JP3816264B2 - Casting resin film, resin film manufacturing method, and casting resin film manufacturing apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a cast resin film, an apparatus for producing a cast resin film, and a method for producing the cast resin film that can be advantageously used for producing a resin film particularly suitable for optical applications. It relates to a method of manufacturing.
[0002]
[Prior art]
In recent years, thin transparent plastic films (resin films) have been used as protective films for polarizing plates, optical compensation films such as retardation plates, plastic substrates, photographic supports or moving cells and optical filters, and optical materials such as OHP films. As demand increases. In particular, liquid crystal displays have recently improved in quality, such as TN, STN, and TFT types, and are lightweight and highly portable, so personal computers, word processors, portable terminals, televisions, and digital still cameras Widely used in video cameras and movie cameras, etc., this liquid crystal display requires a polarizing plate for image display. Along with the improvement in the quality of liquid crystal displays, an improvement in the quality of the polarizing plate is required, and at the same time, a transparent plastic film that is a protective film for the polarizing plate is also required to have a higher quality.
[0003]
For optical films such as protective films for polarizing plates, high transparency, low optical anisotropy, flatness, easy surface treatment, and high durability (dimensions) are necessary due to the need to maintain high resolution and contrast display quality. Degree stability, moist heat resistance, water resistance), no foreign matter in and on the film, no scratches on the surface or difficult to stick (scratch resistance), moderate film rigidity (handleability), moderate It is required to have various characteristics such as water permeability.
[0004]
As plastic films having these properties, there are films made of cellulose ester, norbornene resin, acrylic resin, polyarylate resin, polycarbonate resin, etc., but cellulose ester is mainly used from the viewpoint of productivity and material price. Yes. In particular, a film of cellulose triacetate is particularly advantageously used for optical applications because it has extremely high transparency, low optical anisotropy, and low retardation.
[0005]
As a method for forming these plastic films, various film forming techniques such as a solution film forming method, a melt film forming method and a rolling method can be used, but in order to obtain good flatness and low optical anisotropy. For this, the solution casting method is particularly suitable. The solution casting method involves dissolving raw material flakes in a solvent and adding various additives such as a plasticizer, an ultraviolet absorber, a deterioration inhibitor, a slipping agent and a peeling accelerator as necessary (dope Is cast on a support composed of a horizontal endless metal belt or a rotating drum by a dope supply means (referred to as a die) and then dried to some extent on the support to give rigidity. The self-supporting film is peeled off from the support, and then the solvent is removed by passing through the drying section by various conveying means.
[0006]
In order to develop the industrial production of plastic films, it is important to increase the productivity, and as a result, the manufacturing process must be automated as much as possible. In particular, when carrying out a plastic film production method by a solution casting method, there is a high need for automation of a casting apparatus in order to prevent discharge of an organic solvent unfavorable for environmental hygiene to the outside. No. 244053).
[0007]
[Problems to be solved by the invention]
In the plastic film (resin film) manufacturing process using the solution casting method, when the resin solution (dope) is first fed to the casting die at the start of work, air accumulates at the beginning of the dope stream and bubbles are formed. When the film is discharged and cast as it is on the casting film forming support, holes (bubbles) containing air are formed in the casting resin film immediately after the casting is started. Accompanied by disturbance. In particular, when co-casting using two or more types of dopes, it is impossible to join the dopes at the same time, so a positional shift occurs at the top of each dope, and so-called air pools are generated. Likely to happen. The cast resin film in which bubbles are formed by this air pool must be discarded. Therefore, the cast resin film once formed is passed through the next drying process until the completion of the discharge of the dope containing bubbles is confirmed. Without having to wind it up on another roll. Such a cast resin film must naturally be discarded. Then, after the discharge of the dope flow containing bubbles is completed, it is necessary to pass the normal cast resin film through the next drying / peeling process, but the switching operation is considerably complicated. For this reason, it is extremely difficult to automate the starting operation of film formation, particularly when performing a multilayer casting operation.
[0008]
An object of the present invention is to provide a casting resin film manufacturing method and manufacturing method in which productivity and workability are remarkably improved, and a resin film manufacturing method using the casting resin film manufacturing method. .
[0009]
[Means for Solving the Problems]
The present inventor has conducted research to avoid disturbance of the dope immediately after the start due to an air pool that hinders the automation of the start of film formation, and as a result, other than the flow path to the casting die near the liquid feed port of the casting die. In addition, by providing another channel (dope solution extraction channel) that can be switched by the switching means, the dope containing the air immediately after the start is flowed to this other channel and the air is pushed out. It was found that it is possible to switch and supply dope that does not contain air to the flow path to the die. Thereby, even if it is a multilayer film, the film forming start operation can be automated, and the productivity and workability of the resin film can be remarkably improved.
[0010]
Therefore, in the present invention, the resin solution is continuously fed to the casting die through the feeding path connected to the casting die, and then the support (under the production of the resin film) is moved from the die lip of the casting die. In a method for producing a cast resin film, the resin solution is extruded onto a temporary support such as a belt or a drum used in the process to form a cast resin film. The air bubbles formed near the top of the resin solution flow at the start of the work to be fed into the resin solution are continuously extracted together with the resin solution from the solution extraction path provided at the connection portion between the liquid supply path and the casting die. In another aspect of the present invention, there is provided a method for producing a cast resin film, characterized by starting to feed a resin solution without bubbles from a path to a cast die.
[0011]
The present invention also includes a liquid feeding path for passing a resin solution, a casting die connected to the liquid feeding path, and a support disposed so as to move and pass through a position near the die lip below the die lip of the casting die. In the casting resin film manufacturing apparatus, there is also a casting resin film manufacturing apparatus characterized in that a resin solution extraction path is installed together with a flow path switching unit at a connection portion between a liquid feeding path and a casting die. This casting resin film manufacturing apparatus is configured such that bubbles and the like are mixed and a solution unsuitable for casting can be extracted between the joining portion and the casting die.
[0012]
The present invention also provides that the resin solution is continuously fed to the casting die through a feeding path connected to the casting die, and then the resin solution is extruded from the die lip of the casting die onto the moving support. After the casting resin film is formed, the casting resin film is partially dried to form a self-supporting resin film, and then the self-supporting resin film is peeled off from the support and dried. In the method, a solution extraction path in which bubbles formed near the head of the resin solution flow at the start of the operation of feeding the resin solution from the liquid supply path to the casting die are attached to the connection portion between the liquid feeding path and the casting die There is also a method for producing a resin film characterized in that after the resin solution is continuously extracted from the resin solution, air-free resin solution feeding from the liquid feeding path to the casting die is started.
[0013]
Below, the preferable aspect of the manufacturing method of the cast resin film of this invention, the manufacturing method of a resin film, and the cast resin film manufacturing apparatus is given.
(1) The start of feeding the resin solution without bubbles to the casting die is performed after confirming that there are no bubbles in the extracted resin solution flow.
(2) The resin solution extracted from the solution extraction path is collected and used as a part of the resin solution for feeding the casting die.
(3) Two or more liquid supply paths for the resin solution are provided, and they are connected so as to merge immediately before the connection portion with the casting die.
(4) A bubble sensor is attached to the resin solution extraction path.
(5) The bubble sensor is electrically connected to the flow path switch, and the flow path switch is connected to the flow path and the casting die by the signal from the bubble sensor. Switch to one of the connections with the resin solution extraction path.
(6) The viscosity of the resin solution is in the range of 30 to 3000 P, and the average flow velocity in the liquid feeding path at the start of feeding the resin solution to the liquid feeding path is in the range of 1 to 30 m / min.
(7) The time from the start of feeding the resin solution to the liquid feed path to the start of casting is in the range of 10 seconds to 5 minutes.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
The configuration and operation of a representative example of the cast resin film production apparatus of the present invention will be described with reference to the drawings.
[0015]
FIG. 1 is a cross-sectional view schematically illustrating the configuration and operation of a cast resin film manufacturing apparatus of the present invention. In FIG. 1, a casting resin film manufacturing apparatus 1 includes a co-casting die 3 provided with a dope merging device 2 and a support 4 that moves below the die lip to support the casting resin film. ing. A flow path 5 passes vertically through the center portion of the casting die 3, and both ends thereof are opened by a die liquid supply port 6 and a discharge port (die lip) 7.
[0016]
At the connecting portion between the dope junction device 2 and the casting die 3, a resin solution extraction device (reverse flow channel) 8 for flowing the initial dope, which is a characteristic component of the present invention, and a flow channel to the die 5 and a flow path switching means 9 for switching between the resin solution extraction device 8 are provided. In the middle of the reverse flow path 8, a pressure regulating valve 10 and a bubble sensor 11 are installed, and connected to an extracted resin solution storage tank (resin solution recovery tank, not shown).
[0017]
Next, the method and apparatus for producing a cast resin film and a resin film of the present invention will be described by taking a case of producing a resin film having a three-layer structure as an example.
[0018]
Examples of the raw resin used in the production of the cast resin film and resin film to be produced in the present invention include cellulose lower fatty acid esters, polyolefins (eg, norbornene polymers), polyamides (eg, aromatic polyamides). , Polysulfones, 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) Can. Among these, a lower fatty acid ester of cellulose is preferable as a raw material for an optical use film, and cellulose triacetate is particularly preferable.
[0019]
The raw material resin is dissolved in a suitable organic solvent to prepare two or more kinds of resin solutions (dope). Examples of organic solvents include halogenated hydrocarbons (dichloromethane, etc.), alcohols (methanol, ethanol, butanol, etc.), esters (methyl formate, methyl acetate, etc.), ethers (dioxane, dioxolane, diethyl ether, etc.) Can be mentioned. In the cellulose ester solution, various known plasticizers such as triphenyl phosphate, diethyl phthalate, and polyester polyurethane elastomer, or, if necessary, ultraviolet absorbers, deterioration inhibitors, slipping agents, peeling accelerators, etc. Various known additives may be added.
[0020]
The solution (dope) may be prepared by mixing and dissolving the raw resin in a solvent by a well-known method, or after swelling the raw resin with a solvent by a cooling dissolution method, Then, it may be dissolved by heating to 0 ° C. or higher. The viscosity of the solution is usually in the range of 30 to 3000 P (measured at Poise, 35 ° C.). The resin solution (dope) is cast using the cast film manufacturing apparatus shown in FIG.
[0021]
2 to 5 are schematic sectional views of an apparatus for explaining the casting method according to the present invention step by step.
[0022]
In FIG. 2, the dope flow path after joining at the start of casting is set in advance as a resin solution extraction path (reverse flow path) 8 by the flow path switching means 9 (open side flow path: extraction flow path, closed flow path). Side flow path: flow path to the casting die). Each of the dopes prepared above is sent to the dope junction device 2 from the direction of the thick arrow. The average flow velocity in the flow path in the dope confluence apparatus is generally in the range of 1 to 30 m / min, and preferably in the range of 5 to 20 m / min. At this time, in operation, it is almost impossible to completely match the tops of the respective dopes in the merging means 2, and an air pool ( Bubbles) 12 are generated.
[0023]
In FIG. 3, the dopes that have joined together to form one liquid flow pass through the resin solution extraction path 8 to the resin solution recovery tank (not shown) while containing bubbles.
[0024]
In FIG. 4, after the leading portion of the dope flow containing bubbles is completely pushed out to the extraction path 8, the flow path switching means 9 is operated to start switching the dope flow path to the die liquid supply port 6. At this time, in order to reduce the pressure shock to the dope generated by switching, the die feed port 6 of the casting die, which is a closed-side channel, starts to open almost simultaneously with the start of switching. In addition, when the dope is supplied to the die supply port 6, a pressure regulating valve 10 (see FIG. 1) is provided in the middle of the extraction path 8 so that the tops of the supply dope are aligned. preferable.
[0025]
The flow path can be switched after a preset time has elapsed after the start of casting based on, for example, the flow rate of the dope. Although it depends on the flow rate of the dope, the shape of the dope merging apparatus 2 and the like, it is generally 10 seconds to 5 minutes after the supply to the dope merging apparatus is started. Further, by providing the bubble sensor 11 in the extraction path 8, the completion of extraction of the bubble can be confirmed by detecting the passage of the bubble at the position of the bubble sensor 11, and the flow path switching means 9 can be operated. In this case, the bubble sensor 11 and the flow path switching means 9 are electrically connected, and the flow path switching means 9 is automatically activated by the bubble passage completion signal issued from the bubble sensor 11. Can be set. In order to automatically detect the passage of bubbles, for example, it may be set as an air passage condition that a time during which bubbles do not pass continues for t ₂ seconds after a certain time t ₁ seconds after the top of the dope passes. . If this condition is satisfied, the apparatus can be automated so that a signal is immediately sent from the bubble sensor 11 to the flow path switching means 9 and the switching means 9 is activated. By setting in this way, the dope containing bubbles is automatically prevented from being supplied to the casting die, and the dope not containing bubbles is automatically supplied to the casting die. This makes it possible to completely automate the film forming start operation. As the bubble sensor 11, for example, a sensor utilizing infrared transmission or reflection can be used.
[0026]
In FIG. 5, after the operation of the channel switching means 9 is completed, the dope channel is completely switched to the channel 5 side of the casting die (open side channel: channel to die, closed side channel: extraction Road), an unperturbed dope containing no bubbles is discharged from the die lip 7 through the flow path 5 of the die and cast onto the support 2 (see FIG. 1) moving at a constant speed. On the other hand, although the initial dope containing bubbles reaching the recovery tank is discarded, it can be reused for manufacturing the dope.
[0027]
As the dope merging means that can be used for continuously merging the dopes in the present invention, any known means such as a feed block can be used. The inner shape of the casting die may be any shape such as a coat hanger die or a T die. The cast resin film support may be a continuous metal band having a mirror-finished surface or a rotating drum such as a cooling drum.
[0028]
Thereafter, the cast resin film which has been dried to some extent on the support and becomes self-supporting is peeled off from the support, and further passed through the drying section by a known appropriate conveying means to further remove the solvent. Various known means can be used as means for drying the cast film. By using such a method, a formed resin film can be obtained.
[0029]
The thickness of the resin film produced by the production method of the present invention (in the case of a laminated resin film, the total thickness) varies depending on the raw material of the film and the use, but generally ranges from 20 to 500 μm. Yes, preferably in the range of 40-300 μm.
[0030]
In the above description, the case of a three-layer structure has been described as an example. However, the casting resin film and the resin film manufacturing method of the present invention may be a film having a multilayer structure other than three layers, or a single-layer film. However, it can be suitably implemented.
[0031]
1 and 2 to 5 are examples of the manufacturing apparatus of the present invention, and the apparatus of the present invention is not limited to the above apparatus. For example, it may be an apparatus for single-layer casting in which a resin solution extraction path and a flow path switching means are provided in the vicinity of a die liquid supply port of a casting die for producing a single-layer film that does not include a joining means.
[0032]
【The invention's effect】
According to the present invention, the dope (resin solution) extruded from the casting die at the start of the film forming operation does not contain bubbles, and there is no disturbance of the solution flow at the head of the resin solution. As in the past, it is not necessary to separately wind up and discard only the top portion, and from the beginning of the film forming operation, the resin film product can be obtained through the subsequent drying process. Therefore, the productivity and workability of the resin film can be remarkably improved. Furthermore, since the film forming start operation can be automated, not only the productivity and workability can be improved, but also the work environment can be improved by blocking the leakage of the organic solvent.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view showing an example of an apparatus for producing a cast resin film of the present invention.
FIG. 2 is a diagram for explaining the operation of the cast resin film production apparatus of the present invention, showing a state in which extraction of a dope stream is started.
FIG. 3 is a view for explaining the operation of the apparatus for producing a cast resin film of the present invention, showing a state in which a dope stream in which bubbles are formed is being extracted.
FIG. 4 is a diagram for explaining the operation of the casting resin film production apparatus of the present invention, where extraction of the dope stream in which bubbles are formed is completed, the flow path switching valve is activated, and the dope stream is cast into the casting die; It shows a state where liquid has started to be fed.
FIG. 5 is a diagram for explaining the operation of the casting resin film production apparatus of the present invention, where the extraction of the dope flow in which bubbles are formed is completed, the operation of the flow path switching valve is completed, and the dope flow is The state where the liquid is fed only to the casting die is shown.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 External merge type co-casting apparatus 2 Resin solution (dope) merge means 3 Casting die 4 Support body 5 Casting die flow path 6 Casting die liquid supply port 7 Die lip 8 Extraction resin solution path (reverse flow path)
9 Channel switching means 10 Pressure adjusting valve 11 Bubble sensor 12 Bubble

Claims (12)

The resin solution is continuously fed to the casting die through the liquid feeding path connected to the casting die, and then the resin solution is extruded from the die lip of the casting die onto the support under movement to form the casting resin film. In the method for producing a cast resin film comprising forming, bubbles formed near the head of the resin solution stream at the start of the operation of feeding the resin solution from the solution feed path to the casting die are cast to the liquid feed path. A casting resin characterized by starting the feeding of the resin solution without bubbles from the solution feeding path to the casting die after continuously with the resin solution from the solution drawing path attached to the connecting portion with the die A method for producing a membrane. 2. The casting resin film according to claim 1, wherein the start of feeding the resin solution without bubbles to the casting die is performed after confirming that no bubbles are mixed in the extracted resin solution flow. Production method. The method for producing a cast resin film according to claim 1 or 2, wherein the resin solution extracted in the solution extraction path is collected and used as a part of the resin solution for feeding the casting die. The casting resin according to claim 1 or 2, wherein two or more liquid feeding paths for the resin solution are provided and are connected so as to merge immediately before the connecting portion with the casting die. Manufacturing method of membrane. The resin solution is continuously fed to the casting die through the liquid feeding path connected to the casting die, and then the resin solution is extruded from the die lip of the casting die onto the support under movement to form the casting resin film. In the method for producing a resin film, the resin solution is formed by partially drying the cast resin film to form a self-supporting resin film, and then peeling off the self-supporting resin film from the support and drying. Bubbles formed near the top of the resin solution flow at the start of the work of feeding from the liquid feed path to the casting die are continuously taken together with the resin solution from the solution withdrawal path attached to the connection portion between the liquid feed path and the casting die. A method for producing a resin film is characterized in that, after being drawn out, the feeding of a resin solution free from air bubbles from a liquid feeding path to a casting die is started. 6. The method for producing a resin film according to claim 5, wherein the start of feeding the resin solution without bubbles to the casting die is performed after confirming that no bubbles are mixed in the extracted resin solution flow. . The method for producing a resin film according to claim 5 or 6, wherein the resin solution extracted in the solution extraction path is collected and used as part of a resin solution for feeding a casting die. The resin film according to claim 5 or 6, wherein there are two or more liquid passages for the resin solution, and the resin solution is connected so as to merge immediately before the connection portion with the casting die. Production method. A casting resin film comprising a feeding path for passing a resin solution, a casting die connected to the feeding path, and a support disposed so as to move and pass through a position adjacent to the die lip on the lower side of the casting lip. A casting resin film manufacturing apparatus characterized in that a resin solution extraction path is installed together with a flow path switching unit at a connection portion between a liquid feeding path and a casting die. The flow path according to claim 9, wherein two or more liquid supply paths for the resin solution are provided and are connected to the casting die so that they join together immediately before the connection portion with the casting die. Rolled resin film manufacturing equipment. The apparatus for producing a cast resin film according to claim 9, wherein a bubble sensor is attached to the resin solution extraction path. The bubble sensor is electrically connected to the flow channel switch, and the signal from the bubble sensor causes the flow channel switch to connect the flow channel and the casting die, or to remove the liquid solution and resin solution. The cast resin film manufacturing apparatus according to claim 11, wherein the apparatus is set so as to switch to any one of connections with a path.

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