JP6245878B2 - Method for producing polyene-based polarizing film (film), polyene-based polarizing film, laminated polarizing film, and display device - Google Patents

Description

  The present invention relates to a method for producing a polyene polarizing film, a polyene polarizing film, a laminated polarizing film, and a display device.

  With the spread of organic light emitting display devices using OLEDs (organic light emitting diodes (diodes)), it is required to increase the transmittance of the polarizing film. On the other hand, an iodine-based polarizing film is known as a polarizing film used for various display devices. Iodine polarizing films are widely used.

  In the iodine-based polarizing film, the configuration that contributes to polarized light (that is, the configuration that absorbs visible light) is iodine. Therefore, in order to increase the transmittance, it is necessary to reduce the amount of iodine in the polarizing film. However, since iodine sublimates at high temperature and high humidity, when the amount of iodine in the polarizing film is reduced, iodine in the polarizing film is insufficient, and as a result, the degree of polarization may be significantly reduced. For this reason, the iodine-type polarizing film having a high transmittance (for example, a transmittance of 45% or more) deteriorates the long-term reliability of the polarizing film at high temperature and high humidity.

  As a polarizing film expected to solve such a problem, a dye-based polarizing film and a polyene-based polarizing film disclosed in Patent Document 1 are known. The dye-based polarizing film exhibits excellent heat resistance even when the transmittance is high. However, the dye-based polarizing film has a problem that the degree of polarization tends to decrease when the transmittance is high.

  On the other hand, the polyene polarizing film has a merit that the degree of polarization is slightly inferior to that of the iodine polarizing film, but is highly reliable at high temperature and high humidity even when the transmittance is high. This is because, in the polyene polarizing film, the structure contributing to polarized light (that is, the structure absorbing visible light) is polyene (specifically, a carbon double bond). Carbon double bonds are less susceptible to temperature and humidity. Therefore, the polyene polarizing film is fundamentally highly durable to high temperatures and high humidity. For this reason, the polyene polarizing film has attracted much attention as a polarizing film for display devices.

  As a method for producing a polyene polarizing film, a method of dehydrating polyvinyl alcohol using an acid catalyst is known. Specifically, the polyvinyl alcohol film is impregnated with an aqueous solution of an acid catalyst. Next, the polyvinyl alcohol film is subjected to a heat treatment to cause the polyvinyl alcohol to undergo a dehydration reaction. Thereby, a polyene type polarizing film is produced. As the acid catalyst, hydrochloric acid or sulfuric acid is used.

JP 2006-99076 A

  However, the conventional polyene polarizing film has a problem that the optical properties are still insufficient. In particular, in recent years, a polyene polarizing film having a high degree of polarization while realizing high transmittance has been required.

  Therefore, the present invention has been made in view of the above problems, and an object of the present invention is to produce a novel and improved polarizing film capable of producing a polarizing film having good optical properties. It is to provide a method and the like.

  In order to solve the above problems, according to an aspect of the present invention, a step of producing a dehydrated film by causing a polyvinyl alcohol film to undergo a dehydration reaction using an acid catalyst, and a pH of 4. A step of hydrating a dehydrated film by impregnating an aqueous solution for hydration at 0 ° C. or lower and 85 ° C. or higher for 0.5 to 60 (min), and before or after hydrating the dehydrated film, And a step of wet-stretching in an acidic aqueous solution. A method for producing a polyene-based polarizing film is provided.

  According to this aspect, since the dehydrated film is hydrated before or after the wet stretching process, it is possible to produce a polyene-based polarizing film having a high degree of polarization while realizing high transmittance.

  Here, the method may further include a step of producing a polyvinyl alcohol film using a coating liquid containing polyvinyl alcohol and an acid catalyst.

  According to this aspect, since a high concentration acid catalyst can be uniformly dispersed in the polyvinyl alcohol film, a large number of carbon double bonds can be uniformly formed without accurately controlling the environmental temperature or the like as in the prior art. A polyene-based polarizing film formed in the above can be produced. Therefore, according to this viewpoint, it is possible to stably produce a polyene polarizing film having both high degree of polarization and high transmittance, that is, a polarizing film having good optical characteristics.

  In addition, the method further includes a step of producing a dry stretched film by dry stretching the polyvinyl alcohol film, and a dehydrated film can be produced by causing the dry stretched film to undergo a dehydration reaction using an acid catalyst. Good.

  According to this aspect, since the dry stretching treatment and the dehydration reaction (dehydration treatment) are performed in separate steps, it is possible to produce a polyene polarizing film having a high degree of polarization while realizing high transmittance.

  According to another aspect of the present invention, there is provided a polyene polarizing film produced by the above-described method for producing a polyene polarizing film.

  The polyene polarizing film according to this aspect has both a high degree of polarization and a high transmittance, and is more suitable for an organic light emitting display device, for example, because the reliability (stability) is superior to that of an iodine type polarizing film. is there.

  According to another aspect of the present invention, there is provided a polyene polarizing film characterized by having a transmittance of 44.5% or more and a polarization degree of 98.0% or more.

  The polyene polarizing film according to this aspect has both a high degree of polarization and a high transmittance, and is more suitable for an organic light emitting display device, for example, because the reliability (stability) is superior to that of an iodine type polarizing film. is there.

  Here, the film thickness may be less than 10 μm.

  Since the polyene polarizing film according to this aspect has a film thickness of less than 10 μm, even when the polyene polarizing film according to this aspect is applied to a large screen organic light emitting display device, the shrinkage of the polyene polarizing film is reduced. be able to. Therefore, according to this viewpoint, the warp of the organic light emitting display device can be reduced.

  According to another aspect of the present invention, there is provided a laminated polarizing film comprising the polyene polarizing film.

  The laminated polarizing film according to this aspect is suitable for, for example, an organic light emitting display device because it has both a high degree of polarization and a high transmittance.

  According to another aspect of the present invention, there is provided a display device including the laminated polarizing film described above.

  The display device according to this aspect has a laminated polarizing film that achieves both high degree of polarization and high transmittance, and thus has various optical characteristics.

  Here, the display device may be an organic light emitting display device using an organic light emitting diode.

  A polarizing film applied to an organic light emitting display device using an organic light emitting diode is required to have high transmittance, high degree of polarization, and high reliability, but the polyene polarizing film according to this aspect satisfies these requirements. All are met. Therefore, according to this aspect, there is provided an organic light emitting display device that satisfies all of the optical characteristics (high transmittance, high polarization degree, and high reliability) required for the organic light emitting display device.

  As described above, according to the present invention, since the dehydrated film is hydrated before or after the wet stretching treatment, a polyene-based polarizing film having a high degree of polarization while realizing high transmittance, that is, polarized light with good optical characteristics. A film can be produced.

It is explanatory drawing which compares and shows the polarizing film which concerns on embodiment of this invention, and the conventional polarizing film.

  Exemplary embodiments of the present invention will be described below in detail with reference to the accompanying drawings. In addition, in this specification and drawing, about the component which has the substantially same function structure, the duplicate description is abbreviate | omitted by attaching | subjecting the same code | symbol. In this embodiment, the pH of the aqueous solution for hydration is a value at 85 ° C.

(Production method of polarizing film)
First, the manufacturing method of the polarizing film which concerns on this embodiment is demonstrated. The manufacturing method according to the present embodiment schematically includes a step (first step) of producing a polyvinyl alcohol film (acid catalyst-impregnated film) using a coating liquid containing an acid catalyst and polyvinyl alcohol, and a polyvinyl alcohol film. The step of producing a dehydrated film (second step) by performing the dry stretching and the dehydration process in separate steps, and the step of producing a hydrated film by hydrating the wet stretched film (third step) And a step (fourth step) of producing a wet stretched film by wet-stretching the hydrated film.

(First step)
In the first step, first, a coating liquid containing an acid catalyst and polyvinyl alcohol is prepared. Specifically, polyvinyl alcohol is poured into water, and the mixture of water and polyvinyl alcohol is heated while stirring to sufficiently dissolve the polyvinyl alcohol in water. Next, an acid catalyst and a leveling agent are added to the polyvinyl alcohol aqueous solution and stirred to prepare a coating solution.

  Next, the coating solution is coated on a substrate (for example, an unstretched film) and dried to form an acid catalyst-impregnated film on the substrate. Here, the layer thickness of the acid catalyst-impregnated film is not particularly limited, but it is preferable that the film thickness of the finally produced polyene polarizing film is adjusted to be less than 10 μm.

  Thus, in this embodiment, the acid catalyst is mixed in the coating solution in advance. Thereby, the acid concentration in the acid catalyst-impregnated film can be made more uniform. In other words, the acid catalyst can be more uniformly dispersed in the acid catalyst-impregnated film.

  The type of the acid catalyst is not particularly limited, but is preferably a low volatility acid catalyst. When the acid catalyst has low volatility, evaporation of the acid catalyst is suppressed at the time of polyene production, so that the acid concentration in the acid catalyst-impregnated film can be made more uniform.

  More specifically, the acid catalyst preferably has a weight reduction rate at 100 ° C. of less than 3% by mass. When the weight reduction rate at 100 ° C. is less than 3% by mass, the acid concentration in the acid catalyst-impregnated film can be made more uniform during polyene production.

  Examples of the acid catalyst that satisfies the above requirements include organic acids. The organic acid may have, for example, any one functional group selected from the group consisting of a carboxylic group and a sulfo group. A specific configuration of the organic acid is represented by R—X. R is not particularly limited as long as it is a compound composed of carbon, hydrogen, and fluorine. R is, for example, any one selected from an alkyl group, a perfluoroalkyl group, an aromatic functional group, and a fluorine-substituted aromatic functional group. X is any one functional group selected from the group consisting of a carboxyl group and a sulfo group. Specific examples of the organic acid include p-toluenesulfonic acid.

  For example, the weight reduction rate of paratoluenesulfonic acid when heated at 100 ° C. for 10 minutes is the detection limit (10 ppm or less) of the analytical instrument. In addition, regarding an analytical instrument, ion chromatography (ion chromatography) etc. are mentioned. In the analysis method, a gas generated by heating a sample on a heating plate is collected. Subsequently, the gas is replaced by bubbling in water. Quantitative analysis is performed by substituted ion chromatography.

  In addition, since the saturated aqueous solution density | concentration of paratoluenesulfonic acid is higher than hydrochloric acid, when paratoluenesulfonic acid is used as an acid catalyst, a higher concentration acid catalyst can be disperse | distributed in an acid catalyst impregnation film. In addition, although the acid catalyst remaining in the polyene polarizing film may reduce the durability of the polyene polarizing film, paratoluenesulfonic acid is more easily removed from the polyene polarizing film than hydrochloric acid.

  Although the content ratio of the acid catalyst is not particularly limited, for example, it is preferably 2% by mass or more and 10% by mass or less, and more preferably 4.0% by mass or more and 10.0% by mass or less with respect to the mass of polyvinyl alcohol. Thereby, the time which reaction requires can be reduced and a side reaction can be suppressed. Furthermore, the dehydration reaction can be easily controlled, and corrosion of the production apparatus can be suppressed. For example, when the content ratio of the acid catalyst is less than 4% by mass, at the dehydration temperature of 140 ° C., it takes 10 minutes or more to start the reaction and a long time to complete the reaction (however, the reaction itself proceeds) To do).

  The content ratio of the acid catalyst is most preferably 5% by mass. When the content ratio of the acid catalyst is this value, a polyene polarizing film having both high transmittance and high degree of polarization is produced. The degree of polarization of the polyene polarizing film can be controlled by the content ratio of the acid catalyst. The more acid catalyst, the higher the degree of polarization because the amount of polyene (ie carbon double bond) in the polyvinyl alcohol increases.

  On the other hand, the transmittance tends to increase as the distribution of the components contributing to polarization (carbon double bonds in the polyene polarizing film, iodine in the iodine polarizing film, etc.) is uniform. In the conventional method for producing a polyene polarizing film, the acid concentration in the acid catalyst-impregnated film cannot be made uniform, so the distribution of carbon double bonds in the polyene polarizing film varies. For this reason, not only the degree of polarization varies, but also the transmittance varies. On the other hand, in this embodiment, since the acid catalyst is mixed in advance in the polyvinyl alcohol, the acid catalyst having a desired concentration can be more uniformly dispersed in the acid catalyst-impregnated film. Therefore, in this embodiment, it becomes possible to produce a polyene polarizing film that achieves both high transmittance and high degree of polarization. In addition, although it demonstrates in detail in the modification mentioned later, even when it is a case where a polyvinyl alcohol film is impregnated with the acid catalyst aqueous solution similarly to the past, by performing the third step to the fourth step, It becomes possible to produce a polyene polarizing film having both transmittance and high degree of polarization.

  The leveling agent is not particularly limited, but a leveling agent such as a perfluoroalkylethylene oxide adduct is suitable.

(Second step)
In the second step, dry stretching and dehydration treatment of the acid catalyst-impregnated film are performed in separate steps. Specifically, first, a dry stretched film is produced by dry stretching the acid catalyst-impregnated film in a predetermined direction. Here, the dry stretching is stretching performed in a dry gas (for example, in a dry atmosphere). In addition, the heating temperature at the time of dry extending | stretching and a draw ratio are not restrict | limited in particular. Further, dry stretching and wet stretching described later may be performed together with the substrate.

  Next, polyene (carbon double bond) is formed by subjecting polyvinyl alcohol in the dry stretched film to a dehydration reaction (dehydration treatment). Specifically, the polyvinyl alcohol film is heated to cause the polyvinyl alcohol to undergo a dehydration reaction. In this way, a dehydrated film (dehydrated dry stretched film) is produced. Here, in this embodiment, since the acid catalyst is uniformly distributed in the acid catalyst-impregnated film, the carbon double bond is uniformly formed in the dehydrated film. The heating temperature and heating time are not particularly limited, and may be set as appropriate according to the desired transmittance and polarization degree. In the manufacturing method of this embodiment, since an acid catalyst is previously contained in the coating liquid, dehydration is performed using this acid catalyst. In the second step, since the film that has been dry-drawn in advance, that is, the dry-stretched film can be dehydrated, the orientation of the carbon double bonds after the dehydration treatment can be made uniform.

  Here, the dehydration reaction may be performed by immersing the polyvinyl alcohol film in a high-temperature oil bath. This treatment also produces a polyene polarizing film having a high transmittance and a high degree of polarization. Moreover, when performing a dehydration reaction by immersing a polyvinyl alcohol film in an oil bath, the effect that the quality of a polyene type polarizing film is stabilized is also acquired.

(Third step)
In the third step, the dry stretched film is impregnated with an aqueous solution for hydration at pH 4.0 or lower and 85 ° C. or higher for 0.5 to 60 (min). Thereby, the reaction shown in the following reaction formula (1) proceeds. That is, the dry stretched film is hydrated.

  In addition, as above-mentioned, the double bond in a dry stretched film decreases by hydrating a dry stretched film. Therefore, it is predicted that the transmittance of the dry stretched film increases and the degree of polarization decreases. However, as a result of experiments conducted by the present inventors, it has been found that the degree of polarization hardly fluctuates until only a certain impregnation time, and only the transmittance increases. The upper limit of the impregnation time is 60 min. On the other hand, if the impregnation time is too short, hydration hardly proceeds and the hydration effect is hardly obtained. The lower limit of the impregnation time is 0.5 min. That is, the impregnation time is 0.5 to 60 min.

  Moreover, the pH of the aqueous solution for hydration becomes 3.0 or more and 4.0 or less. The temperature of the aqueous solution for hydration is 85 ° C or higher and 100 ° C or lower. When the pH and temperature of the aqueous solution for hydration are values within these ranges, the transmittance and the degree of polarization are improved. As will be described later, the temperature of the aqueous solution for hydration used for the hydration treatment is higher than that of the acidic aqueous solution used for wet stretching. The type of aqueous solution for hydration is not particularly limited, but for example, an aqueous boric acid solution.

  The method for impregnating the dry stretched film with the aqueous solution for hydration is not particularly limited. For example, the dry stretched film may be immersed in an aqueous hydrating bath, or the dry stretched film may be installed in a space sprayed with the aqueous hydrating solution. Moreover, when the aqueous solution for hydration becomes a boric acid aqueous solution, the third step and the fourth step may be performed in the same boric acid aqueous solution bath. In this case, first, in the third step, the dry stretched film is held in a boric acid aqueous solution bath at 85 ° C. or lower. Next, the boric acid aqueous solution is cooled to 65 ° C. or lower, and wet stretching is performed. In addition, when impregnating the dry stretched film with the aqueous solution for hydration, it is preferable to apply a force (Tension) to the dry stretched film so that the dry stretched film does not shrink.

(Fourth step)
In the fourth step, the hydrated film is put into an acidic aqueous solution bath, and the hydrated film is stretched in the same direction as dry stretching in the acidic aqueous solution bath. That is, the hydrated film is wet-stretched. Thereby, a wet stretched film is produced. The wet stretching is stretching performed in an aqueous solution bath. The kind in particular of acidic aqueous solution is not restrict | limited, The acidic aqueous solution used by the conventional wet extending | stretching is used. The acidic aqueous solution is, for example, a boric acid aqueous solution. Further, the wet stretching ratio is not particularly limited, but is 1.5 times, for example. When the dry stretch ratio is 4 times and the wet stretch ratio is 1.5 times, the polyvinyl alcohol film is stretched 6 times in total.

  Moreover, the temperature of acidic aqueous solution will be 65 degrees C or less. When the temperature of the acidic aqueous solution is within this range, the transmittance and the degree of polarization are further improved. In addition, the lower limit of the temperature of acidic aqueous solution is not restrict | limited in particular, For example, what is necessary is just the temperature comparable as the acidic aqueous solution used by the conventional wet extending process. Subsequently, a polarizing film is produced by drying the wet stretched film.

  Here, the order in which the third step and the fourth step are performed is not particularly limited. That is, in the above-described processing, the third step is performed before the fourth step, but the third step may be performed after the fourth step. In this case, the dehydrated film is wet-stretched, and then the wet stretched film is hydrated. The processing conditions (temperature, pH, etc. of the aqueous solution for hydration) in each step are the same as those described above.

  Thus, in this embodiment, since the acid catalyst is mixed in the coating liquid, a high concentration acid catalyst can be uniformly dispersed in polyvinyl alcohol. Therefore, in this embodiment, a polyene polarizing film in which a large number of carbon double bonds are uniformly dispersed can be produced. That is, in this embodiment, it is possible to produce a polyene polarizing film having both a high degree of polarization and a high transmittance. Moreover, in this embodiment, the nonuniformity of a polyene type polarizing film can be reduced. In addition, since the step of impregnating the polyvinyl alcohol with the acid catalyst aqueous solution is not necessary, the manufacturing process can be simplified.

  Moreover, in this embodiment, since the acid catalyst is mixed in the coating liquid, a high concentration acid catalyst can be uniformly dispersed in the polyvinyl alcohol film even if the polyvinyl alcohol film is thinned. Furthermore, in this embodiment, dry stretching and dehydration treatment of the polyvinyl alcohol film are performed in separate steps. Furthermore, in this embodiment, the dehydration film is also hydrated. Therefore, in this embodiment, a polyene polarizing film having a thin film, a high degree of polarization, and a high transmittance can be produced. For example, in the present embodiment, the thickness of the polyene polarizing film can be less than 10 μm, the transmittance can be 44.5% or more, and the degree of polarization can be 98.0% or more. When an organic acid is used as the acid catalyst, evaporation of the acid catalyst during the production of polyene is suppressed, so that the degree of polarization can be further improved.

  On the other hand, in the conventional manufacturing method, since the polyvinyl alcohol film is impregnated in the acid catalyst aqueous solution bath, when the polyvinyl alcohol film is thinned, the polyvinyl alcohol film cannot be impregnated with a sufficient amount of the acid catalyst. Furthermore, since hydrochloric acid is volatile, hydrochloric acid is volatilized when polyene is produced. For this reason, in the conventional manufacturing method, since a polyene, ie, a carbon double bond, was not able to be fully produced | generated, the polyene type polarizing film of a thin film and high polarization degree was not able to be produced. However, even when a polyvinyl alcohol film is impregnated in an acid catalyst aqueous solution bath, by hydrating the wet stretched film (or dehydrated film), a polyene-based polarizing film having a thin film, a high transmittance, and a high degree of polarization can be obtained. Can be produced.

  The polyene polarizing film is peeled off from the substrate and then bound with a protective film, a retardation film (1 / 4λ film) and the like. Thereby, a laminated polarizing film is produced.

(Example of laminated polarizing film)
An example of the laminated polarizing film is shown in FIG. FIG. 1 shows a comparison between a laminated polarizing film 10 according to the present embodiment and a conventional iodine-based laminated polarizing film 100. 1A shows a conventional iodine-based laminated polarizing film 100, and FIG. 1B shows a laminated polarizing film 10 according to this embodiment.

  The conventional laminated polarizing film 100 includes an iodine polarizing film 110, protective films 120 and 130, pressure-sensitive adhesive layers 140 and 160, and a retardation film (1 / 4λ film) 150. The conventional iodine-based polarizing film 110 has to be thickened in order to achieve a desired degree of polarization. For example, the iodine polarizing film 110 had a film thickness of 22 μm or more. For this reason, the film thickness of the entire laminated polarizing film 100 also tends to be increased. For example, the laminated polarizing film 100 has a film thickness of 190 μm or more.

  On the other hand, the laminated polarizing film 10 according to the present embodiment includes a polyene polarizing film 11, UV adhesive layers 12 and 14, a protective film 13, a retardation film (¼λ film) 15, and a pressure-sensitive adhesive layer 16. With.

  Therefore, the laminated polarizing film 10 is a circularly polarizing film. In addition, the laminated polarizing film 10 which concerns on this embodiment should just be comprised with a well-known material except the polyene type polarizing film 11. FIG. The pressure-sensitive adhesive layer 16 is bonded to, for example, a display surface of a display device. In the present embodiment, since the polyene polarizing film 11 is thinned, the entire laminated polarizing film 10 is also thinned. For example, in this embodiment, the film thickness of the entire laminated polarizing film 10 can be 100 μm or less. Of course, the laminated polarizing film according to this embodiment may have other structures. The laminated polarizing film may not be a circularly polarizing film. Moreover, the laminated polarizing film 10 according to the present embodiment is suitably applied particularly to an organic light emitting display device using an OLED. In recent years, a polarizing film applied to an organic light emitting display device is required to have high transmittance (for example, 44.0% or more), degree of polarization (for example, 97% or more, preferably 98.0% or more), and reliability. The On the other hand, the polyene type | system | group laminated film which concerns on this embodiment has a high transmittance | permeability (44.5% or more) and a polarization degree (98.0% or more), as shown by the Example mentioned later.

(Modification)
In the first step described above, an acid catalyst is included in the coating solution. In the second step, dry stretching and dehydration are performed in separate steps. However, even if these treatments are replaced with conventional treatments, a polarizing film having good optical properties can be produced by performing the third to fourth steps. Therefore, in this modification, a dehydrated film is produced by the following process.

  First, a polyvinyl alcohol film is produced using a coating liquid containing polyvinyl alcohol. Although the specific manufacturing method is not specifically limited, For example, the coating liquid containing polyvinyl alcohol is produced first. Specifically, polyvinyl alcohol is poured into water, and the mixture of water and polyvinyl alcohol is heated while stirring to sufficiently dissolve the polyvinyl alcohol in water. Thereby, a coating liquid is produced. Next, the coating liquid is coated on a substrate (for example, an unstretched film) and dried to form a polyvinyl alcohol film on the substrate. Here, the layer thickness of the polyvinyl alcohol film is not particularly limited, but is preferably adjusted so that the film thickness of the finally produced polyene polarizing film is less than 10 μm. The polyvinyl alcohol film may be a ready-made one.

  Then, the polyvinyl alcohol film is impregnated with an acid catalyst aqueous solution. The impregnation method is not particularly limited. For example, the polyvinyl alcohol film may be immersed in an acid catalyst aqueous solution bath or may be left in a space sprayed with an acid catalyst aqueous solution. Further, the type of acid catalyst and the impregnation time are not particularly limited, and the same acid catalyst and impregnation time as in the conventional case can be applied.

  Next, the acid catalyst-impregnated film is heated to cause polyvinyl alcohol to undergo a dehydration reaction, and at the same time, the acid catalyst-impregnated film is dry-stretched in a predetermined direction. The conditions for the dehydration reaction and dry stretching are not particularly limited, and the same conditions as in the past can be applied. Thereby, a dehydrated film (film subjected to dry stretching and dehydration treatment) is produced. Even if the first step and the second step are replaced with this modification, by performing the third to fourth steps, a high transmittance (for example, 44.5% or more) and a high degree of polarization (for example, 98% or more). ) Is produced. Note that only a part of the first and second steps may be replaced with a conventional process.

(Application example of polyene polarizing film)
The polyene polarizing film according to the present embodiment is applicable to any field as long as the polarizing film is used. However, since the polyene polarizing film according to the present embodiment is a thin film and has good optical characteristics and reliability, it is suitable for a display device, particularly an organic light emitting display device using an organic light emitting diode. In addition, the usage method in particular is not restrict | limited, What is necessary is just to be used similarly to the conventional polarizing film. For example, when using a polyene type polarizing film for a display device, it is used as a laminated polarizing film laminated with other films (retardation film etc.), for example.

Next, examples of the present embodiment will be described.
(Confirmation of effects of hydration)
In order to confirm the effect of hydration, the following Examples 1 to 3 and Comparative Example 1 were carried out.

Example 1
In Example 1, a polyene polarizing film and a laminated polarizing film were produced as follows.

(First step)
First, polyvinyl alcohol (JC-25 manufactured by Nippon Vine & POVAL) was added to water as a solvent. Next, the mixed solution of water and polyvinyl alcohol was heated while being stirred to sufficiently dissolve the polyvinyl alcohol in water. Subsequently, para-toluenesulfonic acid and a leveling agent (MEGAFACE of DIC Corporation) were added to the polyvinyl alcohol aqueous solution and stirred to prepare a coating solution. Here, the impregnation ratio (mass ratio) of water, polyvinyl alcohol, and paratoluenesulfonic acid in the coating liquid was 89.5 mass%: 10 mass%: 0.5 mass%. Moreover, the mass ratio of the leveling agent was an outside number, specifically, 0.002% by mass with respect to the total mass of water, polyvinyl alcohol, and paratoluenesulfonic acid.

  Next, an unstretched film composed of isophthalic acid copolymerized polyethylene terephthalate (PET) was prepared as a substrate, and a coating solution was coated on the substrate. Subsequently, the polyvinyl alcohol film was produced by drying a coating liquid. The film thickness of the polyvinyl alcohol film was 12 μm.

(Second step)
The polyvinyl alcohol film was put into an oven preheated to 110 ° C., and the polyvinyl alcohol film and the substrate were collectively stretched 4.2 times in a predetermined direction. This produced the dry stretched film. Next, the dry stretched film was heated at 110 to 130 ° C. for 120 seconds to cause dehydration of the polyvinyl alcohol in the dry stretched film. That is, polyene (carbon double bond) was formed on the dry stretched film. In this way, a dehydrated dry stretched film (dehydrated film) was produced.

(Third step)
Next, a 7.0% by mass boric acid aqueous solution adjusted to 85 ° C. (a boric acid aqueous solution containing 7% by mass boric acid based on the total mass of the boric acid aqueous solution, pH = 3.9) is prepared as an aqueous solution for hydration. did. And the dry stretched film was thrown into the aqueous solution for hydration, and the dry stretched film was immersed in the aqueous solution for hydration for 60 minutes. Here, the immersion of the dry stretched film was performed while applying a force that does not cause the dry stretched film to shrink. This hydrated the dry stretched film. That is, a hydrated film was produced.

(Fourth step)
Next, the hydrated film was put into a 7.0 mass% boric acid aqueous solution bath adjusted to 65 ° C., and the hydrated film was wet-stretched 1.25 times in the same direction as dry stretching in the boric acid aqueous solution bath. Thereby, the polyvinyl alcohol film was stretched by a total of 5.25 times. This produced the wet stretched film.

  The hydrated wet stretched film was then placed in an oven preheated to 100 ° C. and dried at 100 ° C. for 2 minutes. This produced the polyene type polarizing film concerning Example 1. The film thickness of the polyene polarizing film was 5 μm.

  Next, a UV adhesive having the following composition was prepared.

(A) 90 mass% (b) 10 mass% (c) 1 mass% (d) 2 mass% was mixed using the stirrer. In addition, the content ratio of (c) and (d) is an external number with respect to the mass of (a) + (b).
(A) 4HBA (4-hydroxybutyl acrylate)
(B) Celoxide 2021P (CEL2021P) (3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate) (manufactured by Daicel Corporation)
(C) TPO (2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide) (manufactured by Ciba Specialty Chemicals)
(D) CPI-110P (p-phenylthiophenyldiphenylsulfonium PF ₆ salt) (manufactured by SAN-APRO)

  Next, a UV adhesive was applied to the surface of the polyene polarizing film (the surface on which the polyene polarizing film is exposed, of the front and back surfaces of the laminated film composed of the polyene polarizing film and the substrate) with a thickness of 2 μm. Next, a 50 μm-thick protective film (UV absorber-containing triacetyl cellulose film: “FUJITAC” manufactured by Fuji Film Co., Ltd.) is laminated on the surface of the polyene polarizing film so as to fit the UV adhesive. )did. Thereby, the laminated film which consists of a polyene type polarizing film and a board | substrate was affixed on the protective film. Next, the UV adhesive was cured by irradiating the laminated film with 1000 mJ of UV light. Next, the substrate was peeled from the polyene polarizing film.

  Next, a UV adhesive was applied to the back surface of the polyene polarizing film (the surface exposed by the above peeling) with a thickness of 2 μm. Next, a 50 μm-thick retardation film (¼ wavelength plate, “WRS” manufactured by Teijin Kasei Co., Ltd.) is placed on the back surface of the polyene polarizing film, and the optical absorption axis of the polyene polarizing film and the slow axis of the quarter wavelength plate. And pasted so as to be 45 degrees. Subsequently, the UV adhesive was cured by the same treatment as described above. Thereby, the laminated polarizing film for evaluation was produced.

(Example 2)
In Example 2, a polarizing film corresponding to the above-described modification was produced. Specifically, the laminated polarizing film which concerns on Example 2 was produced by performing the following processes.

  That is, a polyvinyl alcohol film (film thickness 60 um, manufactured by Kuraray) was impregnated with 0.05 mol% hydrochloric acid for 1 minute and then dried at 24 ° C. for 30 minutes. The acid catalyst-impregnated film thus prepared was put into an IR heater having a surface temperature of 450 ° C. and heated at this temperature for 18 seconds. This caused the acid catalyst impregnated film to undergo a dehydration reaction. On the other hand, the acid catalyst-impregnated film was subjected to a dehydration reaction, and at the same time, the acid catalyst-impregnated film was dry-stretched 3.3 times. Thus, a dehydrated film was produced. Thereafter, the same treatment as in Example 1 was performed to produce a laminated polarizing film according to Example 2.

(Example 3)
The process is the same as in Example 1 except that the order of the third step and the fourth step is reversed (that is, the fourth step is performed after the second step, and then the third step is performed). went. Thereby, the laminated polarizing film according to Example 3 was produced.

(Comparative Example 1)
In Comparative Example 1, a laminated polarizing film according to Comparative Example 1 was produced by performing the following treatment.

  That is, a polyvinyl alcohol film (film thickness 60 um, manufactured by Kuraray) was impregnated with 0.05 mol% hydrochloric acid for 1 minute and then dried at 24 ° C. for 30 minutes. The acid catalyst-impregnated film thus prepared was put into an IR heater having a surface temperature of 450 ° C. and heated at this temperature for 18 seconds. This caused the acid catalyst impregnated film to undergo a dehydration reaction. On the other hand, the acid catalyst-impregnated film was subjected to a dehydration reaction, and at the same time, the acid catalyst-impregnated film was dry-stretched 3.3 times. Thus, a dehydrated film was produced.

  Subsequently, the dehydrated film was wet-stretched 1.79 times in a 7 mass% boric acid bath at a temperature of 85 ° C. This produced the wet stretched film. The total stretch ratio of the wet stretched film was 5.9 times. Subsequently, the wet stretched film was dried in an oven at 100 ° C. to produce a polarizing film. Subsequently, the laminated polarizing film which concerns on the comparative example 1 was produced by performing the process similar to Example 1 with respect to a polarizing film.

(Evaluation)
The polarization degree and transmittance (single transmittance) of the laminated polarizing films according to Examples 1 to 3 and the comparative example were evaluated by the following treatment.
Measuring apparatus: UV-visible spectrophotometer (V7100 manufactured by JASCO Corporation)
Measuring method: Measure single transmittance T (%), parallel transmittance Tp (%), and orthogonal transmittance Tc (%) of the polarizing element. These are Y values measured with a 2 degree visual field (C light source) of JIS Z8701 and corrected for visibility. The degree of polarization P was determined by the following equation (1) using the above transmittance.
Polarization degree P (%) = √ {(Tp−Tc) / (Tp + Tc)} × 100 (1)
The measurement results are shown in Table 1.

  According to this evaluation, it can be seen that the laminated polarizing films according to Examples 1 to 3 have both a high degree of polarization and a high transmittance. Specifically, in Examples 1 to 3, the transmittance is 44.5% or more and the degree of polarization is 98.0% or more. On the other hand, the laminated polarizing film according to Comparative Example 1 has a transmittance of less than 44.5%.

  Furthermore, in Examples 1 and 3, since the organic acid that is the acid catalyst is mixed in the coating liquid, the high concentration acid catalyst is uniformly dispersed in the polyvinyl alcohol. Furthermore, organic acids are less volatile and are less likely to evaporate during polyene production. Furthermore, dehydration and dry stretching are performed in separate steps. Therefore, in Examples 1 and 3, both the degree of polarization and the transmittance are higher than those in Example 2.

(Examination of pH of aqueous solution for hydration)
Next, in order to examine the pH required for the aqueous solution for hydration used in the third step (hydration treatment of the film), the following Examples 4-1 and 4-2 and Comparative Examples 2 to 4 are used. went.

(Example 4-1)
In Example 1, the laminated polarizing film was treated in the same manner as in Example 1 except that the pH of the aqueous solution for hydration was 3.0 (mass% of boric acid was 15.0 mass%). Was made.

(Example 4-2)
In Example 1, a laminated polarizing film was obtained by performing the same treatment as in Example 1 except that the pH of the aqueous solution for hydration was 3.7 (mass% of boric acid was 10.0 mass%). Was made.

(Comparative Example 2)
In Example 1, a laminated polarizing film was obtained by performing the same treatment as in Example 1 except that the pH of the aqueous solution for hydration was 5.4 (mass% of boric acid was 1.0 mass%). Was made.

(Comparative Example 3)
In Example 1, a laminated polarizing film was obtained by performing the same treatment as in Example 1 except that the pH of the aqueous solution for hydration was 4.7 (mass% of boric acid was 3.0 mass%). Was made.

(Comparative Example 4)
In Example 1, except that the pH of the aqueous solution for hydration was 4.2 (mass% of boric acid was 5.0 mass%), the same treatment as in Example 1 was carried out, so that the laminated polarizing film Was made.

(Evaluation)
The degree of polarization and transmittance (single transmittance) of the laminated polarizing films according to Examples 4-1 and 4-2 and Comparative Examples 2 to 4 were evaluated by the same method as described above (confirmation of the effect of hydration). The results are shown in Table 2.

  According to this evaluation, in Examples 1, 4-1, and 4-2, the transmittance is 44.5% or more and the degree of polarization is 98.0% or more. In Comparative Examples 2 to 4, the degree of polarization is 98. Less than 0%. Therefore, it can be seen that the pH of the aqueous solution for hydration needs to be 3.0 or more and 4.0 or less.

(Examination of temperature of aqueous solution for hydration)
Next, in order to examine the temperature required for the aqueous solution for hydration used in the third step (film hydration treatment), the following Example 5 and Comparative Examples 5 and 6 were performed.

(Example 5)
In Example 1, the laminated polarizing film was produced by performing the process similar to Example 1 except having set the temperature of the aqueous solution for hydration to 90 degreeC.

(Comparative Example 5)
In Example 1, a laminated polarizing film was produced by performing the same treatment as in Example 1 except that the temperature of the aqueous solution for hydration was 65 ° C.

(Comparative Example 6)
In Example 1, the laminated polarizing film was produced by performing the process similar to Example 1 except having set the temperature of the aqueous solution for hydration to 75 degreeC.

(Evaluation)
The degree of polarization and transmittance (single transmittance) of the laminated polarizing films according to Example 6 and Comparative Examples 5 and 6 were evaluated by the same method as described above (confirmation of the effect of hydration). The results are shown in Table 3.

  According to this evaluation, in Examples 1 and 5, the transmittance is 44.5% or more and the degree of polarization is 98.0% or more. In Comparative Examples 5 to 6, the transmittance is less than 44.5%, and the degree of polarization. Is less than 98.0%. Therefore, it turns out that the temperature of the aqueous solution for hydration needs to be 85 degreeC or more and 100 degrees C or less.

(Hydration time)
Next, in order to examine the time required for hydration, the following Examples 6 to 8 and Comparative Examples 7 to 9 were performed.

(Example 6)
In Example 1, a laminated polarizing film was produced by performing the same treatment as in Example 1 except that the hydration time (the time for impregnating the wet stretched film in the aqueous solution for hydration) was 0.5 min.

(Example 7)
In Example 1, a laminated polarizing film was produced by performing the same treatment as in Example 1 except that the hydration time was 1.0 min.

(Example 8)
In Example 1, a laminated polarizing film was produced by performing the same treatment as in Example 1 except that the hydration time was 50 min.

(Comparative Example 7)
In Example 1, a laminated polarizing film was produced by performing the same treatment as in Example 1 except that the hydration time was 0.1 min.

(Comparative Example 8)
In Example 1, a laminated polarizing film was produced by performing the same treatment as in Example 1 except that the hydration time was 65 min.

(Comparative Example 9)
In the fourth step of Example 1, instead of impregnating the wet stretched film with the aqueous solution for hydration, the wet stretched film was allowed to stand in an environment of 60 ° C. and 95 RH% for 15 hours. Here, at the time of standing, the tension | tensile_strength (Tension) of the grade which a wet stretched film does not shrink was applied to the wet stretched film. Except for this process, the same process as in Example 1 was performed. This produced the laminated polarizing film.

(Evaluation)
The polarization degree and the transmittance (single transmittance) of the laminated polarizing films according to Examples 6 to 8 and Comparative Examples 7 to 9 were evaluated by the same method as described above (confirmation of the effect of hydration). The results are shown in Table 4.

  According to this evaluation, in Examples 1 and 6 to 8, the transmittance is 44.5% or more and the degree of polarization is 98.0% or more. In Comparative Examples 7 to 9, the degree of polarization is less than 98.0%. Become. Therefore, it can be seen that hydration needs to be performed in an acidic atmosphere and that the hydration time needs to be 0.5 min to 60 min.

(Temperature during wet stretching)
Next, in order to examine the temperature necessary for the boric acid aqueous solution used in the third step (wet stretching), the following Example 9 and Comparative Examples 10 and 11 were performed.

Example 9
In Example 1, the laminated polarizing film was produced by performing the process similar to Example 1 except the temperature of the boric-acid aqueous solution at the time of wet extending | stretching having been 55 degreeC.

(Comparative Example 10)
In Example 1, the laminated polarizing film was produced by performing the process similar to Example 1 except the temperature of the boric-acid aqueous solution at the time of wet extending | stretching having been 75 degreeC.

(Comparative Example 11)
In Example 1, the laminated polarizing film was produced by performing the process similar to Example 1 except the temperature of the aqueous solution for hydration at the time of wet extending | stretching having been 85 degreeC.

(Evaluation)
The degree of polarization and transmittance (single transmittance) of the laminated polarizing films according to Example 9 and Comparative Examples 10 and 11 were evaluated by the same method as described above (confirmation of the effect of hydration). The results are shown in Table 5.

  According to this evaluation, in Examples 1 and 9, the transmittance is 44.5% or more and the degree of polarization is 98.0% or more, but in Comparative Examples 10 to 11, the degree of polarization is less than 98.0%. Therefore, it is understood that the temperature of the boric acid aqueous solution at the time of wet stretching needs to be 65 ° C. or less.

  As described above, the method for producing a polyene polarizing film according to the present embodiment performs the hydration treatment of the film before or after the wet stretching treatment. For this reason, the manufacturing method of the polyene type polarizing film according to the present embodiment realizes a very high transmittance of 44.5% or more and a polarization degree of 98.0% or more, and also achieves a high degree of polarization. it can. Furthermore, the manufacturing method of the polyene type polarizing film which concerns on this embodiment can make a polarizing film thin (specifically make it a film thickness of 10 micrometers or less). That is, in this embodiment, a polarizing film with good optical characteristics can be produced.

  Furthermore, in this embodiment, the process of producing a polyvinyl alcohol film using the coating liquid containing an acid catalyst and polyvinyl alcohol is included.

  Accordingly, since a high concentration acid catalyst can be uniformly dispersed in the polyvinyl alcohol film, a large number of carbon double bonds are uniformly formed without accurately controlling the environmental temperature or the like as in the prior art. A polyene polarizing film can be produced. Therefore, according to the manufacturing method concerning this embodiment, it becomes possible to manufacture stably the polyene type | system | group polarizing film which made high polarization degree and high transmittance compatible, ie, a polarizing film with favorable optical characteristics. Furthermore, the polyene polarizing film according to this embodiment is more reliable (stability) than the iodine polarizing film.

  Furthermore, since this embodiment includes a step of performing dry stretching and dehydration treatment of the polyvinyl alcohol film in separate steps, a polarizing film having a high transmittance and a high degree of polarization can also be produced in this respect.

  Therefore, the polyene polarizing film having such a high degree of polarization and high transmittance is used as an antireflection laminated polarizing film of an organic light emitting display device (an organic light emitting display device using an organic light emitting diode) which is expected to spread in the future. Is preferred. That is, when the polarizing film is applied to an organic light emitting display device, the polarizing film is required to have high reliability in addition to high transmittance and degree of polarization. On the other hand, the polyene-type polarizing film is essentially durable (reliable) against high temperature and high humidity. Furthermore, the polyene polarizing film according to this embodiment has high transmittance and polarization degree. That is, the polyene polarizing film according to this embodiment has not only good optical properties but also high reliability. Therefore, the polyene polarizing film according to the present embodiment is suitable for an organic light emitting display device, and is required for the organic light emitting display device by applying the polyene polarizing film according to the present embodiment to the organic light emitting display device. An organic light-emitting display device that satisfies all of the optical characteristics (high transmittance, high polarization degree, and high reliability) is provided.

  Furthermore, since the acid catalyst is a low volatility acid catalyst, it is difficult to evaporate during polyene production. Therefore, the production method according to the present embodiment can make the acid concentration in the polyvinyl alcohol more uniform even when polyene is produced.

  Furthermore, since the acid catalyst has a weight reduction rate at 100 ° C. of less than 3% by mass, it is difficult to evaporate during polyene production. Therefore, the production method according to the present embodiment can make the acid concentration in the polyvinyl alcohol more uniform even when polyene is produced.

  Furthermore, since the acid catalyst is an organic acid, it is difficult to evaporate during polyene production. Therefore, the production method according to the present embodiment can make the acid concentration in the polyvinyl alcohol more uniform even when polyene is produced.

  Furthermore, since the organic acid has any one functional group selected from the group consisting of a carboxyl group and a sulfo group, it is difficult to evaporate when producing a polyene. Therefore, the production method according to the present embodiment can make the acid concentration in the polyvinyl alcohol more uniform even when polyene is produced.

  Furthermore, in the manufacturing method according to the present embodiment, the coating liquid contains an acid catalyst in an amount of 2% by mass to 10% by mass with respect to the mass of polyvinyl alcohol, and more preferably 4.0% by mass to 10.0% by mass. Contains below. Therefore, the production method according to the present embodiment can produce a polyene polarizing film having a higher degree of polarization and a higher transmittance.

  Furthermore, since the content of the acid catalyst is 5% by mass with respect to the mass of the polyvinyl alcohol, the production method according to this embodiment can produce a polyene polarizing film having a higher degree of polarization and a higher transmittance. .

  Furthermore, the manufacturing method according to the present embodiment can reduce the thickness of the polyene polarizing film. Specifically, in the manufacturing method according to this embodiment, the thickness of the polyene polarizing film can be less than 10 μm. Accordingly, even when the polyene polarizing film is applied to a large screen organic light emitting display device, the shrinkage of the polyene polarizing film can be reduced, and hence the warpage of the organic light emitting display device can be reduced. .

  Furthermore, since the dehydration reaction is performed by immersing the polyvinyl alcohol film in an oil bath, it is possible to easily produce a polyene polarizing film having a high degree of polarization and high transmittance. Moreover, the quality of the polyene polarizing film produced from this viewpoint is stable.

  The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited to such examples. It is obvious that a person having ordinary knowledge in the technical field to which the present invention pertains can come up with various changes or modifications within the scope of the technical idea described in the claims. Of course, it is understood that these also belong to the technical scope of the present invention.

DESCRIPTION OF SYMBOLS 10 Laminated polarizing film 11 Polyene type polarizing film 12, 14 UV adhesive layer 13 Protective film 15 Retardation film 16 Pressure sensitive adhesive layer

Claims (3)

Producing a dehydrated film by causing the polyvinyl alcohol film to undergo a dehydration reaction using an acid catalyst;
Hydrating the dehydrated film by impregnating the dehydrated film with a hydrating aqueous solution of pH 3.0 or higher, pH 4.0 or lower, 85 ° C. or higher, and 100 ° C. or lower for 0.5 to 60 (min);
Before or after hydrating the dehydrated film, and wet-stretching the dehydrated film in an acidic aqueous solution at 65 ° C. or lower.   The method for producing a polyene polarizing film according to claim 1, further comprising a step of producing the polyvinyl alcohol film using a coating liquid containing polyvinyl alcohol and the acid catalyst. Further comprising a step of producing a dry stretched film by dry stretching the polyvinyl alcohol film,
The method for producing a polyene polarizing film according to claim 1 or 2, wherein the dehydrated film is produced by causing the dry stretched film to undergo a dehydration reaction using the acid catalyst.

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