JPH01172801A - Light diffusion plate having light transmittability - Google Patents

Abstract

PURPOSE:To improve total ray transmittance and diffusivity by dispersing spherical particles of a solid silicone resin having a prescribed diameter into a transparent resin plate so that said particles exist therein. CONSTITUTION:The silicone resin in which the org. group is directly coupled to a silicon atom, the remaining bonds are directly coupled to oxygen and the silicon atom and oxygen are made into a polymer by the repeating siloxane bonds is used. The silicone resin has the average particle size in a preferably 0.3-5mu, more preferably 0.5-3mu range. The diffusion plate of high transmission and high diffusion is obtd. at a relatively low concn. of about 1% mixing ratio of the spherical particles of the silicone with the transparent resin if the plate is as relatively thick as 1-3mm. About 20% mixing ratio is needed if the plate is as thin about 100mu-200mu. The increasing of the total ray transmittance and the decreasing of the parallel ray transmittance are thereby simultaneously attained with good balance.

Description

[Detailed Description of the Invention] <Industrial Field of Application> The present invention relates to a plastic diffuser plate with excellent light diffusing properties, and more specifically, it relates to a plastic diffuser plate with excellent light diffusing properties. The present invention relates to a light diffusing plate with increased transmittance and color temperature, and a light diffusing plate in which the spherical particles are mixed and dispersed in a transparent paint and coated on a transparent substrate.

<Prior art> As light-diffusing plastic plates, transparent plastic sheets such as methacrylic resin plates, polycarbonate resin plates, and polyvinyl chloride resin plates have been blended with inorganic or organic light-diffusing agents. In addition to this, thin light-diffusing films such as polyester films have also come into use.

These light-diffusing plastic sheets are used for lighting,
In addition to glazing, signboards, letters projected from the rear,
It is also used as an arbor projection screen for projecting images, or as a milky-white diffusion sheet to ensure the brightness of print films for various advertisements and to diffuse light sources. Furthermore, recently, they have come to be used in liquid crystal displays used in office automation equipment such as word processors, and in diffusers for backlight sources in liquid crystal color televisions.

To manufacture these light-diffusing plastic plates, inorganic light-diffusing agents such as calcium carbonate, titanium oxide, barium sulfate, talc, and silica are mixed and dispersed in a transparent plastic material, and the mixture is extruded into a plate shape using an extruder. This is the usual method. Also, a method of applying these light diffusing agents to the surface of a transparent plastic plate is also used.

Other organic dispersants include powders with different refractive indexes, such as fluororesin, methacrylic resin, epoxy resin, penzoguacamine, polyethylene, nylon, and phenol, which are mixed and dispersed in transparent plastics. . However, high light transmittance and high diffusivity are strictly required.

<Problems to be solved by the invention> In particular, it has become extremely difficult to use conventional products for applications such as diffusion plates for backlights, which are essential for LCD displays, which have become rapidly popular in recent years. situation(
There are two.

When attempting to increase the light transmittance (total light transmittance) of conventional products, the amount of light diffusing agent mixed must be reduced, resulting in a decrease in the diffusivity.

In order to increase the diffusivity, it is necessary to increase the amount of light diffusing agent added, and as a result, the total light transmittance decreases. That is, the actual situation is that total light transmittance and diffusivity are in a contradictory relationship.

In view of these circumstances, the inventors of the present invention have developed a technology that increases the diffusion rate without reducing the total light transmittance, and also improves the color temperature required for the diffuser panels of LCD color televisions, which have recently become popular. The present invention was achieved through intensive research aimed at further increasing the luminance distribution and achieving a flatter luminance distribution.

Means for Solving the Problems> The present invention consists of a solid silicone resin having a number average particle diameter of 0, in which a silicon atom is directly connected to a transparent resin or an organic group having an affinity for its monomer, forming a polysiloxane bond. .3
~70μ spherical particles in the transparent resin plate 1=with respect to the transparent resin/~! A light diffusing plate having light transmittance characterized by being mixed and dispersed at 0 wt%. An organic group having an affinity for a coating film-forming material in a transparent paint or its seven molecules is directly bonded to a silicon atom. Spherical particles made of a solid silicone resin forming a polysiloxane bond and having a number average particle diameter of 0.3 to /θμ are added to a transparent paint relative to the coating film-forming material or its constituents in the material. /~s o wt* A light diffusing plate having light transmittance characterized in that the mixed and dispersed paint is coated on at least one side of a transparent substrate.

The silicone resin used in the present invention has an organic group directly bonded to a silicon atom, and the remaining bonds are directly bonded to oxygen, and is a polymer formed by repeating siloxane bonds between silicon atoms and oxygen. The spherical particles of the present invention are solid at room temperature or higher. More preferably, it is one that can maintain a solid state even under the temperature of secondary processing such as press stretching of a transparent resin plate or transparent substrate, which will be described later.

Furthermore, it is preferably a solid polymer in which the silochitin bonds exhibit a three-dimensional network structure.The number of organic groups bonded to the silicon atom varies depending on the type thereof and the affinity for the transparent resin ( Preferably 0.5 to 1.3 on average
, more preferably 0.7 to 7.3.

Spherical particles of silicone resin having a surface covered with organic groups bonded to silicon atoms are well dispersed in organic solvents and have the effect of increasing the viscosity of the solvent. The spherical particles used in the present invention have a viscosity when dispersed in a solvent (the solvent is n-hexitine,
The mixed amount of spherical particles is 100 Wt for n-hexitine,
Measured at room temperature, B-type rotational viscometer, 40 rpm), 200~
Those exhibiting jθQ CpS are preferably employed. More preferably, it is in the range of 300 to 4 t o cps.

FIG. 7 shows seven examples of molecular structure models of silicone resin spherical particles used in the present invention.

The model shown in FIG. 1 is a network structure in which xylochitin bonds extend in three dimensions, and has a structure in which seven organic groups are bonded to a silicon atom. This model is the most preferred embodiment of the present invention.

The silicone resin of the present invention is a substance with intermediate properties having both inorganic properties such as glass and organic properties due to organic groups. In addition, as shown in Figure 7, the surface of the spherical particles has a structure covered with organic groups that are firmly and directly bonded to silicon atoms, so the dispersibility in transparent resins or their polymerizable monomers is extremely good. . Furthermore, it has been revealed for the first time by the present invention that the optical properties are significantly improved as a very unexpected effect.

Examples of organic groups that can be used in the present invention include alkane groups such as methyl, ethyl, propyl, and butyl groups, as well as carboxyl groups, carbonyl groups, ester groups,
It contains an organic group such as an ether group that has an affinity for the transparent resin used in the present invention or its monomer. A typical organic group is a methyl group.

If the number of organic groups directly bonded to silicon atoms is less than 0.5 on average, it may be difficult to monodisperse the organic group into a transparent resin or a coating film-forming material in a transparent paint. There is also a possibility that secondary aggregation occurs and the particles become enlarged, resulting in a tendency to obtain an optically non-uniform diffuser plate.

On the other hand, if the number of organic groups directly bonded to silicon atoms exceeds 5 on average, it becomes difficult to form a three-dimensional network structure of polysiloxane bonds or to form a spherical structure, or it becomes easily deformed by external stress. There may also be a tendency for particles to form easily.

For example, a hydrolyzable silane having three functional groups can be used as a raw material for producing the silicone spherical particles used in the present invention. It is presumed that particles with a three-dimensional network structure as shown in Figure 1 are formed through the following reaction mechanism: hydrolysis and condensation steps.

In this hydrolysis and polycondensation reaction process, the types of functional groups and organic groups of the hydrolyzable silane used, the type and amount of the hydrolysis catalyst (acid, alkali), the structure of the reaction equipment,
The shape and size of the particles are delicately affected by the stirring conditions (2), and by controlling these influencing factors during particle formation, it is possible to produce the desired product.

In the present invention, it is necessary that the shape of the spherical particles is not amorphous in order to obtain optical properties. Although the shape of the particles varies depending on the conditions of use and purpose, it is preferable to have a shape ranging from a round sphere to a true sphere, and among them, a true sphere or a shape close to this is most preferable.

Irregularly shaped particles have poor dispersibility when mixed into transparent resins or transparent paints, and the particles enlarge due to secondary aggregation, causing sedimentation and sedimentation, resulting in poor optical uniformity. A plate-like plate or coating film cannot be obtained.

True spherical particles do not have this problem, exhibit good dispersibility, and greatly improve optical properties.

In particular, if the particles have a true spherical shape or a shape close to it, secondary aggregation of the particles will not occur during the secondary processing (described later) of the plate-shaped polymer resin, which is press stretching, which is particularly preferably employed in the present invention, and the periphery of the particles voids in polymers
The optical properties due to the formation range from 0.3μ to /θμ.

If particles having an average particle diameter of less than 0.3 μm are used, the desired light diffusion efficiency cannot be obtained. In addition, if /θμ is exceeded, the desired light transmittance cannot be obtained, resulting in a dark light diffuser plate, and during secondary processing (around two particles), defects are likely to occur and it is difficult to obtain a diffuser plate of consistent quality. Preferably 0.
3~! The average particle size is preferably in the range of 0.j to 3μ.

In the present invention, the number average particle diameter is measured under the following conditions.

Measuring device: Centrifugal automatic particle size distribution measuring device (particle analyzer) (Type) CAPA-600 model (device manufacturer) Hitachi 1 unit Measuring method: Light transmission liquid phase sedimentation particle size distribution using high-speed centrifugal sedimentation method and natural sedimentation method Measurement method (calculate the number average particle diameter from 2.

Dispersion medium: Aqueous surfactant solution Dispersion conditions: The amount of ultrasonically dispersed silicone spherical particles mixed into the transparent resin should be set to an optimal concentration depending on the thickness of the diffuser plate to be finally used. If the plate thickness is relatively thick, such as /~3mm,
A diffuser plate with high transmittance and high diffusion can be obtained with a relatively low concentration of around 1/2. On the other hand, in the case of a thin plate of about /θθμ to 20θμ, a mixing amount of about 20μ is required. Furthermore, when applying paint 4 to the surface of a transparent substrate, the coating film thickness is usually 3
Since the particle size is approximately 30μ, the particle concentration is approximately j0.

In the present invention, silicone spherical particles are dispersed and mixed in a transparent resin plate to form a diffusion plate, and silicone spherical particles are dispersed and mixed in a transparent paint to form a light-diffusing paint.
Also included are transparent plastic substrates and diffuser plates coated on the surface of glass substrates.

The moisture content of the silicone spherical particles used in the present invention is 7 to
It is relatively expensive at 2 yen, and it is easy to cause problems such as lipoids forming bubbles during secondary processing by heating, and it is difficult to obtain a diffuser plate of stable quality. Therefore, it is dispersed and mixed in transparent plastic material. Before use, it is necessary to sufficiently heat and dry the product to lower the moisture content.

As the transparent resin used in the present invention, methacrylic resin, polycarbonate resin, vinyl chloride resin, polystyrene resin, polyester resin, etc. are preferably employed,
A predetermined amount of silicone spherical particles is mixed into these transparent resins using a sheeting device such as an extruder.

In the present invention, any thickness of the transparent resin plate can be used depending on the purpose, the type of resin, etc.

0 under normal conditions. / species or more are preferably used. For those whose physical properties have been improved by primary processing by press stretching as described above, those with a length of less than 0.1 m are also suitable.

Among these, methacrylic resin can be polymerized by seven-mer casting, so it is also possible to disperse silicone particles in methacrylic monomer and then polymerize it to form a plate.

In the present invention, methacrylic resin is particularly preferably employed as the transparent resin material.

The methacrylic resin that can be used in the present invention is a polymer whose main component is methyl methacrylate (hereinafter abbreviated as MMA),
These include MMA polymers (hereinafter abbreviated as PMMA), copolymers containing MMA, polymer blends in which PMMA or MMA copolymers are blended with other polymers, and those in which various other blends are added. PMMA can be easily polymerized into C-sheets by cell casting. Ultra-high molecular weight PMMA having a weight average molecular weight of 100,000 or more can be easily polymerized and can be favorably used in the present invention.

As the MMA copolymer, MMA and alkyl acrylate copolymers can be used favorably. As the alkyl acrylate, 7 to 10% by weight copolymers of methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, coethylhexyl acrylate, etc. can be used favorably. Heat-resistant acrylic resins such as MMA-maleic anhydride-styrene ternary copolymer and MMA-methylmethacrylamide copolymer can also be used satisfactorily. In addition, MMA
Seven or more copolymers of styrene, styrene derivatives, acrylonitrile, methacrylate, acrylic acid, and methacrylic acid can be used. Compared to other transparent resin materials, methacrylic resin has high transparency, is resistant to yellowing even when used outdoors, and has the best weather resistance.It also has excellent surface hardness and rigidity. Depends on being there.

However, the disadvantages of methacrylic resin are that it has poor image impact resistance and is brittle, making it difficult to be used in applications that strongly require lightness and thinness, such as backlight diffusers for LCD displays. be.

Therefore, in order to greatly improve the drawbacks of this methacrylic resin, the present inventors actively employ a stretching method called press stretching as a secondary processing to strengthen the molecular orientation along the co-axis.

In order to improve the mechanical properties of a diffuser plate in which the spherical particles of the present invention are dispersed and mixed in a transparent resin, a method of press stretching is preferably employed.

That is, it is preferable to adopt a method of heating and pressing with a press to make the material thinner and have a larger area, resulting in highly oriented molecular orientation and strengthening the physical properties.

Here, if an organic diffusing agent (mainly polystyrene particles) conventionally used as spherical particles is used instead of the spherical particles of the present invention, the diffusing agent becomes spherical particles in the transparent resin at the stage of the original fabric before stretching. Even if they are dispersed in the material, the grain shape is deformed during the press-stretching process and becomes flat particles, which significantly reduces the light transmittance.Also, the grain shape changes significantly depending on the conditions such as temperature, press pressure, and press speed during press-stretching. There is a problem that a light diffusing plate having a constant quality cannot be stably manufactured due to large fluctuations. However, by using the spherical particles of the present invention, this disadvantage is overcome.

In the present invention, the method of forming the co-axis (bimolecularly oriented methacrylic resin plate (sheet)) by press stretching is as follows:
The compression molding method disclosed in JP-A-60-2372/2 can be preferably used.

It is preferable that the co-axis oriented sheet (2 is the average orientation release stress (hereinafter abbreviated as OR8) is applied with a co-axis orientation of V- or more.OR8 indicates the degree of sheet orientation, and the sheet is heated. This is the contractile force when it is applied.The OR8 measurement method is based on A8TMD/Twilight θ.

The methacrylic resin plate (sheet) that can be used in the present invention has an average OR8! (more than the value, preferably 10-4tOhz
Particularly preferred are those with a strong - co-axis orientation. The methacrylic resin plate (sheet) should be oriented along the λ axis (the impact resistance will be stronger than the second one, and the ORB will be j l'v/i
Above, especially when /OKg/dl2, the impact resistance becomes significantly large. The relationship between OR8 and counter-impact strength is shown in Japanese Patent Application Laid-open No. 11-11711.

The co-axis orientation described herein refers to uniform orientation in the co-axis direction, and includes slight differences in OR8 in the two axes and differences in stretching ratio. A multiaxially oriented plate (sheet) that is evenly oriented in all directions is included in the present invention, and the best score is 1: it can be used.

By using this press stretching method, methacrylic resin has the characteristics of transparency, weather resistance, and
It is possible to greatly improve impact resistance, which is the biggest drawback, while maintaining hardness and rigidity.

Therefore, thin sheets, for example, film-like sheets of less than 0.7 m, which were conventionally considered impossible to use with methacrylic resin, can be produced successfully (two-sided use).

In addition, as a feature of the methacrylic resin plate using the press stretching method (2), although it is a highly molecularly oriented resin plate, it has the advantage that it is optically extremely uniform and has little birefringence of light.
It has the advantage that it can be used for applications such as liquid crystal display substrates used in lamination with polarizing films, or optical discs, which require a high degree of optical uniformity.

Furthermore, by press-stretching, another disadvantage of methacrylic resin, which is that it is easily oxidized by organic solvents, and when it comes into contact with organic solvents, thin crazing occurs, whitening, and the transparency is significantly reduced, can be overcome. It also has the advantage of being improved.

This also has the advantage of being able to withstand harsh conditions such as when cleaning dirt and dust during use, or under harsh conditions caused by insecticide pine dew in the summer.

In the present invention, transparent resin (2 pairs of silicone spherical particles are generally blended in a predetermined amount during sheeting with an extruder, but when using a methacrylic resin, a methacrylic monomer is used, Preferably, a method is adopted in which particles are mixed and dispersed to a predetermined tn, and then the dispersed monomer is injected between two glass plates, and polymerized to form a plate-like product.The reason for this is that the thermal history is smaller than that of extruder mixing and dispersion. In addition to the fact that there are few extra troubles and easy mixing, the molecular machine of methacrylic resin is
Since the molecular weight of the extruded plate is as high as 10,000 or more (the molecular weight of the extruded plate is about 100,000 to λθ), it is possible to obtain a press-stretched plate with excellent heat resistance and solvent resistance. Furthermore, stretched plates made from cast plates are superior in terms of ease of cutting with a laser beam, machining with a lathe, drilling with a drill, and adhesion with a solvent or adhesive. (It is advantageous for assembly work) Next, the transparent paints of the present invention include solvent evaporation type nitrocellulose lacquer, vinyl chloride resin paint, acrylic lacquer oxidation polymerization type oil-based paint, synthetic resin paint, and phthalate resin paint. , phenolic resin paint, chlorinated rubber paint, silicone alkyd resin paint, addition polymerization type unsaturated polyester resin paint, ultraviolet curing paint, electron beam curing paint, epoxy resin paint, polyurethane resin paint (
Polyisocyanate-polyol resin), heat condensation polymerization type amino alkyd resin paint, amino acrylic resin paint, amino polyester resin paint, silicone polyester resin paint, etc. can be used.

Among the above-mentioned paints, it is necessary to select one that has the best possible coating film transparency since optical properties are particularly required in the present invention. Furthermore, it is preferable that the coating material has excellent dispersibility of silicone resin particles and coating processability. Moreover, it is also required to have excellent weather resistance, scratch resistance, chemical resistance, solvent resistance, etc.

In the present invention, from the above-mentioned viewpoint, consideration is given mainly to scratch resistance, and ultraviolet curable acrylic resin paints, thermosetting silicone resin paints, and polyurethane resin paints are preferably used.

It is usual to add a solvent to these paints as necessary to adjust the viscosity and improve film-forming ability and coating performance. The type and amount of solvent used depends on the coating method used, the desired coating thickness, the type of coating film forming material used,
Appropriate paint, depending on drying method, curing method and conditions, etc.
The amount of mixture is determined. In the present invention, silicone spherical particles are used as wall film-forming materials (2 to 2) present in transparent paints.
r o wts mixed and dispersed.

Silicone spherical particles can be dispersed in a transparent paint by mixing and dispersing them directly into the paint film forming material, or by mixing and dispersing them into a mixture of the paint film forming material and a solvent, that is, the paint. be.

The thus obtained transparent paint in which silicone spherical particles are mixed and dispersed is applied to the surface of a transparent substrate using a spray method, dipping method, curtain flow method, roll coater method, printing method, etc., and then applied using an ultraviolet irradiation device. Alternatively, a method of curing by heating may be used.

The present invention does not particularly limit the type of transparent resin used as the coating film forming material of the transparent paint. However, considering the usage environment in which the diffuser plate of the present invention is used in various applications, a coating material with excellent weather resistance and surface hardness is required, and surface-curing transparent coating materials are particularly preferred. desirable.

In general, a surface-curing transparent paint is a thin transparent cured layer with a thickness of 1 to 50 μm that is coated on the surface of a transparent synthetic resin to harden the synthetic resin surface and improve scratch resistance.It is a polyfunctional acrylate rigid coating layer. Polyorganosiloxane rigid coat layers are generally widely used and can be used satisfactorily in the present invention. The surface hardening layer preferably has a pencil hardness of 98 or more, more preferably jH or more.

The polyfunctional acrylate surface hardening layer described here is a polyfunctional acrylate surface hardening paint containing a polyfunctional acrylate compound as a main component, which is applied to the surface of a synthetic resin substrate using a coating method, a spin method, a spray method, a curtain flow method, etc. It is formed by coating it by a method and then curing it by irradiating it with two ultraviolet rays.

Polyfunctional acrylate compounds are compounds that have multiple acryloyloxy or methacryloyloxy groups (CH2=CR-αphantom-1R is H or CH,) at the end or side chain of the molecule, and are also generally called oligoacrylates. It is. Examples of polyfunctional acrylate compounds are shown in Section 7.
Shown in the table.

Among these polyfunctional acrylate compounds, compounds with excellent UV curability in air, such as pentaerythritol acrylate, can be used particularly well.

For UV curing, a photopolymerization initiator or photosensitizer, typically a benzophenone or acetophenone substance, is added to a multifunctional acrylate surface-curing coating. In addition, various additives such as antioxidants, light stabilizers, thermal polymerization inhibitors, stabilizers such as ultraviolet absorbers, colorants,
A small amount of a fluorine-based or silicon-based surfactant is added to give the coating film smoothness.

As a polyorganosiloxane rigid coat layer,
Those using methyltrialkoxysilane and phenyltrialkoxysilane as starting materials, those in combination with tetraalkoxysilane, or mixtures with other resin coatings, such as methyltriethoxysilane/phenyltriethoxysilane reaction mixtures. (U8P 34tsl♂
3), partial hydrolyzate of methyltriethoxysilane/
Acetic acid/sodium naphthenate (JP-A-Shojθ-/13rs2)
, methyltrimethoxysilane/tetraethoxysilane/
Hydroxyl-terminated dimethylpolysiloxane/acidic catalytic reaction mixture (JP-A-30-//≦g00), tetraalkoxysilane hydrolyzate/alkyltrialkoxysilane hydrolyzate/alkali metal salt mixture of organic carboxylic acid (JP-A There are also polyorganosiloxanes containing functional groups such as vinyl groups, epoxy groups, amino groups, etc., such as copolymerization of vinyl alkoxysilane and vinyl acetate. Combined hydrolyzate/Alkyl silicate hydrolyzate/Vinyl acetate or acrylic acid, methacrylic acid, and their esters/Boron trifluoride monoethylamine complex (JP-A Shogu ♂-2 Otsu 2
2/), ring-opening polymer of r-glycidoxyalkyltrialkoxysilane (Japanese Patent Application Laid-Open No. 2006-0674t), β-(
Reaction mixture of seven or more types of 3,4t-epoxycyclohexyl)ethyltrimethoxysilane, γ-methacryloxypropyltrimexysilane, and vinyltrimethoxysilane (JP-A-Sho-tq/24t), β-(3 , <-epoxycyclohexyl) ethyltrimethoxysilane, r-methacryloxypropyltrimethoxysilane, vinyltrimethoxysilane, and a reaction mixture of epoxy prepolymer, diallyl phthalate, glycidyl methacrylate, etc. 3-0-69/7
4t), (co,3-epoxyproboxy)methyltrimethoxysilane/glycidyl methacrylate reaction mixture (
Tokukai Akira! θ-7♂Otsu 3), aminoalkylalkoxysilane/epoxyalkylalkoxysilane partial hydrolysis reaction mixture (JP-A No. 4T♂-♂4T♂7♂), etc. can be used.

These surface-curing transparent coatings are applied, and before being cured by ultraviolet light or heat, silicone spherical particles are mixed and dispersed using a homomixer or the like. When mixing, it is preferable to mix in a vacuum system to prevent the formation of air bubbles, or to remove bubbles in a vacuum system after mixing, or it is also desirable to use an antifoaming agent or the like in combination.

In any case, if air bubbles are mixed into the liquid mixture, there will be variations in the optical properties of the diffuser plate during the coating process or after curing, making stable production impossible.

The amount of silicone spherical particles added to the surface-curing transparent paint is determined depending on the coating thickness and the optical properties (total light transmittance, diffused light rate) required for the final product (diffusion plate).
The mixing amount is T based on the weight of the film forming material in the paint.
It is in the range of h/~r o wtt4. If it is less than 7 wt%, the diffused light rate will be low! If θwt4 is exceeded, there is a risk of secondary agglomeration during mixing (secondary agglomeration), making it impossible to achieve uniform dispersion.The paint thus obtained is coated on one or both sides of a transparent substrate using a predetermined coating method.

As the transparent substrate, transparent plastic resin plates such as methacrylic resin, polycarbonate resin, polyester resin, polyvinyl chloride resin, and polystyrene can be used.
It is also possible to use an inorganic transparent plate such as a glass plate. In particular, methacrylic resin plates and glass plates are most preferably employed in advanced applications where total light transmittance and diffused light rate are required to be, for example, greater than θ. Here, the methacrylic resin is described below (detailed for the purpose of claim 1):
All of the methacrylic resins used in the transparent resins described may also be used.

Regarding the method of applying the paint, the optimum method should be selected in consideration of the use of the diffuser plate, required performance, and economical efficiency. Generally, coating methods include spray coating, dipping, curtain flow, roll coater, spin coating, screen printing, gravure printing, and offset printing.

There are many methods such as bat printability, and any method can be adopted. However, no matter which application method is adopted, there are two restrictions on the viscosity of the paint from the viewpoint of coating processability, workability, and quality stability, and it is necessary to adjust the paint to an appropriate viscosity.

Spin code methods, spray coating methods, offset printing methods, etc. require relatively low viscosity, and it is necessary to dilute the mixed paint to an appropriate viscosity with an appropriate solvent.

Also, depending on the coating thickness you are trying to obtain, it may be necessary to adjust the viscosity with a solvent. There are many inconveniences, and relatively high boiling point solvents are used in many cases. As a result, the hardness of the paint film will decrease significantly.
It is necessary to carefully consider various factors such as the curing method when selecting the material. Further, regarding the selection of the solvent, since the solvent has a subtle influence on the adhesion between the transparent substrate and the coating film, sufficient care must be taken in the selection from this point of view as well. The transparent substrates preferably adopted by the present inventor are a methacrylic plate and a glass plate, and these materials are difficult to ensure sufficient strength for adhesion between the substrate and the coating film.

It is desirable that materials with poor adhesion be subjected to appropriate pretreatment or primer treatment before coating with paint.

After coating on a transparent substrate in this way, the solvent is sufficiently dried and volatilized, and then cured by ultraviolet irradiation or heating to form the desired diffusion plate.

The optical properties of the diffuser plate thus obtained are as per ASTM D10.
Measure the total light transmittance, diffused light rate, parallel light rate, and haze according to the test method of No. 03.

<Example> The present invention will be explained in detail below with reference to Examples.

Example: A network structure obtained by hydrolyzing a raw material silane having three hydrolyzable functional groups and / of methyl groups on a silicon atom and then condensing it to form fine particles as silicone-based spherical particles. Solid spherical particles were used.

In the silicone-based spherical particles, the organic groups bonded to silicon atoms in the starting materials are naturally methyl groups, and the number of these groups is seven. The product name of this product is Tospar/20 (manufactured by Toshiba Silicone), and the viscosity of the n-hechitin dispersion was J 70 CpS.

As shown in Figure 2, Tospearl/2θ is found to be spherical monodisperse fine particles with extremely uniform individual particle sizes.

The particle size distribution of Tospearl/20 is shown in Figure 3.

As shown in FIG. 3, Tosvar Saw 0 has particles with a relatively narrow particle size distribution, and its average particle size is 2μ.

As a comparative example, parium sulfate (average particle size 3) was used as a light diffusing agent.
μ) was used. Tospearl/20 and barium sulfate were dispersed in a methacrylic prepolymer having a centivoid size of 6θ to 6θ0 using a homomixer.

2 as 30θ~3jO centiboise at the stage of weight adjustment
A plate was made by pouring between two glass templates. During polymerization, 0.03% of polymerization initiator was added! Polymerization was started at Q°C, and then post-curing was performed at ♂°C to obtain an original fabric for press stretching.

The amount of Tospearl 7.20 added was 0. ! 1/, ko, type 4 of evening, the amount of paricum sulfate added is ko,! What is the thickness of the original film for press stretching? ■! And so.

Next, the original plate for press stretching was preheated to /4tθ°C and heated to 30°C.
Press stretching was performed using a 0 ton press. The stretching ratio was 5 times, and the plate thickness after stretching was /■T.

The optical properties of this stretched plate were measured using the following test method.

Total light transmittance (T) ASTM D/θθ3 diffused light transmittance (IyI') Parallel light transmittance (PT) Haze (H) Color temperature JIS Z♂72! The results of optical property measurements are shown in Table 2.

As a comparative example, a conventional methacrylic cast plate containing an organic light diffusing agent (polystyrene particles) was used. ! 1
The optical properties of two commercially available diffuser plates from other companies are also shown in Table 7 (
I showed you two.

In order to clarify the results in Table 2, parallel light transmittance is plotted on the horizontal axis (
FIG. 9 shows the total light transmittance plotted on the vertical axis. Total light transmittance (T), diffuse light transmittance (DT)
, parallel light transmittance (PT), and haze (H).

T = DT + PT H = DT/PT
Even if there is a difference in T value, there is a large difference in whether the outline of the light source can be clearly seen when a diffuser plate is actually placed between the eye and the light source.

In other words, when used as a backlight diffusion plate for a liquid crystal color television, a diffuser plate is required that has a parallel light transmittance as low as /% and a total light transmittance as high as /%.

As can be understood from FIG. 9, it can be said that the diffusion plate using Tospar/2θ as a light diffusing agent has extremely superior properties compared to the conventional product (comparative example).

On the other hand, the color temperature is also required to be high, especially for use in liquid crystal color televisions. In general, when the color temperature is low, a reddish or yellowish tinge appears, and when the color temperature is high, it appears pale. In the case of an LCD color TV, the light from the backlight passes through the liquid crystal cell and is filtered through the three primary colors of red, green, and blue to produce a full-color display.

Therefore, if the color temperature of the backlight is low, the colors of the three primary color filters cannot be faithfully projected, resulting in dull colors, so this color temperature is extremely important. Generally, a color temperature of 6000° or higher is required for use in liquid crystal color televisions, and it can be seen that the diffuser plate of the embodiment of the present invention is extremely superior in this respect.

(Margin below) Table 2 5x stretching Example 2 Acrylic surface hardening transparent paint diluted with a solvent mainly composed of isopropyl alcohol (manufactured by Hayayo Toyo Seishin Co., Ltd., trademark G11)
2θwt% of each of silicon-based spherical particles (manufactured by Toshiba Silicone, trademark Tospar/20) and baricum sulfate (average particle size 3 μm) were added to UVaoo-<tr) and mixed and dispersed using a stirrer.

Next, the paint was spray-painted on one side of a transparent methacrylic resin sheet (trade name: Plaglass A, manufactured by Layer Kasei Co., Ltd.) with a thickness of 7.2 cm, and subjected to ultraviolet curing treatment.

A methacrylic resin sheet coated with a paint containing silicon-based spherical particles has a higher total ray transmittance and a higher diffused ray transmittance, similar to the stretched sheet in Example/, compared to a sheet coated with a paint containing barium sulfate. It exhibited excellent optical properties with high transmittance, high diffusion properties, and high color temperature properties. These optical properties are shown in Table 3.

Table 3 Every time t.

)O <Effects of the Invention> The light diffusing plate obtained by the present invention has succeeded in simultaneously increasing the total light transmittance and decreasing the parallel light transmittance in a well-balanced manner compared to conventional ones. This is what I did.

Further, the characteristics such as color temperature and brightness distribution required for the diffusion plates of recent liquid crystal displays and liquid crystal color televisions can be fully achieved by the present invention.

[Brief explanation of the drawing]

The particle size distribution diagram of the same particles, FIG. 7, is an example of a characteristic diagram of light diffusing plates of the present invention and a comparative example. Patent Applicant: Asahi Kasei Industries, Ltd. Figure 1 Ball a Maeko Reisenyari ■ T Dale Figure 2 Subaru 120 Electron Microscope 5 Shinnobu Figure 3 Particle Size μm Tosvall +20 Particle Size Distribution

Claims (1)

[Scope of Claims] 1. A number average particle size of 0.3 consisting of a solid silicone resin forming a polysiloxane bond in which an organic group having an affinity for a transparent resin or its monomer is directly bonded to a silicon atom.
A light diffusing plate 2 having light transmittance, characterized in that spherical particles of ~10μ are present in a transparent resin plate mixed and dispersed in an amount of 1 to 50 wt% based on the transparent resin.A transparent coating on silicon atoms. Spherical particles with a number average particle diameter of 0.3 to 10 μ made of a solid silicone resin with a polysiloxane bond directly connected to an organic group having an affinity for the coating film-forming material or its monomer are placed in a transparent paint. A light diffusing plate having light transmittance, characterized in that 1 to 50 wt% of the coating film forming material or its monomer is mixed and dispersed in the coating material, and the coating material is coated on at least one side of a transparent substrate.