KR101645760B1 - Method for producing optical film, optical film, and apparatus for producing optical film - Google Patents

Abstract

Disclosed is a method for producing an optical film having no transverse unevenness by improving the releasability of a thermoplastic resin film from a touch roll, and an optical film and an optical film production apparatus manufactured by the above manufacturing method. A flexible process for extruding a melt containing a thermoplastic resin from the flexible die to the surface of a rotating support in the form of a film, and a nip pressurizing process for nipping the film-shaped melt extruded by the flexible process with a rotary support and a nip- , The releasability adjusting agent is applied to the surface of the nip pressurizing rotating body in order to improve releasability between the nipping pressurized rotating body and the film-like melt.

Description

TECHNICAL FIELD [0001] The present invention relates to a method of manufacturing an optical film, an optical film and an apparatus for manufacturing the optical film,

The present invention relates to a method for producing an optical film, an apparatus for producing the optical film and an optical film for producing an optical film containing a thermoplastic resin such as a cellulose resin by the melt-flexible film method.

Compared to a conventional CRT display device, a liquid crystal display device is widely used as a monitor in terms of space saving and energy saving. In addition, the spread of TVs is also in progress. Various optical films such as protective films for polarizing plates and retardation films are used for such liquid crystal display devices.

A protective film for a polarizing plate is a film for protecting a polarizing film attached to a polarizing film made of stretched polyvinyl alcohol or the like, and a film containing a thermoplastic resin such as a cellulose resin is used. Further, the retardation film is used for the purpose of enlarging a viewing angle and improving contrast, and is provided with retardation by stretching a film containing a thermoplastic resin such as a cellulose resin. Sometimes called optical compensation film.

Methods for producing such an optical film are roughly divided into a melt-flexible film-forming method and a solution-fluid-film-forming method. The former is a method in which a melt obtained by heating and melting a thermoplastic resin is plied on a support, cooled and solidified, and optionally stretched to form a film. The latter is a method in which a polymer is dissolved in a solvent, The solvent is evaporated, and if necessary, the film is stretched to form a film.

Conventionally, production by the solution flexible film forming method has been the mainstream for reasons such as that the uniformity of the film thickness is easy. However, since the solution flexible film forming method has a problem of requiring a large production facility due to the recovery of the solvent, the production of the optical film by the melt flexible film forming method free from such a problem has attracted attention.

On the other hand, these optical films are required to have optical performance, in particular, uniform retardation. In particular, monitor and TV have become larger and lighter in weight, and uniformity of retardation has become increasingly demanded, and the optical film has been required to be widened, thinned, and surface smoothly.

The production of the optical film by the melt flex film forming method is carried out by extruding a melt containing a thermoplastic resin such as a cellulose resin from the flexible die into a film on the surface of a rotating support (hereinafter also referred to as a cast roll) It is general to obtain a film by sandwiching and pressing the melt (hereinafter also referred to as a film) with a rotating support and a nip pressure rotary body (hereinafter also referred to as a touch roll). The surface of the touch roll is mirror-finished to increase the surface smoothness of the film.

In order to obtain an optical film having high uniformity of retardation, the pressure applied to the film affects the orientation state of the resin, and the retardation of the obtained film changes. Therefore, It is important to perform the pressurization.

However, with the widening of the optical film, the width of the flexible die is widened, making it difficult to clamp and press the extruded film-like molten material with a uniform pressure by the cast roll and the touch roll.

As a method for coping with such a problem, there is a method of uniformizing the pressure at the time of clamping and pressing by using an elastic roll (hereinafter also referred to as an elastic metal roll) having a metal cylinder on the outer periphery of the touch roll, A method has been proposed in which retardation unevenness is suppressed even if the pressing force of the cast roll and the touch roll is somewhat uneven by setting the temperature of the melt to be supplied to the cast roll from the flexible die to be higher than the conventional one.

Japanese Patent Application Laid-Open No. 2005-172940

However, when a touch roll having a mirror-finished surface is contact-pressed against a melt containing a thermoplastic resin extruded on a cast roll, the peeling failure of the film from the touch roll is liable to occur, and streaks Transverse stain) may occur in some cases. Further, when the elastic metal roll is used as the touch roll or when the temperature of the melt is set at a high temperature as in the case of Patent Document 1, the adhesion to the touch roll is further increased to cause peeling failure and more likely to cause transverse unevenness, There was a problem of getting bigger.

Accordingly, an object of the present invention is to provide an optical film production method which improves the releasability of a film from a touch roll and does not cause transverse unevenness or retardation unevenness, an optical film production apparatus, and an optical film produced by the above- .

In order to solve the above problems, the present invention has the following features.

1. A flexible process for extruding a melt containing a thermoplastic resin from a flexible die into a film on a surface of a rotary support,

And a nip pressurizing step of nip-pressing the film-shaped melt extruded in the above-mentioned softening step with the rotary support and the nip pressure rotary body,

Wherein a releasability adjusting agent is applied to the surface of the nip pressurizing rotating body so as to improve releasability of the nip pressurizing rotating body and the film-like melt.

2. The process for producing an optical film as described in 1 above, wherein the releasability adjusting agent comprises the same material as at least one of the additives contained in the melt.

3. The method for producing an optical film as described in 1 or 2 above, wherein the releasability adjusting agent is an ultraviolet absorbing agent used for absorbing ultraviolet light inside the optical film.

4. The process for producing an optical film as described in any one of 1 to 3 above, wherein the releasability adjusting agent has a boiling point of 150 to 250 占 폚.

5. The method for producing an optical film according to any one of 1 to 4 above, wherein the thickness for applying the releasability adjusting agent is 0.05 to 1000 mu m.

6. The method according to any one of the above items 1 to 4, wherein the contact angle S1 of the surface of the rotating support body and the contact angle S2 of the surface of the nip pressurizing rotating body after application of the releasability adjusting agent is in a range of 0.5 DEG & To (5).

7. A method of manufacturing a film-like molten metal sheet, comprising: conveying tension T1 of the film-like molten material in a state in which the nip pressure rotating body is pressed against the rotating support body; The method for producing an optical film as described in any one of 1 to 6 above, wherein the difference (T1-T2) of the transporting tension T2 is 1 to 250 N.

8. The method for producing an optical film as described in any one of 1 to 7 above, wherein the thermoplastic resin is a cellulose ester-based resin.

9. An optical film produced by the method for producing an optical film according to any one of 1 to 8 above.

10. A process for producing a film, comprising: a flexible die for extruding a melt containing a thermoplastic resin into a film on a surface of a rotary support; and a nip pressurizing means for nipping and pressing the film-shaped melt extruded by the flexible die with the rotary support and a nip- And a releasability adjusting agent applying device for applying a releasability adjusting agent for improving the releasing property of the nip pressurizing rotator and the film-like melt to the surface of the nip pressure rotary body, Wherein the optical film has a thickness of 10 mm.

According to the present invention, after the releasability adjusting agent is applied to the surface of the nip pressurizing rotating body, the film-like molten material is sandwiched and pressed between the rotating support body and the nip pressure rotary body, so that the releasability of the film from the nipping and pressing rotary body is improved. Therefore, there can be provided a production method of an optical film, a production apparatus of an optical film and an optical film produced by the production method in which transverse unevenness and unevenness of retardation do not occur when the film peels from the nip pressurized rotating body.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic view of a softening step and a nip pressurizing step using the method for producing an optical film of the present invention.
Fig. 2 is a schematic view showing an embodiment of a method for producing an optical film of the present invention.

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings, but the present invention is not limited thereto.

In the method for producing an optical film of the present invention, it is preferable that the method of producing an optical film includes a softening step of extruding a melt containing a thermoplastic resin from a flexible die onto a surface of a rotating support (cast roll) in a film form, And a nip pressurizing step of nip pressing with a rotating support and a nip pressurizing rotator (touch roll), characterized in that the releasing properties of the nip pressurizing rotator and the film-like melt are measured on the surface of the nip pressure rotary body The releasability adjusting agent is applied to improve the optical characteristics of the optical film.

Fig. 1 shows a schematic view of a softening step and a nip pressurizing step of a manufacturing apparatus according to an embodiment using the manufacturing method of the optical film of the present invention. As a flexible process, a melt (Y) containing a thermoplastic resin is extruded from the flexible die 4 as a flexible means to the position P1 on the cast roll 5. At this time, on the surface of the touch roll 6, the releasability adjusting agent 104 is applied by the releasability adjusting agent applying device 100 on the upstream side of the position of the clamping pressing portion P2. The molten metal Y extruded from the flexible die 4 to the position P1 on the cast roll 5 is held by the touch roll 6 and the cast roll 5 as the nip pressurizing means at the position P2 as the nip pressurizing step, Lt; / RTI > The nip pressurized melted material is transferred to the cast roll 5 in the form of a film, peeled at the position P3, and the process proceeds to the next step.

The releasability adjusting agent applying device 100 is a device in which the releasing agent 104 in a liquid phase in a storage tank 105 heated to a predetermined temperature is pumped up by a lifting roller 102 and regulated by a regulating blade 103 in a predetermined amount , The releasability adjusting agent 104 on the post-regulation lifting roller 102 is transferred to the application roller 101 and is applied onto the touch roll 6.

As described above, the releasability adjusting agent is applied to the surface of the touch roll 6 before the nip pressurizing process, and then the nip pressurizing is performed by the cast roll 5 and the touch roll 6 in the nip pressurizing process, The adhesion of the film 5 to the touch roll 6 is greater than the adhesive force of the film and the touch roll 6 and the occurrence of peeling failure when the film is peeled from the touch roll 6 can be suppressed. Particularly, in order to increase the smoothness of the surface of the film, the surface of the touch roll 6 is mirror-finished, or when an elastic metal roll is used with a touch roll, and in order to eliminate pressure unevenness in the press- When the nip pressurization is performed at a high temperature, the peeling failure of the touch roll and the film tends to occur, but the peeling failure can be effectively eliminated by the present invention.

The releasability adjusting agent may be applied to both the surfaces of the touch roll 6 and the cast roll 5 and the releasability adjusting agent may be applied to both surfaces of the touch roll 6 and the cast roll 5, It is only necessary to adjust the adhesive force so as to be larger than the adhesive force between the film and the touch roll 6 so as to suppress the occurrence of peeling failure when the film is peeled from the touch roll 6.

The releasability adjusting agent according to the present invention is not particularly limited as long as it is a material for raising the releasability of the touch roll 6 and the film, and is preferably a material which does not adversely affect the optical film properties required for the product, . More preferably, the same material as the additive used in the optical film is preferably used as the releasability adjusting agent. Even if the releasability adjusting agent applied to the touch roll 6 is adhered to the surface of the optical film, there is almost no adverse effect on the optical film characteristics, and by using the releasability adjusting agent of the same material as the above additive, And the peeling failure of the film can be eliminated.

Specific examples of the releasability adjusting agent include silicone oil, dimethylsiloxane, dichloromethane, a plasticizer used as an additive for an optical film, and an ultraviolet absorber. In addition, a liquid phase in which fine particles of organic or inorganic materials are dispersed may be used.

The boiling point of the releasability adjusting agent is preferably 150 to 250 캜. When the boiling point is within this range, the surface temperature of the touch roll is lower than 150 占 폚 on the surface of the touch roll 6, so that the releasability adjusting agent becomes a liquid or solid state and functions as a releasability adjusting agent, The releasability adjusting agent which has been transferred to the surface of the film can be volatilized by making it stand higher than the boiling point in the process of becoming a high temperature such as a subsequent drawing step and the releasability adjusting agent is not left on the surface of the film.

As the releasability adjuster, an ultraviolet absorber is particularly preferable. The ultraviolet absorber exhibits high releasability, exhibits releasability in the thin layer as much as it is, and is therefore preferable in that the surface smoothness of the film released from the touch roll 6 is also increased. In addition, since it is a constituent material of an optical film originally used in addition to an optical film, even if it is incorporated into an optical film in the production process, it is less likely to affect the optical film characteristics.

The coating film thickness of the releasability adjusting agent applied to the surface of the touch roll is preferably 0.05 to 1000 mu m. The coating film thickness in this range is too small to cause coating defects or excessively thick, so that the releasability adjusting agent stays between the touch roller and the cooling rollers, so that there is little risk of occurrence of transverse unevenness or unevenness of the retardation of the film.

It is preferable that the contact angle S1 between the surface of the cast roll 5 and the water and the contact angle S2 of the surface of the touch roll 6 after application of the releasability adjusting agent are 0.5 deg. &Lt; S2-S1 < 100 deg. By setting the range of S2-S1 within this range, it is preferable that defective coating of the releasability adjuster occurs (less than 0.5 degrees) and that the coating unevenness of the releasability adjusting agent is less likely to become film film thickness unevenness (100 degrees or more).

The contact angle between the surface of the roll and the water is measured under a condition of 23 ° C and 50% RH using an automatic contact angle meter "CA-W type roll type" (manufactured by Kyowa Chemical Industry Co., Ltd.). The measurement is terminated within 5 to 30 seconds after the pure dropping in order to make both the change of the measurement value due to the evaporation of pure water and the stability of the measurement compatible. The measurement is based on the θ / 2 method of obtaining the contact angle from the angle with respect to the solid surface of a straight line connecting the left and right end points of the droplet with the apex. The measurement is taken from a direction perpendicular to the axial direction of the roller, and the dropping amount is set to 70 占..

The measurement points are measured at 12 points in total at four points in the circumferential direction at 90 degrees in each of three positions 5 cm from the center of the roll and the left and right ends, and this average value is defined as a contact angle.

The conveying tension of the film-like melt in the state in which the touch roll 6 is pressed against the cast roll 5 is T1 and the film tension of the film in the state in which the touch roll 6 is not pressed against the cast roll 5 It is preferable that the value of T1-T2 when the transporting tension of the melt is T2 is 1 to 250N. The measurement of the conveying tension is carried out by providing a load meter for measuring the load in the vertical direction at both ends of the axis of the roller nearest to the downstream side of the cast roll 5 and by pressing the touch roll 6 against the cast roll 5 If not, the difference between the respective load systems is calculated, and the total value is taken as the value of T1-T2.

When the value of T1-T2, which is the difference between the transporting forces, is in the above-mentioned range, there is no flapping of the film (a somewhat solidified film-like melt) when separated from the touch roll 6, It is possible to stably transport the film peeled off from the touch roll 6 because there is no risk of film thickness unevenness coming from the flap or breakage due to excessive tensile. Particularly, in the case of producing an optical film having a film thickness of 40 탆 or less, it is possible to carry out a more stable film transportation by making the peeling property from the touch roll 6 good and keeping the conveying tension within the above range, A smooth film free from unevenness or retardation unevenness can be obtained, which is preferable.

By using the manufacturing method of the optical film of the present invention as described above, the peeling failure between the touch roll and the film is eliminated, and the film surface is free of transverse unevenness (irregularities appear on the surface due to stripe- ) Or an optical film free from retardation unevenness can be obtained.

Particularly, when the surface of the touch roll is mirror-finished, an elastic metal roll is used with a touch roll, and the temperature of the melt extruded from the flexible die is increased, the stickiness of the touch roll and the film is increased. Method improves the peeling failure of the touch roll and the film and obtains an optical film free from the transverse unevenness of the surface of the film and unevenness of retardation.

Hereinafter, a method for producing an optical film according to the present invention will be described in detail.

In the method for producing an optical film according to the present invention, as a film forming method of a thermoplastic resin film, a film is formed by a melt soft film forming method in which a molten resin is formed by pliability.

The main material of the optical film according to the present invention is preferably one that is easy to manufacture, has good adhesion to a polarizing film, optically transparent, and the like.

The thermoplastic resin film having the above properties is not particularly limited, and examples thereof include a cellulose ester film such as a cellulose diacetate film, a cellulose triacetate film, a cellulose acetate butyrate film, a cellulose acetate propionate film, a polyester film , A polycarbonate film, a polyarylate film, a polysulfone (including polyethersulfone) film, a polyester film such as polyethylene terephthalate and polyethylene naphthalate, a polyethylene film, a polypropylene film, (Trade name, produced by Nippon Zeon Co., Ltd.), Zeonoa (trade name, manufactured by Nippon Zeon Co., Ltd.), polyvinyl alcohol film, ethylene vinyl alcohol film, syndiotactic polystyrene film, polycarbonate film, cycloolefin polymer film, Ltd.), polymethylphen A polyether ketone imide film, a polyamide film, a fluororesin film, a nylon film, a polymethyl methacrylate film, an acrylic film or a glass plate. Among them, a cellulose ester film, a cycloolefin polymer film, a polycarbonate film, and a polysulfone (including a polyethersulfone) film are preferable. In the present invention, in particular, a cellulose ester resin film or a cyclic olefin Is preferably a resin film containing 80% or more of an addition polymer in view of production cost, cost, transparency, adhesiveness, and the like.

The material constituting the optical film of the present invention includes these resins, a stabilizer, a plasticizer, an ultraviolet absorber, a matting agent as a lubricant, and a retardation control agent as necessary. These materials are appropriately selected depending on the required properties of the objective optical film.

When a cellulose resin is used as the material of the optical film of the present invention, the cellulose resin is preferably a cellulose resin having a cellulose ester structure and containing at least one of a fatty acid acyl group and a substituted or unsubstituted aromatic acyl group. (Hereinafter simply referred to as &quot; cellulose resin &quot;) and is amorphous. The term &quot; amorphous &quot; refers to a substance which is not a crystal in an irregular molecular arrangement but becomes a solid, and shows the crystal state at the time of raw materials.

The cellulose resin useful for the use of the present invention is exemplified in Japanese Patent Application Laid-Open No. 2007-98917, but is not limited thereto.

It is preferable that the cellulose resin used in the present invention has a small amount of foreign matter at the time of forming a film. A spots foreign material is a substance in which two polarizing plates are arranged orthogonally (Cross Nicol), a cellulose ester film is disposed therebetween, and when the slow axis of the polarizing plate protective film is positioned parallel to the transmission axis of the polarizing plate on one light source side Means a foreign substance causing leakage of light when observed at a position perpendicular to the surface of the other polarizing plate. At this time, it is preferable that the polarizing plate used for the evaluation is composed of a protective film free from foreign matters at a bright spot, and a glass plate is preferably used for protecting the polarizer. The reason why the esterified portion of the hydroxyl group contained in the cellulose resin is unreacted is considered to be one of the causes of the foreign matter of the spots, and the use of a cellulose resin having a small amount of foreign matter at the spots and filtering the heated and melted cellulose resin, Foreign matter can be reduced. In addition, the thinner the film thickness, the smaller the number of denuded foreign objects per unit area. The smaller the content of the cellulose resin contained in the film is, the smaller the amount of foreign matter in the denuded spot tends to be.

As the number of bright spots, to the area per 250㎜ ^2, polarization cross-Nicol state size of more than 5 to 50㎛ the bending point below 300, which is bent 50㎛ recognized by the zero point individual are preferred. And more preferably 200 or less of the luminous points of 5 to 50 mu m.

If the luminescent spot is large, the image of the liquid crystal display is seriously adversely affected. When the retardation film functions as a polarizing plate protective film, the presence of this luminescent spot is a factor of confusion of birefringence, and adverse effects on the image are large.

In the case where the foreign matter of the spots is removed by melt filtration, it is possible to carry out the step of forming the molten metal continuously, including the step of removing the foreign matter of the spots.

The melt soft film-forming method involving the filtration step of a foreign object by heat melting, in the case of using a plasticizer and a cellulose resin as a composition to be described later, as compared with a system to which a plasticizer is not added, This is a preferable method from the viewpoint of improving the removal efficiency of the foreign matters and avoiding pyrolysis. Further, as another additive to be described later, an ultraviolet absorber and a matte system suitably mixed can be similarly filtrated.

As the filter material, conventionally known ones such as glass fiber, cellulose fiber, filter paper, and fluororesin such as tetrafluoroethylene resin are preferably used, and ceramics, metal and the like are particularly preferably used. The absolute filtration accuracy is not more than 50 mu m, preferably not more than 30 mu m, more preferably not more than 10 mu m, further preferably not more than 5 mu m. These may be used in appropriate combination.

Uniform mixing of a constituent material other than the cellulose resin of the film constituting material with the resin can contribute to imparting a uniform melting property in the melting property upon heating.

A polymer material or oligomer other than a cellulose resin may be appropriately selected and mixed with a cellulose resin. Such a polymer material or oligomer is preferably excellent in compatibility with the cellulose resin and has a transmittance of 80% or more, preferably 90% or more, more preferably 90% or more, over the entire visible region (400 nm to 800 nm) 92% or more is obtained. The purpose of mixing at least one polymer material other than the cellulose resin or oligomer is to control the viscosity at the time of heating and melting and to improve film properties after film processing. These polymer materials and oligomers may be grasped as a concept as other additives.

Next, the additive used in the optical film will be described. These additives can be used as a releasability adjusting agent.

Preferable examples of the plasticizer include phosphate esters such as triphenyl phosphate, tricresyl phosphate, cresyldiphenyl phosphate, octyldiphenyl phosphate, diphenyl biphenyl phosphate, trioctyl phosphate and tributyl phosphate, Diethyl phthalate, dimethoxyethyl phthalate, dimethyl phthalate, dioctyl phthalate, dibutyl phthalate and di-2-ethylhexyl phthalate; in the glycolic acid ester type, triacetin, tributyrin, butyl phthalyl butyl glycolate, Ethyl phthalyl ethyl glycolate, methyl phthalyl ethyl glycolate, butyl phthalyl butyl glycolate and the like are preferably used.

The above plasticizers may be used in combination of two or more as necessary. In this case, it is preferable that the use ratio of the phosphoric acid ester-based plasticizer is 50 mass% or less, because it is difficult to cause the hydrolysis of the cellulose ester-based resin film and the durability is excellent. It is more preferable that the proportion of the phosphoric acid ester-based plasticizer is small, and it is particularly preferable to use only the phthalic acid ester-based or glycolic acid ester-based plasticizer.

The amount of the plasticizer to be added is preferably from 3 to 30% by mass, more preferably from 10 to 25% by mass, more preferably from 15 to 50% by mass with respect to the cellulose ester resin in order to make the water absorption rate and moisture content fall within a specified range. 25% by mass. If the addition amount of the plasticizer exceeds 30 mass%, the mechanical strength and dimensional stability of the cellulose ester based resin film deteriorate, which is not preferable.

As the antioxidant, a hindered phenol-based compound is suitable, and specific examples thereof include 2,6-di-t-butyl-p-cresol, pentaerythrityl-tetrakis [3- (3,5- (3-t-butyl-5-methyl-4-hydroxyphenyl) propionate], 1,6-hexanediol Bis (n-octylthio) -6- (4-hydroxy-3-hydroxyphenyl) propionate, Di-t-butyl anilino) -1,3,5-triazine, 2,2-thio-diethylenebis [3- (3,5- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, 1,3,5-trimethyl-2,4,6- Di-t-butyl-4-hydroxybenzyl) benzene and tris- (3,5-di-t-butyl-4-hydroxybenzyl) -isocyanurate. Particularly, 2,6-di-t-butyl-p-cresol, pentaerythrityl-tetrakis [3- (3,5- -Bis [3- (3-t-butyl-5-methyl-4-hydroxyphenyl) propionate]. Also, hydrazine-based metal inactivators such as N, N'-bis [3- (3,5-di-t-butyl-4- hydroxyphenyl) propionyl] hydrazine, -t-butylphenyl) phosphite may be used in combination. The amount of these compounds to be added is preferably 1 ppm to 1.0%, more preferably 10 to 1000 ppm, in mass ratio with respect to the cellulose ester resin in order to obtain the effect.

It is preferable to add an ultraviolet absorber to the cellulose ester resin film. As the ultraviolet absorber, it is preferable that the ultraviolet absorber has an ability of absorbing ultraviolet rays having a wavelength of not more than 370 nm, and that absorption of visible light having a wavelength of 400 nm or more is preferable as compared with a point of good liquid crystal display property.

In particular, the transmittance of ultraviolet rays at a wavelength of 370 nm is preferably 10% or less, more preferably 5% or less, and more preferably 2% or less.

Examples of the ultraviolet absorber to be used include oxybenzophenone compounds, benzotriazole compounds, salicylic ester compounds, benzophenone compounds, cyanoacrylate compounds, and nickel complex salt compounds. It does not.

It is preferable to use at least one of these ultraviolet absorbers, and at least two other ultraviolet absorbers may be contained.

The ultraviolet absorber preferably used is a benzotriazole-based ultraviolet absorber or a benzophenone-based ultraviolet absorber. A mode in which a benzotriazole-based ultraviolet absorber with less unnecessary coloring is added to the cellulose ester-based resin film is particularly preferable.

The method of adding the ultraviolet absorber may be added to the dope after the ultraviolet absorber is dissolved in an organic solvent such as alcohol, methylene chloride or dioxolane, or may be added directly to the dope composition. In the case of not dissolving in an organic solvent such as an inorganic powder, it is dispersed in an organic solvent and a cellulose ester resin using a dissolver or a sand mill and then added to the dope.

The amount of the ultraviolet absorber to be used is 0.1 to 2.5% by mass, preferably 0.5 to 2.0% by mass, and more preferably 0.8 to 2.0% by mass, with respect to the cellulose ester resin. If the amount of the ultraviolet absorber is more than 2.5% by mass, the transparency of the cellulose ester resin film tends to deteriorate.

In addition, fine particles may be added to the cellulose ester based resin film as a matting agent in order to prevent the films from sticking together or to impart slipperiness and to facilitate handling.

The kind of the fine particles may be an inorganic compound or an organic compound. Examples of the fine particles of the inorganic compound include fine particles such as silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide and tin oxide. Among these, a compound containing a silicon atom is preferable, and silicon dioxide fine particles are particularly preferable. As the silicon dioxide fine particles, for example, AEROSIL-200, 200V, 300, R972, R972V, R974, R976, R976S, R202, R812, R805, OX50, TT600, RY50, RX50, NY50 , NAX50, NA50H, NA50Y, NX90, RY200S, RY200, RX200, R8200, RA200H, RA200HS, NA200Y, R816, R104, RY300, RX300 and R106. Of these, AEROSIL-200V and R972V are preferable in terms of controlling the dispersibility and the particle size.

The average particle diameter of the fine particles in the film is preferably 50 nm to 2 mu m from the viewpoints of imparting slip properties and ensuring transparency. Preferably 100 nm to 1000 nm, and more preferably 100 nm to 500 nm. The average particle diameter in the film can be confirmed by photographing and observing a sectional photograph.

In the case of fine particles, there are many cases in which the primary particle diameter, the particle diameter after dispersion in the solvent, and the particle diameter after being added to the film often change. What is important is that the particle size of the fine particles, which are formed by aggregation with the cellulose ester- .

The amount of the fine particles to be added is 0.02 to 0.5 mass%, preferably 0.04 to 0.3 mass%, based on the cellulose ester resin film.

The additives added to these optical films are applied to the surface of the touch roll to make the tackiness of the touch roll and the film smaller than the tackiness of the cooling roll and the film so that the releasability of the touch roll and the film can be improved.

Fig. 2 is a schematic flow sheet of the first embodiment of the apparatus for carrying out the production method of the optical film of the present invention by using the melt soft film-forming method.

An embodiment in which the film (melt) initially contacts the surface of the cast roll 5 and the point P2 where the film contacts the surface of the touch roll (pinch roller) 6 are shown The point P1 at which the film first contacts the surface of the cast roll 5 and the point P2 at which the film contacts the surface of the touch roll (the nip and pressurized rotating body 6) There are also cases where the same. In addition, the film may reach P2 after first contacting the touch roll 6.

In the present embodiment, a film mixture containing a resin such as a cellulose resin is mixed to obtain a resin mixture, and then the mixture is melt-extruded from the flexible die 4 onto the cast roll 5 using the extruder 1. On the surface of the touch roll 6, a predetermined amount of the ultraviolet absorber is applied as the releasability adjuster 104 by the releasability adjusting agent application device 100. [ The melted material in the form of an extruded film is circumscribed to the cast roll 5 and pressed to the surface of the cast roll 5 by a touch roll 6 at a predetermined pressure. Further, it is circumscribed by the rolls of the cooling rolls 7, 8 in order, cooled and solidified, and peeled off by the peeling roll 9. The peeled film 17 is stretched in the longitudinal direction (conveying direction) and the transverse direction (width direction) of the film by the transverse stretching device 10 and the transverse stretching device 20 and then wound by the winding device 60 .

This will be described in detail below.

The melt containing the film-shaped thermoplastic resin extruded from the flexible die 4 is extruded onto the cast roll 5 having a cooling function, is clamped and pressed against the touch roll 6, cooled together, and then subjected to surface correction. The cast roll 5 and the touch roll 6 are not limited to a roll, and may be a drum, a belt, or the like.

The temperature of the cast roll 5 is preferably set to be not higher than the glass transition temperature (Tg) of the resin mixture and higher than the melting point of the additive.

Here, the touch roll 6 is a rotating body intended to pinch the film from the opposite side of the cast roll 5 toward the cast roll 5 with respect to the film.

The surface of the touch roll 6 is preferably a metal, and the thickness is 1 mm to 10 mm. Preferably 2 mm to 6 mm. The surface of the nipping pressurized rotating body is subjected to a treatment such as chrome plating and the surface roughness is preferably 0.1 탆 or less at the maximum height Ry and is preferably 0.05 탆 or less. The smoother the roll surface, the smoother the surface of the resulting film.

In the nip pressurizing process, it is preferable that the touch roll 6 is made of an elastic roll (elastic metal roll) having a metal cylinder on the outer periphery.

That is, when the pressure of the touch roll 6 becomes uneven, orientation irregularity occurs in the film, and this results in uneven brightness and shade under Cross Nicol. In order to calibrate the film by a uniform pressure, an elastic touch roll having a metal cylinder on the outer periphery as described above is preferable.

The material of the metal on the surface of the touch roll 6 is required to be smooth, suitable elasticity, and durability. Carbon steel, stainless steel, titanium, and nickel produced by an electroforming method. In order to increase the hardness of the surface or improve the releasing property with respect to the resin, it is preferable to perform surface treatment such as hard chrome plating, nickel plating, amorphous chromium plating, or ceramic spraying. The surface-finished surface is preferably polished again to obtain the above-mentioned surface roughness.

The touch roll 6 has a double structure of a metal outer cylinder and an inner cylinder, and has a double cylinder structure having a space for allowing a cooling fluid to flow therebetween.

The inner tube is preferably a lightweight, rigid metal inner tube made of carbon steel, stainless steel, aluminum, titanium or the like. By imparting rigidity to the inner tube, it is possible to suppress the rotation of the roll. The thickness of the inner tube is 2 to 10 times as large as the outer tube, and sufficient rigidity is obtained. An elastic material made of a resin such as silicone, fluorine rubber or the like may further be coated on the inner tube.

The structure of the space through which the cooling fluid flows may be any one that can uniformly control the temperature of the surface of the roll. For example, the temperature of the surface of the roll may be controlled to alternately flow in the width direction and in the return direction, Temperature control with a small distribution can be performed. The cooling fluid is not particularly limited, and water or oil may be used according to the temperature range to be used.

The touch roll 6 is set such that the outer diameter of the center portion is larger than the outer diameter of both end portions. In general, the touch roll is pressed against the film by pressing means at both ends thereof. However, in this case, there is a phenomenon that the touch roll is strongly pressed toward the end portion because it is warped. By making the roll into a drum shape, highly uniform pressurization becomes possible.

The diameter of the touch roll 6 is preferably in the range of 200 mm to 500 mm. The effective width of the touch roll 6 needs to be larger than the width of the film to be clamped and pressed. It is possible to prevent unevenness of streaks or the like occurring at the center of the film by the difference between the radius of the central portion of the touch roll 6 and the radius of the end portion (hereinafter referred to as the crowning amount). The crowning amount is preferably in the range of 50 to 300 mu m.

The cast roll 5 and the touch roll 6 are provided at positions opposite to the plane of the film so as to clamp and press the film. The cast roll 5 and the touch roll 6 may be in contact with the film and may be in contact with the film.

On the surface of the touch roll 6, a predetermined amount of the releasability adjusting agent 104 is applied by the releasability adjusting agent applying device 100 before pinching the film on the cast roll 5. The application of the releasability adjuster 104 has been described in detail, and a description thereof will be omitted.

In the method for producing an optical film according to the present embodiment, the conditions of melt extrusion can be performed in the same manner as the conditions used for the thermoplastic resin such as another polyester. It is preferable to dry the material in advance. It is preferable to dry the water to 1000 ppm or less, preferably 200 ppm or less by using a vacuum or reduced pressure dryer or a dehumidifying hot air dryer.

For example, a cellulose ester resin dried under hot air or vacuum or reduced pressure is melted at an extrusion temperature of about 200 to 300 DEG C by using an extruder 1, filtered with a filter 2 of a leaf disk type, do.

When introducing into the extruder 1 from a feed hopper (not shown), it is preferable to prevent the oxidative decomposition or the like under vacuum or in an inert gas atmosphere under reduced pressure.

If additives such as a plasticizer are not mixed in advance, they may be kneaded and inserted in the middle of an extruder. It is preferable to use a mixing device such as a static mixer 3 in order to uniformly add it.

It is preferable that the additive such as a resin such as cellulose resin and the stabilizer added as required is mixed before being melted. The mixing may be carried out by a mixer or the like, or may be mixed in the course of producing a resin such as a cellulose resin as described above. When a mixer is used, a general mixer such as a V-type mixer, a cone screw type mixer, a horizontal cylindrical mixer, or the like can be used.

After mixing the film constituting materials as described above, the mixture may be directly melted by using the extruder 1, but once the film constituting material is pelletized, the pellets are melted by the extruder 1, . In the case where the film constituting material contains a plurality of materials having different melting points, a semi-molten material having a so-called cupella shape is first formed at a temperature at which only a material having a low melting point is melted and a semi-molten material is put into the extruder 1 It is also possible to form a film by this. In the case where the film constituting material contains a material likely to be thermally decomposed, a method of direct film formation without producing pellets or a method of forming a semi-molten material such as the above-described semi-molten material is preferable for the purpose of reducing the number of melts Do.

As the extruder 1, various extruders available on the market can be used, but a melt-kneading extruder is preferable, and it may be a single-screw extruder or a twin-screw extruder. In the case of direct film formation without forming the pellet as a film constituting material, it is preferable to use a twin screw extruder because an appropriate kneading degree is required. However, even in the case of a single screw extruder, Or the like can be used to obtain an appropriate kneading. As the film constituting material, when a semi-molten material having a pellet shape or a bobbin shape is used, a single-axis extruder can be used and a twin-screw extruder can be used.

It is preferable to reduce the oxygen concentration by replacing the inside of the extruder 1 with an inert gas such as nitrogen gas or by reducing the pressure in the cooling step after extrusion.

The melting temperature of the film constituting material in the extruder 1 differs depending on the viscosity and the discharge amount of the film constituting material, the thickness of the sheet to be produced, etc. In general, the melting temperature of the film constituting material in the extruder 1 is, Tg + 100 deg. C or lower, preferably Tg + 10 deg. C or higher and Tg + 90 deg. C or lower. The melt viscosity at the time of extrusion is 1 to 10000 Pa · s, preferably 10 to 1000 Pa · s. The retention time of the film constituting material in the extruder 1 is preferably as short as possible, within 5 minutes, preferably within 3 minutes, more preferably within 2 minutes. The retention time depends on the type of the extruder 1 and the conditions under which the extruded material is extruded. However, the retention time can be shortened by adjusting the supply amount of the material, the L / D, the screw rotation speed,

The shape and rotation speed of the screw of the extruder 1 are appropriately selected depending on the viscosity of the film constituting material, the discharge amount, and the like. In the present embodiment, the shearing rate in the extruder 1 is 1 / sec to 10000 / sec, preferably 5 / sec to 1000 / sec, and more preferably 10 / sec to 100 / sec. As the extruder 1, a commercially available extruder may be used as a plastic molding machine.

The film constituting material extruded from the extruder 1 is sent to the flexible die 4 and extruded into a film form from the flexible die 4.

The melt discharged from the extruder 1 is supplied to the flexible die 4. The flexible die 4 is not particularly limited as long as it is used for producing a sheet or a film. The material of the flexible die 4 may be selected from the group consisting of hard chrome, chromium carbide, chromium nitride, titanium carbide, titanium carbonitride, titanium nitride, ultra high strength steel, ceramic (tungsten carbide, aluminum oxide, chromium oxide) (Bending), lapping using a grinding wheel after # 1000 number of times, planar cutting using a diamond grinding wheel of # 1000 number or more (cutting direction is perpendicular to the flow direction of the resin), electrolytic polishing, electrolytic hybrid polishing And the like.

The preferred material of the lip portion of the flexible die 4 is the same as the flexible die 4. Further, the surface accuracy of the lip portion is preferably 0.5 S or less, more preferably 0.2 S or less.

In the present embodiment, the melted resin mixture is extruded from a flexible die 4 provided in an extruder, and the extruded film-like resin is brought into close contact with the cast roll 5 and the touch roll 6, And then pulling it.

It is preferable that the temperature decrease until the melted film in the first contact with the surface of the cast roll 5 and then with the surface of the touch roll 6 is within 20 ° C. If the temperature drop from the time the film initially contacts the surface of the cast roll 5 to the time it touches the surface of the touch roll 6 becomes excessively large, unevenness in film thickness becomes large due to uneven shrinkage. If the temperature at the time when the film is in contact with the touch roll 6 is too low, the flatness of the film and the unevenness of the film thickness can not be sufficiently corrected even if the nip pressure is applied from the touch roll 6 due to the high viscosity of the film .

Preferred materials of the cast roll 5 and the touch roll 6 include carbon steel and stainless steel. The surface precision is preferably high, and the surface roughness is preferably 0.1 mu m or less at the maximum height Ry, and more preferably 0.05 mu m or less.

It is preferable that the touch roll 6 presses the film to the cast roll 5 by the pressing means. The line pressure at which the touch roll 6 presses the film at this time can be adjusted by a hydraulic piston or the like, preferably 0.1 to 100 N / mm, more preferably 1 to 50 N / mm.

In addition, the cast roll 5 or the touch roll 6 may have a reduced diameter at both ends of the roll or a flexible rolled surface in order to enhance the uniformity of adhesion to the film.

When the portion from the opening of the flexible die 4 to the cast roll 5 is reduced to 70 kPa or less, the calibrating effect of the above die line is more remarkably manifested. Preferably, the reduced pressure is 50 kPa or more and 70 kPa or less. The method of keeping the pressure of the portion of the flexible die 4 from the lip to the cast roll 5 to 70 kPa or less is not particularly limited and may be a method of covering the periphery of the roll with the pressure member from the flexible die 4, There is a way. At this time, it is preferable that the suction device is subjected to treatment in which the device itself is heated by a heater so as not to become a place where the sublimate is attached. If the suction pressure is too small, it is not possible to suck the sublimate effectively, so it is necessary to set the suction pressure to an appropriate value.

The film-like cellulose ester resin in a molten state from the flexible die 4 is successively brought into close contact with the cast roll 5, the cooling roll 7 and the cooling roll 8 and is cooled and solidified while being conveyed to form a cellulose ester based resin film (17).

In the embodiment of the present invention shown in Fig. 2, the cooled and solidified film 17 peeled off from the cooling roll 8 by the peeling roll 9 is introduced into the longitudinal stretching device 10, Direction).

Subsequently, the film after the longitudinal stretching is led to the transverse stretching device (tenter) 20, and the film 17 is stretched in the transverse direction (width direction) there. By this transverse stretching, molecules in the film are oriented.

After the transverse stretching, the end portion of the film 17 is slit and cut by a slitter 19 to be a product, and then knurled by a knurling machine comprising an embossing ring 53 and a back roll 52 Embossing) is applied to both ends of the film and is wound up by a winding device 60 to prevent adhesion in the optical film (original wound body) F and generation of scratches.

The knurling process can be performed by heating or pressurizing a metal ring having a concavo-convex pattern on its side surface. Further, the gripping portions of the clips at both end portions of the film are usually deformed and can not be used as a film product, so they are cut out and reused as a raw material.

The winding machine to be used is not particularly limited as long as it is generally used, and can be wound by a winding method such as a constant tension method, a constant torque method, a taper tension method, an internal stress, and a constant program tension control method.

Further, the step of knurling after transverse stretching and the step of slitting the thin film at the end of the film may be performed before the winding step.

As described above, when the optical film produced by this embodiment is used as a retardation film and the retardation film is used as a polarizing plate protective film, the thickness of the protective film is preferably 10 to 500 mu m. Particularly, the lower limit is 20 占 퐉 or more, preferably 35 占 퐉 or more. The upper limit is 150 mu m or less, preferably 120 mu m or less. A particularly preferable range is 35 to 90 占 퐉. If the retardation film is thick, the polarizing plate after the polarizing plate processing becomes excessively thick, which is not particularly suitable for the purpose of thin and lightweight in the liquid crystal display used for a notebook computer or a mobile electronic apparatus. On the other hand, if the retardation film is thin, it is not preferable because retardation as retardation film is difficult to be expressed, and further, the moisture permeability of the film becomes high and the ability of protecting the polarizer from humidity is lowered.

The optical film to which the present invention is applied is a functional film used for various displays such as a liquid crystal display, a plasma display, and an organic EL display, especially a liquid crystal display, and is a polarizing plate protective film, a retardation film, An optical compensation film such as a magnifying film, and particularly a retardation film.

(Liquid crystal display device)

The polarizing plate comprising the retardation film constituted by the optical film of the present invention can exhibit a higher display quality than a conventional polarizing plate and is particularly suitable for a multi-domain liquid crystal display device, more preferably a multi- And is suitable for use in a domain type liquid crystal display device.

Multi-domainization is also suitable for improving the symmetry of image display, and various methods have been reported. Oki and Yamauchi: Liquid Crystal, 6 (3), 303 (2002). The above-mentioned liquid crystal display cell is also described in &quot; Yamada and Yamabaru: Liquid crystal, 7 (2), 184 (2003) &quot;

The polarizing plate using the optical film of the present invention can be used in a multi-domain vertical alignment (MVA) mode represented by a vertical alignment mode, in particular, a four-divided MVA mode, a known PVA (Patterned Vertical Alignment) mode , CPA (Continuous Pinpointed Alignment) mode in which electrode arrangement and keying ability are fused. In addition, a proposal of an optically biaxial film for adaptation to OCB (Optical Compensated Bend) mode has also been disclosed (T. Miyashita, T. Uchida: J. SID, 3 (1), 29 )), And the display quality effect can be exhibited by the polarizing plate using the optical film of the present invention.

The arrangement of the liquid crystal mode and the polarizing plate is not limited as long as the display quality effect can be exhibited by the polarizing plate using the optical film of the present invention.

It is preferable that the display quality of the display cell is symmetrical in the left and right in human observation. Therefore, when the display cell is a liquid crystal display cell, the domain can be multiplexed with priority given to the symmetry of the viewing side. The division of the domain can be carried out by a known method, and can be determined in consideration of the property of the known liquid crystal mode by a bipartite method, more preferably a quadruple method.

The liquid crystal display device has been continuously applied as a device for colorization and moving picture display, and the display quality is improved by the optical film of the present invention, and improvement of contrast and resistance of the polarizing plate are improved, .

In the liquid crystal display device, one polarizing plate including a retardation film constituted by the optical film of the present invention is arranged for each liquid crystal cell, or two polarizing plates are arranged on both sides of the liquid crystal cell. At this time, by using the retardation film side included in the polarizing plate facing the liquid crystal cell of the liquid crystal display device, it is possible to contribute to the improvement of the display quality.

In the polarizing plate, a polarizing plate protective film of a cellulose derivative is used on the side opposite to the retardation film as viewed from the polarizer, and a general-purpose TAC film or the like can be used. The polarizing plate protective film located on the side far from the liquid crystal cell can improve the quality of the display device and can arrange other functional layers.

The optical film according to the present invention may be provided with functions such as anti-reflection, anti-glare, anti-scratch, anti-dust adhesion, and brightness enhancement. Or may be attached to the surface of the polarizing plate, but the present invention is not limited thereto.

A functional layer such as an antistatic layer, a hard coat layer, an inactive layer, an adhesive layer, an antiglare layer, or a barrier layer may be applied and formed before and / or after stretching in the production of the retardation film. At this time, various surface treatments such as corona discharge treatment, plasma treatment, and chemical solution treatment can be carried out as needed.

When the optical film of the present invention is used as a protective film of a polarizing plate as a retardation film, the production method of the polarizing plate is not particularly limited and can be produced by a general method. There is a method of bonding a polarizing plate protective film to both surfaces of a polarizer using a completely saponified polyvinyl alcohol aqueous solution on both sides of a polarizer produced by alkali treatment of the obtained retardation film and immersion stretching of a polyvinyl alcohol film in an iodine solution, The retardation film, which is the polarizing plate protective film of the present invention, is directly bonded to the polarizer on one side.

Instead of the above alkali treatment, the polarizing plate may be subjected to an easy-to-adhere processing described in JP-A-6-94915 and JP-A-6-118232.

The polarizing plate is composed of a polarizer and a protective film for protecting both surfaces of the polarizer, and a protective film is bonded to one side of the polarizing plate and a separate film is bonded to the opposite side of the polarizing plate. Protect film and separate film are used to protect the polarizing plate at the time of polarizing plate shipment and product inspection. In this case, the protective film is bonded to protect the surface of the polarizing plate, and is used on the opposite surface side of the polarizing plate bonded to the liquid crystal plate. The separate film is used for the purpose of covering the adhesive layer to be bonded to the liquid crystal plate, and is used on the side of bonding the polarizing plate to the liquid crystal cell.

Example

Examples and comparative examples as methods for producing optical films are described below.

(Examples 1 to 8)

(Resin mixture)

Cellulose acetate propionate (acetyl group degree of substitution: 1.4, propionyl group degree of substitution: 1.35, number average molecular weight: 60000) 89 mass%

9% by mass of trimethylolpropane tribenzoate (plasticizer, melting point 85 캜)

0.25 mass% of an antioxidant (IRGANOX XP420 / FD) (manufactured by Shiba Japan)

1.6 mass% of ultraviolet absorber (TINUVIN 928, manufactured by Shiba Japan, melting point 115 캜)

Mat (silica fine particles) (Sihosta KEP-30, manufactured by Nippon Shokubai Co., Ltd., average particle size 0.3 mu m) 0.15 mass%

The degree of substitution of the acyl group of the acetyl group or the propionyl group of the cellulose acetate propionate was measured according to the method defined in ASTM-D817-96.

The above materials were mixed with a V-type mixer for 30 minutes, and then melted at 230 DEG C under a nitrogen atmosphere using a twin-screw extruder equipped with a stranded die to prepare a cylindrical pellet having a length of 4 mm and a diameter of 3 mm. The glass transition point (Tg) of the obtained pellets was 135 占 폚.

(Production of optical film)

The pellets were dried at 100 DEG C for 5 hours to give a water content of 100 ppm, and the pellets were supplied to the single screw extruder 1 provided with the T die 4 shown in Fig. 2 to perform film formation. The melt contained 11 mass% of additives other than the resin.

The number of revolutions of the screw was adjusted so that the screw diameter was 90 mm, L / D was 30, and the extrusion amount was 140 kg / h in the single screw extruder 1. Nitrogen gas was sealed from the vicinity of the material supply port, and the inside of the extruder 1 was maintained in a nitrogen atmosphere. The temperature of the extruder 1 and the T die 4 was set at 240 캜. The T-die 4 is a coat hanger type, having a width of 1500 mm, hard chrome plating on the inner wall, and finished with a specular surface of 0.1S. The lip gap of the T die 4 was set at 2 mm.

As shown in Fig. 2, the film-shaped melted material from the T die 4 is dropped onto a cast roll 5 having a chrome plated mirror surface with a surface temperature of 120 DEG C and a roll width of 1600 mm, And the film was pressed by a touch roll (pinching and pressing rotary body) 6 having a roll width of 1600 mm,

On the surface of the touch roll, a releasability adjusting agent is previously applied by the releasability adjusting agent applying device 100 as shown in Fig. 1, on the upstream side of the position of P2 contacting the melt (Y) on the cast roll 5. The releasability adjusting agent application device 100 is heated to the same temperature as that of the touch roll 6 at 120 ° C. Tinuvin 928 (T-928), dimethylsiloxane, and tetrafluoroethylene copolymer were used as the releasability adjusting agent. T-928 and dimethylsiloxane were applied in a liquid phase, and 20 parts by mass of the tetrafluoroethylene copolymer was dissolved in 100 parts by mass of the solvent xylene. The tetrafluoroethylene copolymer was applied to the surface of the touch roll in a branched state with the liquid. The coating thickness for the touch roll 6 was set as shown in Table 1, and the manufacturing conditions of Examples 1 to 8 were used. The angle of contact between the surface of the cast roll 5 and the water was 75 °. The contact angle of water on the surface of the touch roll 6 after application of the releasability adjuster was 95 ° for T-928, 109 ° for tetrafluoroethylene copolymer, The siloxane was 120 °.

Further, the touch roll (nip and pressurized rotating body) 6 pressed the film at a linear pressure of 5 N / mm.

Stainless steel was used for the cast roll 5, and the surface roughness was set to 0.1 탆 or less at the maximum height Ry.

In addition, the touch roll 6 has a double cylinder structure having a metal outer cylinder, an inner cylinder, and a hollow portion. The material of the metal outer tube was stainless steel, and the surface roughness was set at 0.05 mm or less at the maximum height Ry, and the thickness was 3 mm. The inner tube was made of aluminum and had a thickness of 30 mm. The space between the metal outer cylinder and the inner cylinder was 5 mm. Oil was poured into the gap portion 47 to set the surface temperature of the metal outer tube to 120 占 폚.

The film pressed on the cast roll 5 and the touch roll (nip and pressurized rotating body) 6 is subsequently cooled and solidified in a circumscribed fashion on the rolls of the cooling roll 7 and the cooling roll 8, 9). The transporting speed of the film was 10 m / min.

Thereafter, in the longitudinal stretching apparatus 10, longitudinal stretching was performed.

In the drawing step of this longitudinal stretching device 10, the unstretched film 17 after the nip press was stretched 2.0 times in the longitudinal direction.

After the longitudinal stretching, the transverse stretching apparatus 20 was transversely stretched using a tenter apparatus, and the stretching magnification at the transverse stretching was 2.0 times.

The stretched film was slit by a slitter so as to have a width of 1300 and wound up by a winding device 60 to produce optical films of Examples 1 to 8 having a width of 1300 mm, a thickness of 100 m and a length of 1000 m.

(Evaluation of optical film)

Next, with respect to the optical films of Examples 1 to 8, the surface of the entire area of the optical film was observed with naked eyes to see whether or not there was a stripe pattern (transverse stain) in the film width direction. Rank 4 that there is no transverse unevenness, Rank 3 which is more than 1 and less than 3, rank 2 that there is more than 3, and less than 6 are ranked as rank 1 having 6 or more. In order to evaluate the uniformity of the retardation, the films of Examples 1 to 8 were sandwiched between two polarizers arranged in a crossed nicol state by a polarizing plate, that is, in an orthogonal state (Cross-Nicol state) And observed from the outside of the other polarizing plate with the naked eye to give a rank of uniformity of retardation. There is no transmission of light over the entire area of the optical film, a rank A with a uniformly dark field as a whole, a rank B with which a light and shade of a stripe shape are partially observed, a rank C with a partially dark and sharpe contrast, Quot; rank D &quot; in which a strong stripe-shaped light and shade is confirmed. Six or more transverse irregularities are observed with the naked eye, and the irregularity of the retardation is rank D, which is a problem in product quality.

(Comparative Example 1)

In the production method of the optical film of Example 1, the releasability adjusting agent was not coated on the surface of the touch roll 6, and the evaluation was made in the same manner as in Example 1 and evaluated.

The evaluation results are shown in Table 1.

(Comparative Example 2)

In the optical film production method of Example 1, the surface of the touch roll 6 was not coated with the releasability adjusting agent, and the surface of the cast roll 5 before dropping the film- T-928) was applied in a thickness of 0.04 mu m in the same manner as in Example 1 and evaluated.

From the results shown in Table 1, it was found that an optical film having high planarity with little transverse unevenness and unevenness of retardation can be produced by applying a releasability adjusting agent to the surface of the rotating support. From the results of Examples 1 to 6, it was also found that the transverse unevenness becomes smaller when the thickness of the releasability adjusting agent applied to the surface of the rotating support is in the range of 0.05 to 1000 mu m.

1: extruder
2: Filter
3: Static Mixer
4: Flexible die
5: cast roll, rotating support
6: touch roll, nip pressurized rotating body
7, 8: cooling roll
P1: The point at which the film initially contacts the cast roll surface
P2: Point at which the film contacts the touch roll surface
P3: Point at which the film is separated from the cast roll
9: peeling roll
10: vertical stretching device
17: Film
19: Slitter
20: transverse stretching device
52: back roll
53: Embossing ring
60: retractor
100: Dissimilarity modifier application device
101: application roller
102: lifting roller
103: Regulating blade
104:
105: Storage tank
Y: Melt
F: Optical film (circular wound body)

Claims (10)

A flexible process for extruding a melt containing a thermoplastic resin from a flexible die into a film on a surface of a rotary support,
And a nip pressurizing step of nip-pressing the film-shaped melt extruded in the above-mentioned softening step with the rotary support and the nip pressure rotary body,
Wherein a releasability adjusting agent for improving releasability of the nip pressurizing rotating body and the film-like melt is applied to the surface of the nip pressure rotary body,
Wherein the releasability adjusting agent comprises the same material as at least one of the additives contained in the melt,
Wherein the releasability adjusting agent is a benzotriazole-based ultraviolet absorber or benzophenone-based ultraviolet absorber used for absorbing ultraviolet light inside the optical film,
Wherein a contact angle S1 between the surface of the rotating support body and water and a contact angle S2 of water on the surface of the nip pressurizing rotating body after application of the releasability adjusting agent are in a relationship of 0.5 DEG < S2-S1 < 100 DEG. Way. The method for producing an optical film according to claim 1, wherein the releasability adjusting agent has a boiling point of 150 to 250 ° C. The method for producing an optical film according to claim 1 or 2, wherein the thickness for applying the releasability adjusting agent is 0.05 to 1000 mu m. The method according to claim 1 or 2, characterized by further comprising: conveying tension (T1) of the film-like molten material in a state in which the nip-pressed rotary body is pressed against the rotary support body and a state in which the nip pressure rotary body is not pressed Wherein the difference (T1-T2) of the transporting tension T2 of the film-like melt in the first film is in the range of 1 to 250N. The method for producing an optical film according to claim 1 or 2, wherein the thermoplastic resin is a cellulose ester-based resin. delete delete delete delete delete

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