JP2003012827A - Optical polyvinyl alcohol-based film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical polyvinyl alcohol-based film such as a polarizing film which, has less breaking frequency at a drawing process and excellent production stability. SOLUTION: The film in which the both ends contain a slit to a flow direction of the film for giving a certain width has a mean surface roughness (Ra) on the slit cross section of 5 μm or less.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical material, particularly a polarizing film, which has a low rupture frequency during uniaxial stretching of a film, can be easily stretched to a high degree, and has a good stretching speed, and is excellent in processing stability. The present invention relates to a polyvinyl alcohol film.

[0002]

2. Description of the Related Art Conventionally, a polyvinyl alcohol-based film has been prepared by dissolving a polyvinyl alcohol-based resin in a solvent, kneading and defoaming to prepare a stock solution, and then forming a stock solution by a solution casting method (casting method). It is manufactured by drying using a heating roll or the like. The polyvinyl alcohol-based film thus obtained is used in many applications as a film having excellent shape stability,
One of its useful uses is an optical film, particularly a polarizing film. Such a polarizing film, so that the polyvinyl alcohol-based film has a predetermined width, after slitting both ends in the direction of flow of the film, uniaxially stretched,
It is a dyed film and is used as a basic component of a liquid crystal display. In recent years, its use has been expanded to devices that require high quality and high reliability.

Under such circumstances, in the case of manufacturing a polarizing film using a polyvinyl alcohol film as a raw material, in order to have excellent optical characteristics, for example, in a stretching step after slitting to a predetermined width, 4 to 6 are used. The uniaxial stretching with a considerably high degree of about twice is performed.

[0004]

However, in such a high stretching step, the polyvinyl alcohol film is likely to be broken, and in order to reduce such a break, it is necessary to reduce the stretching speed. As a result, there is a tendency to cause problems in stability of manufacturing and physical properties, such as deterioration of productivity and sometimes deterioration of physical properties of polarized light.

Therefore, in the present invention, under such a background, the polyvinyl alcohol film for optical use, which has a low breakage frequency even if the drawing speed is increased during the drawing process and is excellent in the production stability, particularly the polyvinyl film for the polarizing film. It is intended to provide an alcoholic film.

[0006]

However, as a result of intensive studies by the present inventors to solve the above-mentioned problems, both ends of the film are slit toward the film flow method so that the film has a predetermined width. A polyvinyl alcohol-based film having a surface average roughness (R
In order that the optical polyvinyl alcohol-based film having a) of 5 μm or less meets the above-mentioned object, and further, to adjust the surface average roughness (Ra), the heat of fusion (ΔH) of the polyvinyl alcohol-based film is adjusted. 30-80J /
The present invention has been completed by finding that a slit can be stably performed with g. The average surface roughness (Ra) is JIS
It is defined in B 0601.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be specifically described below. First, as the polyvinyl alcohol-based resin used in producing the film of the present invention, usually,
It is produced by saponifying polyvinyl acetate obtained by polymerizing vinyl acetate, but the present invention is not necessarily limited to this, and a small amount of unsaturated carboxylic acid (including salt, ester, amide, nitrile, etc.), carbon It may contain components copolymerizable with vinyl acetate, such as olefins having a number of 2 to 30 (ethylene, propylene, n-butene, isobutene, etc.), vinyl ethers, unsaturated sulfonates and the like.

Further, a polyvinyl alcohol resin containing a silyl group may be used, and polyvinyl alcohol may be post-modified with a silylating agent, or a silyl group-containing olefinically unsaturated monomer may be copolymerized with vinyl acetate. Examples of the method include saponifying the resulting copolymer. Examples of the silyl group-containing olefinically unsaturated monomer include vinylsilane and (meth) acrylamide-alkylsilane.

The viscosity average degree of polymerization of the polyvinyl alcohol resin is not particularly limited, but among them, it is 1000-5.
000 is preferable, 1200-5000 is particularly preferable, and 1400-4500 is more preferable. When the viscosity average degree of polymerization is less than 1000, sufficient optical performance cannot be obtained when forming an optical film, and when it exceeds 5,000, stretching is difficult and industrial production becomes difficult, which is not preferable.
Regarding the viscosity average degree of polymerization, JIS K 6726
The measurement was carried out according to.

Further, the saponification degree of the polyvinyl alcohol resin is preferably 80 mol% or more, and particularly 8
It is preferably 5 to 100 mol%, more preferably 98 to 100 mol%. When the degree of saponification is less than 80 mol%, sufficient optical performance cannot be obtained when forming an optical film, which is not preferable.

As the polyvinyl alcohol resin, a commonly used plasticizer such as glycerin, diglycerin, triglycerin, ethylene glycol, triethylene glycol or polyethylene glycol may be added to the polyvinyl alcohol resin, if necessary. 30% by weight or less,
It may be contained in an amount of preferably 3 to 25% by weight, more preferably 5 to 20% by weight. If the amount of the plasticizer exceeds 30% by weight, the film strength becomes poor, which is not preferable.

More preferably, in order to improve the peeling property of the film, a peeling agent selected from nonionic, anionic and cationic surfactants is 5% by weight or less based on the polyvinyl alcohol resin, preferably Is 0.00
1 to 3% by weight, and more preferably 0.001 to 2% by weight. If the amount of the release agent exceeds 5% by weight, the appearance of the film surface becomes poor, which is not preferable.

The polyvinyl alcohol-based resin is used to produce a polyvinyl alcohol-based raw film for a polarizing film. First, the polyvinyl alcohol-based resin is dissolved in water or an organic solvent to prepare a stock solution. The stock solution is cast to form a raw film.

The solvent used for preparing the stock solution is, for example, water or dimethyl sulfoxide (DM).
SO), N-methylpyrrolidone, glycerin, ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, trimethylolpropane, and other polyhydric alcohols, amines such as ethylenediamine, diethylenetriamine, and mixtures thereof.

In the above organic solvent, a small amount, for example, 5 to 3 is used.
It is permissible to include 0% by weight of water. It is practical that the concentration of the polyvinyl alcohol resin in the stock solution is 5 to 50% by weight. The stock solution obtained by using the solvent is formed into a film by any method such as a casting method and an extrusion method. As a film forming method, a dry or wet film forming method, that is, the solution is once discharged from the mouthpiece slit into air or into an inert atmosphere such as nitrogen, helium, or argon, and then introduced into a coagulation bath. Form an unstretched film. Alternatively, the film forming solution is once discharged from a die slit onto a roller, a belt conveyor or the like to form a film and then dried to form an unstretched film. If necessary, after drying, heat treatment or humidity control is performed.

Thus, a polyvinyl alcohol-based film for optics, particularly for a polarizing film, is obtained. Next, the polyvinyl alcohol-based film is slit at both ends in the film flow direction so as to have a predetermined width. It The slit is slit to a predetermined width according to the market demand, but in such a slit, the polyvinyl alcohol-based film obtained above may be slit before being wound into a roll, or, It is also possible to wind the material in a roll shape and then unwind it again for slitting.

In the present invention, in such a slit, the surface average roughness (Ra) of the cross section of the slit is 5 μm.
Or less, preferably 3 μm or less, more preferably 1.5 μm
It is necessary to be m or less. The surface average roughness (R
When a) exceeds 5 μm, the film is likely to be broken in the stretching step described later, the breaking frequency is high, and the production stability is poor, and the stretching ratio cannot be increased, and the optical properties are poor. Become.

The average surface roughness (R
The method for adjusting a) to 5 μm or less, preferably 3 μm or less, and more preferably 1.5 μm or less is not particularly limited. For example, in a polyvinyl alcohol film, the heat of fusion (ΔH) of the polyvinyl alcohol film is 30-80 J / g, and further 40-70 J / g
g, particularly preferably 50 to 70 J / g, and when the heat of fusion (ΔH) is less than 30 J / g, distortion or the like occurs in the slit cross section and causes breakage in the stretching step.
If it exceeds 0 J / g, cracks or the like will occur in the slit cross section and cause breakage in the stretching process, both of which are unfavorable for continuous operation.

Regarding the heat of fusion (ΔH), DSC7 manufactured by Perkin Elmer Co., Ltd. was used, and the measurement temperature range was −30.
The amount of heat of fusion of the polyvinyl alcohol-based film was measured at ˜260 ° C. under the condition of the temperature rising rate of 10 ° C./min. In addition, as described below, the surface average roughness (Ra) depends on factors such as the shape and lateral pressure of the blade at the time of slitting and the amount of meshing of the blade.
It is also preferable to adjust

The heat of fusion (ΔH) of the polyvinyl alcohol-based film is adjusted by adjusting the saponification degree of the polyvinyl alcohol-based resin, the amount of the plasticizer added, and the water content of the polyvinyl alcohol-based film. Alternatively, by controlling the drying conditions of the film as appropriate, the above range can be controlled. The water content of the polyvinyl alcohol film is preferably 0.2 to 8% by weight, particularly preferably 1 to 6% by weight. If the water content is less than 0.2% by weight, cracks or the like are likely to occur in the slit cross section, and if it exceeds 8% by weight, tension control during slitting becomes unstable, and the film is blocked by bleeding of a plasticizer. It is not preferable.

The slitting method is not particularly limited, and examples thereof include a method of slitting with a shear blade or a leather blade, a method of slitting with a laser, and the like. Among them, in the present invention, it is preferable to use a shear blade for slitting because the deformation of the base material is small.

Such shear blades are set such that slit blades are attached to both ends of a pair of rolls and a film can be slit by engaging the upper blade and the lower blade. For example, as the upper blade, , Made of high-speed steel, alloy steel, stainless steel, cemented carbide steel, etc., with a cutting edge angle of 30 ~
90 °, preferably 60-90 °, clearance angle 1 ° 00 '
~ 5 ° 00 ', preferably 2 ° 00'-4 ° 00', blade tip thickness 0.05-1.2 mm, preferably 0.1-
The lower blade is made of alloy steel, high-speed steel, stainless steel, cemented carbide steel, etc., and has a clearance angle of 0 ° 00 'to 8 ° 00', preferably 0 ° 00. ′ 〜
5 ° 00 'is used (see FIGS. 1 to 3).

As a setting condition of the shear blade, the meshing amount of the upper blade and the lower blade is preferably 0.05 to 3 mm, more preferably 0.1 to 3 mm, particularly preferably 0.1 to 3 mm.
It is 1.5 mm, and the lateral pressure is preferably 100 to 3000 gf, more preferably 500 to 2000 gf (see FIG. 4). Here, the lateral pressure means a lateral pressing force against the lower blade of the upper blade.

Furthermore, the base angle of the base material is 90 to 180 °
It is preferable that The base material angle is an angle formed when two points, that is, a point at which the film to be cut comes into contact with the lower blade and a point at which the film is separated from the lower blade, and a roll center point of the lower blade are connected ( (See FIG. 5). The slit speed is not particularly limited, but it is 50 to 200 m / min, especially 80
It is preferably set to 150 m / min.

Thus, the polyvinyl alcohol type film has a surface average roughness (Ra) of 5 in the slit cross section.
μm or less, preferably 3 μm or less, more preferably 1.
It is slit to have a thickness of 5 μm or less and used as a polyvinyl alcohol film for optics, particularly for a polarizing film. The method of manufacturing the polarizing film will be described below.

The polarizing film can be produced by stretching such a polyvinyl alcohol film and immersing it in a solution of iodine or a dichroic dye for dyeing, stretching and dyeing at the same time, or using an iodine or dichroic dye. A method of treating with a boron compound after dyeing and stretching is mentioned. There is also a method of dyeing and then stretching in a solution of a boron compound, which can be appropriately selected and used.

The thickness of the polyvinyl alcohol film used for the polarizing film is preferably from 30 to 100 μm, more preferably from 40 to 90 μm. If the thickness is 30 μm or less, stretching is difficult, and if the thickness is 100 μm or more, the film thickness accuracy decreases, which is not preferable. .

The polyvinyl alcohol film (unstretched film) is then stretched, dyed and treated with a boron compound. Stretching and dyeing The boron compound treatment may be carried out separately or simultaneously, but in the present invention, it is desirable to carry out uniaxial stretching during at least one of the dyeing process and the boron compound treatment process.

It is desirable that the stretching is uniaxially 3 to 10 times, preferably 3.5 to 6 times. At this time, some stretching (stretching to a degree that prevents shrinkage in the width direction or more) may be performed in the direction perpendicular to the above. The temperature condition during stretching is preferably selected from 40 to 170 ° C. Further, the stretching ratio may be finally set within the above range, and the stretching operation may be carried out not only in one stage but also in any stage of the manufacturing process.

In the present invention, the surface average roughness (Ra) of the slit cross section of the polyvinyl alcohol film is as described above.
Is 5 μm or less, preferably 3 μm or less, and more preferably 1.5 μm or less. Therefore, even in such a stretching step, the frequency of breakage of the film is extremely low, production stability is excellent, and high stretching is facilitated.

The dyeing of the film is carried out by bringing the film into contact with a liquid containing iodine or a dichroic dye. Usually, an aqueous solution of iodine-potassium iodide is used, the concentration of iodine is 0.1 to 2 g / l, the concentration of potassium iodide is 10 to 50 g / l, and the weight ratio of potassium iodide / iodine is 20 to 100. Is appropriate. Staining time is 30 ~ 500
Seconds is practical. The temperature of the treatment bath is preferably 5 to 50 ° C. A small amount of an organic solvent compatible with water may be contained in addition to the water solvent. As the contact means, any means such as dipping, coating and spraying can be applied.

The dyed film is then treated with a boron compound. Boric acid and borax are practical as the boron compound. The boron compound is used in the form of an aqueous solution or a water-organic solvent mixture at a concentration of about 0.5 to 2 mol / l, and it is practically desirable to allow a small amount of potassium iodide to coexist in the solution. The treatment method is preferably a dipping method, but of course, a coating method or a spraying method can also be implemented. The temperature during processing is 50-
The treatment time is preferably about 70 ° C. and the treatment time is about 5 to 20 minutes, and if necessary, a stretching operation may be performed during the treatment.

The polarizing film thus obtained can be used by laminating and adhering an optically isotropic polymer film or sheet on one or both sides as a protective film. Examples of such a protective film include films or sheets of cellulose triacetate, cellulose diacetate, polycarbonate, polymethyl methacrylate, polystyrene, polyether sulfone, polyarylene ester, poly-4-methylpentene, polyphenylene oxide and the like.

For the purpose of thinning the polarizing film, a curable resin such as urethane resin, acrylic resin, urea resin or the like is applied to one side or both sides of the protective film instead of the protective film, and laminated. You can also

In such a polarizing film (or a protective film or a curable resin laminated on at least one surface thereof), a transparent pressure-sensitive adhesive layer may be formed on one surface of the polarizing film by a generally known method. It may be formed and put to practical use. As the pressure-sensitive adhesive layer, an acrylic ester,
For example, copolymers of butyl acrylate, ethyl acrylate, methyl acrylate, 2-ethylhexyl acrylate and the like with α-monoolefin carboxylic acids such as acrylic acid, maleic acid, itaconic acid, methacrylic acid, crotonic acid (acrylic Nitriles, vinyl acetate, and those containing vinyl monomers such as styrene) are mainly used, since they do not impair the polarizing properties of the polarizing film, but are not limited thereto. Any transparent pressure-sensitive adhesive can be used, and for example, polyvinyl ether-based or rubber-based adhesive may be used.

Further, it is possible to further provide various functional layers on one surface (the surface on which the pressure-sensitive adhesive is not provided) of the polarizing plate (on which the pressure-sensitive adhesive is provided), and as the functional layer. Is, for example, an anti-glare layer, a hard coat layer,
Examples thereof include an anti-reflection layer, a half-reflection layer, a reflection layer, a light-storing layer, a diffusion layer, and an electroluminescence layer. Further, it is possible to combine two or more kinds, for example, an anti-glare layer, an anti-reflection layer, and a light-storing layer. And a reflective layer, a light storage layer and a half reflection layer, a light storage layer and a light diffusion layer, a light storage layer and an electroluminescence layer, and a combination of a half reflection layer and an electroluminescence layer. However, it is not limited to these.

Such a polarizing film is used for a liquid crystal display device such as an electronic desk calculator, an electronic timepiece, a word processor, a personal computer, a personal digital assistant, an instrument of automobiles and machinery, sunglasses, anti-glare glasses, stereoscopic glasses, a display element (CRT). , LCD, etc.) reflection reducing layers, medical devices, building materials, toys, etc.

[0038]

EXAMPLES The present invention will be specifically described below with reference to examples. In the examples, "part" and "%" are based on weight unless otherwise specified.

Example 1 Using a polyvinyl alcohol resin (a-1) having a viscosity average degree of polymerization of 1700 and a degree of saponification of 99.7 mol%, 45%
After adjusting the concentration of the polyvinyl alcohol-based resin aqueous solution (including the plasticizer and the release agent as the solid content), the film is cast from a T-type slit die by a drum-type roll, dried, heat-treated,
Humidity was adjusted to obtain a polyvinyl alcohol film (F-1) having a water content of 4%. The polyvinyl alcohol film (F-1) thus obtained had a heat of fusion (ΔH) of 57 J /
It was g.

Next, the obtained polyvinyl alcohol film (F-1) was slit into a width of 1 m under the following conditions. [Slit conditions] Share blade: Toyo Cutlery Co., Ltd. Upper blade: Material High-speed steel Dimension 108 mm outer diameter 75 mm Inner diameter 0.7 mm Blade edge angle 60 ° Clearance angle 3 ° 30 'Blade tip thickness 0.7 mm Lower blade: Material Alloy steel dimensions Outer diameter 86 mm Inner diameter 60 mm Thickness 10 mm Clearance angle 5 ° Engagement amount between upper and lower blades: 1.5 mm Side pressure: 1500 gf Base material holding angle: 140 ° Slit speed: 120 m / min Surface average roughness of slit section after slitting ( Ra)
Ultra-depth shape measuring microscope VK-850 manufactured by Keyence Corporation
When measured using 0, it was 0.9 μm.

The polyvinyl alcohol film (F-1) after slitting was unwound at 1.25 m / min, swollen in a water washing tank (24 ° C.), and then put in an iodine tank (20
℃, iodine 0.17g / l) 1.3 times, boric acid tank (50
C., iodine 12 ppm, boric acid 47 g / l) was uniaxially stretched 1.7 times, and further, uniaxially stretched 6 times at a winding speed of 7.5 m / min to obtain a polarizing film.

In the stretching during the production of the polarizing film, the breakage frequency was evaluated as follows. (Breaking frequency) Continuous operation was performed for 8 hours, the number of times the film was broken was counted, and evaluated according to the following criteria. ◎ ・ ・ ・ 0 times ○ ・ ・ ・ 1-2 times △ ・ ・ ・ 3-4 times × ・ ・ ・ 5 times or more

With respect to the obtained polarizing film, the polarizing physical properties (single transmittance and degree of polarization) were measured by using Σ90 manufactured by Nippon Denshoku Industries Co., Ltd. as a measuring device. The results are shown in Table 1.

Example 2 A polyvinyl alcohol resin (a-2) having a viscosity average degree of polymerization of 2600 and a saponification degree of 99.7 mol% was used, and its content was 35%.
After adjusting the concentration of the polyvinyl alcohol-based resin aqueous solution (including the plasticizer and the release agent as the solid content), the film is cast from a T-type slit die by a drum-type roll, dried, heat-treated,
Humidity was adjusted to obtain a polyvinyl alcohol film (F-2) having a water content of 3.5%. The heat of fusion (ΔH) of the obtained polyvinyl alcohol film (F-2) was 63.
It was J / g.

Next, the obtained polyvinyl alcohol film (F-2) was slit into a width of 1 m under the following conditions. [Slit conditions] Share blade: Toyo Cutlery Co., Ltd. Upper blade: Material High-speed steel Dimension 108 mm Outer diameter 75 mm Thickness 0.7 mm Blade edge angle 90 ° Clearance angle 3 ° 30 'Blade tip thickness 0.2 mm Lower blade: Material Carbide Steel dimensions Outer diameter 86 mm Inner diameter 60 mm Thickness 10 mm Relief angle 0 ° Engagement of upper and lower blades: 1.5 mm Side pressure: 1500 gf Base material angle: 140 ° Slit speed: 100 m / min Surface average roughness of slit section after slitting Sa (Ra)
Ultra-depth shape measuring microscope VK-850 manufactured by Keyence Corporation
When measured using 0, it was 1.2 μm.

The polyvinyl alcohol film (F-2) after slitting was stretched 6 times in the same manner as in Example 1 to obtain a polarizing film, and the breaking frequency and the polarizing physical properties were evaluated. The results are shown in Table 1.

Example 3 Using a polyvinyl alcohol resin (a-3) having a viscosity average polymerization degree of 4000 and a saponification degree of 99.7 mol%, 25% was obtained.
After adjusting the concentration of the polyvinyl alcohol-based resin aqueous solution (including the plasticizer and the release agent as the solid content), the film is cast from a T-type slit die by a drum-type roll, dried, heat-treated,
Humidity was adjusted to obtain a polyvinyl alcohol film (F-3) having a water content of 3.7%. The polyvinyl alcohol film (F-3) thus obtained had a heat of fusion (ΔH) of 60.
It was J / g.

Next, the obtained polyvinyl alcohol film (F-3) was slit into a width of 1 m under the following conditions. [Slit conditions] Share blade: Toyo Cutlery Co., Ltd. Upper blade: Material High-speed steel Dimension 108 mm Outer diameter 75 mm Thickness 0.7 mm Blade edge angle 90 ° Clearance angle 3 ° 30 'Blade tip thickness 0.2 mm Lower blade: Material Carbide Steel dimensions Outer diameter 86 mm Inner diameter 60 mm Thickness 10 mm Relief angle 0 ° Engagement between upper and lower blades: 1.5 mm Side pressure: 1500 gf Base material angle: 140 ° Slit speed: 80 m / min Surface average roughness after slitting Sa (Ra)
Ultra-depth shape measuring microscope "VK-850" manufactured by KEYENCE CORPORATION
It was 1.3 μm when measured using “0”.

The polyvinyl alcohol film (F-3) after slitting was stretched 6 times in the same manner as in Example 1 to obtain a polarizing film, and the breakage frequency and polarizing physical properties were evaluated. The results are shown in Table 1.

[Table 1] Breaking frequency of physical properties of polarized light Single transmittance (%) Polarization degree (%) Example 1 ◎ 43.0 99.2 〃 2 ◎ 43.1 99.6 〃 3 ○ 43.3 99.9

Comparative Example 1 According to the same manner as in Example 1, a polyvinyl alcohol film (f- having a water content of 0.1%) was prepared using a polyvinyl alcohol resin having a viscosity average polymerization degree of 1700 and a saponification degree of 99.7 mol%. 1) was obtained. The polyvinyl alcohol film (f-1) thus obtained had a heat of fusion (ΔH) of 71 J / g.
Met.

Next, the obtained polyvinyl alcohol film (f-1) was slit into a width of 1 m under the following conditions. [Slit conditions] Share blade: Toyo Cutlery Co., Ltd. Upper blade: Material High-speed steel Dimension 108 mm outer diameter 75 mm Inner diameter 0.7 mm Blade edge angle 60 ° Clearance angle 3 ° 30 'Blade tip thickness 0.7 mm Lower blade: Material Alloy steel dimensions Outer diameter 86 mm Inner diameter 60 mm Thickness 10 mm Clearance angle 5 ° Engagement amount between upper and lower blades: 1.5 mm Side pressure: 4000 gf Base material angle of hold: 140 ° Slit speed: 120 m / min Surface average roughness of slit section after slitting ( Ra)
Ultra-depth shape measuring microscope VK-850 manufactured by Keyence Corporation
When measured using 0, it was 6.1 μm.

The polyvinyl alcohol film (f-1) after slitting was stretched 6 times in the same manner as in Example 1 and the breaking frequency was evaluated. The obtained polyvinyl alcohol-based film (f-1) had a high breaking frequency of 5 times or more, and was inferior in manufacturing stability of the polarizing film.

[0054]

The polyvinyl alcohol film of the present invention is a polyvinyl alcohol film in which both ends of the film are slit toward the flow direction of the film, and the surface average roughness (Ra) of the slit cross section is 5 μm.
Since it is m or less, the frequency of breakage during the stretching step is low,
It is easy to perform high stretching, has a good stretching speed, exhibits excellent manufacturing stability of a polarizing film and the like, and has excellent optical properties, and is particularly useful as a polarizing film.

[Brief description of drawings]

FIG. 1 is a schematic view showing an example of an upper blade of a shear blade used in the present invention, and is a side view (1) and a front view (2) of the upper blade with respect to the flow direction of the film. The front view (2) shows the shape of the upper half, and the shapes of the upper half and the lower half are the objects.

FIG. 2 is an enlarged view in which a hatched portion of the front view (2) of the upper blade with respect to the flow direction of the film shown in FIG.

FIG. 3 is a schematic view showing an example of a lower blade of a shear blade used in the present invention, and is a side view (1) and a front view (2) of the lower blade with respect to the flow direction of the film. The front view (2) shows the shape of the upper half, and the shapes of the upper half and the lower half are the objects.

FIG. 4 is a schematic view of a state where the upper blade and the lower blade of the shear blade are engaged with each other, and is a front view with respect to the flow direction of the film.

FIG. 5 is a schematic view of a state where the upper blade and the lower blade of the shear blade are engaged with each other, and is a side view with respect to the flow direction of the film.

[Explanation of symbols]

a ... Blade angle of upper blade b ... Top blade clearance angle c ... Clearance angle of lower blade D ... Outer diameter of upper and lower blades d ... Inner diameter of upper and lower blades t ... Thickness of upper and lower blades s: Distance from the innermost side of the lower blade to the cutting edge e ... Amount of engagement between upper and lower blades f ... Base material holding angle g ... film h ... Blade thickness of the upper blade

Continued front page    (72) Inventor Kuniyasu Kato             2-13-1, Muroyama, Ibaraki City, Osaka Prefecture, Japan             Central Research Laboratory, Seisei Kogyo Co., Ltd. F term (reference) 4F071 AA29 BA02 BB02 BB07 BC16                 4F205 AA19 AG01 GA07 GB02 GC02                       GW23

Claims (6)

[Claims] 1. A polyvinyl alcohol-based film in which both ends of the film are slit so as to have a predetermined width toward the film flowing method, and the surface average roughness (Ra) of the slit cross section is 5 μm or less. An optical polyvinyl alcohol-based film characterized by being present. 2. The polyvinyl alcohol film for optics according to claim 1, wherein the polyvinyl alcohol film has a heat of fusion (ΔH) of 30 to 80 J / g. 3. The polyvinyl alcohol film has a viscosity average degree of polymerization of 1000 to 5000 and a saponification degree of 80 mol%.
The polyvinyl alcohol-based film for optics according to claim 1 or 2, wherein the polyvinyl alcohol-based resin as described above is formed into a film. 4. The water content of the polyvinyl alcohol-based film is 0.2 to 8% by weight.
3. The optical polyvinyl alcohol film according to any one of 3 to 3. 5. The material is selected from high-speed steel, alloy steel, stainless steel, and cemented carbide steel, and the edge angle is 30 to 90 °,
Clearance angle is 1 ° 00 'to 5 ° 00', blade tip thickness is 0.0
Upper blade of 5 to 1.2 mm and material selected from alloy steel, high speed steel, stainless steel and cemented carbide steel, clearance angle is 0
The optical polyvinyl alcohol film according to any one of claims 1 to 4, wherein both ends of the film are slit by using a shear blade composed of a lower blade having a angle of 00 'to 8'00'. 6. The shear blade setting conditions include an engagement amount of the upper blade and the lower blade of 0.05 to 3 mm, and a lateral pressure of 100 to 30.
It is 00 gf, The polyvinyl alcohol-type film for optics of Claim 5 characterized by the above-mentioned.