JP2008260886A - Acrylic resin film and use of the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an acrylic resin film usable as a transparent protecting film for a light diffusing plate of a back light, keeping the initial hue of the light diffusing plate in good state and suppressing yellowing of the light diffusing plate by irradiation with light. <P>SOLUTION: The acrylic resin film comprises 0.1-1 g/m<SP>2</SP>of a compound having a specific triazine skeleton as a UV absorbing agent, the light diffusing plate has the film on the surface of the light diffusing plate, and the back light unit is provided with the light diffusing plate, and the liquid crystal display device is provided with the back light unit. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an acrylic resin film suitable for a display member, and particularly to an acrylic resin film suitable for forming a protective layer on the surface of a light diffusion plate.

  As a liquid crystal display device, a backlight type in which a backlight unit is provided on the lower surface side of the liquid crystal layer and the liquid crystal layer is illuminated from the back surface to emit light is widely used. The backlight system is roughly classified into a side type and a direct type according to the arrangement of light sources such as cold cathode tubes. In any liquid crystal display device, it is required to suppress the loss in the light transmission path from the light source to the panel and improve the luminance on the panel. In recent years, however, the liquid crystal has a large screen exceeding 15 inches. The demand for televisions, PC displays, and the like has increased dramatically, and cases where direct type backlight units are used as such large-sized flat light emitting devices are increasing.

The direct type backlight unit is a system in which a reflector is placed on the back of the light source and a light diffusing plate is placed on the light emitting surface to reflect and diffuse the light from the light source. A lamp can be placed just behind the light emitting surface. Therefore, there are advantages that a large number of lamps can be used and high brightness can be exhibited.
As a light diffusing plate used in such a direct type backlight unit, one mainly made of polycarbonate resin has been proposed and put into practical use.
For example, Patent Literature 1 proposes a light diffusion plate for direct backlight of a polycarbonate resin for large liquid crystal displays and liquid crystal televisions. This light diffusing plate is characterized by little warpage, excellent surface light emission, no luminance unevenness, and excellent color tone.
However, in these light diffusing plates, light from the cold cathode tube or the like is directly irradiated to the light diffusing plate, so that the polycarbonate resin turns yellow, adversely affects the color tone in the color liquid crystal display, and the luminous quality is lowered. There was a problem that the service life was shortened.

For the yellowing problem in this polycarbonate resin diffusion plate, it has been proposed to provide a transparent protective layer with excellent light resistance, such as a transparent resin layer containing an ultraviolet absorber, on the light source side surface of the light diffusion plate. (For example, Patent Documents 2, 3, and 4)
In the polycarbonate resin-based light diffusing plate as disclosed in Patent Documents 2, 3, and 4, it is included in the transparent resin layer provided on the light source side surface of the light diffusing plate in order to provide sufficient light resistance. It is necessary to increase the amount of UV absorbers to be used. However, when the amount of the ultraviolet absorber added is increased, the YI value of the protective layer increases, and the color tone of the light diffusing plate itself tends to increase yellowishness.

In Patent Document 2, the transparent resin layer contains a benzotriazole-based ultraviolet absorber. However, if the amount of the ultraviolet absorber added is increased in order to provide sufficient light resistance, the YI value of the transparent resin layer is increased. As a result, the color of the light diffusing plate itself becomes yellowish. When a benzotriazole-based ultraviolet absorber is used, it is difficult to satisfy both requirements for light resistance and color tone of the light diffusion plate.
Patent Documents 3 and 4 do not specifically limit the type and amount of the ultraviolet absorber contained in the transparent resin layer, and also describe that the ultraviolet absorber affects the color tone of the light diffusion plate. Absent.

JP 2004-126185 A WO2004 / 111169 gazette WO 2004/109379 JP 2006-146029 A

  An object of the present invention is to use as a transparent protective layer of a light diffusing plate for a backlight capable of maintaining a good initial color tone of the light diffusing plate and suppressing yellowing of the light diffusing plate due to light irradiation. It is to provide an acrylic resin film that can be used.

  In view of the problems of the prior art as described above, the present inventors have conducted intensive studies on a transparent protective layer for protecting a light diffusing plate to be used for a backlight such as a direct type, and as a result, the surface of the light diffusing plate It has been found that the above problem can be solved by forming the layer with a specific acrylic resin film, and the present invention has been achieved.

２．ＪＩＳ Ｋ ７１０３に準拠したＹＩ値が１．０未満である、上記１に記載のアクリル樹脂フィルム。 Therefore, this invention consists of the following 1-6, for example.
1. An acrylic resin film comprising 0.1 to 1 g / m ^{2 of} a compound represented by the following formula (1).

2. 2. The acrylic resin film according to 1 above, wherein the YI value based on JIS K 7103 is less than 1.0.

3. 3. The acrylic resin film as described in 1 or 2 above, which contains the following rubber-containing multistage polymer (I).
Rubber-containing multistage polymer (I)
Each of the monomer components having the following composition is prepared by (1) monomer mixture (IA), (2) monomer mixture (IB), and (3) monomer mixture (IC). Polymer obtained by sequentially polymerizing in order (1) Monomer mixture (IA)
(I-A1) Alkyl acrylate 50-99.9% by mass
(I-A2) Acrylic methacrylate 0-49.9 mass%
(I-A3) Other monomer having copolymerizable double bond 0 to 20% by mass
(I-A4) Polyfunctional monomer 0 to 10% by mass
(I-A5) Graft crossing agent 0.1 to 10% by mass
(2) Monomer mixture (IB)
(I-B1) Acrylic acrylate 9.9 to 90% by mass
(I-B2) Alkyl methacrylate 9.9 to 90% by mass
(I-B3) Monomer having a copolymerizable double bond 0 to 20% by mass
(I-B4) Polyfunctional monomer 0 to 10% by mass
(I-B5) Graft crossing agent 0.1 to 10% by mass
(3) Monomer or monomer mixture (IC)
(I-C1) Alkyl methacrylate 80-100% by mass
(I-C2) Acrylic acrylate 0-20% by mass
(I-C3) Monomer having a copolymerizable double bond 0 to 20% by mass

4). A light diffusion plate comprising the acrylic resin film described in any one of 1 to 3 on a surface thereof.
5. A backlight unit comprising the light diffusing plate described in 4 above.
6). A liquid crystal display device comprising the backlight unit described in 5 above.

  According to the present invention, an acrylic resin film having an excellent initial color tone of a light diffusion plate and capable of suppressing discoloration due to light from a light source by being used as a protective layer on the surface of the light diffusion plate. Can be provided. A liquid crystal display device having a backlight using the same (for example, one having a direct type backlight) can maintain the color tone and light emission quality in color display for a long time.

  Hereinafter, the present invention will be specifically described, but this is to explain preferred embodiments of the present invention, and the present invention is not limited only to these embodiments, and the spirit and scope of implementation of the present invention. It should be understood that various modifications are possible.

<Acrylic resin film>
A preferred acrylic resin constituting the acrylic resin film of the present invention is not particularly limited, but at least one selected from the group consisting of methyl methacrylate, ethyl methacrylate, propyl methacrylate, and butyl methacrylate is used as a main raw material, and if necessary carbon Examples thereof include a single polymer or a copolymer obtained by using, as a copolymerization component, an acrylate ester having an alkyl group of 1 to 8, vinyl acetate, vinyl chloride, styrene, acrylonitrile, methacrylonitrile, or the like. Further, the weights described in Japanese Patent Publication No. 59-36646, Japanese Patent Publication No. 62-19309, Japanese Patent Publication No. 63-20459, Japanese Patent Publication No. 63-77963, Japanese Patent Publication No. 2006-146029, and the like. Coalescence can be used.

  The acrylic resin constituting the acrylic resin film of the present invention is preferably an acrylic resin containing a rubber-containing polymer containing acrylic (meth) acrylate as a main component. Examples of the rubber-containing polymer are described below. It is preferable to use a rubber-containing multistage polymer (I). Since the acrylic resin film containing these rubber-containing polymers has good light resistance and transparency, it can be suitably used as a protective layer by being laminated on a light diffusion plate.

[Rubber-containing multistage polymer (I)]
The rubber-containing multistage polymer (I) is obtained by polymerizing the monomer mixture (IA), the monomer mixture (IB), the monomer or the monomer mixture (IC) in this order. Polymer.
The monomer mixture (IA) is an alkyl acrylate (I-A1) having an alkyl group having 1 to 8 carbon atoms and an alkyl methacrylate (I-A1) having an alkyl group having 1 to 4 carbon atoms. -A2) 0 to 49.9% by mass, other monomer having a copolymerizable double bond (I-A3) 0 to 20% by mass, polyfunctional monomer (I-A4) 0 to 10 % By weight and graft crossing agent (I-A5) 0.1-10% by weight ((I-A1) + (I-A2) + (I-A3) + (I-A4) + (I-A5)) = 100 % By mass).

  The monomer mixture (IB) is an alkyl acrylate (I-B1) having 9.9 to 90% by mass of an alkyl group having 1 to 8 carbon atoms, and an alkyl methacrylate having a C 1 to 4 alkyl group (I -B2) 9.9 to 90% by mass, another monomer (I-B3) having a copolymerizable double bond (0 to 20% by mass), polyfunctional monomer (I-B4) 0 to 10 % By weight and graft crossing agent (I-B5) 0.1-10% by weight ((I-B1) + (I-B2) + (I-B3) + (I-B4) + (I-B5)) = 100 Mass%) and a composition different from that of the monomer mixture (IA).

  The monomer or monomer mixture (IC) is an alkyl methacrylate having an alkyl group having 1 to 4 carbon atoms (I-C1) 80 to 100% by mass and an alkyl group having 1 to 8 carbon atoms. (I-C2) 0-20% by mass and other monomers having a copolymerizable double bond (I-C3) 0-20% by mass ((I-C1) + (I-C2) + (I -C3) = 100% by mass).

Furthermore, the following composition is preferable.
The alkyl acrylate (I-A1) having an alkyl group having 1 to 8 carbon atoms may be either linear or branched. Specific examples thereof include methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate and the like. These can be used individually or in mixture of 2 or more types. Of these, n-butyl acrylate is preferred.

  The alkyl methacrylate having 1 to 4 carbon atoms (I-A2) may be either linear or branched. Specific examples thereof include methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate and the like. These can be used individually or in mixture of 2 or more types. Of these, methyl methacrylate is preferred.

  Examples of the other monomer (I-A3) having a copolymerizable double bond include acrylic monomers such as lower alkoxy acrylate, cyanoethyl acrylate, acrylamide, acrylic acid, and methacrylic acid; styrene, alkyl-substituted Styrene, acrylonitrile, methacrylonitrile, etc. can be used.

A polyfunctional monomer (I-A4) can be used as needed. A polyfunctional monomer is defined as a monomer having two or more copolymerizable double bonds in one molecule. Preferable specific examples thereof include alkylene glycol dimethacrylates such as ethylene glycol dimethacrylate, 1,3-butylene glycol dimethacrylate, 1,4-butylene glycol dimethacrylate, and propylene glycol dimethacrylate. In addition, polyvinylbenzene such as divinylbenzene and trivinylbenzene can be used. Of these, 1,3-butylene glycol dimethacrylate is preferred.
Even when the polyfunctional monomer does not act at all, as long as the grafting agent is present, a considerably stable multistage polymer is obtained. For example, when the hot strength or the like is strictly required, a polyfunctional monomer may be arbitrarily added depending on the purpose of addition.

The graft crossing agent (I-A5) is defined as a monomer having two or more different copolymerizable double bonds in one molecule. Specific examples thereof include allyl, methallyl or crotyl ester of copolymerizable α, β-unsaturated carboxylic acid or dicarboxylic acid. Particularly preferred are acrylic esters of acrylic acid, methacrylic acid, maleic acid or fumaric acid. Of these, allyl methacrylate is preferable because of its excellent effect. In addition, triallyl cyanurate, triallyl isocyanurate and the like are also effective. In the graft crossing agent (I-A5), mainly the conjugated unsaturated bond of the ester reacts much faster than the allyl group, methallyl group or crotyl group and chemically bonds. A substantially significant portion of the allyl, methallyl or crotyl group works effectively during the polymerization of the next layer polymer and provides a graft bond between two adjacent layers.
In addition, you may superpose | polymerize in presence of a chain transfer agent.

  The content of the alkyl acrylate (I-A1) having an alkyl group having 1 to 8 carbon atoms in 100% by mass of the monomer mixture (I-A) is processed when molding the rubber-containing multistage polymer (I). It is 50-99.9 mass% from the point of physical properties, such as property and intensity | strength, More preferably, it is 55-77.9 mass%, Most preferably, it is 60-69.9 mass%.

  The content of the alkyl methacrylate (I-A2) having an alkyl group having 1 to 4 carbon atoms in 100% by mass of the monomer mixture (IA) is 0 to 49.9% by mass, more preferably 20%. It is at least 30% by mass, most preferably at least 30% by mass. Further, it is more preferably 44.9% by mass or less, and most preferably 39.9% by mass or less.

  The other monomer (IA3) having a copolymerizable double bond in 100% by mass of the monomer mixture (IA) is 0 to 20% by mass, more preferably 15% by mass or less. It is.

  The content of the polyfunctional monomer (IA4) in 100% by mass of the monomer mixture (IA) is 0 to 10% by mass, more preferably 0.1% by mass or more and 6% by mass. % Or less.

  Content of the graft crossing agent (IA5) in 100 mass% of the monomer mixture (IA) is 0.1 to 10 mass%. When the content is 0.1% by mass or more, the obtained rubber-containing multistage polymer can be molded without deteriorating optical properties such as transparency. A content of 10% by mass or less is preferable because sufficient flexibility and toughness can be imparted to the rubber-containing multistage polymer. More preferably, it is 0.5 mass% or more and 2 mass% or less.

  The transparency of the molded body of the acrylic resin composition obtained by molding the rubber-containing multi-stage polymer (I) is that the content of each monomer in the monomer mixture (IA) is in the above range. From the viewpoint of physical properties such as strength.

  The Tg of the polymer obtained by polymerizing the monomer mixture (I-A) is a single unit described later from the viewpoint of physical properties such as the strength of the acrylic resin film obtained by molding the rubber-containing multistage polymer (I). It is preferably less than Tg of the polymer obtained by polymerizing the monomer mixture (IB). More preferably, it is less than 5 degreeC, More preferably, it is 0 degreeC or less, Most preferably, it is -5 degreeC or less.

Here, Tg of a polymer is calculated | required by the following Fox formula, for example in the case of the copolymer which consists of monomer a, b, c ....
1 / Tg = ma / Tga + mb / Tgb + mc / Tgc ...
Tg: Tg [K] of copolymer, ma: mass fraction of monomer a, Tga: Tg [K] of homopolymer obtained from monomer a, mb: mass fraction of monomer b, Tgb: Tg [K] of the homopolymer obtained from the monomer b, mc: Mass fraction of the monomer c, Tgc: Tg [K] of the homopolymer obtained from the monomer c.

  Use amount of monomer mixture (IA) (monomer mixture (IA) + monomer mixture (IB) + (3) monomer mixture (IC)) = 100% by mass Is preferably from 15 to 50% by mass, more preferably from 15 to 35% by mass, in terms of the transparency of the acrylic resin film obtained by molding the rubber-containing multistage polymer (I). In this case, it is advantageous in terms of optical properties when the rubber-containing multistage polymer (I) is laminated on a light diffusion plate.

The monomer mixture (IA) may be polymerized in one stage, but is more preferably polymerized in two stages.
Further, when polymerized in two stages, the monomer mixture (IA-1) used for the first stage polymerization in the monomer mixture (IA) and the second stage polymerization The composition of the monomer mixture (IA-2) used in the above may be the same or different.
Monomer mixture (IA-1) used for the first stage polymerization in the monomer mixture (IA), and monomer mixture (IA-1) used for the second stage polymerization ( When the composition of IA-2) is different, the Tg of the polymer obtained from the monomer mixture (IA-1) used for the first stage polymerization is used for the second stage polymerization. It may be higher or lower than the Tg of the polymer obtained from the monomer mixture (IA-2).

From the viewpoint of transparency, the content of the monomer mixture (IA-1) used for the first stage polymerization in the monomer mixture (IA) (100% by mass) is 1 The content of the monomer mixture (IA-2) used for the second stage polymerization is preferably 80 to 99% by mass. The acrylic resin film laminated on the light diffusing plate or the like preferably has higher transparency.
Preferable polymers obtained by polymerizing the monomer mixture (IA) include rubber-containing multistage polymers described in JP-B-62-19309.

  The alkyl acrylate (I-B1) having an alkyl group having 1 to 8 carbon atoms may be either linear or branched. Specific examples thereof include methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate and the like. These can be used alone or in admixture of two or more. Of these, preferred are methyl acrylate and n-butyl acrylate.

  The alkyl methacrylate (I-B2) having an alkyl group having 1 to 4 carbon atoms may be either linear or branched. Specific examples thereof include methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate and the like. These can be used alone or in admixture of two or more. Of these, methyl methacrylate is preferred.

  Other monomers (I-B3) having a double bond capable of copolymerization include acrylic monomers such as lower alkoxy acrylate, cyanoethyl acrylate, acrylamide, acrylic acid, methacrylic acid, styrene, alkyl-substituted styrene, Acrylonitrile, methacrylonitrile, etc. can be used.

The polyfunctional monomer (I-B4) may be used as necessary. Preferable specific examples thereof include alkylene glycol dimethacrylates such as ethylene glycol dimethacrylate, 1,3-butylene glycol dimethacrylate, 1,4-butylene glycol dimethacrylate, and propylene glycol dimethacrylate. In addition, polyvinylbenzene such as divinylbenzene and trivinylbenzene can be used. Of these, 1,3-butylene glycol dimethacrylate is preferred.
Even when the polyfunctional monomer does not act at all, as long as the grafting agent is present, a fairly stable rubber-containing multistage polymer is obtained. For example, when the hot strength or the like is strictly required, a polyfunctional monomer may be arbitrarily added depending on the purpose of addition.

Examples of the graft crossing agent (I-B5) include allyl, methallyl, or crotyl ester of copolymerizable α, β-unsaturated carboxylic acid or dicarboxylic acid. Particularly preferred are acrylic esters of acrylic acid, methacrylic acid, maleic acid or fumaric acid. Of these, allyl methacrylate is preferable because of its excellent effect. In addition, triallyl cyanurate, triallyl isocyanurate and the like are also effective. In the graft crossing agent (I-B5), mainly the conjugated unsaturated bond of the ester reacts much faster than the allyl group, methallyl group or crotyl group, and chemically bonds. A substantially significant portion of the allyl, methallyl or crotyl group works effectively during the polymerization of the next layer polymer and provides a graft bond between two adjacent layers.
In addition, you may superpose | polymerize in presence of a chain transfer agent.

  Content of the alkyl acrylate (I-B1) which has a C1-C8 alkyl group in 100 mass% of monomer mixtures (IB) is 9.9-90 mass%. From the viewpoint of the transparency of the acrylic resin film containing the rubber-containing multistage polymer (I), it is more preferably 19.9% by mass or more, and most preferably 29.9% by mass or more. Further, it is more preferably 60% by mass or less, and most preferably 50% by mass or less.

  Content of the alkyl methacrylate (I-B2) which has a C1-C4 alkyl group in 100 mass% of monomer mixtures (IB) is 9.9-90 mass%. From the viewpoint of transparency of the acrylic resin film containing the rubber-containing multistage polymer (I), it is more preferably 39.9% by mass or more, and most preferably 49.9% by mass or more. Further, it is more preferably 80% by mass or less, and most preferably 70% by mass or less.

  The content of the other monomer (I-B3) having a copolymerizable double bond in 100% by mass of the monomer mixture (IB) is 0 to 20% by mass, more preferably 15%. It is below mass%.

  The content of the polyfunctional monomer (IB-4) in 100% by mass of the monomer mixture (IB) is 0 to 10% by mass, and more preferably 6% by mass or less.

  Content of the graft crossing agent (IB5) in 100 mass% of the monomer mixture (IB) is 0.1 to 10 mass%. When the content is 0.1% by mass or more, the resulting rubber-containing multistage polymer (I) can be molded without deteriorating optical properties such as transparency. A content of 10% by mass or less is preferable because sufficient flexibility and toughness can be imparted to the rubber-containing multistage polymer (I). More preferably, it is 0.5 mass% or more and 2 mass% or less.

The composition of the monomer mixture (IB) is preferably different from the composition of the monomer mixture (IA). When these compositions are different, physical properties such as impact resistance and transparency when the acrylic resin film containing the rubber-containing multistage polymer (I) is formed can be satisfied.
Here, “different composition” means the type and / or amount of alkyl acrylate, alkyl methacrylate, other monomer having a copolymerizable double bond, multifunctional monomer, and graft crossing agent. Is different.

  The Tg of the polymer obtained by polymerizing the monomer mixture (IB) is preferably in the range of 5 to 100 ° C. When Tg is 5 ° C. or higher, the acrylic resin film containing the rubber-containing multistage polymer (I) is preferable because the heat resistance, scratch resistance and transparency are improved. More preferably, it is 10 degreeC or more, Most preferably, it is 15 degreeC or more. Moreover, when Tg is 100 degrees C or less, since a rubber-containing multistage polymer with favorable moldability is obtained, it is preferable. More preferably, it is 70 degrees C or less, Most preferably, it is 50 degrees C or less.

  Although not particularly limited, the amount of the monomer mixture (IB) used (monomer mixture (IA) + monomer mixture (IB) + (3) monomer The mixture (IC) = 100% by mass) is preferably 5 to 35% by mass, more preferably 20% by mass or less. If it is in this range, functions necessary for the intermediate layer, for example, transparency can be exhibited.

  The alkyl methacrylate (I-C1) having an alkyl group having 1 to 4 carbon atoms may be either linear or branched. Specific examples thereof include methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate and the like. These can be used alone or in admixture of two or more. Of these, methyl methacrylate is preferred.

  The alkyl acrylate (I-C2) having an alkyl group having 1 to 8 carbon atoms may be either linear or branched. Specific examples thereof include methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate and the like. These can be used alone or in admixture of two or more. Of these, preferred are methyl acrylate and n-butyl acrylate.

  Other monomers having a copolymerizable double bond (I-C3) include acrylic monomers such as lower alkoxy acrylate, cyanoethyl acrylate, acrylamide, acrylic acid, methacrylic acid, styrene, alkyl-substituted styrene, Acrylonitrile, methacrylonitrile, etc. can be used.

  The content of the alkyl methacrylate (I-C1) having an alkyl group having 1 to 4 carbon atoms in 100% by mass of the monomer or monomer mixture (IC) is 80 to 100% by mass, and more preferably. Is 85% by mass or more, and most preferably 90% by mass or more.

  The content of the alkyl acrylate (I-C2) having an alkyl group having 1 to 8 carbon atoms in 100% by mass of the monomer or monomer mixture (IC) is 0 to 20% by mass, and more preferably. Is 1% by mass or more. Further, it is more preferably 15% by mass or less, and most preferably 10% by mass or less.

  The content of the monomer (I-C3) having a copolymerizable double bond in 100% by mass of the monomer or monomer mixture (IC) is 0 to 20% by mass, more preferably. Is 15% by mass or less.

  Moreover, although it does not specifically limit, a chain transfer agent can be used at the time of superposition | polymerization of a monomer or a monomer mixture (IC), and the molecular weight of the polymer obtained can be adjusted. This chain transfer agent is preferably selected from those usually used for radical polymerization, and specific examples thereof include alkyl mercaptans having 2 to 20 carbon atoms, mercapto acids, thiophenol, carbon tetrachloride, and the like. These can be used alone or in admixture of two or more. The amount of the chain transfer agent used is 0.01 to 5 with respect to 100 parts by mass of the monomer or monomer mixture (IC) monomer ((I-C1) to (I-C3)). Part by mass is preferred. More preferably, it is 0.2 mass part or more, Most preferably, it is 0.3 mass part or more.

  The content of the alkyl acrylate, alkyl methacrylate, other monomer having a copolymerizable double bond, polyfunctional monomer, and graft crossing agent forming the hard polymer (IC) is within the above range. It is preferable from the viewpoints of moldability and transparency of the acrylic resin film containing the rubber-containing multistage polymer (I).

The Tg of the polymer obtained by polymerizing the monomer or monomer mixture (IC) is preferably 60 ° C. or higher. The Tg of 60 ° C. or higher is preferable because an acrylic resin film having good heat resistance and the like can be obtained. More preferably, it is 80 degreeC or more, Most preferably, it is 90 degreeC or more.
Although not particularly limited, the content of the monomer or monomer mixture (IC) in the rubber-containing multistage polymer (I) (100% by mass) is from 15 to 15 in terms of physical properties of the acrylic resin film. 80 mass% is preferable, More preferably, it is 45-80 mass%, Most preferably, it is 45-70 mass%.

  As the method for producing the rubber-containing multistage polymer (I), the sequential multistage polymerization method is the most suitable method. The production of the rubber-containing multistage polymer (I) is not particularly limited, and for example, it is also carried out by an emulsion suspension polymerization method in which, after emulsion polymerization, conversion to a suspension polymerization system is performed at the time of polymerization of each polymer. be able to.

Although not particularly limited, when the rubber-containing multistage polymer (I) is produced by emulsion polymerization, a part or all of the monomer mixture (IA) is preliminarily mixed with water and a surfactant. An emulsion is prepared by mixing with the above, and this emulsion is supplied to the reactor for polymerization, and then the monomer mixture constituting each remaining layer is supplied to the reactor in order and polymerized.
An emulsion prepared by mixing the monomer mixture (IA) with water and a surfactant in advance is supplied to a reactor and polymerized to disperse the rubber-containing multistage polymer (I) in acetone. The number of particles having a diameter of 55 μm or more present in the dispersion is 0 to 50 per 100 g of the rubber-containing multistage polymer (I). Is preferable and the optical properties are improved. When the rubber-containing multistage polymer (I) is dispersed in acetone, the number of particles having a diameter of 55 μm or more present in the dispersion is more preferably 0-30 per 100 g of the rubber-containing multistage polymer (I). The number is particularly preferably 0 to 20.

  In addition, when the rubber-containing multistage polymer (I) is dispersed in acetone, the number of particles having a diameter of 55 μm or more present in the dispersion is determined by weighing the powdered rubber-containing multistage polymer (I) with acetone. A dispersion is prepared by dispersing the dispersion in a concentration range of 5 to 10% by mass, and the number of particles having a diameter of 55 μm or more present in the dispersion is measured by a light scattering type particle counter according to JIS B 9921. It can be determined by measuring.

  Further, when preparing the dispersion liquid, the rubber-containing multistage polymer (I) is preliminarily contained on a mesh having a mesh size smaller than 55 μm so that acetone sufficiently permeates between the rubber-containing multistage polymer (I) particles. After ultrasonic cleaning with a good solvent for the multistage polymer (I), the dispersion on the mesh is again dispersed in acetone to prepare a dispersion. The exact diameter of 55 μm present in the dispersion is This is preferable for measuring the number of particles.

  Examples of the surfactant used in preparing the emulsion include anionic, cationic and nonionic surfactants, and anionic surfactants are particularly preferable. Examples of the anionic surfactant include rosin soap; potassium oleate, sodium stearate, sodium myristate, sodium N-lauroyl sarcosinate, dipotassium alkenyl succinate; sulfate ester salts such as sodium lauryl sulfate Sulfonic acid salts such as sodium dioctylsulfosuccinate, sodium dodecylbenzenesulfonate, sodium alkyldiphenyl ether disulfonate; phosphate esters such as polyoxyethylene alkylphenyl ether sodium phosphate; polyoxyethylene alkyl ether sodium phosphate And phosphoric acid ester salts. Among these, phosphate esters such as polyoxyethylene alkyl ether sodium phosphates are preferable from the viewpoint of ecological protection from endocrine disrupting chemical substances, which have recently become a problem.

  Preferable specific examples of the surfactant include NC-718 manufactured by Sanyo Kasei Kogyo Co., Ltd., Phosphanol LS-529, Phosphanol RS-610NA, Phosphanol RS-620NA, Phosphorol manufactured by Toho Chemical Industry Co., Ltd. Nord RS-630NA, Phosphanol RS-640NA, Phosphanol RS-650NA, Phosphanol RS-660NA, Latemu P-0404, Latemulu P-0405, Latemulu P-0406, Latemulu P-0407 manufactured by Kao Corporation Is mentioned.

  In addition, as a method for preparing an emulsified liquid, a method in which a monomer mixture is charged in water and then a surfactant is added, a method in which a surfactant is charged in water and then a monomer mixture is charged, Examples thereof include a method of charging water after charging a surfactant into the monomer mixture. Among these, the method of charging the surfactant after charging the monomer in water and the method of charging the monomer mixture after charging the surfactant in water are methods for obtaining the rubber-containing multistage polymer (I). Is preferable.

In addition, as a mixing apparatus for preparing an emulsion prepared by mixing the monomer mixture (IA) with water and a surfactant, a stirrer equipped with a stirring blade; various kinds such as a homogenizer and a homomixer Forced emulsification device; membrane emulsification device and the like.
Further, the emulsion to be prepared may have either a W / O type or an O / W type dispersion structure, particularly an O / W type in which oil droplets of a monomer mixture are dispersed in water, and oil droplets in a dispersed phase. Those having a diameter of 100 μm or less are preferred.

  As the polymerization initiator used when polymerizing the monomer mixture (IA), the monomer mixture (IB), and the monomer or monomer mixture (IC), there are known ones. Can be used. As the addition method, a method of adding to one or both of the aqueous phase and the monomer phase can be adopted. Particularly preferred polymerization initiators include peroxides, azo initiators, or redox initiators in which an oxidizing agent / reducing agent is combined. Among these, redox initiators are more preferable, and sulfoxylate initiators in which ferrous sulfate, ethylenediaminetetraacetic acid disodium salt, longalite, and hydroperoxide are combined are particularly preferable.

In particular, an emulsion prepared by mixing the monomer mixture (IA) with water and a surfactant is supplied to a reactor and polymerized, and then the monomer mixture (IB) and a single amount are mixed. In the method of supplying the polymer or monomer mixture (IC) to the reactor in order, and polymerizing, an aqueous solution containing ferrous sulfate, ethylenediaminetetraacetic acid disodium salt and Rongalite is heated to the polymerization temperature. The prepared emulsion is supplied to the reactor for polymerization, and then the monomer mixture (IB) and the monomer or monomer mixture (IC) containing a polymerization initiator such as peroxide are prepared. The method of sequentially supplying to the reactor and polymerizing is the most preferable method for obtaining the rubber-containing multistage polymer (I).
The polymerization temperature varies depending on the type and amount of the polymerization initiator used, but is preferably 40 to 120 ° C, more preferably 60 to 95 ° C.

When the rubber-containing multistage polymer (I) is obtained by emulsion polymerization as described above, a chain transfer agent, other polymerization aids, and the like may be used. Known chain transfer agents can be used, and mercaptans are preferred.
The rubber-containing multistage polymer (I) can be produced by recovering the rubber-containing multistage polymer from the polymer latex produced by the above-described method. The method for recovering the rubber-containing multistage polymer from the polymer latex is not particularly limited, and examples thereof include salting out or acid precipitation coagulation, spray drying, freeze drying, and the like. It is collected at.

<Ultraviolet absorber>
The acrylic resin film of the present invention contains a triazine-based ultraviolet absorber made of the compound represented by the formula (1) in an amount of 0.1 to 1 g / m ² . When the amount of the ultraviolet absorber is less than 0.1 g / m ² , the acrylic resin film has poor light resistance, and when the acrylic resin film is laminated on the light diffusion plate, the light diffusion plate tends to turn yellow by the light source. is there. On the other hand, when the amount of the ultraviolet absorber is more than 1 g / m ² , the YI value of the acrylic resin film increases, and the color tone of the light diffusion plate tends to deteriorate when this acrylic resin film is laminated on the light diffusion plate. is there. Preferably it is 0.2-0.8 g / m < ² >, More preferably, it is 0.3-0.7 g / m < ² >.

Moreover, the acrylic resin film of this invention can contain a light stabilizer with the said ultraviolet absorber.
Specific examples of such light stabilizers include Adeka Stub LA52, Adeka Stub LA57, Adeka Stub LA62, and Adeka Stub LA67 manufactured by Adeka Corporation .

<Additives>
The acrylic resin film of the present invention includes, in addition to the ultraviolet absorber and the light stabilizer, a general compounding agent, for example, a stabilizer, a lubricant, a processing aid, a plasticizer, an antistatic agent, an anti-resistant agent. Impact aids, foaming agents, fillers, antibacterial agents, fungicides, mold release agents can be included.
Moreover, it is preferable to add the following thermoplastic polymer (V) from the point of shaping | molding stabilization as a processing aid added when shape | molding the acrylic resin film of this invention.

  The thermoplastic polymer (V) is obtained by polymerizing 50 to 100% by mass of methyl methacrylate and 0 to 50% by mass of another vinyl monomer copolymerizable therewith, and the reduced viscosity ( A polymer obtained by dissolving 0.1 g of a polymer in 100 ml of chloroform and measuring at 25 ° C.) to be 0.2 to 2 L / g. Workability and chemical resistance when molding an acrylic resin composition It is a component that shows an important role for sex. The reduced viscosity of the thermoplastic polymer (V) is important, the preferred reduced viscosity is 0.2 to 1.2 L / g, and the particularly preferred reduced viscosity is 0.2 to 0.8 L / g.

  In the thermoplastic polymer (V), other vinyl monomers copolymerizable with methyl methacrylate include alkyl acrylates having an alkyl group having 1 to 8 carbon atoms and alkyl having an alkyl group having 2 to 4 carbon atoms. Methacrylate, aromatic vinyl compound, vinyl cyanide compound and the like can be mentioned. The alkyl acrylate having an alkyl group having 1 to 8 carbon atoms may be linear or branched, and specific examples thereof include methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, and n-octyl. An acrylate etc. are mentioned. Moreover, the alkyl methacrylate having an alkyl group having 2 to 4 carbon atoms may be either linear or branched, and specific examples thereof include ethyl methacrylate, propyl methacrylate, butyl methacrylate and the like. Examples of the aromatic vinyl compound include styrene, α-substituted styrene, nucleus-substituted styrene and derivatives thereof, for example, α-methylstyrene, chlorostyrene, vinyltoluene and the like. Examples of the vinylcyan compound include acrylonitrile and methacrylonitrile.

  Examples of the polymerization initiator used for obtaining the thermoplastic polymer (V) from the above monomers include ordinary inorganic initiators such as persulfates, organic peroxides, and azo compounds. In addition, the above compounds and sulfites, hydrogen sulfites, thiosulfates, first metal salts, sodium formaldehyde sulfoxylate, and the like can be used in combination as redox initiators. Preferred persulfates as the polymerization initiator include sodium persulfate, potassium persulfate, ammonium persulfate and the like. Examples of the organic peroxide include t-butyl hydroperoxide, cumene hydroperoxide, benzoyl peroxide, and lauroyl peroxide. Since the molecular weight and molecular weight distribution of the thermoplastic polymer (V) are important factors for the processability imparting effect, an appropriate chain transfer may be performed according to the purpose in producing the thermoplastic polymer (V). Agents can be used.

The polymerization can be carried out at a temperature equal to or higher than the decomposition temperature of the polymerization initiator under the usual emulsion polymerization conditions, and can be polymerized in one or more stages depending on the purpose. In general, the polymer can be recovered by salting out or solidifying by acid precipitation, followed by filtration, washing with water, and recovering in powder form, or spray drying or freeze drying to recover in powder form.
The thermoplastic polymer (V) is commercially available as Metablene P manufactured by Mitsubishi Rayon Co., Ltd.

  As for the compounding quantity of a thermoplastic polymer (V), 0.1-10 mass parts is preferable with respect to 100 mass parts of acrylic resins. When the blending amount of the thermoplastic polymer (V) is less than 0.1 parts by mass, the molding stability tends to be insufficient when the acrylic resin film is molded. The film stability tends to be insufficient. The film-forming stability described here means that an acrylic resin film having a uniform thickness is stably produced. On the other hand, when the compounding quantity of a thermoplastic polymer (V) exceeds 10 mass parts, it exists in the tendency for the melt viscosity at the time of shape | molding an acrylic resin film to rise, and for a moldability to fall. Furthermore, the compounding quantity of a preferable thermoplastic polymer (V) is 0.5-5 mass parts.

<Compound>
As an additive addition method, when the acrylic resin film of the present invention is formed, a method of supplying the acrylic resin together with the acrylic resin and a mixture in which a compounding agent is added to the acrylic resin in advance are kneaded and mixed in various kneaders. There is a way. Examples of the kneader used in the latter method include ordinary single screw extruders, twin screw extruders, Banbury mixers, roll kneaders, and the like.

<Method for producing acrylic resin film>
The method for producing the acrylic resin film to be laminated on the light diffusion plate of the present invention is not particularly limited. For example, known melt casting methods such as a melt casting method, a T-die method, an inflation method, etc. Among these, the T-die method is most preferable from the viewpoint of economy.
The thickness of the acrylic resin film of the present invention to be laminated on the light diffusing plate is not particularly limited, but for example, it is preferably 10 to 500 μm from the viewpoint of film properties and processability. When the thickness is from 10 to 500 μm, moderate rigidity is obtained, so that the laminating property, the secondary workability, etc. are good, and the film forming property is stabilized and the production of the film becomes easy. More preferably, it is 15-200 micrometers, Most preferably, it is 15-100 micrometers.

<Transparency>
The total light transmittance of the acrylic resin film of the present invention is preferably 80% or more when measured in accordance with JIS K 7361-1. If the total light transmittance of the acrylic resin film is 80% or more, the light from the light source is efficiently transmitted when used as a light diffusion plate in which the acrylic resin film is laminated. Luminous quality is improved. More preferably, it is 85% or more, and particularly preferably 90% or more.

<Lamination method>
The acrylic resin film of the present invention should be laminated on the light source side and the liquid crystal side of the backlight light diffusion plate. The acrylic resin film of the present invention is laminated on a light diffusing plate using a coextrusion method such as a coextrusion T-die method or a coextrusion lamination method. Also, the acrylic resin film is laminated such as dry lamination or thermal lamination. The light diffusing plate can be laminated by appropriately using a known method such as a film lamination method and a coating method for coating a resin solution. Of course, any method applicable to the present invention other than these methods can be adopted. Among these, a coextrusion method and a film lamination method are preferable, and a film lamination method is particularly preferable, which can easily obtain a light diffusion plate having a simple and continuous and stable quality.

<Backlight diffuser>
The material of the light diffusing plate on which the acrylic resin film of the present invention is to be laminated is not particularly limited. For example, when the light diffusing sheet is in a plate state, it is particularly limited as long as it is transparent, has a high light transmittance, a low birefringence, and can be easily laminated with an acrylic resin film. Without limitation, any known one can be used. From the viewpoint that the characteristics (for example) of the acrylic resin film of the present invention can be suitably exhibited, it is preferable to apply the acrylic resin film to the light diffusion plate for direct type backlight, but other types of light diffusion plates are applicable. However, the characteristics of the acrylic resin film of the present invention can be utilized.

  The material of the light diffusing plate is not particularly limited, and examples thereof include methacrylic resin, polycarbonate resin, MS resin (methyl methacrylate-styrene resin), polystyrene resin, polyvinyl chloride resin, polyester resin, and cyclic polyolefin resin. Among these, methacrylic resin and polycarbonate resin having particularly high light transmittance can be preferably used as the light diffusing plate.

  In the above-mentioned resin, transparent, light-resistant, heat-resistant, and moisture-resistant materials having high light diffusibility when used as beads may be contained as necessary. Examples of the light diffusing agent include acrylic resins, styrene resins, polyester resins, melamine resins, silicone resins, epoxy resins, urethane resins, polyethylene resins, nylon resins, norbornene resins, cyclohexane resins, and vinyl chloride resins. Or organic substances such as crystalline silica, glass, lithium fluoride, calcium carbonate, and barium sulfate.

<Application>
The acrylic resin film of the present invention is laminated on, for example, both the light source side and the liquid crystal side of the light diffusion plate, and the light diffusion plate on which the acrylic resin film is laminated is used as, for example, a light diffusion plate of a direct type backlight. It is done. By disposing the acrylic resin film on the light diffusing plate, the initial color tone of the light diffusing plate is good, and discoloration due to light from the light source can be suppressed. Since the liquid crystal display device using this direct type backlight can maintain the color tone and light emission quality in color liquid crystal display for a long time, the acrylic resin film of the present invention is laminated on the light diffusion plate of the direct type backlight. It is very useful for use as a transparent protective layer of a light diffusion plate.

EXAMPLES Hereinafter, although an Example demonstrates this invention, these are only illustrations and this invention is not limited to these.
In the examples and comparative examples, “part” represents “part by mass”, and “%” represents “% by mass”. Abbreviations in the reference examples are as follows.

Methyl methacrylate MMA
Methyl acrylate MA
Butyl acrylate BA
Styrene St
Allyl methacrylate AMA
1,3-butylene glycol dimethacrylate 1,3BD
t-Butyl hydroperoxide tBH
Cumene hydroperoxide CHP
n-octyl mercaptan nOM

Emulsifier (1): sodium mono-n-dodecyloxytetraoxyethylene phosphate [trade name Phosphanol RS-610NA, manufactured by Toho Chemical Co., Ltd.]
Emulsifier (2): sodium hydroxide partial neutralized product of 40% mono (polyoxyethylene nonylphenyl ether) phosphoric acid and 60% di (polyoxyethylene nonylphenyl ether) phosphoric acid [trade name Phosphanol LO529, Toho Chemical Co., Ltd.]

Examples 1 and 2
<Production of rubber-containing multistage polymer (H-1)>
After charging 8.5 parts of ion-exchanged water into a vessel equipped with a stirrer, a monomer mixture consisting of (I) shown below was charged and stirred and mixed. Subsequently, 1.1 parts of emulsifier (1) was added to the vessel while stirring, and stirring was continued again for 20 minutes to prepare an emulsion (N-1). The average particle size of the dispersed phase in the obtained emulsion was 10 μm.
Next, 186.5 parts of ion-exchanged water is placed in a polymerization vessel equipped with a cooler, the temperature is raised to 70 ° C., and a mixture prepared by adding (II) shown below to 5 parts of ion-exchanged water is added all at once. did. Next, the emulsion (N-1) was dropped into the polymerization vessel over 8 minutes while stirring under nitrogen, and then the reaction was continued for 15 minutes to complete the first stage polymerization. Subsequently, a monomer mixture consisting of (III) shown below was added over 90 minutes, and then the reaction was continued for 60 minutes to complete the second stage polymerization, thereby obtaining a rubber elastic body.
Subsequently, the mixture of (IV) shown below was dropped into the polymerization vessel over 45 minutes, and then reacted for 60 minutes.
Next, the monomer mixture consisting of (V) was dropped into the polymerization vessel over 140 minutes, and then reacted for 60 minutes to obtain a polymer latex of a rubber-containing multistage polymer (H-1).
The weight average particle diameter measured after polymerization was 0.12 μm.

(I):
MMA 0.3 part BA 4.5 part 1,3BD 0.2 part AMA 0.05 part CHP 0.025 part

(II):
Sodium formaldehyde sulfoxylate 0.2 part Ferrous sulfate 0.0001 part EDTA 0.0003 part

(III):
MMA 1.5 parts BA 22.5 parts BD 1.0 part AMA 0.25 parts CHP 0.016 parts

(IV):
MMA 6 parts BA 4 parts AMA 0.075 parts CHP 0.0125 parts

(V):
MMA 55.2 parts BA 4.8 parts nOM 0.204 parts tBH 0.08 parts

  The polymer latex of the obtained rubber-containing multi-stage polymer (H-1) was filtered using a vibration type filtration device in which a SUS mesh (average opening 62 μm) was attached to the filter medium, and then 3 parts of calcium acetate was added. The solution was put into an aqueous solution to be salted out, washed with water, separated and recovered, and dried to obtain a powdery rubber-containing multistage polymer (H-1). The gel content of the rubber-containing multistage polymer (H-1) was 60%. Further, when the rubber-containing multistage polymer (H-1) was dispersed in acetone, the number of particles having a diameter of 55 μm or more present in the dispersion was 18.

<Manufacture of acrylic resin film>
Next, 100 parts of a rubber-containing multistage polymer (H-1), 0.1 part of “ADEKA STAB AO-50” manufactured by Adeka Co., Ltd. as an antioxidant, 1 part of the compound of the above formula (1) as an ultraviolet absorber, Addition of “ADEKA STAB LA-57” manufactured by Adeka Co., Ltd. as a hindered amine light stabilizer in the amount shown in Table 1, followed by mixing using a Henschel mixer, and the resulting mixture heated to 230 ° C. Was supplied to a machine (TEM-35B manufactured by Toshiba Machine Co., Ltd.) and kneaded to obtain pellets.

<Manufacture of light diffusion plate>
The pellets produced by the above method were dried at 80 ° C. all day and night, and the dried pellets were supplied to a 40 mmφ non-vent screw type extruder (L / D = 26) equipped with a 300 mm wide T-die to a thickness of 50 μm. An acrylic resin film was prepared. The conditions at that time were a cylinder temperature of 200 to 240 ° C., a T die temperature of 250 ° C., and a cooling roll temperature of 70 ° C. Moreover, the obtained acrylic resin film was heat-laminated to the light diffusion plate at 140 ° C. to obtain a light diffusion plate.
Table 1 shows the difference between the total light transmittance YI value of the obtained acrylic resin film, the initial hue of the light diffusion plate, and the YI value before and after the exposure test.

The various evaluation methods and measurement methods used are shown below.
1) Weight average particle diameter of rubber-containing multistage polymer A dynamic light scattering method using a light-scattering photometer DLS-700 manufactured by Otsuka Electronics Co., Ltd. as a polymer latex of a rubber-containing multistage polymer obtained by emulsion polymerization. Determined by measuring with.

2) Gel content of rubber-containing multistage polymer The weighed rubber-containing multistage polymer was subjected to extraction treatment under reflux in an acetone solvent, and this extraction treatment liquid was fractionated by centrifugation. Subsequently, after drying the obtained solid content, mass measurement (mass after extraction) was carried out, and it calculated | required with the following formula | equation.
Gel content rate (%) = (mass before extraction (g) −mass after extraction (g)) / mass before extraction (g)

3) Total light transmittance of transparent protective layer It evaluated based on JISK7361-1.
4) YI value of acrylic resin film It evaluated based on JISK7103.

5) Initial hue of light diffusing plate It was measured under the reflection condition of standard light C according to the geometric conditions of illumination and light reception (45 ° illumination, vertical light reception) specified in JIS Z 8722.
Evaluation ○: Δx before and after the acrylic resin film is laminated on the light diffusion plate is smaller than 0.004 and Δy is smaller than 0.007 Δ: Δx before and after the acrylic resin film is laminated on the light diffusion plate 0.004 to 0.006, Δy is 0.007 to 0.01
X: Δx before and after the acrylic resin film is laminated on the light diffusion plate is larger than 0.006, and Δy is larger than 0.01.

6) Light resistance of light diffusion plate The cold protective tube was actually exposed on the transparent protective layer side of the light diffusion plate under the following conditions, and the amount of change in the YI value of the light diffusion plate was evaluated.
Cold cathode tube actual exposure conditions Cold cathode tube: φ2.6 lamp Lamp current: 8 mA, 3 in parallel Ambient temperature: 23 ° C., 50 RH%
Lamp-sample surface distance: 1.4mm (design value)
Sample surface temperature: about 50 ° C Exposure period: 6 months

Comparative Example 1
A light diffusing plate was obtained in the same manner as in Example 1 except that the acrylic resin film did not contain an ultraviolet absorber or a light stabilizer.
Comparative Example 2
As an ultraviolet absorber contained in the acrylic resin film, a triazine ultraviolet absorber represented by the following formula (2) (2- (4,6-diphenyl-1,3,5-triazin-2-yl) -5- [ A light diffusing plate was obtained in the same manner as in Example 1 except that (hexyl) oxy] -phenol was used.

Comparative Examples 3 and 4
In the same manner as in Example 2 except that a benzotriazole-based ultraviolet absorber represented by the following formula (3) (manufactured by Adeka Co., Ltd., Adeka Stub LA-31RG) was used as the ultraviolet absorber contained in the acrylic resin film. A light diffusing plate was obtained.

Comparative Example 5
Except that a cyanoacrylate ultraviolet absorber (octabenzone) (BASF, Uvinul 3035) represented by the following formula (4) was used as the ultraviolet absorber contained in the acrylic resin film, light was emitted in the same manner as in Example 1. A diffusion plate was obtained.

比較例７
アクリル樹脂フィルムに紫外線吸収剤の添加量を表１に示す量に変えたこと以外は、実施例１と同様の方法で光拡散板を得た。 Comparative Example 6
Benzophenone ultraviolet absorber (2-ethyl-2-cyano-3,3-diphenyl acrylate) represented by the following formula (5) as an ultraviolet absorber contained in the acrylic resin film (Chimas Specialty 81, Chimassorb 81) A light diffusing plate was obtained in the same manner as in Example 1 except that was used.

Comparative Example 7
A light diffusing plate was obtained in the same manner as in Example 1 except that the amount of the ultraviolet absorber added to the acrylic resin film was changed to the amount shown in Table 1.

From the examples and comparative examples described above, the following became clear.
By laminating the acrylic resin film in Examples 1 and 2 on the light diffusing plate, the initial color tone of the light diffusing plate is good and the discoloration from the light source can be suppressed. Resin films have high industrial utility value.

  On the other hand, when an acrylic resin film having no UV absorber is laminated on the light diffusion plate as in Comparative Example 1, or an acrylic resin film having no sufficient amount of UV absorber as in Comparative Example 3 is used for light. When laminated on a diffusion plate, or when an acrylic resin film having a cyanoacrylate ultraviolet absorber and a benzophenone ultraviolet absorber is laminated on a light diffusion plate as in Comparative Examples 5 and 6, after the light diffusion plate exposure test Discoloration becomes remarkable, and the light diffusion plate has very low industrial utility value. Moreover, when the acrylic resin film which has the triazine type ultraviolet absorber of said Formula (2) like the comparative example 2 is laminated | stacked on the light diffusing plate, the acrylic resin film which has a benzotriazole type ultraviolet absorber like the comparative example 4 When an acrylic resin film having a large amount of the triazine-based ultraviolet absorber of the formula (1) is laminated on the light diffusion plate as in Comparative Example 7, the initial color tone of the light diffusion plate becomes poor. The light diffusion plate has a very low industrial utility value.

  Since the acrylic resin film of the present invention has a low YI value and excellent light resistance, it can be used as a display member. In particular, when the light diffusion plate is laminated on both the light source side and the liquid crystal side, the initial color tone of the light diffusion plate is good. A liquid crystal display device having a direct backlight using this light diffusing plate can maintain the color tone and light emission quality in color display for a long time.

Claims (6)

An acrylic resin film comprising 0.1 to 1 g / m ^{2 of} a compound represented by the following formula (1).

  The acrylic resin film of Claim 1 whose YI value based on JISK7103 is less than 1.0. The acrylic resin film of Claim 1 or 2 containing the following rubber-containing multistage polymer (I).
Rubber-containing multistage polymer (I)
Each of the monomer components having the following composition is prepared by (1) monomer mixture (IA), (2) monomer mixture (IB), and (3) monomer mixture (IC). Polymer obtained by sequentially polymerizing in order (1) Monomer mixture (IA)
(I-A1) Alkyl acrylate 50-99.9% by mass
(I-A2) Acrylic methacrylate 0-49.9 mass%
(I-A3) Other monomer having copolymerizable double bond 0 to 20% by mass
(I-A4) Polyfunctional monomer 0 to 10% by mass
(I-A5) Graft crossing agent 0.1 to 10% by mass
(2) Monomer mixture (IB)
(I-B1) Acrylic acrylate 9.9 to 90% by mass
(I-B2) Alkyl methacrylate 9.9 to 90% by mass
(I-B3) Monomer having a copolymerizable double bond 0 to 20% by mass
(I-B4) Polyfunctional monomer 0 to 10% by mass
(I-B5) Graft crossing agent 0.1 to 10% by mass
(3) Monomer mixture (IC)
(I-C1) Alkyl methacrylate 80-100% by mass
(I-C2) Acrylic acrylate 0-20% by mass
(I-C3) Monomer having a copolymerizable double bond 0 to 20% by mass   A light diffusing plate comprising the acrylic resin film according to claim 1 on a surface thereof.   A backlight unit comprising the light diffusing plate according to claim 4.   A liquid crystal display device comprising the backlight unit according to claim 5.