TWI659989B - Method for manufacturing a polarizer film - Google Patents

Abstract

A method for manufacturing a polarizing film includes passing a polarizing film precursor through a plurality of processing tanks in order to form a polarizing film. This method further includes, for at least one of the processing tanks, performing a total organic carbon amount monitoring program when the polarizing film precursor passes through the processing tank, and the total organic carbon of the tank liquid in the processing tank. When the amount exceeds a monitoring value of the processing tank, a tank liquid adjustment program is performed to reduce the total organic carbon content of the tank liquid in the processing tank to a monitoring value or less, wherein the monitoring value is 800 ppm or less.

Description

Method for manufacturing polarizing film

The present invention relates to a method for manufacturing a polarizing film, and more particularly to a method for manufacturing a polarizing film including a monitoring program.

A polarizing plate is an optical element widely used in liquid crystal displays. With the development of liquid crystal displays, the requirements for the quality of the liquid crystal displays connected with them are getting higher and higher. A polarizing plate is usually formed by attaching a protective film on a polarizing film, wherein the polarizing film can be obtained by passing a flexible polarizing film precursor through a plurality of processing tanks through a roll-to-roll process. Inspection can be performed after the polarizing plate is formed to eliminate defective products.

The invention provides a method for manufacturing a polarizing film, which includes a monitoring program to improve the quality of the polarizing film and a polarizing plate formed therefrom.

According to some embodiments, a method for manufacturing a polarizing film includes sequentially passing a polarizing film precursor through a plurality of processing tanks to form a polarizing film. This method further includes, for at least one of the processing tanks, performing a total organic carbon monitoring program when the polarizing film precursor passes through the processing tank, and during processing, When the total organic carbon content of the tank liquid in the tank exceeds a monitoring value of the processing tank, a tank liquid adjustment program is performed to reduce the total organic carbon content of the tank liquid in the processing tank to less than or equal to the monitoring value. The monitoring value 800 ppm or less.

In order to have a better understanding of the above and other aspects of the present invention, the following specific examples are described in detail below in conjunction with the accompanying drawings:

10‧‧‧Polarizer precursor

10’‧‧‧ polarizing film

20‧‧‧Treatment tank

21‧‧‧Swelling trough

22‧‧‧ Dyeing tank

23‧‧‧ Crosslinking tank

24‧‧‧ complementary color slot

25‧‧‧washing tank

26‧‧‧ drying furnace

30‧‧‧roller

40‧‧‧External bucket

41‧‧‧buffer tank

42‧‧‧filtration device

43‧‧‧Filter membrane

44‧‧‧filtration device

51‧‧‧arrow

52‧‧‧ Arrow

FIG. 1 illustrates a portion of an exemplary system for manufacturing a polarizing film.

FIG. 2 illustrates a portion of an exemplary system for manufacturing a polarizing film.

The method for manufacturing a polarizing film according to an embodiment includes sequentially passing a polarizing film precursor through a plurality of processing tanks to form a polarizing film. The method further includes, for at least one of the processing tanks, performing a total organic carbon (TOC) amount monitoring program when the polarizing film precursor passes through the processing tank, and the total amount of the tank liquid in the processing tanks. When the organic carbon content exceeds a monitoring value of the processing tank, a tank liquid adjustment program is performed to reduce the total organic carbon content of the tank liquid in the processing tank to a monitoring value or less, wherein the monitoring value is 800 ppm or less.

A procedure for sequentially passing a polarizing film precursor through a plurality of processing tanks to form a polarizing film will be described here. Please refer to FIG. 1, which illustrates a part of an exemplary system for manufacturing a polarizing film. The exemplary system shown in FIG. 1 includes a swelling tank 21, a dyeing tank 22, a crosslinking tank 23, a washing tank 25, and a drying furnace 26. The processing tank and processing equipment can be selectively increased, decreased, repeatedly configured, Or make other adjustments. For example, a complementary color tank 24 may be additionally provided between the cross-linking tank 23 and the cleaning tank 25. A polarizing film precursor 10 is conveyed by a plurality of rollers 30 and sequentially passes through each processing tank and processing equipment as indicated by the arrow to form a polarizing film 10 '. The polarizing film 10 ′ can convert light from non-polarized light to polarized light. For example, the polarizing film 10 ′ is formed by a polyvinyl alcohol (PVA) film that adsorbs and aligns a dichroic pigment or is formed by a liquid crystal material doped with absorbing dye molecules. . Specific examples for this are provided below. It can be understood that these embodiments are not intended to limit the present invention. In addition, elements, conditions, and features in one embodiment can be advantageously incorporated into another embodiment without further enumeration.

The material of the polarizing film precursor 10 includes polyvinyl alcohol or other suitable materials. For example, the polarizing film precursor 10 may be a PVA film. Polyvinyl alcohol can be formed by saponifying polyvinyl acetate. According to some embodiments, the saponification degree of polyvinyl alcohol may be 85 mol%, 90 mol%, or 99 mol% to 100 mol%. According to some embodiments, polyvinyl acetate may be a monopolymer of vinyl acetate, or a copolymer of vinyl acetate and vinyl acetate and other copolymers of other monomers capable of copolymerizing with vinyl acetate, said other Monomers can be unsaturated carboxylic acids (e.g. acrylic acid, methacrylic acid, ethyl acrylate, propyl n-acrylate, methyl methacrylate), olefins (e.g. ethylene, propylene, 1-butene, 2-methylpropene) , Unsaturated sulfonic acids (such as ethyl vinyl ether, methyl vinyl ether, n-propyl vinyl ether, isopropyl vinyl ether), or vinyl ethers, and the like. In some embodiments, the polyvinyl alcohol is modified, such as polyvinyl formal modified with aldehydes, polyvinyl acetal, polyvinyl acetaldehyde, or polyvinyl butyral, and the like. Polarized light The film precursor 10 sometimes includes a residual plasticizer, which is one of the sources of total organic carbon in the tank fluid that is subsequently passed. Plasticizers are, for example, polyhydric alcohols and their condensates, including glycerol, diglycerol, triglycerol, ethylene glycol, propylene glycol, polyethylene glycol, and the like. In some cases, a larger total organic carbon source is the residual glycerol included in the polarizing film precursor 10. In some embodiments, the thickness of the polarizing film precursor 10 is about 1 μm to 200 μm, preferably 10 μm to 100 μm, and more preferably 20 μm to 80 μm.

The polarizing film precursor 10 may be first guided to the swelling tank 21 via a roller 30 to perform a swelling process on the polarizing film precursor 10. The swelling treatment can remove foreign matter on the surface of the polarizing film precursor 10 and the plasticizer in the polarizing film precursor 10, and is helpful for the subsequent dyeing treatment and cross-linking treatment. The conditions of the swelling treatment are not particularly limited, as long as the aforementioned effects can be achieved without causing the polarizing film precursor 10 to be extremely dissolved or transparent to disappear. The bath liquid in the swelling tank 21 mainly contains pure water, which reacts with the polarizing film precursor 10. In some embodiments, the temperature of the swelling treatment is 10 ° C to 50 ° C, such as 20 ° C to 50 ° C, and the time of the swelling treatment is 5 seconds to 300 seconds, such as 20 seconds to 240 seconds.

According to some embodiments, an extended polarizing film precursor 10 may be used. According to other embodiments, an extension process may be performed on the polarizing film precursor 10 in a system for manufacturing a polarizing film. The stretching treatment may be performed while passing through the swelling tank 21 and / or the subsequent dyeing tank 22 and the crosslinking tank 23. For example, the roller 30 provided at the inlet of the swelling tank 21 and the roller 30 provided at the outlet of the swelling tank 21 may have a peripheral speed difference to perform a uniaxial stretching process.

According to some embodiments, the roller 30 provided at the exit of the swelling tank 21 It can be a pair of rollers 30 located on two opposite sides of the polarizing film precursor 10, which clamps or even exerts pressure on the polarizing film precursor 10 to prevent the liquid in the swelling tank 21 from being brought to the post-processing. The tank caused contamination of the processing tank. According to some embodiments, the bath liquid from the swelling tank 21 may be scraped off with a spatula before the polarizing film precursor 10 enters the processing tank disposed after. According to some embodiments, the film surface of the polarizing film precursor 10 may be washed before the polarizing film precursor 10 enters the processing tank disposed in the rear. In particular, the fresh polar water may be used to replace the non-circulating water to rinse the polarizing film precursor 10. Film surface. The aforementioned means can be combined and matched to achieve the purpose of avoiding contamination of other treatment tanks.

The polarizing film precursor 10 is then guided to the dyeing tank 22 via a roller 30 to perform a dyeing process on the polarizing film precursor 10. The bath in the dyeing tank 22 contains a dye. The dyeing agent can be a dichroic dye, or other suitable water-soluble dipigment dyes. In some embodiments, the stain comprises iodine and potassium iodide. For example, the colorant 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 process is 10 ° C to 50 ° C, such as 20 ° C to 40 ° C, and the time of the dyeing process is 10 seconds to 600 seconds, such as 30 seconds to 200 seconds. In order to make the dyeing process better, other additives may be included in the bath. For example, in some embodiments, additional boric acid is added. In some embodiments, the extension treatment is performed at the same time as the dyeing treatment. In some embodiments, the means described above can be used to avoid contamination of a subsequent processing tank.

The polarizing film precursor 10 is then guided to the crosslinking tank 23 via a roller 30 to perform a crosslinking treatment on the polarizing film precursor 10. The bath in the crosslinking tank 23 contains a crosslinking agent. As the cross-linking agent, boric acid can be used. The tank liquid in the cross-linking tank 23 may further contain an optical adjusting agent. As the optical modifier, potassium iodide, zinc iodide, or a combination thereof can be used. The hue of the polarizing film can be adjusted by changing the concentration of the optical adjusting agent. In some embodiments, the bath is an aqueous solution containing 1 to 10 parts by weight of boric acid and 1 to 30 parts by weight of potassium iodide. In some embodiments, the temperature of the crosslinking treatment may be 10 ° C to 70 ° C, such as 50 ° C to 65 ° C, and the time of the crosslinking treatment is 1 second to 600 seconds, such as 20 seconds to 300 seconds. In some embodiments, the extension treatment is performed at the same time as the crosslinking treatment. According to some embodiments, from the swelling process to the cross-linking process, the stretch ratio accumulated by the polarizing film precursor 10 is about 4.5 to 8 times, for example, 5 to 7 times. In some embodiments, the means described above can be used to avoid contamination of a subsequent processing tank.

Optionally, in some embodiments, the polarizing film precursor 10 is then guided to the color compensation tank 24 via the roller 30 to perform a color compensation process on the polarizing film precursor 10. The color compensation process further adjusts the polarizing film precursor 10 to achieve the desired hue of the polarizing film 10 ′. The tank liquid in the complementary color tank 24 may have a similar or even the same structure as the tank liquid in the cross-linking tank 23. In some embodiments, the temperature of the complementary color process is 10 ° C. to 70 ° C., and the duration of the complementary color process is 1 second to 15 minutes, such as 1 second to 5 minutes.

According to some embodiments, the processing tanks described so far may be separately connected with a filtering device for processing the tank liquid in the tank, so as to keep the tank liquid clean and avoid the Contamination affects the quality of the polarizing film 10 'produced. Referring to FIG. 2, a processing tank 20, such as any one of the aforementioned swelling tank 21, dyeing tank 22, cross-linking tank 23, and color supplementing tank 24, may be connected to an external barrel tank 40. The outer tub groove 40 is connected to a buffer groove 41. The buffer tank 41 is further connected to a filtering device 42. The filtering device 42 is, for example, an ultrafilter, and the molecular weight retained by the filtering membrane 43 may be 1000 to 10,000 Daltons. The filtering efficiency of the filtering device 42 may be greater than 50%. According to some embodiments, the filter membrane 43 may be replaced when a pressure difference occurs before and after the aqueous solution passes through the filter membrane 43. According to some embodiments, the tank liquid in the processing tank 20 generates a filtered aqueous solution after passing through the filtering device 42, which can be introduced into the external barrel tank 40 as shown by the arrow 51, and the concentrated aqueous solution can be guided as shown by the arrow 52.向 Buffer tank 41. The aqueous solution in the buffer tank 41 is introduced into the filtering device 42 again. The aqueous solution in the outer tub 40 is introduced into the processing tank 20 and becomes the tank liquid therein. Prior to this, in some embodiments, another filtering device 44 may be passed first. The filtering device 44 may include suitable filtering means such as activated carbon or a filter bag. In some embodiments, a particle size of about 2 mm to 500 μm can be used. In some embodiments, activated carbon having a hardness of 90% or more may be used. In some embodiments, the absorption capacity of iodine per gram of activated carbon may be greater than or equal to 1000 mg. In some embodiments, a filter bag with a pore size of less than 1 μm can be used. According to some embodiments, the filter bag may be replaced when a pressure difference occurs before and after the aqueous solution passes through the filter bag. According to some embodiments, the temperature of the filtering device 44 may be lowered to encourage precipitation of impurities that are desired to be filtered out and be capable of being filtered by the filtering device 44. In some embodiments, the temperature of the filtering device 44 is lowered below 20 ° C. According to some embodiments, instead of lowering the temperature of the filtering device 44, the temperature of the aqueous solution may be reduced before the aqueous solution enters the filtering device 44. Degree, can also achieve the effect of promoting the precipitation of impurities, without special restrictions.

Referring to FIG. 1 again, the polarizing film precursor 10 is then guided to the cleaning tank 25 via the roller 30 to perform a cleaning process on the polarizing film precursor 10. The washing treatment can be performed by immersing in water, spraying with a water jet, or a combination thereof. In some embodiments, the temperature of the washing process is 2 ° C to 45 ° C, and the time of the washing process is 2 seconds to 120 seconds.

The polarizing film precursor 10 after the cleaning process can then be guided to the drying furnace 26 via the roller 30 to perform a drying process on the polarizing film precursor 10, and the polarizing film 10 'after the drying process. In some embodiments, the temperature of the drying process is 35 ° C to 105 ° C, and the time of the drying process is 10 seconds to 300 seconds.

In the method for manufacturing a polarizing film according to the embodiment, at least one processing tank among a plurality of processing tanks (for example, a swelling tank 21 to a complementary color tank 24) used in the formation of the polarizing film is placed on the polarizing film precursor. When passing through the processing tank, that is, in the process of forming a polarizing film, a total organic carbon amount monitoring program is performed. The total organic carbon content in the bath can reflect the amount of impurities in it. These impurities are, for example, plasticizers remaining on the polarizing film precursor, organic substances such as glycerol, and polarizing film precursor materials such as PVA dissolved by the bath, etc., which will be affected by the width of the polarizing film precursor and the groove. Influence of factors such as liquid composition and tank temperature. When the amount of impurities in the bath is too high, whether it forms precipitates or suspended particles, it is easy to attach to the precursor of the polarizing film, resulting in defects in the produced polarizing film and polarizing plate, resulting in quality and yield. decline. For example, it may be, but is not limited to, the optical properties are affected by defects. According to the embodiment, it is ensured by monitoring the total organic carbon content that can reflect the impurities in the bath. The cleanliness of the bath is controlled to a certain degree, so the defects of the polarizing film and the polarizing plate can be reduced. Compared with the inspection after the finished product, the adjustment can be performed in a more timely manner, so instead of simply eliminating defective products, it can improve quality and yield.

In the total organic carbon monitoring program, the monitoring value for each processing tank is 800 ppm or less. According to some embodiments, the at least one processing tank to be monitored may include a swelling tank, and the monitoring value of the swelling tank is 800 ppm or less. According to some embodiments, the at least one processing tank for monitoring may include a dyeing tank, and the monitoring value of the dyeing tank is less than or equal to 500 ppm, for example, set between 50 ppm and 500 ppm, such as between 230 ppm and 340 ppm, and more preferably It is set between 50ppm and 230ppm. According to some embodiments, the at least one processing tank for monitoring may include a cross-linking tank, and the monitoring value of the cross-linking tank is less than or equal to 250 ppm, for example, set between 5 ppm and 250 ppm, such as between 50 ppm and 130 ppm, more It is better to set it between 5ppm ~ 50ppm. According to some embodiments, the at least one processing tank for monitoring may include a complementary color tank, and the monitored value of the complementary color tank is less than or equal to 150 ppm, for example, set between 5 ppm and 150 ppm, such as between 40 ppm and 90 ppm, and more preferably The ground is set between 5ppm and 40ppm. According to some embodiments, the at least one processing tank to be monitored includes a processing tank configured first and a processing tank configured rearward, and a monitoring value of the processing tank configured later is less than or equal to a monitoring value of the processing tank configured earlier. Wherein, the processing tanks disposed in front and the processing tanks disposed in the rear may be the same type or different types of processing tanks. For example, in one embodiment, the monitoring values of two dyeing tanks, two cross-linking tanks, and a complementary color tank that are set in sequence can be set at 340ppm, 250ppm, 70ppm, 70ppm, 50ppm. In one embodiment, the monitoring values of the two dyeing tanks, two cross-linking tanks, and a complementary color tank that are sequentially arranged can be set to 230 ppm, 230 ppm, 130 ppm, 120 ppm, and 90 ppm, respectively. In one embodiment, the monitoring values of the two dyeing tanks, three cross-linking tanks, and one complementary color tank that are sequentially arranged can be set to 230 ppm, 230 ppm, 60 ppm, 50 ppm, 50 ppm, and 40 ppm, respectively.

According to some embodiments, the total organic carbon content monitoring program may include taking a portion of the tank liquid from the processing tank as a sample and analyzing the sample with a total organic carbon analyzer. Specifically, you can first use a standard solution to establish a total organic carbon calibration curve. After the total organic carbon content calibration line is established, the tank liquid to be measured is taken out from the processing tank into a sample bottle, and the total organic carbon content analyzer is used for measurement. For example, Shimadzu's TOC-V automatic sample injection series can be used. The measurement procedure can include heating to a set temperature such as 680 ° C, introducing an acid reagent such as phosphoric acid or 2N hydrochloric acid to remove inorganic carbon, and the instrument The sample pipette is inserted into a vial for analysis. However, if there are other suitable total organic carbon analysis methods, they can also be used without special restrictions. According to some embodiments, the total organic carbon monitoring program is periodically monitored. That is, sampling and analysis can be performed at regular intervals.

When the total organic carbon content of the tank liquid exceeds the monitoring value of the processing tank, a tank liquid adjustment procedure is performed to reduce the total organic carbon content of the tank liquid in the processing tank to less than or equal to the monitoring value. According to some embodiments, a filtering device for the bath liquid in the processing tank may be activated. According to some embodiments, a filtering device for cleaning the bath liquid in the processing tank is available. According to some embodiments, a filtering device for the bath liquid in the processing tank may be replaced. According to some embodiments, the tank used in the processing tank can be reduced The temperature of a liquid filtration device. As described in the paragraph with respect to FIG. 2, filtration means such as ultrafiltration and / or activated carbon is used in the bath adjustment procedure. According to some embodiments, the tank liquid in the processing tank may be replaced. The foregoing means may be combined and matched, or other adjustment methods may be adopted in parallel, and there is no particular limitation.

In summary, although the present invention has been disclosed as above with the embodiments, it is not intended to limit the present invention. Those with ordinary knowledge in the technical field to which the present invention pertains can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be determined by the scope of the attached patent application.

Claims (13)

A method for manufacturing a polarizing film, comprising: sequentially passing a polarizing film precursor through a plurality of processing tanks to form a polarizing film, wherein the processing tanks include a swelling tank, a dyeing tank, and a cross-linking tank; And a complementary color tank; and for at least one of the processing tanks, a total organic carbon amount monitoring program is performed when the polarizing film precursor passes through the at least one processing tank, and in the at least one processing tank When a total organic carbon content in the tank fluid exceeds a monitoring value of the at least one processing tank, a tank fluid adjustment program is performed to reduce the total organic carbon content of the tank fluid in the at least one processing tank to less than or equal to the A monitoring value, wherein the monitoring value is less than or equal to 800 ppm, the at least one processing tank includes a processing tank configured earlier and a processing tank configured later, and the monitoring value of the processing tank configured later is less than or equal to the configuration This monitoring value of the previous processing tank. The method according to item 1 of the scope of patent application, wherein the monitoring value of the swelling tank is 800 ppm or less, and / or wherein the monitoring value of the dyeing tank is 500 ppm or less, and / or wherein the crosslinking tank is The monitoring value of 250 ppm is less than or equal to, and / or the monitoring value of the complementary color tank is less than or equal to 150 ppm. The method according to item 1 of the scope of patent application, wherein the source of the total organic carbon content is a plasticizer and / or a polarizing film precursor material dissolved out. The method according to item 1 of the patent application scope, wherein the total organic carbon content monitoring program comprises: taking a part of the bath liquid from the at least one processing tank as a sample; and analyzing the sample with a total organic carbon analyzer. . The method according to item 1 of the scope of patent application, wherein the total organic carbon monitoring program is regularly monitored. The method according to item 1 of the scope of patent application, wherein the bath adjusting procedure comprises at least one of the following procedures: activating a filtering device for the bath liquid in the at least one treatment tank; cleaning for the A filtering device for the bath liquid in at least one processing tank; replacing a filtering device for the bath liquid in the at least one processing tank; lowering a filtering device for the bath liquid in the at least one processing tank Temperature; and replacing the bath in the at least one treatment bath. The method according to item 6 of the patent application scope, wherein the filtering device comprises activated carbon or the filtering device is an ultrafilter. The method according to item 7 of the scope of patent application, wherein the ultrafilter has a filter membrane, and the molecular weight retained by the filter membrane can be 1000 to 10,000 Daltons, and / or wherein the filtering efficiency of the filtering device is greater than 50 %. The method according to item 6 of the scope of patent application, wherein a filtered aqueous solution is generated after the tank fluid passes through the filtering device, the filtered aqueous solution is introduced into an external tank, and the aqueous solution in the external tank is Into the processing tank. The method according to item 9 of the scope of patent application, wherein the aqueous solution in the external tank passes through another filtering device before being introduced into the processing tank. The method according to item 10 of the scope of patent application, wherein the another filtering device comprises activated carbon or a filter bag, wherein a particle diameter of the activated carbon is 2 mm to 500 μm, and / or a hardness of the activated carbon is greater than or equal to 90% And / or wherein the absorption capacity of iodine per gram of activated carbon is 1000 mg or more. The method according to item 6 of the application scope, wherein the temperature of the filter device is lowered to below 20 ° C. in a procedure of reducing the temperature of the filter device for the bath liquid in the at least one treatment tank. The method according to item 6 of the scope of patent application, wherein the bath solution passes through the filtration device to produce a concentrated aqueous solution, the concentrated solution is introduced into a buffer tank, and the aqueous solution in the buffer tank is introduced into the filtration device .