JP2000301588A - Solution film forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a soln. film forming method capable of markedly reducing longitudinal thickness irregularity of a resin film in producing the resin film by a soln. casting method for a resin soln. using a vacuum chamber. SOLUTION: In a soln. film forming method including operation for sucking the surface on the contact side with a temporary support 2 of a resin soln. extruded in a film form under vacuum by a vacuum chamber in emitting the resin soln. in a film form from the leading end of a casting die 1 to cast the same on the temporary support 2 passing the position slightly separated from the leading end of the casting die under the die to move, the emitting speed of the resin soln. is set to 7.0-38.0 m/min and the vacuum degree of the vacuum chamber 3 is set to -1--50 mm Aq to prouce a film enhanced in thickness accuracy.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solution casting method suitable for producing a photographic material or a film suitable for optical use.

[0002]

2. Description of the Related Art In recent years, thin transparent plastic films (resin films) have recently been used as protective films for polarizing plates of liquid crystal displays, optical compensation films such as retardation plates, plastic substrates, photographic supports, moving image cells and optical filters. In addition, demand for optical materials such as OHP films is increasing.

In particular, recently, liquid crystal displays have been improved in quality and lightweight and excellent in portability, so that personal computers, word processors, portable terminals, televisions, digital still cameras, movie cameras, etc. However, this liquid crystal display requires a polarizing plate for displaying images. The quality of the polarizing plate is required to be improved in accordance with the improvement of the quality of the liquid crystal display. At the same time, the transparent resin film as the protective film of the polarizing plate is also required to have higher quality.

For optical films such as protective films for polarizing plates, high transparency, low optical anisotropy, flatness, easy surface treatment, and high durability (dimensional stability, (Moisture and heat resistance, water resistance), no foreign matter in the film and on the surface, no scratches on the surface and no scratches (scratch resistance), moderate film rigidity (handling), and moderate water permeability It is said that it is necessary to have various characteristics such as sex.

[0005] As a resin film having these characteristics, there is a film made of cellulose ester, norbornene resin, acrylic resin, polyarylate resin, polycarbonate resin, and the like, but cellulose ester is mainly used in terms of productivity and material price. It is used. Particularly, a film of cellulose triacetate is used particularly advantageously for optical applications because it has extremely high transparency, low optical anisotropy and low retardation.

As a method for forming these resin films, various film forming techniques such as a solution film forming method, a melt film forming method and a rolling method can be used. In order to obtain, a solution casting method is particularly suitable. In the solution casting method, a raw material flake is dissolved in a solvent, and if necessary, various solutions such as a plasticizer, an ultraviolet absorber, a deterioration preventing agent, a slipping agent, and a peeling accelerator are added to the solution (dope and dope). This dope is placed on a support such as a horizontal endless metal belt or a rotating drum.
After casting by a dope supply means (referred to as a die), the support is dried to a certain extent on the support, whereby the self-supporting film provided with rigidity is peeled off from the support, and then the drying section is transported by various transport means. It is a method consisting of removing the solvent by passing through.

When a resin film is used for optical applications, it is naturally necessary that the above-mentioned various properties be excellent, but it is also necessary that the uniformity of the thickness of the entire film be high. In other words, if there is “unevenness” in the thickness of the entire film, the optical characteristics are “unevenness” in the unevenness portion.
This often causes a problem as an optical film.

That is, the surface of the formed plastic film is subjected to a hard coat treatment, an anti-glare treatment, an anti-reflection treatment, a stain resistance treatment and the like so as to be suitable for the above-mentioned optical use. For example, when applying a coating liquid for an anti-glare layer to provide an anti-reflection function, if the plastic film has thickness unevenness, application unevenness occurs due to the unevenness, thereby impairing the functionality of the film. Tends to reduce the appearance value.

On the other hand, in order to enhance the productivity of the plastic film, in the above-mentioned solution casting method, when the dope is cast on the support by a die, the casting portion is formed from behind the casting die by using a decompression chamber. A method of suction under reduced pressure is used. That is, when the resin solution is extruded into a film from the tip of the casting die, and cast on a temporary support that moves through a position slightly below the tip of the casting die, the resin solution is extruded into a film. This is a solution casting method including an operation of vacuum-suctioning the surface of the resin solution in contact with the temporary support with a vacuum chamber connected to a vacuum blower via a suction duct.

On the other hand, Japanese Patent Application Laid-Open Publication No. 94-2498, which discloses the technique of the present applicant, discloses that the flatness of the flatness is improved by enlarging the lip opening at the tip of the die used for casting by the solution casting method. A method for producing a cellulose triacetate film is disclosed, wherein the flow rate of the dope discharged from the casting die to the temporary support is 2 to 28 per unit sectional area.
It is stated that the range of liter / min / cm ² is preferred.

[0011]

The inventor of the present invention has noticed that the thickness of the formed film tends to be uneven, particularly during the casting in the solution casting method using the above-mentioned decompression chamber. The research on the cause of the occurrence was repeated. As a result of the study, it has been found that even in the above-mentioned range of the dope flow rate, in the solution casting method using the decompression chamber, thickness unevenness tends to occur particularly in the longitudinal direction of the film.

[0012]

As a result of further research, the present inventor has found that the casting speed is set to a specific range by setting the discharge speed of the dope from the casting die and the degree of pressure reduction by the pressure reduction chamber. It has been found that thickness unevenness in the direction can be prevented accurately.

According to the present invention, when a resin solution is discharged in the form of a film from the tip of a casting die, the resin solution is cast on a temporary support that moves through a position slightly away from the tip of the casting die. In a solution casting method including an operation of suctioning the surface of the resin solution extruded in the form of a film in contact with the temporary support with a reduced pressure chamber under reduced pressure, the discharge speed is 7.0 to 38.0.
m / min and the degree of decompression of the decompression chamber is −
A solution casting method for producing a film with improved thickness accuracy, characterized by being in the range of 1 to -50 mmAq.

Preferred embodiments of the solution casting method of the present invention are described below. (1) A solution casting method in which the discharge speed is in the range of 7.0 to 25.0 m / min. (2) Decompression degree in the decompression chamber is -3 to -30 mmAq
The solution casting method according to the above. (3) A solution casting method in which the distance from the surface of the temporary support to the tip of the die (die height) is in the range of 0.5 to 50 mm. (4) A solution casting method in which the resin solution is a cellulose triacetate solution.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a solution casting method for producing a film of the present invention will be described in detail. Examples of the raw material resin used in the production method of the present invention include lower fatty acid esters of cellulose (eg, cellulose triacetate), polyolefins (eg, norbornene-based polymers), polyamides (eg, aromatic polyamide), polysulfones, and polyethers. (Including polyether sulfones and polyether ketones), polystyrenes, polycarbonates, polyacrylic acids, polyacrylamides, polymethacrylic acids (eg, polymethyl methacrylate), polymethacrylamides, polyvinyl alcohols, polyureas , Polyesters, polyurethanes, polyimides, polyvinyl acetates, polyvinyl acetals (eg, polyvinyl formal, polyvinyl butyral), and proteins (eg, gelatin). Kill. Among these, a lower fatty acid ester of cellulose is preferred as a raw material for a photographic material or a film for optical use, and cellulose triacetate is particularly preferred.

First, these raw materials are dissolved in an appropriate organic solvent to prepare a resin solution (dope). Examples of organic solvents include halogenated hydrocarbons (such as methylene chloride) and alcohols (methanol, ethanol,
Butanol), ketones (acetone, methyl ethyl ketone, etc.), esters (methyl formate, methyl acetate, etc.),
Examples thereof include ethers (dioxane, diethyl ether, etc.) and hydrocarbons (benzene, hexane, etc.).
To the resin solution, various known plasticizers such as phosphate plasticizers such as triphenyl phosphate and biphenyldiphenyl phosphate, phthalate plasticizers such as diethyl phthalate, and polyester polyurethane elastomer are added. You may. Further, if necessary, various known additives such as an ultraviolet absorber, a deterioration inhibitor, a slipping agent, and a peeling accelerator may be added.

For the preparation of the resin solution, a method of stirring and mixing the raw material resin or the like in a solvent and dissolving it by a well-known method may be used. Cooling the swollen mixture to below -10 ° C;
Next, a method of dissolving by heating to 0 ° C. or higher may be used.

Next, the resin solution (dope) is cast using a resin solution casting apparatus as shown in FIG. In the manufacturing apparatus shown in FIG. 1, a resin solution (dope) is discharged from the casting die 1 onto the surface of the temporary support 2 moving at a constant speed in the direction of the arrow in the figure and cast. At the same time, casting die 1
(The vicinity of the surface of the resin solution film discharged from the casting die in contact with the temporary support) is suctioned under reduced pressure by the decompression chamber 3 so that the dope 4 adheres to the temporary support 2. Cast it.

At this time, it is preferable that the discharge speed of the dope and the degree of decompression of the decompression chamber are in the range of 7.0 to 38.0 m / min and -1 to -50 mmAq (in water), respectively. Here, the discharge speed of the dope refers to the average discharge speed in the width direction at the tip of the lip of the casting die. Combining the discharge speed and the degree of depressurization of the decompression chamber within these ranges, and performing dope discharge casting, effectively preventing the occurrence of film thickness unevenness and maintaining the appearance value and functionality of the film. Can be. Particularly preferably, the discharge speed is in the range of 7.0 to 25.0 m / min, and the degree of pressure reduction is in the range of -3 to -30 mmAq.

The die height h representing the distance from the temporary support 2 to the tip of the lip of the casting die 1 is usually 0.5 to 0.5.
It is in the range of 50 mm, preferably in the range of 1 to 10 mm.

The apparatus that can be used for casting the solution of the resin composition in the present invention is not limited to the apparatus shown in FIG. 1, but includes a decompression chamber used for a usual solution casting method. The present invention can be implemented in any device provided that it has the device. For example, in the present invention, the casting die 1 may be a single-layer die or a multilayer co-cast die. In addition, the temporary support 2
The surface may be a continuous metallic band having a mirror-finished surface, or a rotating drum such as a cooling drum.

Next, on the temporary support, the casting membrane which has been dried to some extent and given rigidity is peeled off from the temporary support, and then passed through a drying section by a suitable transport means to further remove the solvent. In this way, it is possible to obtain a formed film in which the thickness unevenness is significantly reduced.

In the present invention, the thickness of the film varies depending on the raw material and application of the film.
５００500 μm, preferably 40-200 μm
m.

[0024]

EXAMPLES [Examples 1 to 3] A resin solution (dope) was prepared by stirring and mixing each component so as to have the following composition. Cellulose triacetate 100 parts by weight Triphenyl phosphate 10 parts by weight Biphenyl diphenyl phosphate 5 parts by weight Methylene chloride 400 parts by weight Methanol 70 parts by weight Butanol 3 parts by weight

The prepared dope was discharged at a discharge speed of 8 m / min.
Decompression degree of the decompression chamber is -3, -15, -30 mmA
q, and after casting on a temporary support using a solution casting apparatus (die height (h): 5 mm) as shown in FIG. 1, each resin casting film was separated from the support. The film was peeled off and dried to produce a resin film (thickness: 80 μm).

[Examples 4 to 9] In Example 1, the discharge speed was 10 m / min, and the degree of decompression of the decompression chamber was -1, -3, -10, -15 and -15, respectively, as shown in Table 1.
Example 1 except for changing to -30 and -50 mmAq
In the same manner as in the above, a resin film was produced.

[Comparative Examples 1 and 2] In the same manner as in Example 1, except that the discharge speed was changed to 10 m / min, and the degree of pressure reduction in the vacuum chamber was changed to -0.5 mmAq and -100 mmAq, respectively. A film for comparison was manufactured.

[Embodiments 10 to 12] In the first embodiment,
As shown in Table 1, the discharge speed was 15 m / min, and the degree of decompression of the decompression chamber was -3, -15, and -30 mm, respectively.
A resin film was produced in the same manner as in Example 1 except that the resin film was changed to Aq.

[Evaluation of Film] For each of the obtained films, minute irregularities on the surface were measured using an optical interferometer.
The occurrence of thickness unevenness was evaluated by the following AA to CC. AA: Thickness unevenness did not occur at all. BB: The thickness unevenness was weak, but there was no practical problem. CC: Thickness unevenness occurred strongly and was not suitable for practical use. The results obtained are summarized in Table 1.

[0030]

[Table 1] Table 1 吐出 Discharge speed Decompression degree Thickness unevenness ( m / min) (mmAq) ──────────────────────────────────── Example 1 8 -3 AA Example 2 8-15 AA Example 3 8-30 AA Example 4 10 -1 BB Example 5 10 -3 AA Example 6 10 -10 AA Example 7 10 -15 AA Example 8 10 -30 AA Example 9 10 -50 BB比較 Comparative Example 1 10-0.5 CC Comparative Example 2 10-100 CCＣＣ ─────────────────── {Example 10 15 -3 AA Example 11 15-15 AA Example 12 15-30 AA} ──────────────────

[Examples 13 to 15] In Example 1,
As shown in Table 1, the discharge speed was 20 m / min, and the degree of decompression of the decompression chamber was -5, -20, and -40 mm, respectively.
A resin film was produced in the same manner as in Example 1 except that the resin film was changed to Aq.

Embodiments 16 to 18 In the embodiment 1,
The discharge speed was 25 m / min, and the degree of decompression of the decompression chamber was -5, -20, and -40 mm as shown in Table 1, respectively.
A resin film was produced in the same manner as in Example 1 except that the resin film was changed to Aq.

[Examples 19 to 21] In Example 1,
The discharge speed was 30 m / min, and the degree of decompression of the decompression chamber was -1, -25, and -50 mm as shown in Table 1, respectively.
A resin film was produced in the same manner as in Example 1 except that the resin film was changed to Aq.

[Examples 22 to 24] In Example 1,
The discharge speed was 35 m / min, and the degree of decompression of the decompression chamber was -1, -25, -50 mm as shown in Table 1, respectively.
A resin film was produced in the same manner as in Example 1 except that the resin film was changed to Aq.

Comparative Example 3 A film for comparison was prepared in the same manner as in Example 1 except that the discharge speed was changed to 40 m / min and the degree of pressure reduction in the vacuum chamber was changed to -50 mmAq. Manufactured.

[Evaluation of Film] For each of the obtained films, minute irregularities on the surface were measured using an optical interferometer.
The occurrence of thickness unevenness was evaluated by the following AA to CC. AA: Thickness unevenness did not occur at all. BB: The thickness unevenness was weak, but there was no practical problem. CC: Thickness unevenness occurred strongly and was not suitable for practical use. Table 2 summarizes the obtained results.

[0037]

[Table 2] Table 2 吐出 Discharge speed Decompression degree Thickness unevenness ( m / min) (mmAq) Example 13 20-5 AA Example 14 20-20 AA Example 15 20-40 AA Example 16 25-5 AA Example 17 25-25 AA Example 18 25-40 AA {Example 19 30 -1 BB Example 20 30-25 BB Example 21 30-50 BB}例 Example 235-1 BB Example 23 35-25 BB Example 24 35-50 BB ───────────────────────────────比較 Comparative Example 3 40-50 CC ────────────────────────────────────

As is apparent from the results shown in Tables 1 and 2, films produced by casting a dope at a discharge speed and a reduced pressure of a reduced pressure chamber according to the method of the present invention (Examples 1 to 24). All have a thickness unevenness as compared with a film manufactured at a reduced pressure outside the range of the present invention (Comparative Examples 1 and 2) and a film manufactured at a high discharge rate outside the range of the present invention (Comparative Example 3). It was clearly decreasing.

[0039]

According to the present invention, when producing a resin film by a solution casting method of a resin solution using a decompression chamber (manufacturing by a solution casting method), the discharge speed of the dope and the degree of decompression of the decompression chamber are each set to 7 ° 0.0-38.0 m /
By setting in combination within the range of -1 to -50 mmAq, it is possible to produce a resin film particularly suitable for optical use, in which the occurrence of thickness unevenness during casting is remarkably reduced. Functionality can be enhanced.

[Brief description of the drawings]

FIG. 1 is a schematic side view showing an example of a casting part of an apparatus that can be used in the production method of the present invention.

[Explanation of symbols]

 Reference Signs List 1 casting die 2 temporary support 3 decompression chamber 4 casting dope h die height

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B29L 7:00 F term (Reference) 2H023 FA01 FA13 2K009 AA15 CC38 DD02 DD09 4F205 AA01 AG01 AH73 AH79 AM28 AM32 AR02 AR08 GA07 GB02 GC06 GE02 GF24 GF30 4F207 AA01 AG01 AH73 AH79 AM28 AM32 AR02 AR08 KA07 KA17 KK87 KK88 KL84 KM05 KM15 KM26

Claims (5)

[Claims] When a resin solution is discharged in a film form from the tip of a casting die and cast on a temporary support that moves through a position slightly below the tip of the casting die, In a solution casting method including an operation of vacuum-suctioning the surface of the resin solution extruded into a shape in contact with the temporary support, the discharge speed is in the range of 7.0 to 38.0 m / min. And the degree of pressure reduction of the pressure reducing chamber is -1 to -5.
A solution casting method for producing a film with improved thickness accuracy, characterized by being in the range of 0 mmAq. 2. The solution casting method according to claim 1, wherein the discharge speed is in a range of 7.0 to 25.0 m / min. 3. The pressure reduction degree of the pressure reduction chamber is -3 to -30 m.
3. The solution casting method according to claim 1, wherein the solution casting method is in the range of mAq. 4. The solution casting method according to claim 1, wherein the distance from the surface of the temporary support to the tip of the casting die is in the range of 0.5 to 50 mm. 5. The solution casting method according to claim 1, wherein the resin solution is a cellulose triacetate solution.