JP6903001B2 - Method for manufacturing diagonally stretched film - Google Patents

Description

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

Conventionally, self-luminous display devices such as organic EL (Electro-Luminescence) display devices, which are also called OLEDs (Organic light-Emitting Diodes), have 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 improve the light extraction efficiency. Therefore, the external light incident on the display is reflected by this reflector, and the contrast of the image is lowered. ..

Therefore, in order to improve the contrast between light and dark by preventing reflection of external light, it is known that a stretched film and a polarizer are laminated to form a circularly polarizing plate, and this circularly polarizing plate is arranged on the surface side of a display. At this time, the above-mentioned circularly polarizing plate is formed by laminating the polarizer and the stretched film so that the in-plane slow-phase axis of the stretched film is inclined at a desired angle with respect to the transmission axis of the polarizer. To.

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 manufactured by longitudinal stretching or transverse stretching, and in principle, the in-plane slow-phase axis is in the direction of 0 ° or 90 ° with respect to the longitudinal direction of the film. Therefore, 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, a long polarizing film and / or a stretched film is cut out at a specific angle and the film pieces are cut out from each other. There was no choice but to adopt a batch method in which the films were laminated one by one, and the productivity was deteriorated.

On the other hand, the film is stretched in a direction (obliquely) at a desired angle 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 diagonally stretched film that can be controlled are 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 conveyed by a pair of grippers. Then, the resin film is stretched in an oblique direction by changing the transport direction of the resin film on the way. As a result, a long obliquely stretched film having a slow phase axis at a desired angle of more than 0 ° and less than 90 ° with respect to the longitudinal direction is produced.

By using such a long diagonally stretched film, it becomes possible to manufacture a circular polarizing plate by laminating a long polarizing film and a long diagonally stretched film by a roll-to-roll method. Productivity is dramatically improved.

By the way, when the circularly polarizing plate produced as described above was applied to the OLED, the OLED was placed in a temperature and humidity environment different from the usual one, and the displayed image was observed, diagonally striped display unevenness as shown in FIG. 7 was observed. It turned out to appear. It was also confirmed that when environmental changes (temperature changes, humidity changes) were intentionally applied, the above-mentioned display unevenness became large (prominent).

When the cause of the diagonally striped display unevenness was analyzed, it was found that the cause was the λ / 4 film used for the circularly polarizing plate. More specifically, in the production of a diagonally stretched film that functions as a λ / 4 film, as shown in FIG. 8, both ends of the film in the width direction are gripped by a pair of gripping tools Ci and Co, and one gripping tool Ci Is relatively preceded, and the other gripping tool Co is relatively delayed to convey the film, whereby oblique stretching is performed. When the film is held after the oblique stretching, a contraction force acts on the film due to the reaction of the oblique stretching and the temperature decrease, and this remains as an invisible diagonal residual stress T (crease-like, wrinkle-like). Therefore, as shown in FIG. 9, when the film 51 after oblique stretching and the polarizer 52 are laminated to form the circularly polarizing plate 50, the residual stress T remains on the film 51, so that the temperature and humidity fluctuate. At that time, it is considered that the characteristics of the film 51 are changed by the residual stress T, and the display unevenness shown in FIG. 7 occurs.

FIG. 10 schematically shows how a loose-shaped residual stress T is generated in the production of a diagonally stretched film. In the production of a normal diagonally stretched film, the film passes through the preheating zone Z1 of the stretching machine and then diagonally stretched in the stretching zone Z2, and then the optical axis (slow phase axis) is set in the heat fixing zone Z3. It is fixed. The film obliquely stretched in the stretch zone Z2 is relatively delayed compared to the gripper side (delayed side) that runs with a relative delay among the pair of grippers that grip both ends in the width direction of the film. Since the gripper side (leading side) that travels ahead enters the heat fixing zone Z3 first, the film shrinks from the leading side. Therefore, as shown in the figure, the loose-shaped residual stress T is generated in the order of the leading side, the central portion in the width direction, and the delay side.

As in Patent Document 2, the generation of such loose-shaped residual stress T increases the width of the rail on which the pair of grippers travel in the stretching zone (during diagonal stretching) to widen the film. The same occurs when the width is widened. FIG. 11 schematically shows how a loose-shaped residual stress T is generated when the film is widened in the stretch zone Z2. By widening the film in the stretch zone Z2, the film stretches in the width direction, so that the film does not shrink in the stretch zone Z2, and therefore, a loose residual stress does not occur during diagonal stretching. However, after the diagonal stretching is completed (in the heat fixing zone Z3), the film shrinks from the leading side, so that the film is loosened in the order of the leading side, the central portion in the width direction, and the delay side as in the case of FIG. Residual stress T is generated.

As described above, in the diagonally stretched film manufactured by the conventional manufacturing method, as shown in FIGS. 10 and 11, the film is conveyed in the transport direction (direction from the stretched zone Z2 toward the heat fixing zone Z3) and the width direction. On the other hand, since the arbor-shaped residual stress T is generated in the oblique direction, the OLED has striped display unevenness in the oblique direction as shown in FIG. 7. Therefore, in order to suppress such display unevenness, it is desired to manufacture a diagonally stretched film so that a loose-shaped residual stress T does not remain in the film after diagonally stretched.

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

In view of the above circumstances, an object of the present invention is to provide a method for producing a diagonally stretched film capable of suppressing the occurrence of ribbed residual stress after diagonally stretching.

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

In the method for producing a diagonally stretched film according to one aspect of the present invention, one gripper is relatively preceded and the other gripper is relative while gripping both ends of the film in the width direction with a pair of grippers. A method for producing a diagonally stretched film, which comprises a diagonally stretching step of stretching the film in a diagonal direction with respect to the width direction by transporting the film with a delay.
Further having a heat fixing step for fixing the optical axis of the diagonally stretched film after the completion of the diagonally stretched step.
In the heat fixing step, the width of the diagonally stretched film after the completion of the diagonally stretched step is widened.
After the completion of the diagonal stretching, the width of the diagonally stretched film before widening was set to L1, and in the heat fixing step, the width was widened to the leading side and the delayed side from the portion corresponding to the width L1 of the diagonally stretched film before widening. When the widths of the portions are L2 and L3, respectively, the following conditional expression (1) is satisfied. That is,
L3> L2 ≧ 0 mm ・ ・ ・ (1)
Is.

In the heat fixing step after the diagonal stretching is completed, the diagonally 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 diagonal stretching. As a result, a circularly polarizing plate is constructed using the manufactured obliquely stretched film, and even if the circularly polarizing plate is applied to the OLED and the OLED is placed in a temperature and humidity environment different from the usual one, the above-mentioned ribbed residual stress is obtained. It is possible to suppress the appearance of diagonally striped display unevenness due to this. Moreover, by satisfying the conditional expression (1), it is possible to suppress the occurrence of loose-shaped residual stress with almost no change in the direction of the optical axis (slow phase axis) oriented in a predetermined direction due to oblique stretching. Can be done. Therefore, even if the film is widened in the heat fixing step after the diagonal stretching, the diagonally stretched film having a desired orientation characteristic can be obtained by fixing the optic axis in a predetermined direction.

It is a top view which shows schematic structure of the schematic structure of the manufacturing apparatus of the oblique stretch film which concerns on embodiment of this invention. It is a top view which shows typically an example of the rail pattern of the extension part of the said manufacturing apparatus. It is explanatory drawing which shows typically the shape of the film which passes through the stretched part. It is explanatory drawing which shows typically how the arbor-like residual stress is relaxed when the diagonally stretched film is widened in the heat-fixing zone of the stretched part. It is sectional drawing which shows the schematic structure of the organic EL 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 unevenness on the display screen of the conventional organic EL image display apparatus. It is explanatory drawing which shows typically the conventional general diagonal stretching method. It is an exploded perspective view of the circularly polarizing plate manufactured by using the film obliquely stretched by the conventional method. It is explanatory drawing which shows typically the state that the arbor-like residual stress is generated in the manufacturing of the conventional diagonally stretched film. It is explanatory drawing which shows typically the mode that the arbor-like residual stress is generated when the film is widened in a stretch zone.

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

In the method for producing a long diagonally stretched film according to the present embodiment, a long diagonally stretched film containing a thermoplastic resin is stretched diagonally with respect to the width direction and the longitudinal direction to obtain a long diagonally stretched film. This is a method for producing a long diagonally stretched film.

The orientation direction of the long diagonally 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-phase axis is usually expressed in the stretching direction or a direction perpendicular to the stretching direction, the slow-phase axis is obtained by stretching in a direction exceeding 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 within a range of more than 0 ° and less than 90 °.

In the present embodiment, the long length means a film having a length of at least about 5 times or more with respect to the width of the film, preferably having a length of 10 times or more, and specifically in a roll shape. It is possible to think of a film roll having a length that allows it to be wound around and stored or transported.

In the long diagonally stretched film, after forming a long unaligned film, the film is once wound around a winding core to form a wound film (raw film), and the raw film is diagonally stretched from this wound body. It is also possible to supply the film to the oblique stretching step continuously from the film forming step without winding the long film after the film forming. By continuously performing the film forming step and the oblique stretching step, it is possible to obtain a desired long obliquely stretched film by feeding back the results of the film thickness and the optical value after stretching to change the film forming conditions. It is preferable because it can be done. Further, by continuously producing the long diagonally stretched film, a long diagonally stretched film having a desired length can be obtained.

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

The diagonally stretched film obtained by diagonally stretching the above-mentioned raw film can also be applied to a liquid crystal display device that can be visually recognized by wearing polarized sunglasses. That is, a circularly polarizing plate is formed by laminating a diagonally stretched film on the polarizing element of the polarizing plate on the viewing side of the liquid crystal layer. At this time, both are bonded so that the slow axis of the obliquely stretched film and the transmission axis of the polarizer are at 45 °. In this configuration, the linearly polarized light emitted from the liquid crystal layer and transmitted through the polarizer on the visual side is converted into circularly polarized light by a diagonally stretched film (functioning as a QWP). Therefore, when the observer wears polarized sunglasses and observes the display image of the liquid crystal display device, the transmission axis of the polarizing element and the transmission axis of the polarized sunglasses may be at any angle. The component of light parallel to the transmission axis can be guided to the observer's eyes to observe the displayed image. Therefore, it is possible to prevent the displayed image from becoming difficult to see depending on the observation angle (depending on the direction of the transmission axis of the polarized sunglasses). In particular, by forming the obliquely stretched film using the original film of the present embodiment, unevenness of the orientation angle θ in the film width direction can be suppressed, so that the screen can be used even if the liquid crystal display device is used for a long time. An even and uniform image can be observed through polarized sunglasses.

As described above, when the obliquely stretched film is applied to the circular polarizing plate of the liquid crystal display device compatible with polarized sunglasses, it is desirable to form a hard coat layer for protecting the surface on the visible side of the diagonally 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 film of the present embodiment, a compound containing cellulose acylate satisfying the following formulas (1) and (2) and represented by the following general formula (A) is used. Examples include those contained.
Equation (1) 2.0 ≤ Z1 <3.0
Equation (2) 0 ≤ X <3.0
(In formulas (1) and (2), Z1 represents the total acyl substitution of cellulose acylate, and X represents the sum of propionyl substitution and butyryl substitution 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. (R below 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 substituents represented by R ₁ , R ₂ and R ₃ include halogen atoms (fluorine atom, chlorine atom, bromine atom, iodine atom, etc.), alkyl groups (methyl group, ethyl group, n-propyl group, etc.). 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-cyclopentene-1-yl, 2-cyclohexene-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-nitrophenoxy group) 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, etc.) , 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 Group (methylsulfonylamino group, butylsulfonylamino group, phenylsulfonylamino group, 2,3,5-trichlorophenylsulfonylamino group, p-methylphenylsulfonylamino group, etc.), mercapto group, alkylthio group (methylthio group, ethylthio group, etc.) , N-hexadecylthio group, etc.), arylthio group (phenylthio group, p-chlorophenylthio group, m-methoxyphenylthio group, etc.), sulfamoyl group (N-ethylsulfamoyl group, N- (3-dodecyloxypropyl) sulfamoyl Group, N, N-dimethylsulfamoyl group, N-acetylsulfamoyl group, N-benzoylsulfamoyl group, N- (N'phenylcarbamoyl) Sulfamoyl 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- An octylcarbamoyl group, an N- (methylsulfonyl) carbamoyl group, etc.) can be mentioned.

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

As R _3, is preferably a hydrogen atom, a halogen atom, an alkyl group, an alkenyl group, an aryl group, a heterocyclic group, a hydroxyl group, a carboxyl group, an alkoxy group, an aryloxy group, an acyloxy group, a cyano group, an amino group, More preferably, it is a hydrogen atom, a halogen atom, an alkyl group, a cyano group, or an alkoxy group.

Wa and Wb represent hydrogen atoms or substituents,
(I) Wa and Wb may be combined with 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 substituents represented by Wa and Wb include halogen atoms (fluorine atom, chlorine atom, bromine atom, iodine atom, etc.) and alkyl groups (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 (cycloalkenyl group, allyl group, etc.) 2-Cyclopentene-1-yl, 2-cyclohexene-1-yl group, etc.), alkynyl group (ethynyl group, propargyl group, etc.), aryl group (phenyl group, p-tolyl group, naphthyl group, etc.), heterocyclic group (hetyl group, p-tolyl group, naphthyl group, etc.) 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) Groups, etc.), acyloxy groups (formyloxy groups, acetyloxy groups, pivaloyloxy groups, stearoyloxy groups, benzoyloxy groups, p-methoxyphenylcarbonyloxy groups, etc.), amino groups (amino groups, methylamino groups, dimethylamino groups, etc.), 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 group (methylsulfonylamino group, etc.) 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.) Etc.), arylthio group (phenylthio group, p-chlorophenylthio group, m-methoxyphenylthio group, etc.), sulfamoyl group (N-ethylsulfamoyl group, N- (3-dodecyloxypropyl) sulfamoyl group, N, N -Dimethylsulfamoyl group, N-acetylsulfamoyl group, N-benzoylsulfamoyl group, N- (N'phenylcarbamoyl) sulfamoyl 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-octyl) Carbamoyl group, N- (methylsulfonyl) carbamoyl group, etc.) can be mentioned.

The above-mentioned substituent may be further substituted with the above-mentioned group.

(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. Further, 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 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 Wa and Wb. The Rx is preferably a hydrogen atom, an alkyl group, an aryl group, or a heterocyclic group.

In the general formula (1), X represents a non-metal atom of Group 14-16. As X, = O, = S, = NRc, = C (Rd) Re is preferable. 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 represent a hydrogen atom or a substituent) or Represents −CO−. Here, Ry, Ra, and Rb represent substituents, and examples thereof are synonymous with specific examples of the substituents represented by Wa and Wb.

Y represents a substituent. Examples of the substituent represented by Y are synonymous with the specific examples of the substituents represented by 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, a biphenyl group and the like, and a phenyl group and a naphthyl group are preferable, and a phenyl group is more preferable.

Examples of the heterocyclic group include a heterocyclic group containing at least one heteroatom such as a nitrogen atom such as a frill group, a pyrrolyl group, a thienyl group, a pyridinyl group, a thiazolyl group and a benzothiazolyl group, and a heteroatom such as an oxygen atom and a sulfur atom. A group, a pyrrolyl group, a thienyl group, a pyridinyl group, and a thiazolyl group are preferable.

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 group. Fluoroalkyl group of ~ 6, alkoxy group of 1 to 6 carbons, alkylthio group of 1 to 6 carbons, N-alkylamino group of 1 to 6 carbons, N, N-dialkylamino group of 2 to 12 carbons , N-alkylsulfamoyl group having 1 to 6 carbon atoms, N, N-dialkylsulfamoyl group having 2 to 12 carbon atoms and the like.

_{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 the general formula (A), the following general formula (3) is preferable as a specific example when at least one of Wa and Wb has a ring structure.

In the general formula (3), Q ₃ represents = N- or = CRz- (Rz is a hydrogen atom or a substituent), and Q ₄ represents a non-metal atom of groups 14 to 16. Z represents a group of non-metal atoms forming a ring with _{Q 3} and Q _4.

The ring formed by Q _3, Q ₄ and Z may be condensed rings yet another ring. The ring formed by Q _3, Q ₄ and Z is preferably a condensed nitrogen-containing 5- or 6-membered ring 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 formulas (1), (2) and (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 as compared with the compound represented by the general formula (2). Good solubility in and compatibility with polymers.

The compound represented by the general formula (A) can be contained in an appropriately adjusted amount in order to impart desired wavelength dispersibility and anti-bleeding property, but the addition amount is relative to the cellulose derivative. It is preferably contained in an amount of 1 to 15% by mass, and particularly preferably 2 to 10% by mass. Within this range, sufficient wavelength dispersibility and anti-bleeding property can be imparted to the cellulose derivative.

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

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

Examples of the cellulose acylate include an ester of cellulose and an aliphatic carboxylic acid and / or an 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. It is preferable to have.

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

Specifically, as the cellulose acylate, a propionate group, a butyrate group or a phthalyl group is used in addition to an acetyl group such as cellulose acetate propionate, cellulose acetate butyrate, cellulose acetate propionate butyrate or cellulose acetate phthalate. A mixed fatty acid ester of bound cellulose can be used. The butyryl group forming butyrate may be linear or branched.

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

Further, the above-mentioned cellulose acylate preferably satisfies the following mathematical formulas (i) and (ii) at the same time.
Equation (i) 2.0 ≤ X + Y <3.0
Equation (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 the butyryl group or a mixture thereof.

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

Among the above, cellulose acetate propionate is particularly preferably used as the cellulose acylate. In the cellulose acetate propionate, 0 ≦ Y ≦ 2.5 and 0.5 ≦ X ≦ 3.0 (where 2.0 ≦ X + Y <3.0) are preferable, and 0 ≦ It is more preferable that .5 ≦ Y ≦ 2.0 and 1.0 ≦ X ≦ 2.0 (however, 2.0 ≦ X + Y <3.0). The degree of substitution of the acyl group can be measured according to ASTM-D817-96, which is one of the standards established and published by ASTM (American Society for Testing and Materials).

When the number average molecular weight of the cellulose acylate is in the range of 60,000 to 300,000, the mechanical strength of the obtained film is increased, which is preferable. 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. This measuring method can also be used as a measuring method for other polymers in the present embodiment.

Solvent: Methylene chloride;
Column: Shodex K806, K805, K803G (manufactured 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 Science);
Pump: L6000 (manufactured by Hitachi, Ltd.);
Flow rate: 1.0 ml / min
Calibration curve: Standard polystyrene STK standard polystyrene (manufactured by Tosoh Corporation) A calibration curve with 13 samples of Mw = 1,000,000 to 500 is used. 13 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 sulfur element. These are considered to be contained in the form of salts. If the residual sulfuric acid content exceeds 45% by mass, it tends to break easily during hot stretching or during 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 the method specified in ASTM-D817-96.

The free acid content in the cellulose acylate is preferably 1 to 500 mass ppm. The above range is preferable because it is difficult to break as described above. The free acid content is preferably in the range of 1 to 100 mass ppm, and is more difficult to break. In particular, the range of 1 to 70 mass ppm is preferable. The free acid content can be measured by the method specified in ASTM-D817-96.

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

The cellulose used as a raw material for cellulose acylate is not particularly limited, and examples thereof include cotton linter, wood pulp, and kenaf. In addition, the cellulose acylates obtained from them can be mixed and used in arbitrary proportions.

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 manufacturing 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 insoluble substances by forming salts with polymer decomposition products and the like that may contain organic acidic groups, and are preferably 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 with many ligands, and scum derived from a large amount of insoluble calcium (that is, a complex). It is preferable that the amount is small because there is a risk of forming insoluble starch (turbidity).

Specifically, the content of the iron (Fe) component in the cellulose acylate is preferably 1 mass ppm or less. The content of the calcium (Ca) component in the cellulose acylate is preferably 60 mass ppm or less, more preferably 0 to 30 mass ppm. Further, regarding the magnesium (Mg) component, if it is too large, an insoluble component is generated. Therefore, the content in the cellulose acylate is preferably 0 to 70 mass ppm, and particularly preferably 0 to 20 mass ppm. ..

The content of metal components such as the content of iron (Fe) component, the content of calcium (Ca) component, and the content of magnesium (Mg) component is such that the absolutely dried cellulose acylate is used in a microdigest wet decomposition apparatus. It can be decomposed with sulfuric acid and nitrate, pretreated by alkali melting, and then analyzed using ICP-AES (inductively coupled plasma emission spectrophotometer).

<Alicyclic olefin polymer resin>
Examples of the alicyclic olefin polymer-based resin used for the raw film of the present embodiment are described in JP-A-05-310845, a cyclic olefin random multiple copolymer, and JP-A-05-97978. The hydrogenated polymer, the thermoplastic dicyclopentadiene-based ring-opening polymer described in Japanese Patent Application Laid-Open No. 11-124429, the hydrogenated product thereof, and the like can be adopted.

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 the mechanical strength is usually in the range of 4 to 30, preferably 5 to 20, and more preferably 5 to 15. The heat resistance and moldability characteristics 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 is all. When the ratio of the repeating unit having an alicyclic structure in the alicyclic polyolefin resin is in this range, the transparency and heat resistance of an optical material such as a retardation film obtained from the long diagonally stretched film of the present embodiment are improved. It is preferable because it improves.

Examples of the olefin polymer-based resin having an alicyclic structure include norbornene-based resins, monocyclic cyclic olefin-based resins, cyclic conjugated diene-based resins, vinyl alicyclic hydrocarbon-based resins, and hydrides thereof. Among these, norbornene-based resins can be preferably used because they have 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. Examples thereof include an addition polymer of a monomer having a substance, an addition copolymer of a monomer having a norbornene structure and another monomer, and a hydride thereof. Among these, the ring-opening (co) polymer hydride of the monomer having a norbornene structure is particularly suitable from the viewpoints of transparency, moldability, heat resistance, low hygroscopicity, dimensional stability and light weight. Can be used for.

As a method for forming a long film (raw film) using the norbornene-based resin as described above, a method for producing a solution film forming 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 molding method using a T-die, retardation or a method for maintaining a stable state of a molten thermoplastic resin when it is brought into close contact with a cooling drum, as described in Japanese Patent Application Laid-Open No. 2004-233604, is used. It is possible to manufacture a long film having a small variation in optical characteristics such as an orientation angle.

Specifically, 1) a method of taking a sheet-shaped thermoplastic resin extruded from a die in close contact with a cooling drum under a pressure of 50 kPa or less when producing a long film by a melt extrusion method; 2) melting. When producing a long film by the extrusion method, the area from the die opening to the cooling drum that first adheres is covered with an enclosure member, and the distance from the enclosure member to the die opening or the cooling drum that first adheres is 100 mm or less. Method; 3) A method of heating the temperature of the atmosphere within 10 mm from the sheet-shaped thermoplastic resin extruded from the die opening to a specific temperature when producing a long film by the melt extrusion method; 4) Relationship A method in which a sheet-shaped thermoplastic resin extruded from a die so as to satisfy the above conditions is brought into close contact with a cooling drum under a pressure of 50 kPa or less; A method of blowing wind on the extruded sheet-shaped thermoplastic resin with a speed difference of 0.2 m / s or less from the take-up speed of the cooling drum that is first adhered to the resin;

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

<Polycarbonate resin>
As the polycarbonate-based resin used for the raw film of the present embodiment, various ones can be used without particular limitation, and aromatic polycarbonate resin is preferable from the viewpoint of chemical properties and physical properties, and bisphenol A-based polycarbonate resin is particularly preferable. Among them, 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. Further, a polycarbonate resin having a structure in which the anisotropy in the unit molecule is reduced, which is obtained by using a derivative in which the functional group is asymmetrically introduced with respect to the central carbon of bisphenol A, is particularly preferable. Examples of such a polycarbonate resin include a resin in which two methyl groups of carbon in the center of bisphenol A are replaced with a benzene ring, and a hydrogen in one of the benzene rings of bisphenol A is centered by a methyl group or a phenyl group. Polycarbonate resins obtained using those that are asymmetrically substituted with respect to carbon are particularly preferred.

Specifically, it is obtained from 4,4'-dihydroxydiphenylalkane or a halogen-substituted product thereof by a phosgene method or a transesterification method, for example, 4,4'-dihydroxydiphenylmethane, 4,4'-dihydroxydiphenyl. Examples thereof include ethane, 4,4'-dihydroxydiphenylbutane and the like. In addition, for example, Japanese Patent Application Laid-Open No. 2006-215465, Japanese Patent Application Laid-Open No. 2006-91836, Japanese Patent Application Laid-Open No. 2005-121813, Japanese Patent Application Laid-Open No. 2003-167121, Japanese Patent Application Laid-Open No. 2009-126128, Japanese Patent Application Laid-Open No. Examples thereof include polycarbonate-based resins described in Japanese Patent Application Laid-Open No. 2012-31369, Japanese Patent Application Laid-Open No. 2012-67300, International Publication No. 00/26705, and the like.

The polycarbonate resin may be mixed with a transparent resin such as a polystyrene resin, a methyl methacrylate resin, and a cellulose acetate resin. Further, a resin layer containing a polycarbonate resin may be laminated on at least one surface of a resin film formed by using a cellulose acetate resin.

The polycarbonate resin preferably has a glass transition point (Tg) of 110 ° C. or higher and a water absorption rate (value measured in 23 ° C. water for 24 hours) of 0.3% or less. Further, it is more preferable that the Tg is 120 ° C. or higher and the water absorption rate is 0.2% or lower.

The polycarbonate-based 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 the present embodiment may contain an additive. Additives include plasticizers, UV absorbers, retardation modifiers, antioxidants, antioxidants, release aids, surfactants, dyes, fine particles and the like. In the present embodiment, the additive other than the fine particles may be added at the time of preparing the doping liquid, or may be added at the time of preparing the fine particle dispersion liquid.

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

Polyester-based plasticizers are superior in non-migration and extraction resistance to phthalate-based plasticizers such as dioctyl phthalate. By selecting or using these plasticizers according to the application, it can be applied to a wide range of applications. As the acrylic polymer, homopolymers or copolymers of acrylic acid or methacrylic acid alkyl esters are preferable. Examples of the monomer of acrylate ester include methyl acrylate, ethyl acrylate, propyl acrylate (i-, n-), butyl acrylate (n-, i-, s-, t-), and pentyl acrylate (n-, i-, s-, t-). n-, i-, s-), hexyl acrylate (n-, i-), heptyl acrylate (n-, i-), octyl acrylate (n-, i-), nonyl acrylate (n-, i-) 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 above acrylic acid ester Can be mentioned as a methacrylic acid ester. The acrylic polymer is a homopolymer or a copolymer of the above-mentioned monomer, and it is preferable that the acrylate methyl ester monomer unit has 30% by mass or more, and the methacrylate methyl ester monomer unit has 40% by mass or more. preferable. In particular, a homopolymer of methyl acrylate or methyl methacrylate is preferable.

The polyester-based plasticizer is a reaction product of a monovalent to tetravalent carboxylic acid and a monovalent to hexavalent alcohol, and a product obtained by reacting a divalent carboxylic acid with a glycol is mainly used. .. Typical divalent carboxylic acids include glutaric acid, itaconic acid, adipic acid, phthalic acid, azelaic acid, sebacic acid and the like. Further, the polyester-based plasticizer is preferably an aromatic terminal ester-based plasticizer. As the aromatic terminal ester-based plasticizer, an ester compound having a structure in which phthalic acid, adipic acid, at least one benzenemonocarboxylic acid and at least one alkylene glycol having 2 to 12 carbon atoms are reacted is preferable. It suffices to have an adipic acid residue and a phthalic acid residue as the structure of the final compound, and when producing an ester compound, it may be reacted as an acid anhydride or an esterified product of a dicarboxylic acid.

Examples of the benzene monocarboxylic acid component include benzoic acid, paratarshalibutyl benzoic acid, orthotoluic acid, metatoluic acid, paratoluic acid, dimethyl benzoic acid, ethyl benzoic acid, normal propyl benzoic acid, aminobenzoic acid, acetoxybenzoic acid and the like. Most preferably, it is benzoic acid. In addition, these can be used as one kind or a mixture of two or more kinds, respectively.

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, and the like. 2-Methyl-1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 2,2-dimethyl-1,3-propanediol (neopentyl glycol), 2,2-diethyl-1 , 3-Propylenediol (3,3-dimethylolpentane), 2-n-butyl-2-ethyl-1,3-propanediol (3,3-dimethylolheptan), 3-methyl-1,5-pentane Glycol, 1,6-hexanediol, 2,2,4-trimethyl-1,3-pentanediol, 2-ethyl-1,3-hexanediol, 2-methyl-1,8-octanediol, 1,9- Examples thereof include nonanediol, 1,10-decanediol, and 1,12-octadecanediol. Of these, 1,2-propylene glycol is particularly preferable. These glycols may be used as one or a mixture of two or more.

The aromatic terminal ester-based plasticizer may be in the form of oligoester or polyester, and the molecular weight is preferably in the range of 100 to 10000, but 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 thereof include, but are not limited to, the following compounds.

The sugar ester compound is an ester other than a cellulose ester, which is a compound obtained by esterifying all or part of the OH groups of sugars such as the following monosaccharides, disaccharides, trisaccharides and oligosaccharides, and is more 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 ~R8, which may be the same or may be different.

Hereinafter, the compounds represented by the general formula (4) will be shown more specifically (Compounds 1-1 to 1-23), but are not limited thereto. When the average degree of substitution is less than 8.0 in the table below, _{any one of R 1 to} R ₈ represents a hydrogen atom.

It is preferable to add 0.5 to 30 parts by mass of these plasticizers with respect to 100 parts by mass of the cellulose ester film.

(Retadation adjuster)
As the compound added to adjust the retardation, an aromatic compound having two or more aromatic rings, as described in European Patent No. 911,656A2, can be used.

Further, two or more kinds of aromatic compounds may be used in combination. It is particularly preferable that the aromatic ring of the aromatic compound contains an aromatic heterocycle in addition to the aromatic hydrocarbon ring. Aromatic heterocycles are generally unsaturated heterocycles. Of these, the 1,3,5-triazine ring is particularly preferable.

(Polymer or oligomer)
The raw film of the present 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 preferably contains a polymer or oligomer of a vinyl compound within the range. The mass ratio of the content of the cellulose ester to the polymer or oligomer is preferably in the range of 95: 5 to 50:50.

(Mat agent)
In the present embodiment, fine particles can be contained in the raw film as a matting agent, thereby facilitating the transport and winding of the raw film and the long diagonally stretched film produced by using the raw film. Can be done.

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 needle-like ratio of primary particles of 1.1 or less is preferably used.

As the fine particles, those containing silicon are preferable, and silicon dioxide is particularly preferable. Examples of the silicon dioxide fine particles preferable for this embodiment include Aerosil R972, R972V, R974, R812, 200, 200V, 300, R202, OX50, and TT600 manufactured by Nippon Aerosil Co., Ltd. (all manufactured by Nippon Aerosil Co., Ltd.). Commercially available products under the trade names of Aerosil 200V, R972, R972V, R974, R202, and R812 can be preferably used. Examples of the fine particles of the polymer include silicone resin, fluororesin and acrylic resin. A silicone resin is preferable, and a resin having a three-dimensional network structure is particularly preferable. 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 diameter 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 even more preferably 5 to 12 nm. It is preferable that the average diameter of the primary particles is small because the 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. The larger the apparent specific gravity, the higher the concentration of the fine particle dispersion liquid can be produced, which is preferable because haze and agglomerates do not occur.

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

(Other additives)
In addition, inorganic fine particles such as kaolin, talc, diatomaceous earth, quartz, calcium carbonate, barium sulfate, titanium oxide and alumina, and heat stabilizers such as salts of alkaline earth metals 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 the present embodiment is required to withstand use in a higher temperature environment. Therefore, the tension softening point of the raw film is preferably 105 ° C. to 145 ° C. because it exhibits sufficient heat resistance, and particularly preferably 110 ° C. to 130 ° C.

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

(Dimensional change rate)
When the film obtained by diagonally stretching the original film of the present embodiment is used in an organic EL image display device, problems such as thickness unevenness, retardation value change, contrast decrease, and color unevenness occur due to dimensional changes due to moisture absorption. The dimensional change rate (%) of the obliquely stretched film is preferably less than 0.5%, and more preferably less than 0.3% so as not to occur.

(Disadvantage)
The raw film of the present embodiment preferably has few defects in the film. Here, the defects are cavities (foaming defects) in the film generated due to rapid evaporation of the solvent in the drying process of the solution film forming, foreign substances in the film forming stock solution, and foreign substances mixed in the film forming. It refers to foreign matter (foreign matter defect) in the film caused by it.

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

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

The range of defects is the size of the shadow when the defects are observed with the transmitted light of a differential interference microscope when the defects are bubbles or foreign substances. If the defect is a change in surface shape such as transfer of roll scratches or scratches, observe the defect with the reflected light of a differential interference microscope to confirm the size.

When observing with reflected light, if the magnitude of the defect is unclear, aluminum or platinum is vapor-deposited on the surface for observation. In order to obtain a film having excellent quality represented by such a defect frequency with high productivity, the polymer solution should be filtered with high precision immediately before casting, the cleanliness around the casting machine should be improved, and the flow should be improved. It is effective to set the drying conditions after spreading in stages, and to dry efficiently and suppress foaming.

If the number of defects is more than 1/10 cm square, for example, when tension is applied to the film during processing in a subsequent process, the film may break from the defects as a starting point and productivity may decrease. Further, when the diameter of the defect is 5 μm or more, it can be visually confirmed by observing a polarizing plate or the like, and a bright spot may occur when used as an optical member.

(Total light transmittance)
The raw film of the present 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 the excellent transparency represented by the total light transmittance, it is necessary to avoid introducing additives and copolymerization components that absorb visible light, and to remove foreign substances in the polymer by high-precision filtration. However, it is effective to reduce the diffusion and absorption of light inside the film. In addition, the surface roughness of the film contact portion (cooling roll, calendar roll, drum, belt, coating base material in solution film forming, transport roll, etc.) during film formation should be reduced to reduce the surface roughness of the film surface. It is effective to reduce the diffusion and reflection of light on the film surface.

<Formation method of raw film>
The raw film of the present embodiment containing the above-mentioned resin can be formed by either the solution casting film forming method or the melt casting film forming method shown below. Here, the case where the raw film contains a cellulose ester resin will be described, but the same applies to the case where the raw film contains other resins.

When the raw film is produced by the solution casting film forming method, the dope, which is the raw material solution of the raw film of the cellulose ester resin, is cast on a support made of a rotating metal endless belt by a casting die. .. The dope film or web formed on the support by casting is peeled off by a peeling roll after about one round on the support. The peeled web (film) is then introduced into a stretching device consisting of a tenter.

When the raw film is produced by the melt casting film forming method, in the extrusion method using a T-die, the polymer is melted at a temperature at which it can be melted, and the polymer is extruded from the T-die into a film (sheet) onto a cooling drum. It cools and solidifies and peels the film from the cooling drum. The peeled film is then introduced into a stretching device consisting of a tenter.

The details of each film forming method will be described below.

[Solution casting film forming method]
In the method for producing a raw 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 in the range of poison.

Here, first, for the dissolution of the cellulose ester, means such as a stirring dissolution method, a heat dissolution method, and an ultrasonic dissolution method in a dissolution kettle are usually used, and the solvent is at or above the boiling point of the solvent at normal pressure under pressure. A method of heating the solvent at a temperature within a range where it does not boil and dissolving it while stirring is more preferable because it prevents the generation of massive undissolved substances called gels and mamaco. Further, the cooling melting method described in JP-A-9-95538 or the method of melting 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 to wet or swell, and then further mixed with a good solvent to dissolve the cellulose ester is also preferably used. At this time, the device for mixing the cellulose ester with a poor solvent to wet or swell and the device for mixing with a good solvent and dissolving the cellulose ester may be separately separated.

The type of 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 arranged in the pressure vessel. Pressurization may be performed by a method of press-fitting an inert gas such as nitrogen gas or by increasing the vapor pressure of the solvent by heating. The heating is preferably performed from the outside, and for example, the jacket type is preferable because the temperature can be easily controlled.

The heating temperature at which the solvent is added is equal to or higher than the boiling point of the solvent used, and in the case of two or more mixed solvents, the temperature is within the range in which the solvent is heated to a temperature higher than the boiling point of the solvent having the lower boiling point and the solvent does not boil. Temperature is preferred. If the heating temperature is too high, the pressure required will be high and productivity will be poor. The preferred heating temperature range is 20 to 120 ° C, more preferably 30 to 100 ° C, and even more preferably 40 to 80 ° C. The pressure is adjusted at the set temperature so that the solvent does not boil.

In addition to the cellulose ester and solvent, necessary additives such as plasticizers and ultraviolet absorbers may be 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 of.

After the cellulose ester is dissolved, it is taken out from the container while being cooled, or it is taken out from the container with a pump or the like, cooled by a heat exchanger or the like, and used for forming a dope of the obtained cellulose ester. May go up to room temperature.

When the mixture of the cellulose ester raw material and the solvent is dissolved in a dissolving apparatus having a stirrer, it is preferable that the peripheral speed of the stirring blade is at least 0.5 m / sec or more and the mixture is stirred for 30 minutes or more.

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

The filter medium used for filtration preferably has a low absolute filtration accuracy, but if the absolute filtration accuracy is too small, the filter medium is likely to be clogged, and the filter medium must be replaced frequently, which reduces productivity. There is a problem of letting it. Therefore, the filter medium used for the cellulose ester dope is preferably an absolute filtration accuracy of 0.008 mm or less, more preferably 0.001 to 0.008 mm, and further preferably a filter medium in the range of 0.003 to 0.006 mm. preferable.

The material of the filter medium is not particularly limited, and a normal filter medium can be used. However, a filter medium made of plastic fibers such as polypropylene and Teflon (registered trademark) and a metal filter medium such as stainless steel fibers may fall off. It is preferable because there is no such thing.

The cellulose ester-doped can be filtered by a usual method, but the method of filtering while heating under pressure at a temperature above the boiling point of the solvent at normal pressure and within the range where the solvent does not boil is the differential pressure before and after the filter medium ( Hereafter, it may be referred to as filtration pressure), which is preferable because the increase is small.

The preferred filtration temperature range is 45-120 ° C, more preferably 45-70 ° C, and even more preferably 45-55 ° C.

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

The dope can be cast on the support in the temperature range of the support from 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 of -5 ° C. Although it can be cast, it is more preferably cast on the support in the temperature range of 5-30 ° C. At this time, it is necessary to control the ambient humidity above the dew point.

Further, the dope adjusted to have a dope viscosity of 1 to 200 poise is cast from the casting die onto the support so as to have a substantially uniform film thickness, and the amount of residual solvent in the casting film is relative to solid. When the weight is 200% or more, the casting film temperature is below the boiling point of the solvent, and the amount of residual solvent is 200% or less to peeling, so that the casting film temperature is in the range of the boiling point of the solvent + 20 ° C. or less. To dry the casting film (web).

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

On the support, the web is dried and solidified until it has a film strength that allows it to be peeled off from the support. Therefore, the amount of the residual solvent in the web is preferably dried to 150% by mass or less, more preferably 50 to 120%.

The web temperature at the time of peeling the web from the support is preferably 0 to 30 ° C. Immediately after peeling from the support, the temperature of the web drops rapidly due to solvent evaporation from the support contact surface side, and volatile components such as water vapor and solvent vapor in the atmosphere tend to condense during peeling. The web temperature is more preferably 5 to 30 ° C.

In the process of drying the web (or film), a roll suspension method, a pin tenter method, or a clip tenter method is generally used to carry and dry the web.

The peeled web is introduced into, for example, a primary drying device. Inside the primary dryer, the web is meandered by a plurality of transport rolls staggered when viewed from the side, during which the web is blown from the ceiling of the dryer and discharged from the bottom of the dryer. Dry by the wind.

Next, the obtained film (sheet) is stretched in the uniaxial direction. The numerator is oriented by stretching. The method of stretching is not particularly limited, but a known pin tenter, clip-type tenter, or the like can be preferably used. The stretching direction can be a length direction, a width direction, or an arbitrary direction (oblique direction), but it is preferable to set the stretching direction to the width direction because it is easy to adjust the breaking elongation of the raw fabric film.

In particular, in the drying step after peeling from the support, the web tends to shrink in the width direction due to the evaporation of the solvent. The higher the temperature, the greater the shrinkage. It is preferable to dry the finished film while suppressing this shrinkage as much as possible in order to improve the flatness of the finished film. From this point of view, for example, a method of drying all or a part of the drying process as shown in JP-A-62-46625 while holding both ends of the width of the web with clips in the width direction (tenter method). ) Is preferable.

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

When the breaking elongation property of the thermoplastic resin film produced by the above method is modified to a desired property suitable for the purpose, the film may be stretched or contracted in the length direction or the width direction. To shrink in the length direction, for example, the width stretching is temporarily clipped out and relaxed in the length direction, or the distance between adjacent clips of the transverse stretching device is gradually reduced to shrink the film. There is. The latter method can be performed by using a general simultaneous biaxial stretching device to smoothly and gradually narrow the distance between adjacent clips in the vertical direction by driving the clip portion by, for example, a pantograph method or a linear drive method. it can.

Gripping and stretching with a tenter can be performed anywhere in the range where the residual solvent amount of the film immediately after peeling is 50 to 150% by mass and the substantial residual solvent amount immediately before winding is 0% by mass, but the residual solvent amount. Is preferably carried out in the range of 5 to 10%.

It is also common practice to divide the tenter into several temperature zones in the direction of travel of the base. The temperature at the time of stretching is selected so that the desired physical properties and flatness can be obtained, but the temperature of the drying zone before and after the tenter is also selected to be different from the temperature at the time of stretching for various reasons. Sometimes. For example, if the ambient temperature of the drying zone before the tenter is different from the temperature inside the tenter, set the temperature of the zone near the inlet of the tenter to an intermediate temperature between the temperature of the drying zone before the tenter and the temperature of the center of the tenter. Is commonly done. Similarly, when the temperature after the tenter and the temperature inside the tenter are different, the temperature of the zone near the outlet of the tenter is set to an intermediate temperature between the temperature after the tenter and the temperature inside 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 stretched portion in the tenter is 50 to 180 ° C., preferably 80 to 170 ° C. The temperature of is appropriately selected from those intermediate temperatures.

The stretching pattern, that is, the locus of the gripping clip, is selected from the optical properties and flatness of the film as well as the temperature, and is various. Retained patterns are often used. In the vicinity of the end of clip gripping near the outlet of the tenter, width relaxation is generally performed in order to suppress base vibration by releasing the gripping.

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

Further, the web (film) after drying by the above tenter method is then introduced into the secondary drying device. In the secondary drying device, the web is meandered by a plurality of transport rolls arranged in a staggered manner when viewed from the side, during which the web is blown from the ceiling of the secondary drying device and the bottom portion of the secondary drying device. It is dried by the warm air discharged from the ceiling and wound up in a winder as a raw film of a cellulose ester resin.

The means for drying the web is not particularly limited, and hot air, infrared rays, heating rolls, microwaves, or the like is generally used. From the viewpoint of convenience, it is preferable to dry with hot air. The drying temperature is preferably 40 to 150 ° C, more preferably 80 to 130 ° C because it improves flatness and dimensional stability.

As described above, 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 order to obtain a film having good dimensional stability.

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

It should be noted that the raw film of the cellulose ester resin that has completed the transport drying step is embossed on both side edges of the raw film of the cellulose ester resin by an embossing apparatus before the film is introduced into the winding step. It is preferable to perform processing. As the embossing apparatus, for example, the apparatus described in JP-A-63-74850 can be used.

The winder involved in the production of raw film of cellulose ester resin may be a commonly used one, such as constant tension method, constant torque method, taper tension method, program tension control method with constant internal stress, etc. It can be wound by the winding method.

The film thickness of the raw film after winding varies depending on the purpose of use, but the film thickness range is 20 to 200 μm, preferably 30 to 120 μm, and particularly preferably 40 to 100 μm for the recent tendency toward thinness.

When the raw film of the present embodiment is produced by the melt casting film forming method, the ultraviolet absorbers that can be used include those used in the method of producing the raw film by the solution casting film forming method. Almost the same 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, based on the thermoplastic resin. If the amount used is too small, the ultraviolet absorption effect may be insufficient, and conversely, if the amount used is too large, the transparency of the film may deteriorate. The ultraviolet absorber preferably has high thermal stability.

It is preferable to add fine particles to the raw film in order to impart slipperiness to the film. The fine particles to be used may be either an inorganic compound or an organic compound as long as they have heat resistance at the time of melting. For example, the inorganic compound includes a compound containing silicon, silicon dioxide, aluminum oxide, zirconium oxide, calcium carbonate, talc, clay. , Calcined kaolin, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, magnesium silicate, calcium phosphate and the like are preferable, and inorganic compounds containing silicon and zirconium oxide are more preferable. Among them, silicon dioxide is particularly preferably used because the haze can be suppressed to be small. Even when the raw fabric film is manufactured by the melt casting film forming method, the matting agent used is almost the same as that used in the method for producing the raw fabric 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. Of these, a method using a T-die that has small thickness unevenness, is easy to process 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 meltable temperature, extruded from the T-die into a film (sheet-like) onto a cooling drum, cooled and solidified, and peeled from the cooling drum. The thickness accuracy of the film is excellent, and it can be preferably used.

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

It is preferable that the extrusion flow rate is stable by introducing a gear pump or the like. Further, as the filter used for removing foreign substances, a stainless fiber sintered filter is preferably used. The stainless fiber sintered filter is made by creating a complicated entangled state of stainless steel fibers, compressing them, and sintering the contact points to integrate them. The density is changed according to the thickness and compression amount of the fibers to improve the filtration accuracy. Can be adjusted. It is preferable to use a multilayer body in which the filtration accuracy is coarsely and densely repeated a plurality of times continuously. Further, it is preferable to adopt a configuration in which the filtration accuracy is gradually increased, or a method of repeating coarse and dense filtration accuracy because the filtration life of the filter can be extended and the accuracy of capturing foreign matter and gel can be improved.

If scratches 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 as small as possible. .. In addition, it is preferable to use a die with as few scratches as possible inside the die or on the lip. Since volatile components may precipitate from the resin around the die and cause a die line, it is preferable to suck the atmosphere containing the volatile components. Further, since precipitation may occur in a device such as electrostatic application, it is preferable to apply alternating current or prevent precipitation by other heating means.

Additives such as plasticizers may be mixed with the resin in advance, or may be kneaded in the middle of the extruder. It is preferable to use a mixing device such as a static mixer for uniform addition.

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 of bringing the resin into close contact by applying static electricity, a method in which the resin is brought into close contact by wind pressure, a method in which the entire width or the end is niped and brought into close contact, and a method in which the resin is brought into close contact with reduced pressure.

Unlike the raw film formed by the solution casting film forming method, the thermoplastic resin raw film formed by the melt casting film forming method is characterized by having a small thickness direction retardation (Rt). Therefore, stretching conditions different from those of the solution casting film forming method may be required. In order to obtain desired optical properties, in some cases, both stretching in the traveling direction of the film and stretching in the lateral direction of the film may be performed simultaneously or sequentially. In some cases, the film may only be stretched in the lateral direction. This stretching operation orients the molecules and adjusts the film to the required retardation value.

<Specifications of original film>
The thickness of the raw film in the present embodiment is 1 to 400 μm, preferably 20 to 200 μm, more preferably 30 to 120 μm, and particularly preferably in the range of 40 to 100 μm. Further, in the present embodiment, the thickness unevenness σm in the flow direction (conveyance direction) of the raw film supplied to the stretching zone described later keeps the take-up tension of the film at the inlet of the diagonally stretched tenter described later constant, and the orientation angle. From the viewpoint of stabilizing optical characteristics 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 raw film is 0.30 μm or more, the variation in optical characteristics such as the retardation and the orientation angle of the long diagonally stretched film is remarkably deteriorated.

Further, in the present embodiment, it is preferable that the thickness unevenness in the width direction of the raw film is small in order to prevent the orientation angle unevenness from occurring in the width direction due to the thickness unevenness in the width direction due to the oblique stretching. For example, in the width direction of the raw film, the thickness difference between the thick end and the thin end is less than 2.0%, preferably less than 1.0% of the thickness, and further. It is desirable that the range is preferably less than 0.5%.

The width of the raw film is not particularly limited, but may be 500 to 4000 mm, preferably 1000 to 2000 mm.

The preferred elastic modulus at the stretching temperature during diagonal 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 in terms of 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 becomes large, and it becomes necessary to increase the strength of the portion holding both side edges of the film, which increases the load on the tenter in the subsequent process.

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 of the orientation of the raw film in the width direction may be arched, 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 desired.

<Manufacturing method and equipment for diagonally stretched film>
Next, a method and an apparatus for producing a diagonally stretched film, which manufactures a long diagonally stretched film by stretching the above-mentioned long film diagonally with respect to the width direction, will be described.

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

The film feeding portion 2 feeds out the above-mentioned long film and supplies it to the stretched portion 5. The film feeding portion 2 may be configured separately from the film forming apparatus for a long film, or may be integrally configured. In the former case, the long film is wound around the core once after the film is formed to form a wound body (long film original fabric), which is then loaded into the film feeding section 2 to be long from the film feeding section 2. The film is fed out. On the other hand, in the latter case, the film feeding portion 2 is fed to the stretched portion 5 without winding the long film after forming the long film.

The transport direction changing section 3 changes the transport direction of the long film fed from the film feeding section 2 toward the inlet of the stretching section 5 as the diagonal stretching tenter. Such a transport direction changing unit 3 includes, for example, a turn bar that changes the transport direction by folding back while transporting the film, and a rotary table that rotates the turn bar in a plane parallel to the film.

By changing the transport direction of the long film in the transport direction changing unit 3 as described above, the width of the entire manufacturing apparatus 1 can be narrowed, and the film feeding position and angle can be finely controlled. This makes it possible to obtain a diagonally stretched film having a small variation in film thickness and optical value. Further, if the film feeding portion 2 and the transport direction changing portion 3 are movable (sliding and swivelable), the left and right clips (grasping tools) that sandwich both ends of the long film in the width direction in the stretched portion 5 It is possible to effectively prevent poor biting into the film.

The film feeding portion 2 may be slidable and swivelable so that the long film can be fed at a predetermined angle with respect to the inlet of the stretched portion 5. In this case, the installation of the transport direction changing unit 3 may be omitted.

At least one guide roll 4 is provided on the upstream side of the stretched portion 5 in order to stabilize the trajectory of the long film during traveling. The guide roll 4 may be composed of a pair of upper and lower rolls sandwiching the film, or may be composed of a plurality of roll pairs. The guide roll 4 closest to the inlet of the stretched portion 5 is a driven roll that guides the running of the film, and is rotatably supported by a bearing portion (not shown). As the material of the guide roll 4, a known material can be used. In order to prevent the film from being scratched, it is preferable to reduce the weight of the guide roll 4 by applying a ceramic coat to the surface of the guide roll 4 or chrome plating a light metal such as aluminum.

Further, it is preferable that one of the rolls on the upstream side of the guide roll 4 closest to the inlet of the stretched portion 5 is niped by pressure contacting the rubber roll. By using such a nip roll, it is possible to suppress fluctuations in the feeding tension in the film flow direction.

A pair of bearing portions at both ends (left and right) of the guide roll 4 closest to the inlet of the stretched portion 5 have 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 detection device is provided for each. As the film tension detection device, for example, a load cell can be used. As the load cell, a known tension or compression type load cell can be used. A load cell is a device that converts a load acting on a force point into an electric signal by a strain gauge attached to a strain generating body and detects it.

The load cell is installed in the left and right bearing portions of the guide roll 4 closest to the inlet of the stretched portion 5, so that the force exerted on the roll by the running film, that is, in the film traveling direction generated near both side edges of the film. The tension is detected independently on the left and right. A strain gauge may be directly attached to the support constituting the bearing portion of the roll, and the load, that is, the film tension may be detected based on the strain generated in the support. The relationship between the generated strain and the film tension shall be measured and known in advance.

If the position and transport direction of the film supplied from the film feeding section 2 or the transport direction changing section 3 to the stretched section 5 deviate from the position toward the inlet of the stretched section 5 and the transport direction, depending on the amount of this misalignment. A difference will occur in the tension near both side edges of the film in the guide roll 4 closest to the inlet of the stretched portion 5. Therefore, the degree of the deviation can be determined by providing the film tension detecting device as described above and detecting the tension difference described above. That is, if the transport position and transport direction of the film are appropriate (if the position and direction are toward the inlet of the stretched portion 5), the load acting on the guide roll 4 is roughly equal at both ends in the axial direction. If it is not appropriate, there will be a difference in film tension between the left and right.

Therefore, for example, the position and the transport direction (angle with respect to the inlet of the stretched portion 5) of the film are set by the above-mentioned transport direction changing portion 3 so that the difference in film tension between the left and right of the guide roll 4 closest to the inlet of the stretched portion 5 becomes equal. If properly adjusted, the gripping tool at the inlet of the stretched portion 5 stabilizes the gripping of the film, and the occurrence of obstacles such as the gripping tool coming off can be reduced. Further, it is possible to stabilize the physical properties of the film in the width direction after the film is diagonally stretched by the stretched portion 5.

At least one guide roll 6 is provided on the downstream side of the stretched portion 5 in order to stabilize the trajectory of the film obliquely stretched by the stretched portion 5 during running.

The transport direction changing section 7 changes the transport direction of the stretched film transported from the stretched section 5 toward the film winding section 8.

Here, in order to fine-tune the orientation angle (direction of the in-plane slow axis of the film) and to cope with product variations, the film advancing direction at the inlet of the stretched portion 5 and the film advancing direction at the outlet of the stretched portion 5. It is necessary to adjust the angle of the film. For this angle adjustment, the traveling direction of the formed film is changed by the transport direction changing portion 3 to guide the film to the inlet of the stretched portion 5, and / or the traveling direction of the film exiting from the outlet of the stretched portion 5. It is necessary to change the film by the transport direction changing section 7 to return the film to the direction of the film winding section 8.

In addition, continuous film formation and diagonal stretching are preferable in terms of productivity and yield. When the film forming step, the oblique stretching step, and the winding step are continuously performed, the traveling direction of the film is changed by the transport direction changing section 3 and / or the transport direction changing section 7, and the film is formed in the film forming step and the winding step. That is, as shown in FIG. 1, the traveling direction of the film unwound from the film feeding unit 2 (feeding direction) and the traveling direction of the film immediately before being wound by the film winding unit 8 (the traveling direction of the film). By matching the winding direction), the width of the entire device with respect to the film traveling direction can be reduced.

Although it is not always necessary to match the traveling directions of the film between the film forming step and the winding step, the transport direction changing section 3 and the transport direction changing section 3 and the film winding section 8 are arranged so that the film feeding section 2 and the film winding section 8 do not interfere with each other. / Or it is preferable to change the traveling direction of the film by the transport direction changing unit 7.

The transport direction changing portions 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 winding unit 8 winds the film conveyed from the stretching unit 5 via the conveying direction changing unit 7, and is composed of, for example, a winder device, an accumulator device, a drive device, and the like. The film winding unit 8 preferably has a structure that can slide in the lateral direction in order to adjust the film winding position.

The film take-up portion 8 can finely control the take-up position and angle of the film so that the film can be taken up at a predetermined angle with respect to the outlet of the stretched portion 5. This makes it possible to obtain a long obliquely stretched film having a small variation in film thickness and optical value. In addition, it is possible to effectively prevent the occurrence of wrinkles in the film and improve the windability of the film, so that the film can be wound in a long length.

The film winding unit 8 constitutes a taking-up unit that takes up the film stretched and conveyed by the stretching unit 5 with a constant tension. A take-up roll for taking up the film with a constant tension may be provided between the stretched portion 5 and the film winding portion 8. Further, the above-mentioned guide roll 6 may be provided with a function as the above-mentioned take-back roll.

In the present embodiment, the take-back tension T (N / m) of the stretched film 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, the film is liable to sag or wrinkle, and the retardation and the profile of the orientation angle in the film width direction are also deteriorated. On the contrary, 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 (take-up efficiency in the width direction) is deteriorated.

Further, in the present embodiment, it is preferable to control the fluctuation of the take-back tension T with an accuracy of less than ± 5%, preferably less than ± 3%. When the fluctuation of the take-up tension T is ± 5% or more, the variation in the optical characteristics in the width direction and the flow direction (conveyance direction) becomes large. 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 stretched portion 5, that is, the tension of the film is measured, and the value becomes constant. As described above, a method of controlling the rotation speed of the take-up roll or the take-up roll of the film take-up unit 8 by a general PID control method can be 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 the load applied to the guide roll 6, that is, the tension of the film is measured. As the load cell, a known tension type or compression type can be used.

The stretched film is released from the gripping tool of the stretched portion 5, discharged from the outlet of the stretched portion 5, and both ends (both sides) of the film gripped by the gripping tool are trimmed, and then the winding core is sequentially wound. It is wound on a (winding roll) to form a wound body of a long diagonally stretched film. The above trimming may be performed as needed.

Further, before winding the long diagonally stretched film, the masking film may be stacked on the long diagonally stretched film and wound at the same time for the purpose of preventing blocking between the films, or the long diagonally stretched film overlapped by winding. The film may be wound while a tape or the like is attached to at least one (preferably both) ends of the film. The masking film is not particularly limited as long as it can protect the long diagonally stretched film, and examples thereof include a polyethylene terephthalate film, a polyethylene film, and a polypropylene film.

Further, before winding the long diagonally stretched film, at least one surface (preferably both surfaces) of the film is made bulkier than the film surface, which is called a knurled portion or an embossed portion, at both ends in the width direction. By forming the formed portion (convex portion), blocking between the films when the films are wound may be prevented. The height and shape of the knurled portion may be different (may be asymmetric) at both ends in the width direction.

(Details of stretched part)
Next, the details of the stretched portion 5 described above will be described. FIG. 2 is a plan view schematically showing an example of the rail pattern of the stretched portion 5. However, this is an example, and the configuration of the stretched portion 5 is not limited to this.

The production of the long diagonally stretched film in the present embodiment is performed by using a tenter (diagonal stretching machine) capable of diagonally stretching as the stretched portion 5. This tenter is a device that heats a long film to an arbitrary temperature at which it can be stretched and stretches it diagonally. This tenter is a heating zone Z, a pair of rails Ri / Ro on the left and right, and a large number of gripping tools Ci / Co (in FIG. 2, one set of gripping tools) that travel along the rails Ri / Ro to convey the film. Only shown). The 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 tools Ci and Co are composed of clips that grip 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 diagonally 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 °.

As described above, since the feeding direction D1 and the winding direction D2 are different, the rail pattern of the tenter has an asymmetrical shape on the left and right, and the film transport path is bent in the middle. The rail pattern can be manually or automatically adjusted according to the orientation angle θ, the draw ratio, and the like given to the long diagonally stretched film to be manufactured. In the diagonal 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 tools Ci / Co keep a constant distance from the front and rear gripping tools Ci / Co and travel at a constant speed. The traveling speed of the gripping tool Ci / Co can be appropriately selected, but is usually 1 to 150 m / min. In the present embodiment, the temperature is preferably 20 to 100 m / min in consideration of the fact that the film is surely heated in the width direction to change the temperature as described later and the productivity of the film is taken into consideration. The difference in running speed between the pair of left and right grippers Ci and Co is usually 1% or less, preferably 0.5% or less, and more preferably 0.1% or less of the running speed. This is because if there is a difference in traveling speed between the left and right sides of the film at the outlet of the stretching process, wrinkles and deviations occur at the exit of the stretching process, so that the speed difference between the left and right grippers Ci and Co is substantially the same. Is required. In a general tenter device, there is speed unevenness that occurs on the order of seconds or less depending on the tooth cycle of the sprocket that drives the chain, the frequency of the drive motor, etc., and often causes unevenness of several percent. It does not correspond to the speed difference described in the embodiment of the invention.

In the diagonal stretching machine used in the manufacturing method of the present embodiment, a rail that regulates the trajectory of the gripper is often required to have a large bending ratio, especially in a place where the film is conveyed at an angle. For the purpose of avoiding interference between the grippers due to sudden bending or local stress concentration, it is desirable that the locus of the grips draws a curve at the bent portion.

In this way, the diagonally stretched tenter used to impart diagonal orientation to a 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 preferable that the tenter can orient the (slow-phase axis) evenly on the left and right sides in the film width direction with high accuracy, and can control the film thickness and retardation with high accuracy.

Next, the stretching operation in the stretching portion 5 will be described. Both ends of the long film are gripped by the left and right gripping tools Ci / Co, and the long film is conveyed in the heating zone Z as the gripping tools Ci / Co travel. The left and right gripping tools Ci and Co face each other in a direction substantially perpendicular to the film traveling direction (feeding direction D1) at the inlet portion (position A in the figure) of the stretched portion 5, and are asymmetrical rails. The film runs on Ri and Ro, respectively, and the film gripped at the outlet portion (position B in the figure) at the end of stretching is released. The film released from the gripping tools Ci and Co is wound around the winding core by the film winding unit 8 described above. The pair of rails Ri and Ro each have an endless continuous track, and the gripping tool Ci and Co that have released the film grip at the outlet of the tenter travel on the outer rail and are sequentially returned to the inlet. It is designed to be used.

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

That is, of the gripping tools Ci and Co that were opposed to the film feeding direction D1 at the position A in the drawing, one gripping tool Ci precedes the position B at the end of stretching the film. 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 actions, the long film is stretched diagonally at an angle of θL with respect to the width direction. Here, substantially vertical means that it is in the range of 90 ± 1 °.

Next, the details of the heating zone Z described above will be described. The heating zone Z of the stretched portion 5 is composed of a preheating zone Z1, a stretching zone Z2, and a heat fixing zone Z3. In the stretched portion 5, the film gripped by the gripping tools Ci and 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 wall, and the stretching zone Z2 and the heat fixing zone Z3 are separated by a partition wall. A partition wall may be appropriately provided in each of the preheating zone Z1, the stretching zone Z2, and the heat fixing zone Z3 (the inside of each zone may be further divided by a partition wall).

The preheating zone Z1 refers to a section at the entrance of the heating zone Z where the gripping tools Ci and Co that grip both ends of the film travel while maintaining a constant interval (in the film width direction) on the left and right sides.

The stretch zone Z2 refers to a section in which the gap between the gripping tools Ci and Co that grips both ends of the film is widened and the gap becomes a predetermined distance. At this time, the diagonal stretching as described above is performed, but if necessary, it may be stretched in the vertical direction or the horizontal direction before and after the diagonal stretching. That is, in the stretching zone Z2, while gripping both ends of the film in the width direction with a pair of gripping tools Ci and Co, one gripping tool Ci is relatively preceded and the other gripping tool Co is relatively delayed. By transporting the film and bending the transport path of the film in the middle, a diagonal stretching step of stretching the film diagonally with respect to the width direction is performed.

The heat fixing zone Z3 refers to a section for fixing the optical axis (slow phase axis) of the diagonally stretched film after the diagonal stretching step in the stretching zone Z2 is completed. That is, in the heat fixing zone Z3, a heat fixing step for fixing the optical axis of the obliquely stretched film is performed. In the heat fixing zone Z3, the gripping tools Ci and Co at both ends run while being parallel to each other. As a result, the optical axis of the obliquely stretched film is fixed.

After passing through the heat-fixing zone Z3, the stretched film 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. You may.

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 temperature of the heat fixing zone Z3 and the cooling zone is Tg-40 to Tg + 30 ° C. It is preferable to set it.

The lengths of the preheating zone Z1, the stretching zone Z2, and the heat fixing zone Z3 can be appropriately selected, and the length of the preheating zone Z1 is usually 50 to 200% with respect to the length of the stretching zone Z2. The length is usually 50-150%.

Further, assuming that the width of the film before stretching is Wo (mm) and the width of the film after stretching is W (mm), the stretching ratio R (W / Wo) in the stretching step is preferably 1.1 to 3. It is 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 reduced, which is preferable.

The method of diagonal stretching in the stretched portion 5 is not limited to the above-mentioned method, and even if diagonal stretching is performed by simultaneous biaxial stretching as disclosed in, for example, Japanese Patent Application Laid-Open No. 2008-23775. Good. Simultaneous biaxial stretching means that both ends of the supplied long film in the width direction are gripped by each gripping tool, and the long film is conveyed while moving each gripping tool, and the long film is conveyed. This is a method of stretching a long film diagonally 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, diagonal stretching may be performed by a method as disclosed in Japanese Patent Application Laid-Open No. 2011-11434.

(About widening the film in the heat fixing 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 diagonally stretched film before widening after the completion of diagonal stretching in the stretched zone Z2 is L1, and in the heat fixing zone Z3 (heat fixing step), the width L1 of the diagonally stretched film before widening is set. Let L2 and L3 be the widths of the portions widened to the leading side and the delay side from the portion corresponding to. The leading side refers to the gripping tool Ci side that travels relatively ahead of the pair of gripping tools Ci / Co that grips both ends of the film, and the delay side is relatively delayed. Refers to the Co side of the gripper that travels. The units of L1, L2, and L3 are all mm.

In the present embodiment, in the heat fixing step after the diagonal stretching step is completed, the width of the diagonally stretched film is widened so as to satisfy the following conditional expression (1). That is,
L3> L2 ≧ 0 mm ・ ・ ・ (1)
Is.

FIG. 4 schematically shows how the loose-shaped residual stress is relaxed when the obliquely stretched film is widened in the heat-fixing zone Z3. The film obliquely stretched in the stretch zone Z2 enters the heat-fixing zone Z3, but at this time, the leading side enters the heat-fixing zone Z3 earlier than the delay side, so that the film shrinks from the leading side. A loose residual stress T is generated up to the vicinity of the central portion in the width direction. However, by widening the film in the heat fixing zone Z3, the film extends in the width direction, so that the loose-shaped residual stress generated in the heat fixing zone Z3 is relaxed and does not remain in the film.

As described above, in the heat fixing step after the diagonal stretching step is completed, by widening the diagonally stretched film, it is possible to suppress the generation of loose-shaped residual stress in the film after the diagonal stretching. As a result, even if the obliquely stretched film produced is used to form a circularly polarizing plate to be described later, this circularly polarizing plate is applied to an OLED (organic EL image display device), and the OLED is placed in a temperature and humidity environment different from the usual one. , It is possible to suppress the appearance of diagonally striped display unevenness.

Moreover, the conditional equation (1) is satisfied, that is, the optical axis (slow phase axis) oriented in a predetermined direction by oblique stretching by increasing the widening width of the film on the delay side rather than the leading side. It is possible to suppress the occurrence of loose-shaped residual stress with almost no deviation from the predetermined direction.

That is, when the diagonally stretched film is widened, if the leading side is widened too much, the film is pulled in the direction of widening the leading side (the direction toward the lower right in FIG. 4), and the direction of the optical axis of the film shifts. In some cases. For example, the orientation angle of a film oriented in the direction of 45 ° with respect to the width direction becomes as small as 44 ° if the leading side is widened too much.

On the other hand, the orientation angle of the film tends to be smaller on the delay side (due to the bowing phenomenon), and the direction of widening the delay side (direction toward the upper left in FIG. 4) is the orientation angle of the delay side (for example). Since the direction is increased (from 44 ° to 45 °), there is no problem even if the delay side is widened more than the leading side, but rather the orientation direction approaches a predetermined direction, which is preferable.

By satisfying the conditional expression (1) in this way, 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. .. As a result, even if the film is widened in the heat fixing step, the optic axis can be fixed in a predetermined direction to obtain a diagonally stretched film having desired orientation characteristics.

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

When the ratio B is 5% or more, the widening width on the delay side becomes too large, and the optical characteristic value adjusted in the stretching zone changes due to the stretching of the heat-fixing zone, and the uniformity deteriorates. Therefore, by satisfying 5%> B, it is possible to achieve both a loose residual stress and uniformity. Further, by satisfying B> A ≧ 0%, it is possible to widen at least the delayed side of the film from the leading side and suppress the occurrence of loose-shaped residual stress in the film after oblique stretching.

Further, by cooling the obliquely stretched film in the heat fixing step, the optical axis imparted by the oblique stretching in the diagonally stretching step can be reliably fixed. Therefore, in the heat fixing step, it is desirable to widen the diagonally stretched film at a temperature 10 ° C. to 60 ° C. lower than the stretching temperature in the diagonal stretching step, and more preferably 20 ° C. to 50 ° C. lower.

Further, when the ratio B is less than 1%, the widening width on the delay side is small, and the effect of widening the film, that is, the effect of suppressing the generation of loose-shaped residual stress is small. Further, when the ratio B is larger than 4%, the effect of stretching in the heat-fixing zone becomes stronger, 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 surely obtaining the effect of widening the film.

Further, when the leading side of the film is widened, the film may be pulled toward the leading side, and the orientation angle of the film applied in the oblique stretching step may fluctuate (become smaller) as described above. Therefore, the width L2 of the widened portion of the film on the leading side may be L2 = 0 mm.

Further, when the obliquely stretched film contains a cellulose ester resin having high moisture permeability and hygroscopicity, the orientation angle tends to fluctuate due to absorption of water. Therefore, as described above, in the heat fixing step, the delayed side of the film is widened more than the leading side, whereby the method of the present embodiment that suppresses the generation of loose-shaped residual stress while suppressing the fluctuation of the orientation angle is oblique. It is very effective when the stretched film contains a cellulose ester resin.

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

That is, in the long diagonally stretched film obtained by the production method of the present embodiment, the variation of the in-plane retardation Ro is 2 nm or less, preferably 1 nm or less in 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 circular polarizing plate, and when this is applied to an organic EL image display device, external light at the time of black display is displayed. Color unevenness due to leakage of reflected light can be suppressed. Further, when the long diagonally 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 diagonally stretched film obtained by the production method of the present embodiment, the variation of the orientation angle θ is less than 0.6 ° and less than 0.4 ° in 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 an orientation angle θ of more than 0.6 ° is bonded to a polarizing element to form a circular polarizing plate and installed on an image display device such as an organic EL display device, light leakage occurs and the contrast is bright and dark. May reduce the contrast of.

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

The average thickness of the long diagonally 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 to 400 μm, preferably 10 to 200 μm, from the viewpoint of mechanical strength and the like. It is 45 μm. Further, the thickness unevenness in the width direction of the long diagonally stretched film affects whether or not it can be wound, and therefore, it is preferably 2 μm or less, and more preferably 1 μm or less.

The long diagonally stretched film obtained by the production method of the present embodiment may have a functional layer on its 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 adjusting layer, UV absorption layer, and 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.

<Circular polarizing plate>
In the circular 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 are used. The angle formed by the polarized light is 45 °. When the circular polarizing plate of the present embodiment is used in an organic EL display device, the above-mentioned polarizing plate protective film, polarizer, and λ / 4 film are used on the protective film 313, polarizer 311, and λ / 4 film 316 of FIG. Corresponds to each. In the present 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 the present embodiment is used in a liquid crystal display device, the above-mentioned polarizing plate protective film, polarizer, and λ / 4 film are the protective film 506, polarizer 501, and λ / 4 film 503 of FIG. Corresponds to each. Since the protective film 506 and the polarizer 501 are arranged on the outside (visual side) of the display cell 401, and the λ / 4 film 503 is arranged on the outer side (visual side) of the polarizer 501, the display is displayed. 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 transmission axis of the polarizer 501 (perpendicular to the absorption axis) and the polarized sunglasses are observed at any angle. (No matter how the transmission axis is misaligned), the light component parallel to the transmission axis of the polarized sunglasses can be guided to the observer's eyes to observe the displayed image, and the displayed image is difficult to see depending on the observation angle. It can be suppressed from becoming.

The circularly polarizing plate of the present embodiment can be produced by using a stretched polyvinyl alcohol doped with iodine or a dichroic dye as a polarizer and laminating it in a λ / 4 film / polarizer configuration. 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 alkali-saponified λ / 4 film is preferably bonded to one surface of a polarizer produced by immersing and stretching a polyvinyl alcohol-based film in an iodine solution using a completely saponified polyvinyl alcohol aqueous solution.

The polarizing plate can be further formed by laminating a release film on 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, at the time of product inspection, and the like.

<Organic EL display device>
FIG. 5 is a cross-sectional view showing a schematic configuration of an organic EL display device 100 as an 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 the organic EL element 101 via an adhesive layer 201. The organic EL element 101 is configured to have a metal electrode 112, a light emitting layer 113, a transparent electrode (ITO or the like) 114, and a sealing layer 115 in this order 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 circular 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 this order from the organic EL element 101 side, and the polarizing element 311 is λ. It is sandwiched between the / 4 film 316 and the protective film 313. By laminating both 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 diagonally stretched film of the present embodiment is about 45 ° (or 135 °). , Circular polarizing plate 301 is configured.

It is preferable that the cured layer 314 is laminated on the protective film 313. The cured layer 314 not only has the effect of preventing scratches on the surface of the organic EL display device 100, but also has the effect of preventing warpage due to the circularly polarizing plate 301. Further, an antireflection layer may be formed on the cured 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 that becomes the cathode among the metal electrode 112 and the transparent electrode 114, and the electrode becomes the anode. Holes are injected from the light emitting layer 113, and the two are recombined with each other in the light emitting layer 113 to generate visible light emission corresponding to the light emitting characteristics of the light emitting layer 113. The light generated in the light emitting layer 113 is directly reflected by the metal electrode 112 or then taken out to the outside through the transparent electrode 114 and the circularly polarizing plate 301.

Generally, in an organic EL display device, an element (organic EL element) that is a light emitting body is formed by laminating a metal electrode, a light emitting layer, and a transparent electrode in this order on a transparent substrate. 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 or the like and a light emitting layer made of a fluorescent organic solid such as anthracene, or a laminate thereof. There are known configurations having various combinations such as a laminate of such a light emitting layer and an electron injection layer made of a perylene derivative or the like, a laminate of these hole injection layers, a light emitting layer, an electron injection layer, and the like.

In the organic EL display device, 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 the recombination of these holes and electrons excites the fluorescent substance. , It emits light on the principle that the excited fluorescent substance emits light when it returns to the ground state. The mechanism of intermediate recombination is the same as that of a general diode, and as can be expected from this, the current and the emission intensity show strong non-linearity with rectification with respect to the applied voltage.

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

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

The circularly polarizing plate of the present 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, half of the 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, it is incident on 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 so as to intersect at 45 ° (or 135 °), the light incident on the λ / 4 film 316 is λ / 4. It is converted into circularly polarized light by passing through the film 316.

When the metal electrode 112 of the organic EL element 101 mirror-reflects the circularly polarized light emitted from the λ / 4 film 316, the phase is reversed by 180 degrees and the circularly polarized light is reflected as a reversely rotating circularly polarized light. When this reflected light is incident on the λ / 4 film 316, it is converted into linearly polarized light perpendicular to the transmission axis of the polarizer 311 (parallel to the absorption axis), so that it is completely absorbed by the polarizer 311 and emitted to the outside. Will not be done. That is, the circularly polarizing plate 301 can reduce the reflection of external light on the organic EL element 101.

<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 arranging a polarizing plate 402 on one surface side of the display cell 401.

In the case of a liquid crystal display device, the display cell 401 can be thought of as a liquid crystal cell in which a liquid crystal layer is sandwiched between a pair of substrates. On the side opposite to the polarizing plate 402 with respect to the liquid crystal cell, another polarizing plate arranged in a cross-nicoled state with the polarizing plate 402 and a backlight for illuminating the liquid crystal cell are provided. , Their illustrations are omitted.

Further, the display device 400 may have a front window 403 on the side opposite to the display cell 401 with respect to the polarizing plate 402. The front window 403 serves as 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. If there is no filler 404, an air layer is formed between the front window 403 and the polarizing plate 402. Therefore, due to the reflection of light at the interface between the front window 403 and the polarizing plate 402 and the air layer, the display image is 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 deterioration of the visibility of the displayed image due to the reflection of light at the interface.

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

The polarizer 501 is obtained, for example, by dyeing a polyvinyl alcohol film with a dichroic dye and stretching it at a high magnification. After the polarizer 501 is subjected to alkali treatment (also referred to as saponification treatment), a λ / 4 film 503 is bonded to one surface side via an adhesive layer 502, and a protective film 506 attaches an adhesive layer 505 to the other surface side. It is pasted together.

Assuming that the thickness of the polarizer 501 is B μm, from the viewpoint of reducing the thickness of the polarizing plate 402,
1 μm <B ≦ 20 μm
Is desirable,
1 μm <B ≦ 15 μm
Is even more desirable.

The adhesive layers 502 and 505 are, for example, layers made of polyvinyl alcohol adhesive (PVA adhesive, water glue), but may be layers made of ultraviolet curable adhesive (UV adhesive). These adhesives are liquid when applied to the adhesive surface, and after application, they are dried or cured by ultraviolet irradiation to bond the two. 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, by changing the state from the liquid state. In this way, the adhesive layers 502 and 505 adhere the two parties by changing the state from the liquid state, and the adhesive layer (adhesive is applied on the base material) that adheres the two parties without causing such a change of state. It is different from the sheet-like adhesive layer).

The λ / 4 film 503 is a layer that imparts an in-plane phase difference of about 1/4 of the wavelength to transmitted light, and in this embodiment, for example, a cellulosic resin (cellulosic polymer) is contained. The λ / 4 film 503 may contain a polycarbonate resin (polycarbonate polymer) instead of the cellulosic 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 cellulosic polymer or a polycarbonate polymer.

The λ / 4 film 503 is a thin film λ / 4 film having a thickness of 10 μm to 70 μm. Further, the angle (intersection angle) formed by the slow axis of the λ / 4 film 503 and the absorption axis of the polarizer 501 is 30 ° to 60 °, so that the linearly polarized light from the polarizer 501 is λ /. 4 Converted to circularly polarized light or elliptically polarized light by film 503.

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

The protective film 506 is composed of, for example, an optical film made of a cellulosic resin (cellulosic polymer), an acrylic resin, a cyclic polyolefin (COP), and a polycarbonate (PC). The protective film 506 is provided as a film that simply protects the back surface 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 arranged 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 above-mentioned polarizer and optical film, the same ones as those of the polarizer 501 and the protective film 506 of the polarizing plate 402 can be used.

Here, the above-mentioned polarizer 501 and the λ / 4 film 503 may each have a long shape. 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, a long λ / 4 film 503 is produced by diagonal stretching to form a roll-shaped film, which is bonded to a roll-shaped polarizing element 501 by a so-called roll-to-roll method to form a long-shaped film. The polarizing plate 402 of the above can be produced. Therefore, the productivity can be dramatically improved and the yield can be significantly improved as compared with the case where the polarizing plate 402 is manufactured by the batch method in which the film pieces are bonded one by one.

An easy-adhesion layer for improving the adhesiveness 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 treatment on the adhesive layer 502 side of the λ / 4 film 503. The easy-adhesion treatment includes corona (discharge) treatment, plasma treatment, frame treatment, itro treatment, glow treatment, ozone treatment, primer coating treatment, and the like, and at least one of them may be carried out. Of these easy-adhesion treatments, corona treatment and plasma treatment are preferable as easy-adhesion treatments from the viewpoint of productivity.

<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, the notation of "parts" or "%" will be used, but unless otherwise specified, these shall represent "parts by mass" or "% by mass".

[Preparation of raw film]
Long films 1 and 2 as raw film were produced by the following methods.

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

≪Particle dispersion liquid≫
Fine particles (Aerodil R972V, manufactured by Nippon Aerodil Co., Ltd.) 11 parts by mass Ethanol 89 parts by mass or more were stirred and mixed with a dissolver for 50 minutes, and then dispersed with manton gorin to prepare a fine particle dispersion liquid 1.

≪Particle additive liquid≫
Based on the following composition, the fine particle dispersion was slowly added to the dissolution tank containing methylene chloride while sufficiently stirring. Further, the particles were dispersed by an attritor so that the particle size of the secondary particles became a predetermined size. This was filtered through Finemet NF manufactured by Nippon Seisen Co., Ltd. to prepare a fine particle additive solution 1.
Methylene chloride 99 parts by mass Fine particle dispersion 15 parts by mass

≪Main doping liquid≫
A main doping solution having the following composition was prepared. First, methylene chloride and ethanol were added to the pressurized dissolution tank. Cellulose acetate was poured into a pressurized dissolution tank containing a solvent with stirring. This is heated and completely melted while stirring, and this is Azumi Filter Paper No. 1 manufactured by Azumi Filter Paper Co., Ltd. Filtration was performed using 244 to prepare the main doping solution. As the sugar ester compound and the ester compound, compounds synthesized by the following synthetic examples were used.

<< Composition of main doping liquid >>
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 mass Ultraviolet absorber 1.5 parts by mass Fine particle addition liquid 1 1 part by mass

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

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

Next, the inside of Kolben ^{was depressurized to 4 × 10 2} Pa or less, excess pyridine was distilled off at 60 ° C., and then the inside of Kolben was depressurized to 1.3 × 10 Pa or less, the temperature was raised to 120 ° C., and benzoic anhydride was used. The acid, most of the benzoic acid produced, was distilled off.

Finally, 100 g of water is added to the separated toluene layer, washed 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) to compound the compound.} 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. It was 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 unit Equipment: JASCO Corporation 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 Co., Ltd.)
Column temperature: 40 ° C
Flow velocity: 1 ml / min
Mobile phase: THF (1% acetic acid): H ₂ O (50:50)
Injection volume: 3 μl
2) MS unit Equipment: 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 compounds≫
The 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, and a 2 L four-neck equipped with a thermometer, a stirrer, and a slow-speed cooling tube. Place in a flask and gradually raise the temperature in a nitrogen stream until the temperature reaches 230 ° C. with stirring. A dehydration condensation reaction was carried out for 15 hours, and after completion of the reaction, unreacted 1,2-propylene glycol was distilled off under reduced pressure at 200 ° C. to obtain an ester compound. The ester compound has an ester of benzoic acid at the end of a polyester chain formed by condensing 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 device, the casting was uniformly spread on the stainless belt support.

In the endless belt casting device, the main doping liquid was uniformly cast on the stainless steel belt support. Evaporate the solvent on the stainless steel belt support until the amount of residual solvent in the cast long film reaches 75%, peel it off from the stainless steel belt support, and transport it with a large number of rolls. Drying was completed to obtain a long film 1 having a width of 1500 mm.

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

In a nitrogen atmosphere, 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 placed in a reactor at room temperature and mixed with 500 parts by mass of dehydrated cyclohexane, and then 45 ° C. 20 parts by mass of tricyclo [4.3.0.12.5] deca-3,7-diene (dicyclopentadiene, hereinafter abbreviated as DCP), 1,4-methano-1,4,4a, 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] -dodeca-3-ene (hereinafter abbreviated as MTD) A mixture of norbornene-based monomers composed of parts and 40 parts by mass of tungsten hexachloride (0.7% toluene solution) were continuously added and polymerized over 2 hours. 1.06 parts by mass of butyl glycidyl ether and 0.52 parts by mass of isopropyl alcohol were added to the polymerization solution to inactivate the polymerization catalyst and stop the polymerization reaction.

Next, 270 parts by mass of cyclohexane was added to 100 parts by mass of the reaction solution containing the obtained ring-opening polymer, and 5 parts by mass of a nickel-alumina catalyst (manufactured by JGC Catalysts and Chemicals Co., Ltd.) was added as a hydrogenation catalyst. In addition, the mixture was pressurized to 5 MPa with hydrogen, heated to a temperature of 200 ° C. with stirring, and then reacted for 4 hours to obtain a reaction solution containing 20% of the 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 Chivas Specialty Chemicals Co., Ltd .; Irganox 1010) were added to the obtained solutions, respectively. And dissolved (0.1 parts by mass per 100 parts by mass of the polymer). Next, the solvent cyclohexane and other volatile components were removed from the solution using a cylindrical concentrated dryer (manufactured by Hitachi, Ltd.), and the hydrogenated polymer was extruded in a molten state from an extruder into strands. After cooling, it was pelletized and recovered. When the copolymerization ratio of each norbornene-based monomer in the polymer was calculated from the residual norbornene composition (by gas chromatography) in the solution after polymerization, it was almost charged at DCP / MTF / MTD = 10/70/20. It was equal to the composition. The weight average molecular weight (Mw) of this ring-opening polymer hydrogenated product was 31,000, the molecular weight distribution (Mw / Mn) was 2.5, the hydrogenation rate was 99.9%, and Tg was 134 ° C.

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

[Preparation of diagonally stretched film]
The long film 1 made of the cellulosic resin produced above was obliquely stretched by the stretched portion 5 to obtain a long diagonally stretched film (see Examples 1 to 4 and Comparative Examples 1 and 2 in Table 1). At this time, the moving speed of the film is set to 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 fixing zone Z3 is 188 ° C, and the stretching ratio is 1.16 times. The thickness was 40 μm, and the final film width after the trimming treatment was 1300 mm.

Further, in the production of the diagonally stretched film of Examples 1 to 4, the width of the diagonally stretched film was widened in the heat fixing zone Z3. That is, in the heat fixing zone Z3, the width of the long diagonally stretched film before widening after the completion of diagonal stretching is set to L1 (mm), and in the heat fixing step, from the portion corresponding to the width L1 of the diagonally stretched film before widening. When the widths of the portions widened to the leading side and the delay side are L2 (mm) and L3 (mm), respectively, the width L1, the width L2, and the width L3 are obliquely stretched so as to be the values shown in Table 1. The film was widened. In Table 1, the ratio A and the ratio B represented by the following formulas are also shown. In particular, in the production of the obliquely stretched film of Example 2, the temperature in the heat-fixing zone Z3 was adjusted to a temperature 30 ° C. lower than the temperature in the stretched zone Z2.
A = (L2 / L1) x 100
B = (L3 / L1) x 100

Further, in the production of the obliquely stretched film of Comparative Example 1, the width was not widened in the heat fixing zone Z3. On the other hand, in the production of the diagonally stretched film of Comparative Example 2, the width of the diagonally stretched film was widened not in the heat fixing zone Z3 but in the stretched zone Z2. At this time, in the stretch zone Z2, the width of the long diagonally stretched film before widening is set to L1 (mm), and the portion widened to the leading side and the delayed side from the portion corresponding to the width L1 of the diagonally stretched film before widening. The widths of were L2 (mm) and L3 (mm), respectively.

Further, the raw 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 of the heating zone Z, both ends of the unstretched film A sent from the film feeding portion 2 are used as the first clip as the gripping tool Ci on the leading side and the gripping tool Co on the delay side. It was gripped by the second clip of. When gripping the unstretched film A, the clip levers of the first and second clips are moved by the clip closer to grip the unstretched film A. When gripping the clips, both ends of the unstretched film A are gripped by the first and second clips at the same time, and the line connecting the gripping positions of both ends is parallel to the axis parallel to the width direction of the film. Hold it so that it becomes.

Next, the unstretched film A (long film 2) was diagonally stretched by the stretched portion 5 described above to obtain a long diagonally stretched film (see Example 5 and Comparative Example 3 in Table 1). That is, the unstretched film A that has been gripped is conveyed while being gripped by the first and second clips, and is heated by passing through the preheating zone Z1, the stretching zone Z2, and the heat fixing zone Z3 in the heating zone Z, and has a width. 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 diagonally stretched film of Example 5, the diagonally stretched film was widened in the heat fixing zone Z3 so that the width L1, the width L2, and the width L3 had the values shown in Table 1. On the other hand, in the production of the diagonally stretched film of Comparative Example 3, the width was widened not in the heat fixing zone Z3 but in the stretched zone Z2. 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 the width is also widened in the stretching zone Z2.

The film moving speed during 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 fixing zone Z3 was 140 ° C. The stretch ratio of the film before and after stretching was 1.16 times, and the thickness of the film after stretching was 50 μm.

[Preparation of circularly polarizing plates 1 to 8]
Circularly polarizing plates 1 to 8 were prepared as follows using a long diagonally stretched film that was diagonally stretched under the same conditions as described above.

That is, a 120 μm-thick polyvinyl alcohol film is uniaxially stretched (temperature 110 ° C., stretching ratio 5 times), immersed in an aqueous solution consisting of 0.075 g of iodine, 5 g of potassium iodide, and 100 g of water for 60 seconds, and then potassium iodide. It was immersed in an aqueous solution at 68 ° C. consisting of 6 g, 7.5 g of boric acid and 100 g of water. The film after immersion was washed with water and dried to obtain a polarizer.

Subsequently, the prepared long diagonally stretched films of Examples 1 to 5 and Comparative Examples 1 to 3 were bonded to one side of the above-mentioned polarizer using a 5% aqueous solution of polyvinyl alcohol as an adhesive. At that time, the transmission axis of the polarizer and the slow axis of the obliquely stretched film were bonded so as to be 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 prepare circularly polarizing plates 1 to 8.

[Preparation of circularly polarizing plates 11 to 18]
Using a long diagonally stretched film diagonally stretched under the same conditions as above, circularly polarizing plates 11 to 18 were produced as follows.

That is, a 120 μm-thick polyvinyl alcohol film is uniaxially stretched (temperature 110 ° C., stretching ratio 5 times), immersed in an aqueous solution consisting of 0.075 g of iodine, 5 g of potassium iodide, and 100 g of water for 60 seconds, and then potassium iodide. It was immersed in an aqueous solution at 68 ° C. consisting of 6 g, 7.5 g of boric acid and 100 g of water. The film after immersion was washed with water and dried to obtain a polarizer.

Subsequently, the prepared long diagonally stretched films of Examples 1 to 5 and Comparative Examples 1 to 3 were bonded to one side of the above-mentioned polarizer using a 5% aqueous solution of polyvinyl alcohol as an adhesive. At that time, the transmission axis of the polarizer and the slow axis of the obliquely stretched film were bonded so as to be oriented at 45 °. Then, Konica Minolta Tack Film KC2CT1 (manufactured by Konica Minolta Co., Ltd.) subjected to alkali saponification treatment was similarly bonded to the other surface of the polarizer to prepare circularly polarizing plates 11 to 18.

[Manufacturing 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 a sputtering method. 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 on the anode as a hole transport layer by a sputtering method to a thickness of 80 nm. Then, using a shadow mask on the hole transport layer, each light emitting layer of RGB was formed with a film thickness of 100 nm.

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

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

On the insulating film of the organic EL element produced above, the circularly polarizing plates 1 to 8 produced 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. To become. As a result, organic EL display devices 1 to 8 were manufactured.

[Manufacturing of liquid crystal display devices 1 to 8]
<< Manufacturing of liquid crystal display device >>
Peel off the polarizing plate on the visual side that was previously attached to the commercially available 10-inch liquid crystal display device, and place the circularly polarizing plates 11 to 18 produced above so that the surface of the Konica Minolta tack film KC2CT1 faces the surface of the liquid crystal cell. , The liquid crystal display devices 1 to 8 were manufactured by laminating with an adhesive. The bonding of the circular polarizing plates 11 to 18 was performed so that the absorption axis of the polarizing elements of the circular polarizing plates 11 to 18 was oriented in the same direction as the absorption axis of the polarizer of the previously bonded polarizing plate. ..

[Quantitative evaluation]
In order to investigate the variation in the orientation angle in the width direction of the produced film, the orientation angles in the width direction of the diagonally stretched films produced by the same methods as in Examples 1 to 5 and Comparative Examples 1 to 3 in Table 1 are as follows. The difference between the left and right orientation angles was determined by measurement using the above method. That is, after the obliquely stretched film was left in a room at 23 ° C. and 55% RH for 24 hours, 10 film pieces were cut out in the transport direction 30 mm inside from the edge of the diagonally stretched film. Then, for each film piece, the orientation angle is measured at each position in the width direction using a phase difference measuring device (KOBRA-WXK manufactured by Oji Measurement Co., Ltd.), and the average of 10 sheets of the difference between the left and right orientation angles is measured. Was obtained, and the obtained average value was used as the difference between the left and right orientation angles. Then, based on the following evaluation criteria, the uneven orientation angle in the width direction was quantitatively evaluated.
"Evaluation criteria"
A: The difference between the left and right orientation angles is less than 0.3 °.
B: The difference between the left and right orientation angles is 0.3 ° or more and less than 0.6 °.
C: The difference between the left and right orientation angles is 0.6 ° or more and less than 0.8 °.
D: The difference between the left and right orientation angles is 0.8 ° or more.

〔sensory evaluation〕
The produced organic EL display devices 1 to 8 and liquid crystal display devices 1 to 8 are allowed to stand 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. The liquid crystal display devices 1 to 8 were visually observed with polarized sunglasses worn and evaluated based on the following criteria.
<Evaluation criteria>
A: The screen was uniformly displayed in black, and no color unevenness due to uneven reflected light amount was observed.
B: Slightly striped unevenness was observed at the edge of the screen, but this is a level that is not a problem in practical use.
C: Thin striped unevenness was observed on the entire screen.
D: Striped unevenness was observed on the entire screen.

Table 1 shows the evaluation results of the obliquely stretched films of Examples 1 to 5 and Comparative Examples 1 to 3. It should be noted that Examples 1, 3 to 5 are merely reference examples of the present invention and do not belong to the scope of the present invention.

From Table 1, in Comparative Example 1 in which the film is not widened, both the quantitative evaluation and the sensory evaluation are not good (both evaluations are D), and Comparative Examples 2 and 3 in which the film is widened in the oblique stretching step are also Comparative Examples. Although the quantitative evaluation is higher than 1, the evaluation is C or D, which cannot be said to be good. On the other hand, in Examples 1 to 5 in which the film is widened in the heat fixing step after the oblique stretching, both the quantitative evaluation and the sensory evaluation are good (the evaluation is A or B). This is because in the heat fixing step after the diagonal stretching, the width of the diagonally stretched film is widened, so that it is possible to suppress the occurrence of loose residual stress in the diagonally stretched film, and in particular, during the diagonal stretching. By widening the delay side more than the leading side, it is possible to suppress the generation of loose residual stress in the film with almost no change in the optical axis oriented in a predetermined direction due to oblique stretching. it is conceivable that.

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

The method for producing the obliquely stretched film of the present embodiment described above can be expressed as follows.

1. 1. While gripping both ends of the film in the width direction with a pair of grippers, one gripper is relatively preceded and the other gripper is relatively delayed to convey the film, thereby carrying the film. A method for producing a diagonally stretched film, which comprises a diagonally stretched step of stretching diagonally with respect to the width direction.
Further having a heat fixing step for fixing the optical axis of the diagonally stretched film after the completion of the diagonally stretched step.
In the heat fixing step, the width of the diagonally stretched film after the completion of the diagonally stretched step is widened.
After the completion of the diagonal stretching, the width of the diagonally stretched film before widening was set to L1, and in the heat fixing step, the width was widened to the leading side and the delayed side from the portion corresponding to the width L1 of the diagonally stretched film before widening. A method for producing a diagonally stretched film, which satisfies the following conditional expression (1) when the widths of the portions are L2 and L3, respectively;
L3> L2 ≧ 0 mm ・ ・ ・ (1)
Is.

2. The method for producing a diagonally stretched film according to 1 above, which further satisfies the following conditional expression (2);
5%>B> A ≧ 0% ・ ・ ・ (2)
However,
A = (L2 / L1) x 100
B = (L3 / L1) x 100
Is.

3. 3. The method for producing a diagonally stretched film according to 1 or 2, wherein in the heat fixing step, the diagonally stretched film is widened at a temperature 10 ° C. to 60 ° C. lower than the stretching temperature in the diagonally stretched step. ..

4. 4% ≧ B ≧ 1%
The method for producing a diagonally stretched film according to 2 above.

5. L2 = 0mm
The method for producing a diagonally stretched film according to any one of 1 to 4 above.

6. The method for producing an optical film according to any one of 1 to 5, wherein the film diagonally stretched in the diagonal stretching step contains a cellulose ester resin.

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

1 Oblique stretched film manufacturing equipment 5 Stretched part Ci gripper Co gripper

Claims (3)

While gripping both ends of the film in the width direction with a pair of grippers, one gripper is relatively preceded and the other gripper is relatively delayed to convey the film, thereby carrying the film. A method for producing a diagonally stretched film, which comprises a diagonally stretched step of stretching diagonally with respect to the width direction.
Further having a heat fixing step for fixing the optical axis of the diagonally stretched film after the completion of the diagonally stretched step.
In the heat fixing step, the width of the diagonally stretched film after the completion of the diagonally stretched step is widened.
After the completion of the diagonal stretching, the width of the diagonally stretched film before widening was set to L1, and in the heat fixing step, the width was widened to the leading side and the delayed side from the portion corresponding to the width L1 of the diagonally stretched film before widening. When the widths of the portions are L2 and L3, respectively, the following conditional expression (1) is satisfied.
L3>L2> 0 mm ・ ・ ・ (1)
After the diagonal stretching step is completed, the diagonally stretched film enters the heat fixing step earlier on the leading side than on the delayed side.
A method for producing a diagonally stretched film , which comprises widening the diagonally stretched film at a temperature 10 ° C. to 60 ° C. lower than the stretching temperature in the diagonally stretching step in the heat fixing step. The method for producing a diagonally stretched film according to claim 1, further satisfying the following conditional expression (2);
5%>B>A> 0% ・ ・ ・ (2)
However,
A = (L2 / L1) x 100
B = (L3 / L1) x 100
Is. The method for producing a diagonally stretched film according to claim 1 or 2, wherein the film diagonally stretched in the diagonally stretched step contains a cellulose ester resin.

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