JP2010191385A - Retardation plate - Google Patents

Abstract

Provided is a retardation plate that has optical properties advantageous as a retardation plate and that does not change in birefringence compensation ability even when left in a high temperature environment.
An A layer made of a material having a deflection temperature under load Ts (A), a B layer made of a material having a deflection temperature under load Ts (B), and a laminated film comprising a C layer interposed therebetween. A phase difference plate, wherein the difference between Ts (A) and Ts (B) is 5 ° C. or more, the A layer is made of polynorbornene resin, and the B layer is a vinyl alicyclic hydrocarbon polymer. Made of resin, and the C layer is composed of 5 to 80% by weight of polymer blocks composed of polymer units based on styrene, polymer units based on butadiene, polymer units based on isoprene, polymer units that are hydrides of these polymer units, And a retardation plate comprising a resin comprising a copolymer composed of 95 to 20% by weight of a block comprising polymer units selected from the group consisting of combinations thereof.
[Selection] Figure 1

Description

  The present invention relates to a phase difference plate.

In order to reduce the angle dependency of the color tone of the liquid crystal display device, the relationship between retardation Re at an incident angle of 0 ° and retardation R ₄₀ at an incident angle of 40 ° is 0.92 ≦ R ₄₀ /Re≦1.08. and phase feedboard satisfying, the slow axis direction of the refractive indices n _x in the plane, it and the refractive index n _y in the direction perpendicular in the plane, and the refractive index n _z in the thickness direction, n _x> n retardation plate satisfying the relation _z> n _y (viewing angle compensating plate) has been proposed.

For example, in Patent Document 1, a polycarbonate resin film is uniaxially stretched to obtain a first anisotropic film, while a polystyrene resin film is uniaxially stretched to obtain a second anisotropic film. by overlapping the anisotropic film and the second anisotropic film so that the stretching direction is perpendicular, it is described that to obtain a retardation plate satisfying the relation of n _x> n _z> n _y Yes.
In Patent Document 2, a polycarbonate resin film is uniaxially stretched to obtain a first anisotropic film, while a polystyrene resin film is uniaxially stretched to obtain a second anisotropic film. It is described that a retardation film satisfying (Re-Re ₄₀ ) /Re≦0.07 was obtained by superimposing an isotropic film and a second anisotropic film so that the stretching direction was a right angle. Has been.

In Patent Document 3, when a resin film is stretched, a shrinkable film is adhered to one or both sides of the resin film to form a laminate, and the laminate is heated and stretched to stretch the resin film. by imparting direction shrinkage force perpendicular to the _{direction, 0 <(n x -n z} ) / (n x -n y) < can obtain a phase difference plate which satisfies the first relationship is described.

In Patent Document 4, a polycarbonate resin is melt-extruded to obtain a rod rod, the rod rod is cut into circles to obtain a disc, a rectangular plate is cut out from the disc, and the rectangular plate is uniaxially stretched. , 0.92 ≦ Re ₄₀ /Re≦1.08 is obtained.

Japanese Patent Laid-Open No. 3-24502 Japanese Patent Laid-Open No. 3-141303 JP-A-5-157911 JP-A-2-160204

However, when the retardation plate described in the above-mentioned patent document is left in a high temperature environment, the retardation value may fluctuate, causing a shift in birefringence compensation.
An object of the present invention is to provide a retardation plate that has optical properties advantageous as a retardation plate and that does not change in birefringence compensation ability even when left in a high temperature environment. .

  As a result of investigations to achieve the above object, the present inventor has found that a retardation plate having a plurality of layers each made of a predetermined material having a predetermined specification can solve the problem. completed.

That is, the present invention includes the following aspects.
[1] An A layer made of a material having a deflection temperature under load of Ts (A) ° C., a B layer made of a material having a deflection temperature under load of Ts (B) ° C., and interposed between the A layer and the B layer. A retardation film comprising a laminated film comprising a C layer as a bonding layer,
There is a difference of 5 ° C. or more between the Ts (A) and the Ts (B),
The A layer is made of polynorbornene resin,
The B layer is made of a vinyl alicyclic hydrocarbon polymer resin,
From the group consisting of 5 to 80% by weight of a polymer block composed of polymer units based on styrene, a polymer unit based on butadiene, a polymer unit based on isoprene, and a polymer unit that is a hydride of these polymer units. A phase difference plate comprising a resin comprising a copolymer composed of 95 to 20% by weight of a block comprising at least one polymerized unit selected.
[2] One direction in the plane of the retardation plate is the X axis, the direction perpendicular to the X axis in the plane is the Y axis, and the thickness direction is the Z axis. When measured with a uniaxial stretching of 1.25 times in the direction, the incident light is incident at an incident angle of 0 °, and the vibration plane of the electric vector is incident at an incident angle of 0 ° with respect to the linearly polarized light ΨY on the YZ plane. The phase difference plate, wherein the phase of the linearly polarized light ΨX having the vibration plane in the XZ plane has a stretching temperature T _α lagging behind that before stretching and a stretching temperature T _β proceeding more than before stretching.
[3] The retardation plate has a retardation R ₄₅₀ at an incident angle of 0 ° in light having a wavelength of 450 nm, a retardation R ₅₅₀ at an incident angle of 0 ° in light having a wavelength of 550 nm, and an incident angle of 0 ° in light having a wavelength of 650 nm. The retardation plate in which retardation R ₆₅₀ satisfies the relationship of R ₄₅₀ <R ₅₅₀ <R ₆₅₀ .
[4] The refractive index nx in the in-plane slow axis direction of the retardation plate, the refractive index ny in the direction orthogonal to the slow axis in the plane, and the refractive index nz in the thickness direction are 0 <(nx -Nz) / (nx-ny) <1 which satisfies the relationship.

  The retardation plate of the present invention has advantageous optical properties as a retardation plate by the combination of the A layer and the B layer, and does not cause problems such as peeling even when left in a high temperature environment. The birefringence compensation does not fluctuate and has excellent durability. Therefore, an optical device such as a liquid crystal display device having excellent durability can be configured.

FIG. 1 shows the temperature dependence of the development of retardation when a film consisting only of a layer and a film consisting only of b layer are each stretched, and when a pre-stretching film including a layer and b layer is stretched It is a graph which shows the temperature dependence of the expression of phase difference.

  The retardation plate of the present invention includes an A layer made of a material having a deflection temperature under load of Ts (A), a B layer made of a material having a deflection temperature under load of Ts (B), and the A layer and the B layer. It consists of a laminated film comprising a C layer as a bonding layer interposed therebetween.

  The retardation plate of the present invention may have only one A layer and one B layer, or may have two or more A layers and / or B layers. Specifically, for example, A layer-C layer-B layer, B layer-C layer-A layer-C layer-B layer, A layer-C layer-B layer-C layer-A layer, B layer-C layer It can have various layer configurations such as -A layer-C layer-B layer-C layer-A layer. In particular, a layer configuration in which B layers are provided on both sides of the A layer, such as B layer-C layer-A layer-C layer-B layer, is preferable from the viewpoint of securing strength and reducing warpage.

(A layer)
The A layer is made of polynorbornene resin. The polynorbornene resin is a resin containing a norbornene polymer.
Norbornene polymers include ring-opening polymers of norbornene monomers, ring-opening copolymers of norbornene monomers and other monomers capable of ring-opening copolymerization thereof, hydrides thereof, addition polymers of norbornene monomers, norbornene monomers And other copolymers copolymerizable therewith. Examples of the norbornene monomer include bicyclo [2.2.1] -hept-2-ene (common name: norbornene) and derivatives thereof (having a substituent in the ring), tricyclo [4.3.1 ^2,5 . 0 ^1,6 ] -deca-3,7-diene, tetracyclo [7.4.1 ^10,13 . 0 ^1,9 . 0 ^2,7 ] -trideca-2,4,6,11-tetraene, tetracyclo [4.4.1 ^2,5 . 1 ^7,10 . 0] -dodecaene and derivatives having a substituent on these rings. Examples of the substituent present in the ring include an alkyl group, an alkylene group, a vinyl group, and an alkoxycarbonyl group, and the norbornene monomer may have two or more of these. These norbornene monomers may be used alone or in combination of two or more. Examples of other monomers capable of ring-opening copolymerization with norbornene monomer include monocyclic olefin monomers such as cyclohexene, cycloheptene, and cyclooctene. These other monomers copolymerizable with the norbornene monomer can be used alone or in combination of two or more. In the case of addition copolymerization of a norbornene monomer and another monomer copolymerizable therewith, the ratio of the structural unit derived from the norbornene monomer and the structural unit derived from the other monomer copolymerizable in the addition copolymer is The weight ratio is appropriately selected to be in the range of 30:70 to 99: 1, preferably 50:50 to 97: 3, and more preferably 70:30 to 95: 5. Other monomers capable of addition copolymerization with norbornene monomer include α-olefins having 2 to 12 carbon atoms such as ethylene, propylene and 1-butene; styrenes such as styrene and α-methylstyrene; 1,3-butadiene And chain conjugated dienes such as isoprene; and vinyl ethers such as ethyl vinyl ether.

  The polynorbornene resin can contain various compounding agents as required in addition to the norbornene polymer. Compounding agents include, for example, lubricants; layered crystal compounds; antioxidants, heat stabilizers, light stabilizers, weathering stabilizers, UV absorbers, near infrared absorbers and other stabilizers; plasticizers; dyes and pigments, etc. Coloring agents; antistatic agents; and the like. In particular, it is preferable to add a lubricant or an ultraviolet absorber since flexibility and weather resistance can be improved.

  As the lubricant, inorganic particles such as silicon dioxide, titanium dioxide, magnesium oxide, calcium carbonate, magnesium carbonate, barium sulfate, strontium sulfate; polymethyl acrylate, polymethyl methacrylate, polyacrylonitrile, polystyrene, cellulose acetate, cellulose acetate propionate Organic particles such as In the present invention, organic particles are preferred as the lubricant.

  UV absorbers include oxybenzophenone compounds, benzotriazole compounds, salicylic acid ester compounds, benzophenone UV absorbers, benzotriazole UV absorbers, acrylonitrile UV absorbers, triazine compounds, nickel complex compounds, inorganic Examples include powder. Suitable ultraviolet absorbers include 2,2′-methylenebis (4- (1,1,3,3-tetramethylbutyl) -6- (2H-benzotriazol-2-yl) phenol), 2- (2 '-Hydroxy-3'-tert-butyl-5'-methylphenyl) -5-chlorobenzotriazole, 2,4-di-tert-butyl-6- (5-chlorobenzotriazol-2-yl) phenol, 2 2,2′-dihydroxy-4,4′-dimethoxybenzophenone, 2,2 ′, 4,4′-tetrahydroxybenzophenone, and particularly preferred is 2,2′-methylenebis (4- (1, 1,3,3-tetramethylbutyl) -6- (2H-benzotriazol-2-yl) phenol).

  The amount of the compounding agent can be appropriately determined within a range not impairing the object of the present invention. For example, it can be set to an amount within a range in which the total light transmittance at 1 mm thickness can be maintained at 80% or more. The content ratio of the norbornene polymer in the polynorbornene resin composed of the norbornene polymer and the compounding agent can be 90 to 100% by weight.

  As the polynorbornene resin, a norbornene polymer having a positive intrinsic birefringence value can be preferably used. The intrinsic birefringence value being positive means that the refractive index in the stretching direction is larger than the refractive index in the direction orthogonal thereto. Intrinsic birefringence can also be calculated from the dielectric constant distribution.

  The load deflection temperature Ts (A) of the polynorbornene resin is preferably 80 ° C. or higher, more preferably 110 ° C. or higher, and particularly preferably 120 ° C. or higher. When the deflection temperature under load is lower than the lower limit value, it is not preferable because the orientation is easily relaxed.

(B layer)
The B layer is made of a vinyl alicyclic hydrocarbon polymer resin.
The vinyl alicyclic hydrocarbon polymer resin contains a vinyl alicyclic hydrocarbon polymer. With vinyl alicyclic hydrocarbon polymer
(i) a polymer having a polymer unit obtained by vinyl addition polymerization of an alicyclic hydrocarbon compound having a vinyl group (hereinafter abbreviated as vinyl alicyclic hydrocarbon compound), or
(ii) A polymer having the same structure as that of the polymer (i) and obtained by another method (for example, a method in which an aromatic hydrocarbon compound having a vinyl group is polymerized and then hydrogenated). This refers to coalescence.

  The vinyl alicyclic hydrocarbon polymer is mainly composed of, for example, the vinyl alicyclic hydrocarbon compound such as vinyl cycloalkene or vinyl cycloalkane or an aromatic hydrocarbon compound having a vinyl group (vinyl aromatic compound), If a monomer mixture containing a monomer copolymerizable with these compounds is subjected to vinyl addition polymerization as necessary, and an unsaturated bond (including an aromatic ring moiety) is present in the polymer, It is obtained by hydrogenating the unsaturated bond. A polymer unit obtained by vinyl addition polymerization of the above alicyclic hydrocarbon compound having a vinyl group is represented by the following general formula (1).

  [In Formula (1), X is an alicyclic hydrocarbon group, and R1 to R3 are each independently a hydrogen atom, a chain hydrocarbon group, a halogen atom, an alkoxy group, a hydroxyl group, an ester group, a cyano group, It is a chain hydrocarbon group substituted with an amide group, an imide group, a silyl group, or a polar group (halogen atom, alkoxy group, hydroxyl group, ester group, cyano group, amide group, imide group, or silyl group). n1 is an integer of 1 or more. ] Is represented.

  X in Formula (1) represents an alicyclic hydrocarbon group, and the number of carbon atoms constituting the ring is usually 4 to 20, preferably 5 to 7, from the viewpoint of mechanical strength and the like.

In the present invention, the vinyl alicyclic hydrocarbon polymer may have a group containing a carbon-carbon unsaturated bond such as an aromatic hydrocarbon group in part, but the content of the unsaturated bond Is 20% or less, preferably 10% or less, more preferably 5% or less of the total carbon-carbon bonds in the vinyl alicyclic hydrocarbon polymer from the viewpoint of low birefringence, transparency and the like. In addition, content of a carbon-carbon unsaturated bond can be calculated | required by < ¹ > H-NMR measurement.

  R1 to R3 are each preferably a hydrogen atom or a chain hydrocarbon group having 1 to 6 carbon atoms from the viewpoints of heat resistance, mechanical strength, and the like. Examples of the chain hydrocarbon group include an alkyl group and an alkenyl group, and an alkyl group is preferable.

  The content of the above polymerized units in the vinyl alicyclic hydrocarbon polymer is usually 50% by weight or more, preferably 70% by weight or more, more preferably 80% by weight or more, from the viewpoint of heat resistance and mechanical strength. Preferably it is 90 weight% or more.

  The weight average molecular weight (Mw) of the vinyl alicyclic hydrocarbon polymer is a polystyrene conversion value measured by GPC, and is usually 10,000 to 1,000,000, preferably 50,000 to 500,000. Preferably, it is in the range of 80,000 to 300,000, and the molecular weight distribution is a weight average molecular weight (Mw) and a number average molecular weight (Mn) in terms of polystyrene measured by gel permeation chromatography (GPC) method. The ratio (Mw / Mn) is usually 5 or less, preferably 3 or less, more preferably 2.5 or less, and most preferably 2 or less. When Mw / Mn is in the above range, the polymer is particularly excellent in mechanical strength and heat resistance, and when the weight average molecular weight (Mw) is in the above range, the obtained retardation plate is excellent in mechanical strength and moldability. Therefore, it is preferable.

  Specific examples of the vinyl aromatic compound as a monomer used for the polymerization of the vinyl alicyclic hydrocarbon polymer include styrene, α-methyl styrene, α-ethyl styrene, α-propyl styrene, α-isopropyl styrene, α -T-butylstyrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, 2,4-diisopropylstyrene, 2,4-dimethylstyrene, 4-t-butylstyrene, 5-t-butyl-2- Styrenes such as methylstyrene, monochlorostyrene, dichlorostyrene, monofluorostyrene, 4-phenylstyrene, and the like. Specific examples of vinyl alicyclic hydrocarbon compounds include vinyl cyclohexane, vinyl such as 3-methylisopropenylcyclohexane, and the like. Cyclohexanes; 4-vinylcyclohexene, 4-isopro Examples thereof include vinylcyclohexenes such as penylcyclohexene, 1-methyl-4-vinylcyclohexene, 1-methyl-4-isopropenylcyclohexene, 2-methyl-4-vinylcyclohexene and 2-methyl-4-isopropenylcyclohexene.

  In the present invention, the above compound may be copolymerized with another monomer copolymerizable with the compound. Examples of the copolymerizable monomer include α-olefin monomers such as ethylene, propylene, isobutene, 2-methyl-1-butene, 2-methyl-1-pentene, and 4-methyl-1-pentene; Cyclopentadiene-based monomers such as pentadiene, 1-methylcyclopentadiene, 2-methylcyclopentadiene, 2-ethylcyclopentadiene, 5-methylcyclopentadiene, 5,5-dimethylcyclopentadiene, dicyclopentadiene; cyclobutene, cyclopentene, Monocyclic olefin monomers such as cyclohexene; Conjugated diene monomers such as butadiene, isoprene, 1,3-pentadiene, furan, thiophene, and 1,3-cyclohexadiene; Acrylonitrile, methacrylonitrile, α-chloroacrylonitrile Nitori (Meth) acrylate monomers such as methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, methyl acrylate, ethyl acrylate, propyl acrylate, and butyl acrylate Ethylenically unsaturated carboxylic acid monomers such as acrylic acid, methacrylic acid and maleic anhydride; phenylmaleimide; methyl vinyl ether; heterocycle-containing vinyl compounds such as N-vinylcarbazole and N-vinyl-2-pyrrolidone Examples include masses.

  The vinyl alicyclic hydrocarbon polymer is obtained by polymerizing the above compound by a known polymerization method such as radical polymerization, anionic polymerization, or cationic polymerization, and hydrogenating the compound as necessary. The polymer may be a random copolymer or a block copolymer of the above-mentioned vinyl aromatic compound or vinyl alicyclic hydrocarbon compound and the above-mentioned compound copolymerizable with these compounds. When used, the resulting sheet is excellent in mechanical strength. As the form of polymerization, bulk polymerization, emulsion polymerization, suspension polymerization, solution polymerization and the like can be used, but solution polymerization is preferable in order to continuously perform the polymerization reaction and the hydrogenation reaction.

  After the polymerization reaction, the polymer can be recovered by a known method such as a steam stripping method, a direct desolvation method, or an alcohol coagulation method. Further, when a solvent inert to the hydrogenation reaction is used during the polymerization, the polymer can be used as it is without recovering the polymer from the polymerization solution.

  The hydrogenation method is performed using, for example, a hydrogenation catalyst containing at least one metal selected from nickel, cobalt, iron, titanium, rhodium, palladium, platinum, ruthenium and rhenium in an organic solvent. Among these hydrogenation catalysts, use of a nickel catalyst is preferable because the Mw / Mn of the polymer becomes small. The hydrogenation catalyst may be a heterogeneous catalyst or a homogeneous catalyst. In the hydrogenation reaction, the temperature is usually in the range of 10 to 250 ° C, preferably 50 to 200 ° C, more preferably 80 to 180 ° C, and the hydrogen pressure is usually 0.1 to 30 MPa, preferably 0.5. -25 MPa, more preferably in the range of 1-20 MPa. The hydrogenation rate of the polymer hydride obtained by the above method is usually 80% or more, preferably 90% or more, more preferably 95% or more.

  In addition to the said vinyl alicyclic hydrocarbon polymer, the vinyl alicyclic hydrocarbon polymer resin used for this invention can contain various compounding agents as needed. As a compounding agent, the same thing as the compounding agent of the said polynorbornene resin can be mentioned. The content of the vinyl alicyclic hydrocarbon polymer in the vinyl alicyclic hydrocarbon polymer resin comprising the vinyl alicyclic hydrocarbon polymer and the compounding agent can be 90 to 100% by weight.

  As the vinyl alicyclic hydrocarbon polymer resin used for the B layer, a resin having a negative intrinsic birefringence value can be used. Negative intrinsic birefringence means that the refractive index in the stretching direction is smaller than the refractive index in the direction perpendicular thereto. Intrinsic birefringence can also be calculated from the dielectric constant distribution.

  The deflection temperature under load Ts (B) of the vinyl alicyclic hydrocarbon polymer resin is preferably 70 ° C. or higher, more preferably 85 ° C. or higher, and particularly preferably 100 ° C. or higher. When the deflection temperature under load is lower than the lower limit value, it is not preferable because the orientation is easily relaxed.

(C layer)
In the present invention, the C layer is a bonding layer interposed between the A layer and the B layer. By having such a C layer, it is possible to obtain a laminate in which the A layer having excellent strength and the B layer advantageous for expressing a desired phase difference are firmly attached, and as a result, the present invention. The retardation plate can be made excellent in durability.

  The material constituting the C layer is made of a resin containing a predetermined copolymer (hereinafter sometimes referred to as copolymer C). Copolymer C is a polymer block composed of polymer units based on styrene (hereinafter sometimes referred to as block C (i)) 5 to 80% by weight, polymer units based on butadiene, polymer units based on isoprene, And 95 to 20% by weight of a polymer unit selected from the group consisting of a polymer unit selected from the group consisting of combinations thereof (hereinafter also referred to as block C (ii)). It is a copolymer. Specifically, a hydrogenated block copolymer of styrene-isoprene-styrene can be used as the material constituting the C layer.

  The polymerized units based on styrene in block C (i) are broadly understood and include styrene and its derivatives such as styrene, α-methylstyrene, α-ethylstyrene, α-propylstyrene, α-isopropylstyrene, α-t. -Butylstyrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, 2,4-diisopropylstyrene, 2,4-dimethylstyrene, 4-t-butylstyrene, 5-t-butyl-2-methylstyrene Monomer such as monochlorostyrene, dichlorostyrene, monofluorostyrene, and 4-phenylstyrene is a unit obtained by polymerization by reaction at the vinyl group. The butadiene-based polymer unit and the isoprene-based polymer unit in the block C (ii) are units obtained by polymerizing butadiene and isoprene by reaction of their double bonds. In addition, a polymerized unit that is a hydride of these polymerized units is a unit obtained by converting unreacted double bonds remaining in the polymerized units after polymerization of butadiene and isoprene into single bonds by hydrogenation. is there.

  The molecular weight of each of the blocks C (i) is preferably 1800 to 120,000. The molecular weight of each of the blocks C (ii) is preferably 7000 to 140000. The weight ratio of (unit based on block C (i)) / (unit based on block C (ii)) in copolymer C1 is preferably 0.05-4.

(Relationship between each layer)
The difference between the load deflection temperature Ts (A) of the polynorbornene resin that is the material of the A layer and the load deflection temperature Ts (B) of the vinyl alicyclic hydrocarbon polymer resin that is the material of the B layer is 5 ° C. or more. Preferably, it is 5-50 degreeC, More preferably, it is 8-40 degreeC. By making the load deflection temperature difference equal to or greater than a predetermined value, the temperature dependence of the phase difference can be greatly increased, and the phase difference can be effectively controlled. As a result, the desired phase difference can be reduced. It is possible to easily obtain a retardation plate having the same. On the other hand, if the difference in the deflection temperature under load is too large, it becomes difficult to stretch a resin having a high deflection temperature under load, and the flatness of the retardation plate is likely to deteriorate, such being undesirable. The deflection temperature under load Ts (A) is preferably higher than the deflection temperature under load Ts (B).

  Both the breaking elongation of the material of the A layer at the temperature Ts (B) and the breaking strength of the material of the B layer at the temperature Ts (A) are both preferably 50% or more, and particularly preferably 80% or more. . When materials having a breaking elongation in this range are combined, a retardation film can be stably produced by stretching. The elongation at break is determined at a tensile speed of 100 mm / min using a type 1B test piece described in JIS K7127.

The phase difference plate of the present invention has one direction as the X axis, the direction perpendicular to the X axis in the plane as the Y axis, and the thickness direction as the Z axis. When uniaxially stretched at a magnification of 1.25 times, it is incident at an incident angle of 0 ° and the plane of vibration of the electric vector is incident at an incident angle of 0 ° with respect to the linearly polarized light ΨY on the YZ plane, and the plane of vibration of the electric vector is the XZ plane It is preferable that the phase of the linearly polarized light ΨX in FIG. 2 has a stretching temperature T _α that is delayed from that before stretching and a stretching temperature T _β that is advanced than before stretching. That is, in the retardation plate of the present invention, it is preferable that the increase / decrease of the retardation generated when uniaxially stretching is different from the retardation before stretching depends on the stretching temperature.

The linearly polarized light ΨX is represented by ΨX = sin (ωt + θ). The linearly polarized light ΨY is represented by ΨY = sin (ωt). θ is the phase difference between the linearly polarized light ΨX and the linearly polarized light ΨY in the retardation plate of the present invention. ω is the angular velocity and t is time. When the retardation plate of the present invention is uniaxially stretched at a draw ratio of 1.25 times in the X-axis direction in a temperature range in which the phase difference plate can be stretched, the phase of ΨX changes by Δθ with respect to ΨY. That is, the linearly polarized light ΨX ′ after stretching is represented by ΨX ′ = sin (ωt ′ + θ−Δθ). The linearly polarized light ΨY ′ after stretching is represented by ΨY ′ = sin (ωt ′). t ′ is time. When ΨY ′ = ΨY, the retardation plate according to a preferred embodiment of the present invention has the stretching temperature T _{α at} which Δθ is positive and the stretching temperature T _β at which Δθ is negative.

Phase difference is a value obtained by multiplying the thickness d to the difference between the refractive index n _Y between the refractive index n _X in the X-axis direction the Y-axis direction (= n _X -n _Y). The phase difference of the laminate including the A layer and the B layer is synthesized from the phase difference of the A layer and the phase difference of the B layer.
For the C layer, a material having a small retardation can be selected and / or the layer can be thinned so that the retardation is sufficiently reduced.
In order to have a stretching temperature T _{α at} which Δθ becomes positive and a stretching temperature T _β at which Δθ becomes negative, the phase difference of a layer made of a material having a high load deflection temperature caused by uniaxial stretching at a high temperature T _{H can} be obtained. The change Δθ _H is larger than the change Δθ _L of the layer made of the material having a low deflection temperature under load, and the change Δθ of the phase difference of the layer made of the material having a high load deflection temperature caused by uniaxial stretching at the low temperature T _L. It is preferable to adjust the thicknesses of the A layer and the B layer so that _H is smaller than the change Δθ _{L in} the retardation of the layer made of a material having a low deflection temperature under load.

  The temperature at which the phase difference change Δθ turns from plus to minus or minus to plus is usually [Ts (A) or Ts (B), whichever is higher}} and {{Ts (A) or Ts (B ) Whichever is the lower temperature} −10 ° C.].

  The ratio of the total thickness of the A layer / the total thickness of the B layer is preferably 1/4 to 1/10, more preferably 1/5 to 1/9. By making the ratio of the total thickness within this range, the temperature dependence of the phase difference expression can be further increased. The thicknesses of the A layer and the B layer were measured by measuring the total thickness of the film using a commercially available contact thickness gauge, then cutting the thickness measurement portion and observing the cross section with an optical microscope. The ratio is obtained, and the thicknesses of the A layer and the B layer are calculated from the ratio. The above operations are performed at regular intervals in the MD direction of the film (the film flow direction in the stretching apparatus, that is, the longitudinal direction of the film) and the TD direction (the direction perpendicular to the MD direction on the film surface). And variation can be obtained.

The thickness variation is based on the arithmetic average value T _ave of the measured values obtained above, and the maximum value of the measured thickness T is T _max and the minimum value is T _min. calculate.
Thickness variation (μm) = T _ave −T _min , and
The larger of T _max -T _ave .

The variation in the thicknesses of the A layer and the B layer is preferably 1 μm or less over the entire surface. Thereby, variation in color tone is reduced. Moreover, the color tone change after long-term use becomes uniform.
In order to make the variation in the thicknesses of the A layer and the B layer 1 μm or less on the entire surface, in the co-extrusion of the film before stretching described later, (1) a polymer filter having an opening of 20 μm or less is provided in the extruder; ) Rotate the gear pump at 5 rpm or higher; (3) Place surrounding means around the die; (4) Set the air gap to 200 mm or less; (5) Perform edge pinning when casting the film on a cooling roll; And (6) one or more means such as a twin screw extruder or a double flight type single screw extruder is used as the extruder.

  The thickness of C layer can be 0.1-50 micrometers. Moreover, it is preferable that tensile strength is 2 Mpa or more, and it is more preferable that it is 4 Mpa or more. When the tensile strength is less than 2 MPa, there is a possibility that the retardation plate is cracked when the retardation plate is produced by stretching. Here, the tensile strength is a value measured according to JIS K 6251. Further, the tensile elongation at break is preferably 400% or more, and more preferably 600% or more. If the tensile elongation at break is less than 400%, the film may be cracked when the laminated film of the present invention is stretched. Here, the tensile strength is a value measured according to JIS K 6251.

(Other layers)
The retardation plate of the present invention may have a layer other than the A layer to the C layer. For example, a mat layer for improving the slipperiness of the film, a hard coat layer such as an impact-resistant polymethacrylate resin layer, an antireflection layer, an antifouling layer and the like can be mentioned.

(Properties of retardation plate)
The total thickness of the retardation plate of the present invention is preferably 20 to 300 μm, more preferably 30 to 280 μm, and particularly preferably 40 to 260 μm. Mechanical strength can be easily ensured by having a thickness of 20 μm or more. When the thickness is 300 μm or less, good flexibility can be obtained, whereby handling can be performed well.

  The retardation plate of the present invention may have a peel strength of 0.7 N / 25 mm or more. Here, the peel strength is a value measured by 180 ° peeling at a peeling speed of 100 mm / min in accordance with JIS K-6854-2. Furthermore, the phase difference plate of the present invention can have a small decrease in the peel strength before and after the endurance test conditions. Specifically, the difference in peel strength between before and after being subjected to a durability test condition of 500 hours at 60 ° C. and 95% RH can be 0.1 to 0.2 N / 25 mm. The retardation plate of the present invention can be a highly durable retardation plate with the peel strength in this range.

The retardation plate of the present invention has a retardation Re (nm) when light having a wavelength of 550 nm is incident at an incident angle of 0 °, and R ₄₀ when light having a wavelength of 550 nm is incident at an incident angle of 40 °. (Nm), 0.92 ≦ R ₄₀ /Re≦1.08 may be satisfied.

In the retardation plate of the present invention, the retardation Re when light having a wavelength of 550 nm is incident at an incident angle of 0 ° is preferably 50 to 400 nm, and more preferably 65 to 350 nm. Re and R ₄₀ are values measured at a wavelength of 550 nm using a parallel Nicol rotation method (manufactured by Oji Scientific Instruments, KOBRA-WR).
Furthermore, the phase difference plate of the present invention can have a small change in the Re value before and after the endurance test condition. Specifically, the change rate of Re before and after being subjected to a durability test condition of 500 hours at 60 ° C. and 95% RH can be 5% or less. The retardation plate of the present invention can be a highly durable retardation plate having such a low Re change rate.

In the retardation plate of the present invention, the refractive index nx in the in-plane slow axis direction, the refractive index ny in the direction orthogonal to the slow axis in the plane, and the refractive index nz in the thickness direction are 0 <( It is preferable to satisfy the relationship of nx−nz) / (nx−ny) <1. The refractive indexes nx, ny and nz can be calculated from the thicknesses and refractive indexes of the Re, R ₄₀ and retardation plates. By having such a refractive index relationship, when the retardation plate is applied to a display device such as a liquid crystal display device, the angle dependency of the color tone of the display of the device can be reduced particularly well. In the method for producing a retardation plate satisfying the above relationship, a thermoplastic resin A having a positive intrinsic birefringence is used, and a thermoplastic resin B having a negative intrinsic birefringence is used before stretching. In the film, the ratio of the total thickness of the a layer / the total thickness of the b layer is preferably 1/4 to 1/12, more preferably 1/5 to 1/10.

The retardation plate of the present invention has a retardation R _{450 at} an incident angle of 0 ° in light having a wavelength of ₄₅₀ nm, a retardation R ₅₅₀ at an incident angle of 0 ° in light having a wavelength of 550 nm, and an incident angle of 0 in light having a wavelength of 650 nm. It is preferable that the retardation R ₆₅₀ at ° satisfies the relationship of R ₄₅₀ <R ₅₅₀ <R ₆₅₀ . By having such a relationship, it can function well as a phase difference plate in a wide wavelength region within the visible light region. In the method for producing a retardation plate satisfying the above relationship, a thermoplastic resin A having a positive intrinsic birefringence is used, and a thermoplastic resin B having a negative intrinsic birefringence is used before stretching. In the film, the ratio of the total thickness of the a layer / the total thickness of the b layer is preferably 1/4 to 1/12, more preferably 1/5 to 1/10.

  The retardation plate of the present invention has a shrinkage ratio of preferably 0.5% or less, more preferably 0.3% or less in the longitudinal and transverse directions by heat treatment at 60 ° C. and 90% RH for 100 hours. It may be. If the shrinkage rate exceeds this range, the retardation plate may be deformed or peeled off from the display device due to shrinkage stress when used in a high temperature / high humidity environment.

  The retardation plate of the present invention preferably has a total light transmittance of 85% or more. It is preferable for the optical member that the total light transmittance is in the above-mentioned preferable range. The light transmittance is an average value obtained by measuring five locations using “turbidimeter NDH-300A” manufactured by Nippon Denshoku Industries Co., Ltd. in accordance with JIS K7361-1997.

  The haze of the retardation plate of the present invention is preferably 5% or less, more preferably 3% or less, and particularly preferably 1% or less. By setting the haze to the above preferable range, the sharpness of the display image can be improved. Here, the haze is an average value obtained by measuring five points using a “turbidimeter NDH-300A” manufactured by Nippon Denshoku Industries Co., Ltd. according to JIS K7361-1997.

  In the retardation plate of the present invention, ΔYI is preferably 5 or less, and more preferably 3 or less. When this ΔYI is in the above range, there is no coloring and visibility is improved. ΔYI is measured according to ASTM E313 using a “spectral color difference meter SE2000” manufactured by Nippon Denshoku Industries Co., Ltd., and the same measurement is performed five times to obtain the arithmetic average value.

The retardation plate of the present invention preferably has a hardness of H or higher in terms of JIS pencil hardness. The adjustment of the JIS pencil hardness can be performed by changing the type of resin, changing the layer thickness of the resin, or the like. JIS pencil hardness is the hardness of a pencil that begins to scratch, scratching the film surface by tilting a pencil of various hardness by 45 °, applying a load of 500 g weight from the top, in accordance with JIS K5600-5-4. .

(Production method)
The retardation plate of the present invention is not particularly limited by the manufacturing method. A preferred production method of the retardation plate of the present invention is a layer comprising a polynorbornene resin, a vinyl alicyclic hydrocarbon polymer resin, and a copolymer C, which are materials constituting the A layer, the B layer, and the C layer, It is a method including the process of obtaining the film before extending | stretching containing b layer and c layer, and the process of extending | stretching the said film before extending | stretching. Hereinafter, this preferable production method will be described.
The stretching step includes co-stretching the pre-stretched film in a first direction at a temperature T1 (° C.) that is 5 ° C. higher than the lower temperature of Ts (A) and Ts (B). One stretching step and second stretching co-stretching in a second direction at a temperature T2 (° C.) lower than the higher temperature of Ts (A) or Ts (B) and different from T1 And a process including a process.

  The pre-stretch film used in the method for producing a retardation plate of the present invention has one direction as an X axis, a direction perpendicular to the X axis in the plane as a Y axis, and a thickness direction as a Z axis. The phase of the linearly polarized light incident perpendicularly to the principal plane with respect to the linearly polarized light whose plane of incidence is in the YZ plane and perpendicular to the principal plane and whose plane of electrical vector is in the XZ plane is X at temperature T1. It is preferable that it is delayed when uniaxially stretched in the axial direction and advanced when uniaxially stretched in the X-axis direction at the temperature T2.

In a film in which the slow axis appears in the X axis by uniaxial stretching, the phase of the linearly polarized light having the vibration plane in the XZ plane is delayed with respect to the linear polarization having the vibration plane in the YZ plane. Conversely, in a film in which a fast axis appears on the X axis by uniaxial stretching, the phase of linearly polarized light whose vibration surface is in the XZ plane is advanced relative to linear polarization whose vibration surface is in the YZ plane. The pre-stretch film preferably used in the present invention is a film in which the appearance of the slow axis or the fast axis changes depending on the stretching temperature.
Such a film having temperature dependency in the retardation development is related to the intrinsic birefringence value and thickness ratio of the a layer made of polynorbornene resin and the b layer made of vinyl alicyclic hydrocarbon polymer resin. It is obtained by adjusting.

The film before stretching used in the method for producing a retardation plate of the present invention may have one layer or two or more layers a to c corresponding to the desired layer structure of the retardation plate. .
Phase difference, multiplied by the thickness d to the difference between the refractive index n _Y in a direction orthogonal to the stretching direction and a refractive index n _X in the X-axis direction is a stretching direction Y-axis direction (= n _X -n _Y) This is the value obtained by The retardation of the pre-stretched film including the a layer and the b layer is synthesized from the retardation of the a layer and the retardation of the b layer. For the c layer, a material that exhibits little retardation due to stretching conditions in the stretching step may be selected and / or the layer may be thinned so that the retardation is sufficiently reduced.

In order to reverse the sign of the phase difference of the pre-stretching film including the a layer and the b layer by stretching at the high temperature T _H and the low temperature T _L , the deflection temperature under load at the stretching at the low temperature T _L the absolute value of the phase difference highly resins is expressed is smaller than the absolute value of the phase difference lower resin is expression of heat deflection temperature, at a stretching at high temperature T _H, the phase difference lower resin having a deflection temperature under load expressed It is preferable to adjust the thicknesses of the a layer and the b layer so that the absolute value of is smaller than the absolute value of the phase difference developed by the resin having a high deflection temperature under load. Thus, the difference between a layer and the X-axis direction of the refractive index expressed in each of the b layer n _X and Y-axis direction of the refractive index n _Y by uniaxial stretching, the sum of the thickness of a layer, b layer By adjusting the total thickness of the linearly polarized light whose plane of incidence is perpendicular to the surface of the film before stretching and whose vibration plane of the electric vector is in the XZ plane, A phase before linearly polarized light whose vector vibration plane is in the YZ plane is delayed when uniaxially stretched in the X-axis direction at a temperature T1, and a pre-stretched film is obtained that proceeds when uniaxially stretched in the X-axis direction at a temperature T2 different from the temperature T1. be able to. The temperature T1 is either T _H or T _L , and the temperature T2 is either T _H or T _L that is different from T1.

FIG. 1 shows the temperature dependence of retardation when a film consisting only of a layer and a film consisting only of b layer are each stretched alone, and retardation when a pre-stretching film containing a layer and b layer is stretched. It is a graph which shows the temperature dependence of. In this example, the load deflection temperature Ts (A) of the a layer is greater than the load deflection temperature Ts (B) of the b layer.
In the stretching at the temperature Tb, the negative phase difference expressed by the stretching of the b layer is larger than the positive retardation expressed by the stretching of the a layer. Therefore, the stretching of the film before stretching including the a layer and the b layer is negative. A phase difference Δ is developed. On the other hand, in the stretching at the temperature Ta, the negative phase difference expressed by the stretching of the b layer is smaller than the positive retardation expressed by the stretching of the a layer. Therefore, the stretching of the film before stretching including the a layer and the b layer is positive. The phase difference Δ is expressed.

  In the pre-stretched film, the ratio of the total thickness of layer a / the total thickness of layer b is preferably 1/4 to 1/12, more preferably 1/5 to 1/10. By making the ratio of the total thickness within this range, the temperature dependence of the phase difference expression can be further increased.

  The total thickness of the film before stretching is preferably 10 to 500 μm, more preferably 20 to 400 μm, and particularly preferably 30 to 300 μm. By setting it to 10 μm or more, a sufficient phase difference can be obtained and sufficient mechanical strength can be ensured. By setting the thickness to 500 μm or less, good flexibility can be obtained, whereby handling can be performed well.

  The thickness of layer a to layer c is measured using a commercially available contact-type thickness meter, the total thickness of the film before stretching is measured, the thickness measurement part is cut, and the cross section is observed with an optical microscope. Thickness ratio is calculated | required and the thickness of a layer-c layer is calculated from the ratio. The above operation is performed at regular intervals in the MD direction and TD direction of the pre-stretched film, and the average value and variation of the thickness are obtained.

The thickness variation is calculated from the following equation, with the arithmetic mean value T _ave of the measured values measured above as a reference, the maximum value of the measured thickness T as T _max and the minimum value as T _min. To do.
Thickness variation (μm) = T _ave −T _min , and
The larger of T _max -T _ave .

  When the thickness variation of the a layer and the b layer is 1 μm or less over the entire surface, the variation in color tone is reduced. Moreover, the color tone change after long-term use becomes uniform.

  In order to make the variation in the thickness of the a layer and the b layer 1 μm or less on the entire surface, (1) a polymer filter having an opening of 20 μm or less is provided in the extruder; (2) the gear pump is rotated at 5 rpm or more; 3) Arranging means around the die; (4) Air gap is 200 mm or less; (5) Edge pinning is performed when the film is cast on a cooling roll; and (6) Twin screw extrusion as an extruder. Use a double-flight type single screw extruder.

  The thickness of c layer can be 0.1-50 micrometers. Moreover, it is preferable that tensile strength is 2 Mpa or more, and it is more preferable that it is 4 Mpa or more. If the tensile strength is less than 2 MPa, there is a risk of cracking the retardation plate when the retardation plate is produced by stretching. Here, the tensile strength is a value measured according to JIS K 6251. Further, the tensile elongation at break is preferably 400% or more, and more preferably 600% or more. If the tensile elongation at break is less than 400%, the film may be cracked when the laminated film of the present invention is stretched. Here, the tensile strength is a value measured according to JIS K 6251.

  The step of obtaining the film before stretching includes, for example, a coextrusion molding method such as a coextrusion T-die method, a coextrusion inflation method, a coextrusion lamination method, a film lamination molding method such as dry lamination, and a resin solution on the surface of the resin film. Known methods such as a coating molding method such as coating or a co-casting method may be mentioned. Of these, the coextrusion molding method is preferable from the viewpoint of production efficiency and that volatile components such as a solvent do not remain in the film before stretching. Among the coextrusion molding methods, the coextrusion T-die method is preferable. The coextrusion T-die method includes a feed block method and a multi-manifold method, and the multi-manifold method is particularly preferable in that variation in the thickness of the A layer can be reduced.

  When the co-extrusion T-die method is adopted as a method for obtaining a pre-stretch film, the melting temperature of the resin material in the extruder having the T-die is the glass transition temperature of the polynorbornene resin constituting the A layer, which constitutes the B layer. Assuming that the glass transition temperature of the resin is high, it is preferably 80 to 180 ° C. higher than the glass transition temperature (Tg) of the polynorbornene resin constituting the A layer, and 100 to 150 ° C. higher than the glass transition temperature. More preferably, the temperature is set. If the melting temperature in the extruder is excessively low, the fluidity of the resin material may be insufficient. Conversely, if the melting temperature is excessively high, the resin may be deteriorated, which is not preferable.

  What is necessary is just to select extrusion temperature suitably according to the polynorbornene resin to be used. The temperature in the extruder is such that the resin inlet is Tg to (Tg + 100) ° C. relative to the glass transition temperature Tg of the polynorbornene resin constituting the A layer, and the extruder outlet is (Tg + 50) ° C. to (Tg + 170) ° C., die temperature Is preferably (Tg + 50) ° C. to (Tg + 170) ° C.

  In the extrusion molding method, the sheet-like molten resin material extruded from the opening of the die is brought into close contact with the cooling drum. The method for bringing the molten resin material into close contact with the cooling drum is not particularly limited, and examples thereof include an air knife method, a vacuum box method, and an electrostatic contact method.

  The number of cooling drums is not particularly limited, but is usually two or more. Examples of the arrangement method of the cooling drum include, but are not limited to, a linear type, a Z type, and an L type. Further, the way of passing the molten resin extruded from the opening of the die through the cooling drum is not particularly limited.

  In the present invention, the degree of adhesion of the extruded sheet-shaped resin material to the cooling drum changes according to the temperature of the cooling drum. When the temperature of the cooling drum is raised, the adhesion is improved. However, when the temperature is raised too much, the sheet-like resin material is not peeled off from the cooling drum, and there is a possibility that a problem of winding around the drum may occur. Therefore, the cooling drum temperature is preferably (Tg + 30) ° C. or less, more preferably in the range of (Tg−5) ° C. to (Tg−45) ° C., where Tg is the glass transition temperature of the polynorbornene resin A extruded from the die. can do. By doing so, problems such as slipping and scratches can be prevented.

  Further, it is preferable to reduce the content of residual solvent in the film. Means for that purpose include (1) reducing the residual solvent of the thermoplastic resin used as a raw material; and (2) pre-drying the resin material before forming the film. The preliminary drying is performed by, for example, a hot air dryer or the like in the form of pellets or the like of the resin material. The drying temperature is preferably 100 ° C. or more, and the drying time is preferably 2 hours or more. By performing preliminary drying, the residual solvent in the film can be reduced, and foaming of the extruded sheet-shaped resin material can be prevented.

  You may provide the process of pre-heating the film before extending | stretching before extending | stretching the said film before extending | stretching. Examples of means for heating the pre-stretched film include an oven-type heating device, a radiation heating device, or immersion in a liquid. Of these, an oven-type heating device is preferable. The heating temperature in the preheating step is usually stretching temperature −40 ° C. to stretching temperature + 20 ° C., preferably stretching temperature −30 ° C. to stretching temperature + 15 ° C. The stretching temperature means the set temperature of the heating device.

(First stretching process)
In the stretching step in a preferred embodiment, first, the pre-stretched film is moved in the first direction at a temperature T1 (° C.) that is 5 ° C. or more higher than the lower temperature of Ts (A) and Ts (B). Uniaxial stretching.

When Ts (A)> Ts (B), the temperature T1 is set to a temperature higher by 5 ° C. or more than Ts (B), more preferably 5 to 50 ° C. higher than Ts (B).
When Ts (B)> Ts (A), the temperature T1 is set to a temperature 5 ° C. or more higher than Ts (A), more preferably 5 to 15 ° C. higher than Ts (A).

  The first stretching treatment can be performed by a conventionally known method. For example, a method of uniaxially stretching in the longitudinal direction using a difference in peripheral speed between rolls, a method of uniaxially stretching in the lateral direction using a tenter, and the like can be mentioned. Examples of the method of uniaxially stretching in the longitudinal direction include an IR heating method between rolls and a float method. The float method is preferable because a retardation plate with high optical uniformity can be obtained. An example of a method of uniaxially stretching in the transverse direction is a tenter method.

  In order to reduce stretching unevenness and thickness unevenness, it is possible to make a temperature difference in the film width direction in the stretching zone. In order to create a temperature difference in the film width direction in the stretching zone, a known method such as adjusting the opening degree of the hot air nozzle in the width direction or controlling the heating by arranging IR heaters in the width direction can be used.

(Second stretching process)
Next, the film is uniaxially stretched in the second direction at a temperature T2 (° C.) lower than the higher of Ts (A) or Ts (B). The temperature T2 is not particularly limited as long as it is different from the temperature T1, but is preferably lower than the temperature T1. Further, the temperature T2 is more preferably lower than the Ts (A).
In the second stretching process, a method that can be adopted in the first stretching process can be applied as it is. The second stretching process is preferably performed at a stretching ratio smaller than the stretching ratio of the first stretching process.

  It is preferable that the first direction in the first stretching process and the second direction in the second stretching process intersect at an angle in the range of 89 ° to 91 °.

  After the first stretching process and / or the second stretching process, the stretched film may be fixed. The temperature in the fixing treatment is usually room temperature to stretching temperature + 30 ° C., preferably stretching temperature−40 ° C. to stretching temperature + 20 ° C.

The aforementioned stretching treatment (first stretching treatment and second stretching treatment), in other words, the first stretching treatment causes the phase difference of the polynorbornene resin constituting the a layer to be expressed greatly, and then the second stretching treatment performs the a layer. The polynorbornene resin constituting the layer b and the vinyl alicyclic hydrocarbon polymer resin constituting the layer b are each subjected to stretching treatment (the layer formed by stretching the layer a is the A layer and the layer b. A retardation plate satisfying the relationship 0 <(nx−nz) / (nx−ny) <1.
At this time, in the a layer and the b layer constituting the film before stretching, the polynorbornene resin constituting the a layer becomes R ₄₅₀ > R ₅₅₀ > R ₆₅₀ , and the vinyl alicyclic hydrocarbon heavy constituting the b layer. The coalesced resin preferably satisfies R ₄₅₀ <R ₅₅₀ <R ₆₅₀ . According to such a configuration, in the retardation plate obtained by the stretching process described above, the slow axis of the A layer made of polynorbornene resin having a positive intrinsic birefringence and the vinyl fat having a negative intrinsic birefringence. Since the slow axis of the B layer made of the cyclic hydrocarbon polymer resin is in the same direction, the retardation of the retardation plate that is a laminate of these layers can be obtained as the sum of the retardations of the respective layers. it can. Therefore, by appropriately adjusting the thickness ratio of the A layer and the B layer so that the retardation of the B layer greatly contributes, the obtained retardation plate has the above 0 <(nx−nz) / (nx -ny) <1 in addition to the _{relationship,} the relationship of _{R 450 <R} 550 _{<R 650} may impart.

(Use)
Since the retardation plate of the present invention can highly compensate birefringence, the liquid crystal display device, the organic EL display device, the plasma display device, the FED (field emission) display device, alone or in combination with other members, It can be applied to an SED (surface electric field) display device.

  The liquid crystal display device includes a liquid crystal panel in which a light incident side polarizing plate, a liquid crystal cell, and a light emitting side polarizing plate are arranged in this order. By arranging the retardation plate of the present invention between the liquid crystal cell and the light incident side polarizing plate and / or between the liquid crystal cell and the light emitting side polarizing plate, the visibility of the liquid crystal display device can be greatly improved. it can. Liquid crystal cell driving methods include in-plane switching (IPS) mode, vertical alignment (VA) mode, multi-domain vertical alignment (MVA) mode, continuous spin wheel alignment (CPA) mode, hybrid alignment nematic (HAN) mode, Examples include twisted nematic (TN) mode, super twisted nematic (STN) mode, and optically compensated bend (OCB) mode.

The retardation plate of the present invention may be bonded to a liquid crystal cell or a polarizing plate. The retardation plate may be bonded to both sides of the polarizing plate, or may be bonded only to one side. Two or more retardation plates may be used. A known adhesive can be used for bonding.
A polarizing plate consists of a polarizer and the protective film bonded together on both surfaces. Instead of the protective film, the retardation plate of the present invention can be directly bonded to a polarizer and the retardation plate can be used as a protective film. Since the protective film is omitted, the liquid crystal display device can be thinned.

  Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples. Parts and% are based on weight unless otherwise specified.

  In this example, various physical properties were measured as follows.

(Thickness of transparent film)
The film thickness was measured using a contact-type thickness meter.
Regarding the layer thickness of each layer constituting the film, the film was embedded in an epoxy resin, then sliced using a microtome (manufactured by Yamato Kogyo Co., Ltd., product name “RUB-2100”), and the cross section was observed using a scanning electron microscope. And measured.

(Load deflection temperature)
The deflection temperature under load of the resin was measured by preparing a test piece in accordance with JISK7191.

(Re, R ₄₀ )
Re, R ₄₀ , 450 nm. At a wavelength of 590 nm using a parallel Nicol rotation method (manufactured by Oji Scientific Instruments, KOBRA-WR). Retardations R450, R550, and R650 at 550 nm and 650 nm were measured. The same measurement was performed at 10 points at equal intervals in the width direction of the retardation film, and the average value was calculated. Further, the average refractive index n _ave of the laminated film was determined by the following formula.
n _ave = Σ (n _i × L _i ) / ΣL _i
n _i: refractive index of the i-layer resin L _i: film thickness of the i layer further the Re, R _40, n _ave, the thickness of the film was calculated n _x, n _y, n _z of the laminated film.

(Peel strength)
The peel strength of the laminated film was measured using an autograph [AGS-J, manufactured by Shimadzu Corporation] based on JIS K 6854-2 (180 ° peel at a tensile speed of 100 mm / min).

<Production Example 1>
(1-1: Production of resin B1 for B layer)
In a stainless steel autoclave equipped with a magnetic stirrer, thoroughly dried and purged with nitrogen, 320 parts of dehydrated cyclohexane, the composition is (styrene (St) / isoprene (IP)) = (95/5) by weight. 4 parts of mixed monomer and 0.1 part of dibutyl ether were charged, and 0.18 part of n-butyllithium solution (15% hexane solution) was added while stirring at 50 ° C. to initiate polymerization. After performing the polymerization for 30 minutes under the same conditions (the conversion rate at this point was 96%), the same mixed monomer as above was added to the polymerization reaction solution in the autoclave while continuing the polymerization under the same conditions. 76 parts were added continuously over 1 hour. After completion of the addition (the conversion rate at this time was 95%), the polymerization was carried out for 30 minutes under the same conditions, then 0.1 part of isopropyl alcohol was added to stop the reaction, and the styrene-isoprene copolymer (A) was synthesized.
Next, 8 parts of a stabilized nickel hydrogenation catalyst E22U (manufactured by JGC Chemical Industry Co., Ltd .; 60% nickel-supported silica-alumina carrier) is added to and mixed with 400 parts of the cyclohexane solution of the polymer (a) to adjust the hydrogenation reaction temperature. A stainless steel autoclave equipped with an electric heating device and an electromagnetic stirring device was prepared. After completion of the preparation, the inside of the autoclave was replaced with hydrogen gas, and a hydrogenation reaction was carried out for 6 hours at 160 ° C. with stirring while supplying hydrogen so that the pressure inside the autoclave was maintained at 45 kg / cm ² . After completion of the reaction, the hydrogenation catalyst was removed by filtration, 1200 parts of cyclohexane was added, and the mixture was poured into 10 liters of isopropanol to precipitate a vinyl alicyclic hydrocarbon polymer resin. The vinyl alicyclic hydrocarbon polymer resin was separated by filtration and dried by a vacuum dryer to obtain a B layer resin B1.
Next, the B layer resin B1 is kneaded with a biaxial kneader (TEM-35B manufactured by Toshiba Machine Co., Ltd., screw diameter 37 mm, L / D = 32, screw rotation speed 250 rpm, resin temperature 240 ° C., feed rate 10 kg / hour). Extruded and pelletized to obtain a pellet of B layer resin B1. The hydrogenation rate of the B layer resin B1 was 99.9%, and the deflection temperature under load was 103 ° C.

(1-2: Production of film before stretching)
A film forming apparatus for coextrusion molding of 3 types and 5 layers is prepared, and a double layer of pellets of resin for layer A (trade name “Zeonor 1420R”, manufactured by Nippon Zeon Co., Ltd., polynorbornene resin, deflection temperature under load 136 ° C.) It was put into one single screw extruder equipped with a flight type screw and melted.
The pellet of the B layer resin B1 obtained in the above (1-1) was put into another single screw extruder equipped with a double flight type screw and melted.
C-layer resin C1 (styrene-isoprene-styrene hydrogenated block copolymer, (unit based on styrene) / (unit based on diene) weight ratio 20/80) pellets were equipped with a double flight type screw Furthermore, it was put into another single screw extruder and melted.
The melted resin for layer A at 250 ° C. is passed through a polymer filter in the form of a leaf disk having a mesh size of 10 μm to one manifold of a multi-manifold die (die slip surface roughness Ra: 0.1 μm). The B-layer resin is passed through a leaf disk-shaped polymer filter with 10 μm openings to another manifold, and the molten 250-degree C resin is passed through a leaf-disk-shaped polymer filter with 10 μm openings to another manifold. Each was supplied.

  A layer resin, B layer resin and C layer resin are simultaneously extruded from the multi-manifold die at 250 ° C., and (B layer)-(C layer)-(A layer)-(C layer)-(B layer) A film-like molten resin having the following layer structure was continuously produced. The film-like molten resin was cast on a cooling roll adjusted to a surface temperature of 110 ° C., and then passed between two cooling rolls adjusted to a surface temperature of 50 ° C. to obtain (B layer)-(C layer)-( A pre-stretched film E1 having a width of 500 mm and a total thickness of 260 μm having a layer structure of (A layer) − (C layer) − (B layer) was obtained. The thickness of the A layer was 30 μm, the thickness of the B layer was 110 μm, and the thickness of the C layer was 5 μm.

<Production Example 2 to Production Example 10>
Except having changed the resin for A layer-C layer, and the thickness of each layer as shown in Table 2 and Table 3, it operated similarly to manufacture example 1 and obtained film E2-E10 before extending | stretching.

<Production Example 11>
Instead of a film forming apparatus for coextrusion molding of 3 types and 5 layers, a film forming apparatus for coextrusion molding of 2 types and 3 layers is used, the C layer is not formed, and the layer configuration is (B layer)-(A layer The film E11 before stretching was obtained in the same manner as in Production Example 1 except that it was changed to-(B layer).

<Phase change of film before stretching>
Films E1 to E11 before stretching were uniaxially stretched 1.25 times in the film longitudinal direction at stretching temperatures of 70 ° C, 80 ° C, 120 ° C, 130 ° C, 135 ° C, 140 ° C, 145 ° C, and 150 ° C. When the uniaxial stretching direction is the X axis, the direction perpendicular to the X axis in the film plane is the Y axis, and the film thickness direction is the Z axis, the plane of incidence is perpendicular to the film plane and the vibration plane of the electric vector is The phase delay of the linearly polarized light that was incident perpendicularly to the film plane with respect to the linearly polarized light on the YZ plane and whose electric vector vibration plane was on the XZ plane was measured. The results are shown in Table 1.

<Example 1>
The unstretched film E1 obtained in Production Example 1 was supplied to a longitudinal uniaxial stretching machine and stretched in the longitudinal direction at a stretching temperature of 145 ° C. and a stretching ratio of 1.5. Subsequently, the longitudinally uniaxially stretched film was supplied to a tenter stretching machine and stretched in the transverse direction at a stretching temperature of 130 ° C. and a stretching ratio of 1.25 to obtain a retardation plate.
The peel strength of the obtained retardation plate was measured. The measured retardation _was determined _{R 450, R 550, R 650} , nx, ny and nz. Further, after placing the retardation plate under the durability test conditions (60 ° C., 500% at 95% RH), the peel strength and retardation were measured again to obtain R ₄₅₀ , R ₅₅₀ and R ₆₅₀ . The results are shown in Table 2.

<Examples 2-5 and Comparative Examples 1-6>
A retardation film was obtained and evaluated in the same manner as in Example 1 except that the film before stretching and the stretching conditions were changed as shown in Tables 2 and 3. The results are shown in Table 2 and Table 3.

The trade names and abbreviations in Table 2 and Table 3 are as follows.
A1: ZNR1420R: trade name “Zeonor 1420R”, manufactured by Nippon Zeon Co., Ltd., polynorbornene resin, breaking elongation at Ts; 120%
A2: Arton D4532: trade name, manufactured by JSR, polynorbornene resin, elongation at break at Ts; 100%
A3: Wonderlite PC-110: trade name, manufactured by Asahi Kasei Corporation, polycarbonate resin, elongation at break at Ts; 180%
A4: ZNR1020R: trade name “ZEONOR 1020R”, manufactured by Nippon Zeon Co., Ltd., polynorbornene resin, breaking elongation at Ts; 150%
B1: Vinyl alicyclic hydrocarbon polymer resin, hydrogenation rate; 99.9%, elongation at break at Ts; 100%
B2: Dilark D332: trade name, manufactured by Nova Chemical Co., styrene-maleic anhydride copolymer, elongation at break at Ts; 100%
C1: Hydrogenated block copolymer of styrene-isoprene-styrene, weight ratio of 20/80 (unit based on styrene) / (unit based on diene), tensile strength 12 MPa, tensile elongation at break 700%
C2: hydrogenated block copolymer of styrene-butadiene-styrene, weight ratio 30/70 (unit based on styrene) / (unit based on diene), tensile strength 15 MPa, tensile elongation at break 650%
C3: ethylene-vinyl acetate copolymer, manufactured by Mitsui DuPont Polychemical Co., Ltd., trade name “Evaflex EV260”, (unit based on ethylene) / weight ratio 72/28 (unit based on vinyl acetate), tensile strength 13 MPa , Tensile elongation at break 700%
C4: hydrogenated block copolymer of styrene-butadiene-styrene (unit based on styrene) / (unit based on diene) 90/10, tensile strength 30 MPa, tensile elongation at break 200%
A) Fracture during longitudinal stretching B) Peeling during durability test C) Peeling between A and B layers during longitudinal stretching

<Phase change of retardation plate>
The retardation plates obtained in Examples 1 to 5 and Comparative Examples 1 to 6 were 1.25 at stretching temperatures of 70 ° C, 80 ° C, 120 ° C, 130 ° C, 135 ° C, 140 ° C, 145 ° C, and 150 ° C. The film was uniaxially stretched twice in the longitudinal direction of the film. When the uniaxial stretching direction is the X axis, the direction perpendicular to the X axis in the film plane is the Y axis, and the film thickness direction is the Z axis, the plane of incidence is perpendicular to the film plane and the vibration plane of the electric vector is Measure the phase lag of linearly polarized light that is incident perpendicularly to the film plane with respect to the linearly polarized light in the YZ plane and the vibration plane of the electric vector is in the XZ plane, and how the phase appears at the same temperature as the corresponding film before stretching. We investigated whether it would turn from minus to plus. As a result, it was found that the appearance of the phase changed at the same temperature as the corresponding film before stretching.

From the results of Table 2 and Table 3, the retardation plate of the present embodiment satisfies the relationship of 0 <(nx−nz) / (nx−ny) <1 and / or the relationship of R ₄₅₀ <R ₅₅₀ <R _650. It can be seen that the peel strength was high and these properties could be maintained well even after being subjected to the durability test conditions. On the other hand, Comparative Example 1 in which the A layer is not specified in the present invention, Comparative Example 2 in which the B layer is not specified in the present invention, and Comparative Example 3 in which the deflection temperature difference is outside the prescribed range of the present invention. In Comparative Examples 4 and 5, in which the C layer is not the one specified in the present invention, and in Comparative Example 6 lacking the C layer, the product could not be constituted due to peeling or breaking in the stretching stage, or the product was placed in a durable condition. At that time, peeling occurred or physical properties were remarkably lowered.

Claims (4)

A layer made of a material having a deflection temperature under load of Ts (A) ° C., B layer made of a material having a deflection temperature under load of Ts (B) ° C., and a bonding layer interposed between the A layer and the B layer. A retardation plate comprising a laminated film comprising a C layer as
There is a difference of 5 ° C. or more between the Ts (A) and the Ts (B),
The A layer is made of polynorbornene resin,
The B layer is made of a vinyl alicyclic hydrocarbon polymer resin,
From the group consisting of 5 to 80% by weight of a polymer block composed of polymer units based on styrene, a polymer unit based on butadiene, a polymer unit based on isoprene, and a polymer unit that is a hydride of these polymer units. A phase difference plate comprising a resin comprising a copolymer composed of 95 to 20% by weight of a block comprising at least one polymerized unit selected. The phase difference plate according to claim 1,
One direction in the plane of the retardation plate is the X axis, the direction perpendicular to the X axis in the plane is the Y axis, and the thickness direction is the Z axis. When uniaxially stretched at a magnification of 1.25 times, the incident angle is 0 °, and the vibration plane of the electric vector is incident at an incident angle of 0 ° with respect to the linearly polarized light ΨY on the YZ plane. A phase difference plate in which the phase of the linearly polarized light ΨX in the XZ plane has a stretching temperature T _α that is delayed from that before stretching and a stretching temperature T _β that proceeds more than before stretching. The phase difference plate according to claim 1 or 2,
The retardation plate has retardation R ₄₅₀ at an incident angle of 0 ° in light having a wavelength of 450 nm, retardation R ₅₅₀ at an incident angle of 0 ° in light having a wavelength of 550 nm, and letter at an incident angle of 0 ° in light having a wavelength of 650 nm. Deshon _{R 650 satisfies} the relation of _{R 450 <R 550 <R 650} , a phase difference plate. The phase difference plate according to any one of claims 1 to 3,
The refractive index nx in the in-plane slow axis direction of the retardation plate, the refractive index ny in the direction orthogonal to the slow axis in the plane, and the refractive index nz in the thickness direction are 0 <(nx−nz). A retardation plate satisfying the relationship of / (nx−ny) <1.

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