JP2007199509A - Method and apparatus for manufacturing polarizing film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and an apparatus for manufacturing a polarizing film having one further uniformly-dyed layer, which is considered that the polarizing performance of the polarizing film is improved much more. <P>SOLUTION: The method for manufacturing the polarizing film comprises the steps of: swelling a polyvinyl alcohol film 10 in swelling water 12 in a swelling tank 11; heating/humidifying the swelled film by using high-humidity low-temperature warm air from a high-humidity low-temperature warm-air heater/humidifier 13; dyeing the heated/humidified film in a dyeing liquid 15 of a dichroic dyestuff in a dyeing tank 14; weakly stretching the dyed film in a stretching liquid 18a in a weakly-stretching tank 16; and strongly stretching the weakly-stretched film in another stretching liquid 18b in a strongly-stretching tank 17. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method, that is, a method and an apparatus for manufacturing a polarizing film as a polarizer used for a polarizing plate of a liquid crystal display device.

  In general, a polarizing film is obtained by swelling a polyvinyl alcohol film (hereinafter abbreviated as “PVA film”) with swelling water, and then dyeing (dying) with a dyeing solution of a dichroic dye (iodine, organic dye, etc.) and stretching. It is manufactured by stretching in a liquid in one direction (uniaxial stretching) (for example, see Patent Document 1).

  However, in this general PVA film manufacturing method, microscopically, it is difficult for the dye solution of the dichroic dye to permeate to the center (inner center) of the PVA film in the dyeing process. The part from both front and back surfaces to the central part adjoining part (at most the central part adjoining part) is dyed, leaving the central part to be included, and in the stretching process, the surface part of the dyeing part in the dyeing process and the inner part adjacent to it Since the dye solution that has permeated into the part flows into the stretching solution and the surface part and the inner adjacent part thereof are unstained, the PVA film after the stretching process has a central part adjacent part (at least a central part adjacent part). ) Both middle portions become a relatively thin dyed layer.

However, in such a form in which two dyed layers are present at a distance between the central part and the central part, the optical characteristics of the polarizing film, particularly the polarization characteristics, and hence the polarization can be improved in terms of light attenuation. It is difficult to improve the polarization performance such as high brightness and high contrast of the plate, especially high transmittance and high degree of polarization, and it is difficult to further improve the display performance (performance improvement) of the liquid crystal display device. Has been.
JP-A-10-153709

  In view of the above-described problem of difficulty in improving the polarization performance, which is recognized in a general PVA film production method, the present invention has a polarizing film having a dyeing layer that is more uniform than one that is considered to improve the polarization performance. The main problem is to provide a method and an apparatus capable of manufacturing the above.

  According to this invention, in order to solve the above-mentioned problem, as described in claim 1 of the claims, after the PVA film is swollen with swelling water, it is heated and humidified with high-humidity low-temperature hot air, Next, the present invention provides a method for producing a polarizing film comprising dyeing with a dye solution of a dichroic dye, weakly stretching (low stretching) in the stretching solution, and then strongly stretching (highly stretching).

  In the method for producing a polarizing film according to claim 1 of the present invention, as described in claim 2, in the dyeing step with the dyeing solution of the PVA film, at least one surface of the front and back surfaces of the PVA film is dyed with low pressure. It is desirable to apply (spray) the liquid.

  Moreover, in order to implement the manufacturing method of the polarizing film of Claim 1, this invention is a swelling tank which accommodates swelling water, and a high-humidity low-temperature hot-air heating and humidifier, as described in Claim 3. An apparatus for producing a polarizing film is provided, in which a dyeing tank containing a dyeing liquid for a dichroic dye, a weak drawing tank containing a drawing liquid, and a strong drawing tank are sequentially arranged adjacent to each other.

  Furthermore, in the manufacturing apparatus of the polarizing film of Claim 3, in order to implement the manufacturing method of the polarizing film of Claim 2, as described in Claim 4, in the dyeing | staining liquid of a dyeing tank, a PVA film Installed with a low pressure dyeing liquid discharge type cylinder-shaped film guide roller that has a large number of dyeing liquid discharge holes that open in the front or back facing part and supplies low pressure dyeing liquid through a dye supply pipe inside It is preferable to do.

  In the method and apparatus for producing a PVA film according to the present invention as set forth in claims 1 and 3, the PVA film swollen with swelling water is microscopically high-humidity low-temperature hot air. By the heating and humidification through the water, the entire PVA film, that is, the hollow portion (bubble cell) in the entire region from the surface to the central portion is filled with water vapor, and then in the dyeing process, the dichroic dye dyeing solution As a result of condensation of water vapor in all the cavities through cooling due to cooling, the pressure in the entire cavities becomes low, and as a result, the dyeing solution permeates into the entire cavities in a capillary manner, and the PVA film includes the entire central portion. Becomes substantially uniformly dyed. Then, in the subsequent weak stretching step in the stretching solution, the dye solution that has permeated from both front and back surfaces of the PVA film to the central portion adjacent portion (at most the central portion adjacent portion) flows out into the stretching solution, and the central portion ( After the dyeing state having only one uniform dyeing layer at least in the central part), in the next strong drawing step, it is strongly drawn to the final draw ratio in this dyeing state, and finally in the central part or the central part. A polarizing film having one substantially homogeneous dyed layer is produced. In this polarizing film, since the polarization is performed through one substantially homogeneous dyed layer, the polarizing film is more excellent in polarizing performance.

  Moreover, according to the application structure of the low pressure dyeing liquid in the dyeing process according to claim 2 and claim 4 and the arrangement structure of the low pressure dyeing liquid discharge type cylinder-shaped film guide roller, the dyeing liquid is made of the PVA film. PVA film is more uniformly dyed to the center because it is forced to penetrate inside through at least one side of the front and back. Therefore, a more homogeneous layer useful for further improving the polarization performance can be obtained as the dyeing layer in the central portion (at least the central portion) formed in the subsequent weak stretching step and strong stretching step.

  Hereinafter, preferred embodiments of a method and an apparatus for producing a polarizing film according to the present invention will be described with reference to the drawings.

  The polarizing film manufacturing apparatus of the present invention is basically connected to a swelling tank 11 for containing swelling water 12 and a high humidity low temperature hot air generator (not shown) as schematically shown in FIG. High-humidity low-temperature hot-air heating / humidifier 13, a dyeing tank 14 containing the dyeing liquid 15, a weak drawing tank 16 containing the drawing liquid 18a, and a drawing liquid 18b higher in temperature than the drawing liquid 18a in the weak drawing tank 16 Can be configured by sequentially arranging adjacently adjacent strong stretching tanks 17.

  In this manufacturing apparatus, the PVA film 10 swollen by the impregnation of the swelling water 12 in the swelling tank 11 is heated and humidified by the high-humidity low-temperature hot air heating / humidifier 13 with the high-humidity low-temperature hot air, and the entire PVA film 10 is obtained. That is, after making the water vapor permeate and fill all the internal cavities, the dyeing solution 14 is cooled by the dyeing liquid 15 in the dyeing tank 14 to bring the whole cavity into a low pressure state through condensation of the water vapor, and the dyeing liquid 15 is completely discharged. Absorb and penetrate into the cavity to make the entire PVA film 10 in a uniform dyed state, and then from the surface to the center adjacent part, at most the center adjacent part during the weak drawing in the drawing liquid 18a in the weak drawing tank 16 The dyeing solution absorbed and permeated until it flows out into the drawing solution 18a to form a central part, at least one layer dyed substantially uniformly at the center part, and then a strong drawing tank In strong stretching at 7 in the form of stretched to a final stretch ratio in this stain state, to form a polarizing film having a single substantially homogeneous dyed layer in the central portion or center portion.

  Here, as the swelling water 12 in the swelling tank 11, water having a temperature of 20 to 40 ° C. can be usually used.

  Further, as the high-humidity low-temperature hot air in the high-humidity low-temperature hot air heating / humidifier 13, generally, the humidity is 10 to 90% and the temperature is 100 ° C. or less based on the tension or the conveyance speed of the PVA film 10. A warm air of 40-60 ° C. can be used.

  Furthermore, as the dyeing solution 15 in the dyeing tank 14, an iodine solution having a temperature lower than that of high humidity, low temperature and warm air, for example, 30 to 40 ° C. can be used.

  As the film guide roller 20 for guiding the PVA film 10 in the dye solution 15, a conventional film contact type can be used. In particular, as shown in an enlarged view in FIG. Staining liquid discharge type cylinder type having a staining liquid discharge hole 21 (here, both ends extend through the inside and a staining liquid supply having a staining liquid supply hole 23 and a partition vane plate 24 attached to the inside portion) The film guide roller 20 can be used for the PVA film 10 as shown in FIG. 1 in order. Both the front and back sides of the PVA film 10 are arranged in a zigzag manner in such a manner that the staining liquid supply holes 23 of the staining liquid supply pipe 22 occupy the opposite side of the PVA film 10 so that the front and back surfaces can be alternately guided. It can be made to the low pressure 圧染 Iroeki is applied to.

  According to the low pressure dyeing liquid discharge type cylinder type film guide roller 20, when the PVA film 10 passes, the low pressure dyeing liquid discharged from the dyeing liquid discharge hole 21 is forcibly permeated into the inside. As a result, the entire PVA film 10 is more uniformly dyed.

  The low pressure dyeing liquid discharged from the dyeing liquid discharge hole 21 is generally suitable for making the PVA film 10 separated from the surface of the film guide roller 20 by a minute amount (for example, about 1 mm) to be in a non-contact state. A fluidized layer of low pressure dyeing liquid having a minute thickness (for example, about 1 mm) is formed between the conditions (pressure, flow rate, flow rate, etc.), that is, between the PVA film 10 and the surface of the film guide roller 20. It can be discharged under suitable conditions.

  The discharge conditions for these low-pressure dyeing liquids can be appropriately set according to the size (thickness, width) and conveying conditions (tension, speed, etc.) of the PVA film, the temperature of the dyeing liquid, and the like. The discharge conditions of the dyeing liquid, the transport conditions of the PVA film 10, the temperature of the dyeing liquid 15, the temperature of the swelling water 12 and the stretching liquid 17, the humidity and the temperature of the hot air can be adjusted by automatic control. .

  As the stretching liquid 18a in the weak stretching tank 16 and the stretching liquid 18b in the strong stretching tank 17, generally, a boric acid aqueous solution having a temperature of 30 to 40 ° C. or 45 to 60 ° C. can be used.

  Moreover, the draw ratio in the former and the final draw ratio in the latter (the overall draw ratio including weak stretching) can usually be 1.1 to 1.5 times and 6 to 8 times, respectively.

  In addition to this, the polarizing film manufacturing method and apparatus according to the present invention have various forms such as a non-moving type by fixing both ends of a low-pressure dyeing liquid discharge type cylindrical film guide roller to a dyeing liquid supply pipe. However, the present invention is not limited to the above embodiment.

  Contains a swelling tank containing swelling water (temperature: 30 ° C), high-humidity low-temperature hot air (humidity: 85%, temperature: 40 ° C), humidifier, and iodine dye dyeing solution (temperature: 35 ° C) In addition, a dyeing tank having a film contact type conventional film guide roller, a weak stretching tank containing a boric acid aqueous solution (temperature: 35 ° C.), and the same stretching liquid (temperature is 55 ° C.) were accommodated. In a polarizing film manufacturing apparatus in which a drying apparatus is placed after a strong stretching tank, a PVA film having a width of 1100 mm and a thickness of 80 μm is conveyed while being conveyed at 1.5 m / min, swelling, high humidity low temperature hot air heating / humidification, Dyeing, uniaxial weak stretching (stretching ratio: 1.2 times), uniaxial strong stretching (final stretching ratio: 6.0 times), and drying are carried out to produce a plurality of polarizing films. Acetylcellulose (TAC The polarizing plate formed by gluing the film) was measured for single penetration, polarization, and cross as polarization properties. The average values were 43.5%, 99.98%, and 0.01%, respectively. was gotten.

  As a film guide roller in the dyeing liquid in the dyeing tank, a plurality of polarizing films manufactured with an apparatus having the same configuration as in Example 1 are used except that a cylinder having a number of low pressure dyeing liquid discharge holes is used. When the single polarizer, the degree of polarization, and the degree of crossing of the formed polarizing plate were measured, the average values were 44.5%, 99.99%, and 0.01%, respectively.

Comparative example

  About the polarizing plate formed by using a plurality of polarizing films manufactured by the apparatus of the so-called conventional form in which the high-humidity low-temperature hot-air heating / humidifier and the weak stretching tank are removed in Example 1, the single transmittance, the polarization degree, When the degree of crossing was measured, the respective average values were 42.3%, 99.95%, and 0.03%.

It is a structure schematic diagram of embodiment of the manufacturing apparatus of the polarizing film which concerns on this invention. FIG. 2 is an enlarged cross-sectional view of a preferred embodiment of a film guide roller installed in a dyeing tank constituting the apparatus shown in FIG. 1, showing a state of guiding the surface side of the PVA film on the lower side in the dyeing tank.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 PVA film 11 Swelling tank 12 Swelling water 13 High humidity low temperature warm air heating and humidifier 14 Dyeing tank 15 Dyeing liquid 16 Weak drawing tank 17 Strong drawing tank 18a Stretching liquid 18b Stretching liquid 20 Film guide roller 21 Dyeing liquid discharge hole 22 Dyeing Liquid supply pipe 23 Staining liquid supply hole 24 Partition blade 25 Bearing

Claims (4)

  After the polyvinyl alcohol film is swollen with swelling water, heated and humidified with high-humidity low-temperature hot air, then dyed with a dye solution of a dichroic dye, weakly stretched in a stretching solution, and then strongly stretched. A method for producing a polarizing film.   The manufacturing method of the polarizing film of Claim 1 which applies the low pressurization dyeing liquid to the at least one surface of the front and back of a polyvinyl alcohol film in the dyeing process by the dyeing liquid of a polyvinyl alcohol film.   A swelling tank containing swelling water, a high-humidity low-temperature hot-air heating / humidifier, a dyeing tank containing a dichroic dye dyeing liquid, a weak drawing tank and a strong drawing tank containing drawing liquid are sequentially adjacent to each other. An apparatus for manufacturing a polarizing film.   Low pressure dyeing that has a large number of dyeing liquid discharge holes that open to the front or back facing part of the polyvinyl alcohol film in the dyeing liquid in the dyeing tank and supplies low pressure dyeing liquid to the inside via a dyeing liquid supply pipe The polarizing film manufacturing apparatus according to claim 3, wherein a liquid discharge type cylindrical film guide roller is installed.

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