JP6641700B2 - Method for producing film and method for producing polarizing plate - Google Patents

Description

  The present invention relates to a film, and more particularly, to a film that can be suitably used as a retardation film to be bonded to a polarizing plate used for a liquid crystal display, and a method for producing the same. The present invention also relates to a retardation film comprising the film, a polarizing plate using the film, and a liquid crystal display device having the polarizing plate.

  In recent years, liquid crystal displays have been widely used as display devices for televisions, personal computers, digital cameras, mobile phones, and the like. When the display side is the front side and the opposite side (backlight side) is the rear side, the liquid crystal display has a configuration of front side polarizing plate / liquid crystal / rear side polarizing plate. Further, in some liquid crystal systems, a retardation film is interposed to prevent light leakage of the liquid crystal device. For example, in a VA (vertical alignment) type liquid crystal system, a front side polarizing plate / a retardation film / liquid crystal / a retardation film is used. / Rear-side polarizing plate.

  Conventionally, as a retardation film for preventing light leakage of a liquid crystal, it has been proposed to use a triacetyl cellulose film (hereinafter sometimes abbreviated as a TAC film) because of its high transparency and optical isotropy. (For example, Non-Patent Document 1).

  However, as the size and quality of liquid crystal displays have increased in recent years, liquid crystal panel members have been required to have improved mechanical strength and stability under high-temperature, high-humidity environments. On the other hand, a TAC film is inferior in dimensional stability and wet heat resistance, and therefore, a polarizing plate employing a TAC film as a retardation film has problems such as generation of stress due to shrinkage and functional deterioration of a polarizer. It has been a problem to affect the image quality of a liquid crystal display device using a plate.

  Further, in the VA (vertical alignment) type liquid crystal system, the specifications are not common to each manufacturer, and the degree of blending of the liquid crystal in the vertical direction may be different. Therefore, a retardation film having a high thickness retardation (Rth) may be used in order to prevent light leakage from liquid crystal aligned in the vertical direction.

KONICA MINOLTA TECHNOLOGY REPORT VOL. 3 (2006) pp. 133-136, "Development of VA-TAC Film for Enlarging Viewing Angle for VA Liquid Crystal TV"

  SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has a problem to be solved. It is excellent in wet heat resistance and dimensional stability, and is also excellent in mechanical strength, and is bonded to a polarizing plate used for a liquid crystal display. An object of the present invention is to provide a film suitable as a retardation film and a method for producing the same, and a retardation film made of the film, a polarizing plate and a liquid crystal display device using the film.

  The present inventors have conducted intensive studies in view of the above circumstances, and as a result, have found that the use of a film having a specific configuration can easily solve the above-mentioned problems, and have completed the present invention.

That is, according to the first aspect of the present invention, there is provided a film having a polycarbonate resin as a main component and produced through a stretching step and a heat setting step, and having the following characteristics (1) to (3). Is done.
(1) Three-dimensional birefringence (Nx, Ny, Nz) is Nx>Ny> Nz.
(2) The ratio of the thickness retardation (Rth) to the in-plane retardation (Re) is 1.5 nm ≦ Rth / Re ≦ 6.0 nm.
(3) The thickness retardation (Rth) is 130 nm ≦ Rth ≦ 180 nm.

According to a second aspect of the present invention, there is provided the film according to the first aspect, which is a biaxially stretched film, the stretching temperature (T1) and the stretching ratio (V1) of the uniaxial stretching, and the biaxial stretching. The stretching temperature (T2) and stretching ratio (V2) of the eyes, the heat setting temperature (T3) of the heat setting zone immediately after the stretching of the biaxial stretching, and the resin containing polycarbonate as a main component according to claim 1. A film having a glass transition temperature (Tg) satisfying the following conditions (4) to (6) is provided.
(4) 10 ° C <(T2-T1) <20 ° C
(5) -0.2 times <(V2-V1) <0.5 times (6) (Tg-30) .degree. C..ltoreq.T3.ltoreq. (Tg-10) .degree.

  Further, according to a third aspect of the present invention, in the first or second aspect, the polycarbonate resin contains a structural unit derived from a dihydroxy compound represented by the following formula (I). A film is provided.

  According to a fourth aspect of the present invention, in the third aspect, the polycarbonate resin further contains a structural unit derived from tricyclodecane dimethanol represented by the following formula (II). Is provided.

Further, according to the fifth aspect of the present invention, a film having the following characteristics (1) to (3) is produced by biaxially stretching a film obtained by forming a raw material to be a polycarbonate resin. A stretching temperature (T1) and a stretching ratio (V1) of the uniaxial stretching in the biaxial stretching, a stretching temperature (T2) and a stretching ratio (V2) of the biaxial stretching, and a biaxial stretching. The heat setting temperature (T3) of the heat setting zone immediately after eye stretching and the glass transition temperature (Tg) of the resin containing polycarbonate as a main component according to claim 1 are the following conditions (4) to (6). Provided is a method for producing a film, characterized by satisfying the following.
(1) Three-dimensional birefringence (Nx, Ny, Nz) is Nx>Ny> Nz.
(2) The ratio of the thickness retardation (Rth) to the in-plane retardation (Re) is 1.5 nm ≦ Rth / Re ≦ 6.0 nm.
(3) The thickness retardation (Rth) is 130 nm ≦ Rth ≦ 180 nm.
(4) 10 ° C <(T2-T1) <20 ° C
(5) -0.2 times <(V2-V1) <0.5 times (6) (Tg-30) .degree. C..ltoreq.T3.ltoreq. (Tg-10) .degree.

  According to a sixth aspect of the present invention, there is provided a film manufactured by the method for manufacturing a film according to the fifth aspect.

  According to a seventh aspect of the present invention, there is provided a retardation film comprising the film according to any one of the first to fourth aspects or the sixth aspect.

  According to an eighth aspect of the present invention, there is provided a polarizing plate manufactured using the film according to any one of the first to fourth aspects or the sixth aspect.

  According to a ninth aspect of the present invention, there is provided a liquid crystal display device provided with the polarizing plate according to the eighth aspect.

  According to the present invention, it is possible to provide a film which is excellent in wet heat resistance and dimensional stability, is excellent in mechanical strength, and is suitable as a retardation film to be bonded to a polarizing plate used in a liquid crystal display, Its industrial value is high.

[the film]
The film of the present invention contains a polycarbonate resin as a main component, and has three-dimensional birefringence (Nx, Ny, Nz), in-plane retardation (Re), and thickness retardation (Rth) of the following (1) to (3). ).
(1) Three-dimensional birefringence (Nx, Ny, Nz) is Nx>Ny> Nz.
(2) The ratio of thickness retardation (Rth) to in-plane retardation (Re) is 1.5 ≦ Rth / Re ≦ 6.0 nm.
(3) The thickness retardation (Rth) is 130 nm ≦ Rth ≦ 180 nm.

Here, the in-plane retardation (Re) and the thickness retardation (Rth) are calculated by the following equations, where Nx is a slow axis.
Re = (Nx−Ny ) × film thickness Rth = ((Nx + Ny) / 2−Nz) × film thickness

  The term “main component” as used herein means that the component in the film is preferably 50% by weight or more, more preferably 80% by weight or more, and still more preferably 90% by weight or more.

  The film of the present invention may have a single-layer structure or a multi-layer structure. In the case of a multi-layer structure, four or more layers as long as it does not exceed the gist of the present invention other than the two-layer and three-layer structures. It may be a multilayer, and is not particularly limited.

1. Hereinafter, the physical properties and the like of the film of the present invention will be specifically described.

(1) Three-dimensional birefringence The three-dimensional birefringence (Nx, Ny, Nz) of the film of the present invention is Nx>Ny> Nz.
That is, when the film of the present invention is used for a liquid crystal, particularly a retardation film of a VA liquid crystal device, in order to obtain a viewing angle enlarging effect without the necessity of sequentially laminating a plurality of retardation films, Nx is required. >Ny> Nz.

(2) In-plane retardation (Re)
Although the in-plane retardation (Re) of the film of the present invention is not particularly limited, it is preferably 30 nm or more and 100 nm or less, and particularly preferably 35 nm or more and 60 nm or less. That is, when the film of the present invention is used for a liquid crystal, particularly a retardation film of a VA liquid crystal device, it is necessary to have an in-plane retardation (Re) in the above range in order to effectively prevent light leakage. is there. If the in-plane retardation (Re) of the film is out of the above range, it is impossible to prevent light leakage from the liquid crystal from an oblique direction.

(3) Thickness phase difference (Rth)
The thickness retardation (Rth) of the film of the present invention is from 130 nm to 180 nm, preferably from 135 nm to 160 nm. That is, when the film of the present invention is used as a retardation film of a liquid crystal device, particularly a liquid crystal device of a VA mode, in which a liquid crystal having a high degree of vertical orientation is used, in order to effectively prevent light leakage. Needs to have a thickness retardation (Rth) in the above range. If the thickness retardation (Rth) of the film is out of the above range, it is impossible to cancel out the effect of the light incident on the liquid crystal from the vertical direction and the liquid crystal having the positive-C three-dimensional birefringence distribution.

(4) Ratio between thickness retardation (Rth) and in-plane retardation (Re) The ratio of the thickness retardation (Rth) to the in-plane retardation (Re) of the film of the present invention is 1.5 or more and 6.0 or more. Or less, and particularly preferably 2.0 or more and 5.0 or less. That is, when the film of the present invention is used as a retardation film of a liquid crystal device, particularly a liquid crystal device of a VA mode, in which a liquid crystal having a high degree of vertical orientation is used, in order to effectively prevent light leakage. Needs to have a ratio of the thickness retardation (Rth) to the in-plane retardation (Re) within the above range. When the ratio of the thickness retardation (Rth) to the in-plane retardation (Re) of the film is out of the above range, the light incident on the liquid crystal from the oblique direction, the light incident from the vertical direction, and the three-dimensional composite of the Positive-C. Both effects of the liquid crystal having the refractive index distribution and the liquid crystal cannot be offset.

  A film whose three-dimensional birefringence (Nx, Ny, Nz), in-plane retardation (Re), and thickness retardation (Rth) satisfy the above conditions (1) to (3) is, for example, a polycarbonate resin as a main component. Preferably, the film can be produced by the method for producing a film of the present invention through a specific sequential biaxial stretching step described later using a polycarbonate resin described below.

  The specific measurement method of the three-dimensional birefringence (Nx, Ny, Nz), in-plane retardation (Ro), and thickness retardation (Rth) of the film is as described in Examples below. is there.

The thickness of the film of the present invention is not particularly limited, but the upper limit is preferably 80 μm or less, more preferably 70 μm or less, and particularly preferably 60 μm or less. When the thickness of the film exceeds 80 μm, the total thickness of the polarizing plate using the film increases, and it is difficult to reduce the thickness of the liquid crystal panel. The thickness of the film can be adjusted by the film forming conditions and the like. For example, when a film is produced by melt extrusion, the film thickness can be adjusted by the amount of extrusion and the take-off speed. When a film is produced by the solution dripping method, the film thickness can be adjusted by the concentration of the solution and the like.
Although the lower limit of the film thickness of the film of the present invention is not particularly limited, it is usually 3 μm or more, preferably 5 μm or more, more preferably 10 μm or more from the viewpoint of mechanical strength.

2. Polycarbonate Resin The film of the present invention contains a polycarbonate resin (hereinafter sometimes referred to as “the polycarbonate resin of the present invention”) as a main component.
Polycarbonate resin has excellent dimensional stability and wet heat resistance, and it is also possible to increase mechanical strength and optical characteristics by raw material design.Polarization used for liquid crystal display by using polycarbonate resin as a main component A high-characteristic film suitable as a retardation film to be bonded to a plate can be obtained.

  Representative examples of the polycarbonate resin of the present invention include aromatic polycarbonates having a structural unit of 2,2′-bis (4-hydroxyphenyl) -propane (commonly known as bisphenol-A). The polycarbonate resin to be used is not limited to this, and for example, 1,1-bis (4-hydroxyphenyl) -alkylcycloalkane, 1,1-bis (3-substituted-4-hydroxyphenyl) -alkylcycloalkane At least one dihydric phenol selected from the group consisting of 1,1-bis (3,5-substituted-4-hydroxyphenyl) -alkylcycloalkanes and 9,9-bis (4-hydroxyphenyl) fluorenes Or a homo- or copolycarbonate having the above-mentioned dihydric phenol and bispheno as a monomer component Mixtures of Le A and polycarbonate as a monomer component, such as a copolycarbonate of the above dihydric phenol and the bisphenol A monomers components.

As the polycarbonate resin of the present invention, a structure derived from a dihydroxy compound having a site represented by the following formula (I) in a part of the structure in terms of high transparency, high strength, high heat resistance, high weather resistance and the like. Polycarbonate resins containing units are preferred. More specifically, examples of the dihydroxy compound represented by the above formula (I) include, for example, isosorbide, isomannide and isoidet, which are in a stereoisomeric relationship.

  The dihydroxy compound represented by the formula (I) is an ether diol that can be produced from a saccharide using a biological substance as a raw material. In particular, isosorbide can be produced at low cost by hydrogenating D-glucose obtained from starch and then dehydrating it, and can be obtained abundantly as a resource. Under these circumstances, isosorbide is most preferred as the dihydroxy compound represented by the above formula (I).

  The polycarbonate resin of the present invention may further contain a structural unit other than the structural unit derived from the dihydroxy compound having the site represented by the formula (I). By further including a structural unit other than the structural unit derived from the dihydroxy compound having the site represented by the formula (I), it becomes possible to improve workability and impact resistance.

  Among the structural units other than the structural unit derived from the dihydroxy compound having the site represented by the formula (I), a structural unit derived from a dihydroxy compound having no aromatic ring is preferably used.

  More specifically, for example, a structural unit derived from an aliphatic dihydroxy compound described in WO2004 / 111106 and a structural unit derived from an alicyclic dihydroxy compound described in WO2007 / 148604 may be mentioned. it can.

  Among the structural units derived from the aliphatic dihydroxy compound, at least one kind selected from ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, and 1,6-hexanediol It preferably contains a structural unit derived from a dihydroxy compound.

  Among the structural units derived from the alicyclic dihydroxy compound, those having a 5-membered ring structure or a 6-membered ring structure are preferable. The six-membered ring structure may be fixed in a chair shape or a boat shape by a covalent bond.

  By including a structural unit derived from an alicyclic dihydroxy compound having a 5-membered ring structure or a 6-membered ring structure, the heat resistance of the obtained polycarbonate resin can be increased.

  The number of carbon atoms contained in the alicyclic dihydroxy compound is usually preferably 70 or less, more preferably 50 or less, and even more preferably 30 or less.

Examples of the alicyclic dihydroxy compound having a 5-membered ring structure or a 6-membered ring structure include those described in the above-mentioned WO 2007/148604.
Among them, cyclohexanedimethanol, tricyclodecanedimethanol, adamantanediol and pentacyclopentadecanedimethanol can be preferably exemplified. Among them, cyclohexane dimethanol or tricyclodecane dimethanol is more preferable from the viewpoint of economy and heat resistance. In particular, it is most preferable to contain a structural unit derived from tricyclodecane dimethanol represented by the following formula (II) in terms of balance with economic efficiency, heat resistance, and optical characteristics.
In addition, only one kind of these other structural units may be contained in the polycarbonate resin, or two or more kinds thereof may be contained.

In the polycarbonate resin, the content ratio of the structural unit derived from the dihydroxy compound having the site represented by the formula (I) in a part of the structure, relative to the structural units derived from all dihydroxy compounds in the polycarbonate resin, It is preferably at least 30 mol%, more preferably at least 40 mol%, particularly preferably at least 50 mol%, and preferably at most 90 mol%, more preferably at most 80 mol%.
If the content of the structural unit derived from the dihydroxy compound having the site represented by the formula (I) in a part of the structure of the polycarbonate resin is equal to or higher than the lower limit, the heat resistance is improved by maintaining the glass transition temperature. Is possible, and a film satisfying a high tear strength described below can be obtained, which is preferable. On the other hand, by being equal to or less than the upper limit, it is possible to suppress coloring derived from the carbonate structure, coloring derived from impurities contained in a trace amount because a biological material is used as a raw material, and the transparency normally required for a polycarbonate film. There is a possibility that the property is not impaired. In addition, it is difficult to achieve a suitable molding processability, mechanical strength and mechanical strength which are difficult to achieve with a polycarbonate resin or the like composed only of a structural unit derived from a dihydroxy compound having a site represented by the formula (I) in a part of the structure. A balance such as heat resistance can be obtained.

  The polycarbonate resin includes a structural unit derived from a dihydroxy compound having a site represented by the formula (I) in a part of the structure, and a structural unit derived from an aliphatic dihydroxy compound and / or an alicyclic dihydroxy compound. It is preferable that the structural unit is derived from a structural unit derived from the compound. However, a structural unit derived from a dihydroxy compound other than these may be further included as long as the object of the present invention is not impaired.

  The polycarbonate resin can be produced by a commonly used polymerization method. The method for producing the polycarbonate resin may be either the phosgene method or the transesterification method of reacting with a carbonic acid diester. Above all, in the presence of a polymerization catalyst, a dihydroxy compound having a site represented by the above formula (I) in a part of the structure, an aliphatic and / or alicyclic dihydroxy compound, and other A transesterification method of reacting a dihydroxy compound with a carbonic acid diester is preferred.

  In the transesterification method, one or two or more dihydroxy compounds having a site represented by the above formula (I) in a part of the structure and one or two or more aliphatic and / or alicyclic dihydroxy compounds are used. And one or more other dihydroxy compounds used as necessary and a carbonic acid diester with a basic catalyst and further an acidic substance that neutralizes the basic catalyst to effect a transesterification reaction. It is a manufacturing method to be performed.

  Representative examples of the carbonic acid diester include diphenyl carbonate, ditolyl carbonate, bis (chlorophenyl) carbonate, m-cresyl carbonate, dinaphthyl carbonate, bis (biphenyl) carbonate, diethyl carbonate, dimethyl carbonate, dibutyl carbonate, dicyclohexyl carbonate, and the like. Is mentioned. These may be used alone or as a mixture of two or more. Of these, diphenyl carbonate is particularly preferably used.

The molecular weight of the polycarbonate resin of the present invention can be represented by a reduced viscosity. The lower limit of the reduced viscosity is preferably 0.20 dl / g or more, more preferably 0.30 dL / g or more, and further preferably 0.35 dL / g or more. Preferably, the upper limit of the reduced viscosity is preferably 2.00 dL / g or less.
If the reduced viscosity of the polycarbonate resin is too low, the mechanical strength of the obtained film may be low, and if it is too high, the fluidity at the time of molding tends to decrease, and productivity and moldability tend to decrease.

The reduced viscosity of the polycarbonate resin was determined by using an Ubbelohde viscometer with a DT-504 type automatic viscometer manufactured by Chuo Rika Co., using methylene chloride as a solvent, and adjusting the polycarbonate resin concentration to 0.60 g / dl. After the adjustment, the temperature is calculated from the measured value at 20.0 ° C. ± 0.1 ° C. based on the following.
From the passage time t _{0 of the} solvent and the passage time t of the solution, the following formula:
η _rel = t / t ₀
More seek relative viscosity eta _rel, from the relative viscosity eta _rel, the formula:
η _sp = (η−η ₀ ) / η ₀ = η _rel −1
Then, the specific viscosity ηsp is determined.
Dividing the specific viscosity η _sp by the concentration c (g / dl) gives the following formula:
η _red = η _sp / c
The reduced viscosity (converted viscosity) η _red is determined from the equation.

The glass transition temperature (Tg), which is an index of the heat resistance of the polycarbonate resin of the present invention, is preferably 100 ° C. or higher, and more preferably 110 ° C. or higher. The upper limit of the glass transition temperature (Tg) is not particularly limited, but is usually 160 ° C. or lower.
The method for measuring the glass transition temperature of the polycarbonate resin is as described in the Examples section below.

3. Other components The film of the present invention may contain an ultraviolet absorber. When an ultraviolet absorber is contained, the weather resistance of the film can be improved, and the deterioration of the liquid crystal and the polarizing film by ultraviolet light can be prevented. As the ultraviolet absorber used for the film of the present invention, known ones, for example, various commercially available ones can be used without any particular limitation. Among them, those commonly used for addition to known aromatic polycarbonate resins can be suitably used.

  Examples of the ultraviolet absorber include 2- (2′-hydroxy-5′-tert-octylphenyl) benzotriazole and 2- (3-tert-butyl-5-methyl-2-hydroxyphenyl) -5-chlorobenzo. Triazole, 2- (5-methyl-2-hydroxyphenyl) benzotriazole, 2- [2-hydroxy-3,5-bis (α, α-dimethylbenzyl) phenyl] -2H-benzotriazole, 2,2′- Methylenebis (4-cumyl-6-benzotriazolephenyl) and 2,2′-methylenebis [6- (2H-benzotriazol-2-yl) -4- (1,1,3,3-tetramethylbutyl) phenol] Benzotriazole ultraviolet absorbers such as 2- (4,6-diphenyl-1,3,5-triazin-2-yl) -5- (hex Trioxy-based ultraviolet absorbers such as loxy) -phenol; benzoxazine-based ultraviolet absorbers such as 2,2'-p-phenylenebis (1,3-benzoxazin-4-one); 2- (4,6-diphenyl) Hydroxyphenyltriazine-based ultraviolet absorbers such as -1,3,5-triazin-2-yl) -5- (hexyl) oxy-phenol;

  The melting point of the ultraviolet absorber is particularly preferably in the range of 120C to 250C. By using an ultraviolet absorber having a melting point of 120 ° C. or higher, the surface of the film becomes dirty due to a bleed-out phenomenon in which the ultraviolet absorber aggregates with time, or when the film is formed using a die or a metal roll, Bleed-out prevents them from becoming dirty and makes it easier to reduce and improve fogging on the film surface.

  From these viewpoints, as the ultraviolet absorber, 2,2′-methylenebis [6- (2H-benzotriazol-2-yl) -4- (1,1,3,3-tetramethylbutyl) phenol], -(2'-hydroxy-5'-methylphenyl) benzotriazole, 2- (2'-hydroxy-3'-tert-butyl-5'-methylphenyl) -5-chlorobenzotriazole, 2- [2'- Hydroxy-3 '-(3 ", 4", 5 ", 6" -tetrahydrophthalimidomethyl) -5'-methylphenyl] benzotriazole, 2,2-methylenebis [4- (1,1,3,3-tetra Methylbenzo) -6- (2H-benzotriazol-2-yl)] phenol and benzotriazoles such as 2- (2-hydroxy-3,5-dicumylphenyl) benzotriazole A sol-based ultraviolet absorber and a hydroxyphenyltriazine-based ultraviolet absorber such as 2- (4,6-diphenyl-1,3,5-triazin-2-yl) -5- (hexyl) oxy-phenol can be preferably used. .

Among these, benzotriazole-based and triazine-based UV absorbers can be preferably used from the viewpoint of compatibility with the polycarbonate resin of the present invention and efficient prevention of UV deterioration of liquid crystals and polarizing films.
One of these ultraviolet absorbers may be used alone, or two or more thereof may be used in combination.

The ultraviolet absorber is preferably contained in the film of the present invention in a proportion of 0.0001 to 20 parts by weight, based on 100 parts by weight of the polycarbonate resin, and 0.0005 to 15 parts by weight. The content is more preferably at a ratio of not more than 0.001 part by weight, more preferably at a ratio of not less than 0.001 part by weight and not more than 10 parts by weight.
By containing an ultraviolet absorber in such a range, the bleeding of the ultraviolet absorber on the film surface and the deterioration of the mechanical properties of the film do not occur, the weather resistance of the film of the present invention is improved, and the ultraviolet light of the liquid crystal or the polarizing film is also improved. Deterioration can be prevented.

  To the extent that the object of the present invention is not impaired, the film of the present invention may also contain other additives such as a silane coupling agent, an antioxidant, and a weather stabilizer in appropriate amounts as additives other than the ultraviolet absorber. It may be contained. Further, a resin other than the polycarbonate resin of the present invention may be contained as long as the object of the present invention is not impaired.

4. The method for producing a film of the present invention is a film comprising the above-mentioned polycarbonate resin of the present invention as a main component and undergoing a stretching step and a heat setting step, and has three-dimensional birefringence (Nx, Ny, Nz), Any method can be used as long as it can produce a film having the internal retardation (Re) and the thickness retardation (Rth) satisfying the above-mentioned conditions (1) to (3), and there is no particular limitation. There is a method of biaxially stretching a film obtained by forming a raw material containing the polycarbonate resin of the present invention as a main component under specific conditions and heat fixing the film. Hereinafter, a method for producing this film will be described.

4-1. As a method for forming a film of the present invention, known methods, for example, a solution dripping method, a single-screw extruder, a multi-screw extruder, a Banbury mixer, having a melt-mixing equipment such as a kneader, An extrusion casting method using a T die, a calendar method, or the like can be adopted, and is not particularly limited. However, in the present invention, an extrusion casting method using a T die is preferable in terms of handling properties and productivity. Used for The molding temperature in the extrusion casting method using a T die is appropriately adjusted depending on the flow characteristics and film forming properties of the polycarbonate resin to be used, but is generally about 80 ° C. or higher, preferably 100 ° C. or higher, more preferably 120 ° C. or higher, furthermore It is preferably 140 ° C. or higher, and generally 320 ° C. or lower, preferably 300 ° C. or lower, more preferably 280 ° C. or lower, and still more preferably 260 ° C. or lower. When a silane coupling agent or the like is added, the reaction is accompanied. It is preferable to lower the molding temperature in order to suppress an increase in resin pressure and an increase in fish eyes. Various additives such as a silane coupling agent, an antioxidant, an ultraviolet absorber, and a weathering stabilizer may be dry-blended with the polycarbonate resin in advance and then supplied to the hopper, or all the materials such as the polycarbonate resin may be used in advance. The pellets may be melt-mixed to produce pellets and then supplied, or a masterbatch in which only additives are previously concentrated in a resin such as a polycarbonate resin may be produced and supplied.

4-2. Film stretching method The film of the present invention whose three-dimensional birefringence (Nx, Ny, Nz), in-plane retardation (Re), and thickness retardation (Rth) satisfy the above conditions (1) to (3) is The film obtained as described above can be further subjected to a stretching treatment. As the stretching method of the film, a general biaxial stretching method such as the following (1) to (4) can be adopted, and is not particularly limited, but in the present invention, in the film transport direction It is preferable from the viewpoint of productivity that successive biaxial stretching in which a tenter stretching is performed in a direction orthogonal to the film transport direction after performing the roll stretching is performed.
(1) After performing roll stretching in the film transport direction, sequential biaxial stretching in which tenter stretching is performed in a direction perpendicular to the film transport direction
(2) After performing tenter stretching in the direction perpendicular to the film transport direction, successive biaxial stretching in which roll stretching is performed in the film transport direction
(3) Sequential biaxial stretching in which the tenter stretching is performed in the direction perpendicular to the film transport direction, and then the film itself is perpendicularized and the tenter stretching is performed again
(4) Simultaneous biaxial stretching

In the biaxial stretching method carried out in the present invention, in particular, the in-plane retardation (Re) and the thickness retardation (Rth) of the obtained film satisfy the conditions (2) and (3). The stretching temperature (T1) and stretching ratio (V1) of the uniaxial stretching, the stretching temperature (T2) and the stretching ratio (V2) of the biaxial stretching, and the heat setting temperature of the heat setting zone immediately after the stretching of the biaxial stretching. (T3) The glass transition temperature (Tg) of the resin containing polycarbonate as a main component according to claim 1 preferably satisfies the following conditions (4) to (6), and particularly, the following (4A) It is preferable to satisfy the following conditions.
(4) 10 ° C <(T2-T1) <20 ° C
(5) -0.2 times <(V2-V1) <0.5 times (6) (Tg-25) C≤T3≤ (Tg-10) C
(4A) 12 ° C ≦ (T2-T1) ≦ 18 ° C
(5A) -0.1 times ≦ (V2-V1) ≦ 0.4 times (6A) (Tg−30) ° C. ≦ T3 ≦ (Tg−15) ° C.

  Here, the units of the stretching temperatures (T1), (T2) and (T3) are “° C.”, and the stretching ratios (V1) and (V2) are “times”.

When the difference (T2−T1) in the stretching temperature is 10 or less, the rate of increase in the three-dimensional birefringence Nx, Ny, and Nz during stretching is high, and the difference between Nx, Ny, and Nz becomes too large, and the predetermined in-plane When the phase difference (Re) and the thickness phase difference (Rth) cannot be kept within the range, and (T2−T1) is 20 or more, the difference between Nx and Ny becomes small and the predetermined in-plane phase difference (Re) cannot be satisfied.
When the difference (V2−V1) in the stretching ratio is −0.2 or less, the difference between the three-dimensional birefringences Nx, Ny, and Nz becomes too large to fall within a predetermined thickness phase difference (Rth). In addition, it is difficult to produce a wide film industrially, and when (V1-V2) is 0.5 or more, the difference between Nx and Ny becomes small and the predetermined thickness phase difference ( Rth).

  The heat setting temperature (T3) of the heat setting zone immediately after the stretching in the biaxial stretching preferably satisfies the above condition (6), preferably the condition (6A). When (T3) is smaller than (Tg−25), the difference between Nx and Ny of the three-dimensional birefringence during stretching is too large to be within the predetermined range of in-plane retardation (Re). When (T3) is larger than (Tg-10), the difference between the three-dimensional birefringences Nx, Ny, and Nz at the time of stretching becomes too large to fall within a predetermined thickness phase difference (Rth). I can't do things.

  In the tenter stretching step, a heat setting zone is usually provided in several zones, but the temperature of the heat setting zone immediately after the film stretching satisfies the above condition (6). Is good. When the heat setting temperature of the zone other than the heat setting zone immediately after stretching is set to the above condition (6), the difference between Nx, Ny, and Nz of the three-dimensional birefringence after stretching becomes too large, and the predetermined Cannot be kept within the range of the thickness retardation (Rth).

  In the biaxial stretching process, the stretching temperature (T1) of the uniaxial stretching, the stretching ratio (V1), the stretching temperature of the biaxial stretching (T2), and the stretching ratio (V2) are as described in (4) and (4). The condition (5), preferably the condition (4A) and the condition (5A) may be satisfied. As a specific stretching condition, the stretching temperature (T1) of the uniaxial stretching is (Tg-10) to (Tg-10). Tg + 20) ° C., stretching ratio (V1) is in the range of 1.1 to 2.5 times, and stretching temperature (T2) of biaxial stretching is in the range of (Tg + 10) to (Tg + 40) ° C., stretching ratio (V2) is preferably set in a range of 1.1 to 3.0 times so as to satisfy the above condition. Here, “Tg” is a glass transition temperature (Tg) of a film forming raw material of a film containing a polycarbonate resin as a main component.

5. Liquid crystal display device The film of the present invention is excellent in transparency, dimensional stability, moisture and heat resistance, and also excellent in optical properties. Therefore, the retardation film of the present invention using such a film of the present invention is preferably used for televisions and personal computers. Thus, a high-quality display screen can be realized as a member of a liquid crystal display device such as a digital camera and a mobile phone, and the workability in manufacturing the liquid crystal display device is excellent.

  As described above, when the display side is the front side and the opposite side (backlight side) is the back side, the liquid crystal display has a configuration of front side polarizing plate / liquid crystal / back side polarizing plate. Further, in some liquid crystal systems, a retardation film is interposed in order to prevent light leakage of the liquid crystal device. For example, in a VA liquid crystal system, it is called front side polarizing plate / phase difference film / liquid crystal / phase difference film / rear side polarizing plate. Configuration.

  The film of the present invention has a polarizing film adhered to one film surface side via an adhesive layer, and a liquid crystal or another functional film or a transparent substrate to the other film surface side via an adhesive layer. Can be glued. The other functional film is not particularly limited, for example, a high refractive index film, a low refractive index film, an antireflection film in which these are laminated, an optical film such as a color correction film, a hard coat film, an antifouling film, Examples include an electromagnetic wave shielding film, an infrared absorbing film, and an ultraviolet absorbing film. Examples of the transparent substrate include glass as a support substrate and various transparent films.

  Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited by these Examples and Comparative Examples. In the following, the transport direction at the time of stretching the film is referred to as MD, and the perpendicular direction thereof is referred to as TD.

[Evaluation method]
Hereinafter, the measurement and evaluation of various physical properties and the like were performed as follows.

<Glass transition temperature (Tg)>
Using a differential scanning calorimeter (manufactured by Perkin Elmer Co., Ltd., trade name: Pyris1 DSC), about 10 mg of the sample was heated from room temperature to 250 ° C. at a heating rate of 10 ° C./min according to JIS K7122, and 250 After holding at 5 ° C. for 5 minutes, the temperature was lowered to room temperature at a cooling rate of 10 ° C./min, and the glass transition temperature (Tg) was determined from a thermogram measured when the temperature was raised again to 250 ° C. at a heating rate of 10 ° C./min. Was read.

<Three-dimensional birefringence (Nx, Ny, Nz), in-plane retardation (Ro) and thickness retardation (Rth)>
Each film was measured using a phase difference measuring device (manufactured by Oji Scientific Co., Ltd., trade name: KOBRA-WR). Note that Rth was calculated from the phase difference between when the incident angle was 0 ° and when it was 40 °. From the measurement results, evaluation was made as follows.
<Three-dimensional birefringence (Nx, Ny, Nz)>
：: Nx>Ny> Nz is satisfied.
X: Nx>Ny> Nz is not satisfied.
<Ratio of in-plane retardation (Re) to thickness retardation (Rth)>
：: 1.5 ≦ Rth / Re ≦ 6.0.
×: Rth / Re <1.5 or 6.0 <Rth / Re.
<Comprehensive evaluation>
：: All three-dimensional birefringence (Nx, Ny, Nz), ratio Rth / Re of in-plane retardation (Re) and thickness retardation (Rth) are ○.
×: at least one of three-dimensional birefringence (Nx, Ny, Nz) and the ratio Rth / Re of in-plane retardation (Re) to thickness retardation (Rth) is ×.

[Polycarbonate resin]
The polycarbonate resin used for the production of the film was obtained by a method according to JP-A-2008-024919, and was obtained by a molar ratio of a structural unit derived from isosorbide, which is a dihydroxy compound, and a structural unit derived from tricyclodecanedimethanol. Is a polycarbonate copolymer having isosorbide / tricyclodecane dimethanol = 6/4 and a glass transition temperature (Tg) of 132 ° C.

[Example 1]
The above polycarbonate resin is put into a φ65 mm single screw extruder, melt-kneaded at a barrel setting temperature of 220 to 240 ° C., extruded from a die having a width of 1350 mm and a lip gap of 0.5 mm (setting temperature of 240 ° C.), and then heated to 100 ° C. The film was rolled up by a cast roll adjusted to a temperature of 100 μm to produce a single-layer film having a thickness of 100 μm.

  This single-layer film was roll-stretched to MD and then stretched to TD by sequential biaxial stretching in which tenter stretching was performed. At that time, the stretching temperature (T1) and stretching ratio (V1) of the uniaxial stretching, the stretching temperature (T2) and the stretching ratio (V2) of the biaxial stretching, and the heat setting temperature (T3) are as shown in Table 1. The relationship was T2-T1 = 16 ° C., V2-V1 = 0 times, and T3 = 115 ° C. The thickness of the obtained stretched film was 51 μm.

[Comparative Example 1]
The single-layer film of Example 1 was roll-stretched to MD, and then stretched to a TD by a sequential biaxial stretching method in which tenter stretching was performed. At that time, the stretching temperature (T1) and stretching ratio (V1) of the uniaxial stretching, the stretching temperature (T2) and the stretching ratio (V2) of the biaxial stretching, and the heat setting temperature (T3) are as shown in Table 1. The relationship was T2-T1 = 16 ° C., V2-V1 = 0 times, and T3 = 125 ° C. The thickness of the obtained stretched film was 50 μm.

[Comparative Example 2]
The single-layer film of Example 1 was roll-stretched to MD, and then stretched to a TD by a sequential biaxial stretching method in which tenter stretching was performed. At that time, the stretching temperature (T1) and stretching ratio (V1) of the uniaxial stretching, the stretching temperature (T2) and the stretching ratio (V2) of the biaxial stretching, and the heat setting temperature (T3) are as shown in Table 1. The relationship was T2-T1 = 16 ° C., V2-V1 = 0.8 times, and T3 = 115 ° C. The thickness of the obtained stretched film was 36 μm.
[Comparative Example 3]
The single-layer film of Example 1 was roll-stretched to MD, and then stretched to a TD by a sequential biaxial stretching method in which tenter stretching was performed. At that time, the stretching temperature (T1) and stretching ratio (V1) of the uniaxial stretching, the stretching temperature (T2) and the stretching ratio (V2) of the biaxial stretching, and the heat setting temperature (T3) are as shown in Table 1. The relationship was T2-T1 = 16 ° C., V2-V1 = 0 times, and T3 = 125 ° C. However, the heat setting temperature other than the heat setting zone immediately after film stretching was 115 ° C. The thickness of the obtained stretched film was 51 μm.
[Comparative Example 4]
The single-layer film of Example 1 was roll-stretched to MD, and then stretched to a TD by a sequential biaxial stretching method in which tenter stretching was performed. At that time, the stretching temperature (T1) of the uniaxial stretching and the stretching ratio (V1), the stretching temperature (T2) of the biaxial stretching and the stretching ratio (V2) are as shown in Table 1, and the relationship is T2-T1. = 0 ° C, V2-V1 = 0.4 times. The thickness of the obtained stretched film was 51 μm.

  Table 1 shows the evaluation results of the films of Examples and Comparative Examples.

As is clear from Table 1, the film of Example 1 was made of a polycarbonate resin, and sequentially biaxially stretched and heat-set under specific stretching conditions, thereby obtaining three-dimensional birefringence (Nx, Ny, Nz) and surface. The internal retardation (Re) and the thickness retardation (Rth) satisfy predetermined conditions, and are excellent in optical properties as a retardation film.
On the other hand, in Comparative Example 1, the heat setting temperature T3 does not satisfy the condition (6), and the thickness retardation (Rth) is an optical characteristic out of the range of the present invention. In Comparative Example 2, (V2-V1) at the time of sequential biaxial stretching did not satisfy the condition (5), and the ratio of the thickness retardation (Rth) to the in-plane retardation (Re) and the thickness retardation (Rth) were different. It is outside the scope of the invention. In Comparative Example 3, although the temperature setting of the heat setting zone other than the present invention is the condition (6), the heat setting temperature after stretching does not satisfy the condition (6), and the thickness phase difference (Rth) of the present invention is low. Are out of the range. In Comparative Example 4, (T2−T1) at the time of sequential biaxial stretching did not satisfy the condition (4), and the ratio of the thickness retardation (Rth) to the in-plane retardation (Re) and the thickness retardation (Rth) were the present invention. And the optical properties are unsuitable for a retardation film.

Claims (6)

A structural unit derived from a dihydroxy compound represented by the following formula (I) and a structural unit derived from an alicyclic dihydroxy compound containing a 5-membered or 6-membered ring structure and having no aromatic ring (however, And a stretching step of stretching a film containing a polycarbonate resin as a main component, which contains a structural unit derived from a dihydroxy compound represented by the following formula (I)):
A heat setting step of heat setting the film after the stretching treatment,
A method for producing a film having the following characteristics (1) to (3).
(1) Three-dimensional birefringence (Nx, Ny, Nz) is Nx>Ny> Nz.
(2) The ratio of in-plane retardation (Re) to thickness retardation (Rth) is 1.5 ≦ Rth / Re ≦ 6.0.
(3) The thickness retardation (Rth) is 130 nm ≦ Rth ≦ 180 nm.

Biaxial stretching is performed in the stretching step, and the stretching temperature (T1) and stretching ratio (V1) of the uniaxial stretching, the stretching temperature (T2) and the stretching ratio (V2) of the biaxial stretching, and the biaxial stretching The heat setting temperature (T3) of the heat setting zone immediately after eye stretching and the glass transition temperature (Tg) of the polycarbonate resin satisfy the following conditions (4) to (6). 3. The method for producing a film according to 1.
(4) 10 ° C <(T2-T1) <20 ° C
(5) -0.2 times <(V2-V1) <0.5 times (6) (Tg-30) .degree. C..ltoreq.T3.ltoreq. (Tg-10) .degree. The method for producing a film according to claim 2, wherein the polycarbonate resin contains a structural unit derived from tricyclodecane dimethanol represented by the following formula (II) as the alicyclic dihydroxy compound. .

  A method for producing a retardation film, comprising producing a retardation film by the method for producing a film according to claim 1.   A method for manufacturing a polarizing plate, comprising: manufacturing a polarizing plate using the film obtained by the method for manufacturing a film according to claim 1.   A method for manufacturing a liquid crystal display device, wherein a liquid crystal display device is manufactured using the polarizing plate obtained by the method for manufacturing a polarizing plate according to claim 5.