TWI553046B - Method of manufacturing polarizer film - Google Patents

Description

Method for manufacturing polarizing film

The present invention relates to a method of producing a polarizing film, and more particularly to a method of crosslinking treatment in a polarizing film manufacturing process.

The polarizing plate is an optical component widely used in liquid crystal displays. The polarizing plate is generally obtained by bonding a protective film such as triacetate cellulose (TAC) or cyclo-olefin polymer (COP) to a polyvinyl alcohol (PVA) polarizing film. Nowadays, the application of liquid crystal displays is becoming more and more widespread. For example, mobile phones, wearable devices, etc., the requirements for the quality of polarizing plates are also increasing.

The polarizing film is the most important component of the polarizing plate, and the polarizing film is generally formed by adsorbing a dichroic dye in a polyvinyl alcohol film, for example, an iodine-based polarizing film containing iodine as a dichroic dye. The formation of the polarizing film generally has the following steps: a swelling treatment, a dyeing treatment, a stretching treatment, a crosslinking treatment, a washing treatment, and a drying treatment. Among them, the stretching treatment causes the polyvinyl alcohol to have a polarizing effect.

The invention provides a method for manufacturing a polarizing film, comprising: The polarizing film precursor is subjected to a crosslinking treatment to form a polarizing film, wherein the crosslinking treatment comprises: adding a reaction solution in the crosslinking tank; and ion-exchange the ion exchange resin with the cation of the reaction solution in the crosslinking tank to Provide hydrogen ions.

10‧‧‧Polarized film precursor

10'‧‧‧ polarizing film

12‧‧‧Swelling trough

14‧‧‧Dyeing tank

16‧‧‧crosslinking slot

18‧‧‧Washing tank

20‧‧‧ drying oven

30‧‧‧Transfer wheel

1 shows a schematic diagram of a process apparatus for a polarizing film in accordance with some embodiments of the present invention.

The embodiments of the present invention will be described in detail below with reference to the accompanying drawings, in which the following drawings are not drawn to scale. In fact, the dimensions of the elements may be arbitrarily enlarged or reduced to clearly show the features of the present invention. In the description and drawings, the same or similar elements will be denoted by like reference numerals.

The various features of the invention are set forth in the description of the various embodiments of the invention. Of course, these are only examples and should not limit the scope of the invention. In addition, repeated reference numerals or signs may be used in the various embodiments, which are merely for the purpose of simplicity and clarity of the disclosure, and do not represent a particular relationship between the various embodiments and/or structures discussed.

Furthermore, it should be understood that there may be additional operational steps before, during or after the method is performed, and some of the operational steps may be It can be replaced or deleted in the methods of other embodiments.

In the step of forming the polarizing film, a large amount of chemical solution is required to be reacted, and the pH of the reaction solution is controlled to an appropriate range. Generally, an acidic solution is added to the reaction tank to maintain the pH of the reaction solution. However, ions (for example, metal ions, non-metal ions) generated by the dissociation of the additional acidic solution will accumulate in the reaction tank, so that the specific ion concentration in the reaction solution continuously increases, which may further affect the quality of the produced polarizing film.

In order to solve the above problems, the method for producing a polarizing film according to the present invention replaces the addition of an acidic solution by using an ion exchange resin in the crosslinking treatment and the stretching treatment of the polarizing film. Therefore, it is possible to prevent a large amount of specific ions (for example, metal ions, non-metal ions) generated by dissociation of the acidic solution from accumulating in the reaction solution, thereby impairing the quality of the prepared polarizing film.

1 shows a schematic diagram of a process apparatus for a polarizing film in accordance with some embodiments of the present invention. As shown in Fig. 1, the polarizing film precursor 10 is sequentially passed through the conveying roller 30: a swelling tank 12 for performing swelling treatment, a dyeing tank 14 for performing dyeing treatment, and a cross-linking treatment. Coupling 16. Next, the reaction solution to which the surface of the polarizing film precursor 10 adheres is washed by the washing tank 18. Thereafter, it is dried by the drying furnace 20 to obtain a polarizing film 10'.

It should be noted that Fig. 1 shows an example in which one swelling tank, a dyeing tank, a crosslinking tank, and a water washing tank are provided, but a plurality of reaction tanks may be provided in each treatment as needed. The method for producing the polarizing film of the present invention will be described in more detail below.

The polarizing film precursor 10 may be a polyvinyl alcohol (PVA) film. Polyvinyl alcohol can be formed by saponifying polyvinyl acetate. In some embodiments, the polyvinyl alcohol may have a degree of saponification of 85 mol%, 90 mol%, or 99 to 100 mol%. Further, in some embodiments, the polyvinyl acetate may be a monomer of vinyl acetate or a copolymer of vinyl acetate and other monomers, and the like. The above other monomers may be unsaturated carboxylic acids, olefins, unsaturated sulfonic acids or vinyl ethers.

In other embodiments, the polyvinyl alcohol may be a modified polyvinyl alcohol, for example, an aldehyde-modified polyvinylformal, polyvinyl acetal or polyvinyl butyral ( Polyvinylbutyral) and so on. In some embodiments, the polarizing film precursor 10 may have a thickness of about 20 μm to 100 μm or 30 μm to 80 μm.

First, the polarizing film precursor 10 is transferred to the swelling tank 12 for swelling treatment. The swelling treatment removes the foreign matter on the surface of the polarizing film precursor 10 and the plasticizer therein, and allows the polarizing film precursor 10 to be easily dyed and plasticized in a subsequent step. The conditions of the swelling treatment are not particularly limited as long as the above effects can be achieved without causing extreme dissolution or clear disappearance of the polarizing film precursor.

The swelling tank 12 mainly contains pure water to react with the polarizing film precursor 10. In some embodiments, the temperature of the swelling treatment may be from 10 ° C to 50 ° C or from 20 ° C to 50 ° C, and the swelling treatment time may be from 5 seconds to 300 seconds or from 20 seconds to 240 seconds.

Further, since the polarizing film precursor 10 is likely to be laterally swollen in the swelling treatment step, it has wrinkles. Thus, in some embodiments, Expansion rolls such as expander roll, spiral roll, crown roll, cloth guider, bend bar or tenter clip can be set. The device is placed at the entrance and exit of the swelling tank 12, and the polarizing film precursor 10 is conveyed while removing the wrinkles of the polarizing film precursor 10. In some embodiments, it may be desirable to extend the polarizing film precursor 10 in this step.

Furthermore, in order to stabilize the transfer of the polarizing film precursor 10 in the swelling tank 12, in some embodiments, an underwater jet or edge position control device may be used to control the flow of water in the swelling tank 12.

Next, the polarizing film precursor 10 is sent to the dyeing tank 14 for dyeing treatment. The dyeing agent used for the dyeing treatment may be a dichroic dye or other water-soluble di dye dye or the like. In some embodiments, the staining agent comprises iodine, potassium iodide. For example, in some embodiments, the coloring agent may be an aqueous solution containing 0.003 parts by weight to 0.2 parts by weight of iodine and 3 parts by weight to 30 parts by weight of potassium iodide. In some embodiments, the temperature of the dyeing treatment may be from 10 ° C to 50 ° C or from 20 ° C to 40 ° C, and the duration of the dyeing treatment may be from 10 seconds to 600 seconds or from 30 seconds to 200 seconds.

Further, other compounds may be added to the dyeing tank 14 to provide a better effect on the dyeing treatment. In some embodiments, boric acid may be additionally added.

Furthermore, similar to the swelling treatment, in some implementations, an expander roll, a spiral roll, a crown roll, a cloth guider or a bendbar may be provided. It is equal to the entrance and exit of the dyeing tank 14. In addition, when dyeing is performed, it can be simultaneously The polarizing film precursor 10 is subjected to an elongation treatment, for example, a uniaxial stretching treatment. In some embodiments, the above-described stretching process can be performed by a method of generating a peripheral speed difference between a conveying roller disposed at the entrance of the dyeing tank 14 and a conveying roller disposed at the outlet of the dyeing tank 14.

Next, the polarizing film precursor 10 is transferred to the crosslinking tank 16 to perform a crosslinking treatment. The cross-linking treatment hydrates the polarizing film precursor 10 or adjusts the color tone thereof. In some embodiments, the reaction solution in the crosslinking tank 16 may comprise boric acid, potassium iodide, zinc iodide or a combination thereof. Boric acid is a crosslinking agent, and potassium iodide and zinc iodide are used for optical adjustment, and the color of the polarizing film can be adjusted by changing the concentration thereof.

In some embodiments, the crosslinking reaction solution may be an aqueous solution containing 1 part by weight to 10 parts by weight of boric acid and 1 part by weight to 30 parts by weight of potassium iodide. In some embodiments, the temperature of the crosslinking treatment may be from 10 ° C to 70 ° C or from 50 ° C to 65 ° C, and the crosslinking treatment may be from 1 second to 600 seconds or from 20 seconds to 300 seconds.

Further, when the crosslinking treatment is performed, the polarizing film precursor 10 may be simultaneously subjected to elongation treatment. In some embodiments, the stretching process can be performed by a method of generating a peripheral speed difference between the conveying roller disposed at the inlet of the crosslinking tank 16 and the conveying roller disposed at the outlet of the crosslinking tank 16.

In some embodiments, the stretching ratio of the polarizing film precursor 10 from the swelling treatment step to the crosslinking treatment step is about 4.5 to 8 times or 5 to 7 times.

Further, in some embodiments, the crosslinking treatment can be carried out at pH 2 to pH 5 or pH 2.5 to pH 4.5. In the prior art, except for the cross-linking office In addition to the boric acid used, an additional acidic solution is usually added to the crosslinking tank 16 to maintain the pH of the cross-linking reaction solution in a suitable range.

In contrast, the present invention uses an ion exchange resin to at least partially replace the addition of an acidic solution. Specifically, the ion exchange resin is subjected to an ion exchange reaction with a cation of the crosslinking reaction reaction solution, that is, a cation obtained by dissociating the crosslinking reaction solution by an ion exchange resin is replaced with a hydrogen ion to provide crosslinking. The acidic source of the tank 16.

In some embodiments, the potassium ion produced by the potassium iodide in the cross-linking reaction solution is replaced with a hydrogen ion using an ion exchange resin. In some embodiments, the zinc ions produced by the zinc iodide in the cross-linking reaction solution are replaced with hydrogen ions using an ion exchange resin. The above ion exchange resin may be any resin or column capable of performing an ion exchange reaction. In one embodiment, the ion exchange resin of the present invention may be a cation exchange resin or an amphoteric ion exchange resin. In one embodiment, the cation exchange resin of the present invention can be a strongly acidic cation exchange resin.

In some embodiments, the ion exchange resin may completely replace the addition of the acidic solution, that is, the reaction solution in the crosslinking tank 16 substantially does not contain the added acidic solution, except for the boric acid used in the crosslinking treatment, for example, , sulfuric acid, acetic acid or gluconic acid. In other embodiments, the ion exchange resin may partially replace the addition of the acidic solution, i.e., the reaction solution in the crosslinking tank 16 may still contain a small amount of an additional acidic solution, such as sulfuric acid, acetic acid or gluconic acid.

In some embodiments, the reaction solution of the crosslinking tank 16 may contain no added acidic solution at all except for boric acid. In other implementations In the example, the reaction solution of the crosslinking tank 16 may contain 0.1 to 10% by weight, 0.1 to 5% by weight or 0.1 to 3% by weight of an additional acidic solution in addition to boric acid.

Next, the polarizing film precursor 10 is transferred to the water washing tank 18 to perform a washing treatment. The washing treatment can be carried out by immersing in water, spraying with a water jet, or a combination thereof. In some embodiments, the temperature of the cleaning process may range from 2 ° C to 45 ° C, and the time of the cleaning process may range from 2 seconds to 120 seconds.

Thereafter, the polarizing film precursor 10 is transferred to the drying furnace 20, and the polarizing film precursor 10 is dried to form a polarizing film 10'. In some embodiments, the drying process may have a temperature of from 35 ° C to 105 ° C, and the drying process may range from 10 seconds to 300 seconds.

In summary, the method for producing a polarizing film according to the present invention maintains the pH of the crosslinking reaction solution in an appropriate range by replacing the acidic solution with an ion exchange resin in the crosslinking treatment of the polarizing film. in. Thereby, it is possible to prevent a large amount of specific ions (for example, metal ions, non-metal ions) generated by dissociation of the external acidic solution from accumulating in the reaction solution, which may impair the quality of the prepared polarizing film.

The foregoing description of the various embodiments of the invention may be Those skilled in the art can readily design or modify other processes and structures based on the present invention to achieve the same objectives and/or achieve the same advantages as the embodiments of the present invention. It should be understood by those of ordinary skill in the art that such equivalents can be made without departing from the spirit and scope of the invention.

10‧‧‧Polarized film precursor

10'‧‧‧ polarizing film

12‧‧‧Swelling trough

14‧‧‧Dyeing tank

16‧‧‧crosslinking slot

18‧‧‧Washing tank

20‧‧‧ drying oven

30‧‧‧Transfer wheel

Claims (9)

A method for producing a polarizing film, comprising: performing a cross-linking treatment on a polarizing film precursor to form a polarizing film, the polarizing film precursor being a polyvinyl alcohol film, wherein the crosslinking treatment comprises: adding a reaction solution In a crosslinking tank, the reaction solution comprises monoboric acid, potassium monoiodide, zinc iodide or a combination thereof; and an ion exchange resin is ion-exchanged with a cation of a reaction solution in the crosslinking tank to Provide hydrogen ions. The method for producing a polarizing film according to claim 1, wherein the reaction solution in the crosslinking tank comprises: the potassium iodide, and the ion exchange resin replaces potassium ions of potassium iodide with hydrogen ions. The method for producing a polarizing film according to claim 1, wherein the reaction solution in the crosslinking tank comprises: the zinc iodide, and the ion exchange resin replaces the zinc ion of zinc iodide with hydrogen ions. . The method for producing a polarizing film according to claim 1, wherein the crosslinking treatment is carried out at pH 2 to pH 5. The method for manufacturing a polarizing film according to claim 1, further comprising: Before the crosslinking treatment, the polarizing film precursor is subjected to a swelling treatment and a dyeing treatment; and after the crosslinking treatment, the polarizing film precursor is sequentially subjected to a washing treatment and a drying treatment, wherein the drying treatment When the dyeing treatment and the crosslinking treatment are carried out, the stretching process of the polarizing film precursor is also included. The method for producing a polarizing film according to claim 1, wherein the reaction solution in the crosslinking tank substantially does not include sulfuric acid, acetic acid or gluconic acid. The method for producing a polarizing film according to claim 1, wherein the crosslinking treatment is carried out at 10 ° C to 70 ° C. The method for producing a polarizing film according to claim 1, wherein the ion exchange resin is a cation exchange resin or an amphoteric ion exchange resin. The method for producing a polarizing film according to claim 8, wherein the cation exchange resin is a strongly acidic cation exchange resin.