JP2005326613A - Prism sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a prism sheet excellent in not only brightness characteristics but also in heat resistance and cracking resistance. <P>SOLUTION: The prism sheet has a plurality of triangular prisms comprising a resin, each having a triangular cross section with 70 to 110° apex and arranged parallel at a ≤100 μm pitch on at least one surface of a substrate comprising a resin composition containing an acrylic resin (A) having 10 to 40 wt.% of glutaric acid anhydride unit expressed by structural formula (1). In formula (1), R<SP>1</SP>and R<SP>2</SP>represent same or different hydrogen atoms or 1-5C alkyl groups. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a prism sheet.

  In recent years, liquid crystal display devices have been widely used in various fields as monitors for personal computers and desktop personal computers, televisions, and the like.

  A liquid crystal display device is basically composed of a backlight unit and a liquid crystal display element unit, and the backlight unit uses an edge light system with a light source on the side of the light guide. Has been used a lot. In this edge light type backlight, a prism sheet in which a large number of prisms having a specific shape are formed is used for the purpose of improving the front luminance (see Patent Document 1).

  As the base material of the prism sheet, a polyester resin film is mainly used (see claim 6 of Patent Document 2), but there is a limit to the improvement in luminance because the light transmittance of the base film is low.

On the other hand, it is conceivable to use a film made of an acrylic resin such as polymethyl methacrylate as a base material, but it is difficult to perform post-processing such as hard coating or antireflection treatment because of its low heat resistance and solvent resistance. there were. For example, in Patent Document 2, although it is described that an acrylic film such as PMMA can be used as a base material, it is only one example of many materials. Biaxially-stretched PET is preferable because of its chemical and optical properties "(refer to 0049 stage of Patent Document 2).
JP-A-6-67004 (page 1) JP 2001-166116 A (Claim 6, 0049 stage)

  An object of the present invention is to provide a prism sheet that solves the above-described problems of the conventional prism sheet, has a large front luminance improvement effect, and is excellent in post-processability.

  That is, the present invention provides at least one surface of a substrate composed of a resin composition containing an acrylic resin (A) containing 10 to 40% by weight of a glutaric anhydride unit represented by the following structural formula (1). A prism sheet comprising a plurality of triangular prisms made of a resin and having a triangular cross section having a vertex angle of 70 to 110 ° arranged in parallel at a pitch of 100 μm or less.

(In the above formula, R ¹ and R ² represent the same or different hydrogen atoms or alkyl groups having 1 to 5 carbon atoms.)

  According to the present invention, it is possible to provide a prism sheet that has a large front luminance improvement effect and excellent post-processability.

  In the prism sheet of the present invention, it is important that the resin composition constituting the substrate contains an acrylic resin (A) containing a glutaric anhydride unit represented by the following structural formula (1).

In said formula, R < ¹ >, R < ² > represents the same or different hydrogen atom or a C1-C5 alkyl group.
Heat resistance can be improved by containing a glutaric anhydride unit having such a structure.

  As content with respect to the acrylic resin (A) of the said glutaric anhydride unit, it is important to set it as 10 to 40 weight%, Preferably it is 20 to 35 weight%. By setting it to 10% by weight or more, excellent heat resistance and chemical resistance can be obtained, and an acrylic resin having a high glass transition temperature can be obtained as described later. On the other hand, the fall of toughness can be prevented by setting it as 40 weight% or less.

In particular, from the viewpoint of heat resistance, R ¹ and R ² are preferably hydrogen or a methyl group, and particularly preferably a methyl group.

  Moreover, it is preferable that an acrylic resin (A) contains the unit derived from vinylcarboxylic acid alkylester. By adopting a unit derived from vinyl carboxylic acid alkyl ester as the basic structural unit of the acrylic resin, an acrylic resin that is stable against heat and water can be obtained.

  Examples of the carboxylic acid alkyl ester unit include those represented by the following general formula (2).

In the above formula, R ³ represents a hydrogen atom or an alkyl group having 1 to 5 carbon atoms. R ⁴ represents an aliphatic or alicyclic hydrocarbon group having 1 to 5 carbon atoms.

  Preferable specific examples of the vinyl carboxylic acid alkyl ester unit include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, n-butyl (meth) acrylate, and (meth) acrylic acid. t-butyl, n-hexyl (meth) acrylate, cyclohexyl (meth) acrylate, chloromethyl (meth) acrylate, 2-chloroethyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, (meth) Examples include 3-hydroxypropyl acrylate, 2,3,4,5,6-pentahydroxyhexyl (meth) acrylate and 2,3,4,5-tetrahydroxypentyl (meth) acrylate. 1 type may be included independently and 2 or more types may coexist. Of these, methyl (meth) acrylate is most preferred because of its excellent thermal stability.

  As content of the vinyl carboxylic-acid alkylester unit with respect to an acrylic resin (A), 60 to 90 weight% is preferable, More preferably, it is 65 to 75 weight%. By setting it to 60% by weight or more, transparency as an acrylic resin can be obtained. On the other hand, the upper limit value corresponds to the lower limit value of the preferable addition amount of the aforementioned glutaric anhydride unit.

  The acrylic resin (A) may contain vinyl units within a range not impairing the effects of the present invention, but the content of styrene units such as styrene and α-methylstyrene is 1% by weight or less, that is, It is preferable to set it as 0 to 1 weight%, More preferably, it is 0 to 0.1 weight%. By making the content concentration of the styrenic unit 1% by weight or less, it is possible to prevent the heat resistance and transparency from being lowered.

  The acrylic resin (A) preferably has an unsaturated carboxylic acid unit content of 10% by weight or less, that is, 0 to 10% by weight, more preferably 0 to 5% by weight, and still more preferably 0 to 1. % By weight. By setting it to 10% by weight or less, colorless transparency, retention stability, and moisture resistance can be maintained.

  Moreover, as a weight average molecular weight of an acrylic resin (A), 80,000-150,000 are preferable. By setting it to 80,000 or more, the mechanical strength of the acrylic resin film can be maintained. Moreover, coloring of resin can be prevented by setting it as 150,000 or less.

  Further, the glass transition temperature (Tg) of the acrylic resin (A) is preferably 120 ° C. or higher from the viewpoint of heat resistance. Moreover, it is preferable to set it as 160 degrees C or less from the point of the ease of a process.

  In order to set the glass transition temperature within the above range, the content of the glutaric anhydride unit represented by the general formula (1) with respect to the acrylic resin (A) is set to 20 to 40% by weight as described above. preferable. The glass transition temperature here is measured at a rate of temperature increase of 20 ° C./min using a differential scanning calorimeter (for example, DSC-7 manufactured by Perkin Elmer).

  As content with respect to the resin composition which comprises the base material of a prism sheet of an acrylic resin (A), it is preferable to set it as 60 to 93 weight%. By setting the content to 60% by weight or more, a prism sheet utilizing the characteristics of the acrylic resin (A) such as transparency can be obtained. On the other hand, the upper limit value corresponds to the lower limit value of the addition amount of acrylic elastic particles (B) described later.

  Moreover, as a resin composition which comprises the base material of a prism sheet, it is preferable to contain an acrylic elastic body particle (B) other than an acrylic resin (A). By dispersing the acrylic elastic particles (B) in the resin composition constituting the base material of the prism sheet, it is possible to obtain excellent toughness as the base material of the prism sheet and thus the prism sheet.

  The rubbery polymer constituting the acrylic elastic particles (B) has an acrylic component such as an ethyl acrylate unit or a butyl acrylate unit as an essential component, and other components preferably include a dimethylsiloxane unit or a phenylmethylsiloxane unit. Silicone components such as, styrene components such as styrene units and α-methylstyrene units, nitrile components such as acrylonitrile units and methacrylonitrile units, conjugated diene components such as butanediene units and isoprene units, urethane components or ethylene components, propylene components, An isobutene component etc. can be mentioned.

  Among these, those composed of an acrylic component, a silicone component, a styrene component, a nitrile component, and a conjugated diene component are preferable.

  A rubber elastic body composed of a combination of two or more of these components is also preferable. For example, a rubber elastic body composed of an acrylic component and a silicone component, a rubber elastic body composed of an acrylic component and a styrene component, Examples thereof include a rubber elastic body composed of an acrylic component and a conjugated diene component, and a rubber elastic body composed of an acrylic component, a silicone component and a styrene component.

  In addition to these components, those containing a crosslinkable component such as a divinylbenzene unit, an allyl acrylate unit, or a butylene glycol diacrylate unit are also preferred.

  Of these, a combination of an alkyl acrylate unit and an aromatic vinyl unit is preferred. Alkyl acrylate units, especially butyl acrylate, are extremely effective in improving toughness, and by adjusting the refractive index of acrylic elastic particles (B) by copolymerizing aromatic vinyl units such as styrene. Can do.

  The average particle diameter of the acrylic elastic particles (B) is preferably 70 to 300 nm, and more preferably 100 to 200 nm. The effect of improving toughness can be obtained by setting the thickness to 70 nm or more, and the decrease in heat resistance can be suppressed by setting the thickness to 300 nm or less.

  The content of the acrylic elastic particles (B) with respect to the base material is preferably 7 to 40% by weight, more preferably 12% to 20% by weight. By setting the content of the acrylic elastic particles to the base material within the above range, a prism sheet having particularly excellent processability such as folding resistance and heat resistance can be obtained.

  In addition, the base material constituting the prism sheet of the present invention is a polyethylene, polypropylene, polyamide, polyphenylene sulfide, polyether ether ketone, polyester, polysulfone, polyphenylene oxide, polyacetal, polyimide, poly, as long as the object of the present invention is not impaired. It may further contain other thermoplastic resins such as ether imide, thermosetting resins such as phenol, melamine, polyester, silicone, and epoxy. In addition, hindered phenol, benzotriazole, benzophenone, benzoate, and cyanoacrylate ultraviolet absorbers or antioxidants, higher fatty acids, acid esters, acid amides, higher alcohols and other lubricants or plasticizers, Release agents such as montanic acid, its salts, its esters, its half esters, stearyl alcohol, stearamide and ethylene wax, anti-coloring agents such as phosphites and hypophosphites, halogen-based, phosphorus-based and silicone-based It may contain additives such as non-halogen flame retardants, nucleating agents, amine-based, sulfonic acid-based, polyether-based antistatic agents, pigments and other colorants. However, in light of the characteristics required by the application to be applied, it is preferable to add the additive within a range where the color of the additive does not adversely affect the thermoplastic polymer and the transparency is not lowered. Specifically, the total content of the resin and additives other than the acrylic resin (A) and the acrylic elastic particles (B) with respect to the base material of the prism sheet is preferably 10% by weight or less.

  The substrate constituting the prism sheet of the present invention preferably has a retardation of 5 nm or less, that is, 0 to 5 nm, and more preferably 2 nm or less. By setting the retardation to 5 nm or less, it is possible to suppress the occurrence of luminance unevenness.

  The prism sheet of the present invention comprises a plurality of prisms made of resin arranged in parallel on at least one surface of a base material. By providing a plurality of prisms in parallel on the liquid crystal display element, it is possible to obtain a liquid crystal display device that suppresses light diffusion and has high luminance and directivity.

  The resin constituting the prism preferably includes at least one of an acrylic ester resin and a methacrylic ester resin from the viewpoint of transparency.

  As the shape of the prism, it is important that the cross-sectional shape is a triangle and the apex angle is 70 to 110 °, preferably 75 to 95 °. If the apex angle is less than 70 °, the directivity becomes so remarkable that the screen becomes extremely dark when viewed from the front. On the other hand, when the angle exceeds 110 °, the light condensing property is lowered and the effect of improving the luminance cannot be obtained.

  The pitch of the prisms needs to be 100 μm or less, preferably 70 to 90 μm. When the prism pitch is 100 μm or less, it is possible not only to suppress the occurrence of luminance unevenness and moire for each pixel of the color filter, but also to obtain a prism sheet with high luminance. In particular, when the thickness is 70 to 90 μm, it is possible to obtain a prism sheet that has a stable shape in processing and has an excellent brightness enhancement effect.

Further, the height of the irregularities of the prism is determined by the apex angle and pitch value of the prism, but is preferably in the range of 30 to 50 μm.
Further, the triangular prism sheet is preferably thicker from the viewpoint of strength, but optically, it is preferably thinner to suppress light absorption.

  In the prism sheet of the present invention, it is also preferable to provide a hard coat layer on the surface opposite to the side where the prism is provided. By doing so, a damage | wound can be prevented and handling property can be improved.

Further, by further providing an antireflection film on the surface of the hard coat layer, further improvement in luminance can be achieved. There are various configurations of the antireflection film, but it is practical to include at least a light absorption layer, for example, a configuration including a low refractive index layer, a high refractive index layer, and a light absorption layer. Can be adopted. Examples of the low refractive index layer material include SiO ₂ and MgF ₂ . Examples of the high refractive index layer material include TiO ₂ , ZrO ₂ , ITO, SnO ₂ , Y ₂ O ₃ , and ZnO. As the light absorption film, a film of TiNx, Au, Ag, NiOx, etc. can be inserted as a constituent element when constituting a composite film.

  The prism sheet of the present invention preferably has a total light transmittance of 91% or more, more preferably 92% or more. By setting the total light transmittance to 91% or more, the effect of improving the luminance can be obtained.

  In addition, the prism sheet of the present invention preferably has a thermal elongation rate defined below which is 2% or less. By setting the thermal elongation rate to 2% or less, in post-processing steps such as hard coat processing, problems such as single elongation and poor flatness occur when processing is performed at a process tension of about 120 ° C. Can be prevented.

  The prism sheet of the present invention can be used by being installed on a liquid crystal display element installed on a sidelight type or direct type backlight. The prism sheet may be placed on the liquid crystal display element so that the side on which the prism is provided and the liquid crystal display element face each other.

  Next, a method for producing the prism sheet of the present invention will be described.

  The acrylic resin (A) containing the glutaric anhydride unit represented by the general formula (1) can be basically produced by the method shown below.

  An unsaturated carboxylic acid monomer represented by the following general formula (3), an unsaturated carboxylic acid alkyl ester monomer represented by the following general formula (4), and other vinyl monomer units: When it is contained, the vinyl monomer giving the unit is polymerized to obtain a copolymer (a).

However, R ⁵ represents hydrogen or an alkyl group having 1 to 5 carbon atoms.

R ⁶ represents hydrogen or an aliphatic or alicyclic hydrocarbon group having 1 to 5 carbon atoms, and R ⁷ represents an aliphatic hydrocarbon group having 1 to 5 carbon atoms.

  As a proportion of the monomer, the total of the blended monomers is 100% by weight, and the unsaturated carboxylic acid monomer is preferably 15 to 45% by weight, more preferably 20 to 40 parts by weight. The unsaturated carboxylic acid alkyl ester monomer is preferably 55 to 85% by weight, more preferably 60 to 80% by weight.

  Inclusion of the glutaric anhydride unit represented by the above general formula (1) when the copolymer (a) is heated by setting the content of the unsaturated carboxylic acid monomer content to 15 to 45% by weight. The amount is preferably in the range of 20 to 40% by weight, which is preferable because the acrylic resin (A) is excellent in heat resistance, colorless transparency, and retention stability.

  As a polymerization method for producing the copolymer (a), a known polymerization method such as bulk polymerization, solution polymerization, suspension polymerization, emulsion polymerization or the like basically by radical polymerization can be used, and there are fewer impurities. Particularly preferred are solution polymerization, bulk polymerization and suspension polymerization.

  The polymerization temperature for producing the copolymer (a) is preferably 95 ° C. or lower, more preferably 85 ° C. or lower, from the viewpoint of preventing the resin from being colored and having a good color tone. Preferably it is 75 degrees C or less. Further, the lower limit of the polymerization temperature is preferably 50 ° C. or higher, more preferably 60 ° C. or higher from the viewpoint of productivity in consideration of the polymerization rate. Further, for the purpose of improving the polymerization yield or the polymerization rate, the polymerization temperature may be raised according to the progress of the polymerization. In this case as well, the upper limit temperature is preferably controlled to 95 ° C. or lower throughout the process, and the polymerization initiation temperature is increased. Is preferably performed at a relatively low temperature of 75 ° C. or lower.

  Moreover, as polymerization time which produces | generates a copolymer (a), 60-360 minutes are preferable from the point of production efficiency, More preferably, it is 90-180 minutes.

  Since the molecular weight of the acrylic resin (A) depends on the molecular weight of the copolymer (a), as described above, the acrylic resin (A) is within the range of its preferred polymerization average molecular weight (80,000 to 150,000). The molecular weight of the copolymer (a) is also preferably 80,000 to 150,000 in terms of weight average molecular weight.

  The molecular weight of the copolymer (a) is, for example, a radical polymerization initiator such as an azo compound or a peroxide, or a chain transfer agent such as an alkyl mercaptan, carbon tetrachloride, carbon tetrabromide, dimethylacetamide, dimethylformamide, triethylamine or the like. It can control by adjusting the addition amount. In particular, a method of adjusting the addition amount of alkyl mercaptan as a chain transfer agent can be preferably employed from the viewpoint of stability of polymerization, ease of handling, and the like.

  Examples of the alkyl mercaptan used here include n-octyl mercaptan, t-dodecyl mercaptan, n-dodecyl mercaptan, n-tetradecyl mercaptan, n-octadecyl mercaptan, and among them, t-dodecyl mercaptan, n-dodecyl. Mercaptans are preferably used.

  The addition amount of the alkyl mercaptan is preferably 0.2 to 5.0 parts by weight, more preferably 0.3 to 4.0 parts by weight, and still more preferably 0.8 to 100 parts by weight of the total amount of monomers. 4 to 3.0 parts by weight.

  When the copolymer (a) is heated in the presence or absence of a suitable catalyst, the copolymer (a) is dehydrated from adjacent carboxyl groups of two unsaturated carboxylic acid units or adjacent to each other. The alcohol is eliminated from the unsaturated carboxylic acid unit and the unsaturated carboxylic acid alkyl ester unit to produce one unit of the glutaric anhydride unit.

  Examples of a method for heating the copolymer (a) to dehydrate and / or dealcoholate, that is, performing an intramolecular cyclization reaction, include a method using a heated extruder having a vent, an inert gas atmosphere or a vacuum. From the viewpoint of productivity, a method using an apparatus that can be heated and devolatilized below is preferable.

  As a specific apparatus, for example, a single screw extruder equipped with a “unimelt” type screw, a twin screw extruder, a triaxial extruder, a continuous or batch kneader type kneader, etc. can be used. It is preferable to use a twin screw extruder in terms of continuous productivity, reaction temperature, time, and shear rate, and quality stability. The length / diameter ratio (L / D) of the screw of the extruder is preferably 40 or more. By setting the L / D to 40 or more, it is possible to secure a sufficient heating time for advancing the intramolecular cyclization reaction. The residual amount of saturated carboxylic acid units can be reduced, and a polymer with less generation of bubbles in the molded product due to re-advancement of the reaction during heat molding can be obtained, and deterioration of color tone during molding residence can be suppressed.

  Moreover, it is more preferable that the apparatus has a structure capable of introducing an inert gas such as nitrogen into them. This is because when the intramolecular cyclization reaction by heating in the presence of oxygen tends to increase yellowness, it is preferable to sufficiently replace the system with an inert gas such as nitrogen. For example, as a method of introducing an inert gas such as nitrogen into a twin screw extruder, a method of flowing an inert gas of about 10 to 100 L / min by connecting piping from the upper part and / or the lower part of the hopper can be mentioned.

  The temperature for heating for the intramolecular cyclization reaction is preferably from 180 to 300 ° C, more preferably from 200 to 280 ° C, from the viewpoint that the reaction proceeds smoothly.

  The heating time for the intramolecular cyclization reaction may be appropriately set according to the desired copolymer composition, but is usually preferably 1 to 60 minutes, more preferably 2 to 30 minutes, and even more preferably 3 ~ 20 minutes.

  Moreover, when heating for the intramolecular cyclization reaction, it is also preferable to add one or more of an acidic catalyst, an alkaline catalyst, and a salt catalyst. Examples of the acidic catalyst include hydrochloric acid, sulfuric acid, p-toluenesulfonic acid, phosphoric acid, phosphorous acid, phenylphosphonic acid, methyl phosphate, and the like. Examples of the basic catalyst include metal hydroxides, amines, imines, alkali metal derivatives, alkoxides and the like. Examples of the salt-based catalyst include acetic acid metal salt, stearic acid metal salt, metal carbonate salt, ammonium hydroxide salt and the like. Among them, a basic catalyst or a salt-based catalyst containing an alkali metal can be preferably used because it exhibits an excellent reaction promoting effect with a relatively small addition amount. Specifically, alkali metal hydroxides such as lithium hydroxide, sodium hydroxide and potassium hydroxide, sodium methoxide, sodium ethoxide, sodium phenoxide, potassium methoxide, potassium ethoxide, alkoxide compounds such as potassium phenoxide, Examples thereof include organic carboxylates such as lithium acetate, sodium acetate, potassium acetate, and sodium stearate. Among them, sodium hydroxide, sodium methoxide, lithium acetate, and sodium acetate can be preferably used.

  The amount of these catalysts added is preferably about 0.01 to 1 part by weight per 100 parts by weight of the copolymer (a). By making it 0.01 parts by weight or more, the effect as the catalyst can be obtained, and by making it 1 parts by weight or less, the color of the catalyst has an adverse effect on the coloring of the thermoplastic polymer or is transparent. Can be prevented from decreasing.

  In the case where the resin composition acrylic elastic particles (B) constituting the base material of the prism sheet is contained, the acrylic elastic particles are dispersed when the acrylic elastic particles (B) are dispersed in the acrylic resin (A) or its precursor. It is preferable to perform (B) in a state where an acrylic resin having a glass transition temperature of 60 ° C. or higher is laminated on the surface layer or a vinyl monomer is graft copolymerized. By doing so, adhesion / aggregation of acrylic elastic particles (B) made of a rubbery polymer is prevented, the handleability is improved, and the dispersibility in the acrylic resin (A) is also improved.

  In the acrylic elastic particles (B) having an aspect in which an acrylic resin having a glass transition temperature of 60 ° C. or higher is laminated on the surface layer (hereinafter also referred to as “core-shell type”), a shell portion is formed. The “acrylic resin having a glass transition temperature of 60 ° C. or higher” is preferably one containing an unsaturated carboxylic acid alkyl ester unit or an unsaturated carboxylic acid unit. When the core-shell type acrylic elastic particles (B) containing these in the shell part are added to the copolymer (a), for example, and heated, the affinity with the matrix resin is good and the dispersibility is improved. To do. Moreover, since the intramolecular cyclization reaction also proceeds in the shell portion by the heating, and the shell portion and the matrix resin are assimilated, it is possible to prevent the transparency of the acrylic resin film from being inhibited by the shell portion. . Further, since the acrylic elastic particles (B) are firmly held in the matrix resin, mechanical properties such as impact resistance are also improved.

  As a monomer used as a raw material of the unsaturated carboxylic acid alkyl ester unit, (meth) acrylic acid alkyl ester is preferable, and methyl (meth) acrylate is more preferably used.

  Moreover, as a monomer used as the raw material of an unsaturated carboxylic acid-type unit, (meth) acrylic acid is preferable and methacrylic acid is more preferably used.

  In the core-shell type acrylic elastic particles (B), the weight ratio between the core and the shell is preferably 50 to 90% by weight of the core (rubber polymer) with respect to the sum of both. More preferably, it is 60 to 80% by weight.

  Examples of commercially available core / shell type acrylic elastic particles (B) include “Metablen” manufactured by Mitsubishi Rayon Co., Ltd., “Kane Ace” manufactured by Kaneka Chemical Co., Ltd., “Paralloid” manufactured by Kureha Chemical Co., Ltd., and Rohm and Haas Co. “Acryloid” manufactured by Gantz Kasei Kogyo Co., Ltd., “Parapet SA” manufactured by Kuraray Co., Ltd. and the like may be used, and these may be used alone or in combination of two or more.

  Further, in the aspect of graft copolymerization of a vinyl monomer (hereinafter also referred to as “graft copolymer type”) in the acrylic elastomer particles (B), the vinyl monomer is an unsaturated group having a vinyl group. A carboxylic acid ester monomer, an unsaturated carboxylic acid monomer having a vinyl group, an aromatic vinyl monomer and the like can be employed. Further, other vinyl monomers may be copolymerized in accordance with the compatibility with the rubbery polymer or the matrix resin constituting the acrylic elastic particles (B).

  As a quantity of the vinyl-type monomer provided to acrylic elastic-body particle | grains (B), (10-80) :( 20-90) is preferable with the weight ratio of rubber-like polymer: vinyl-type monomer, More Preferably it is (20-70) :( 30-80), More preferably, it is (30-60) :( 40-70). By making the vinyl monomer 20% by weight or more, the effect of this embodiment can be obtained. On the other hand, by setting the vinyl monomer to 90% by weight or less, it is possible to suppress a reduction in impact strength.

  The graft copolymer type acrylic elastic particles (B) may contain a component derived from a vinyl monomer that is not graft copolymerized, but from the viewpoint of impact strength, the graft ratio is 10 to 100. % Is preferred. Here, the graft ratio is a weight ratio of a graft copolymerized vinyl monomer provided to the rubber polymer. The intrinsic viscosity of the ungrafted copolymer is not particularly limited, but the impact strength and molding processability are those with a methyl ethyl ketone solvent and an intrinsic viscosity measured at 30 ° C. of 0.1 to 0.6 dl / g. It is preferably used from the viewpoint of balance.

  Polymerization methods such as bulk polymerization, solution polymerization, suspension polymerization, and emulsion polymerization can be employed as a method for making the acrylic elastic particles (B) into a graft copolymerization type.

  The particle diameter and content of the core / shell type or graft copolymer type acrylic elastic particles (B) are evaluated for rubbery polymers excluding the shell part and the graft copolymer part. The particle diameter can be evaluated by excluding the shell portion and the graft copolymer portion from, for example, cross-sectional observation with a transmission electron microscope. Moreover, content can be evaluated from the insoluble component after making it melt | dissolve in solvents, such as acetone, which melt | dissolves an acrylic resin.

  As a method of blending the acrylic elastic particles (B) and other additives into the acrylic resin (A) or a precursor thereof, for example, after blending the acrylic resin (A) and other additive components in advance, usually 200 to 350 A method of uniformly melting and kneading with a single-screw or twin-screw extruder at ° C can be employed.

  In addition, the acrylic elastic particles (B) and other additives are added to the copolymer (a), which is the precursor of the acrylic resin (A), and simultaneously with the intramolecular cyclization reaction using a twin screw extruder or the like. Further, blending by melt kneading of the acrylic elastic particles (B) and other additives can be performed.

  In the melt-kneading, a cyclization reaction of unsaturated carboxylic acid monomer units such as a shell portion or the like and an unsaturated carboxylic acid alkyl ester monomer unit imparted to the acrylic elastic particles (B) can be simultaneously performed.

  In the case of solution casting described later, a method of removing the solvent after mixing the acrylic resin (A) and the acrylic elastic particle (B) component in a solvent that dissolves or disperses can be used.

  Particularly in solution casting, the resin constituting the base material of the prism sheet of the present invention is preferably filtered for the purpose of removing foreign substances. By removing the foreign matter, the resin can be prevented from being colored and can be usefully used as the base material of the prism sheet. Filters made of sintered metal, porous ceramics, sand, wire mesh, etc. at a temperature of 25 ° C. to 100 ° C. with a resin dissolved in a solvent such as tetrahydrofuran, acetone, methyl ethyl ketone, dimethylformamide, dimethyl sulfoxide, N-methylpyrrolidone Can be filtered.

  The base material of the prism sheet of the present invention can be formed by melt film formation or solution film formation. Examples of the melt film formation include an inflation method, a T-die method, a calendar method, a cutting method, and the T-die method can be particularly preferably employed. Examples of the solution casting include a casting method on a polymer film, a casting drum method, a casting method on a metal belt, and the casting method on a polymer film can be preferably used. Hereinafter, each manufacturing method will be described as an example.

For melt film formation, an extruder type melt extrusion apparatus equipped with a single screw or a twin screw can be used. The L / D of the screw is preferably 25 to 120 in order to prevent coloring. The melt extrusion temperature is preferably 150 to 350 ° C, more preferably 200 to 300 ° C. The melt shear rate, 1000 s ^-1 or 5000 s ^-1 or less. Moreover, when melt-kneading using a melt-extrusion apparatus, it is preferable to perform melt-kneading under reduced pressure using a vent or nitrogen stream from a viewpoint of coloring suppression.

  In the T-die method, molten resin is measured by a gear pump and then discharged from a T-die die, and is adhered to a cooling medium such as a drum by an electrostatic application method, an air chamber method, an air knife method, a press roll method, or the like. The film can be obtained by cooling and solidifying. In particular, the press roll method is preferable for obtaining a transparent film with little thickness unevenness.

  In solution casting, the matrix resin of the resin composition is dissolved in a solvent. As such a solvent, tetrahydrofuran, acetone, methyl ethyl ketone, dimethylformamide, dimethyl sulfoxide, N-methylpyrrolidone, or the like can be used, and particularly acetone or methyl ethyl ketone can be preferably used.

  The polymer film cast method is a method of casting a solution in which a resin composition is dissolved onto a heat-resistant film such as polyethylene terephthalate using a bar coater or a die coater and evaporating and removing the solvent (dry method) or removing the solution. It can be produced by solidifying with a coagulating liquid (wet method).

  Next, a method for installing a prism on the prism sheet of the present invention will be described. For the prism, the active energy ray-curable resin composition is applied to a mold corresponding to the prism pattern, such as a mold or a resin mold, and the surface of the resin composition is smoothed. It is manufactured by irradiating with active energy rays and curing. With this method, it is possible to easily manufacture a fine pitch prism pattern that can cope with finer color filters associated with colorization of liquid crystal display devices without impairing optical characteristics.

  That is, in the prism sheet of the present invention, the resin constituting the prism is preferably a cured product of the active energy ray-curable resin composition. Such an active energy ray-curable resin composition is not particularly limited as long as it is excellent in transparency, but from the viewpoint of the mechanical properties of the triangular prism sheet, one that gives a crosslinked cured polymer is preferable. Examples of such a resin composition include unsaturated polyester-styrene type, epoxy resin-Lewis acid type, polyene-thiol type, (meth) acrylic acid ester type, and the like. Among them, a highly transparent (meth) acrylic acid ester is particularly preferable. For example, prepolymers such as polyester (meth) acrylate, epoxy (meth) acrylate, polyurethane (meth) acrylate, and monofunctional or polyfunctional (meth) ) A combination with an acrylate monomer.

  Examples of the active energy ray used for curing the active energy ray-curable resin composition include electron rays, ion rays and other particle rays, γ rays, X rays, ultraviolet rays, visible rays, electromagnetic rays such as infrared rays, and the like. Ultraviolet rays are particularly preferable from the viewpoint of curing speed and production equipment.

  As a method of applying the active energy ray-curable resin composition to the mold, the necessary resin composition may be applied to the mold by one application, but the pattern portion of the mold on which the prism pattern is formed is used. A two-step coating process including a first coating process for coating a resin composition for forming a prism portion tip so as to uniformly fill and a second coating process for coating a resin composition for forming a prism base on the first coating process. You may apply by. In this case, it is preferable to obtain a uniform triangular prism sheet free from thickness spots by smoothing the surface of the resin composition coating layer after coating after the first coating step. In addition, when the resin composition layer is cured or semi-cured by irradiating active energy rays after the first coating layer is smoothed, generation of bubbles due to the flow of the first resin composition coating layer in the second coating step Can be suppressed.

  The hard coat agent used for forming the hard coat layer is, for example, a thermosetting cross-linked resin mainly composed of an organosilicon compound, an epoxy resin, a melamine resin, etc. ) Active energy ray-curing properties having an acryloyloxy group, particularly preferably UV-curable crosslinkable resins.

[Measuring method]
(1) Each component composition Acetone is added to the acrylic resin film used as the base material of the prism sheet, and the mixture is refluxed for 4 hours. separated. The acetone-soluble component was dried under reduced pressure at 60 ° C. for 5 hours, and each component unit was quantified to obtain each component composition of the acrylic resin (A).

  Quantification of each component unit was performed by a proton nuclear magnetic resonance (1H-NMR) method.

In the 1H-NMR method, for example, in the case of a copolymer composed of glutaric anhydride units, methacrylic acid, and methyl methacrylate, the attribution of the spectrum in dimethyl sulfoxide heavy solvent is 0.5 to 1.5 ppm. Α-methyl group hydrogen of methacrylic acid, methyl methacrylate and glutaric anhydride ring compound, peak of 1.6 to 2.1 ppm is hydrogen of methylene group of polymer main chain, peak of 3.5 ppm is methyl methacrylate The hydrogen of carboxylic acid ester (—COOCH ₃ ), the peak at 12.4 ppm can determine the copolymer composition from the hydrogen of carboxylic acid of methacrylic acid and the integral ratio of the spectrum. In addition to the above, in the case of a copolymer containing styrene as another copolymer component, hydrogen of an aromatic ring of styrene is seen at 6.5 to 7.5 ppm, and the copolymer is similarly obtained from the spectral ratio. The composition can be determined.

In addition to the 1H-NMR method, each component unit can be quantified by infrared spectroscopy. In this method, glutaric anhydride units are characterized by absorption at 1800 cm ⁻¹ and 1760 cm ⁻¹ , and can be distinguished from units derived from vinyl carboxylic acids and units derived from vinyl carboxylic acid alkyl esters.

(2) Weight average molecular weight (absolute molecular weight)
Gel permeation chromatograph (pump: model 515, manufactured by Waters, column: TSK-gel-GMHXL, Tosoh Corporation) equipped with a DAWN-DSP type multi-angle light scattering photometer (manufactured by Wyatt Technology) using dimethylformamide as a solvent. ).

(3) Glass transition temperature (Tg)
Using a differential scanning calorimeter (DSC-7 manufactured by Perkin Elmer), the measurement was performed at a temperature increase rate of 20 ° C./min in a nitrogen atmosphere.

  When measuring from a prism sheet provided with a prism, the remaining substrate can be measured by peeling the prism portion with a single blade.

(4) Retardation Retardation was measured using an automatic birefringence meter (KOBRA-21ADH) manufactured by Oji Seiki Co., Ltd.

(5) Total light transmittance The total light transmittance (%) at 589.3 nm and 23 ° C. was measured using a direct reading haze meter manufactured by Toyo Seiki Co., Ltd. according to JIS K 7361. In the prism sheet provided with a prism on one side, incident light was applied from the side opposite to the side where the prism was provided.

(6) Luminance characteristics Using a liquid crystal display device using a sidelight type backlight having a surface luminance of 7000 cd / m ² , the obtained prism sheet is placed on the backlight, and the surface on which the prism is provided is a liquid crystal display. It installed so that it might oppose a part, and the surface brightness in the front was measured. In addition, the surface brightness | luminance when not using a prism sheet was 200 cd / m < ² >.

(7) Thermal elongation rate The prism sheet was sampled in a strip shape with a width of 10 mm and a length of 200 mm parallel to the longitudinal direction of the prism sheet, and a 100 mm section in the center in the length direction was defined by marking. Next, after adjusting the humidity in an atmosphere of 20 ° C. and 65% Rh for 10 hours, an accurate length of the section defined by the marking as an initial length was measured using a universal projector. One of the samples was lowered with a 100 g weight, treated in an oven at 110 ° C. for 10 minutes, removed from the weight, conditioned at 20 ° C. and 65% Rh for 10 hours, and then used a universal projector. The length of the section defined by the marking was measured, and the thermal elongation rate was obtained as the elongation rate relative to the initial length. The measurement was performed 10 times on separate samples, and the average value was used.

(8) Crack resistance The prism sheet was sampled in a strip shape with a width of 10 mm and a length of 300 mm parallel to the longitudinal direction of the prism sheet, a weight of 100 g was lowered at one end, and a metal fixing roll with a diameter of 25 mm and a diameter of 5 mm was 180 °. The sample was wound around a holding angle and observed for the presence or absence of cracks, and the following determinations were made.
Defect: A crack occurs when wound around a metal guide having a diameter of 25 mm.
Good: Cracks do not occur when wound around a metal guide with a diameter of 25 mm, but cracks occur when wound around a metal guide with a diameter of 5 mm.
Excellent: No cracking occurs when wound around a metal guide having a diameter of 5 mm.

[Examples 1-3, Comparative Examples 1-3]
(1) Preparation of acrylic resin precursor Acrylic resin precursor (a-1)
First, a methyl methacrylate / acrylamide copolymer suspension was prepared as follows.
20 parts by weight of methyl methacrylate,
80 parts by weight of acrylamide,
0.3 parts by weight of potassium persulfate,
1500 parts by weight of ion-exchanged water was charged into the reactor, and while the reactor was replaced with nitrogen gas, the reaction was allowed to proceed at 70 ° C. until the monomer was completely converted to a polymer. The obtained aqueous solution was used as a suspending agent.
A solution obtained by dissolving 0.05 part of the above suspending agent in 165 parts of ion-exchanged water is supplied to a stainless steel autoclave having a capacity of 5 liters and equipped with a baffle and a foudra-type stirring blade, and the inside of the system is replaced with nitrogen gas. The mixture was stirred at 400 rpm.
Next, a mixed substance having the following charge composition was added while stirring the reaction system.
Methacrylic acid: 27 parts by weight Methyl methacrylate: 73 parts by weight t-dodecyl mercaptan: 1.2 parts by weight 2,2′-azobisisobutyronitrile: After 0.4 parts by weight, the temperature was raised to 70 ° C., The time when the internal temperature reached 70 ° C. was set as the polymerization start time, and the polymerization was continued for 180 minutes.
Thereafter, the reaction system was cooled, the polymer was separated, washed and dried in accordance with a normal method to obtain a bead-shaped copolymer (a-1). The polymerization rate of this copolymer (a-1) was 98%, and the weight average molecular weight was 130,000.

Acrylic resin precursor (a-2)
An acrylic resin precursor (a-2) was obtained in the same manner as in the above a-1 except that the mixed substance used for the suspension polymerization had the following composition.
Methacrylic acid: 13 parts by weight Methyl methacrylate: 87 parts by weight t-dodecyl mercaptan: 1.0 part by weight 2,2′-azobisisobutyronitrile: 0.4 part by weight

Acrylic resin precursor (a-3)
An acrylic resin precursor a-3 was obtained in the same manner as in the a-1 except that the mixed material used for the suspension polymerization had the following composition.
Methacrylic acid: 6 parts by weight Methyl methacrylate: 84 parts by weight Styrene: 10 parts by weight t-dodecyl mercaptan: 1.0 part by weight 2,2′-azobisisobutyronitrile: 0.4 parts by weight

Acrylic resin precursor (a-4)
An acrylic resin precursor a-4 was obtained in the same manner as a-1 except that the mixed material used for suspension polymerization had the following composition.
Methacrylic acid: 37 parts by weight Methyl methacrylate: 63 parts by weight t-dodecyl mercaptan: 1.5 parts by weight 2,2′-azobisisobutyronitrile: 0.4 parts by weight

(2) Preparation of acrylic elastic particles Core / shell type acrylic elastic particles (B)
In a glass container with a cooler (capacity 5 liters), as an initial adjustment solution,
120 parts by weight of deionized water,
0.5 parts by weight of potassium carbonate,
0.5 parts by weight of dioctyl sulfosuccinate,
After charging 0.005 part by weight of potassium persulfate and stirring in a nitrogen atmosphere,
53 parts by weight of butyl acrylate,
17 parts by weight of styrene,
1 part by weight of allyl methacrylate (crosslinking agent) was charged. These mixtures were reacted at 70 ° C. for 30 minutes to obtain a rubbery polymer.
Then
21 parts by weight of methyl methacrylate,
9 parts by weight of methacrylic acid,
A mixture of 0.005 parts by weight of potassium persulfate was subsequently continuously added at 70 ° C. over 90 minutes and held for another 90 minutes to polymerize the shell layer.
The polymer latex was coagulated with sulfuric acid, neutralized with caustic soda, washed, filtered, and dried to obtain core / shell type acrylic elastic particles (B). The average particle size of the rubbery polymer portion of the acrylic elastic particles measured with an electron microscope was 140 nm.

(3) Preparation of acrylic resin composition Acrylic resin composition (C-1)
80 parts by weight of the acrylic resin precursor (a-1), 20 parts by weight of acrylic elastic particles (B) and 0.2% by weight of additive (NaOCH ₃ ) were blended, and a twin-screw extruder (TEX30). (Manufactured by Nippon Steel Co., Ltd., L / D = 44.5)), while purging nitrogen from the hopper at an amount of 10 L / min, screw rotation speed 100 rpm, raw material supply rate 5 kg / h, cylinder temperature 290 ° C Intramolecular cyclization reaction was performed to obtain a pellet-shaped acrylic resin composition (C-1).

Acrylic resin composition (C-2)
The acrylic resin composition (C-) was prepared in the same manner as in C-1 except that the amount of the acrylic resin precursor (a-1) was 100 parts by weight and the acrylic elastic particles (B) were not blended. 2) was obtained.

Acrylic resin composition (C-3)
An acrylic resin composition (C-3) was obtained in the same manner as in C-1, except that 80 parts by weight of the precursor (a-2) was blended instead of the acrylic resin precursor (a-1).

Acrylic resin composition (C-4)
An acrylic resin composition (C-4) was obtained in the same manner as in C-1, except that 80 parts by weight of the precursor (a-3) was blended instead of the acrylic resin precursor (a-1).

Acrylic resin composition (C-5)
Instead of the acrylic resin precursor (a-1), 100 parts by weight of the precursor (a-4) was blended, and the same procedure as C-1 except that the acrylic elastic particles (B) were not blended. An acrylic resin composition (C-5) was obtained.

  Table 1 shows the composition and properties of the acrylic resin or acrylic resin composition (C-1 to 5).

(4) Film Formation In each Example / Comparative Example, as shown in Table 2, any of the acrylic resin compositions (C1 to 5) was employed to prepare a prism sheet substrate.

  The acrylic resin composition was vacuum-dried at 80 ° C. for 8 hours, then dissolved in methyl ethyl ketone so as to have a solid content concentration of 30% by weight, and filtered using a 1 μm cut filter. This solution is cast on a PET film through a T die having a slit gap of 0.5 mm using a gear pump, and heat-treated at 60 ° C., 110 ° C. and 170 ° C. for 30 minutes in a hot air oven, respectively, and an acrylic resin substrate having a thickness of 100 μm Got.

(5) Formation of Prism In each of the examples and comparative examples, the following mixture was applied as an ultraviolet curable resin composition on the substrate, and the top of the prism after molding as shown in Table 3 on the coated surface. Molds designed to have corners and pitch were crimped.
FANCLIL FA-321M (Hitachi Chemical Co., Ltd. ethylene oxide modified bisphenol A methacrylate)
: 45 parts by weight of NK ester A-BPE-4 (manufactured by Shin-Nakamura Chemical Co., Ltd., ethylene oxide-modified bisphenol A diacrylate)
: 25 parts by weight Sartomer 285 (tetrahydrofurfuryl acrylate manufactured by Sartomer)
: 30 parts by weight Darocur 1173 (2-hydroxy-2-methyl-1-phenylpropan-1-one manufactured by Merck Japan)
: 3 parts by weight.

Subsequently, 1000 mJ / cm < ² > of ultraviolet rays were irradiated with the integrated ultraviolet irradiation amount of 320-390 nm, and the ultraviolet curable resin composition was hardened. Then, it peeled from the metal mold | die and the triangular prism sheet was obtained.
All the triangular prism sheets had the shape as designed.

  Table 3 shows the performance and the like of the obtained prism sheet.

  The prism sheets of Examples 1 to 3 were prism sheets having excellent luminance characteristics, heat resistance, and cracking properties, but the prism sheets of Comparative Examples 1 to 3 were either of luminance characteristics, heat resistance, or cracking properties. It was inferior.

  The prism sheet obtained in the present invention can be widely used in liquid crystal display devices having sidelight type or direct type backlights, and because of its excellent luminance characteristics and heat resistance, thin liquid crystal display devices such as laptop computers, PDAs, It is most suitable for mobile liquid crystal display devices such as portable game machines, and liquid crystal display devices that are expected to be used at high temperatures such as in-vehicle TVs and car navigation systems.

Claims (10)

A cross section made of a resin on at least one side of a substrate composed of a resin composition containing an acrylic resin (A) containing 10 to 40% by weight of a glutaric anhydride unit represented by the following structural formula (1) A prism sheet comprising a plurality of triangular prisms each having a triangular shape with an apex angle of 70 to 110 ° arranged in parallel at a pitch of 100 μm or less.

(In the above formula, R ¹ and R ² represent the same or different hydrogen atoms or alkyl groups having 1 to 5 carbon atoms.) The prism sheet according to claim 1, wherein the acrylic resin (A) contains 60 to 90% by weight of units derived from vinyl carboxylic acid alkyl ester. The prism sheet of Claim 2 in which an acrylic resin (A) contains a methyl (meth) acrylate unit as a unit derived from vinylcarboxylic acid alkylester. The prism sheet according to any one of claims 1 to 3, wherein the resin composition constituting the substrate contains 60 to 93% by weight of the acrylic resin (A) and 7 to 40% by weight of the acrylic elastic particles (B). . The prism sheet according to claim 4, wherein an average particle diameter of the acrylic elastic particles (B) is 70 to 300 nm. The prism sheet according to any one of claims 1 to 5, wherein a glass transition temperature of a resin composition constituting the substrate is 120 ° C or higher. The prism sheet according to any one of claims 1 to 6, wherein the retardation of the substrate is 5 nm or less. The prism sheet according to any one of claims 1 to 7, wherein the resin constituting the prism includes at least one of an acrylic ester resin and a methacrylic ester resin. The prism sheet according to any one of claims 1 to 8, wherein the resin constituting the prism is a cured product of an active energy ray-curable resin composition. The prism sheet according to any one of claims 1 to 9, wherein the total light transmittance is 91% or more.