KR102741859B1 - Polarizing film laminate with adhesive layer attached, and optical display panel using the polarizing film laminate with adhesive layer attached - Google Patents

Abstract

Provided are polarizing film laminates that can comprehensively solve problems of polyenization, color fading, and heat discoloration. A polarizing film comprising a polyvinyl alcohol-based resin, and an adhesive layer formed directly or through an optically transparent polarizing film protective film on at least one surface of the polarizing film, wherein the adhesive layer comprises an adhesive polymer, and the adhesive polymer is a copolymer of an acid component, and the amount of the acid component among the total monomer components constituting the adhesive polymer is 5 wt% or less, and in an x-y orthogonal coordinate system in which the x-axis represents the iodine concentration of the polarizing film and the y-axis represents the moisture content of the polarizing film laminate, a first line segment and a second coordinate point connecting a first coordinate point having an iodine concentration of 7.0 wt. % and a moisture content of 0.7 g/m2 and a second coordinate point having an iodine concentration of 2.2 wt. % and a moisture content of 3.2 g/m2, and a second line segment and a third coordinate point connecting a third coordinate point having an iodine concentration of 2.2 wt. % and a moisture content of 4.0 g/m2, A polarizing film laminate having an iodine concentration and a moisture content included within an area surrounded by a third line segment connecting a fourth coordinate point having an iodine concentration of 3.0 wt. % and a moisture content of 4.0 g/m2, a fourth line segment connecting the fourth coordinate point and a fifth coordinate point having an iodine concentration of 10.0 wt. % and a moisture content of 0.7 g/m2, and a fifth line segment connecting the first coordinate point and the fifth coordinate point.

Description

Polarizing film laminate with adhesive layer attached, and optical display panel using the polarizing film laminate with adhesive layer attached

The present invention relates to a polarizing film laminate having an adhesive layer attached thereto, and an optical display panel in which the polarizing film laminate having an adhesive layer attached thereto is used.

Recently, optical display panels such as liquid crystal panels and organic EL panels have been found to have various possibilities for use in not only electronic devices such as smartphones and personal computers, and telephone products such as IoT home appliances, but also in motorized vehicles such as automobiles, trains, and airplanes. For example, it is thought that optical display panels can be installed on various parts of the car body such as the windshield, dashboard, exterior, and others to provide various information to the driver and also transmit various information to the outside.

However, unlike smartphones and the like, motorized vehicles are often used in harsh outdoor environments, and depending on the usage environment, such as high temperature or high humidity, the performance of optical display panels, particularly polarizing film laminates (polarizing plates) used in optical display panels, and polarizing films (polarizers) used in polarizing film laminates may deteriorate, and in the worst case, may become unusable.

Patent Document 1 discloses a polarizer having improved durability in high temperature and high humidity environments, a polarizing plate using the polarizer, and an example of a liquid crystal display device using the polarizing plate. As for durability, red fading (polarization fading of long-wavelength light) in orthogonal Nicols that occurs when left under high temperature conditions is a problem, and in order to solve this problem, it is proposed to contain zinc and adjust the zinc content to a predetermined range in relation to the iodine content.

Similarly, Patent Document 2 relates to a polarizing plate used in a vehicle-mounted image display device with improved durability under high temperature and high humidity environments, and focuses on the moisture content of the polarizing plate and the saturated absorption amount of the protective film. Since high temperature durability is required for a vehicle-mounted polarizing plate, there are cases where the transmittance of the polarizing plate is significantly reduced due to polyene in a high temperature environment, and in order to solve this problem, Patent Document 2 proposes using a transparent protective film bonded to a polarizer having a saturated absorption amount within a predetermined range, and furthermore, reducing the moisture content of the polarizing plate.

Patent Document 3 also relates to a polarizing plate with improved durability under high temperature and high humidity conditions, and focuses on the moisture content of the polarizing plate and the moisture permeability of the protective film. In a high temperature environment, etc., the inside of the polarizing plate becomes high temperature and high humidity, and as a result, the amount of change in light transmittance, polarization degree, image color, etc. increases, and the reliability of the polarizing plate becomes low. Therefore, it is proposed to bond a protective film with low moisture permeability while reducing the moisture content of the polarizer as much as possible.

Japanese Patent Publication No. 2003-29042 Japanese Patent Publication No. 2014-102353 Japanese Patent Publication No. 2002-90546

Regarding optical display panels, particularly, polarizing film laminates used in optical display panels or polarizing films used in polarizing film laminates, problems that occur under high temperature or high humidity environments include “polyenization,” “color fading,” and “heat discoloration.”

In general, "polyenization" is known as a phenomenon in which the unit transmittance of a polarizing film laminate decreases when placed in a high temperature or high humidity environment, and "color fading" and "heating discoloration" are also known as phenomena in which, when placed in a high temperature or high humidity environment and the orthogonal transmittance of a polarizing film laminate is measured by arranging cross Nicols at wavelengths of 410 nm and 700 nm, the orthogonal transmittance increases, and "color fading" is known as a phenomenon in which the transmittance of the long wavelength side of about 700 nm and the short wavelength side of about 410 nm increases in particular, causing color fading in a black display, while "heating discoloration" is known as a phenomenon in which the transmittance of the long wavelength side of about 700 nm increases in particular, causing the polarizing film to turn red.

Patent document 1 mainly focuses on the problem of "color fading", patent document 2 mainly focuses on the problem of "polyeneization", and patent document 3 mainly focuses on the problem of "red discoloration upon heating". The solutions proposed in each document are thought to be effective at least for solving each problem. However, the inventions described in each patent document are not sufficient to comprehensively solve these problems.

Based on the fact that "polyenization", "color fading", and "discoloration upon heating" are all related to each other through iodine and moisture, and also through temperature and humidity that affect moisture, the applicant of the present application, through repeated research, has obtained the knowledge that these problems can be comprehensively solved by adjusting the iodine concentration of the polarizing film and the moisture content of the polarizing film laminate.

The present invention aims to comprehensively solve these three problems by adjusting the iodine concentration of a polarizing film and the moisture content of a polarizing film laminate.

When attaching a polarizing film to a liquid crystal cell, etc., an adhesive is usually used. In addition, since it has the merits of being able to attach a polarizing film to a liquid crystal cell, etc. in an instant and not requiring a drying process to attach a polarizing film to a liquid crystal cell, etc., the adhesive is often formed as an adhesive layer on one side of the polarizing film in advance. In other words, a polarizing plate with an adhesive layer attached is generally used for attaching a polarizing plate.

The properties required for the adhesive layer include adhesiveness that does not decrease over time, high durability, and the ability to peel the polarizing film from the surface of the liquid crystal panel and re-attach (rework) even when the bonding position is incorrect or foreign matter gets caught in the bonding surface when bonding the polarizing film to the liquid crystal cell.

When an optical display panel is used in a powered vehicle, high-temperature durability is also required for the adhesive used to adhere the polarizing film constituting the optical display panel to the liquid crystal cell, etc. For this purpose, an adhesive composition constituting the adhesive, which includes an acid component such as acrylic acid among the monomer components of the adhesive polymer, can be suitably used.

The inventors of the present invention have found that a new problem arises in that polyene is worsened by an acid component copolymerized with an adhesive polymer. In the above-mentioned prior art, although studies have been conducted on polyene of polarizing films, no studies have been conducted on the durability or rework of the adhesive layer, and no disclosure has been made on this problem.

The present invention aims to obtain a polarizing plate having an adhesive layer attached thereto, in which an adhesive layer is formed directly on a polarizing film or through an optically transparent polarizing film protective film, which has excellent reliability of optical properties, adhesion durability, and reworkability.

The present inventors have completed the present invention by focusing on the influence of the acid component among the monomer components of the adhesive polymer included in the adhesive layer on the performance of the polarizing film. In the prior art, there has been no examination at all of the relationship between the ratio of the acid component among the monomer components of the adhesive polymer included in the adhesive layer and the performance of the adhesive layer-attached polarizing film laminate, such as reliability of optical characteristics, adhesion durability, and rework. The present inventors have found the amount of the acid component among the total monomer components of the adhesive polymer required to obtain a adhesive layer-attached polarizing film laminate having excellent characteristics.

Although not bound by any theory, it is thought that when an acid component such as acrylic acid is included in the monomer components of the adhesive polymer, high-temperature durability is improved by hydrogen bonding of the COOH group of the acid component, but the acid component acts as a catalyst for dehydration and condensation of the polyvinyl alcohol (PVA)-based resin film that constitutes the polarizing film, thereby promoting polyenization.

In order to solve the above problem, a polarizing film laminate according to one embodiment of the present invention is a polarizing film laminate with an adhesive layer, which comprises a polarizing film containing a polyvinyl alcohol-based resin, and an adhesive layer formed directly or through an optically transparent polarizing film protective film on at least one surface of the polarizing film,

The above adhesive layer comprises an adhesive polymer, the adhesive polymer is copolymerized with an acid component, and the amount of the acid component among the total monomer components constituting the adhesive polymer is 5 wt% or less,

In an x-y orthogonal coordinate system in which the iodine concentration (wt.%) of the polarizing film is taken on the x-axis and the moisture content (g/m2) of the polarizing film laminate is taken on the y-axis, a first line segment connecting a first coordinate point of an iodine concentration of 7.0 wt.% and a moisture content of 0.7 g/m2 and a second coordinate point of an iodine concentration of 2.2 wt.% and a moisture content of 3.2 g/m2, a second line segment connecting the second coordinate point and a third coordinate point of an iodine concentration of 2.2 wt.% and a moisture content of 4.0 g/m2, a third line segment connecting the third coordinate point and a fourth coordinate point of an iodine concentration of 3.0 wt.% and a moisture content of 4.0 g/m2, and a fourth line segment connecting the fourth coordinate point and a fifth coordinate point of an iodine concentration of 10.0 wt.% and a moisture content of 0.7 g/m2 It is characterized by having an iodine concentration and a moisture content included within an area surrounded by a line segment and a fifth line segment connecting the first coordinate point and the fifth coordinate point.

According to the polarizing film laminate with adhesive layer of this embodiment, the problems of “polyenization”, “color fading”, “discoloration upon heating”, “adhesion durability”, and “rework” can be comprehensively solved.

In the polarizing film laminate of the above embodiment, the polydispersity (weight average molecular weight (Mw)/number average molecular weight (Mn)) of the adhesive polymer may be 3.0 or less. This also applies to a (further) separate embodiment of the present invention.

In the polarizing film laminate of the above aspect, the polarizing film may have a film thickness of 4 to 20 ㎛.

In addition, in a polarizing film laminate according to a separate aspect of the present invention, a polarizing film laminate having an adhesive layer, comprising a polarizing film including a polyvinyl alcohol-based resin, and an adhesive layer formed directly or through an optically transparent polarizing film protective film on at least one surface of the polarizing film,

The above adhesive layer comprises an adhesive polymer, the adhesive polymer is copolymerized with an acid component, and the amount of the acid component among the total monomer components constituting the adhesive polymer is 5 wt% or less,

In an x-y orthogonal coordinate system in which the iodine concentration (wt.%) of the polarizing film is taken on the x-axis and the moisture content (g/m2) of the polarizing film laminate is taken on the y-axis, a sixth line segment connecting the sixth coordinate point of the iodine concentration of 4.5 wt.% and the moisture content of 2.0 g/m2 and the second coordinate point of the iodine concentration of 2.2 wt.% and the moisture content of 3.2 g/m2, a second line segment connecting the second coordinate point and the third coordinate point of the iodine concentration of 2.2 wt.% and the moisture content of 4.0 g/m2, a third line segment connecting the third coordinate point and the fourth coordinate point of the iodine concentration of 3.0 wt.% and the moisture content of 4.0 g/m2, and a seventh line segment connecting the fourth coordinate point and the seventh coordinate point of the iodine concentration of 4.5 wt.% and the moisture content of 3.3 g/m2 It is characterized by having an iodine concentration and a moisture content included within an area surrounded by a line segment and an eighth line segment connecting the sixth coordinate point and the seventh coordinate point.

In the polarizing film laminate of the above aspect, the sixth coordinate point may be a coordinate point of iodine concentration of 4.0 wt.% and moisture content of 2.3 g/m2, and the seventh coordinate point may be a coordinate point of iodine concentration of 4.0 wt.% and moisture content of 3.5 g/m2.

In the polarizing film laminate of the above aspect, the polarizing film thickness may be 11 to 20 ㎛.

A polarizing film laminate according to a further separate aspect of the present invention is a polarizing film laminate having a polarizing film including a polyvinyl alcohol-based resin and an adhesive layer formed directly or through an optically transparent polarizing film protective film on at least one surface of the polarizing film, wherein the polarizing film laminate has an adhesive layer attached thereto,

The above adhesive layer comprises an adhesive polymer, the adhesive polymer is copolymerized with an acid component, and the amount of the acid component among the total monomer components constituting the adhesive polymer is 5 wt% or less,

In an x-y orthogonal coordinate system in which the x-axis represents the iodine concentration (wt.%) of the polarizing film and the y-axis represents the moisture content (g/m2) of the polarizing film laminate, an eleventh line segment connecting a first coordinate point of an iodine concentration of 7.0 wt.% and a moisture content of 0.7 g/m2, an eighth coordinate point of an iodine concentration of 3.0 wt.% and a moisture content of 2.6 g/m2, a tenth line segment connecting the eighth coordinate point and a ninth coordinate point of an iodine concentration of 6.0 wt.% and a moisture content of 2.6 g/m2, a twelfth line segment connecting the ninth coordinate point and a fifth coordinate point of an iodine concentration of 10.0 wt.% and a moisture content of 0.7 g/m2, and a fifth line segment connecting the first coordinate point and the fifth coordinate point, the iodine concentration and the moisture content are included within an area surrounded by It has as a feature.

According to the polarizing film laminate with adhesive layer of this embodiment, the problems of “polyenization”, “color fading”, “discoloration upon heating”, “adhesion durability”, and “rework” can be comprehensively solved.

In the polarizing film laminate of the above aspect, the 8th coordinate point may be the 6th coordinate point having an iodine concentration of 4.5 wt.% and a moisture content of 2.0 g/m2, and the 9th coordinate point may be the 10th coordinate point having an iodine concentration of 7.2 wt.% and a moisture content of 2.0 g/m2.

In addition, in the polarizing film laminate of the above aspect, the film thickness of the polarizing film may be 4 to 11 ㎛.

In addition, in the polarizing film laminate of the above aspect, it is preferable that the polarizing film contains zinc.

In addition, in the polarizing film laminate of the above aspect, it is preferable that the group transmittance of a sample comprising a polarizing film laminate and glass plates laminated on both sides of the polarizing film laminate via an adhesive after heating at 95°C/500 hours is equal to or greater than the group transmittance before heating.

By this, the problem of polyenization can be effectively solved.

In the polarizing film laminate of the above aspect, it is preferable that the change in orthogonal transmittance at a wavelength of 410 nm is less than 1%, and further, the change in orthogonal transmittance at a wavelength of 700 nm is less than 5%, in a sample comprising a polarizing film laminate and a glass plate laminated on both sides of the polarizing film laminate via an adhesive, upon heat treatment at 95°C/500 hours.

By this, the problem of color fading can be effectively solved.

In the polarizing film laminate of the above aspect, it is preferable that the change in orthogonal transmittance at a wavelength of 410 nm is 1% or more, and further, the change in orthogonal transmittance at a wavelength of 700 nm is less than 5%, in a sample comprising the polarizing film laminate and glass plates laminated on both sides of the polarizing film laminate via an adhesive, upon heat treatment at 95°C/500 hours.

By this, the problem of heating change can be effectively solved.

In the polarizing film laminate of the above aspect, an anti-reflection layer may be formed through a substrate on the viewing side of the polarizing film, and the moisture permeability of the anti-reflection film formed of the substrate and the anti-reflection layer may be 15 g/㎡·24 h or more.

In addition, in the polarizing film laminate of the above aspect, a liquid crystal cell having a liquid crystal layer including liquid crystal molecules oriented in one direction in the plane in a state of no electric field application is provided, a first polarizing film arranged on one side of the liquid crystal cell, and a second polarizing film arranged on the other side of the liquid crystal cell such that an absorption axis is orthogonal to the absorption axis of the first polarizing film, and a first phase difference layer and a second phase difference layer are sequentially arranged from the side of the first polarizing film between the first polarizing film and the liquid crystal cell, and when the first phase difference layer has a refractive index in the slow axis x direction in the plane as nx1, a refractive index in the fast axis direction as ny1, and a refractive index in the thickness z direction as nz1, the relationship nx1>ny1>nz1 is satisfied, and when the second phase difference layer has a refractive index in the slow axis x direction in the plane as nx2, a refractive index in the fast axis direction as ny2, and a refractive index in the thickness z direction as nz2, At times, it is desirable to satisfy the relationship nz2＞nx2≥ny2.

In addition, in the polarizing film laminate of the above aspect, a liquid crystal cell having a liquid crystal layer including liquid crystal molecules oriented in one direction in the plane in a state of no electric field application is provided, a first polarizing film arranged on one side of the liquid crystal cell, and a second polarizing film arranged on the other side of the liquid crystal cell such that an absorption axis is orthogonal to the absorption axis of the first polarizing film, and a first phase difference layer and a second phase difference layer are sequentially arranged from the side of the first polarizing film between the first polarizing film and the liquid crystal cell, and when the first phase difference layer has a refractive index in the slow axis x direction in the plane as nx1, a refractive index in the fast axis direction as ny1, and a refractive index in the thickness z direction as nz1, the relationship nz1>nx1=ny1 is satisfied, and when the second phase difference layer has a refractive index in the slow axis x direction in the plane as nx2, a refractive index in the fast axis direction as ny2, and a refractive index in the thickness z direction as nz2, At times, it is desirable to satisfy the relationship nx2＞ny2=nz2.

Furthermore, in the polarizing film laminate of the above aspect, the liquid crystal cell having a liquid crystal layer including liquid crystal molecules oriented in one direction in the plane in a state of no electric field application, and the polarizing film arranged on one side of the liquid crystal cell, the phase difference layer is arranged between the polarizing film and the liquid crystal cell, and it is preferable that the phase difference layer satisfies the relationship nx > nz > ny, where nx is the refractive index in the slow axis x direction in the plane, ny is the refractive index in the fast axis direction, and nz is the refractive index in the thickness z direction.

In addition, in order to solve the above problem, an optical display panel according to one embodiment of the present invention comprises an optical display cell, a polarizing film laminate as described above, which is bonded directly or through another optical film to one surface of the optical display cell, and an optically transparent cover plate arranged along the polarizing film laminate on the opposite side to the optical display cell, characterized in that the optical display panel is formed by bonding the optical display cell, the polarizing film laminate, and the transparent cover plate with a transparent adhesive layer that fills a space therebetween without a gap.

In the optical display panel of the above aspect, the transparent cover plate may have the function of a capacitive touch sensor.

In addition, in the optical display panel of the above aspect, an ITO layer that becomes a component of a capacitive touch sensor may be formed between the transparent cover plate and the polarizing film laminate.

According to the present invention, the problems of “polyenization”, “color fading”, “discoloration upon heating”, “adhesion durability”, and “rework” can be comprehensively solved.

Figure 1 is a schematic diagram showing the layer structure of an optical display panel.
Figure 2 is a drawing explaining an example of a method for manufacturing a polarizing film.
Figure 3 is a diagram showing a calibration curve for determining the iodine concentration of a polarizing film.
Figure 4 is a drawing showing a structure for reliability testing.
Figure 5 is a drawing plotting the results of examples and comparative examples.

Hereinafter, with reference to the attached drawings, a suitable embodiment of the present invention will be described. For the convenience of explanation, only a suitable embodiment is shown, but of course, the present invention is not intended to be limited thereby.

The present invention relates to an optical display panel, and particularly, to an optical display panel attached to a body of a motor vehicle such as an automobile, a tram, an airplane, or other powered vehicle, and to a polarizing film laminate used in the optical display panel. Here, the term "attached to a body" includes not only the case where the optical display panel or the polarizing film laminate is fixed to the body, but also the case where, for example, the optical display panel or the polarizing film laminate used in smartphones or the like is freely mounted or carried onto a motor vehicle. In other words, the term "attached to a body" includes all situations in which the optical display panel or the polarizing film laminate is used together with a motor vehicle and is likely to be exposed to a high temperature or high humidity environment.

1. Optical display panel

Fig. 1 schematically shows an example of a layered configuration of an optical display panel (1). The optical display panel (1) includes at least an optical display cell (10), a polarizing film laminate (12) laminated on one side (10a) (viewing side) of the optical display cell (10), and an optically transparent cover plate (14) arranged along the polarizing film laminate (12) on the opposite side to the optical display cell (10), i.e., the viewing side. On the other side (10b) of the optical display cell (10), another polarizing film laminate (17) is arranged via a transparent adhesive (16). The optical display cell (10), the polarizing film laminate (12), and the cover plate (14) are bonded by layers of a transparent adhesive (11, 13) that fill the space between them without a gap. In addition, in this specification, unless otherwise specifically stated, the term "adhesion" includes adhesion (pressure-sensitive adhesion). The optical display cell (10) and the polarizing film laminate (12) may be directly adhered by a transparent adhesive (11), but may also be adhered via another optical film (not shown), such as a phase difference film or a viewing angle compensation film, as needed.

1-1. Optical display cell

As examples of optical display cells (10), liquid crystal cells or organic EL cells can be mentioned.

As an organic EL cell, one in which a transparent electrode, an organic light-emitting layer, and a metal electrode are sequentially laminated on a transparent substrate to form a light-emitting body (organic electroluminescence light-emitting body) is suitably used. The organic light-emitting layer is a laminate of various organic thin films, and for example, a laminate of a hole injection layer made of a triphenylamine derivative or the like and a light-emitting layer made of a fluorescent organic solid such as anthracene, a laminate of these light-emitting layers and an electron injection layer made of a perylene derivative or the like, or a laminate of a hole injection layer, a light-emitting layer, and an electron injection layer, etc., various layer structures can be adopted.

As the liquid crystal cell, any of a reflective liquid crystal cell that uses external light, a transmissive liquid crystal cell that uses light from a light source such as a backlight (18), and a semi-transmissive semi-reflective liquid crystal cell that uses both light from the outside and light from a light source may be used. When the liquid crystal cell uses light from a light source, as shown in Fig. 1, a polarizing film laminate (17) is arranged on the opposite side to the viewing side of the optical display cell (liquid crystal cell) (10), and further, a light source (18), for example, a backlight, is arranged. The polarizing film laminate (17) on the light source side and the liquid crystal cell (10) are bonded by a layer of an appropriate transparent adhesive (17). As the driving method of the liquid crystal cell, any type, for example, VA mode, IPS mode, TN mode, STN mode, or bend alignment (π type), can be used.

1-2. Cover plate

As examples of the cover plate (14), a transparent plate (window layer) or a touch panel can be mentioned. As the transparent plate, a transparent plate having appropriate mechanical strength and thickness is used. As such a transparent plate, for example, a transparent resin plate such as an acrylic resin or a polycarbonate resin, or a glass plate, etc. can be used. The surface of the cover plate (14) may be subjected to a low-reflection treatment, for example, using a low-reflection film (not shown). As the touch panel, various touch panels such as a resistive film type, an electrostatic capacitance type, an optical type, an ultrasonic type, or a glass plate or a transparent resin plate having a touch sensor function can be used.

When a capacitive touch panel is used as the cover plate (14), it is preferable that a front transparent plate made of glass or a transparent resin plate be installed further from the viewing side than the touch panel. In addition, in this case, an ITO layer (not shown) that becomes a component of the capacitive touch sensor is formed on a transparent adhesive (13) that bonds between the cover plate (14) and the polarizing film laminate (12).

[Adhesive composition]

An adhesive composition that can be used for transparent adhesive (11), etc. is described.

<Adhesive polymer>

The adhesive polymer included in the adhesive composition is not particularly limited as long as it is a polymer having adhesiveness that is generally used as a base polymer of the adhesive, but a polymer having a Tg of 0°C or lower (usually -100°C or higher) is suitable because it is easy to achieve a balance in adhesive performance. Among these adhesive polymers, polyester-based polymers, (meth)acrylic polymers, etc. are suitably used.

The adhesive polymer used in the present invention contains an acid component copolymerized therein.

As polyester polymers, saturated polyesters or copolyesters of polyhydric alcohols and polyhydric carboxylic acids are commonly used.

Examples of polyhydric alcohols include diols such as ethylene glycol, propylene glycol, hexamethylene glycol, neopentyl glycol, 1,2-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, decamethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexadiol, 2,2-bis(4-hydroxyphenyl)propane, and bis(4-hydroxyphenyl)sulfone.

Examples of polycarboxylic acids include aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, orthophthalic acid, 2,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, diphenylcarboxylic acid, diphenoxyethanedicarboxylic acid, diphenylsulfonecarboxylic acid, and anthracenedicarboxylic acid; alicyclic dicarboxylic acids such as 1,3-cyclopentanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, hexahydroterephthalic acid, and hexahydroisophthalic acid; Examples thereof include aliphatic dicarboxylic acids such as malonic acid, dimethylmalonic acid, succinic acid, 3,3-diethylsuccinic acid, glutaric acid, 2,2-dimethylglutaric acid, adipic acid, 2-methyladipic acid, trimethyladipic acid, pimelic acid, azelaic acid, dimer acid, sebacic acid, suberic acid, and dodecadicarboxylic acid. As the polycarboxylic acids, two or more polycarboxylic acids are often used in combination, for example, an aromatic dicarboxylic acid and an aliphatic dicarboxylic acid.

In the present invention, since the adhesive polymer contains such an acid component, the durability of the adhesive is improved, and the occurrence of foaming or peeling, etc., can be prevented over a long period of time. The upper limit of the amount of the acid component is less than 5 wt%, preferably less than 3 wt%, and further preferably less than 2 wt%, based on the amount of the total monomer components constituting the adhesive polymer. If the amount of the acid component exceeds the upper limit, the polyenization of the polarizing film is adversely affected, and the reworkability of the adhesive layer tends to deteriorate. The lower limit of the amount of the acid component is preferably 0.01 wt% or more, more preferably 0.2 wt% or more, and further preferably 0.5 wt% or more, based on the amount of the total monomer components constituting the adhesive polymer. If the amount of the acid component is small, the durability of the adhesive layer tends to deteriorate.

Polyhydric alcohols and polyhydric carboxylic acids used in polyester polymers can be used without any particular limitation, and polymer polyols such as polycarbonate diol can be used as polyhydric alcohols. In addition, polyester polymers can be obtained from the above diol component and a trihydric or higher polyhydric alcohol and/or a trihydric or higher polycarboxylic acid. The weight average molecular weight of the polyester polymer used is usually 11,000 or more.

(Meth)acrylic polymers usually contain alkyl (meth)acrylate as a main component as a monomer unit. In addition, (meth)acrylate means acrylate and/or methacrylate.

As the alkyl (meth)acrylate constituting the main skeleton of the (meth)acrylic polymer, examples thereof include linear or branched alkyl groups having 1 to 18 carbon atoms. For example, examples of the alkyl group include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, an amyl group, a hexyl group, a cyclohexyl group, a heptyl group, a 2-ethylhexyl group, an isooctyl group, a nonyl group, a decyl group, an isodecyl group, a dodecyl group, an isomyristyl group, a lauryl group, a tridecyl group, a pentadecyl group, a hexadecyl group, a heptadecyl group, an octadecyl group, etc. These can be used alone or in combination. It is preferable that the average number of carbon atoms of these alkyl groups is 3 to 9.

In addition, alkyl (meth)acrylates containing an aromatic ring, such as phenoxyethyl (meth)acrylate and benzyl (meth)acrylate, can be used. The alkyl (meth)acrylate containing an aromatic ring can be used by mixing the polymer obtained by polymerizing it with the (meth)acrylic polymer of the above example, but from the viewpoint of transparency, it is preferable to use the alkyl (meth)acrylate containing an aromatic ring by copolymerizing it with the above alkyl (meth)acrylate.

Among the above (meth)acrylic polymers, one or more copolymerizable monomers having a polymerizable functional group having an unsaturated double bond such as a (meth)acryloyl group or a vinyl group can be introduced by copolymerization for the purpose of improving adhesiveness or heat resistance. Specific examples of such copolymerizable monomers include, for example, hydroxyl group-containing monomers such as (meth)acrylic acid 2-hydroxyethyl, (meth)acrylic acid 3-hydroxypropyl, (meth)acrylic acid 4-hydroxybutyl, (meth)acrylic acid 6-hydroxyhexyl, (meth)acrylic acid 8-hydroxyoctyl, (meth)acrylic acid 10-hydroxydecyl, (meth)acrylic acid 12-hydroxylauryl, or (4-hydroxymethylcyclohexyl)-methylacrylate; Examples thereof include carboxyl group-containing monomers such as (meth)acrylic acid, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, itaconic acid, maleic acid, fumaric acid, and crotonic acid; acid anhydride group-containing monomers such as maleic anhydride and itaconic anhydride; caprolactone adducts of acrylic acid; sulfonic acid group-containing monomers such as styrenesulfonic acid, allylsulfonic acid, 2-(meth)acrylamide-2-methylpropanesulfonic acid, (meth)acrylamidepropanesulfonic acid, sulfopropyl (meth)acrylate, and (meth)acryloyloxynaphthalenesulfonic acid; and phosphoric acid group-containing monomers such as 2-hydroxyethylacryloylphosphate.

Among the copolymerizable monomers as described above, the acid component in the present invention may be a copolymerizable monomer having a polymerizable functional group having an unsaturated double bond such as a (meth)acryloyl group or a vinyl group. Specific examples of the copolymerizable monomer as the acid component include carboxyl group-containing monomers such as acrylic acid, (meth)acrylic acid, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, itaconic acid, maleic acid, fumaric acid, and crotonic acid; acid anhydride group-containing monomers such as maleic anhydride and itaconic anhydride; a caprolactone adduct of acrylic acid; Examples thereof include sulfonic acid group-containing monomers such as styrenesulfonic acid, allylsulfonic acid, 2-(meth)acrylamide-2-methylpropanesulfonic acid, (meth)acrylamidepropanesulfonic acid, sulfopropyl(meth)acrylate, and (meth)acryloyloxynaphthalenesulfonic acid; and phosphoric acid group-containing monomers such as 2-hydroxyethylacryloylphosphate.

In the case where an acid component is present, it is thought that a relatively weak acid such as a carboxyl group-containing monomer is preferable from the viewpoint of the adverse effects of the acid, and further, a phosphoric acid group-containing monomer, a sulfonic acid group-containing monomer, etc. may also be used.

Monomers used for the purpose of modification include (N-substituted) amide monomers such as (meth)acrylamide, N,N-dimethyl(meth)acrylamide, N-butyl(meth)acrylamide, N-methylol(meth)acrylamide, N-methylolpropane(meth)acrylamide; (meth)acrylic acid alkylaminoalkyl monomers such as (meth)acrylic acid aminoethyl, (meth)acrylic acid N,N-dimethylaminoethyl, (meth)acrylic acid t-butylaminoethyl; (meth)acrylic acid alkoxyalkyl monomers such as (meth)acrylic acid methoxyethyl, (meth)acrylic acid ethoxyethyl; Examples thereof include succinimide monomers such as N-(meth)acryloyloxymethylene succinimide, N-(meth)acryloyl-6-oxyhexamethylene succinimide, N-(meth)acryloyl-8-oxyoctamethylene succinimide, and N-acryloylmorpholine; maleimide monomers such as N-cyclohexylmaleimide, N-isopropylmaleimide, N-laurylmaleimide, and N-phenylmaleimide; itaconimide monomers such as N-methylitaconimide, N-ethylitaconimide, N-butylitaconimide, N-octylitaconimide, N-2-ethylhexylitaconimide, N-cyclohexylitaconimide, and N-laurylitaconimide.

In addition, as modifying monomers, vinyl monomers such as vinyl acetate, vinyl propionate, N-vinylpyrrolidone, methylvinylpyrrolidone, vinylpyridine, vinylpiperidone, vinylpyrimidine, vinylpiperazine, vinylpyrazine, vinylpyrrole, vinylimidazole, vinyloxazole, vinylmorpholine, N-vinylcarboxylic acid amides, styrene, α-methylstyrene, and N-vinylcaprolactam; cyanoacrylate monomers such as acrylonitrile and methacrylonitrile; epoxy group-containing acrylic monomers such as (meth)acrylate glycidyl; glycol acrylic ester monomers such as (meth)acrylate polyethylene glycol, (meth)acrylate polypropylene glycol, (meth)acrylate methoxyethylene glycol, and (meth)acrylate methoxypolypropylene glycol; (Meth)Acrylic acid tetrahydrofurfuryl, fluoro(meth)acrylate, silicone(meth)acrylate, 2-methoxyethylacrylate, etc., acrylic acid ester monomers can also be used. In addition, isoprene, butadiene, isobutylene, vinyl ether, etc. can be used.

In addition, as copolymerizable monomers other than the above, silane monomers containing silicon atoms, etc. can be mentioned. Examples of the silane monomers include 3-acryloxypropyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, 4-vinylbutyltrimethoxysilane, 4-vinylbutyltriethoxysilane, 8-vinyloctyltrimethoxysilane, 8-vinyloctyltriethoxysilane, 10-methacryloyloxydecyltrimethoxysilane, 10-acryloyloxydecyltrimethoxysilane, 10-methacryloyloxydecyltriethoxysilane, 10-acryloyloxydecyltriethoxysilane, and the like.

In addition, as a copolymerizable monomer, there are polyfunctional monomers having two or more unsaturated double bonds such as (meth)acryloyl groups, vinyl groups, etc., such as (meth)acrylic acid and esterified polyhydric alcohols, such as tripropylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, bisphenol A diglycidyl ether di(meth)acrylate, neopentyl glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, caprolactone-modified dipentaerythritol hexa(meth)acrylate, etc. Polyester (meth)acrylate, epoxy (meth)acrylate, urethane (meth)acrylate, etc., which have two or more unsaturated double bonds, such as (meth)acryloyl groups and vinyl groups, added as functional groups similar to the monomer components to the skeleton of monomer, polyester, epoxy, urethane, etc., can also be used.

Among these copolymerizable monomers, hydroxyl group-containing monomers and carboxyl group-containing monomers are preferably used in terms of adhesiveness and durability. Hydroxyl group-containing monomers and carboxyl group-containing monomers can be used together. These copolymerizable monomers become reaction sites with the crosslinking agent when the adhesive composition contains a crosslinking agent. Hydroxyl group-containing monomers, carboxyl group-containing monomers, etc. have high reactivity with intermolecular crosslinking agents, and are therefore preferably used for improving the cohesion and heat resistance of the resulting adhesive layer. Hydroxyl group-containing monomers are preferable in terms of reworkability, and carboxyl group-containing monomers are preferable in terms of achieving both durability and reworkability.

The hydroxyl group-containing monomer can be used in an amount of about 0.01 to 30 wt%, preferably about 0.03 to 20 wt%, and more preferably about 0.05 to 10 wt% of the total monomer components constituting the adhesive polymer.

In addition to the above, a copolymer monomer other than the acid component can be used in an amount of about 0 to 30 wt%, preferably about 0.1 to 20 wt%, and more preferably about 0.1 to 10 wt% of the total monomer components constituting the adhesive polymer.

The weight average molecular weight (Mw) of the adhesive polymer used in the present invention is preferably 900,000 to 3,000,000. Considering durability, especially heat resistance, the weight average molecular weight is more preferably 1,200,000 to 2,500,000. If the weight average molecular weight is less than 900,000, the low molecular weight polymer component increases, the crosslinking density of the gel (adhesive layer) increases, and accordingly the adhesive layer becomes hard and the stress relaxation property is impaired, which is not preferable. In addition, if the weight average molecular weight exceeds 3,000,000, the viscosity increases or gelation occurs during polymerization of the polymer, which is not preferable.

The polydispersity (weight average molecular weight (Mw)/number average molecular weight (Mn)) of the adhesive polymer used in the present invention is preferably 3.0 or less, more preferably 1.05 to 2.5, and even more preferably 1.05 to 2.0. When the polydispersity (Mw/Mn) exceeds 3.0, the amount of low-molecular-weight polymer increases, and in order to increase the gel fraction of the adhesive layer, it is necessary to use a large amount of crosslinking agent, and as a result, excess crosslinking agent reacts with the already gelled polymer, the crosslinking density of the gel (adhesive layer) increases, and accordingly, the adhesive layer becomes hard and the stress relaxation property is impaired, which is not preferable. In addition, when there is a large amount of low-molecular-weight polymers and uncrosslinked polymers or oligomers (sol powder), it is presumed that the uncrosslinked polymers segregating near the interface of the adhesive layer in contact with the adherend under heating and humidification conditions cause destruction of the adhesive layer, which in turn causes peeling of the adhesive layer. In addition, the weight average molecular weight and polydispersity (Mw/Mn) are measured by GPC (gel permeation chromatography) and obtained from the values calculated by polystyrene conversion.

The adhesive polymer used in the present invention can be manufactured by suitably selecting a known manufacturing method such as solution polymerization, bulk polymerization, emulsion polymerization, or various radical polymerizations. In addition, the obtained adhesive polymer may be any of a random copolymer, a block copolymer, or a graft copolymer.

In addition, in solution polymerization, for example, ethyl acetate, toluene, etc. are used as a polymerization solvent. As a specific example of solution polymerization, the reaction is carried out under an inert gas stream such as nitrogen, by adding a polymerization initiator, and usually at about 50 to 70°C, for about 10 minutes to 30 hours under reaction conditions. In particular, by shortening the polymerization time to about 30 minutes to 3 hours, the production of low molecular weight oligomers generated in the later stage of polymerization can be suppressed, and the polydispersity (Mw/Mn) can be adjusted to a desirable range of 3.0 or less.

The polymerization initiator, chain transfer agent, emulsifier, etc. used in radical polymerization are not particularly limited and can be appropriately selected and used. In addition, the weight average molecular weight of the adhesive polymer can be controlled by the amount of the polymerization initiator and chain transfer agent used and the reaction conditions, and the appropriate amount used is adjusted depending on the type of these.

Examples of polymerization initiators include azo initiators such as 2,2'-azobisisobutyronitrile, 2,2'-azobis(2-amidinopropane)dihydrochloride, 2,2'-azobis[2-(5-methyl-2-imidazolin-2-yl)propane]dihydrochloride, 2,2'-azobis(2-methylpropionamidine)disulfate, 2,2'-azobis(N,N'-dimethyleneisobutylamidine), 2,2'-azobis[N-(2-carboxyethyl)-2-methylpropionamidine]hydrate (manufactured by Wako Pure Chemical Industries, Ltd., VA-057), persulfates such as potassium persulfate and ammonium persulfate, di(2-ethylhexyl)peroxydicarbonate, Examples thereof include peroxide initiators such as di(4-t-butylcyclohexyl)peroxydicarbonate, di-sec-butylperoxydicarbonate, t-butylperoxyneodecanoate, t-hexylperoxypivalate, t-butylperoxypivalate, dilauroyl peroxide, di-n-octanoyl peroxide, 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate, di(4-methylbenzoyl)peroxide, dibenzoyl peroxide, t-butylperoxyisobutyrate, 1,1-di(t-hexylperoxy)cyclohexane, t-butyl hydroperoxide, hydrogen peroxide, and redox initiators combining peroxides and reducing agents such as combinations of persulfates and sodium bisulfite, and combinations of peroxides and sodium ascorbate, but not limited to these. It is not limited.

The above polymerization initiator may be used alone or in combination of two or more, but the total content is preferably about 0.005 to 1 part by weight per 100 parts by weight of the monomer, and more preferably about 0.02 to 0.5 parts by weight.

In addition, in order to produce a (meth)acrylic polymer having the above weight average molecular weight using, for example, 2,2'-azobisisobutyronitrile as a polymerization initiator, the amount of the polymerization initiator used is preferably about 0.06 to 0.2 parts by weight based on 100 parts by weight of the total amount of the monomer component, and more preferably about 0.08 to 0.175 parts by weight.

Examples of chain transfer agents include lauryl mercaptan, glycidyl mercaptan, mercaptoacetic acid, 2-mercaptoethanol, thioglycolic acid, 2-ethylhexyl thioglucolate, and 2,3-dimercapto-1-propanol. The chain transfer agent may be used alone or in combination of two or more, but the total content is 0.1 part by weight or less relative to 100 parts by weight of the total amount of the monomer component.

In addition, emulsifiers used in emulsion polymerization include, for example, anionic emulsifiers such as sodium lauryl sulfate, ammonium lauryl sulfate, sodium dodecylbenzene sulfonate, ammonium polyoxyethylene alkyl ether sulfate, and sodium polyoxyethylene alkyl phenyl ether sulfate; and nonionic emulsifiers such as polyoxyethylene alkyl ethers, polyoxyethylene alkyl phenyl ethers, polyoxyethylene fatty acid esters, and polyoxyethylene-polyoxypropylene block polymers. These emulsifiers may be used alone or in combination of two or more.

In addition, as a reactive emulsifier, an emulsifier having a radical polymerizable functional group such as a propenyl group or an allyl ether group introduced therein, specifically, examples thereof include Aqualon HS-10, HS-20, KH-10, BC-05, BC-10, BC-20 (all manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), Adecariasope SE10N (manufactured by Asahi Denkako Co., Ltd.), etc. Reactive emulsifiers are preferable because they improve water resistance since they are introduced into the polymer chain after polymerization. The amount of the emulsifier to be used is 0.3 to 5 parts by weight per 100 parts by weight of the total amount of the monomer component, and 0.5 to 1 part by weight is more preferable from the viewpoint of polymerization stability and mechanical stability.

The adhesive polymer used in the present invention usually has a weight average molecular weight of 300,000 to 4 million. Considering durability, especially heat resistance, it is preferable to use a weight average molecular weight of 500,000 to 3 million. In addition, it is more preferable to use a weight average molecular weight of 650,000 to 2 million. If the weight average molecular weight is less than 300,000, it is not preferable in terms of heat resistance. In addition, if the weight average molecular weight is greater than 4 million, it is also not preferable in terms of reduced bonding and adhesive strength. In addition, the weight average molecular weight is measured by GPC (gel permeation chromatography) and refers to a value calculated by polystyrene conversion.

<Other ingredients in the adhesive composition>

In addition, the adhesive composition used in the present invention may contain a crosslinking agent. As the crosslinking agent, an organic crosslinking agent or a polyfunctional metal chelate can be used. As the organic crosslinking agent, an isocyanate crosslinking agent, a peroxide crosslinking agent, an epoxy crosslinking agent, an imine crosslinking agent, etc. can be mentioned. A polyfunctional metal chelate is one in which a polyvalent metal is covalently bonded or coordinated with an organic compound. Examples of the polyvalent metal atom include Al, Cr, Zr, Co, Cu, Fe, Ni, V, Zn, In, Ca, Mg, Mn, Y, Ce, Sr, Ba, Mo, La, Sn, Ti, etc. Examples of the organic compound to which a covalent or coordinated bond is formed include an oxygen atom, etc., and examples of the organic compound include an alkyl ester, an alcohol compound, a carboxylic acid compound, an ether compound, a ketone compound, etc.

As the crosslinking agent, an isocyanate-based crosslinking agent and/or a peroxide-based crosslinking agent is preferable. As compounds according to the isocyanate-based crosslinking agent, examples thereof include isocyanate monomers such as tolylene diisocyanate, chlorphenylene diisocyanate, tetramethylene diisocyanate, xylylene diisocyanate, diphenylmethane diisocyanate, and hydrogenated diphenylmethane diisocyanate, and isocyanate compounds obtained by adding these isocyanate monomers with trimethylolpropane or the like, isocyanurates, biuret-based compounds, and also urethane prepolymer-type isocyanates obtained by addition-reacting polyether polyol, polyester polyol, acrylic polyol, polybutadiene polyol, and polyisoprene polyol. Particularly preferred is a polyisocyanate compound, and is at least one selected from the group consisting of hexamethylene diisocyanate, hydrogenated xylylene diisocyanate, and isophorone diisocyanate, or a polyisocyanate compound derived therefrom. Here, the polyisocyanate compound selected from the group consisting of hexamethylene diisocyanate, hydrogenated xylylene diisocyanate, and isophorone diisocyanate, or a polyisocyanate compound derived therefrom includes hexamethylene diisocyanate, hydrogenated xylylene diisocyanate, isophorone diisocyanate, polyol-modified hexamethylene diisocyanate, polyol-modified hydrogenated xylylene diisocyanate, trimer type hydrogenated xylylene diisocyanate, and polyol-modified isophorone diisocyanate. The polyisocyanate compound exemplified is preferable because the reaction with the hydroxyl group proceeds rapidly, especially by using an acid or base contained in the polymer as a catalyst, and particularly because it contributes to the speed of crosslinking.

As a peroxide type crosslinking agent, any one that generates radical active species by heating or light irradiation to promote crosslinking of the base polymer of the adhesive composition may be suitably used; however, considering workability and stability, it is preferable to use a peroxide having a half-life temperature of 80 to 160°C for 1 minute, and it is more preferable to use a peroxide having a half-life temperature of 90 to 140°C.

Examples of peroxides that can be used as crosslinking agents include di(2-ethylhexyl) peroxydicarbonate (half-life temperature for 1 minute: 90.6°C), di(4-t-butylcyclohexyl) peroxydicarbonate (half-life temperature for 1 minute: 92.1°C), di-sec-butyl peroxydicarbonate (half-life temperature for 1 minute: 92.4°C), t-butyl peroxyneodecanoate (half-life temperature for 1 minute: 103.5°C), t-hexyl peroxypivalate (half-life temperature for 1 minute: 109.1°C), t-butyl peroxypivalate (half-life temperature for 1 minute: 110.3°C), dilauroyl peroxide (half-life temperature for 1 minute: 116.4°C), di-n-octanoyl peroxide (half-life temperature for 1 minute: 117.4°C), Examples include 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate (half-life temperature for 1 minute: 124.3°C), di(4-methylbenzoyl)peroxide (half-life temperature for 1 minute: 128.2°C), dibenzoyl peroxide (half-life temperature for 1 minute: 130.0°C), t-butylperoxyisobutyrate (half-life temperature for 1 minute: 136.1°C), and 1,1-di(t-hexylperoxy)cyclohexane (half-life temperature for 1 minute: 149.2°C). Among these, di(4-t-butylcyclohexyl)peroxydicarbonate (half-life temperature for 1 minute: 92.1°C), dilauroyl peroxide (half-life temperature for 1 minute: 116.4°C), and dibenzoyl peroxide (half-life temperature for 1 minute: 130.0°C) are particularly advantageous in that they have excellent crosslinking reaction efficiency.

In addition, the half-life of peroxide is an indicator of the decomposition speed of peroxide, and refers to the time until the remaining amount of peroxide is reduced by half. The decomposition temperature for obtaining the half-life at any time, or the half-life time at any temperature, is described in the manufacturer's catalog, etc., and for example, it is described in the "Organic Peroxide Catalog 9th Edition (May 2003)" of Nippon Oil & Fat Co., Ltd.

The amount of the crosslinking agent to be used is preferably 0.01 to 20 parts by weight, and more preferably 0.03 to 10 parts by weight, per 100 parts by weight of the adhesive polymer. In addition, if the amount of the crosslinking agent is less than 0.01 parts by weight, the cohesive strength of the adhesive tends to be insufficient, and there is a risk of foaming when heated. On the other hand, if the amount of the crosslinking agent is more than 20 parts by weight, the moisture resistance is insufficient, and peeling easily occurs in reliability tests, etc.

The above isocyanate crosslinking agent may be used alone or as a mixture of two or more, but the total content is preferably 0.01 to 2 parts by weight of the polyisocyanate compound crosslinking agent per 100 parts by weight of the adhesive polymer, more preferably 0.02 to 2 parts by weight, and even more preferably 0.05 to 1.5 parts by weight. It is possible to appropriately contain the polyisocyanate compound crosslinking agent by taking into consideration cohesion, prevention of peeling in durability tests, etc.

The above peroxide may be used alone or as a mixture of two or more types, but the total content is 0.01 to 2 parts by weight of the peroxide per 100 parts by weight of the adhesive polymer, preferably 0.04 to 1.5 parts by weight, and more preferably 0.05 to 1 part by weight. It is appropriately selected within this range for adjusting processability, reworkability, crosslinking stability, peelability, etc.

In addition, the amount of decomposed peroxide remaining after the reaction can be measured, for example, by HPLC (high-performance liquid chromatography).

More specifically, for example, about 0.2 g of the adhesive composition after the reaction treatment is taken out, immersed in 10 ml of ethyl acetate, extracted by shaking in a shaker at 25°C and 120 rpm for 3 hours, and then allowed to stand at room temperature for 3 days. Next, 10 ml of acetonitrile is added, shaken at 25°C and 120 rpm for 30 minutes, and about 10 μl of the obtained extract is filtered through a membrane filter (0.45 μm) and injected into HPLC for analysis, which can be used as the amount of peroxide after the reaction treatment.

As an additive, it is particularly preferable to blend a silane coupling agent. As the silane coupling agent, silicon compounds having an epoxy structure, such as 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, and 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane; amino group-containing silicon compounds, such as 3-aminopropyltrimethoxysilane, N-(2-aminoethyl)3-aminopropyltrimethoxysilane, and N-(2-aminoethyl)3-aminopropylmethyldimethoxysilane; (meth)acryl group-containing silane coupling agents, such as 3-chloropropyltrimethoxysilane; acetoacetyl group-containing trimethoxysilane, 3-acryloxypropyltrimethoxysilane, and 3-methacryloxypropyltriethoxysilane; Examples thereof include silane coupling agents containing an isocyanate group, such as 3-isocyanatepropyltriethoxysilane. In particular, 3-glycidoxypropyltrimethoxysilane and acetoacetyl group-containing trimethoxysilane are preferably used because they can effectively suppress peeling. The silane coupling agent can provide durability, particularly the effect of suppressing peeling in a humid environment. The amount of the silane coupling agent used is 1 part by weight or less, more preferably 0.01 to 1 part by weight, and preferably 0.02 to 0.6 part by weight per 100 parts by weight of the adhesive polymer. If the amount of the silane coupling agent used increases, the adhesive strength to the liquid crystal cell may increase excessively, which may affect reworkability, etc.

In addition, the adhesive composition used in the present invention may contain other known additives, for example, colorants, pigments, powders, dyes, surfactants, plasticizers, tackifiers, surface lubricants, leveling agents, softeners, antioxidants, anti-aging agents, light stabilizers, ultraviolet absorbers, polymerization inhibitors, inorganic or organic fillers, metal powders, particles, thin films, etc. may be appropriately added to the adhesive composition depending on the intended use. In addition, a redox system with a reducing agent added may be employed within a controllable range.

An adhesive layer is formed by the above adhesive composition, but when forming the adhesive layer, it is preferable to adjust the total amount of crosslinking agent added and to sufficiently consider the influence of the crosslinking treatment temperature and crosslinking treatment time.

Depending on the crosslinking agent used, it is possible to adjust the crosslinking treatment temperature and crosslinking treatment time. The crosslinking treatment temperature is preferably 170°C or lower.

In addition, this cross-linking treatment may be performed at the temperature during the drying process of the adhesive layer, or may be performed by installing a separate cross-linking treatment process after the drying process.

Also, the cross-linking processing time can be set by considering productivity and workability, but it is usually around 0.2 to 20 minutes, and preferably around 0.5 to 10 minutes.

[Adhesive layer]

Describes the adhesive layer.

The polarizing film laminate with an adhesive layer of the present invention has an adhesive layer formed directly on at least one surface of a polarizing film or via an optically transparent polarizing film protective film.

Examples of methods for forming an adhesive layer include a method in which the adhesive composition is applied to a separator or the like that has undergone a peeling treatment, a method in which a polymerization solvent or the like is dried and removed to form an adhesive layer, and then the adhesive layer is transferred to an optical film, or a method in which the adhesive composition is applied to an optical film, and a method in which the polymerization solvent or the like is dried and removed to form an adhesive layer on the optical film. In addition, when applying the adhesive, one or more types of solvents other than the polymerization solvent may be newly added as appropriate.

As a separator that has undergone peeling treatment, a silicone peeling liner is preferably used. In the process of forming an adhesive layer by applying and drying the adhesive composition on such a liner, an appropriate method may be adopted as a method for drying the adhesive, depending on the purpose. Preferably, a method of superheating and drying the coating film is used. The heating and drying temperature is preferably 40°C to 200°C, more preferably 50°C to 180°C, and particularly preferably 70°C to 170°C. By setting the heating temperature within the above range, an adhesive layer having excellent adhesive properties can be obtained.

The drying time may be suitably selected, and an appropriate time may be adopted. The drying time is preferably 5 seconds to 20 minutes, more preferably 5 seconds to 10 minutes, and particularly preferably 10 seconds to 5 minutes.

In addition, an anchor layer can be formed on the surface of the polarizing film, or an adhesive layer can be formed after various types of adhesion treatment such as corona treatment or plasma treatment. An adhesion treatment may also be performed on the surface of the adhesive layer.

When forming an adhesive layer on the surface of a polarizing film, it is preferable to use an anchor layer or adhesive layer that does not contain acid.

A specific method for forming an anchor layer includes a method in which a solution containing a urethane polymer (such as Denatoron B510-C manufactured by Nagase Chemtex Co., Ltd.) is adjusted to a solid content of 0.2 wt% in a mixed solution of water and isopropyl alcohol (volume ratio, 65:35), the adjusted solution is applied to a polarizing film laminate using Mayaba #5, and dried at 50°C for 30 seconds to form an anchor coat layer having a thickness of 25 nm.

Various methods are used as a method for forming the adhesive layer. Specifically, for example, methods such as roll coating, kiss roll coating, gravure coating, reverse coating, roll brush, spray coating, dip roll coating, bar coating, knife coating, air knife coating, curtain coating, lip coating, and extrusion coating using a die coater can be mentioned.

The thickness of the adhesive layer is not particularly limited and is, for example, about 1 to 500 ㎛. It is preferably 1 to 250 ㎛, more preferably 1 to 100 ㎛, and even more preferably 1 to 35 ㎛.

By making the thickness of the adhesive layer thin, the total amount of acid in the adhesive for the polarizing film is reduced, and the influence of the adhesive layer-attached polarizing film laminate on polyene can be reduced.

In addition, as the thickness of the adhesive layer becomes thinner, the adhesive strength decreases, and under high temperature and high humidity, the adhesive durability tends to decrease due to the shrinkage stress of the polarizing plate caused by the shrinkage of the polarizing film, resulting in peeling or other problems, and it is not desirable to make the thickness of the adhesive layer thin. However, by making the polarizing film thinner, the shrinkage stress of the polarizing plate can be reduced, and as a result, even if the thickness of the adhesive layer is made thin, the adhesive durability can be maintained or improved.

In cases where the above adhesive layer is exposed, the adhesive layer may be protected with a peel-off sheet (separator) until it is put into practical use.

As the constituent materials of the separator, examples thereof include plastic films such as polyethylene, polypropylene, polyethylene terephthalate, and polyester films; porous materials such as paper, cloth, and nonwoven fabrics; and suitable thin films such as nets, foam sheets, metal foils, and laminates thereof. However, plastic films are suitably used because of their excellent surface smoothness.

As the plastic film, any film capable of protecting the adhesive layer is not particularly limited, and examples thereof include polyethylene film, polypropylene film, polybutene film, polybutadiene film, polymethylpentene film, polyvinyl chloride film, vinyl chloride copolymer film, polyethylene terephthalate film, polybutylene terephthalate film, polyurethane film, and ethylene-vinyl acetate copolymer film.

The thickness of the above separator is usually 5 to 200 ㎛, preferably 5 to 100 ㎛. The above separator may be subjected to a release and antifouling treatment using a silicone-based, fluorine-based, long-chain alkyl-based or fatty acid amide-based release agent, silica powder, etc., or an antistatic treatment such as a coating type, a mixing type or a deposition type, as needed. In particular, by appropriately performing a peeling treatment such as a silicone treatment, a long-chain alkyl treatment or a fluorine treatment on the surface of the separator, the peelability of the separator from the adhesive layer can be further enhanced.

In addition, the peel-treated sheet used in the production of the adhesive layer-attached polarizing film laminate can be used as a separator of the adhesive layer-attached polarizing film laminate, thereby enabling simplification in terms of process.

2. Polarizing film laminate

The polarizing film laminate (12) includes at least a polarizing film (120) and a polarizing film protective film (121) bonded to at least one side of the polarizing film (120), for example, the viewing side. As in the present embodiment, polarizing film protective films (121, 122) may be bonded to both sides of the polarizing film (120), that is, the viewing side and the side opposite to the viewing side of the polarizing film (120), respectively, via an appropriate adhesive (not shown). Although not specifically shown, another optical film may be formed between the polarizing film (120) and the polarizing film protective films (121, 122).

The present invention comprehensively solves problems occurring under high temperature and high humidity environments, particularly problems of "polyenization", "color fading", and "heat discoloration", and focuses particularly on the iodine concentration (wt.%) of the polarizing film (120) and the moisture content (g/m2) of the polarizing film laminate (12). These values can be adjusted, for example, during the production of the polarizing film or the production of the polarizing film laminate.

2-1. Polarizing film

The polarizing film (120) is made of a polyvinyl alcohol (PVA)-based resin film containing iodine. PVA or a derivative thereof is used as a material of the PVA-based film applied to the polarizing film. Examples of PVA derivatives include polyvinyl formal, polyvinyl acetal, etc., and those modified with olefins such as ethylene and propylene, unsaturated carboxylic acid alkyl esters such as acrylic acid, methacrylic acid, and crotonic acid, acrylamide, etc. PVA having a polymerization degree of about 1,000 to 10,000 and a saponification degree of about 80 to 100 mol% is generally used. PVA-based films made of these materials tend to easily contain moisture.

The PVA film may contain additives such as a plasticizer. Examples of the plasticizer include polyols and condensates thereof, and examples thereof include glycerin, diglycerin, triglycerin, ethylene glycol, propylene glycol, and polyethylene glycol. The amount of the plasticizer used is not particularly limited, but 20 wt% or less of the PVA film is suitable.

2-1-1. Manufacturing of polarizing film

In the production of a polarizing film having a thickness of 6 ㎛ or more, for example, a dyeing treatment in which the PVA-based film is dyed with iodine, and a stretching treatment in which the PVA-based film is stretched in at least one direction are performed. Generally, a method is adopted in which the PVA-based film is subjected to a series of treatments including swelling, dyeing, crosslinking, stretching, washing with water, and drying.

The swelling treatment is performed, for example, by immersing the PVA film in a swelling bath (water bath). By this treatment, contamination or anti-blocking agent on the surface of the PVA film can be washed away, and by swelling the PVA film, unevenness such as dyeing deviation can be prevented. Glycerin or potassium iodide may be appropriately added to the swelling bath. The temperature of the swelling bath is, for example, about 20 to 60°C, and the immersion time in the swelling bath is, for example, about 0.1 to 10 minutes.

The dyeing treatment is carried out, for example, by immersing the PVA film in an iodine solution. The iodine solution is usually an aqueous iodine solution and contains iodine and potassium iodide as a dissolution aid. The iodine concentration is, for example, about 0.01 to 1 wt%, preferably about 0.02 to 0.5 wt%. The potassium iodide concentration is, for example, about 0.01 to 10 wt%, preferably about 0.02 to 8 wt%.

In the dyeing treatment, the temperature of the iodine solution is, for example, about 20 to 50°C, preferably about 25 to 40°C. The immersion time is, for example, about 10 to 300 seconds, preferably about 20 to 240 seconds. In the iodine dyeing treatment, conditions such as the concentration of the iodine solution, the immersion temperature of the PVA film in the iodine solution, and the immersion time are adjusted so that the iodine content and potassium content in the PVA film are within the above ranges.

The crosslinking treatment is carried out, for example, by immersing an iodine-dyed PVA film in a treatment bath containing a crosslinking agent. Any appropriate crosslinking agent may be employed as the crosslinking agent. Specific examples of the crosslinking agent include boron compounds such as boric acid and borax, glyoxal, and glutaraldehyde. These are used alone or in combination. The solvent used in the crosslinking bath solution is generally water, but an appropriate amount of an organic solvent compatible with water may be added. The crosslinking agent is used in a ratio of, for example, 1 to 10 parts by weight per 100 parts by weight of the solvent. It is preferable that the crosslinking bath solution further contains an agent such as iodide. The concentration of the agent is preferably 0.05 to 15 wt%, more preferably 0.5 to 8 wt%. The temperature of the crosslinking bath is, for example, about 20 to 70°C, preferably 40 to 60°C. The immersion time in the cross-linking bath is, for example, about 1 second to 15 minutes, preferably about 5 seconds to 10 minutes.

Stretching treatment is a treatment in which a PVA film is stretched in at least one direction. Generally, the PVA film is stretched uniaxially in the transport direction (longitudinal direction). The stretching method is not particularly limited, and both a wet stretching method and a dry stretching method can be adopted. When a wet stretching method is adopted, the PVA film is stretched at a predetermined ratio in a treatment bath. As a solution for the stretching bath, a solution in which compounds necessary for various treatments are added to a solvent such as water or an organic solvent (e.g., ethanol) is suitably used. Examples of the dry stretching method include a roll-to-roll stretching method, a heated roll stretching method, and a compression stretching method. In the production of a polarizing film, the stretching treatment may be performed at any stage. Specifically, it may be performed simultaneously with swelling, dyeing, and crosslinking, or it may be performed at any time before or after each of these treatments. In addition, the stretching may be performed in multiple stages. The cumulative elongation ratio of the PVA film is, for example, 5 times or more, and preferably 5 to 7 times.

The PVA film (stretched film) subjected to each of the above treatments is provided for water washing and drying treatment in accordance with the commercial law.

The washing treatment is carried out, for example, by immersing the PVA film in a washing bath. The washing bath may be pure water or an aqueous solution of iodide (e.g., potassium iodide, sodium iodide, etc.). The concentration of the iodide aqueous solution is preferably 0.1 to 10 wt%. An additive such as zinc sulfate or zinc chloride may be added to the iodide aqueous solution.

The washing temperature is, for example, in the range of 5 to 50°C, preferably 10 to 45°C, and more preferably 15 to 40°C. The immersion time is, for example, about 10 to 300 seconds, and preferably 20 to 240 seconds. The washing treatment may be performed only once, or may be performed multiple times as needed. When the washing treatment is performed multiple times, the type and concentration of additives included in the washing bath used for each treatment are appropriately adjusted.

The drying treatment of the PVA film is carried out by any appropriate method (e.g., natural drying, air drying, heat drying).

2-1-2. Manufacturing of polarizing film

A polarizing film having a thickness of less than 6 ㎛ can be manufactured by, for example, the manufacturing method disclosed in Japanese Patent No. 4751481. This manufacturing method includes a laminate manufacturing process for forming a PVA-based resin layer on a thermoplastic substrate, a stretching process for stretching the PVA-based resin layer integrally with the thermoplastic resin substrate, a dyeing process for adsorbing a dichroic substance onto the PVA resin layer, etc. Depending on the need, an insolubilization process and a crosslinking process, a drying process, a washing process, etc. of the PVA-based resin layer can also be applied. The stretching process can be performed before or after the dyeing process, and any stretching method of stretching in air or in water such as a boric acid aqueous solution can be adopted. In addition, the stretching may be a single-stage stretching or a multi-stage stretching of two or more stages.

An example of a method for manufacturing a polarizing film is described with reference to Fig. 2. Here, a polarizing film is manufactured by stretching a PVA-based resin layer formed on a resin substrate integrally with the resin substrate.

[Laminated body manufacturing process (A)]

First, a 200 ㎛ thick, amorphous ester thermoplastic resin substrate having a glass transition temperature of 75 ℃, for example, isophthalic acid copolymerized polyethylene terephthalate (hereinafter referred to as “amorphous PET”) (6) copolymerized with 6 mol% isophthalic acid, and a PVA aqueous solution having a concentration of 4 to 5 wt%, in which PVA powder having a degree of polymerization of 1000 or more and a degree of saponification of 99% or more is dissolved in water, are prepared. Next, in a laminate manufacturing device (20) equipped with a coating means (21), a drying means (22), and a surface modification treatment device (23), the PVA aqueous solution is applied to the amorphous PET substrate (6), and dried at a temperature of 50 to 60 ℃, so as to form a 7 ㎛ thick PVA layer (2) having a glass transition temperature of 80 ℃ on the PET substrate (6). Thereby, a laminate (7) including a 7 ㎛ thick PVA layer is manufactured. At this time, by corona-treating the surface of the amorphous PET substrate (6) with a surface modification treatment device (23), the adhesion between the amorphous PET substrate (6) and the PVA layer (2) formed thereon can be improved.

Next, the laminate (7) including the PVA layer is finally manufactured as a polarizing film having a thickness of 3 ㎛ through the following processing, including a two-stage stretching treatment of air-assisted stretching and boric acid underwater stretching.

[Airborne Auxiliary Extension Processing (B)]

In the first-stage air-assisted stretching treatment (B), a laminate (7) including a 7-μm-thick PVA layer (2) is stretched integrally with a PET substrate (6), thereby generating a "stretched laminate (8)" including a 5-μm-thick PVA layer (2). Specifically, in an air-assisted stretching treatment device (30) in which a stretching means (31) is arranged inside an oven (33), a laminate (7) including a 7-μm-thick PVA layer (2) is hung on the stretching means (31) of an oven (33) set to a stretching temperature environment of 130°C, and is stretched along one axis of the free end so that a stretching ratio becomes 1.8 times, thereby generating a stretched laminate (8). At this stage, a roll (8') of the stretched laminate (8) can be manufactured by a winding device (32) installed in conjunction with the oven (30).

[Dyeing Treatment (C)]

Next, by a dyeing treatment (C), a colored laminate (9) is produced in which iodine of a dichroic substance is adsorbed onto a 5 ㎛ thick PVA layer (2) in which PVA molecules are aligned. Specifically, in a dyeing device (40) equipped with a dyeing bath (42) of a dyeing solution (41), a stretched laminate (8) unwound from an extruding device (43) equipped with a roll (8') installed in parallel to the dyeing device (40) is immersed in a dyeing solution (41) containing iodine and potassium iodide at a liquid temperature of 30° C. for an arbitrary period of time so that the single-body transmittance of the PVA layer constituting the polarizing film finally formed becomes 40 to 44%, thereby producing a colored laminate (9) in which iodine is adsorbed onto the oriented PVA layer (2) of the stretched laminate (8).

In this treatment, the dyeing solution (41) uses water as a solvent and has an iodine concentration of 0.30 wt% so as not to dissolve the PVA layer (2) included in the stretched laminate (8). In addition, the dyeing solution (41) has a potassium iodide concentration of 2.1 wt% for dissolving iodine in water. The ratio of the concentrations of iodine and potassium iodide is 1 to 7. More specifically, by immersing the stretched laminate (8) in a dyeing solution (41) having an iodine concentration of 0.30 wt% and a potassium iodide concentration of 2.1 wt% for 60 seconds, a colored laminate (9) is produced in which iodine is adsorbed onto a 5 µm thick PVA layer (2) in which PVA molecules are aligned.

[Boric acid underwater stretching treatment (D)]

By the second stage of boric acid aqueous stretching treatment, the colored laminate (9) including the PVA layer (2) oriented with iodine is further stretched, and an optical film laminate (60) including the PVA layer oriented with iodine constituting a 3 ㎛ thick polarizing film is produced. Specifically, in a boric acid aqueous stretching treatment device (50) equipped with a boric acid bath (52) of a boric acid aqueous solution (51) and a stretching means (53), a colored laminate (9) continuously released from a dyeing device (40) is immersed in a boric acid aqueous solution (51) set to a stretching temperature environment of 65° C. containing boric acid and potassium iodide, and then is stretched along one axis of the free end so that a stretching ratio becomes 3.3 times by being hung on a stretching means (53) arranged in the boric acid aqueous treatment device (50), thereby producing an optical film laminate (60) including a PVA layer having a thickness of 3 µm.

[Cleansing treatment (G)]

Next, the optical film laminate (60) including the polarizing film is preferably sent as is to a cleaning treatment (G). The purpose of the cleaning treatment (G) is to wash away unnecessary residues attached to the surface of the polarizing film by a cleaning solution (81) of a cleaning device (80). However, the cleaning treatment (G) may be omitted, and the optical film laminate (60) including the taken out polarizing film may be directly sent to a drying treatment (H).

[Dry treatment (H)]

The cleaned optical film laminate (60) is sent to a drying process (H) and dried therein. Subsequently, the dried optical film laminate (60) is wound as a continuous web optical film laminate (60) by a winding device (91) installed in conjunction with a drying device (90), and a roll of the optical film laminate (60) including a polarizing film is produced. Any appropriate method, for example, natural drying, air drying, or heat drying, can be employed as the drying process (H). For example, in a drying device (90) of an oven, drying can be performed in warm air of 60° C. for 240 seconds.

2-1-3. Other

It is preferable that the polarizing film contains zinc. When the polarizing film contains zinc, there is a tendency for the decrease in transmittance and color deterioration of the polarizing film laminate after the heating test to be suppressed. When the polarizing film contains zinc, the content of zinc in the polarizing film is preferably 0.002 to 2 wt%, and more preferably 0.01 to 1 wt%.

The polarizing film also preferably contains sulfate ions. When the polarizing film contains sulfate ions, there is a tendency for the decrease in the transmittance of the polarizing film laminate after the heating test to be suppressed. When the polarizing film contains sulfate ions, the content of sulfate ions in the polarizing film is preferably 0.02 to 0.45 wt%, more preferably 0.05 to 0.35 wt%, and even more preferably 0.1 to 0.25 wt%. In addition, the content of sulfate ions in the polarizing film is calculated from the content of sulfur atoms.

In order to contain zinc in the polarizing film, it is preferable that zinc impregnation treatment is performed in the manufacturing process of the polarizing film. In addition, in order to contain sulfate ions in the polarizing film, it is preferable that sulfate ion treatment is performed in the manufacturing process of the polarizing film.

Zinc impregnation treatment is carried out, for example, by immersing a PVA film in a zinc salt solution. As the zinc salt, an inorganic salt compound in an aqueous solution such as zinc halides such as zinc chloride and zinc iodide, zinc sulfate, and zinc acetate is suitable. In addition, various zinc complex compounds may be used for the zinc impregnation treatment. In addition, it is preferable to use an aqueous solution containing potassium ions and iodine ions, such as potassium iodide, as the zinc salt solution, because it is easy to impregnate zinc ions. The concentration of potassium iodide in the zinc salt solution is preferably 0.5 to 10 wt%, and further preferably 1 to 8 wt%.

The sulfate ion treatment is carried out, for example, by immersing the PVA film in an aqueous solution containing a sulfate metal salt. As the sulfate metal salt, one that is easy to separate into sulfate ions and metal ions in the treatment solution and in which the sulfate metal salt is easy to be introduced in an ion state into the PVA film is preferable. For example, examples of the type of metal that forms the sulfate metal salt include alkali metals such as sodium and potassium; alkaline earth metals such as magnesium and calcium; and transition metals such as cobalt, nickel, zinc, chromium, aluminum, copper, manganese, and iron.

In the production of a polarizing film, the zinc impregnation treatment and the sulfate ion treatment may be performed at any stage. That is, the zinc impregnation treatment and the sulfate ion treatment may be performed before the dyeing treatment or after the dyeing treatment. The zinc impregnation treatment and the sulfate ion treatment may be performed simultaneously. It is preferable that the zinc sulfate is used as the zinc salt and the sulfate metal salt, and the PVA-based film is immersed in a treatment bath containing zinc sulfate, so that the zinc impregnation treatment and the sulfate ion treatment are performed simultaneously. In addition, the zinc salt or the sulfate metal salt may be allowed to coexist in the dyeing solution, and the zinc impregnation treatment and/or the sulfate ion treatment may be performed simultaneously with the dyeing treatment. The zinc impregnation treatment and the sulfate ion treatment may be performed simultaneously with stretching.

2-2. Polarizing film protection film

As a material constituting the polarizing film protective film (121, 122), for example, a thermoplastic resin having excellent transparency, mechanical strength, and thermal stability can be mentioned. Specific examples of such thermoplastic resins include cellulose-based resins such as triacetyl cellulose, polyester-based resins, polyether sulfone-based resins, polysulfone-based resins, polycarbonate-based resins, polyamide-based resins, polyimide-based resins, polyolefin-based resins, (meth)acrylic-based resins, cyclic polyolefin-based resins (norbornene-based resins), polyarylate-based resins, polystyrene-based resins, PVA-based resins, and mixtures thereof.

It would be good if the polarizing film protective film also had the function of a phase difference film.

The thickness of the polarizing film protective film is appropriately adjusted to control the moisture content of the polarizing film laminate. From the viewpoints of workability such as strength and handleability, thin layer property, etc., the thickness is preferably about 1 to 500 ㎛, more preferably 2 to 300 ㎛, and even more preferably 5 to 200 ㎛.

The polarizing film protective film may contain one or more types of additives. Examples of the additives include ultraviolet absorbers, antioxidants, activators, plasticizers, release agents, anti-coloring agents, flame retardants, nucleating agents, antistatic agents, pigments, and colorants.

2-3. Other optical films

The polarizing film and the polarizing film protective film may be directly bonded, but may also be laminated with other optical films. There is no particular limitation on other optical films, but for example, a phase difference film, a viewing angle compensation film, etc. may be used. The phase difference film as another optical film may also have a function as a protective film.

As described above, the polarizing film protective film may also have the function of a phase difference film, but in this case, the phase difference film as another optical film may be omitted. On the other hand, even if the polarizing film protective film has the function of a phase difference film, the phase difference film may be formed as another optical film. In this case, two or three or more phase difference films are actually included.

2-4. Adhesive

For bonding of polarizing film (120) and polarizing film protective film (121, 122), or bonding of them with other optical films such as phase difference films, a radical polymerization curable adhesive, a cationic polymerization curable adhesive, or a water-based adhesive can be used, for example.

(Radical polymerization curing adhesive)

The above radical polymerization curable adhesive comprises a radical polymerizable compound as a curable compound. The radical polymerizable compound may be a compound that is cured by an active energy ray or a compound that is cured by heat. Examples of the active energy ray include electron beams, ultraviolet rays, and visible light.

As the radical polymerizable compound, for example, a compound having a radical polymerizable functional group having a carbon-carbon double bond, such as a (meth)acryloyl group or a vinyl group, can be mentioned. As the radical polymerizable compound, a polyfunctional radical polymerizable compound is preferably used. The radical polymerizable compound may be used alone, or two or more types may be used in combination. In addition, a polyfunctional radical polymerizable compound and a monofunctional radical polymerizable compound may be used together.

As the above polymerizable compound, it is preferable to use a compound having a high logP value (octanol/water partition coefficient), and it is also preferable to select a compound having a high logP value as the radical polymerizable compound. Here, the logP value is an indicator of the lipophilicity of a substance, and means the logarithm of the octanol/water partition coefficient. A high logP value means lipophilicity, that is, low absorption. The logP value can be measured (flask infiltration method described in JIS-Z-7260), and can also be calculated (ChemDraw Ultra manufactured by Cambridge Soft) based on the structure of each compound which is a component (curing component, etc.) of the curable adhesive.

The logP value of the radical polymerizable compound is preferably 2 or more, more preferably 3 or more, and particularly preferably 4 or more. Within this range, deterioration of the polarizer due to moisture can be prevented, and a polarizing film having excellent durability under high temperature and high humidity can be obtained.

As the above-mentioned multifunctional radical polymerizable compounds, for example, tripropylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, 1,10-decanediol diacrylate, 2-ethyl-2-butylpropanediol di(meth)acrylate, bisphenol A di(meth)acrylate, bisphenol A ethylene oxide adduct di(meth)acrylate, bisphenol A propylene oxide adduct di(meth)acrylate, bisphenol A diglycidyl ether di(meth)acrylate, neopentyl glycol di(meth)acrylate, tricyclodecane dimethanol di(meth)acrylate, cyclic trimethylolpropane formal(meth)acrylate, Examples thereof include esters of (meth)acrylates with polyhydric alcohols, such as dioxane glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, and EO-modified diglycerin tetra(meth)acrylate; 9,9-bis[4-(2-(meth)acryloyloxyethoxy)phenyl]fluorene; epoxy(meth)acrylates; urethane(meth)acrylates; and polyester(meth)acrylates.

Among the above polyfunctional radical polymerizable compounds, polyfunctional radical polymerizable compounds having a high logP value are preferable. Examples of such compounds include alicyclic (meth)acrylates such as tricyclodecane dimethanol di(meth)acrylate (logP=3.05) and isobornyl (meth)acrylate (logP=3.27); long-chain aliphatic (meth)acrylates such as 1,9-nonanediol di(meth)acrylate (logP=3.68) and 1,10-decanediol diacrylate (logP=4.10); multibranched (meth)acrylates such as hydroxypivalic neopentyl glycol (meth)acrylic acid adduct (logP=3.35) and 2-ethyl-2-butylpropanediol di(meth)acrylate (logP=3.92); Examples thereof include (meth)acrylates containing aromatic rings, such as bisphenol A di(meth)acrylate (log P = 5.46), bisphenol A ethylene oxide 4 mol adduct di(meth)acrylate (log P = 5.15), bisphenol A propylene oxide 2 mol adduct di(meth)acrylate (log P = 6.10), bisphenol A propylene oxide 4 mol adduct di(meth)acrylate (log P = 6.43), 9,9-bis[4-(2-(meth)acryloyloxyethoxy)phenyl]fluorene (log P = 7.48), and p-phenylphenol (meth)acrylate (log P = 3.98).

When a polyfunctional radical polymerizable compound and a monofunctional radical polymerizable compound are used in combination, the content ratio of the polyfunctional radical polymerizable compound is preferably 20 to 97 wt%, more preferably 50 to 95 wt%, still more preferably 75 to 92 wt%, and particularly preferably 80 to 92 wt%, based on the total amount of the radical polymerizable compound. With this range, a polarizing film having excellent durability under high temperature and high humidity can be obtained.

As the above-mentioned monofunctional radical polymerizable compound, there can be mentioned, for example, a (meth)acrylamide derivative having a (meth)acrylamide group. By using a (meth)acrylamide derivative, an adhesive layer having excellent adhesiveness can be formed with high productivity. Specific examples of the (meth)acrylamide derivative include, for example, N-methyl (meth)acrylamide, N,N-dimethyl (meth)acrylamide, N,N-diethyl (meth)acrylamide, N-isopropyl (meth)acrylamide, N-butyl (meth)acrylamide, N-hexyl (meth)acrylamide derivatives containing an N-alkyl group; Examples thereof include N-hydroxyalkyl group-containing (meth)acrylamide derivatives such as N-methylol(meth)acrylamide, N-hydroxyethyl(meth)acrylamide, and N-methylol-N-propane(meth)acrylamide; N-aminoalkyl group-containing (meth)acrylamide derivatives such as aminomethyl(meth)acrylamide and aminoethyl(meth)acrylamide; N-alkoxy group-containing (meth)acrylamide derivatives such as N-methoxymethylacrylamide and N-ethoxymethylacrylamide; N-mercaptoalkyl group-containing (meth)acrylamide derivatives such as mercaptomethyl(meth)acrylamide and mercaptoethyl(meth)acrylamide. In addition, as a heterocycle-containing (meth)acrylamide derivative in which the nitrogen atom of the (meth)acrylamide group forms a heterocycle, for example, N-acryloylmorpholine, N-acryloylpiperidine, N-methacryloylpiperidine, N-acryloylpyrrolidine, etc. may be used. Among these, an N-hydroxyalkyl group-containing (meth)acrylamide derivative is preferable, and N-hydroxyethyl (meth)acrylamide is more preferable.

In addition, as the above-mentioned monofunctional radical polymerizable compound, (meth)acrylic acid derivatives having a (meth)acryloyloxy group; carboxyl group-containing monomers such as (meth)acrylic acid, carboxyethyl acrylate, carboxypentylacrylate, itaconic acid, maleic acid, fumaric acid, crotonic acid, and isocrotonic acid; lactam vinyl monomers such as N-vinylpyrrolidone, N-vinyl-ε-caprolactam, and methylvinylpyrrolidone; vinyl monomers having a nitrogen-containing heterocycle such as vinylpyridine, vinylpiperidone, vinylpyrimidine, vinylpiperazine, vinylpyrazine, vinylpyrrole, vinylimidazole, vinyloxazole, and vinylmorpholine, etc. may be used.

When a polyfunctional radical polymerizable compound and a monofunctional radical polymerizable compound are used in combination, the content ratio of the monofunctional radical polymerizable compound is preferably 3 to 80 wt%, more preferably 5 to 50 wt%, still more preferably 8 to 25 wt%, and particularly preferably 8 to 20 wt%, based on the total amount of the radical polymerizable compound. Within this range, a polarizing film having excellent durability under high temperature and high humidity can be obtained.

The radical polymerization curable adhesive may further include other additives. When the radical polymerization curable adhesive includes a curable compound that is cured by an active energy ray, the adhesive may further include, for example, a photopolymerization initiator, a photoacid generator, a silane coupling agent, etc. In addition, when the radical polymerization curable adhesive includes a curable compound that is cured by heat, the adhesive may further include a thermal polymerization initiator, a silane coupling agent, etc. In addition, other additives may include, for example, a polymerization inhibitor, a polymerization initiator, a leveling agent, a hygroscopicity improving agent, a surfactant, a plasticizer, an ultraviolet absorber, an inorganic filler, a pigment, a dye, etc.

(cationic polymerization curing adhesive)

The above-mentioned cationic polymerization curable adhesive contains a cationic polymerizable compound as a curable compound. As the cationic polymerizable compound, for example, a compound having an epoxy group and/or an oxetanyl group can be mentioned. As the compound having an epoxy group, a compound having at least two epoxy groups in the molecule is preferably used. As the compound having an epoxy group, for example, a compound having at least two epoxy groups and at least one aromatic ring (aromatic epoxy compound), a compound having at least two epoxy groups in the molecule, at least one of which is formed between two adjacent carbon atoms forming an alicyclic ring (alicyclic epoxy compound), etc. can be mentioned.

It is preferable that the above cationic polymerization curable adhesive contain a photocationic polymerization initiator. The photocationic polymerization initiator generates cationic species or Lewis acids upon irradiation with active energy rays such as visible light, ultraviolet light, X-rays, or electron rays, and initiates a polymerization reaction of an epoxy group or an oxetanyl group. In addition, the cationic polymerization curable adhesive may further contain the above additive.

(mercury based adhesive)

As the above-mentioned water-based adhesive, an aqueous solution (e.g., solid content concentration of 0.5 to 60 wt%) of a water-based adhesive such as an isocyanate-based adhesive, a PVA-based adhesive, a gelatin-based adhesive, a vinyl-based latex-based adhesive, or a water-based polyester is suitably used.

The application of the adhesive may be performed on any of the polarizing film (120), the polarizing film protective film (121, 122), and other optical films, or on both of them. In general, a method of immersing the polarizing film in an adhesive solution and then laminating it with the polarizing film protective film (121, 122) using a roll laminator or the like is suitable. The thickness of the adhesive layer is not particularly limited, but is, for example, about 30 nm to 1000 nm in thickness after drying.

After the polarizing film, the polarizing film protective film, and other optical films are laminated using an adhesive, the laminate is subjected to a drying process. In the drying process of the laminate, in addition to the purpose of drying and solidifying the adhesive, it is performed for the purpose of reducing the moisture content to improve the initial optical properties of the polarizing film laminate. As a drying method, heat drying is generally used. As a drying condition, the range is preferably 50 to 95°C, more preferably 60 to 85°C.

The drying conditions of the above laminate are not particularly limited, but considering the efficiency and practicality of the processing, the drying temperature is preferably 50°C or higher, and from the viewpoint of uniformizing the optical properties of the polarizing film laminate, it is preferably 95°C or lower. The drying temperature may be carried out by gradually increasing the temperature within the above temperature range.

Drying of the laminate may be performed continuously with the bonding treatment of the polarizing film, the polarizing film protective film, and other optical films. In addition, after the laminate of the polarizing film, the polarizing film protective film, and other optical films is once rolled up, drying may be performed as a separate treatment.

In general, in order to reduce the moisture content of a polarizing film laminate, high temperature and long-term drying conditions are required. High temperature and long-term drying is desirable from the viewpoint of reducing the moisture content of a polarizing film laminate, but on the other hand, it may lead to a deterioration of the optical properties of the polarizing film laminate, etc. By using a polarizing film protective film having a small saturated absorption amount or a polarizing film protective film having a high moisture permeability, the moisture content of the polarizing film laminate can be adjusted to the desired range even without adopting harsh drying conditions.

2-5. Adhesive

The adhesive described in “1-3. Transparent Adhesive” above can be used in the same manner.

3. Reliability evaluation items

Several phenomena that can occur in a polarizing film laminate are evaluated, namely polyenization, color fading, and heat discoloration. The mechanism by which each phenomenon occurs is not necessarily clear, but it is roughly assumed to be as follows.

<Polyene>

In a high temperature and high humidity environment, the group transmittance of the polarizing film laminate decreases. This decrease is presumed to be caused by polyeneization of PVA. Polyene refers to -(CH=CH) _n -, and can be formed in the polarizing film by heating. Polyene significantly decreases the transmittance of the polarizing film. In addition, in a high temperature and high humidity environment, the PVA-polyiodine complex is easily destroyed, causing I ^- and I ₂ to be generated.

It is believed that polyenization of PVA occurs by promoting the dehydration reaction by heating and iodine (I ₂ ) generated in a high temperature and high humidity environment, as shown in the chemical formula 1 below.

(chemical formula 1)

It is thought that the PVA-polyiodide complex present in the polarizing film is destroyed by _heating , and the OH group in the PVA forms a charge transfer complex (HO···I ₂ ), which is then polyenated via the OI group. It is thought that when the adhesive layer contains a large amount of an acid component, the proton generated from the acid component acts as a catalyst for the dehydration reaction of PVA, thereby further promoting the polyenation.

<Color fading>

In the iodine-dyed and also stretched PVA film (polarizing film), iodine forms a complex with the aligned PVA in the form of polyiodine ions of I ₃ ^- and I ₅ ^- (PVA polyiodine complex). At this time, the PVA forms cross-linking points by a cross-linking agent such as boric acid, and thereby maintains the orientation.

However, when the polarizing film is placed under high temperature and high humidity, hydrolysis of the boric acid crosslink occurs, the orientation of the PVA deteriorates, and the collapse of the PVA polyiodine complex occurs. As a result, the visible light absorption based on the PVA polyiodine complex deteriorates, and the transmittance on the long wavelength side of about 700 nm and the short wavelength side of about 410 nm increases. In this way, color fading in black display occurs in the polarizing film placed under high temperature and high humidity.

<Heating and Redness>

In iodine-dyed and also stretched PVA-based films (polarizing films), iodine forms complexes with PVA in the form of polyiodide ions of I ₃ ^- and I ₅ ^- (PVA polyiodide complex). I ₃ ^- has a broad absorption peak around 470 nm, and I ₅ ^- has a broad absorption peak around 600 nm. That is, the PVA-I ₃ ^- complex is responsible for absorption on the short-wavelength side (blue side), and the PVA-I ₅ ^- complex is responsible for absorption on the long-wavelength side (red side).

However, this PVA-I ₅ ^- complex is weak to heating, and when the polarizing film is placed at a high temperature, the complex formation between PVA and I ₅ ^- collapses, and I ₅ ^- decomposes.

Therefore, in a polarizing film placed at a high temperature, the PVA-I ₅ ^- complex responsible for absorption on the long-wavelength side decreases, that is, the transmittance on the long-wavelength side of about 700 nm increases, and the polarizing film turns red.

Example

4. Examples and Comparative Examples

Below, examples are described together with comparative examples, but of course, the present invention is not limited to what is described in these examples.

As examples and comparative examples, samples of various polarizing film laminates were prepared, each having different “polarizing film thickness (㎛)”, “polarizing film iodine concentration (wt.%)”, and/or “moisture content (g/㎡) of polarizing film laminate.”

<Polarizing film thickness>

The thickness (㎛) of the polarizing film is measured using a spectroscopic film thickness meter MCPD-1000 (manufactured by Otsuka Electronics Co., Ltd.). The thickness of the polarizing film protective film is also measured using this. The polarizing film included in the sample can be withdrawn by immersing the sample in a solvent and dissolving the polarizing film protective film. As the solvent, for example, when the polarizing film protective film is a triacetyl cellulose resin, dichloromethane can be used, when the polarizing film protective film is a cycloolefin resin, cyclohexane can be used, and when the polarizing film protective film is an acrylic resin, methyl ethyl ketone can be used. In addition, when the resin of the polarizing film protective film formed on one surface of the polarizing film and the resin of the polarizing film protective film formed on the other surface are different, the respective resins are sequentially dissolved using the above-mentioned solvent.

<Iodine concentration in polarizing film>

The iodine concentration (wt.%) of the polarizing film can be changed by adjusting the concentration of the iodine aqueous solution in which the PVA film or PVA layer is immersed or the immersion time during the manufacture of the polarizing film.

The iodine concentration of the polarizing film is measured by the following method. In addition, the polarizing film included in the sample can be extracted by immersing the sample in a solvent and dissolving the polarizing film protective film, similar to when measuring the film thickness of the polarizing film.

(X-ray fluorescence measurement)

When measuring the iodine concentration of a polarizing film, first, the iodine concentration is quantified using the calibration curve method of fluorescence X-ray analysis. The device used is a fluorescence X-ray analysis device ZSX-PRIMUS IV (Rigaku Corporation).

The value obtained directly by the fluorescence X-ray analyzer is not the concentration of each element, but the fluorescence X-ray intensity (kcps) of a wavelength unique to each element. Therefore, in order to obtain the iodine concentration contained in the polarizing film, it is necessary to convert the fluorescence X-ray intensity into a concentration using a calibration curve. The iodine concentration of the polarizing film in this specification and elsewhere means the iodine concentration (wt%) based on the weight of the polarizing film.

(Creating a calibration curve)

The calibration curve is prepared in the following order.

1. By dissolving a base amount of potassium iodide in a PVA solution, seven types of PVA solutions containing iodine at a base concentration were prepared. The PVA solutions were applied to polyethylene terephthalate, dried, and peeled off, thereby producing samples 1 to 7 of PVA films containing iodine at a base concentration.

In addition, the iodine concentration (wt%) of the PVA film is calculated using the following equation 1.

[Formula 1] Iodine concentration (wt%) = {Amount of potassium iodide (g) / (Amount of potassium iodide (g) + Amount of PVA (g))} × (127/166)

(Molecular weight of iodine: 127, molecular weight of potassium: 39)

2. For the manufactured PVA film, the fluorescence X-ray intensity (kcps) corresponding to iodine is measured using a fluorescence X-ray analyzer ZSX-PRIMUS IV (manufactured by Rigaku Co., Ltd.). In addition, the fluorescence X-ray intensity (kcps) is the peak value of the fluorescence X-ray spectrum. In addition, the film thickness of the manufactured PVA film is measured using a spectroscopic film thickness meter MCPD-1000 (manufactured by Otsuka Denshi Co., Ltd.).

3. Divide the fluorescence X-ray intensity by the thickness of the PVA film (㎛) and obtain the fluorescence X-ray intensity per unit thickness of the film (kcps/㎛). The iodine concentration and fluorescence X-ray intensity per unit thickness of each sample are shown in Table 1.

4. Based on the results shown in Table 1, a calibration curve is created with the fluorescence X-ray intensity per unit thickness of the PVA film (kcps/㎛) as the horizontal axis and the iodine concentration (wt%) contained in the PVA film as the vertical axis. The created calibration curve is shown in Fig. 3. An equation for obtaining the iodine concentration from the fluorescence X-ray intensity per unit thickness of the PVA film from the calibration curve is determined as shown in Equation 2. In addition, R ² in Fig. 3 is a correlation coefficient.

[Formula 2] (Iodine concentration) (wt%) = 14.474 × (fluorescence X-ray intensity per unit thickness of PVA film) (kcps/㎛)

(Calculation of iodine concentration)

The fluorescence X-ray intensity obtained from the sample measurement is divided by the thickness to obtain the fluorescence X-ray intensity per unit thickness (kcps/㎛). The fluorescence X-ray intensity per unit thickness of each sample is substituted into Equation 2 to obtain the iodine concentration.

<Moisture content of polarizing film laminate>

The moisture content (g/㎡) of the polarizing film laminate can be determined mainly by adjusting the thickness of the polarizing film, or the material and thickness of the polarizing film protective film bonded to the polarizing film. In addition, it can also be adjusted by crosslinking treatment (boric acid content, etc.) during the manufacturing of the polarizing film.

The moisture content of a polarizing film laminate is measured by the following method.

First, the polarizing film laminate obtained in the examples and comparative examples is cut into a 0.1 m × 0.1 m square.

The cut sample is placed in a constant temperature and humidity chamber and left for 48 hours under an environment of 23°C and 55% relative humidity. Thereafter, the sample is taken out into a clean room set to the same environment as that of the constant temperature and humidity chamber, that is, a temperature of 23°C and a relative humidity of 55%, and its weight is measured within 5 minutes after taking it out. The sample weight at this time is called the initial weight (W1 (g)). In addition, as long as it is within about 15 minutes after taking it out, even if the temperature inside the clean room fluctuates by about 2°C to 3°C, or even if the relative humidity inside the clean room fluctuates by about ±10%, there is no substantial effect on the initial weight.

Next, the taken out sample is placed in a dryer and dried at 120°C for 2 hours. Thereafter, the dried sample is taken out in a clean room set to the above-mentioned temperature of 23°C and a relative humidity of approximately 55%, and its weight is measured within 10 minutes after taking it out. The sample weight at this time is called the weight after drying (W2(g)). Unlike the above, the reason it is set to within 10 minutes instead of within 5 minutes is to take the cooling time into consideration. In addition, as above, if it is within approximately 15 minutes after taking it out, there is no substantial effect on the weight after drying.

From the initial weight (W1) and the weight after drying (W2) of the sample thus obtained, the equilibrium moisture content (M (g/㎡)) of the polarizing film laminate is calculated using the following formula.

(Formula) M=(W1-W2)/(0.1×0.1)

The “moisture content of the polarizing film laminate” referred to in the present invention means the equilibrium moisture content calculated by the above method.

(Preparation of adhesive layer A)

First, 80.9 parts of butylacrylate, 18 parts of benzyl acrylate, 1 part of acrylic acid, and 0.1 part of 4-hydroxybutylacrylate were charged into a four-necked flask equipped with a stirring blade, a thermometer, a nitrogen gas introduction tube, and a condenser, thereby obtaining a monomer mixture. In addition, 0.1 part of 2,2'-azobisisobutyronitrile as a polymerization initiator was charged together with 100 parts of ethyl acetate for 100 parts of the monomer mixture (solid content). While gently stirring the mixture, nitrogen gas was introduced into the flask to perform nitrogen replacement. By maintaining the liquid temperature inside the flask at around 55°C and performing a polymerization reaction for 8 hours, a solution of an acrylic polymer having a weight-average molecular weight (Mw) of 1,850,000 and Mw/Mn = 3.8 was prepared.

Next, by further adding 0.45 parts of an isocyanate crosslinking agent (Coronate L, trimethylolpropanetolylene diisocyanate, manufactured by Tosoh Corporation), 0.1 part of benzoyl peroxide (Nifer BMT, manufactured by NOF Corporation), and 0.2 part of γ-glycidoxypropylmethoxysilane (KBM-403, manufactured by Shin-Etsu Chemical Co., Ltd.) to 100 parts of the solid content of the acrylic polymer solution, a solution of an acrylic adhesive composition was prepared.

Next, the obtained solution was applied to one side of a separator (MRF38 manufactured by Mitsubishi Chemical Polyester Film Co., Ltd.). The separator was a polyethylene terephthalate film treated with a silicone-based release agent. The obtained coating film was dried at 155°C for 1 minute to form an adhesive layer A on the surface of the separator. The thickness of the adhesive layer was 20 μm.

(Preparation of adhesive layer B)

First, 99 parts by weight of butyl acrylate (hereinafter the same), 1.0 part of 4-hydroxybutyl acrylate, and 0.3 part of 2,2'-azobisisobutyronitrile were charged together with 100 parts of ethyl acetate into a four-necked flask equipped with a stirring blade, a thermometer, a nitrogen gas introduction tube, and a condenser. While gently stirring the mixture, nitrogen gas was introduced into the flask to perform nitrogen replacement. By maintaining the liquid temperature inside the flask at around 55°C and performing a polymerization reaction for 4 hours, a solution of an acrylic polymer having a weight-average molecular weight (Mw) of 1.65 million and Mw/Mn = 3.7 was prepared.

Next, an adhesive composition was adjusted by mixing 0.3 parts of dibenzoyl peroxide (Nippon Yushi Co., Ltd.: Nipper BMT), 0.1 parts of trimethyrolpropane xylene diisocyanate (Mitsui Takeda Chemical Co., Ltd.: Takenate D110N), and 0.2 parts of a silane coupling agent (Rokken Chemical Co., Ltd.: A-100, an acetoacetyl group-containing silane coupling agent) per 100 parts of the solid content of the acrylic polymer solution.

Next, the obtained solution was applied to one side of a separator (MRF38 manufactured by Mitsubishi Chemical Industries, Ltd.). The separator was a polyethylene terephthalate film treated with a silicone-based release agent. The obtained coating film was dried at 155°C for 1 minute to form an adhesive layer B on the surface of the separator. The thickness of the adhesive layer was 20 μm.

(Preparation of adhesive layer C)

In the preparation of adhesive layer A, adhesive layer C was prepared in the same manner as before, except that the polymerization time of the acrylic polymer was 2 hours. The weight average molecular weight (Mw) of the acrylic polymer was 1.9 million, Mw/Mn = 2.5.

(Preparation of adhesive layer D)

In preparing the adhesive layer A, the adhesive layer D was prepared in the same manner as before, except that the composition of the acrylic polymer was changed to 80.9 parts of butylacrylate, 18 parts of benzyl acrylate, 4.8 parts of acrylic acid, and 0.1 part of 4-hydroxybutylacrylate. The weight average molecular weight (Mw) of the acrylic polymer was 2.1 million, and Mw/Mn = 4.0.

(Preparation of adhesive layer E)

First, 71.9 parts of butylacrylate, 18 parts of benzyl acrylate, 10 parts of acrylic acid, and 0.1 part of 4-hydroxybutylacrylate were charged into a four-necked flask equipped with a stirring blade, a thermometer, a nitrogen gas introduction tube, and a condenser, thereby obtaining a monomer mixture. In addition, 0.1 part of 2,2'-azobisisobutyronitrile as a polymerization initiator was charged together with 70 parts of ethyl acetate and 30 parts of toluene for 100 parts of the monomer mixture (solid content). While gently stirring the mixture, nitrogen gas was introduced into the flask to perform nitrogen replacement. By maintaining the liquid temperature inside the flask at around 55°C and performing a polymerization reaction for 8 hours, a solution of an acrylic polymer having a weight-average molecular weight (Mw) of 800,000 and Mw/Mn = 3.6 was prepared.

Next, by further adding 1 part of an isocyanate crosslinking agent (Coronate L, trimethylolpropanetolylene diisocyanate, manufactured by Tosoh Corporation), 0.1 part of benzoyl peroxide (Nipher BMT, manufactured by NOF Corporation), and 0.2 part of γ-glycidoxypropylmethoxysilane (KBM-403, manufactured by Shin-Etsu Chemical Co., Ltd.) to 100 parts of the solid content of the acrylic polymer solution, a solution of an acrylic adhesive composition was prepared.

Next, the obtained solution was applied to one side of a separator (MRF38 manufactured by Mitsubishi Chemical Industries, Ltd.). The separator was a polyethylene terephthalate film treated with a silicone-based release agent. The obtained coating film was dried at 155°C for 1 minute to form an adhesive layer E on the surface of the separator. The thickness of the adhesive layer was 20 μm.

[Example 1]

(Creating a polarizing film)

As a resin substrate, an amorphous elongated isophthalic copolymer polyethylene terephthalate film (degree of isophthalic acid group modification: 5 mol%, thickness: 100 μm) was used. (Degree of modification = ethylene isophthalate unit / (ethylene terephthalate unit + ethylene isophthalate unit)) One side of the resin substrate was subjected to corona treatment (treatment conditions: 55 W·min/m2), and 90 parts by weight of PVA (degree of polymerization 4200, degree of saponification 99.2 mol%) and 10 parts by weight of acetoacetyl-modified PVA (manufactured by Nippon Gosei Chemical Industry Co., Ltd., trade name "Gosei Pymer Z410") were mixed, and an aqueous solution in which PVA and potassium iodide were mixed so that the amount was 13 parts by weight with respect to the PVA was applied at room temperature. Afterwards, the laminate was manufactured by drying at 60℃ and forming a PVA resin layer with a thickness of 13㎛.

The obtained laminate was stretched uniaxially in the longitudinal direction (length direction) 2.4 times in an oven at 130°C between rolls at different speeds (air-assisted stretching).

Next, the laminate was immersed in an insolubilizing bath (boric acid aqueous solution obtained by mixing 4 parts by weight of boric acid per 100 parts by weight of water) at a temperature of 40°C for 30 seconds (insolubilizing treatment).

Next, the sample was immersed in a dyeing bath (iodine solution obtained by mixing iodine and potassium iodide in a weight ratio of 1:7 for 100 parts by weight of water) at a temperature of 30°C for 60 seconds while adjusting the concentration to achieve the specified transmittance (dyeing treatment).

Next, it was immersed in a crosslinking bath (boric acid aqueous solution obtained by mixing 3 parts by weight of potassium iodide and 5 parts by weight of boric acid with respect to 100 parts by weight of water) at a temperature of 40°C for 30 seconds (crosslinking treatment).

Thereafter, the laminate was immersed in a boric acid solution (boric acid concentration 3.0 wt%) at a temperature of 70°C, and uniaxial stretching was performed between rolls with different speeds so that the total stretching ratio in the longitudinal direction was 5.5 times (underwater stretching).

After that, the laminate was immersed in a washing bath (aqueous solution obtained by mixing 4 parts by weight of potassium iodide per 100 parts by weight of water) at a temperature of 20°C (washing treatment).

Afterwards, it was dried (drying treatment) in an oven maintained at 90℃, and then contacted with a SUS metal roll whose surface temperature was maintained at 75℃ for more than 2 seconds (heat roll drying treatment).

In this way, a polarizing film with a thickness of 5.4 μm was obtained on the resin substrate.

(Preparation of polarizing film laminate)

On the side opposite to the resin substrate of the obtained polarizing film, a cycloolefin film (ZT12, 18 μm, manufactured by Nippon Zeon Corporation) as a polarizing film protective film was bonded using an ultraviolet-curable adhesive. Specifically, the total thickness of the curable adhesive described below was applied to 1.0 μm, and bonded using a roller. Thereafter, UV light was irradiated from the cycloolefin film side to harden the adhesive. Subsequently, the resin substrate was peeled off, and a polarizing film laminate including the cycloolefin polarizing film protective film and the polarizing film was obtained.

The details of the curable adhesive are as follows. An adhesive was prepared by mixing 40 parts by weight of N-hydroxyethylacrylamide (HEAA), 60 parts by weight of acryloylmorpholine (ACMO), and 3 parts by weight of a photoinitiator, "IRGACURE 819" (manufactured by BASF). The adhesive layer was applied on a polarizing film so that the thickness of the cured adhesive layer became 1.0 μm, and the adhesive was cured by irradiating it with ultraviolet rays as an active energy ray. The ultraviolet irradiation was performed using a gallium-filled metal halide lamp, irradiation device: Light HAMMER 10 manufactured by Fusion UV Systems, Inc., valve: V valve, peak illuminance: 1600 mW/cm2, and accumulated irradiance 1000/mJ/cm2 (wavelength 380 to 440 nm), and the illuminance of the ultraviolet rays was measured using a Sola-Check system manufactured by Solatell.

(Withdrawal of polarizing film)

By using cyclohexane as a solvent, the polarizing film was taken out from the polarizing film laminate and the iodine concentration of the polarizing film was measured.

(Preparation of a polarizing film laminate with an adhesive layer attached)

By transferring the adhesive layer A to the surface of the polarizing film of the polarizing film laminate, the adhesive layer-attached polarizing film laminate of Example 1 was produced.

[Example 2]

In the production of the polarizing film of Example 1, the concentration of the iodine aqueous solution and the immersion time were adjusted in the dyeing treatment to change the iodine concentration, and the moisture content of the polarizing film laminate was also changed by adjusting the thickness of the polarizing film protective film. Other conditions are the same as in Example 1.

[Example 3]

When creating the polarizing film of Example 1, the concentration of the iodine aqueous solution and the immersion time were adjusted in the dyeing treatment to change the iodine concentration, and also the moisture content of the polarizing film laminate was changed by adjusting the thickness of the polarizing film protective film. In addition, when creating the polarizing film laminate of Example 1, a cycloolefin film (manufactured by Nippon Zeon Co., Ltd., ZF12, 13 μm) was bonded as the polarizing film protective film. The other conditions are the same as in Example 1.

[Example 4]

When preparing the polarizing film laminate of Example 1, a triacetyl cellulose film type film (TJ40UL, 40 µm thick, manufactured by Fujifilm Corporation) was laminated as a polarizing film protective film. In addition, when preparing the polarizing film of Example 1, the concentration of the iodine aqueous solution and the immersion time were adjusted in the dyeing treatment to change the iodine concentration. The other conditions are the same as in Example 1.

[Example 5]

When preparing the polarizing film laminate of Example 1, a 40 ㎛ thick transparent protective film (manufactured by Nitto Denko Corporation) made of a modified acrylic polymer having a lactone ring structure was laminated as a polarizing film protective film. In addition, when preparing the polarizing film of Example 1, in the dyeing treatment, the concentration of the iodine aqueous solution and the immersion time were adjusted to change the iodine concentration. The other conditions are the same as in Example 1.

[Example 6]

(Creating a polarizing film)

A PVA film having an average degree of polymerization of 2700 and a thickness of 30 μm was stretched and returned while dyeing between rolls at different speed ratios. First, the PVA film was immersed in a 30°C water bath for 1 minute to swell and stretched 1.2 times in the return direction, and then, by immersing in an aqueous solution (solution temperature: 30°C) of potassium iodide (0.03 wt%) and iodine (0.3 wt%) for 1 minute, it was stretched 3 times (based on the unstretched film) in the return direction while dyeing. Next, this stretched film was stretched 6 times (based on the unstretched film) in the return direction while immersing in an aqueous solution (bath solution) of boric acid (4 wt%), potassium iodide (5 wt%), and zinc sulfate (3.5 wt%) for 30 seconds. After stretching, it was dried in an oven at 40°C for 3 minutes to obtain a 12.0 μm polarizing film.

(Preparation of polarizing film laminate)

As an adhesive, an aqueous solution containing a polyvinyl alcohol resin (average degree of polymerization 1200, degree of saponification 98.5 mol%, degree of acetoacetylation 5 mol%) containing an acetoacetyl group and methylolmelamine in a weight ratio of 3:1 was used. Using this adhesive, under a temperature condition of 30°C, a 20 μm thick transparent protective film (manufactured by Nitto Denko Corporation) made of a modified acrylic polymer having a lactone ring structure was bonded to one side of a polarizing film, and a 27 μm thick transparent protective film in which a 2 μm thick hard coat layer (HC) was formed on a 25 μm thick triacetylcellulose film (manufactured by Konica Minolta, trade name "KC2UA"), was bonded to the other side using a roll bonder, and then the film was heated and dried in an oven at 70°C for 5 minutes to obtain a polarizing film laminate in which the transparent protective films were bonded to both sides of the polarizing film.

The hard coat layer was formed by the following method. First, a hard coat layer-forming material is prepared. This is produced by adding 5 parts by weight of a photopolymerization initiator (product name: "IRGACURE 906" manufactured by BASF Co., Ltd., product name: "GRANDICPC 4100" manufactured by DIC Co., Ltd.) and 0.01 parts by weight of a leveling agent (product name: "GRANDICPC 4100" manufactured by DIC Co., Ltd.) per 100 parts by weight of the solid content in the solution to a resin solution in which an ultraviolet-curable resin monomer or oligomer containing urethane acrylate as a main component is dissolved in butyl acetate (product name: "UNIDIC 17-806" manufactured by DIC Co., Ltd., solid content concentration: 80 wt%), and adding cyclopentanone (hereinafter referred to as "CPN") and propylene glycol monomethyl ether (hereinafter referred to as "PGM") at a ratio of 45:55 to the compound solution so that the solid content concentration in the solution becomes 36 wt%. The hard coat layer forming material thus produced was applied onto a transparent protective film so that the thickness of the hard coat after curing would be 2 ㎛ to form a coating film. Next, it was dried at 90°C for 1 minute, and thereafter, the coating film was cured by irradiating it with ultraviolet rays at an accumulated light amount of 300 mJ/cm2 using a high-pressure mercury lamp.

(Withdrawal of polarizing film)

By using dichloromethane and methyl ethyl ketone as solvents, the polarizing film was taken out from the polarizing film laminate and the iodine concentration of the polarizing film was measured.

(Preparation of a polarizing film laminate with an adhesive layer attached)

By transferring the adhesive layer A to the surface of the acrylic transparent protective film of the polarizing film laminate, a polarizing film laminate with an adhesive layer of Example 6 was produced.

[Example 7]

In the preparation of the polarizing film of Example 6, the concentration of the iodine aqueous solution and the immersion time were adjusted in the dyeing treatment to change the iodine concentration. In addition, in the preparation of the polarizing film laminate of Example 6, on one side of the obtained polarizing film, a 30 µm thick transparent protective film (manufactured by Nitto Denko Corporation) made of a modified acrylic polymer having a lactone ring structure as a polarizing film protective film was bonded, and on the other side, a 49 µm thick transparent protective film in which a 9 µm thick HC was formed on a 40 µm thick triacetyl cellulose film (manufactured by Konica Minolta, trade name “KC4UY”) was bonded. The other conditions are the same as in Example 6.

[Example 8]

In Example 7, a polarizing film laminate with an adhesive layer was produced in the same manner as in Example 7, except that the adhesive layer C was transferred to the surface of the acrylic transparent protective film of the polarizing film laminate.

[Example 9]

In the production of the polarizing film of Example 6, in the stretching treatment, a PVA film having a thickness of 45 μm was stretched and returned to obtain a polarizing film having a thickness of 18.0 μm, and further, in the dyeing treatment, the concentration of the iodine aqueous solution and the immersion time were adjusted to change the iodine concentration. In addition, in the production of the polarizing film laminate of Example 6, a 30 μm thick transparent protective film (manufactured by Nitto Denko Corporation) made of a modified acrylic polymer having a lactone ring structure as a polarizing film protective film was bonded to one side of the obtained polarizing film, and a triacetyl cellulose film-type film (TJ40UL, thickness 40 μm, manufactured by Fujifilm Corporation) was bonded to the other side. The other conditions are the same as in Example 6.

[Example 10]∼[Example 13]

In the production of the polarizing film of Example 9, the concentration of the iodine aqueous solution and the immersion time were adjusted in the dyeing treatment to change the iodine concentration, and the moisture content of the polarizing film laminate was also changed by adjusting the thickness of the polarizing film protective film. The other conditions are the same as in Example 9.

[Example 14]

In Example 9, a polarizing film laminate with an adhesive layer was produced in the same manner as in Example 9, except that the adhesive layer C was transferred to the surface of the acrylic transparent protective film of the polarizing film laminate.

[Example 15]

In Example 9, a polarizing film laminate with an adhesive layer was produced in the same manner as in Example 9, except that the adhesive layer D was transferred to the surface of the acrylic transparent protective film of the polarizing film laminate.

[Comparative Example 1]∼[Comparative Example 2]

In the production of the polarizing film of Example 1, the concentration of the iodine aqueous solution and the immersion time were adjusted in the dyeing treatment to change the iodine concentration, and the moisture content of the polarizing film laminate was also changed by adjusting the thickness of the polarizing film protective film.

In addition, adhesive layer-attached polarizing film laminates of Comparative Examples 1 and 2 were produced by transferring the adhesive layer B to the surface of the polarizing film of the polarizing film laminate. Other conditions are the same as in Example 1.

[Comparative Example 3]∼[Comparative Example 4]

In the production of the polarizing film of Example 6, the concentration of the iodine aqueous solution and the immersion time were adjusted in the dyeing treatment to change the iodine concentration, and the moisture content of the polarizing film laminate was also changed by adjusting the thickness of the polarizing film protective film.

In addition, adhesive layer B was transferred to the surface of the acrylic transparent protective film of the polarizing film laminate, thereby producing the adhesive layer-attached polarizing film laminates of Comparative Examples 3 and 4. Other conditions were the same as in Example 6.

[Comparative Example 5]

In the production of the polarizing film of Example 7, the concentration of the iodine aqueous solution and the immersion time were adjusted in the dyeing treatment to change the iodine concentration, and the moisture content of the polarizing film laminate was also changed by adjusting the thickness of the polarizing film protective film.

In addition, a polarizing film laminate with an adhesive layer of Comparative Example 5 was produced by transferring the adhesive layer B to the surface of the acrylic transparent protective film of the polarizing film laminate. Other conditions are the same as those of Example 7.

[Comparative Example 6]

In the production of the polarizing film of Example 9, the concentration of the iodine aqueous solution and the immersion time were adjusted in the dyeing treatment to change the iodine concentration, and the moisture content of the polarizing film laminate was also changed by adjusting the thickness of the polarizing film protective film.

In addition, a polarizing film laminate with an adhesive layer of Comparative Example 6 was produced by transferring the adhesive layer B to the surface of the acrylic transparent protective film of the polarizing film laminate. Other conditions are the same as those of Example 9.

[Comparative Example 7]

(Creating a polarizing film)

In the production of the polarizing film of Example 9, in the stretching treatment, a PVA film having a thickness of 60 μm was stretched and returned to obtain a polarizing film having a thickness of 22.0 μm. In addition, in the dyeing treatment, the concentration of the iodine aqueous solution and the immersion time were adjusted to change the iodine concentration, and the thickness of the polarizing film protective film was also adjusted to change the moisture content of the polarizing film laminate. The other conditions are the same as in Example 9.

(Preparation of polarizing film laminate)

On one side of the obtained polarizing film, a 30 µm thick transparent protective film (manufactured by Nitto Denko Corporation) made of a modified acrylic polymer having a lactone ring structure was bonded as a polarizing film protective film, and on the other side, a 49 µm thick transparent protective film in which a 9 µm thick HC was formed on a 40 µm thick triacetyl cellulose film (manufactured by Konica Minolta, trade name “KC4UY”) was bonded. Other treatments were the same as in Example 9.

(Withdrawal of polarizing film)

The withdrawal conditions are the same as in Example 9.

(Preparation of a polarizing film laminate with an adhesive layer attached)

By transferring the adhesive layer B to the surface of the acrylic transparent protective film of the polarizing film laminate, a polarizing film laminate with an adhesive layer of Comparative Example 7 was produced.

[Comparative Example 8]

In the production of the polarizing film of Comparative Example 7, in the dyeing treatment, the concentration of the iodine aqueous solution and the immersion time were adjusted to change the iodine concentration, and also the moisture content of the polarizing film laminate was changed by adjusting the thickness of the polarizing film protective film. In addition, a transparent protective film (manufactured by Nitto Denko Corporation) having a thickness of 20 ㎛ and made of a modified acrylic polymer having a lactone ring structure was bonded to one side of the polarizing film as a polarizing film protective film. The other conditions are the same as in Comparative Example 7.

[Comparative Example 9]

In the production of the polarizing film of Example 9, in the stretching treatment, a PVA film having a thickness of 75 μm was stretched and returned to obtain a polarizing film having a thickness of 28 μm. In addition, in the dyeing treatment, the concentration of the iodine aqueous solution and the immersion time were adjusted to change the iodine concentration, and the thickness of the polarizing film protective film was also adjusted to change the moisture content of the polarizing film laminate.

In addition, a polarizing film laminate with an adhesive layer of Comparative Example 9 was produced by transferring the adhesive layer B to the surface of an acrylic transparent protective film of the polarizing film laminate. Other conditions are the same as those of Example 9.

[Comparative Example 10]

In Comparative Example 9, a polarizing film laminate with an adhesive layer of Comparative Example 10 was produced in the same manner as in Comparative Example 9, except that the adhesive layer C was transferred to the surface of the acrylic transparent protective film of the polarizing film laminate.

[Comparative Example 11]

In Comparative Example 6, a polarizing film laminate with an adhesive layer of Comparative Example 11 was produced in the same manner as in Comparative Example 6, except that the adhesive layer F was transferred to the surface of the acrylic transparent protective film of the polarizing film laminate.

4-1. Reliability test

A polarizing film laminate (12) obtained in the examples and comparative examples was used, and as shown in Fig. 4, a glass plate (Matsunam Glass slide glass, product number: S2000423, specifications: hand-polished 65×165 mm, thickness 1.3 mm) was laminated on each of both sides of the polarizing film laminate (12) using an adhesive (11, 13), as a sample.

As an adhesive, CS9868US (manufactured by Nitto Denko Corporation) having a thickness of 200 ㎛ was used on the surface where adhesive layers A to D were not formed in the polarizing film laminate.

The above sample was left at 95°C for 250 hours (95°C/250H), then color fading and heat discoloration were evaluated, and polyenization was evaluated after leaving the sample at 95°C for 500 hours (95°C/500H).

4-2. Evaluation criteria

The evaluation criteria for polyenization, heat discoloration, and color fading are shown below.

<Polyene>

The group transmittance of the sample was measured before and after the heating test at 95℃/500H, and the change in group transmittance ΔTs was calculated using the following formula.

(Formula)ΔTs=Ts ₅₀₀ -Ts ₀

Here, Ts ₀ is the group transmittance of the sample before heating, and Ts ₅₀₀ is the group transmittance after heating at 95℃/500H.

The negative value of the change amount ΔTs was evaluated as "polyenization (decrease in group transmittance)" of the sample. In other words, if the group transmittance after heating at 95℃/500 hours was equal to or greater than the group transmittance before heating, it was evaluated that there was no problem of polyenization.

The group transmittance was measured for the above sample using a spectrophotometer (product name: "DOT-3" manufactured by Murakami Shikisai Kijutsu Kenkyuso Co., Ltd.). In addition, the group transmittance can be obtained according to JIS Z 8701.

<Discoloration/Heating Redness>

Before and after the heating test at 95℃/250H, the sample was placed in Cross Nicol and the orthogonal transmittance (%) at wavelengths of 410㎚ and 700㎚ was measured using the above spectrophotometer, and the respective changes ΔHs ₄₁₀ and ΔHs ₇₀₀ were obtained.

The “color fading” of a sample was evaluated when both of the following two conditions were met.

·Change ΔHs ₄₁₀ is 1% or more

·Change ΔHs ₇₀₀ is 5% or more

In other words, it was evaluated that there was no problem of color fading when the change in orthogonal transmittance at a wavelength of 410 nm was less than 1% and the change in orthogonal transmittance at a wavelength of 700 nm was less than 5% due to heat treatment at 95℃/500 hours.

In addition, the following conditions were evaluated as “heating change” of the sample.

·Change ΔHs ₄₁₀ is less than 1%

·Change ΔHs ₇₀₀ is 5% or more

In other words, if the change in the orthogonal transmittance at a wavelength of 410 nm is 1% or more and the change in the orthogonal transmittance at a wavelength of 700 nm is less than 5% due to heat treatment at 95℃/500 hours, it was evaluated that there was no problem with heat discoloration.

<Adhesive Durability>

The adhesive-attached polarizing film laminate was cut to 420 mm in length × 320 mm in width, and was adhered to both sides of a 0.7 mm thick alkali-free glass plate using a laminator. Then, the sample was treated in an autoclave at 50°C and 5 atm for 15 minutes, and the sample was completely adhered to the alkali-free glass plate. The sample that had been treated in this manner was treated at 95°C for 500 hours (heat test), and the state of foaming, peeling, and lifting was visually evaluated according to the following criteria.

「◎」: No changes in appearance such as foaming, peeling, or lifting.

「○」: There is a little bit of peeling or foaming at the end, but it is not a practical problem.

「△」: There is peeling or foaming at the end, but if it is not for a special purpose, there is no practical problem.

「×」: There is significant peeling or foaming at the end, and it is problematic for practical use.

<Reworkability>

The adhesive layer-attached polarizing film laminate obtained in the examples and comparative examples was cut to 200 mm in length × 100 mm in width as a sample. The sample was adhered to alkali-free glass (trade name: EG-XG, Corning Inc.) having a thickness of 0.7 mm using a laminator. Next, the sample was autoclaved at 50° C. and 0.5 MPa for 15 minutes, and the sample was completely adhered. For this sample, the sample was peeled off from the alkali-free glass by hand, and the reworkability was evaluated according to the following criteria. The reworkability evaluation was performed by producing three sheets in the above order and repeating the process three times.

◎: All 3 sheets can be peeled off smoothly without any adhesive residue or film breakage.

○:Some of the 3 sheets had film breakage, but they were able to be peeled off again.

△: All three films were torn, but could be peeled off again.

×: All three sheets have adhesive residue, or the film breaks even after peeling several times.

The evaluation results for each example and comparative example are shown in Table 2 below.

5. Summary of evaluation results

Figure 5 is a plot of the results of examples and comparative examples (except Comparative Example 11) in an x-y orthogonal coordinate system. The x-axis (horizontal axis) represents the iodine concentration (wt.%) of the polarizing film, and the y-axis (vertical axis) represents the moisture content (g/m2) of the polarizing film laminate.

(1) From the results of the plot and technical common sense, it can be said that, in general, when the iodine concentration is small and the moisture content is excessively small, the problem of heat discoloration occurring under high temperature conditions is likely to occur, and on the other hand, when the iodine concentration is large and the moisture content is excessively large, the problems of polyenization and color fading are likely to occur. In addition, when the iodine concentration is small and the moisture content is excessively large, the problem of color fading occurring under high temperature and high humidity conditions is likely to occur, and in this case, the problem of polyenization is likely to occur as the iodine concentration increases. In particular, a transition region (Comparative Examples 13 and 15) was also observed between the color fading and the polyenization.

Meanwhile, it can be seen that when the iodine concentration and moisture content fall within a certain range, all of the heat discoloration, polyenization, and color fading can be comprehensively resolved. For example, the results of the examples are all above the partition line "α", that is, y=(1043-125x)/240, which passes through the periphery of the plot showing the results of Example 3 having the smallest moisture content, that is, the coordinate point of the iodine concentration of 7.0 wt. % and the moisture content of 0.7 g/m2 (hereinafter, the first coordinate point), and the periphery of the plot showing the results of Example 9 having the smallest iodine concentration, that is, the coordinate point of the iodine concentration of 2.2 wt. % and the moisture content of 3.2 g/m2 (hereinafter, the second coordinate point), and also the periphery of the plot showing the results of Example 8 having the largest moisture content, that is, the coordinate point of the iodine concentration of 3.0 wt. % and the moisture content of 4.0 g/m2 (hereinafter, the fourth coordinate point), and the periphery of the plot showing the results of Example 2 having the largest iodine concentration, that is, the iodine concentration of 10.0 wt. % and the moisture content of The partition line "β" passing through the coordinate point of 0.7 g/㎡ (hereinafter, the fifth coordinate point) is positioned below y = (379 - 33x) / 70. Therefore, the area partitioned by these partition lines "α" and "β" can be understood as a line representing the requirement necessary to comprehensively solve all of heat discoloration, polyenization, and color fading. In addition, these partition lines "α" and "β" are applied to all polarizing films having a film thickness of approximately 4 to 20 ㎛, regardless of the film thickness of the polarizing film.

In addition, in Comparative Example 6 using adhesive B (amount of acid component among the total monomer components constituting the adhesive polymer: 0 wt%), although heat discoloration was confirmed and the problem of polyenization did not occur, in Comparative Example 11 where the adhesive was changed to adhesive E (amount of acid component among the total monomer components constituting the adhesive polymer: 10 wt%), polyenization was confirmed. From this point of view, it is presumed that if the monomer components of the adhesive polymer containing an acid component are used in excess of a predetermined amount, polyenization is promoted.

(2) In addition, from the results of the plot and technical common sense, especially for all polarizing films having a film thickness of about 4 to 20 ㎛, the iodine concentration and the moisture content of the polarizing film laminate are in the region surrounded by a to e, more specifically, the first line segment, the second coordinate point "b" connecting the first coordinate point ("a" in the drawing) of the iodine concentration of 7.0 wt. % and the moisture content of 0.7 g/m2, the second coordinate point ("b" in the drawing) of the iodine concentration of 2.2 wt. % and the moisture content of 3.2 g/m2, the second line segment, the third coordinate point "c" connecting the third coordinate point ("c" in the drawing) of the iodine concentration of 2.2 wt. % and the moisture content of 4.0 g/m2, the fourth coordinate point ("c" in the drawing) of the iodine concentration of 3.0 wt. % and the moisture content of 4.0 g/m2. When included within an area surrounded by a third line segment connecting the fourth coordinate point "d" and the fifth coordinate point ("e" in the drawing) having an iodine concentration of 10.0 wt.% and a moisture content of 0.7 g/㎡, and a fifth line segment connecting the first coordinate point "a" and the fifth coordinate point "e", it can be seen that all of "polyenization", "color fading", and "red discoloration upon heating" can be comprehensively resolved.

(3) Similarly, particularly, for a polarizing film having a film thickness of about 11 to 20 ㎛, an area surrounded by f, b, c, d, and g, iodine concentration and moisture content of a polarizing film laminate, more specifically, a sixth line segment connecting the sixth coordinate point (“f” in the drawing) with an iodine concentration of 4.5 wt. % and a moisture content of 2.0 g/㎡ and the second coordinate point “b”, a second line segment connecting the second coordinate point “b” and the third coordinate point “c”, a third line segment connecting the third coordinate point “c” and the fourth coordinate point “d”, a seventh line segment connecting the fourth coordinate point “d” and the seventh coordinate point (“g” in the drawing) with an iodine concentration of 4.5 wt. % and a moisture content of 3.3 g/㎡, and an eighth line segment connecting the sixth coordinate point “f” and the seventh coordinate point “g”. It can be seen that all of the “polyenization”, “color fading”, and “heating reddening” can be comprehensively resolved when included within the area surrounded by the line segment.

In particular, it is thought that a desirable result is obtained when the 6th coordinate point "f" is the coordinate point "f-1" of an iodine concentration of 4.0 wt.% and a moisture content of 2.3 g/m2, and the 7th coordinate point "g" is the coordinate point "g-1" of an iodine concentration of 4.0 wt.% and a moisture content of 3.5 g/m2.

In addition, for a polarizing film having a film thickness of about 11 to 20 ㎛, an area in which the iodine concentration and the moisture content of the polarizing film laminate are surrounded by f, b, c, d, and g, and further partitioned by a line segment connecting h and i, more specifically, a ninth line segment connecting the 8th coordinate point (“h” in the drawing) having an iodine concentration of 3.3 wt. % and a moisture content of 2.6 g/㎡ and the 2nd coordinate point “b”, a second line segment connecting the 2nd coordinate point “b” and the 3rd coordinate point “c”, a third line segment connecting the 3rd coordinate point “c” and the 4th coordinate point “d”, a seventh line segment connecting the 4th coordinate point “d” and the 7th coordinate point “g”, an eighth line segment connecting the 6th coordinate point “f” and the 7th coordinate point “g”, and an eighth coordinate point “h” and an iodine concentration It is presumed that better results are obtained in all of “polyenization,” “color fading,” and “heating discoloration” when included within an area surrounded by a 10th line segment connecting the 9th coordinate point (“i” in the drawing) of 6.0 wt.% and a moisture content of 2.6 g/㎡.

(4) In addition, for a polarizing film having a film thickness of about 4 to 11 ㎛, preferably 4 to 7 ㎛, and more preferably 4.5 to 6 ㎛, it can be seen that all of “polyenization”, “color fading”, and “heating discoloration” can be comprehensively resolved when the iodine concentration and the moisture content of the polarizing film laminate are included in the region surrounded by a, h, i, and e, and more specifically, the region surrounded by the 11th line segment connecting the 1st coordinate point “a” and the 8th coordinate point “h”, the 10th line segment connecting the 8th coordinate point “h” and the 9th coordinate point “i”, the 12th line segment connecting the 9th coordinate point “i” and the 5th coordinate point “e”, and the 5th line segment connecting the 1st coordinate point “a” and the 5th coordinate point “e”.

In particular, it is thought that a desirable result is obtained when the 8th coordinate point "h" is the 6th coordinate point "f" and the 9th coordinate point "i" is the 10th coordinate point ("j" in the drawing) with an iodine concentration of 7.2 wt.% and a moisture content of 2.0 g/㎡.

In addition, for a polarizing film having a film thickness of about 4 to 11 ㎛, preferably 4 to 7 ㎛, and more preferably 4.5 to 6 ㎛, when the iodine concentration and the moisture content of the polarizing film laminate are included in the region surrounded by a, k, i, and e, and more specifically, the 13th line segment connecting the first coordinate point "a" and the 11th coordinate point ("k" in the drawing) having an iodine concentration of 6.0 wt.% and a moisture content of 1.2 g/㎡, the 14th line segment connecting the 11th coordinate point "k" and the 9th coordinate point "i", the 12th line segment connecting the 9th coordinate point "i" and the 5th coordinate point "e", and the 5th line segment connecting the 1st coordinate point "a" and the 5th coordinate point "e", all of "polyenization", "color fading", and "heating discoloration" are prevented. It is presumed that better results are obtained because of this.

In particular, it is thought that more preferable results are obtained when the 11th coordinate point "k" is the coordinate point (k-1) of an iodine concentration of 6.5 wt.% and a moisture content of 1.0 g/m2, and the 9th coordinate point "i" is the coordinate point (i-1) of an iodine concentration of 6.5 wt.% and a moisture content of 2.3 g/m2.

1: Optical display panel
10: Optical display cell
11: Clear adhesive
12: Polarizing film laminate
13: Clear adhesive
14: Transparent cover plate
120: Polarizing film
121: Polarizing protective film
122: Polarizing protective film

Claims (16)

A polarizing film laminate having an adhesive layer, comprising a polarizing film including a polyvinyl alcohol-based resin, and an adhesive layer formed directly or through an optically transparent polarizing film protective film on at least one surface of the polarizing film,
The above adhesive layer comprises an adhesive polymer, the adhesive polymer is copolymerized with an acid component, and the amount of the acid component among the total monomer components constituting the adhesive polymer is 5 wt% or less,
In the xy orthogonal coordinate system, where the iodine concentration (wt.%) of the polarizing film is taken on the x-axis and the moisture content (g/㎡) of the polarizing film laminate is taken on the y-axis,
A first line segment connecting a first coordinate point having an iodine concentration of 7.0 wt.% and a moisture content of 0.7 g/㎡ and a second coordinate point having an iodine concentration of 2.2 wt.% and a moisture content of 3.2 g/㎡;
A second line segment connecting the second coordinate point and the third coordinate point having an iodine concentration of 2.2 wt.% and a moisture content of 4.0 g/㎡;
A third line segment connecting the third coordinate point and the fourth coordinate point having an iodine concentration of 3.0 wt.% and a moisture content of 4.0 g/㎡;
A fourth line segment connecting the fourth coordinate point and the fifth coordinate point having an iodine concentration of 10.0 wt.% and a moisture content of 0.7 g/㎡, and
A fifth line segment connecting the first coordinate point and the fifth coordinate point
A polarizing film laminate characterized by having an iodine concentration and a moisture content included within an area surrounded by . In paragraph 1,
A polarizing film laminate, wherein the polydispersity (weight average molecular weight (Mw)/number average molecular weight (Mn)) of the above adhesive polymer is 3.0 or less. In claim 1 or 2,
A polarizing film laminate having a polarizing film thickness of 4 to 20 μm. A polarizing film laminate having an adhesive layer, comprising a polarizing film including a polyvinyl alcohol-based resin, and an adhesive layer formed directly or through an optically transparent polarizing film protective film on at least one surface of the polarizing film,
The above adhesive layer comprises an adhesive polymer, the adhesive polymer is copolymerized with an acid component, and the amount of the acid component among the total monomer components constituting the adhesive polymer is 5 wt% or less,
In the xy orthogonal coordinate system, where the iodine concentration (wt.%) of the polarizing film is taken on the x-axis and the moisture content (g/㎡) of the polarizing film laminate is taken on the y-axis,
A sixth line segment connecting the sixth coordinate point of 4.5 wt.% iodine concentration and 2.0 g/㎡ moisture content and the second coordinate point of 2.2 wt.% iodine concentration and 3.2 g/㎡ moisture content,
A second line segment connecting the second coordinate point and the third coordinate point having an iodine concentration of 2.2 wt.% and a moisture content of 4.0 g/㎡;
A third line segment connecting the third coordinate point and the fourth coordinate point having an iodine concentration of 3.0 wt.% and a moisture content of 4.0 g/㎡;
A seventh line segment connecting the fourth coordinate point and the seventh coordinate point having an iodine concentration of 4.5 wt.% and a moisture content of 3.3 g/㎡, and
The 8th line segment connecting the 6th coordinate point and the 7th coordinate point
A polarizing film laminate characterized by having an iodine concentration and a moisture content included within an area surrounded by . In paragraph 4,
A polarizing film laminate, wherein the sixth coordinate point is a coordinate point of an iodine concentration of 4.0 wt.% and a moisture content of 2.3 g/㎡, and the seventh coordinate point is a coordinate point of an iodine concentration of 4.0 wt.% and a moisture content of 3.5 g/㎡. In clause 4 or 5,
A polarizing film laminate having a polarizing film thickness of 11 to 20 μm. A polarizing film laminate having an adhesive layer, comprising a polarizing film including a polyvinyl alcohol-based resin, and an adhesive layer formed directly or through an optically transparent polarizing film protective film on at least one surface of the polarizing film,
The above adhesive layer comprises an adhesive polymer, the adhesive polymer is copolymerized with an acid component, and the amount of the acid component among the total monomer components constituting the adhesive polymer is 5 wt% or less,
In the xy orthogonal coordinate system, where the iodine concentration (wt.%) of the polarizing film is taken on the x-axis and the moisture content (g/㎡) of the polarizing film laminate is taken on the y-axis,
An 11th line segment connecting the first coordinate point of iodine concentration 7.0 wt.% and moisture content 0.7 g/㎡ and the 8th coordinate point of iodine concentration 3.3 wt.% and moisture content 2.6 g/㎡;
A 10th line segment connecting the 8th coordinate point and the 9th coordinate point having an iodine concentration of 6.0 wt.% and a moisture content of 2.6 g/㎡;
A 12th line segment connecting the 9th coordinate point and the 5th coordinate point having an iodine concentration of 10.0 wt.% and a moisture content of 0.7 g/㎡, and
A fifth line segment connecting the first coordinate point and the fifth coordinate point
A polarizing film laminate characterized by having an iodine concentration and a moisture content included within an area surrounded by . In paragraph 7,
A polarizing film laminate, wherein the above-mentioned eighth coordinate point is the sixth coordinate point having an iodine concentration of 4.5 wt.% and a moisture content of 2.0 g/m2, and the above-mentioned ninth coordinate point is the tenth coordinate point having an iodine concentration of 7.2 wt.% and a moisture content of 2.0 g/m2. In clause 7 or 8,
A polarizing film laminate having a polarizing film thickness of 4 to 11 μm. In any one of paragraphs 1, 2, 4, 5, 7, or 8,
A polarizing film laminate, wherein the polarizing film contains zinc. In any one of paragraphs 1, 2, 4, 5, 7, or 8,
A polarizing film laminate, wherein the polarizing film laminate comprises a glass plate laminated on both sides of the polarizing film laminate with an adhesive, and the group transmittance after heating at 95°C/500 hours is equal to or greater than the group transmittance before heating. In any one of paragraphs 1, 2, 4, 5, 7, or 8,
A polarizing film laminate, wherein, in a sample comprising the polarizing film laminate and glass plates laminated on both sides of the polarizing film laminate via an adhesive, the change in orthogonal transmittance at a wavelength of 410 nm is less than 1% upon heat treatment at 95°C/500 hours, and further, the change in orthogonal transmittance at a wavelength of 700 nm is less than 5%. In any one of paragraphs 1, 2, 4, 5, 7, or 8,
A polarizing film laminate, wherein, in a sample comprising the polarizing film laminate and glass plates laminated on both sides of the polarizing film laminate via an adhesive, the change in orthogonal transmittance at a wavelength of 410 nm is 1% or more and the change in orthogonal transmittance at a wavelength of 700 nm is less than 5% when heat treated at 95°C/500 hours. Optical display cells,
A polarizing film laminate according to any one of claims 1, 2, 4, 5, 7, or 8, bonded directly or through another optical film to one side of the optical display cell,
An optically transparent cover plate is provided along the polarizing film laminate on the opposite side from the optical display cell,
An optical display panel characterized in that the optical display cell, the polarizing film laminate, and the transparent cover plate are bonded by a transparent adhesive layer that fills the space between them without a gap. In Article 14,
An optical display panel, wherein the transparent cover plate has the function of a capacitive touch sensor. In Article 15,
An optical display panel, wherein an ITO layer, which becomes a component of a capacitive touch sensor, is formed between the transparent cover plate and the polarizing film laminate.