WO2013035249A1

WO2013035249A1 - Optical film manufacturing method

Info

Publication number: WO2013035249A1
Application number: PCT/JP2012/005175
Authority: WO
Inventors: 忠浩金子
Original assignee: コニカミノルタアドバンストレイヤー株式会社
Priority date: 2011-09-08
Filing date: 2012-08-16
Publication date: 2013-03-14
Also published as: KR20140035527A; JPWO2013035249A1; KR101594265B1

Abstract

The invention relates to an optical film manufacturing method for manufacturing optical films using a cast film extruder, which has at least a flow-casting unit for forming the flow-cast film by discharging a dope of a mixed resin of acrylic resin and cellulose ester resin starting materials solubilized in a solvent from a die and flow-casting a dope film onto an endless belt support, a drawing unit for drawing the flow-cast film after being peeled from the endless belt support, a drying unit for drying, and a take-up unit for winding. The optical film manufacturing method is characterized in that the flow-casting unit has an edge-reinforcing solution-supplying means for supplying an edge-reinforcing solution containing the cellulose ester resin in a higher mass ratio than the mass ratio of the cellulose ester resin configuring the dope onto both edges of the dope film or the flow-cast film, and performs flow-casting while supplying the edge-reinforcing solution onto both edges from the edge-reinforcing solution-supplying means.

Description

Manufacturing method of optical film

The present invention relates to a method for producing an optical film. More specifically, when an optical film is produced by a solution casting method, a dope in which a resin is dissolved in a solvent is cast from a nozzle onto an endless support, and the formed casting film is peeled from the endless support. The present invention relates to a method for producing an optical film in which an end of a cast film remains on an endless support and cracks at the end are prevented.

In recent years, various display devices such as liquid crystal televisions, plasma displays (PDP), and organic EL displays that use optical films have been developed. As an optical film used for a liquid crystal display device, for example, a polarizing film of a polarizing plate is formed by laminating a cellulose ester film as a protective film on one or both sides of a polarizer made of a stretched polyvinyl alcohol film. Such an optical film is required to have a smooth surface without optical defects. In particular, as the size of monitors and TVs increases and the definition becomes higher, these required qualities are becoming stricter.

In addition, the display device can be used as a large display installed in a street or a store, or used as an advertising display in a public place using a display device called digital signage.

In such a use, since it is assumed that the optical film is used outdoors and degradation due to moisture absorption of the optical film becomes a problem, an optical film in which a cellulose ester resin and an acrylic resin are mixed is being studied.

In recent years, there has been a demand for thinner and lighter display devices. Along with this, the quality of optical films used in these display devices will become more severe. From the viewpoint of reducing the cost of LCD panel materials and productivity, optical films will be wider, thinner, longer, and faster. Is underway.

One of the optical film manufacturing methods is a solution casting film forming method. In this method, a resin is dissolved in a solvent, and the solution (dope) is cast from a dope outlet of a casting die onto a metal endless support, and a predetermined amount of solvent is evaporated on the endless support. Then, it peels from an endless support body, and also is extended | stretched as needed, and is the method of producing an optical film.

In addition, the cast film on the endless support is dried to a predetermined concentration on the endless support, but the end of the cast film is dried and harder than the center part of the cast film. When the cast film is peeled off, a tear may occur at the end of the cast film. Once such a rift is formed, the tear proceeds due to the conveying tension, leading to rupture.

Especially when using a dope in which cellulose ester resin and acrylic resin are mixed and dissolved in a solvent, the casting film on the endless support is thin, and the width is wide and the moving speed of the endless support is high. A tear may occur at the end.

In order to solve such a problem, the solvent that dissolves the raw material resin is allowed to flow from both ends of the dope outlet to the end of the casting film, thereby preventing the formation of a film due to drying of the end of the casting film. There is a known method (see, for example, Patent Document 1).

However, Patent Document 1 uses a dope in which a cellulose ester resin and an acrylic resin are mixed and dissolved in a solvent, and when the moving speed of the wide, thin film, and endless support is high, a casting film is formed from the endless support. How to prevent cracking and tearing at the end of the casting film when peeling the casting film from the endless support has not been thoroughly investigated for prevention of cracking and tearing at the end of the casting film when peeling. Was not found, and the study was desired.

JP 2010-179475 A

The present invention has been made in view of the above situation, and its purpose is to use a dope prepared by mixing a cellulose ester resin and an acrylic resin and dissolving in a solvent, and forming a wide, thin film formed on an endless support. It is an object of the present invention to provide a method for producing an optical film in which a tear is prevented from occurring at the end of a cast film when the cast film is peeled off from an endless support that moves at high speed.

The above object of the present invention can be achieved by the following configuration.

That is, one aspect of the present invention is
A dope in which a mixed resin of a raw material acrylic resin and a cellulose ester resin is dissolved in a solvent flows out of a die, and a dope film is cast on an endless belt support, and a casting part that forms a cast film; ,
Optics for producing an optical film by a solution casting production apparatus having at least a stretching part that stretches after peeling the casting film from the endless belt support, a drying part that dries, and a winding part that winds. In the film manufacturing method,
The casting portion includes an end reinforcement including the cellulose ester resin at a mass ratio larger than a mass ratio of the cellulose ester resin constituting the dope at both ends of the dope film or the casting film. Having an edge reinforcing solution supply means for supplying the solution;
The optical film is produced by casting while supplying the end portion reinforcing solution from the end portion reinforcing solution supply means to the both end portions.

With such a configuration, an endless support that uses a dope prepared by mixing a cellulose ester resin and an acrylic resin and dissolved in a solvent, and moves a wide, thin cast film formed on the endless support at high speed. It is possible to provide a method for producing an optical film that prevents the tearing from occurring at the end of the cast film when the film is peeled off.

FIG. 1 is a schematic diagram of an apparatus for producing an optical film by a solution casting method for supplying an edge reinforcing solution to both ends of a dope film. FIG. 2 is a schematic view of an optical film manufacturing apparatus using a solution casting method in which an edge reinforcing solution is supplied to both ends of a casting film. FIG. 3 is an enlarged schematic view of a portion indicated by T in FIG. FIG. 4 is a schematic plan view of the tip of the end portion reinforcing solution supply nozzle.

The present inventor uses a dope prepared by mixing a cellulose ester resin and an acrylic resin and dissolving in a solvent in the production of an optical film by a solution casting method, and casting a wide, thin film formed on an endless support. As a result of investigating why the tear occurs at the end of the cast film that occurs when the film is peeled off from the endless support moving at high speed, the following was found.
1. When the casting film is peeled from the endless metal support, tensile stress is concentrated on both ends of the casting film, and in addition, the peeling force from the endless metal support varies depending on the position in the longitudinal direction. Yes (due to differences in surface roughness and dirt condition), and where it is difficult to peel off, a high stress is applied to both ends of the cast film, resulting in tears.
2. By mixing the acrylic resin, the cast film is more brittle (lower toughness) than the cellulose ester resin alone, so it can not withstand the stress when peeling from the endless support made of metal, and a tear will occur To do.
3. Even when a good solvent of cellulose ester resin is supplied to both ends of the cast film, the physical properties that became brittle by mixing the acrylic resin cannot be changed, and the stress when peeling from the endless metal support Can not withstand, and a tear occurs.

Therefore, using a dope in which cellulose ester resin and acrylic resin are mixed and dissolved in a solvent is used to prevent tearing that occurs at the end of the casting film when the wide, thin casting film is peeled off from the endless metal support. In order to achieve this, it has been found effective to impart to the end of the cast film toughness that can withstand the stress when it is peeled off from a metal endless support.

Furthermore, as a result of investigating the method of imparting toughness to the end of the cast film, the end reinforcement solution containing a large amount of cellulose ester resin among the resin materials constituting the dope at the end of the cast film is supplied. It has been found that it is effective to do so, and the present invention has been achieved.

The embodiment of the present invention will be described with reference to FIGS. 1 and 2, but the present invention is not limited to this.

In the drawings, 1a and 1b are manufacturing apparatuses, 101 is a casting part, 101a is an endless specular belt and / or a metal casting belt support (endless belt support), 101b is a die, 101c is a decompression chamber, 101d is an end reinforcing solution supply means, 101d1 is an end reinforcing solution supply nozzle, 101d2 is an end reinforcing solution tank, 101d3 is an end reinforcing solution supply pump, 101d4 is an end reinforcing solution supply pipe, 101e is a dope film, 101f Is a casting film, 102 is a first drying section, 103 is a stretching section, 104 is a second drying section, 105 is a knurling forming section, and 106 is a collection section.

FIG. 1 is a schematic diagram of an optical film manufacturing apparatus using a solution casting method in which an edge reinforcing solution is supplied to both ends of a dope film.

The solution casting method is an acrylic prepared by dissolving the raw material resin in a solvent and adding various additives such as plasticizers, ultraviolet absorbers, deterioration inhibitors, slipping agents, peeling accelerators as necessary. A dope prepared by dissolving a mixed resin of a cellulose resin and a cellulose ester resin in a solvent is discharged from a die onto an endless metal support (for example, a belt or a drum) that moves indefinitely, cast, and then an endless support. In this method, after removing the solvent to a certain extent, it is peeled off from the endless support, and then passed through a drying section by various conveying means to remove the solvent and wind it around a winding shaft.

In the figure, reference numeral 1a denotes an optical film manufacturing apparatus using a solution casting method. The manufacturing apparatus 1a includes a casting unit 101, a first drying unit 102, an extending unit 103, a second drying unit 104, a knurling forming unit 105, and a recovery unit 106.

The casting part 101 includes two support rolls 101h and an endless specular belt-like metal casting belt support (hereinafter referred to as an endless belt support) 101a that is wound around the support roll 101i and travels endlessly (in the direction of the arrow in the figure). And a die 101b, a decompression chamber 101c, and an end portion reinforcing solution supply means 101d. The moving speed of the endless belt support 101a is preferably 20 m / min to 200 m / min in consideration of productivity, film flatness, and the like.

The edge reinforcing solution supply means 101d has an edge reinforcing solution supply nozzle 101d1, an edge reinforcing solution tank 101d2 having an edge reinforcing solution supply pump 101d3, and an edge reinforcing solution supply pipe 101d4. Two end reinforcing solution supply nozzles 101d are arranged so as to supply the end reinforcing solution to both ends of the dope film 101e (see FIG. 3).

The end reinforcing solution supply nozzle 101d1 receives an end reinforcing solution whose supply amount is adjusted from the end reinforcing solution tank 101d2 by the end reinforcing solution supply pump 101d3 via the end reinforcing solution supply pipe 101d4. An end portion reinforcing solution is supplied to the end portion of the dope film 101e supplied to the supply nozzle 101d1. The end portion refers to a range of about 10 mm in the width direction from the end side of the doped film 101e (see FIG. 3).

If the distance between the tip of the end reinforcing solution supply nozzle 101d1 and the surface of the end of the dope film 101e (see FIG. 3) is too far away, the end reinforcing solution due to solvent evaporation is flowing while the end reinforcing solution is flowing. The increase in concentration increases and the viscosity is increased, so that the end portion does not spread uniformly and water condensation occurs due to the evaporation of the solvent resulting in a decrease in the temperature of the end portion reinforcing solution channel. On the other hand, even if the distance is too close, the fluctuation of the flow rate of the edge reinforcing solution directly leads to the fluctuation of the amount that spreads to the edge part, and the uniformity is lowered. Is needed. Considering these factors, the distance from the tip of the end portion reinforcing solution supply nozzle 101d1 to the surface of the end portion of the dope film 101e (see FIG. 3) is preferably 2 mm to 20 mm.

As the end portion reinforcing solution supply pump 101d3, a commercially available general pump such as a gear pump, a plunger pump, a diaphragm, or a Mono pump can be used.

The dice 101b is supplied with a dope whose supply amount is adjusted by a dope supply pump 101b3 from a dope tank 101b1 that stores dopes via a supply pipe 101b2, and the dope film 101e (see FIG. 3) is placed on the endless belt support 101a. To be cast.

The decompression chamber 101c is disposed on the upstream side of the die 101b with respect to the traveling direction of the endless belt support 101a, and the dope film 101e (see FIG. 3) flowing out of the die 101b is decompressed by reducing the inside of the endless belt 101c. It is possible to stably land on the support 101a.

Reference numeral 101g denotes a peeling roll which is cast and formed on the endless belt support 101a and peels off the casting film 101f. In this embodiment, the peeled cast film is referred to as an unstretched film 2 for convenience.

When the casting film 101f is peeled off from the endless belt support 101a, when the residual solvent amount of the casting film 101f is high, the casting film is soft, so that the flatness is easily lost at the time of peeling. Therefore, in consideration of the balance between economic speed and quality, the content is preferably 10% by mass to 90% by mass. The amount of residual solvent shows the value measured by the method shown below.

Measuring method of residual solvent Put the cast film peeled from the endless belt support into a sealed container and measure the mass of the tare together. Then, dry the cast film at 120 ° C for 2 hours and then measure the mass again. And obtained from the following equation.
Residual solvent amount (%) = 100 × (mass before heat treatment of cast film−mass after heat treatment of cast film) / (mass after heat treatment of cast film)

The first drying step 102 includes a drying box 102a having a drying air intake port 102c, a discharge port 102b, and a transport roll 102d composed of a plurality of sets, one set at the top and bottom for transporting the unstretched film 2. The slitter 102e which cuts off the both ends of the unstretched film 2 is provided. The dry air intake port 102c and the discharge port 102b may be reversed.

It is possible to adjust the amount of solvent contained in the unstretched film 2 before entering the stretching step 103 in the first drying step 102, and it can be installed as necessary.

The stretching step 103 includes an MD (Machine Direction) stretching portion (not shown), a TD (Transverse Direction) stretching portion (not shown), and a slitter 103a that cuts both ends of the stretched film 2a. The unstretched film 2 conveyed from the first drying step 102 is stretched to form a stretched film 2a.

In the second drying step 104, a drying box (104a) having a drying air intake port 104c, a discharge port 104b, and a transport roll 104d composed of a plurality of sets, one set at the top and bottom for transporting the stretched film 2a. Have. Note that the dry air inlet 104c and the outlet 104b may be reversed.

The collection unit 106 has a winder (not shown) that winds the stretched film 2a, and controls the winding tension corresponding to the winding length so as to wind the stretched film 2a around the winding shaft. It has become. In addition, before winding by the collection | recovery part 106, you may provide the knurling part which forms a knurling in both ends as needed.

As shown in this figure, at the casting part 101, the resin of the raw material is dissolved in a solvent, and various additions such as a plasticizer, an ultraviolet absorber, a deterioration preventing agent, a slipping agent and a peeling accelerator are added to this as necessary. An endless belt support that travels endlessly (in the direction of the arrow in the figure) by discharging the end portion reinforcing solution from the end portion reinforcing solution supply nozzle 101d to both ends of the dope film flowing out from the die 101b. On the endless belt support, the cast film formed by casting on both ends is reinforced on the endless belt support to a certain extent, and then peeled off from the endless belt support, and then dried by various conveying means, An optical film is manufactured by passing the stretched portion 103 and forming a knurling at both ends as necessary, and then winding the sample around the winding shaft by the collecting portion 106. The length of the optical film wound on the winding shaft is preferably 2000 m to 8000 m. The width is preferably 1000 mm to 3500 mm. The thickness is preferably 10 μm to 120 μm.

FIG. 2 is a schematic view of an apparatus for producing an optical film by a solution casting method in which an edge reinforcing solution is supplied to both ends of the casting membrane.

In the figure, 1b represents an optical film manufacturing apparatus using a solution casting method. Other reference numerals are the same as those in FIG. The difference from the manufacturing apparatus 1a shown in FIG. 1 is that the position of the end reinforcing solution supply nozzle 101d1 of the end reinforcing solution supply means 101d is arranged at a position where the end reinforcing solution can be supplied to the end of the casting membrane 101f. It is only provided, and everything else is the same as the manufacturing apparatus 1a shown in FIG. The end portion means a range of 10 mm in the width direction from the end side of the casting film 101f. Two end reinforcing solution supply nozzles 101d are provided so as to supply the end reinforcing solution to both ends of the casting film 101f.

If the distance between the tip of the end reinforcing solution supply nozzle 101d1 and the surface of the end of the casting membrane 101f is too far, the end reinforcing solution concentration rises greatly due to solvent evaporation while the end reinforcing solution is flowing. As a result of thickening, the casting film does not spread evenly, or evaporation of the solvent causes water condensation due to a decrease in the temperature of the end reinforcing solution flow path. On the other hand, even if the distance is too close, the flow rate fluctuation of the edge reinforcing solution directly leads to the fluctuation of the amount that spreads and spreads on the casting film. Distance is needed. Considering these and the like, 2 mm to 20 mm is preferable.

When supplying the end portion reinforcing solution to both ends of the casting membrane 101f, the positions where the end portion reinforcing solution supply nozzle 101d1 is disposed in the casting step 101 are located at both ends of the casting membrane 101f from the end portion reinforcing solution supply nozzle 101d1. The position at which the solvent of the edge reinforcing solution is removed to such an extent that the edge reinforcing solution supplied to the edge does not become an obstacle when the cast film 101f is peeled off from the endless belt support 101a (the toughness required for the edge is The position is not particularly limited.

This embodiment relates to a method for producing an optical film by the solution casting method shown in FIGS. 1 and 2, and more specifically, a mixed resin of a raw acrylic resin and a cellulose ester resin on an endless belt support. The present invention relates to a method for producing an optical film, in which a dope dissolved in a solvent is cast, and a tear is prevented from occurring in the cast film when the cast film formed is peeled off from an endless belt support.

FIG. 3 is an enlarged schematic view of a portion indicated by T in FIG. FIG. 3A is an enlarged schematic view showing the arrangement position of the end portion reinforcing solution supply nozzle indicated by T in FIG. FIG.3 (b) is an expansion schematic front view from the edge part reinforcement solution supply nozzle side shown by Fig.3 (a).

In the figure, reference numeral 101e denotes a doped film formed from a dope discharged from the die 101b in a film shape. The position where the end portion reinforcing solution supply nozzle 101d1 is disposed is not particularly limited as long as the end portion reinforcing solution can be supplied until the dope film 101e discharged from the die 101b reaches the endless belt support 101a. For example, when supplying an end portion reinforcing solution to both ends of the dope film 101e, the end portion reinforcing solution supply nozzle 101d1 may be incorporated inside the die 101b or may be disposed outside the die 101b. This figure shows the case where it arrange | positions on the outer side of the dice | dies 101b.

This figure shows a case where end reinforcement solutions are supplied to both ends of the dope film 101e, and two end reinforcement solution supply nozzles 101d are disposed outside the die 101b. The two end reinforcing solution supply nozzles 101d1 may each have an independent end reinforcing solution tank 101d2 (see FIG. 1) and an end reinforcing solution supply pipe 101d4 (see FIG. 1). One end reinforcing solution tank 101d2 (see FIG. 1) is used as one to branch the end reinforcing solution supply pipe 101d4 (see FIG. 1) and supply the end reinforcing solution to the two end reinforcing solution supply nozzles 101d1. May be selected as necessary.

In addition, when supplying an edge reinforcement solution to the both ends of the casting membrane shown in FIG.

FIG. 4 is a schematic plan view of the tip of the end reinforcing solution supply nozzle.

FIG. 4A shows the case where the end of the end portion reinforcing solution supply nozzle 101d1 is formed of a single tube. U indicates the inner diameter of the tip of the end portion reinforcing solution supply nozzle 101d1. The inner diameter U is preferably 1 mm to 10 mm in view of the fact that if it is too large, the solvent will evaporate in the middle and the solution concentration will change, and if it is too small, the liquid will clog and become difficult to flow.

FIG. 4B shows a case where the tip of the end portion reinforcing solution supply nozzle 101d1 is formed of a plurality of thin tubes. W represents the inner diameter of the thin tube. The inner diameter W is preferably 0.5 mm to 3.0 mm considering that the solution does not stay in the tube and can maintain a constant flow rate. The number of capillaries is preferably 3 to 10.

The shape of the tip of the end reinforcing solution supply nozzle 101d1 is a rain gutter that is narrowed down gradually toward the shape of the injection needle, the dope film or the casting film so as not to widen the end reinforcing solution. , A shape obtained by narrowing a circular pipe such as the tip of a mechanical pencil, and a circle. Among these, a circle is particularly preferable. Further, the tip of the end portion reinforcing solution supply nozzle 101d1 may be formed by combining a plurality of nozzles having a thin tip at a circular shape.

If the supply amount of the edge reinforcement solution from the edge reinforcement solution supply nozzle 101d1 is too small, the effect of increasing the strength of the edge of the casting film is small, and if too large, the edge of the casting film becomes thick. In consideration of the fact that it may not be possible to dry the remaining melt until the endless belt makes one round after passing, it is preferably 0.2 ml / min to 50 ml / min.

(End reinforcement solution)
In the present embodiment, the edge reinforcing solution is prepared so as to include the cellulose ester resin at a mass ratio larger than the mass ratio of the cellulose ester resin constituting the dope. Specifically, for example, the end portion reinforcing solution preferably contains 40% or more of a cellulose ester resin by mass ratio.

It is preferable that the end portion reinforcing solution contains 45% to 100% of cellulose ester resin by mass ratio.

By using a cellulose ester resin, the end of the cast film formed from the dope and the thin resin layer formed by the end reinforcement solution formed at the end are integrated to form an end. When the cast film is peeled off from the belt support, toughness that is resistant to stress applied to both ends is imparted to both ends of the cast film, and it is possible to prevent the tearing of both ends.

The cellulose ester-based resin has a total acyl group substitution degree (T) of 2.0 to 3.0, an acyl group substitution number of 3 to 7 carbon atoms of 1.2 to 3.0, and a carbon number of The substitution degree of the acyl group of 3 to 7 is preferably 2.0 to 3.0. That is, the cellulose ester resin of the present embodiment is a cellulose ester resin substituted with an acyl group having 3 to 7 carbon atoms. Specifically, propionyl, butyryl and the like are preferably used, and a propionyl group is particularly preferable. Used.

Examples of the solvent used for the edge reinforcing solution include the solvent used for preparing the dope.

The viscosity of the edge reinforcing solution is 5 mPa · s (25 ° C.) in consideration of the fluidity of the liquid feeding in the pipe and the appropriate spreading and wetting when supplied to the edge of the dope film or the edge of the casting film. ) To 500 mPa · s (25 ° C.). The viscosity is a value measured at a temperature of 25 ° C. by a model LVT manufactured by BROOKFIELD, generically called a B-type viscometer.

As shown in FIGS. 1 to 4, cellulose using a dope in which a mixed resin of an acrylic resin and a cellulose ester resin is dissolved in a solvent, and a dope is formed at both ends of the dope film or the casting film The effects shown below were obtained by producing an optical film while supplying an end portion reinforcing solution containing the cellulose ester resin more than the mass ratio of the ester resin.
1. When the unstretched film is soft because the amount of residual solvent immediately after peeling and peeling is soft, the strength of both ends of the unstretched film is high, which reduces skewing during conveyance, and reduces creases and wrinkles. Wideness of optical characteristics such as, and longitudinal variations have been greatly reduced.
2. When the cast film is peeled off from the endless belt support, it is possible to prevent a tear from occurring at the end, and a stable thin film and a wide optical film can be produced.
3. In the first slitter after peeling, charging of the slit trim is easy to attenuate, and there is no problem caused by sticking by charging.

Next, the materials related to the method for producing the optical film of the present embodiment will be described.

<Acrylic resin>
Methacrylic resin is also contained in the acrylic resin concerning the manufacturing method of the optical film of this embodiment. Although it does not restrict | limit especially as an acrylic resin, What is 50 to 99 mass% of methylmethacrylate units and 1 to 50 mass% of other monomer units copolymerizable with this is preferable. .

Other monomers that can be copolymerized include alkyl methacrylates having 2 to 18 alkyl carbon atoms, alkyl acrylates having 1 to 18 carbon atoms, acrylic acid, methacrylic acid, and other α, β-insoluble monomers. Unsaturated group-containing divalent carboxylic acids such as saturated acid, maleic acid, fumaric acid and itaconic acid, aromatic vinyl compounds such as styrene and α-methylstyrene, α, β-unsaturated nitriles such as acrylonitrile and methacrylonitrile, Examples thereof include maleic anhydride, maleimide, N-substituted maleimide, glutaric anhydride and the like, and these can be used alone or in combination of two or more monomers.

Among these, methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, s-butyl acrylate, 2-ethylhexyl acrylate, and the like are preferable from the viewpoint of thermal decomposition resistance and fluidity of the copolymer. n-Butyl acrylate is particularly preferably used.

The acrylic resin related to the method for producing an optical film of the present embodiment has a weight average molecular weight (Mw) particularly from the viewpoint of improving brittleness as an optical film and improving transparency when compatible with a cellulose ester resin. 80,000 or more. When the weight average molecular weight (Mw) of the acrylic resin is less than 80000, sufficient brittle improvement cannot be obtained, and the compatibility with the cellulose ester resin is deteriorated. The weight average molecular weight (Mw) of the acrylic resin is more preferably in the range of 80,000 to 1,000,000, particularly preferably in the range of 100,000 to 600,000, and most preferably in the range of 150,000 to 400,000. The upper limit of the weight average molecular weight (Mw) of the acrylic resin is not particularly limited, but is preferably 1000000 or less from the viewpoint of production.

The weight average molecular weight of the acrylic resin related to the method for producing the optical film of the present embodiment can be measured by gel permeation chromatography. The measurement conditions are as follows.

Solvent: Methylene chloride Column: Shodex K806, K805, K803G
(Used by connecting three Showa Denko Co., Ltd.)
Column temperature: 25 ° C
Sample concentration: 0.1% by mass
Detector: RI Model 504 (manufactured by GL Sciences)
Pump: L6000 (manufactured by Hitachi, Ltd.)
Flow rate: 1.0 ml / min
Calibration curve: Standard polystyrene STK standard polystyrene (manufactured by Tosoh Corp.) Mw = 2,800,000-500 calibration curves with 13 samples were used. The 13 samples are preferably used at approximately equal intervals.

The production method of the acrylic resin in the present embodiment is not particularly limited, and any known method such as suspension polymerization, emulsion polymerization, bulk polymerization, or solution polymerization may be used. Here, as a polymerization initiator, a normal peroxide type and an azo type can be used, and a redox type can also be used. Regarding the polymerization temperature, it can be carried out at 30 to 100 ° C. for suspension or emulsion polymerization, and at 80 to 160 ° C. for bulk or solution polymerization. In order to control the reduced viscosity of the obtained copolymer, the polymerization can also be carried out using alkyl mercaptan or the like as a chain transfer agent.

As the acrylic resin related to the method for producing the optical film of the present embodiment, a commercially available resin can also be used. For example, Delpet 60N, 80N (manufactured by Asahi Kasei Chemicals Corporation), Dynal BR52, BR80, BR83, BR85, BR88, BR85 (manufactured by Mitsubishi Rayon Co., Ltd.), KT75 (manufactured by Denki Kagaku Kogyo Co., Ltd.), etc. Can be mentioned. Two or more acrylic resins can be used in combination.

<Cellulose ester resin>
The cellulose ester resin relating to the method for producing an optical film of the present embodiment has a total acyl group substitution degree (T) of 2. from the viewpoint of transparency particularly when it is improved in brittleness or compatible with an acrylic resin. The substitution degree of the acyl group having 0 to 3.0 and 3 to 7 carbon atoms is 1.2 to 3.0, and the substitution degree of the acyl group having 3 to 7 carbon atoms is 2.0 to 3.0. Preferably there is. That is, the cellulose ester resin of the present embodiment is a cellulose ester resin substituted with an acyl group having 3 to 7 carbon atoms. Specifically, propionyl, butyryl and the like are preferably used, and a propionyl group is particularly preferable. Used.

When the total substitution degree of the acyl group of the cellulose ester resin is less than 2.0, that is, when the residual degree of the hydroxyl groups at the 2, 3, and 6 positions of the cellulose ester molecule is more than 1.0, the acrylic resin and When the acrylic resin is not sufficiently compatible and used as an optical film, haze becomes a problem. In addition, even when the total substitution degree of the acyl group is 2.0 or more, if the substitution degree of the acyl group having 3 to 7 carbon atoms is less than 1.2, still sufficient compatibility cannot be obtained, Brittleness will decrease. For example, even when the total substitution degree of the acyl group is 2.0 or more, the substitution degree of the acyl group having 2 carbon atoms, that is, the acetyl group is high, and the substitution degree of the acyl group having 3 to 7 carbon atoms is 1. When it is less than 2, the compatibility is lowered and the haze is increased. Further, even when the total substitution degree of the acyl group is 2.0 or more, the substitution degree of the acyl group having 8 or more carbon atoms is high, and the substitution degree of the acyl group having 3 to 7 carbon atoms is less than 1.2. In such a case, the brittleness deteriorates and desired characteristics cannot be obtained.

The acyl substitution degree of the cellulose ester resin relating to the method for producing an optical film of the present embodiment is such that the total substitution degree (T) is 2.0 to 3.0, and the substitution degree of the acyl group having 3 to 7 carbon atoms is 1.2 to 3.0 is not a problem, but the total substitution degree of acyl groups other than 3 to 7 carbon atoms, that is, acetyl groups or acyl groups having 8 or more carbon atoms is 1.3 or less. It is preferable.

Further, the total substitution degree (T) of the acyl group of the cellulose ester resin is more preferably in the range of 2.5 to 3.0.

In this embodiment, the acyl group may be an aliphatic acyl group or an aromatic acyl group. In the case of an aliphatic acyl group, it may be linear or branched and may further have a substituent. The number of carbon atoms of the acyl group in this embodiment includes the substituent of the acyl group.

When the cellulose ester resin related to the method for producing an optical film of the present embodiment has an aromatic acyl group as a substituent, the number of substituents X substituted on the aromatic ring is preferably 0 to 5. . In this case, attention should be paid so that the substitution degree of the acyl group having 3 to 7 carbon atoms including the substituent is 1.2 to 3.0. For example, since the benzoyl group has 7 carbon atoms, when it has a substituent containing carbon, the benzoyl group has 8 or more carbon atoms and is not included in the acyl group having 3 to 7 carbon atoms. Become.

Further, when the number of substituents substituted on the aromatic ring is 2 or more, they may be the same or different from each other, but they may be linked together to form a condensed polycyclic compound (for example, naphthalene, indene, indane, phenanthrene, quinoline). , Isoquinoline, chromene, chroman, phthalazine, acridine, indole, indoline, etc.).

In the cellulose ester resin as described above, having a structure having at least one aliphatic acyl group having 3 to 7 carbon atoms is used as a structure used for the cellulose ester resin used in the present embodiment.

The substitution degree of the cellulose ester resin related to the method for producing the optical film of the present embodiment is that the substitution degree of the acyl group having a total substitution degree (T) of the acyl group of 2.0 to 3.0 and 3 to 7 carbon atoms. Is 1.2 to 3.0.

Further, it is preferable that the total substitution degree of the acyl group other than the acyl group having 3 to 7 carbon atoms, that is, the acetyl group and the acyl group having 8 or more carbon atoms is 1.3 or less.

The cellulose ester resin used in the present embodiment is preferably at least one selected from cellulose acetate propionate, cellulose acetate butyrate, cellulose acetate benzoate, cellulose propionate, and cellulose butyrate, Those having an acyl group having 3 or 4 carbon atoms as a substituent are preferred.

Among these, particularly preferable cellulose ester resins are cellulose acetate propionate and cellulose propionate.

The portion not substituted with an acyl group usually exists as a hydroxyl group. These can be synthesized by known methods.

Incidentally, the substitution degree of acetyl group and the substitution degree of other acyl groups are determined by the method prescribed in ASTM-D817-96.

The weight average molecular weight (Mw) of the cellulose ester resin related to the method for producing an optical film of the present embodiment is 75000 or more from the viewpoint of compatibility with an acrylic resin and improvement in brittleness, particularly in the range of 75,000 to 300,000. It is preferred that it is within the range of 100,000 to 240,000, particularly preferably 160,000 to 240,000. When the important average molecular weight (Mw) of the cellulose ester resin is less than 75,000, the heat resistance and brittleness improvement effects are not sufficient. In the present embodiment, two or more kinds of cellulose ester resins can be mixed and used.

The mass ratio of the acrylic resin and the cellulose ester resin in the dope relating to the method for producing the optical film of the present embodiment is from 95: 5 to 30:70 in consideration of the performance, moisture resistance, etc. of the cellulose ester resin. Although it is contained in a mass ratio and in a compatible state, it is preferably 95: 5 to 50:50, and more preferably 90:10 to 60:40.

The acrylic resin and the cellulose ester resin in the dope related to the method for producing the optical film of the present embodiment must be contained in a compatible state. This is achieved by mutually complementing physical properties and quality required for an optical film produced by compatibilizing an acrylic resin and a cellulose ester resin.

Whether or not the acrylic resin and the cellulose ester resin are in a compatible state can be determined by, for example, the glass transition temperature Tg.

For example, when the two resins have different glass transition temperatures, when the two resins are mixed, there are two or more glass transition temperatures for each resin because there is a glass transition temperature for each resin. When they are compatible, the glass transition temperature specific to each resin disappears and becomes one glass transition temperature, which is the glass transition temperature of the compatible resin.

The glass transition temperature referred to here is an intermediate value determined according to JIS K7121 (1987) using a differential scanning calorimeter (DSC-7 model manufactured by Perkin Elmer) at a heating rate of 20 ° C./min. The point glass transition temperature (Tmg).

The acrylic resin and the cellulose ester-based resin are each preferably an amorphous resin, and either one may be a crystalline polymer or a partially crystalline polymer. It is preferable that an acrylic resin and a cellulose ester resin are compatible with each other to form an amorphous resin.

The weight average molecular weight (Mw) of the acrylic resin used in the present embodiment, the weight average molecular weight (Mw) of the cellulose ester resin, and the degree of substitution are classified using the difference in solubility in the solvent of both resins. Then, it is obtained by measuring each. When fractionating the resin, it is possible to extract and separate the soluble resin by adding a compatible resin in a solvent that is soluble only in either one. At this time, heating operation or reflux is performed. May be. A combination of these solvents may be combined in two or more steps to separate the resin. The dissolved resin and the resin remaining as an insoluble matter are filtered off, and the solution containing the extract can be separated by an operation of evaporating the solvent and drying. These fractionated resins can be identified by general structural analysis of polymers.

When the dope relating to the production of the optical film of the present embodiment contains a resin other than an acrylic resin or a cellulose ester resin, it can be separated by the same method.

When the weight average molecular weights (Mw) of the compatible resins are different, the high molecular weight substances are eluted earlier by gel permeation chromatography (GPC), and the lower molecular weight substances are eluted after a longer time. Therefore, it can be easily fractionated and the molecular weight can be measured.

In addition, the molecular weight of the compatible resin is measured by GPC, and at the same time, the resin solution eluted every time is separated, the solvent is distilled off, and the dried resin is different by quantitatively analyzing the structure. By detecting the resin composition for each molecular weight fraction, it is possible to identify each compatible resin. By measuring the molecular weight distribution of each of the resins separated in advance by the difference in solubility in a solvent by GPC, it is possible to detect each of the compatible resins.

Further, in the present embodiment, “containing acrylic resin or cellulose ester resin in a compatible state” means that mixing each resin (polymer) results in a compatible state. This means that a state in which a precursor of acrylic resin such as monomer, dimer or oligomer is mixed with cellulose ester resin and then polymerized to be mixed resin is not included.

For example, the step of obtaining a mixed resin by mixing a precursor of an acrylic resin such as a monomer, dimer, or oligomer with a cellulose ester resin and then polymerizing the polymerization reaction is complicated, and was prepared by this method. The resin is difficult to control the reaction, and it is difficult to adjust the molecular weight. In addition, when a resin is synthesized by such a method, graft polymerization, cross-linking reaction or cyclization reaction often occurs. In many cases, the resin is soluble in a solvent or cannot be melted by heating. It is also difficult to measure the weight average molecular weight (Mw) by eluting the system resin, so that it is difficult to control the physical properties and cannot be used as a resin for stably producing an optical film.

The dope relating to the production of the optical film of the present embodiment may be configured to contain resins and additives other than acrylic resins and cellulose ester resins, as long as the function as the produced optical film is not impaired. good.

When a resin other than an acrylic resin or a cellulose ester resin is contained, the resin to be added may be mixed without being dissolved even if it is in a compatible state.

The total mass of the acrylic resin and the cellulose ester resin in the optical film produced by the production of the optical film of the present embodiment is preferably 55% by mass or more of the optical film, more preferably 60% by mass or more. Especially preferably, it is 70 mass% or more.

When using resins and additives other than acrylic resins and cellulose ester resins, it is preferable to adjust the addition amount in a range that does not impair the function of the optical film produced by the production of the optical film of the present embodiment.

<Acrylic particles>
The dope relating to the production of the optical film of the present embodiment preferably contains acrylic particles. An acrylic particle represents the acrylic component which exists in the state of particle | grains (it is also called an incompatible state) in the optical film which contains acrylic resin and a cellulose-ester resin in a compatible state.

The acrylic particles used in the present embodiment are not particularly limited, but are preferably acrylic particles described in International Publication No. 2009-047924. Examples of commercially available products include, for example, Mitsubishi Rayon Co. (Metablene W-341 (C2)), Kaneka Chemical Co., Ltd. (Kane Ace), Kureha Chemical Co., Ltd. (Paraloid), Rohm and Haas Co., Ltd. (Acryloid) ), Manufactured by Gantz Kasei Kogyo Co., Ltd. (Staffyroid), manufactured by Kuraray Co., Ltd. (Parapet SA), manufactured by Soken Chemical Co., Ltd. (Chemisnow MR-2G (C3), MS-300X (C4)), and the like. A single compound or two or more compounds can be used.

In the present embodiment, the method of blending the acrylic particles with the acrylic resin is not particularly limited, and after the acrylic resin and other optional components are previously blended, the acrylic particles are usually added at 200 ° C. to 350 ° C. However, a method of uniformly melting and kneading with a single screw or twin screw extruder is preferably used.

In addition, a solution in which acrylic particles are dispersed in advance is added to and mixed with a dope in which acrylic resin and cellulose ester resin are dissolved, or a solution in which acrylic particles and other optional additives are dissolved and mixed is acrylic. A method such as in-line addition to a dope in which a cellulose resin and a cellulose ester resin are dissolved can be used. The addition amount of the acrylic particles is preferably 0.5 to 30% by mass with respect to the total mass of the resin constituting the optical film, and is contained in the range of 1.0 to 15% by mass. More preferably.

<Other additives>
In the dope relating to the production of the optical film of the present embodiment, a plasticizer can be used in combination in order to improve the fluidity and flexibility of the composition. Examples of the plasticizer include phthalate ester, fatty acid ester, trimellitic ester, phosphate ester, polyester, and epoxy.

Of these, polyester-based and phthalate-based plasticizers are preferably used. Polyester plasticizers are superior in non-migration and extraction resistance compared to phthalate ester plasticizers such as dioctyl phthalate, but are slightly inferior in plasticizing effect and compatibility.

Therefore, it can be applied to a wide range of uses by selecting or using these plasticizers according to the use.

The polyester plasticizer is a reaction product of a monovalent or tetravalent carboxylic acid and a monovalent or hexavalent alcohol, and is mainly obtained by reacting a divalent carboxylic acid with a glycol. . Representative divalent carboxylic acids include glutaric acid, itaconic acid, adipic acid, phthalic acid, azelaic acid, sebacic acid and the like.

In particular, when adipic acid, phthalic acid, or the like is used, those having excellent plasticizing properties can be obtained. Examples of the glycol include glycols such as ethylene, propylene, 1,3-butylene, 1,4-butylene, 1,6-hexamethylene, neopentylene, diethylene, triethylene, and dipropylene. These divalent carboxylic acids and glycols may be used alone or in combination.

The ester plasticizer may be any of ester, oligoester, and polyester types, and the molecular weight is preferably in the range of 100 to 10,000, preferably in the range of 600 to 3000, which has a large plasticizing effect.

The viscosity of the plasticizer has a correlation with the molecular structure and molecular weight. In the case of an adipic acid plasticizer, the range is from 200 MPa · s (25 ° C.) to 5000 MPa · s (25 ° C.) because of compatibility and plasticizing efficiency. Is good. Furthermore, some polyester plasticizers may be used in combination.

The plasticizer is preferably added in an amount of 0.5 to 30 parts by mass with respect to 100 parts by mass of the optical film produced by the production of the optical film of the present embodiment. If the added amount of the plasticizer exceeds 30 parts by mass, the surface becomes sticky, which is not preferable for practical use.

The dope relating to the production of the optical film of the present embodiment preferably contains an ultraviolet absorber, and examples of the ultraviolet absorber used include benzotriazole-based, 2-hydroxybenzophenone-based or salicylic acid phenyl ester-based ones. It is done. For example, 2- (5-methyl-2-hydroxyphenyl) benzotriazole, 2- [2-hydroxy-3,5-bis (α, α-dimethylbenzyl) phenyl] -2H-benzotriazole, 2- (3 Triazoles such as 5-di-t-butyl-2-hydroxyphenyl) benzotriazole, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-octoxybenzophenone, 2,2′-dihydroxy-4-methoxybenzophenone Benzophenones such as

Here, among ultraviolet absorbers, ultraviolet absorbers having a molecular weight of 400 or more are difficult to volatilize at a high boiling point and hardly disperse even during high-temperature molding, so that the weather resistance is effectively improved with a relatively small amount of addition. I can do it.

Examples of the ultraviolet absorber having a molecular weight of 400 or more include 2- [2-hydroxy-3,5-bis (α, α-dimethylbenzyl) phenyl] -2-benzotriazole, 2,2-methylenebis [4- (1, 1,3,3-tetrabutyl) -6- (2H-benzotriazol-2-yl) phenol], bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate, bis ( Hindered amines such as 1,2,2,6,6-pentamethyl-4-piperidyl) sebacate and 2- (3,5-di-t-butyl-4-hydroxybenzyl) -2-n-butylmalonic acid Bis (1,2,2,6,6-pentamethyl-4-piperidyl), 1- [2- [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionyloxy] Such as til] -4- [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionyloxy] -2,2,6,6-tetramethylpiperidine A hybrid system having both structures can be mentioned, and these can be used alone or in combination of two or more. Among these, 2- [2-hydroxy-3,5-bis (α, α-dimethylbenzyl) phenyl] -2-benzotriazole and 2,2-methylenebis [4- (1,1,3,3- Tetrabutyl) -6- (2H-benzotriazol-2-yl) phenol] is particularly preferred.

Furthermore, various antioxidants can be added to the dope relating to the production of the optical film of the present embodiment in order to improve the thermal decomposability and thermal colorability during molding. It is also possible to add an antistatic agent to give the optical film antistatic performance.

A flame retardant acrylic resin composition containing a phosphorus flame retardant may be used for the dope relating to the production of the optical film of the present embodiment.

Phosphorus flame retardants used here include red phosphorus, triaryl phosphate ester, diaryl phosphate ester, monoaryl phosphate ester, aryl phosphonate compound, aryl phosphine oxide compound, condensed aryl phosphate ester, halogenated alkyl phosphorus. Examples thereof include one or a mixture of two or more selected from acid esters, halogen-containing condensed phosphates, halogen-containing condensed phosphonates, halogen-containing phosphites, and the like.

Specific examples include triphenyl phosphate, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, phenylphosphonic acid, tris (β-chloroethyl) phosphate, tris (dichloropropyl) Examples thereof include phosphate and tris (tribromoneopentyl) phosphate.

(Organic solvent)
The organic solvent useful for preparing the dope relating to the method for producing the optical film of the present embodiment can be used without limitation as long as it dissolves acrylic resin, cellulose ester resin, and other additives simultaneously. I can do it. For example, as a chlorinated organic solvent, methylene chloride, as a non-chlorinated organic solvent, methyl acetate, ethyl acetate, amyl acetate, acetone, tetrahydrofuran, 1,3-dioxolane, 1,4-dioxane, cyclohexanone, ethyl formate, 2,2,2-trifluoroethanol, 2,2,3,3-hexafluoro-1-propanol, 1,3-difluoro-2-propanol, 1,1,1,3,3,3-hexafluoro- 2-methyl-2-propanol, 1,1,1,3,3,3-hexafluoro-2-propanol, 2,2,3,3,3-pentafluoro-1-propanol, nitroethane, etc. Methylene chloride, methyl acetate, ethyl acetate and acetone can be preferably used.

In addition to the organic solvent, the dope preferably contains 1% to 40% by weight of a linear or branched aliphatic alcohol having 1 to 4 carbon atoms. When the proportion of alcohol in the dope increases, the web gels and peeling from the metal support becomes easy. When the proportion of alcohol is small, acrylic resins and cellulose ester resins in non-chlorine organic solvents are used. There is also a role of promoting dissolution of the.

Examples of the linear or branched aliphatic alcohol having 1 to 4 carbon atoms include methanol, ethanol, n-propanol, iso-propanol, n-butanol, sec-butanol, and tert-butanol. Ethanol is preferred because of the stability of these dopes, the relatively low boiling point, and good drying properties.

In particular, in a solvent containing methylene chloride and a linear or branched aliphatic alcohol having 1 to 4 carbon atoms, acrylic resin (A), cellulose ester resin (B), and acrylic particles (C) 3 A dope composition in which at least 15 to 45% by mass of the seed is dissolved is preferable.

This specification discloses various modes of technology as described above, and the main technologies are summarized below.

One aspect of the present invention is:
A dope in which a mixed resin of a raw material acrylic resin and a cellulose ester resin is dissolved in a solvent flows out of a die, and a dope film is cast on an endless belt support, and a casting part that forms a cast film; ,
Optics for producing an optical film by a solution casting production apparatus having at least a stretching part that stretches after peeling the casting film from the endless belt support, a drying part that dries, and a winding part that winds. In the film manufacturing method,
The casting portion includes an end reinforcement including the cellulose ester resin at a mass ratio larger than a mass ratio of the cellulose ester resin constituting the dope at both ends of the dope film or the casting film. Having an edge reinforcing solution supply means for supplying the solution;
The optical film is produced by casting while supplying the end portion reinforcing solution from the end portion reinforcing solution supply means to the both end portions.

With such a configuration, when an optical film is produced using a dope in which a cellulose ester resin and an acrylic resin are mixed and dissolved in a solvent, the strength can be increased at the end of the cast film. Therefore, when using a dope in which cellulose ester resin and acrylic resin are mixed and dissolved in a solvent, the wide and thin cast film formed on the endless support is peeled off from the endless support moving at high speed. The manufacturing method of the optical film which prevented generation | occurrence | production of the tear at the edge part of a cast film can be provided.

Furthermore, in the manufacturing method of the optical film, it is preferable that the supply amount of the edge reinforcing solution is 0.2 ml / min to 50 ml / min.

By supplying the end reinforcement solution at such a supply amount, the effect of increasing the strength at the end of the casting film can be obtained more reliably, and the end of the casting film becomes too thick. Can also be suppressed.

Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto.

Example 1
(Preparation of dope)
Dianar BR85 (Mw 280000 manufactured by Mitsubishi Rayon Co., Ltd.)
85 parts by mass Cellulose ester resin (cellulose acetate propionate acyl group total substitution degree 2.75,
Acetyl group substitution degree 0.19, propionyl group substitution degree 2.56,
Mw = 200000) 15 parts by mass Methylene chloride 300 parts by mass Ethanol 40 parts by mass The above composition was sufficiently dissolved while stirring at 60 ° C. to prepare a dope solution.

(Preparation of edge reinforcement solution)
10 parts by mass of a mixed resin obtained by mixing the resin A and the resin B shown in Table 1 at a resin mass ratio shown in Table 1 is sufficiently dissolved in 100 parts by mass of methylene chloride while stirring at 60 ° C. to prepare an edge reinforcing solution. No. 1-a to 1-e.

The viscosity (25 ° C.) of the prepared edge reinforcing solution indicates a value measured with a model LVT manufactured by BROOKFIELD.

* 1: Cellulose ester resin: Same as the cellulose ester used for the dope * 2: Acrylic resin: Dianal BR88 (Mitsubishi Rayon Co., Ltd.) Mw 480000
* 3: Norbornene resin (manufactured by Arton G JSR)

[Optical film sample No. Production of 101 to 105]
Using the manufacturing apparatus shown in FIG. 1, the prepared dope solution is end-reinforced to have a diameter of about 6 mm at both ends of a dope film discharged from a die on an endless belt support that rotates at a temperature of 22 ° C. and 100 m / min. Solution No. While supplying 1-a to 1-e with an end reinforcing solution supply nozzle having an inner diameter of 7 mm shown in FIG. 4 (a) under the conditions shown below, the remaining cast film remains on the endless belt support. The solvent was evaporated until the amount of the solvent reached 50% by mass, and the film was peeled off from the endless belt support with a peeling tension of 100 N / m as a converted value per 1 m film width to obtain an unstretched film. While peeling the unstretched film at 40 ° C., the solvent was evaporated, both ends were slit, and then the stretched portion was stretched at an MD stretch rate of 110% in the MD direction and stretched at a TD stretch rate of 170% in the TD direction. It was dried at a drying temperature of 150 ° C. After stretching, the drying is completed while the second drying section at 120 ° C. is transferred by a number of rolls, and a knurling with a height of 5 μm is provided at both ends 10 mm of the stretched film. As a converted value per 1 m of the film width at / min, the film is wound on a winding shaft having an initial tension of 220 N / m, a final tension of 110 N / m and an inner diameter of 11 inches, and an optical film having a width of 2500 mm and a thickness of 20 μm is wound. 20 continuous rolls of 7800 m were manufactured and sample No. 101 to 105. The residual solvent amount of the wound optical film was 0.02%.

The MD stretching ratio indicates a value obtained by calculation according to the following method.
MD stretch ratio = 100 × (winding speed−endless belt conveyance speed) / endless belt conveyance speed

The stretch ratio of TD shows the value calculated by the following method.
TD stretch ratio = 100 × (film width of tenter film−film width with tenter) / film width with tenter

The measurement of the residual solvent amount was performed by the gas chromatograph mass spectrometry shown below under heating conditions of 120 ° C. for 30 minutes.

Analytical device manufacturer name: Agilent Technologies
Device type: HP 5890 Series II (GC)
HP 7694 (HS: Head Space)
Column type: DB-624 ID 0.25mm x capacity 30ml
(End reinforcement solution supply conditions)
Supply amount of edge reinforcement solution: 10 ml / min
Distance between the tip of the end reinforcing solution supply nozzle and the end of the dope film: 15 mm

[Optical film sample No. Fabrication of 106 to 110]
Using the production apparatus shown in FIG. 2, all samples except for the end reinforcement solution were supplied to the both end portions 10 mm of the casting membrane. An optical film roll was produced under the same conditions as in 101, and sample No. 106 to 110. In addition, the position which supplies an edge part reinforcement solution to the both ends of a casting film was made into the position 15 mm away from the position where the dope film landed on the endless belt support body.

[Optical film comparative sample No. 111 production)
Sample No. A roll body of the optical film was manufactured under the same conditions except that methylene chloride was used instead of the edge reinforcing solution when manufacturing the 101, and Comparative Sample No. 111.

[Optical film comparative sample No. 112)
Sample No. A roll body of the optical film was manufactured under the same conditions except that methylene chloride was used instead of the edge reinforcing solution when manufacturing the edge 106, and Comparative Sample No. 112.

Evaluation The produced optical film No. Table 2 shows the results of visually observing the occurrence of tearing between 101 and 112, after the cast film was peeled from the endless belt support, and until both ends were excised.

Sample No. according to the present invention. 101 to 103 and sample no. In Nos. 106 to 108, there was no tearing of the edge portion of the film, but sample No. 106 using an end portion reinforcing resin solution having a mass ratio of cellulose ester resin to acrylic resin of 15:85 was used. 104, 109, sample No. supplied with norbornene resin. 105 and sample no. 110 and sample No. supplied only with solvent. At the edges of 111 and 112, tears of about 10 mm occur almost continuously, and if the film is shocked due to changes in the film forming conditions, etc., it is dangerous that the entire width can be easily torn and broken. It was in a state.

Example 2
Sample No. 1 prepared in Example 1 was used. When producing 101, the optical film was manufactured under the same conditions except that the supply amount of the edge reinforcing solution was changed as shown in Table 3. 201 to 206.

Evaluation The manufactured sample No. Table 3 shows the results of visually observing the presence or absence of breakage and the presence or absence of cracks between 201 and 206, after the cast film was peeled from the endless belt support, and until both ends were cut off.

Specimen No. manufactured in the range of 0.2 ml / min to 50 ml / min supplied end reinforcement solution. All of 202 to 205 showed no performance and showed excellent performance.

Specimen No. manufactured with a supply amount of the edge reinforcement solution of 0.1 ml / min. In 201, there was no cracking, but slight cracks that did not affect the production occurred.

Sample No. manufactured with an end reinforcement solution supply rate of 60 ml / min. 206, no breakage or cracking occurred, but both ends of the cast film became thick over a wide range, so the belt was not sufficiently dried around the circumference of the belt. Although it slipped further downstream and caused peeling and wrinkles in the release film, it was a weak level that did not affect production.

This application is based on Japanese Patent Application No. 2011-195753 filed on Sep. 8, 2011, the contents of which are included in the present application.

In order to express the present invention, the present invention has been described appropriately and sufficiently through the embodiments with reference to the drawings and the like. However, those skilled in the art can easily change and / or improve the above-described embodiments. It should be recognized that it can be done. Therefore, unless the modifications or improvements implemented by those skilled in the art are at a level that departs from the scope of the claims recited in the claims, the modifications or improvements are not limited to the scope of the claims. To be construed as inclusive.

The present invention has wide industrial applicability in the technical field related to the method for producing an optical film.

Claims

A dope in which a mixed resin of a raw material acrylic resin and a cellulose ester resin is dissolved in a solvent flows out of a die, and a dope film is cast on an endless belt support, and a casting part that forms a cast film; ,
Optics for producing an optical film by a solution casting production apparatus having at least a stretching part that stretches after peeling the casting film from the endless belt support, a drying part that dries, and a winding part that winds. In the film manufacturing method,
The casting portion includes an end reinforcement including the cellulose ester resin at a mass ratio larger than a mass ratio of the cellulose ester resin constituting the dope at both ends of the dope film or the casting film. Having an edge reinforcing solution supply means for supplying the solution;
A method for producing an optical film, wherein the end portion reinforcing solution supply means is cast while supplying the end portion reinforcing solution to both ends.
The method for producing an optical film according to claim 1, wherein the supply amount of the edge reinforcing solution is 0.2 ml / min to 50 ml / min.