WO2022153785A1

WO2022153785A1 - Film roll and method for manufacturing film roll

Info

Publication number: WO2022153785A1
Application number: PCT/JP2021/046677
Authority: WO
Inventors: 葉月中江; 博文田中; 裕介市川; 奈々恵藤枝; 崇南條
Original assignee: コニカミノルタ株式会社
Priority date: 2021-01-15
Filing date: 2021-12-17
Publication date: 2022-07-21
Also published as: KR20230111231A; CN116745662A; JPWO2022153785A1

Abstract

A problem addressed by the present invention is to provide a film roll that can maintain quality while causing less winding failure during transportation or long-term storage, and also to provide a method for manufacturing the film roll, the method achieving high yield and drastically reducing inspection load.　The film roll according to the present invention is a film roll in which a single-layer optical film is wound, the film roll being characterized in that the average maximum height difference of the film thickness (P-V) ave1 as measured in a region of 1000mm diameter around an arbitrary point in the optical film as the center is 0.15 to 0.40μm, and that the ratio (Dc/De) of the outer diameter Dc of the central section to the outer diameter De of the end section of the film roll is 0.98 to 1.02.

Description

Film rolls and film roll manufacturing methods

The present invention relates to a film roll and a method for producing a film roll.
More specifically, the present invention relates to a film roll that has few winding failures during transportation and long-term storage and can maintain quality.
The present invention also relates to a method for producing the film roll, which has a high production yield and a significantly reduced inspection load.

Recently, there has been a demand for thinning of image display devices, and optical protective films and optical functional films provided in image display devices such as liquid crystal displays (LCDs), organic electroluminescence displays (ELDs), and electronic papers are usually rolled. Since it is supplied to the next step, there is a demand for thinning the optical film as described above.
Further, the optical film is also required to be longer and wider in order to improve production efficiency.

Since an optical film is usually manufactured and then wound into a roll and stored or transported as a film roll, the following techniques are generally known as a technique for winding the film into a roll. ..
(1) Technology for winding the optical film together with a protective film having a sticking suppressing function (2) Technology for winding the optical film with an anti-blocking layer that suppresses sticking on one surface (3) In advance By winding the edge of the optical film that has been nerled, the air layer (air layer) is taken in when the optical film is wound, which suppresses the sticking of the optical film on the product parts. Technology

Regarding the technique (1), there is a problem that a customer who uses a film roll generates waste due to a protective film in the manufacturing process of a product to which an optical film is applied.
Further, since the protective film is provided with an anti-blocking function by particles or the like, there is a problem that the optical film is dented or scratched by being pushed into the product portion by the particles or the like.

Regarding the technique (2), there is a problem that the optical film is dented or scratched by being pushed into the product part by particles or the like, as in the case of the protective film.
In addition to the above, there is a problem of process contamination associated with transportation in the manufacturing process of a product to which a customer who uses a film roll applies an optical film.

Regarding the technique (3), the air layer (air layer) taken into the film roll is deflated due to the air being released during product transportation or over time, and the film roll core is stuck. As a result, the core portion of the film roll becomes unusable waste, and the environmental load becomes large.

Since there are problems with the winding techniques (1) to (3) above, various improvements are required for the film roll.
Regarding the above problem, an invention in which the edge of the optical film is subjected to a nerling process, an air layer (air layer) is taken in, and the uniformity in the surface of the optical film is improved to suppress the variation in the phase difference and improve the display quality. Is disclosed (see Patent Document 1).
However, in the above invention, since the end portion of the film roll is knurled, the roll diameter at the end portion becomes larger than the roll diameter at the center portion, and the air layer is formed during product transportation or over time. There remains a problem that the quality deteriorates due to the difference in stress in the circumferential direction (longitudinal direction) of the roll due to the release of air from the (air layer) and the bending of the roll with the knurling as a support. rice field.

From the above, it is resistant to the external environment such as vibration deterioration due to transportation of trucks and ships and the passage of time, and it can be provided with almost the same quality as when the product was shipped, realizing procurement assuming long-term product storage. In addition, it is required to reduce distribution costs and to provide high-quality film rolls from the core to the outside.

Japanese Unexamined Patent Publication No. 2007-254699

The present invention has been made in view of the above problems and situations, and the problem to be solved is to provide a film roll capable of maintaining quality with few winding failures during transportation and long-term storage. Another object of the present invention is to provide a method for producing the film roll, which has a high production yield and a significantly reduced inspection load.

The present inventor is in the process of examining the cause of the above problem in order to solve the above problem.
We have found that the problem can be solved by controlling the film thickness of the optical film, the reflectance of the surface, and the like within a specific range, and have arrived at the present invention.
That is, the above problem according to the present invention is solved by the following means.

1. 1. A film roll in which a single-layer optical film is wound.
The average maximum height difference (PV) _ave1 of the film thickness within the range of 1000 mm in diameter is 0.15 to 0.40 μm around an arbitrary point in the optical film.
Moreover, the film roll is characterized in that the ratio of the central portion to the end portion (outer diameter of the central portion / outer diameter of the end portion) of the film roll is 0.98 to 1.02.

2. A film roll in which a single-layer optical film is wound.
The average maximum height difference (PV) _ave1 of the film thickness within the range of 1000 mm in diameter is 0.15 to 0.40 μm around an arbitrary point in the optical film.
Moreover, the a ^* value and the b ^* value defined by the CIE1976L ^* a ^* b ^* color system obtained from the reflectance of the surfaces of the central portion and the end portion of the film roll satisfy the following equation (1) (1). :
-1.0 <(end a ^* -center a ^* ) + (end b ^* -center b ^* ) <1.0
A film roll characterized by that.

3. 3. The average maximum height difference (PV) _ave2 of the film thickness measured in the following steps 1 to 3 diagonally with respect to the width direction of the optical film is 0.15 to 0.40 μm. The film roll according to the feature 1 or 2.
Step 1:
After measuring the film thickness at an arbitrary position on the end, measure the film thickness at a position moved 50 mm in the width direction and 620 mm in the longitudinal direction from the arbitrary position for each measurement, and repeat this until the other end. Then, the maximum height difference of each of the film thicknesses in the diagonal direction with respect to the width direction of the optical film is calculated.
Step 2:
After the completion of the step 1, the same measurement as in the step 1 is performed until the total distance of the moving positions in the longitudinal direction reaches 1000 m, and the maximum film thickness in the oblique direction with respect to the width direction of the optical film is maximized. The height difference is further calculated.
Step 3:
From the maximum height difference of the thickness in the diagonal direction with respect to the width direction of the optical film obtained from steps 1 and 2, the average maximum height difference of the film thickness in the diagonal direction with respect to the width direction of the optical film ( PV) _{Calculate ave2} .

4. When the average differential orientation angle θ _ave ° and the average differential film thickness d _ave μm within the range of 1000 mm in diameter are calculated around an arbitrary point in the optical film, the average differential orientation angle θ _ave ° and the average differential film thickness are calculated. Equation (2): in which d _ave μm satisfies the following equation (2):
800 << | Average differential orientation angle θ _ave / Average differential film thickness d _ave × 10 ^-3 | <10000
The film roll according to any one of the items 1 to 3, wherein the film roll is characterized by the above.

5. The film roll according to any one of items 1 to 4, wherein the optical film contains inorganic fine particles.

6. The film roll according to any one of items 1 to 5, wherein the width of the optical film is 2400 to 3000 mm.

7. The film roll according to any one of items 1 to 6, wherein the length of the film roll is 7500 to 10000 m.

8. The method for producing a film roll according to any one of paragraphs 1 to 7.
It has at least a stretching step of stretching the optical film in a stretching furnace and a flattening treatment step.
A method for producing a film roll, which comprises flattening a film roll at a temperature as high as 50 to 200 ° C. with respect to the temperature inside the stretching furnace in the flattening treatment step.

9. In the stretching step, the flattening treatment is performed using an infrared (IR) heater, and
Equation (3): The average value B of the amount of heat A at the center and the amount of heat at the end at a position 100 mm away from the infrared (IR) heater satisfies the following equation (3):
0.2 <(B / A) <0.6
The method for producing a film roll according to Item 8, wherein the film roll is produced.

According to the above means of the present invention, it is possible to provide a film roll capable of maintaining quality with few winding failures during transportation and long-term storage.
Further, it is possible to provide a method for producing the film roll, which has a high production yield and a significantly reduced inspection load.

The mechanism of expression or mechanism of action of the effect of the present invention has not been clarified, but it is inferred as follows.

Conventionally, as disclosed in Patent Document 1, when a person skilled in the art manufactures a film roll, the edge of the optical film is subjected to a nerling process from the viewpoint of industrial productivity, cost, etc., and an air layer (air) is formed. A means of winding the optical film while winding the layer) has been adopted.

By the way, it is considered that the main functions of the knurling processing portion are two functions, that is, the function of suppressing the sticking of the optical film by taking in the air layer (air layer) and the function of suppressing the unwinding of the film roll due to the physical unevenness. ..
Immediately after the narrated film roll is rolled up (immediately after manufacturing), the above-mentioned air layer (air layer) suppresses the sticking of the optical films to each other, but during transportation by sea mail, truck, etc., or When stored in the customer's warehouse, the air in the air layer (air layer) is released over time, which interferes with the above two functions.

Not only during transportation, customers rarely start production immediately using rolls stored in the warehouse, and in some cases they are stored for a long time in the warehouse, so there was a problem that the sticking timing could not be predicted.

FIG. 1A is a schematic view immediately after winding (immediately after manufacturing) of a conventional film roll whose end is knurled.
FIG. 1B is an enlarged view of a part A of the end portion of the film roll in FIG. 1A.
FIG. 1C is an enlarged cross-sectional view of the film of a part B of the uneven shape of the knurling process in FIG. 1B.

FIG. 2 is a schematic view showing a state of deflection of the film roll after a lapse of a certain period of time.
Here, when the present inventors analyzed the step of sticking optical films whose ends were knurled, the film roll whose ends were knurled as shown in FIG. 1A was optically knurled. As the knurling height is laminated by stacking multiple layers of film (see FIG. 1B), the end portion protrudes as shown in FIG. 1C, so that the roll diameter at the end portion is compared with the roll diameter at the center portion. As shown in FIG. 2, on the outer surface of the winding, the air in the air layer (air layer) gradually escapes with the passage of time, while the films at the knurled ends do not shift due to friction.
However, it was found that under the environment, the weight of the film roll itself causes deflection on the upper and lower sides of the film roll due to the weight of the film roll itself, and sticking begins to occur.

Next, FIG. 3 shows a schematic view showing the core side of the film roll of FIG. 2 on the film roll after a lapse of a certain period of time.
When a film roll is made, the air in the air layer (air layer) gradually escapes with the passage of time on the surface on the core side (hereinafter, also referred to as the surface on the core side) among the surfaces in which the films come into contact with each other. As a result, several sticking parts (sticking failure; part D in FIG. 3) overlap as shown in FIG. 3, and in order to release the force, the length is added to the fine wrinkles (wrinkles) of the width as shown in FIG. Sticking in the width direction with a period (gradual failure; see part C in FIG. 3) occurs.

In addition, when giving priority to the function of suppressing the sticking of the optical film by taking in the air layer (air layer) and the function of suppressing the unwinding due to physical unevenness in the optical film with the edge processed, when transporting by truck or the like. Due to the influence of the air layer (air layer), the film roll is strongly impacted against the vibration that occurs in the film roll, and the film roll is more likely to be unwound or is easily affected by seasonal fluctuations, so control is extremely difficult. It is presumed that the problem was not solved due to the difficulty.

On the other hand, in the present invention, the air layer (air layer) is appropriately taken into the film roll on which the single-layer optical film is wound, and the end portion is not subjected to nerling processing, and the entire contact surface where the optical films face each other is not applied. The problem was solved with the idea of reversing the conventional technique of dispersing the unwinding function by causing moderate and minute contact (at a level where sticking is not recognized).

That is, in the optical film of the present invention, the average maximum height difference (PV) _ave1 of the film thickness measured within the range of 1000 mm in diameter around an arbitrary point in the optical film is 0.15 to 0. This means is characterized in that it is 40 μm and the value (Dc / De) of the ratio of the outer diameter Dc of the central portion to the outer diameter De of the end portion of the film roll is 0.98 to 1.02. Can solve the problem.

That is, as shown in FIG. 4, the film roll of the present invention is not subjected to the knurling process at the end portion, and the average maximum height difference of the film thickness of the entire surface of the film roll, that is, the film thickness difference is small.
Therefore, the air layer (air layer) between the optical films becomes uniform, and the upper side of the film roll becomes flat.
Although the lower side of the film roll is also affected by its own weight, the lower side can be suppressed by eliminating the upper side bending in the width direction.

Further, on the surface of the optical film on the core side, the stress in the circumferential direction (longitudinal direction) of the film roll becomes uniform, and in the width direction, the optical films stick to each other due to contact with each other centering on the convex portions of the optical films. Stress concentration due to is suppressed.

Furthermore, unlike the conventional optical film, the air layer (air layer) taken in at the time of winding does not suppress the contact of the entire width in the product part, but the edge of the optical film is not knurled. The unwinding function is also dispersed by controlling the average maximum height difference (PV) _ave2 of the film thickness in the diagonal direction with respect to the width direction of the optical film in a specific range in consideration of the variation in the longitudinal direction. It is presumed that it was possible to provide a film roll that can maintain the quality with few winding failures during transportation and long-term storage.
In addition, it is presumed that it was possible to provide a method for producing the film roll, which has a high production yield and a significantly reduced inspection load.

If the average maximum height difference (PV) _ave2 of the film thickness in the diagonal direction with respect to the width direction of the optical film is less than 0.15, the sticking is recognized immediately after winding. If it is 0.40 or more, minute sticking due to variation occurs and the problem cannot be solved.

Schematic diagram of a film roll with knurled edges immediately after winding (immediately after manufacturing) An enlarged view of a part A of the end portion of the film roll in FIG. 1A. FIG. 1B is an enlarged cross-sectional view of the film of a part B of the uneven shape of the knurling process. Schematic diagram showing the state of deflection of a film roll after a certain period of time Schematic diagram showing how stress is applied to the surface on the core side of the film roll after a certain period of time has passed. Schematic of the film roll of the present invention Flow chart showing the flow of the manufacturing process of the solution casting film forming method Schematic diagram of an apparatus for manufacturing an optical film by a solution casting film forming method Top view schematically showing the internal configuration of the tenter stretching device Side view of three zones in the tenter stretching device Top view of the three zones in the tenter stretching device Schematic diagram of nozzle and heater installation parts when the three zones in the tenter stretching device are viewed from the front Schematic diagram showing the process of winding an optical film and the cross section of the film roll of the present invention after being wound. Flow chart showing the flow of the manufacturing process of the melt casting film forming method Schematic configuration diagram of an apparatus for manufacturing an optical film by the melt casting film forming method

The film roll of the present invention is a film roll in which a single-layer optical film is wound, and has an average maximum height difference (P) of film thickness within a range of 1000 mm in diameter centered on an arbitrary point in the optical film. -V) _ave1 is 0.15 to 0.40 μm, and the ratio of the central portion to the end portion (outer diameter of the central portion / outer diameter of the end portion) of the film roll is 0.98 to 1.02. It is characterized by that.
With the above features, the problem of the present invention can be solved.

Further, in addition to the above characteristics, the film roll of the present invention has a CIE1976L ^* a ^* b ^* a ^* value and b specified by the color system obtained from the reflectance of the surfaces of the central portion and the end portion of the film roll. ^{* The} value satisfies the above equation (1).
With the above features, it is possible to solve the problem of the present invention, enhance the applicability of the optical film to the display device, and particularly improve the contrast and the like.

The above two features are technical features common to or corresponding to the following embodiments.

In the embodiment of the present invention, the average maximum height difference (PV) _ave2 of the film thickness measured in the order of steps 1 to 3 diagonally with respect to the width direction of the optical film is 0.15. It is preferably about 0.40 μm from the viewpoint of exhibiting the effect of the present invention.

When the average differential orientation angle θ _ave ° and the average differential film thickness d _ave μm within the range of 1000 mm in diameter are calculated around an arbitrary point in the optical film, the average differential orientation angle θ _ave ° and the average differential film thickness are calculated. It is preferable that d _ave μm satisfies the above formula (2) from the viewpoint of exhibiting the effect of the present invention.

It is preferable that the optical film contains inorganic fine particles from the viewpoint of being able to adjust the surface of the optical film to an appropriate uneven state and imparting low birefringence, and from the viewpoint of improving heat resistance and storage stability and environmental stability. ..

The width of the optical film is preferably 2400 to 3000 mm from the viewpoint of thinning and productivity.

The length of the optical film is preferably 7500 to 10000 m from the viewpoint of thinning and productivity.

The method for producing a film roll of the present invention is a method for producing a film roll for producing the film roll, and includes at least a stretching step of stretching an optical film in a stretching furnace and a flattening treatment step, and the flattening. In the treatment step, the flattening treatment is performed at a temperature as high as 50 to 200 ° C. with respect to the temperature in the stretching furnace, and in the stretching step, the flattening treatment is performed using an infrared (IR) heater. Moreover, it is preferable from the viewpoint of the effect of flattening that the average value B of the heat quantity A at the center portion and the heat quantity at the end portion at a position 100 mm away from the infrared (IR) heater satisfies the above formula (3).

Hereinafter, the present invention, its constituent elements, and modes and modes for carrying out the present invention will be described in detail. In the present application, "-" is used to mean that the numerical values described before and after the value are included as the lower limit value and the upper limit value.

1. 1. Outline of the Film Roll of the Present Invention The film roll of the present invention is a film roll in which a single-layer optical film is wound, and has a film thickness within a range of 1000 mm in diameter centered on an arbitrary point in the optical film. Average maximum height difference (PV) _ave1 is 0.15 to 0.40 μm, and the ratio of the center to the edge of the film roll (outer diameter of the center / outer diameter of the edge) is 0.98 to It is characterized by being 1.02.

(Definition of terms)
First, the meanings of the main terms according to the present invention will be described below.
The "average maximum height difference (PV) _ave1 of the film thickness of the optical film" is the maximum height of the peaks and valleys of the uneven shape of the thickness of the optical film measured and observed by the film thickness measurement described later. The average value of the differences is used to calculate the height difference between the highest part of the convex structure and the lowest part of the concave structure of the optical film by measuring the film thickness, and the average value is calculated as (P-). V) It was set to _ave1 .

The "end" refers to a region within a range of 15 to 30 mm inside from the end of the optical film (roll) in the width direction.

The "central portion" refers to the region portion of the optical film excluding both ends in the width direction.

The "outer diameter" refers to the diameter of a circle formed at the outermost circumference of the roll, where the cross section perpendicular to the central axis (core) of the film roll is a circle.
Therefore, the "outer diameter of the end portion" means the diameter (average value) of the circular cross section observed in the end region.
Further, the "outer diameter of the central portion" means the diameter of the circular cross section observed at the central point of the central portion.

In the embodiment of the present invention, the outer diameter at a position 30 mm from both ends in the width direction of the film roll was measured with a tape measure and used as the outer diameter of the end portion.
The outer diameter of the end portion was taken as the average value of the outer diameters of both ends.
Other methods can also be used to measure the outer diameter of the film roll. For example, a laser of a laser displacement meter (LK-G5000 manufactured by Keyence) is placed outside the position 30 mm from both ends in the width direction of the film roll. It is also possible to measure the outer diameter by installing it so as to irradiate the diameter and the center position of the central part.

(1.1) Shape of Optical Film of the Present Invention, etc. The optical film of the present invention has an average maximum height difference (P-) of film thickness measured within a diameter of 1000 mm centered on an arbitrary point in the optical film. V) _ave1 is 0.15 to 0.40 μm.
Further, the value (Dc / De) of the ratio of the outer diameter Dc of the central portion to the outer diameter De of the end portion of the film roll is 0.98 to 1.02.

The average maximum height difference (PV) _ave2 of the film thickness measured in the following steps 1 to 3 diagonally with respect to the width direction of the optical film is 0.15 to 0.40 μm. It is preferable from the viewpoint of solving the problem according to the present invention by the above-mentioned action mechanism.
Step 1:
After measuring the film thickness at an arbitrary position on the end, measure the film thickness at a position moved 50 mm in the width direction and 620 mm in the longitudinal direction from the arbitrary position for each measurement, and repeat this until the other end. Calculate the maximum height difference in the diagonal direction.
Step 2:
After the completion of the step 1, the same measurement as in the step 1 is performed until the total distance of the moving positions in the longitudinal direction reaches 1000 m, and the maximum height difference in the oblique direction is further calculated.
Step 3:
From the maximum height difference in each oblique direction obtained from steps 1 and 2, the average maximum height difference (PV) _ave2 of the film thickness in the diagonal direction is calculated.

When the average differential orientation angle θ _ave ° and the average differential film thickness d _ave μm within the range of 1000 mm in diameter are calculated around an arbitrary point in the optical film, the average differential orientation angle θ _ave ° and the average differential film thickness are calculated. It is preferable that d _ave μm satisfies the following formula (2) from the viewpoint of exhibiting the effect.
Equation (2):
800 << | Average differential orientation angle θ _ave / Average differential film thickness d _ave × 10 ^-3 | <10000

Here, the "average differential orientation angle θ _ave " means a value obtained by measuring and calculating by the following method.
That is, the value of the orientation angle at a position moved 5 mm in the width direction and 5 mm in the longitudinal direction from an arbitrary position at one end within a range of 1000 mm in diameter with an arbitrary point in the optical film as the center is measured. And it was measured repeatedly up to the other end.
Next, the average value of the absolute values obtained by taking the difference between the values of the adjacent orientation angles was calculated and used as the average difference orientation angle θ _ave °.
The timing of measurement was set at room temperature immediately before the winding step in both the solution casting film forming method and the melt casting film forming method.

The "average differential film thickness _dave " means a value obtained by measuring and calculating by the following method.
That is, the value of the film thickness at a position moved 5 mm in the width direction and 5 mm in the longitudinal direction from an arbitrary position at one end within a range of 1000 mm in diameter with an arbitrary point in the optical film as the center is measured. And it was measured repeatedly up to the other end.
Next, the average value of the absolute values obtained by taking the difference between the values of the adjacent film thicknesses was calculated and used as the average difference film thickness _dave μm.
The timing of measurement was set at room temperature immediately before the winding step in both the solution casting film forming method and the melt casting film forming method.

In the present invention, the average maximum height difference (PV) _ave1 of the film thickness has a slight height difference of 0.15 to 0.40 in the longitudinal direction, and | average difference orientation angle θ _ave / average difference. The film roll having a film thickness _dave × 10 ^-3 | having a large value to some extent as described above defines that the film is an optical film having a minute stress relaxation portion and a non-stress relaxation portion in adjacent regions. Therefore, it is presumed that the non-stress relaxation portion suppresses the local sticking by performing the local relaxation at the time of the local sticking due to the characteristics of the optical film.

Although the average film thickness of the optical film decreases in the heat-treated portion, the orientation angle is slightly disturbed, and it is presumed that this results in an optical film having a minute stress relaxation portion and a non-stress relaxation portion. Therefore, it is considered that some kind of heat treatment is required when a person skilled in the art manufactures a film roll having a reduced film thickness deviation.
The process of setting the temperature within the predetermined range is called "flattening process", which will be described later.

It is preferable that the optical film contains inorganic fine particles from the viewpoint of imparting low birefringence, and it is preferable from the viewpoint of improving heat resistance and storage stability and environmental stability.

It is preferable that the width of the optical film is in the range of 2400 to 3000 mm from the viewpoint of thinning and productivity.

It is preferable that the length of the film roll is in the range of 7500 to 10000 m from the viewpoint of thinning and productivity.

(1.2) Uniformity of Color Tone of Optical Film As another example of the embodiment of the film roll of the present invention, CIE1976L ^* a ^* b ^* color system obtained from the spectral reflectance of the surfaces of the central portion and the edge portion. The a ^* value and the b ^* value defined by the above satisfy the following equation (1).
Satisfying such characteristics means that there is little difference in hue and saturation depending on the location of the optical film, and the color tone of the optical film is uniform as a whole. From the viewpoint of solving the problem and when the optical film is applied to the display device, it is easy to obtain an image with good contrast.

Equation (1):
-1.0 <(end a ^* -center a ^* ) + (end b ^* -center b ^* ) <1.0
(In the above formula, the a ^* value is a coordinate value indicating the hue and saturation in the color system and the position of the red-green transition line. The b ^* value is the coordinate value in the color system. It is a coordinate value that indicates the hue and saturation of, and indicates the position of the yellow-blue transition line.)

The a ^* value and the b ^* value can be measured using a colorimeter. For example, it can be measured by a pallet cube (Palette CUBE; manufactured by Palette Pty Ltd).

2. Resin Constituting an Optical Film (2.1) Thermoplastic Resin The thermoplastic resin material used for the optical film according to the present invention is not limited as long as it can be handled as a film roll after film formation.

For example, thermoplastic resins used for polarizing plates include cellulose ester-based resins such as triacetyl cellulose (TAC), cellulose acetate propionate (CAP), and diacetyl cellulose (DAC), and cycloolefin polymers (cycloolefin-based). Cyclic olefin resin such as resin (COP) (hereinafter, also referred to as cycloolefin resin), polypropylene resin such as polypropylene (PP), acrylic resin such as polymethylmethacrylate (PMMA), and polyethylene terefterate. A polyester resin such as (PET) can be applied.

In particular, in an optical film having a low elastic modulus, for example, a resin having an elastic modulus of less than 3.0 GPa, it is difficult to relieve stress related to a plurality of parts of the film when forming a film roll. This makes it difficult to expand and contract, and when the optical film is in a roll state, stress cannot be completely absorbed on the surface, and winding misalignment is likely to occur.
Further, when the above-mentioned optical film having a low elastic modulus is viewed from another viewpoint, if there is a height difference between the longitudinal direction and the longitudinal direction of the optical film, the expansion and contraction of the high part and the expansion and contraction of the low part of the optical film The difference will be large.
Therefore, in the embodiment of the present invention, it is possible to control the average maximum height difference (PV) _ave1 of the film thickness in the oblique direction with respect to the width direction of the optical film in a specific range in consideration of the variation in the longitudinal direction. Preferably, it is effective to apply a cycloolefin polymer (cycloolefin resin (COP)) or polymethylmethacrylate (acrylic resin (PMMA)), which is a resin having a low elasticity, to a film roll using the thermoplastic resin. be.

However, cycloolefin-based resin (COP) can be used because it is easy to control the stretchability and crystallinity, and it is easy for the adhesive to penetrate and it is possible to secure better adhesion to the polarizer. desirable.
The optical film may be surface-modified after production.

Moreover, the effect of the present invention increases in value in the thin film region.
The film thickness of the optical film is preferably in the range of 5 to 80 μm, more preferably in the range of 10 to 65 μm, and even more preferably in the range of 10 to 45 μm.
When the film thickness is 5 μm or more, the rigidity of the film roll is high, and it becomes easy to maintain the roll shape.
If the film thickness is 80 μm or less, the mass does not increase too much, and it becomes easy to produce a long film roll.

(2.1.1) Cycloolefin-based resin The cycloolefin-based resin contained in the film roll of the present invention is a polymer of a cycloolefin monomer, or a copolymer of a cycloolefin monomer and other copolymers. It is preferably a copolymer with the body.

The cycloolefin monomer is preferably a cycloolefin monomer having a norbornene skeleton, and is a cycloolefin monomer having a structure represented by the following general formula (A-1) or (A-2). More preferably.

In the general formula (A-1), R ¹ to R ⁴ independently represent a hydrogen atom, a hydrocarbon group having 1 to 30 carbon atoms, or a polar group. p represents an integer of 0 to 2. However, all of R ¹ to R ⁴ do not represent hydrogen atoms at the same time, R ¹ and R ² do not represent hydrogen atoms at the same time, and R ³ and R ⁴ do not represent hydrogen atoms at the same time. do.

As the hydrocarbon group having 1 to 30 carbon atoms represented by R ¹ to R ⁴ in the general formula (A-1), for example, a hydrocarbon group having 1 to 10 carbon atoms is preferable, and the hydrocarbon group has 1 to 10 carbon atoms. It is more preferably 1 to 5 hydrocarbon groups.
The hydrocarbon group having 1 to 30 carbon atoms may further have a linking group containing, for example, a halogen atom, an oxygen atom, a nitrogen atom, a sulfur atom or a silicon atom.
Examples of such linking groups include divalent polar groups such as carbonyl groups, imino groups, ether bonds, silyl ether bonds, thioether bonds and the like.
Examples of the hydrocarbon group having 1 to 30 carbon atoms include a methyl group, an ethyl group, a propyl group, a butyl group and the like.

Examples of the polar groups represented by R ¹ to R ⁴ in the general formula (A-1) include a carboxy group, a hydroxy group, an alkoxy group, an alkoxycarbonyl group, an aryloxycarbonyl group, an amino group, an amide group and a cyano group. Is included.
Of these, a carboxy group, a hydroxy group, an alkoxycarbonyl group and an aryloxycarbonyl group are preferable, and an alkoxycarbonyl group and an aryloxycarbonyl group are preferable from the viewpoint of ensuring solubility during solution film formation.

P in the general formula (A-1) is preferably 1 or 2 from the viewpoint of increasing the heat resistance of the optical film.
This is because when p is 1 or 2, the obtained polymer becomes bulky and the glass transition temperature tends to be improved.

In the general formula (A-2), R ⁵ represents an alkylsilyl group having a hydrogen atom, a hydrocarbon group having 1 to 5 carbon atoms, or an alkyl group having 1 to 5 carbon atoms. R ⁶ represents a carboxy group, a hydroxy group, an alkoxycarbonyl group, an aryloxycarbonyl group, an amino group, an amide group, a cyano group, or a halogen atom (fluorine atom, chlorine atom, bromine atom or iodine atom). p represents an integer of 0 to 2.

R ⁵ in the general formula (A-2) preferably represents a hydrocarbon group having 1 to 5 carbon atoms, and more preferably represents a hydrocarbon group having 1 to 3 carbon atoms.

R ⁶ in the general formula (A-2) preferably represents a carboxy group, a hydroxy group, an alkoxycarbonyl group and an aryloxycarbonyl group, and from the viewpoint of ensuring solubility during solution film formation, the alkoxycarbonyl group and aryl Oxycarbonyl groups are more preferred.

P in the general formula (A-2) preferably represents 1 or 2 from the viewpoint of increasing the heat resistance of the optical film.
This is because when p represents 1 or 2, the obtained polymer becomes bulky and the glass transition temperature tends to improve.

A cycloolefin monomer having a structure represented by the general formula (A-2) is preferable from the viewpoint of improving the solubility in an organic solvent.
In general, an organic compound loses its symmetry and thus its crystallinity is lowered, so that its solubility in an organic solvent is improved.
Since R ⁵ and R ⁶ in the general formula (A-2) are substituted with only the ring-constituting carbon atom on one side with respect to the axis of symmetry of the molecule, the symmetry of the molecule is low, that is, the general formula (A-). Since the cycloolefin monomer having the structure represented by 2) has high solubility, it is suitable for producing an optical film by a solution casting method.

The content ratio of the cycloolefin monomer having the structure represented by the general formula (A-2) in the polymer of the cycloolefin monomer is the total of all the cycloolefin monomers constituting the cycloolefin resin. For example, it can be 70 mol% or more, preferably 80 mol% or more, and more preferably 100 mol%.
When a cycloolefin monomer having a structure represented by the general formula (A-2) is contained in a certain amount or more, the orientation of the resin is increased, so that the retardation value is likely to increase.

Hereinafter, specific examples of the cycloolefin monomer having the structure represented by the general formula (A-1) are shown in Examples Compounds 1 to 14, and the cycloolefin single having the structure represented by the general formula (A-2) is shown. Specific examples of the merits are shown in Exemplified Compounds 15 to 34.

Examples of copolymerizable monomers that can be copolymerized with cycloolefin monomers include copolymerizable monomers that can be ring-opened and copolymerized with cycloolefin monomers, and addition copolymerization with cycloolefin monomers. Possible copolymerizable monomers and the like are included.

Examples of ring-opening copolymerizable copolymerizable monomers include cycloolefins such as cyclobutene, cyclopentene, cycloheptene, cyclooctene and dicyclopentadiene.

Examples of copolymerizable monomers that can be additionally copolymerized include unsaturated double bond-containing compounds, vinyl-based cyclic hydrocarbon monomers, (meth) acrylates, and the like.

Examples of unsaturated double bond-containing compounds include olefin compounds having 2 to 12 (preferably 2 to 8) carbon atoms, and examples thereof include ethylene, propylene and butene.

Examples of vinyl-based cyclic hydrocarbon monomers include vinyl cyclopentene-based monomers such as 4-vinylcyclopentene and 2-methyl-4-isopropenylcyclopentene.

Examples of (meth) acrylates include alkyl (meth) acrylates having 1 to 20 carbon atoms such as methyl (meth) acrylate, 2-ethylhexyl (meth) acrylate and cyclohexyl (meth) acrylate.

The content ratio of the cycloolefin monomer in the copolymer of the cycloolefin monomer and the copolymerizable monomer is, for example, 20 to 80 mol% with respect to the total of all the monomers constituting the copolymer. It can be within the range, preferably within the range of 30 to 70 mol%.

As described above, the cycloolefin-based resin is obtained by polymerizing a cycloolefin monomer having a norbornene skeleton, preferably a cycloolefin monomer having a structure represented by the general formula (A-1) or (A-2). It is a polymer obtained by copolymerization, and examples thereof include the following polymers (1) to (7).

(1) Ring-opening polymer of cycloolefin monomer (2) Ring-opening copolymer of cycloolefin monomer and copolymerizable monomer that can be ring-opened and copolymerized (3) The above (1) Alternatively, a hydrogenated product of the ring-opened (co) polymer of (2) (4) The ring-opened (co) polymer of (1) or (2) above was cyclized by the Friedelcrafts reaction, and then hydrogen was added. (Co) polymer (5) Saturated copolymer of cycloolefin monomer and unsaturated double bond-containing compound (6) Addition copolymer of vinyl-based cyclic hydrocarbon monomer of cycloolefin monomer Coalescence and its hydrogenated product (7) Alternating copolymer of cycloolefin monomer and (meth) acrylate

The polymers of (1) to (7) above can be obtained by known methods, for example, the methods described in JP-A-2008-107534 and JP-A-2005-227606.

For example, as the catalyst and solvent used for the ring-opening copolymerization of (2) above, those described in paragraphs 0019 to 0024 of JP-A-2008-107534 can be used.
As the catalyst used for the hydrogenated additives of (3) and (6) above, for example, those described in paragraphs 0025 to 0028 of JP-A-2008-107534 can be used.
As the acidic compound used in the Friedel-Crafts reaction of (4) above, for example, those described in paragraph 0029 of JP-A-2008-107534 can be used.
As the catalyst used for the addition polymerization of the above (5) to (7), for example, those described in paragraphs 0058 to 0063 of JP-A-2005-227606 can be used.
The alternating copolymerization reaction of (7) above can be carried out, for example, by the method described in paragraphs 0071 and 0072 of JP-A-2005-227606.

Among them, the polymers of the above (1) to (3) and (5) are preferable, and the polymers of the above (3) and (5) are more preferable.

That is, the cycloolefin-based resin has a structural unit represented by the following general formula (B-1) in that the glass transition temperature of the obtained cycloolefin-based resin can be raised and the light transmittance can be raised. It is preferable that at least one of the structural units represented by the following general formula (B-2) is included, and only the structural unit represented by the general formula (B-2) is included, or the general formula (B-1) is used. It is more preferable to include both the structural unit represented and the structural unit represented by the general formula (B-2).

The structural unit represented by the general formula (B-1) is a structural unit derived from the cycloolefin monomer represented by the above-mentioned general formula (A-1), and is represented by the general formula (B-2). The structural unit is a structural unit derived from the cycloolefin monomer represented by the above-mentioned general formula (A-2).

In the general formula (B-1), X represents -CH = CH- or -CH ₂ CH _2- . R ¹ to R ⁴ and p are synonymous with R ¹ to R ⁴ and p of the general formula (A-1), respectively.

In the general formula (B-2), X represents -CH = CH- or -CH ₂ CH _2- . R5 to R6 and p are synonymous with R5 to R6 and p of the general ^formula ⁽ A ^- ² ), respectively.

The cycloolefin-based resin according to the present invention may be a commercially available product.
Examples of commercially available cycloolefin resins include Arton G (eg, G7810, etc.), Arton F, Arton R (eg, R4500, R4900, R5000, etc.), and Arton RX, manufactured by JSR Corporation. ..

The intrinsic viscosity [η] inh of the cycloolefin resin is preferably in the range of 0.2 to 5 cm ³ / g, and preferably in the range of 0.3 to 3 cm ³ / g when measured at 30 ° C. Is more preferable, and more preferably in the range of 0.4 to 1.5 cm ³ / g.

The number average molecular weight (Mn) of the cycloolefin resin is preferably in the range of 8000 to 100,000, more preferably in the range of 10,000 to 80,000, and further preferably in the range of 12,000 to 50,000. ..

The weight average molecular weight (Mw) of the cycloolefin resin is preferably in the range of 20,000 to 300,000, more preferably in the range of 30,000 to 250,000, and further preferably in the range of 40,000 to 200,000. ..

The number average molecular weight and weight average molecular weight of the cycloolefin resin can be measured by gel permeation chromatography (GPC) in terms of polystyrene.

(Gel Permeation Chromatography)
Solvent: Methylene chloride Column: Shodex K806, K805, K803G (Three made by Showa Denko KK were connected and used)
Column temperature: 25 ° C
Sample concentration: 0.1% by mass
Detector: RI Model 504 (manufactured by GL Science)
Pump: L6000 (manufactured by Hitachi, Ltd.)
Flow rate: 1.0 ml / min
Calibration curve: Standard polystyrene STK standard polystyrene (manufactured by Tosoh Corporation) A calibration curve with 13 samples in the range of Mw = 500 to 2800000 was used. The 13 samples are preferably used at approximately equal intervals.

When the intrinsic viscosity [η] inh, the number average molecular weight and the weight average molecular weight are within the above ranges, the heat resistance, water resistance, chemical resistance, mechanical properties, and molding processability as a film of the cycloolefin resin are good. Become.

The glass transition temperature (Tg) of the cycloolefin resin is usually 110 ° C. or higher, preferably in the range of 110 to 350 ° C., more preferably in the range of 120 to 250 ° C., and 120 to 120 ° C. It is more preferably in the range of 220 ° C.

When the glass transition temperature (Tg) is 110 ° C. or higher, deformation under high temperature conditions can be easily suppressed.
On the other hand, when the glass transition temperature (Tg) is 350 ° C. or lower, the molding process is facilitated, and deterioration of the resin due to heat during the molding process is also easily suppressed.

The content of the cycloolefin resin is preferably 70% by mass or more, more preferably 80% by mass or more with respect to the film.

(2.1.2) Acrylic Resin The acrylic resin according to the present invention is a polymer of an acrylic acid ester or a methacrylic acid ester, and also includes a copolymer with another monomer.
Therefore, the acrylic resin according to the present invention also includes a methacrylic resin.

The resin is not particularly limited, but the methyl methacrylate unit is in the range of 50 to 99% by mass, and other monomer units copolymerizable therewith are in the range of 1 to 50% by mass. Is preferable.

Other units constituting the acrylic resin formed by copolymerization include alkyl methacrylate having an alkyl number of 2 to 18, alkyl acrylate having an alkyl number of 1 to 18, isobornyl methacrylate, and 2-. Hydroxyalkyl acrylates such as hydroxyethyl acrylates, α, β-unsaturated acids such as acrylic acid and methacrylic acid, acrylamides such as acryloylmorpholine and N-hydroxyphenylmethacrylate, N-vinylpyrrolidone, maleic acid, fumaric acid, itaconic acid and the like. Unsaturated group-containing divalent carboxylic acid, aromatic vinyl compounds such as styrene and α-methylstyrene, α, β-unsaturated nitriles such as acrylonitrile and methacrylic nitrile, maleic anhydride, maleimide, N-substituted maleimide, and glutal. Examples thereof include imide and glutaric acid anhydride.

Examples of copolymerizable monomers that form units excluding glutarimide and glutaric anhydride from the above units include monomers corresponding to the above units.

That is, alkyl methacrylate having 2 to 18 carbon atoms of alkyl number, alkyl acrylate having 1 to 18 carbon atoms of alkyl number, hydroxyalkyl acrylate such as isobornyl methacrylate and 2-hydroxyethyl acrylate, acrylic acid, methacrylic acid and the like. Unsaturated group-containing divalent carboxylic acids such as α, β-unsaturated acid, acryloylmorpholine, acrylamide such as N-hydroxyphenylmethacrylate, N-vinylpyrrolidone, maleic acid, fumaric acid, and itaconic acid, styrene, α-methylstyrene. Examples thereof include aromatic vinyl compounds such as, acrylonitrile, α, β-unsaturated nitriles such as methacrylonitrile, maleic anhydride, maleimide and N-substituted maleimide, and the like.

Further, the glutarimide unit can be formed, for example, by reacting an intermediate polymer having a (meth) acrylic acid ester unit with a primary amine (imidizing agent) to imidize it (see JP-A-2011-26563). ).

The glutaric acid anhydride unit can be formed, for example, by heating an intermediate polymer having a (meth) acrylic acid ester unit (see Japanese Patent No. 4961164).

Among the above-mentioned structural units, the acrylic resin according to the present invention contains isobornyl methacrylate, acryloylmorpholine, N-hydroxyphenylmethacrylicamide, N-vinylpyrrolidone, styrene, hydroxyethylmethacrylate, and anhydride from the viewpoint of mechanical strength. It is particularly preferred that maleic acid, maleimide, N-substituted maleimide, glutaric anhydride or glutarimide are included.

The acrylic resin according to the present invention has the viewpoint of controlling dimensional changes with respect to changes in the temperature and humidity atmosphere of the environment, peelability from a metal support during film production, drying properties of an organic solvent, heat resistance and mechanical strength. From the viewpoint of improvement, the weight average molecular weight (Mw) is preferably in the range of 50,000 to 1,000,000, more preferably in the range of 100,000 to 1,000,000, and particularly preferably in the range of 200,000 to 800,000.

If it is 50,000 or more, the heat resistance and mechanical strength are excellent, and if it is 1,000,000 or less, the peelability from the metal support and the drying property of the organic solvent are excellent.

The method for producing the acrylic resin according to the present invention is not particularly limited, and any known method such as suspension polymerization, emulsion polymerization, bulk polymerization, or solution polymerization may be used.

Here, as the polymerization initiator, ordinary peroxide-based and azo-based ones can be used, and redox-based ones can also be used.

The polymerization temperature can be carried out within the range of 30 to 100 ° C. for suspension or emulsion polymerization, and within the range of 80 to 160 ° C. for massive or solution polymerization.

In order to control the reducing viscosity of the obtained copolymer, polymerization can also be carried out using an alkyl mercaptan or the like as a chain transfer agent.

The glass transition temperature (Tg) of the acrylic resin is preferably in the range of 80 to 120 ° C. from the viewpoint of maintaining the mechanical strength of the film.

As the acrylic resin according to the present invention, commercially available ones can also be used.
For example, Delpet 60N, 80N, 980N, SR8200 (all manufactured by Asahi Kasei Chemicals Co., Ltd.), Diamondal BR52, BR80, BR83, BR85, BR88, EMB-143, EMB-159, EMB-160, EMB-161, EMB. -218, EMB-229, EMB-270, EMB-273 (all manufactured by Mitsubishi Rayon Co., Ltd.), KT75, TX400S and IPX012 (all manufactured by Denki Kagaku Kogyo Co., Ltd.) and the like.
Two or more kinds of acrylic resins can be used in combination.

The acrylic resin according to the present invention preferably contains an additive, and as an example of the additive, the acrylic particles (rubber elastic particles) described in International Publication No. 2010/001668 are used as the mechanical strength of the film. It is preferably contained for improvement and adjustment of the dimensional change rate.

Examples of commercially available products of such a multilayer structure acrylic granular composite are, for example, "Metabrene W-341" manufactured by Mitsubishi Rayon, "Kaneka" manufactured by Kaneka, "Paraloid" manufactured by Kureha, and Roam and Hearth. Examples include "Acryloid" manufactured by Aica, "Staphyroid" manufactured by Aica, Chemisnow MR-2G, MS-300X (above, manufactured by Soken Chemical Co., Ltd.) and "Parapet SA" manufactured by Kuraray. , Alone or two or more can be used.

The volume average particle diameter of the acrylic particles is 0.35 μm or less, preferably in the range of 0.01 to 0.35 μm, and more preferably in the range of 0.05 to 0.30 μm.
When the particle size is above a certain level, the film can be easily stretched under heating, and when the particle size is below a certain level, the transparency of the obtained film is not easily impaired.

From the viewpoint of flexibility, the optical film of the present invention preferably has a flexural modulus (JIS K7171) of 10.5 GPa or less.
This flexural modulus is more preferably 1.3 GPa or less, still more preferably 1.2 GPa or less.
This flexural modulus varies depending on the type and amount of acrylic resin and rubber elastic particles in the film. For example, the larger the content of rubber elastic particles, the smaller the flexural modulus.

Further, as the acrylic resin, the flexural modulus is generally smaller when a copolymer of alkyl methacrylate and alkyl acrylate or the like is used than when a homopolymer of alkyl methacrylate is used.

(2.1.3) Cellulose ester resin In the film roll of the present invention, it is also preferable to use a cellulosic ester resin.

The cellulose ester used in the present invention is a part or all of the hydrogen atoms of the hydroxy groups (-OH) at the 2-position, 3-position and 6-position in the β-1,4-bonded glucose unit constituting the cellulose. Refers to a cellulose acylate resin substituted with an acyl group.

The cellulose ester used is not particularly limited, but is preferably a linear or branched carboxylic acid ester having about 2 to 22 carbon atoms.
The carboxylic acid constituting the ester may be an aliphatic carboxylic acid, may form a ring, or may be an aromatic carboxylic acid.

For example, the hydrogen atom of the hydroxy group portion of cellulose is an acyl group having 2 to 22 carbon atoms such as an acetyl group, a propionyl group, a butyryl group, an isobutyryl group, a valeryl group, a pivaloyl group, a hexanoyl group, an octanoyl group, a lauroyl group and a stearoyl group. Substituted cellulose esters can be mentioned.

The carboxylic acid (acyl group) constituting the ester may have a substituent.
The carboxylic acid constituting the ester is particularly preferably a lower fatty acid having 6 or less carbon atoms, and more preferably a lower fatty acid having 3 or less carbon atoms.
The acyl group in the cellulose ester may be a single type or a combination of a plurality of acyl groups.

Specific examples of preferable cellulose esters include cellulose acetates such as diacetyl cellulose (DAC) and triacetyl cellulose (TAC), as well as cellulose acetate propionate (CAP), cellulose acetate butyrate, and cellulose acetate propionate butyrate. In addition to such an acetyl group, a mixed fatty acid ester of cellulose to which a propionate group or a butyrate group is bonded can be mentioned.
These cellulose esters may be used alone or in combination of two or more.

(Type of acyl group / degree of substitution)
By adjusting the type and degree of substitution of the acyl group of the cellulose ester, the humidity fluctuation of the phase difference can be controlled within a desired range, and the uniformity of the film thickness can be improved.

The smaller the degree of substitution of the acyl group of the cellulose ester, the better the phase difference expression, so that the film can be thinned.
On the other hand, if the degree of substitution of the acyl group is too small, the durability may deteriorate, which is not preferable.

On the other hand, the larger the degree of substitution of the acyl group of the cellulose ester, the less the phase difference appears. Therefore, it is necessary to increase the stretching ratio at the time of film formation, but it is difficult to uniformly stretch at a high stretching ratio. The variation in film thickness becomes large (worse).
Further, the Rt humidity fluctuation, which is the retardation (phase difference) in the thickness direction, is caused by the coordination of water molecules to the carbonyl group of cellulose, so that the degree of substitution of the acyl group is high, that is, the carbonyl group in the cellulose has a high degree of substitution. The larger the amount, the worse the Rt humidity fluctuation tends to be.

The total degree of substitution of the cellulose ester is preferably in the range of 2.1 to 2.5.
Within this range, environmental fluctuations (particularly Rt fluctuations due to humidity) can be suppressed and the uniformity of the film thickness can be improved.
More preferably, it is in the range of 2.2 to 2.45 from the viewpoint of improving the ductility and stretchability during film formation and further improving the uniformity of the film thickness.

More specifically, the cellulose ester satisfies both the following formulas (a) and (b). In the following formulas (a) and (b), X is the degree of substitution of an acetyl group, Y is the degree of substitution of a propionyl group or a butyryl group, or a mixture thereof.

Equation (a): 2.1 ≤ X + Y ≤ 2.5
Equation (b): 0 ≤ Y ≤ 1.5

As the cellulose ester, cellulose acetate (Y = 0) and cellulose acetate propionate (CAP) (Y; propionyl group, Y> 0) are more preferable, and more preferably, Y = 0 from the viewpoint of reducing the film thickness variation. There is a cellulose acetate.

Cellulose acetate, which is particularly preferably used, has 2.1 ≦ X ≦ 2.5 (more preferably 2.15 ≦ X ≦ 2.45) from the viewpoint of setting the desired range of phase difference expression, Rt humidity fluctuation, and film thickness variation. ) Cellulose diacetate (DAC).

When Y> 0, the cellulose acetate propionate (CAP) that is particularly preferably used is 0.95 ≦ X ≦ 2.25, 0.1 ≦ Y ≦ 1.2, 2.15 ≦ X + Y ≦. It is 2.45.

By using the above-mentioned cellulose acetate or cellulose acetate propionate, a film roll having excellent retardation, mechanical strength, and environmental change can be obtained.

The degree of substitution of the acyl group indicates the average number of acyl groups per glucose unit, and how many hydrogen atoms of the hydroxy groups at the 2, 3, and 6 positions of the 1 glucose unit are substituted with the acyl group. Is shown.
Therefore, the maximum degree of substitution is 3.0, which means that all the hydrogen atoms of the hydroxy groups at the 2-position, 3-position and 6-position are substituted with acyl groups.
These acyl groups may be substituted at the 2-position, 3-position, and 6-position of the glucose unit on average, or may be substituted with a distribution.
The degree of substitution is determined by the method specified in ASTM-D817-96.

Cellulose acetates having different degrees of substitution may be mixed and used in order to obtain desired optical properties.
In the above case, the mixing ratio of different cellulose acetates is not particularly limited.

The number average molecular weight (Mn) of the cellulose ester is in the range of 2 × 10 ⁴ to 3 × 105, further in the range of 2 × 10 ⁴ to 1.2 × 105, and further in the range of ⁴ × 10 ⁴ to ⁴ . The range of 8 × 10 ⁴ is preferable from the viewpoint of increasing the mechanical strength of the obtained film roll.

The number average molecular weight Mn of the cellulose ester is calculated by measurement using gel permeation chromatography (GPC) under the above-mentioned measurement conditions.

The weight average molecular weight (Mw) of the cellulose ester is in the range of 2 × 10 ⁴ to 1 × 10 ⁶ , further in the range of 2 × 10 ⁴ to 1.2 × 105, and further in the range of 4 × 10 ⁴ to ⁴ . The range of 8 × 10 ⁴ is preferable from the viewpoint of increasing the mechanical strength of the obtained film roll.

The raw material cellulose of the cellulose ester is not particularly limited, and examples thereof include cotton linter, wood pulp, and kenaf.
In addition, the cellulose esters obtained from them can be mixed and used in any ratio.

Cellulose esters such as cellulose acetate and cellulose acetate propionate can be produced by known methods.

Generally, cellulose as a raw material is mixed with a predetermined organic acid (acetic acid, propionic acid, etc.), an acid anhydride (acetic acid anhydride, propionic anhydride, etc.), and a catalyst (sulfuric acid, etc.) to esterify the cellulose and carry out cellulose. Proceed with the reaction until the triester is formed.

In the triester, the three hydroxy groups of the glucose unit are replaced with the acyl acid of the organic acid.

By using two kinds of organic acids at the same time, it is possible to prepare a mixed ester type cellulose ester such as cellulose acetate propionate or cellulose acetate butyrate.

Then, the cellulose ester is hydrolyzed to synthesize a cellulose ester resin having a desired degree of acyl substitution.
After that, the cellulose ester resin is completed through steps such as filtration, precipitation, washing with water, dehydration, and drying. Specifically, it can be synthesized with reference to the method described in JP-A No. 10-45804.

(2.2) Other Additives The film roll of the present invention may contain the following as other additives in addition to the above-mentioned thermoplastic resin.

(2.2.1) Plasticizer The film roll of the present invention preferably contains at least one type of plasticizer for the purpose of imparting processability to, for example, a polarizing plate protective film.
It is preferable to use the plasticizer alone or in combination of two or more.

Among the plasticizers, containing at least one plasticizer selected from the group consisting of sugar esters, polyesters, and styrene-based compounds effectively controls the moisture permeability and is compatible with the base resin such as cellulose esters. It is preferable from the viewpoint that the solubility can be highly compatible.

It is preferable that the plasticizer has a molecular weight of 15,000 or less, more preferably 10,000 or less, from the viewpoint of achieving both improvement in moisture and heat resistance and compatibility with a base resin such as a cellulose ester.

When the compound having a molecular weight of 10,000 or less is a polymer, the weight average molecular weight (Mw) is preferably 10,000 or less.
The preferred weight average molecular weight (Mw) range is in the range of 100 to 10000, more preferably in the range of 400 to 8000.

In particular, in order to obtain the effects of the present invention, the compound having a molecular weight of 1500 or less is preferably contained in the range of 6 to 40 parts by mass with respect to 100 parts by mass of the base resin, and is preferably 10 to 20 parts by mass. It is more preferable to contain it within the range.
By containing it within the above range, it is possible to achieve both effective control of moisture permeability and compatibility with the base resin, which is preferable.

<Sugar ester>
The film roll of the present invention may contain a sugar ester compound for the purpose of preventing hydrolysis.
Specifically, as the sugar ester compound, a sugar ester having at least one or more and 12 or less pyranose structures or at least one furanose structure and esterifying all or part of the OH groups having that structure can be used. can.

<polyester>
The film roll of the present invention may also contain polyester.

The polyester is not particularly limited, but for example, a polymer (polyester polyol) having a hydroxy group at the end, which can be obtained by a condensation reaction between a dicarboxylic acid or an ester-forming derivative thereof and glycol, or a hydroxy at the end of the polyester polyol. A polymer whose group is sealed with a monocarboxylic acid (end-sealed polyester) can be used.
The ester-forming derivative referred to here is an esterified product of a dicarboxylic acid, a dicarboxylic acid chloride, or an anhydride of a dicarboxylic acid.

<Styrene compound>
In addition to or instead of the above-mentioned sugar ester and polyester, a styrene-based compound may be used for the film roll of the present invention for the purpose of improving the water resistance of the optical film.

The styrene-based compound may be a homopolymer of a styrene-based monomer, or may be a copolymer of a styrene-based monomer and another copolymerization monomer.
The content ratio of the structural unit derived from the styrene-based monomer in the styrene-based compound is preferably in the range of 30 to 100 mol%, more preferably 50 to 100 mol% in order for the molecular structure to have a certain bulkiness or more. It can be within the range.

Examples of styrene-based monomers include styrene; alkyl-substituted styrenes such as α-methylstyrene, β-methylstyrene, and p-methylstyrene; halogen-substituted styrenes such as 4-chlorostyrene and 4-bromostyrene; p-hydroxy. Hydroxystyrenes such as styrene, α-methyl-p-hydroxystyrene, 2-methyl-4-hydroxystyrene, 3,4-dihydroxystyrene; vinylbenzyl alcohols; p-methoxystyrene, p-tert-butoxystyrene, m -Alkoxy-substituted styrenes such as tert-butoxystyrene; vinyl benzoic acids such as 3-vinylbenzoic acid and 4-vinylbenzoic acid; 4-vinylbenzylacetrene;4-acetoxystyrene;2-butylamide styrene, 4-methylamide Amid styrenes such as styrene and p-sulfonamide styrene; aminostyrenes such as 3-aminostyrene, 4-aminostyrene, 2-isopropenylaniline and vinylbenzyldimethylamine; 3-nitrostyrene, 4-nitrostyrene and the like. Nitrostyrenes; cyanostyrenes such as 3-cyanostyrene and 4-cyanostyrene; vinylphenylacetrene; arylstyrenes such as phenylstyrene, indens and the like are included.
The styrene-based monomer may be one type or a combination of two or more types.

(2.2.2) Optional components The film roll of the present invention contains other optional components such as antioxidants, colorants, ultraviolet absorbers, matting agents, acrylic particles, hydrogen-bonding solvents and ionic surfactants. Can include.
These components can be added in the range of 0.01 to 20 parts by mass with respect to 100 parts by mass of the base resin.

(Antioxidant)
As the film roll of the present invention, commonly known antioxidants can be used.
In particular, lactone-based, sulfur-based, phenol-based, double-bonded, hindered amine-based, and phosphorus-based compounds can be preferably used.

These antioxidants and the like are added in the range of 0.05 to 20% by mass, preferably in the range of 0.1 to 1% by mass, with respect to the resin which is the main raw material of the optical film.
These antioxidants and the like can obtain a synergistic effect by using several kinds of compounds of different systems in combination rather than using only one kind.
For example, the combined use of lactone-based, phosphorus-based, phenol-based and double-bonding compounds is preferable.

(Colorant)
The film roll of the present invention preferably contains a colorant for color tone adjustment within a range that does not impair the effects of the present invention.

The colorant means a dye or a pigment, and in the present invention, it means a colorant having the effect of making the color tone of the liquid crystal screen blue, the adjustment of the yellow index, and the reduction of haze.

Various dyes and pigments can be used as colorants, but anthraquinone dyes, azo dyes, phthalocyanine pigments, etc. are effective.

(UV absorber)
Since the film roll of the present invention can also be used on the visible side or the backlight side of the polarizing plate, it may contain an ultraviolet absorber for the purpose of imparting an ultraviolet absorbing function.

The ultraviolet absorber is not particularly limited, and examples thereof include ultraviolet absorbers such as benzotriazole-based, 2-hydroxybenzophenone-based, and salicylic acid phenyl ester-based.
For example, 2- (5-methyl-2-hydroxyphenyl) benzotriazole, 2- [2-hydroxy-3,5-bis (α, α-dimethylbenzyl) phenyl] -2H-benzotriazole, 2- (3,5) Triazoles such as -di-t-butyl-2-hydroxyphenyl) benzotriazole, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-octoxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone, etc. Benzophenones can be exemplified.
The above-mentioned ultraviolet absorber may be used alone or in combination of two or more.

The amount of the ultraviolet absorber used is not uniform depending on the type of the ultraviolet absorber, the conditions of use, etc., but is generally in the range of 0.05 to 10% by mass, preferably 0.1, based on the base resin. It is added in the range of ~ 5% by mass.

(Fine particles)
For the film roll of the present invention, it is preferable to add fine particles that impart slipperiness to the film roll.
In particular, it is effective to add fine particles from the viewpoint of improving the slipperiness of the surface of the optical film according to the present invention, improving the slipperiness at the time of winding, and preventing the occurrence of scratches and blocking.

The fine particles may be either inorganic fine particles or organic fine particles as long as they do not impair the transparency of the obtained film roll and have heat resistance at the time of melting, but inorganic fine particles are more preferable.
These fine particles can be used alone or in combination of two or more.

By using particles with different particle sizes and shapes (for example, needle-shaped and spherical), it is possible to achieve both high transparency and slipperiness.

Among the compounds constituting the fine particles, silicon dioxide having excellent transparency (haze) is particularly preferably used because it has a refractive index close to that of the cycloolefin resin, acrylic resin or cellulose ester resin.

Specific examples of silicon dioxide include Aerodil (registered trademark) 200V, Aerodil (registered trademark) R972V, Aerodil (registered trademark) R972, R974, R812, 200, 300, R202, OX50, TT600, NAX50 (above Japan Aerozil Co., Ltd.) , Seahoster (registered trademark) KEP-10, Seahoster (registered trademark) KEP-30, Seahoster (registered trademark) KEP-50 (all manufactured by Nippon Catalyst Co., Ltd.), Silohobic (registered trademark) 100 (Fuji Silicia) Commercial products having trade names such as Nip Seal (registered trademark) E220A (manufactured by Nippon Silica Industry Co., Ltd.) and Admafine (registered trademark) SO (manufactured by Admatex Co., Ltd.) can be preferably used.

The shape of the particles can be used without particular limitation such as amorphous, needle-shaped, flat, and spherical, but it is particularly preferable to use spherical particles because the transparency of the obtained film roll can be improved.

When the size of the particles is close to the wavelength of visible light, light is scattered and the transparency is deteriorated. Therefore, the size of the particles is preferably smaller than the wavelength of visible light, and more preferably 1/2 or less of the wavelength of visible light. ..

If the particle size is too small, the slipperiness may not be improved, so the range of 80 to 180 nm is particularly preferable.
The particle size means the size of the agglomerates when the particles are agglomerates of primary particles.
When the particles are not spherical, it means the diameter of a circle corresponding to the projected area.

The fine particles are preferably added in the range of 0.05 to 10% by mass, preferably in the range of 0.1 to 5% by mass, with respect to the base resin.

(Use of optical film)
The optical film unwound from the film roll of the present invention is suitably used as a protective film for a polarizing plate as an optical film, and is used for various optical measuring devices and display devices such as liquid crystal display devices and organic electroluminescence display devices. Can be done.

3. 3. Method for Producing Film Roll The method for producing a film roll of the present invention includes at least a stretching step of stretching an optical film in a stretching furnace and a flattening treatment step, and in the flattening treatment step, in the stretching furnace. It is characterized in that it is flattened at a high temperature within the range of 50 to 200 ° C. with respect to the temperature.

The "film roll" as used in the present invention refers to an optical film wound in a roll shape.
For the film formation of the optical film according to the present invention, a usual production method such as an inflation method, a T-die method, a calendar method, a cutting method, a casting method, an emulsion method, a hot press method, etc. can be used, but color suppression and foreign matter can be formed. From the viewpoint of suppressing defects and suppressing optical defects such as die lines, the solution casting film forming method and the melt casting film forming method are preferable, and the solution casting film forming method is particularly suitable for obtaining a uniform surface. More preferred.

(3.1) Flattening of uneven shape on the surface of the optical film: Film thickness control means The average maximum height difference (PV) _ave1 of the film thickness of the optical film according to the present invention and the outer diameter of the central portion of the film roll. In order to adjust the value of the ratio (Dc / De) of Dc to the outer diameter De of the end portion to a desired value, a means for flattening the uneven shape of the optical film surface can be considered, for example, the following. Examples thereof include flattening treatments 1 to 4.
Moreover, you may combine them.

(Flatification process 1)
The film thickness is controlled by a method of controlling the pitch of pump pulsation.
The dope discharge amount is controlled by increasing the rotation speed according to the gear ratio of the gear pump, the pulsation at the time of dope feeding (extrusion of resin in the case of melting) is controlled, and the pitch of the pump pulsation is controlled.

Here, the liquid feeding capacity of the pump will be supplementarily described.
In the casting process described later, if the length of the pipe from the pump to the casting die is not too short, the pulsation will not increase due to the influence of the rotation speed of the pump, and if it is not too long, the pressure loss will be large. Not too much, it is possible to prevent the pump's liquid feeding capacity from dropping beyond the lower limit.
Further, if the rotation speed of the pump is not too slow, it is possible to prevent the liquid feeding capacity from being lowered, and if it is not too fast, the pressure loss is not too large and it is possible to prevent the liquid feeding capacity from being lowered.

From the above viewpoint, the length of the pipe from the pump to the casting die should be within the range of 50 to 100 m, and the gear ratio of the gear pump used for dope feeding (extruding resin in the case of melting) should be adjusted to pump. The rotation speed of the above is preferably in the range of 10 to 50 rpm.

<Definition of whether or not flattening process 1 is performed>
In the examples and comparative examples of the present invention, performing the flattening process 1 means that the length of the pipe from the pump to the casting die is 60 m in the casting step described later, and the gear pump used for the dope feed is fed. It means adjusting the gear ratio and setting the rotation speed of the pump to 20 rpm.
Further, not performing the flattening process 1 means that in the casting process described later, the length of the pipe from the pump to the casting die is set to 30 m, which is outside the range of 50 to 100 m, and the gear pump used for doping liquid feeding. The gear ratio of the pump is adjusted to 70 rpm, which is outside the range of 10 to 50 rpm.

(Flattening process 2)
The initial discharge film thickness is controlled by the heat bolt of the casting die.
The casting die is provided with a mechanism for adjusting the slit for discharging the dope (extruding the resin in the case of melting).

Here, a method of adjusting the gap between the widths of the slits for discharging the dope by using the heat bolt of the casting die to control the initial discharge film thickness of the casting film will be supplementarily described.
In the casting step described later, if the gap between the widths of the slits for discharging the dope is not too small by the heat bolt of the casting die, the preparation can be performed relatively easily technically and it does not take much time.
Further, if the gap between the widths of the slits for discharging the dope is too large, the initial discharge film thickness of the cast film cannot be flattened.

From the above viewpoint, in the casting process described later, the heat bolt of the casting die is used to reduce the gap between the widths of the slits that discharge the dope and the film thickness deviation immediately after discharge from 1.0 to the entire casting film. It is preferable to adjust the thickness within the range of 5.0% and control the initial discharge film thickness of the cast film.

<Definition of whether or not flattening process 2 is performed>
In the examples and comparative examples of the present invention, performing the flattening process 2 means that in the casting step described later, the heat bolt of the casting die is used to create a gap in the width of the slit for discharging the dope, and the film immediately after the discharge. It means that the thickness deviation is adjusted to 1.5% with respect to the entire casting film to control the initial discharge film thickness of the casting film.
Further, not performing the flattening process 2 means that in the casting step described later, the width of the slit for discharging the dope is determined by the heat bolt of the casting die, and the film thickness deviation immediately after the ejection is determined as the casting film. It is defined as adjusting the initial discharge film thickness of the cast film to 5.5%, which is outside the range of 1.0 to 5.0% with respect to the whole.

<Capturing the definition of whether or not the flattening process 2 is performed>
However, the film thickness deviation immediately after ejection in the definition of whether or not the flattening process 2 is performed can be appropriately changed depending on the film thickness required for the optical film to be produced.

(Flatification process 3)
Warm air is blown onto the flow film, and the heat flattens the protrusions to control the film thickness.
On the belt in the casting step (S2), wind may be blown with the surface layer on the opposite side of the casting film forming a film, or warm air may be blown immediately after the casting film is peeled off from the belt. You may.
At this time, since the inside of the casting film is soft because it contains a solvent, in order to flatten the protrusions, the non-uniformity in the width direction of the casting film is measured online, and the temperature, wind speed, or air volume of the dry air is measured. The film thickness is controlled by adjusting and adjusting the amount of residual solvent.

Here, the temperature, air velocity or air volume of the dry air, and the residual solvent amount will be supplementarily described.
If the temperature of the dry air is not too low, the wind speed is too low, or the air volume is not too small, the film thickness can be appropriately controlled.
Also, unless the temperature is too high, the wind speed is too high, or the air volume is too high, the film thickness will not be locally uncontrollable.

If the amount of residual solvent is not too small, it will not occur that the film is not soft and cannot be flattened in a state closer to an optical film than in a cast film state.
Further, if it is not too much, the film thickness does not vary when flattened.

From these facts, flattening 3 can be performed with a thin film formed on the surface layer by adjusting the amount of residual solvent to an appropriate level.

From the above viewpoint, the temperature of the dry air is preferably in the range of 10 to 80 ° C., and the wind speed is preferably in the range of 5 to 40 m / sec.
The amount of residual solvent is preferably 150 to 550% by mass.

If the above operation is performed while the surface layer on the opposite side of the casting film is not a film, it becomes streaks and it is not preferable that the inside is dry.
When measuring the non-uniformity of the film thickness deviation of the casting film in the width direction online on the belt of the casting step (S2) and blowing warm air to reduce the non-uniformity, The film thickness is controlled by adjusting the temperature.

<Definition of whether or not flattening process 3 is performed>
In the examples and comparative examples of the present invention, to carry out the flattening treatment 3 means that the surface layer is coated by drying the casting film on the belt until the residual solvent amount becomes 200% by mass in the casting step described later. It is said that the protrusions are flattened by blowing warm air at a wind speed of 16 m / sec (40 ° C.) after the formation.
Further, not performing the flattening treatment 3 means that in the casting step described later, the casting film on the belt is dried until it reaches 5% by mass, which is outside the range of 150 to 550% by mass. After the film is formed on the surface layer, warm air of 45 m / sec (40 ° C.), which is outside the range of wind speed of 5 to 40 m / sec, is blown to flatten the protrusions.

(Flattening process 4)
In the stretching step, the film thickness is controlled by changing the temperature inside the furnace in the tenter stretching device and the timing of heat treatment.
In the present invention, the above heat treatment is performed by an infrared (IR) heater, but the heat treatment may be performed by another method.
Further, the flattening treatment 4 can be performed in a furnace of another step other than the stretching step by changing the corresponding environmental temperature and the timing of the heat treatment.
The tenter stretching device is a device that stretches the optical film by grasping both ends of the optical film in the width direction with clips and widening the interval while running the clips together with the optical film, and is usually a plurality of zones (preheating zones). , Stretching zone and heat fixing zone), and in the present invention, the timing of applying heat treatment among the above zones is (1-1) when passing through the preheating zone in the tenter stretching device, and (1-2) passing through the stretching zone. At the time, (1-3) at least one of the three when passing through the heat treatment zone is to be used.

Here, the temperature difference between the furnace temperature and the heat treatment will be supplementarily described.
The inside of the stretching furnace defined in the present application refers to three zones, a preheating zone, a stretching zone and a heat fixing zone, and the temperature inside the stretching furnace is a stretching furnace in which the position 100 mm above the center of the optical film immediately before stretching is measured in the stretching zone. The temperature inside.
If the temperature difference between the furnace temperature and the heat treatment is not too small or too large, the flattening process can be easily controlled.

From the above viewpoint, the temperature difference between the furnace temperature and the heat treatment is preferably in the range of 50 to 200 ° C.

<Definition of whether or not flattening process 4 is performed>
In the examples and comparative examples of the present invention, performing the flattening treatment 4 means that a required number of infrared (IR) heaters are installed and heat-treated in the stretching process described later.
Further, not performing the flattening treatment 4 means that the infrared (IR) heater is not installed and the heat treatment is not performed in the stretching process described later.

(Infrared (IR) heater)
Details of the infrared (IR) heater used in the present invention will be described.
The infrared (IR) heater that can be used in carrying out the present invention is designed so that the infrared irradiation range can be narrowed pinpointly by using a mirror that reflects infrared rays, unlike a general infrared (IR) heater. Is preferable.
Examples of mirrors that reflect infrared rays include cold mirrors (manufactured by Sigma Kouki Co., Ltd.) and aluminum augmentation reflection mirrors for infrared rays (manufactured by Novo Optics Co., Ltd.).
As the mirror used in carrying out the present invention, an aluminum brightening reflection mirror for infrared rays (manufactured by Novo Optics), which is a mirror using aluminum, was used.
The infrared irradiation range of one current general infrared (IR) heater is, for example, MCHNNNS3, irradiation energy 400 W (manufactured by Misumi Co., Ltd.) and 500 mm in the width direction, whereas it was used in the practice of the present invention. The infrared irradiation range of one infrared (IR) heater is 100 to 150 mm in the width direction with an irradiation energy of 550 W (manufactured by Heat Tech Co., Ltd.).

(Relationship between the amount of heat A in the center and the average value B of the amount of heat at the edges)
In the stretching step, the flattening process is performed using an infrared (IR) heater, and the average value B of the heat amount A at the center and the heat amount B at the end at a position 100 mm away from the infrared (IR) heater is By satisfying the above formula (3), the flattening process can be effectively realized.
In the present invention, the temperature distribution of the average value B of the heat quantity A at the center and the heat quantity B at the end at a position 100 mm away from the infrared (IR) heater is measured by a thermo-viewer (VIM-640G2ULC manufactured by Vision Sensing Co., Ltd.). , It was calculated by taking the average value, but when the heat treatment was performed by another method, it corresponded accordingly.

The principle and calculation method are shown in detail below.
The optical film is heated by the infrared (IR) heater.
The heated parts are integrated in the longitudinal direction, the integrated value in the longitudinal direction of the central portion is defined as the calorific value A, and the integrated values in the longitudinal direction at a position 75 mm from the center are calculated on both sides of the optical film end. Let the average value be the average value B of the amount of heat at the end.
(B / A) is calculated from the above values.
At this time, when (B / A) is too large, the infrared (IR) heater is not designed to pinpoint the infrared irradiation range, but when (B / A) is too small, it is not designed. The range of the (B / A) value can be controlled by increasing the number of installed infrared (IR) heaters.

(3.2) Manufacturing process of a film roll by the solution casting film forming method FIG. 5 is a flowchart showing the flow of the manufacturing process of the solution casting film forming method.
Further, FIG. 6 is a schematic view of an apparatus for manufacturing an optical film by a solution casting film forming method.

Hereinafter, the solution casting film forming method will be described with reference to FIGS. 5 and 6.
The method for producing an optical film by the solution casting film forming method is a dope preparation step (S1), a casting step (S2), a peeling step (S3), a shrinkage step (S4), a first drying step (S5), and a first. Stretching step (S6), first cutting step (S7), second stretching step (S8), second cutting step (S9), second drying step (S10), third cutting step (S11), and winding step. (S12) is included.

The manufacturing method does not have to include both the first drying step (S5) and the second drying step (S10), and may include at least one of the steps.
Further, the cutting step of any one of the first stretching step (S6), the second stretching step (S8), the first cutting step (S7), the second cutting step (S9), and the third cutting step (S11) is included. Just do it.

(3.2.1) Dope preparation (stirring preparation) step (S1)
In the dope preparation (stirring preparation) step (S1), at least the resin and the solvent are agitated in the stirring tank 1a of the stirring device 1 to prepare a dope to be cast on the support 3 (endless belt).

As the solvent, a mixed solvent of a good solvent and a poor solvent is used.
Hereinafter, as an embodiment of the present invention, a dope preparation step will be described by taking as an example a case where a cycloolefin resin (hereinafter, also referred to as COP) is used as the thermoplastic resin, but the present invention is not limited thereto.

This step is a step of dissolving the COP and, in some cases, other compounds in a solvent mainly containing a good solvent for the cycloolefin resin (COP) while stirring, or the COP solution. In some cases, other compound solutions are mixed to form a dope which is a main solution.

The concentration of the cycloolefin resin (COP) in the dope is preferably high because the drying load after casting on the support can be reduced.
However, if the COP concentration is too high, the load during filtration increases and the accuracy deteriorates.
The concentration at which these are compatible is preferably in the range of 10 to 35% by mass, more preferably in the range of 15 to 30% by mass.

The solvent used for doping may be used alone or in combination of two or more, but it is preferable to use a mixture of a good solvent and a poor solvent of cycloolefin resin (COP) in terms of production efficiency. , The one having a large amount of good solvent is preferable in terms of the solubility of COP.

The preferable range of the mixing ratio of the good solvent and the poor solvent is in the range of 70 to 98% by mass for the good solvent and in the range of 2 to 30% by mass for the poor solvent.
The good solvent and the poor solvent are defined as a good solvent in which the cycloolefin resin (COP) to be used is dissolved alone, and a poor solvent in which the cycloolefin resin (COP) used alone is swelled or not dissolved.
Therefore, the good solvent and the poor solvent change depending on the average degree of substitution of COP.

The good solvent used in the present invention is not particularly limited, and examples thereof include organic halogen compounds such as methylene chloride, dioxolanes, acetone, methyl acetate, and methyl acetoacetate.
Particularly preferred are methylene chloride or methyl acetate.

The poor solvent used in the present invention is not particularly limited, but for example, methanol, ethanol, n-butanol, cyclohexane, cyclohexanone and the like are preferably used.
Further, it is preferable that the dope contains 0.01 to 2% by mass of water.

Further, as the solvent used for dissolving the cycloolefin resin (COP), the solvent removed from the film by drying in the optical film film forming process is recovered and reused.

The recovery solvent may contain a small amount of additives added to the COP, such as a plasticizer, an ultraviolet absorber, a polymer, and a monomer component, but even if these are contained, they are preferably reused. It can be purified and reused if necessary.

As the above-mentioned method for dissolving COP when preparing a dope, a general method can be used.
Specifically, a method performed at normal pressure, a method performed below the boiling point of the main solvent, and a method performed by pressurizing above the boiling point of the main solvent are preferable, and when heating and pressurization are combined, heating can be performed above the boiling point at normal pressure.

Further, a method of stirring and dissolving the solvent at a temperature above the boiling point at normal pressure and at a temperature within which the solvent does not boil under pressure is also preferable in order to prevent the generation of massive undissolved substances called gels and mamaco. ..

Further, a method in which a cycloolefin resin (COP) is mixed with a poor solvent to wet or swell, and then a good solvent is further added to dissolve the resin is also preferably used.

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

It is preferable that the heating temperature to which the solvent is added is high from the viewpoint of the solubility of the cycloolefin resin (COP), but if the heating temperature is too high, the required pressure increases and the productivity deteriorates.

The preferred heating temperature is in the range of 30 to 120 ° C., more preferably in the range of 60 to 110 ° C., and even more preferably in the range of 70 to 105 ° C.
In addition, the pressure is adjusted so that the solvent does not boil at the set temperature.

Alternatively, a cooling dissolution method is also preferably used, whereby the cycloolefin resin (COP) can be dissolved in a solvent such as methyl acetate.

Next, it is preferable to filter this cycloolefin resin (COP) solution (dope during or after dissolution) using an appropriate filter material such as filter paper.

As the filter material, it is preferable that the absolute filtration accuracy is small in order to remove insoluble matter and the like, but if the absolute filtration accuracy is too small, there is a problem that clogging of the filter material is likely to occur.
Therefore, a filter medium having an absolute filtration accuracy of 0.008 mm or less is preferable, a filter medium in the range of 0.001 to 0.008 mm is more preferable, and a filter medium in the range of 0.003 to 0.006 mm is further preferable.

The material of the filter medium is not particularly limited, and a normal filter medium can be used, but a plastic filter medium such as polypropylene or Teflon (registered trademark) or a metal filter medium such as stainless steel does not cause fibers to fall off. preferable.

It is preferable to remove and reduce impurities contained in the raw material cycloolefin resin (COP), particularly bright spot foreign matter, by filtration.

Bright spot foreign matter is the opposite when two polarizing plates are placed in a cross-nicoled state, a film or the like is placed between them, light is applied from the side of one polarizing plate, and observation is performed from the side of the other polarizing plate. It is a point (foreign matter) in which light from the side appears to leak, and it is preferable that the diameter is 0.01 mm or more and the number of bright spots is 200 / cm ² or less.
It is more preferably 100 pieces / cm ² or less, further preferably 50 pieces / m ² or less, and further preferably 0 to 10 pieces / cm ² or less.
Further, it is preferable that there are few bright spots of 0.01 mm or less.

Dope filtration can be performed by a usual method, but the method of filtering while heating at a temperature above the boiling point of the solvent at normal pressure and within the range where the solvent does not boil under pressure is the method of filtering the filtration pressure before and after filtration. The increase in difference (called differential pressure) is small, which is preferable.

The preferred temperature is in the range of 30 to 120 ° C, more preferably in the range of 45 to 70 ° C, and even more preferably in the range of 45 to 55 ° C.

It is preferable that the filtration pressure is small.
Specifically, it is preferably 1.6 MPa or less, more preferably 1.2 MPa or less, and even more preferably 1.0 MPa or less.

(3.2.2) Hypersalivation step (S2)
In the casting step (S2), the casting film 5 formed by the dope spread on the support 3 is heated on the support 3, and the casting film 5 is peeled from the support 3 by the peeling roll 4. Evaporate the solvent until possible.

The above evaporation is preferably carried out in an atmosphere in the range of 5 to 75 ° C.
To evaporate the solvent, there are a method of applying warm air to the upper surface of the casting film, and / or a method of transferring heat from the back surface of the support 3 with a liquid, and a method of transferring heat from the front and back surfaces by radiant heat. A method of transferring heat from the front and back is preferable because of its high drying efficiency.
In addition, a method of combining them is also preferably used.

The width of the cast is preferably 1.3 m or more from the viewpoint of productivity.
More preferably, it is in the range of 1.3 to 4.0 m.
If the width of the cast does not exceed 4.0 m, no stripes will be formed in the manufacturing process, and the stability in the subsequent conveying process will be high.
From the viewpoint of transportability and productivity, the range of 1.3 to 3.0 m is more preferable.

The support 3 in the casting step (S2) preferably has a mirror-finished surface, and the support 3 preferably uses a stainless steel belt or a drum whose surface is plated with a casting.

The surface temperature of the support 3 in the casting step (S2) is in the range of −50 ° C. to the boiling point of the solvent, and the higher the temperature, the faster the drying rate of the casting film is, which is preferable.

The preferred support temperature is in the range of 0 to 55 ° C, more preferably in the range of 22 to 50 ° C.

The method of controlling the temperature of the support 3 is not particularly limited, but there are a method of blowing hot air or cold air and a method of bringing hot water into contact with the back side of the support.
It is preferable to use hot water because the heat transfer is more efficient and the time until the temperature of the support becomes constant is short.
When using warm air, air with a temperature higher than the target temperature may be used.

In the casting step (S2), the dope prepared in the dope preparation step (S1) is fed to the casting die (casting die) 2 by a conduit through a pressurized metering gear pump or the like, and is transferred indefinitely. The dope is cast from the casting die 2 at the casting position on the support 3 made of stainless steel endless belt.

In order for those skilled in the art to improve the uniformity of the film thickness in the casting process, there is a method of controlling the slit gap of the lip portion of the casting die in both the solution casting film forming method and the melt casting film forming method. Be done.
For example, when extruding a highly viscous dope (including melt), the width of the slit gap varies. To prevent this, a method of installing multiple heat bolts with the width to control the slit gap is used. be.
However, this method has a problem that there is a physical installation limit of the number of heat bolts.
In addition, there is a method of changing the internal structure of the casting die by the width in order to suppress the pressure fluctuation in the width that causes the variation in the width of the slit gap, but the casting die is switched for each production type. There is a problem that it is indispensable and takes time and cost.

(Pump pulsation pitch control)
Controlling the pitch of the pump pulsation is one of the means for controlling the film thickness of the optical film according to the present invention (flattening process 1).
It is known that a high-precision gear pump is used for the dope feed (extrusion of resin in the case of melting) in the pipe leading to the casting die, but the gear pump controls the rotation speed of the pump by its gear ratio. Therefore, the pitch of the pump pulsation can be controlled, and the pulsation at the time of liquid feeding greatly affects the longitudinal film thickness, that is, the average maximum height difference (PV) _ave1 of the film thickness.

At this time, the length of the pipe from the pump to the flow die is preferably in the range of 50 to 100 m from the viewpoint of eliminating the influence of pressure loss and pulsation of the pump.
The rotation speed of the pump is preferably in the range of 10 to 50 rpm from the viewpoint of preventing pressure loss and the like.

(Initial discharge film thickness control by heat bolt of casting die)
Controlling the initial discharge film thickness with the heat bolt of the casting die is the film thickness control means for the optical film according to the present invention.
The casting die is provided with a mechanism for adjusting the slit for discharging the dope (extruding the resin in the case of melting).
By using the heat bolt of the casting die, the gap between the widths of the slits for discharging the dope is adjusted so that the film thickness deviation immediately after the ejection is within the range of 1.0 to 5.0% with respect to the entire casting film. It is preferable to control the initial discharge film thickness of the casting film.

(others)
Here, the place where the dope of the casting die slit appears is called a lip, and a casting die is preferable because the slit shape of the lip portion can be adjusted and the film thickness can be easily made uniform.
Examples of the casting die include a coat hanger die and a T die, all of which are preferably used.
In the present invention, the flow-cast film refers to a dope film cast from the lip portion.
In order to increase the film forming speed of the optical film according to the present invention, two or more of the above-mentioned casting dies may be provided on the support, and the doping amount may be divided and layered.
Alternatively, it is also preferable to obtain a film roll having a laminated structure by a co-flow spreading method in which a plurality of dope is cast at the same time.
In order to increase the film forming speed, two or more casting dies may be provided on the support, and the doping amount may be divided and layered.

The slit can be narrowed by manually turning the heat bolt and pushed in to reduce the film thickness, or conversely open and thicken.
A method of pushing by heat by applying a voltage to the heat bolt is also common, but it is usually used in combination.
It is also possible to take a push-pull method.
This greatly affects the average maximum height difference (PV) _ave2 of the film thickness measured in the order of steps 1 to 3 diagonally with respect to the width direction.
However, due to the mechanism of the casting die, the bolt pitch may not be narrowed, and in the case of a highly viscous dope (including melting), the pressure load is large on the lip when the casting die is discharged, and the load after discharge is rapid. There may be variations in the width film thickness, such as a decrease in film thickness and an increase in film thickness (ballas effect).
Therefore, it is necessary to design the lip of the casting die so that the lip of the casting die is not overloaded due to the internal structure of the casting die.

In the casting step (S2), the casting dope is dried on the support 3 to form the casting film 5.
At that time, the inclination of the casting die 2, that is, the ejection direction of the dope from the casting die 2 to the support 3, is 0 to 90 at an angle with respect to the normal of the surface of the support 3 (the surface on which the dope is spread). It may be set appropriately so as to be within the range of °.

The support 3 is composed of, for example, a stainless steel belt, and is held by a pair of

rolls

3a and 3b and a plurality of rolls located between them.
At this time, the surface of the support is preferably a mirror surface.

One or both of the

rolls

3a and 3b is provided with a driving device that applies tension to the support 3, whereby the support 3 is used in a tensioned state.
The support 3 may be a drum.

(3.2.3) Peeling step (S3)
In this step, in the casting step (S2), the solvent is evaporated on the support 3 until the casting film 5 has a peelable film strength, and the support 3 is optically solidified or cooled and solidified. The optical film is peeled from the support 3 before the film goes around.
That is, this step is a step of peeling the optical film in which the solvent has evaporated on the support 3 at the peeling position.
At this time, from the viewpoint of surface quality, moisture permeability, and peelability, it is preferable to peel the optical film from the support within a range of 30 to 600 seconds.
The position where the optical film is peeled from the support is called a peeling point, and the roll that assists the peeling is called a peeling roll.
In the peeling step (S3), the optical film is peeled by the peeling roll 4 while maintaining self-supporting property.
The temperature at the peeling position on the support is preferably in the range of −50 to 40 ° C., more preferably in the range of 10 to 40 ° C., and most preferably in the range of 15 to 30 ° C.

(Amount of residual solvent)
The amount of residual solvent of the optical film on the support 3 at the time of peeling is appropriately adjusted depending on the strength of the drying conditions, the length of the support 3, and the like.
Although it depends on the thickness of the optical film, if the amount of residual solvent at the peeling point is too large, the optical film may be too soft and difficult to peel off, resulting in impaired flatness, horizontal steps due to peeling tension, slippage, and vertical length. Streaks may easily occur.
On the contrary, if the amount of residual solvent is too small, a part of the optical film may be peeled off in the middle.
In order for the optical film to exhibit good flatness, it is desirable that the amount of residual solvent is in the range of 10 to 50% by mass from the viewpoint of the balance between economic speed and quality.

In the flattening treatment 3 according to the present invention, the temperature of the dry air is 10 to 80 ° C. when a film is formed on the surface layer in which the residual solvent amount of the casting film on the belt is in the range of 150 to 550% by mass. It is preferable to apply a wind having a wind speed of 5 to 40 m / sec within the range of 1 to flatten the protrusions from the viewpoint of preventing the occurrence of streaks.

As a method of increasing the film-forming speed (the film-forming speed can be increased because the film is peeled off while the amount of residual solvent is as large as possible), there is a gel casting method that can peel off even if the amount of residual solvent is large.
As the method, a poor solvent for cycloolefin resin (COP) is added to the dope, and after the dope casting, the casting film is gelled, and the casting film is gelled by cooling the support. There is a method of peeling off with a large amount of residual solvent.
There is also a method of adding a metal salt during doping.
As described above, by gelling the casting film on the support and strengthening the film, peeling can be accelerated and the film forming speed can be increased.

The amount of residual solvent is defined by the following formula.
Residual solvent amount (mass%) = {(MN) / N} x 100
In addition, M is the mass of the sample collected at any time during or after the casting film or optical film is being manufactured, and N is the mass after heating M at 115 ° C. for 1 hour.

(Peeling tension)
The peeling tension when peeling the support and the optical film is preferably 300 N / m or less.
More preferably, it is in the range of 196 to 245 N / m, but when wrinkles are likely to occur during peeling, it is preferable to peel with a tension of 190 N / m or less.

(3.2.4) Shrinkage step (S4)
The shrinkage step is a step of shrinking the optical film in-plane.
This shrinkage step is performed by stretching the optical film after peeling from the support in the transport direction (Machine Direction, hereinafter also referred to as "MD direction").
In this case, the optical film shrinks in the width direction (Transverse Direction, hereinafter also referred to as “TD direction”) orthogonal to the MD direction in the optical film plane.

The shrinkage step promotes entanglement between polymer molecules (matrix molecules) in the thickness direction of the optical film, so that even when the optical film is adhered to the optical film via an adhesive during the production of the polarizing plate, the above-mentioned adhesive Is more likely to penetrate into the optical film through the entangled portion (crosslinked portion) between the matrix molecules.
As a result, the optical film can be firmly fixed to the polarizer via an adhesive, and the peel strength of the optical film with respect to the polarizer can be improved.
That is, good adhesion between the optical film and the polarizer can be ensured.

(Definition of shrinkage rate)
In the present invention, the shrinkage rate is defined by the following formula.

Formula: Shrinkage rate [%] = width of optical film at the end of shrinkage process [mm] / width of optical film at start of shrinkage process [mm] x 100

Here, in the shrinkage step, if the shrinkage rate of the optical film is too small, the effect of promoting entanglement between matrix molecules is insufficient, and if it is too large, there is a concern that the production efficiency of the optical film (stretched film) is lowered. Will be done.
Therefore, the shrinkage rate of the optical film in the shrinkage step is preferably in the range of 1 to 40%, and more preferably in the range of 5 to 20%.

(Measurement method and calculation method of shrinkage rate)
In the present invention, the width of the optical film was measured with LS-9000 manufactured by KEYENCE CORPORATION.
The shrinkage ratio of the optical film according to the present invention is determined by the above formula, where the average value of each value obtained by measuring the width of the optical film with the above measuring instrument for 5 minutes (300 seconds) every 1 second is taken as the width of the optical film. Although it was obtained by substituting, it is not limited to the above method. For example, the width of the optical film may be used as the width of the optical film by using a value read from a ruler and substituted into the above formula.

In the shrinking step (S4), the optical film F is shrunk in the width direction.
Examples of the method of shrinking the optical film include (1) high-temperature treatment without holding the width of the optical film to increase the density of the optical film, and (2) tension in the transport direction (MD direction) with respect to the optical film. The optical film is shrunk in the width direction (TD direction), and (3) the amount of residual solvent in the optical film is sharply reduced.

(3.2.5) First drying step (S5)
The drying step is a step of heating the optical film on the support to evaporate the solvent.

In the drying apparatus 6 in FIG. 6, the optical film is conveyed by a plurality of conveying rolls arranged in a staggered pattern when viewed from the side surface, and the optical film is dried between them.
The drying method in the drying device 6 is not particularly limited, and generally, the optical film is dried using hot air, infrared rays, heating rolls, microwaves, etc., but from the viewpoint of simplicity, the optical film is dried with hot air. The method is preferred.
Also, a method of combining them is also preferable.
The first drying step (S5) may be performed as needed.

If the film thickness of the optical film is thin, it dries quickly, but if it dries too rapidly, the flatness of the finished optical film tends to be impaired.
When drying at a high temperature, it is necessary to consider the amount of residual solvent, but if the amount of residual solvent is not too large, failure due to foaming of the solvent can be prevented.
The amount of the residual solvent is preferably about 30% by mass or less, and drying is generally carried out in the range of 30 to 250 ° C. throughout.
In particular, it is preferable to dry in the range of 35 to 200 ° C., and the drying temperature is preferably gradually increased.
The amount of residual solvent of the optical film on the support 3 at the time of peeling in the peeling step (S3) is appropriately adjusted according to the strength of the drying conditions, the length of the support 3, and the like, and is appropriately adjusted in the shrinking step (S4). Since the amount of the residual solvent is greatly affected by the film thickness, the resin, and the like, the peeling step (S3) and the shrinkage step (S4) have a range that overlaps with the preferable range of the residual solvent amount.

The temperature of the support may be the same as a whole or may differ depending on the position.
In the first drying step (S5), the optical film is peeled from the support by the drying device 6 and further dried.

In the process of drying the optical film, a roll drying method (a method in which the optical film is alternately passed through a large number of rolls arranged one above the other to dry) or a tenter method is adopted while the optical film is conveyed and dried.

When a tenter stretching device is used, it is preferable to use a device that can independently control the gripping length (distance from the start of gripping to the end of gripping) of the optical film by the left and right gripping means of the tenter stretching device in the stretching step described later.
Further, in the stretching step, it is also preferable to intentionally create sections having different temperatures in order to improve the flatness.

It is also preferable to provide a neutral zone so that the respective compartments do not interfere with each other between different temperature compartments.

(3.2.6) First stretching step (S6)
The stretching step may be a step of stretching the optical film only in the MD direction in the plane of the optical film, a step of stretching only in the TD direction, or a step of stretching only in the MD direction and the TD direction. It may be a step of stretching in an oblique direction.
Further, although the stretching direction is not limited, from the viewpoint of obtaining a wide optical film, it is preferable that there is a step including stretching at least in the width direction.
Such stretching can be performed using the stretching device 7.

In order to secure a high phase difference, secure a wide width, and promote the penetration of the adhesive when adhering to the polarizer, it is preferable to stretch the optical film at a high magnification in the stretching step.
However, if the draw ratio is too high, the draw stress may cause crazes in the optical film or dissociate the entanglement between the matrix molecules that maintain the strength of the optical film, which may weaken the optical film. ..

Therefore, the stretching ratio in the stretching step is preferably in the range of 1.1 to 5.0 times, and more preferably in the range of 1.3 to 3.0 times.

When the stretching is performed a plurality of times, it is preferable that the stretching at the highest magnification, which has the highest risk of dissociation of the matrix molecules, is performed in the final stretching.
For example, in FIG. 5, stretching at the highest magnification is preferably performed in the second stretching step.
In this case, since the entanglement of the matrix molecules can be strengthened by the stretching at the maximum magnification, the dissociation of the entanglement of the matrix molecules can be suppressed and the aggregation failure can be suppressed even if the stretching at the maximum magnification is performed.

In the first stretching step (S6), the optical film F is stretched by the tenter stretching device 7.
As a stretching method at this time, a method of stretching in the transport direction (longitudinal direction of the optical film; film forming direction; casting direction; MD direction) by providing a difference in peripheral speed of the roll, or both side edges of the optical film F are stretched. The tenter method, which is fixed with a clip or the like and stretched in the width direction (direction orthogonal to the optical film plane; TD direction), is preferable in order to improve the performance / productivity, flatness and dimensional stability of the film.

Further, in the case of the so-called tenter method, it is preferable to drive the clip portion by the linear drive method because smooth stretching can be performed and the risk of breakage can be reduced.

These width holding or lateral stretching in the film forming step is preferably performed by a tenter stretching device, and may be a pin tenter or a clip tenter.
In the tenter stretching device 7, drying may be performed in addition to stretching.

(Tenter stretching device)
Hereinafter, the device used as the tenter stretching device 7 will be described with reference to FIGS. 7, 8, 9, and 10.
FIG. 7 is a plan view schematically showing the internal configuration of the tenter stretching device, and is a cross-sectional view of the tenter stretching device as viewed from above with a plane perpendicular to the plane of the optical film.
Note that FIG. 7 shows a state in which the cover is removed, and the cover is shown by a chain double-dashed line.

The tenter stretching device 40 includes a large number of clips 42 that grip both ends of the optical film F in the width direction, and the clips 42 are attached to the endless chain 48 at regular intervals.
The endless chains 48 are arranged on both sides of the optical film F, and each is hung between the driving sprocket 50 on the inlet side and the driven sprocket 52 on the outlet side.
The driving sprocket 50 is connected to a motor (not shown), and the driving sprocket 50 is rotated by driving this motor.
As a result, the endless chain 48 orbits between the driving sprocket 50 and the driven sprocket 52, so that the clip 42 attached to the endless chain 48 orbits.

A rail 54 for guiding the endless chain 48 (or clip 42) is provided between the driving sprocket 50 and the driven sprocket 52.
The rails 54 are arranged on both sides of the optical film F so that the distance between the rails 54 is wider on the downstream side than on the upstream side in the transport direction of the optical film F.
As a result, when the clips 42 orbit the clips 42, the distance between the clips 42 is widened, so that the optical film F gripped by the clips 42 can be laterally stretched in the width direction.

An opening member 56 is attached to each of the driving sprocket 50 and the driven sprocket 52.
The opening member 56 is a device that displaces the flapper (not shown) of the clip 42, which will be described later, from the gripping position to the opening position, and the opening member 56 automatically performs the gripping operation and the opening operation of the optical film F. ..

By the way, as shown in FIG. 7, the inside of the tenter stretching device 40 is provided with a preheating zone, a (horizontal) stretching zone, and a heat fixing zone.
The zones are separated by a windbreak curtain (not shown) (not shown).
Further, inside each zone, hot air is supplied from above, below, or both of the optical film F.
The hot air is uniformly blown out in the width direction of the optical film F in a state where the temperature is controlled to a predetermined temperature for each zone.
As a result, the inside of each zone is controlled to a desired temperature. Hereinafter, each zone will be described.

The preheating zone is a zone for preheating the optical film F, and heats the optical film F without widening the interval between the clips 42.

The optical film F preheated in the preheating zone moves to the transverse stretching zone.
The laterally stretched zone is a zone in which the optical film F is laterally stretched in the width direction by increasing the distance between the clips 42.
The stretching ratio in this transverse stretching treatment is preferably in the range of 1.0 to 2.5 times, more preferably in the range of 1.05 to 2.3 times, still more preferably in the range of 1.1 to 2 times. ..

The optical film F laterally stretched in the transversely stretched zone moves to the heat fixing zone.

In the present embodiment, the inside of the tenter 40 is divided into a preheating zone, a (horizontal) stretching zone, and a heat fixing zone, but the type and arrangement of the zones are not limited to this, for example, after the lateral stretching zone. , A cooling zone for cooling the optical film F may be provided.
Further, a heat relaxation zone may be provided in the heat fixing zone.

In the present embodiment, only the transverse stretching is performed by the tenter 40, but the stretching may be performed in the longitudinal direction at the same time.
In this case, when the clips 42 are moved, the pitch of the clips 42 (the distance between the clips 42 in the transport direction) may be changed.
As a mechanism for changing the pitch of the clip 42, for example, a pantograph mechanism or a linear guide mechanism can be used.

As a method of stretching the optical film, a method of stretching in the longitudinal (longitudinal) direction (longitudinal stretching), a method of stretching in the lateral (width) direction (transverse stretching), and a method of sequentially performing longitudinal stretching and transverse stretching (sequential biaxial). (Stretching), a method of simultaneously performing longitudinal stretching and transverse stretching (simultaneous biaxial stretching), and among these, a tenter stretching apparatus is used in transverse stretching and simultaneous biaxial stretching (including diagonal stretching).
The tenter stretching device is a device that stretches an optical film by grasping both ends of the optical film in the width direction with clips and widening the interval while running the clips together with the optical film.

(Heat treatment timing)
The tenter stretching device is usually divided into a plurality of zones, for example, a preheating zone for heating an optical film, a transverse stretching zone for stretching the optical film in the lateral direction, and a heat fixing zone for crystallizing the optical film as shown in FIG. , A relaxation zone for removing the thermal stress of the optical film is provided.

The timing of the heat treatment in the stretching step in the tenter stretching apparatus (flattening treatment 4 according to the present invention) is divided according to whether the heat treatment is applied when the optical film passes through any of the following zones, and is combined with the temperature inside the furnace. It is used as a means for controlling the film thickness.
(1-1) When passing through the preheating zone in the tenter stretching device (1-2) When passing through the stretching zone in the tenter stretching device (1-3) When passing through the heat fixing zone in the tenter stretching device In addition, in the above three zones Infrared (IR) heaters are used for the heat treatment, and a necessary number of infrared (IR) heaters are appropriately installed in each zone.
As an example of the case where the infrared (IR) heater is installed in each zone, FIG. 8 shows a side view of the three zones in the tenter stretching device when the infrared (IR) heater is installed in the preheating zone.

(Temperature in the furnace)
Generally, the temperature inside the furnace is preferably in the range of 120 to 200 ° C, more preferably in the range of 120 to 180 ° C.
Here, the temperature inside the furnace in the present invention is a temperature (see FIG. 8) measured at a position 100 mm above the center of the film immediately before stretching in the stretching zone of the tenter stretching device described later, and each of them is taken every minute. The temperature value was measured for 1 hour, and the average value thereof was calculated.
Generally, the temperature inside the furnace is preferably in the range of 120 to 200 ° C, more preferably in the range of 120 to 180 ° C.
Here, when a temperature gradient is provided in the longitudinal direction in a plurality of compartments, the heat treatment compartment is targeted.
Further, in the present invention, the temperature inside the furnace differs depending on whether the heat treatment is performed in the stretching zone or not, but when the heat treatment is performed in the stretching zone, the temperature inside the furnace is in the stretching zone before the heat treatment is performed. It shall mean the temperature inside the furnace.

(Amount of residual solvent)
The amount of residual solvent in the optical film at the time of stretching is preferably 20% by mass or less, and more preferably 15% by mass or less.

FIG. 9 is a plan view of the three zones in the tenter stretching device, and FIG. 10 is a schematic view of a nozzle and a heater installation portion when the three zones in the tenter stretching device are viewed from the front.
As shown in FIG. 10, the infrared (IR) heater is arranged only on the upper side of the nozzle so that the optical film does not come into contact with the infrared (IR) heater when the optical film is broken.
In addition, when the infrared (IR) heater is brought closer to the optical film, the radiant energy generated by the infrared (IR) heater can be concentrated in a narrower range. Bring the infrared (IR) heater as close as possible.

FIG. 10 mainly shows the heat treatment from the central nozzle, and although the heat treatment by the end nozzle is not performed in this embodiment, it can be used together in this embodiment.

In the stretching device, when the infrared (IR) heater is emitted from the nozzle gap as shown in FIG. 8, the radiant energy can be transmitted to the optical film without waste.
As shown in FIG. 9, infrared (IR) heaters were arranged in a row so that the entire width could be heated even in the optical film before stretching.
The heaters may be arranged in a staggered manner in the longitudinal direction.

(3.2.7) First cutting step (S7)
In the first cutting step (S7), the cutting portion 8 made of a slitter cuts both ends of the optical film F stretched by the first stretching step (S6) in the width direction.
In the optical film F, the portion remaining after cutting both ends constitutes a product portion to be an optical film product.
On the other hand, the portion cut from the optical film F may be recovered and reused as a part of the raw material for film formation of the optical film.

(3.2.8) Second stretching step (S8)
In the second stretching step (S8), the optical film F is stretched by the stretching device 9 in the same manner as in the first stretching step (S6).
As a stretching method at this time, a stretching method is provided in the transport direction (MD direction) by providing a difference in peripheral speed of the roll, or both side edges of the optical film F are fixed with clips or the like and stretched in the width direction (TD direction). The tenter method is preferable in order to improve the performance / productivity, flatness and dimensional stability of the film.
In the stretching device 9, drying may be performed in addition to stretching.

(3.2.9) Second cutting step (S9)
In the second cutting step (S9), similarly to the first cutting step (S7), the cutting portion 10 made of a slitter cuts both ends of the formed optical film F in the width direction.
The gripped portions of the clips at both ends of the optical film are usually cut because the optical film is deformed and cannot be used as a product.
If the material has not deteriorated due to heat, it will be reused after recovery.
In the optical film F, the portion remaining after cutting both ends constitutes a product portion to be an optical film product.
On the other hand, the portion cut from the optical film F is recovered and reused as a part of the raw material for film formation of the optical film.

(3.2.10) Second drying step (S10)
In the second drying step (S10), the optical film F is dried by the drying device 11 in the same manner as in the first drying step (S5).
In the drying device 11, the optical film F is conveyed by a plurality of conveying rolls arranged in a staggered pattern when viewed from the side surface, and the optical film F is dried between them.
The drying method in the drying device 6 is not particularly limited, and generally includes hot air, infrared rays, heating rolls, microwaves, and the like.
Among the above drying methods, the method of drying the optical film F with hot air is preferable from the viewpoint of simplicity.
The second drying step (S10) may be performed as needed.

(3.2.11) Third cutting step (S11)
In the third cutting step (S11), similarly to the first cutting step (S7) and the second cutting step (S9), the cutting portion 12 made of a slitter forms both ends of the formed optical film F in the width direction. Disconnect.
In the optical film F, the portion remaining after cutting both ends constitutes a product portion to be an optical film product.
On the other hand, the portion cut from the optical film F is recovered and reused as a part of the raw material for film formation of the optical film.

(3.2.12) Winding process (S12)
Finally, in the winding step (S12), the optical film F is wound by the winding device 13 to obtain a film roll.
That is, in the winding step, a film roll is manufactured by winding the optical film F around the winding core while conveying it.
The preferable range of the initial tension when winding the optical film in the winding step is in the range of 20 to 300 N / m.

(Amount of residual solvent)
More specifically, it is a step of winding the optical film as an optical film by the winding device 12 after the residual solvent amount in the optical film becomes 2% by mass or less, and by reducing the residual solvent amount to 0.4% by mass or less. An optical film having good dimensional stability can be obtained.
In particular, it is preferable to wind up the residual solvent amount in the range of 0.00 to 0.20% by mass.

(How to wind)
As the winding method of the optical film F, a commonly used winder may be used, and there are methods for controlling the 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 them properly.

Before winding, the edges may be slit to the width of the product and cut off, and surface modification treatment may be applied to both ends of the optical film to prevent sticking and scratches during winding.

(After winding)
The film roll of the present invention is preferably a long film, specifically, one in the range of about 100 to 10,000 m, and usually provided in the form of a roll.

<Details of optical film winding method>
The optical film according to the present invention is preferably wound by the following winding method.
The winding method includes a straight winding step of winding the optical film around the winding core so that the side edges of the optical film are aligned, and after the straight winding step, the side edges have a certain range with respect to the width direction of the optical film. It is preferable to have an oscillating winding step of winding the optical film around the winding core by periodically vibrating the optical film or the winding core in the width direction of the optical film so as to periodically shift the optical film.

In particular, when the winding length of the optical film reaches a predetermined switching winding length within a range of 1 to 30% of the total winding length of the optical film, the straight winding step is changed to the oscillating winding step. It is preferable to switch.

The optical film winding device includes an optical film winding unit that rotates the winding core to wind the optical film around the winding core, and the optical film is placed on the winding core within a certain range in the width direction of the optical film. The oscillating portion that vibrates the optical film or the winding core in the width direction of the optical film in conjunction with the winding of the optical film and the winding length of the optical film are set in advance so that the oscillating winding is periodically deviated. It is preferable to include a switching portion for switching the winding of the optical film from the straight winding to the oscillating winding when the predetermined winding length at the time of switching is reached.
Details of the oscillating winding will be omitted below.

FIG. 11 is a schematic view showing a process in which an optical film is wound and a cross section of the film roll of the present invention after being wound.
In FIG. 11, the film-formed optical film 31 is wound by a roll 32 and a touch roll 33, and is wound as a film roll 30.

(3.3) Manufacturing Process of Film Roll by Melt Casting Method The optical film according to the present invention can also be filmed by the melt casting method.
The "melt film forming method" is a method in which a composition containing a thermoplastic resin and the above-mentioned additives is heated and melted to a temperature indicating fluidity, and then a melt containing the fluid thermoplastic resin is cast. To say.

The molding method for heating and melting can be specifically classified into a melt extrusion molding method, a press molding method, an inflation method, an injection molding method, a blow molding method, a stretch molding method and the like.
Among these molding methods, the melt extrusion method is preferable from the viewpoint of mechanical strength, surface accuracy and the like.

FIG. 12 is a flowchart showing the flow of the manufacturing process of the melt casting film forming method.
Further, FIG. 13 is a schematic view of an apparatus for manufacturing an optical film by a melt casting film forming method.
Hereinafter, the solution casting film forming method will be described with reference to FIGS. 12 and 13.
The method for producing a film roll by the melt casting film forming method is an extrusion step (M1), a casting / molding step (M2), a first stretching step (M3), a first cutting step (M4), and a second stretching step (M4). M5), a second cutting step (M6), and a winding step (M7) are included.

The manufacturing method does not have to include both the first stretching step (M3) and the second stretching step (M5), and may include at least one of the steps.
Further, the first cutting step (M4) and the second cutting step (M6) may also include at least one of the steps.

(3.3.1) Extrusion step (M1)
In the extrusion step (M1), at least the resin is melt-extruded by the extruder 14 and formed on the cast drum 16.
Details of the above resin that can be used in the present invention will be described later.

Further, it is preferable that the resin is kneaded in advance and pelletized.
Pelletization may be carried out by a known method.

For example, dry resin, plasticizer, and other additives are supplied to the extruder with a feeder, kneaded using a single-screw or twin-screw extruder, extruded into strands from a casting die, water-cooled or air-cooled, and cut. It can be pelletized.

The additive may be mixed with the resin before being supplied to the extruder, or the additive and the resin may be supplied to the extruder by separate feeders.
Further, since a small amount of additives such as particles and antioxidants are mixed uniformly, it is preferable to mix them with the resin in advance.

When introducing pellets from the supply hopper to the extruder, it is preferable to prevent oxidative decomposition and the like by drying, under vacuum, under reduced pressure, or under an inert gas atmosphere.

It is preferable that the extruder can be pelletized and processed at a low temperature as much as possible so as to suppress the shearing force and prevent the resin from deteriorating (reducing molecular weight, coloring, gel formation, etc.).

For example, in the case of a twin-screw extruder, it is preferable to use a deep groove type screw to rotate in the same direction.
The meshing type is preferable because of the uniformity of kneading.
When the resin / pellet is melted, it is preferable to filter it with a leaf disk type filter or the like to remove foreign substances.

Film formation is performed using the pellets obtained as described above.
Of course, it is also possible to supply the raw material resin (powder or the like) to the extruder as it is with a feeder without pelletizing it, and to form a film as it is.

(3.3.2) Casting / molding process (M2)
In the casting / forming step (M2), the resin / pellet melted in the extrusion step is cast in a film form from the casting die 15 by a conduit through a pressure type metering gear pump or the like, and is made of rotary drive stainless steel to be transferred indefinitely. The resin / pellet melted from the casting die 15 is cast at the casting position on the endless cast drum 16.
Then, the cast resin / pellet in the molten state is formed on the cast drum 16 to form the cast film 18.

The inclination of the casting die 15, that is, the discharge direction of the molten resin / pellet from the casting die 15 to the support 16 is the surface of the cast drum 16 (the surface on which the molten resin / pellet is cast). The angle with respect to the normal may be appropriately set so as to be within the range of 0 to 90 °.

The optical film F may be formed by appropriately using the touch roll 16a and the cooling drum 17 assisting the cast drum 16 alone or in combination.

The method for improving the uniformity of the film thickness in the casting / molding process (M2), the pitch control of the pump pulsation, the initial discharge film thickness control by the heat bolt of the casting die, and other matters are described above. Similar to the casting step (S2) in the film roll manufacturing step by the solution casting film forming method, the amount of residual solvent in the peeling step (S3), the shrinkage rate in the shrinkage step (S4), and the drying step (S5). Since the description of the drying method and the like is duplicated, it is omitted.

(3.3.3) First stretching step (M3)
In the first stretching step (M3), the optical film F is stretched by the stretching device 19.
As the stretching method at this time, a stretching method in the MD direction by providing a difference in peripheral speed of the rolls and a tenter method in which both side edges of the optical film F are fixed with clips or the like and stretched in the TD direction are used to perform the optical film. -Preferable for improving productivity, flatness and dimensional stability.
In the stretching device 19, drying may be performed in addition to stretching.

Regarding the description of the tenter stretching apparatus, heat treatment timing, furnace temperature, stretching temperature, stretching furnace temperature, residual solvent amount, etc., the first stretching step (S6) in the film roll manufacturing step by the solution casting film forming method. ), So omit it.

(3.3.4) First cutting step (M4)
In the first cutting step (M4), the cutting portion 20 made of a slitter cuts both ends of the formed optical film F in the width direction.
In the optical film F, the portion remaining after cutting both ends constitutes a product portion to be an optical film product.
On the other hand, the portion cut from the optical film F may be recovered and reused as a part of the raw material for film formation of the optical film.

(3.3.5) Second stretching step (M5)
In the second stretching step (M5), the optical film F is stretched by the stretching device 21 in the same manner as in the first stretching step (M3).
As the stretching method at this time, a stretching method in the MD direction by providing a difference in peripheral speed of the roll, and a tenter method in which both side edges of the optical film F are fixed with clips or the like and stretched in the TD direction are used to perform the optical film. -Preferable for improving productivity, flatness and dimensional stability.
In the stretching device 21, drying may be performed in addition to stretching.

(3.3.6) Second cutting step (M6)
In the second cutting step (M6), similarly to the first cutting step (M4), the cutting portion 22 made of a slitter cuts both ends of the formed optical film F in the width direction.
In the optical film F, the portion remaining after cutting both ends constitutes a product portion to be an optical film product.
On the other hand, the portion cut from the optical film F may be recovered and reused as a part of the raw material for film formation of the optical film.

(3.3.7) Winding process (M7)
Finally, in the winding step (M7), the optical film F is wound by the winding device 23 to obtain a film roll.
That is, in the winding step, a film roll is manufactured by winding the optical film F around the winding core while conveying it.
As the winding method of the optical film F, a commonly used winder may be used, and there are methods for controlling the 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 them properly.

Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. In the examples, the indication of "parts" or "%" is used, but unless otherwise specified, it indicates "parts by mass" or "% by mass".

<Making a film roll>
(Preparation of Film Roll No. 101)
A solution casting film forming method was used for forming the optical film.

(Dope preparation step (S1))
<Synthesis of cyclic polyolefin polymer P-1>
100 parts by mass of purified toluene and 100 parts by mass of norbornene carboxylic acid methyl ester were put into a stirrer.
Then, ethyl hexanoate-Ni dissolved in toluene (25 mmol% with respect to monomer), tri (pentafluorophenyl) boron 0.225 mol% (mass with respect to monomer) and triethylaluminum dissolved in toluene (0.25 mol% with respect to monomer (mass)). ) Was put into the stirring device.
The reaction was carried out for 18 hours with stirring at room temperature.
After completion of the reaction, the reaction mixture was put into excess ethanol to form a polymer precipitate.
The polymer (P-1) obtained by purifying the precipitate was vacuum dried at 65 ° C. for 24 hours.

<Preparation of Dope D-1>
The following composition 1 was put into a mixing tank, stirred to dissolve each component, and then filtered through a filter paper having an average pore size of 34 μm and a sintered metal filter having an average pore size of 10 μm to prepare a dope.

(Composition 1)
Cyclic polyolefin polymer (P-1) 150 parts by mass Dichloromethane 380 parts by mass Methanol 70 parts by mass Next, the following composition 2 containing the cyclic polyolefin solution (dope) prepared by the above method was put into a disperser, and fine particles were added as additives. A dispersion (M-1) was prepared.

(Composition 2)
Fine particles (Aerosil R812: manufactured by Nippon Aerosil Co., Ltd., primary average particle size: 7 nm, apparent specific gravity 50 g / L) 4 parts by mass dichloromethane 76 parts by mass Methanol 10 parts by mass Cyclic polyolefin solution (dope D-1) 10 parts by mass The above cyclic polyolefin solution 100 parts by mass and 0.75 parts by mass of the fine particle dispersion were mixed to prepare a dope for film formation (resin composition cycloolefin resin COP1).

(Discharging step (S2))
A rotary drive stainless steel endless belt in which the dope (resin composition cycloolefin resin COP1) prepared in the dope preparation step (S1) is sent to a casting die by a conduit through a pressurized metering gear pump and transferred indefinitely. Dope is cast from the casting die to the casting position on the support with a width of 1800 mm on the film forming line, heated on the support until the dope is self-supporting, and flowed from the support by a peeling roll. The film was dried by evaporating the solvent until the film could be peeled off to form a cast film.

The length of the pipe from the pump to the casting die was set to 30 m, the gear ratio of the gear pump used for dope feeding was adjusted, and the rotation speed of the pump was set to 70 rpm (flattening process 1 not performed).

The heat bolt of the casting die adjusts the gap between the widths of the slits that discharge the dope to 5.5% of the film thickness deviation immediately after discharge with respect to the entire casting film, and the initial discharge film thickness of the casting film. Was controlled (flattening process 2 was not performed).

After the surface layer was formed by drying the cast film on the belt until the residual solvent amount became 5% by mass, warm air at a wind speed of 45 m / sec (40 ° C.) was blown to flatten the protrusions (flatness). Chemical treatment 3 not implemented).

(Peeling step (S3))
In the casting step (S2), after forming the casting film, the casting film was peeled from the support by a peeling roll while maintaining self-supporting property.

(Shrinkage step (S4))
The optical film was subjected to high temperature treatment without holding the width of the optical film to increase the density of the optical film, so that the optical film was shrunk in the width direction at a shrinkage rate of 7%.

(First drying step (S5))
The optical film was then heated on the support to evaporate the solvent.
The amount of residual solvent in the optical film was measured by the following method and found to be 5% by mass or less.

(Measurement of residual solvent amount)
The amount of residual solvent was mass-analyzed as follows by gas chromatography.
That is, a piece of film was collected at an arbitrary location, and in order to prevent volatilization of the solvent remaining in the film, it was promptly secured in a vial and plugged.
Next, a needle was inserted into the vial and mass spectrometry was performed using a gas chromatograph (manufactured by Agilent Technologies).

The amount of residual solvent is defined by the following formula.
Residual solvent amount (mass%) = {(MN) / N} x 100
In addition, M in the above formula is the mass (g) of the sample collected at an arbitrary time point during or after the production of the casting film or film, and N in the above formula is 1 for the above sample at 115 ° C. The mass (g) after heating for hours.

(First stretching step (S6))
Then, the optical film was conveyed in the tenter stretching device and stretched laterally.
Under the conditions shown in Table I, a required number of infrared (IR) heaters were installed and heat-treated (implementation of flattening treatment 4).

(First cutting step (S7))
Both ends of the stretched optical film in the width direction were cut.

(Second stretching step (S8))
Similar to the first stretching step, the optical film was stretched by a tenter stretching device.
The amount of residual solvent in the optical film was measured by the following method and found to be 1 to 5% by mass.

(Second cutting step (S9))
Similar to the first cutting step, both ends of the stretched optical film in the width direction were cut.

(Second drying step (S10))
Similar to the first drying step, the optical film was heated on the support to evaporate the solvent.
The amount of residual solvent in the optical film was measured and found to be 0.1 to 2% by mass.

(Third cutting step (S11))
Similar to the first cutting step and the second cutting step, both ends of the stretched optical film in the width direction were cut.

(Winding process (S12))
The above optical film was wound up.
The initial tension was 50 N, 70% taper, and 25% corner.
Using TR (touch roll), the average air layer (air layer) thickness contained in the film roll was suppressed to 0.8 μm.
The film roll width was 2000 mm and the winding length was 3900 m.
The line speed for transporting the optical film was 60 m / min.
By the above steps, the film roll No. 101 was produced.

(Preparation of Film Roll No. 102)
A solution casting film forming method was used for forming the optical film.

(Dope preparation step (S1))
Film roll No. A film-forming dope (resin composition cycloolefin-based resin COP1) was prepared in the same procedure as in 101.

(Discharging step (S2))
The formation of the casting film in the casting step is performed by the film roll No. The procedure was the same as that for 101.
In the casting step, the length of the pipe from the pump to the casting die was set to 60 m, the gear ratio of the gear pump used for dope feeding was adjusted, and the rotation speed of the pump was set to 20 rpm (flattening process 1). implementation).
Flattening

treatments

2 and 3 were not performed.

(Peeling step (S3) to first drying step (S5))
In the peeling step (S3) to the first drying step (S5), the film roll No. The procedure was the same as that for 101.
When the amount of residual solvent in the optical film in the first drying step (S5) was measured, it was 5% by mass or less.

(First stretching step (S6))
Then, the optical film was conveyed in the tenter stretching device and stretched laterally.
The temperature inside the furnace was 175 ° C., and no heat treatment was performed without installing an infrared (IR) heater on the optical film (flattening treatment 4 not performed: no heat treatment).

(First cutting step (S7)) to (Third cutting step (S11))
In the first cutting step (S7) to the third cutting step (S11), the film roll No. The procedure was the same as that for 101.

(Winding process (S12))
The above optical film was wound up.
The initial tension was 50 N, 70% taper, and 25% corner.
Using TR (touch roll), the average air layer (air layer) thickness contained in the film roll was suppressed to 0.6 μm.
The film roll width was 2000 mm and the winding length was 3900 m.
The line speed for transporting the optical film was 60 m / min.
By the above steps, the film roll No. 102 was produced.

(Preparation of Film Roll No. 103)
A solution casting film forming method was used for forming the optical film.
(Dope preparation step (S1))
Film roll No. A film-forming dope (resin composition cycloolefin-based resin COP1) was prepared in the same procedure as in 101.

(Discharging step (S2))
The formation of the casting film in the casting step is performed by the film roll No. The procedure was the same as that for 101.
The film thickness deviation immediately after ejection of the width of the slit for ejecting the dope was adjusted to 1.5% by the heat bolt of the casting die, and the initial ejection film thickness of the casting film was controlled (flattening process 2). Implementation).
Flattening processes 1 and 3 were not performed.

(First cutting step (S7)) to (Third cutting step (S11))
The first cutting step (S7)) to (third cutting step (S11) were performed in the same procedure as the film roll No. 101.

(Winding process (S12))
The above optical film was wound up.
The initial tension was 50 N, 70% taper, and 25% corner.
Using TR (touch roll), the average air layer (air layer) thickness contained in the film roll was suppressed to 0.4 μm.
The film roll width was 2000 mm and the winding length was 3900 m.
The line speed for transporting the optical film was 60 m / min.
By the above steps, the film roll No. 103 was produced.

(Preparation of Film Roll No. 104)
A solution casting film forming method was used for forming the optical film.
(Dope preparation step (S1))
Film roll No. A film-forming dope (resin composition cycloolefin-based resin COP1) was prepared in the same procedure as in 101.

(Discharging step (S2))
The formation of the casting film in the casting step is performed by the film roll No. The procedure was the same as that for 101.
After the surface layer was formed by drying the cast film on the belt until the residual solvent amount reached 200% by mass, warm air at a wind speed of 16 m / sec (40 ° C.) was blown to flatten the protrusions (flatness). Implementation of chemical processing 3).
Flattening processes 1 and 2 were not performed.

(Peeling step (S3) to first drying step (S5))
In the peeling step (S3) to the first drying step (S5), the film roll No. The procedure was the same as that for 101.
The amount of residual solvent in the optical film in the first drying step (S5) was measured and found to be 5 to 15% by mass.

(Winding process (S12))
The above optical film was wound up.
The initial tension was 50 N, 70% taper, and 25% corner.
Using TR (touch roll), the average air layer (air layer) thickness contained in the film roll was suppressed to 0.5 μm.
The film roll width was 2000 mm and the winding length was 3900 m.
The line speed for transporting the optical film was 60 m / min.
By the above steps, the film roll No. 104 was produced.

(Preparation of Film Roll No. 105)
A solution casting film forming method was used for forming the optical film.
(Dope preparation step (S1))
Film roll No. A film-forming dope (resin composition cycloolefin-based resin COP1) was prepared in the same procedure as in 101.

(Discharging step (S2))
The formation of the casting film in the casting step is performed by the film roll No. The procedure was the same as that for 101.
In the casting step, the length of the pipe from the pump to the casting die was set to 60 m, the gear ratio of the gear pump used for dope feeding was adjusted, and the rotation speed of the pump was set to 20 rpm (flattening process 1). implementation).
The heat bolt of the casting die adjusts the gap between the widths of the slits that discharge the dope to 1.5% of the film thickness deviation immediately after discharge with respect to the entire casting film, and the initial discharge film thickness of the casting film. (Implementation of flattening process 2).

Flattening process 3 was not performed.

(Winding process (S12))
The above optical film was wound up.
The initial tension was 50 N, 70% taper, and 25% corner.
Using TR (touch roll), the average air layer (air layer) thickness contained in the film roll was suppressed to 0.4 μm.
The film roll width was 2000 mm and the winding length was 3900 m.
The line speed for transporting the optical film was 60 m / min.
By the above steps, the film roll No. 105 was prepared.

(Preparation of Film Roll No. 106)
A solution casting film forming method was used for forming the optical film.
(Dope preparation step (S1))
Film roll No. A film-forming dope (resin composition cycloolefin-based resin COP1) was prepared in the same procedure as in 101.

(Discharging step (S2))
The formation of the casting film in the casting step is performed by the film roll No. The procedure was the same as that for 101.
In the casting step, the length of the pipe from the pump to the casting die was set to 60 m, the gear ratio of the gear pump used for dope feeding was adjusted, and the rotation speed of the pump was set to 20 rpm (flattening process 1). implementation).
The heat bolt of the casting die adjusts the gap between the widths of the slits that discharge the dope to 1.5% of the film thickness deviation immediately after discharge with respect to the entire casting film, and the initial discharge film thickness of the casting film. (Implementation of flattening process 2).
After the surface layer was formed by drying the cast film on the belt until the residual solvent amount reached 200% by mass, warm air at a wind speed of 16 m / sec (40 ° C.) was blown to flatten the protrusions (flatness). Implementation of chemical processing 3)

(First stretching step (S6))
Then, the optical film was conveyed in the tenter stretching device and stretched laterally.
The temperature inside the furnace was 175 ° C, and heat treatment was performed by installing the required number of infrared (IR) heaters in the preheating zone so that the difference from the temperature inside the furnace was 60 ° C on the optical film (implementation of flattening treatment 4: The timing of heat treatment is the preheating zone.).

From (first cutting step (S7)) to (third cutting step (S11)), the film roll No. The procedure was the same as that for 101.

(Winding process (S12))
The above optical film was wound up.
The initial tension was 50 N, 70% taper, and 25% corner.
Using TR (touch roll), the average air layer (air layer) thickness contained in the film roll was suppressed to 0.4 μm.
The film roll width was 2000 mm and the winding length was 3900 m.
The line speed for transporting the optical film was 60 m / min.
By the above steps, the film roll No. 106 was prepared.

(Preparation of Film Roll No. 107)
A solution casting film forming method was used for forming the optical film.
(Dope preparation step (S1))
Film roll No. A film-forming dope (resin composition cycloolefin-based resin COP1) was prepared in the same procedure as in 101.

(Discharging step (S2))
The formation of the casting film in the casting step is performed by the film roll No. The procedure was the same as that for 101.
Film roll No. In the same manner as in 106, all the flattening treatments 1 to 3 were carried out.

(First stretching step (S6))
Then, the optical film was conveyed in the tenter stretching device and stretched laterally.
The temperature inside the furnace was 175 ° C, and heat treatment was performed by installing the required number of infrared (IR) heaters in the preheating zone so that the difference from the temperature inside the furnace was 190 ° C on the optical film (implementation of flattening treatment 4: The timing of heat treatment is the preheating zone.).

(Winding process (S12))
The above optical film was wound up.
The initial tension was 50 N, 70% taper, and 25% corner.
Using TR (touch roll), the average air layer (air layer) thickness contained in the film roll was suppressed to 0.2 μm.
The film roll width was 2000 mm and the winding length was 3900 m.
The line speed for transporting the optical film was 60 m / min.
By the above steps, the film roll No. 107 was produced.

(Preparation of Film Roll No. 108)
A solution casting film forming method was used for forming the optical film.
(Dope preparation step (S1))
Film roll No. A film-forming dope (resin composition cycloolefin-based resin COP1) was prepared in the same procedure as in 101.

(First stretching step (S6))
Then, the optical film was conveyed in the tenter stretching device and stretched laterally.
The temperature inside the furnace was 175 ° C., and heat treatment was performed by installing the required number of infrared (IR) heaters in the stretching zone so that the difference from the temperature inside the furnace was 60 ° C. on the optical film (implementation of flattening treatment 4: The timing of heat treatment is the stretching zone.).

(First cutting step (S7)) to (Third cutting step (S11))
The first cutting step (S7)) to (third cutting step (S11) were carried out in the same procedure as the film roll No. 101.

(Winding process (S12))
The above optical film was wound up.
The initial tension was 50 N, 70% taper, and 25% corner.
Using TR (touch roll), the average air layer (air layer) thickness contained in the film roll was suppressed to 0.2 μm.
The film roll width was 2000 mm and the winding length was 3900 m.
The line speed for transporting the optical film was 60 m / min.
By the above steps, the film roll No. 108 was prepared.

(Preparation of Film Roll No. 109)
A solution casting film forming method was used for forming the optical film.
(Dope preparation step (S1))
Film roll No. A film-forming dope (resin composition cycloolefin-based resin COP1) was prepared in the same procedure as in 101.

(First stretching step (S6))
Then, the optical film was conveyed in the tenter stretching device and stretched laterally.
The temperature inside the furnace was 175 ° C, and the optical film was heat-treated by installing the required number of infrared (IR) heaters in the heat-fixing zone so that the difference from the temperature inside the furnace was 60 ° C (implementation of flattening treatment 4). : The timing of heat treatment is the heat fixing zone.).

(Winding process (S12))
The above optical film was wound up.
The initial tension was 50 N, 70% taper, and 25% corner.
Using TR (touch roll), the average air layer (air layer) thickness contained in the film roll was suppressed to 0.3 μm.
The film roll width was 2000 mm and the winding length was 3900 m.
The line speed for transporting the optical film was 60 m / min.
By the above steps, the film roll No. 109 was produced.

(Preparation of Film Roll No. 110)
A solution casting film forming method was used for forming the optical film.

(Dope preparation step (S1) to third cutting step (S11))
In the dope preparation step (S1) to the third cutting step (S11), the film roll No. In carrying out the flattening treatment 2 such as increasing the width of the casting die or the thickness at the time of the casting die in the same procedure as in 106, some conditions were changed.

(Winding process (S12))
The above optical film was wound up.
The initial tension was 50 N, 70% taper, and 25% corner.
Using TR (touch roll), the average air layer (air layer) thickness contained in the film roll was suppressed to 0.4 μm.
The film roll width was 2900 mm and the winding length was 3900 m.
The line speed for transporting the optical film was 60 m / min.
By the above steps, the film roll No. 110 was produced.

(Preparation of Film Roll No. 111)
A solution casting film forming method was used for forming the optical film.

(Dope preparation step (S1) to third cutting step (S11))
In the dope preparation step (S1) to the third cutting step (S11), the film roll No. The procedure was the same as in 106.

(Winding process (S12))
The above optical film was wound up.
The initial tension was 50 N, the taper was 70%, and the corner was 25%.
Using TR (touch roll), the average air layer (air layer) thickness contained in the film roll was suppressed to 0.3 μm.
The film roll width was 2000 mm and the winding length was 9100 m.
The line speed for transporting the optical film was 60 m / min.
By the above steps, the film roll No. 111 was produced.

(Preparation of Film Roll No. 112)
A solution casting film forming method was used for forming the optical film.
(Dope preparation step (S1))
Film roll No. A film-forming dope (resin composition cycloolefin-based resin COP1) was prepared in the same procedure as in 101.

(First stretching step (S6))
Then, the optical film was conveyed in the tenter stretching device and stretched laterally.
The temperature inside the furnace was 175 ° C, and heat treatment was performed by installing the required number of infrared (IR) heaters in the preheating zone so that the difference from the temperature inside the furnace was 140 ° C on the optical film (implementation of flattening treatment 4: The timing of heat treatment is the preheating zone.).

(Winding process (S12))
The above optical film was wound up.
The initial tension was 50 N, 70% taper, and 25% corner.
Using TR (touch roll), the average air layer (air layer) thickness contained in the film roll was suppressed to 0.3 μm.
The film roll width was 2000 mm and the winding length was 3900 m.
The line speed for transporting the optical film was 60 m / min.
By the above steps, the film roll No. 112 was produced.

(Preparation of Film Roll No. 113)
A solution casting film forming method was used for forming the optical film.
(Dope preparation step (S1))
Film roll No. A film-forming dope (resin composition cycloolefin-based resin COP1) was prepared in the same procedure as in 101.

(First stretching step (S6))
Then, the optical film was conveyed in the tenter stretching device and stretched laterally.
The temperature inside the furnace was 165 ° C, and heat treatment was performed by installing the required number of infrared (IR) heaters in the preheating zone so that the difference from the temperature inside the furnace was 30 ° C on the optical film (implementation of flattening treatment 4: The timing of heat treatment is the preheating zone.).

(Winding process (S12))
The above optical film was wound up.
The initial tension was 50 N, 70% taper, and 25% corner.
Using TR (touch roll), the average air layer (air layer) thickness contained in the film roll was suppressed to 0.5 μm.
The film roll width was 2000 mm and the winding length was 3900 m.
The line speed for transporting the optical film was 60 m / min.
By the above steps, the film roll No. 113 was produced.

(Preparation of Film Roll No. 114)
A solution casting film forming method was used for forming the optical film.
(Dope preparation step (S1))
Film Roll No. 1 except that fine particles (Aerosil R812: manufactured by Nippon Aerosil Co., Ltd., primary average particle size: 7 nm, apparent specific gravity 50 g / L) are not used as additives. A film-forming dope (resin composition cycloolefin-based resin COP1) was prepared in the same procedure as in 101.

(Winding process (S12))
The above optical film was wound up.
The initial tension was 50 N, 70% taper, and 25% corner.
Using TR (touch roll), the average air layer (air layer) thickness contained in the film roll was suppressed to 0.5 μm.
The film roll width was 2000 mm and the winding length was 3900 m.
The line speed for transporting the optical film was 60 m / min.
By the above steps, the film roll No. 114 was prepared.

(Preparation of Film Roll No. 115)
A melt casting film forming method was used for forming the optical film.
(Extrusion process (M1))
Film roll No. A resin (resin composition cycloolefin resin COP2) was prepared by the same procedure as 101, pelletized and additives (fine particles (Aerosil R812: manufactured by Nippon Aerosil Co., Ltd., primary average particle size: 7 nm, apparent specific gravity 50 g). / L)) was supplied to the extruder, melted in the extruder, and extruded into a film from the casting die onto the cast drum through a pressurized metering gear pump.

(Collapse / molding process (M2))
In the above extrusion step, the length of the pipe from the pump to the casting die was set to 60 m, the gear ratio of the gear pump used for liquid feeding was adjusted, and the rotation speed of the pump was set to 20 rpm (implementation of flattening process 1). ..

The heat bolt of the casting die adjusts the gap between the widths of the slits that discharge the dope to 1.5% of the film thickness deviation immediately after discharge with respect to the entire casting film, and the initial discharge film thickness of the casting film. (Implementation of flattening process 2).

The flattening treatment 3 was not carried out.
The extruded resin was molded by cooling with a cooling drum to form a cast film.

(First stretching step (M3))
Then, the optical film was conveyed in the tenter stretching device and stretched laterally.
The temperature inside the furnace was 150 ° C, and heat treatment was performed by installing the required number of infrared (IR) heaters in the preheating zone so that the difference from the temperature inside the furnace was 100 ° C on the optical film (implementation of flattening treatment 4: The timing of heat treatment is the preheating zone.).

(First cutting step (M4))
Both ends of the stretched optical film in the width direction were cut.

(Second stretching step (M5))
Similar to the first stretching step, the optical film was stretched by a tenter stretching device.

(Second cutting step (M6))
Similar to the first cutting step, both ends of the stretched optical film in the width direction were cut.

(Winding process (M7))
The above optical film was wound up.
The initial tension was 50 N, 70% taper, and 25% corner.
Using TR (touch roll), the average air layer (air layer) thickness contained in the film roll was suppressed to 0.5 μm.
The film roll width was 2000 mm and the winding length was 3900 m.
The line speed for transporting the optical film was 60 m / min.
By the above steps, the film roll No. 115 was prepared.

(Preparation of Film Roll No. 116)
A melt casting film forming method was used for forming the optical film.
(Extrusion step (M1) to second cutting step (M6))
Film Roll No. 1 except that fine particles (Aerosil R812: manufactured by Nippon Aerosil Co., Ltd., primary average particle size: 7 nm, apparent specific gravity 50 g / L) are not used as additives. The extrusion step (M1) to the second cutting step (M6) were carried out in the same procedure as in 115.

(Winding process (M7))
The above optical film was wound up.
The initial tension was 50 N, 70% taper, and 25% corner.
Using TR (touch roll), the average air layer (air layer) thickness contained in the film roll was suppressed to 0.5 μm.
The film roll width was 2000 mm and the winding length was 3900 m.
The line speed for transporting the optical film was 60 m / min.
By the above steps, the film roll No. 116 was prepared.

(Preparation of Film Roll No. 117)
A solution casting film forming method was used for forming the optical film.
(Dope preparation step (S1))
Film Roll No. 1 except that TAC is used instead of COP1 as the resin composition. A film-forming dope was prepared in the same procedure as in 101.

(Collecting step (S2) to first drying step (S5))
In the casting step (S2) to the first drying step (S5), the optical film No. The procedure was the same as in 106.
The amount of residual solvent in the optical film in the first drying step (S5) was measured and found to be 5 to 15% by mass.

(First stretching step (S6))
Then, the optical film was conveyed in the tenter stretching device and stretched laterally.
The temperature inside the furnace was 150 ° C, and heat treatment was performed by installing the required number of infrared (IR) heaters in the preheating zone so that the difference from the temperature inside the furnace was 140 ° C on the optical film (implementation of flattening treatment 4: The timing of heat treatment is the preheating zone.).

(Winding process (S12))
The above optical film was wound up.
The initial tension was 50 N, 70% taper, and 25% corner.
Using TR (touch roll), the average air layer (air layer) thickness contained in the film roll was suppressed to 0.5 μm.
The film roll width was 2000 mm and the winding length was 3900 m.
The line speed for transporting the optical film was 60 m / min.
By the above steps, the film roll No. 117 was prepared.

(Preparation of film roll No. 118)
A solution casting film forming method was used for forming the optical film.
(Dope preparation step (S1))
Film Roll No. 1 except that polymethylmethacrylate (PMMA) was used instead of COP1 as the resin composition. A film-forming dope was prepared in the same manner as in 101.

(Collecting step (S2) to first drying step (S5))
In the casting step (S2) to the first drying step (S5), the optical film No. The procedure was the same as in 106.
The amount of residual solvent in the cast film in the first drying step (S5) was measured and found to be 5 to 15% by mass.

(First stretching step (S6))
Then, the optical film was conveyed in the tenter stretching device and stretched laterally.
The temperature inside the furnace was 115 ° C, and heat treatment was performed by installing the required number of infrared (IR) heaters in the preheating zone so that the difference from the temperature inside the furnace was 120 ° C on the optical film (implementation of flattening treatment 4: The timing of heat treatment is the preheating zone.).

(Winding process (S12))
The above optical film was wound up.
The initial tension was 50 N, 70% taper, and 25% corner.
Using TR (touch roll), the average air layer (air layer) thickness contained in the film roll was suppressed to 0.3 μm.
The film roll width was 2000 mm and the winding length was 3900 m.
The line speed for transporting the optical film was 60 m / min.
By the above steps, the film roll No. 118 was prepared.

(Preparation of Film Roll No. 119)
In the winding step (S12), the film roll No. 1 was used except that the film roll width was 2400 mm. The procedure was the same as in 106.
By using TR (touch roll), the average thickness of the air layer (air layer) contained in the film roll was suppressed to 0.4 μm.
The line speed for transporting the optical film was 60 m / min.
By the above steps, the film roll No. 119 was prepared.

(Preparation of Film Roll No. 120)
In the winding step (S12), the film roll No. 1 was used except that the winding length was 7500 m. The procedure was the same as in 106.
By using TR (touch roll), the average thickness of the air layer (air layer) contained in the film roll was suppressed to 0.3 μm.
The line speed for transporting the optical film was 60 m / min.
By the above steps, the film roll No. 120 were made.

(Preparation of Film Roll No. 121)
A solution casting film forming method was used for forming the optical film.

(Dope preparation step (S1) to first drying step (S5))
In the dope preparation step (S1) to the first drying step (S5), the film roll No. The procedure was the same as that for 101.
The amount of residual solvent in the casting film was measured and found to be 5% by mass or less.

(First stretching step (S6))
Then, the optical film was conveyed in the tenter stretching device and stretched laterally.
The temperature inside the furnace was 165 ° C, and heat treatment was performed by installing the required number of infrared (IR) heaters in the preheating zone so that the difference from the temperature inside the furnace was 60 ° C on the optical film (implementation of flattening treatment 4: The timing of heat treatment is the preheating zone.).

(Winding process (S12))
The above optical film was wound up.
The initial tension was 50 N, 70% taper, and 25% corner.
Using TR (touch roll), the average air layer (air layer) thickness contained in the film roll was suppressed to 0.5 μm.
The film roll width was 2000 mm and the winding length was 3900 m.
The line speed for transporting the optical film was 60 m / min.
By the above steps, the film roll No. 121 was produced.

(Preparation of Film Roll No. 122)
A solution casting film forming method was used for forming the optical film.

(Winding process (S12))
The above optical film was wound up.
The initial tension was 50 N, 70% taper, and 25% corner.
Using TR (touch roll), the average air layer (air layer) thickness contained in the film roll was suppressed to 0.8 μm.
The film roll width was 2000 mm and the winding length was 3900 m.
The line speed for transporting the optical film was 60 m / min.
By the above steps, the film roll No. 122 was produced.

(Preparation of film roll No. 123)
A solution casting film forming method was used for forming the optical film.

(Winding process (S12))
The above optical film was wound up.
The initial tension was 50 N, 70% taper, and 25% corner.
Using TR (touch roll), the average air layer (air layer) thickness contained in the film roll was suppressed to 0.5 μm.
The film roll width was 2000 mm and the winding length was 3900 m.
The line speed for transporting the optical film was 60 m / min.
By the above steps, the film roll No. 123 was produced.

(Preparation of film roll No. 124) (for Comparative Example 1)
A solution casting film forming method was used for forming the optical film.

(Dope preparation step (S1) to first drying step (S5))
In the dope preparation step (S1) to the first drying step (S5), the film roll No. The procedure was the same as that for 101.
The amount of residual solvent in the casting film was measured and found to be 5 to 15% by mass.

(First cutting step (S7) to third cutting step (S11))
In the first cutting step (S7) to the third cutting step (S11), the film roll No. The procedure was the same as that for 101.

(Winding process (S12))
The above optical film was wound up.
The initial tension was 50 N, 70% taper, and 25% corner.
Using TR (touch roll), the average air layer (air layer) thickness contained in the film roll was suppressed to 1.9 μm.
The film roll width was 2000 mm and the winding length was 3900 m.
The line speed for transporting the optical film was 60 m / min.
By the above steps, the film roll No. 124 was prepared.

(Preparation of film roll No. 125) (for Comparative Example 2)
A solution casting film forming method was used for forming the optical film.

(Dope preparation step (S1) to third cutting step (S11))
In the dope preparation step (S1) to the third cutting step (S11), the film roll No. The procedure was the same as that for 101.

(Knurling process)
After that, the optical film was irradiated with laser light to form a knurling processed portion (site A).

The knurling width at both ends was 15 mm from the film edge.
The line speed for transporting the optical film was 60 m / min.

As a laser device, a carbon dioxide laser device was used, the output of the laser device was 20 W, the center wavelength of the emission wavelength was 9.4 μm, and the emission wavelength range was ± 0.01 μm or less centered on the center wavelength.

To irradiate the optical film with laser light, the parallel beam emitted from the carbon dioxide gas laser device is reflected by two galvanometer mirrors, and the surface of the optical film is conveyed via an fθ lens (focal length 200 mm). It was done by condensing the light on the surface.
By controlling the angle of the galvanometer mirror, the condensing position was moved in the plane direction of the optical film, thereby controlling the trajectory of laser light irradiation on the surface of the optical film.

(Atmospheric pressure plasma treatment process: surface modification treatment)
AGP-500 manufactured by Kasuga Electric Co., Ltd. was installed on the back surface side of the knurled portion of the optical film and irradiated with 0.5 kW.
The distance between the probe that emits atmospheric pressure plasma and the optical film was 5 mm.
The installation position of the atmospheric pressure plasma to be irradiated was set so that it could be irradiated to a width of 110% of the knurling width on the back surface side of the optical film facing the knurling portion.

(Winding process (S12))
The above optical film was wound up.
The initial tension was 50 N, 70% taper, and 25% corner.
Using TR (touch roll), the average air layer (air layer) thickness contained in the film roll was suppressed to 1.7 μm.
The film roll width was 2000 mm and the winding length was 3900 m.
The line speed for transporting the optical film was 60 m / min.
By the above steps, the film roll No. 125 was prepared.

(Production of film roll No. 126) (For Comparative Example 3: With protective film)
A solution casting film forming method was used for forming the optical film.

(Manufacturing process of optical film with protective film)
The optical film obtained above is continuously conveyed via an expander roll, and a long protective film [Toray Film Processing Co., Ltd. Tretec 7832C total thickness: 30 μm] is continuously conveyed and stacked. A laminated film with a protective film was produced by pressing the laminate of the protective film and the optical film from above and below and laminating them by passing them between the bonding rolls.

(Winding process (S12))
The above laminated film was wound up.
The initial tension was 50 N, 70% taper, and 25% corner.
Using TR (touch roll), the average air layer (air layer) thickness contained in the film roll was suppressed to 0.7 μm.
The film roll width was 2000 mm and the winding length was 3900 m.
The line speed for transporting the optical film was 60 m / min.
By the above steps, the film roll No. 126 was prepared.

(Preparation of Film Roll No. 127) (For Comparative Example 4: Anti-blocking film)
A solution casting film forming method was used for forming the optical film.

(Dope preparation step (S1) to third cutting step (S11))
From the dope preparation step (S1) to the third cutting step (S11), the film roll No. The procedure was the same as that for 101.

(Making process of optical film with anti-blocking layer)
The following materials were used to form the anti-blocking layer.

Binder resin: Arrow base SE1030N manufactured by Unitica Co., Ltd .: Aqueous dispersion of modified polyolefin resin (modified polyethylene) Cross-linking agent: Epocross WS700 manufactured by Nippon Catalytic Chemical Industry Co., Ltd .: Aqueous dispersion of polyoxazoline compound Particle B: Nippon Catalyst ( Seahoster KE-P30 manufactured by Co., Ltd .: Powder of silica particles, number of primary particles Average particle size: 300 nm
Dispersion medium: water

<Preparation of particle B dispersion liquid>
Seahoster KE-P30 and water were combined and ultrasonically dispersed to prepare an aqueous dispersion. The dispersion concentration was adjusted to be 5% by mass.

<Preparation of composition for anti-blocking layer>
Arrow base SE1030N, Epocross WS700, particle B dispersion, and pure water were combined to prepare a composition for an anti-blocking layer. Prepared so that the solid content concentration in the composition is 2.5% by mass, the proportion of each component in the solid content is 91% by mass of the binder resin, 5.0% by mass of the cross-linking agent, and 4.0% by mass of the particles B, respectively. did.

<Manufacturing of laminated film>
One side of the optical film produced above was subjected to a corona discharge treatment.
The electron beam beam in the corona discharge was 500 W / m ² / min.
The prepared composition for an anti-blocking layer was applied to the corona-treated portion of the obtained optical film with a bar coater so that the thickness of the binder resin after drying was 100 nm, and then 3 at 100 ° C. It was dried for minutes to form a functional layer.
As a result, a laminated film containing an optical film and an anti-blocking layer was obtained.

(Winding process (S12))
The above laminated film was wound up.
The initial tension was 50 N, 70% taper, and 25% corner.
Using TR (touch roll), the average air layer (air layer) thickness contained in the film roll was suppressed to 0.7 μm.
The film roll width was 2000 mm and the winding length was 3900 m.
The line speed for transporting the optical film was 60 m / min.
By the above steps, the film roll No. 127 was prepared.

(Various measurements and evaluations)
The measurement / calculation method and evaluation method of the characteristics such as the outer diameter of the various film rolls are shown below.

A. Outer diameter of film roll <Measurement method>
After storing the prepared film roll at 40 ° C. and 80% RH for one week, the outer diameter at a position 30 mm from both ends in the width direction of the film roll and the outer diameter at the center position of the central portion were measured with a tape measure. The outer diameters of the end and the center are used, respectively.
The outer diameter of the end portion was taken as the average value of the outer diameters of both ends.

B. The average maximum height difference (PV) _ave1 and (PV) _ave2 of the film thickness (height of peaks and valleys of uneven shape) were measured as follows.

(B.1) Average maximum height difference of film thickness (PV) _ave1
<Measurement method and calculation method>
The film thickness was measured by measuring 1612 points with an in-line retardation / film thickness measuring device RE-200L2T-Rth + film thickness (manufactured by Otsuka Electronics Co., Ltd.).
At this time, the traverse moving speed was 100 mm / sec.

From the above film thickness measurement value, the difference in height between the highest portion and the lowest portion of the uneven structure formed on the surface of the optical film was calculated, and the average value was defined as (PV) _ave1 .

(B.2) Average maximum height difference of film thickness (PV) _ave2
<Measurement method and calculation method>
The average maximum height difference (PV) _ave2 of the film thickness was measured by an in-line retardation / film thickness measuring device RE-200L2T-Rth + film thickness (manufactured by Otsuka Electronics Co., Ltd.).
At this time, the traverse moving speed was 100 mm / sec.

The measurement was performed in the following steps 1 to 3 in an oblique direction with respect to the width direction of the produced optical film.
The data used to calculate the average maximum height difference (PV) _ave2 in step 3 is the measured value at 1612 points.

Step 1:
After measuring the film thickness at an arbitrary position on the end, measure the film thickness at a position moved 50 mm in the width direction and 620 mm in the longitudinal direction from the arbitrary position for each measurement, and transfer it to the other end. The maximum height difference in the diagonal direction is calculated repeatedly.
Step 2:
After the end of step 1, the same measurement as in step 1 is performed until the total distance of the moving positions in the longitudinal direction reaches 1000 m, and the maximum height difference in the oblique direction is further calculated.
Step 3:
The average maximum height difference (PV) _ave2 of the film thickness in the diagonal direction is calculated from the maximum height difference in each diagonal direction obtained from steps 1 and 2.

C. Evaluation of color tone uniformity of optical film CIE1976L * a ^* b ^* CIE1976L ^* a * b ^* determined from the spectral reflectance of the surface at the center and edge of the film roll ^. The uniformity of color tone was evaluated.
That is, the color tone of the film is calculated by calculating the difference between the a ^* value and b ^* representing the hue and saturation of the edge and the center of the optical film based on the L ^* a ^* b ^* color space chromaticity diagram. The uniformity was evaluated.

<Measuring method>
Each value (L ^* , a ^* , b ^* ) at a position 30 mm from both ends in the width direction of the film roll and each value (L ^* , a ^* , b ^* ) at the center position of the central part are the film roll. Was stored at 40 ° C. and 80% RH for 1 week, and then measured by Palattete CUBE manufactured by Palatte Pty Ltd.
The values of a ^* and b ^* at the ends were taken as the average value of the values at both ends.

<Calculation method>
From the above measured values, the value of (end a ^* -center a ^* ) + (end b ^* -center b ^* ) was calculated.

D. Average differential orientation angle The average differential orientation angle was measured and calculated by the following method.
The timing of measurement was set at room temperature immediately before the winding step in both the solution casting film forming method and the melt casting film forming method.

<Measuring method>
Measure the value of the orientation angle at a position moved 5 mm in the width direction and 5 mm in the longitudinal direction from an arbitrary position at the end within a range of 1000 mm in diameter around an arbitrary point in the optical film, and measure it. The measurement was repeated up to the other end.

<Calculation method>
The average value of the absolute values obtained by taking the difference between the values of the adjacent orientation angles was calculated and used as the average difference orientation angle θ _ave °.

E. Average differential film thickness The detailed definition of the average differential film thickness is as described above.

<Measuring method>
Measure the film thickness value at a position moved 5 mm in the width direction and 5 mm in the longitudinal direction from an arbitrary position at the end within a range of 1000 mm in diameter around an arbitrary point in the optical film, and measure it. The measurement was repeated up to the other end.
The timing of measurement was set at room temperature immediately before the winding step in both the solution casting film forming method and the melt casting film forming method.

<Calculation method>
The average value of the absolute values obtained by taking the difference between the values of adjacent film thicknesses was calculated and used as the average difference film thickness _dave μm.

F. Average air layer The average air layer thickness [μm] was calculated by subtracting the value obtained by multiplying the film roll diameter by the core diameter and the thickness of the optical film by the number of layers of the optical film and doubling the value.

G. Ratio (B / A) of the amount of heat A at the center of the optical film and the average value B of the amount of heat at the edges (B / A)
The ratio (B / A) of the amount of heat A at the center of the optical film and the average value B of the amount of heat at the edges in the stretching zone is explained in (Relationship between the amount of heat A at the center and the average value B of the amount of heat at the edges). I did, so I will omit it.

[evaluation]
(Attachment evaluation method)
For sticking failure, after storing the film roll at 40 ° C. and 80% RH for one week, the film is unwound from the roll, and the sticking state of the overlapping films (hereinafter, blocking) is visually observed and the following criteria are met. Evaluated based on.

(Attachment evaluation criteria)
⊚: No blocking ○: Occasionally at a weak blocking level, but there is no problem in practical use △: Blocking is weak, but there is no problem in practical use ×: Blocking is at a level other than the above (complaints by users) Level to go out)
(The weak level in the above evaluation criteria is a level where it is difficult to judge whether it is stuck or not.)

(Contrast evaluation method)
A liquid crystal display device (8K, BRAVIA KJ-85Z9H (manufactured by Sony Corporation [85 inches]) was turned on continuously for one week in an environment of 23 ° C. and 55% RH, and then the front contrast was measured. rice field.
In the measurement of the front contrast, the unevenness of the brightness in the white display (500 cd / m ² ) state of the liquid crystal display device was visually evaluated from the normal direction.

(Contrast evaluation standard)
◎: No occurrence 〇: Small unevenness with weak contrast occasionally occurs ◇: Large unevenness with weak contrast occasionally occurs △: Elongated unevenness with weak contrast occasionally occurs ×: Unevenness other than the above occurs (level at which users complain) )

[Evaluation results of Examples 1 to 20 and Comparative Examples 1 to 4]
Table I shows the measurement results of the film-forming means, the resin composition, the additive, the flattening treatment of the uneven shape of the surface, the layer structure of the film roll, the width, the length, etc. of the optical film prepared from the above.
Table II shows the values and evaluation results of Examples and Comparative Examples calculated using the above film rolls.

As is clear from the conditions and evaluation results shown in Tables I and II, it can be seen that the examples of the present invention have better sticking resistance and contrast when used in a display device than the comparative examples.

It is possible to provide a film roll that can maintain quality with few winding failures during transportation and long-term storage.
Further, it is possible to provide a method for producing the film roll, which has a high production yield and a significantly reduced inspection load.

1,1a Stirrer (stirring tank)
2 Flowing die 3 Support (endless belt, drum)
3a, 3b roll 4 peeling roll 5 casting film 6 drying device 7 stretching device (tenter stretching device, diagonal stretching device)
8 Cutting part 9 Stretching device (Tenter stretching device)
10 Cutting part 11 Drying device 12 Cutting part 13 Winding device 14 Extruder 15 Casting die 16 Cast drum, support 16a Touch roll 17 Cooling drum 19 Stretching device (Tenter stretching device)
20 Cutting part 21 Stretching device (Tenter stretching device)
22 Cutting part 23 Winding device 30 Film roll 31 Optical film 32 roll 33 Touch roll 40 Tenter (stretching device)
42 Clip 46 Cover 48 Endless chain 50 Driven sprocket 52 Driven sprocket 54 Rail 56 Opening member 80 Temperature distribution sensor 101 Nozzle fixing part 102 Nozzle 103 Nozzle film 104 End nozzle 105 Central nozzle 106 Clip cover A Part of the end of the film roll B Part of the uneven shape of the nozzle processing C Width sticking part D Longitudinal sticking part F Optical film _HA , H _B width Q Thermocouple, infrared (IR) heater

Claims

A film roll in which a single-layer optical film is wound.
The average maximum height difference (PV) ave1 of the film thickness within the range of 1000 mm in diameter is 0.15 to 0.40 μm around an arbitrary point in the optical film.
Moreover, the film roll is characterized in that the ratio of the central portion to the end portion (outer diameter of the central portion / outer diameter of the end portion) of the film roll is 0.98 to 1.02.
A film roll in which a single-layer optical film is wound.
The average maximum height difference (PV) ave1 of the film thickness within the range of 1000 mm in diameter is 0.15 to 0.40 μm around an arbitrary point in the optical film.
Moreover, the a * value and the b * value defined by the CIE1976L * a * b * color system obtained from the reflectance of the surfaces of the central portion and the end portion of the film roll satisfy the following equation (1) (1). :
-1.0 <(end a * -center a * ) + (end b * -center b * ) <1.0
A film roll characterized by that.
The average maximum height difference (PV) ave2 of the film thickness measured in the following steps 1 to 3 diagonally with respect to the width direction of the optical film is 0.15 to 0.40 μm. The film roll according to claim 1 or 2.
Step 1:
After measuring the film thickness at an arbitrary position on the end, measure the film thickness at a position moved 50 mm in the width direction and 620 mm in the longitudinal direction from the arbitrary position for each measurement, and repeat this until the other end. Then, the maximum height difference of each of the film thicknesses in the diagonal direction with respect to the width direction of the optical film is calculated.
Step 2:
After the completion of the step 1, the same measurement as in the step 1 is performed until the total distance of the moving positions in the longitudinal direction reaches 1000 m, and the maximum film thickness in the oblique direction with respect to the width direction of the optical film is maximized. The height difference is further calculated.
Step 3:
From the maximum height difference of the thickness in the diagonal direction with respect to the width direction of the optical film obtained from steps 1 and 2, the average maximum height difference of the film thickness in the diagonal direction with respect to the width direction of the optical film ( PV) Calculate ave2 .
When the average differential orientation angle θ ave ° and the average differential film thickness d ave μm within the range of 1000 mm in diameter are calculated around an arbitrary point in the optical film, the average differential orientation angle θ ave ° and the average differential film thickness are calculated. Equation (2): in which d ave μm satisfies the following equation (2):
800 << | Average differential orientation angle θ ave / Average differential film thickness d ave × 10 -3 | <10000
The film roll according to any one of claims 1 to 3, wherein the film roll.
The film roll according to any one of claims 1 to 4, wherein the optical film contains inorganic fine particles.
The film roll according to any one of claims 1 to 5, wherein the width of the optical film is 2400 to 3000 mm.
The film roll according to any one of claims 1 to 6, wherein the length of the film roll is 7500 to 10000 m.
The method for producing a film roll according to any one of claims 1 to 7.
It has at least a stretching step of stretching the optical film in a stretching furnace and a flattening treatment step.
A method for producing a film roll, which comprises flattening a film roll at a temperature as high as 50 to 200 ° C. with respect to the temperature inside the stretching furnace in the flattening treatment step.
In the stretching step, the flattening treatment is performed using an infrared (IR) heater, and
Equation (3): The average value B of the amount of heat A at the center and the amount of heat at the end at a position 100 mm away from the infrared (IR) heater satisfies the following equation (3):
0.2 <(B / A) <0.6
The method for producing a film roll according to claim 8.