JP7058230B2 - How to manufacture a extruder - Google Patents

Description

The present invention relates to a method for manufacturing a polarizing element.

Conventionally, as a polarizing element used in various image display devices such as a liquid crystal display device and an organic EL display device, since it has both high transmittance and high degree of polarization, it has been dyed (contains a dichroic substance). A polyvinyl alcohol-based film is used. The polarizing element is produced by subjecting a polyvinyl alcohol-based film to various treatments such as swelling, dyeing, crosslinking, stretching, etc. in a bath, washing treatment, and then drying. Further, the polarizing element is usually used as a polarizing film in which a protective film such as triacetyl cellulose is bonded to one side or both sides thereof using an adhesive.

The extruder is required to have good optical characteristics, and as a method for producing such a substituent, for example, a production method for controlling the water content of a polyvinyl alcohol-based film in a drying step (Patent Document 1). , A manufacturing method including a step of drying a polyvinyl alcohol-based film while restraining the width direction in the drying step is known (Patent Document 2).

Japanese Unexamined Patent Publication No. 2009-163202 Japanese Unexamined Patent Publication No. 2014-146835

The splitter disclosed in the patent document as described above has good optical characteristics, but in the market, as the performance of an image display device having a polarizing element is improved, a splitter having higher optical characteristics is required. ing.

In view of the above circumstances, it is an object of the present invention to provide a method for manufacturing a polarizing element, which can obtain a polarizing element having excellent optical characteristics.

That is, the present invention is a method for producing a polarizing element obtained by subjecting a polyvinyl alcohol-based film to at least a dyeing step, a cross-linking step, and a stretching step, followed by a washing step and a drying step in order, wherein the drying is performed. The step includes a step of drying the polyvinyl alcohol-based film while applying a tension of 0.1 N / mm or more and 1 N / mm or less in the transport direction of the polyvinyl alcohol-based film, and the polyvinyl alcohol-based film is washed. When the total stretching ratio after the step is defined as x and the total stretching ratio after the drying step is defined as y, the formula (1): y ≧ 0.7x + 1.77 (x is 5 in the formula (1)). It relates to a method for manufacturing a polarizing element, which satisfies the condition that the content is 6 or more and y is 7 or less).

The details of the mechanism of action of the effect in the method for producing a stator of the present invention are unknown, but it is presumed as follows. However, the present invention does not have to be construed as being limited to this mechanism of action.

In the method for producing a polarizing element of the present invention, the drying step is a step of drying the polyvinyl alcohol-based film while applying a tension of 0.1 N / mm or more and 1 N / mm or less in the transport direction of the polyvinyl alcohol-based film. In the case of the polyvinyl alcohol-based film, when the total draw ratio after the washing step is defined as x and the total draw ratio after the drying step is defined as y, the formula (1): y ≧ 0.7x + 1 It is a manufacturing method satisfying the condition of .77 (in the formula (1), x is 5.6 or more and y is 7 or less). In the method for producing a polarizing element, it is known that tension is applied in the width direction and the vertical direction (conveyance direction) of the polyvinyl alcohol-based film in the drying step as in Patent Document 2 described above. In the method for producing a child, by drying the polyvinyl alcohol-based film while applying a certain value of tension in the transport direction, it is possible to confirm that the orientation of the substituent is improved and the optical characteristics of the obtained splitter are improved. Found. In particular, in the method for producing a polarizing element, when the total draw ratio (x) after the washing step and the total draw ratio (y) after the drying step satisfy the relationship of the above formula (1), the orientation becomes more oriented. In order to improve, a extruder having excellent optical characteristics can be obtained.

It is a conceptual diagram which shows the manufacturing method of the stator of this invention.

<Manufacturing method of modulator>
The method for producing a polarizing element of the present invention is a polarization obtained by subjecting a polyvinyl alcohol-based film to an arbitrary swelling step and at least a dyeing step, a cross-linking step, and a stretching step, followed by a washing step and a drying step in order. In the method for producing a child, the drying step includes a step of drying the polyvinyl alcohol-based film while applying a tension of 0.1 N / mm or more and 1 N / mm or less in the transport direction of the polyvinyl alcohol-based film. Further, in the polyvinyl alcohol-based film, when the total draw ratio after the washing step is defined as x and the total draw ratio after the drying step is defined as y, the formula (1): y ≧ 0.7x + 1.77. (In the formula (1), x is 5.6 or more and y is 7 or less.) This is a method for producing a substituent that satisfies the condition.

The concept of the method for manufacturing a polarizing element of the present invention will be described with reference to FIG. In FIG. 1, a polyvinyl alcohol (PVA) -based film (original PVA-based film) F is arranged in a roll shape on the left side of the drawing, and is conveyed to the right of the drawing by a feed roll 8. The polyvinyl alcohol (PVA) -based film F is usually subjected to a swelling step in a swelling treatment tank 1, a dyeing step in a dyeing treatment tank 2, a crosslinking step in a crosslinking treatment tank 3, a stretching step in a stretching treatment tank 4, and a cleaning treatment. A washing step is performed in the tank 5 and a drying step is performed in the drying processing unit 6, and the obtained crosslinker F1 is recovered in the form of a roll.

The polyvinyl alcohol (PVA) -based film has translucency in the visible light region, and a film that disperses and adsorbs a dichroic substance such as iodine or a dichroic dye can be used without particular limitation. Further, the PVA-based film usually used as a raw fabric preferably has a thickness of about 10 to 300 μm, more preferably about 20 to 100 μm, and preferably a width of about 100 to 5000 mm.

Examples of the material of the polyvinyl alcohol-based film include polyvinyl alcohol or a derivative thereof. Examples of the polyvinyl alcohol derivative include polyvinyl formal, polyvinyl acetal; olefins such as ethylene and propylene; unsaturated carboxylic acids such as acrylic acid, methacrylic acid and crotonic acid, and alkyl esters thereof and those modified with acrylamide and the like. Can be mentioned. The polyvinyl alcohol preferably has an average degree of polymerization of about 100 to 10,000, more preferably about 1,000 to 10,000, and even more preferably about 2,000 to 4,500. .. Further, the polyvinyl alcohol preferably has a saponification degree of about 80 to 100 mol%, more preferably about 95 mol% to 99.95 mol. The average degree of polymerization and the saponification degree can be determined according to JIS K 6726.

The polyvinyl alcohol-based film may contain additives such as a plasticizer and a surfactant. Examples of the plasticizer include polyols and condensates thereof such as glycerin, diglycerin, triglycerin, ethylene glycol, propylene glycol and polyethylene glycol. The amount of the additive used is not particularly limited, but is preferably about 20% by weight or less in the polyvinyl alcohol-based film, for example.

As shown in FIG. 1, before and after the processing tank (processing unit) of each of the above steps, a feed roll 8 and first to sixth pinch rolls (10, 20, 30, 40, 50, 60) are respectively. Have been placed. In the feed roll 8 and the 1st to 6th pinch rolls (10, 20, 30, 40, 50, 60), the polyvinyl alcohol (PVA) -based film is conveyed, and further, the 1st to 5th pinch rolls (10) are carried out. , 20, 30, 40, 50) also drains the treatment liquid used in each treatment tank.

The feed roll 8 and the first to sixth pinch rolls are linked to a drive roll (02, 12, 22, 32, 42, 52, 62) that is rotationally driven in conjunction with a motor (not shown) and the drive roll. It is configured to have driven rolls (01, 11, 21, 31, 41, 51, 61) that rotate in a row. Further, the positional relationship between the drive roll and the driven roll in FIG. 1 may be reversed, and both rolls may be configured as drive rolls. Further, the two rolls (pair of rolls) in the feed roll 8 and the first to sixth pinch rolls can be used as long as the above-mentioned polyvinyl alcohol (PVA) -based film is conveyed and the above-mentioned drainage treatment is performed. It may be arranged in the horizontal direction, may be arranged in the vertical direction, or may be arranged at an angle of inclination.

In the method for producing a polarizing element of the present invention, the drying step is a step of drying the polyvinyl alcohol-based film while applying a tension of 0.1 N / mm or more and 1 N / mm or less in the transport direction of the polyvinyl alcohol-based film. include. The tension is preferably 0.15 N / mm or more, and more preferably 0.2 N / mm or more, from the viewpoint of improving the optical characteristics of the stator. Then, for transport stability during stretching, it is preferably 0.8 N / mm or less, more preferably 0.7 N / mm or less, and even more preferably 0.6 N / mm or less. As shown in FIG. 1, the tension can be detected by a tension controller (not shown) provided on the guide roll 7, and the peripheral speed of the fifth pinch roll (50) and the sixth pinch roll (60) can be detected. It can be set by adjusting the peripheral speed of. Normally, in order to increase the tension, the peripheral speed of the sixth pinch roll (60) may be controlled to be faster than the peripheral speed of the fifth pinch roll (50). The peripheral speed can be detected by an encoder connected to the servo motor, and the peripheral speed of each roll, which will be described later, can be detected in the same manner.

Further, in the method for producing a polarizing element of the present invention, the polyvinyl alcohol-based film defines the total draw ratio after the washing step as x (unit: times), and the total draw ratio after the drying step is y (). When defined as unit: times), the condition is that equation (1): y ≧ 0.7x + 1.77 (in equation (1), x is 5.6 or more and y is 7 or less). Meet. When the polyvinyl alcohol-based film satisfies the above-mentioned relational expression, the orientation of the substituent is improved, so that the optical characteristics of the obtained splitter are improved. The total draw ratio (x) after the cleaning step is preferably 5.7 or more, and more preferably 5.8 or more, from the viewpoint of improving the optical characteristics of the stator. Further, the total draw ratio (y) after the drying step is preferably 6.8 or less, more preferably 6.6 or less, from the viewpoint of transport stability during stretching. The total draw ratio (x) after the cleaning step is determined by the peripheral speed ratio (winding peripheral speed / feeding peripheral speed) of the feeding peripheral speed in the feed roll 8 and the winding peripheral speed in the fifth pinch roll (50). The total draw ratio (y) after the drying step can be calculated, and is the peripheral speed ratio (winding peripheral speed / feeding peripheral speed) of the feeding peripheral speed in the feed roll 8 and the winding peripheral speed in the sixth pinch roll (60). It can be calculated by speed). Further, in the drying step, the polyvinyl alcohol-based film also has a force of shrinking in the transport direction due to the evaporation of water, so that even if a certain tension is applied to the polyvinyl alcohol-based film, the total amount after the drying step is applied. The draw ratio (y) may be smaller than the total draw ratio (x) after the washing step.

Further, in the method for producing a polarizing element of the present invention, from the viewpoint of improving the optical characteristics of the polarizing element, the polyvinyl alcohol-based film is used in the formula (2): y ≦ 0.7x + 1.94 (in the formula (2), x. And y are preferably the same as those in the above formula (1)), and formula (3): y ≦ 0.7x + 1.84 (in the formula (3), x and y are It is more preferable that the condition of the above formula (1) is satisfied.

Further, the draw ratio in the swelling step can be calculated from the peripheral speed ratio (winding peripheral speed / feeding peripheral speed) of the feeding peripheral speed in the feed roll 8 and the winding peripheral speed in the first pinch roll (10). The stretching ratio in the dyeing step can be calculated from the peripheral speed ratio (winding peripheral speed / feeding peripheral speed) of the winding peripheral speed of the first pinch roll (10) and the winding peripheral speed of the second pinch roll (20). The draw ratio in the cross-linking step can be calculated from the peripheral speed ratio (winding peripheral speed / feeding peripheral speed) of the winding peripheral speed of the second pinch roll (20) and the winding peripheral speed of the third pinch roll (30). The stretching ratio in the stretching step can be calculated from the peripheral speed ratio (winding peripheral speed / feeding peripheral speed) of the winding peripheral speed in the third pinch roll (30) and the winding peripheral speed in the fourth pinch roll (40). When there is one pinch roll arranged between the processing tanks (processing units), the winding peripheral speed and the feeding peripheral speed in the pinch roll have the same value.

The draw ratio in the swelling step is preferably about 1.5 to 3.0 times, more preferably about 1.8 to 2.6 times. The draw ratio in the dyeing step is preferably about 1.1 to 2.0 times, more preferably about 1.1 to 1.6 times. The draw ratio in the cross-linking step is preferably about 1.1 to 1.7 times, more preferably about 1.1 to 1.4 times. The stretching ratio in the stretching step is preferably about 1.2 to 1.9 times, more preferably about 1.5 to 1.9 times.

Hereinafter, each treatment bath and the like in each treatment step will be described.

The swelling step is an optional step in the method for producing a polarizing element of the present invention, and is a treatment step of immersing a polyvinyl alcohol-based film in a swelling bath to remove stains and blocking agents on the surface of the polyvinyl alcohol-based film. In addition, uneven dyeing can be suppressed by swelling the polyvinyl alcohol-based film. As the swelling bath, a medium containing water as a main component, such as water, distilled water, and pure water, is usually used. A surfactant, alcohol or the like may be appropriately added to the swelling bath according to a conventional method.

The temperature of the swelling bath is preferably about 10 to 60 ° C, more preferably about 15 to 45 ° C. The immersion time in the swelling bath cannot be unconditionally determined because the degree of swelling of the polyvinyl alcohol-based film is affected by the temperature of the swelling bath, but is preferably about 5 to 300 seconds, preferably 10 to 200 seconds. More preferably. The swelling step may be performed only once, or may be performed a plurality of times as needed.

The dyeing step is a treatment step of immersing the polyvinyl alcohol-based film in a dyeing bath (iodine solution), and adsorbing and orienting a dichroic substance such as iodine or a dichroic dye on the polyvinyl alcohol-based film. can. The iodine solution is usually preferably an aqueous iodine solution and contains iodine and iodide as a solubilizing agent. The iodide includes potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, and iodide. Examples include titanium. Among these, potassium iodide is preferable from the viewpoint of controlling the content of the potassium in the substituent.

In the dyeing bath, the iodine concentration is preferably about 0.01 to 1% by weight, more preferably about 0.02 to 0.5% by weight. In the dyeing bath, the concentration of the iodide is preferably about 0.01 to 10% by weight, more preferably about 0.05 to 5% by weight.

The temperature of the dyeing bath is preferably about 10 to 50 ° C, more preferably about 15 to 45 ° C. The immersion time in the dyeing bath cannot be unconditionally determined because the degree of dyeing of the polyvinyl alcohol-based film is affected by the temperature of the dyeing bath, but is preferably about 10 to 300 seconds, preferably 20 to 240 seconds. More preferably. The dyeing step may be performed only once, or may be performed a plurality of times as needed.

The cross-linking step is a treatment step of immersing the polyvinyl alcohol-based film dyed in the dyeing step in a treatment bath (cross-linking bath) containing a boron compound, and the polyvinyl alcohol-based film is cross-linked by the boron compound. Iodine molecules or dye molecules can be adsorbed on the crosslinked structure. Examples of the boron compound include boric acid, borate, borax and the like. The cross-linking bath is generally an aqueous solution, but may be, for example, a mixed solution of an organic solvent and water that is miscible with water. Further, the crosslinked bath preferably contains potassium iodide from the viewpoint of controlling the content of potassium in the substituent.

In the cross-linking bath, the concentration of the boron compound is preferably about 1 to 15% by weight, more preferably about 1.5 to 10% by weight, and more preferably about 2 to 5% by weight. preferable. When potassium iodide is used in the cross-linking bath, the concentration of potassium iodide in the cross-linking bath is preferably about 1 to 15% by weight, preferably about 1.5 to 10% by weight. More preferred.

The temperature of the cross-linking bath is preferably about 20 to 70 ° C, more preferably about 30 to 60 ° C. The immersion time in the cross-linking bath cannot be unconditionally determined because the degree of cross-linking of the polyvinyl alcohol-based film is affected by the temperature of the cross-linking bath, but is preferably about 5 to 300 seconds, preferably 10 to 200 seconds. More preferably. The cross-linking step may be carried out only once, or may be carried out a plurality of times as needed.

The stretching step is a treatment step of stretching a polyvinyl alcohol-based film to a predetermined magnification in at least one direction. Generally, a polyvinyl alcohol-based film is uniaxially stretched in the transport direction (longitudinal direction). The stretching method is not particularly limited, and either a wet stretching method or a dry stretching method can be adopted. The stretching step may be carried out only once, or may be carried out a plurality of times as needed. The stretching step may be performed at any stage in the production of the substituent.

As the treatment bath (stretching bath) in the wet stretching method, a solvent such as water or an organic solvent miscible with water and a mixed solution of water can be usually used. The stretching bath preferably contains potassium iodide from the viewpoint of controlling the content of potassium in the substituent. When potassium iodide is used in the stretching bath, the concentration of potassium iodide in the stretching bath is preferably about 1 to 15% by weight, more preferably about 2 to 10% by weight. Further, the treatment bath (stretching bath) can contain the boron compound in order to improve the degree of crosslinking. In this case, the concentration of the boron compound in the stretching bath is about 1 to 15% by weight. It is preferably present, and more preferably about 1.5 to 10% by weight.

The temperature of the stretching bath is preferably about 25 to 80 ° C, more preferably about 40 to 75 ° C. The immersion time in the stretching bath cannot be unconditionally determined because the degree of stretching of the polyvinyl alcohol-based film is affected by the temperature of the stretching bath, but is preferably about 10 to 800 seconds, preferably 30 to 500 seconds. More preferably. The stretching treatment in the wet stretching method may be performed together with any one or more of the swelling step, the dyeing step, the cross-linking step, and the washing step.

Examples of the dry stretching method include an inter-roll stretching method, a heating roll stretching method, and a compression stretching method.

The cleaning step is a treatment step of immersing the polyvinyl alcohol-based film in a washing bath, and can remove foreign substances remaining on the surface of the polyvinyl alcohol-based film or the like. As the washing bath, a medium containing water as a main component, such as water, distilled water, and pure water, is usually used. Further, from the viewpoint of controlling the content of the potassium in the polarizing element, it is preferable to use potassium iodide in the washing bath, and in this case, the concentration of potassium iodide in the washing bath is 1 to 10. It is preferably about 7% by weight, more preferably about 2 to 4% by weight, and even more preferably about 1.6 to 3.8% by weight.

The temperature of the washing bath is preferably about 5 to 50 ° C, more preferably about 10 to 40 ° C, and even more preferably about 15 to 30 ° C. The immersion time in the washing bath cannot be unconditionally determined because the degree of washing of the polyvinyl alcohol-based film is affected by the temperature of the washing bath, but is preferably about 1 to 100 seconds, preferably 2 to 50 seconds. It is more preferably about 3 to 20 seconds. The swelling step may be performed only once, or may be performed a plurality of times as needed.

The drying step includes a step of drying the polyvinyl alcohol-based film while applying a tension of 0.1 N / mm or more and 1 N / mm or less in the transport direction of the polyvinyl alcohol-based film, and was washed in the washing step. This is a step of drying a polyvinyl alcohol-based film to obtain a polarizing element, and the drying gives a polarizing element having a desired moisture content. The drying is carried out by any suitable method, and examples thereof include natural drying, blast drying, and heat drying. The water content of the polarizing element is preferably about 12 to 25% by weight, more preferably about 13 to 20% by weight. The water content of the polarizing element is calculated by the following formula based on the initial weight of the sample cut into a size of 100 mm square and the dry weight after drying at 120 ° C. for 2 hours.
Moisture content (% by weight) = {(initial weight-dry weight) / initial weight} x 100

The drying temperature is preferably about 20 to 150 ° C, more preferably about 25 to 100 ° C. Further, the drying time cannot be unconditionally determined because the degree of drying of the polarizing element is affected by the drying temperature, but is preferably about 30 to 600 seconds, more preferably about 60 to 300 seconds. preferable. The drying step may be carried out only once, or may be carried out a plurality of times as needed.

The thickness of the polarizing element is preferably about 1 to 30 μm, more preferably about 5 to 25 μm. In particular, in order to obtain a polarizing element having a thickness of 10 μm or less, the polyvinyl alcohol-based film disclosed in JP-A-2009-098653, JP-A-2013-238640, etc. is used on a thermoplastic resin substrate. A method for producing a thin polarizing element using a laminate containing a film-formed polyvinyl alcohol-based film can be applied.

<Polarizing film>
The obtained polarizing element is usually used as a polarizing film by attaching a transparent protective film to at least one surface thereof according to a conventional method. The transparent protective film is not particularly limited, and various transparent protective films conventionally used for polarizing films can be used. As the material constituting the transparent protective film, for example, a thermoplastic resin having excellent transparency, mechanical strength, thermal stability, moisture barrier property, isotropic property, etc. is used. Examples of the thermoplastic resin include a cell roll ester resin such as triacetyl cell roll, a polyester resin such as polyethylene terephthalate and polyethylene naphthalate, a polyether sulfone resin, a polysulfone resin, a polycarbonate resin, nylon and aroma. Polyamide-based resin such as group polyamide, polyimide-based resin, polyethylene, polypropylene, polyolefin-based resin such as ethylene / propylene copolymer, (meth) acrylic-based resin, cyclo-based or cyclic polyolefin-based resin having norbornene structure (norbornene-based resin) ), Polyallylate-based resin, polystyrene-based resin, polyvinyl alcohol-based resin, and mixtures thereof.

When the transparent protective film is attached to both sides of the polarizing element, the transparent protective films on both sides may be the same or different.

As the transparent protective film, a retardation plate having a front retardation of 40 nm or more and / or a retardation of thickness direction of 80 nm or more can be used. The frontal phase difference is usually controlled in the range of 40 to 200 nm, and the thickness direction phase difference is usually controlled in the range of 80 to 300 nm. When a retardation plate is used as the transparent protective film, the retardation plate also functions as a transparent protective film, so that the thickness can be reduced.

Examples of the retardation plate include a birefringent film formed by uniaxially or biaxially stretching a polymer material, an alignment film of a liquid crystal polymer, and a film in which an alignment layer of a liquid crystal polymer is supported by a film. The thickness of the retardation plate is not particularly limited, but is generally about 20 to 150 μm. The phase plate may be attached to a transparent protective film having no phase difference before use.

The transparent protective film may be surface-modified. Examples of the surface modification treatment include corona treatment, plasma treatment, primer treatment, saponification treatment and the like.

The surface of the transparent protective film to which the polarizing element is not bonded may be subjected to a hard coat treatment, an antireflection treatment, a sticking prevention treatment, and a treatment for the purpose of diffusion or antiglare. The hard coat treatment, antireflection layer, anti-sticking layer, diffusion layer, anti-glare treatment, etc. can be provided on the transparent protective film itself, and the optical layer is separate from the transparent protective film. It can also be provided as.

The transparent protective film contains any suitable additives such as UV absorbers, antioxidants, lubricants, plasticizers, mold release agents, color inhibitors, flame retardants, antistatic agents, pigments, colorants and the like. You may.

An adhesive is usually used to bond the polarizing element to the transparent protective film. Examples of the adhesive include isocyanate-based adhesives, polyvinyl alcohol-based adhesives, gelatin-based adhesives, vinyl-based latex-based adhesives, and water-based polyesters. The adhesive is usually used as an adhesive consisting of an aqueous solution, and usually contains 0.5 to 60% by weight of a solid content. Examples of the adhesive include an ultraviolet curable adhesive, an electron beam curable adhesive, and the like, in addition to the above. Further, the adhesive may contain a metal compound filler or the like.

The adhesive may be applied to either the transparent protective film or the polarizing element, or both may be applied. After bonding, a drying step is performed to form an adhesive layer composed of a coated dry layer. The polarizing element and the transparent protective film can be bonded by a roll laminator or the like. After the drying step, ultraviolet rays or electron beams can be irradiated as needed. The thickness of the adhesive layer is not particularly limited, but is preferably about 30 to 5000 nm, and more preferably about 100 to 1000 nm.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

<Example 1>
<Manufacturing of modulator>
A polyvinyl alcohol film having a degree of polymerization of 2,400, a degree of saponification of 99.9 mol%, a thickness of 45 μm, and a width of 3390 mm was prepared. The polyvinyl alcohol film was subjected to the following steps by the production method as shown in FIG. Specifically, the polyvinyl alcohol film was immersed in a swelling bath (water bath) at 27 ° C. for 70 seconds and swelled while being stretched so that the stretching ratio of the swelling step was 2.210 times in the transport direction (swelling step). ). Subsequently, the obtained polyvinyl alcohol film is immersed in a dyeing bath at 30 ° C. (an aqueous solution having an iodine concentration of 8% by weight) for 45 seconds to dye, and the draw ratio of the dyeing step is 1.176 times in the transport direction. It was stretched so as to be (dyeing step). Next, the dyed polyvinyl alcohol film is immersed in a cross-linking bath at 40 ° C. (an aqueous solution having a boric acid concentration of 4% by weight and a potassium iodide concentration of 3% by weight) for 43 seconds, and the stretching ratio of the cross-linking step in the transport direction. Was stretched to 1.296 times (crosslinking step). Further, the obtained polyvinyl alcohol film is immersed in a stretching bath at 60 ° C. (an aqueous solution having a boric acid concentration of 3% by weight and a potassium iodide concentration of 5% by weight) for 31 seconds to stretch the stretching step in the transport direction. It was stretched so that the magnification was 1.786 times (stretching step). Further, the obtained polyvinyl alcohol film is immersed in a washing bath at 27 ° C. (an aqueous solution having a potassium iodide concentration of 5.5% by weight) for 10 seconds, and the total draw ratio (x) after the washing step in the transport direction. Was stretched to be 6.020 times (cleaning step). The washed polyvinyl alcohol film is dried at 55 ° C. for 1 minute while applying a tension of 0.29 N / mm in the transport direction so that the total draw ratio (y) after the drying step becomes 6.075 times in the transport direction. A ligand was prepared in. The thickness of the splitter was 17 μm, and the water content of the splitter was 15% by weight.

As described above, each of the above stretching ratios and the above total stretching ratio can be calculated from the peripheral speed ratio (winding peripheral speed / feeding peripheral speed) of the feed roll and each pinch roll. The peripheral speed can be set up to three digits after the decimal point, and when a deviation from the peripheral speed setting value occurs, the system is such that an abnormality can be detected by an encoder connected from a servo motor manufactured by Mitsubishi Electric.

<Manufacturing of polarizing film>
As the adhesive, the following radically polymerizable compound (a) 12 parts by weight, radically polymerizable compound (b) 35 parts by weight, radically polymerizable compound (c) 40 parts by weight, oligomer compound (d) 10 parts by weight, light. 2 parts by weight of the polymerization initiator (e) and 1 part by weight of the photosensitizer (f) were mixed and stirred at 50 ° C. for 1 hour to obtain an active energy ray-curable adhesive. The above-mentioned active energy ray-curable type is applied to each of the bonded surfaces of the first transparent protective film (acrylic film, manufactured by Toyo Kohan Co., Ltd.) and the second transparent protective film (COP film, manufactured by Nippon Zeon Corporation, trade name "Zeonoa"). Apply the adhesive to a thickness of 0.7 μm using an MCD coater (manufactured by Fuji Machinery Co., Ltd.) (cell shape: honeycomb, number of gravure roll wires: 1000 lines / inch, rotation speed 140% / line speed). It was processed and bonded to both sides of the above-mentioned polarizing element X with a roll machine. Then, from the bonded transparent protective film side (both sides), the visible light is irradiated on both sides by an active energy ray irradiator to cure the active energy ray-curable adhesive, and then hot air dried at 70 ° C. for 3 minutes. A polarizing film having transparent protective films on both sides of the polarizing element was obtained.
The above radically polymerizable compound (a) is HEAA (hydroxyethylacrylamide), manufactured by KJ Chemicals Co., Ltd .; the radically polymerizable compound (b) is ACMO (acroylmorpholin), manufactured by KJ Chemicals Co., Ltd .; c) is light acrylate 1,9ND-A (1,9-nonanediol diacrylate), manufactured by Kyoeisha Chemical Co., Ltd .; oligomer compound (d) is ARUFON UG-4010 (epoxy radical modified acrylic oligomer) manufactured by Toa Synthetic Co., Ltd. The photopolymerization initiator (e) is Omnirad 907 (2-methyl-1- (4-methylthiophenyl) -2-morpholinopropan-1-one), IGM Resins B.I. V. The photosensitizer (f) is manufactured by KAYACURE DETX-S (2,4-diethylthioxanthone), manufactured by Nippon Kayaku Co., Ltd.;

[Evaluation of optical characteristics of polarizing film]
The simple substance transmittance (Ts) and the degree of polarization (P) of the polarizing film obtained above were measured. The simple substance transmittance and the degree of polarization can be measured using a spectrophotometer (manufactured by JASCO Corporation, product name "V7100"). As a specific method for measuring the degree of polarization, the parallel transmittance (H ₀ ) and the orthogonal transmittance (H ₉₀ ) of the above-mentioned polarizing element are measured, and the formula: degree of polarization (%) = {(H ₀ -H ₉₀ ). ) / (H ₀ + H ₉₀ )} ^1/2 × 100. The parallel transmittance (H ₀ ) is a value of the transmittance of a parallel laminated polarizing element manufactured by superimposing two identical polarizing elements so that their absorption axes are parallel to each other. Further, the orthogonal transmittance (H ₉₀ ) is a value of the transmittance of an orthogonal laminated polarizing element manufactured by superimposing two identical polarizing elements so that their absorption axes are orthogonal to each other. These transmittances are Y values corrected for luminosity factor by the 2 degree field of view (C light source) of JlS Z 8701-1982. In addition, the orthogonal transmittance (%) having a wavelength of 410 nm was also measured at the same time. The results are shown in Table 1.

The simple transmittance is preferably 40% or more, more preferably 43% or more, and further preferably 43.1% or more. The degree of polarization is preferably 90% or more, more preferably 95% or more, further preferably 99% or more, still more preferably 99.9% or more, and 99. It is even more preferable that it is .99% or more. The orthogonal transmittance at a wavelength of 410 nm is preferably 0.1% or less, more preferably 0.06% or less, and even more preferably 0.05% or less.

<Manufacturing of a polarizing element and manufacturing of a polarizing film>
<Examples 2 to 14, Comparative Examples 1 to 4>
Except that the stretching ratio in the stretching step, the total stretching ratio (x) after the washing step, the total stretching ratio (y) after the drying step, and the tension in the drying step were adjusted to the values shown in Tables 1 and 2. Manufactured a splitter and produced a polarizing film by the same operation as in Example 1. The immersion time in each treatment liquid and the drying time are slightly different from those in Example 1 due to the influence of the stretching ratio and the total stretching ratio.

Using the polarizing films of Examples 2 to 14 and Comparative Examples 1 to 4 obtained above, the evaluation in the above [evaluation of optical characteristics of the polarizing film] was performed. The results are shown in Tables 1 and 2.

The single transmittance (%) and the orthogonal transmittance (%) at a wavelength of 410 nm in the polarizing film obtained in the above example, and the single transmittance (%) and the orthogonal transmittance at a wavelength of 410 nm in the polarizing film obtained in the comparative example. Compared with the rate (%), the polarizing film of the example tends to have a higher single transmittance (%) and a lower orthogonal transmittance (%) at a wavelength of 410 nm than that of the comparative example. It can be said that the characteristics are excellent. In particular, when comparing the polarizing films of Examples and Comparative Examples having the same level of simple substance transmittance (%), it is clear that the polarizing film of Examples has a low orthogonal transmittance (%) at a wavelength of 410 nm, and the optics It can be said that it has excellent characteristics.

Further, the single transmittance (%) and the degree of polarization (%) in the polarizing film obtained in the above example are compared with the single transmittance (%) and the degree of polarization (%) in the polarizing film obtained in the comparative example. Then, it can be said that the polarizing film of the example is superior in optical characteristics because the single transmittance (%) tends to be higher and the degree of polarization (%) tends to be higher than that of the comparative example. In particular, when the polarizing films of Examples and Comparative Examples having the same level of simple substance transmittance (%) are compared, it is clear that the polarizing film of Examples has a high degree of polarization (%) and is excellent in optical characteristics. It can be said that there is.

F Polyvinyl alcohol (PVA) film F1 Polarizer 1 Swelling treatment tank 2 Dyeing treatment tank 3 Crosslinking treatment tank 4 Stretching treatment tank 5 Cleaning treatment tank 6 Drying treatment section 7 Guide roll 8 Feed roll 01, 11, 21, 31, 41 , 51, 61 Driven roll 02, 12, 22, 32, 42, 52, 62 Drive roll 10 1st pinch roll 20 2nd pinch roll 30 3rd pinch roll 40 4th pinch roll 50 5th pinch roll 60 6th pinch roll

Claims (2)

A method for manufacturing a polarizing film in which a transparent protective film is bonded to at least one surface of a polarizing element.
The polarizing element is obtained by subjecting a polyvinyl alcohol-based film to at least a swelling step, a dyeing step, a crosslinking step, and a stretching step, followed by a washing step and a drying step in order.
The cross-linking step is the first cross-linking step after the dyeing step.
The drying step includes a step of drying the polyvinyl alcohol-based film while applying a tension of 0.1 N / mm or more and 1 N / mm or less in the transport direction of the polyvinyl alcohol-based film, and the polyvinyl alcohol-based film comprises a step of drying the polyvinyl alcohol-based film. The stretching ratio in the swelling step is 1.5 to 3.0 times, the stretching ratio in the dyeing step is 1.1 to 2.0 times, and the stretching ratio in the cross-linking step is 1.1 to 1.7 times. When the total draw ratio after the washing step is defined as x and the total draw ratio after the drying step is defined as y.
Equation (1): y ≧ 0.7x + 1.77
(In equation (1), x is 5.6 or more and y is 6.3 or less .) , And.
Equation (2): y ≦ 0.7x + 1.94
(In the formula (2), x and y are the same as those in the formula (1)).
The polarizing film is a method for producing a polarizing film, characterized in that the simple substance transmittance is 43.18% or more and the degree of polarization is 99.99% or more . The method for producing a polarizing film according to claim 1 , wherein the polyvinyl alcohol-based film has a degree of polymerization of 2,000 or more.

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