JP2012036293A - Resin composition for coating and reflective film using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inexpensive reflective film that is less liable to deflection due to heat, has excellent adhesion, and substantially avoids deflection, yellowing and the like even when subjected to heat generation and ultraviolet irradiation from a light source.SOLUTION: In order to provide the reflective film, a resin composition for coating is provided that contains an acrylic polymer obtained by polymerizing a monomer mixture having a specific glass transition temperature and containing a substantial amount of methyl methacrylate, and a compound having a specific molecular weight and a specific skeleton. The reflective film uses the resin composition.

Description

TECHNICAL FIELD The present invention relates to a coating resin composition that can be used as an LED liquid crystal display component and a reflective film using the same.

The liquid crystal display uses a backlight that illuminates the liquid crystal cell, the liquid crystal monitor employs an edge light type backlight, and the liquid crystal television employs a direct backlight. As these reflective films for a backlight, a porous white film formed of bubbles is generally used (Patent Document 1). In recent years, backlight units using LEDs instead of cold-cathode tubes as a light source have been increasing, and a metal thin film layer excellent in heat dissipation and UV resistance corresponding to LED lamps is laminated on a base thermoplastic resin. A film has also been proposed (Patent Document 2).
JP-A-8-262208 JP 2010-85585 A

Since the reflective film is generally formed of a film-like thermoplastic resin, it has a drawback that it is easily subjected to deformation or discoloration (yellowing or the like) due to heat, moisture, ultraviolet rays, or the like. In particular, in the case of an LED lamp, heat is generated simultaneously with light emission, so the vicinity of the LED lamp is exposed to a high temperature of 80 ° C. or higher, and is also exposed to moisture in the atmosphere. Under such high temperature and high humidity, there is a problem that the reflective film is partially bent due to thermal deformation, and as a result, the reflection characteristics are deteriorated. Reflective films of the type in which a metal thin film layer is laminated on a base thermoplastic resin have excellent heat dissipation and improved deflection due to heat, but the metal thin film layer is made into a thermoplastic resin base via a polyurethane adhesive. Since it is affixed or the like, there is a limit to cost reduction because of complicated processes. The present invention has been made in view of these inconveniences, and is less expensive to bend due to heat, has excellent adhesion, and is less likely to be bent or yellowed even when heated by an LED lamp or irradiated with ultraviolet rays. The purpose is to provide a simple reflective film.

As a means for achieving the above object, the first invention of the present application is an acrylic polymer (A) obtained by polymerizing a monomer mixture containing a considerable amount of methyl methacrylate having a specific glass transition temperature; A coating resin composition comprising a compound (B) having a hydroxyphenyltriazine skeleton having a specific molecular weight.
The second invention is a coating resin composition comprising a compound having a hydroxyphenyl triazine skeleton having a specific structure.
A third invention is a coating resin composition characterized in that the monomer component of the acrylic polymer (A) further contains a specific amount of a monomer having a triazole skeleton.
A fourth invention is a reflective film characterized in that it is a laminate having an application layer formed from the resin composition for coating of the first to third inventions on at least one surface of a thermoplastic resin film.

When the coating agent of the present invention and the reflective film coated with the coating agent are used, the above-mentioned problems are overcome, that is, a reflective film having excellent adhesion can be obtained with less deflection due to heat from the light source. Reflectors for edge-lighted backlights for liquid crystal displays that require characteristics, and backlight-type backlights and backlight reflective films equipped with LEDs, solar cell sealing films and backsheets that require reflective characteristics Is done. Especially, it can be used conveniently as a reflective film of the backlight which mounts LED.

Hereinafter, a preferred embodiment as an example of the present invention will be described in detail. However, this detailed description does not limit the present invention to this embodiment.
<Basic configuration of the coating agent of the present invention>
The coating resin composition of the present invention has an acrylic polymer (A) obtained by polymerizing a monomer mixture having a glass transition temperature of 75 ° C. or higher and lower than 110 ° C. and containing 50% by mass or more of methyl methacrylate, and a molecular weight. And a compound (B) having 600 or more hydroxyphenyltriazine skeletons.

<Essential monomer composition of acrylic polymer (A)>
In the acrylic polymer (A), when the total mass of all the monomer components is 100% by mass, the methyl methacrylate is preferably 50% by mass or more. More preferably, it is 60 mass% or more, More preferably, it is 70 mass% or more, Most preferably, it is preferable to set it as 80 mass% or more. If it is less than 50% by mass, the compatibility with the compound (B) having a hydroxyphenyltriazine skeleton having a specific molecular weight, which will be described later, decreases, and the adhesion to the substrate decreases. Moreover, it is likely to bend due to heat, and the reflectance may be reduced.

<Selectable monomer composition of acrylic polymer (A)>
Although it does not specifically limit as another copolymerizable monomer which can be used for monomer components other than methyl methacrylate, For example, the following monomer etc. are mentioned. These may be used alone or in combination of two or more. Monomers having a carboxyl group such as (meth) acrylic acid, itaconic acid, maleic anhydride; acidic phosphate ester monomers such as 2- (meth) acryloyloxyethyl acid phosphate; 2-hydroxyethyl (meth) acrylate, hydroxy Monomers having a group having active hydrogen, such as propyl (meth) acrylate, hydroxybutyl (meth) acrylate, caprolactone-modified hydroxy (meth) acrylate (for example, trade name “Placcel FM” manufactured by Daicel Chemical Industries, Ltd.); ) (Meth) acrylates such as acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, butyl (meth) acrylate, cyclohexyl (meth) acrylate, etc .; epoxy groups such as glycidyl (meth) acrylate Monomers. (Meth) acrylamide, N, N′-dimethylaminoethyl (meth) acrylate, N, N-diethylaminoethyl (meth) acrylate, imide (meth) acrylate, hindered amine monomer, for example, “ADK STAB LA-82”, “ADK STAB” LA-87 "(both trade names, manufactured by Asahi Denka Kogyo Co., Ltd.) and other monomers having nitrogen atoms; ethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, tripropylene glycol di (meth) acrylate, Monomers having two or more polymerizable double bonds such as trimethylolpropane tri (meth) acrylate and pentaerythritol tetra (meth) acrylate; monomers having a halogen atom such as vinyl chloride; excellent monomers such as styrene and alpha-methylstyrene Aromatic monomers; vinyl esters such as vinyl acetate; vinyl ethers.

In addition, it is preferable to use a monomer having a benzotriazole skeleton from the viewpoint of reducing thermal deflection of a laminate having an application layer formed from the coating resin composition of the present invention. Specific examples include “RUVA93” (trade name, manufactured by Otsuka Chemical Co., Ltd.) and “BP-1A” (trade name, manufactured by Osaka Organic Chemical Co., Ltd.). The amount of the monomer having a benzotriazole skeleton is preferably 0.5% by mass or more and 30% by mass or less, assuming that the total mass of all monomer components is 100% by mass. More preferably, the content is 1% by mass or more and 20% by mass or less. More preferably, the content is 2% by mass or more and 10% by mass or less. If the amount is less than 0.5% by mass, there is a risk of large deflection due to heat.
On the other hand, when it exceeds 20% by mass, the compatibility with the compound (B) having a hydroxyphenyltriazine skeleton having a specific molecular weight described later is decreased, transparency as a coating film and bending due to heat are decreased, There is a possibility that the adhesiveness of the material will be lowered.

<Design of acrylic polymer (A): Glass transition temperature>
The glass transition temperature of the acrylic polymer (A) is 75 ° C. or higher and lower than 110 ° C. The monomer is selected so as to fall within this range with reference to a known monomer glass transition temperature. Thus, the acrylic polymer (A) which shows the effect of this invention can be manufactured by selecting a monomer and polymerizing a polymer. However, since the glass transition temperature is not disclosed or some of the monomers are not clear, the glass transition temperature in the present invention is determined using a differential scanning calorimeter (DSC) based on the provisions of JIS K7121. The value obtained by the starting point method.

<Polymerization method of acrylic polymer (A)>
The polymerization method for producing the acrylic polymer (A) is not particularly limited, and various conventionally known polymerization methods such as a solution polymerization method and a suspension polymerization method can be employed. Examples of the solvent that can be used when the monomer composition is copolymerized by employing the solution polymerization method include toluene, xylene, and other high-boiling aromatic solvents; ethyl acetate, butyl acetate, cellosolve acetate. Ester solvents such as methyl ketone, and ketone solvents such as methyl isobutyl ketone, but are not particularly limited. Only one kind of these solvents may be used, or two or more kinds may be appropriately mixed and used. Moreover, the usage-amount of a solvent is not specifically limited. What is necessary is just to set suitably as the usage-amount of a solvent by polymerization conditions, the weight ratio of the polymer component in an acrylic polymer, etc. Furthermore, when the monomer composition is copolymerized by employing a suspension polymerization method or the like, an emulsifier can be used.

Moreover, when copolymerizing a monomer composition, a polymerization initiator can be used. The polymerization initiator is not particularly limited, and examples thereof include 2,2′-azobis- (2-methylbutyronitrile), tert-butylperoxy-2-ethylhexanoate, and 2,2′-azobisisobutyrate. Common radical polymerization initiators such as ronitrile, benzoyl peroxide, and di-tert-butyl peroxide can be used. These may be used alone or in combination of two or more. Further, the amount of the polymerization initiator used is not particularly limited, but the amount used may be appropriately set from the desired polymer characteristic value, etc. For example, when the monomer component is 100% by mass 0.01 to 50% by mass is preferable. More preferably, it is 0.05-20 mass%.
Although reaction temperature is not specifically limited, The range of room temperature-200 degreeC is preferable, and the range of 40 degreeC-140 degreeC is more preferable. The reaction time may be appropriately set so that the polymerization reaction is completed according to the reaction temperature, the composition of the monomer composition to be used, the kind of the polymerization initiator, or the like.

<Design of acrylic polymer (A): molecular weight>
As a weight average molecular weight of the polymer which comprises the said acrylic polymer, it is preferable that it is 2000-1 million, for example. More preferably, it is 4000-300,000, More preferably, it is 5000-100,000. For example, the acrylic polymer (A) which shows the effect of this invention can be manufactured by making the range of a preferable molecular weight by selecting the polymerization method and conditions described in the previous section. The weight average molecular weight is a value measured with polystyrene standard GPC.

<Quantity ratio of acrylic polymer (A) in composition>
The acrylic polymer (A) contained in the coating composition of the present invention is contained in 60% by mass or more, preferably 80% or more in 100% by mass of the resin constituting the coating composition of the present invention. desirable. If it is less than 50% by mass, the compatibility with the compound (B) having a hydroxyphenyl triazine skeleton having a specific molecular weight, which will be described later, decreases, transparency as a coating film and bending due to heat decrease, and adhesion to a substrate. May decrease.

<Skeletal characteristics of compound (B)>
The compound (B) having a hydroxyphenyltriazine skeleton has a structure represented by the following formula {1}. The molecular weight is preferably 600 or more, more preferably 700 or more. The hydroxyphenyltriazine skeleton is a skeleton ((2-hydroxyphenyl) -1,3,5-triazine skeleton) composed of triazine and three hydroxyphenyl groups bonded to the triazine. The hydrogen atom of the hydroxyl group in the hydroxyphenyl group forms a hydrogen bond with the nitrogen atom of triazine, and the formed hydrogen bond increases the action of the phenyl triazine as a chromophore. The hydroxyphenyl group in the hydroxyphenyltriazine skeleton may have a substituent such as an alkyl group or an alkyl ester group, but the substituent has a structure that can serve as a crosslinking point with the acrylic polymer (A). Preferably not.
The following general formula {1};

[R ^{1 to} R ³ in {1} above are each independently a hydrogen atom, an alkyl group having 1 to 18 carbon atoms, or an alkyl ester group. The alkyl ester group is preferably a group represented by the formula “—CH (—R ⁴ ) C (═O) OR ⁵ ”. In the above formula, R ⁴ is a hydrogen atom or a methyl group, and R ⁵ is It is a linear or branched alkyl group. When R ^{1 to} R ³ are alkyl groups, they may be linear alkyl groups or branched alkyl groups. ]
R ^{1 to} R ³ are preferably alkyl ester groups from the viewpoint of compatibility with the acrylic polymer (A) and reduction in flexibility due to heat.

  Particularly preferred compound (B) having a hydroxyphenyltriazine skeleton is, for example, CGL77MPA (manufactured by Ciba Specialty Chemicals) or CGL777MPAD (manufactured by Ciba Specialty Chemicals) containing the following {2} as a main component.

<Quantity ratio of compound (B) in composition>
The content of the compound (B) having a hydroxyphenyltriazine skeleton in the coating resin composition of the present invention is, for example, 0.5 to 20 parts with respect to 100 parts of the acrylic polymer (A). When the content of the compound (B) having a hydroxyphenyltriazine skeleton is 20 parts or more, the compatibility with the acrylic polymer (A) is lowered, and the adhesion with the substrate is lowered. Moreover, it is likely to bend due to heat, and the reflectance may be reduced. On the other hand, when the content of the compound (B) having a hydroxyphenyltriazine skeleton is 0.5 parts or less, there is a risk that the bending due to heat tends to occur and the reflectance is lowered.

<Basic composition of coating composition>
The coating resin composition of the present invention may contain, for example, one or more solvents, additives, and the like. Examples of such solvents include the same organic solvents as described above, and examples of additives include conventionally known additives that are generally used in resin compositions that form films and coating films. Can be used, for example, leveling agent; inorganic fine particles such as colloidal silica, alumina sol, organic fine particles of polymethyl methacrylate, antifoaming agent, anti-sagging agent, silane coupling agent, titanium white, carbon black, organic pigment Pigment dispersants; Phosphorous and phenolic antioxidants; Viscosity modifiers; UV stabilizers; Metal deactivators; Peroxide decomposing agents; Fillers; Flame retardants; Reinforcing agents; Agent; rust preventive agent; fluorescent brightener; organic and inorganic ultraviolet absorber, inorganic heat ray absorber; organic and inorganic flameproof agent; organic and inorganic antistatic agent; methyl orthoformate, etc. Water agent, and the like.

<Method for forming coating layer using coating composition>
The coating resin composition of the present invention that can be prepared by the above-described method can be applied by a known method to form a resin layer. The resin layer can be formed by simply forming a coating film on the surface of the base material or laminating it with another base material or functional layer. The resin layer may be provided with a function by a known method depending on the required performance, and for example, any method of crosslinking and non-crosslinking can be used. Taking the case where the coating film needs to have solvent resistance as an example, it is preferable to add a crosslinking agent such as a polyisocyanate compound to form a cured coating film and impart solvent resistance.

<Reflection film used as a substrate>
The reflective film used as the substrate of the present invention is not particularly limited, but it is better if the visible light reflectance is high. In particular, a white film containing bubbles and / or incompatible particles inside is preferably used. . Although these white films are not limited, porous unstretched or biaxially stretched polypropylene films and porous unstretched or stretched polyethylene terephthalate films are preferably used as examples. More preferably, it is a porous white biaxially stretched polyethylene terephthalate film mixed and / or copolymerized with polyethylene naphthalate from the viewpoint of heat resistance and reflectance. Examples of white films include Lumirror (registered trademark) E20 (manufactured by Toray Industries, Inc.), SY64 (manufactured by SKC), etc., as examples of single-layer structures. (Registered trademark) film UXZ1 (manufactured by Teijin DuPont Films Co., Ltd.) and the like, and as a white film having a three-layer structure, Lumirror (registered trademark) E6SL, E6SR, Tetron (registered trademark) film UX (Teijin DuPont Film ( Etc.).

  The structure of the base film may be appropriately selected depending on the intended use and required properties, and is not particularly limited, but is a single layer and / or two or more composite films having a structure of at least one layer. It is preferable that at least one layer contains bubbles and / or inorganic particles. An example of a single layer configuration (= 1 layer) is, for example, a white film having only a single A layer, and includes a configuration in which inorganic particles and / or bubbles are contained in the A layer. The content of is preferably 2% by weight or more, more preferably 7% by weight or more, and most preferably 10% by weight or more based on the total weight of the white film. Moreover, as an example of 2 layer structure, it is a white film of 2 layer structure of A layer / B layer which laminated | stacked the white film as B layer on the said A layer. In addition, as an example of the three-layer configuration, as described above, a white film having a three-layer laminated structure in which three layers of A layer / B layer / A layer and / or A layer / B layer / C layer are laminated, Examples of the structure include inorganic particles and / or bubbles in at least one of the layers, and the content of the inorganic particles is 2% by weight or more based on the total weight of the white film as described above. Preferably, it is 7 wt% or more, more preferably 30 wt% or more. In the case of a two-layer configuration or a three-layer configuration, a transparent film may be laminated on the light incident side of the LED lamp. Moreover, you may bond between the layers of a base material using a urethane type drynate adhesive.

<Coated reflective film using coating composition>
The coated reflective film using the coating composition of the present invention has a heat shrinkage ratio in the longitudinal direction and width direction of the film as measured after coating at a heating temperature of 90 ° C. for a heating time of 30 minutes or 60 minutes. Are preferably -0.1% or more and 0.2% or less. More preferably, it is -0.05 to 0.15% or less. Heating temperature 90 ° C Heating time 30 minutes or 60 minutes When the heat shrinkage in the film longitudinal direction or width direction is out of the range of -0.1% or more and 0.2% or less, Tends to be bent. In particular, reflective films for backlights equipped with LEDs are not only used at high temperatures, but are often stamped to match the position where the LEDs are installed. Contact with the LED after mounting on the light is likely to occur, and film defects may impair the characteristics and safety of the backlight.

The film heat-shrinkage in the film longitudinal direction measured at the heating temperature of 90 ° C. for the heating time of 30 minutes or 60 minutes is to prepare a film sample of a certain size and constant in the longitudinal direction (extrusion direction during production) at room temperature The length (A) of the sample was measured, and the sample was allowed to stand for 30 minutes in a thermostat kept at 90 ° C. or left for 60 minutes, and then slowly cooled to the same room temperature. It is a numerical value obtained by measuring the length and calculating the following formula {1} from the length (B) and the initial length (A). Heat shrinkage rate (%) = {(A−B) / A} × 100 {1}
Negative numbers indicate that the polymer film has grown.
Moreover, the heating shrinkage rate in the width direction of the film measured at a heating temperature of 90 ° C. for a heating time of 30 minutes or 60 minutes is the width direction of the polymer film (perpendicular to the extrusion direction during production). A value measured in the same manner as in the longitudinal direction.

The present invention will be described in more detail with reference to synthesis examples and examples of acrylic polymers below, but the present invention is not limited to these examples.
<Synthesis Example 1>
100 g of ethyl acetate was charged into a 300 ml flask equipped with a stirrer, a dripping port, a thermometer, a cooling pipe and a nitrogen gas inlet, and the temperature was raised to the reflux temperature. When it began to reflux, a mixture of 80 g of methyl methacrylate, 10 g of butyl methacrylate, 10 g of 2-hydroxyethyl methacrylate and 1.5 g of 2,2′-azobis- (2-methylbutyronitrile) as an initiator was continuously added dropwise over 2 hours. did. Further, after heating for 4 hours, a solution having an acrylic polymer nonvolatile content of 50.0% was obtained. In addition, the weight average molecular weight of the polymer which comprises this acrylic polymer is 30000.

<Measuring method of glass transition temperature>
The glass transition temperature of the acrylic polymer was determined in accordance with JIS K7121 regulations. Specifically, a differential scanning calorimeter (manufactured by Rigaku Corporation, DSC-8230) is used to raise a temperature of about 10 mg from room temperature to 200 ° C. (temperature increase rate: 20 ° C./min) in a nitrogen gas atmosphere. From the obtained DSC curve, it was evaluated by the starting point method. Alpha-alumina was used as a reference.
Table 1 shows the composition of the monomer components used for the synthesis of the acrylic polymer and the characteristic values of the resulting acrylic polymer.

<Synthesis Examples 2-4>
An acrylic polymer was obtained in the same manner as in Synthetic Example 1 except that the composition of the monomer components used in the synthesis of the acrylic polymers of Synthesis Examples 2 to 4 was as shown in Table 1. Table 1 shows the characteristic values of the obtained acrylic polymer.
Next, the following coating resin composition was blended using an acrylic polymer.

<Example 1>
For 100 parts of the acrylic polymer obtained in Synthesis Example 1, a compound having a hydroxyphenyl triazine skeleton (molecular weight 958) is a main component, and a compound having a hydroxyphenyl triazine skeleton having a molecular weight of 773 and a molecular weight of 1142 is used as a subcomponent. A resin composition 1 was prepared by placing 5 parts of CGL777MPA (manufactured by Ciba Specialty Chemicals, active ingredient 80%) in a container and further diluting with toluene until the nonvolatile content became a 20% solution. Next, a three-layer thermoplastic resin film (Lumirror (registered trademark) E6SL, manufactured by Toray Industries, Inc., thickness 25000 μm) composed of porous biaxially stretched polyethylene terephthalate was prepared as a thermoplastic resin film. The resin composition 1 is applied to both surfaces of this thermoplastic resin film using Metabar # 35, and heated and dried at 120 ° C. for 1 minute. The thickness after drying is 10 μm on each side, and the total thickness on both sides is 20 μm. The coating layer was provided to obtain a reflective film.
<Examples 2 to 7, Comparative Examples 1 and 2>
A reflective film of the present invention was obtained in the same manner as in Example 1 except that the composition of the resin composition was as shown in Table 2.
[Evaluation method of evaluation sample]
{1} Adhesion
Evaluation was made by cellophane tape peeling. A cellophane tape CT-405 manufactured by Nichiban Co., Ltd. having a width of 10 mm was applied to the coated surface on which the resin composition of the present invention was formed, and the remaining rate of the coating film after peeling in the 90 ° direction was visually determined. Judgment was made based on evaluation criteria.
○: Residual rate 100%
Δ: Residual rate 50% or more and less than 100%
X: Residual rate less than 50% {2} Heat shrinkage rate
Each of the longitudinal direction and the width direction of the film is cut into a length of 10 mm × 230 mm, marks at intervals of 200 mm are put in the length direction, and the distance between the marks is accurately read with a metal ruler (alpha mm). After aging the sample in a hot air oven at 90 ° C. for 30 minutes or 60 minutes, the distance between marks of the sample is read by the above method (β mm). The heat shrinkage percentage was calculated from the distance between the marks by the following formula and expressed in%. Judgment was made according to the following evaluation criteria.
Heat shrinkage rate (%) = (alpha−β) / alpha × 100.
[Longitudinal direction]
A: -0.05% or more and 0.15% or less
○: -0.1% or more and 0.2% or less
×: smaller than −0.1% or larger than 0.2% [lateral direction]
A: -0.05% or more and 0.15% or less
○: -0.1% or more and 0.2% or less
X: Less than -0.1% or more than 0.2%

According to the invention, it is possible to provide an inexpensive reflective film that is less likely to bend due to heat, has excellent adhesion, and is less likely to be bent or yellowed even when the LED lamp receives intense and continuous heat generation.

It is an example of the cross-sectional schematic diagram of the reflective film of this invention. It is an example of the cross-sectional schematic diagram of the reflective film of this invention.

1: White film 2: Coating layer 3: Polyurethane-based dry laminate adhesive 4; Transparent PET
5; Reflective film

Claims (4)

An acrylic polymer (A) obtained by polymerizing a monomer mixture having a glass transition temperature of 75 ° C. or higher and lower than 110 ° C. and containing 50% by mass or more of methyl methacrylate, and a compound having a hydroxyphenyl triazine skeleton having a molecular weight of 600 or more A coating resin composition comprising (B)
The compound (B) having the hydroxyphenyltriazine skeleton is represented by the following general formula {1};

[R ^{1 to} R ³ in {1} above are each independently a hydrogen atom, an alkyl group having 1 to 18 carbon atoms, or an alkyl ester group. The alkyl ester group is preferably a group represented by the formula “—CH (—R ⁴ ) C (═O) OR ⁵ ”. In the above formula, R ⁴ is a hydrogen atom or a methyl group, and R ⁵ is It is a linear or branched alkyl group. When R ^{1 to} R ³ are alkyl groups, they may be linear alkyl groups or branched alkyl groups. ]
The coating resin composition according to claim 1, which is a compound having a hydroxyphenyltriazine skeleton.
The resin composition for coating according to claim 1 or 2, wherein the monomer component of the acrylic polymer (A) further contains 1 to 20% by mass of a monomer having a triazole skeleton.
A reflective film comprising a laminate having a coating layer in which the coating resin composition according to claim 1 is formed on at least one surface of a thermoplastic resin film.

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