JP2006309206A - Light diffusion film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light diffusion film having a light diffusion layer which has adequate light transmitting property and light diffusing property, has high abrasion resistance and hardly separates resin particles therefrom. <P>SOLUTION: The light diffusion film 1 is composed of a transparent sheet-like substrate 3 and the light diffusion layer 2 having resin particles 4 dispersed in resin binder 5, formed on at least one side surface of the substrate 3. The resin binder 5 includes acrylic monomer unit with OH group by 1 to 50 mass% and is made of acrylic copolymer crosslinked by polyisocyanate. The resin particles 4 are made of acrylic-urethane resin particles including a curing catalyst which catalyzes crosslinking reaction between acrylic polyol and polyisocyanate. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a light diffusing film, and more particularly to a light diffusing film used as a component of a backlight unit of a liquid crystal display device.

  The light diffusing film is used for diffusing the light of a point light source or a linear light source, or adjusting the angle of outgoing light to obtain uniform surface illumination with high front luminance. This light diffusion film is widely used in, for example, liquid crystal displays and liquid crystal televisions equipped in mobile phones, digital cameras, and the like.

  As a conventional light diffusing film, a light diffusing layer composed of a transparent synthetic resin layer in which transparent acrylic resin particles are mixed as a light diffusing material is formed on the surface of a transparent substrate, and is made of a transparent acrylic resin. Some particles are composed of particles embedded in a synthetic resin layer and particles partially protruding from the synthetic resin layer (see, for example, Patent Document 1). Moreover, a light diffusing layer is provided on a transparent support, and the light diffusing layer includes a transparent resin and polystyrene spherical particles as a light diffusing material (for example, see Patent Document 2).

However, conventional light diffusing films have not been studied to improve scratch resistance and prevent resin particles from dropping as much as optical characteristics, and have insufficient scratch resistance and prevent resin particles from falling off. In the processing step, particularly in the step of cutting out into a shape according to the design of the backlight unit, the problem that the light diffusing surface is damaged and the resin particles fall off easily occurs. For this reason, this problem has caused the light diffusion film to become dirty and scratched, which has been a factor in reducing production efficiency.
Japanese Utility Model Publication No. 5-73602 Registered Utility Model Publication No. 3010871

  An object of the present invention is to provide a light diffusing film having a light diffusing layer that has sufficient light transmittance and light diffusibility, high scratch resistance, and in which resin particles are not easily detached from the light diffusing layer. is there.

As a result of intensive studies to achieve the above object, the present inventor has improved the scratch resistance of the light diffusion layer surface by using a specific resin binder and resin particles, and the resin particles do not easily fall off from the light diffusion layer. I found a diffusion film.
That is, the present invention is a light diffusing film in which a light diffusing layer in which resin particles are dispersed in a resin binder is provided on at least one surface of a transparent sheet-like substrate, wherein the resin binder is an acrylic monomer having a hydroxyl group. An acrylic copolymer containing 1 to 50% by mass of a unit, crosslinked with polyisocyanate, and containing a curing catalyst in which the resin particles serve as a catalyst for a crosslinking reaction between an acrylic polyol and a polyisocyanate. Provided is a light diffusion film characterized by being urethane resin particles.

  The light diffusing film of the present invention uses acrylic urethane resin particles containing a curing catalyst as a light diffusing material, and is obtained by crosslinking an acrylic copolymer containing a hydroxyl group-containing acrylic monomer as a monomer unit with a polyisocyanate as a resin binder. Therefore, it is possible to provide a light diffusion layer in which the cross-linking reaction of the resin binder at the interface between the resin particles and the resin binder proceeds preferentially and quickly, and the resin particles do not easily fall off from the resin binder. In addition, since the polyisocyanate cross-linked acrylic copolymer with which the coating film hardness is easily obtained is used, the light diffusion layer surface is hardly damaged. On the other hand, the amount of the curing catalyst is not so much as to impair the optical characteristics, and it is possible to maintain the same light transmittance and light diffusibility as those of the conventional light diffusion film.

  First, the structure of the light diffusion film of the present invention will be described. The light diffusion film of the present invention comprises at least a transparent sheet-like substrate and a light diffusion layer formed on at least one surface of the substrate. Further, if necessary, a back layer having one or more of a sticking prevention function, an antistatic function, a scratch prevention function, a second light diffusion layer function and the like may be provided on the other surface of the base material. .

  The material for the transparent sheet-like substrate in the present invention is not particularly limited, but a polyethylene terephthalate (PET) film is preferably used from the surface smoothness and mechanical strength. The thickness of the substrate is preferably 10 to 300 μm. When the thickness is less than 10 μm, not only handling becomes difficult, but also curability due to heat shrinkage occurs and workability is remarkably lowered. When it is thicker than 300 μm, the visible light transmittance of the substrate itself is lowered, and the front luminance of the backlight unit tends to be lowered. An easy adhesion treatment layer can be provided on the surface of the transparent sheet-like substrate in order to improve adhesion between the substrate surface and the light diffusion layer or a back layer formed as necessary. Examples of the easy adhesion treatment include applying and forming a resin that improves the adhesion between the two, or applying a corona treatment to the substrate surface.

The light diffusion layer in the light diffusion film of the present invention contains at least a light diffusion material and a resin binder. The resin particles used as the light diffusing material of the present invention are acrylic urethane resin particles.
Since the acrylic urethane resin particles have a high-density cross-linked structure, they are particularly excellent in heat resistance and solvent resistance, and also have high transparency, which is a characteristic of acrylic resins. The inventor, when using acrylic urethane resin particles as a light diffusing material, maintains the haze and transmittance required as a light diffusing film, and is commonly used as a conventional light diffusing material, polymethyl methacrylate As compared with resin particles such as (PMMA), polystyrene, silicone, etc., the present inventors have found that the light diffusion layer hardly causes scratches to remain.

For this reason, the inventors have compared the resin particles such as polymethyl methacrylate, polystyrene, and silicone, which are generally used as conventional light diffusing materials, while the acrylic urethane resin particles have a high-density crosslinked structure. The light diffusion layer in which acrylic urethane resin particles are dispersed in the resin binder is easily deformed due to the plasticity of the acrylic urethane resin particles, and the surface is easily deformed due to the plasticity of the acrylic urethane resin particles. The structure was protected by a hard resin binder that was three-dimensionally cross-linked.
When resin particles having a hydroxyl group on the surface are used as the resin particles, in the crosslinking reaction of the resin binder, the hydroxyl group on the surface of the resin particles undergoes a crosslinking reaction with the excess polyisocyanate in the resin binder. Since a crosslinked structure is formed also with the resin binder, the crosslinking density as the light diffusion layer is further increased, which is preferable.

These acrylic urethane resin particles can be granulated through a known production process such as a polymerization process such as suspension polymerization or emulsion polymerization or an emulsification process of a resin dissolved in an organic solvent in an aqueous medium. By adding an appropriate amount of the curing catalyst to the raw material before the granulation step, one having a curing catalyst at least on the surface of the resin particles can be used.
The surface of these acrylic urethane resin particles not containing a curing catalyst can be surface-treated using a solvent containing the curing catalyst, but the coating material forming the light diffusion layer can be stably applied without fear of gelation. For this purpose, it is preferable to use a curing catalyst which is added at the resin particle production stage and remains on the surface of the resin particles as it is.

Since the curing catalyst for catalyzing the crosslinking reaction by the polyisocyanate of the synthetic resin layer used in the present invention is for accelerating the crosslinking reaction at the interface between the synthetic resin layer and the resin particles, It is not necessary to relate to a polymerization reaction or a crosslinking reaction. However, since these curing catalysts can be used to exert a catalytic effect even when resin particles are formed, the added catalyst should be used so that it effectively functions as a catalyst in both the resin particles and the synthetic resin layer. Is preferred.
As a method for producing acrylic urethane resin particles using a curing catalyst, for example, a monomer having a hydroxyl group and a diisocyanate or polyisocyanate are copolymerized in the presence of a curing catalyst to obtain a prepolymer having a urethane bond, and then an acrylic component. And a polymerization initiator together with the polymerization initiator can produce resin particles containing a curing catalyst in the resin particles and capable of exhibiting a curing catalyst action on the surface of the resin particles.
Examples of the monomer having a hydroxyl group include diols such as polyester diols, polyether diols, polyester amide diols, and polycarbonate diols, lactone polyester polyols obtained by ring-opening polymerization of cyclic ester monomers, polyether polyols, polyether esters. Examples thereof include polyols such as polyol and polycarbonate polyol, and polyalkylene glycol (meth) acrylates having a vinyl group in the molecule.
Examples of diisocyanates include hexamethylene diisocyanate and isophorone diisocyanate. Examples of polyisocyanates include polyisocyanates based on HDI (hexamethylene diisocyanate) -based and XDI (xylene diisocyanate) -based aliphatic isocyanates, which are not easily yellowed, and adducts based on HDI. Examples include a trimerized isocyanurate type, a biuret type based on HDI, and the like.
As the types of curing catalysts, triethylenediamine, N-methylpiperazine, N, N′-dimethylpentylamine, N, N′-dimethyldodensylamine, N, N, N, which are generally used as urethane curing catalysts. ', N'-tetramethylethylenediamine, N, N, N', N'-tetramethylhexamethylenediamine, amines such as N, N, N ', N'-tetramethyl1,3-diaminobutane, tributyl chloride Metal compounds such as tin, tetrabutyltin, dibutyltin dilaurate, dioctyltin dilaurate, potassium oleate, 2-ethylhexyl titanate, and zinc naphthenate, and acids such as sulfonic acid, phosphate ester, and carboxylic acid can be used. In particular, dibutyltin dilaurate and dioctyltin dilaurate are preferable because they have an excellent catalytic effect on aliphatic isocyanate groups. The amount of the curing catalyst contained in the resin particles is preferably 0.0001 to 0.5% by mass, and more preferably 0.001 to 0.1% by mass.
In particular, in the case of a curing catalyst containing tin, it is preferable that the tin content attributable to the curing catalyst in the resin particles measured by ICP emission spectroscopy or fluorescent X-ray analysis is 1 to 300 ppm.
Examples of the acrylic component to be radically polymerized with the prepolymer having a urethane bond include, for example, esterified products of (meth) acrylic acid, nitrile derivatives and organic acid vinyl esters copolymerizable with (meth) acrylate, unsaturated acid esters, and benzene derivatives. And systemic monomers.
Any polymerization initiator may be used as long as it generates radicals during polymerization, such as organic peroxides such as benzoyl peroxide, t-butyl peroxypivalate, and t-butyl peroxy-2-ethylhexanate. Azo compounds such as azobis (cyclohexane-1-carbonitrile).
Examples of the suspension stabilizer used in suspension polymerization include cellulose water-soluble resins such as methyl cellulose, hydroxyethyl cellulose, and carboxymethyl cellulose, polyvinyl alcohol, polyethylene glycol, polyvinyl pyrrolidone, and polyacrylates. The amount and type of the suspension stabilizer to be used can be arbitrarily determined according to the stability of the suspension system. Generally, the larger the amount of the suspension stabilizer, the smaller the particle size obtained by increasing the stability. Tend.

  The shape of the acrylic urethane resin particles is preferably a true sphere. The resin particles preferably have an average particle diameter in the range of 1 to 30 μm. When the average particle diameter is smaller than 1 μm, the light transmitted through the light diffusion layer is transmitted without being diffused, and the light diffusion effect tends to be lowered. When the average particle diameter exceeds 30 μm, the coarse resin particles are likely to fall off, so that a defect is likely to be caused, and the appearance of the coating film tends to be lacking in uniformity with a sense of foreign matter.

  It is also possible to use other resin particles, inorganic particles, or inorganic-organic hybrid particles that do not contain a curing catalyst as part of the light diffusing material and resin particles that contain a curing catalyst. is there. In that case, the amount of addition less than the amount of the acrylic urethane resin particles containing the curing catalyst dispersed in the resin binder within the range that does not impair the properties of the light diffusing film increases the effect of preventing the resin particles from falling off. It is preferable from the point.

  Furthermore, as a part of the light diffusing material, the average particle is preferably used in order to fill the gaps between the coarse particles that are easily formed to protrude on the surface of the light diffusing layer, smooth the surface shape of the light diffusing layer, and improve the appearance. True spherical resin fine particles having a diameter of 1 to 5 μm can be contained.

The binder resin used for the synthetic resin layer that is the light diffusion layer of the light diffusion film of the present invention is a copolymer obtained by crosslinking acrylic polyol with polyisocyanate.
In the present invention, the acrylic polyol is an acrylic resin obtained by polymerizing a monomer component containing an unsaturated monomer having a hydroxyl group and having a (meth) acryl unit as a constituent element.
The copolymer obtained by crosslinking the acrylic polyol with polyisocyanate preferably contains 1 to 50% by mass of an acrylic monomer unit having a hydroxyl group that is a constituent element of the acrylic polyol in the copolymer.

Examples of the unsaturated monomer having a hydroxyl group include an acrylic monomer having a hydroxyl group selected from hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, and the like, and a hydroxyl group-containing unsaturated monomer such as allyl alcohol, cinnamon alcohol, and crotonyl alcohol. . Or, for example, a hydroxyl group-containing unsaturated monomer obtained by reacting a dihydric alcohol or epoxy compound such as ethylene glycol, propylene glycol, or phenyl glycidyl ether with an unsaturated carboxylic acid such as acrylic acid, maleic acid, or fumaric acid. Can be mentioned. An acrylic polyol can be produced by selecting and polymerizing at least one or more of the above hydroxyl group-containing unsaturated monomers so as to include a (meth) acrylic unit.
Also, methyl methacrylate, butyl methacrylate, lauryl methacrylate, methyl acrylate, ethyl acrylate, butyl acrylate, isobutyl acrylate, 2-ethylhexyl acrylate, acrylic acid, methacrylic acid, acrylamide, methacrylamide, N-methylol acrylamide, glycidyl acrylate, glycidyl methacrylate, etc. An acrylic polyol can be produced by polymerizing an acrylic monomer and one or more ethylenically unsaturated monomers selected from styrene, acrylonitrile and the like with the hydroxyl group-containing unsaturated monomer.
As a monomer component ratio in the copolymer, the acrylic monomer component having a hydroxyl group is 1 to 50% by mass, preferably 10 to 50% by mass, and the other monomer components are preferably 5 to 80%.

  The hydroxyl value of the acrylic polyol is preferably 25 to 500. When the hydroxyl value is less than 25, the crosslink density is too low, so that the hardness and solvent resistance of the light diffusion layer are likely to be lowered. When the hydroxyl value is greater than 500, the crosslink density is too high, so that it becomes brittle, the light diffusing layer is easily cracked and chipped, and the workability during processing tends to be lowered.

  Here, the hydroxyl value generally refers to the number of milligrams of potassium hydroxide required to neutralize acetic acid generated when 1 g of a sample is acetylated. The hydroxyl value is a numerical value converted into a hydroxyl value per gram of solid content of the sample when the acrylic polyol as a sample is a varnish (solution).

  Further, the copolymer is one kind selected from diethyl maleate, dibutyl maleate, bis (2-ethylhexyl) maleate, dibutyl fumarate, bis (2-ethylhexyl) fumarate, N-phenylmaleimide, and the like as necessary. Alternatively, it can be copolymerized with two or more kinds of resin modifiers. The resin modifier component ratio in the copolymer is preferably 50% or less.

  Specific examples of acrylic polyols that can be used in the acrylic copolymer used in the present invention include two-part curable resins “Acridic A-801-P”, “Acridic 56-719”, “Acridic”. "Dick AU-1042", "Acridick WDU-938", "Acridick A-817", "Acridick A-823", "Aclidick A-829" (manufactured by Dainippon Ink & Chemicals, Inc.).

  The polyisocyanate used in the present invention is based on aliphatic isocyanates such as HDI and XDI, which can be crosslinked with the hydroxyl groups of acrylic polyol, and based on aromatic isocyanates such as TDI and MDI. However, polyisocyanates based on HDI (hexamethylene diisocyanate) -based and XDI (xylene diisocyanate) -based aliphatic isocyanates are preferred because they do not have the disadvantage of being easily yellowed by ultraviolet rays. Examples of the modification types in which these isocyanates are polyisocyanates include adducts obtained by adding polyhydric alcohols to aliphatic isocyanates such as HDI and XDI, isocyanurates obtained by trimerization based on HDI, and biurets based on HDI. Examples include molds. Among these, an adduct type polyisocyanate obtained by adding a polyhydric alcohol to HDI is particularly preferable because it can easily obtain extremely advantageous mechanical properties in the processing step of the light diffusion film.

  The equivalent ratio of isocyanate to hydroxyl group in acrylic polyol in polyisocyanate is preferably 0.7 to 3.0. When the equivalence ratio is less than 0.7, the crosslink density tends to be low, and the light diffusion layer tends to have insufficient scratch resistance and solvent resistance, and the resin particles tend to fall off. When the equivalent ratio is larger than 3.0, crosslinking between polyisocyanate molecules proceeds, and the light diffusion layer tends to become brittle.

上記の数式において、Ｉｗ、Ｉｎ、Ａｗ、Ａｏ はそれぞれ下記のとおりである。
Ｉｗ：ポリイソシアネートの固形分換算質量部
Ｉｎ：ポリイソシアネートにおける固形分中の有効ＮＣＯ含有量（％）
Ａｗ：アクリルポリオールの固形分換算質量部
Ａｏ：アクリルポリオールにおける固形分水酸基価 Here, the equivalent ratio of isocyanate to hydroxyl group (NCO / OH) is generally determined by the following formula 1.

In the above formula, Iw, In, Aw, and Ao are as follows.
Iw: part by mass in terms of solid content of polyisocyanate In: effective NCO content in solid content in polyisocyanate (%)
Aw: solid content equivalent mass part of acrylic polyol Ao: solid content hydroxyl value in acrylic polyol

  In the light diffusing film of the present invention, the blending amount of the resin particles with respect to the resin binder cannot be generally described because it varies depending on the average particle diameter of the resin particles used and the film thickness of the light diffusing layer. It is 5-400 mass parts with respect to 100 mass parts, Preferably it is 10-250 mass parts. If the resin particles are less than 5 parts by mass with respect to 100 parts by mass of the resin binder, light diffusibility tends to be difficult to obtain. On the other hand, when it exceeds 400 parts by mass, it tends to be difficult to obtain light transmittance.

The resin particles used in the present invention are resin particles containing a curing catalyst as a light diffusing material,
Because the resin binder is an acrylic polyol cross-linked with polyisocyanate, the cross-linking reaction of the resin binder at the interface between the resin particles and the resin binder proceeds preferentially and quickly, and the resin particles do not easily fall off from the resin binder. A diffusion layer can be provided.

  In the light diffusing layer of the light diffusing film of the present invention, in addition to the above materials, for example, a dispersant, a plasticizer, an antistatic agent, an anti-degradation agent and the like are blended within a range that does not impair various properties of the light diffusing film. May be.

  The film thickness of the light diffusing layer varies depending on the average particle diameter of the resin particles to be used and the blending amount of the resin particles, but it cannot be generally stated, but is 5 to 50 μm, preferably 8 to 40 μm.

In the light diffusing film of the present invention, the back layer may be omitted, but in many cases, it prevents friction scratches on the surface of the light diffusing film opposite to the light diffusing layer and prevents sticking with the light guide plate. For example, a back layer is provided.
The back layer of the light diffusion film of the present invention contains at least a resin binder. If necessary, a lubricant for preventing sticking, an antistatic agent for suppressing electrostatic charge on the light diffusing film, an ultraviolet absorber, an ultraviolet shielding agent, a light diffusing material, and the like can be contained.
The resin binder contained in the back layer of the light diffusion film of the present invention is not particularly limited as long as it does not hinder the transparency of the light diffusion film, thermoplastic methacrylic resin, thermoplastic methacryl-styrene copolymer resin, It is preferable if a polyester resin or an acrylic resin is crosslinked with polyisocyanate.

When the back layer has a function as the second light diffusion layer, the light diffusion layer of the present invention can be preferably used. By providing light diffusing layers on both surfaces of the light diffusing film, in addition to the function as an anti-sticking layer, it can be used for applications requiring higher haze.
As the film thickness of the back layer, about 1 to 15 μm is preferably used, but when the back layer has a function as the second light diffusion layer, 5 to 50 μm, particularly 8 to 40 μm is preferable. Used.

  In order to produce the light diffusion film in the present invention, the light diffusion layer is formed by applying a coating material for the light diffusion layer to at least one surface of the transparent sheet-like substrate. On the other surface, a back layer is formed by applying a back layer coating material as necessary.

As a coating method, a general coating method can be used. For example, blades, knives,
Coating methods such as casting, dipping, impregnating machine, screen, spin, reverse roll, air doctor, gravure, spray, curtain, extrusion, fountain, kiss, rod, squeeze, forward rotating roll, and kiss roll can be used.
A general drying method can be used to dry the coating film. For example, drying methods such as hot air, infrared rays, microwaves, and induction heating can be used. After drying, heat aging treatment is performed at a predetermined temperature and time as necessary.

  The light diffusion film of the present invention produced as described above is particularly useful for use as a light diffusion film constituting a backlight unit for a liquid crystal display device, but is not limited to this application. The present invention can be applied to various uses that require light diffusion light.

Hereinafter, the present invention will be described using examples.
(Synthesis Example 1)
In a reaction vessel equipped with a dried stirrer, thermometer, cooler and nitrogen gas inlet tube, 42 parts by mass of polycaprolactone triol (Placcel 308, manufactured by Daicel Chemical Industries) and 50 parts by mass of hexamethylene diisocyanate (hereinafter abbreviated as HDI). Part and 0.1 part by mass of dibutyltin dilaurate were allowed to react under stirring in a nitrogen atmosphere at 120 ° C. for 10 hours. Then, after removing unreacted HDI under reduced pressure, toluene was added to obtain a prepolymer (1) having a nonvolatile content of 90% by mass.
In a separable flask equipped with a stirrer, 670 parts by weight of 2% methylcellulose water was charged, and while stirring, 102 parts by weight of prepolymer (1), 100 parts by weight of methyl methacrylate, 10 parts by weight of toluene, t-butyl peroxypivalate (perbutyl PV, A solution consisting of 2 parts by mass is added to make a suspension. The suspension was heated to 60 ° C. and allowed to react for 5 hours under stirring. After that, the temperature was raised to 100 ° C. over 1 hour and toluene was azeotropically separated. Washing, drying and classification yielded acrylic urethane resin particles (I). The average particle size of these particles was 16 μm, and the curing catalyst content was about 0.05% by mass.

(Synthesis Example 2)
In the same manner as in Synthesis Example 1, 48 parts by mass of polycaprolactone diol (Placcel 210, manufactured by Daicel Chemical Industries), 42 parts by mass of HDI, and 0.1 parts by mass of dioctyltin dilaurate were reacted, and toluene was added to obtain a nonvolatile content of 70 masses. % Prepolymer (2) was obtained.
A separable flask equipped with a stirrer was charged with 700 parts by mass of 3% methylcellulose water, and while stirring, 128 parts by mass of prepolymer (2), 75 parts by mass of methyl methacrylate, 25 parts by mass of n-butyl methacrylate, t-butylperoxy-2- A solution consisting of 3 parts by mass of ethylhexanate (Kaya Ester O, manufactured by Kayaku Akzo) is added to prepare a suspension. The suspension was heated to 60 ° C. and allowed to react for 5 hours under stirring. After that, the temperature was raised to 100 ° C. over 1 hour and toluene was azeotropically separated. After washing and drying, classification was performed to obtain acrylic urethane resin particles (II). The average particle diameter of these particles was 6 μm, and the curing catalyst content was about 0.05 mass%.

(Synthesis Example 3)
In the same manner as in Synthesis Example 1, after reacting 44 parts by mass of polycaprolactone diol (Placcel L212AL, manufactured by Daicel Chemical Industries), 25 parts by mass of HDI, and 0.15 parts by mass of dioctyltin dilaurate, lactone-modified (meth) acrylate (Placcel FM3, manufactured by Daicel Chemical Industries, Ltd.) 15 parts by mass, polyalkylene glycol (meth) acrylate (Blenmer E, manufactured by Nippon Oil & Fats Co., Ltd.) 81 parts by mass and toluene 18 parts by mass were reacted at 80 ° C. and nonvolatile content 90% by mass of a prepolymer (3) was obtained.
A separable flask with a stirrer was charged with 1000 parts by weight of 3% methylcellulose water, and while stirring, 150 parts by weight of prepolymer (3), 150 parts by weight of methyl methacrylate, 3 parts by weight of t-butyl peroxypivalate (perbutyl PV), toluene A solution consisting of 20 parts by mass is added to make a suspension. The suspension was heated to 55 ° C. and allowed to react for 5 hours under stirring, and then heated to 100 ° C. over 1 hour to separate toluene azeotropically. After washing and drying, classification was performed to obtain acrylic urethane resin particles (III). The average particle size of these particles was 6 μm, and the curing catalyst content was about 0.04% by mass.

(Synthesis Example 4)
After reacting 15 parts by mass of polycaprolactone diol (Placcel L212AL), 75 parts by mass of HDI and 0.09 parts by mass of dioctyltin dilaurate in the same manner as in Synthesis Example 1, lactone-modified (meth) acrylate (Placcel FM3) 15 Mass parts, 30 parts by mass of polyalkylene glycol (meth) acrylate (Blemmer E) and 34 parts by mass of toluene were added and reacted at 80 ° C. to obtain a prepolymer (4) having a nonvolatile content of 80% by mass.
A separable flask with a stirrer was charged with 1000 parts by weight of 3% methylcellulose water, and while stirring, 150 parts by weight of prepolymer (4), 180 parts by weight of methyl methacrylate, 15 parts by weight of n-butyl methacrylate, t-butyl peroxypivalate ( A solution consisting of 4 parts by weight of perbutyl PV) is added to make a suspension. The suspension was heated to 55 ° C. and allowed to react for 5 hours under stirring, and then heated to 100 ° C. over 1 hour to separate toluene azeotropically. After washing and drying, classification was performed to obtain acrylic urethane resin particles (IV). The average particle size of these particles was 6 μm, and the curing catalyst content was about 0.03% by mass.

(Synthesis Example 5)
In Synthesis Example 1, charging was carried out without adding dibutyltin dilaurate, and the mixture was reacted with stirring at 120 ° C. for 24 hours in a nitrogen atmosphere. After cooling, toluene was added to obtain prepolymer (5) having a nonvolatile content of 90% by mass. Except for the above, acrylic urethane resin particles (V) were obtained in the same manner as in Synthesis Example 1. The average particle size of these particles was 16 μm.

Example 1
<Preparation process of coating material a for light diffusion layer>
Toluene 250 parts by mass Cyclohexanone 40 parts by mass Acrylic urethane resin particles (I) 125 parts by mass Acrylic polyol “Acridic WDU-938” 100 parts by mass [solid content 50%, solid content hydroxyl value 50, manufactured by Dainippon Ink & Chemicals, Inc. ]
15 parts by mass of polyisocyanate “Coronate HL” (solid content: 75%, HDI, effective NCO content in solid content: 17%, manufactured by Nippon Polyurethane Industry Co., Ltd.)
The above was stirred and mixed with a dispersion stirrer to obtain a light diffusion layer coating material a. At this time, the equivalent ratio of isocyanate to hydroxyl group was 1.0.

  As a substrate, a polyethylene terephthalate (PET) film having a thickness of 100 μm is used, and the light diffusion layer coating material “a” is applied on one surface so that the dry film thickness is about 30 μm, and dried by hot air to produce light. A dry coating film of the diffusion layer was obtained. After the coating process was completed, a light diffusing film was produced by performing a thermal aging treatment for 48 hours in a constant temperature room at 40 ° C.

(Example 2)
<Preparation process of coating material b for light diffusion layer>
Toluene 250 parts by mass Cyclohexanone 40 parts by mass Acrylic urethane resin particles (II) 125 parts by mass Acrylic polyol “Acridic WDU-938” 100 parts by mass Polyisocyanate “Coronate HL” 15 parts by mass A layer coating b was obtained. At this time, the equivalent ratio of isocyanate to hydroxyl group was 1.0. After the coating step, a thermal aging treatment was performed in a 40 ° C. room for 48 hours.
In the same manner as in Example 1, except that the light diffusion layer coating material b was used instead of the light diffusion layer coating material a in Example 1, a dry coating film was formed on the substrate to produce a light diffusion film. did

(Example 3)
<Preparation process of coating material c for light diffusion layer>
Toluene 300 parts by mass Cyclohexanone 55 parts by mass Acrylic urethane resin particles (III) 150 parts by mass Acrylic polyol “Acridic WDU-938” 100 parts by mass Polyisocyanate “Coronate HL” 30 parts by mass or more are stirred and mixed with a dispersion stirrer, and light diffusion is performed. A layer coating c was obtained. At this time, the equivalent ratio of isocyanate to hydroxyl group was 2.0. After the coating process, a thermal aging treatment was performed in a constant temperature room at 40 ° C. for 48 hours.
In the same manner as in Example 1, except that the light diffusion layer coating c was used in place of the light diffusion layer coating a in Example 1 and the dry film thickness was about 15 μm, a dry coating film was formed on the substrate. To form a light diffusion film.

(Comparative Example 1)
<Preparation process of coating material d for light diffusion layer>
Toluene 250 parts by mass Cyclohexanone 40 parts by mass Acrylic resin particle “MBX-15” 125 parts by mass [average particle size of about 13 μm, no curing catalyst contained, manufactured by Sekisui Plastics Co., Ltd.]
Acrylic polyol “Acridic WDU-938” 100 parts by mass Polyisocyanate “Coronate HL” 15 parts by mass or more were stirred and mixed with a dispersion stirrer to obtain a d-coating for the light diffusion layer. At this time, the equivalent ratio of isocyanate to hydroxyl group was 1.0.
In the same manner as in Example 1 except that the light diffusion layer coating material d was used in place of the light diffusion layer coating material a in Example 1 and the dry film thickness was about 29 μm, a dry coating film was formed on the substrate. To form a light diffusion film.

(Comparative Example 2)
<Preparation process of coating material e for light diffusion layer>
Toluene 300 parts by mass Cyclohexanone 55 parts by mass Styrene resin particles “SBX-6” 150 parts by mass [average particle size of about 6 μm, no curing catalyst contained, manufactured by Sekisui Plastics Co., Ltd.]
Acrylic polyol “Acridic WDU-938” 100 parts by mass Polyisocyanate “Coronate HL” 30 parts by mass or more was stirred and mixed with a dispersion stirrer to obtain a coating material e for the light diffusion layer. At this time, the equivalent ratio of isocyanate to hydroxyl group was 2.0.
In the same manner as in Example 1, except that the light diffusion layer coating material e was used in place of the light diffusion layer coating material a in Example 1 and the dry film thickness was about 15 μm, a dry coating film was formed on the substrate. To form a light diffusion film.

(Comparative Example 3)
<Preparation process of coating material f for light diffusion layer>
Toluene 290 parts by mass Cyclohexanone 50 parts by mass Dibutyltin dilaurate 0.2 parts by mass Silicone resin particles “Tospearl 2000B” 150 parts by mass (average particle diameter of about 6 μm, no curing catalyst contained, manufactured by GE Toshiba Silicone)
Acrylic polyol “Acridic WDU-938” 100 parts by mass Polyisocyanate “Coronate HL” 15 parts by mass or more were stirred and mixed with a dispersion stirrer to obtain a light diffusion layer coating material f. At this time, the equivalent ratio of isocyanate to hydroxyl group was 1.0.
In the same manner as in Example 1, except that the light diffusion layer coating material f was used in place of the light diffusion layer coating material a in Example 1 and the dry film thickness was about 15 μm, a dry coating film was formed on the substrate. To form a light diffusion film.

(Comparative Example 4)
In Example 1, except that the acrylic urethane resin particles (V) were used instead of the acrylic urethane resin particles (I), a dry coating film was formed on the substrate in the same manner as in Example 1, and light diffusion was performed. A film was prepared.

(Evaluation of resin particle shedding)
Using a surface property tester, Souzaland Love Tester (manufactured by Toyo Seiki Seisakusho Co., Ltd.), the light diffusion film was fixed so that the light diffusion layer surfaces were rubbed with each other, and the light diffusion surface was rubbed 1000 times with a load of 18N. After rubbing, the light diffusion film rubbed on the lower side was cut into a 10 mm square, and the falling state of the resin particles on the surface of the light diffusion layer was observed with a microscope. The following criteria were used for evaluation of the resin particle detachability.
○ ... No dropout is observed.
Δ: Dropping points are 1 to 3.
X ... The drop-off location is 4 or more.
The evaluation results are shown in Table 1. As can be seen from Table 1, when resin particles containing a curing catalyst were used, the resin particles did not easily fall off from the surface of the light diffusing layer, and were excellent as a light diffusing film. On the other hand, when a curing catalyst was added to the paint, in addition to being inferior in scratch resistance, gelation of the paint was accelerated, which was not preferable for practical use.

(Evaluation of scratch resistance of light diffusion layer)
With a surface property tester HEIDON-14D (manufactured by Shinto Kagaku Co., Ltd.), using a stainless steel ball indenter (SUS304, diameter 4.76 mm), applying a load of 20 gf, 50 reciprocations at a moving speed of 60 mm / second, light The diffusion surface was rubbed. After rubbing, the light diffusing surface was turned up and the light of the fluorescent lamp was applied from the back to visually observe the transmitted light, and the light diffusing surface was illuminated under the fluorescent lamp and the surface reflected light was visually observed. The evaluation results are shown in Table 1. The scratch was evaluated visually using the following criteria.
○: No scratches were observed by visual observation with transmitted light and surface reflected light.
Δ: No scratch was confirmed by visual observation with transmitted light, but scratch was confirmed by visual observation with surface reflected light.
X: Scratches were confirmed by visual observation with transmitted light and surface reflected light.
The evaluation results are shown in Table 1. As can be seen from Table 1, when resin particles containing a curing catalyst were used, the scratch resistance was the best.

(Evaluation of optical properties)
Using a haze meter NDH2000 (manufactured by Nippon Denshoku), the total light transmittance and haze of the light diffusion film were measured. The evaluation results are shown in Table 1. As can be seen from Table 1, even when resin particles containing a curing catalyst were used, no difference was observed in light transmittance and light diffusibility.

  As is apparent from Table 1, Examples 1 to 3 using acrylic urethane resin particles having a curing catalyst have good scratch resistance and drop-off resistance. It can be seen that the resin particles of Comparative Examples 1 to 3 have lower scratch resistance and significantly lower drop resistance than Examples 1 to 3. It can be seen that even when a curing catalyst is added to the paint as in Comparative Example 3, the drop-off resistance is not improved. Moreover, the comparative example 4 using the acrylic urethane resin particle | grains which do not have a curing catalyst reduces abrasion resistance and drop-off resistance compared with Example 1- Example 3 using the acrylic urethane resin particle | grains which have a curing catalyst. I understand that

It is sectional drawing which shows one Example of the light-diffusion film of this invention. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Light diffusing film 2 Light diffusing layer 3 Transparent sheet base material 4 Light diffusing material 5 Resin binder

Claims (1)

A light diffusing film provided with a light diffusing layer in which resin particles are dispersed in a resin binder on at least one surface of a transparent sheet-like substrate, wherein the resin binder contains 1 to 50 acrylic monomer units having a hydroxyl group. Acrylic urethane resin particles containing an acrylic copolymer that is contained in mass% and crosslinked with polyisocyanate, and wherein the resin particles contain a curing catalyst that serves as a catalyst for the crosslinking reaction between acrylic polyol and polyisocyanate. Light diffusing film characterized by things.

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