JP2002036266A - Method for manufacturing film, film and film for polarizing sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a film manufacturing method capable of efficiently obtaining a film with a thickness of 20-85 μm having high quality, and a film (a film for a polarizing sheet). SOLUTION: The film manufacturing method includes a dope casting process 1 for casting a dope, which is a raw material solution of the film, on a support from a die 10, a peeling process for feeling the web W, which is formed on the support in the dope casting process, from the support, drying processes 4, 5 for drying the web W peeled from the support while feeding the same from a plurality of feed rolls 12 and a taking-up process 7 for taking up the film obtained by drying the web. In the dope casting process 1, a ratio value α/V (s/m) of the concentration of solvent vapor [=(volume of solvent vapor/ volume of solvent-containing space)×100] α(%) in the vicinity of the lower end part of the side surface of the die 10 and wind velocity V (m/s) in the vicinity of the lower end part of the side surface of the die 10 is set to 10 or more.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for producing a film suitable as a protective film and a retardation film for a polarizing plate in, for example, a liquid crystal display device or organic electroluminescence.

[0002]

2. Description of the Related Art Liquid crystal display devices (hereinafter referred to as LCDs) have various excellent characteristics, and are currently used for display of word processors, personal computers, and various information communication devices. Widely used as a device.

[0003] The LCD basically has a structure in which polarizing plates are attached to both sides of a liquid crystal cell, and the polarizing plate functions to pass only light having a certain polarization plane. That is, LCD
In, the polarizing plate plays an important role of visualizing the change in the orientation of the liquid crystal due to the electric field. Therefore, the performance of the LCD greatly depends on the quality of the polarizing plate.

Here, the structure of the polarizing plate will be briefly described. The polarizing plate has a three-layer structure in which a polarizer is sandwiched between polarizing films on both sides thereof. As described above, the LCD is configured by laminating the thus obtained polarizing plate on a liquid crystal cell.

[0005] Among the above components, the polarizer is obtained by adsorbing iodine or the like on a polymer film and stretching the polymer film. More specifically, after a solution called an H ink containing a dichroic substance (iodine) is wet-adsorbed to a polyvinyl alcohol film, the film is uniaxially stretched to orient the dichroic substance in one direction. It was obtained. On the other hand, a cellulose resin, particularly cellulose triacetate, is used as the polarizing plate protective film.

[0006] The polarizing plate protective film is manufactured using a band casting system. The structure of the band casting system is already known, but generally speaking, a casting die is installed immediately above the casting band, and a peeling roll, a drying unit, and a winding unit are provided following the casting band. A take-up roll is provided in order. Polarizer protection film
First, the dope is cast from the casting die onto the casting band, and then the web (dope film) formed on the casting band is separated from the casting band by a peeling roll, and then completely dried in the drying unit. To be obtained. Thereafter, the film thus obtained is taken up by a take-up roll.

Incidentally, the polarizing plate protective film currently used has a thickness of 85 μm or more. However, recently, a thin polarizing plate protective film having a thickness of less than 85 μm, particularly a thickness of 20 μm or more and less than 85 μm has been required.

However, according to the conventional manufacturing technique, the thickness is 20 mm.
It is difficult to obtain a polarizing plate protective film of up to 85 μm and high quality. That is, the thickness is 20 to 8 according to the prior art.
To manufacture a thin polarizing plate protective film having a thickness of 5 μm, the widthwise edge of the web formed on the casting band has a sawtooth shape. These defects cause the web to break when the web is peeled from the casting band by the peeling roll.

[0009] Even if such a serious trouble does not occur, in the conventional manufacturing technique, it is unavoidable that the resulting film has defects such as streaks or a locally insufficient thickness. Needless to say, such defects significantly lower the quality of the polarizing plate protective film.

Accordingly, an object of the present invention is to provide a film manufacturing method and a high-quality film (a film for a polarizing plate) capable of efficiently obtaining a high-quality film having a thickness of 20 to 85 μm. That is.
In particular, when manufacturing a film having a thickness of 20 to 85 μm,
An object of the present invention is to provide a method for producing a film, which can effectively prevent the widthwise edge of a web formed on a support from being saw-toothed.

[0011]

An object of the present invention is to provide a method for producing a film having a thickness of 20 to 85 μm by using a solution casting method, wherein a raw material solution of the film is formed on a support. A dope casting step of casting a certain dope from a die, a peeling step of peeling the web formed on the support in the dope casting step from the support, and the support in the peeling step A drying step of drying the web separated from the web while being transported through a plurality of transport rolls, and a winding step of winding a film obtained by drying the web in the drying step. In the dope casting step, the solvent vapor concentration [= (volume of solvent vapor / volume of space containing solvent) × 100] α (%) in the vicinity of the lower end portion on the side surface of the die, Near the bottom Definitive air wind speed V (m / s)
The ratio α / V (s / m) is set to 10 or more.

In the film manufacturing method of the present invention, the ambient temperature near the lower end of the side surface of the die is set to 15 to 4
The temperature is preferably set to 0 ° C., particularly preferably 15 to 25 ° C. Thereby, the quality can be further improved. For the same reason, in the dope casting step, a wind is supplied to the web along the surface of the web from the downstream side in the traveling direction to the web, and the wind speed of the wind is 4 (m / m).
s) It is preferable that the air be discharged from the lower end of the die on the side surface side.

In addition, in the film production method of the present invention,
It is preferable that an enclosure is provided in the vicinity of the lower end portion on the side surface side of the die, or that the vicinity of the lower end portion on the side surface side of the die is set to a desired solvent vapor concentration by spraying the solvent vapor. This can further improve the quality of the film.

For the same purpose, in the dope casting step, the dope-soluble solvent is allowed to flow from the lower end of the side surface of the die onto the support, and the amount of the dope-soluble solvent is reduced. 0.1 to 1.0 (cm ³ / min),
Further, it is desirable that the temperature of the solvent soluble in the dope be lower than its boiling point.

Further, in order to make the air velocity near the die particularly preferable (and, in order to further improve the quality of the film), in the film production method of the present invention, the surface of the support and the slit inside the die are used. The angle between the wall and the wall is preferably from 40 to 90 °, more preferably from 60 to 75 °. For the same reason, in the film manufacturing method of the present invention, the width of the slit for discharging the dope in the die is set to 150 to 1500 μm, and the linear flow rate U ₁ (m / s) of the dope discharged from the slit and the support are set. It is preferable that the draft ratio β defined as a ratio value U ₁ / U _{2 with} respect to the traveling speed U ₂ (m / s) is 0.4 to 2.0.

In the dope casting step, the film is provided so as to face the support in order to effectively suppress the occurrence of fluctuations and undulations in the film (and to further improve the quality of the film). The wind is blown to the web from the plurality of slits, and the difference W ₁ (m / s) between the maximum and minimum wind speeds of the wind along the die width direction and the wind speed in the die width direction are determined. It is preferable that the ratio value W ₁ / W ₂ to the average wind speed W ₂ (m / s) along the direction be 0.3 or less.

For the same purpose, in the film production method of the present invention, after the drying step, a web stretching step of stretching the web using a tenter, or
The ratio value t _{F /} t _R of the free span residence time t _F and the web transport rollers contact time t _R, after a closely inter-roll process to 5 or less, further be provided with a heat straightening process for cooling process Is preferred.

In addition to this, in order to effectively suppress the occurrence of warpage in the film (and, in order to further improve the quality of the film), in the film production method of the present invention, after the peeling step, The method may further include a web stretching step of stretching the web using a tenter, and a difference in tension acting on the web in the transport direction between before and after the tenter may be 8 N / mm ² or less. preferable.

Further, in order to effectively suppress the dust-dust failure from remaining in the product (film) (and, in order to further improve the quality of the film), in the film manufacturing method of the present invention, after the peeling step, A preheating step of preheating the web, a stretching step of stretching the web using a tenter after the preheating step, and a relaxation step of relaxing the web by an amount smaller than the stretching amount in the stretching step after the stretching step. comprising the door, the temperatures T ₁ in the preheating step and the stretching step, (the glass transition temperature of the film T _g -6
0) The temperature is ₂ ° C. or higher, and the temperature T ₂ in the relaxation step
Is preferably (T ₁ -10) ° C. or lower. In particular, the stretching rate of the web in the stretching step is 0 to 30% as a ratio to the web width immediately before entering the stretching step, and the stretching rate of the web in the relaxation step is -10 to 10%. It is desirable. The above-described film manufacturing method is particularly suitable for manufacturing a polarizing plate film. That is, as a film to be manufactured, a film for a polarizing plate is particularly exemplified.

On the contrary, the above problem is solved by a film characterized by being obtained by using the above-mentioned film production method. In particular, the problem is solved by a film for a polarizing plate, which is made of this film.

In the present invention, a solution casting method is used.
In producing a film having a thickness of 20 to 85 μm,
In the dope casting process, the solvent vapor concentration [= (volume of solvent vapor / volume of space including solvent) × 100] α (%) in the vicinity of the lower end of the side of the die and the air in the vicinity of the lower end of the side of the die Ratio value α / V (s) to wind speed V (m / s)
/ M) is set to 10 or more. Therefore, the solvent vapor concentration in the vicinity of the lower end of the side surface of the die is always kept at an optimum value, and as a result, the edge in the width direction of the web formed on the support becomes saw-toothed (that is, the sawtooth shape). The formation of a coating, which comes into contact with the edge of the web and which becomes serrated, is effectively suppressed. That is, no defect causing breakage or other failure occurs at the edge of the web in the width direction. Therefore, by using the technique of the present invention, it is possible to efficiently obtain a high-quality film (in particular, a polarizing plate film) having a thickness of 20 to 85 μm.

When peeling the web from the support,
When the amount of the solvent remaining in the web is in the range of 40 to 70% by weight with respect to the entire web, the web is difficult to peel off from the support, and a horizontal line is formed in the width direction thereof, and the quality is deteriorated. Sometimes. Therefore, it is desirable to peel the web from the support in a state where the amount of the solvent remaining on the web is out of the range. In other words, when the web is peeled from the support in the peeling step, the amount of the solvent remaining on the web is set to 40% or less or 71% or more by weight based on the entire web. It is particularly preferable in the method for producing a film.

For reference, the film to which the technique of the present invention is applied comprises, for example, a cellulose ester, especially a lower fatty acid ester of cellulose. However, "lower" means that the number of carbon atoms is 6 or less, and specifically, for example, cellulose acetate such as cellulose diacetate and cellulose triacetate, cellulose propionate, cellulose butyrate, cellulose acetate propionate And mixed fatty acid esters such as cellulose acetate butyrate. But
The most preferred lower fatty acid ester of cellulose is cellulose triacetate.

Further, the dope, which is a raw material solution for the film, may contain a matting agent such as fine particles of silicon oxide in addition to the cellulose ester. Specific examples of the matting agent include silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, calcium carbonate, talc, clay, calcined kaolin, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, and silica. Fine particles composed of magnesium phosphate and calcium phosphate can be exemplified. However, most preferred is silicon dioxide. In addition, polymer fine particles (for example, fine particles made of silicone resin, fluorine resin, or acrylic resin) can be used as the matting agent.

The dope may contain one or more ultraviolet absorbers. This ultraviolet absorber is excellent in the ability to absorb ultraviolet light having a wavelength of 370 nm or less from the viewpoint of preventing deterioration of the liquid crystal, and has a wavelength of 4 nm from the viewpoint of liquid crystal display properties.
Those having little absorption of visible light of 00 nm or more are preferable.
Specifically, oxybenzophenone-based compounds, benzotriazole-based compounds, salicylate-based compounds, benzophenone-based compounds, cyanoacrylate-based compounds,
Nickel complex salt compounds and the like can be mentioned. Among them, benzotriazole compounds are particularly preferred.

The dope may contain one or more plasticizers. Specifically, triphenyl phosphate, tricresyl phosphate, cresyl diphenyl phosphate, octyl diphenyl phosphate, diphenyl biphenyl phosphate, trioctyl phosphate, phosphate plasticizers such as tributyl phosphate, diethyl phthalate, dimethoxyethyl phthalate, Dimethyl phthalate, dioctyl phthalate, dibutyl phthalate, phthalate plasticizers such as di-2-ethylhexyl phthalate, triacetin, tributyrin, butyl phthalyl butyl glycolate, ethyl phthalyl ethyl glycolate, methyl phthalyl ethyl glycolate, Glycolic acid ester-based plasticizers such as butylphthalylbutylglycolate are exemplified. Among them, phthalic acid ester type and glycolic acid ester type plasticizers are particularly preferable because they hardly cause hydrolysis of cellulose ester.

It is preferable that the dope further contains a plasticizer having a freezing point (a true freezing point described in Kyoritsu Shuppan's Dictionary of Chemistry) of 20 ° C. or less. Examples of such a plasticizer include tricresyl phosphate, cresyl phenyl phosphate, tributyl phosphate, diethyl phthalate, dimethyl phthalate, dioctyl phthalate, dibutyl phthalate, di-2-ethylhexyl phthalate, triacetin, and ethyl phthalyl ethyl glycolate. Is mentioned. However, a preferable content of the plasticizer is 1 to 10% by weight, particularly 3 to 7% by weight based on the cellulose ester from the viewpoint of dimensional stability.

Next, as a solvent for forming a dope (dope composition), for example, methanol, ethanol, n-propyl alcohol, iso-propyl alcohol, n-
Examples include alcohols (especially lower alcohols) such as butanol, aliphatic hydrocarbons such as cyclohexane, dioxane, and methylene chloride, and chlorides. The ratio of this solvent is preferably about 70 to 95% by weight for methylene chloride, and about 30 to 5% by weight for other solvents.

Generally speaking, the above-mentioned raw materials (cellulose ester, plasticizer, ultraviolet absorber, matting agent, etc.) are dissolved in a solvent and filtered to obtain a dope, which is then used to form a film by a solution casting method. By doing so, a film of the present invention having a thickness of 20 to 85 μm, particularly using a lower fatty acid ester of cellulose as a raw material, can be obtained.

Incidentally, in producing such a film, for example, US Pat. Nos. 2,492,978 and 2,7
39,070, 2,739,069, 2,49
No. 2,977, No. 2,336,310, No. 2,36
7,603 and 2,607,704, British Patent 6
4,071 and 735,892, JP-B-45-90
No. 74, No. 49-4554, No. 49-5614, No. 60-27562, No. 61-39890, No. 62-
No. 4208 can be referred to.

[0031]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of the present invention (film manufacturing method) will be described in detail with reference to FIGS. However, FIG. 1 is an overall schematic view of an apparatus used for manufacturing a film using the film manufacturing method according to the present embodiment, and FIGS. 2 and 3 are a perspective view and a sectional view, respectively, showing a main part of the apparatus.

The film manufacturing method according to the present embodiment (hereinafter, simply referred to as the present film manufacturing method) includes a solution casting method,
In particular, using a band casting method, the thickness is 20 μm or more,
This is a technique for producing a film having a thickness of less than 85 μm, in particular, a protective film for a polarizing plate (that is, a film for a polarizing plate; hereinafter also referred to as a film used for a liquid crystal display member).

The film manufacturing operation according to the present film manufacturing method is performed using a film manufacturing apparatus whose overall structure is shown in FIG. Here, the configuration and function of the film manufacturing apparatus will be described.

The film production apparatus shown in FIG. 1 comprises a dope casting means 1, a circulating running belt (support) 2, a peeling roll (peeling means) 3, and a drying roll provided in two stages in the transport direction. Winding means 7 including boxes (drying means) 4 and 5 and a winding core 6 for winding the obtained film F are used as basic components.

The dope casting means 1 includes a tank 8 having a stirring function, a liquid feeding pump 9, and a casting solution for casting a dope, which is a raw material solution of the film F, onto the casting band 2. It has a die (hereinafter simply referred to as a die) 10. This allows the dope casting means 1 to cast the dope in the tank 8 from the die 10 onto the casting band 2 by a predetermined amount.

Next, the casting band 2 on which the dope is cast.
Is an endless one that circulates (circulates) as described above, and is stretched between a pair of drums 11a and 11b. Driving means (not shown) is connected to one of the drums 11a and 11b, and by operating the driving means, the belt 2 circulates in the direction of the arrow in FIG. It has become.

The peeling roll 3 provided adjacent to the surface of the belt 2 is separated from the belt 2 by the dope casting means 1.
Of the web W formed on the surface of the casting band 2. That is, the web W that has not been dried sufficiently and is still soft is changed in direction toward the drying boxes 4 and 5 by the peeling tension and the action of the peeling roll 3.

The drying boxes 4 and 5 have the same structure. That is, the inside of the transport roll 12
Are provided. Therefore, the web W is
The sheet is conveyed while being in close contact with the peripheral surface of the transfer roll 12 and sewn in between. In addition, drying boxes 4,5
Inside, air (dry air) can be separately introduced.

The winding means 7 is for winding the film F obtained through the drying boxes 4 and 5, and has the winding core 6 around which the film F is wound as described above. The take-up core 6 is connected to a drive unit (not shown). By operating the drive unit, the take-up core 6 rotates to wind the film F at a constant speed.

The procedure for manufacturing the film F (basic steps of the present film manufacturing method) using the film manufacturing apparatus configured as described above is as follows.

First, a dope, which is a raw material solution of the film F, is cast from the casting die 10 onto the casting band 2, and a web (doped film) W having a uniform thickness is formed on the casting band 2. It is formed (dope casting step). Next, in the dope casting step, the casting belt 2 is circulated.
The web W formed thereon is peeled off (peeling step), and is further fed to the drying box 4 and subsequently to the drying box 5. Then, the web W is completely dried while being transported through the plurality of transport rolls 12 in the drying boxes 4 and 5, and finally has a thickness of 20 to 85 μm (20 μm).
As a result, the film F (less than 85 μm) is obtained (drying step). Thereafter, the film F thus obtained may be wound by the winding core 6 provided at the end of the production line (winding step), whereby the film F becomes a winding roll (film winding body). .

In the present film manufacturing method, the web W formed on the belt 2 is air (dry air).
Is sprayed. In this air blowing,
For example, the header 21 shown in FIGS. 2 and 3 is used. Incidentally, there are a total of two headers 21, which are arranged to face each other with the casting band 2 interposed therebetween. In addition,
In FIG. 1, the header 21 is omitted.

In the present embodiment, in the dope casting step, an air flow (a region indicated by X in FIG. 2) formed near the lower end of the side surface of the die 10 by the header 21 or other means. (The direction is not limited), that is, the air wind speed V (m / s), and the solvent vapor concentration [= (volume of solvent vapor /
(Volume of space containing solvent) × 100] α (%) so as to satisfy the following relationship. That is, in the present embodiment, the ratio α / V between the solvent vapor concentration α (%) near the lower end on the side surface of the die 10 (region X) and the air velocity V (m / s) near the lower end on the same side surface. (S / m) is 10
It was above.

Further, in the present embodiment, in the dope casting step, air (dry air) flowing along the surface of the web W (casting band 2) toward the die 10 from the downstream of the running (advancing) direction is fed to the web. W (for which the header 21 is mainly used). In particular, here, the wind speed is set to 4 (m / s) or less, and the air (dry air) finally collides with the die 10 and is discharged from the lower end of the side surface to the outside of the film forming region. I did it. In addition, in the present embodiment, the ambient temperature near the lower end of the side surface of the die 10 (region X) is set to 15 to 40 ° C., particularly 15 to 25 ° C.
° C.

In order to obtain a desired solvent vapor concentration near the lower end of the side surface of the die 10 (region X), in the present film manufacturing method, the region is sprayed with the solvent vapor (blown). Means are not shown). However, the same object can be achieved by providing an enclosure (cover) for suppressing diffusion of the solvent vapor near the lower end of the side surface of the die 10 (region X).

In the present embodiment, in the dope casting step, a solvent that is soluble in the dope flows down onto the casting band 2 from the lower end of the die 10 on the side surface. However, in this process, a pair of solvent flow-down means 2 provided near the die 10 is used.
2 (only one of them is shown in FIG. 2).
The dope-soluble solvent that has flowed down from the solvent flow-down means 22 adheres to the edge of the web W and plays a role in suppressing the drying of that portion. In the present embodiment, the flow rate of the solvent soluble in the dope is set to 0.1 to 1.0 (cm ³ / mi).
n), and the temperature of the solvent soluble in the dope was set to the boiling point or lower. In other words, the solvent was sufficiently cooled so as not to generate bubbles.

Next, in this film manufacturing method, the die 10
, That is, the angle (indicated by θ in FIG. 3) between the surface of the casting band 2 and the slit wall surface inside the die.
The angle is 40 to 90 °, particularly 60 to 75 °. Further, the width (indicated by δ in FIG. 3) of the slit 10 a from which the dope is discharged in the die 10 is set to 150 to 1500 μm, particularly 200 to 450 μm, and the slit 10 a
Ratio U ₁ / of the linear flow rate U ₁ (m / s) of the dope discharged from the nozzle and the traveling (progressing) speed U ₂ (m / s) of the casting band 2.
The draft ratio β, which is defined as U _2, 0.4 to 2.0
And

On the contrary, in the dope casting step, air (dry air) is blown on the web W from the plurality of slits 21a of the header 21 provided so as to face the casting band 2 as described above. In the embodiment, the difference W ₁ (m / s) between the maximum and minimum wind speeds of the air (dry air) along the die width direction is defined as:
Average wind speed W of the air (dry air) along the die width direction
The ratio W ₁ / W ₂ to ₂ (m / s) is set to 0.3 or less.

The above apparatus used for producing a film using the present film production method has a tenter 23 provided between the drying box 5 and the winding means 7. That is, in the present film manufacturing method, after the drying step, the tenter 23 is used to stretch the web W, or more precisely, the film F obtained by drying the web W.
After this web stretching process, the web W (film F) that has undergone the web stretching process is subjected to a cooling process using a cooling unit (not shown). That is, the present film manufacturing method further includes a heat straightening step of the web W (film F).

[0050] Incidentally, the thermal corrective process, after a closely inter-roll process which is mainly performed in the dry box 4 and 5, more particularly, also the transport rolls contact the web W and the free span residence time t _F of the web W Ratio value t _F / with time t _R /
The t _R, (is this Mitsukan roll process) treatment step of 5 or less after a, it may perform the cooling process.

The film production method is used to fill
The apparatus used to manufacture the system comprises a peel roll 3
And between the drying box 4 and the tenter 23
Is provided. That is, this book
After the peeling step, the tenter 24 is used
And a web stretching step of stretching the web W.
And especially in this embodiment, this tenter 24 and
The web W is transported before and after the tenter 23.
The difference in tension acting along the direction is 8 N / mm ²And
are doing.

As described before and after, in the present film manufacturing method, after the peeling step, a preheating step of preheating the web W by using a preheating means (not shown) is carried out. A stretching step of stretching the web W using the web is performed. Further, after the stretching step, a relaxation step of relaxing the web W by an amount smaller than the stretching amount in the stretching step is performed. However, temperatures T ₁ in the preheating step and the stretching step is set to be (the glass transition temperature T _g -60 films) ° C. or higher. on the other hand,
Temperature _{T 2} in the relaxation step _is set to be (T 1 -10) ℃ or less. Incidentally, the stretching ratio of the web W in this stretching step is 0 to 30% in proportion to the web width immediately before entering the stretching step, and the stretching ratio of the web W in the relaxing step is -10 to -10. 10%.

According to the present film production method having the above-described steps, a film (a polarizing plate protective film, that is, a film for a polarizing plate) which is an embodiment of the present invention and is formed by using a solution casting method for film formation is obtained. More specifically, when the web W is peeled off from the belt 2, the amount of the solvent remaining on the web W is set to 40% or less or 71% or more by weight with respect to the entire web W (polarized light). A plate protective film, that is, a polarizing plate film) is formed.

When the above-described film manufacturing method is used, the solvent vapor concentration near the lower end of the side surface of the die 10 (region X) is always kept in an optimum range. The phenomenon in which the edge of the web W formed in the width direction in the width direction has a saw-tooth shape is effectively suppressed. That is,
Defects that cause breakage and other defects do not occur at the widthwise edge of the web W. Therefore, by using the present film production method, it is possible to efficiently obtain a high-quality film having a thickness of 20 to 85 μm, particularly a polarizing plate film.

Here, for reference, a liquid crystal display member, for example, a polarizing plate, comprising a film obtained by using the technique of the present embodiment as a component, is manufactured as follows.

First, iodine or the like is adsorbed on a polymer film, and the above-mentioned alkali-treated film is bonded to both surfaces of a stretched polarizer using a completely saponified polyvinyl alcohol aqueous solution. Thereby, the polarizing plate is obtained. However, instead of the alkali treatment,
-94915 and JP-A-6-118232 may be adopted. Incidentally, the “liquid crystal display member” referred to in this specification refers to a member used in a liquid crystal display device. For example, in addition to the above-mentioned polarizing plate, a polarizing plate protective film, a retardation plate, a reflecting plate, a viewing angle improving film, an antiglare film, a non-reflective film, an antistatic film and the like can be mentioned.

[0057]

According to the present invention, the thickness is 20 to 85 μm.
High-quality film (film for polarizing plate) can be efficiently obtained. In particular, when a film (a film for a polarizing plate) having a thickness of 20 to 85 μm is produced, it is possible to effectively prevent the widthwise edge of the web formed on the support from becoming saw-toothed.

[Brief description of the drawings]

FIG. 1 is an overall schematic view of an apparatus used for manufacturing a film using a film manufacturing method according to an embodiment of the present invention.

FIG. 2 is a perspective view showing a main part of an apparatus used for manufacturing a film using the film manufacturing method according to the embodiment of the present invention.

FIG. 3 is a cross-sectional view showing a main part of an apparatus used for manufacturing a film using the film manufacturing method according to the embodiment of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 dope casting means 2 casting band (support) 3 peeling roll (peeling means) 4, 5 drying box (drying means) 6 winding core 7 winding means 8 tank 9 liquid feed pump 10 casting die (die) 10a Slit of casting die 11a, 11b Drum 12 Conveying roll 21 Header 21a Slit of header 22 Solvent flowing down means 23, 24 Tenter W Web (doped film) F film

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) // G02F 1/1335 510 G02F 1/1335 510 B29K 1:00 B29K 1:00 B29L 11:00 B29L 11:00 C08L 101 : 00 C08L 101: 00 (72) Inventor Shoichi Kurokawa 1 Sakuracho, Hino-shi, Tokyo Konica Corporation F-term (reference) 2H049 BA02 BA27 BB33 BB51 BC01 BC03 BC09 BC22 2H091 FA07X FA07Z FC01 FC29 GA16 LA02 LA12 4F071 AA01 AA09 AH12 AH19 BA02 BB02 BB07 BC01 BC02 BC12 4F205 AA01 AC05 AG01 AH73 AM30 AR04 AR06 AR07 AR08 AR12 AR14 AR20 GA07 GB02 GC07 GE22 GF01 GF06 GF24 GF25 GF29 GF47 GN19 GN22 GN24 GN29 AR04 A07 AR04 A07 GW06 AR12 AR14 AR20 QA02 QC03 QD25 QG01 QG18 QL17 QL18 QW12 QW15

Claims (15)

[Claims] 1. A thickness of 20 to 8 using a solution casting method.
A method for producing a 5 μm film, comprising: a dope casting step of casting a dope, which is a raw material solution of the film, from a die on a support; and a dope casting step on the support in the dope casting step. A peeling step of peeling the formed web from the support; and a drying step of drying the web peeled from the support in the peeling step while transporting the web through a plurality of transport rolls. And a winding step of winding a film obtained by drying the web in the drying step. In the dope casting step, the solvent vapor concentration near the lower end of the side surface of the die [=
(Volume of solvent vapor / volume of space containing solvent) × 100]
A method for producing a film, wherein a ratio α / V (s / m) between α (%) and an air wind velocity V (m / s) near a lower end portion on the side surface of the die is 10 or more. 2. The method according to claim 1, wherein the ambient temperature near the lower end of the side surface of the die is 15 to 40 ° C. 3. In the dope casting step, wind is supplied to the web along the surface of the web from the downstream in the direction of travel to the web, and the wind speed of the wind is set to 4 (m / s) or less. The method according to claim 1, wherein the wind is discharged from a lower end portion on a side surface of the die. 4. An enclosure is provided near the lower end on the side surface of the die, or by spraying a solvent vapor.
The method according to any one of claims 1 to 3, wherein the solvent vapor concentration in the vicinity of the lower end on the side surface of the die is set as an expected concentration. 5. In the dope casting step, a dope-soluble solvent is allowed to flow from the lower end of the side surface of the die onto the support, and the amount of the dope-soluble solvent is reduced to 0.1 to 0.1.
The method for producing a film according to claim 1, wherein the temperature is 1.0 (cm ³ / min), and the temperature of the solvent soluble in the dope is not more than its boiling point. 6. The film production method according to claim 1, wherein the angle between the surface of the support and the slit wall surface inside the die is 40 to 90 °. 7. The width of the slit for discharging the dope in the die is set to 150 to 1500 μm, and the linear flow rate U ₁ (m / s) of the dope discharged from the slit and the traveling speed U ₂ (m / s) of the support are set. the method of film production according to any one of claims 1 to 6) and a draft ratio β, which is defined as the ratio value U _{1 /} U _2, characterized in that a 0.4 to 2.0. 8. In the dope casting step, the support and the support are oriented.
Blow the web from multiple slits
And the largest of the wind speeds along the die width direction.
Difference W from minimum₁(M / s) and the die width of the wind
Average wind speed W along the direction₂(M / s) ₁/ W₂
Is set to 0.3 or less.
Item 8. The method for producing a film according to any one of Items 7. 9. After the drying step, a web stretching step of stretching the web using a tenter, or a ratio value t _F / t _R of the free span stay time t _F and the web contact time t _R of the web is determined. The film production method according to any one of claims 1 to 8, further comprising a heat straightening step of performing a cooling treatment after a dense roll step of 5 or less. 10. A web stretching step of stretching the web using a tenter after the peeling step, and a difference in tension acting on the web along the transport direction before and after the tenter. the method of film production according to any one of claims 1 to 9, characterized in that a 8N / mm ² or less. 11. Preheating the web after the stripping step
After this step and this preheating step, the web is
A stretching step of stretching, and after the stretching step, the web is
Relaxation to relax by a smaller amount than the stretching amount in the stretching process
A temperature T in the preheating step and the stretching step.₁To
(Glass transition temperature T of film_g-60) ℃ or more,
And the temperature T in the relaxation step.₂To (T ₁-1
0) The temperature is not higher than 0 ° C.
0. The method for producing a film according to any one of the above items. 12. The stretching ratio of the web in the stretching step is 0 to 30 as a ratio to the web width immediately before entering the stretching step.
%, The stretching ratio of the web in the relaxation step is -10 to 10%.
The method for producing a film according to claim 11, wherein: 13. The method for producing a film according to claim 1, wherein the film is a polarizing plate film. 14. A film obtained by using the method for producing a film according to any one of claims 1 to 13. 15. A film for a polarizing plate, comprising the film according to claim 14.