JPWO2016152381A1 - Manufacturing method of obliquely stretched film - Google Patents

Abstract

The manufacturing method of a diagonally stretched film has a diagonally stretching process and a heat setting process. In the oblique stretching step, while gripping both ends of the width direction of the film with a pair of gripping tools, one of the gripping tools is relatively advanced, and the other gripping tool is relatively delayed to transport the film. The film is stretched obliquely with respect to the width direction. The heat setting step is a step for fixing the optical axis of the obliquely stretched film after the oblique stretching step. In this heat setting step, the obliquely stretched film after the oblique stretching step is widened. The width of the part that has been widened to the leading side and the delay side from the part corresponding to the width L1 of the obliquely stretched film before widening in the heat setting step, where L1 is the width of the obliquely stretched film before widening after the end of oblique stretching Where L2 and L3 are satisfied, L3> L2 ≧ 0 mm is satisfied.

Description

  The present invention relates to a method for producing an obliquely stretched film in which a film is stretched in an oblique direction with respect to the width direction.

  2. Description of the Related Art Conventionally, a self-luminous display device such as an organic EL (Electro-Luminescence) display device called an OLED (Organic light-Emitting Diode) has been attracting attention. In the OLED, a reflector such as an aluminum plate is provided on the back side of the display in order to increase the light extraction efficiency. Therefore, external light incident on the display is reflected by the reflector to reduce the image contrast. .

  Therefore, in order to improve contrast of light and darkness by preventing reflection of external light, it is known that a stretched film and a polarizer are bonded to form a circularly polarizing plate, and this circularly polarizing plate is disposed on the surface side of the display. At this time, the circularly polarizing plate is formed by bonding the polarizer and the stretched film so that the in-plane slow axis of the stretched film is inclined at a desired angle with respect to the transmission axis of the polarizer. The

  However, a general polarizer (polarizing film) is obtained by stretching at a high magnification in the longitudinal direction, and its transmission axis coincides with the width direction. Further, the conventional retardation film is produced by longitudinal stretching or transverse stretching, and in principle, the in-plane slow axis is in the direction of 0 ° or 90 ° with respect to the longitudinal direction of the film. For this reason, in order to incline the transmission axis of the polarizer and the slow axis of the stretched film at a desired angle as described above, the long polarizing film and / or the stretched film are cut out at a specific angle and the film pieces are separated from each other. The batch method of bonding the sheets one by one had to be adopted, and the productivity was deteriorated.

  In contrast, the film is stretched in a desired angle direction (obliquely) with respect to the longitudinal direction, and the direction of the slow axis can be freely set to a direction that is neither 0 ° nor 90 ° with respect to the longitudinal direction of the film. Various methods for producing a long and obliquely stretched film that can be controlled have been proposed. For example, in the manufacturing method of Patent Document 1, the resin film is unwound from a direction different from the winding direction of the stretched film, and both ends of the resin film are gripped and transported by a pair of gripping tools. And the resin film is extended | stretched in the diagonal direction by changing the conveyance direction of a resin film in the middle. Thereby, the long diagonally stretched film which has a slow axis in the desired angle of more than 0 degrees and less than 90 degrees with respect to a longitudinal direction is manufactured.

  By using such a long diagonally stretched film, it becomes possible to produce a circularly polarizing plate by laminating a long polarizing film and a long diagonally stretched film in a roll-to-roll manner. Productivity will be dramatically improved.

  By the way, when the circularly polarizing plate manufactured as described above is applied to an OLED, and the display image is observed by placing the OLED in a temperature / humidity environment different from a normal one, an oblique stripe-shaped display unevenness as shown in FIG. I knew it would appear. Further, it was confirmed that the display unevenness was increased (becomes significant) when an environmental change (temperature change, humidity change) was intentionally applied.

  As a result of analyzing the cause of the above-mentioned oblique stripe-shaped display unevenness, it was found that there was a cause in the λ / 4 film used for the circularly polarizing plate. More specifically, in the production of an obliquely stretched film functioning as a λ / 4 film, as shown in FIG. 8, both ends in the width direction of the film are gripped by a pair of grippers Ci · Co, and one gripper Ci Is relatively advanced, and the other gripping tool Co is relatively delayed so as to convey the film, thereby performing oblique stretching. At the time of holding the film after the oblique stretching, a shrinkage force acts on the film due to the reaction of the oblique stretching and the temperature decrease, and this remains as a residual stress T in a slanted direction (slave shape, wrinkle shape) invisible. For this reason, as shown in FIG. 9, when the circularly polarizing plate 50 is formed by laminating the obliquely stretched film 51 and the polarizer 52, since the residual stress T remains in the film 51, there is a change in temperature and humidity. It is considered that the characteristics of the film 51 change due to the residual stress T and the display unevenness shown in FIG. 7 occurs.

  FIG. 10 schematically shows a state in which an avalan-like residual stress T is generated in manufacturing an obliquely stretched film. In the production of a normal obliquely stretched film, the film is passed through a preheating zone Z1 of a stretching machine and then obliquely stretched in the stretching zone Z2, and then the optical axis (slow axis) in the heat setting zone Z3. Fixed. The film stretched obliquely in the stretching zone Z2 is relatively more than the gripping tool side (delay side) that travels relatively delayed among the pair of gripping tools that grip both ends of the width direction of the film. Since the gripping tool side (leading side) traveling in advance enters the heat setting zone Z3 first, the film shrinkage starts from the leading side. For this reason, as shown in the figure, an avalan-like residual stress T is generated in the order of the leading side, the center in the width direction, and the delay side.

  The occurrence of such an avalan-like residual stress T is caused by increasing the width of the rail on which the pair of gripping tools travels within the stretching zone (while performing oblique stretching) as in Patent Document 2. This also occurs in the case of widening. FIG. 11 schematically shows a state in which an avalan-like residual stress T is generated when the film is widened in the stretching zone Z2. By widening the film in the stretching zone Z2, the film extends in the width direction, so that the film does not shrink in the stretching zone Z2, and therefore no loose residual stress is generated during the oblique stretching. However, after the oblique stretching is finished (in the heat setting zone Z3), the film shrinks from the leading side, and as in the case of FIG. Residual stress T is generated.

  Thus, in the diagonally stretched film manufactured by the conventional manufacturing method, as shown in FIGS. 10 and 11, in the film transport direction (direction from the stretching zone Z2 toward the heat setting zone Z3) and the width direction. On the other hand, since an avalan residual stress T is generated in an oblique direction, striped display unevenness occurs in the oblique direction in the OLED as shown in FIG. Therefore, in order to suppress such display unevenness, it is desired to manufacture an obliquely stretched film so that no avalan residual stress T remains in the obliquely stretched film.

International Publication No. 2007/111313 pamphlet (see claim 1, FIG. 1, etc.) JP 2007-203556 A (refer to claim 1, paragraphs [0046], [0060], [0061], FIGS. 1 to 4)

  In view of the above circumstances, an object of the present invention is to provide a method for producing an obliquely stretched film that can suppress the occurrence of an avalan residual stress after oblique stretching.

  The above object of the present invention is achieved by the following configurations.

In the manufacturing method of the obliquely stretched film according to one aspect of the present invention, one gripping tool is relatively advanced while the other gripping tool is relatively positioned while gripping both ends in the width direction of the film with a pair of gripping tools. A method of producing an obliquely stretched film having an oblique stretching step of stretching the film in an oblique direction with respect to the width direction by conveying the film with a delay,
Further comprising a heat fixing step for fixing the optical axis of the obliquely stretched film after the oblique stretching step is completed;
In the heat setting step, widening the obliquely stretched film after the oblique stretching step is completed,
With the width of the obliquely stretched film before widening after the end of oblique stretching as L1, in the heat setting step, the width was widened to the leading side and the delay side from the portion corresponding to the width L1 of the obliquely stretched film before widening. When the widths of the portions are L2 and L3, the following conditional expression (1) is satisfied. That is,
L3> L2 ≧ 0 mm (1)
It is.

  In the heat setting step after the end of the oblique stretching, the obliquely stretched film is widened and the film is pulled in the width direction, so that it is possible to suppress the occurrence of loose residual stress in the film after the oblique stretching. Thus, a circularly polarizing plate is formed using the manufactured obliquely stretched film, and even if this circularly polarizing plate is applied to an OLED and the OLED is placed in a different temperature and humidity environment, the above-described avalan-like residual stress is obtained. It is possible to suppress the occurrence of oblique stripe-like display unevenness. In addition, by satisfying conditional expression (1), it is possible to suppress the occurrence of an avalan-like residual stress without substantially changing the direction of the optical axis (slow axis) oriented in a predetermined direction by oblique stretching. Can do. Therefore, even if the film is widened in the heat setting step after oblique stretching, an obliquely stretched film having desired orientation characteristics can be obtained by fixing the optical axis in a predetermined direction.

It is a top view which shows typically the structure of the outline of the manufacturing apparatus of the diagonally stretched film which concerns on embodiment of this invention. It is a top view which shows typically an example of the rail pattern of the extending | stretching part of the said manufacturing apparatus. It is explanatory drawing which shows typically the shape of the film which passes the said extending | stretching part. It is explanatory drawing which shows typically a mode that an avalan-like residual stress is relieve | moderated when widening a diagonally stretched film within the heat setting zone of the said extending | stretching part. It is sectional drawing which shows the structure of the outline of the organic electroluminescent image display apparatus to which the said diagonally stretched film is applied. It is sectional drawing which shows the schematic structure of the liquid crystal display device to which the said diagonally stretched film is applied. It is explanatory drawing which shows the display nonuniformity in the display screen of the conventional organic EL image display apparatus. It is explanatory drawing which shows typically the method of the conventional general diagonal stretch. It is a disassembled perspective view of the circularly-polarizing plate manufactured using the film diagonally stretched by the conventional method. It is explanatory drawing which shows typically a mode that an avalan-like residual stress generate | occur | produces in manufacture of the conventional diagonally stretched film. It is explanatory drawing which shows typically a mode that an avalan-like residual stress generate | occur | produces, when expanding a film within an extending | stretching zone.

  An embodiment of the present invention will be described below with reference to the drawings. In the present specification, when the numerical range is expressed as A to B, the numerical value range includes the values of the lower limit A and the upper limit B.

  The method for producing a long obliquely stretched film according to the present embodiment is a method for producing a long obliquely stretched film by stretching a long original fabric film containing a thermoplastic resin in an oblique direction with respect to the width direction and the longitudinal direction. This is a method for producing a long obliquely stretched film.

  The orientation direction of the long obliquely stretched film, that is, the direction of the slow axis is an angle of more than 0 ° and less than 90 ° with respect to the width direction of the film in the film plane (in the plane perpendicular to the thickness direction). (The direction automatically forms an angle of more than 0 ° and less than 90 ° with respect to the longitudinal direction of the film). Since the slow axis is usually expressed in the stretching direction or a direction perpendicular to the stretching direction, the slow axis has such a slow axis by stretching in a direction of more than 0 ° and less than 90 ° with respect to the width direction of the film. A long diagonally stretched film can be produced. The angle formed by the width direction of the long obliquely stretched film and the slow axis, that is, the orientation angle, can be arbitrarily set to a desired angle in the range of more than 0 ° and less than 90 °.

  In the present embodiment, the long length refers to a film having a length of at least about 5 times the width of the film, preferably a length of 10 times or more, specifically a roll shape. It is possible to consider one having a length (film roll) that is wound around and stored or transported.

  A long diagonally stretched film is formed by forming a long unoriented film and then winding it around a core to form a wound body (raw film), and the raw film is obliquely stretched from the wound body. The film may be supplied and manufactured, or may be continuously supplied from the film forming process to the oblique stretching process without winding the long film after film formation. Continuously performing the film forming step and the oblique stretching step can feed back the film thickness and optical value results of the stretched film to change the film forming conditions to obtain a desired long obliquely stretched film. It is preferable because it is possible. Moreover, the long diagonally stretched film of desired length can be obtained by manufacturing a long diagonally stretched film continuously.

  Moreover, as a thermoplastic resin contained in a raw fabric film, an alicyclic olefin polymer resin (COP), a polycarbonate resin (PC), a cellulose ester resin, or the like can be used. Among these, the cellulose ester-based resin easily absorbs moisture, and the orientation angle θ is likely to vary due to humidity fluctuations associated with long-term use. Therefore, this embodiment suppresses the variation in the orientation angle θ in the width direction of the obliquely stretched film. The effect will be greater.

  In addition, the diagonally stretched film obtained by diagonally stretching the above-described raw film can be applied to a liquid crystal display device that can be visually recognized by wearing polarized sunglasses. That is, a circularly polarizing plate is constructed by further bonding an obliquely stretched film on the viewing side of the polarizer of the polarizing plate on the viewing side with respect to the liquid crystal layer. At this time, they are bonded together so that the slow axis of the obliquely stretched film and the transmission axis of the polarizer are 45 °. In this configuration, the linearly polarized light emitted from the liquid crystal layer and transmitted through the viewer-side polarizer is converted into circularly polarized light by the obliquely stretched film (functioning as QWP). Therefore, when an observer wears polarized sunglasses and observes the display image of the liquid crystal display device, the polarization sunglasses and the transmission axes of the polarized sunglasses are not limited to any angle. A display image can be observed by guiding a light component parallel to the transmission axis to the eyes of the observer. Therefore, it is possible to suppress the display image from becoming difficult to see depending on the viewing angle (depending on the direction of the transmission axis of the polarized sunglasses). In particular, by forming an obliquely stretched film using the raw film of the present embodiment, unevenness of the orientation angle θ in the width direction of the film can be suppressed, so even if the liquid crystal display device is used for a long time, the screen A uniform image with no unevenness as a whole can be observed through polarized sunglasses.

  Thus, when applying an obliquely stretched film to the circularly polarizing plate of a liquid crystal display device compatible with polarized sunglasses, it is desirable to form a hard coat layer for protecting the surface on the viewing side of the obliquely stretched film.

  Hereinafter, embodiments of the present invention will be specifically described with reference to the drawings as appropriate.

<Cellulose ester resin>
As the cellulose ester-based resin film used for the raw fabric film of the present embodiment, a cellulose acylate satisfying the following formulas (1) and (2) is contained, and a compound represented by the following general formula (A) is used. The thing to contain is mentioned.
Formula (1) 2.0 <= Z1 <3.0
Formula (2) 0 ≦ X <3.0
(In formulas (1) and (2), Z1 represents the total acyl substitution degree of cellulose acylate, and X represents the sum of the propionyl substitution degree and butyryl substitution degree of cellulose acylate.)

Hereinafter, the general formula (A) will be described in detail. In the general formula (A), L ₁ and L ₂ each independently represent a single bond or a divalent linking group. Examples of L ₁ and L ₂ include the following structures. (The following R represents a hydrogen atom or a substituent.)

L ₁ and L ₂ are preferably —O—, —COO—, and —OCO—.

R ₁ , R ₂ and R ₃ each independently represent a substituent. Specific examples of the substituent represented by R ₁ , R ₂ and R ₃ include a halogen atom (fluorine atom, chlorine atom, bromine atom, iodine atom, etc.), alkyl group (methyl group, ethyl group, n-propyl group, Isopropyl group, tert-butyl group, n-octyl group, 2-ethylhexyl group, etc.), cycloalkyl group (cyclohexyl group, cyclopentyl group, 4-n-dodecylcyclohexyl group, etc.), alkenyl group (vinyl group, allyl group, etc.) , Cycloalkenyl groups (2-cyclopenten-1-yl, 2-cyclohexen-1-yl groups, etc.), alkynyl groups (ethynyl group, propargyl group, etc.), aryl groups (phenyl group, p-tolyl group, naphthyl group, etc.) , Heterocyclic groups (2-furyl group, 2-thienyl group, 2-pyrimidinyl group, 2-benzothiazolyl group, etc.), cyano group, hydride Roxyl group, nitro group, carboxyl group, alkoxy group (methoxy group, ethoxy group, isopropoxy group, tert-butoxy group, n-octyloxy group, 2-methoxyethoxy group, etc.), aryloxy group (phenoxy group, 2- Methylphenoxy group, 4-tert-butylphenoxy group, 3-nitrophenoxy group, 2-tetradecanoylaminophenoxy group, etc.), acyloxy group (formyloxy group, acetyloxy group, pivaloyloxy group, stearoyloxy group, benzoyloxy group) , P-methoxyphenylcarbonyloxy group, etc.), amino group (amino group, methylamino group, dimethylamino group, anilino group, N-methyl-anilino group, diphenylamino group etc.), acylamino group (formylamino group, acetylamino) Group, pivaloylamino group Lauroylamino group, benzoylamino group, etc.), alkyl and arylsulfonylamino groups (methylsulfonylamino group, butylsulfonylamino group, phenylsulfonylamino group, 2,3,5-trichlorophenylsulfonylamino group, p-methylphenylsulfonylamino group) Group), mercapto group, alkylthio group (methylthio group, ethylthio group, n-hexadecylthio group, etc.), arylthio group (phenylthio group, p-chlorophenylthio group, m-methoxyphenylthio group, etc.), sulfamoyl group (N-ethyl). Sulfamoyl group, N- (3-dodecyloxypropyl) sulfamoyl group, N, N-dimethylsulfamoyl group, N-acetylsulfamoyl group, N-benzoylsulfamoyl group, N- (N′phenylcarbamoyl) ) Sulf Moyl group, etc.), sulfo group, acyl group (acetyl group, pivaloylbenzoyl group, etc.), carbamoyl group (carbamoyl group, N-methylcarbamoyl group, N, N-dimethylcarbamoyl group, N, N-di-n-) Octylcarbamoyl group, N- (methylsulfonyl) carbamoyl group and the like.

R ₁ and R ₂ are preferably a substituted or unsubstituted phenyl group, a substituted or unsubstituted cyclohexyl group, more preferably a substituted phenyl group or a substituted cyclohexyl group, Preferred are a phenyl group having a substituent at the 4-position and a cyclohexyl group having a substituent at the 4-position.

R ₃ is preferably a hydrogen atom, halogen atom, alkyl group, alkenyl group, aryl group, heterocyclic group, hydroxyl group, carboxyl group, alkoxy group, aryloxy group, acyloxy group, cyano group, amino group, More preferably, they are a hydrogen atom, a halogen atom, an alkyl group, a cyano group, and an alkoxy group.

Wa and Wb represent a hydrogen atom or a substituent,
(I) Wa and Wb may be bonded to each other to form a ring;
(II) At least one of Wa and Wb may have a ring structure, or (III) At least one of Wa and Wb may be an alkenyl group or an alkynyl group.

  Specific examples of the substituent represented by Wa and Wb include a halogen atom (fluorine atom, chlorine atom, bromine atom, iodine atom, etc.), alkyl group (methyl group, ethyl group, n-propyl group, isopropyl group, tert- Butyl group, n-octyl group, 2-ethylhexyl group, etc.), cycloalkyl group (cyclohexyl group, cyclopentyl group, 4-n-dodecylcyclohexyl group, etc.), alkenyl group (vinyl group, allyl group, etc.), cycloalkenyl group ( 2-cyclopenten-1-yl, 2-cyclohexen-1-yl group etc.), alkynyl group (ethynyl group, propargyl group etc.), aryl group (phenyl group, p-tolyl group, naphthyl group etc.), heterocyclic group ( 2-furyl group, 2-thienyl group, 2-pyrimidinyl group, 2-benzothiazolyl group, etc.), cyano group, hydroxyl group , Nitro group, carboxyl group, alkoxy group (methoxy group, ethoxy group, isopropoxy group, tert-butoxy group, n-octyloxy group, 2-methoxyethoxy group, etc.), aryloxy group (phenoxy group, 2-methylphenoxy) Group, 4-tert-butylphenoxy group, 3-nitrophenoxy group, 2-tetradecanoylaminophenoxy group, etc.), acyloxy group (formyloxy group, acetyloxy group, pivaloyloxy group, stearoyloxy group, benzoyloxy group, p -Methoxyphenylcarbonyloxy group etc.), amino group (amino group, methylamino group, dimethylamino group, anilino group, N-methyl-anilino group, diphenylamino group etc.), acylamino group (formylamino group, acetylamino group, Pivaloylamino group, Lauro Alkyl group, arylsulfonylamino group (methylsulfonylamino group, butylsulfonylamino group, phenylsulfonylamino group, 2,3,5-trichlorophenylsulfonylamino group, p-methylphenylsulfonylamino group). Etc.), mercapto group, alkylthio group (methylthio group, ethylthio group, n-hexadecylthio group etc.), arylthio group (phenylthio group, p-chlorophenylthio group, m-methoxyphenylthio group etc.), sulfamoyl group (N-ethylsulfuryl group) Famoyl group, N- (3-dodecyloxypropyl) sulfamoyl group, N, N-dimethylsulfamoyl group, N-acetylsulfamoyl group, N-benzoylsulfamoyl group, N- (N′phenylcarbamoyl) Sulfamoyl Group), sulfo group, acyl group (acetyl group, pivaloylbenzoyl group, etc.), carbamoyl group (carbamoyl group, N-methylcarbamoyl group, N, N-dimethylcarbamoyl group, N, N-di-n-octyl) Carbamoyl group, N- (methylsulfonyl) carbamoyl group, etc.).

  The above substituents may be further substituted with the above groups.

  (I) When Wa and Wb are bonded to each other to form a ring, the ring is preferably a nitrogen-containing 5-membered ring or a sulfur-containing 5-membered ring. The general formula (A) is particularly preferably a compound represented by the following general formula (1) or general formula (2).

In the general formula (1), A ₁ and A ₂ each independently represent —O—, —S—, —NRx— (Rx represents a hydrogen atom or a substituent) or —CO—. The example of the substituent represented by Rx is synonymous with the specific example of the substituent represented by said Wa and Wb. Rx is preferably a hydrogen atom, an alkyl group, an aryl group, or a heterocyclic group.

In the general formula (1), X represents a nonmetallic atom belonging to Groups 14-16. X is preferably ═O, ═S, ═NRc, ═C (Rd) Re. Here, Rc, Rd, and Re represent substituents, and examples thereof are synonymous with specific examples of the substituents represented by Wa and Wb. _{L 1, L 2, R 1} , R _{2, R} 3, n is _{L 1, L 2, R 1} , same meanings as R _{2, R} 3, n in the general formula (A).

In the general formula (2), _{Q 1} is -O -, - S -, - NRy- (Ry represents a hydrogen atom or a substituent), - CRaRb- (Ra and Rb represents a hydrogen atom or a substituent), or -CO- is represented. Here, Ry, Ra, and Rb represent substituents, and examples thereof are synonymous with the specific examples of the substituents represented by Wa and Wb.

  Y represents a substituent. As an example of the substituent represented by Y, it is synonymous with the specific example of the substituent represented by said Wa and Wb. Y is preferably an aryl group, a heterocyclic group, an alkenyl group, or an alkynyl group.

  Examples of the aryl group represented by Y include a phenyl group, a naphthyl group, an anthryl group, a phenanthryl group, and a biphenyl group. A phenyl group and a naphthyl group are preferable, and a phenyl group is more preferable.

  Examples of the heterocyclic group include heterocyclic groups containing at least one hetero atom such as a nitrogen atom, an oxygen atom, a sulfur atom such as a furyl group, a pyrrolyl group, a thienyl group, a pyridinyl group, a thiazolyl group, and a benzothiazolyl group. Group, pyrrolyl group, thienyl group, pyridinyl group and thiazolyl group are preferred.

  These aryl groups or heterocyclic groups may have at least one substituent. Examples of the substituent include a halogen atom, an alkyl group having 1 to 6 carbon atoms, a cyano group, a nitro group, an alkylsulfinyl group having 1 to 6 carbon atoms, an alkylsulfonyl group having 1 to 6 carbon atoms, a carboxyl group, and 1 carbon atom. -6 fluoroalkyl group, C1-C6 alkoxy group, C1-C6 alkylthio group, C1-C6 N-alkylamino group, C2-C12 N, N-dialkylamino group And an N-alkylsulfamoyl group having 1 to 6 carbon atoms and an N, N-dialkylsulfamoyl group having 2 to 12 carbon atoms.

_{L 1, L 2, R 1} , R _{2, R} 3, n is _{L 1, L 2, R 1} , same meanings as R _{2, R} 3, n in the general formula (A).

  (II) In general formula (A), a specific example in which at least one of Wa and Wb has a ring structure is preferably the following general formula (3).

In the general formula (3), Q ₃ represents ═N— or ═CRz— (Rz represents a hydrogen atom or a substituent), and Q ₄ represents a nonmetallic atom belonging to Groups 14-16. Z represents a nonmetallic atom group forming a ring together with Q ₃ and Q ₄ .

The ring formed from Q ₃ , Q ₄ and Z may be condensed with another ring. The ring formed from Q ₃ , Q ₄ and Z is preferably a nitrogen-containing 5-membered or 6-membered ring condensed with a benzene ring.

_{L 1, L 2, R 1} , R _{2, R} 3, n is _{L 1, L 2, R 1} , same meanings as R _{2, R} 3, n in the general formula (A).

  (III) When at least one of Wa and Wb is an alkenyl group or an alkynyl group, they are preferably a vinyl group or an ethynyl group having a substituent.

  Of the compounds represented by the general formula (1), general formula (2) and general formula (3), the compound represented by the general formula (3) is particularly preferable.

  The compound represented by the general formula (3) is superior in heat resistance and light resistance to the compound represented by the general formula (1), and is an organic solvent compared to the compound represented by the general formula (2). The solubility with respect to and the compatibility with a polymer are favorable.

  The compound represented by the general formula (A) can be contained by appropriately adjusting the amount for imparting desired wavelength dispersibility and anti-bleeding property. It is preferable to contain 1-15 mass%, and it is preferable to contain 2-10 mass% especially. If it is in this range, sufficient wavelength dispersibility and bleeding prevention property can be imparted to the cellulose derivative.

  In addition, the compound represented by General formula (A), General formula (1), General formula (2), and General formula (3) can be obtained with reference to a known method. Specifically, it can be synthesized with reference to Journal of Chemical Crystallography (1997); 27 (9); 512-526), JP 2010-31223 A, JP 2008-107767 A, and the like.

(About cellulose acylate)
The cellulose acylate film according to this embodiment contains cellulose acylate as a main component. For example, the cellulose acylate film according to the present embodiment preferably contains cellulose acylate in the range of 60 to 100% by mass with respect to the total mass (100% by mass) of the film. Further, the total acyl group substitution degree of cellulose acylate is 2.0 or more and less than 3.0, and more preferably 2.2 to 2.7.

  Examples of the cellulose acylate include esters of cellulose and an aliphatic carboxylic acid and / or aromatic carboxylic acid having about 2 to 22 carbon atoms, and in particular, an ester of cellulose and a lower fatty acid having 6 or less carbon atoms. Preferably there is.

  The acyl group bonded to the hydroxyl group of cellulose may be linear or branched, and may form a ring. Furthermore, another substituent may be substituted. In the case of the same substitution degree, birefringence decreases when the number of carbon atoms described above is large. Therefore, the number of carbon atoms is preferably selected from acyl groups having 2 to 6 carbon atoms, and the propionyl substitution degree and the butyryl substitution degree. Is a sum of 0 or more and less than 3.0. The cellulose acylate preferably has 2 to 4 carbon atoms, more preferably 2 to 3 carbon atoms.

  Specifically, cellulose acylate includes propionate group, butyrate group or phthalyl group in addition to acetyl group such as cellulose acetate propionate, cellulose acetate butyrate, cellulose acetate propionate butyrate or cellulose acetate phthalate. Bound cellulose mixed fatty acid esters can be used. The butyryl group forming butyrate may be linear or branched.

  In the present embodiment, cellulose acetate, cellulose acetate butyrate, or cellulose acetate propionate is particularly preferably used as the cellulose acylate.

The cellulose acylate preferably satisfies the following mathematical formulas (i) and (ii) at the same time.
Formula (i) 2.0 ≦ X + Y <3.0
Formula (ii) 0 ≦ X <3.0
In the formula, Y represents the degree of substitution of the acetyl group, and X represents the degree of substitution of the propionyl group or butyryl group or a mixture thereof.

  Further, in order to obtain optical characteristics that meet the purpose, resins having different degrees of substitution may be mixed and used. In this case, the mixing ratio is preferably 1:99 to 99: 1 (mass ratio).

  Among those mentioned above, cellulose acetate propionate is particularly preferably used as the cellulose acylate. In cellulose acetate propionate, 0 ≦ Y ≦ 2.5 and 0.5 ≦ X ≦ 3.0 (where 2.0 ≦ X + Y <3.0) are preferable, and 0 More preferably, 0.5 ≦ Y ≦ 2.0 and 1.0 ≦ X ≦ 2.0 (where 2.0 ≦ X + Y <3.0). In addition, the substitution degree of an acyl group can be measured according to ASTM-D817-96, which is one of standards established and issued by ASTM (American Society for Testing and Materials).

  The number average molecular weight of the cellulose acylate is preferably in the range of 60,000 to 300,000 because the mechanical strength of the resulting film becomes strong. More preferably, cellulose acylate having a number average molecular weight of 70,000 to 200,000 is used.

  The weight average molecular weight (Mw) and number average molecular weight (Mn) of cellulose acylate are measured using gel permeation chromatography (GPC). The measurement conditions are as follows. In addition, this measuring method can be used also as a measuring method of the other polymer in this embodiment.

Solvent: methylene chloride;
Column: Three Shodex K806, K805, K803G (made by Showa Denko KK) are connected and used;
Column temperature: 25 ° C .;
Sample concentration: 0.1% by mass;
Detector: RI Model 504 (manufactured by GL Sciences);
Pump: L6000 (manufactured by Hitachi, Ltd.);
Flow rate: 1.0 ml / min
Calibration curve: Standard polystyrene STK standard polystyrene (manufactured by Tosoh Corporation) Mw = 100000 to 500 samples are used. Thirteen samples are used at approximately equal intervals.

  The residual sulfuric acid content in the cellulose acylate is preferably in the range of 0.1 to 45 mass ppm in terms of elemental sulfur. These are considered to be contained in the form of salts. If the residual sulfuric acid content exceeds 45 ppm by mass, there is a tendency to break during hot stretching or slitting after hot stretching. The residual sulfuric acid content is more preferably in the range of 1 to 30 mass ppm. The residual sulfuric acid content can be measured by a method prescribed in ASTM-D817-96.

  Moreover, it is preferable that the free acid content in a cellulose acylate is 1-500 mass ppm. The above range is preferable because it is difficult to break as described above. In addition, it is preferable that free acid content is the range of 1-100 mass ppm, and also it becomes difficult to fracture | rupture. The range of 1-70 mass ppm is especially preferable. The free acid content can be measured by the method prescribed in ASTM-D817-96.

  By washing the synthesized cellulose acylate more sufficiently than when used in the solution casting method, the residual alkaline earth metal content, residual sulfuric acid content, and residual acid content are within the above ranges. And is preferable.

  The cellulose as a raw material for cellulose acylate is not particularly limited, and examples thereof include cotton linter, wood pulp, and kenaf. Moreover, the cellulose acylate obtained from them can be mixed and used at an arbitrary ratio.

  Cellulose acylate can be produced by a known method. Specifically, for example, it can be synthesized with reference to the method described in JP-A-10-45804.

  Cellulose acylate is also affected by trace metal components in cellulose acylate. These trace metal components are considered to be related to water used in the production process, but it is preferable that there are few components that can become insoluble nuclei. In particular, metal ions such as iron, calcium and magnesium may form an insoluble matter by forming a salt with a polymer decomposition product or the like which may contain an organic acidic group, and it is preferable that the amount of the metal ion is small. In addition, the calcium (Ca) component easily forms a coordination compound (that is, a complex) with an acidic component such as a carboxylic acid or a sulfonic acid, and many ligands. Insoluble starch, turbidity) may be formed, so it is preferable that the amount be small.

  Specifically, for the iron (Fe) component, the content in cellulose acylate is preferably 1 mass ppm or less. Moreover, about calcium (Ca) component, content in a cellulose acylate becomes like this. Preferably it is 60 mass ppm or less, More preferably, it is 0-30 mass ppm. Furthermore, regarding the magnesium (Mg) component, too much is also insoluble, so the content in the cellulose acylate is preferably 0 to 70 ppm by mass, and particularly preferably 0 to 20 ppm by mass. .

  In addition, the content of metal components such as the content of iron (Fe) component, the content of calcium (Ca) component, the content of magnesium (Mg) component, etc. After being decomposed with sulfur nitrate and pretreated with alkali fusion, it can be analyzed using ICP-AES (Inductively Coupled Plasma Atomic Emission Spectrometer).

<Alicyclic olefin polymer resin>
Examples of the alicyclic olefin polymer resin used in the raw film of the present embodiment include cyclic olefin random multi-component copolymers described in JP-A No. 05-310845 and JP-A No. 05-97978. The hydrogenated polymer, the thermoplastic dicyclopentadiene ring-opening polymer described in JP-A No. 11-124429, the hydrogenated product thereof, and the like can be employed.

  The alicyclic olefin polymer resin is a polymer having an alicyclic structure such as a saturated alicyclic hydrocarbon (cycloalkane) structure or an unsaturated alicyclic hydrocarbon (cycloalkene) structure. The number of carbon atoms constituting the alicyclic structure is not particularly limited, but is usually 4 to 30, preferably 5 to 20, more preferably 5 to 15 in the mechanical strength, The properties of heat resistance and formability of the long film are highly balanced and suitable.

  The proportion of the repeating unit containing the alicyclic structure in the alicyclic olefin polymer may be appropriately selected, but is preferably 55% by weight or more, more preferably 70% by weight or more, and particularly preferably 90% by weight. That's it. When the ratio of the repeating unit having an alicyclic structure in the alicyclic polyolefin resin is within this range, the transparency and heat resistance of an optical material such as a retardation film obtained from the long obliquely stretched film of the present embodiment are improved. Since it improves, it is preferable.

  Examples of olefin polymer resins having an alicyclic structure include norbornene resins, monocyclic olefin resins, cyclic conjugated diene resins, vinyl alicyclic hydrocarbon resins, and hydrides thereof. Among these, norbornene-based resins can be suitably used because of their good transparency and moldability.

  Examples of the norbornene-based resin include a ring-opening polymer of a monomer having a norbornene structure, a ring-opening copolymer of a monomer having a norbornene structure and another monomer, a hydride thereof, and a norbornene structure. And an addition copolymer of a monomer having a norbornene structure and an addition copolymer of another monomer or a hydride thereof. Among these, a ring-opening (co) polymer hydride of a monomer having a norbornene structure is particularly suitable from the viewpoints of transparency, moldability, heat resistance, low hygroscopicity, dimensional stability and lightness. Can be used.

  As a method for forming a long film (raw film) using the norbornene-based resin as described above, a solution casting method or a melt extrusion method is preferred. Examples of the melt extrusion method include an inflation method using a die, but a method using a T die is preferable in terms of excellent productivity and thickness accuracy.

  As an extrusion method using a T die, as described in JP-A-2004-233604, a method of maintaining a molten thermoplastic resin in a stable state when closely contacting a cooling drum, retardation, A long film with small variations in optical properties such as the orientation angle can be produced.

  Specifically, 1) When producing a long film by the melt extrusion method, a sheet-like thermoplastic resin extruded from a die is brought into close contact with a cooling drum under a pressure of 50 kPa or less; 2) melting When producing a long film by extrusion, the enclosure member covers from the die opening to the first cooling drum that is in close contact, and the distance from the enclosure member to the die opening or the first contact cooling drum is 100 mm or less. Method: 3) Method of heating the temperature of the atmosphere within 10 mm to a specific temperature from the sheet-like thermoplastic resin extruded from the die opening when producing a long film by the melt extrusion method; A sheet-like thermoplastic resin extruded from a die so as to satisfy the above condition is brought into close contact with a cooling drum under a pressure of 50 kPa or less; A method in which a wind having a speed difference of 0.2 m / s or less from the take-up speed of the cooling drum that is first brought into close contact with the sheet-like thermoplastic resin extruded from the die opening is produced. .

  This long film may be a single layer or a laminated film of two or more layers. The laminated film can be obtained by a known method such as a coextrusion molding method, a co-casting molding method, a film lamination method, or a coating method. Of these, the coextrusion molding method and the co-casting molding method are preferable.

<Polycarbonate resin>
As the polycarbonate resin used for the raw film of the present embodiment, various resins can be used without particular limitation. An aromatic polycarbonate resin is preferable from the viewpoint of chemical properties and physical properties, and a bisphenol A polycarbonate resin is particularly preferable. Among these, those using a bisphenol A derivative in which a benzene ring, a cyclohexane ring, an aliphatic hydrocarbon group and the like are introduced into bisphenol A are more preferable. Furthermore, a polycarbonate resin having a structure in which the anisotropy in the unit molecule is reduced, obtained by using a derivative in which the functional group is introduced asymmetrically with respect to the central carbon of bisphenol A, is particularly preferable. As such a polycarbonate resin, for example, two methyl groups in the center carbon of bisphenol A are replaced by benzene rings, and one hydrogen of each benzene ring of bisphenol A is centered by a methyl group or a phenyl group. A polycarbonate resin obtained by using an asymmetrically substituted carbon is particularly preferable.

  Specifically, 4,4′-dihydroxydiphenylalkane or a halogen-substituted product thereof can be obtained by a phosgene method or a transesterification method. For example, 4,4′-dihydroxydiphenylmethane, 4,4′-dihydroxydiphenyl Examples include ethane and 4,4'-dihydroxydiphenylbutane. In addition, for example, JP 2006-215465 A, JP 2006-91836 A, JP 2005-121813 A, JP 2003-167121 A, JP 2009-126128 A, JP Examples thereof include polycarbonate resins described in 2012-31369, JP 2012-67300 A, International Publication No. 00/26705, and the like.

  The polycarbonate resin may be used by mixing with a transparent resin such as a polystyrene resin, a methyl methacrylate resin, and a cellulose acetate resin. Moreover, you may laminate | stack the resin layer containing a polycarbonate-type resin on the at least one surface of the resin film formed using the cellulose acetate type resin.

  The polycarbonate resin preferably has a glass transition point (Tg) of 110 ° C. or higher and a water absorption rate (measured under conditions of 23 ° C. water and 24 hours) of 0.3% or less. Moreover, Tg is 120 degreeC or more, and a water absorption rate is 0.2% or less more preferable.

  The polycarbonate resin film that can be used in the present embodiment can be formed by a known method, and among them, the solution casting method and the melt casting method are preferable.

<Additives>
The raw film of this embodiment may contain an additive. Examples of the additive include a plasticizer, an ultraviolet absorber, a retardation adjusting agent, an antioxidant, a deterioration preventing agent, a peeling aid, a surfactant, a dye, and fine particles. In the present embodiment, additives other than the fine particles may be added when preparing the dope solution, or may be added when preparing the fine particle dispersion.

(Plasticizer)
Examples of the plasticizer added to the raw film include phthalate ester, fatty acid ester, trimellitic ester, phosphate ester, polyester, sugar ester, and acrylic polymer. Among these, from the viewpoint of moisture permeability, polyester-based and sugar ester-based polymer plasticizers are preferably used.

  Polyester plasticizers are superior in non-migration and extraction resistance compared to phthalate ester plasticizers such as dioctyl phthalate. It can be applied to a wide range of uses by selecting or using these plasticizers according to the use. The acrylic polymer is preferably a homopolymer or copolymer of acrylic acid or methacrylic acid alkyl ester. Examples of the acrylate monomer include methyl acrylate, ethyl acrylate, propyl acrylate (i-, n-), butyl acrylate (n-, i-, s-, t-), pentyl acrylate ( n-, i-, s-), hexyl acrylate (n-, i-), heptyl acrylate (n-, i-), octyl acrylate (n-, i-), nonyl acrylate (n-, i-), myristyl acrylate (n-, i-), acrylic acid (2-ethylhexyl), acrylic acid (ε-caprolactone), acrylic acid (2-hydroxyethyl), acrylic acid (2-hydroxypropyl), acrylic Acid (3-hydroxypropyl), acrylic acid (4-hydroxybutyl), acrylic acid (2-hydroxybutyl), acrylic acid (2-methoxyethyl), acrylic acid 2-ethoxyethyl), etc., or the acrylic acid ester may include those obtained by changing the methacrylic acid ester. The acrylic polymer is a homopolymer or copolymer of the above-mentioned monomers, but the acrylic acid methyl ester monomer unit preferably has 30% by mass or more, and the methacrylic acid methyl ester monomer unit has 40% by mass or more. preferable. In particular, a homopolymer of methyl acrylate or methyl methacrylate is preferred.

  The polyester plasticizer is a reaction product of a monovalent or tetravalent carboxylic acid and a monovalent or hexavalent alcohol, and is mainly obtained by reacting a divalent carboxylic acid with a glycol. . Representative divalent carboxylic acids include glutaric acid, itaconic acid, adipic acid, phthalic acid, azelaic acid, sebacic acid and the like. The polyester plasticizer is preferably an aromatic terminal ester plasticizer. As the aromatic terminal ester plasticizer, an ester compound having a structure obtained by reacting phthalic acid, adipic acid, at least one benzene monocarboxylic acid and at least one alkylene glycol having 2 to 12 carbon atoms is preferable. As long as it has an adipic acid residue and a phthalic acid residue as the final compound structure, it may be reacted as an acid anhydride or esterified product of a dicarboxylic acid when an ester compound is produced.

  Examples of the benzene monocarboxylic acid component include benzoic acid, para-tert-butylbenzoic acid, orthotoluic acid, metatoluic acid, p-toluic acid, dimethylbenzoic acid, ethylbenzoic acid, normal propylbenzoic acid, aminobenzoic acid, acetoxybenzoic acid and the like. Most preferred is benzoic acid. Moreover, these can each be used as a 1 type, or 2 or more types of mixture.

  Examples of the alkylene glycol component having 2 to 12 carbon atoms include ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butanediol, 1,3-butanediol, 1,2-propanediol, 2-methyl-1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 2,2-dimethyl-1,3-propanediol (neopentyl glycol), 2,2-diethyl-1 , 3-propanediol (3,3-dimethylolpentane), 2-n-butyl-2-ethyl-1,3-propanediol (3,3-dimethylolheptane), 3-methyl-1,5-pentane Diol, 1,6-hexanediol, 2,2,4-trimethyl-1,3-pentanediol, 2-ethyl-1,3-hexane Ol, 2-methyl-1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,12-octadecane diol. Among these, 1,2-propylene glycol is particularly preferable. These glycols may be used as one kind or a mixture of two or more kinds.

  The aromatic terminal ester plasticizer may be of an oligoester type or a polyester type, and the molecular weight is preferably in the range of 100 to 10,000, but is preferably in the range of 350 to 3000. The acid value is 1.5 mgKOH / g or less, the hydroxy (hydroxyl group) value is 25 mgKOH / g or less, more preferably the acid value is 0.5 mgKOH / g or less, and the hydroxy (hydroxyl group) value is 15 mgKOH / g or less.

  Specific examples include the following compounds, but are not limited thereto.

  The sugar ester compound is an ester other than a cellulose ester, and is a compound obtained by esterifying all or part of the OH group of a sugar such as the following monosaccharide, disaccharide, trisaccharide or oligosaccharide. Specific examples thereof include a compound represented by the general formula (4).

In the formula, R _{1 to} R ₈ represent a hydrogen atom, a substituted or unsubstituted alkylcarbonyl group having 2 to 22 carbon atoms, or a substituted or unsubstituted arylcarbonyl group having 2 to 22 carbon atoms. R _{1 to} R ₈ may be the same or different.

Although the compound shown by General formula (4) is shown more concretely below (compound 1-1-compound 1-23), it is not limited to these. In the following table, when the average degree of substitution is less than 8.0, any one of R _{1 to} R ₈ represents a hydrogen atom.

  These plasticizers are preferably added in an amount of 0.5 to 30 parts by mass with respect to 100 parts by mass of the cellulose ester film.

(Retardation adjuster)
As a compound to be added for adjusting the retardation, an aromatic compound having two or more aromatic rings as described in the specification of European Patent 911,656A2 can be used.

  Two or more aromatic compounds may be used in combination. The aromatic ring of the aromatic compound particularly preferably contains an aromatic hetero ring in addition to the aromatic hydrocarbon ring. The aromatic heterocycle is generally an unsaturated heterocycle. Of these, a 1,3,5-triazine ring is particularly preferred.

(Polymer or oligomer)
The raw film of this embodiment has a cellulose ester and a substituent selected from a carboxyl group, a hydroxyl group, an amino group, an amide group, and a sulfonic acid group, and has a weight average molecular weight of 500 to 200,000. It is preferable to contain a polymer or oligomer of a vinyl compound within the range. The mass ratio of the content of the cellulose ester and the polymer or oligomer is preferably in the range of 95: 5 to 50:50.

(Matting agent)
In the present embodiment, fine particles can be contained in the original film as a matting agent, thereby facilitating the conveyance and winding of the original film and a long obliquely stretched film produced using the original film. Can do.

  The particle size of the matting agent is preferably primary particles or secondary particles of 10 nm to 0.1 μm. A substantially spherical matting agent having a primary particle acicular ratio of 1.1 or less is preferably used.

  As the fine particles, those containing silicon are preferable, and silicon dioxide is particularly preferable. As fine particles of silicon dioxide preferable for this embodiment, for example, Aerosil R972, R972V, R974, R812, 200, 200V, 300, R202, OX50, TT600 (manufactured by Nippon Aerosil Co., Ltd.) manufactured by Nippon Aerosil Co., Ltd. And commercially available products such as Aerosil 200V, R972, R972V, R974, R202, and R812 can be preferably used. Examples of the polymer fine particles include silicone resin, fluorine resin, and acrylic resin. Silicone resins are preferred, and those having a three-dimensional network structure are particularly preferred. Examples of such resins include Tospearl 103, 105, 108, 120, 145, 3120, and 240 (manufactured by Toshiba Silicone Co., Ltd.).

  The fine particles of silicon dioxide preferably have a primary average particle size of 20 nm or less and an apparent specific gravity of 70 g / L or more. The average diameter of the primary particles is more preferably 5 to 16 nm, and further preferably 5 to 12 nm. A smaller primary particle average diameter is preferred because haze is low. The apparent specific gravity is preferably 90 to 200 g / L or more, and more preferably 100 to 200 g / L or more. Higher apparent specific gravity makes it possible to produce a high-concentration fine particle dispersion, which is preferable because no haze or aggregates are generated.

The addition amount of the matting agent in this embodiment is preferably 0.01 to 1.0 g, more preferably 0.03 to 0.3 g, and still more preferably 0.08 to 0.16 g per 1 m ^{2 of} the raw film.

(Other additives)
In addition, heat stabilizers such as inorganic fine particles such as kaolin, talc, diatomaceous earth, quartz, calcium carbonate, barium sulfate, titanium oxide, and alumina, and alkaline earth metal salts such as calcium and magnesium may be added. Further, a surfactant, a peeling accelerator, an antistatic agent, a flame retardant, a lubricant, an oil agent and the like may be added.

(Tension softening point)
The raw film of this embodiment is required to withstand use in a higher temperature environment. For this reason, if the tension | softening softening point of a raw film is 105 to 145 degreeC, in order to show sufficient heat resistance, it is preferable that it is especially 110 to 130 degreeC.

  As a specific method for measuring the tension softening point, for example, using a Tensilon tester (produced by ORIENTEC, RTC-1225A), a sample film is cut out at 120 mm (length) × 10 mm (width) and pulled with a tension of 10 N. However, the temperature can be continuously increased at a temperature increase rate of 30 ° C./min, and the temperature at 9 N can be measured three times, and the average value can be obtained.

(Dimensional change rate)
When the film after the original fabric film of this embodiment is obliquely stretched is used in an organic EL image display device, due to dimensional changes due to moisture absorption, there are problems such as thickness unevenness and retardation value change, contrast reduction and color unevenness. In order not to generate it, the dimensional change rate (%) of the obliquely stretched film is preferably less than 0.5%, and more preferably less than 0.3%.

(Disadvantage)
The raw film of this embodiment preferably has few defects in the film. Here, the defect is a void in the film (foaming defect) generated due to the rapid evaporation of the solvent in the drying process of the solution casting, a foreign matter in the film forming stock solution, or a foreign matter mixed in the film forming. This refers to the foreign matter (foreign matter defect) in the film.

  Specifically, it is preferable that the number of defects having a diameter of 5 μm or more in the film plane is 1/10 cm square or less. More preferably, it is 0.5 piece / 10 cm square or less, more preferably 0.1 piece / 10 cm square or less.

  The diameter of the defect indicates the diameter when the defect is circular, and when the defect is not circular, the range of the defect is determined by observing with a microscope according to the following method, and is defined as the maximum diameter (diameter of circumscribed circle).

  The range of the defect is the size of the shadow when the defect is observed with the transmitted light of the differential interference microscope when the defect is a bubble or a foreign object. When the defect is a change in the surface shape, such as transfer of a roll flaw or an abrasion, the size is confirmed by observing the defect with the reflected light of a differential interference microscope.

  In addition, when observing with reflected light, if the size of the defect is unclear, aluminum or platinum is deposited on the surface for observation. In order to obtain a film having excellent quality expressed by such a defect frequency with high productivity, it is necessary to filter the polymer solution with high precision immediately before casting, to increase the cleanliness around the casting machine, It is effective to set drying conditions after rolling stepwise and to dry efficiently while suppressing foaming.

  When the number of defects is greater than 1/10 cm square, for example, when the film is tensioned during processing in a later process, the film may break with the defects as a starting point, and productivity may decrease. Moreover, when the diameter of a defect becomes 5 micrometers or more, it can confirm visually by polarizing plate observation etc., and when used as an optical member, a bright spot may arise.

(Total light transmittance)
The raw film of this embodiment preferably has a total light transmittance of 90% or more, more preferably 93% or more. The practical upper limit of the total light transmittance is about 99%. In order to achieve excellent transparency expressed by such total light transmittance, it is necessary not to introduce additives and copolymerization components that absorb visible light, or to remove foreign substances in the polymer by high-precision filtration. It is effective to reduce the diffusion and absorption of light inside the film. Also, reduce the surface roughness of the film surface by reducing the surface roughness of the film contact part (cooling roll, calender roll, drum, belt, coating substrate in solution casting, transport roll, etc.) during film formation. It is effective to reduce the diffusion and reflection of light on the film surface.

<Formation method of raw film>
The raw film of this embodiment containing the resin described above can be formed by either the solution casting film forming method or the melt casting film forming method described below. In addition, although the case where a raw fabric film contains a cellulose ester-based resin will be described here, the same applies to a case where another resin is included.

  When producing a raw film by a solution casting method, a dope, which is a raw material solution of a cellulose ester resin raw film, is cast on a support made of a rotating metal endless belt by a casting die. . The dope film, that is, the web formed on the support by casting is peeled off by a peeling roll when it has made a full turn on the support. The peeled web (film) is then introduced into a stretching device comprising a tenter.

  When the raw film is produced by the melt casting film forming method, in the extrusion method using the T die, the polymer is melted at a temperature capable of melting, and extruded from the T die into a film shape (sheet shape) on a cooling drum, Cool and solidify and peel the film from the cooling drum. Then, the peeled film is introduced into a stretching apparatus composed of a tenter.

  Details of each film forming method will be described below.

[Solution casting film forming method]
In the manufacturing method of the raw fabric film by the solution casting film forming method, the solid content concentration of the dope which is a cellulose ester solution is usually about 10 to 40% by mass, and the dope viscosity at the time of casting in the casting step is 1 to 200. Prepared with a range of poises.

  Here, first, the dissolution of the cellulose ester is usually performed by means such as a stirring dissolution method, a heating dissolution method, an ultrasonic dissolution method, etc. in a dissolution vessel, and the pressure is higher than the boiling point of the solvent at normal pressure. A method in which the solvent is heated at a temperature at which it does not boil and is dissolved while stirring is more preferable because it prevents the formation of a massive undissolved material called gel or mamaco. Further, a cooling dissolution method described in JP-A-9-95538 or a method of dissolving under high pressure described in JP-A-11-21379 may be used.

  A method in which the cellulose ester is mixed with a poor solvent and wetted or swollen, and then mixed with a good solvent and dissolved is also preferably used. At this time, an apparatus for mixing or dissolving cellulose ester with a poor solvent and an apparatus for mixing and dissolving with a good solvent may be separately provided.

  The type of the pressure vessel used for dissolving the cellulose ester is not particularly limited as long as it can withstand a predetermined pressure and can be heated and stirred under pressure. In addition, instruments such as a pressure gauge and a thermometer are appropriately disposed in the pressurized container. The pressurization may be performed by a method of injecting an inert gas such as nitrogen gas or by increasing the vapor pressure of the solvent by heating. Heating is preferably performed from the outside. For example, a jacket type is preferable because temperature control is easy.

  The heating temperature after adding the solvent is higher than the boiling point of the solvent to be used. In the case of two or more mixed solvents, the heating temperature is higher than the boiling point of the lower boiling solvent and the solvent does not boil. Is preferred. If the heating temperature is too high, the required pressure increases and productivity decreases. The range of preferable heating temperature is 20-120 degreeC, 30-100 degreeC is more preferable, The range of 40-80 degreeC is further more preferable. The pressure is adjusted so that the solvent does not boil at the set temperature.

  In addition to cellulose ester and solvent, additives such as necessary plasticizers and UV absorbers are mixed with the solvent in advance, dissolved or dispersed, and then added to the solvent before dissolving the cellulose ester. It may be put into the dope.

  After dissolving the cellulose ester, take it out from the container while cooling, or remove it from the container with a pump, etc., cool it with a heat exchanger, etc., and use it for film formation of the obtained cellulose ester dope. May be performed up to room temperature.

  When the mixture of the cellulose ester raw material and the solvent is dissolved by a dissolution apparatus having a stirrer, the peripheral speed of the stirring blade is preferably at least 0.5 m / second or more and stirred for 30 minutes or more to dissolve.

  Foreign matter contained in the cellulose ester dope (especially foreign matter recognized as an image in a liquid crystal display device and mistaken) must be removed by filtering. It may be said that the quality as an optical film is determined by this filtration.

  Filter media used for filtration preferably have low absolute filtration accuracy, but if the absolute filtration accuracy is too low, the filter media is likely to be clogged, and the filter media must be replaced frequently, reducing productivity. There is a problem of making it. For this reason, the filter medium used for the cellulose ester dope preferably has an absolute filtration accuracy of 0.008 mm or less, more preferably in the range of 0.001 to 0.008 mm, and further in the range of 0.003 to 0.006 mm. preferable.

  There are no particular restrictions on the material of the filter medium, and normal filter media can be used. However, plastic fiber filter media such as polypropylene and Teflon (registered trademark), and metal filter media such as stainless steel fibers are used to remove fibers. This is preferable.

  Filtration of the cellulose ester dope can be carried out by a usual method, but the method of filtering while heating under pressure at a temperature not lower than the boiling point at the normal pressure of the solvent and in which the solvent does not boil is a differential pressure before and after the filter medium ( Hereinafter, the increase in the filtration pressure may be small and preferable.

  The range of preferable filtration temperature is 45-120 degreeC, 45-70 degreeC is more preferable, and it is more preferable that it is the range of 45-55 degreeC.

  The filtration pressure is preferably 3500 kPa or less, more preferably 3000 kPa or less, and even more preferably 2500 kPa or less. The filtration pressure can be controlled by appropriately selecting the filtration flow rate and the filtration area.

  In order to produce an original film of cellulose ester resin, first, cellulose ester is dissolved in a mixed solvent of a good solvent and a poor solvent, and the above plasticizer and ultraviolet absorber are added to the cellulose ester solution ( Dope) is prepared.

  The dope can be cast on the support in the range where the temperature of the support is generally 0 ° C. to less than the boiling point of the solvent, and further on the support in the temperature range of 5 ° C. to the boiling point of the solvent −5 ° C. Although it can cast, it is still more preferable to cast on a support body in the temperature range of 5-30 degreeC. At this time, it is necessary to control the ambient atmospheric humidity above the dew point.

  In addition, a dope adjusted to have a dope viscosity of 1 to 200 poise is cast from the casting die so as to have a substantially uniform film thickness, and the amount of residual solvent in the casting film is solid. When the partial weight is 200% or more, the drying film temperature is lower than the boiling point of the solvent, and until the residual solvent amount is 200% or less to peeling, the casting film temperature is in the range of the boiling point of the solvent + 20 ° C. or less. To dry the cast membrane (web).

Here, the residual solvent amount can be expressed by the following equation.
Residual solvent amount (% by mass) = {(MN) / N} × 100
In the formula, M is the weight of the web at an arbitrary time point, and N is the weight when a weight M is dried at 110 ° C. for 3 hours.

  On the support, in order to dry and solidify the web until the film has a peelable film strength, the residual solvent amount in the web is preferably dried to 150% by mass or less, more preferably 50 to 120%.

  The web temperature when peeling the web from the support is preferably 0 to 30 ° C. In addition, immediately after the web is peeled off from the support, the temperature once drops rapidly due to solvent evaporation from the support close-contact surface side, and volatile components such as water vapor and solvent vapor in the atmosphere tend to condense. The web temperature is more preferably 5 to 30 ° C.

  In the drying process of the web (or film), a method of drying while conveying the web by a roll suspension method, a pin tenter method or a clip tenter method is generally adopted.

  The peeled web is introduced into a primary drying apparatus, for example. In the primary drying device, the web is meandered and conveyed by a plurality of conveying rolls arranged in a staggered manner as viewed from the side, while the web is blown from the ceiling of the drying device and discharged from the bottom portion of the drying device. Dried by wind.

  Next, the obtained film (sheet) is stretched in a uniaxial direction. The molecules are oriented by stretching. The stretching method is not particularly limited, but a known pin tenter or clip type tenter can be preferably used. The stretching direction can be a length direction, a width direction, or an arbitrary direction (an oblique direction). However, by setting the stretching direction to the width direction, the elongation at break of the original film can be easily adjusted, which is preferable.

  In particular, in the drying process after peeling from the support, the web tends to shrink in the width direction by evaporation of the solvent. Shrinkage increases with drying at higher temperatures. Drying while suppressing this shrinkage as much as possible is preferable for improving the flatness of the finished film. From this point, for example, a method of drying the whole drying process or a part of the process as shown in Japanese Patent Application Laid-Open No. Sho 62-46625 while holding the width at both ends of the web with a clip in the width direction (tenter method) ) Is preferred.

  As stretching conditions for the raw film, the temperature and magnification can be selected so that desired breaking elongation characteristics can be obtained. Usually, the draw ratio is 1.1 to 2.0 times, preferably 1.2 to 1.5 times, and the draw temperature is usually the glass transition temperature (Tg) of the resin constituting the sheet−40 ° C. to Tg + 50. It is set in a temperature range of ° C, preferably Tg-40 ° C to Tg + 40 ° C. If the draw ratio is too small, the desired elongation at break property may not be obtained. Conversely, if the draw ratio is too large, it may break. If the stretching temperature is too low, it will break, and if it is too high, the desired elongation at break property may not be obtained.

  When the breaking elongation characteristic of the thermoplastic resin film produced by the above method is corrected to a desired characteristic suitable for the purpose, the film may be stretched or shrunk in the length direction or the width direction. In order to shrink in the length direction, for example, a method of shrinking the film by temporarily clipping out the width stretching and relaxing in the length direction, or by gradually narrowing the interval between adjacent clips of the transverse stretching apparatus. There is. The latter method can be performed by using a general simultaneous biaxial stretching apparatus, and by gradually and gradually narrowing the interval between adjacent clips in the longitudinal direction by driving the clip portion by, for example, a pantograph method or a linear drive method. it can.

  Gripping / stretching with a tenter can be performed anywhere from 50 to 150% by mass of the residual solvent of the film immediately after peeling to 0% by mass of the residual residual solvent immediately before winding. Is preferably in the range of 5 to 10%.

  It is also common to divide the tenter into several temperature zones in the direction of travel of the base. The temperature during stretching is selected so that desired physical properties and planarity can be obtained, but the temperature in the drying zone before and after the tenter is also selected from a temperature different from the temperature during stretching for various reasons. Sometimes. For example, if the atmospheric temperature in the drying zone before the tenter is different from the temperature in the tenter, the temperature in the zone near the tenter inlet is set to an intermediate temperature between the temperature in the drying zone before the tenter and the temperature in the center of the tenter. It is generally done. Similarly, when the temperature in the tenter is different from that in the tenter, the temperature in the zone near the tenter outlet is set to an intermediate temperature between the temperature after the tenter and the temperature in the tenter. The temperature of the drying zone before and after the tenter is generally 30 to 120 ° C., preferably 50 to 100 ° C., and the temperature of the stretching portion in the tenter is 50 to 180 ° C., preferably 80 to 170 ° C. The temperature is appropriately selected from intermediate temperatures thereof.

  The pattern of stretching, i.e. the trajectory of the grip clip, is selected from the optical properties and flatness of the film as well as the temperature, and varies, but for a while after the start of gripping, it is stretched for a while, then stretched and then stretched again at a constant width. A retained pattern is often used. In the vicinity of the end of gripping near the tenter outlet, width relaxation is generally performed to suppress base vibration by releasing the gripping.

  The drawing pattern is also related to the drawing speed, but the drawing speed is generally 10 to 1000 (% / min), preferably 100 to 500 (% / min). This stretching speed is not constant when the clip trajectory is a curve, and gradually changes in the base traveling direction.

  Furthermore, the web (film) after drying by the tenter method is then introduced into a secondary drying apparatus. In the secondary drying apparatus, the web is meandered and conveyed by a plurality of conveying rolls arranged in a staggered manner as viewed from the side, while the web is blown from the ceiling of the secondary drying apparatus, and the bottom part of the secondary drying apparatus It is dried by the warm air discharged more and wound on a winder as a raw film of cellulose ester resin.

  The means for drying the web is not particularly limited, and hot air, infrared rays, heating rolls, microwaves and the like are generally used. In terms of simplicity, it is preferable to dry with hot air. The drying temperature is preferably 40 to 150 ° C., and more preferably 80 to 130 ° C. in order to improve the flatness and dimensional stability.

  In this way, in the web drying step, the web peeled from the support is further dried, and finally the residual solvent amount is 3% by mass or less, preferably 1% by mass or less, more preferably 0.5% by mass. The following is preferable in obtaining a film having good dimensional stability.

  These steps from casting to post-drying may be performed in an air atmosphere or an inert gas atmosphere such as nitrogen gas. In this case, it goes without saying that the dry atmosphere is carried out in consideration of the explosion limit concentration of the solvent.

  In addition, the embossing is formed on both side edges of the cellulose ester resin raw film by an embossing device before the introduction to the winding process with respect to the cellulose ester resin raw film after the transport drying process. It is preferable to perform processing. As the embossing apparatus, for example, an apparatus described in JP-A-63-74850 can be used.

  Winders related to the production of cellulose ester resin film can be generally used, such as constant tension method, constant torque method, taper tension method, program tension control method with constant internal stress, etc. It can be wound up by a winding method.

  Although the film thickness of the original film after winding varies depending on the purpose of use, the film thickness range is 20 to 200 μm, and the range of 30 to 120 μm is preferable for the recent thin tendency, and the range of 40 to 100 μm is particularly preferable.

  When the raw film of the present embodiment is produced by a melt casting film forming method, as an ultraviolet absorber that can be used, those used in the method for producing an original film by the solution casting film forming method, Almost the same one can be used.

  The blending amount of these ultraviolet absorbers is preferably in the range of 0.01 to 10% by mass, more preferably 0.1 to 5% by mass with respect to the thermoplastic resin. If the amount used is too small, the UV absorption effect may be insufficient, and conversely if too large, the transparency of the film may deteriorate. The ultraviolet absorber is preferably one having high heat stability.

  It is preferable to add fine particles to the raw film in order to impart film slipperiness. The fine particles used may be either an inorganic compound or an organic compound as long as it has heat resistance during melting. For example, the inorganic compound includes a compound containing silicon, silicon dioxide, aluminum oxide, zirconium oxide, calcium carbonate, talc, clay. Of these, calcined kaolin, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, magnesium silicate, calcium phosphate and the like are preferred, and silicon-containing inorganic compounds and zirconium oxide are more preferred. Among these, silicon dioxide is particularly preferably used because haze can be kept small. Even when the raw film is produced by the melt casting film forming method, the matting agent used is substantially the same as that used in the method for producing an original film by the solution casting film forming method. be able to.

  Examples of the melt casting film forming method include a method using a T die, a melt extrusion method such as an inflation method, a calendar method, a hot press method, and an injection molding method. Among these, a method using a T-die that is small in thickness unevenness, can be easily processed to a thickness of about 50 to 500 μm, and can reduce film thickness unevenness and retardation unevenness is preferable. The extrusion method using a T die is a method in which a polymer is melted at a temperature at which it can be melted, extruded onto a cooling drum from a T die on a cooling drum, solidified by cooling, and peeled off from the cooling drum. The thickness accuracy of the film is excellent and can be preferably used.

  The melt extrusion can be performed under the same conditions as those used for other thermoplastic resins such as polyester. For example, the cellulose ester dried under hot air, vacuum, or reduced pressure is melted at an extrusion temperature of about 200-300 ° C using a single-screw or twin-screw extruder, and filtered through a leaf disk type filter to remove foreign matter. Then, the film is cast from the T die into a film (sheet) and solidified on a cooling drum. When introducing into the extruder from the supply hopper, it is preferable to prevent oxidative decomposition or the like under reduced pressure or in an inert gas atmosphere.

  The extrusion flow rate is preferably performed stably by introducing a gear pump or the like. Moreover, as a filter used for removal of a foreign material, a stainless fiber sintered filter is preferably used. A stainless steel fiber sintered filter is an integrated stainless steel fiber body that is intricately entangled and then compressed and sintered at the contact point. The density is changed according to the thickness of the fiber and the amount of compression, and the filtration accuracy is improved. Can be adjusted. It is preferable to use a multilayer body in which the filtration accuracy is repeated coarsely and densely a plurality of times. In addition, it is preferable to adopt a configuration in which the filtration accuracy is sequentially increased or a method in which coarse and dense filtration accuracy is repeated, so that the filtration life of the filter is extended and the accuracy of supplementing foreign matters and gels can be improved.

  If flaws or foreign matter adhere to the die, streaky defects may occur. Such defects are called die lines, but in order to reduce surface defects such as die lines, it is preferable that the piping from the extruder to the die has a structure in which the resin retention portion is minimized. . Further, it is preferable to use a die that has as few scratches as possible in the lip or lip. Since the volatile component may be deposited from the resin around the die and cause a die line, it is preferable to suck the atmosphere containing the volatile component. Moreover, since it may precipitate also in apparatuses, such as an electrostatic application, it is preferable to apply alternating current or to prevent precipitation with another heating means.

  Additives such as plasticizers may be mixed with the resin in advance, or may be kneaded in the middle of the extruder. In order to add uniformly, it is preferable to use a mixing apparatus such as a static mixer.

  The temperature of the cooling drum is preferably equal to or lower than the glass transition temperature of the thermoplastic resin. In order to bring the resin into close contact with the cooling drum, it is preferable to use a method in which the resin is brought into contact by applying electrostatic force, a method in which the resin is brought into contact with wind pressure, a method in which the full width or the end is attached in a nip, a method in which the resin is brought into contact with reduced pressure.

  Unlike the original film formed by the solution casting film forming method, the thermoplastic resin original film formed by such a melt casting film forming method has a feature that the thickness direction retardation (Rt) is small. In some cases, stretching conditions different from the solution casting film-forming method may be required. In order to obtain desired optical properties, depending on the case, both stretching in the film traveling direction and stretching in the film width direction may be performed simultaneously or sequentially. Moreover, depending on the case, it may be only extending | stretching of a film width direction. By this stretching operation, the molecules are oriented and the film is adjusted to the necessary retardation value.

<Specifications of the original film>
The thickness of the raw film in this embodiment is 1 to 400 μm, preferably 20 to 200 μm, more preferably 30 to 120 μm, and particularly preferably 40 to 100 μm. Further, in this embodiment, the thickness unevenness σm in the flow direction (conveying direction) of the original film supplied to the stretching zone, which will be described later, maintains the film take-up tension at the oblique stretching tenter inlet, which will be described later, and the orientation angle. From the viewpoint of stabilizing optical properties such as retardation and retardation, it is necessary to be less than 0.30 μm, preferably less than 0.25 μm, and more preferably less than 0.20 μm. When the thickness unevenness σm in the flow direction of the original film is 0.30 μm or more, variations in optical properties such as retardation and orientation angle of the long obliquely stretched film are remarkably deteriorated.

  Moreover, in this embodiment, in order to suppress the occurrence of orientation angle unevenness in the width direction due to thickness unevenness in the width direction due to oblique stretching, it is preferable that the thickness unevenness in the width direction of the original film is small. For example, in the width direction of the raw film, the difference in thickness between the thick-side end and the thin-side end is less than about 2.0% of the thickness, preferably less than about 1.0%. It is desirable that the range be less than 0.5%.

  Although the width | variety of a raw film is not specifically limited, 500-4000 mm, Preferably it can be 1000-2000 mm.

  A preferable elastic modulus at a stretching temperature at the time of oblique stretching of the raw film is 0.01 MPa or more and 5000 MPa or less, more preferably 0.1 MPa or more and 500 MPa or less, expressed as Young's modulus. If the elastic modulus is too low, the shrinkage rate during and after stretching becomes low and wrinkles are difficult to disappear. On the other hand, if the elastic modulus is too high, the tension applied during stretching increases, and it is necessary to increase the strength of the portions that hold the side edges of the film, which increases the load on the tenter in the subsequent step.

  As the raw film, a non-oriented film may be used, or a film having an orientation in advance may be supplied. Further, if necessary, the distribution in the width direction of the orientation of the raw film may be bow-shaped, so-called bowing. In short, the orientation state of the raw film can be adjusted so that the orientation of the film at the position where the stretching in the subsequent step is completed can be made desirable.

<The manufacturing method and manufacturing apparatus of a diagonally stretched film>
Next, a manufacturing method and a manufacturing apparatus for an obliquely stretched film, in which the above-described long film is stretched in an oblique direction with respect to the width direction to produce a long oblique stretched film, will be described.

(Outline of the device)
FIG. 1 is a plan view schematically showing a schematic configuration of a manufacturing apparatus 1 for an obliquely stretched film. The manufacturing apparatus 1 includes, in order from the upstream side in the transport direction of the long film, a film feeding unit 2, a transport direction changing unit 3, a guide roll 4, a stretching unit 5, a guide roll 6, and a transport direction changing unit 7. The film winding unit 8 is provided. In addition, a film cutting device is provided between the conveyance direction changing unit 7 and the film winding unit 8 so that the film after oblique stretching is cut at a desired length and wound by the film winding unit 8. Also good. The details of the extending portion 5 will be described later.

  The film feeding unit 2 feeds the above-described long film and supplies it to the stretching unit 5. This film supply part 2 may be comprised separately from the film-forming apparatus of a long film, and may be comprised integrally. In the case of the former, a long film is wound around a core after film formation, and a wound body (long film original fabric) is loaded into the film unwinding section 2 so that the film unwinds from the film unwinding section 2. The film is paid out. On the other hand, in the latter case, the film feeding unit 2 feeds the long film to the stretching unit 5 without winding the long film after the long film is formed.

  The transport direction changing unit 3 changes the transport direction of the long film fed from the film feed unit 2 to a direction toward the entrance of the stretching unit 5 as an oblique stretching tenter. Such a conveyance direction change part 3 is comprised including the turntable which rotates the turn bar which changes the conveyance direction by, for example, returning while conveying a film, and the turn bar in the surface parallel to a film.

  By changing the transport direction of the long film as described above by the transport direction changing unit 3, the width of the entire manufacturing apparatus 1 can be made narrower, and the film feed position and angle are finely controlled. Accordingly, it is possible to obtain a diagonally stretched film with small variations in film thickness and optical value. Further, if the film feeding unit 2 and the conveyance direction changing unit 3 can be moved (slidable and turnable), the left and right clips (gripping tools) sandwiching both ends of the long film in the width direction in the stretching unit 5 can be used. It is possible to effectively prevent the biting into the film.

  In addition, the above-described film feeding unit 2 may be slidable and turnable so that a long film can be fed out at a predetermined angle with respect to the entrance of the stretching unit 5. In this case, a configuration in which the installation of the conveyance direction changing unit 3 is omitted may be employed.

  At least one guide roll 4 is provided on the upstream side of the stretching portion 5 in order to stabilize the track during running of the long film. In addition, the guide roll 4 may be comprised by a pair of upper and lower rolls which pinch | interpose a film, and may be comprised by several roll pairs. The guide roll 4 closest to the entrance of the extending portion 5 is a driven roll that guides the travel of the film, and is rotatably supported via a bearing portion (not shown). A known material can be used as the material of the guide roll 4. In order to prevent the film from being damaged, it is preferable to reduce the weight of the guide roll 4 by applying a ceramic coat on the surface of the guide roll 4 or applying chrome plating to a light metal such as aluminum.

  Further, it is preferable that one of the rolls upstream of the guide roll 4 closest to the entrance of the extending portion 5 is nipped by pressing the rubber roll. By setting it as such a nip roll, it becomes possible to suppress the fluctuation | variation of the drawing tension | tensile_strength in the flow direction of a film.

  A pair of bearing portions at both ends (left and right) of the guide roll 4 closest to the entrance of the extending portion 5 includes a first tension detecting device as a film tension detecting device for detecting the tension generated in the film in the roll, A second tension detecting device is provided. For example, a load cell can be used as the film tension detection device. As the load cell, a known tensile or compression type can be used. A load cell is a device that detects a load acting on an applied point by converting it into an electrical signal using a strain gauge attached to the strain generating body.

  The load cell is installed in the left and right bearing portions of the guide roll 4 closest to the entrance of the extending portion 5, whereby the force of the running film on the roll, that is, in the film traveling direction generated in the vicinity of both side edges of the film. The tension is detected independently on the left and right. In addition, a strain gauge may be directly attached to a support that constitutes the bearing portion of the roll, and a load, that is, a film tension may be detected based on the strain generated in the support. The relationship between the generated strain and the film tension is measured in advance and is known.

  When the position and the transport direction of the film supplied from the film feeding unit 2 or the transport direction changing unit 3 to the stretching unit 5 are shifted from the position toward the entrance of the stretching unit 5 and the transport direction, according to the amount of shift, A difference will arise in the tension | tensile_strength near the both-sides edge of the film in the guide roll 4 nearest to the entrance of the extending part 5. FIG. Therefore, by providing the above-described film tension detecting device and detecting the above-described tension difference, the degree of the deviation can be determined. That is, if the transport position and transport direction of the film are appropriate (if it is the position and direction toward the entrance of the stretching unit 5), the load acting on the guide roll 4 is roughly uniform at both ends in the axial direction. If not appropriate, there will be a difference in film tension between left and right.

  Therefore, the position and the transport direction of the film (angle with respect to the entrance of the stretching unit 5) are changed by, for example, the transport direction changing unit 3 so that the difference in film tension between the left and right sides of the guide roll 4 closest to the entrance of the stretching unit 5 becomes equal. When properly adjusted, the film can be stably held by the gripping tool at the entrance of the stretching portion 5, and the occurrence of obstacles such as detachment of the gripping tool can be reduced. Furthermore, the physical properties in the width direction of the film after oblique stretching by the stretching portion 5 can be stabilized.

  At least one guide roll 6 is provided on the downstream side of the stretching section 5 in order to stabilize the track during running of the film that is obliquely stretched in the stretching section 5.

  The transport direction changing unit 7 changes the transport direction of the stretched film transported from the stretching unit 5 to a direction toward the film winding unit 8.

  Here, in order to cope with fine adjustment of the orientation angle (in-plane slow axis direction of the film) and product variations, the film traveling direction at the entrance of the stretching portion 5 and the film traveling direction at the exit of the stretching portion 5 It is necessary to adjust the angle between the two. In order to adjust the angle, the traveling direction of the formed film is changed by the transport direction changing unit 3 to guide the film to the inlet of the stretching unit 5 and / or the traveling direction of the film from the outlet of the stretching unit 5 Needs to be changed by the transport direction changing unit 7 to return the film to the direction of the film winding unit 8.

  Moreover, it is preferable from the point of productivity and a yield to perform film forming and diagonal stretch continuously. When the film forming process, the oblique stretching process, and the winding process are continuously performed, the traveling direction of the film is changed by the transport direction changing unit 3 and / or the transport direction changing unit 7, and the film is formed by the film forming process and the winding process. 1, that is, as shown in FIG. 1, the traveling direction (feeding direction) of the film fed from the film feeding unit 2 and the traveling direction of the film immediately before being wound by the film winding unit 8 ( The width of the entire apparatus with respect to the film traveling direction can be reduced by matching the winding direction.

  Note that the film traveling direction and the film winding process do not necessarily coincide with each other in the film forming process and the film winding process. It is preferable that the traveling direction of the film is changed by the transport direction changing unit 7.

  The transport direction changing units 3 and 7 as described above can be realized by a known method such as using an air flow roll or an air turn bar.

  The film take-up unit 8 takes up a film conveyed from the stretching unit 5 via the conveyance direction changing unit 7, and includes, for example, a winder device, an accumulator device, and a drive device. It is preferable that the film winding unit 8 has a structure that can be slid in the horizontal direction in order to adjust the film winding position.

  The film take-up unit 8 can finely control the film take-up position and angle so that the film can be taken at a predetermined angle with respect to the outlet of the stretching unit 5. Thereby, it becomes possible to obtain a long obliquely stretched film with small variations in film thickness and optical value. In addition, it is possible to effectively prevent wrinkling of the film and to improve the winding property of the film, so that the film can be wound up in a long length.

  The film take-up unit 8 constitutes a take-up unit that takes up the film that is drawn and conveyed by the drawing unit 5 with a certain tension. Note that a take-up roll for taking up the film with a constant tension may be provided between the stretching unit 5 and the film take-up unit 8. Moreover, you may give the function as said take-up roll to the guide roll 6 mentioned above.

  In the present embodiment, the take-up tension T (N / m) of the film after stretching is preferably adjusted between 100 N / m <T <300 N / m, preferably 150 N / m <T <250 N / m. When the take-up tension is 100 N / m or less, sagging and wrinkles of the film are likely to occur, and the retardation and orientation angle profile in the film width direction are also deteriorated. On the other hand, when the take-up tension is 300 N / m or more, the variation of the orientation angle in the film width direction is deteriorated, and the width yield (taken efficiency in the width direction) is deteriorated.

  In the present embodiment, it is preferable to control the fluctuation of the take-up tension T with an accuracy of less than ± 5%, preferably less than ± 3%. When the variation in the take-up tension T is ± 5% or more, the variation in the optical characteristics in the width direction and the flow direction (conveying direction) increases. As a method of controlling the fluctuation of the take-up tension T within the above range, the load applied to the first roll (guide roll 6) on the outlet side of the stretching section 5, that is, the film tension is measured, and the value becomes constant. Thus, the method of controlling the rotational speed of the take-up roll or the take-up roll of the film take-up part 8 by a general PID control system is mentioned. Examples of the method for measuring the load include a method in which a load cell is attached to the bearing portion of the guide roll 6 and a load applied to the guide roll 6, that is, a film tension is measured. As the load cell, a known tensile type or compression type can be used.

  The stretched film is released from the outlet of the stretching unit 5 by being held by the gripping tool of the stretching unit 5 and trimmed at both ends (both sides) of the film that has been gripped by the gripping tool. It is wound up by (winding roll), and becomes a wound body of a long diagonally stretched film. Note that the above trimming may be performed as necessary.

  Moreover, before winding up a long diagonally stretched film, in order to prevent blocking between films, a masking film may be piled up on a long diagonally stretched film, and it may wind up simultaneously, and the long diagonal stretch which overlaps by winding up You may wind up, sticking a tape etc. to the edge of at least one (preferably both) of a film. The masking film is not particularly limited as long as it can protect the long obliquely stretched film, and examples thereof include a polyethylene terephthalate film, a polyethylene film, and a polypropylene film.

  In addition, before winding up the long diagonally stretched film, at least one side (preferably both sides) of the film is bulkier than the film side, which is called a knurling part or an embossed part, at both ends in the width direction. You may make it prevent blocking of films when a film is wound up by forming the part (convex part) which did. The height and shape of the knurling portion may be different at both ends in the width direction (may be asymmetric).

(Details of stretched part)
Next, the detail of the extending | stretching part 5 mentioned above is demonstrated. FIG. 2 is a plan view schematically showing an example of the rail pattern of the extending portion 5. However, this is an example, and the configuration of the extending portion 5 is not limited to this.

  The production of the long obliquely stretched film in the present embodiment is performed by using a tenter (obliquely stretching machine) capable of oblique stretching as the stretching part 5. This tenter is an apparatus that heats a long film to an arbitrary temperature at which it can be stretched and obliquely stretches it. This tenter includes a heating zone Z, a pair of rails Ri and Ro on the left and right, and a number of gripping tools Ci and Co that travel along the rails Ri and Ro to convey a film (in FIG. 2, a set of gripping tools). Only). Details of the heating zone Z will be described later. Each of the rails Ri and Ro is configured by connecting a plurality of rail portions with connecting portions (white circles in FIG. 2 are examples of connecting portions). The gripping tool Ci / Co is composed of a clip that grips both ends of the film in the width direction.

  In FIG. 2, the feeding direction D1 of the long film is different from the winding direction D2 of the long oblique stretched film after stretching, and forms a feeding angle θi with the winding direction D2. The feeding angle θi can be arbitrarily set to a desired angle in the range of more than 0 ° and less than 90 °.

  Thus, since the feeding direction D1 and the winding direction D2 are different, the rail pattern of the tenter has an asymmetric shape on the left and right, and the film transport path is bent halfway. And a rail pattern can be adjusted now manually or automatically according to the orientation angle | corner (theta) given to the long diagonally stretched film which should be manufactured, a draw ratio, etc. FIG. In the oblique stretching machine used in the manufacturing method of the present embodiment, it is preferable that the positions of the rail portions and the rail connecting portions constituting the rails Ri and Ro can be freely set and the rail pattern can be arbitrarily changed.

  In the present embodiment, the tenter gripping tool Ci · Co travels at a constant speed with a constant distance from the front and rear gripping tools Ci · Co. The traveling speed of the gripping tool Ci / Co can be selected as appropriate, but is usually 1 to 150 m / min. In the present embodiment, it is preferably 20 to 100 m / min in consideration of giving a temperature change by reliably heating the film in the width direction as described later and the productivity of the film. The difference in travel speed between the pair of left and right grippers Ci / Co is usually 1% or less, preferably 0.5% or less, more preferably 0.1% or less of the travel speed. This is because if there is a difference in the traveling speed on the left and right of the film at the exit of the stretching process, wrinkles and misalignment will occur at the exit of the stretching process. Is required. In general tenter devices, etc., there are speed irregularities that occur on the order of seconds or less depending on the period of the sprocket teeth that drive the chain, the frequency of the drive motor, etc. This does not correspond to the speed difference described in the embodiment of the invention.

  In the oblique stretching machine used in the manufacturing method of the present embodiment, a rail that regulates the trajectory of the gripping tool is often required to have a high bending rate, particularly in a portion where the film is transported obliquely. In order to avoid interference between gripping tools due to sudden bending or local stress concentration, it is desirable that the trajectory of the gripping tool draws a curve at the bent portion.

  As described above, the obliquely stretched tenter used for imparting the oblique orientation to the long film can freely set the orientation angle of the film by changing the rail pattern in various ways, and further, the orientation axis of the film It is preferred that the tenter be capable of orienting the (slow axis) in the left and right direction with high precision across the film width direction and controlling the film thickness and retardation with high precision.

  Next, the extending | stretching operation | movement in the extending part 5 is demonstrated. Both ends of the long film are gripped by the left and right grippers Ci · Co, and are conveyed in the heating zone Z as the grippers Ci • Co travel. The left and right grips Ci / Co are opposed to a direction substantially perpendicular to the film traveling direction (feeding direction D1) at the entrance portion (position A in the drawing) of the extending portion 5, and are asymmetric rails. Each travels on Ri and Ro, and the film gripped at the exit portion (position B in the figure) at the end of stretching is released. The film released from the gripping tool Ci · Co is wound around the core by the film winding portion 8 described above. Each of the pair of rails Ri and Ro has an endless continuous track, and the grippers Ci and Co that have released the film at the exit portion of the tenter travel on the outer rail and sequentially return to the entrance portion. It is supposed to be.

  At this time, since the rails Ri and Ro are asymmetrical in the left and right directions, in the example of FIG. 2, the left and right gripping tools Ci and Co, which are opposed to each other at the position A in the figure, move as the rails run on the rails Ri and Ro. The gripping tool Ci traveling on the Ri side (in-course side) has a positional relationship preceding the gripping tool Co traveling on the rail Ro side (out-course side).

  That is, of the gripping tools Ci and Co that are opposed to the film feeding direction D1 at the position A in the figure, one gripping tool Ci is first in position B at the end of film stretching. When it reaches, the straight line connecting the gripping tools Ci and Co is inclined by an angle θL with respect to the direction substantially perpendicular to the film winding direction D2. With the above operation, the long film is obliquely stretched at an angle of θL with respect to the width direction. Here, “substantially vertical” indicates that the angle is in a range of 90 ± 1 °.

  Next, the details of the heating zone Z will be described. The heating zone Z of the stretching section 5 is composed of a preheating zone Z1, a stretching zone Z2, and a heat fixing zone Z3. In the stretching unit 5, the film gripped by the gripping tool Ci / Co passes through the preheating zone Z1, the stretching zone Z2, and the heat fixing zone Z3 in this order. In the present embodiment, the preheating zone Z1 and the stretching zone Z2 are separated by a partition, and the stretching zone Z2 and the heat fixing zone Z3 are separated by a partition. In addition, you may provide a partition suitably in each zone of the preheating zone Z1, the extending | stretching zone Z2, and the heat setting zone Z3 (The inside of each zone may be further divided | segmented by a partition).

  The preheating zone Z1 refers to a section in which the gripping tool Ci / Co that grips both ends of the film travels at the left and right (in the film width direction) while maintaining a constant interval at the entrance of the heating zone Z.

  The stretching zone Z2 refers to a section in which the gap between the gripping tools Ci and Co that grips both ends of the film opens and reaches a predetermined interval. At this time, the oblique stretching as described above is performed, but the stretching may be performed in the longitudinal direction or the transverse direction before and after the oblique stretching as necessary. That is, in the stretching zone Z2, while gripping both ends in the width direction of the film with a pair of gripping tools Ci and Co, one gripping tool Ci is relatively advanced and the other gripping tool Co is relatively delayed. Then, the film is transported, and the film transport path is bent halfway, thereby performing an oblique stretching process of stretching the film in an oblique direction with respect to the width direction.

  The heat setting zone Z3 refers to a section for fixing the optical axis (slow axis) of the obliquely stretched film after the oblique stretching process in the stretching zone Z2. That is, in the heat setting zone Z3, a heat setting process for fixing the optical axis of the obliquely stretched film is performed. In the heat setting zone Z3, the gripping tools Ci and Co at both ends travel while being kept parallel to each other. Thereby, the optical axis of the obliquely stretched film is fixed.

  The stretched film passes through the heat setting zone Z3 and then passes through a section (cooling zone) in which the temperature in the zone is set to be equal to or lower than the glass transition temperature Tg (° C.) of the thermoplastic resin constituting the film. May be.

  With respect to the glass transition temperature Tg of the thermoplastic resin, the temperature of the preheating zone Z1 is Tg to Tg + 60 ° C., the temperature of the stretching zone Z2 is Tg to Tg + 50 ° C., and the temperatures of the heat setting zone Z3 and the cooling zone are Tg−40 to Tg + 30 ° C. It is preferable to set.

  Note that the lengths of the preheating zone Z1, the stretching zone Z2, and the heat setting zone Z3 can be appropriately selected. The length of the preheating zone Z1 is usually 50 to 200% of the length of the stretching zone Z2, and the length of the heat setting zone Z3. The length is usually 50 to 150%.

  Moreover, when the width of the film before stretching is Wo (mm) and the width of the film after stretching is W (mm), the draw ratio R (W / Wo) in the stretching step is preferably 1.1 to 3. 0, more preferably 1.15 to 2.0. When the draw ratio is in this range, the thickness unevenness in the width direction of the film is preferably reduced.

  Note that the method of oblique stretching in the stretching portion 5 is not limited to the above-described method. For example, even if oblique stretching is performed by simultaneous biaxial stretching as disclosed in Japanese Patent Application Laid-Open No. 2008-23775. Good. Note that simultaneous biaxial stretching means that both ends in the width direction of the supplied long film are gripped by each gripping tool, and the long film is transported while moving each gripping tool, and the long film is transported. This is a method of stretching a long film in an oblique direction with respect to the width direction by making the moving speed of one gripping tool different from the moving speed of the other gripping tool while keeping the direction constant. In addition, oblique stretching may be performed by a method as disclosed in JP 2011-11434 A.

(About film widening in the heat setting process)
FIG. 3 schematically shows the shape of the film passing through the stretched portion 5 of FIG. As shown in the figure, the width of the obliquely stretched film before widening after the end of the oblique stretching in the stretching zone Z2 is L1, and the width L1 of the obliquely stretched film before widening in the heat setting zone Z3 (heat setting step). Let L2 and L3 be the widths of the portions widened to the leading side and the delay side relative to the portion corresponding to. The preceding side refers to the gripping tool Ci side that travels relatively ahead of the pair of gripping tools Ci and Co that grips both ends of the film, and the delay side relatively delays. It points to the gripping tool Co side that travels. The units of L1, L2, and L3 are all mm.

In this embodiment, in the heat setting step after the end of the oblique stretching step, the obliquely stretched film is widened so as to satisfy the following conditional expression (1). That is,
L3> L2 ≧ 0 mm (1)
It is.

  FIG. 4 schematically shows how the avalan-like residual stress is relaxed when the obliquely stretched film is widened in the heat setting zone Z3. The film stretched obliquely in the stretching zone Z2 enters the heat setting zone Z3, but at this time, since the leading side enters the heat setting zone Z3 earlier than the delay side, the shrinkage of the film starts from the leading side, Abalone residual stress T is generated up to the vicinity of the center in the width direction. However, since the film extends in the width direction by widening the film in the heat setting zone Z3, the loose residual stress generated in the heat setting zone Z3 is relaxed and does not remain in the film.

  In this way, in the heat setting step after the end of the oblique stretching step, it is possible to suppress the occurrence of loose residual stress in the film after the oblique stretching by widening the obliquely stretched film. Thereby, the circularly-polarizing plate mentioned later is comprised using the manufactured diagonally stretched film, even if this circularly-polarizing plate is applied to OLED (organic EL image display apparatus), and OLED is put in the temperature / humidity environment different from usual. Thus, it is possible to suppress the appearance of oblique stripe-shaped display unevenness.

  Moreover, the optical axis (slow axis) oriented in a predetermined direction by oblique stretching by satisfying the conditional expression (1), that is, by increasing the width of the film on the delay side rather than the preceding side, It is possible to suppress the occurrence of an avalan-like residual stress without causing any deviation from the predetermined direction.

  That is, when widening the obliquely stretched film, if the leading side is too wide, the film is pulled in the direction in which the leading side is widened (the direction toward the lower right in FIG. 4), so that the direction of the optical axis of the film is shifted. There is a case. For example, if the orientation angle of the film oriented in the direction of 45 ° with respect to the width direction is too wide on the leading side, it becomes as small as 44 °.

  On the other hand, the delay side of the film originally tends to have a small orientation angle (due to the bowing phenomenon), and the direction in which the delay side is widened (the direction toward the upper left in FIG. 4) is the orientation angle on the delay side (for example, Since it is a direction to increase the angle (from 44 ° to 45 °), there is no problem even if the delay side is wider than the preceding side, and it is preferable because the orientation direction approaches a predetermined direction.

  Thus, by satisfying conditional expression (1), it is possible to prevent the optical axis from deviating from a predetermined direction (for example, a direction of 45 ° with respect to the width direction) on the leading side and the delay side of the film. . Thus, even if the film is widened in the heat setting step, an obliquely stretched film having desired orientation characteristics can be obtained by fixing the optical axis in a predetermined direction.

In the present embodiment, it is desirable that the following conditional expression (2) is further satisfied. That is,
5%>B> A ≧ 0% (2)
However,
A = (L2 / L1) × 100
B = (L3 / L1) × 100
It is.

  If the ratio B is 5% or more, the widening width on the delay side becomes too large, and the optical property value adjusted in the stretching zone changes due to the heat-fixing zone stretching, and the uniformity is deteriorated. For this reason, by satisfying 5%> B, it is possible to achieve both avalan residual stress and uniformity. Moreover, by satisfying B> A ≧ 0%, at least the delay side of the film is widened more than the preceding side, and it is possible to suppress the occurrence of loose residual stress in the film after oblique stretching.

  Further, by cooling the obliquely stretched film in the heat setting step, the optical axis provided by the oblique stretching in the oblique stretching step can be reliably fixed. For this reason, in the heat setting step, it is desirable to widen the obliquely stretched film at a temperature that is 10 ° C to 60 ° C lower than the stretching temperature in the oblique stretching step, and more preferably a temperature that is 20 ° C to 50 ° C lower.

  When the ratio B is less than 1%, the delay-side widening width is small, and the effect of widening the film, that is, the effect of suppressing the occurrence of avalan-like residual stress is small. On the other hand, if the ratio B is larger than 4%, the effect of stretching in the heat setting zone becomes strong, and the level of uniformity decreases. Therefore, it is desirable that 4% ≧ B ≧ 1% from the viewpoint of avoiding a decrease in the level of uniformity while ensuring the effect of widening the film.

  Moreover, if the leading side of the film is widened, the film is pulled to the leading side, and the orientation angle of the film applied in the oblique stretching process may vary (become small) as described above. For this reason, the width L2 of the widened portion of the leading film may be L2 = 0 mm.

  Further, when the obliquely stretched film contains a cellulose ester resin having high moisture permeability and moisture absorption, the orientation angle is likely to fluctuate due to absorption of moisture. For this reason, as described above, in the heat setting step, the film delay side is broadened more than the preceding side, thereby suppressing the occurrence of avalan residual stress while suppressing the fluctuation of the orientation angle. This is very effective when the stretched film contains a cellulose ester resin.

<Quality of long diagonally stretched film>
In the long obliquely stretched film obtained by the production method of the present embodiment, the orientation angle θ is inclined in the range of, for example, greater than 0 ° and less than 90 ° with respect to the winding direction, and at least at a width of 1300 mm. The variation in the in-plane retardation Ro in the width direction is preferably 2 nm or less, and the variation in the orientation angle θ is preferably less than 0.6 °. The in-plane retardation value Ro (550) measured at a wavelength of 550 nm of the long obliquely stretched film is preferably in the range of 80 nm to 160 nm, and more preferably in the range of 90 nm to 150 nm.

  That is, in the long obliquely stretched film obtained by the manufacturing method of the present embodiment, the variation of the in-plane retardation Ro is 2 nm or less and preferably 1 nm or less at least 1300 mm in the width direction. By setting the variation of the in-plane retardation Ro within the above range, a long obliquely stretched film is bonded to a polarizer to form a circularly polarizing plate. When this is applied to an organic EL image display device, external light during black display is displayed. Color unevenness due to leakage of reflected light can be suppressed. In addition, when a long obliquely stretched film is used as, for example, a retardation film for a liquid crystal display device, the display quality can be improved.

  Further, in the long obliquely stretched film obtained by the production method of the present embodiment, the variation in the orientation angle θ is less than 0.6 ° and less than 0.4 ° or less at least 1300 mm in the width direction. Is preferable, and less than 0.2 ° is most preferable. When a long diagonally stretched film with a variation in the orientation angle θ exceeding 0.6 ° is bonded to a polarizer to form a circularly polarizing plate, and this is installed in an image display device such as an organic EL display device, light leakage occurs, and light and dark May reduce the contrast.

  The optimum value of the in-plane retardation Ro of the long obliquely stretched film obtained by the production method of the present embodiment is selected depending on the design of the display device used. Note that Ro is a value obtained by multiplying the difference between the refractive index nx in the in-plane slow axis direction and the refractive index ny in the direction perpendicular to the slow axis by the average thickness d of the film (Ro = (nx −ny) × d).

  The average thickness of the long obliquely stretched film obtained by the production method of the present embodiment is 1 to 400 μm, preferably 10 to 200 μm, more preferably 10 to 60 μm, and particularly preferably 15 to 15 μm from the viewpoint of mechanical strength and the like. 45 μm. Moreover, since the thickness unevenness in the width direction of the long obliquely stretched film affects whether or not winding is possible, it is preferably 2 μm or less, and more preferably 1 μm or less.

  The long diagonally stretched film obtained by the manufacturing method of this embodiment may have a functional layer on the surface. Functional layers include antireflection layer, low refractive index layer, hard coat layer, light scattering layer, light diffusion layer, antistatic layer, conductive layer, electrode layer, birefringence layer, surface energy adjustment layer, UV absorption layer, color A material layer, a water resistant layer, a specific gas barrier layer, a heat resistant layer, a magnetic layer, an antioxidant layer, an overcoat layer and the like can be considered.

<Circularly polarizing plate>
In the circularly polarizing plate of the present embodiment, a polarizing plate protective film, a polarizer, and a λ / 4 film are laminated in this order, and the slow axis of the λ / 4 film and the absorption axis (or transmission axis) of the polarizer Is an angle of 45 °. When the circularly polarizing plate of this embodiment is used in an organic EL display device, the above polarizing plate protective film, polarizer, and λ / 4 film are the same as the protective film 313, polarizer 311, and λ / 4 film 316 in FIG. Each corresponds. In this embodiment, it is preferable that a long polarizing plate protective film, a long polarizer, and a long λ / 4 film (long diagonally stretched film) are laminated in this order.

  When the circularly polarizing plate of this embodiment is used in a liquid crystal display device, the above polarizing plate protective film, polarizer, and λ / 4 film are the protective film 506, polarizer 501, and λ / 4 film 503 in FIG. Correspond to each. Since the protective film 506 and the polarizer 501 are disposed outside the display cell 401 (viewing side), and the λ / 4 film 503 is disposed further outside (on the viewing side) of the polarizer 501, display is performed. The linearly polarized light emitted from the cell 401 and transmitted through the polarizer 501 is converted into circularly polarized light or elliptically polarized light by the λ / 4 film 503. Therefore, when the observer wears polarized sunglasses and observes the display image of the display device 400, the observation angle is whatever (at the transmission axis of the polarizer 501 (perpendicular to the absorption axis)) the polarization sunglasses. Even if the transmission axis is misaligned), the display image can be observed by guiding the light component parallel to the transmission axis of the polarized sunglasses to the observer's eyes, and the display image is difficult to see depending on the viewing angle. It can be suppressed.

  The circularly polarizing plate of the present embodiment can be manufactured by using a stretched polyvinyl alcohol doped with iodine or a dichroic dye as a polarizer, and laminating with a configuration of λ / 4 film / polarizer. it can. The film thickness of the polarizer is 5 to 40 μm, preferably 5 to 30 μm, and particularly preferably 5 to 20 μm.

  The polarizing plate can be produced by a general method. The λ / 4 film subjected to the alkali saponification treatment is preferably bonded to one surface of a polarizer produced by immersing and stretching a polyvinyl alcohol film in an iodine solution using a completely saponified polyvinyl alcohol aqueous solution.

  The polarizing plate can be constituted by further bonding a release film to the opposite surface of the polarizing plate protective film of the polarizing plate. The protective film and the release film are used for the purpose of protecting the polarizing plate at the time of shipping the polarizing plate, product inspection, and the like.

<Organic EL display device>
FIG. 5 is a cross-sectional view showing a schematic configuration of the organic EL display device 100 as the OLED of the present embodiment. The configuration of the organic EL display device 100 is not limited to this.

  The organic EL display device 100 is configured by forming a circularly polarizing plate 301 on an organic EL element 101 via an adhesive layer 201. The organic EL element 101 includes a metal electrode 112, a light emitting layer 113, a transparent electrode (ITO, etc.) 114, and a sealing layer 115 on a substrate 111 made of glass, polyimide, or the like. The metal electrode 112 may be composed of a reflective electrode and a transparent electrode.

  The circularly polarizing plate 301 is formed by laminating a λ / 4 film 316, an adhesive layer 315, a polarizer 311, an adhesive layer 312, a protective film 313, and a cured layer 314 in order from the organic EL element 101 side. / 4 film 316 and protective film 313. By pasting both together so that the angle formed by the transmission axis of the polarizer 311 and the slow axis of the λ / 4 film 316 made of the long obliquely stretched film of this embodiment is about 45 ° (or 135 °). A circularly polarizing plate 301 is configured.

  A cured layer 314 is preferably laminated on the protective film 313. The hardened layer 314 not only prevents scratches on the surface of the organic EL display device 100 but also has an effect of preventing warpage due to the circularly polarizing plate 301. Furthermore, an antireflection layer may be formed on the hardened layer 314. The thickness of the organic EL element 101 itself is about 1 μm.

  In the above configuration, when a voltage is applied to the metal electrode 112 and the transparent electrode 114, electrons are injected into the light emitting layer 113 from the electrode serving as the cathode among the metal electrode 112 and the transparent electrode 114, and the electrode serving as the anode. Holes are injected from and recombined in the light emitting layer 113, whereby visible light emission corresponding to the light emission characteristics of the light emitting layer 113 occurs. The light generated in the light emitting layer 113 is directly or after being reflected by the metal electrode 112 and then extracted to the outside through the transparent electrode 114 and the circularly polarizing plate 301.

  In general, in an organic EL display device, a metal electrode, a light emitting layer, and a transparent electrode are sequentially laminated on a transparent substrate to form a light emitting element (organic EL element). Here, the light emitting layer is a laminate of various organic thin films, for example, a laminate of a hole injection layer made of a triphenylamine derivative and the like and a light emitting layer made of a fluorescent organic solid such as anthracene, Structures having various combinations such as a laminate of such a light emitting layer and an electron injection layer made of a perylene derivative, a hole injection layer, a light emitting layer, and a laminate of an electron injection layer are known.

  In organic EL display devices, holes and electrons are injected into the light-emitting layer by applying a voltage to the transparent electrode and the metal electrode, and the energy generated by recombination of these holes and electrons excites the fluorescent material. It emits light on the principle that it emits light when the excited fluorescent material returns to the ground state. The mechanism of recombination on the way is the same as that of a general diode, and as can be expected from this, the current and the light emission intensity show strong nonlinearity with rectification with respect to the applied voltage.

  In an organic EL display device, in order to extract light emitted from the light emitting layer, at least one of the electrodes must be transparent, and a transparent electrode usually formed of a transparent conductor such as indium tin oxide (ITO) is used as an anode. Used. On the other hand, in order to facilitate electron injection and increase luminous efficiency, it is important to use a material having a small work function for the cathode, and usually metal electrodes such as Mg—Ag and Al—Li are used.

  In the organic EL display device having such a configuration, the light emitting layer is formed of a very thin film having a thickness of about 10 nm. For this reason, the light emitting layer transmits light almost completely like the transparent electrode. As a result, the light that is incident from the surface of the transparent substrate when not emitting light, passes through the transparent electrode and the light emitting layer, and is reflected by the metal electrode again exits to the surface side of the transparent substrate. The display surface of the EL display device looks like a mirror surface.

  The circularly polarizing plate of this embodiment is suitable for an organic EL display device in which such external light reflection is particularly problematic.

  That is, when the organic EL element 101 is not emitting light, external light incident from the outside of the organic EL element 101 due to indoor lighting or the like is absorbed by the polarizer 311 of the circularly polarizing plate 301 and the other half is transmitted as linearly polarized light. Then, the light enters the λ / 4 film 316. Since the transmission axis of the polarizer 311 and the slow axis of the λ / 4 film 316 are arranged to intersect at 45 ° (or 135 °), the light incident on the λ / 4 film 316 is λ / 4 By passing through the film 316, it is converted into circularly polarized light.

  When the circularly polarized light emitted from the λ / 4 film 316 is specularly reflected by the metal electrode 112 of the organic EL element 101, the phase is inverted by 180 degrees and reflected as reverse circularly polarized light. Since the reflected light is incident on the λ / 4 film 316 and converted into linearly polarized light perpendicular to the transmission axis of the polarizer 311 (parallel to the absorption axis), all of the reflected light is absorbed by the polarizer 311 and emitted to the outside. Will not be. That is, external light reflection at the organic EL element 101 can be reduced by the circularly polarizing plate 301.

<Liquid crystal display device>
FIG. 6 is a cross-sectional view showing a schematic configuration of a display device 400 as a liquid crystal display device of the present embodiment. The display device 400 is configured by disposing a polarizing plate 402 on one surface side of the display cell 401.

  Note that in the case of a liquid crystal display device, the display cell 401 can be a liquid crystal cell in which a liquid crystal layer is sandwiched between a pair of substrates. Note that, on the side opposite to the polarizing plate 402 with respect to the liquid crystal cell, another polarizing plate arranged in a crossed Nicols state with the polarizing plate 402 and a backlight for illuminating the liquid crystal cell are provided. These are not shown in the figure.

  Further, the display device 400 may include a front window 403 on the side opposite to the display cell 401 with respect to the polarizing plate 402. The front window 403 is an exterior cover of the display device 400, and is made of, for example, a cover glass. A filler 404 made of, for example, an ultraviolet curable resin is filled between the front window 403 and the polarizing plate 402. In the absence of the filler 404, an air layer is formed between the front window 403 and the polarizing plate 402. Therefore, reflection of light at the interface between the front window 403 and the polarizing plate 402 and the air layer causes a display image to be displayed. Visibility may be reduced. However, since the air layer is not formed between the front window 403 and the polarizing plate 402 by the filler 404, it is possible to avoid a decrease in visibility of the display image due to light reflection at the interface.

  The polarizing plate 402 has a polarizer 501 that transmits predetermined linearly polarized light. On one surface side of the polarizer 501 (the side opposite to the display cell 401), a λ / 4 film 503 and a cured layer 504 made of an ultraviolet curable resin are laminated in this order via an adhesive layer 502. ing. A protective film 506 is attached to the other surface side (display cell 401 side) of the polarizer 501 with an adhesive layer 505 interposed therebetween.

  The polarizer 501 is obtained, for example, by dyeing a polyvinyl alcohol film with a dichroic dye and stretching the film at a high magnification. The polarizer 501 is subjected to alkali treatment (also referred to as saponification treatment), and then a λ / 4 film 503 is bonded to one surface via an adhesive layer 502, and a protective film 506 is bonded to the other surface. Are pasted together.

When the thickness of the polarizer 501 is B μm, from the viewpoint of reducing the thickness of the polarizing plate 402,
1μm <B ≦ 20μm
It is desirable that
1μm <B ≦ 15μm
It is further desirable that

  The adhesive layers 502 and 505 are layers made of, for example, a polyvinyl alcohol adhesive (PVA adhesive, water glue), but may be layers made of an ultraviolet curable adhesive (UV adhesive). These adhesives are liquid in a state where they are applied to an adhesive surface, and are bonded to each other by being dried or cured by ultraviolet irradiation after application. That is, the adhesive layers 502 and 505 adhere the polarizer 501 and the λ / 4 film 503, and the polarizer 501 and the protective film 506, respectively, according to the state change from the liquid state. In this way, the adhesive layers 502 and 505 adhere the two by changing the state from the liquid state, and the adhesive layer (adhesive on the base material) that adheres the two without causing such a change in state. The sheet-like adhesive layer).

  The λ / 4 film 503 is a layer that imparts an in-plane retardation of about ¼ of the wavelength to transmitted light. In the present embodiment, the λ / 4 film 503 includes, for example, a cellulose resin (cellulose polymer). The λ / 4 film 503 may contain a polycarbonate resin (polycarbonate polymer) instead of the cellulose polymer, or may contain a cycloolefin resin (cycloolefin polymer). However, from the viewpoint of chemical resistance, it is desirable that the λ / 4 film 503 contains a cellulose polymer or a polycarbonate polymer.

  The λ / 4 film 503 is a thin λ / 4 film having a thickness of 10 μm to 70 μm. In addition, the angle (crossing angle) formed between the slow axis of the λ / 4 film 503 and the absorption axis of the polarizer 501 is 30 ° to 60 °, whereby linearly polarized light from the polarizer 501 is λ / It is converted into circularly polarized light or elliptically polarized light by the 4 film 503.

  The hardened layer 504 (also referred to as a hard coat layer) is made of an active energy ray curable resin (for example, an ultraviolet curable resin).

  The protective film 506 is composed of an optical film made of, for example, a cellulose resin (cellulose polymer), an acrylic resin, a cyclic polyolefin (COP), or a polycarbonate (PC). The protective film 506 is simply provided as a film that protects the back side of the polarizer 501, but may be provided as an optical film that also serves as a retardation film having a desired optical compensation function.

  In the case of a liquid crystal display device, another polarizing plate disposed on the side opposite to the polarizing plate 402 with respect to the display cell 401 (liquid crystal cell) is configured by sandwiching the surface of the polarizer between two optical films. However, as the polarizer and the optical film, those similar to the polarizer 501 and the protective film 506 of the polarizing plate 402 can be used.

  Here, each of the polarizer 501 and the λ / 4 film 503 described above may be long. In this case, it is desirable that the slow axis of the λ / 4 film 503 is inclined by 30 ° to 60 ° with respect to the longitudinal direction of the λ / 4 film 503. In this case, the long λ / 4 film 503 is produced by oblique stretching to form a roll film, which is bonded to the roll polarizer 501 by a so-called roll-to-roll method to form a long film. The polarizing plate 402 can be manufactured. Therefore, productivity can be dramatically improved and yield can be greatly improved as compared with the case where the polarizing plate 402 is manufactured by a batch method in which film pieces are bonded one by one.

  An easy adhesion layer for improving the adhesion of the λ / 4 film 503 may be provided on the adhesive layer 502 side of the λ / 4 film 503. The easy adhesion layer is formed by performing an easy adhesion process on the adhesive layer 502 side of the λ / 4 film 503. Examples of the easy adhesion treatment include corona (discharge) treatment, plasma treatment, flame treatment, itro treatment, glow treatment, ozone treatment, primer coating treatment, and the like, and at least one of them may be performed. Among these easy adhesion treatments, from the viewpoint of productivity, corona treatment and plasma treatment are preferable as the easy adhesion treatment.

<Example>
Hereinafter, specific examples relating to the production of the obliquely stretched film in the present embodiment will be described with reference to comparative examples. The present invention is not limited to the following examples. In the following description, “parts” or “%” is used, but unless otherwise specified, these represent “parts by mass” or “mass%”.

[Production of raw film]
By the following method, the elongate films 1-2 as an original fabric film were produced.

(Long film 1)
The long film 1 is a cellulose ester resin film and was produced by the following production method.

≪Fine particle dispersion≫
Fine particles (Aerosil R972V manufactured by Nippon Aerosil Co., Ltd.) 11 parts by weight Ethanol 89 parts by weight The above was stirred and mixed with a dissolver for 50 minutes, and then dispersed with Manton Gorin to prepare a fine particle dispersion 1.

≪Particulate additive liquid≫
Based on the following composition, the fine particle dispersion was slowly added to a dissolution tank containing methylene chloride with sufficient stirring. Further, the particles were dispersed by an attritor so that the secondary particles had a predetermined particle size. This was filtered through Finemet NF manufactured by Nippon Seisen Co., Ltd. to prepare a fine particle additive solution 1.
99 parts by mass of methylene chloride 5 parts by mass of fine particle dispersion 1

≪Main dope liquid≫
A main dope solution having the following composition was prepared. First, methylene chloride and ethanol were added to the pressure dissolution tank. Cellulose acetate was added to a pressurized dissolution tank containing a solvent while stirring. This was heated and stirred to dissolve completely, and this was dissolved in Azumi Filter Paper No. The main dope solution was prepared by filtration using 244. In addition, the compound synthesize | combined by the following synthesis examples was used for the sugar ester compound and the ester compound.

<Composition of main dope solution>
Methylene chloride 340 parts by mass Ethanol 64 parts by mass Cellulose acetate propionate (acetyl group substitution degree 1.50, propionyl group substitution degree 0.90, total substitution degree 2.40) 100 parts by mass Sugar ester compound 5.0 parts by mass Ester Compound 5.0 parts by weight Ultraviolet absorber 1.5 parts by weight Particulate additive liquid 1 part by weight

≪Synthesis of sugar ester compounds≫
A sugar ester compound was synthesized by the following steps.

  Four-headed Kolben equipped with a stirrer, a reflux condenser, a thermometer, and a nitrogen gas inlet tube was charged with 34.2 g (0.1 mol) of sucrose, 180.8 g (0.6 mol) of benzoic anhydride, pyridine 379. 7 g (4.8 mol) was charged, the temperature was raised while bubbling nitrogen gas through a nitrogen gas inlet tube with stirring, and an esterification reaction was carried out at 70 ° C. for 5 hours.

Next, the inside of the Kolben was depressurized to 4 × 10 ² Pa or less, and after excess pyridine was distilled off at 60 ° C., the inside of the Kolben was depressurized to 1.3 × 10 Pa or less and the temperature was raised to 120 ° C. Most of the acid and benzoic acid formed were distilled off.

Finally, 100 g of water is added to the collected toluene layer, and after washing with water at room temperature for 30 minutes, the toluene layer is separated, and toluene is distilled off at 60 ° C. under reduced pressure (4 × 10 ² Pa or less). A mixture (sugar ester compound) of A-1, A-2, A-3, A-4 and A-5 was obtained.

  When the obtained mixture was analyzed by HPLC and LC-MASS, A-1 was 1.3% by mass, A-2 was 13.4% by mass, A-3 was 13.1% by mass, and A-4 was 31%. 0.7% by mass and A-5 was 40.5% by mass. The average degree of substitution was 5.5.

<< Measurement conditions for HPLC-MS >>
1) LC section Device: JASCO CO., LTD. Column oven (JASCO CO-965), detector (JASCO UV-970-240 nm), pump (JASCO PU-980), degasser (JASCO DG-980-50)
Column: Inertsil ODS-3 Particle size 5 μm 4.6 × 250 mm (manufactured by GL Sciences Inc.)
Column temperature: 40 ° C
Flow rate: 1 ml / min
Mobile phase: THF (1% acetic acid): H ₂ O (50:50)
Injection volume: 3 μl
2) MS unit Device: LCQ DECA (manufactured by Thermo Quest Co., Ltd.)
Ionization method: Electrospray ionization (ESI) method Spray Voltage: 5 kV
Capillary temperature: 180 ° C
Vaporizer temperature: 450 ° C

≪Synthesis of ester compound≫
An ester compound was synthesized by the following steps.

  251 g of 1,2-propylene glycol, 278 g of phthalic anhydride, 91 g of adipic acid, 610 g of benzoic acid, 0.191 g of tetraisopropyl titanate as an esterification catalyst, 2 L four-neck equipped with a thermometer, stirrer, and slow cooling tube The flask is charged and gradually heated while being stirred until it reaches 230 ° C. in a nitrogen stream. The ester compound was obtained by making it dehydrate-condense for 15 hours, and distilling unreacted 1, 2- propylene glycol under reduced pressure at 200 degreeC after completion | finish of reaction. The ester compound has an ester of benzoic acid at the end of a polyester chain formed by condensation of 1,2-propylene glycol, phthalic anhydride and adipic acid. The acid value of the ester compound was 0.10, and the number average molecular weight was 450.

  Then, using an endless belt casting apparatus, it was cast uniformly on a stainless belt support.

  In the endless belt casting apparatus, the main dope solution was uniformly cast on a stainless steel belt support. On the stainless steel belt support, the solvent is evaporated until the residual solvent amount in the cast (cast) long film reaches 75%, peeled off from the stainless steel belt support, and transported by many rolls. Drying was terminated, and a long film 1 having a width of 1500 mm was obtained.

(Long film 2)
The long film 2 is a cycloolefin resin film (COP), and was produced by the following production method.

  In a nitrogen atmosphere, 500 parts by mass of dehydrated cyclohexane, 1.2 parts by mass of 1-hexene, 0.15 parts by mass of dibutyl ether and 0.30 parts by mass of triisobutylaluminum were mixed in a reactor at room temperature, and then mixed at 45 ° C. 20 parts by mass of 1,4-methano-1,4,4a, tricyclo [4.3.0.12,5] deca-3,7-diene (dicyclopentadiene, hereinafter abbreviated as DCP) 140 parts by mass of 9a-tetrahydrofluorene (hereinafter abbreviated as MTF) and 40 parts by mass of 8-methyl-tetracyclo [4.4.0.12, 5.17,10] -dodec-3-ene (hereinafter abbreviated as MTD) A norbornene-based monomer mixture composed of parts and 40 parts by mass of tungsten hexachloride (0.7% toluene solution) were continuously added over 2 hours for polymerization. To the polymerization solution, 1.06 parts by mass of butyl glycidyl ether and 0.52 parts by mass of isopropyl alcohol were added to deactivate the polymerization catalyst and stop the polymerization reaction.

  Subsequently, 270 parts by mass of cyclohexane is added to 100 parts by mass of the reaction solution containing the obtained ring-opening polymer, and further 5 parts by mass of a nickel-alumina catalyst (manufactured by JGC Catalysts & Chemicals) as a hydrogenation catalyst. In addition, the pressure was increased to 5 MPa with hydrogen and the mixture was heated to 200 ° C. with stirring and then reacted for 4 hours to obtain a reaction solution containing 20% of a DCP / MTF / MTD ring-opening polymer hydrogenated polymer.

  After removing the hydrogenation catalyst by filtration, a soft polymer (manufactured by Kuraray Co., Ltd .; Septon 2002) and an antioxidant (manufactured by Ciba Specialty Chemicals Co., Ltd .; Irganox 1010) were added to the resulting solutions, respectively. And dissolved (both 0.1 parts by mass per 100 parts by mass of the polymer). Next, cyclohexane and other volatile components, which are solvents, are removed from the solution using a cylindrical concentration dryer (manufactured by Hitachi, Ltd.), and the hydrogenated polymer is extruded in a strand form from an extruder in a molten state. After cooling, it was pelletized and collected. When the copolymerization ratio of each norbornene monomer in the polymer was calculated from the composition of residual norbornenes in the solution after polymerization (by gas chromatography method), it was almost charged at DCP / MTF / MTD = 10/70/20. It was equal to the composition. This hydrogenated ring-opened polymer had a weight average molecular weight (Mw) of 31,000, a molecular weight distribution (Mw / Mn) of 2.5, a hydrogenation rate of 99.9%, and a Tg of 134 ° C.

  The obtained pellets of the ring-opened polymer hydrogenated product were dried at 70 ° C. for 2 hours using a hot air dryer in which air was circulated to remove moisture. Next, the pellets were melted by using a short-shaft extruder having a coat hanger type T die (manufactured by Mitsubishi Heavy Industries, Ltd .: screw diameter 90 mm, T die lip member quality is tungsten carbide, peel strength 44N from molten resin). Extrusion molding produced a cycloolefin polymer film. In extrusion molding, a long film 2 having a width of 1500 mm was obtained in a clean room of class 10,000 or less under molding conditions of a molten resin temperature of 240 ° C. and a T die temperature of 240 ° C.

[Preparation of obliquely stretched film]
The long film 1 made of the cellulose-based resin produced above was obliquely stretched by the stretching part 5 to obtain long diagonally stretched films (see Examples 1 to 4 and Comparative Examples 1 and 2 in Table 1). At this time, the moving speed of the film is 15 m / min, the temperature of the preheating zone Z1 is 196 ° C., the temperature of the stretching zone Z2 is 196 ° C., the temperature of the heat setting zone Z3 is 188 ° C., and the stretching ratio is 1.16 times. The thickness was 40 μm, and the final film width after trimming was 1300 mm.

Moreover, in manufacture of the diagonally stretched film of Examples 1-4, the widening of the diagonally stretched film was performed in the heat setting zone Z3. That is, in the heat setting zone Z3, the width of the long diagonally stretched film before widening after the end of the diagonal stretching is L1 (mm), and in the heat setting step, from the portion corresponding to the width L1 of the diagonally stretched film before widening Also, when the widths of the widened portions on the leading side and the delay side are L2 (mm) and L3 (mm), respectively, the diagonally stretched so that the width L1, the width L2, and the width L3 are the values shown in Table 1. The film was widened. In Table 1, the ratio A and the ratio B represented by the following formula are also shown. In particular, in the production of the obliquely stretched film of Example 2, the temperature in the heat setting zone Z3 was adjusted to a temperature 30 ° C. lower than the temperature in the stretch zone Z2.
A = (L2 / L1) × 100
B = (L3 / L1) × 100

  Moreover, in manufacture of the diagonally stretched film of the comparative example 1, the widening in the heat setting zone Z3 was not performed. On the other hand, in the production of the obliquely stretched film of Comparative Example 2, the obliquely stretched film was widened not in the heat setting zone Z3 but in the stretching zone Z2. At this time, in the stretching zone Z2, the width of the long diagonally stretched film before widening is L1 (mm), and the portion widened to the leading side and the delay side than the portion corresponding to the width L1 of the diagonally stretched film before widening The width of each was L2 (mm) and L3 (mm), respectively.

  Further, the original film (long film 2) made of COP was also obliquely stretched in the same manner as described above. That is, first, in the vicinity of the front side of the heating zone Z, both ends of the unstretched film A sent from the film feeding unit 2 are used as the first clip as the preceding holding tool Ci and the holding tool Co on the delay side. Of the second clip. When the unstretched film A is gripped, the unstretched film A is gripped by moving the clip levers of the first and second clips with the clip closer. When gripping the clip, both ends of the unstretched film A are simultaneously gripped by the first and second clips, and the line connecting the grip positions at both ends is parallel to the axis parallel to the width direction of the film. Grab so that

  Subsequently, the unstretched film A (long film 2) was diagonally stretched by the stretching portion 5 described above to obtain a long diagonally stretched film (see Example 5 and Comparative Example 3 in Table 1). That is, the gripped unstretched film A is transported while being gripped by the first and second clips, and heated by passing through the preheating zone Z1, the stretching zone Z2, and the heat fixing zone Z3 in the heating zone Z, A stretched film A ′ stretched in an oblique direction with respect to the hand direction was obtained.

  At this time, in the production of the obliquely stretched film of Example 5, the obliquely stretched film was widened so that the width L1, the width L2, and the width L3 were values shown in Table 1 in the heat setting zone Z3. On the other hand, in the production of the obliquely stretched film of Comparative Example 3, the widening was performed in the stretching zone Z2 instead of the heat setting zone Z3. Note that the definitions of the width L1, the width L2, and the width L3 in Comparative Example 3 are the same as the definitions in Comparative Example 2 in which widening is performed in the stretching zone Z2.

  In addition, the film moving speed at the time of heating and stretching was 15 m / min. The temperature of the preheating zone Z1 was 147 ° C., the temperature of the stretching zone Z2 was 147 ° C., and the temperature of the heat setting zone Z3 was 140 ° C. The stretching ratio of the film before and after stretching was 1.16 times, and the film thickness after stretching was 50 μm.

[Production of circularly polarizing plates 1 to 8]
Circular polarizing plates 1 to 8 were produced as follows using a long obliquely stretched film obliquely stretched under the same conditions as described above.

  That is, a 120 μm-thick polyvinyl alcohol film was uniaxially stretched (temperature 110 ° C., stretch ratio 5 times), immersed in an aqueous solution composed of 0.075 g of iodine, 5 g of potassium iodide, and 100 g of water, and then potassium iodide. It was immersed in a 68 ° C. aqueous solution consisting of 6 g, boric acid 7.5 g, and water 100 g. The film after immersion was washed with water and dried to obtain a polarizer.

  Then, the produced long diagonally stretched films of Examples 1 to 5 and Comparative Examples 1 to 3 were bonded to one side of the polarizer using a 5% aqueous solution of polyvinyl alcohol as an adhesive. At that time, the lamination was performed so that the transmission axis of the polarizer and the slow axis of the obliquely stretched film were oriented at 45 °. Then, Konica Minolta Tack Film KC4UAH (manufactured by Konica Minolta Co., Ltd.) subjected to alkali saponification treatment was similarly bonded to the other surface of the polarizer to produce circularly polarizing plates 1 to 8.

[Production of Circular Polarizing Plates 11 to 18]
Circular polarizing plates 11 to 18 were produced as follows using a long obliquely stretched film obliquely stretched under the same conditions as described above.

  That is, a 120 μm-thick polyvinyl alcohol film was uniaxially stretched (temperature 110 ° C., stretch ratio 5 times), immersed in an aqueous solution composed of 0.075 g of iodine, 5 g of potassium iodide, and 100 g of water, and then potassium iodide. It was immersed in a 68 ° C. aqueous solution consisting of 6 g, boric acid 7.5 g, and water 100 g. The film after immersion was washed with water and dried to obtain a polarizer.

  Then, the produced long diagonally stretched films of Examples 1 to 5 and Comparative Examples 1 to 3 were bonded to one side of the polarizer using a 5% aqueous solution of polyvinyl alcohol as an adhesive. At that time, the lamination was performed so that the transmission axis of the polarizer and the slow axis of the obliquely stretched film were oriented at 45 °. And the Konica Minolta-tack film KC2CT1 (made by Konica Minolta Co., Ltd.) which carried out the alkali saponification process was similarly stuck on the other surface of the polarizer, and the circularly-polarizing plates 11-18 were produced.

[Production of organic EL display devices 1 to 8]
A reflective electrode made of chromium having a thickness of 80 nm was formed on a glass substrate by sputtering. Next, ITO (indium tin oxide) was formed on the reflective electrode as an anode to a thickness of 40 nm by a sputtering method. Subsequently, poly (3,4-ethylenedioxythiophene) -polystyrene sulfonate (PEDOT: PSS) was formed as a hole transport layer on the anode with a thickness of 80 nm by a sputtering method. Thereafter, each of the RGB light emitting layers was formed to a thickness of 100 nm on the hole transport layer using a shadow mask.

  Further, calcium was formed to a thickness of 4 nm by vacuum deposition as a first cathode having a low work function so that electrons can be efficiently injected onto the light emitting layer. Thereafter, aluminum was formed to a thickness of 2 nm as a second cathode on the first cathode. Here, the aluminum used as the second cathode has a role of preventing the calcium as the first cathode from being chemically altered when the transparent electrode formed thereon is formed by sputtering. . As described above, an organic light emitting layer was obtained.

  Next, a transparent conductive film with a thickness of 80 nm was formed on the cathode by sputtering. Here, ITO was used as the transparent conductive film. Furthermore, 200 nm of silicon nitride was formed on the transparent conductive film by a CVD method (chemical vapor deposition method) to obtain an insulating film. This produced the organic EL element. The size of the produced organic EL element was 1296 mm × 784 mm.

  On the insulating film of the organic EL element prepared above, the circularly polarizing plates 1 to 8 prepared as described above are fixed with an adhesive so that the surface of the obliquely stretched film faces the surface of the insulating film of the organic EL element. Turn into. Thus, organic EL display devices 1 to 8 were produced.

[Production of liquid crystal display devices 1 to 8]
<Production of liquid crystal display device>
The polarizing plate on the viewing side, which has been pasted in a commercially available 10-inch liquid crystal display device, is peeled off, and the circularly polarizing plates 11 to 18 thus prepared are placed so that the surface of the Konica Minolta-tack film KC2CT1 faces the surface of the liquid crystal cell. And it bonded by the adhesive and produced the liquid crystal display devices 1-8. In addition, bonding of the circularly polarizing plates 11 to 18 was performed so that the absorption axis of the polarizer of the circularly polarizing plates 11 to 18 was in the same direction as the absorption axis of the polarizer of the polarizing plate that had been bonded in advance. .

[Quantitative evaluation]
In order to investigate the variation in the orientation angle in the width direction of the produced film, the orientation angle in the width direction is as follows for the obliquely stretched films prepared in the same manner as in Examples 1 to 5 and Comparative Examples 1 to 3 in Table 1. The difference between the left and right orientation angles was determined. That is, the obliquely stretched film was left in a room at 23 ° C. and 55% RH for 24 hours, and then 10 pieces of film pieces were cut out in the transport direction 30 mm inside from the end of the obliquely stretched film. And about each film piece, an orientation angle is measured in each position of a width direction using a phase difference measuring apparatus (Oji Scientific Co., Ltd. product, KOBRA-WXK), and the average of the difference of 10 right and left orientation angles And the obtained average value was defined as the difference between the left and right orientation angles. Based on the following evaluation criteria, the orientation angle unevenness in the width direction was quantitatively evaluated.
"Evaluation criteria"
A: The difference between the right and left orientation angles is less than 0.3 °.
B: The difference between the right and left orientation angles is 0.3 ° or more and less than 0.6 °.
C: The difference between the right and left orientation angles is 0.6 ° or more and less than 0.8 °.
D: The difference between the right and left orientation angles is 0.8 ° or more.

〔sensory evaluation〕
The produced organic EL display devices 1 to 8 and the liquid crystal display devices 1 to 8 were placed in an environment of 60 ° C. and 90% RH for 500 hours, and then allowed to stand in an environment of 23 ° C. and 55% RH for 24 hours. A black screen was displayed on the display device, and the color display state was visually observed and evaluated based on the following criteria. In addition, about the liquid crystal display devices 1-8, in the state which mounted | wearing with the polarized sunglasses, it observed visually and evaluated based on the following references | standards.
<Evaluation criteria>
A: The screen was uniformly displayed in black, and color unevenness due to unevenness in the amount of reflected light was not observed.
B: Slight striped unevenness was observed at the edge of the screen, but this is a level that does not cause a problem in practice.
C: Thin striped unevenness was observed on the entire screen.
D: Striped unevenness was observed on the entire screen.

  Table 1 has shown the result of evaluation about the diagonally stretched film of Examples 1-5 and Comparative Examples 1-3.

  From Table 1, in Comparative Example 1 where the film is not widened, neither quantitative evaluation nor sensory evaluation is good (both evaluations are D), and even in Comparative Examples 2 and 3 where the film is widened in the oblique stretching step, Comparative Example Although the quantitative evaluation is higher than 1, the evaluation is C or D, which is not good. On the other hand, in Examples 1-5 which widen a film in the heat setting process after diagonally stretching, both quantitative evaluation and sensory evaluation are favorable (evaluation is A or B). In the heat setting step after oblique stretching, by performing widening on the obliquely stretched film, it is possible to suppress the occurrence of loose residual stress in the obliquely stretched film, particularly during oblique stretching. By widening the delay side to be larger than the preceding side, it is possible to suppress the occurrence of avalan residual stress in the film without substantially changing the optical axis oriented in a predetermined direction by oblique stretching. it is conceivable that.

  In particular, as in Examples 3 to 5, when the ratio B is as small as 4% or less, the quantitative evaluation is the best with A, so it can be said that such widening (setting of the width L1 and the width L3) is desirable. Furthermore, as in Examples 4 to 5, when the width L2 of the leading side widening is 0 mm, both quantitative evaluation and sensory evaluation are the best with A, so it is more desirable to widen at L2 = 0 mm. It can be said.

  The manufacturing method of the diagonally stretched film of this embodiment demonstrated above can be expressed as follows.

1. While gripping both ends of the width direction of the film with a pair of gripping tools, one of the gripping tools is relatively advanced, and the other gripping tool is relatively delayed to convey the film. A method for producing an obliquely stretched film having an obliquely stretching step of stretching in an oblique direction with respect to the width direction,
Further comprising a heat fixing step for fixing the optical axis of the obliquely stretched film after the oblique stretching step is completed;
In the heat setting step, widening the obliquely stretched film after the oblique stretching step is completed,
With the width of the obliquely stretched film before widening after the end of oblique stretching as L1, in the heat setting step, the width was widened to the leading side and the delay side from the portion corresponding to the width L1 of the obliquely stretched film before widening. When the width of the part is L2 and L3, respectively, the following conditional expression (1) is satisfied:
L3> L2 ≧ 0 mm (1)
It is.

2. The method for producing an obliquely stretched film according to 1 above, further satisfying the following conditional expression (2):
5%>B> A ≧ 0% (2)
However,
A = (L2 / L1) × 100
B = (L3 / L1) × 100
It is.

  3. In the heat setting step, the obliquely stretched film is widened at a temperature that is 10 ° C to 60 ° C lower than the stretch temperature in the obliquely stretched step. .

4). 4% ≧ B ≧ 1%
The manufacturing method of the diagonally stretched film of said 2 characterized by the above-mentioned.

5. L2 = 0mm
The manufacturing method of the diagonally stretched film in any one of said 1 to 4 characterized by being.

  6). 6. The method for producing an optical film as described in any one of 1 to 5, wherein the film that is obliquely stretched in the oblique stretching step contains a cellulose ester resin.

  The present invention can be used, for example, for manufacturing a circularly polarizing plate for preventing external light reflection of an organic EL image display device.

DESCRIPTION OF SYMBOLS 1 Manufacturing apparatus of diagonally stretched film 5 Stretching part Ci gripping tool Co gripping tool

Claims (6)

While gripping both ends of the width direction of the film with a pair of gripping tools, one of the gripping tools is relatively advanced, and the other gripping tool is relatively delayed to convey the film. A method for producing an obliquely stretched film having an obliquely stretching step of stretching in an oblique direction with respect to the width direction,
Further comprising a heat fixing step for fixing the optical axis of the obliquely stretched film after the oblique stretching step is completed;
In the heat setting step, widening the obliquely stretched film after the oblique stretching step is completed,
With the width of the obliquely stretched film before widening after the end of oblique stretching as L1, in the heat setting step, the width was widened to the leading side and the delay side from the portion corresponding to the width L1 of the obliquely stretched film before widening. When the width of the part is L2 and L3, respectively, the following conditional expression (1) is satisfied:
L3> L2 ≧ 0 mm (1)
It is. The method for producing an obliquely stretched film according to claim 1, further satisfying the following conditional expression (2):
5%>B> A ≧ 0% (2)
However,
A = (L2 / L1) × 100
B = (L3 / L1) × 100
It is.   In the said heat setting process, the said diagonally stretched film is widened at the temperature 10-60 degreeC lower than the stretching temperature in the said diagonally stretching process, The manufacture of the diagonally stretched film of Claim 1 or 2 characterized by the above-mentioned. Method. 4% ≧ B ≧ 1%
The manufacturing method of the diagonally stretched film of Claim 2 characterized by the above-mentioned. L2 = 0mm
The manufacturing method of the diagonally stretched film in any one of Claim 1 to 4 characterized by the above-mentioned.   The method for producing an optical film according to claim 1, wherein the film that is obliquely stretched in the oblique stretching step contains a cellulose ester-based resin.

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