverse draw molding, air slip molding, plug assist molding, plug assist reverse draw molding method. Etc. These molding methods involve stretching of the material, but recently, due to the complicated shape of the molded product such as a lighting cover and the improvement of molding processing technology, a high stretching ratio partially exceeding 50% is achieved. Molding has begun to take place.

[0003]

When the conventional light diffusing plate is molded in this manner, the surface condition, that is, the matting tends to be non-uniform, and the high stretched portion tends to be easily cracked. For example, the resin plate described in JP-A No. 58-29622 has a non-uniform matte surface state with uneven gloss when subjected to high stretch molding. Furthermore, the impact resistance after molding is also reduced. JP 61-7
The composition described in Japanese Patent No. 8859 has a uniform matte state even after high stretch molding, but its impact strength is significantly reduced.

Therefore, the present invention provides a light-diffusing methacrylic resin plate which has a uniform matte surface and has little deterioration in impact resistance even when molded at a high draw ratio by secondary processing. is there.

[0005]

According to the present invention, 100 parts by weight of a methacrylic resin whose main component is methyl methacrylate having an intrinsic viscosity [η] of 0.25 to 1.5 dl / g is added to a multilayer structure elastic body 5. -50 parts by weight, weight average particle size 10-5
Provided is a light diffusing methacrylic resin plate in which 5 to 20 parts by weight of a 0 μm acrylic crosslinked polymer and 0.5 to 5 parts by weight of light diffusing agent particles having a weight average particle diameter of 1 to 10 μm are dispersed.

The methacrylic resin containing methyl methacrylate as the main component used in the present invention is a methyl methacrylate homopolymer or a copolymer of 50% by weight or more of methyl methacrylate with another vinyl monomer. is there. Examples of the vinyl monomer include ethyl methacrylate, butyl methacrylate, cyclohexyl methacrylate, phenyl methacrylate, benzyl methacrylate, 2-methacrylic acid.
Methacrylic acid esters such as ethylhexyl and 2-hydroxyethyl methacrylate, methyl acrylate, ethyl acrylate, butyl acrylate, cyclohexyl acrylate, phenyl acrylate, benzyl acrylate, 2-ethylhexyl acrylate, 2-hydroxy acrylate. Examples thereof include acrylic acid esters such as ethyl, unsaturated acids such as methacrylic acid and acrylic acid, styrene, α-methylstyrene, acrylonitrile, methacrylonitrile, maleic anhydride, phenylmaleimide, cyclohexylmaleimide and the like. The copolymer may further contain a glutaric anhydride unit and a glutarimide unit. In the present invention, among these methacrylic resins, those having an intrinsic viscosity [η] of 0.25 to 1.5 dl / g are suitable. If [η] is less than 0.25 dl / g, high stretch molding becomes difficult. Further, if the temperature at the time of molding is insufficient even slightly, peeling may occur at the interface between the base resin, the crosslinked polymer particles and the light diffusing agent, and the impact resistance tends to decrease. When [η] exceeds 1.5 dl / g, there is no problem in moldability, but the mechanical properties of the molded product deteriorate.

The multi-layered elastic body in the present invention is a granular material having at least a two-layered structure and containing 20 to 60% by weight of a rubber elastic layer or an elastomer layer, for example, JP-B-55-27576. The materials described in Japanese Patent Laid-Open No. 1-252653 and Japanese Patent Laid-Open No. 1-252653 can be used.

The amount of the elastic material having a multilayer structure is 5 to 50 parts by weight, preferably 1 part by weight based on 100 parts by weight of the methacrylic resin.
It is 0 to 40 parts by weight. If it is less than 5 parts by weight, the impact resistance becomes insufficient, and if it is more than 50 parts by weight, the rigidity becomes low, which is not preferable.

The acrylic cross-linked polymer means 50 wt% or more of acrylic monomer, 49.9 wt% or less of other monomer having one unsaturated double bond in the molecule, and unsaturated dimer. It is a copolymer of 0.1 to 50% by weight of a polyfunctional monomer having at least two heavy bonds in the molecule.

Acrylic monomers include methyl methacrylate, ethyl methacrylate, butyl methacrylate, cyclohexyl methacrylate, phenyl methacrylate, benzyl methacrylate, 2-ethylhexyl methacrylate, 2-hydroxyethyl methacrylate, acrylic acid. Methyl,
Examples thereof include ethyl acrylate, butyl acrylate, cyclohexyl acrylate, phenyl acrylate, benzyl acrylate, 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, acrylic acid and methacrylic acid.
Two or more kinds of these monomers may be used in combination.

The monomer having one unsaturated double bond in the molecule is not particularly limited as long as it is other than the above acrylic monomer component, but styrene, α-methylstyrene, acrylonitrile, methacryloyl are used. Examples include nitrile, maleic anhydride, phenylmaleimide, cyclohexylmaleimide and the like. Two or more kinds of these monomers may be used in combination.

The polyfunctional monomer is one that is copolymerizable with the above-mentioned monomer and excludes a conjugated diene. For example, 1,
4-butanediol di (meth) acrylic acid ester,
Alkyldiol di (meth) acrylic acid esters such as 1,6-hexanediol di (meth) acrylic acid ester and neopentyl glycol di (meth) acrylic acid ester; ethylene glycol di (meth) acrylic acid ester, diethylene glycol di Alkylene glycol di (meth) acrylic acid ester such as (meth) acrylic acid ester, tetraethylene glycol di (meth) acrylic acid ester, propylene glycol di (meth) acrylic acid ester, tetrapropylene glycol di (meth) acrylic acid ester Aromatic polyfunctional compounds such as divinylbenzene and diallylphthalic acid ester; trimethylolpropane tri (meth) acrylic acid ester,
Examples thereof include (meth) acrylic acid esters of polyhydric alcohols such as pentaerythritol tetra (meth) acrylic acid ester and allyl methacrylic acid ester.
Two or more kinds of these monomers may be used in combination.

The acrylic cross-linked polymer is obtained by polymerizing a mixture of the above-mentioned monomers into a spherical shape by a suspension polymerization method, a micro suspension polymerization method or the like. For example, Japanese Patent Laid-Open No. 5-1559
There are particles and the like obtained by the method described in JP-A-07.

The particle diameter of the acrylic crosslinked polymer is 10 to 50 μm, preferably 15 to 40 μm on a weight average basis.
If the particle size is less than 10 μm, a sufficient matte surface cannot be obtained. On the other hand, if it exceeds 50 μm, cracks are apt to occur from the part of the particles during molding, and the impact resistance is lowered.

The amount of the acrylic crosslinked polymer added is 5 to 20 parts by weight, preferably 10 to 20 parts by weight, based on 100 parts by weight of the methacrylic resin. If it is less than 5 parts by weight, uniform matte cannot be obtained, and if it exceeds 20 parts by weight, impact resistance is lowered.

As the light diffusing agent, either organic type or inorganic type can be used. For example, in the inorganic system, calcium carbonate,
Barium sulfate, aluminum hydroxide, talc, mica,
In organic systems such as glass and silica, styrene cross-linked polymers,
Examples include silicon-based cross-linked polymers, fluoropolymers, acrylic cross-linked polymers, and the like. Above all, the absolute value of the difference in refractive index of the methacrylic resin as the base material is 0.03 to 0.16.
The thing of can be used suitably.

The particle diameter of the light diffusing agent is 1 to 10 μm on a weight average.
m. If it is less than 1 μm, the light diffusivity is lowered, and 1
When it exceeds 0 μm, the matteness after stretching becomes uneven and the impact resistance is lowered.

The amount of the light diffusing agent added is 0.5 to 5 parts by weight. If the amount is less than 0.5 part by weight, the light diffusivity is insufficient, and 5
If it exceeds the weight part, the matte effect after stretching is affected and the impact resistance is lowered.

[0019] As a more sophisticated composition of methacrylic resin plate of the present invention, the weight (W _R) of the multilayer structure elastic member, a weight average particle diameter of the acrylic crosslinked polymer (D _P), acrylic crosslinked polymer There are some that satisfy the following formula (2), where (W _P ) is the weight of

[0020]

[Formula 2] (W _R / W _P ) ² / D _P > 0.02

The above formula is the amount of multi-layered elastic body and acrylic
The particle size and amount of the cross-linked polymer is large enough to impact the molded product.
It shows that it has an influence. Among these
(W _R) And (W_P) Has a particularly large effect.
won. Based on these findings, impact resistance at a high level
The composition range that can be maintained
Was. The upper limit of the value of the above formula is 10.

The light diffusing methacrylic resin plate of the present invention is a so-called sheet or plate. The thickness is not particularly limited, but is generally 0.8 mm to 10 mm.
It is a degree.

In order to form the light-diffusing methacrylic resin plate of the present invention from the methacrylic resin as a base material and each component to be dispersed, the both are mechanically mixed with a Henschel mixer, a tumbler, etc., and uniaxially or biaxially mixed. After melt-kneading with an extruder etc.,
Extrusion molding, that is, a method of forming a plate shape through a T-die and a roll unit: Mechanically mixing both, pelletizing with a uniaxial or biaxial extruder, etc., and making the pellet into a plate shape by injection molding or press molding There is a well-known method.

Further, there is a method in which each component to be dispersed is mixed with a syrup containing a monomer constituting the methacrylic resin of the base material and a partial polymer thereof, and cast-polymerized or continuous cast-polymerized to form a plate. is there.

Various well-known additives may be added to the methacrylic light diffusing resin plate of the present invention.

[0026]

The light-diffusing methacrylic resin plate of the present invention has a uniform matte surface and has a high level of impact resistance even when subjected to a high-stretching secondary molding process.
A highly stretched molded product molded from the resin plate can be suitably used for a lighting cover or the like which requires light diffusibility, matteness and impact resistance.

[0027]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. The evaluation method is as follows.・ Push-up molding; 17 cm of resin plate of 30 cm x 20 cm in oven
Heat to 0 ℃ and push up molding machine (TF-3 manufactured by Osaka Sheet Machinery Co., Ltd.
00 type, thrust area 10cm × 5cm, thrust height 10c
m) was used to form a stretched sample by forming a side stretch ratio of about 70%. -Press molding; a resin plate is pressed at 230 ° C for 5 minutes using a pressing machine (manufactured by Shindo Metal Industry Co., Ltd., hydraulic pressure 210 kg / cm ² ), and a non-stretched sample having almost the same thickness as the stretch-molded sample is prepared. did. -Intrinsic viscosity; measured in chloroform at 25 ° C. -Average particle diameter; measured by a light diffraction scattering particle size measuring device (manufactured by Malvern Instruments, Mastersizer), and the value of D50 was defined as the average particle diameter.・ Total light transmittance (T _t ); in accordance with ASTM D1003-61,
Poic integrating sphere type haze meter (Japan Precision Optics SEP-
HS-30D). -Hidden property and light diffusing property: transmitted light intensity (I ₀ ) at a transmission angle of 0 ° by vertical incident light, transmitted light intensity at a transmission angle of 5 ° by vertical incident light (I ₅ ), transmission angle at 70 ° by vertical incident light Of the transmitted light intensity (I ₇₀ ) of Murakami Color Research Laboratory Co., Ltd., using an automatic goniophotometer GP-1R, I ₅ / I ₀ as concealment, I ₇₀ / I ₀ as wide angle It was made to be side diffusive. -Surface gloss: 60 with a gloss meter (UGV-4D manufactured by Suga Test Instruments Co., Ltd.) in accordance with JIS Z-8741 gloss measurement
It was measured by reflection. -Impact strength: A 7 cm x 7 cm sample was supported around the sample, and a steel ball weighing 200 g was dropped in the center of the sample, and the cracked height (cm) was taken as the impact resistance.・ Stretching rate: Measure the thickness of the resin plate before and after stretching, and
((Thickness of original plate / thickness after forming) -1) * 100 (%)
It was calculated by the formula.

Reference Example Production of Acrylic Cross-Linked Polymer Acrylic cross-linked polymer particles (methyl methacrylate 96 obtained by the method described in Example 4 of JP-A-5-155907)
% / Methyl acrylate 4% copolymer D ₅₀ = 50 μm)
Wind classifier (TC-15 manufactured by Nisshin Engineering Co., Ltd.)
N), the D ₅₀ values are 20 μm and 35, respectively.
Particles of μm and 80 μm were obtained.

Examples 1 to 4, Comparative Examples 1 to 3 Methacrylic resin beads (methyl methacrylate 94% / 6% methyl acrylate copolymer [η] = 0.8 dl /
g) 100 parts by weight of the acrylic crosslinked polymer particles obtained in Reference Example, a multilayer elastic body having a three-layer structure (obtained by the method described in JP-B-55-27576, Example 3), and light. After mixing the amount of diffusing agent particles shown in Table 1 with a Henschel mixer, melt-kneading with an extruder (uniaxial, screw diameter 40 mm, Tanabe Plastic Co., Ltd.) at a resin temperature of 265 ° C., then T-die, polishing roll. A sheet having a thickness of 2 mm and a width of 24 cm was obtained through the three pieces. The obtained sheets were respectively subjected to the bump forming and the press forming to prepare evaluation samples. Table 2 shows the evaluation results
And shown in Table 3.

[0030]

[Table 1]

[0031]

[Table 2]

[0032]

[Table 3]

Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display area C08L 51:00 33:08)

Claims (2)

[Claims] 1. The intrinsic viscosity [η] is 0.25 to 1.5 dl /
100 parts by weight of methacrylic resin containing methyl methacrylate as a main component, multilayer elastic body: 5 to 50 parts by weight, acrylic cross-linked polymer having a weight average particle diameter of 10 to 50 μm: 5 to 20 parts by weight, Light diffusing agent particles having an average particle diameter of 1 to 10 μm: 0.5
A light-diffusing methacrylic resin plate having 5 to 5 parts by weight dispersed therein. The weight of 2. A multi-layer structure elastic body (W _R), a weight average particle diameter of the acrylic crosslinked polymer (D _P), when the weight of the acrylic crosslinked polymer and (W _P), the following The light diffusing methacrylic resin plate according to claim 1, which satisfies the formula [1]. [Equation 1] (W _R / W _P ) ² / D _P > 0.02