KR20210089630A - Polarizing film, polarizing film, laminated polarizing film, image display panel, and image display device - Google Patents

Abstract

A polarizing film formed by adsorption orientation of iodine on a polyvinyl alcohol-based film, wherein the iodine concentration is 6% by weight or more, and in the presence of an inert gas in the generated gas analysis method, the temperature increase rate is 10°C/min and the temperature increase range is 40°C A polarizing film in which the peak temperature of the maximum intensity of water to be detected is 200°C or higher under the conditions of from 350°C. The polarizing film has a good initial polarization degree, and is excellent in the effect of suppressing a decrease in single transmittance due to coloring of the polarizing film in a high-temperature environment.

Description

Polarizing film, polarizing film, laminated polarizing film, image display panel, and image display device

The present invention relates to a polarizing film, a polarizing film, a laminated polarizing film, an image display panel, and an image display device.

Conventionally, as a polarizing film used for various image display devices such as liquid crystal display devices and organic EL display devices, since it has high transmittance and high polarization, it is dyed (contains dichroic substances such as iodine and dichroic dyes) ) A polyvinyl alcohol-based film is used. The said polarizing film is manufactured by performing each process, such as swelling, dyeing|staining, crosslinking, and extending|stretching, in a bath in a bath, and performing washing process, and then drying the said polarizing film. In addition, the said polarizing film is normally used as a polarizing film (polarizing plate) by which protective films, such as a triacetyl cellulose, were bonded together on the single side|surface or both surfaces using the adhesive agent.

The polarizing film is used as a laminated polarizing film (optical laminate) by laminating other optical layers as needed, and the polarizing film or the laminated polarizing film (optical laminate) is an image display cell such as a liquid crystal cell or an organic EL element It is bonded through an adhesive layer or an adhesive layer between the front transparent plate (window layer) and front transparent members, such as a touch panel, on the visual recognition side, and is used as said various image display apparatuses (patent document 1).

In recent years, in addition to mobile devices, such as a cellular phone and a tablet terminal, such various image display apparatuses are used also as vehicle-mounted image display apparatuses, such as a car navigation apparatus and a back monitor, the use is expanding. Accordingly, the image display device is required to have high durability under harsher environments (eg, under high-temperature environments) than conventionally required, and an image for the purpose of ensuring such durability A display device has been proposed (Patent Document 2).

Japanese Patent Laid-Open No. 2014-102353 Japanese Patent Laid-Open No. 2018-101117

When a polarizing film or laminated polarizing film using an iodine-based polarizing film is exposed to a high-temperature environment, polyvinyl alcohol constituting the polarizing film is polyeneized by a dehydration reaction, resulting in coloration of the polarizing film, and a problem that the single transmittance decreases. there was.

As a result of the present inventors earnestly examining, it discovered that the iodine contained in an iodine type polarizing film accelerated|stimulates polyenization in a high temperature environment. Therefore, in order to suppress the fall of the single transmittance by coloring of the polarizing film in a high-temperature environment, it is effective to reduce the iodine concentration (content) in a polarizing film. On the other hand, it was difficult to obtain a polarizing film rich in iodine having a good degree of polarization.

In view of the above circumstances, the present invention provides a polarizing film having a good initial polarization degree in a polarizing film with a high iodine concentration, and having an excellent effect of suppressing a decrease in the single transmittance due to coloring of the polarizing film under a high-temperature environment. aim to

Another object of the present invention is to provide a polarizing film, a laminated polarizing film, an image display panel, and an image display device using the polarizing film.

That is, the present invention is a polarizing film formed by adsorption orientation of iodine on a polyvinyl alcohol-based film, wherein the iodine concentration is 6% by weight or more, and in the presence of an inert gas in the generated gas analysis method, the temperature increase rate is 10°C/min. It relates to a polarizing film in which the peak temperature of the maximum intensity of water detected under the condition that the temperature rise range is from 40°C to 350°C is 200°C or more.

Moreover, this invention relates to the polarizing film by which the transparent protective film is bonded by at least one surface of the said polarizing film.

Moreover, this invention relates to the laminated polarizing film by which the said polarizing film is bonded to the optical layer.

Moreover, this invention relates to the image display panel by which the said polarizing film or the said laminated|multilayer polarizing film is bonded by the image display cell.

Moreover, this invention relates to the image display apparatus provided with a front transparent member on the polarizing film or laminated polarizing film side of the said image display panel.

Although the detail of the action mechanism of the effect in the polarizing film of this invention has an unclear part, it is estimated as follows. However, the present invention does not need to be interpreted as being limited to this mechanism of action.

The polarizing film of the present invention is an iodine-based polarizing film formed by adsorption orientation of iodine on a polyvinyl alcohol-based film, the iodine concentration is 6% by weight or more, and in the presence of an inert gas in the generated gas analysis method, the temperature increase rate is 10° C. /min, and under the condition that the temperature increase range is from 40°C to 350°C, the peak temperature of the maximum intensity of water detected is 200°C or more. As described above, in the iodine-based polarizing film, polyeneization occurs due to the dehydration reaction of polyvinyl alcohol under a high-temperature environment, but in the polarizing film of the present invention, the temperature at which this dehydration reaction occurs is detected (observed) on the high-temperature side, that is, by the generated gas analysis method. By setting the peak temperature of the maximum intensity of water used to be 200°C or higher, it is possible to suppress a decrease in the single transmittance due to coloring of the polarizing film in a high-temperature environment. In addition, in the polarizing film of the present invention, by setting the iodine concentration in the polarizing film to a certain range or more, the peak temperature of the maximum intensity of water detected (observed) by the generated gas analysis method can be controlled to 200° C. or more, and the initial polarization degree is good becomes

On the other hand, the present inventors observed the generation of radicals from the polarizing film as a result of exposing the polarizing film formed by adsorbing iodine to the iodine-containing polyvinyl alcohol-based film under a high temperature environment for a certain period of time. Since the timing at which a polarizing film is colored by polyenization and the timing at which this radical generate|occur|produces were abused, the phenomenon which a radical generate|occur|produces by advancing of polyenization of a polarizing film was suggested. Therefore, in the polarizing film, in order to set the temperature at which the above-mentioned dehydration reaction occurs on the high temperature side, that is, the peak temperature of the maximum intensity of water detected (observed) by the generated gas analysis method, to 200° C. or higher, the polarizing film has a radical trapping function. It is preferable to contain a compound.

Moreover, the polarizing film of this invention is useful as a thin-shaped polarizing film from a viewpoint of preventing panel curvature at the time of heating of a polarizing film or a laminated polarizing film in accordance with the reduction in the thickness of the panel of an image display device.

BRIEF DESCRIPTION OF THE DRAWINGS It is an example of the chart which shows the peak of water detected in the generated gas analysis method using the iodine type polarizing film as a sample.

<Polarizing film>

The polarizing film of the present invention is an iodine-based polarizing film formed by adsorption orientation of iodine on a polyvinyl alcohol-based film, the iodine concentration is 6% by weight or more, and in the presence of an inert gas in the generated gas analysis method, the temperature increase rate is 10° C. /min and under the condition that the temperature rise range is from 40°C to 350°C, the peak temperature of the maximum intensity of water detected is 200°C or more.

The polyvinyl alcohol (PVA)-based film has light transmittance in a visible light region, and dispersion and adsorption of iodine can be used without particular limitation. Moreover, normally, it is preferable that thickness is about 1-100 micrometers, as for the PVA-type film used as a raw material, it is more preferable that it is about 1-50 micrometers, It is preferable that it is about 100-5000 mm in width.

As a material of the said polyvinyl alcohol type film, polyvinyl alcohol or its derivative(s) is illustrated. As a derivative of the said polyvinyl alcohol, For example, polyvinyl formal, polyvinyl acetal; olefins such as ethylene and propylene; Unsaturated carboxylic acids, such as acrylic acid, methacrylic acid, and a crotonic acid, and the thing modified|denatured with its alkylester, acrylamide, etc. are illustrated. The polyvinyl alcohol preferably has an average degree of polymerization of about 100 to 10,000, more preferably about 1,000 to 10,000, and still more preferably about 1,500 to 4,500. Further, the polyvinyl alcohol preferably has a degree of saponification of about 80 to 100 mol%, and more preferably about 95 mol% to about 99.95 mol. In addition, the said average degree of polymerization and the said saponification degree can be calculated|required according to JISK6726.

The said polyvinyl alcohol-type film may contain additives, such as a plasticizer and surfactant. As said plasticizer, polyols, such as glycerol, diglycerol, triglycerol, ethylene glycol, propylene glycol, polyethyleneglycol, its condensate, etc. are illustrated, for example. Although there is no restriction|limiting in particular in the usage-amount of the said additive, For example, about 20 weight% or less in a polyvinyl alcohol-type film is suitable.

In the polarizing film, the iodine concentration (content) is 6% by weight or more from the viewpoint of improving the initial degree of polarization of the polarizing film. The polarizing film preferably has an iodine concentration (content) of 7 wt% or more, more preferably 8 wt% or more, from the viewpoint of improving the initial polarization degree of the polarizing film, and the peak temperature of the maximum intensity of water detected by the generated gas analysis method It is preferable that it is 12 weight% or less from a viewpoint of controlling to 200 degreeC or more, and it is more preferable that it is 10 weight% or less.

The polarizing film shows a peak temperature of the maximum intensity of water detected in the presence of an inert gas in the presence of an inert gas in the presence of an inert gas, a temperature increase rate of 10°C/min and a temperature increase range of 40°C to 350°C, of 200°C or higher. In the polarizing film, the temperature at which the dehydration reaction of polyvinyl alcohol occurs is set to the high temperature side, that is, the peak temperature of the maximum intensity of water detected by the generated gas analysis method is 200° C. or higher, thereby reducing the single transmittance due to the coloring of the polarizing film in a high temperature environment can suppress. On the other hand, when the peak temperature of the maximum intensity of water is lower than 200 ° C. or higher, the single transmittance of the polarizing film before and after a heating durability test (95 ° C. x 750 hours) which is an index of high temperature durability required for a low-end vehicle-mounted display It becomes difficult to control the amount of change of 0% or more to 5% or less.

Fig. 1 is an example of a chart showing a peak of water detected by the generated gas analysis method, and the peak temperature of the maximum intensity of water detected is 200°C or higher.

In addition, the generated gas analysis method is an analysis method in which a gas chromatography apparatus and a mass spectrometer are directly connected by an inert metal capillary or the like, and the gas generated when the sample is heated to an elevated temperature is monitored in real time, generally EGA/ It is called MS method, EGA/TOF MS method, etc.

It is preferable that the said polarizing film contains the compound which has a radical trapping function. It is estimated that the compound having the radical trapping function traps radicals generated by heating of polyvinyl alcohol of the polarizing film, and can set the temperature at which the dehydration reaction of polyenization occurs to the high temperature side. As the compound having the above radical trapping function, for example, hindered phenol-based, hindered amine-based, phosphorus-based, sulfur-based, benzotriazole-based, benzophenone-based, hydroxylamine-based, salicylic acid ester-based, triazine-based compounds, etc. The compound (For example, antioxidant etc.) which has a radical trapping function is illustrated. The compound having a radical trapping function is preferably a compound having, for example, a nitroxy radical or a nitroxide group from the viewpoint of being able to easily set the temperature at which the dehydration reaction of polyenization occurs to the high temperature side.

As the compound having a nitroxy radical or a nitroxide group, an N-oxyl compound (as a functional group, a compound having CN(-C)-O· (O· is an oxy radical) from the viewpoint of having a relatively stable radical at room temperature and air. )) are exemplified, and well-known ones can be used. As an N-oxyl compound, the compound etc. which have an organic group of the following structures are illustrated, for example.

(In the general formula (1), R ¹ represents an oxy radical, R ² to ^{R 5} independently represent a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, and n represents 0 or 1.) The left side of the dotted line part in Formula (1) shows arbitrary organic groups.

As a compound which has the said organic group, the compound etc. which are represented by the following general formula (2) - (5) are illustrated, for example.

(In general formula (2), R ¹ to ^{R 5} and n are the same as above, R ⁶ represents a hydrogen atom or an alkyl group, acyl group, or aryl group having 1 to 10 carbon atoms, and n is 0 or represents 1)

(In general formula (3), R ¹ to ^{R 5} and n are the same as above, and R ⁷ and R ⁸ independently represent a hydrogen atom or an alkyl group, acyl group, or aryl group having 1 to 10 carbon atoms. )

(In general formula (4), R ¹ to ^{R 5} and n are the same as above, and R ⁹ to ^{R 11} are independently a hydrogen atom or an alkyl group, acyl group, amino group, or alkoxy group having 1 to 10 carbon atoms. , a hydroxy group, or an aryl group)

(In general formula (5), R ¹ to ^{R 5} and n are the same as above, and R ¹² represents a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, an amino group, an alkoxy group, a hydroxyl group, or an aryl group)

In the general formulas (1) to (5), R ² to ^{R 5} are preferably an alkyl group having 1 to 6 carbon atoms, more preferably an alkyl group having 1 to 3 carbon atoms, from the viewpoint of availability. Moreover, in the said General formula (2), from a viewpoint of availability ^{, it is preferable that R<6>} is a hydrogen atom or a C1-C10 alkyl group, and it is more preferable that it is a hydrogen atom. Moreover, in the said General formula (3) ^{, it is preferable from a viewpoint of availability that R<7>} and R<^8> are independently a hydrogen atom or a C1-C10 alkyl group, and it is more preferable that it is a hydrogen atom. Moreover, in the said General formula (4) ^{, it is preferable from a viewpoint of availability that R<9> -R<11>} is a hydrogen atom or a C1-C10 alkyl group. Moreover, in the said General formula (5), ^{it is preferable from a viewpoint of availability that R<12>} is a hydroxyl group, an amino group, or an alkoxy group. In the general formulas (1) to (5), n is preferably 1 from the viewpoint of availability.

In addition, as said N-oxyl compound, for example, the N described in Unexamined-Japanese-Patent No. 2003-64022, Unexamined-Japanese-Patent No. 11-222462, Unexamined-Japanese-Patent No. 2002-284737, International Publication No. 2016/047655, etc. -oxyl compounds are exemplified.

Further, the compound having a radical trapping function has a molecular weight of preferably 1000 or less, more preferably 500 or less, and still more preferably 300 or less from the viewpoint of efficiently trapping radicals generated in the polyenization reaction.

The compound having the radical trapping function can efficiently permeate the polarizing film together with water during the production of the polarizing film, from the viewpoint of impregnating the polarizing film at a high concentration, even when a thick polyvinyl alcohol-based film is used for a short time It is preferable that 1 part by weight or more can be dissolved with respect to 100 parts by weight of water at 25°C from the viewpoint of increasing the productivity of the polarizing film because it can be impregnated with, and 2 parts by weight with respect to 100 parts by weight of water at 25°C It is more preferable that it can melt|dissolve more than that, and it is still more preferable that it can melt|dissolve 5 weight part or more with respect to 100 weight part of 25 degreeC water.

Moreover, as a compound which has the said nitroxy radical or a nitroxide group, the following compounds etc. are illustrated, for example.

(In the general formula (6), R represents a hydrogen atom or an alkyl group, acyl group, or aryl group having 1 to 10 carbon atoms)

When the polarizing film contains the compound having the radical trapping function, the content of the compound having the radical trapping function is from the viewpoint of suppressing a decrease in the single transmittance due to coloring of the polarizing film in a high temperature environment, in the polarizing film, It is preferable that it is 0.005 weight% or more, It is more preferable that it is 0.01 weight% or more, It is still more preferable that it is 0.02 weight% or more, And from the viewpoint of an external appearance, it is preferable that it is 15 weight% or less, It is more preferable that it is 12 weight% or less, 10 weight% % or less is more preferable.

<Method for producing a polarizing film>

The manufacturing method of the said polarizing film is obtained by giving an arbitrary swelling process and a washing|cleaning process to the said polyvinyl alcohol-type film, and at least a dyeing|staining process, a bridge|crosslinking process, and an extending|stretching process. The content of the iodine contained in the polarizing film is the concentration of iodide such as iodine and potassium iodide contained in any one of the treatment baths in the swelling step, the dyeing step, the crosslinking step, the stretching step and the washing step, It is controllable by the processing temperature and processing time by each said processing bath.

In addition, when manufacturing a polarizing film containing a compound having the radical trapping function, the radical trapping function is provided in the treatment bath of any one or more of the swelling step, the washing step, the dyeing step, the crosslinking step, and the stretching step. What is necessary is just to contain the compound which has. The concentration of the compound having a radical trapping function contained in any one of the above treatment baths cannot be determined uniformly because it is affected by the number of treatments, treatment time, treatment temperature, etc. of each treatment, but the radical trapping function in the polarizing film is not determined. From the viewpoint of being able to efficiently control the content of the compound having, it is usually preferably 0.01% by weight or more, more preferably 0.05% by weight or more, still more preferably 0.1% by weight or more, and preferably 30% by weight or less, It is more preferable that it is 25 weight% or less, and it is still more preferable that it is 20 weight% or less.

In particular, when the washing process is performed after the dyeing process, the crosslinking process, and the stretching process are performed, the washing process is performed in consideration of the treatment conditions in the dyeing process, the crosslinking process, and the stretching process, and has iodine or the radical trapping function. It is easy to adjust content of the said iodine and the compound which has the said radical trapping function to a desired range from a viewpoint of being able to elute components, such as a compound from a polyvinyl alcohol-type film, or adsorb|suck to a polyvinyl alcohol-type film.

Further, each treatment bath in the swelling step, the dyeing step, the crosslinking step, the stretching step and the washing step may contain additives such as zinc salt, a pH adjuster, a pH buffer, and other salts. Examples of the zinc salt include zinc halides such as zinc chloride and zinc iodide; Inorganic zinc salts, such as zinc sulfate and zinc acetate, etc. are illustrated. As said pH adjuster, strong acids, such as hydrochloric acid, sulfuric acid, and nitric acid, and strong bases, such as sodium hydroxide and potassium hydroxide, are illustrated, for example. Examples of the pH buffer include carboxylic acids and salts thereof such as acetic acid, oxalic acid, and citric acid, and weak inorganic acids and salts thereof such as phosphoric acid and carbonic acid. Examples of the other salts include chlorides such as sodium chloride, potassium chloride and barium chloride, nitrates such as sodium nitrate and potassium nitrate, sulfates such as sodium sulfate and potassium sulfate, and salts of alkali metals and alkaline earth metals.

The swelling step is a treatment step of immersing the polyvinyl alcohol-based film in a swelling bath, it is possible to remove contamination and blocking agents, etc. on the surface of the polyvinyl alcohol-based film, and by swelling the polyvinyl alcohol-based film, dyeing unevenness can be suppressed As for the said swelling bath, the medium which has water as a main component, such as water, distilled water, and pure water, is used normally. The said swelling bath follows a conventional method, and surfactant, alcohol, etc. may be added suitably.

It is preferable that the temperature of the said swelling bath is about 10-60 degreeC, It is more preferable that it is about 15-45 degreeC, It is more preferable that it is about 18-30 degreeC. In addition, the immersion time in the swelling bath cannot be uniformly determined because the degree of swelling of the polyvinyl alcohol-based film is affected by the temperature of the swelling bath, but it is preferably about 5 to 300 seconds, and about 10 to 200 seconds. It is more preferable that it is, and it is still more preferable that it is about 20 to 100 second. The said swelling process may be performed only once, and may be performed multiple times as needed.

The said dyeing process is a treatment process of immersing a polyvinyl alcohol-type film in a dyeing bath (iodine solution), and it can adsorb|suck and orientate an iodine to a polyvinyl alcohol-type film. The iodine solution is usually preferably an aqueous iodine solution, and contains iodine and iodide as a dissolution aid. Examples of the iodide include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, titanium iodide, and the like. Among these, potassium iodide is suitable from a viewpoint of controlling content of potassium in the said polarizing film.

In the said dyeing bath, it is preferable that it is about 0.01 to 1 weight%, and, as for the density|concentration of an iodine, it is more preferable that it is about 0.02 to 0.5 weight%. In the said dyeing bath, it is preferable that the density|concentration of the said iodide is about 0.01 to 20 weight%, It is more preferable that it is about 0.05 to 10 weight%, It is more preferable that it is about 0.1 to 5 weight%.

It is preferable that the temperature of the said dyeing bath is about 10-50 degreeC, It is more preferable that it is about 15-45 degreeC, It is more preferable that it is about 18-30 degreeC. In addition, the immersion time in the dyeing bath cannot be determined uniformly because the degree of dyeing of the polyvinyl alcohol-based film is affected by the temperature of the dyeing bath, but it is preferably about 10 to 300 seconds, and about 20 to 240 seconds. It is more preferable that The said dyeing process may be performed only once, and may be performed multiple times as needed.

The crosslinking step is a treatment step in which the polyvinyl alcohol-based film is immersed in a treatment bath (crosslinking bath) containing a boron compound, the polyvinyl alcohol-based film is crosslinked by the boron compound, and iodine molecules or dye molecules are crosslinked adsorbed to the structure. As said boron compound, boric acid, a borate, borax etc. are illustrated, for example. The crosslinking bath is generally an aqueous solution, but may be, for example, a mixed solution of an organic solvent miscible with water and water. Moreover, the said crosslinking bath may contain potassium iodide from a viewpoint of controlling content of potassium in the said polarizing film.

It is preferable that the density|concentration of the said boron compound in the said crosslinking bath is about 1 to 15 weight%, It is more preferable that it is about 1.5 to 10 weight%, It is more preferable that it is about 2 to 5 weight%. Further, when potassium iodide is used in the crosslinking bath, the concentration of potassium iodide in the crosslinking bath is preferably about 1 to 15% by weight, more preferably about 1.5 to 10% by weight, and 2 to 5% by weight. % is more preferable.

It is preferable that it is about 20-70 degreeC, and, as for the temperature of the said crosslinking bath, it is more preferable that it is about 30-60 degreeC. In addition, the immersion time in the crosslinking bath cannot be determined uniformly because the degree of crosslinking of the polyvinyl alcohol-based film is affected by the temperature of the crosslinking bath, but it is preferably about 5 to 300 seconds, and about 10 to 200 seconds. It is more preferable that The said crosslinking process may be performed only once, and may be performed multiple times as needed.

The stretching step is a treatment step of stretching the polyvinyl alcohol-based film in at least one direction at a predetermined magnification. Generally, a polyvinyl alcohol-type film is uniaxially stretched in a conveyance direction (longitudinal direction). The stretching method is not particularly limited, and either a wet stretching method or a dry stretching method may be employed. The said extending process may be performed only once, and may be performed multiple times as needed. The said extending process may be performed at any stage in manufacture of a polarizing film.

As the treatment bath (stretching bath) in the wet stretching method, a solvent such as water or a water-miscible organic solvent and a mixed solution of water can be used normally. The said stretching bath may contain potassium iodide from a viewpoint of controlling content of the said potassium in the said polarizing film. When using potassium iodide for the said extending|stretching bath, it is preferable that the density|concentration of potassium iodide in the said extending|stretching bath is about 1 to 15 weight%, It is more preferable that it is about 2 to 10 weight%, It is about 3 to 6 weight%. It is more preferable that In addition, the treatment bath (stretching bath) may contain the boron compound from the viewpoint of suppressing film breakage during stretching. In this case, the concentration of the boron compound in the stretching bath is about 1 to 15% by weight. It is more preferable that it is about 1.5 to 10 weight%, and it is more preferable that it is about 2 to 5 weight%.

It is preferable that the temperature of the said drawing bath is about 25-80 degreeC, It is more preferable that it is about 40-75 degreeC, It is more preferable that it is about 50-70 degreeC. The immersion time in the stretching bath cannot be determined uniformly because the degree of stretching of the polyvinyl alcohol-based film is affected by the temperature of the stretching bath, but it is preferably about 10 to 800 seconds, and about 30 to 500 seconds. It is more preferable that In addition, you may implement the extending|stretching process in the said wet extending|stretching method together with the treatment process of any one or more of the said swelling process, the said dyeing|staining process, the said bridge|crosslinking process, and the said washing|cleaning process.

Examples of the dry stretching method include an inter-roll stretching method, a heated roll stretching method, and a compression stretching method. In addition, you may implement the said dry stretching method together with the said drying process.

The total draw ratio (accumulated draw ratio) applied to the polyvinyl alcohol-based film can be appropriately set depending on the purpose, but is preferably about 2 to 7 times, more preferably about 3 to 6.8 times, and 3.5 to It is more preferable that it is about 6.5 times.

The cleaning step is a treatment step of immersing the polyvinyl alcohol-based film in a cleaning bath, and foreign substances remaining on the surface of the polyvinyl alcohol-based film can be removed. As the washing bath, a medium containing water as a main component, such as water, distilled water, or pure water, is usually used. In addition, from the viewpoint of controlling the content of potassium in the polarizing film, potassium iodide may be included in the washing bath, and in this case, the concentration of potassium iodide in the washing bath is preferably about 1 to 10% by weight, and 1.5 It is more preferable that it is about -4 weight%, and it is still more preferable that it is about 1.8-3.8 weight%.

It is preferable that the temperature of the said washing|cleaning bath is about 5-50 degreeC, It is more preferable that it is about 10-40 degreeC, It is still more preferable that it is about 15-35 degreeC. In addition, the immersion time in the cleaning bath cannot be determined uniformly because the degree of cleaning of the polyvinyl alcohol-based film is affected by the temperature of the cleaning bath, but it is preferably about 1 to 100 seconds, and about 2 to 50 seconds. It is more preferable that it is, and it is still more preferable that it is about 3 to 20 second. The said swelling process may be performed only once, and may be performed multiple times as needed.

The manufacturing method of the polarizing film of this invention may provide a drying process. The said drying process is a process of drying the polyvinyl alcohol-type film wash|cleaned in the said washing|cleaning process, and obtaining a polarizing film, The polarizing film which has a desired moisture content is obtained by drying. Said drying is performed by arbitrary suitable methods, for example, natural drying, air drying, and heat drying are illustrated.

It is preferable that it is about 20-150 degreeC, and, as for the said drying temperature, it is more preferable that it is about 25-100 degreeC. The drying time cannot be determined uniformly because the degree of drying of the polarizing film is affected by the drying temperature, but it is preferably about 10 to 600 seconds, and more preferably about 30 to 300 seconds. The said drying process may be performed only once, and may be performed multiple times as needed.

The polarizing film preferably has a thickness of 1 µm or more from the viewpoint of improving the initial polarization degree of the polarizing film, more preferably 2 µm or more, and preferably 15 µm or less from the viewpoint of preventing warpage of the panel, and more preferably 10 µm or less It is preferable, and it is more preferable that it is 8 micrometers or less. In particular, in order to obtain a polarizing film having a thickness of about 8 μm or less, as the polyvinyl alcohol-based film, a laminate including a polyvinyl alcohol-based resin layer formed on a thermoplastic resin substrate is used. This can be applied.

<Method for producing thin polarizing film>

A method for producing a thin polarizing film is to form a polyvinyl alcohol-based resin layer (PVA-based resin layer) containing a polyvinyl alcohol-based resin (PVA-based resin) on one side of a long thermoplastic resin substrate to form a laminate, and lamination It includes performing an aerial auxiliary extending|stretching process, a dyeing|staining process, an underwater extending|stretching process, and a drying shrinkage process to a sieve in this order. In particular, in order to obtain a polarizing film having high optical properties, a method of two-stage stretching in which an air-assisted stretching treatment (dry stretching) and an underwater stretching treatment in an aqueous boric acid solution are combined is selected.

Any suitable method is employ|adopted as a method of producing the said laminated body, For example, the method is illustrated by apply|coating the coating liquid containing the said PVA-type resin to the surface of the said thermoplastic resin base material, and drying. It is preferable that it is about 20-300 micrometers, and, as for the thickness of the said thermoplastic resin base material, it is more preferable that it is about 50-200 micrometers. It is preferable that it is about 3-40 micrometers, and, as for the thickness of the said PVA-type resin layer, it is more preferable that it is about 3-20 micrometers.

The thermoplastic resin substrate absorbs water to significantly reduce the stretching stress, and from the viewpoint of being able to stretch at a high magnification, the water absorption is preferably about 0.2% or more, and more preferably about 0.3% or more. On the other hand, in the thermoplastic resin substrate, the dimensional stability of the thermoplastic resin substrate is significantly reduced, and from the viewpoint of preventing problems such as deterioration of the appearance of the resulting polarizing film, the water absorption is preferably about 3% or less, and about 1% or less. more preferably. In addition, the said water absorption rate can be adjusted by introduce|transducing a modifier into the constituent material of the said thermoplastic resin base material, for example. The said water absorption is a value calculated|required according to JISK7209.

The thermoplastic resin substrate preferably has a glass transition temperature (Tg) of about 120°C or less from the viewpoint of sufficiently securing the stretchability of the laminate while suppressing crystallization of the PVA-based resin layer. Further, in consideration of plasticization of the thermoplastic resin substrate with water and good stretching in water, the glass transition temperature (Tg) is more preferably about 100° C. or less, and still more preferably about 90° C. or less. On the other hand, the glass transition temperature of the thermoplastic resin substrate is preferably about 60° C. or higher from the viewpoint of preventing problems such as deformation of the thermoplastic resin substrate when the coating liquid is applied and dried, and thus a good laminate can be produced. In addition, the said glass transition temperature can be adjusted by heating using the crystallization material which introduce|transduces a modifying group into the constituent material of the said thermoplastic resin base material, for example. The said glass transition temperature (Tg) is a value calculated|required according to JISK7121.

Any suitable thermoplastic resin may be employed as the constituent material of the thermoplastic resin substrate. Examples of the thermoplastic resin include ester resins such as polyethylene terephthalate resins, cycloolefin resins such as norbornene resins, olefin resins such as polypropylene, polyamide resins, polycarbonate resins, and these A copolymer resin etc. are illustrated. Among these, norbornene-based resins and amorphous (non-crystalline) polyethylene terephthalate-based resins are preferable, and the thermoplastic resin substrate is extremely excellent in stretchability and amorphous (secret) from the viewpoint that crystallization at the time of stretching can be suppressed. Qualitative) A polyethylene terephthalate-based resin is preferably used. As the amorphous (non-crystalline) polyethylene terephthalate-based resin, a copolymer containing isophthalic acid and/or cyclohexanedicarboxylic acid as dicarboxylic acid, and a copolymer containing cyclohexanedimethanol or diethylene glycol as glycol is exemplified

The thermoplastic resin substrate may be subjected to surface treatment (eg, corona treatment, etc.) before forming the PVA-based resin layer, or an easy-adhesive layer may be formed on the thermoplastic resin substrate. By performing such a process, the adhesiveness of a thermoplastic resin base material and a PVA-type resin layer can be improved. In addition, the said thermoplastic resin base material may be extended|stretched before forming a PVA-type resin layer.

The coating solution is a solution in which a PVA-based resin is dissolved in a solvent. Examples of the solvent include water, dimethylsulfoxide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, various glycols, polyhydric alcohols such as trimethylolpropane, ethylenediamine, and diethylenetriamine. Amines are illustrated, and water is preferable. These can be used individually or in combination of 2 or more types. The concentration of the PVA-based resin in the coating solution is preferably about 3 to 20 parts by weight based on 100 parts by weight of the solvent from the viewpoint of forming a uniform coating film in close contact with the thermoplastic resin substrate.

It is preferable that a halide is mix|blended with the said coating liquid from a viewpoint of improving the orientation of polyvinyl alcohol molecules by extending|stretching. Any suitable halide may be employed as the halide, and examples thereof include iodide and sodium chloride. As said iodide, potassium iodide, sodium iodide, lithium iodide etc. are illustrated, for example, Potassium iodide is preferable. It is preferable that it is about 5-20 weight part with respect to 100 weight part of PVA-type resin, and, as for the density|concentration of the said halide in the said coating liquid, it is more preferable that it is about 10-15 weight part.

Moreover, you may mix|blend an additive with the said coating liquid. As said additive, For example, plasticizers, such as ethylene glycol and glycerol; Surfactants, such as a nonionic surfactant, etc. are illustrated.

Any suitable method can be adopted as the coating method of the coating liquid, for example, a roll coating method, a spin coating method, a wire bar coating method, a dip coating method, a die coating method, a curtain coating method, a spray coating method, and a knife. A coating method (comma coating method, etc.) etc. are illustrated. Moreover, it is preferable that the drying temperature of the said coating liquid is about 50 degreeC or more.

Since the above-mentioned aerial assisted stretching treatment enables stretching while suppressing crystallization of the thermoplastic resin substrate, the laminate can be stretched at a high magnification. The stretching method of the aerial auxiliary stretching treatment may be fixed-end stretching (eg, stretching using a tenter stretching machine), or free-end stretching (eg, uniaxial by passing a laminate between rolls having different peripheral speeds) stretching method), but free-end stretching is preferable from the viewpoint of obtaining high optical properties.

It is preferable that the draw ratio in the said aerial auxiliary extending|stretching is about 2-3.5 times. The said aerial auxiliary extending|stretching may be performed in one step, and may be performed in multiple steps. When carrying out in multiple steps, the draw ratio is the product of the draw ratios of each step.

The stretching temperature in the air-assisted stretching can be set to any appropriate value depending on the forming material of the thermoplastic resin substrate, the stretching method, etc., for example, it is preferably not less than the glass transition temperature (Tg) of the thermoplastic resin substrate, the glass It is more preferable that it is transition temperature (Tg)+10 degreeC or more, and it is still more preferable that it is the said glass transition temperature (Tg)+15 degreeC or more. On the other hand, the upper limit of the stretching temperature suppresses the rapid progress of crystallization of the PVA-based resin, and from the viewpoint of suppressing problems due to crystallization (for example, interfering with the orientation of the PVA-based resin layer due to stretching). It is preferable that it is about 170 degreeC.

If necessary, you may perform an insolubilization process after the said aerial auxiliary extending|stretching process, before a dyeing|staining process or an underwater extending|stretching process. The insolubilization treatment is typically performed by immersing the PVA-based resin layer in an aqueous boric acid solution. By performing an insolubilization process, water resistance can be provided to a PVA-type resin layer, and the orientation fall of PVA at the time of being immersed in water can be prevented. The concentration of the boric acid aqueous solution is preferably about 1 to 5 parts by weight based on 100 parts by weight of water. It is preferable that the liquid temperature of an insolubilization treatment bath is about 20-50 degreeC.

The dyeing treatment is performed by dyeing the PVA-based resin layer with iodine. As the adsorption method, for example, a method of immersing a PVA-based resin layer (laminate) in a dyeing solution containing iodine, a method of applying the dyeing solution to the PVA-based resin layer, and applying the dyeing solution to a PVA-based resin layer The method of spraying etc. are illustrated, The method of immersing the PVA-type resin layer (laminated body) in the dyeing liquid containing iodine is preferable.

It is preferable that the compounding quantity of the iodine in the said dyeing bath is about 0.05-0.5 weight part with respect to 100 weight part of water. In order to improve the solubility of iodine in water, it is preferable to mix|blend the said iodide with iodine aqueous solution. It is preferable that it is about 0.1-10 weight part with respect to 100 weight part of water, and, as for the compounding quantity of the said iodide, it is more preferable that it is about 0.3-5 weight part. It is preferable that the liquid temperature of a dyeing bath is about 20-50 degreeC in order to suppress dissolution of PVA-type resin. Moreover, it is preferable that they are about 5 second - about 5 minutes from a viewpoint of ensuring the transmittance|permeability of a PVA-type resin layer, and, as for immersion time, it is more preferable that they are about 30 second - 90 second. From a viewpoint of obtaining the polarizing film which has favorable optical properties, it is preferable that the ratio of content of iodine and iodide in an aqueous iodine solution is about 1:5-1:20, and it is more preferable that it is about 1:5-1:10.

If necessary, after the dyeing treatment, before the underwater stretching treatment, a crosslinking treatment may be performed. The crosslinking treatment is typically performed by immersing the PVA-based resin layer in an aqueous boric acid solution. By performing a crosslinking process, water resistance can be provided to a PVA-type resin layer, and the orientation fall of PVA at the time of immersing in hot water by subsequent underwater extending|stretching can be prevented. The boric acid concentration of the boric acid aqueous solution is preferably about 1 to 5 parts by weight based on 100 parts by weight of water. Moreover, when performing a crosslinking process, it is further preferable to mix|blend the said iodide with the crosslinking bath in a crosslinking process. By mix|blending the said iodide, the elution of the iodine made to adsorb|suck to the PVA-type resin layer can be suppressed. It is preferable that the compounding quantity of the said iodide is about 1-5 weight part with respect to 100 weight part of water. It is preferable that the liquid temperature of a crosslinking bath (boric acid aqueous solution) is about 20-50 degreeC.

The underwater stretching treatment is performed by immersing the laminate in a stretching bath. According to the underwater stretching treatment, stretching can be performed at a temperature lower than the glass transition temperature (typically, about 80° C.) of the thermoplastic resin substrate or the PVA-based resin layer, and the PVA-based resin layer is stretched at a high magnification while suppressing its crystallization. can do. The stretching method of the underwater stretching treatment may be fixed-end stretching (for example, a method of stretching using a tenter stretching machine), or free-end stretching (eg, uniaxial stretching by passing a laminate between rolls having different peripheral speeds) method) may be used, but free-end stretching is preferable from the viewpoint of obtaining high optical properties.

It is preferable that the said underwater extending|stretching process immerses a laminated body in boric-acid aqueous solution, and performs (boric-acid water-in-water extending|stretching). By using the aqueous boric acid solution as the stretching bath, it is possible to impart rigidity to the PVA-based resin layer to withstand the tension applied during stretching and water resistance insoluble in water. It is preferable that it is 1-10 weight part with respect to 100 weight part of water, and, as for the boric acid concentration of boric-acid aqueous solution, it is more preferable that it is 2.5-6 weight part. Moreover, you may mix|blend an iodide with the said extending|stretching bath (boric acid aqueous solution). It is preferable that it is about 40-85 degreeC, and, as for the liquid temperature of a drawing bath, it is more preferable that it is about 60 degreeC - 75 degreeC. It is preferable that the immersion time to the extending|stretching bath of a laminated body is about 15 second - about 5 minutes.

It is preferable that it is about 1.5 times or more, and, as for the draw ratio in the said underwater extending|stretching, it is more preferable that it is about 3 times or more.

Moreover, it is preferable that it is about 5 times or more with respect to the original length of a laminated body, and, as for the total draw ratio of a laminated body, it is more preferable that it is about 5.5 times or more.

The said dry shrinkage process may be performed by zone heating performed by heating the whole zone, and may be performed by heating a conveyance roll (a so-called heating roll is used), but both are preferably used. By drying using a heating roll, it is possible to efficiently suppress heating curl of the laminate to produce a polarizing film excellent in appearance, and also to keep the laminate in a flat state while drying it, thereby suppressing the occurrence of wrinkles as well as curls. can do. Further, from the viewpoint of improving the optical properties of the polarizing film obtained by shrinking in the width direction during the drying shrinkage treatment, the shrinkage rate in the width direction of the laminate by the dry shrinkage treatment is preferably about 1 to 10%, and 2 to It is more preferable that it is about 8 %.

Drying conditions are controllable by adjusting the heating temperature (temperature of a heating roll) of a conveyance roll, the number of heating rolls, contact time with a heating roll, etc. It is preferable that the temperature of a heating roll is about 60-120 degreeC, It is more preferable that it is about 65-100 degreeC, It is still more preferable that it is 70-80 degreeC. From the viewpoint of increasing the crystallinity of the thermoplastic resin favorably and suppressing curl favorably, the number of conveying rolls is usually about 2 to 40, preferably about 4 to 30. It is preferable that it is about 1 to 300 second, as for the contact time (total contact time) of a laminated body and a heating roll, it is more preferable that it is 1 to 20 second, It is more preferable that it is 1 to 10 second.

A heating roll may be installed in a heating furnace, and may be installed in a normal production line (under a room temperature environment). Preferably, it is installed in the heating furnace provided with the blowing means. By using together drying by a heating roll and hot air drying, the rapid temperature change between heating rolls can be suppressed and the shrinkage|contraction of the width direction can be controlled easily. It is preferable that the temperature of hot air drying is about 30-100 degreeC. Moreover, it is preferable that hot air drying time is about 1-300 second.

It is preferable to perform a washing|cleaning process before a dry shrinkage process after an underwater extending|stretching process. The washing treatment is typically performed by immersing the PVA-based resin layer in an aqueous potassium iodide solution.

In addition, when manufacturing a thin polarizing film containing the compound having the radical trapping function, at least one treatment bath of dyeing treatment, underwater stretching treatment, insolubilization treatment, crosslinking treatment, and washing treatment has the radical trapping function It is good to contain a compound. The concentration of the compound having a radical trapping function contained in any one of the above treatment baths cannot be determined uniformly because it is affected by the number of treatments, treatment time, treatment temperature, etc. of each treatment, but the radical trapping function in the polarizing film is not determined. From the viewpoint of being able to efficiently control the content of the compound having, it is usually preferably 0.01% by weight or more, more preferably 0.05% by weight or more, still more preferably 0.1% by weight or more, and preferably 30% by weight or less, It is more preferable that it is 25 weight% or less, and it is still more preferable that it is 20 weight% or less.

In particular, in the case of performing a washing treatment, the washing treatment is performed by elution of components such as iodine or a compound having a radical trapping function from the polyvinyl alcohol-based film, or polyvinyl alcohol in a state in which treatment conditions such as dyeing treatment and underwater stretching treatment are taken into consideration. It is easy to adjust content of the said iodine and the compound which has the said radical trapping function to a desired range from a viewpoint which can be made to adsorb|suck to an alcohol-type film.

<Polarizing film>

In the polarizing film of the present invention, a transparent protective film is bonded to at least one surface of the polarizing film.

The transparent protective film is not particularly limited, and various kinds of transparent protective films used for polarizing films can be used. As a material constituting the transparent protective film, for example, a thermoplastic resin excellent in transparency, mechanical strength, thermal stability, moisture barrier property, isotropy, and the like is used. Examples of the thermoplastic resin include cellulose ester-based resins such as triacetyl cellulose, polyester-based resins such as polyethylene terephthalate and polyethylene naphthalate, polyethersulfone-based resins, polysulfone-based resins, polycarbonate-based resins, nylon, Polyamide-based resins such as aromatic polyamide, polyimide-based resins, polyolefin-based resins such as polyethylene, polypropylene, and ethylene/propylene copolymers, (meth)acrylic-based resins, and cyclic polyolefin-based resins having a cyclo or norbornene structure ( norbornene-based resins), polyarylate-based resins, polystyrene-based resins, polyvinyl alcohol-based resins, and mixtures thereof. In addition, as the transparent protective film, a cured layer formed of a thermosetting resin or ultraviolet curable resin such as (meth)acrylic, urethane, acrylic urethane, epoxy, or silicone may be used. Among these, cellulose ester-type resin, polycarbonate-type resin, (meth)acrylic-type resin, cyclic polyolefin-type resin, and polyester-type resin are suitable.

Although the thickness of the transparent protective film can be appropriately determined, in general, it is preferably about 1-500 µm, more preferably about 1-300 µm, from the viewpoint of workability such as strength and handleability, thin layer properties, etc. , more preferably about 5 to 100 µm.

When bonding the said transparent protective film to both surfaces of the said polarizing film, the transparent protective film of the both surfaces may be same or different.

As the transparent protective film, a retardation plate having a phase difference of 40 nm or more and/or a thickness direction retardation of 80 nm or more may be used. The front retardation is normally controlled in the range of 40 to 200 nm, and the thickness direction retardation is usually controlled in the range of 80 to 300 nm. When using a retardation plate as the said transparent protective film, since the said retardation plate also functions as a transparent protective film, thickness reduction can be aimed at.

Examples of the retardation plate include a birefringent film formed by uniaxially or biaxially stretching a polymer material, an alignment film of a liquid crystal polymer, and a film in which an alignment layer of a liquid crystal polymer is supported on the film. Although the thickness in particular of a retardation plate is not restrict|limited, About 20-150 micrometers is common. Moreover, you may use by bonding the said phase plate to the transparent protective film which does not have a phase difference.

The transparent protective film may contain any appropriate additives such as an ultraviolet absorber, antioxidant, lubricant, plasticizer, mold release agent, color inhibitor, flame retardant, antistatic agent, pigment, and colorant. In particular, when a UV absorber is included in the transparent protective film, light resistance of the polarizing film may be improved.

Functional layers such as a hard coat layer, an antireflection layer, an antisticking layer, a diffusion layer and an antiglare layer may be formed on the surface of the transparent protective film on which the polarizing film is not bonded. In addition, the functional layers such as the hard coat layer, the anti-reflection layer, the anti-sticking layer, the diffusion layer and the anti-glare layer may be formed on the protective film itself, or may be formed separately from the protective film.

The polarizing film and the transparent protective film, or the polarizing film and the functional layer are usually bonded through an adhesive layer or an adhesive layer.

As the pressure-sensitive adhesive for forming the pressure-sensitive adhesive layer, various pressure-sensitive adhesives used in polarizing films can be applied, for example, rubber-based pressure-sensitive adhesives, acrylic pressure-sensitive adhesives, silicone pressure-sensitive adhesives, urethane pressure-sensitive adhesives, vinyl alkyl ether pressure-sensitive adhesives, polyvinyl alcohol pressure-sensitive adhesives, Although polyvinylporrolidone-type adhesive, polyacrylamide-type adhesive, a cellulose-type adhesive etc. are illustrated, Among these, an acrylic adhesive is suitable.

As a method of forming the pressure-sensitive adhesive layer, for example, the pressure-sensitive adhesive is applied to a peeling-treated separator or the like, dried to form the pressure-sensitive adhesive layer, then transferred to a polarizing film or the like, or the pressure-sensitive adhesive is applied to a polarizing film or the like and dried A method of forming the pressure-sensitive adhesive layer and the like may be exemplified. The thickness in particular of the said adhesive layer is not restrict|limited, For example, it is about 1-100 micrometers, and it is preferable that it is about 2-50 micrometers.

As the adhesive for forming the adhesive layer, various adhesives used in polarizing films can be applied, for example, isocyanate-based adhesives, polyvinyl alcohol-based adhesives, gelatin-based adhesives, vinyl-based latex-based adhesives, water-based polyesters, etc. is exemplified These adhesives are normally used as an adhesive agent (water-based adhesive) which consists of aqueous solution, and contains 0.5 to 60 weight% of solid content.

The water-based adhesive may contain a crosslinking agent. As said crosslinking agent, the compound which has at least 2 functional groups which have reactivity with components, such as a polymer which comprises an adhesive agent, in 1 molecule is used normally as said crosslinking agent, For example, alkylenediamine; isocyanates; epoxies; aldehydes; and amino-formaldehyde such as methylol urea and methylol melamine. The compounding quantity of the crosslinking agent in an adhesive agent is about 10-60 weight part normally with respect to 100 weight part of components, such as a polymer which comprises an adhesive agent.

As said adhesive agent, other than the above, active energy ray hardening adhesives, such as an ultraviolet curing adhesive and an electron beam curing adhesive, are illustrated. As said active energy ray hardening-type adhesive agent, a (meth)acrylate-type adhesive agent is illustrated, for example. As a curable component in the said (meth)acrylate-type adhesive agent, the compound which has a (meth)acryloyl group, and the compound which has a vinyl group are illustrated, for example. Examples of the compound having a (meth)acryloyl group include alkyl (meth)acrylates such as chain alkyl (meth)acrylates having 1 to 20 carbon atoms, alicyclic alkyl (meth)acrylates, and polycyclic alkyl (meth)acrylates. ) acrylates; hydroxyl group-containing (meth)acrylate; Epoxy group-containing (meth)acrylates, such as glycidyl (meth)acrylate, etc. are illustrated. The (meth)acrylate-based adhesive is hydroxyethyl (meth)acrylamide, N-methylol (meth)acrylamide, N-methoxymethyl (meth)acrylamide, N-ethoxymethyl (meth)acrylamide, ( Nitrogen-containing monomers, such as meth)acrylamide and (meth)acryloylmorpholine, may be included. The (meth)acrylate-based adhesive is a crosslinking component, and includes tripropylene glycol diacrylate, 1,9-nonanediol diacrylate, tricyclodecane dimethanol diacrylate, cyclic trimethylol propane formal acrylate, and dioxane glycol. Polyfunctional monomers, such as diacrylate and EO modified|denatured diglycerol tetraacrylate, may be included. Moreover, the compound which has an epoxy group or oxetanyl group can also be used as a cationic polymerization hardening-type adhesive agent. The compound having an epoxy group is not particularly limited as long as it has at least two epoxy groups in the molecule, and various generally known curable epoxy compounds can be used.

The said adhesive may contain the appropriate additive as needed. Examples of the additives include coupling agents such as silane coupling agents and titanium coupling agents, adhesion promoters such as ethylene oxide, ultraviolet absorbers, deterioration inhibitors, dyes, processing aids, ion trapping agents, antioxidants, tackifiers, fillers , a plasticizer, a leveling agent, a foaming inhibitor, an antistatic agent, a heat-resistant stabilizer, a hydrolysis-resistant stabilizer, and the like.

Application of the said adhesive may be performed to any of the said transparent protective film side (or the said functional layer side), the said polarizing film side, and may be performed to both. After bonding, a drying step is performed to form an adhesive layer comprising a coating and drying layer. After the drying process, ultraviolet rays or electron beams may be irradiated as needed. The thickness of the adhesive layer is not particularly limited, and when a water-based adhesive or the like is used, it is preferably about 30 to 5000 nm, more preferably about 100 to 1000 nm, and an ultraviolet curing adhesive, electron beam curing adhesive, etc. is used. In this case, it is preferable that it is about 0.1-100 micrometers, and it is more preferable that it is about 0.5-10 micrometers.

The transparent protective film and the polarizing film, or the polarizing film and the functional layer may be laminated through an intervening layer such as a surface modification treatment layer, an easy-adhesive layer, a block layer, and a refractive index adjusting layer.

Examples of the surface modification treatment for forming the surface modification layer include corona treatment, plasma treatment, primer treatment, saponification treatment, and the like.

Examples of the easy-to-adhesive agent for forming the easy-to-adhesive layer include various resins having a polyester skeleton, polyether skeleton, polycarbonate skeleton, polyurethane skeleton, silicone skeleton, polyamide skeleton, polyimide skeleton, polyvinyl alcohol skeleton, etc. A forming material is exemplified. The said easily adhesive layer is normally formed in advance in a protective film, and the said adhesive layer or the said adhesive bond layer laminates|stacks the easily adhesive layer side of the said protective film, and a polarizing film.

The blocking layer is a layer having a function of preventing impurities such as oligomers and ions eluted from the transparent protective film or the like from migrating (infiltrating) into the polarizing film. The block layer may be a layer that has transparency and can prevent impurities eluted from the transparent protective film or the like. As a material for forming the block layer, for example, a urethane prepolymer-based forming material, a cyanoacrylate-based forming material Ash, an epoxy-based forming material, and the like are exemplified.

The refractive index adjusting layer is a layer formed to suppress a decrease in transmittance caused by reflection between the transparent protective film and layers having different refractive indices, such as a polarizing film. As a refractive index adjusting material which forms the said refractive index adjusting layer, the forming agent containing various resin and additives which have, for example, a silica type, an acryl type, an acryl-styrene type, a melamine type, etc. are illustrated.

The polarization film preferably has a polarization degree of 99.98% or more, and more preferably a polarization degree of 99.99% or more.

<Lamination Polarizing Film>

As for the laminated polarizing film (optical laminated body) of this invention, the said polarizing film is bonded by the optical layer. The optical layer is not particularly limited, but for example, a reflective plate, a transflective plate, a retardation plate (including a wave plate such as 1/2 or 1/4), and a liquid crystal display device such as a visual compensation film One or two or more optical layers may be used. As the laminated polarizing film, in particular, a reflective polarizing film or a transflective polarizing film in which a reflecting plate or a transflective reflecting plate is further laminated on the polarizing film, an elliptically polarizing film or a circularly polarizing film in which a retardation plate is further laminated on the polarizing film; A wide viewing angle polarizing film in which a visual compensation film is further laminated on a polarizing film, or a polarizing film in which a brightness enhancing film is further laminated on the polarizing film is exemplified.

On one or both surfaces of the polarizing film or the laminated polarizing film, an image display cell such as a liquid crystal cell or an organic EL element, and a front transparent member such as a front transparent plate or a touch panel on the viewing side are other An adhesive layer for joining members may be laid. An adhesive layer is suitable as said adhesive bond layer. The pressure-sensitive adhesive for forming the pressure-sensitive adhesive layer is not particularly limited, but for example, an acrylic polymer, silicone-based polymer, polyester, polyurethane, polyamide, polyether, fluorine-based or rubber-based polymer as the base polymer is appropriately selected and used. can In particular, like the adhesive containing an acrylic polymer, it is excellent in optical transparency, shows moderate wettability, cohesiveness, and adhesiveness, and is excellent in weather resistance, heat resistance, etc. are used preferably.

Laying of the pressure-sensitive adhesive layer on one side or both sides of the polarizing film or the laminated polarizing film can be performed by an appropriate method. As laying of the pressure-sensitive adhesive layer, for example, a method of preparing an pressure-sensitive adhesive solution and directly laying it on the polarizing film or the laminated polarizing film by a suitable development method such as a casting method or a coating method, or a pressure-sensitive adhesive layer on a separator The method of forming it and attaching it on the said polarizing film or the said laminated polarizing film, etc. are illustrated. The thickness of the pressure-sensitive adhesive layer can be appropriately determined depending on the purpose of use, adhesive strength, and the like, and is generally 1 to 500 μm, preferably 5 to 200 μm, and more preferably 10 to 100 μm. Thus, what an adhesive layer was formed in the at least one surface of the said polarizing film or the said laminated polarizing film is called a polarizing film with an adhesive layer, or a laminated polarizing film with an adhesive layer.

The exposed surface of the pressure-sensitive adhesive layer is preferably covered by a separator for the purpose of preventing contamination thereof while it is practically provided. Thereby, contamination of the pressure-sensitive adhesive layer and the like in a normal handling condition can be prevented. As the separator, for example, a suitable thin leaf body such as a plastic film, rubber sheet, paper, cloth, nonwoven fabric, net, foam sheet, metal foil, and laminates thereof may be used, as necessary, silicone-based, long-chain alkyl-based, fluorine-based or molybdenum sulfide, etc. Those coated with an appropriate release agent of

<Image display panel and image display device>

As for the image display panel of this invention, the said polarizing film or the said laminated polarizing film is bonded by the image display cell. Moreover, the image display apparatus of this invention is equipped with a front transparent member on the polarizing film or laminated polarizing film side (viewing side) of the said image display panel.

As said image display cell, a liquid crystal cell, organic electroluminescent cell, etc. are illustrated, for example. As the liquid crystal cell, for example, any of a reflective liquid crystal cell using external light, a transmissive liquid crystal cell using light from a light source such as a backlight, and a transflective liquid crystal cell using both light from the outside and light from the light source you may use that In the case where the liquid crystal cell uses light from a light source, in the image display device (liquid crystal display device), a polarizing film is disposed also on the side opposite to the viewing side of the image display cell (liquid crystal cell), and a light source is disposed. It is preferable that the polarizing film on the side of the said light source and the liquid crystal cell are bonded together through a suitable adhesive bond layer. As a drive method of the said liquid crystal cell, the thing of arbitrary types, such as a VA mode, an IPS mode, a TN mode, an STN mode, and a band orientation (pi type), can be used, for example.

As said organic electroluminescent cell, what laminated|stacked in order a transparent electrode, an organic light emitting layer, and a metal electrode on a transparent substrate, and formed the light emitting body (organic electroluminescent light emitting body) etc. are used suitably, for example. The organic light emitting layer is a laminate of various organic thin films, for example, a laminate of a hole injection layer made of a triphenylamine derivative and a light emitting layer made of a fluorescent organic solid such as anthracene, or a layered product of these light emitting layers and a perylene derivative. Various layer structures, such as a laminated body of an electron injection layer, or a laminated body of a hole injection layer, a light emitting layer, and an electron injection layer, etc. can be employ|adopted.

As a front transparent member arrange|positioned on the visual recognition side of the said image display cell, a front transparent plate (window layer), a touch panel, etc. are illustrated, for example. As the front transparent plate, a transparent plate having an appropriate mechanical strength and thickness is used. As such a transparent plate, a transparent resin plate, such as an acrylic resin or polycarbonate-type resin, or a glass plate, etc. are used, for example. As said touch panel, various touch panels, such as a resistive film method, a capacitive method, an optical method, and an ultrasonic method, a glass plate, a transparent resin board, etc. provided with a touch sensor function are used, for example. When a capacitive touch panel is used as the front transparent member, it is preferable that a front transparent plate made of glass or a transparent resin plate is formed on a more visible side than the touch panel.

Since the polarizing film of the present invention has a good initial polarization degree and is excellent in the inhibitory effect of lowering the single transmittance due to coloring of the polarizing film under a high temperature environment, the polarizing film of the present invention, and a polarizing film using the polarizing film, and a laminated polarizing film , an image display panel, and an image display apparatus are suitable for use in a vehicle-mounted image display apparatus such as a car navigation device and a back monitor.

Example

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

<Example 1>

<Production of polarizing film>

As the thermoplastic resin substrate, an amorphous isophthalic copolymerized polyethylene terephthalate film (thickness: 100 µm) having a long water absorption rate of 0.75% and a Tg of about 75°C was used. Corona treatment was performed on one side of the resin substrate. Polyvinyl alcohol (degree of polymerization 4200, degree of saponification of 99.2 mol%) and acetacetyl-modified PVA (manufactured by The Nippon Synthetic Chemical Industry Co., Ltd., trade name "Gohsephimer Z410") are mixed in a ratio of 9: 1 PVA-based resin 100 parts by weight 13 weight part of potassium iodide was added to this, and the PVA aqueous solution (coating liquid) was prepared. The said PVA aqueous solution was apply|coated to the corona-treated surface of a resin base material, and the PVA type resin layer of thickness 13 micrometers was formed by drying at 60 degreeC, and the laminated body was produced. The free-end uniaxial stretching of the obtained laminated body was carried out by 2.4 times in the longitudinal direction (longitudinal direction) between rolls with different circumferential speeds in 130 degreeC oven (air-assisted stretching process). Next, the layered product was immersed in an insolubilization bath (aqueous solution having a boric acid concentration of 4.0 wt%) at a liquid temperature of 40°C for 30 seconds (insolubilization treatment). Next, in a dyeing bath (aqueous solution of iodine obtained by mixing iodine and potassium iodide in a weight ratio of 1:7 with respect to 100 parts by weight of water) at a liquid temperature of 30°C, the concentration is adjusted so that the iodine concentration of the finally obtained polarizing film is 9.3%. While immersing for 60 seconds (dye treatment). Next, it was made to immerse for 30 second in the crosslinking bath (a potassium iodide concentration of 3.0 weight%, and a boric acid concentration of 5.0 weight%) of a bridge|crosslinking bath with a liquid temperature of 40 degreeC (crosslinking process). Thereafter, while the laminate was immersed in a boric acid aqueous solution (boric acid concentration of 4.0% by weight) at a liquid temperature of 70° C., uniaxial stretching was performed between rolls having different peripheral speeds so that the total draw ratio in the longitudinal direction (longitudinal direction) was 5.5 times (under water). stretching treatment). Thereafter, the laminate was immersed in a washing bath at a liquid temperature of 20°C (aqueous solution having a potassium iodide concentration of 3% by weight, a compound having a radical trapping function and a compound concentration of 1.0% by weight represented by the following general formula (9)) ( cleaning treatment). Thereafter, while drying in an oven maintained at 90°C, it was brought into contact with a heating roll made of SUS whose surface temperature was maintained at 75°C for about 2 seconds (dry shrinkage treatment). In this way, a polarizing film having a thickness of 5 µm was formed on the resin substrate. Moreover, in the obtained polarizing film, the peak temperature of the maximum intensity of water detected by the generated gas analysis method was 204 degreeC, and content of the compound represented by the following general formula (9) in a polarizing film was 0.3 weight%.

[Method for Measuring Iodine Concentration (wt%) in Polarizing Film]

About the polarizing film, the iodine concentration (weight%) was calculated|required using the following formula using the fluorescent X-ray analyzer (The Rigaku Corporation make, brand name "ZSX-PRIMUS IV", measurement diameter: phi 20mm).

Iodine concentration (wt%) = 14.474 × (fluorescence X-ray intensity) / (film thickness) (kcps/㎛)

In addition, the coefficient at the time of calculating a density|concentration differs depending on the measuring apparatus, but the said coefficient can be calculated|required using an appropriate calibration curve.

[Generated gas analysis method]

A polarizing film is introduced into a furnace-type pyrolizer (manufactured by Frontier Laboratories, Ltd., PY-2020iD), and the generated gas is directly introduced into TOF MS (manufactured by JEOL, Ltd., JMS-T100GCV) to analyze the generated gas (EGA/ TOF MS) method was performed.

[Measuring conditions]

Temperature rise condition: 40℃→+10℃/min→350℃

Interface: Inert Fused Silica Tube, 2.5m×0.15mm id

Carrier gas: He (1.0 mL/min)

Inlet temperature: 300℃

Inlet: Split ratio 20:1

Interface temperature: 300℃

Mass Spectrometer: TOF MS

Ionization method: EI method

Mass range: m/z=18

[Method for measuring content (wt%) of a compound having a radical trapping function in a polarizing film]

About 20 mg of the polarizing film was collected, quantified, dissolved by heating in 1 ml of water, diluted with 4.5 ml of methanol, and the resulting extract was filtered through a membrane filter, and the filtrate was subjected to HPLC (ACQUITY UPLC H-class Bio manufactured by Waters Corporation). was used to measure the concentration of the compound having a radical trapping function.

<Production of polarizing film>

As the adhesive, an aqueous solution containing a polyvinyl alcohol resin containing an acetoacetyl group (average degree of polymerization 1,200, saponification degree 98.5 mol%, acetoacetylation degree 5 mol%) and methylolmelamine in a weight ratio of 3:1 was used. Using this adhesive, a transparent protective film with a thickness of 30 µm made of a (meth)acrylic resin (modified acrylic polymer having a lactone ring structure) on the surface (image display cell side) opposite to the resin substrate of the polarizing film obtained above ( Nippon Shokubai Co., Ltd. make, water vapor transmission rate of 125 g/(m<2>*24h)) was joined using the roll bonding machine. Next, the resin substrate was peeled off, and HC was formed on a triacetyl cellulose film (manufactured by Fujifilm Corporation, trade name "TJ40UL") as a transparent protective film on the peeled side (visible side), and a transparent protective film (water vapor transmission rate was 380 g/(m 2 ·24h)) was bonded by a roll bonding machine through an ultraviolet curing adhesive, and then UV rays were irradiated from the transparent protective film surface to cure the adhesive, and a polarizing film was produced.

[Evaluation of polarization degree]

The polarization degree of a polarizing film can be measured using the spectrophotometer (The JASCO Corporation make, product name "V7100"). As a specific method for measuring the degree of polarization, parallel transmittance (H0) and orthogonal transmittance (H90) of the polarizing film are measured, and the formula: Polarization degree (%) = {(H0-H90)/(H0+H90)}1/2×100 can be obtained from The parallel transmittance (H0) is a value of transmittance of a parallel laminated polarizing film prepared by stacking two identical polarizing films so that their absorption axes are parallel to each other. In addition, the orthogonal transmittance (H90) is a value of transmittance of the orthogonal laminated polarizing film prepared by superimposing the same two polarizing films so that their absorption axes are orthogonal to each other. In addition, these transmittance|permeability is the Y value which performed the visibility correction|amendment with the 2 degree field of view (C light source) of JIS Z 8701-1982. A result is shown in Table 1.

[Evaluation of simplex transmittance under high temperature environment]

The polarizing film obtained above is cut to a size of 5.0 x 4.5 cm so that the absorption axis of the polarizing film is parallel to the long side, and on the protective film side of the polarizing film on the image display cell side, a glass plate ( pseudo-image display cell), and autoclave-processed at 50 degreeC and 0.5 MPa for 15 minutes, and the laminated body was produced. The obtained laminate was left still in a hot-air oven with a temperature of 95 degreeC for 750 hours, and the single transmittance ((DELTA)Ts) before and behind injection|throwing-in (heating) was measured. The single transmittance was measured using a spectrophotometer (manufactured by JASCO Corporation, product name "V7100"), and evaluated by the following standards. In addition, the measurement wavelength is 380-700 nm (every 5 nm)). A result is shown in Table 1.

ΔTs(%)=Ts ₇₅₀ -Ts ₀

Here, Ts ₀ is the single transmittance of the laminate before heating, and Ts ₇₅₀ is the single transmittance of the laminate after heating for 750 hours. The ΔTs(%) is preferably 5≧ΔTs(%)≧0, and more preferably 3≧ΔTs(%)≧0.

[Evaluation of panel warpage]

The polarizing film is cut to a size of 145 x 105 mm so that the absorption axis of the polarizing film is parallel to the long side, and an acrylic pressure-sensitive adhesive layer having a thickness of 20 µm is interposed on the protective film surface of the image display cell side of the polarizing film, and the thickness is 0.4 mm A glass plate having a size of 155 x 115 mm was bonded. After leaving the obtained glass with a polarizing film (pseudo panel) sample still in 85 degreeC hot-air oven for 5 hours, the curvature amount of the glass after leaving still in normal temperature normal humidity environment for 1 hour was evaluated. The warpage refers to the amount of warpage in which the glass and the polarizing plate become convex downwards. A result is shown in Table 1.

○: less than 1.0 mm deflection

x: warp amount 1.0 mm or more

<Example 2>

<Preparation of a polarizing film and a polarizing film>

Preparation of a polarizing film WHEREIN: A polarizing film and a polarizing film were produced by operation similar to Example 1 except having adjusted the iodine concentration of a dyeing bath so that the iodine concentration of the polarizing film finally obtained might be 6.3 weight%. The obtained polarizing film had a peak temperature of the maximum intensity of water detected by the generated gas analysis method of 207° C., the content of the compound represented by the general formula (9) in the polarizing film was 0.3 wt %, and the thickness of the polarizing film was 5 μm.

<Example 3>

<Preparation of a polarizing film and a polarizing film>

A polyvinyl alcohol film having an average degree of polymerization of 2,400, a degree of saponification of 99.9 mol%, and a thickness of 30 µm was prepared. The polyvinyl alcohol film is immersed for 30 seconds in a swelling bath at 20 ° C. between rolls having different peripheral speed ratios and stretched 2.2 times in the conveying direction while swelling (swelling step), followed by a dyeing bath at 30 ° C. (with respect to 100 parts by weight of water) , while adjusting the concentration so that the iodine concentration of the polarizing film finally obtained in an aqueous iodine solution obtained by mixing iodine and potassium iodide in a weight ratio of 1:7) is 6.1% by weight, immersion for 30 seconds and dyeing the original polyvinyl alcohol film (transfer It was extended|stretched 3.3 times in the conveyance direction on the basis of the polyvinyl alcohol film which is not fully extended|stretched in a direction (dyeing process). Next, the dyed polyvinyl alcohol film was immersed for 28 seconds in a crosslinking bath (boric acid concentration of 3.5 wt%, potassium iodide concentration of 3.0 wt%, and zinc sulfate concentration of 3.6 wt%) in a crosslinking bath at 40 °C for 28 seconds to obtain the original polyvinyl alcohol. It extended|stretched up to 3.6 times in the conveyance direction on the basis of the film (crosslinking process). Further, the obtained polyvinyl alcohol film was immersed in a drawing bath at 64° C. (aqueous solution having a boric acid concentration of 4.5% by weight, potassium iodide concentration of 5.0% by weight, and zinc sulfate concentration of 5.0% by weight) for 60 seconds to obtain the original polyvinyl alcohol film. After stretching to 6.0 times in the conveying direction as a reference (stretching step), a cleaning bath at 27°C (potassium iodide concentration of 2.3% by weight, a compound having a radical trapping function, compound concentration represented by the following general formula (6) was immersed in an aqueous solution of 1.0 wt%) for 10 seconds (washing step). The wash|cleaned polyvinyl alcohol film was dried at 40 degreeC for 30 second, and the polarizing film was produced. The obtained polarizing film had a peak temperature of the maximum intensity of water detected by the generated gas analysis method of 209° C., the content of the compound represented by the general formula (9) in the polarizing film was 0.2 wt %, and the polarizing film had a thickness of 12 µm.

Subsequently, an aqueous solution containing polyvinyl alcohol resin containing acetoacetyl group (average degree of polymerization of 1,200, degree of saponification of 98.5 mol%, degree of acetoacetylation of 5 mol%) and methylolmelamine in a weight ratio of 3:1 was used as an adhesive. did. Using this adhesive, on one side (image display device cell side) of the polarizing film obtained above, a (meth)acrylic resin (modified acrylic polymer having a lactone ring structure) is made of a 30 µm thick transparent protective film (Nippon Shokubai Co., Ltd.). , Ltd., the moisture permeability is 125 g/(m 2 ·24h)), and HC is formed on the other side (visible side) on a triacetyl cellulose film (manufactured by Fujifilm Corporation, trade name "TJ40UL"), transparent protection with a thickness of 47 µm After the film (water vapor transmission rate is 380 g/(m2·24 h)) was further bonded with a roll bonding machine, it was subsequently heated and dried in an oven (temperature is 90° C., time is 10 minutes), and a transparent protective film is bonded to both sides of the polarizing film. polarizing film was produced.

<Example 4>

<Preparation of a polarizing film and a polarizing film>

In the production of the polarizing film, the iodine concentration of the dyeing bath is adjusted so that the iodine concentration of the polarizing film finally obtained is 7.9% by weight, and as a compound having a radical trapping function in the bath of the washing step, instead of the above general formula (9) The polarizing film and the polarizing film were produced by operation similar to Example 1 except having added 1.0 weight% of density|concentrations of the compound represented by the said General formula (8). The obtained polarizing film had a peak temperature of the maximum intensity of water detected by the generated gas analysis method of 206 ° C., the content of the compound represented by the general formula (8) in the polarizing film was 0.3 wt %, and the thickness of the polarizing film was 5 µm.

<Comparative Example 1>

<Preparation of a polarizing film and a polarizing film>

In the preparation of the polarizing film, the iodine concentration of the dyeing bath is adjusted so that the iodine concentration of the polarizing film finally obtained is 8.5% by weight, and a compound having a radical trapping function in the washing bath, the compound represented by the general formula (9) Except not having added, the polarizing film and the polarizing film were produced by operation similar to Example 1. The obtained polarizing film had a peak temperature of the maximum intensity of water detected by the generated gas analysis method of 193° C., the content of the compound represented by the general formula (9) in the polarizing film was 0 wt%, and the polarizing film had a thickness of 5 µm.

<Comparative Example 2>

<Preparation of a polarizing film and a polarizing film>

In the preparation of the polarizing film, the iodine concentration of the dyeing bath is adjusted so that the iodine concentration of the polarizing film finally obtained is 5.6% by weight, and a compound represented by the general formula (9) as a compound having a radical trapping function in the washing bath Except not having added, the polarizing film and the polarizing film were produced by operation similar to Example 1. The obtained polarizing film had a peak temperature of the maximum intensity of water detected by the generated gas analysis method of 203° C., the content of the compound represented by the general formula (9) in the polarizing film was 0 wt%, and the polarizing film had a thickness of 5 µm.

Said [evaluation of polarization degree], [evaluation of the single transmittance in a high-temperature environment], and [evaluation of the curvature of a panel] were performed using the polarizing film of the Example and comparative example obtained above. A result is shown in Table 1.

Claims (10)

A polarizing film formed by adsorption orientation of iodine on a polyvinyl alcohol-based film,
an iodine concentration of 6% by weight or more, and
A polarizing film, characterized in that the peak temperature of the maximum intensity of water detected is 200°C or higher in the presence of an inert gas in the analysis of the generated gas, under the condition that the temperature increase rate is 10°C/min and the temperature increase range is 40°C to 350°C. The method of claim 1,
A polarizing film having a thickness of 15 μm or less. 3. The method according to claim 1 or 2,
A polarizing film comprising a compound having a radical trapping function. 4. The method of claim 3,
The polarizing film, wherein the compound having a radical trapping function is a compound having a nitroxy radical or a nitroxide group. A transparent protective film is bonded to at least one surface of the polarizing film in any one of Claims 1-4, The polarizing film characterized by the above-mentioned. 6. The method of claim 5,
A polarizing film, characterized in that the degree of polarization is 99.98% or more. The polarizing film of Claim 5 or 6 is bonded by the optical layer, The laminated polarizing film characterized by the above-mentioned. The polarizing film of Claim 5 or 6, or the laminated polarizing film of Claim 7 is bonded by the image display cell, The image display panel characterized by the above-mentioned. A front transparent member is provided in the polarizing film or laminated polarizing film side of the image display panel of Claim 8, The image display apparatus characterized by the above-mentioned. 10. The method of claim 9,
An image display device for mounting on a vehicle.

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