JP4821552B2 - Light diffusion film - Google Patents

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 beads 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 beads are composed of beads embedded in a synthetic resin layer and beads 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). Furthermore, attempts have been made to improve the heat resistance of the light diffusion sheet by incorporating polyester polyol or acrylic polyol and a fine inorganic filler in the binder (see, for example, Patent Document 3).

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 are not sufficiently scratch resistant 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. H05-076022. Utility model registration No. 3010871 JP 2004-004598 A

  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 research to achieve the above object, the present inventors have improved the scratch resistance of the light diffusion layer surface by using a specific resin binder and resin particles, and the resin particles are less likely to 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 comprises a polyester polyol and a polyisocyanate. A light diffusing film is provided, which contains a resin cross-linked as a main component and the resin particles are acrylic urethane resin particles.

  The light diffusing film of the present invention uses a resin obtained by cross-linking polyester polyol with polyisocyanate as a resin binder of a light diffusing material, and uses acrylic urethane fine particles as resin particles, so that the resin at the interface between the resin particles and the resin binder is used. It is possible to provide a light diffusion layer in which the cross-linking reaction of the binder proceeds preferentially and quickly, and the resin particles are not easily dropped from the resin binder. In addition, the resin binder obtained by crosslinking polyester polyol and polyisocyanate is an elastic body, absorbs external impact, and has a self-healing ability if it is a scratch on the extreme surface, so that the light diffusion layer surface is hardly damaged.

The resin binder used in the present invention contains, as a main component, a resin obtained by crosslinking a polyester polyol with a polyisocyanate. However, in order to combine properties such as light transmittance and scratch resistance as a resin binder, a polyester polyol is used. It is preferable to consist only of resin cross-linked with polyisocyanate.
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 (see FIG. 1). 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 resin particles used as the light diffusing material of the present invention are acrylic urethane resin particles. The resin binder of the present invention is a resin obtained by crosslinking polyester polyol with polyisocyanate. Therefore, as the acrylic urethane resin particles, cross-linked acrylic urethane resin particles that are familiar with the resin binder are preferable. Since the acrylic urethane resin fine 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 fine particles as a light diffusing material, maintains the haze and transmittance required as a light diffusing film, and is generally used as a conventional light diffusing material, polymethyl methacrylate As compared with resin fine 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 that are generally used as conventional light diffusing materials while the acrylic urethane resin particles have a high-density crosslinked structure. This is attributed to the fact that it is easily plastically deformed. That is, the light diffusion layer in which the acrylic urethane resin fine particles are dispersed in the resin binder is easily deformed due to the plasticity of the acrylic urethane resin fine particles, while the acrylic resin is three-dimensionally cross-linked with the polyisocyanate on the surface. The structure protected by a hard resin binder seems to have been able to have a characteristic that is not easily damaged by external stress.
As the acrylic urethane resin fine particles, when resin fine particles having hydroxyl groups on the surface are used, the hydroxyl groups on the surface of the resin fine particles crosslink with the excess polyisocyanate in the resin binder in the crosslinking reaction of the resin binder, thereby light diffusion. Since the effect of the resin binder around the material is promoted and a crosslinked structure is formed between the light diffusing material and the resin binder, the crosslink density as the light diffusing layer is further increased, which is preferable.
Further, the acrylic urethane resin particles preferably contain a curing catalyst for the crosslinking reaction between the polyester polyol and the polyisocyanate.

These acrylic urethane resin fine 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. Then, by adding an appropriate amount of the curing catalyst to the raw material before the granulation step, it is possible to obtain one having a curing catalyst at least on the surface of the resin particles.
Although the surface of the resin particles not containing these curing catalysts can be surface-treated using a solvent containing the above-mentioned curing catalyst, the paint that forms the light diffusion layer can be stably applied without fear of gelation. It is preferable to use a curing catalyst that is used in the production stage of the resin particles and remains on the surface of the resin particles as it is.

In the resin binder used in the present invention, the curing catalyst that catalyzes the crosslinking reaction by polyisocyanate is for accelerating the crosslinking reaction at the interface between the resin binder and the resin particles, and therefore, it is not necessarily a polymerization reaction at the time of resin particle formation. It does not have to be related to the 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 adduct types in which polyhydric alcohols are added based on HDI (hexamethylene diisocyanate) -based and XDI (xylene diisocyanate) -based aliphatic isocyanates, which are difficult to yellow, and isocyanurates trimerized on the basis of HDI. And a biuret type based on HDI.

As a kind of curing catalyst, any catalyst may be used as long as it catalyzes a crosslinking reaction between a polyester polyol and a polyisocyanate. For example, triethylenediamine, N-methylpiperazine, N, N'-, which are generally used as a urethane curing catalyst. Dimethylpentylamine, N, N′-dimethyldodensylamine, N, N, N ′, N′-tetramethylethylenediamine, N, N, N ′, N′-tetramethylhexamethylenediamine, N, N, N ′ , Amines such as N′-tetramethyl 1,3-diaminobutane, metal compounds such as tributyltin chloride, tetrabutyltin, dibutyltin dilaurate, dioctyltin dilaurate, potassium oleate, 2-ethylhexyl titanate, zinc naphthenate, Acids such as sulfonic acid and carboxylic acid, phosphate esters, etc. 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, when a curing catalyst containing tin is used, 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. When the resin particles contain these curing catalysts, curing of the binder resin is promoted in the vicinity of the curing catalyst distributed on the surface of the resin particles, so that desorption of the resin particles from the light diffusion layer can be suppressed.

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, the light transmitted through the light diffusion layer is transmitted without being diffused, and the light diffusion effect tends to be reduced. If the average particle diameter exceeds 30 μm, the coarse resin particles are likely to fall off, which tends to cause loss of the resin particles, and the coating film appearance 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, from the point of increasing the effect of preventing the resin particles from falling off, the addition amount is smaller than the addition amount of the resin particles containing the curing catalyst dispersed in the resin binder within a range not inhibiting the various characteristics of the light diffusion film. preferable.

Furthermore, it has an average particle diameter of about 1/10000 to 1/100 of the resin particles for the purpose of preventing coalescence of the particles during the production of the acrylic urethane resin particles and facilitating the dispersion of the resin particles in the resin binder. Inorganic particles such as silica, alumina, and titania may be attached to the surface of the resin particles. The inorganic particle adhering step is preferably a drying and / or crushing step in the resin particle production step, and these inorganic particles are preferably coexisted. After the resin particles are prepared, the inorganic particles are added, mixed, and stirred. The inorganic particles may be fixed to the surface of the resin particles by performing the above. The adhesion amount is added at a ratio of 0.05 to 3% by mass with respect to the resin particles.
In addition,

  The inorganic particles may be surface-treated. In particular, if the hydrophobic treatment is performed by adding a hydrophobic substance such as a silane coupling agent or a titanate coupling agent to the inorganic powder, the adhesion to the resin particles is improved. It is preferable in terms of improvement.

  As the resin particles used in the present invention, acrylic urethane resin particles are used, and a resin obtained by cross-linking polyester polyol with polyisocyanate is used as a resin binder. It is possible to provide a light diffusing layer that proceeds preferentially and quickly, and in which resin particles are less likely to fall off from the resin binder. On the other hand, when a curing catalyst is contained in the resin particles, it effectively and effectively catalyses at the interface between the resin particles and the resin binder. Tends to be shortened. The pot life of the light diffusing layer paint used in the present invention is longer than that when a curing catalyst is added to the paint, and there is no problem in practical use. Although it does not receive, by attaching inorganic particles to the surface of the resin particles, it has the effect that the pot life of the coating for the light diffusion layer can be extended without impairing the effect of preventing the resin particles from falling off the light diffusion layer. Demonstrated.

  The resin obtained by crosslinking the polyester polyol used in the present invention with polyisocyanate can be used without particular limitation as long as it has transparency when formed into a coating film. Usually, polyester polyol is excellent in weather resistance, scratch resistance, processability, and the like, and these characteristics are further improved by crosslinking with polyisocyanate. Furthermore, since the transparency is high and the fine filler can be easily dispersed in the binder, the total light transmittance of the light diffusion film can be increased, and yellowing, deterioration, etc. due to ultraviolet rays can be reduced. The coating film of the light diffusing layer used in the present invention has a function of absorbing the load caused by the abrasion as an elastic deformation of the coating film and reducing the occurrence of permanent scratches on the coating film surface. A coating film having self-healing properties is preferred.

  Examples of the polyester polyol used in the present invention include ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, neopentyl glycol, and hexamethylene glycol. , Decamethylene glycol, 2,2,4-trimethyl-1,3-pentanediol, trimethylolpropane, hexanetriol, glycerin, pentaerythritol, cyclohexanediol, hydrogenated bisphenol A, bis (hydroxymethyl) cyclohexane, hydroquinonebis ( Polyhydric alcohols such as hydroxyethyl ether), tris (hydroxyethyl) isosinurate, xylylene glycol and the like, for example, maleic acid, fumaric acid, succinic acid Reaction with a polybasic acid such as adipic acid, sebacic acid, azelaic acid, trimet acid, terephthalic acid, phthalic acid, isophthalic acid, etc. under conditions where the number of hydroxyl groups in the polyhydric alcohol is greater than the number of carboxyl groups in the polybasic acid. Can be manufactured.

  The number average molecular weight of the polyester polyol obtained under such an excessive hydroxyl group condition is 500 or more and 300,000 or less, and preferably 2000 or more and 100,000 or less. The hydroxyl value is 5 or more and 300 or less, preferably 10 or more and 200 or less, more preferably 20 or more and 150 or less.

  The number of hydroxyl groups in the polyester polyol is not particularly limited as long as it is 2 or more per molecule, but if the hydroxyl value in the solid content is 10 or less, the number of crosslinking points decreases, and the solvent resistance and water resistance are reduced. , Film properties such as heat resistance and surface hardness tend to decrease.

  Specific examples of polyester polyols that can be used for resins obtained by crosslinking the polyester polyols used in the present invention with polyisocyanates include two-part curable resins “Bernock D6-439”, “Bernock D-115-80”, “Burnock D7-885”, “Burnock DS-1000”, “Burnock D-161” (manufactured by Dainippon Ink & Chemicals, Inc.), and the like.

  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 polyester polyols, 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 adduct types obtained by adding polyhydric alcohols to aliphatic isocyanates such as HDI and XDI, isocyanurate types obtained by trimerization based on HDI, and biurets based on HDI. Examples include molds. Among them, an adduct type polyisocyanate obtained by adding a polyhydric alcohol to HDI is particularly preferable because mechanical properties such as scratch resistance that are extremely advantageous in the processing step of the light diffusion film can be easily obtained.

  The equivalent ratio of isocyanate to the hydroxyl group of the polyester polyol in the polyisocyanate is preferably 0.6 to 3.5, and more preferably 0.7 to 3.0. When the equivalent ratio is less than 0.6, the crosslink density tends to be low, and the light diffusion layer tends to be rubbed off and the resin particles are liable to fall off. When the equivalent ratio is larger than 3.5, crosslinking between polyisocyanate molecules proceeds, and the light diffusion layer tends to become brittle and easily damaged.

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含量（％）
Ａｗ：ポリエステルポリオールの固形分換算質量部
Ａｏ：ポリエステ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: terms of solid content of the polyisocyanate In: effective NCO containing amount in the solid component of the polyisocyanate (%)
Aw: Solid content equivalent mass part of polyester polyol Ao: Solid content hydroxyl value in polyester 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, and it is difficult to obtain uniform brightness on the light diffusing surface due to increased straight light. . On the other hand, when the amount exceeds 400 parts by mass, light transmission tends to be difficult to obtain, loss due to light diffusion increases, and the luminance of the light diffusion surface tends to decrease.

  In the resin particles used in the present invention, resin particles containing a curing catalyst are used as a light diffusing material, and acrylic resin or polyester polyol cross-linked with polyisocyanate is used as a resin binder. It is possible to provide a light diffusing layer in which the resin binder cross-linking reaction at the resin binder interface proceeds preferentially and quickly, and the resin particles are less likely to fall off from the resin binder.

  In addition to the above materials, the light diffusion layer of the light diffusion film of the present invention includes, for example, a dispersant, a slip agent, a plasticizer, an antistatic agent, an anti-degradation agent, etc., as long as the properties of the light diffusion film are not impaired. It may be blended.

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

On the back surface of the light diffusion film of the present invention, it is preferable to provide a back layer for the purpose of preventing friction scratches and preventing sticking with a light guide plate or the like.
The back layer contains at least a transparent resin binder layer. Alternatively, if necessary, a lubricant for preventing sticking, an antistatic agent for suppressing electrostatic charge on the light diffusion 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 diffusing film of the present invention is not particularly limited as long as it does not inhibit the transparency of the light diffusing film, but a thermoplastic methacrylic resin, a thermoplastic methacryl-styrene copolymer resin, Any polyester resin or acrylic resin crosslinked with polyisocyanate is preferable.

As the lubricant, antistatic agent, ultraviolet absorber, ultraviolet shielding agent and the like to be contained in the back layer, known commercially available materials can be used within a range of addition amounts that do not impair various properties of the light diffusion film.
When giving a function as a 2nd light-diffusion layer to a back surface layer, the structure and mixing | blending of the light-diffusion layer of this invention can be used conveniently. 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 diffusing film in the present invention, a coating for a light diffusing layer containing resin particles, a resin binder and various additives as required is applied to at least one surface of a transparent sheet-like substrate. To form a light diffusion layer. On the other surface, a back layer can be formed by applying a back layer coating material containing a resin binder and various additives as required.

As a coating method, a general coating method can be used. For example, coating methods such as blade, knife, cast, dipping, impregnation machine, screen, spin, reverse roll, air doctor, gravure, spray, curtain, extrusion, fountain, kiss, rod, squeeze, forward rotation roll, kiss roll, etc. Available.
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.
(Adhesion of inorganic fine particles to resin particle surface)
(Production Example 1)
0.5 parts by mass of silica particles having a primary particle diameter of about 10 nm hydrophobized with dimethyl silicone oil are added to the acrylic urethane resin particles (I) prepared in Synthesis Example 1 and mixed for 10 minutes with a Henschel mixer. Then, acrylic urethane resin particles (IV) having silica particles fixed on the surface were produced. Silica particles did not adhere to the inner wall of the Henschel mixer.
(Production Example 2)
Instead of the acrylic urethane resin particles (I), the acrylic urethane resin particles (II) prepared in Synthesis Example 2 were used, and the silica particles were added in an amount of 1.5% by mass with respect to the resin particles. Similarly, acrylic urethane resin particles (V) having silica particles fixed on the surface were produced. Silica particles did not adhere to the inner wall of the Henschel mixer.
(Production Example 3)
In place of the acrylic urethane resin particles (II), the acrylic urethane particles (VI) having silica particles fixed on the surface in the same manner as in Production Example 2 except that the acrylic urethane resin particles (III) prepared in Synthesis Example 3 are used. Manufactured.
The light diffusing film in the case of using a resin obtained by crosslinking a polyester polyol-containing resin as a binder resin with polyisocyanate will be examined for scratch resistance, drop-off resistance, and the like.
Example 1
<Preparation process of coating material a for light diffusion layer>
Toluene 765 parts by mass Cyclohexanone 255 parts by mass Acrylic urethane resin particles (I) 385 parts by mass Polyester resin solution “Bernock D6-439” 150 parts by mass [solid content 80%, solid content hydroxyl value 140, manufactured by Dainippon Ink & Chemicals, Inc. ]
95 parts by mass of polyisocyanate solution “Bernock DN-950” [solid content 75%, HDI, effective NCO content 13% in solid content, manufactured by Dainippon Ink & Chemicals, Inc.]
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 0.7.
Using a polyethylene terephthalate (PET) film with a thickness of 100 μm as a base material, the light diffusion layer coating material a is applied to one surface so as to have a dry film thickness of about 27 μm, and dried with hot air to diffuse light. A dry coating of the layer was obtained. After the coating process was completed, a light diffusing film was prepared by performing a thermal aging treatment in a constant temperature room at 40 ° C. for 48 hours.

(Example 2)
<Preparation process of coating material b for light diffusion layer>
Toluene 765 parts by mass Cyclohexanone 255 parts by mass Acrylic urethane resin particles (II) 385 parts by mass Polyester resin solution “Bernock D6-439” 150 parts by mass Polyisocyanate solution “Bernock DN-950” A light diffusion layer coating b was obtained. At this time, the equivalent ratio of isocyanate to hydroxyl group was 0.7.
In the same manner as in Example 7, 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 850 parts by mass Cyclohexanone 290 parts by mass Acrylic urethane resin particles (III) 235 parts by mass Polyester resin solution “Bernock D6-439” 150 parts by mass Polyisocyanate solution “Bernock DN-950” 130 parts by mass or more were stirred and mixed with a dispersion stirrer. Thus, a light diffusion layer coating material c was obtained. 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 c was used instead of the light diffusion layer coating material a in Example 1 and the dry film thickness was about 13 μm, a dry coating film was formed on the substrate. To form a light diffusion film.
Example 4
<Adjustment process of coating material d for light diffusion layer>
A light diffusing paint d was prepared in the same manner as in Example 1 except that the acrylic urethane resin particles (IV) prepared in Production Example 1 were used in place of the acrylic urethane resin particles (I). A light diffusion film was prepared.
(Example 5)
<Adjusting process of coating material e for light diffusion layer>
A light diffusing paint e was prepared in the same manner as in Example 2 except that the acrylic urethane resin particles (V) prepared in Production Example 2 were used instead of the acrylic urethane resin particles (II). A light diffusion film was prepared (Example 6).
<Adjusting step of light diffusion layer coating material f>
A light diffusion paint f was prepared in the same manner as in Example 3 except that the acrylic urethane resin particles (VI) prepared in Production Example 3 were used instead of the acrylic urethane resin particles (III). Made a light diffusion film

(Comparative Example 1)
<Preparation process of coating material g for light diffusion layer>
Toluene 500 parts by mass Methyl ethyl ketone 375 parts by mass Cyclohexanone 75 parts by mass Styrene resin particles “SBX-12” 275 parts by mass [average particle diameter of about 12 μm, no curing catalyst contained, manufactured by Sekisui Plastics Co., Ltd.]
125 parts by mass of polyester resin “Elitel UE3600” [100% solids, hydroxyl value 4, manufactured by Unitika Ltd.]
The polyisocyanate solution “Bernock DN-950” 10 parts by mass or more was stirred and mixed with a dispersion stirrer to obtain a light-diffusing layer g coating material. At this time, the equivalent ratio of isocyanate to hydroxyl group was 3.4.
In the same manner as in Example 1, except that the light diffusion layer coating g was used in place of the light diffusion layer coating a in Example 1 and the dry film thickness was about 24 μm, a dry coating film was formed on the substrate. To form a light diffusion film.

(Comparative Example 2)
<Preparation process of coating material h for light diffusion layer>
Toluene 900 parts by mass Cyclohexanone 120 parts by mass Silicone resin particles “Tospearl 2000B” 150 parts by mass [average particle size 6 μm GE manufactured by Toshiba Silicones Co., Ltd.]
72 parts by mass of acrylic resin “Dianal BR-85” (100% solids, no hydroxyl value, manufactured by Mitsubishi Rayon Co., Ltd.)
The above was stirred and mixed with a dispersion stirrer to obtain a light diffusion layer coating material h.
In the same manner as in Example 1, except that the light diffusion layer coating material h was used in place of the light diffusion layer coating material a in Example 1 and the dry film thickness was about 13 μm, a dry coating film was formed on the substrate. To form a light diffusion film.

(Comparative Example 3)
<Preparation process of coating material i for light diffusion layer>
Toluene 810 parts by mass Cyclohexanone 150 parts by mass Dibutyltin dilaurate 0.5 parts by mass Acrylic resin particles “MBX-20” 315 parts by mass [average particle diameter of about 17 μm, no curing catalyst contained, manufactured by Sekisui Plastics Co., Ltd.]
Acrylic resin solution “Acridic A-801-P” 265 parts by mass Polyisocyanate solution “Bernock DN-950” 36 parts by mass or more was stirred and mixed with a dispersion stirrer to obtain a coating material i for light diffusion layer. At this time, the equivalent ratio of isocyanate to hydroxyl group was 0.4.
In the same manner as in Example 1, except that the light diffusion layer coating material i was used in place of the light diffusion layer coating material a in Example 1 and the dry film thickness was about 30 μm, a dry coating film was formed on the substrate. To form a light diffusion film.

(Comparative Example 4)
<Preparation process of coating material j for light diffusion layer>
Toluene 765 parts by mass Cyclohexanone 255 parts by mass Acrylic resin particles “MBX-20” 385 parts by mass Polyester resin solution “Bernock D6-439” 150 parts by mass Polyisocyanate solution “Bernock DN-950” 95 parts by mass or more with a dispersion stirrer Thus, a coating material j for the light diffusion layer was obtained. At this time, the equivalent ratio of isocyanate to hydroxyl group was 0.7.
In the same manner as in Example 1, except that the light diffusion layer coating material j was used in place of the light diffusion layer coating material a in Example 1 and the dry film thickness was about 30 μm, a dry coating film was formed on the substrate. To form a light diffusion film.

  The following evaluation was performed about the light-diffusion film which has the light-diffusion layer described in each Example of the above Examples 1-6 and Comparative Examples 1-4, and a comparative example.

  Table 1 shows the composition of the light diffusion layers of the light diffusion films prepared in Examples 1 to 6 and Comparative Examples 1 to 4 described above.

(Table 1)

  The following evaluation was performed about the light-diffusion film which has a light-diffusion layer of the mixing | blending shown in each Example of Table 1, and a comparative example.

(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 2. As can be seen from Table 2, the light diffusion film using the polyester polyol crosslinked with the diisocyanate compound as the binder resin and the acrylic urethane resin particles as the resin particles is difficult to remove the resin particles from the surface of the light diffusion layer. It was extremely excellent. On the other hand, when a curing catalyst was added to the paint, in addition to inferior scratch resistance, gelation of the paint was accelerated.

(Evaluation of scratch resistance of light diffusion layer)
Using a surface property tester HEIDON-14D (manufactured by Shinto Kagaku Co., Ltd.), a stainless steel ball indenter (SUS304, diameter 4.76 mm) is used to place 50 g of weight, 50 reciprocations at a moving speed of 60 mm / second, and light diffusion Rubbed the surface. The scratches remaining after rubbing were visually observed. The evaluation results are shown in Table 2. 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 2. As can be seen from Table 2, a light diffusion film using a polyester polyol crosslinked with a diisocyanate compound as a binder resin and using acrylic urethane resin particles as a resin particle has good drop-off resistance and scratch resistance. In particular, since resin particles containing a curing catalyst are used, the resin particles hardly fall off from the surface of the light diffusion layer, and the film is extremely excellent as a light diffusion film.

(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 2. As can be seen from Table 2, a light diffusion film using polyester polyol crosslinked with a diisocyanate compound as binder resin and acrylic urethane resin particles as resin particles has good haze and transmittance. In addition, even when resin particles containing a curing catalyst were used, or when resin particles with inorganic fine particles adhered to the surface were used, no reduction was observed in light transmittance and light diffusibility.

(Patent pot life evaluation)
For the paints of Examples 1 to 6 and Comparative Examples 1 to 4, the pot life (time until the paint becomes gelled and cannot be used) was compared by visual observation of the paint state. For the evaluation of pot life, the following criteria were used based on the paint of Example 1 having a pot life with no practical problems. The evaluation results are shown in Table 2.
◎ ... Has a pot life of 10 hours or longer when left indoors at 23 ° C and 6 hours or longer when left standing in a constant temperature bath at 40 ° C.
O ... It has a pot life of 8 hours or more when left indoors at 23 ° C and 5 hours or more when left still in a constant temperature bath at 40 ° C.
Δ: A pot life of 5 hours or longer when left indoors at 23 ° C. and 3 hours or longer when left still in a constant temperature bath at 40 ° C.
X ... It has a pot life of less than 5 hours when left indoors at 23 ° C and less than 3 hours when left still in a constant temperature bath at 40 ° C.
As can be seen from Table 2, the pot life is better when no curing catalyst is contained, but even when a curing catalyst is contained in the resin particles, a pot life having no practical problem can be obtained. In particular, when inorganic fine particles are adhered to the resin particle surface, a very good pot life can be obtained. On the other hand, when a curing catalyst is added to the coating, gelation of the coating is accelerated, which is not preferable for practical use.

(Table 2)

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

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 (3)

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 a resin obtained by crosslinking a polyester polyol with a polyisocyanate. containing as a main component, the resin particles are light diffusing, characterized in that that contain a curing catalyst for the crosslinking reaction of Ri Oh acrylic urethane resin particles, and the acrylic urethane resin particles and a polyester polyol and a polyisocyanate the film. Inorganic particles are attached to the surface of the resin particles, the average particle diameter of the inorganic particles is 1/10000 to 1/100 of the resin particles, and the amount of the inorganic particles attached is 0.000 with respect to the resin particles. The light-diffusion film of Claim 1 which is 05-3 mass%. The polyisocyanate is a light diffusion film according to claim 1 or 2 equivalent ratio to the hydroxyl group of the isocyanate is 0.6 to 3.5.

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