KR20190086354A - Method of producing obliquely stretched film - Google Patents

Abstract

The present invention relates to a production method of a warp stretched film, which has a warp stretched process producing the warp stretched film by bending the conveyance direction on the way while conveying a film base material in one direction. The dimensional change rate in one direction of the film base material when heat-processing about each of the film base material before warp stretch and the warp stretched film is T1 (%), and the dimensional change rate in one direction of the warp stretched film is T2 (%), when heat processing for 90 seconds at the glass transition temperature of a resin of Tg+5°C, thereby satisfying T1<0%<=T2, and -7.0%<T1<=-0.5%, wherein the film base material consists of the resin.

Description

METHOD OF PRODUCING OBLIQUELY STRETCHED FILM [0002]

The present invention relates to a method for producing an oblique stretched film.

Heretofore, various proposals have been made for producing an obliquely-stretched film by stretching the film substrate in an oblique direction crossing both the width direction and the longitudinal direction. Among them, for example, in Patent Document 1, by changing the resin composition at both end portions in the width direction of the film substrate and other portions (portions sandwiched between the respective end portions) and stretching the film substrate in the oblique direction, Even when a warp stretched film is produced by using a resin (e.g., an acrylic resin), the warp stretched film is prevented from breaking in the stretching direction.

Further, for example, in Patent Documents 2 and 3, a method of obliquely stretching a film substrate after stretching in the carrying direction (longitudinal stretching) is disclosed. Particularly, in Patent Document 2, longitudinal stretching and oblique stretching are performed using a film base material in which the film thickness at the central portion in the width direction is increased to be larger than that at the end portion, thereby suppressing the fluctuation of the thickness and optical characteristics of the film after warping and stretching. Further, in Patent Document 3, the orientation angle of the film base is adjusted by adjusting the elongation or contraction ratio in the carrying direction.

In addition, for example, in Patent Document 4, the film base material is stretched to the neck by raising a part of the film base material to which tension is applied from a temperature at which the width of the film base material does not change to a temperature at which necking occurs, Thereby obtaining a stretched film having less unevenness in stretching. Further, the necking stretching refers to a method of stretching the film base by generating necking (narrowed portion) in a narrow range of the film base.

Japanese Patent Application Laid-Open No. 2014-69436 (claims 1, 6, 7, paragraphs [0010] to [0010], [0013] Japanese Patent No. 5233746 (Claim 1, paragraphs 0009 and 0011, Figs. 1 and 3, etc.) Japanese Patent No. 4841191 (Claim 1, paragraph [0012], Fig. 1, etc.) Japanese Patent No. 5542579 (see claim 1, paragraphs [0003], [0010], [0012], Figure 1, etc.)

6A is a perspective view schematically showing a state in which both ends in the width direction are gripped by a clip Cp (only one side clip Cp in the width direction is shown) and the warp stretched film F is transported And Fig. 6B is a sectional view taken along line A-A 'in Fig. 6A. When a resin (for example, a polycarbonate resin) having a small shrinkage due to heat is used as the resin constituting the film substrate in the case of producing the warp stretched film F by bending the film substrate during the conveying, When the base material is obliquely stretched at a desired stretching temperature, wave-like deformation occurs at the end portion in the width direction of the warp stretched film (F) as shown in Fig. 6B. This wave-like deformation is thought to occur with the following principle.

7, when the transport direction of the film base material is changed from E1 direction to E2 direction (direction intersecting at an angle of θo (°) in the film plane with respect to the E1 direction) to perform oblique stretching, , It is possible to bend during the conveyance, whereby it contracts mechanically in the E1 direction. For example, in the film base before the oblique stretching, the portion where the dimension in the E1 direction is Lo (mm) becomes Lo · cos θo (mm) after the oblique stretching and mechanically contracts by cosθo times in the E1 direction. Therefore, if the film substrate does not shrink spontaneously in the E1 direction during oblique stretching, &quot; margin &quot; occurs, and the &quot; margin &quot; Respectively.

When a resin having a high heat shrinkability (for example, a cellulose ester resin) is used, since the thermal shrinkage of the resin follows the mechanical shrinkage peculiar to warp stretching in the E1 direction, the above wave-like deformation hardly occurs. However, in the case of using a resin having a low heat shrinkability, the heat shrinkage of the resin in the E1 direction can not follow the mechanical shrinkage peculiar to the warp stretching, and consequently wavy deformation appears in the film end portion.

The film produced by the wave-like deformation is discharged from the warp stretching machine (tenter), and when it is surrounded and conveyed by the peripheral surface of the conveying roll, it is likely to break and be broken. In addition, when wavy deformation occurs at the film edge, the orientation angle tends to vary between the edge of the film and the center of the film without wavy deformation. However, in the above-described Patent Documents 1 to 4, when the warp stretched film is manufactured using a resin having a low heat shrinkability, the wavy deformation is suppressed and the fluctuation of the orientation angle in the width direction is reduced It has not been reviewed at all. Also, as in Patent Document 1, the method of changing the resin composition in the film width direction is not realistic in terms of cost.

Further, for example, when the film substrate is stretched too much in the E1 direction, the film is excessively shrunk along the E1 direction at a high temperature (stretching temperature) during oblique stretching. Therefore, when the produced obliquely drawn film is heated and subjected to an endurance test, the retardation Ro in the in-plane direction is lowered than before the durability test. Therefore, as in Patent Documents 2 and 3, when longitudinal stretching is performed before warp stretching, it is necessary to properly suppress the rate of dimensional change in the E1 direction before and after the heat treatment of the film base material before warp stretching after longitudinal stretching. However, this point has not been examined at all in Patent Documents 2 and 3. Also in Patent Document 1, no consideration has been made on the rate of dimensional change in the E1 direction before and after the heat treatment of the film base material before warp stretching.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for manufacturing a warp stretched film by using a resin having a low heat shrinkability and a method for manufacturing the warp stretched film, And a method for producing an oblique stretched film capable of suppressing a decrease in in-plane retardation Ro after an endurance test.

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

A method of producing an obliquely-drawn film according to one aspect of the present invention is a method of stretching a film base material in an oblique direction crossing the one direction and within a film plane by transporting the film base material in one direction and bending the carrying direction in the middle A method of producing an obliquely-drawn film having an oblique stretching step of producing an obliquely stretched film,

The dimensional change rate of the film base material in the one direction when heat treatment is performed on each of the film base material and the warp stretched film before the oblique stretching is referred to as T1 (%), and the one direction of the obliquely- And the heat treatment is performed for 90 seconds at a glass transition temperature Tg + 5 占 폚 of the resin constituting the film base material,

A method for producing an oblique stretched film characterized by satisfying the following conditional expressions (1) and (2):

T1 < 0%? T2 (1)

-7.0% < T1? -0.5% (2)

only,

T1 = {(A2-A1) / A1} x100

T2 = {(B2-B1) / B1} x100

A1: the dimension (mm) of the film base in the one direction before the heat treatment;

A2: the dimension (mm) in the one direction after the heat treatment of the film base material,

B1: dimension (mm) of the obliquely-drawn film in the one direction before the heat treatment;

B2 is a dimension (mm) in the one direction after the heat treatment of the obliquely-

to be.

According to the above production method, even when a warp stretched film is produced by using a resin having a low heat shrinkability, it is possible to suppress the wavy distortion generated at the film end portion, and thereby, in the produced warp stretched film, Can be reduced. In addition, by appropriately defining the range of the dimensional change ratio before and after the heat treatment of the film base before the oblique stretching, the in-plane retardation Ro after the durability test in the produced obliquely-stretched film can be suppressed.

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is an explanatory view showing a schematic structure of a film base material manufacturing apparatus according to an embodiment of the present invention; FIG.
2 is a flow chart showing the flow of the manufacturing process of the film base material.
3 is a plan view schematically showing a schematic configuration of an apparatus for producing an obliquely-drawn film.
4 is a plan view schematically showing an example of a rail pattern of a stretching portion of the apparatus for producing an oblique-drawn film.
5 is an explanatory diagram for explaining a method of cutting a film piece of a predetermined size from a film roll.
FIG. 6A is a perspective view schematically showing a state in which an end portion in the width direction is gripped by a clip and the obliquely-drawn film is transported.
6B is a sectional view taken along line A-A 'in Fig. 6A.
Fig. 7 is an explanatory diagram schematically showing a state in which the film substrate is mechanically contracted in one direction by bending the film substrate during conveyance at the time of oblique stretching. Fig.

An embodiment of the present invention will be described below with reference to the drawings. In the present specification, when numerical ranges are denoted by A to B, values of lower limit A and upper limit B are included in the numerical range.

[Outline of Manufacturing Method of Inclined Film]

The method of producing an obliquely-drawn film according to the present embodiment is a method of stretching a film substrate in an oblique direction crossing the one direction and within the film plane by conveying a long film base in one direction, And an oblique stretching step of producing an obliquely stretched film.

The orientation direction of the molecules in the obliquely drawn film, that is, the direction of the slow axis, is preferably in the range of from 0 DEG to less than 90 DEG with respect to the width direction of the film in the film plane (in the plane perpendicular to the thickness direction) (It automatically becomes an angle of more than 0 DEG and less than 90 DEG with respect to the longitudinal direction of the film). Since the slow axis is usually expressed in the stretching direction or the direction perpendicular to the stretching direction, stretching is performed at an angle of more than 0 DEG and less than 90 DEG with respect to the width direction of the film, Can be manufactured. The angle formed between the width direction of the obliquely drawn film and the slow axis, that is, the orientation angle can be arbitrarily set at a desired angle in a range of more than 0 DEG and less than 90 DEG.

In the present embodiment, the term &quot; long &quot; means a film having a length of at least about 5 times or more, preferably 10 times or more the width of the film, and more specifically, (Film roll).

In the production of an elongated obliquely-drawn film having a long shape, a film substrate having a long shape is formed, and this is once wound around a winding core to form a rolled body (film roll, film fabric) (Stretched) to prepare an obliquely drawn film. Further, the film base material after film formation may be supplied continuously to the oblique stretching step from the film-forming step without winding the film base material to produce the warp stretched film. The film-forming step and the oblique stretching step are preferably carried out consecutively because the film-forming conditions are changed by feeding back the results of film thickness and optical value after stretching to obtain a desired long warp stretched film.

[Manufacturing method of oblique stretched film]

In the present embodiment, the dimensional change rate in the one direction (transport direction, longitudinal direction) of the film substrate when the heat treatment is performed on each of the film base before the warp stretching and the film after warp stretching (warp stretching film) (%), And the rate of dimensional change in the one direction (the same direction as the transport direction of the film base before warp stretching (before bending)) of the warp stretched film is defined as T2 (%), (1) and (2) below when the film is heated for 90 seconds at a glass transition temperature Tg + 5 占 폚 of the resin constituting the film base material. In other words,

T1 < 0%? T2 (1)

-7.0% < T1? -0.5% (2)

only,

T1 = {(A2-A1) / A1} x100

T2 = {(B2-B1) / B1} x100

A1: the dimension (mm) of the film base in the one direction before the heat treatment;

A2: the dimension (mm) in the one direction after the heat treatment of the film base material,

B1: dimension (mm) of the obliquely-drawn film in the one direction before the heat treatment;

B2 is a dimension (mm) in the one direction after the heat treatment of the obliquely-

to be.

When the conditional formula (1) is satisfied, since the dimensional change rate T1 of the film substrate before and after the heat treatment is a negative value, the film substrate becomes a characteristic of contracting in one direction (conveying direction) after heat treatment, 2). In this case, even when a warp-stretched film is produced using a resin having a low heat-shrinkability, mechanical shrinkage in the one direction specific to oblique stretching at a high temperature (stretching temperature) The shrinkage (heat shrinkage) in one direction is followed. Thereby, occurrence of &quot; margin &quot; in the film end portion can be reduced, and occurrence of wave-like deformation in the film end portion can be suppressed. Therefore, at the time of subsequent film transportation, it is possible to reduce the breakage caused by the inclined stretched film being surrounded by the transport roll. In addition, by suppressing the wave-like deformation of the film edge portion, it is possible to reduce the occurrence of variations in the orientation angle between the film width center portion where the wave-like deformation has not originally occurred and the film edge portion.

Further, since the dimensional change rate T1 before and after the heat treatment of the film base before the warp stretching is converged to an appropriate range defined by the conditional expression (2), shrinkage in the one direction after the heat treatment of the film base is appropriately suppressed. As a result, even when the film substrate is subjected to oblique stretching, the film substrate is prevented from excessively shrinking in the one direction at a high temperature (stretching temperature) during oblique stretching. As a result, even when the produced obliquely-drawn film is heated to perform the durability test, it is possible to suppress the retardation Ro in the in-plane direction from being lowered before the durability test.

Further, for example, if the film substrate is stretched (transversely stretched) in a direction perpendicular to the one direction (transport direction) in the film plane (transverse direction), after heat treatment of the film substrate, (T1 > 0) by the relaxation of the residual stress in the stretching direction (width direction). Therefore, when the film substrate is obliquely stretched at a high temperature, since the film substrate does not shrink in one direction, the above-described wave-like deformation occurs and the orientation angle varies in the width direction. Therefore, as indicated by the conditional expression (1), by defining T1 < 0, it is possible to reduce the fluctuation of the wavy shape deformation and the orientation angle in the width direction.

It is preferable to satisfy the following conditional expression (2a), more preferably satisfy the following conditional formula (2b), and more preferably satisfy the following conditional formula (2c) from the viewpoint of ensuring the above- More preferable. In other words,

-7.0% < T1? -2.0% (2a)

-6.8% <T1? -4.5% (2b)

-6.8% <T1? -5.0% (2c)

to be.

The method for producing an oblique-stretched film according to the present embodiment further includes a longitudinal stretching step of stretching the film base in the one direction, wherein in the oblique stretching step, May be stretched in the oblique direction to produce the warp stretched film.

(Longitudinal stretching) in one direction before the film substrate is subjected to oblique stretching, the film substrate after the heat treatment can be given shrinkage (heat shrinkage) in one direction. This makes it possible to suppress the mechanical shrinkage in one direction by the shrinkage in one direction caused by the heat of the film substrate at a high temperature at the time of oblique stretching so as to suppress the occurrence of the wave- .

The method of producing an obliquely-drawn film according to the present embodiment may further include a transporting step of transporting the film base material in the one direction by including a solvent in the film base material. In the oblique stretching step, May be stretched in the oblique direction to produce the warp stretched film. Rather than including a solvent in the film substrate, when the film substrate is transported in one direction, the film substrate is liable to be stretched in one direction. Thus, also by this method, since the film substrate can be imparted with the property of shrinking in the one direction after the heat treatment, the mechanical shrinkage in the one direction can be prevented from reaching the film substrate It is possible to reliably suppress the occurrence of the wave-like deformation at the film end portion.

In the oblique stretching step, the film substrate is heated to a preheating temperature before the oblique stretching, and the preheating temperature is preferably not lower than the stretching temperature at the time of oblique stretching. The preheating temperature higher than the stretching temperature at the time of oblique stretching is given before the oblique stretching, whereby the film base can be efficiently shrunk at a predetermined stretching temperature during the oblique stretching. Therefore, this method is very effective when a film base material is constituted using a resin having a low heat shrinkability and a small dimensional change due to heat, and the film base material is obliquely stretched.

The resin constituting the film base material may include any of a polycarbonate resin, a cycloolefin resin and a polyester resin. Since any of the resins described above has a low heat shrinkability and a small dimensional change due to heat, when the film base material is formed using such a resin, the above-described production method of the present embodiment becomes very effective.

(Production of film substrate)

The film substrate of this embodiment can be produced, for example, by a solution casting film forming method. Hereinafter, a method for producing a film substrate by a solution casting method will be described.

&Lt; Solution flexible film-forming method &

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory diagram showing a schematic configuration of a production apparatus 1 for a film base material according to the embodiment; FIG. 2 is a flowchart showing the flow of the production process of the film base. As shown in Fig. 2, the production method of the film base material of the present embodiment is characterized in that the stirring step (S1), the softening step (S2), the peeling step (S3), the stretching step (S4) A cutting step (S6), an embossing step (S7), and a winding step (S8). Hereinafter, each step will be described with reference to Figs. 1 and 2. Fig.

(S1: stirring and preparing process)

In the stirring and dispensing step, at least the resin and the solvent are stirred in the stirring tank 101 of the stirring apparatus 100 to prepare a dope which is flexible on the support 3 (endless belt).

(S2)

In the softening step, a support 3 (see FIG. 1) including a rotary driven stainless steel endless belt for feeding the dope prepared in the stirring and mixing process to the flexible die 2 through a conduit through a pressurized metering gear pump or the like, The flexible dies 2 are made flexible. Then, the support 3 carries while supporting the flexible dope (flexible dope). Thereby, the web 5 as a flexible film is formed on the support 3.

The support 3 is held by a pair of rolls 3a and 3b and a plurality of rolls (not shown) located therebetween. On one or both sides of the rolls 3a and 3b, a driving device (not shown) for applying a tension to the supporting body 3 is provided, whereby the supporting body 3 is used in a state in which a tensile force is applied.

In the flexible process, the web 5 is heated on the support 3 and the solvent is evaporated from the support 3 until the web 5 is peelable by the peeling roll 4. In order to evaporate the solvent, a method of blowing air from the web side, a method of transferring heat from the back surface of the support 3 by liquid, a method of transferring heat from the front and back by radiant heat, and the like may be used alone or in combination .

(S3: peeling step)

In the above-mentioned softening step, the web 5 is dried and solidified or coagulated until the web 5 becomes peelable film strength on the support 3, and then in the peeling step, the web 5 is peeled off 4). The peeled web 5 constitutes a film base.

The amount of the residual solvent in the web 5 on the support 3 at the time of peeling is preferably in the range of 50 to 120 mass%, depending on the strength of the drying condition, the length of the support 3 and the like. If the web 5 is too soft when peeled off at a point where the amount of the residual solvent is larger, the planarity is deteriorated when peeling off, and wrinkles or vertical stripes are liable to occur due to peeling tension. Therefore, The amount of residual solvent is determined. Further, the amount of residual solvent is defined by the following formula.

(Mass%) = (mass before heat treatment of web - mass after heat treatment of web) /

(Mass after heat treatment of web) x 100

Here, the heat treatment at the time of measuring the residual solvent amount means that the heat treatment is performed at 115 캜 for one hour.

(S4: stretching process)

In the stretching step, the web 5 (film base) peeled off from the support 3 is stretched by the tenter 6 in the same direction as the transport direction. Therefore, the softening step of S4 constitutes a vertical stretching step of stretching the film substrate in one direction identical to the carrying direction. In the stretching process, a tenter system in which both side edges of the web 5 are fixed by a clip or the like and stretched is preferable because it improves the planarity and dimensional stability of the film. In addition, in the tenter 6, drying may be performed in addition to drawing.

(S5: drying step)

The web 5 stretched in the tenter 6 is dried in the drying device 7. In the drying apparatus 7, the web 5 is transported by a plurality of transport rolls arranged in a zigzag shape as viewed from the side, and the web 5 is dried therebetween. The drying method in the drying apparatus 7 is not particularly limited, and generally, the web 5 is dried using hot air, infrared rays, a heating roll, a microwave, or the like. From the viewpoint of simplicity, a method of drying the web 5 with hot air is preferred.

The web 5 is dried in the drying device 7, and then transported toward the winding device 10 as an optical film.

(S6; cutting step, S7: embossing step)

Between the drying device 7 and the winding device 10, a cutting portion 8 and an embossing portion 9 are arranged in this order. In the cut portion 8, a cutting process is performed in which the formed optical film is transported and both end portions in the width direction thereof are cut by a slitter. In the optical film, the portions remaining after cutting at both ends constitute a product portion to be a film product. On the other hand, the portion cut from the optical film is recovered as a shooter, and is reused as a part of the raw material to form a film.

After the cutting process, embossing (knurling) is carried out at both end portions in the width direction of the optical film by the embossing portion 9. The embossing is performed by pressing the heated embossing rollers on both ends of the optical film. Fine irregularities are formed on the surface of the embossing roller, and concave and convex portions are formed at both ends by pressing the embossing roller against both ends of the optical film. By such embossing, winding displacement and blocking (adhesion between films) in the next winding step can be suppressed as much as possible.

(S8; winding step)

Finally, the optical film on which the embossing has been finished is wound up by the winding device 10 to obtain the original roll (film roll) of the optical film. That is, in the winding step, a film roll is produced by winding the optical film on a winding core while conveying the optical film. As a method of winding the optical film, a commonly used winder may be used and there is a method of controlling a tension such as a constant torque method, a constant tension method, a taper tension method, and a program tension control method with a constant internal stress, You can use it. The winding length of the optical film is preferably 1000 to 7200 m. The width at that time is preferably 500 to 3200 mm, and the film thickness is preferably 30 to 150 mu m.

In the above description, the film base material stretched in one direction is obtained by longitudinal stretching in the course of film formation of the film base material. However, the film base material thus formed may be fed to a longitudinal stretching device And then longitudinal stretching is performed to obtain a stretched film base in one direction.

(For preferred longitudinal stretching)

In the above-described stretching step S4, the both ends of the film substrate are gripped by the gripping members in the tenter 6, and are stretched in the transport direction, thereby stretching the film base material by applying tension in the transport direction. In the stretching step, any means capable of imparting tensile force in the conveying direction to the unstretched film base can be used without particular limitation, and can be appropriately selected in accordance with the purpose. For example, longitudinal stretching may be performed using a tension applying means having a low-speed roll and a high-speed roll. It is preferable to use a tension applying means having a low-speed roll and a high-speed roll in that tension can be continuously applied to the film in the carrying direction.

When a tension applying means having a low speed roll and a high speed roll is used, a low speed roll is disposed on the upstream side in the transport direction of the film substrate, a high speed roll is disposed on the downstream side, By placing a major speed difference in these rolls, it is possible to impart a tensile force in the transport direction to the film substrate. The conveying speed of the film substrate is not particularly limited and can be appropriately selected in accordance with the purpose.

When the film base material is longitudinally stretched, longitudinal stretching is performed at a temperature higher than the glass transition temperature Tg of the resin constituting the film base material by 5 DEG C or more. After the stretching, the film is transported to a temperature zone lower than Tg by 10 DEG C or more, It is preferable to quench. In this case, after stretching in the longitudinal direction, a film base material having more uneven physical properties can be obtained.

Further, in the above-described Patent Document 2, longitudinal stretching is carried out under the condition that the change in physical properties of the film can be suppressed, and then oblique stretching is performed. In this embodiment, the film base material is longitudinally stretched so as to impart unevenness to the physical properties of the film. In this respect, the production method of this embodiment is different from the conventional production method.

&Lt; Other film forming method >

The film base material of the present embodiment can also be produced by a melt soft-film forming method. The melt soft-film-forming method refers to a method in which a composition containing a resin and an additive such as a plasticizer is heated and melted to a temperature at which fluidity is exhibited, and then the melt is fluidized to form a film. The method of forming by melt casting can be classified into a melt extrusion (molding) method, a press molding method, an inflation method, an injection molding method, a blow molding method, and a stretch molding method. Among them, the melt extrusion method is preferable in which a film having excellent mechanical strength and surface precision is obtained. Further, it is preferable that a plurality of raw materials used in the melt extrusion method are usually previously kneaded and pelletized.

After the film base material is formed by the melt soft film-forming method, the longitudinally stretched film base material can be obtained by stretching the film base material in one direction while conveying the film base material in one direction by a longitudinal stretching device (not shown).

[Film substrate]

In this embodiment, as the resin constituting the film base material, it is effective to use a resin (for example, a resin having a dimensional change rate of 0.01% or less by heating) less likely to cause dimensional fluctuation due to heating in an unstretched state. The rate of dimensional change due to heating refers to {(dimension after heating - dimension before heating) / (dimension before heating)} x 100. Examples of the resin which hardly undergo dimensional fluctuation due to heating include polycarbonate resin, cycloolefin resin (alicyclic olefin polymer), polyester resin, polyether sulfone resin, polyethylene terephthalate resin, Based resin, a polyarylate-based resin, a polyethylene-based resin, a polyethylene-based resin, a polyvinyl chloride-based resin, and an acrylic resin.

As the polycarbonate resin, various resins can be used without particular limitation. From the viewpoints of chemical properties and physical properties, aromatic polycarbonate resins are preferable, polycarbonates having a fluorene skeleton, bisphenol A- Polycarbonate resins are preferred. Among them, it is more preferable to use a bisphenol A derivative having a benzene ring, a cyclohexane ring and an aliphatic hydrocarbon group introduced into bisphenol A. Particularly preferred is a polycarbonate resin having a structure in which anisotropy in a unit molecule is reduced, obtained by using a derivative in which the functional group is introduced asymmetrically to the central carbon of bisphenol A.

Examples of such polycarbonate resins include those obtained by replacing two methyl carbon groups in the center of bisphenol A with benzene rings and substituting asymmetrically the central hydrogen atoms in each benzene ring of bisphenol A with methyl groups or phenyl groups And a polycarbonate resin obtained by using one of them is particularly preferable. Specifically, 4,4'-dihydroxydiphenylalkane or a halogen substituent thereof is obtained by a phosgene process or an ester exchange process. For example, 4,4'-dihydroxydiphenyl methane, 4,4'- Dihydroxydiphenyl ethane, 4,4'-dihydroxydiphenyl butane, and the like. In addition, examples of a specific polycarbonate resin may be mentioned, for example, in JP-A-2006-215465, JP-A-2006-91836, JP-A- 2005-121813, Polycarbonate resins described in JP-A-2003-167121, JP-A-2009-126128, JP-A-2012-67300, WO-A-2000 / have.

The cycloolefin-based resin is not particularly limited as long as it is a resin having a unit of a monomer containing a cyclic olefin (cycloolefin). The cycloolefin-based resin may be either a cycloolefin polymer (COP) or a cycloolefin copolymer (COC). The cycloolefin copolymer refers to an amorphous cycloolefin resin that is a copolymer of a cyclic olefin and an olefin such as ethylene.

As the cyclic olefin, a polycyclic cyclic olefin and a monocyclic cyclic olefin exist. Examples of such polycyclic cyclic olefins include norbornene, methyl norbornene, dimethyl norbornene, ethyl norbornene, ethylidene norbornene, butyl norbornene, dicyclopentadiene, dihydrodicyclopentadiene, Methyldicyclopentadiene, dimethyldicyclopentadiene, tetracyclododecene, methyltetracyclododecene, dimethylcyclotetradodecene, tricyclopentadiene, tetracyclopentadiene, and the like. Examples of the monocyclic cyclic olefin include cyclobutene, cyclopentene, cyclooctene, cyclooctadiene, cyclooctatriene, cyclododecatriene, and the like.

Examples of the polyester-based resin include polyethylene terephthalate (PET) and polyethylene naphthalate (PEN). As the polyethylene naphthalate resin, for example, polyethylene naphthalate prepared by polycondensation of a lower alkyl ester of naphthalene dicarboxylic acid with ethylene glycol can be suitably used.

[additive]

To the film substrate, an additive may be added as required. Examples of the additives include plasticizers, ultraviolet absorbers, retardation-adjusting agents, antioxidants, deterioration inhibitors, release aids, surfactants, dyes, and fine particles. In the present embodiment, additives other than the fine particles may be added at the time of preparing the dope, or may be added at the time of producing the fine particle dispersion.

[Method and apparatus for producing oblique stretched film]

Next, a method and an apparatus for producing a long obliquely-drawn film using the above-described film substrate will be described.

(Overview of the device)

3 is a plan view schematically showing a schematic configuration of an apparatus for manufacturing an obliquely-drawn film 11. The production apparatus 11 includes a film feed section 12, a transport direction changing section 13, a guide roll 14, a stretching section 15, and a guide roll 12 in this order from the upstream side in the transport direction of the film substrate. A transporting direction changing section 17, and a film winding section 18. The transporting direction changing section 17 and the film winding section 18 are constituted by a transporting section 16, Details of the extension portion 15 will be described later.

The film feeding portion 12 feeds the film base material produced as described above to the stretching portion 15. The film feeding portion 12 may be configured separately from the manufacturing apparatus 1 of the film base shown in Fig. 1, or may be integrally formed. In the case of the former, the film substrate is taken out from the film feeding portion 12 by winding the film substrate on the winding core once and winding the film substrate (film roll) into the film feeding portion 12. On the other hand, in the latter case, after the film base material is formed, the film feeding portion 12 is fed to the stretching portion 15 without winding the film base material.

The carrying direction changing section 13 changes the carrying direction of the film base material fed out from the film feeding section 12 to the direction toward the entrance of the extending section 15 as the warp stretching tenter. The carrying direction changing section 13 includes a turn bar for changing the carrying direction by folding while transporting the film, for example, and a rotary table for rotating the turn bar in a plane parallel to the film.

By changing the carrying direction of the film base material in the carrying direction changing section 13 as described above, it is possible to make the entire width of the manufacturing apparatus 11 narrower. In addition to finely controlling the delivery position and angle of the film It becomes possible to obtain a long oblique stretched film having a small variation in film thickness and optical value. When the film feeding portion 12 and the feeding direction changing portion 13 are movable (slidable and pivotable), the right and left clips It is possible to effectively prevent defective binding of the film to the film.

The film feed portion 12 may be slidable and pivotable so that the film base can be fed to the entrance of the stretching portion 15 at a predetermined angle. In this case, it is also possible to adopt a configuration in which the installation of the transport direction changing section 13 is omitted.

At least one guide roll 14 is provided on the upstream side of the stretching portion 15 in order to stabilize the trajectory of the film base during traveling. Further, the guide roll 14 may be constituted by a pair of upper and lower rolls sandwiching the film, or a pair of rolls. The guide roll 14 closest to the entrance of the stretching portion 15 is a driven roll for guiding the traveling of the film and is rotatably supported by a bearing portion (not shown). As the material of the guide roll 14, known rollers can be used. In order to prevent the occurrence of scratches on the film, it is preferable to reduce the weight of the guide roll 14 by applying a ceramic coating to the surface of the guide roll 14, or chrome plating the light metal such as aluminum.

It is preferable that one of the rolls on the upstream side of the guide roll 14 closest to the entrance of the stretching portion 15 is nipped by pressing the rubber roll. By using such a nip roll, it is possible to suppress fluctuation of the tension force in the film flow direction.

A pair of bearing portions at both ends (left and right) of the guide roll 14 closest to the entrance of the stretching section 15 are provided with film tension detecting devices for detecting the tension generated in the film in the roll, A tension detecting device, and a second tension detecting device are provided, respectively. As the film tension detecting device, for example, a load cell can be used. As the load cell, a known type of tensile or compression type can be used. The load cell is a device that converts a load acting on a point of contact into an electric signal by a strain gauge provided on a strain body and detects the load.

The load cell is provided on the left and right bearing portions of the guide roll 14 closest to the entrance of the stretching portion 15 so that the force exerted by the film during running on the roll, And independently detects the tension in the left and right directions. In addition, a strain gauge may be provided directly on a support constituting a bearing portion of the roll, and the load, that is, the film tension may be detected based on deformation occurring in the support. The relationship between the generated strain and the film tension is measured in advance and is assumed to be known.

When the position and transport direction of the film supplied from the film feed portion 12 or the transport direction changing portion 13 to the stretching portion 15 are shifted from the position toward the entrance of the stretching portion 15 and the transport direction, A difference occurs in the tension in the vicinity of the edge portions on both sides of the film in the guide roll 14 closest to the entrance of the stretching portion 15 in accordance with the displacement amount. Therefore, by detecting the tension difference by installing the film tension detecting device as described above, it is possible to determine the degree of the deviation. That is, if the conveying position and the conveying direction of the film are proper (the position and direction toward the entrance of the extending portion 15), the load acting on the guide roll 14 is roughly equalized at both ends in the axial direction However, if it is not proper, difference in film tension occurs between right and left.

Therefore, in order to equalize the film tension difference between the left and right sides of the guide roll 14 closest to the entrance of the stretching section 15, for example, the film direction and the film thickness direction are changed by the transport direction changing section 13, It is possible to stabilize gripping of the film by the gripping tool at the entrance portion of the stretching portion 15 and to reduce the occurrence of troubles such as peeling of the gripping tool. Further, it is possible to stabilize the physical properties of the film in the width direction after the warp stretching by the stretching portion 15.

At least one guide roll 16 is provided on the downstream side of the stretching section 15 in order to stabilize the trajectory at the time of running of the warp stretched film in the stretching section 15.

The carrying direction changing section 17 changes the film carrying direction after stretching, which is carried from the stretching section 15, in the direction toward the film winding section 18. [

Here, the film advancing direction at the entrance of the elongating section 15 and the film advancing direction at the exit of the elongating section 15 are set so as to correspond to the fine adjustment of the orientation angle (the direction of the in-plane slow axis in the film) It is necessary to adjust the angle. In order to adjust the angle, the direction in which the film is formed is changed by the transporting direction changing section 13 to guide the film to the entrance of the stretching section 15 and / or the film from the exit of the stretching section 15 It is necessary to change the traveling direction of the film by the carrying direction changing section 17 so as to return the film to the direction of the film winding section 18. [

Further, it is preferable to continuously perform film formation and warp stretching in view of productivity and yield. In the case where the film forming process, the warp stretching process, and the winding process are continuously performed, the traveling direction of the film is changed by the carrying direction changing section 13 and / or the carrying direction changing section 17, As shown in Fig. 3, the moving direction of the film fed from the film feeding portion 12 and the film advancing direction immediately before being wound by the film winding portion 18 Winding direction), it is possible to reduce the width of the entire device with respect to the film advancing direction.

It is not necessary that the film advancing direction in the film forming process and the winding process necessarily coincides with each other. However, in order to provide a layout in which the film feeding portion 12 and the film winding portion 18 do not interfere, Or the carrying direction changing section 17 to change the traveling direction of the film.

The above-described transport direction changing unit 13 · 7 can be realized by a known method such as using an air flow roll or an air turn bar.

The film take-up portion 18 is for winding a film conveyed from the stretching portion 15 through the conveying direction changing portion 17, and is constituted by, for example, a winder device, an algebraic device, a drive device or the like. It is preferable that the film take-up portion 18 is a structure that can slide in the lateral direction so as to adjust the winding position of the film.

The film take-up portion 18 is capable of finely controlling the take-in position and angle of the film so that the film can be pulled at a predetermined angle with respect to the exit of the stretching portion 15. [ This makes it possible to obtain a long oblong stretched film having a small variation in film thickness and optical value. Further, wrinkle generation of the film can be effectively prevented, and at the same time, the winding-up property of the film is improved, so that the film can be wound up a long time.

The film take-up portion 18 constitutes a pulling portion for pulling the film stretched and conveyed by the stretching portion 15 with a predetermined tension. Between the stretching portion 15 and the film take-up portion 18, there can be provided a pulling roll for pulling the film at a constant tension, or a cutting device for cutting the film at a predetermined length. The guide roll 16 described above may also have the function of the pulling roll.

In the present embodiment, it is preferable that the film pulling tension T (N / m) after stretching is adjusted to be 50 N / m <T <300 N / m, preferably 150 N / m <T <250 N / m. When the pulling tension is 50 N / m or less, sagging and wrinkling of the film tend to occur, and the profile of the retardation and the orientation angle in the film width direction is also deteriorated. On the other hand, when the pulling tension is 300 N / m or more, the variation of the orientation angle in the film width direction is deteriorated and the width yield (acquisition efficiency in the width direction) is deteriorated. In addition, in the present embodiment, by satisfying the above-mentioned conditional expression, it is possible to suppress the wavy deformation of the film end portion after warp stretching, so that it can be wound without generating wrinkles even at a low tension of 50 to 100 N / m.

In the present embodiment, it is preferable to control the fluctuation of the take-up tension T at an accuracy of less than ± 5%, preferably less than ± 3%. If the variation of the take-up tension T is ± 5% or more, fluctuations in the optical characteristics in the width direction and the flow direction (transport direction) become large. As a method of controlling the fluctuation of the take-up tension T within the above range, a load applied to the first roll (guide roll 16) on the exit side of the stretching section 15, that is, the tensile force of the film is measured, The rotation speed of the take-up roll of the take-up roll or film take-up portion 18 is controlled by a general PID control method. As a method for measuring the load, there is a method in which a load cell is provided in the bearing portion of the guide roll 16 and the load applied to the guide roll 16, that is, the tensile force of the film is measured. As the load cell, a known type of tensile type or compression type can be used.

The film after stretching is gripped by the gripping tool of the stretching portion 15 and discharged from the outlet of the stretching portion 15. After both ends (both sides) of the film gripped by the gripping tool are trimmed, And wound around a winding core (winding roll) to form a winding body of a long warp stretched film. Further, the trimming may be performed as necessary.

Further, before winding the long oblong stretched film, for the purpose of preventing blocking between the films, the masking film may be superposed and wound on the long oblong stretched film at the same time, or at least one of the long oblong stretched films Tape or the like may be wound while being joined to the end portions of both ends. The masking film is not particularly limited as long as it can protect the long warp stretched film. Examples of the masking film include a polyethylene terephthalate film, a polyethylene film, and a polypropylene film.

(Details of extension section)

Next, the above-described stretching portion 15 will be described in detail. 4 is a plan view schematically showing an example of the rail pattern of the extending portion 15. Fig. However, this is merely an example, and the configuration of the extending portion 15 is not limited to this.

The slant stretching film in the present embodiment is produced by using a tenter (slant stretching machine) capable of warp stretching as the stretching portion 15. [ The tenter is a device for heating a film base material to an arbitrary stretchable temperature and obliquely stretching the film base material. This tenter is provided with a number of holding tools Ci · Co (see FIG. 4 (a)) for traveling the heating zone Z, a pair of right and left rails Ri · Ro and a rail Ri · Ro, Only one set of gripping tools is shown). Details of the heating zone Z will be described later. Each of the rails Ri and Ro is constituted by connecting a plurality of rail portions by connecting portions (white circles in Fig. 4 are examples of connecting portions). The gripping tool Ci · Co is constituted by a clip holding both ends in the width direction of the film.

4, the feeding direction D1 (corresponding to the direction E1 in Fig. 7) of the film substrate is different from the winding direction D2 (corresponding to the direction E2 in Fig. 7) of the elongated oblong drawn film after stretching, I &lt; / RTI &gt; between the direction D2 and the direction D2. The leading angle? I is in a range of more than 0 ° and less than 90 °, and can be set arbitrarily at a desired angle.

As described above, since the feeding direction D1 and the winding direction D2 are different from each other, the rail pattern of the tenter is asymmetrical in the right and left directions. The rail pattern can be manually or automatically adjusted in accordance with the orientation angle (?) Given to the long obliquely drawn film to be produced, the stretching magnification, and the like. In the warp 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 are freely set and the rail pattern can be arbitrarily changed.

In the present embodiment, the gripping tool Ci · Co of the tenter is driven at a constant speed while maintaining a certain distance from the gripping tools Ci · Co of the front and rear. The traveling speed of the gripping tool Ci · Co can be appropriately selected, but is usually 1 to 150 m / min. The difference in the running speed of the pair of gripping tools Ci · Co on the left and right is usually 1% or less, preferably 0.5% or less, 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 exit of the stretching process, wrinkles and leaning occur at the exit of the stretching process, so that the speed difference between the left and right gripping tools Ci · Co is required to be substantially the same Because. In a general tenter apparatus or the like, due to the period of the teeth of the sprocket for driving the chain, the frequency of the drive motor, etc., there is a speed variation occurring on the order of seconds or less, This does not apply to the speed difference described in Fig.

In a warp stretcher used in the production method of the present embodiment, a rail for regulating the locus of the gripping tool is often required to have a large bending rate, particularly at a position where the conveyance of the film becomes oblique. For the purpose of avoiding interference between gripping tools caused by sudden bending or local concentration of stress, it is desirable that the locus of the gripping tool curve in the bent portion.

As described above, the oblique stretching tenters used for imparting the oblique directional orientation to the film base material can freely set the orientation angle of the film by variously changing the rail pattern, and the orientation axis (slow axis) Can be uniformly left-right uniformly spread over the film width direction, and the film thickness and retardation can be controlled with high precision.

Next, the drawing operation in the stretching section 15 will be described. Both ends of the film substrate are gripped by gripping tools (Ci · Co) on the left and right sides and transported in the heating zone (Z) according to the running of the gripping tool (Ci · Co). The gripping tools Ci and Co on the left and right are opposed to each other in a direction substantially perpendicular to the advancing direction D1 of the film at the entrance portion (position A in the drawing) of the stretching portion 15 , And left and right asymmetric rails (Ri and Ro), respectively, and the film gripped at the exit portion (position B in the figure) at the end of drawing is opened. The film released from the gripping tool Ci · Co is wound on the winding core in the film winding portion 18 described above. Each of the pair of rails Ri and Ro has a continuous trajectory of an endless shape and the gripping tool Ci · Co that has opened the grip of the film at the exit of the tenter runs the outer rail, To be returned to the bottom.

In this case, since the rails Ri and Ro are asymmetric in the left and right directions, the left and right holding tools Ci and Co, which are opposed to each other at the position A in the figure, travel on the rails Ri and Ro The gripping tool Ci that travels on the rail Ri side (in the course side) becomes a preceding positional relationship with the gripping tool Co running on the rail Ro side (outcourse side).

That is, the gripping tool Ci of one of the gripping tools Ci · Co opposed to each other in the direction substantially perpendicular to the feeding direction D1 of the film at the position of A B, the straight line connecting the gripping tool Ci 占 경 is inclined by an angle? L with respect to a direction substantially perpendicular to the winding direction D2 of the film. As a result of the above cauterization, the film substrate is obliquely elongated at an angle? L with respect to the width direction. Here, the term &quot; substantially perpendicular &quot;

Next, the details of the heating zone Z will be described. The heating zone Z of the stretching section 15 is composed of a preheating zone Z1, a stretching zone Z2 and a heat fixing zone Z3. In the stretching section 15, the film gripped by the holding tool Ci 占 통과 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 partitioned by partition walls, and the stretching zone Z2 and the heat fixing zone Z3 are partitioned by partition walls.

The preheating zone Z1 is a zone in which the holding tool Ci · Co holding both ends of the film at the inlet of the heating zone Z travels with a constant interval from left to right (in the film width direction) Lt; / RTI &gt;

The stretching zone Z2 indicates a section from the beginning of the interval of the gripping tools Ci · Co holding the both ends of the film to a predetermined interval. At this time, the oblique stretching as described above is carried out, but it may be stretched in the longitudinal direction or in the transverse direction before and after oblique stretching, if necessary.

The heat fixing zone Z3 is a section in which the interval between the gripping tools Ci and Co is constant after the stretching zone Z2 and the gripping tools Ci and Co at both ends are running parallel to each other Indicates a section.

The stretched film may pass through a section (cooling zone) where the temperature in the zone is set to be equal to or lower than the glass transition temperature Tg (占 폚) of the thermoplastic resin constituting the film after passing through the heat fixing zone Z3. At this time, in consideration of shrinkage of the film due to cooling, a rail pattern may be used which narrows the interval of the holding tool Ci · Co facing in advance.

The temperature of the preheating zone Z1 is from Tg to Tg + 30 占 폚, the temperature of the stretching zone Z2 is from Tg to Tg + 30 占 폚, the heat fixing zone Z3 and the cooling zone The temperature is preferably set at Tg-30 to Tg + 20 deg.

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 100 to 400 mm, 150%, and the length of the heat fixing zone Z3 is usually 50 to 100%.

When the width of the film before stretching is Wo (mm) and the film width after stretching is W (mm), the stretch ratio R (W / W0) in the stretching step is preferably 1.3 to 3.0, more preferably Is from 1.5 to 2.8. When the stretching magnification falls within this range, thickness irregularity in the width direction of the film becomes small, which is preferable. In the stretching zone Z2 of the oblique stretching tenter, if the stretching temperature in the width direction is made different from the stretching temperature in the width direction, the thickness nonuniformity in the width direction can be set to a better level. Further, the draw ratio R is equal to the magnification (W2 / W1) when the interval W1 between both ends of the clip gripped by the tenter inlet portion becomes equal to the interval W2 at the tenter outlet portion.

&Lt; Quality of long oblique stretched film >

In the obliquely-drawn film obtained by the production method of the present embodiment, the orientation angle? Is inclined to a range of, for example, greater than 0 ° and less than 90 ° with respect to the winding direction. In a width of at least 1300 mm, Plane retardation Ro is less than 3 nm, and the variation of the orientation angle? Is small. The in-plane retardation value Ro (550) measured at a wavelength of 550 nm of the warp stretched film is preferably in a range of 120 nm to 160 nm, more preferably in a range of 130 nm to 150 nm.

That is, in the warp stretched film obtained by the production method of the present embodiment, the fluctuation of the in-plane retardation Ro is preferably less than 3 nm and not more than 1 nm at least at 1300 mm in the width direction. When the fluctuation of the in-plane retardation Ro is in the above range, for example, when an obliquely-stretched film is bonded to a polarizer to form a circularly polarizing plate and this is applied to an organic EL image display apparatus, It is possible to suppress color unevenness. Further, when the obliquely drawn film is used, for example, as a retardation film for a liquid crystal display device, the display quality can be made good.

In the warp stretched film obtained by the production method of the present embodiment, the variation of the orientation angle? Is preferably 1.0 deg. Or less, preferably 0.5 deg. Or less, at most 1300mm in the width direction, Most preferred. When an obliquely stretched film having a variation of an orientation angle? Of more than 0.5 is bonded to a polarizer to form a circularly polarizing plate and this film is provided in an image display apparatus such as an organic EL display device, light leakage occurs, .

The in-plane retardation Ro of the warp stretched film obtained by the production method of this embodiment is selected according to the design of the display device to be used. Ro is a value obtained by multiplying the difference between the refractive index nx in the in-plane slow axis direction and the refractive index ny in the plane perpendicular to the slow axis in the plane (Ro = (nx-ny) xd )to be.

The average thickness of the warp stretched film obtained by the production method of the present embodiment is 10 to 200 占 퐉, preferably 10 to 80 占 퐉, and more preferably 15 to 60 占 퐉 in view of mechanical strength and the like. The thickness unevenness of the warp stretched film in the width direction is preferably less than 3 占 퐉 and more preferably 2 占 퐉 or less because it affects the winding ability of the winding.

[Example]

Specific examples and examples of the warp stretched film according to the present embodiment will now be described with reference to comparative examples. The present invention is not limited to the following examples.

&Lt; Example 1 >

(Acquisition of film substrate before warp stretching)

A polycarbonate resin having a glass transition temperature Tg (hereinafter, simply referred to as Tg) of 138 占 폚 and a dimensional change ratio of 0.001% before and after the heat treatment at a film thickness of 100 占 퐉, a width of 1000 mm and a Tg + 5 占 폚 A film substrate was prepared. Then, in the longitudinal stretching apparatus, the film base was wound vertically (stretched in the conveying direction) at a stretching temperature Tg + 20 ° C and a stretching ratio of 1.1 times to obtain a roll body (film roll) of the film base before warping and stretching.

(Measurement of dimensional change rate T1)

A sample of the film base material before the warp stretching was taken from the film roll, and the film base material before the oblique stretching was cut out by the following method according to JIS K 7133: 1999 (JIS is abbreviated to Japanese Industrial Standards) The dimensional change rate T1 was measured.

That is, as shown in Fig. 5, the film base before the warp and stretch was cut out from the film roll at 120 mm x 120 mm square, and a line having a width of 50 mm was drawn in the feed direction and the vertical direction (width direction) , A square of 50 mm was drawn, and then the dimension of the feeding direction (corresponding to A1) was measured with a dimension reader (IM-6120 manufactured by KYENCE CORP.). Subsequently, the film substrate was heat-treated by heating it for 90 seconds by setting it to Tg + 5 DEG C in an oven (AS ONE made by DO-600FPA) without applying tension to the film substrate, (In order not to change the dimension), and the dimension of the feeding direction (corresponding to the dimension A2) was measured with the above-mentioned dimension reader. Then, the dimensional change rate T1 (%) of the film base material was calculated based on the following formula.

T1 = {(A2-A1) / A1} x100

A1: Dimension in one direction (feeding direction) before heat treatment of the film base material (mm)

A2: Dimension in one direction (feeding direction) after heat treatment of the film base material (mm)

(Production of warp stretched film)

The film roll obtained above was set in a warp stretcher and the film base was fed, and the film base was heated to a preheating temperature through a preheating zone before oblique stretching. Thereafter, the film base was passed through a stretching zone to obliquely stretch at a stretch magnification of 2.5, An oblique stretched film having a film thickness of 50 탆, a width of 1500 mm and an orientation angle (?) (Angle with respect to the width direction) = 44.8 占 was produced. The prepared warp stretched film was wound into a film roll. The preheating temperature in the preheating zone was set at Tg + 30 占 폚, which is not less than the drawing temperature (Tg + 10 占 폚) during the warp stretching.

(Measurement of dimensional change rate T2)

A sample of the obliquely drawn film was taken from the film roll, and the dimensional change rate T2 of the obliquely drawn film was measured in the same manner as the measuring method of the dimensional change rate T1 of the film substrate.

That is, from the film roll, the obliquely drawn film was cut into a 120 mm x 120 mm square, and a mark having a width of 50 mm in the direction of feed (the same direction as that of the film base before stretching) and a square of 50 mm (Corresponding to the dimension B1) was measured by a dimension reader (IM-6120 manufactured by KYENCE CORPORATION). Subsequently, heat treatment for heating for 90 seconds was performed by setting the temperature at Tg + 5 占 폚 in a state where tension was not applied to the obliquely drawn film using an oven (AS ONE made DO-600FPA), and the drawn obliquely- , And the dimension (corresponding to the dimension B2) of the feeding direction was measured with the above-mentioned dimension reader. Then, on the basis of the following expression, the dimensional change rate T2 (%) of the warp stretched film was calculated.

T2 = {(B2-B1) / B1} x100

B1: Dimension (mm) of one direction of the obliquely drawn film before heat treatment (direction of film substrate feeding)

B2: Dimension (mm) in one direction (film feeding direction) after heat treatment of the warp stretched film

&Lt; Examples 2 to 7 and Comparative Examples 1 to 3 >

An obliquely stretched film was produced in the same manner as in Example 1 except that the resin constituting the film substrate, the stretching magnification at the time of longitudinal stretching of the film substrate, the preheating temperature at the oblique stretching step and the stretching temperature were changed as shown in Table 1 And the dimensional change rate T1 of the film substrate and the dimensional change rate T2 of the obliquely drawn film were measured.

<Evaluation>

(Wave shape transformation)

The slit was cut in the longitudinal direction for 1 m, and the film was allowed to stand on a horizontal plane. The slit was peeled off at 23 ° C and 55 RH% Humidity) for 24 hours or more, and the central portion of the width of the film was brought into close contact with the flat surface. Then, the amount (maximum value) at which both ends of the width of the film were lifted from the flat surface was measured at intervals of 100 mm in the longitudinal direction, and the average value thereof was calculated. The wavy deformation was evaluated based on the following evaluation criteria.

"Evaluation standard"

?: The average value of the floating amount is 2 mm or less.

?: The average value of the floating amount is larger than 2 mm and not larger than 5 mm.

?: The average value of the floating amount is larger than 5 mm and 8 mm or less.

X: The average value of the floating amount is larger than 8 mm (there is a problem).

(Uniformity of orientation angle)

The obliquely stretched film thus produced was slitted by gripping a clip (an area of 150 mm from the end), and the film after slitting was cut 1 m in the longitudinal direction to stand on a horizontal plane, and 24 Over a period of time to cool and stabilize. The orientation angle [theta] was measured at the center portion and the end portion in the width direction of the film using an Ro measuring apparatus (AXOSCAN manufactured by Axometrics), and the variation of the orientation angle [theta] in the width direction And the uniformity of the orientation angle in the width direction was evaluated based on the following evaluation criteria.

"Evaluation standard"

?: The variation of the orientation angle? In the width direction is 1.0 占 or less.

?: Variation of the orientation angle? In the width direction is larger than 1.0 占 and 1.5 占 or less.

?: Variation of the orientation angle? In the width direction is larger than 1.5 占 and 2 占 or less.

X: Variation of the orientation angle? In the width direction is larger than 2 占 (there is a problem).

(Degree of deterioration of the retardation Ro in the surface after the endurance test)

The obliquely stretched film thus produced was slitted by gripping a clip (an area of 150 mm from the end), and the film after slitting was cut 1 m in the longitudinal direction to stand on a horizontal plane, and 24 Over a period of time to cool and stabilize. Then, the in-plane retardation Ro was measured at a plurality of positions in the width direction of the film using an Ro measuring apparatus (AXOSCAN manufactured by Axometrics), and the average value Ro1 (mm) of in-plane retardation Ro was calculated.

Thereafter, the film was allowed to stand in an environment of 80 ° C. dry for 500 hours, returned to an environment of 23 ° C. and 55 RH%, stabilized for 24 hours or more, and stabilized (endurance test). After this endurance test, the in-plane retardation Ro was measured at a plurality of locations in the width direction of the film using the Ro measuring apparatus, and the average value Ro2 of the in-plane retardation Ro was calculated to calculate the average value (Ro1-Ro2) were obtained. Then, the degree of deterioration of the in-plane retardation Ro after the endurance test was evaluated based on the following evaluation criteria.

"Evaluation standard"

?: Ro1-Ro2 is within 5 nm.

?: Ro1-Ro2 is larger than 5 nm and 7 nm or less.

X: Ro1-Ro2 is larger than 7 nm (there is a problem).

Table 1 shows the production conditions of the warp stretched films in Examples 1 to 7 and Comparative Examples 1 to 3 and the results of the evaluation on the oblique stretched films produced. In Table 1, PC denotes a polycarbonate resin, COP denotes a cycloolefin resin, PEs denotes a polyester resin (PET (polyethylene terephthalate resin) in this case), Tg denotes a glass And the transition temperature. When the longitudinal stretching magnification is negative, it indicates that transverse stretching (stretching in the film width direction) is being performed.

From Table 1, in Comparative Examples 1 and 3, the evaluation of the wave shape deformation became poor (X). In Comparative Example 1, it was impossible to give the film base material the property of shrinking in the conveying direction (drafting direction) before the warp stretching without performing the longitudinal stretching before warp stretching, Shrinkage due to heat of the film base material can not follow shrinkage, and consequently, wave-like deformation occurs in the film edge portion. In Comparative Example 3, since the transverse stretching was performed before the warp stretching, it was impossible to give the film substrate a shrinking property in the conveying direction (feeding direction) before the warp stretching. As a result, It is considered that deformation has occurred. Particularly in Comparative Example 3, T1 was increased by transverse stretching, so that the wavy deformation occurred at the film end portion after the warp stretching became larger than that of Comparative Example 1. As a result, the film width central portion, It is considered that a large variation of the orientation angle occurred between the film ends.

Further, in Comparative Example 2, the degree of decrease in in-plane retardation Ro after the endurance test is large. In Comparative Example 2, since the dimensional change ratio T1 of the film base before and after the heat treatment was as large as -7.5% and the film base was shrunk excessively in the transport direction by longitudinal stretching, It is thought that the temperature is excessively shrunk in the above direction, and as a result, the decrease in the retardation Ro in the in-plane direction after the durability test is increased.

On the other hand, in Examples 1 to 7, good results (?,?,?) Were obtained in any of the wavy deformations of the film edge portions, the uniformity of orientation angles, and the degree of decrease in retardation Ro in the surface after the durability test lost. In Examples 1 to 7, since both of T1 <0%? T2 and -7.0% <T1? -0.5% are satisfied, a resin having low heat shrinkability such as PC, COP, (The same direction as the transport direction of the film substrate before the warp stretching) specific to the oblique stretching at the high temperature (stretching temperature) at the time of oblique stretching is suppressed by the mechanical shrinkage in the direction The contraction of. By this, it is considered that &quot; margin &quot; occurs in the end portion of the film and generation of wave-like deformation is suppressed. Further, it is considered that the wavy deformation of the film end portion is suppressed, and the occurrence of the variation in the orientation angle between the film width central portion where the wavy deformation is not originally generated and the film end portion is reduced.

Further, since the dimensional change ratio T1 of the film base material is converged within a predetermined range, shrinkage in the above-mentioned direction in the film base material after heat treatment is suitably suppressed. Thus, it is considered that the film base material does not excessively shrink in the above direction during oblique stretching, and the retardation Ro in the in-plane direction after the durability test is suppressed from being lowered.

It is also understood from the results of Examples 2 and 3 that when the preheating temperature of the film base before the warp stretching is equal to or higher than the stretching temperature at the warp stretching, the effect of suppressing the wave- It can be said that the reduction effect is high. This is because, prior to oblique stretching, a preheating temperature higher than the stretching temperature is imparted to the film substrate to efficiently heat shrink the film substrate at a predetermined stretching temperature during oblique stretching to cause mechanical shrinkage peculiar to oblique stretching, I think it is because I can surely pursue contraction.

The above-described method of producing the warp stretched film can be expressed as follows.

1. An oblique stretching process for producing an obliquely-stretched film by stretching the film base material in an oblique direction crossing the one direction and within the film plane by conveying the film substrate in one direction and bending the conveying direction in the middle, A method for producing a film,

The dimensional change rate of the film base material in the one direction when heat treatment is performed on each of the film base material and the warp stretched film before the oblique stretching is referred to as T1 (%), and the one direction of the obliquely- And the heat treatment is performed for 90 seconds at a glass transition temperature Tg + 5 占 폚 of the resin constituting the film base material,

A method for producing an oblique stretched film characterized by satisfying the following conditional expressions (1) and (2):

T1 < 0%? T2 (1)

-7.0% < T1? -0.5% (2)

only,

T1 = {(A2-A1) / A1} x100

T2 = {(B2-B1) / B1} x100

A1: the dimension (mm) of the film base in the one direction before the heat treatment;

A2: the dimension (mm) in the one direction after the heat treatment of the film base material,

B1: dimension (mm) of the obliquely-drawn film in the one direction before the heat treatment;

B2 is a dimension (mm) in the one direction after the heat treatment of the obliquely-

to be.

2. The film-forming method according to claim 1, further comprising a longitudinal stretching step of stretching the film base in one direction,

In the oblique stretching step, the warp stretched film according to (1), wherein the obliquely stretched film is stretched in the oblique direction by stretching the film base material stretched in the one direction in the longitudinal stretching step Gt;

3. In the oblique stretching step, the film substrate is heated to the pre-heating temperature before the oblique stretching,

The method of producing an oblique stretched film according to 1 or 2, wherein the preheating temperature is not lower than a stretching temperature at the time of oblique stretching.

4. The warp stretching according to any one of 1 to 3 above, wherein the resin constituting the film base material includes any of a polycarbonate resin, a cycloolefin resin and a polyester resin &Lt; / RTI &gt;

The present invention is applicable to the production of warp stretched films.

5: web (film substrate)

Claims (4)

A warp stretching film having an oblique stretching step of stretching the film base material in an oblique direction intersecting with the one direction and within the film plane by conveying the film base material in one direction and bending the conveying direction in the middle, And
The dimensional change rate of the film base material in the one direction when heat treatment is performed on each of the film base material and the warp stretched film before the oblique stretching is referred to as T1 (%), and the one direction of the obliquely- And the heat treatment is performed for 90 seconds at a glass transition temperature Tg + 5 占 폚 of the resin constituting the film base material,
A method for producing an oblique stretched film characterized by satisfying the following conditional expressions (1) and (2):
T1 < 0%? T2 (1)
-7.0% < T1? -0.5% (2)
only,
T1 = {(A2-A1) / A1} x100
T2 = {(B2-B1) / B1} x100
A1: the dimension (mm) of the film base in the one direction before the heat treatment;
A2: the dimension (mm) in the one direction after the heat treatment of the film base material,
B1: dimension (mm) of the obliquely-drawn film in the one direction before the heat treatment;
B2 is a dimension (mm) in the one direction after the heat treatment of the obliquely-
to be. The method according to claim 1, further comprising a longitudinal stretching step of stretching the film base in one direction,
Wherein in the oblique stretching step, the film base material stretched in the one direction in the longitudinal stretching step is stretched in the oblique direction to produce the obliquely stretched film. The method according to claim 1 or 2, wherein in the warp stretching step, the film substrate is heated to a preheat temperature before warping and stretching,
Wherein the preheating temperature is not lower than a stretching temperature at the time of oblique stretching. The film substrate according to any one of claims 1 to 3, wherein the resin constituting the film substrate comprises a polycarbonate resin, a cycloolefin resin, and a polyester resin, Lt; / RTI &gt;

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