JPS63199713A - Actinic radiation-curable resin composition - Google Patents

Abstract

PURPOSE:To obtain the title composition which is lowly viscous and has high light transmission, orientability and hardness, by adding silicon oxide powder of a specified particle diameter to a resin comprising three acrylates of specified chemical structures. CONSTITUTION:A resin composition prepared by adding 1-20pts.wt. silicon oxide powder of an average particle diameter of 1-10mu to 100pts.wt. acrylate resin having a viscosity of 1-150cP and a refractive index after curing of 1.49-1.55, comprising 20-70wt.% acrylate having at least one aromatic ring, at least one hydroxyl group and one acryloyl group in the molecule, 25-75wt.% acrylate of an MW of 180-400, having at least one moiety of the formula (wherein R1 and R2 are each a 1-4C alkyl) and two acryloyl groups in the molecule and 5-55wt.% acrylate having at least three acryloyl groups in the molecule.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an active energy ray-curable resin composition suitable for cast molding of rear projection screens.

(Prior art) The screen (transmissive screen) used for rear projection television sets usually has a Fresnel lens to collect light from a projector, and the light that passes through this is formed into an image and distributed. It consists of a lenticular lens for This lenticular lens must have an appropriate lens shape to image the light focused by the Fresnel lens, high light distribution (light scattering) to obtain a wide viewing angle, and a bright image. In order to achieve this, it is necessary to have high light transmittance, high mechanical strength to withstand stress and impact, and high hardness to withstand scratches.

Conventionally, lenticular lenses have been manufactured using a composition in which light scattering agent particles with a limited particle size are mixed with a binder having an appropriate refractive index difference, and then a lens shape is imparted to this composition. However, by forming a composition containing light scattering agent particles into a lenticular lens shape, a lenticular lens with extremely excellent light distribution and light transmittance has been obtained. However, such thin lenses do not have sufficient mechanical strength, so in order to compensate for this, a method has been adopted in which the lenticular lenses are laminated on a separately molded transparent base material.

Methods for manufacturing such lenticular lenses include JP-A-57-5742, ζ JP-A-56-25719, JP-A-56-69619, and JP-A-58-1.
As seen in JP-A No. 78341, JP-A-58-57122, and JP-A-59-143618, sheets that have been given a lens shape by cast molding, hot pressing, roll forming, etc. There are methods such as bonding and integrating on a transparent base material by hot pressing or coating with adhesive, and laminating on a transparent base material during extrusion molding.

(Problems to be Solved by the Invention) However, the roll forming method cannot provide precise dimensional accuracy to the lens shape, and the deep drawing method intended by the inventors has a large thickness difference and high hardness. The product has the disadvantage that it lacks strength in thin parts and cannot be molded due to cracking or deformation. In addition, although the hot press method has good dimensional accuracy,
The high pressure during pressing easily deforms expensive molds, and deep drawing is as difficult as roll forming. Furthermore, there is a drawback that a subsequent step is required in which the sheet-shaped article having a lens shape obtained in this manner is laminated on a separately molded transparent substrate.

To solve this problem, a low viscosity liquid resin is placed between the transparent base material and the mold, and this is cured.
There is a cast molding method in which a lens shape is imparted and at the same time layers are laminated on a base. Liquid resins that can be used in this method include low-viscosity thermosetting and active energy ray-curing resins, but conventionally these liquid resins have low hardness and low viscosity and high refractive index. However, in the case of low viscosity and high hardness, there are problems such as low refractive index, lack of toughness and brittleness, and cracks occur during molding. Furthermore, in the case of a thermosetting type, it takes time to cure, and the thermoplastic transparent base material is deformed by the heat during curing, so it cannot be used.

(Means for solving the problem) As a result of intensive study in view of the above situation, the present inventors have found that
By mixing light-scattering particles with a limited particle size into a transparent resin made of three types of acrylic esters with a limited chemical structure, it has a low viscosity, is easy to cast, and has high light transmittance and distribution. The present inventors have discovered an active energy ray-curable resin composition that has optical properties, high hardness, and sufficient mechanical strength, and has completed the present invention.

That is, the present invention comprises: (A) 20 to 70% by weight of an acrylic ester having at least one aromatic ring, at least one hydroxyl group, and one acryloyl group in the molecule, I (B) molecule At least one 10- (but,
R1 and R2 in the formula represent an alkyl group having 1 to 4 carbon atoms. ) and having two acryloyl groups, 25 to 75% by weight of an acrylic ester with a molecular weight of 180 to 400
, and (C) consisting of 5 to 55% by weight of an acrylic ester having three or more acryloyl groups in the molecule and having a viscosity of 1 to 1
At 50 centipoise, the refractive index after curing is 1.49 to 1.
Active energy ray curing for rear projection screen cast molding characterized by mixing 3 to 15 parts by weight of silicon oxide powder with an average particle size of 1 to 4 μm to 100 parts by weight of acrylic ester resin No. 55. A mold resin composition is provided.

The present invention will be explained in more detail below.

As the acrylic ester (A) used in the present invention, any acrylic ester can be used as long as it has at least one aromatic ring, at least one hydroxyl group, and one acryloyl group in the molecule. However, among these, those having a molecular weight of 400 or less are preferred since they can reduce the viscosity. Specific examples of these include OH (wherein R3 represents a hydrogen atom, an alkyl group, an alkoxy group, or an aryl group; the same applies hereinafter), OH 0H, and the like.

The acrylic ester (B) used in the present invention has at least one -C- (wherein R1 and R2 in the formula represent an alkyl group having 1 to 4 carbon atoms) in the molecule,
and has two acryloyl groups and has a molecular weight of 180 to 400
Any acrylic ester can be used, and specific examples thereof include Hs 0 CHa GHI υ.

If the molecular weight of the acrylic ester (B) is less than 180, the boiling point will be low, it will be volatile, and PII (primary skin irritation) will be high, which is undesirable.If the molecular weight exceeds 400, the viscosity will become high and the It is not desirable because it cannot be converted into

As the acrylic ester (C) used in the present invention, any acrylic ester having three or more acryloyl groups in the molecule can be used, but among them, acrylic esters with a molecular weight of 2°000 or less can be used because they can reduce the viscosity. Preferably. Specific examples of these include CH2CH20CC1h -CH2 (R4-R9 in the formula represents an acryloyl group or an alkylyl group. However, at least three of RA to R9 are acryloyl groups.), (However, in the formula, at least three are acryloyl groups. Rrm
+ n indicates 0 or an integer, and J + m + n is 1 to
It is an integer of 30. ), CH20CCH-CH2, etc.

The above acrylic esters (A), (B) and (C)
) usage ratio is the sum of (A), (B), and (C) as 1
00% by weight, usually (A) is 20 to 70% by weight
, (B) is in the range of 25 to 75% by weight and (C) is in the range of 5 to 55% by weight, among which (A) is in the range of 30 to 50% by weight.
, (B) is 40-60% by weight and (C) is 10-30%
It is preferable to use the acrylic acid ester resin within the range of % by weight, since an acrylic ester resin having a good balance of viscosity, hardness, toughness, and refractive index can be obtained.

If (A) is less than 20% by weight, a cured product with an appropriate refractive index and high toughness cannot be obtained, and if it exceeds 70% by weight, the low viscosity required for cast molding cannot be obtained. Undesirable. If (B) is less than 25% by weight, high hardness and low viscosity cannot be obtained, and if it exceeds 75% by weight, an appropriate refractive index cannot be obtained, so these are not preferable. Furthermore, if (C) is less than 5% by weight, a cured product with high hardness cannot be obtained, and if it exceeds 55% by weight, low viscosity cannot be obtained and the cured product becomes brittle, which are both undesirable.

The acrylic ester resins used in the above acrylic esters (A), (B) and (C) have a viscosity of 1 to 150 centivoise because it is necessary to obtain suitable moldability, workability, etc. for cast molding. Usually, those within the range of . If the viscosity is less than 1 centivoise, the volatility and pH (primary skin irritation) of the resin will increase;
If it exceeds 0 centipoise, the viscosity is too high and it becomes difficult to charge the resin between the base material and the mold, which is not preferable.

Furthermore, since it is necessary to obtain a rear projection screen having high light distribution and high light transmittance, the above-mentioned acrylic ester resin has a refractive index in the range of 1°49 to 1.55 after curing. Usually used.

Among them, it is easy to obtain particularly high light distribution such that the 173 value angle is 8@ or more and particularly high light transmittance such that the total light transmittance is 85% or more. A value in the range of 1.53 is preferred. If this refractive index is less than 1.49, the difference in refractive index with the silicon oxide powder dispersed as light-scattering particles will be too small and only a low light distribution will be obtained; if it exceeds 1.55, the refractive index If the difference is too large, only low light transmittance can be obtained, so each is not preferable.

In the present invention, the silicon oxide powder used in combination with the acrylic ester resin includes crystalline silicon oxide powder and amorphous silicon oxide powder, but among them, higher light transmittance at the same blendability level is included. Amorphous silicon oxide is preferred because it provides the following. The average particle size of the silicon oxide powder used here is usually in the range of 1 to 10 μm, and especially in the range of 2 to 10 μm because it is easy to obtain particularly high light distribution and light transmittance.
A range of 4 μm is preferred.

The amount of the silicon oxide powder used is usually in the range of 1 to 20 parts by weight per 100 parts by weight of the acrylic ester resin. A range of 15 to 15 parts by weight is preferred.

In addition, in addition to the acrylic ester resin and the silicon oxide powder, the active energy ray-curable resin composition of the present invention may further contain a photopolymerization initiator, a photosensitizer, a coupling agent, and a dispersion agent, if necessary. Additives such as improvers and anti-settling agents, dyes for improving contrast, etc. can be added.

As a method for obtaining the active energy ray-curable resin composition of the present invention, raw materials such as acrylic esters (A) to (C), silicon oxide powder, various additives, and dyes are mixed in an impeller mixer, a turbo mixer, etc. A method of stirring and mixing using a stirring device is common, but a method of dispersing and mixing using a dispersion mixing device such as a ball mill or a sand mill is preferred in order to improve the dispersibility of the silicon oxide powder.

Here, active energy rays refer to electromagnetic waves and particle beams that can cure acrylic acid ester resins, such as visible light, ultraviolet rays, infrared rays (heat rays), electron beams, and ion beams.

The viscosity shown in the present invention was measured using a B-type viscometer, the refractive index was measured using an Atsube refractometer at 25±1°C, and the average particle diameter of the silicon oxide powder was measured using a laser scattering method. It is expressed as the particle diameter at the point where the cumulative weight of the particles is 50% by weight. In addition, the 1/2 value angle and 1/3 value angle mean that when a parallel ray of light incident perpendicularly to the rear projection screen is viewed from the transmission side and the brightness on the optical axis is the maximum brightness Go, the brightness is 1/3. This refers to the angle between the optical axis and the optical axis required for the reduction to 2Go and 1/3Go. Furthermore, the total light transmittance was measured using an integrating sphere light transmittance measuring device according to ASTM D.
-1003.

(Effect of the invention) The active energy ray-curable resin composition of the present invention has hardness,
It has the advantage that a rear projection screen with excellent toughness, light distribution, and light transmittance can be easily obtained by cast molding.

(Example) The present invention will be explained in more detail by showing Examples and Comparative Examples below. Note that all parts and percentages in the examples are based on weight (excluding total light transmittance).

Examples 1 to 3 and Comparative Examples 1 to 3 Acrylic esters (A-
1) to (C-3) are used in the number of copies shown in Table 1,
After adding 1 part of 1-hydroxycyclohexylphenyl ketone as a photopolymerization initiator to 100 parts of the total amount, the mixture was heated to 60°C to dissolve it and stirred to mix uniformly. Next, to this liquid were added amorphous silicon oxide powder in the number of parts shown in Table 1, and 2 parts of Cabcomorad C (a zircoaluminum coupling agent manufactured by Capton Chemical Co., USA) per 100 parts of this powder. , after dispersion for 30 minutes in a sand mill, further LaetllO
n (manufactured by Bickchem, West Germany, anti-sedimentation and dispersion improver) was added at a ratio of 0.5 parts to 1%00 parts of the above acid-based silicon powder, mixed and dispersed for 30 minutes using a sand mill, and then cured with ultraviolet rays. A mold resin composition was obtained.

Acrylic ester (A-1) Niacrylic ester (A-2) Niacrylic ester (B-1): CH3 Acrylic ester (B-2) Niacrylic ester (B-3) Niacrylic ester (C-1) Niacrylic ester (C-2): CH2CH20CCH-CH2 Acrylic ester (C-3): (However, R111""RI5 in the formula represents an alkylyl group or an acryloyl group, of which an average of 5 is an acryloyl group. ) These resin compositions were then placed between a polymethyl methacrylate plate with a thickness of 5mm and a fluororesin plate with a thickness of 2mm, with a spacer inserted between them to give a width of 50+gn.

It was injected into a cavity with a length of 50III11 and a thickness of 400 μm, and cured by irradiating 800 mJ/c of ultraviolet light through a polymethyl methacrylate plate with a high-pressure mercury lamp, then released from the mold and deposited on a polymethyl methacrylate plate with a thickness of 400 μm. 40
A rear projection screen on which a 0 μm light scattering layer was laminated was obtained.

The rear projection screens obtained in Examples 1 to 3 all had high light distribution with a 1/2 value angle of 7 @ or more and a 1/3 value angle of 10 @ or more, and a total light transmittance of 85% or more. It exhibits high light transmittance and has a high pencil hardness of H or higher. Furthermore, there is no generation of air bubbles during casting, and injection filling can be performed quickly, preventing cracks from occurring during curing or mold release, and preventing polymethyl methacrylate plates from forming. There was no peeling, and cast moldability was good.

On the other hand, the ultraviolet curable resin composition obtained in Comparative Example 1 had a high viscosity, took a long time to be injected into the cavity, produced bubbles, and had poor casting moldability. Furthermore, the rear projection screen obtained in Comparative Example 2 had a low pencil hardness of B, and was easily scratched. Furthermore, the rear projection screen obtained in Comparative Example 3 had cracks and peeling from the polymethyl methacrylate plate during curing.

In addition, the viscosity and refractive index of the acrylic acid ester resin used in Examples 1 to 3 and Comparative Examples 1 to 3, the average particle diameter of the amorphous silicon oxide powder, and 1/2 of the obtained rear projection screen.
Table 1 shows the binary angle, 1/I value angle, total light transmittance, pencil hardness, and cast moldability of the ultraviolet curable resin composition.

Claims (1)

Scope of Claims: (A) 20 to 70% by weight of an acrylic ester having at least one aromatic ring, at least one hydroxyl group, and one acryloyl group in the molecule; (B) molecule There is at least one ▲mathematical formula, chemical formula, table, etc.▼ (however, R_1 and R_2 in the formula represent an alkyl group having 1 to 4 carbon atoms), and a molecular weight having two acryloyl groups. (C) 5-55% by weight of an acrylic ester having 3 or more acryloyl groups in the molecule, and a viscosity of 1-150%.
Refractive index after curing is 1.49 to 1.55 in centipoise
1 to 20 parts by weight of silicon oxide powder having an average particle diameter of 1 to 10 μm is mixed with 100 parts by weight of an acrylic ester resin. Resin composition.