JP2003170491A - Polyvinyl alcohol film to be stretched and polarizing film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain the roll of a polyvinyl alcohol film to be stretched which can easily be stretched uniformly and is useful as a raw material for producing a polarizing film. <P>SOLUTION: In the polyvinyl alcohol film to be stretched which is taken up in the shape of a roll, thickness spots in the widthwise direction is 1-10 μm, and both ends of the film are slit in the widthwise direction to be 1-15 cm in swing width. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a stretchable vinyl alcohol polymer film which is useful as a raw material for producing a polarizing film and which can be uniformly stretched easily, and a polarizing film produced using the same. Is.

[0002]

2. Description of the Related Art A polarizing plate having a light transmitting and shielding function is a basic component of a liquid crystal display (LCD) together with a liquid crystal having a light switching function. The field of application of this LCD is from small devices such as calculators and wristwatches in the early stages of development to laptop computers in recent years.
There is a demand for a vinyl alcohol-based polymer film for a polarizing film, which spreads over a wide range of word processors, liquid crystal color projectors, in-vehicle navigation systems, liquid crystal televisions, etc., and can be more uniformly stretched than ever before.

Generally, a polarizing plate is a vinyl alcohol polymer film (hereinafter, abbreviated as "PVA film", and a vinyl alcohol polymer as a raw material thereof may be abbreviated as "PVA"). Is uniaxially stretched and dyed, and a protective film such as a cellulose triacetate (TAC) film or an acetic acid / cellulose butyrate (CAB) film is laminated on both surfaces of the polarizing film.

With the rationalization and mechanization of agriculture, PV
Attention has also been paid to the A-made ginseng and the PVA heat-insulating curtain in a vinyl house. Again, there is a demand for a PVA film for stretching which is easy to uniformly stretch.

[0005]

In order to make the polarizing performance of the polarizing plate uniform and to perform stable and uniform stretching,
Although there are many precautions such as ensuring the surface smoothness and thickness uniformity of the PVA film, it is extremely important to be able to stretch uniformly. When the PVA film cannot be stretched uniformly, it is difficult to make the polarizing performance of the obtained polarizing plate uniform.

Therefore, an object of the present invention is to provide a PVA film for stretching which is capable of obtaining a PVA film which can be uniformly stretched easily, which is particularly useful as a raw material for producing a polarizing film, and which can be a polarizing film having uniform polarizing performance. To do.

[0007]

In order to solve the above-mentioned problems, the PVA film for stretching according to the present invention has a thickness variation in the width direction of 1 μm to 10 μm, and both ends of the film are 1 cm in the width direction. It is slit with an oscillating width of 15 to 15 cm and is supposed to be wound into a roll. At this time, it is preferable that the rocking cycle is 10 seconds to 3 hours. A polarizing film is obtained using this PVA film for stretching.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below.
PVA that can be used in the present invention is produced, for example, by converting all or part of the ester groups of a polyvinyl ester obtained by polymerizing a vinyl ester into hydroxyl groups. Modified PVA obtained by graft-copolymerizing PVA with unsaturated carboxylic acid or its derivative, unsaturated sulfonic acid or its derivative, olefin and the like.
Or a modified PVA produced by converting all or part of the ester groups of a modified polyvinyl ester obtained by copolymerizing vinyl ester and unsaturated carboxylic acid or its derivative, unsaturated sulfonic acid or its derivative, olefin, etc. Alternatively, there may be mentioned a so-called polyvinyl acetal resin obtained by crosslinking unmodified or modified PVA with aldehydes to partially crosslink the hydroxyl groups.

Examples of the vinyl ester include vinyl acetate, vinyl formate, vinyl propionate, vinyl butyrate, vinyl pivalate, vinyl versatate, vinyl laurate, vinyl stearate, vinyl benzoate and the like. One or more can be used, but vinyl acetate is preferred.

On the other hand, the comonomer used in the modified PVA is a copolymer which is mainly used for the purpose of modifying the PVA, and is used within a range not impairing the gist of the present invention. Examples of such comonomers include olefins, acrylic acid and its derivatives, methacrylic acid and its derivatives, maleic acid and its derivatives, itaconic acid and its derivatives, acrylamide derivatives, methacrylamide derivatives, N-vinylamides, vinyl ethers. , Nitriles, vinyl halides, allyl compounds, vinylsilyl compounds, fatty acid isopropenyl, and the like, and one or more of these can be used.

When the modified PVA is used, the amount of modification is preferably 15 mol% or less, more preferably 5 mol% or less. As the comonomer, α-olefin having 2 to 30 carbon atoms is preferable, and ethylene is particularly preferable.

The degree of saponification of PVA is preferably 95 mol% or more, more preferably 98 mol% or more, further preferably 99 mol% or more, and particularly 9 from the viewpoint of polarization performance and durability.
Most preferably, it is 9.5 mol% or more.

The above-mentioned degree of saponification indicates the proportion of units actually saponified into vinyl alcohol units among units which can be converted into vinyl alcohol units by a saponification reaction or the like. The degree of saponification of PVA is JI
The measurement was performed by the method described in S.

The degree of polymerization of PVA is preferably 1000 or more, more preferably 2500 or more, and most preferably 3500 or more, from the viewpoint of polarization performance and durability. The upper limit of the degree of PVA polymerization is preferably 8000 or less, more preferably 6000 or less.

The degree of polymerization of the PVA is JIS K 67.
It is measured according to 26. That is, it is determined from the intrinsic viscosity measured in 30 ° C. water after re-saponifying PVA and purifying it.

As a method for producing a PVA film using the above PVA, in addition to the melt extrusion film forming method performed by melting hydrous PVA (which may contain an organic solvent etc.),
For example, by using a PVA solution in which PVA is dissolved in a solvent, it is possible to adopt a casting film forming method, a wet film forming method, a gel film forming method, or a combination thereof. Among these, the cast film forming method and the melt extrusion film forming method are preferable because a good polarizing film can be obtained.

As the solvent for dissolving PVA used in producing the PVA film, known solvents can be used, but dimethyl sulfoxide, water, or a mixed solvent of glycerin and water is preferably used.

The PVA concentration of the PVA solution or the water-containing PVA used for producing the PVA film is preferably 10 to 70% by weight, more preferably 10 to 60% by weight, and 13 to 55% by weight. More preferred, 1
Most preferred is 5 to 50% by weight. If necessary, the PVA solution or the water-containing PVA may contain a plasticizer, a surfactant, a dichroic dye, or the like.

It is preferable to add a polyhydric alcohol such as glycerin as a plasticizer when producing a PVA film. The amount of polyhydric alcohol added is PVA1
The amount is preferably 30 parts by weight or less, more preferably 3 to 25 parts by weight, and most preferably 5 to 20 parts by weight with respect to 00 parts by weight. If it exceeds 30 parts by weight, the PVA film may become too flexible and the handleability may deteriorate.

When producing a PVA film, it is preferable to add a surfactant. The type of surfactant is not particularly limited, but anionic or nonionic surfactant is preferable. The amount of surfactant added is
It is preferably 0.01 to 1 part by weight, more preferably 0.02 to 0.5 part by weight, based on 100 parts by weight of PVA,
Most preferably 0.05 to 0.3 parts by weight. If the amount is less than 0.01 part by weight, the effect of improving the stretchability and the dyeability is difficult to appear, and if the amount exceeds 1 part by weight, it may be eluted on the surface of the PVA film to cause blocking and the handling property may be deteriorated. .

In the present invention, as a method for drying the PVA film, it is preferable to first dry it with a metal belt or a metal roll. When the film is first dried with hot air as in the inflation film forming method, it may be difficult to perform uniform stretching.

Each of the drying surfaces of the multi-stage roll having two or more stages can be heated by steam, a heat medium, hot water, an electric heater or the like. Further, a means such as blowing hot air or cold air onto the PVA film or sucking air or steam around the PVA film may be used in combination. Furthermore, for the third and subsequent dryings, not only roll drying but also a floating dryer such as a tenter system or a free system can be used.

The PVA film has a thickness of 10 to 100 μm.
m, preferably 15 to 90 μm, and 20 to 80
μm is more preferable. The thickness of PVA film is 20μ
If it is less than m, the stretching ratio cannot be increased, and the polarizing performance of the obtained polarizing film may be deteriorated. On the other hand, even if the thickness of the PVA film exceeds 100 μm, the polarization performance is not improved and it is not economical, and it may not be possible to uniformly stretch the film.

The thickness variation in the width direction of the PVA film is 1 μm.
m to 10 μm, and 3 μm to 6
It is particularly preferable that the thickness is μm. Thickness unevenness in the width direction is 1μ
If it is less than m, uniform stretching is often possible without rocking. On the other hand, when the thickness unevenness in the width direction exceeds 10 μm, the polarization performance of the obtained polarizing film is not uniform even if the stretching can be performed uniformly.

The thickness unevenness in the width direction of the PVA film is measured by slitting both ends in the width direction of the film, cutting out a sample in the entire width direction at an arbitrary position of the PVA film, and using a film thick tester KG601A manufactured by Anritsu Corporation. However, it can be obtained from the difference between the maximum value and the minimum value.

The PVA film thus obtained may be wound into a roll after slitting both ends in the width direction of the film to a film width that meets the requirements of the manufacturing process of the polarizing film, or may be rolled once. After being wound into a shape, both ends of the film in the width direction are separately slit to a film width that meets the requirements of the polarizing film manufacturing process.

At this time, it is important that the slits at both ends in the width direction of the PVA film are swung by a width of 1 cm to 15 cm in the width direction of the film while keeping the width of the film after slitting constant. More preferably, the rocking is performed in a width of 10 cm, and particularly, the rocking is performed in a width of 3 cm to 6 cm. When the swing width is less than 1 cm, the thickness unevenness of the PVA film is accumulated at a specific place of the wound PVA film roll,
The roll diameter obtained depends on the location. After long-term storage, the film having a large roll diameter becomes talumi, and uniform stretching cannot be performed. On the other hand, the swing width is 15 cm
If it exceeds, it will be uneconomical because more parts will be discarded as trim. The swing width does not always have to be constant, and may be changed as appropriate while observing the thickness of the PVA film in the width direction. Further, one film roll may be wound up before one cycle of rocking is completed. However, in any case, it is important that the swing width is within the above range.

The oscillation period is preferably 10 seconds to 3 hours, more preferably 30 seconds to 1 hour, and particularly 1 minute to 3 hours.
0 minutes is more preferred. The swinging is preferably performed continuously, but it is also possible to perform it intermittently. Even when the rocking is performed intermittently, the preferable range of the rocking cycle is the same as the above time. If the rocking cycle is less than 10 seconds, the slits may not be stable and the PVA film may be more easily cut than the end portion in the film width direction during stretching. On the other hand, when the rocking cycle exceeds 3 hours, the thickness unevenness of the PVA film is likely to be accumulated in a specific place of the wound PVA film roll, and becomes a partial tarmi of the film after long-term storage, In some cases, uniform stretching cannot be performed.

As the swinging method, the left and right deckles of a deckle with a deckle such as an outer deckle and an inner deckle are simultaneously moved in the same direction in the film width direction, or only the die is moved in the film width direction. Method, by fixing the relative position of the die and the most upstream roll for drying, and moving the die and the most upstream roll for drying (may include the second and subsequent rolls) in the width direction of the film , Fixing the relative position of the film cutting and the winding machine, and moving the film cutting position and the winding machine in the width direction of the film, the axis of the roll with respect to the axis of the drying roll In a film forming machine having rolls that can be set in parallel positions, a method of changing the angle formed by the axis of the drying roll and the axis of the roll, the roll of the axis of the drying roll. In a film forming machine having a roll that can be set to a non-parallel position, it is desirable to change the distance between the roll and the closest roll, especially at a position where the roll axis is non-parallel to the axis of the drying roll. With a film forming machine having a roll that can be set, a method that changes the angle formed by the axis of the drying roll and the axis of the roll, and a roll that can set the axis of the roll in a non-parallel position with respect to the axis of the drying roll. It is more preferable that the film forming machine has a method of changing the distance between the roll and the closest roll.

It is preferable that no slipping powder is attached to the PVA film. When the slip powder is attached, the powder is attached to the drawing roll and the drawing cannot be performed uniformly, or the liquid in the cleaning tank or the swelling tank is contaminated when the polarizing film is manufactured. Tend.

The PVA film thus obtained is wound into a roll. PVA films are generally
The outer diameter of the core (the diameter of the circumscribing circle in the case of a square tube) is 10c
m or more, more preferably 12 cm or more, the length of the core is equal to or longer than the width of the PVA film, more preferably 10 cm or more, and the outer surface is made of metal or plastic It is wound around a tubular core. The PVA film wound into a roll is preferably stored in an air-suspended state on a moisture-proof package.

If the outer diameter of the core is less than 10 cm, the film roll may be bent and wrinkled, which may prevent uniform stretching. Further, when the outermost layer of the core is not metal or plastic, the stretching conditions are not constant and stable stretching cannot be often performed. Furthermore, the length of the core is PVA
When the width is shorter than the width of the film, breakage is likely to occur from the end portion in the width direction of the film during stretching, and uniform stretching may be difficult in some cases.

As a method for suspending the PVA film wound into a roll in a suspended state, a method of placing a core protruding from both end surfaces of the roll on a support or a method of suspending the core protruding from both end surfaces of the roll by a support body , A method of inserting a part of the support into the core, a method of placing the rod-shaped jig inserted into the core on the support, a method of suspending the rod-shaped jig inserted into the core by the support, especially both end surfaces of the roll The method of placing the more protruding core on the support is more preferable.

The PVA film wound into a roll preferably has a length of 1300 m or more and 260
0 m or more is more preferable, and 3000 m or more is the most preferable. When the winding length of the PVA film is less than 1300 m, the tightening of the winding due to thickness unevenness is unlikely to occur, so that the effect of rocking is difficult to be obtained, and the length yield of the polarizing film is often deteriorated, which is not economical.

To produce a polarizing film from the PVA film of the present invention, for example, the PVA film may be dyed, uniaxially stretched, fixed, dried, and optionally heat-treated, and dyed or uniaxially stretched. There is no particular limitation on the order of fixed processing operations. Also, each operation may be performed twice or more.

Dyeing can be performed before uniaxial stretching, during uniaxial stretching, or after uniaxial stretching. As a dye, iodine-
Potassium iodide or a dichroic direct dye can be used. Usually, the dyeing is generally performed by immersing the PVA film in a solution containing the above dye,
There are no particular restrictions on the processing conditions and processing method, such as coating on a PVA film or forming a film by mixing with a PVA film.

The uniaxial stretching can be performed by a wet stretching method or a dry heat stretching method, and is performed in warm water (in a solution containing the dye or in a fixing treatment bath described later) or in the air using a PVA film after absorbing water. be able to. The stretching temperature is not particularly limited, but is preferably 30 ° C. to 90 ° C. when the PVA film is stretched in warm water (wet stretching), and is preferably 50 ° C. to 180 ° C. when dry heat stretching. The stretching ratio of uniaxial stretching (in the case of multi-stage uniaxial stretching, the total stretching ratio) is preferably 4 times or more from the viewpoint of polarization performance, and is 4.5.
It is more preferably at least twice, and most preferably at least five times.
The upper limit of the stretching ratio is not particularly limited, but if it is 8 times or less, uniform stretching is easily obtained, which is preferable. The thickness of the stretched film is preferably 3 μm to 75 μm, and 5 μm
To 50 μm is more preferable.

Fixing treatment is often carried out for the purpose of strengthening the adsorption of the above dye to the PVA film. Boric acid and / or a boron compound are usually added to the treatment bath used for the fixing treatment. Moreover, you may add an iodine compound in a process bath as needed.

Drying treatment (heat treatment) of the PVA film
Is preferably performed at 30 ° C. to 150 ° C., more preferably 50 ° C. to 150 ° C.

The polarizing film of the present invention obtained as described above is usually used as a polarizing plate by laminating an optically transparent protective film having mechanical strength on one or both sides thereof. It Examples of the protective film include a fatty acid cellulose-based film, an acrylic film, a polyester-based film, a polyolefin-based film, a polycarbonate-based film, a polyether ether ketone-based film, a polysulfone-based film, and the like, and a cellulose triacetate film is preferable. An ultraviolet absorber may be added to the protective film. In order to increase the adhesive strength between the polarizing film and the protective film, it is preferable to perform surface treatment such as corona treatment or flame treatment on the surfaces of the two films or one of the films to be bonded. Examples of the adhesive for bonding include PVA-based, urethane-based, and acrylic-based adhesives, and among them, PVA-based adhesives are preferable.

[0041]

EXAMPLES The present invention will be described in detail below with reference to examples, but the present invention is not limited thereto. Example 1 PVA10 having a saponification degree of 99.9 mol% and a polymerization degree of 1750
P containing 10 parts by weight of glycerin to 0 parts by weight, P
The aqueous solution having a VA concentration of 15% by weight was cast by a film forming machine having a roll whose roll axis could be set in a position not parallel to the axis of the drying roll.

By changing the angle formed by the axis of the drying roll and the axis of the roll which can be set in a position not parallel to the axis of the drying roll,
The PVA film was slit at both ends in the width direction with a swing width of 5 cm and a swing cycle of 10 minutes to give an outer diameter of 12.7.
cm, the length of the core was 20 cm longer than the film width, and 2600 m was wound around it to obtain a stretching PVA film roll having a width of 2.5 m and a thickness of 75 μm and a thickness variation of 6 μm in the width direction. The PVA film roll for stretching was double-wound with a high-density polyethylene film, and both ends of the core were placed on a pedestal to be stored in a suspended state.

This PVA film roll was processed in the order of pre-swelling, dyeing, uniaxial stretching, fixing treatment, drying and heat treatment to prepare a polarizing film. That is, the PVA film was immersed in water at 30 ° C. for 5 minutes to be pre-swelled, and the iodine concentration was 0.4 g / liter and the potassium iodide concentration was 40 g.
It was immersed in an aqueous solution of 35 ° C./liter for 3 minutes. Subsequently, it was uniaxially stretched 5.5 times in a 40 ° C. aqueous solution having a boric acid concentration of 4% to give a potassium iodide concentration of 40 g / liter, a boric acid concentration of 40 g / liter, and a zinc chloride concentration of 10 g.
Immobilization treatment was carried out by immersing it in a 30 ° C./liter aqueous solution for 5 minutes. After this, the stretched film was taken out, dried under constant length with hot air at 40 ° C., and further heat treated at 100 ° C. for 5 minutes. The stretching was stable and could be performed uniformly.

The thickness of the obtained polarizing film was 22 μm, and there were no color spots, and a 50 cm square of the obtained polarizing film was sandwiched between two polarizing plates in a crossed Nicol state at an angle of 45 ° to allow transmitted light to pass through. Upon observation, no abnormality was found.

Example 2 PVA10 having a saponification degree of 99.9 mol% and a polymerization degree of 4000
0 parts by weight, 10 parts by weight of glycerin, and 110 parts by weight of water are melt-kneaded by an extruder, and a film forming machine having a roll in which the roll axis can be set in a position not parallel to the axis of the drying roll is used. , Melt extruded into a heated metal roll.

The PVA film was slit at both ends in the width direction with a swing width of 3 cm and a swing cycle of 20 minutes by a method of changing the distance between the roll which can be set in non-parallel positions and the closest roll. A PVA film roll having a thickness of 75 μm and a thickness unevenness of 5 μm in the film width direction of 3000 m wound around 3000 m on a cylindrical aluminum core having an outer diameter of 15.3 cm and a length of 30 cm longer than the film width, and having a width of 3 m. And The stretching PVA
The high-density polyethylene film was double wound on a film roll, and both ends of the core were placed on a pedestal to be stored in a suspended state.

The procedure other than the above was performed in the same manner as in Example 1 to obtain a polarizing film. The thickness of the obtained polarizing film was 22 μm, there was no color spot, and 50 cm of the polarizing film obtained between two polarizing plates in the crossed Nicols state.
No abnormality was found when the transmitted light was observed by sandwiching the four sides at an angle of 45 °.

Example 3 A polarizing film was obtained in the same manner as in Example 2 except that the rocking period was changed to 4 hours.

Occasionally, wrinkles were formed during the stretching, and the stretching was slightly stable only at that time. The obtained polarizing film had no color spots, but when 50 cm square of the obtained polarizing film was sandwiched at an angle of 45 ° between two polarizing plates in a crossed nicols state, a slight spot was found when the transmitted light was observed. Seen, L
It was ready for use as a CD.

Example 4 In Example 1, the outer diameter of the core was 7.5 cm, the width of the film was the same as the length of the core, and a protective pad was attached to one end face of the roll, and the roll was placed upside down. A polarizing film was obtained in the same manner as in Example 1 except that the polarizing film was stored.

Occasionally, wrinkles were formed during the stretching, and the stretching was slightly stable only at that time. Further, a break occurred once from the edge of the film during stretching. The obtained polarizing film had no color spots, but when 50 cm square of the obtained polarizing film was sandwiched at an angle of 45 ° between two polarizing plates in a crossed nicols state, a slight spot was found when the transmitted light was observed. Seen, L
It was ready for use as a CD.

Comparative Example 1 In Example 1, except that the angle formed by the axis of the drying roll and the axis of the roll which can be set in a non-parallel position was fixed at 0 ° (parallel) and was not rocked. The same treatment as in Example 1 was carried out to obtain a polarizing film. Wrinkles were formed during stretching, and stable stretching could not be performed. The 50 cm square of the polarizing film obtained between the two polarizing plates in the crossed Nicols state is
When sandwiched at an angle of 5 ° and observing the transmitted light, spots are seen,
It could not be used for LCD.

Comparative Example 2 A polarizing film was obtained in the same manner as in Example 2, except that the melt extrusion film formation was carried out without adjusting the die lip interval to make the thickness unevenness in the film width direction 15 μm. It was The thick part of the PVA film was slack and could not be stretched uniformly, and the selected polarizing film had light and dark spots.
It was in a state where it could not be used for a CD.

Comparative Example 3 A PVA film roll for stretching was obtained in the same manner as in Example 2, except that talc was applied to both sides of the film immediately before slitting.

The PVA film roll was dry-heated by heating two sets of stretching rolls capable of nipping the film to 100 ° C. and making the peripheral speed of the downstream roll 4 times as high as that of the upstream roll. It was stretched. Immediately after the start of the work, talc was adhered to the spots on the stretching roll, the nip of the film became localized, and uniform stretching could not be performed, so the stretching work was stopped.

[0056]

As described above, according to the present invention, a PVA film roll for stretching which is useful as a raw material for manufacturing a polarizing film and which can be uniformly stretched easily can be obtained.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Iso ▲ Zaki ▼ Takanori             1621 Sakata, Kurashiki City, Okayama Prefecture Kura Co., Ltd.             Within F term (reference) 2H049 BA02 BB43 BC03 BC09 BC22                 4F210 AA19 AG01 AH73 AR12 QA03                       QC02 QD02 QD06 QD19 QG01                       QG18 QW06

Claims (6)

[Claims] 1. The thickness unevenness in the width direction is 1 μm to 10 μm, and both ends of the film are 1 cm to 15 cm in the width direction.
A vinyl alcohol-based polymer film for stretching, which is slit in the swing width of and is wound into a roll. 2. The vinyl alcohol-based polymer film for stretching according to claim 1, wherein the rocking cycle is 10 seconds to 3 hours. 3. The method according to claim 1, which has a metal or plastic outer surface and has an outer diameter of 10 cm or more and is wound around a tubular core having a diameter equal to or longer than the film width. A vinyl alcohol polymer film for stretching. 4. The vinyl alcohol polymer film for stretching according to claim 1, which is not coated with the slip powder. 5. The vinyl alcohol-based polymer film for stretching according to claim 1, which is for optical use. 6. A polarizing film produced by using the vinyl alcohol polymer film for stretching according to claim 4.