JP2670916B2 - Retardation film manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a retardation film, in particular, a synthetic polymer solution is cast on a support of an endless metal plate to form a film, and then dried.
The present invention relates to a method for producing a retardation film for liquid crystal display (LCD) using a plastic film, which is peeled off from a support and further dried.

[0002]

2. Description of the Related Art As a conventional method for producing a retardation film, a film having birefringence is formed by a solution casting method and stretched to produce a retardation. (JP-A-56
(See JP-130703)

[0003]

However, in the general method for casting a polymer film by casting a polymer solution dissolved in an organic solvent on a running support,
If the organic solvent used contains a particularly large amount of low-boiling solvents, when the polymer solution is extruded from the die, solvent evaporation starts immediately at the tip of the die, and the polymer solution sticks to the tip of the die, causing streak failure. May be caused. If the flow of dry air is not uniform even if a small amount of dry air hits it,
Since the evaporation of the solvent changes depending on how the drying air hits, drying unevenness due to the drying air is generated on the surface of the film-like material, and this is present as optical unevenness inside the film. Since there is no problem in terms of planarity, there is no problem as a mere support for a photosensitive material, but in the case of optically utilizing, for example, birefringence such as retardation film for liquid crystal display (LCD), the quality is It becomes an upper problem. Further, particularly in the case of manufacturing a retardation film for LCD, when peeling the casting film from the support, the adhesive force with the support is strong and there are cases where it cannot be peeled off, which is a problem. Further, in the case of solution casting, when peeling the casting film from the support, if the adhesive strength to the support is strong, stepwise unevenness may occur during peeling or the peeling may not be possible. In addition, since the solution system is used, if the time from casting to peeling is shortened, the evaporation of the solvent is reduced, the strength of the film is weakened, and elongation occurs at the time of peeling, resulting in unevenness in the width direction, and the film on the support is There was a case where the phenomenon of peeling residue remained. An object of the present invention is to solve the above conventional problems, to provide a retardation film manufacturing method capable of preventing unevenness during peeling and peeling residual phenomenon, having stable quality, and increasing the film forming speed. is there.

[0004]

Means and Actions for Solving the Problems The above object of the present invention is to provide a method for producing a retardation film by casting a polymer solution on a support to form a film, and then stretching the polymer solution. A method for producing a retardation film, characterized in that the phosphoric acid ester-based surfactant represented by the general formula (1) is added and cast.

The general formula

Embedded image

However, R ^{1 is} an alkyl group having 6 or more carbon atoms, or an alkenyl group is an aryl group having an alkyl group or an alkenyl group having 6 or more carbon atoms R ² : a hydrocarbon group L ¹ : a divalent linking group n 1: 0 or 1 M ^1: a hydrogen atom or a cation R ^3: M ² or _{^{R 4 - (L 2) n2}} -R 5 (R 4 and R ¹ as defined, L ² is L ¹ synonymous, _n2 is _n1 synonymous, R ⁵ has the same meaning as R ² and M ² has the same meaning as M ^1. ) and the solution casting film-forming method is such that the polymer solution dissolved in an organic solvent is cast on an endless metal plate support. A method for casting a plastic film, which comprises drying a film, peeling the film from the support, and further drying the film, wherein the support is radiant heat source from the back side of the support. It is heated and the residual solvent of the film is 3
2. The method for producing a retardation film according to claim 1, wherein the surface side film-like material on the support is heated and dried only by a radiant heat source without using drying air in a range up to 5% by weight or less. To be achieved.

The retardation film used in the present invention has birefringence and is made of polystyrene, styrene-acrylonitrile copolymer, polycarbonate, polymethyl methacrylate, polypropylene, polyvinyl chloride, polyethylene, polyacrylate, polyether sulfone. ,
Examples thereof include polyphenylene oxide. The solvent used in the present invention includes chlorinated hydrocarbons such as methylene chloride, ketones such as acetone and methyl ethyl ketone,
It is selected from aromatic compounds such as toluene. The amount of the phosphoric acid ester compound used in the present invention is 0.0001 to 0.2 wt% based on the solid content, preferably 0.001 to
It is 0.1 wt%. The phosphoric acid ester compound used in the present invention has the general formula (1)

General formula (1)

Embedded image

However, R ^{1 is} an alkyl group having 6 or more carbon atoms,
Or an alkenyl group, an aryl group having an alkyl group having 6 or more carbon atoms or an alkenyl group R ² : a hydrocarbon group L ¹ : a divalent linking group n 1: 0 or 1 M ^{1, a} hydrogen atom or a cation R ³ : M ² or R _{^{4 - (L 2) n2 -R}} 5 (R 4 and R ¹ as defined, L ² is L ¹ synonymous, _n2 is _n1 synonymous, R ⁵ is R ² as defined, M ² is M ¹ synonymous) specific Specifically, the hydrocarbon group of R ² is an alkylene group or a phenylene group, and the divalent linking group of L ¹ is —O (C ₂ H ₄ O) _{m 1} —, —
_{O (C 3 H 6 O)} m2 - (m1, m2: 0~50), - SO
₂ NH- or -CONH-, and the cation of M ¹ is an alkali metal, alkaline earth metal, or alkylammonium salt. R ¹ is preferably an alkyl group or alkenyl group having 8 to 36 carbon atoms, or a phenyl group having an alkyl group or alkenyl group having 8 to 36 carbon atoms. Specific examples include the following groups.

[0010]

Embedded image

R ^{2 is} an alkylene group having 1 to 10 carbon atoms or a phenylene group. As examples of compounds,
This is as shown in Chemical formula 7. _{^{L 1: -O (C 2 H}} 4 O) m1 -, - O (C 3 H 6 O) m2 -
(M1, m2: 1 to 10) and -CONH-. M ¹ is a hydrogen atom, Na, Ka, Li, Ca, Mg, or HNH _t (R ⁶ ) _3-t [wherein R ⁶ is a substituted or unsubstituted alkyl group, _t is 0, 1 or 2, HNH
₂ CH ₂ CH ₂ OH, HNH (CH ₂ CH ₂ OH) ₂ , HN
(CH ₂ CH ₂ OH) ₃ , HN (C ₂ H ₅ ) ₃ ]

[0012]

Embedded image

[0013]

Embedded image

[0014]

Embedded image

In the casting film forming method of the present invention, the concentration of the polymer in the polymer solution is preferably 40% by weight or less, but it varies depending on the molecular weight of the polymer. The dope temperature is preferably 40 ° C. or lower. The film thickness at the time of casting varies depending on the completed film thickness, and the completed film thickness is preferably 50 μm to 200 μm. In the present invention, heating the support from the back surface side of the support by a radiant heat source means that far infrared heating or high frequency heating is performed on the entire back surface of the support,
Specifically, the above heater, a dielectric heater, or the like is used for this. This is compared to the conventional drying only by hot air on the front surface side, whereas the back surface side of the film-like material remains cold due to the evaporation of the solvent, but the present invention rather supplies the heat of evaporation of the solvent from the film surface from the back surface. The difference is that the temperature of the filmy substance on the surface to be heated rises more on the back side than on the front side.
Overall, the transfer of solvent to the surface side for evaporation is favored.

In the present invention, the residual solvent of the film is 35
Until the amount of the solvent is 35% by weight or less, the film on the surface side of the support is heated by only a radiant heat source and dried without using the drying air in the case where the residual solvent is 35% by weight or more. Conventional drying unevenness causes unevenness of the film surface due to partial difference in convection of dry air on the film surface, that is, convective drying by hot air causes partial drying of the boundary film by the flow of dry air on the film surface. While partial unevenness occurs due to the difference in the drying speed, in the present invention, the drying by evaporation only due to the temperature rise of the film itself causes a great difference in that the entire surface can be slowly and uniformly dried. Therefore,
The method of the present invention is characterized by causing only natural evaporation on the entire surface by heating the film-like material by radiant heat. Therefore, it is important to provide a radiant heat source so as to uniformly irradiate the surface of the film, and it is necessary to control the upper limit temperature so that the film does not foam.

In the present invention, the residual solvent of the film is 35
When it is less than weight%, there is no worry of uneven drying, so
Although it may be forced to dry with hot air as in the past,
When the residual solvent is 35% by weight or more, the film on the surface side is not dried by hot air, and the solvent concentration is high. Radiant heating is performed from both the front and back sides in the atmosphere (because dry air is not used). In the above method, a method of uniformly drying the whole surface to make a residual solvent of 35% by weight or less, peeling it from the band, and then performing full-scale drying may be performed by a post-drying device. By doing so, it can be expected that the production speed will be further increased. Further, as the support for the endless metal plate of the present invention, the support may be a band or a drum, but the present invention is rather effective when a band having a long path is used as a support in a casting apparatus. Is.

In order to more clearly explain the effects of the present invention, description will be made with reference to the drawings. FIG. 1 is a side sectional view of a band type casting apparatus of one embodiment of the casting film forming method of the present invention. In FIG. 1, the polymer solution dissolved in the organic solvent is the dye 1
The film is cast on the band-shaped support 2 made of an endless metal plate from the die 1 to form a film, and then the upper band portion of the casting device is advanced as the support is advanced. The front drum 4 located right below the die 1 at the casting portion is usually passed with cold water 7 to cool the surface of the front drum portion, and also to cool the endless band running on the front drum surface. It is designed to improve the set of the polymer-like film material that is more cast. The cast film material receives the radiant heat from the backside of the band from the steam heater or the dielectric heater 3 in the upper band portion of the casting apparatus, and raises the temperature of the band, whereby the film material is also heated and heated. To rise. Radiation heat is applied to the film material by a steam heater or dielectric heater 3 on this surface as well, and there is no drying air, so that the entire surface of the film is dried naturally and uniformly by the heat. The vapor pressure increases due to the vaporization of the air, so it is necessary to exchange a suitable atmosphere, but this atmosphere exchange must be exchanged so as not to have a strong and localized effect on the drying speed of the film. I have to.

FIG. 1 shows a band type casting film forming apparatus.
All processes are made uniform by radiant heating and slowly dried,
7 shows a state of the casting film forming apparatus when the film 6 is peeled off at the end of the casting film forming apparatus and then sufficiently dried by a post-drying device (not shown). For a film that requires extremely flatness, by maintaining a calm state for a while after casting as described above, the leveling effect can be promoted and the flatness can be improved. Drying progresses on the support,
Dry air may be applied when the flow of the film-like material completely stops, that is, when the residual solvent becomes 35% by weight or less, but the dry air should be designed so as not to affect the casting port. There is a need. According to the present invention, in FIG. 2, the solvent is dried so that the residual solvent of the film-like substance is 35% by weight or less in the range from the casting portion to about 2/3 of the support, and the drying is performed in the area after 2/3. In the sense of promoting the
A method of drying with hot air as 0 can also be adopted.

[0020]

【Example】

The effects of the present invention will be shown with examples.
However, the present invention is not limited only to the present embodiment. (Example-1) A styrene / acrylonitrile copolymer (ratio 66/34, average molecular weight 200,000, Stylac AS-703, Asahi Kasei) was dissolved in methylene chloride to prepare a 25 wt% polymer solution (dope), and phosphorus was added. As the acid ester-based surfactant, the one shown in Chemical formula 1 was added in an amount of 0.01% by weight based on the solid content to form a completely homogeneous solution.
The solution is filtered and the film thickness is 400μ from the casting die.
m, cast on a support, dried for 12 minutes at a temperature at which foaming did not occur, and peeled from the support. When the residual volatile content during stripping was 21% by weight or less, there was no resistance when stripped from the support, and a good film without step unevenness was obtained. When this film was sufficiently dried by post-drying and stretched 2.5 times in an atmosphere of 105 ° C., the retardation value (R
The e value) was 300 nm and exhibited the function as a retardation film. (Example-2) When compounds 7 and 16 of Chemical formula 5 were added as surfactants in Example-1 under the same conditions, peeling became very light and a good film was formed.

(Comparative Example-1) When no surfactant was used in Example-1, the residual volatile content was 21% by weight, and unevenness occurred during stripping. When the volatile content is high, the film stretches and the phenomenon of stripping remains, and when it is low,
The peeling load increased and could not be peeled off.

(Example-3) In Example-1, as shown in FIG. 1, a fin-shaped indirect heating heater using steam as a radiant heat source was placed on the surface of the support, the drying air was stopped, and the casting was performed. Then, after peeling off with a residual solvent of 35% by weight and drying with a post-drying device, a product having no wind unevenness, streaks or step unevenness and having an extremely optically excellent surface condition was obtained.
Also, it has become possible to speed up.

[0024]

According to the method for producing a retardation film of the present invention, the peeling load of the film is reduced, and a uniform film having excellent optical quality, which is free from unevenness and streaks during peeling, can be obtained. In addition, since the time from casting to peeling can be shortened, high-speed production becomes possible.

[Brief description of the drawings]

FIG. 1 is a side sectional view of a band-type casting film forming apparatus according to an embodiment of a casting film forming method which is effective when used in the present invention.

FIG. 2 is a side sectional view of an apparatus of another embodiment of the casting film forming method which is effective when used in the present invention.

FIG. 3 is a side sectional view of an apparatus as an example of a conventional casting manufacturing method.

[Explanation of symbols]

 1 Die 2 Support 3 Heater 4 Front Drum 5 Rear Drum 6 Film 7 Cold Water Pipe 8 Hot Water Pipe 9 Dry Air for Upper Band 10 Dry Air for Lower Band

Claims (2)

(57) [Claims] 1. A polymer solution is cast on a support to form a film,
In the method for producing a retardation film by stretching thereafter, a method for producing a retardation film, which comprises adding the phosphoric acid ester surfactant represented by the general formula (1) to a polymer solution and casting. General formula (1) However, R ¹ : an alkyl group having 6 or more carbon atoms, or an alkenyl group, an aryl group having an alkyl group or an alkenyl group having 6 or more carbon atoms R ² : a hydrocarbon group L ¹ : a divalent linking group n 1: 0 or 1 M ^1: a hydrogen atom or a cation R ^3: M ² or _{^{R 4 - (L 2) n2}} -R 5 (R 4 and R ¹ as defined, L ² is L ¹ synonymous, _n2 is _n1 synonymous, R ⁵ is R (Synonymous with ² , M ² is synonymous with M ¹ ) 2. The solution casting film forming method comprises casting the polymer solution dissolved in an organic solvent on a support of an endless metal plate running to form a film, and then drying. A method for casting a plastic film by stripping from the support and further drying the support, wherein the support is heated from the back side of the support by a radiant heat source and the residual solvent of the film is 35 2. The method for producing a retardation film according to claim 1, wherein the surface side film-like material on the support is heated and dried only by a radiant heat source without using drying air in a range up to a weight% of less.