Retardation film, polarizing plate, liquid crystal display panel, and resin composition

Abstract

Provided is a retardation film obtained by molding a resin composition containing an acrylic resin, wherein the ratio Re(450) / Re(550) of the frontal retardation Re(450) at a wavelength of 450 nm to the frontal retardation Re(550) at a wavelength of 550 nm (450) is 1.00-1.04, and the resin composition contains 20 wt% or more of a styrene unit, has a glass transition temperature of 118°C or higher, and has a birefringence development ∆nxy of -3.0 × 10-3 to -1.1 × 10-3.

Description

Retardation film, polarizing plate, liquid crystal display panel and resin composition

[0001] The present invention relates to a retardation film, a polarizing plate, a liquid crystal display panel, and a resin composition.

[0002] A retardation film is used in a liquid crystal display panel for the purpose of preventing a decrease in contrast and a change in color due to a change in viewing angle, that is, for the purpose of optical compensation or viewing angle compensation.

[0003] In IPS-type liquid crystal display panels, a retardation film (negative C plate) made of a polymer material with positive intrinsic birefringence and a retardation film (positive B plate) made of a polymer material with negative intrinsic birefringence are used in combination (see, for example, Patent Document 1). Here, the negative C plate contains polynorbornene. Also, the positive B plate contains an acrylic copolymer containing acrylic monomer units, aromatic vinyl monomer units, maleic anhydride monomer units, and vinylcyan monomer units.

[0004] However, the negative C plate has flat dispersion, whereas the positive B plate has normal dispersion, resulting in a color shift.

[0005] Patent Document 2 describes a retardation film containing a composition including an acrylate resin having a glass transition temperature of 120°C or higher, a retardation adjuster containing a styrene unit, and a triazine birefringence adjuster. The retardation film contains 15 to 80 parts by weight of a retardation adjuster containing a styrene unit, and more than 5 to 15 parts by weight of a triazine birefringence adjuster, based on 100 parts by weight of the acrylate resin. The acrylate resin has one or more monomers selected from the group consisting of an N-substituted maleimide structure, a lactone ring structure, and a glutarimide structure in the acrylate molecular chain. Furthermore, the retardation in the in-plane direction at wavelengths of 450 nm and 550 nm is determined by R ｉｎ (450) and R ｉｎ (550), then the formula 0.7≦R ｉｎ (450) / R ｉｎ (550)≦1.0 is satisfied.

[0006] JP 2012-501464 A JP 2021-517990 A JP 2011-209627 A

[0007] However, the retardation film described in Patent Document 2 contains a high content of a triazine-based birefringence adjuster, which results in poor heat resistance and birefringence expression, and also leads to contamination of the casting roll during film formation.On the other hand, the retardation film described in Patent Document 3 contains 1,6-diphenyl-1,3,5-hexatriene, which leads to contamination of the casting roll during film formation.

[0008] The present invention aims to provide a retardation film that has high heat resistance and birefringence development properties and is capable of suppressing color shift when used in combination with a flat-dispersion negative C-plate. Another object of the present invention is to provide a resin composition that can be used to produce a retardation film that has high heat resistance and birefringence development properties and is capable of suppressing color shift when used in combination with a flat-dispersion negative C-plate and suppressing contamination of a casting roll during film formation.

[0009] [1] A retardation film obtained by molding a resin composition containing an acrylic resin, wherein the ratio Re(450) / Re(550) of the front retardation Re(450) at a wavelength of 450 nm to the front retardation Re(550) at a wavelength of 550 nm is 1.00 or more and 1.04 or less, and the resin composition contains 20% by weight or more of a styrene unit, has a glass transition temperature of 118°C or more, and has a birefringence expression Δnxy of -3.0 × 10 －３ Above -1.1 x 10 －３ The following is a retardation film.

[0010] [2] The retardation film according to [1], wherein the resin composition contains a triazine compound, and the content of the triazine compound is 2% by weight or more and less than 5% by weight.

[0011] [3] The retardation film according to [2], wherein the triazine compound has a 1% weight loss temperature of 340° C. or higher.

[0012] [4] The retardation film according to [2] or [3], wherein the triazine compound has a maximum absorption wavelength of 340 nm or more.

[0013] [5] The retardation film according to any one of [2] to [4], wherein the triazine compound is represented by the following formula (1) or the following formula (2): (In the formula, X １ is a substituted or unsubstituted aryl group, and Y １ and Z １ are each independently an aryl group substituted with an aryl group. (In the formula, X ２ is an aryl group substituted with a hydroxyl group or an alkoxy group having 5 or less carbon atoms and an alkoxy group having 5 or less carbon atoms; Y ２ and Z ２ are each independently an aryl group substituted with a hydroxyl group and an alkoxy group having 5 or less carbon atoms.

[0014] [6] The retardation film according to any one of [1] to [5], wherein the acrylic resin contains a ring structure in the main chain.

[0015] [7] The retardation film according to any one of [1] to [6], which has a yellowness index of 2.0 or less.

[0016] [8] A polarizing plate comprising the retardation film according to any one of [1] to [7].

[0017] [9] A liquid crystal display panel comprising the polarizing plate according to [8].

[0018]

[10] A resin composition containing an acrylic resin and a triazine compound, wherein the content of the triazine compound is 2% by weight or more and less than 5% by weight, the resin composition contains 20% by weight or more of styrene units, the glass transition temperature is 118°C or more, and the birefringence expression Δnxy is -3.0 × 10 －３ Above -1.1 x 10 －３ The resin composition is as follows, wherein the triazine compound is represented by the following formula (1) or the following formula (2): (In the formula, X １ is a substituted or unsubstituted aryl group, and Y １ and Z １ are each independently an aryl group substituted with an aryl group. (In the formula, X２ is an aryl group substituted with a hydroxyl group or an alkoxy group having 5 or less carbon atoms and an alkoxy group having 5 or less carbon atoms; Y ２ and Z ２ are each independently an aryl group substituted with a hydroxyl group and an alkoxy group having 5 or less carbon atoms.

[0019]

[11] The resin composition according to

[10] , wherein the triazine compound has a 1% weight loss temperature of 340°C or higher.

[0020]

[12] The resin composition according to

[10] or

[11] , wherein the triazine compound has a maximum absorption wavelength of 340 nm or more.

[0021]

[13] The resin composition according to any one of

[10] to

[12] , wherein the acrylic resin contains a ring structure in the main chain.

[0022]

[14] The resin composition according to any one of

[10] to

[13] , which is a pellet.

[0023] According to the present invention, it is possible to provide a retardation film that has high heat resistance and birefringence development ability, and is capable of suppressing color shift when used in combination with a negative C plate having flat dispersion. Also, according to the present invention, it is possible to provide a resin composition that can be used to produce a retardation film that has high heat resistance and birefringence development ability, and is capable of suppressing color shift when used in combination with a negative C plate having flat dispersion, and suppressing contamination of a casting roll during film formation.

[0024] Hereinafter, an embodiment of the present invention will be described.

[0025] [Features of the First Aspect of the Present Embodiment] (Retardation Film) The retardation film of the present embodiment is formed by molding a resin composition containing an acrylic resin. The retardation film of the present embodiment is obtained, for example, by forming the resin composition into a film to obtain a non-stretched film, and then stretching the non-stretched film. The method for forming a film from the resin composition is not particularly limited, but examples include melt extrusion and solution casting. Among these, melt extrusion is preferred from the viewpoint of productivity. When stretching the non-stretched film, uniaxial stretching (e.g., free-end uniaxial stretching, fixed-end uniaxial stretching) and / or biaxial stretching (e.g., sequential biaxial stretching, simultaneous biaxial stretching) may be performed.

[0026] In this specification and claims, acrylic resin refers to a polymer of a monomer having an acryloyl group and / or a monomer having a methacryloyl group. In this case, the acrylic resin may be either a homopolymer or a copolymer. When the acrylic resin is a copolymer, it may be a copolymer of a monomer not having an acryloyl group or a methacryloyl group.

[0027] The content of styrene units in the resin composition is 20% by weight or more, more preferably 22% by weight or more, and even more preferably 24% by weight or more. Since the content of styrene units in the resin composition is 20% by weight or more, sufficient retardation is exhibited even when the thickness of the retardation film of this embodiment is small. The content of styrene units in the resin composition is, for example, 50% by weight or less.

[0028] The birefringence expression Δnxy of the resin composition is −3.0×10 －３ Above -1.1 x 10 －３ is less than or equal to -2.5 × 10 －３ Above -1.1 x 10 －３ It is preferable that the value is equal to or less than -1.3 × 10 －３ Above -1.2 x 10 －３ It is more preferable that the birefringence development Δnxy of the resin composition is −3.0×10 or less. －３ Above -1.1 x 10 －３or less, even if the thickness of the retardation film of this embodiment is small, sufficient retardation is exhibited and retardation unevenness is reduced.

[0029] In this specification and claims, the birefringence development property Δnxy of a resin composition means the birefringence developed when an unstretched film obtained by forming the resin composition into a film is uniaxially stretched at its free end so that the stretching ratio in the machine direction (longitudinal direction) becomes 2 times at a temperature 5°C higher than the glass transition temperature of the resin composition.

[0030] The ratio Re(450) / Re(550) of the front retardation Re(450) at a wavelength of 450 nm to the front retardation Re(550) at a wavelength of 550 nm of the retardation film of this embodiment is 1.00 or more and 1.04 or less, preferably 1.01 or more and 1.04 or less, and more preferably 1.02 or more and 1.03 or less. Since Re(450) / Re(550) is 1.00 or more and 1.04 or less, color shift is suppressed when used in combination with a negative C plate with flat dispersion.

[0031] The glass transition temperature of the resin composition is 118° C. or higher, more preferably 119° C. or higher, and even more preferably 120° C. or higher. Since the glass transition temperature of the resin composition is 118° C. or higher, the retardation of the retardation film of the present embodiment is less likely to change even in a high-temperature environment, and the heat resistance is increased. The glass transition temperature of the resin composition is, for example, 160° C. or lower.

[0032] The yellowness index of the retardation film of the present embodiment is preferably 2.0 or less, more preferably 1.5 or less, and even more preferably 1.4 or less. When the yellowness index of the retardation film of the present embodiment is 2.0 or less, the retardation film of the present embodiment is less colored, and therefore the influence on the color rendering properties of the liquid crystal display panel is reduced. The yellowness index of the retardation film of the present embodiment is, for example, 0.01 or more.

[0033] The resin composition preferably contains a triazine compound.

[0034] The resin composition may further contain a thermoplastic resin other than the acrylic resin. In this case, the content of the acrylic resin in the resin composition is preferably 60% by weight or more, more preferably 70% by weight or more, and even more preferably 85% by weight or more.

[0035] The resin composition may further contain additives, such as antioxidants, light stabilizers, near-infrared absorbers, antistatic agents, plasticizers, resin modifiers, lubricants, antiblocking agents, and flame retardants.

[0036] The form of the resin composition is not particularly limited, but may be, for example, pellets.

[0037] The retardation film of the present embodiment may be coated with a coating layer. Examples of the coating layer include an easy-adhesion layer, an adhesive layer, and a hard coat layer.

[0038] (Triazine Compound) A triazine compound has positive intrinsic birefringence and steep wavelength dispersion characteristics. Therefore, by adding a triazine compound to an acrylic resin having negative intrinsic birefringence, the retardation film of the present embodiment exhibits flat dispersion.

[0039] The content of the triazine compound in the retardation film of the present embodiment is preferably 2% by weight or more and less than 5% by weight, more preferably 2.5% by weight or more and less than 4.5% by weight, and even more preferably 3% by weight or more and less than 4% by weight. When the content of the triazine compound in the retardation film of the present embodiment is 2% by weight or more, the Re(450) / Re(550) of the retardation film of the present embodiment becomes small, and when it is less than 5% by weight, the yellowness of the retardation film of the present embodiment becomes low, and in addition to improving the heat resistance and birefringence expression, contamination of the cast roll during film formation is suppressed.

[0040] The molecular weight of the triazine compound is preferably from 100 to 1,500, more preferably from 300 to 1,000, even more preferably from 400 to 700, and particularly preferably from 500 to 680. When the molecular weight of the triazine compound is from 100 to 1,500, the compatibility with the acrylic resin is increased.

[0041] The 1% weight loss temperature of the triazine compound is preferably 340° C. or higher, more preferably 350° C. or higher, and even more preferably 360° C. or higher. When the 1% weight loss temperature of the triazine compound is 340° C. or higher, contamination of the casting roll during film formation is suppressed. The 1% weight loss temperature of the triazine compound is, for example, 420° C. or lower.

[0042] The maximum absorption wavelength of the triazine compound is preferably 340 nm or more, more preferably 345 nm or more, and even more preferably 350 nm or more. When the maximum absorption wavelength of the triazine compound is 340 nm or more, the Re(450) / Re(550) of the retardation film of the present embodiment becomes small. The maximum absorption wavelength of the triazine compound is, for example, 400 nm or less.

[0043] The triazine compound is preferably represented by the following formula (1) or (2): This reduces Re(450) / Re(550) of the retardation film of the present embodiment. (In the formula, X １ is a substituted or unsubstituted aryl group, and Y １ and Z １ are each independently an aryl group substituted with an aryl group. (In the formula, X ２ is an aryl group substituted with a hydroxyl group or an alkoxy group having 5 or less carbon atoms and an alkoxy group having 5 or less carbon atoms; Y ２ and Z ２ are each independently an aryl group substituted with a hydroxyl group and an alkoxy group having 5 or less carbon atoms.

[0044] X １Examples of the aryl group in X include a phenyl group and a naphthyl group. Examples of the substituent in X include a hydroxyl group and a substituted or unsubstituted alkoxy group. The carbon number of the alkoxy group is, for example, 1 to 10. Examples of the substituent in the alkoxy group include an alkoxycarbonyl group. The carbon number of the alkoxycarbonyl group is, for example, 1 to 10. X １ When the aryl group in is a phenyl group, it is preferably substituted with a hydroxyl group at the 2-position and with a substituted or unsubstituted alkoxy group at the 4-position, and in this case, it is preferable that the 3-, 5-, and 6-positions of the phenyl group are not substituted.

[0045] Y １ and Z １ Examples of the aryl group in Y include a phenyl group and a naphthyl group. １ and Z １ Examples of the aryl group as a substituent in Y include a phenyl group and a naphthyl group. １ and Z １ When the aryl group in is a phenyl group, it is preferably substituted at the 4-position with an aryl group, and in this case, it is preferably not substituted at the 2-, 3-, 5- and 6-positions of the phenyl group.

[0046] X ２ Examples of the aryl group in X include a phenyl group and a naphthyl group. ２ The number of carbon atoms of the alkoxy group as a substituent in X is, for example, 1 or more and 5 or less. ２ When the aryl group in is a phenyl group, it is preferably substituted with a hydroxyl group at the 2-position and an alkoxy group at the 4-position, and in this case, it is preferable that the 3-, 5-, and 6-positions of the phenyl group are not substituted.

[0047] Y ２ and Z ２ Examples of the aryl group in Y include a phenyl group and a naphthyl group. ２ and Z ２The number of carbon atoms of the alkoxy group as a substituent in Y is, for example, 1 or more and 5 or less. ２ and Z ２ When the aryl group in is a phenyl group, it is preferably substituted with a hydroxyl group at the 2-position and an alkoxy group at the 4-position, and in this case, it is preferable that the 3-, 5-, and 6-positions of the phenyl group are not substituted.

[0048] X ２ , Y ２ or Z ２ When the carbon number of the alkoxy group as a substituent in the formula (I) is 6 or more, the Re(450) / Re(550) of the retardation film of this embodiment becomes large. The reason for this is not clear, but is presumed as follows. When the carbon number of the alkoxy group is 6 or more, a free volume proportional to the alkyl chain length is generated. As a result, the interaction between the triazine compound and the acrylic resin is reduced, and when the non-stretched film is stretched, the triazine compounds are less likely to be oriented cooperatively.

[0049] Examples of the compound represented by formula (1) include 6-methylheptyl 2-[4-[4,6-bis(biphenyl-4-yl)-1,3,5-triazin-2-yl]-3-hydroxyphenoxy]propanoate and 2-[4,6-bis(1,1'-biphenyl-4-yl)-1,3,5-triazin-2-yl]-5-[(2-ethylhexyl)oxy]phenol.

[0050] Examples of the compound represented by formula (2) include 2,4,6-tris(4-butoxy-2-hydroxyphenyl)-1,3,5-triazine and 2,4-bis[4-butoxy-2-hydroxyphenyl]-6-(2,4-dibutoxyphenyl)-1,3,5-triazine.

[0051] (Acrylic Resin) The acrylic resin contains a (meth)acrylic acid ester unit and may or may not contain a styrene unit. The acrylic resin containing a styrene unit may be a random copolymer, a graft copolymer, or a block copolymer.

[0052] The resin composition may contain an acrylic resin and a resin containing a styrene unit. The resin containing a styrene unit is not particularly limited as long as it has good compatibility with the acrylic resin, but examples thereof include a styrene-acrylonitrile copolymer, a styrene-methacrylic acid copolymer, and a styrene-maleic anhydride copolymer. Among these, a styrene-acrylonitrile copolymer is preferred.

[0053] Examples of (meth)acrylic acid esters include alkyl (meth)acrylates such as methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, n-butyl (meth)acrylate, and isobutyl (meth)acrylate; aryl (meth)acrylates such as phenyl (meth)acrylate; aralkyl (meth)acrylates such as benzyl (meth)acrylate; and cycloalkyl (meth)acrylates such as cyclohexyl (meth)acrylate, and two or more of these may be used in combination. Among these, alkyl methacrylates are preferred, and methyl methacrylate is particularly preferred.

[0054] The acrylic resin preferably contains a ring structure in the main chain. The acrylic resin containing a ring structure in the main chain preferably contains one or more rings selected from the group consisting of glutarimide rings, lactone rings, maleic anhydride rings, maleimide rings, and glutaric anhydride rings in the main chain. Hereinafter, an acrylic resin containing a glutarimide ring or lactone ring in the main chain will be described as an example of an acrylic resin containing a ring structure in the main chain.

[0055] The acrylic resin containing a glutarimide ring in the main chain contains, for example, a constitutional unit represented by the following formula (3).

[0056] (In the formula, R １ and R ２ are each independently a hydrogen atom or an alkyl group having 1 to 8 carbon atoms, and R ３ is a hydrogen atom, an alkyl group having 1 to 18 carbon atoms, or a cycloalkyl group having 3 to 12 carbon atoms.

[0057] The acrylic resin containing the structural unit represented by formula (3) can be produced by a known method. An example of a method for producing the acrylic resin containing the structural unit represented by formula (3) will be described below.

[0058] First, a twin-screw extruder equipped with a die at the outlet is used to melt the methyl methacrylate-styrene copolymer, followed by imidization, and a strand is extruded from the die. Next, the strand is cooled using a water bath, and then pelletized using a pelletizer, to obtain an imidized methyl methacrylate-styrene copolymer. Next, a twin-screw extruder equipped with a die at the outlet is used to melt the imidized methyl methacrylate-styrene copolymer, followed by esterification, and a strand is extruded from the die. Next, the strand is cooled using a water bath, and then pelletized using a pelletizer, to obtain an acrylic resin containing a structural unit represented by formula (3).

[0059] Examples of the imidizing agent used to imidize the methyl methacrylate-styrene copolymer include ammonia and primary amines represented by the following formula (4). Among these, monomethylamine is preferred.

[0060] R ３ NH ２ (4) (wherein, R ３ is synonymous with formula (3).

[0061] Examples of esterifying agents used in esterifying the imidized methyl methacrylate-styrene copolymer include dimethyl carbonate, 2,2-dimethoxypropane, dimethyl sulfoxide, triethyl orthoformate, trimethyl orthoacetate, trimethyl orthoformate, diphenyl carbonate, dimethyl sulfate, methyl toluene sulfonate, methyl trifluoromethyl sulfonate, methyl acetate, methanol, ethanol, methyl isocyanate, p-chlorophenyl isocyanate, dimethyl carbonate, Examples of suitable glycidyl ethers include diimide, dimethyl-t-butylsilyl chloride, isopropenyl acetate, dimethylurea, tetramethylammonium hydroxide, dimethyldiethoxysilane, tetra-n-butoxysilane, dimethyl(trimethylsilane)phosphite, trimethyl phosphite, trimethyl phosphate, tricresyl phosphate, diazomethane, ethylene oxide, propylene oxide, cyclohexene oxide, 2-ethylhexyl glycidyl ether, phenyl glycidyl ether, and benzyl glycidyl ether. Among these, dimethyl carbonate is preferred.

[0062] The acrylic resin having a lactone ring in the main chain can be obtained, for example, by polymerizing a monomer represented by the following formula (5) and then heat treating it to form a lactone ring.

[0063] (In the formula, R ４ and R ５ are each independently a hydrogen atom or an alkyl group having 1 to 20 carbon atoms.

[0064] Examples of the monomer represented by formula (5) include methyl 2-(hydroxymethyl)acrylate, ethyl 2-(hydroxymethyl)acrylate, isopropyl 2-(hydroxymethyl)acrylate, n-butyl 2-(hydroxymethyl)acrylate, and t-butyl 2-(hydroxymethyl)acrylate, and two or more of these may be used in combination. Among these, methyl 2-(hydroxymethyl)acrylate and ethyl 2-(hydroxymethyl)acrylate are preferred, and methyl 2-(hydroxymethyl)acrylate is particularly preferred.

[0065] As the acrylic resin containing a ring structure in the main chain other than the acrylic resin containing a glutarimide ring or lactone ring in the main chain, known acrylic resins used in retardation films can be used.

[0066] The content of the structural unit containing a ring structure in the acrylic resin containing a ring structure in the main chain is preferably 2% by weight or more and 50% by weight or less, and more preferably 4% by weight or more and 30% by weight or less. When the content of the structural unit containing a ring structure in the acrylic resin containing a ring structure in the main chain is 2% by weight or more, the heat resistance of the retardation film of the present embodiment is increased, and when it is 50% by weight or less, sufficient retardation is exhibited even if the thickness of the retardation film of the present embodiment is small.

[0067] The acrylic resin may further contain other monomer units. Examples of the other monomers include, but are not limited to, aromatic vinyls other than styrene, such as methylstyrene, and (meth)acrylonitrile.

[0068] (Method for Producing Retardation Film) The retardation film of this embodiment can be produced by a known method. An example of the method for producing the retardation film of this embodiment will be described below.

[0069] First, an acrylic resin and a triazine compound are kneaded using an extruder equipped with a die at the outlet, and then a strand is extruded from the die. Next, the strand is cooled using a water tank, and then the strand is pelletized using a pelletizer to obtain a resin composition. Next, the resin composition is melted using an extruder equipped with a T-die at the outlet, and then a sheet is extruded from the T-die and cooled with a cooling roll to obtain a non-stretched film. Next, the non-stretched film is uniaxially stretched to obtain the retardation film of this embodiment.

[0070] The temperature when the non-stretched film is uniaxially stretched is preferably (Tg + 5)°C or higher and (Tg + 20)°C or lower, more preferably (Tg + 6)°C or higher and (Tg + 18)°C or lower, and even more preferably (Tg + 7)°C or higher and (Tg + 15)°C or lower, where Tg is the glass transition temperature of the resin composition. The areal stretching ratio when the non-stretched film is uniaxially stretched is, for example, 2 times or higher and 10 times or lower. The stretching speed when the non-stretched film is uniaxially stretched is, for example, 1.1 times or higher / min and 100 times or lower.

[0071] [Features of the Second Aspect of the Present Embodiment] (Resin Composition) The resin composition of the present embodiment contains an acrylic resin and a triazine compound. The resin composition of the present embodiment is used, for example, for producing a retardation film.

[0072] The content of styrene units in the resin composition of this embodiment is 20% by weight or more, more preferably 22% by weight or more, and even more preferably 24% by weight or more. Since the content of styrene units in the resin composition of this embodiment is 20% by weight or more, sufficient retardation is exhibited even if the thickness of the retardation film is small. The content of styrene units in the resin composition of this embodiment is, for example, 50% by weight or less.

[0073] The glass transition temperature of the resin composition of this embodiment is 118°C or higher, more preferably 119°C or higher, and even more preferably 120°C or higher. Since the glass transition temperature of the resin composition is 118°C or higher, the phase difference of the retardation film is less likely to change even in a high-temperature environment, and heat resistance is improved. The glass transition temperature of the resin composition is, for example, 160°C or lower.

[0074] The birefringence expression Δnxy of the resin composition of this embodiment is −3.0 × 10 －３ Above -1.1 x 10 －３ is less than or equal to -2.5 × 10 －３ Above -1.1 x 10 －３ It is preferable that the value is equal to or less than -1.3 × 10 －３ Above -1.2 x 10 －３ The birefringence development Δnxy of the resin composition of the present embodiment is more preferably −3.0×10 or less.－３ Above -1.1 x 10 －３ Since the thickness of the retardation film is small, sufficient retardation is exhibited and the unevenness of the retardation is reduced.

[0075] In this specification and claims, the birefringence development property Δnxy of a resin composition means the birefringence developed when an unstretched film obtained by forming the resin composition into a film is uniaxially stretched at its free end so that the stretching ratio in the machine direction (longitudinal direction) becomes 2 times at a temperature 5°C higher than the glass transition temperature of the resin composition.

[0076] The resin composition of the present embodiment may further contain a thermoplastic resin other than the acrylic resin. In this case, the content of the acrylic resin in the resin composition of the present embodiment is preferably 60% by weight or more, more preferably 70% by weight or more, and even more preferably 85% by weight or more.

[0077] The resin composition of the present embodiment may further contain additives, such as antioxidants, light stabilizers, near-infrared absorbers, antistatic agents, plasticizers, resin modifiers, lubricants, antiblocking agents, and flame retardants.

[0078] The form of the resin composition of the present embodiment is not particularly limited, but may be, for example, pellets.

[0079] (Retardation Film) The retardation film is formed by molding the resin composition of this embodiment. The retardation film can be obtained, for example, by forming the resin composition of this embodiment into a film to obtain a non-stretched film, and then stretching the non-stretched film. The film-forming method of the resin composition of this embodiment is not particularly limited, and examples thereof include melt extrusion and solution casting. Among these, melt extrusion is preferred from the viewpoint of productivity. When stretching the non-stretched film, uniaxial stretching (e.g., free-end uniaxial stretching, fixed-end uniaxial stretching) and / or biaxial stretching (e.g., sequential biaxial stretching, simultaneous biaxial stretching) may be performed.

[0080] The ratio Re(450) / Re(550), which is the ratio of the front retardation Re(450) at a wavelength of 450 nm to the front retardation Re(550) at a wavelength of 550 nm of the retardation film, is preferably 1.00 or more and 1.04 or less, more preferably 1.01 or more and 1.04 or less, and even more preferably 1.02 or more and 1.03 or less. When Re(450) / Re(550) is 1.00 or more and 1.04 or less, color shift is suppressed when used in combination with a negative C plate with flat dispersion.

[0081] The yellowness index of the retardation film is preferably 2.0 or less, more preferably 1.5 or less, and even more preferably 1.4 or less. When the yellowness index of the retardation film is 2.0 or less, the retardation film is less colored, and therefore the influence on the color rendering properties of the liquid crystal display panel is reduced. The yellowness index of the retardation film is, for example, 0.01 or more.

[0082] The retardation film may be coated with a coating layer, such as an easy-adhesion layer, an adhesive layer, or a hard coat layer.

[0083] (Triazine Compound) A triazine compound has positive intrinsic birefringence and steep wavelength dispersion characteristics, and therefore, when added to an acrylic resin having negative intrinsic birefringence, the retardation film exhibits flat dispersion.

[0084] The triazine compound is represented by the following formula (1) or (2): This reduces Re(450) / Re(550) of the retardation film. (In the formula, X １ is a substituted or unsubstituted aryl group, and Y １ and Z １ are each independently an aryl group substituted with an aryl group. (In the formula, X ２ is an aryl group substituted with a hydroxyl group or an alkoxy group having 5 or less carbon atoms and an alkoxy group having 5 or less carbon atoms; Y ２ and Z ２are each independently an aryl group substituted with a hydroxyl group and an alkoxy group having 5 or less carbon atoms.

[0085] X １ Examples of the aryl group in X include a phenyl group and a naphthyl group. Examples of the substituent in X include a hydroxyl group and a substituted or unsubstituted alkoxy group. The carbon number of the alkoxy group is, for example, 1 to 10. Examples of the substituent in the alkoxy group include an alkoxycarbonyl group. The carbon number of the alkoxycarbonyl group is, for example, 1 to 10. X １ When the aryl group in is a phenyl group, it is preferably substituted with a hydroxyl group at the 2-position and with a substituted or unsubstituted alkoxy group at the 4-position, and in this case, it is preferable that the 3-, 5-, and 6-positions of the phenyl group are not substituted.

[0086] Y １ and Z １ Examples of the aryl group in Y include a phenyl group and a naphthyl group. １ and Z １ Examples of the aryl group as a substituent in Y include a phenyl group and a naphthyl group. １ and Z １ When the aryl group in is a phenyl group, it is preferably substituted at the 4-position with an aryl group, and in this case, it is preferably not substituted at the 2-, 3-, 5- and 6-positions of the phenyl group.

[0087] X ２ Examples of the aryl group in X include a phenyl group and a naphthyl group. ２ The number of carbon atoms of the alkoxy group as a substituent in X is, for example, 1 or more and 5 or less. ２ When the aryl group in is a phenyl group, it is preferably substituted with a hydroxyl group at the 2-position and an alkoxy group at the 4-position, and in this case, it is preferable that the 3-, 5-, and 6-positions of the phenyl group are not substituted.

[0088] Y ２ and Z ２Examples of the aryl group in Y include a phenyl group and a naphthyl group. ２ and Z ２ The number of carbon atoms of the alkoxy group as a substituent in Y is, for example, 1 or more and 5 or less. ２ and Z ２ When the aryl group in is a phenyl group, it is preferably substituted with a hydroxyl group at the 2-position and an alkoxy group at the 4-position, and in this case, it is preferable that the 3-, 5-, and 6-positions of the phenyl group are not substituted.

[0089] X ２ , Y ２ or Z ２ When the carbon number of the alkoxy group as a substituent in the above formula is 6 or more, the Re(450) / Re(550) of the retardation film increases. The reason for this is unclear, but is presumed as follows. When the carbon number of the alkoxy group is 6 or more, a free volume proportional to the alkyl chain length is generated. As a result, the interaction between the triazine compound and the acrylic resin is reduced, making it difficult for the triazine compounds to be cooperatively oriented when the unstretched film is stretched.

[0090] Examples of the compound represented by formula (1) include 6-methylheptyl 2-[4-[4,6-bis(biphenyl-4-yl)-1,3,5-triazin-2-yl]-3-hydroxyphenoxy]propanoate and 2-[4,6-bis(1,1'-biphenyl-4-yl)-1,3,5-triazin-2-yl]-5-[(2-ethylhexyl)oxy]phenol.

[0091] Examples of the compound represented by formula (2) include 2,4,6-tris(4-butoxy-2-hydroxyphenyl)-1,3,5-triazine and 2,4-bis[4-butoxy-2-hydroxyphenyl]-6-(2,4-dibutoxyphenyl)-1,3,5-triazine.

[0092] The content of the triazine compound in the resin composition of this embodiment is 2% by weight or more and less than 5% by weight, preferably 2.5% by weight or more and less than 4.5% by weight, and more preferably 3% by weight or more and less than 4% by weight. When the content of the triazine compound in the resin composition of this embodiment is 2% by weight or more, the Re(450) / Re(550) of the retardation film becomes small, and when it is less than 5% by weight, the yellowness of the retardation film becomes low, and in addition to improving the heat resistance and birefringence expression, contamination of the cast roll during film formation is suppressed.

[0093] The molecular weight of the triazine compound is preferably from 100 to 1,500, more preferably from 300 to 1,000, even more preferably from 400 to 700, and particularly preferably from 500 to 680. When the molecular weight of the triazine compound is from 100 to 1,500, the compatibility with the acrylic resin is increased.

[0094] The 1% weight loss temperature of the triazine compound is preferably 340° C. or higher, more preferably 350° C. or higher, and even more preferably 360° C. or higher. When the 1% weight loss temperature of the triazine compound is 340° C. or higher, contamination of the casting roll during film formation is suppressed. The 1% weight loss temperature of the triazine compound is, for example, 420° C. or lower.

[0095] The maximum absorption wavelength of the triazine compound is preferably 340 nm or more, more preferably 345 nm or more, and even more preferably 350 nm or more. When the maximum absorption wavelength of the triazine compound is 340 nm or more, the Re(450) / Re(550) of the retardation film becomes small. The maximum absorption wavelength of the triazine compound is, for example, 400 nm or less.

[0096] (Acrylic Resin) The acrylic resin contains a (meth)acrylic acid ester unit and may or may not contain a styrene unit. The acrylic resin containing a styrene unit may be a random copolymer, a graft copolymer, or a block copolymer.

[0097] The resin composition of this embodiment may contain an acrylic resin and a resin containing a styrene unit. The resin containing a styrene unit is not particularly limited as long as it has good compatibility with the acrylic resin, and examples thereof include a styrene-acrylonitrile copolymer, a styrene-methacrylic acid copolymer, a styrene-methyl methacrylate copolymer, and a styrene-maleic anhydride copolymer. Among these, a styrene-acrylonitrile copolymer and a styrene-methyl methacrylate copolymer are preferred.

[0098] Examples of (meth)acrylic acid esters include alkyl (meth)acrylates such as methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, n-butyl (meth)acrylate, and isobutyl (meth)acrylate; aryl (meth)acrylates such as phenyl (meth)acrylate; aralkyl (meth)acrylates such as benzyl (meth)acrylate; and cycloalkyl (meth)acrylates such as cyclohexyl (meth)acrylate, and two or more of these may be used in combination. Among these, alkyl methacrylates are preferred, and methyl methacrylate is particularly preferred.

[0099] The acrylic resin preferably contains a ring structure in the main chain. The acrylic resin containing a ring structure in the main chain preferably contains one or more rings selected from the group consisting of glutarimide rings, lactone rings, maleic anhydride rings, maleimide rings, and glutaric anhydride rings in the main chain. Hereinafter, an acrylic resin containing a glutarimide ring or lactone ring in the main chain will be described as an example of an acrylic resin containing a ring structure in the main chain.

[0100] The acrylic resin containing a glutarimide ring in the main chain contains, for example, a constitutional unit represented by the following formula (3).

[0101] (In the formula, R １ and R ２ are each independently a hydrogen atom or an alkyl group having 1 to 8 carbon atoms, and R ３ is a hydrogen atom, an alkyl group having 1 to 18 carbon atoms, or a cycloalkyl group having 3 to 12 carbon atoms.

[0102] The acrylic resin containing the structural unit represented by formula (3) can be produced by a known method. An example of a method for producing the acrylic resin containing the structural unit represented by formula (3) will be described below.

[0103] First, a twin-screw extruder equipped with a die at the outlet is used to melt the methyl methacrylate-styrene copolymer, followed by imidization, and a strand is extruded from the die. Next, the strand is cooled using a water bath, and then pelletized using a pelletizer, to obtain an imidized methyl methacrylate-styrene copolymer. Next, a twin-screw extruder equipped with a die at the outlet is used to melt the imidized methyl methacrylate-styrene copolymer, followed by esterification, and a strand is extruded from the die. Next, the strand is cooled using a water bath, and then pelletized using a pelletizer, to obtain an acrylic resin containing a structural unit represented by formula (3).

[0104] Examples of the imidizing agent used to imidize the methyl methacrylate-styrene copolymer include ammonia and primary amines represented by the following formula (4). Among these, monomethylamine is preferred.

[0105] R ３ NH ２ (4) (wherein, R ３ is synonymous with formula (3).

[0106] Examples of esterifying agents used in esterifying the imidized methyl methacrylate-styrene copolymer include dimethyl carbonate, 2,2-dimethoxypropane, dimethyl sulfoxide, triethyl orthoformate, trimethyl orthoacetate, trimethyl orthoformate, diphenyl carbonate, dimethyl sulfate, methyl toluene sulfonate, methyl trifluoromethyl sulfonate, methyl acetate, methanol, ethanol, methyl isocyanate, p-chlorophenyl isocyanate, dimethyl carbonate, Examples of suitable glycidyl ethers include diimide, dimethyl-t-butylsilyl chloride, isopropenyl acetate, dimethylurea, tetramethylammonium hydroxide, dimethyldiethoxysilane, tetra-n-butoxysilane, dimethyl(trimethylsilane)phosphite, trimethyl phosphite, trimethyl phosphate, tricresyl phosphate, diazomethane, ethylene oxide, propylene oxide, cyclohexene oxide, 2-ethylhexyl glycidyl ether, phenyl glycidyl ether, and benzyl glycidyl ether. Among these, dimethyl carbonate is preferred.

[0107] The acrylic resin having a lactone ring in the main chain can be obtained, for example, by polymerizing a monomer represented by the following formula (5) and then heat treating it to form a lactone ring.

[0108] (In the formula, R ４ and R ５ are each independently a hydrogen atom or an alkyl group having 1 to 20 carbon atoms.

[0109] Examples of the monomer represented by formula (5) include methyl 2-(hydroxymethyl)acrylate, ethyl 2-(hydroxymethyl)acrylate, isopropyl 2-(hydroxymethyl)acrylate, n-butyl 2-(hydroxymethyl)acrylate, and t-butyl 2-(hydroxymethyl)acrylate, and two or more of these may be used in combination. Among these, methyl 2-(hydroxymethyl)acrylate and ethyl 2-(hydroxymethyl)acrylate are preferred, and methyl 2-(hydroxymethyl)acrylate is particularly preferred.

[0110] As the acrylic resin containing a ring structure in the main chain other than the acrylic resin containing a glutarimide ring or lactone ring in the main chain, known acrylic resins used in retardation films can be used.

[0111] The content of the structural unit containing a ring structure in the acrylic resin containing a ring structure in the main chain is preferably 2% by weight or more and 50% by weight or less, and more preferably 4% by weight or more and 30% by weight or less. When the content of the structural unit containing a ring structure in the acrylic resin containing a ring structure in the main chain is 2% by weight or more, the heat resistance of the retardation film is increased, and when it is 50% by weight or less, sufficient retardation is exhibited even if the retardation film is thin.

[0112] The acrylic resin may further contain other monomer units. Examples of the other monomers include, but are not limited to, aromatic vinyls other than styrene, such as methylstyrene, and (meth)acrylonitrile.

[0113] (Method for Producing Retardation Film) The retardation film can be produced by using a known method. An example of the method for producing a retardation film will be described below.

[0114] First, an acrylic resin and a triazine compound are kneaded using an extruder equipped with a die at the outlet, and then a strand is extruded from the die. Next, the strand is cooled using a water tank, and then the strand is pelletized using a pelletizer to obtain the resin composition of this embodiment. Next, the resin composition of this embodiment is melted using an extruder equipped with a T-die at the outlet, and then a sheet is extruded from the T-die and cooled with a cooling roll to obtain a non-stretched film. Next, the non-stretched film is uniaxially stretched to obtain a retardation film.

[0115] The temperature when the non-stretched film is uniaxially stretched is preferably (Tg + 5)°C or higher and (Tg + 20)°C or lower, more preferably (Tg + 6)°C or higher and (Tg + 18)°C or lower, and even more preferably (Tg + 7)°C or higher and (Tg + 15)°C or lower, where Tg is the glass transition temperature of the resin composition of this embodiment. The areal stretching ratio when the non-stretched film is uniaxially stretched is, for example, 2 times or higher and 10 times or lower. The stretching speed when the non-stretched film is uniaxially stretched is, for example, 1.1 times or higher / min and 100 times or lower.

[0116] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and the above-described embodiments may be modified as appropriate within the scope of the spirit of the present invention.

[0117] Examples of the present invention will be described below, but the present invention is not limited to these examples.

[0118] (Imidization rate) The imidization rate of the acrylic resin was calculated using a Fourier transform infrared spectrophotometer FT / IR-4X (manufactured by JASCO Corporation). That is, the IR spectrum of a solution in which the acrylic resin was dissolved in methylene chloride was measured at room temperature, and then the imidization rate was calculated by measuring the IR spectrum at 1720 cm －１ Absorption intensity Abs attributed to the carbonyl group of the ester ｅｓｔｅｒ and 1660 cm －１ Absorption intensity Abs attributed to the carbonyl group of the imide ｉｍｉｄｅ From the formula Abs ｉｍｉｄｅ / (Abs ｅｓｔｅｒ +Abs ｉｍｉｄｅ ) × 100 to determine the imidization rate (%).

[0119] (1% Weight Loss Temperature Td1) Using a thermogravimetric and differential scanning calorimeter STA7200 (manufactured by Hitachi High-Tech Science), 10 mg of a compound was heated from room temperature at a heating rate of 10°C / min in a nitrogen atmosphere, and the temperature Td1 at which the weight lost 1% was determined.

[0120] (Maximum absorption wavelength λmax) Using a UV-visible spectrophotometer V-560 (manufactured by JASCO Corporation), the UV-visible absorption spectrum of a solution prepared by dissolving the compound in a chloroform solution at a concentration of 10 mg / L was measured to determine the maximum absorption wavelength λmax.

[0121] (Glass transition temperature Tg) Using a high-sensitivity differential scanning calorimeter DSC7000X (manufactured by Hitachi High-Tech Science), 10 mg of the resin composition was heated at a heating rate of 10°C / min in a nitrogen atmosphere, and the glass transition temperature Tg was determined by the midpoint method.

[0122] (Birefringence development Δnxy) After cutting out a range of 30 × 100 mm from the raw film, the raw film was subjected to free-end uniaxial stretching at a temperature 5 ° C. higher than the glass transition temperature of the film so that the stretching ratio in the machine direction (longitudinal direction) was 2 times, and after annealing for 20 seconds, the film was removed from the stretching oven to obtain a uniaxially stretched film. Next, using a retardation measuring device KOBRA-WR (manufactured by Oji Scientific Instruments), the front retardation of the center part of the uniaxially stretched film was measured, and then divided by the thickness of the uniaxially stretched film to obtain birefringence development Δnxy.

[0123] (Wavelength dispersion) Using a retardation measuring device KOBRA-WR (manufactured by Oji Scientific Instruments), the wavelength dispersion of the retardation film was evaluated. First, from the measured values ​​of the front retardation at wavelengths of 450 nm, 550 nm, and 650 nm, the approximation function of the software was used to fit to the Sellmeirer equation, and a wavelength dispersion curve was obtained. At this time, the absorption edge wavelength was set to 0 nm. Next, from the front retardation Re (450), Re (550), and Re (650) at wavelengths of 450 nm, 550 nm, and 650 nm obtained from the wavelength dispersion curve, Re (450) / Re (550) and Re (650) / Re (550) were calculated.

[0124] (Yellowness Index YI) The yellowness index YI of the retardation film was measured using a color meter SC-P (manufactured by Suga Test Instruments) in accordance with JIS K7373:2006.

[0125] (Total Light Transmittance) The total light transmittance of the retardation film was measured using a haze meter HZ-V3 (manufactured by Suga Test Instruments) in accordance with JIS K7361-1:1997.

[0126] (Haze) The haze of the retardation film was measured using a haze meter NDH2000 (manufactured by Nippon Denshoku Industries Co., Ltd.) in accordance with JIS 7136:2000.

[0127] (Roll Contamination Resistance) During the production of the raw film, the cast roll was visually observed to evaluate the roll contamination resistance. The criteria for roll contamination resistance are as follows: A: When no deposits are found on the cast roll B: When deposits are found on the cast roll

[0128] (Production of Acrylic Resin 1) The temperature setting for each temperature control zone of a 40 mm diameter co-rotating intermeshing twin-screw extruder (L / D = 90) equipped with a die at the outlet was 250 to 280 ° C., the screw rotation speed was 225 rpm, and a methyl methacrylate-styrene copolymer MS750LF (manufactured by Toyo Styrene) having a styrene unit content of 25 wt% was melted and filled using a kneading block. Next, 3.6 wt% of monomethylamine (manufactured by Mitsubishi Gas Chemical Company) was added to the methyl methacrylate-styrene copolymer through a nozzle to imidize the methyl methacrylate-styrene copolymer. Next, the strand extruded from the die was cooled using a water bath, and then the strand was pelletized using a pelletizer to obtain Resin (I).

[0129] The temperature setting for each temperature-controlled zone of a 40 mm diameter co-rotating intermeshing twin-screw extruder (L / D = 90) equipped with a die at the outlet was set to 240-280°C, and the screw rotation speed was set to 225 rpm. Resin (I) was melted and filled using a kneading block. Next, 2.0 wt% of dimethyl carbonate was added to resin (I) through the nozzle to esterify the carboxyl groups in resin (I). At this time, by-products and excess dimethyl carbonate were removed after the reaction. Next, the strand extruded from the die was cooled in a water bath and then pelletized using a pelletizer to obtain acrylic resin 1. Acrylic resin 1 had an imidization rate of 30%.

[0130] Example 1: A mixture of 98 wt% acrylic resin 1 and 2 wt% Tinuvin 479 (manufactured by BASF) (hereinafter referred to as TA-1) was kneaded using a 15 mm diameter co-rotating intermeshing twin-screw extruder (L / D = 45) equipped with a die at the outlet. The strand extruded from the die at the extruder outlet was then cooled in a water bath, pelletized using a pelletizer, and dried at 100°C for 5 hours to obtain a resin composition. The resin composition had a glass transition temperature of 120°C. TA-1 is 6-methylheptyl 2-[4-[4,6-bis(biphenyl-4-yl)-1,3,5-triazin-2-yl]-3-hydroxyphenoxy]propanoate.

[0131] The resin composition was melted using a 15 mm diameter intermeshing co-rotating twin-screw extruder (L / D = 45) equipped with a T-die at the outlet, and then the sheet extruded from the T-die was cooled using a cooling roll to obtain a raw film having a width of 160 mm and a thickness of 160 μm. Next, the raw film was uniaxially stretched using a uniaxial stretching machine at a stretching temperature of 130 ° C. and a stretch ratio of 2 to obtain a retardation film.

[0132] Example 2 A retardation film was obtained in the same manner as in Example 1, except that 2,4,6-tris(4-butoxy-2-hydroxyphenyl)-1,3,5-triazine (hereinafter referred to as TA-2) was used instead of TA-1.

[0133] Example 3 A retardation film was obtained in the same manner as in Example 1, except that the contents of acrylic resin 1 and TA-1 were changed to 97 wt % and 3 wt %, respectively.

[0134] Example 4 A retardation film was obtained in the same manner as in Example 3, except that TA-2 was used instead of TA-1.

[0135] Example 5 A retardation film was obtained in the same manner as in Example 3, except that 1.5% by weight of TA-1 and 1.5% by weight of TA-2 were used instead of 3% by weight of TA-1.

[0136] Example 6 A retardation film was obtained in the same manner as in Example 3, except that UV-460 (manufactured by Rianlon) (hereinafter referred to as TA-3) was used instead of TA-1. Here, TA-3 is 2,4-bis[4-butoxy-2-hydroxyphenyl]-6-(2,4-dibutoxyphenyl)-1,3,5-triazine.

[0137] Example 7 A retardation film was obtained in the same manner as in Example 1, except that Tinuvin 1600 (manufactured by BASF) (hereinafter referred to as TA-4) was used instead of TA-1, and the contents of Acrylic Resin 1 and TA-4 were changed to 96 wt % and 4 wt %, respectively. Here, TA-4 is 2-[4,6-bis(1,1'-biphenyl-4-yl)-1,3,5-triazin-2-yl]-5-[(2-ethylhexyl)oxy]phenol.

[0138] Comparative Example 1 A retardation film was obtained in the same manner as in Example 1, except that TA-1 was not used.

[0139] Comparative Example 2 A retardation film was obtained in the same manner as in Example 3, except that LA-F70 (manufactured by ADEKA) (hereinafter referred to as TA-5) was used instead of TA-1. Here, TA-5 is 2,4,6-tris(2-hydroxy-4-hexyloxy-3-methylphenyl)-1,3,5-triazine.

[0140] Comparative Example 3 A retardation film was obtained in the same manner as in Example 3, except that 1,6-diphenyl-1,3,5-hexatriene (DPH) was used instead of TA-1.

[0141] Comparative Example 4 A retardation film was obtained in the same manner as in Example 3, except that LA-31 (manufactured by ADEKA) (hereinafter referred to as BT-1) was used instead of TA-1. Here, BT-1 is 2,2'-methylenebis[6-(2H-benzotriazol-2-yl)-4-(1,1,3,3-tetramethylbutyl)phenol].

[0142] (Comparative Example 5) A retardation film was obtained in the same manner as in Example 1, except that the contents of acrylic resin 1 and TA-1 were changed to 94% by weight and 6% by weight, respectively. (Comparative Example 6) A retardation film was obtained in the same manner as in Example 3, except that Tinuvin 477 (manufactured by BASF) (hereinafter referred to as TA-6) was used instead of TA-1. Here, TA-6 is 2,4-bis[4-(1-octoxy-1-oxopropan-2yl)-2-hydroxyphenyl]-6-(2,4-bis(1-octoxy-1-oxopropan-2yl))-1,3,5-triazine.

[0143] Comparative Example 7 A retardation film was obtained in the same manner as in Example 3, except that LA-46 (manufactured by ADEKA) (hereinafter referred to as TA-7) was used instead of TA-1. Here, TA-7 is 2-(4,6-diphenyl-1,3,5-triazin-2-yl)-5-[2-(2-ethylhexanoyloxy)ethoxy]phenol.

[0144] Comparative Example 8 A retardation film was obtained in the same manner as in Example 3, except that Tinuvin 400 (manufactured by BASF) (hereinafter referred to as TA-8) was used instead of TA-1. Here, TA-8 is a mixture of 2-[4-[(2-hydroxy-3-dodecyloxypropyl)oxy]-2-hydroxyphenyl]-4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine and 2-[4-[(2-hydroxy-3-tridecyloxypropyl)oxy]-2-hydroxyphenyl]-4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine.

[0145] Table 1 shows the properties of TA, BT and DPH.

[0146]

[0147] Table 2 shows the properties and evaluation results of the retardation film.

[0148]

[0149] From Table 2, it can be seen that the retardation films of Examples 1 to 7 have high heat resistance, birefringence development, and roll contamination resistance. Furthermore, since the retardation films of Examples 1 to 7 have an Re(450) / Re(550) of 1.01 to 1.04, as described below, color shift is suppressed when used in combination with a flat-dispersion negative C-plate. In contrast, the retardation films of Comparative Examples 1, 2, 4, and 6 to 8 have an Re(450) / Re(550) of 1.05 to 1.07, as described below, color shift occurs when used in combination with a flat-dispersion negative C-plate. The retardation film of Comparative Example 3 contains DPH with a Td1 of 193 ° C., and therefore has low roll contamination resistance. The retardation film of Comparative Example 4 contains BT-1 with a Td1 of 321 ° C., and therefore has low roll contamination resistance. The retardation film of Comparative Example 5 has a TA-1 content of 6 wt%, and therefore has low heat resistance, birefringence development, and roll contamination resistance. The retardation films of Comparative Examples 6 and 8 contain TA-6 and TA-8, respectively, and therefore have low birefringence development. The retardation film of Comparative Example 7 contains TA-7, which has a Td1 of 331°C, and therefore has low birefringence development and roll contamination resistance.

[0150] (Color Shift) Using a liquid crystal simulator LCD Master (manufactured by Shintech), the influence of the Re(450) / Re(550) of the positive B plate on the color shift was calculated. At this time, a light source side polarizing plate, an IPS liquid crystal cell, a negative C plate, a positive B plate, and a viewer side polarizing plate were stacked in this order. The optical axis of the positive B plate was set parallel to the absorption axis of the viewer side polarizing plate. The color difference ΔE in the LAB color system when the polar angle and azimuth angle were changed relative to the frontal observation in the black display state was calculated. ＊ ａｂ The values ​​were plotted as contour lines, and the value at the point with the largest value was taken as the color difference.

[0151] The light source data was the attached BackLight, the polarizer data was the attached SEG1423, and the liquid crystal cell was the attached MLC-6686 with a gap thickness of 2 μm. The negative C plate was set to a thickness of 40 μm, with a front retardation of 0 nm and a thickness direction retardation of 110 nm, and no wavelength dispersion was set (assuming flat dispersion). The positive B plate was set to a thickness of 40 μm, with a front retardation of 110 nm and a thickness direction retardation of -130 nm at a wavelength of 550 nm, and the front retardation Re (550) at a wavelength of 450 nm was set so that Re (450) / Re (550) was a predetermined value.

[0152] Table 3 shows the evaluation results of the color difference.

[0153]

[0154] From Table 3, when the negative C plate has flat dispersion, if the Re(450) / Re(550) of the negative B plate is 1.07 (normal dispersion), ΔE ＊ ａｂ On the other hand, when the Re(450) / Re(550) of the negative B plate is 1.00 to 1.03 (flat dispersion), ΔE ＊ ａｂ is smaller, so the color shift is smaller.

Claims

1. A retardation film formed from a resin composition containing an acrylic resin, wherein the ratio Re(450) / Re(550) of the front retardation at a wavelength of 450 nm to the front retardation at a wavelength of 550 nm, Re(450) / Re(550), is 1.00 or more and 1.04 or less, and the resin composition contains 20% by weight or more of styrene units, has a glass transition temperature of 118°C or more, and has a birefringence development index Δnxy of -3.0 × 10 －３ Above -1.1 x 10 －３ The following is a retardation film.

2. The retardation film according to claim 1, wherein the resin composition contains a triazine compound, and the content of the triazine compound is 2% by weight or more and less than 5% by weight.

3. The retardation film according to claim 2, wherein the triazine compound has a 1% weight loss temperature of 340°C or higher.

4. The retardation film according to claim 2 or 3, wherein the triazine compound has a maximum absorption wavelength of 340 nm or more.

5. The retardation film according to claim 2 or 3, wherein the triazine compound is represented by the following formula (1) or (2): (In the formula, X １ is a substituted or unsubstituted aryl group, and Y １ and Z １ are each independently an aryl group substituted with an aryl group. (In the formula, X ２ is an aryl group substituted with a hydroxyl group or an alkoxy group having 5 or less carbon atoms and an alkoxy group having 5 or less carbon atoms; Y ２ and Z ２ are each independently an aryl group substituted with a hydroxyl group and an alkoxy group having 5 or less carbon atoms.

6. A retardation film according to any one of claims 1 to 3, wherein the acrylic resin contains a ring structure in the main chain.

7. The retardation film according to any one of claims 1 to 3, having a yellowness index of 2.0 or less.

8. A polarizing plate comprising the retardation film according to any one of claims 1 to 3.

9. A liquid crystal display panel comprising the polarizing plate according to claim 8.

10. A resin composition containing an acrylic resin and a triazine compound, wherein the content of the triazine compound is 2% by weight or more and less than 5% by weight, the resin composition contains 20% by weight or more of styrene units, the glass transition temperature is 118°C or more, and the birefringence Δnxy is -3.0 × 10 －３ Above -1.1 x 10 －３ The resin composition is as follows: wherein the triazine compound is represented by the following formula (1) or the following formula (2). (In the formula, X １ is a substituted or unsubstituted aryl group, and Y １ and Z １ are each independently an aryl group substituted with an aryl group. (In the formula, X ２ is an aryl group substituted with a hydroxyl group or an alkoxy group having 5 or less carbon atoms and an alkoxy group having 5 or less carbon atoms; Y ２ and Z ２ are each independently an aryl group substituted with a hydroxyl group and an alkoxy group having 5 or less carbon atoms.

11. The resin composition according to claim 10, wherein the triazine compound has a 1% weight loss temperature of 340°C or higher.

12. The resin composition according to claim 10 or 11, wherein the triazine compound has a maximum absorption wavelength of 340 nm or more.

13. The resin composition according to claim 10 or 11, wherein the acrylic resin contains a ring structure in the main chain.

14. The resin composition according to claim 10 or 11, which is in the form of pellets.

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