TWI825661B - Polarizing plate and image display device using the polarizing plate - Google Patents

Abstract

The present invention provides a polarizing plate that is thin and has through holes. When the through holes are filled with an adhesive, air bubbles can be suppressed. The polarizing plate has excellent reliability in high temperature and high humidity environments and can suppress poor conduction when applied to an image display device. The polarizing plate according to the embodiment of the present invention has: a polarizer; a first protective layer disposed on one side of the polarizer and including a resin film and a hard coating layer formed on the side of the resin film opposite to the polarizer; and a second protective layer layer, which is disposed on the other side of the polarizer; and, an adhesive layer, which is disposed on the side opposite to the polarizer of the second protective layer. The total thickness of the polarizing plate is 70 μm or less, and the polarizing plate is formed with through holes. The thickness of the polarizer is less than 12 μm; the thickness of the first protective layer is less than 29 μm and the moisture permeability is 200g/m ² ·24h to 500g/m ² ·24h; the moisture permeability of the second protective layer is less than 100g/m ² ·24h; The thickness of the adhesive layer is 12 μm~17 μm and the surface resistance value is 1.0×10 ⁸ Ω/□ to 2.0×10 ⁹ Ω/□.

Description

Polarizing plate and image display device using the polarizing plate

The present invention relates to a polarizing plate and an image display device using the polarizing plate.

Background technology Image display devices such as mobile phones and notebook personal computers widely use polarizing plates in order to realize image display and/or improve the performance of the image display. In recent years, due to the rapid spread of smart phones and touch panel information processing devices, image display devices equipped with cameras are widely used. In response to this, polarizing plates having through holes at positions corresponding to the camera units are also widely used. Typically, the through holes are filled with the adhesive used to laminate the cover glass. Image display devices that include polarizing plates with through-holes filled with adhesive may sometimes produce bubbles in the through-holes. The thinner the thickness of the adhesive that fills the through-holes, the more obvious these bubbles will be. In order to suppress such bubbles, attempts are being made to reduce the thickness of polarizing plates (essentially, through holes). As an attempt to reduce thickness, a technology that omits the adhesive side protective layer in the polarizing plate has been proposed. However, if this technology is used, there is a problem of discoloration occurring in high temperature and high humidity environments. Advanced technical documents patent documents

[Patent Document 1] International Publication No. 2017/047510

Summary of the invention The problem to be solved by the invention The present invention is made to solve the above-mentioned conventional problems. The main purpose of the present invention is to provide a polarizing plate that is thin and has through-holes. When the through-holes are filled with an adhesive, air bubbles can be suppressed, and the polarizing plate has excellent reliability in high temperature and high humidity environments. And when applied to image display devices, poor conduction can be suppressed. means to solve problems

The polarizing plate according to the embodiment of the present invention has: a polarizer; a first protective layer disposed on one side of the polarizer and including a resin film and a hard coating layer formed on the opposite side of the resin film to the polarizer; 2 protective layer, which is disposed on the other side of the polarizer; and, an adhesive layer, which is disposed on the side opposite to the polarizer of the second protective layer. The total thickness of the polarizing plate is 70 μm or less, and the polarizing plate is formed with through holes. The thickness of the polarizer is less than 12 μm; the thickness of the first protective layer is less than 29 μm and the moisture permeability is 200g/m ² ·24h to 500g/m ² ·24h; the moisture permeability of the second protective layer is less than 100g/m ²・24h; the thickness of the adhesive layer is 12μm~17μm and the surface resistance value is 1.0×10 ⁸ Ω/□ to 2.0×10 ⁹ Ω/□. In one embodiment, the thickness of the hard coat layer is 5 μm or less. In one embodiment, the above-mentioned hard coat layer is a hardened layer of a resin composition, and the resin composition includes six or more functional urethane acrylates, tricyclodecane dimethanol dimethacrylate and photopolymerization initiator agent. In one embodiment, the above-mentioned resin composition contains the above-mentioned 6-functional or higher urethane acrylate and the above-mentioned tricyclodecanedi in a ratio of 60/40 (weight ratio) to 40/60 (weight ratio) Methanol dimethacrylate. In one embodiment, the resin film of the first protective layer is a cellulose triacetate film, and the second protective layer is composed of a cycloolefin resin film. In one embodiment, the diameter of the through hole is 5 mm or less. According to another aspect of the present invention, an image display device can be provided. The image display device has: an image display unit; the above-mentioned polarizing plate, which is bonded to the viewing side of the image display unit through the aforementioned adhesive layer; and, another adhesive layer, which is arranged on the viewing side of the polarizing plate. side; and, the through-hole of the polarizing plate is filled with the adhesive constituting the other adhesive layer. In one embodiment, the thickness of the other adhesive layer is 120 μm or less. In one embodiment, the image display device further has a cover glass on the viewing side of the other adhesive layer. In one embodiment, the image display device has a camera unit at a position corresponding to the through hole of the polarizing plate. Invention effect

According to the embodiment of the present invention, a polarizing plate can be realized that is thin and has through-holes. When the through-holes are filled with an adhesive, air bubbles can be suppressed, and the polarizing plate has excellent reliability in high-temperature and high-humidity environments (for example, the change in polarization degree is small). , end discoloration is suppressed, the change in the surface resistance value of the adhesive layer is small, peeling from the image display unit is suppressed), and when applied to an image display device, poor conduction can be suppressed.

Form used to implement the invention Hereinafter, specific embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited to these embodiments. In addition, the drawings are represented schematically for ease of viewing. Furthermore, the ratios and angles of length, width, thickness, etc. in the drawings are different from the actual conditions.

A. Overall structure of polarizing plate FIG. 1 is a schematic cross-sectional view of main parts of a portion near a through hole in a polarizing plate according to an embodiment of the present invention. The polarizing plate 100 in the illustrated example has: a polarizer 10; a first protective layer 20, which is arranged on one side of the polarizer 10; a second protective layer 30, which is arranged on the other side of the polarizer 10; and an adhesive. Layer 40 is provided on the side opposite to the polarizer 10 of the second protective layer 30 . The first protective layer 20 includes a resin film 21 and a hard coat layer 22 formed on the opposite side of the resin film 21 from the polarizer 10 . The adhesive layer 40 is used to adhere the polarizing plate 100 to the image display unit. In terms of practicality, before the polarizing plate is used, the surface of the adhesive layer 40 should be temporarily attached with a separation member (not shown). By temporarily attaching the separation member, the polarizing plate can be formed into a roll while protecting the adhesive layer.

The polarizing plate 100 is formed with a through hole 50 . By forming through holes, for example, when a camera is built into an image display device, adverse effects on the performance of the camera can be prevented. Typically, the through hole is formed at or near the end of the polarizing plate. With this structure, when the polarizing plate is used in an image display device, the impact on the image display can be minimized. A plurality of through holes may be provided. In addition, the shape of the through hole in plan view may be any appropriate shape depending on the purpose. Specific examples of planar shapes include circles, ovals, squares, rectangles, polygons (such as pentagons, hexagons, octagons) and combinations thereof (such as rectangles with long or short sides that are round). arc-shaped). The diameter of the through hole is preferably 10 mm or less, more preferably 8 mm or less, and more preferably 5 mm or less. The lower limit of the diameter of the through hole may be, for example, 2 mm. According to the embodiment of the present invention, even if the diameter of the through hole is extremely small as described above, bubbles can be well suppressed when filling the adhesive.

The total thickness of the polarizing plate is 70 μm or less, preferably 68 μm or less, more preferably 65 μm or less, and more preferably 62 μm or less. By setting the total thickness of the polarizing plate below a predetermined value, bubbles can be more significantly suppressed when the through holes are filled with adhesive. In particular, even if the thickness of the adhesive (essentially another adhesive layer to be described later) is thin, bubbles can still be significantly suppressed. The lower limit of the total thickness of the polarizing plate may be, for example, 48 μm. In addition, in this specification, "the total thickness of the polarizing plate" means the total thickness of the first protective layer, polarizer, second protective layer and adhesive layer.

The thickness of the polarizer is 12 μm or less, and preferably 10 μm or less, more preferably 8 μm or less, more preferably 6 μm or less, especially 5 μm or less. The lower limit of the thickness of the polarizer may be, for example, 2 μm, or may be 1 μm, for example. By setting the thickness of the polarizer into this range, the above-mentioned total thickness can be easily achieved.

The thickness of the first protective layer is 29 μm or less, and preferably 22 μm ~ 28 μm. By setting the thickness of the first protective layer in this range, the above-mentioned total thickness can be easily achieved. Furthermore, the moisture permeability of the first protective layer is 200g/m ² ·24h to 500g/m ² ·24h, and preferably 220g/m ² ·24h to 480g/m ² ·24h, preferably 300g/m ² · 24h to 450g/m ² ·24h. If the moisture permeability of the first protective layer is within this range, a polarizing plate with excellent reliability under high-temperature and high-humidity environments can be realized. More specifically, it is a polarizing plate that can realize small changes in polarization degree under high temperature and high humidity environments (for example, the change in the durability test is less than 0.02%). If the moisture permeability is too high, reliability may sometimes be insufficient in high temperature and high humidity environments. If a film with low moisture permeability (such as a cyclic olefin resin (COP) film) is used as the first protective layer, in a high-temperature environment (for example, in a harsh high-temperature environment such as a thermal shock test), it will interact with polarized light. Due to differences in the linear expansion coefficients of parts, cracks may sometimes occur near the through holes. The thickness and water permeability of the first protective layer respectively mean the thickness and water permeability of the laminate of the resin film and the hard coat layer.

The moisture permeability of the second protective layer is less than 100g/m ² ·24h, and is preferably 10g/m ² ·24h to 70g/m ² ·24h, preferably 20g/m ² ·24h to 50g/m ² ·24h. If the moisture permeability is too high, the surface resistance value of the adhesive layer may not be stable enough in high temperature and high humidity environments (for example, the change in the durability test exceeds 10 times). As a result, when the polarizing plate is applied to an image display device, poor conduction may occur in the image display device.

The thickness of the adhesive layer is 12 μm ~ 17 μm, and preferably 13 μm ~ 16 μm. If the thickness is too large, concave glue (a phenomenon in which the adhesive layer is sunken) may sometimes occur during through-hole processing, deteriorating the appearance, and/or the total thickness of the polarizing plate becomes too thick and the adhesive (in essence, Bubbles are generated when the through hole is filled with the adhesive that constitutes another adhesive layer described later. If the thickness is too small, the polarizing plate may sometimes peel off from the image display unit in a high temperature and high humidity environment. Furthermore, the surface resistance value of the adhesive layer is 1.0×10 ⁸ Ω/□ to 2.0×10 ⁹ Ω/□, and is preferably 3.0×10 ⁸ Ω/□ to 1.2×10 ⁹ Ω/□, and is preferably 5.0 ×10 ⁸ Ω/□ to 1.0×10 ⁹ Ω/□. If the surface resistance value is too small, the touch sensitivity of the display becomes excessive, and malfunction may sometimes occur. If the surface resistance value is too high, the conduction of the film is poor, and sometimes the static electricity charged during the manufacturing process cannot be removed, resulting in poor image display.

The polarizing plate according to the embodiment of the present invention can be used as a viewing side polarizing plate or a back side polarizing plate. The polarizing plate according to the embodiment of the present invention can be suitably used as a viewing side polarizing plate. Furthermore, the polarizing plate according to the embodiment of the present invention may further have any appropriate optical functional layer depending on the purpose. Examples of optically functional layers include retardation layers, conductive layers for touch panels, and reflective polarizers. The number, type, combination and arrangement position of the optical functional layers can be appropriately set according to the purpose.

Hereinafter, the polarizer, the first protective layer, the second protective layer and the adhesive layer constituting the polarizing plate will be described in detail.

B.Polarizer Typically, the polarizer is composed of a resin film containing a dichroic substance. The resin film can be any suitable resin film that can be used as a polarizer. Typically, the resin film is a polyvinyl alcohol-based resin (hereinafter referred to as "PVA-based resin") film. The resin film may be a single-layer resin film or a laminate of two or more layers.

Specific examples of polarizers composed of a single-layer resin film include subjecting a PVA-based resin film to dyeing treatment with iodine and stretching treatment (representatively uniaxial stretching). The above-described dyeing with iodine is performed, for example, by immersing a PVA-based film in an iodine aqueous solution. The extension ratio of the above-mentioned uniaxial extension is preferably 3 to 7 times. Extending can be done after dyeing or while dyeing. In addition, it can also be dyed after stretching. If necessary, the PVA-based resin film is subjected to swelling treatment, cross-linking treatment, washing treatment, drying treatment, etc. For example, by immersing the PVA resin film in water and washing it before dyeing, not only can the dirt and anti-caking agent on the surface of the PVA film be washed away, but the PVA resin film can also be swollen to prevent uneven dyeing. .

Specific examples of the above-mentioned polarizing element produced using a laminate of two or more layers include a polarizing element produced using the following laminate: a resin base material and a PVA-based resin layer (PVA-based resin layer) laminated on the resin base material. A laminate of a resin film); or a laminate of a resin base material and a PVA-based resin layer coated on the resin base material. A polarizing element produced using a laminate of a resin base material and a PVA-based resin layer coated on the resin base material can be produced by, for example, the following steps: Coating a PVA-based resin solution on the resin base The material is dried and a PVA-based resin layer is formed on the resin base material to obtain a laminated body of the resin base material and the PVA-based resin layer; and the laminated body is stretched and dyed to make the PVA-based resin layer polarized pieces. In this embodiment, it is preferable to form a polyvinyl alcohol-based resin layer containing a halide and a polyvinyl alcohol-based resin on one side of the resin base material. Typically, stretching includes immersing the laminate in a boric acid aqueous solution and stretching. Furthermore, if necessary, stretching may further include stretching the laminate in the air at a high temperature (for example, 95° C. or above) before stretching in a boric acid aqueous solution. In addition, in this embodiment, it is preferable that the laminated body is subjected to drying and shrinkage treatment in which the laminate is heated to shrink by 2% or more in the width direction while being conveyed in the longitudinal direction. Typically, the manufacturing method of this embodiment includes sequentially performing an air-assisted stretching process, a dyeing process, an underwater stretching process, and a drying shrinkage process on the laminate. By introducing auxiliary stretching, even when PVA is coated on thermoplastic resin, the crystallinity of PVA can still be improved and high optical properties can be achieved. In addition, by simultaneously improving the alignment of PVA in advance, problems such as the decrease in alignment and dissolution of PVA can be prevented when immersed in water in subsequent dyeing steps and stretching steps, thereby achieving high optical properties. Furthermore, when the PVA-based resin layer is immersed in liquid, compared with when the PVA-based resin layer does not contain halides, the alignment disorder and the decrease in alignment of polyvinyl alcohol molecules can be suppressed. Thereby, the optical characteristics of the polarizer produced by immersing the laminate in a liquid, such as dyeing treatment and water stretching treatment, can be improved. Furthermore, the optical properties can be improved by shrinking the laminate in the width direction through drying and shrinkage treatment. The obtained laminated body of the resin base material/polarizing element can be used directly (that is, the resin base material can also be used as a protective layer of the polarizing element), or it can be peeled off from the laminated body of the resin base material/polarizing element if necessary. It is used by laminating any appropriate protective layer on the peeling surface behind the resin base material or on the surface opposite to the peeling surface. Details of the manufacturing method of such a polarizer are described in, for example, Japanese Patent Application Laid-Open No. 2012-73580 and Japanese Patent No. 6470455. This manual refers to the entire contents of these publications as a reference.

The thickness of the polarizer is as described in item A above.

The polarizer should show absorption dichroism at any wavelength from 380nm to 780nm. For example, the single transmittance of the polarizer is 41.5%~44.0%, and is preferably 42.5%~44.0%, and more preferably 43.0%~44.0%. The polarization degree of the polarizer is preferably above 97.0%, more preferably above 99.0%, more preferably above 99.9%.

C. 1st layer of protection C-1. Resin film As for the resin film, as long as the above-mentioned desired moisture permeability can be obtained as the first protective layer, any appropriate resin film that can be used as a polarizer protective layer can be used. Specific examples of the material that becomes the main component of the resin film include cellulose-based resins such as triacetylcellulose (TAC). By combining such a film made of resin with a specific hard coat layer described below, a first protective layer having the desired moisture permeability can be formed with an appropriate thickness.

The moisture permeability of the resin film is preferably 600g/m ² ·24h to 2000g/m ² ·24h, preferably 800g/m ² ·24h to 1500g/m ² ·24h. If the moisture permeability of the resin film is within this range, the first protective layer having the above-described desired moisture permeability can be formed by combining it with a specific hard coat layer described below.

The thickness of the resin film is preferably 15 μm ~ 28 μm, more preferably 20 μm ~ 26 μm. If the thickness of the resin film is within this range, the first protective layer having the above-described desired thickness can be formed.

C-2. Hard coating The hard coating should have excellent surface hardness (such as excellent pencil hardness, excellent steel wool scratch resistance), excellent mechanical strength and excellent light transmittance. The hard coat layer may have any appropriate structure as long as it has such desired characteristics. Typically, the hard coat layer is a hardened layer of a resin composition containing a hardened resin.

Specific examples of the curable resin include thermosetting resin, ultraviolet curing resin, electron beam curing resin, and two-liquid mixed resin. Ultraviolet curable resin is suitable. This is because the hard coat layer can be formed with simple operation and high efficiency. Specific examples of ultraviolet curable resins include polyester resins, (meth)acrylic resins, urethane resins, amide resins, polysilicone resins, epoxy resins, and urethane resins. Acid ester (meth)acrylate resin. UV-curable resins include UV-curable monomers, oligomers and polymers. The resin composition may contain a (meth)acrylic resin, for example, a urethane (meth)acrylate resin, or a combination thereof. The hard coat layer may also contain copolymers of oligomers and monomers such as functional groups. Examples of the monomer having a functional group include polyfunctional (meth)acrylate. For example, the (meth)acrylate may be bifunctional or higher, and may be trifunctional or higher. Examples of the oligomer having a functional group include hardened urethane (meth)acrylate. The hardened urethane (meth)acrylate is, for example, 6 or more functional, and may also be 8 to 10 functional. In one embodiment, the resin composition preferably contains a total of at least 60 parts by weight of curable urethane (meth)acrylate and polyfunctional (meth)acrylate relative to 100 parts by weight of the curable resin, and is relatively It is preferably 70 parts by weight or more, more preferably 80 parts by weight or more, especially 90 parts by weight or more, especially 95 parts by weight or more. The total amount may also be 100 parts by weight. The blending ratio of hardened urethane (meth)acrylate and multifunctional (meth)acrylate in hardening resin is preferably 60/40 (weight ratio) to 40/60 (weight ratio). It is suitable to be 55/45 (weight ratio) to 45/55 (weight ratio). In one embodiment, the curable resin is composed of urethane (meth)acrylate and multifunctional (meth)acrylate with more than six functions. For example, the hardening resin can be composed of 10-functional urethane (meth)acrylate/tricyclodecane dimethanol dimethacrylate (50/50: weight ratio).

Typically, the resin composition contains a photopolymerization initiator. Regarding the photopolymerization initiator, any suitable photopolymerization initiator can be used according to the curable resin.

The resin composition (and in the case of the hard coat layer) may contain silicon. For example, silicon can be a constituent element of surface modifiers. Therefore, the resin composition (resultally a hard coat layer) contains a surface adjuster (represented by a leveling agent), which may include, for example, silicon having a skeleton such as dimethylsiloxane. compound. The silicon compound can be dimethylsiloxane modified methacrylate, polydimethylsiloxane cyclic compound, etc.

The pencil hardness of the hard coat layer is preferably F or higher, more preferably H or higher, and more preferably 3H or higher. If the pencil hardness of the hard coating is within this range, it can be used as the outermost layer on the viewing side to achieve sufficient protection.

The moisture permeability per unit thickness of the hard coating should be 100g/m ²・24h・μm to 400g/m ²・24h・μm, preferably 120g/m ²・24h・μm to 250g/m ²・24h・μm . If the moisture permeability of the hard coat layer is within this range, the first protective layer having the desired moisture permeability can be formed by combining it with the above-mentioned specific resin film. In addition, the water permeability per unit thickness of the hard coat layer is the value obtained by subtracting the water permeability of the resin film from the water permeability of the first protective layer and dividing it by the thickness of the hard coat layer.

The haze value of the hard coat layer is, for example, 5% or more, another example is 10% or more, another example is 15% or more, and another example is 20% or more. On the other hand, the haze value of the hard coat layer is, for example, 50% or less, another example is 45% or less, another example is 40% or less, another example is 35% or less. If the haze value is within this range, the occurrence of shading and external reflection can be suppressed, and the display characteristics of the image display device (such as sharpness and contrast in dark places) can be suppressed from being reduced. Typically, the haze value can be measured in accordance with JIS K 7136.

The thickness of the hard coating layer is preferably 5 μm or less, preferably 2 μm to 4 μm. If the thickness of the hard coat layer is within this range, a first protective layer having a desired thickness can be formed while maintaining the desired moisture permeability.

The hard coat layer can be formed using any appropriate method. For example, the hard coat layer can be formed by applying a resin composition (coating liquid) for forming a hard coat layer on a resin film and drying it, and then irradiating the dried coating film with ultraviolet rays to harden it. .

D. The moisture permeability of the second protective layer is less than 100g/m ² ·24h as mentioned above, and is preferably 10g/m ² ·24h to 70g/m ² ·24h, and is preferably 20g/m ² · 24h to 50g/m ²・24h. If the moisture permeability of the second protective layer is within this range, when the through-holes are filled with an adhesive (described later) constituting another adhesive layer, the generation of bubbles can be suppressed and the surface resistance of the adhesive layer can be increased in a high-temperature and high-humidity environment. The change in value is reduced.

As long as the above-mentioned desired moisture permeability can be obtained, the second protective layer can be formed by any suitable resin film that can be used as a polarizer protective layer. Specific examples of the material that becomes the main component of the resin film include cycloolefin-based resin (eg, norbornene-based resin).

The thickness of the second protective layer is preferably 10 μm ~ 30 μm, more preferably 10 μm ~ 16 μm. If the thickness of the second protective layer is within this range, a polarizing plate having the above-described desired characteristics and the above-described desired total thickness can be formed.

E. Adhesive layer As mentioned above, the adhesive layer is used to bond the polarizing plate to the image display unit. The surface resistance value of the adhesive layer is as above 1.0×10 ⁸ Ω/□ to 2.0×10 ⁹ Ω/□, and preferably 3.0×10 ⁸ Ω/□ to 1.2×10 ⁹ Ω/□, preferably 5.0× 10 ⁸ Ω/□ to 1.0×10 ⁹ Ω/□. If the surface resistance value of the adhesive layer is within this range, conduction defects can be suppressed when the polarizing plate is applied to an image display device.

The adhesion force of the adhesive layer to the glass should be more than 1.5N/25mm and less than 5.5N/25mm, more preferably more than 2.5N/25mm and less than 4.5N/25mm, more preferably more than 3.0N/25mm and less than 4.0N/25mm the following. If the adhesive force is within this range, the adhesion to the image display panel will be excellent and the reworkability will be excellent.

The storage elastic modulus of the adhesive layer at 25°C is preferably 1.0×10 ⁴ Pa to 1.0×10 ⁶ Pa, more preferably 1.0×10 ⁴ Pa to 1.0×10 ⁵ Pa. If the storage elastic modulus of the adhesive layer is within this range, poor appearance of the polarizing plate in high temperature and high humidity environments can be suppressed. In addition, the storage elastic modulus can be obtained by dynamic viscoelasticity measurement.

The latent variable ΔCr of the adhesive layer at 70°C is, for example, 120 μm or less. It may also be 50 μm or less, 45 μm or less, 40 μm or less, 35 μm or less, 30 μm or less, 25 μm or less, 20 μm or less, or it may be further 15 μm or less. The lower limit of the latent variable ΔCr is, for example, 0.5 μm. If the latent variable is in this range, it will be the same as when the elastic modulus is stored, and it can suppress the poor appearance of the polarizing plate in a high-temperature and high-humidity environment. In addition, for example, the creep value can be measured in the following sequence: For the adhesive layer that has been attached to the stainless steel test plate through the joint surface of 20mm long x 20mm wide, in the state where the test plate has been fixed , apply a load of 500gf below the vertical. At each time point 100 seconds after the load is applied and 3600 seconds after the load is applied, the latent variable (offset amount) of the adhesive layer to the test plate is measured, and let them be Cr ₁₀₀ and Cr ₃₆₀₀ respectively. The latent variable ΔCr can be calculated from the measured Cr ₁₀₀ and Cr ₃₆₀₀ using the formula ΔCr=Cr ₃₆₀₀ -Cr ₁₀₀ .

As mentioned above, the thickness of the adhesive layer is 12 μm ~ 17 μm, and preferably 13 μm ~ 16 μm. If the thickness of the adhesive layer is within this range, peeling in a high temperature and high humidity environment can be suppressed. At the same time, when the through holes are filled with an adhesive (described later) constituting another adhesive layer, the occurrence of bubbles can also be suppressed.

As for the adhesive (adhesive composition) constituting the adhesive layer, any appropriate adhesive can be used as long as it satisfies the above characteristics. Typically, the adhesive composition includes a base polymer and a conductive component.

Examples of the base polymer include (meth)acrylic polymers, urethane polymers, silicone polymers, and rubber polymers. Preferably it is a (meth)acrylic polymer. In this specification, the (meth)acrylic polymer used as a base polymer may be called a (meth)acrylic base polymer.

Typically, the (meth)acrylic base polymer contains alkyl (meth)acrylate as a monomer component as a main component. Examples of the alkyl group of (meth)acrylic acid alkyl ester include a linear or branched alkyl group having 1 to 18 carbon atoms. The average carbon number of the alkyl group is preferably 3 to 9, more preferably 3 to 6. The preferred alkyl (meth)acrylate is butyl acrylate. The content of the alkoxy group-containing monomer in the base polymer is preferably 50 parts by weight relative to 100 parts by weight of all monomer components, and is more preferably 60 parts by weight or more, more preferably 70 parts by weight or more, and especially 80 parts by weight. More than one serving. The alkyl (meth)acrylate may be used alone, or two or more types may be used in combination.

Typically, the (meth)acrylic base polymer contains a monomer component (copolymerizable monomer component) copolymerizable with an alkyl (meth)acrylate. Examples of copolymerizable monomer components include carboxyl group-containing monomers, hydroxyl group-containing monomers, alkoxy group-containing monomers, amide group-containing monomers, aromatic ring-containing (meth)acrylates, and heterocyclic ring-containing vinyl systems. Single body. By appropriately adjusting the type, quantity, combination, blending amount (content), etc. of the copolymerized monomers, a base polymer (in the end, an adhesive layer) with desired characteristics can be obtained. In one embodiment, the (meth)acrylic base polymer may be a copolymer of the following monomers: (meth)acrylic acid alkyl ester (such as butyl acrylate), aromatic ring-containing (meth)acrylic acid ester ( For example, phenoxyethyl acrylate), heterocyclic-containing vinyl monomers (such as N-vinyl-2-pyrrolidinone), carboxyl-containing monomers (such as acrylic acid) and hydroxyl-containing monomers (such as 4-hydroxy Butyl acrylate).

The weight average molecular weight Mw of the (meth)acrylic base polymer is preferably 1 million to 3 million, more preferably 1 million to 2 million, and more preferably 1 million to 1.6 million. If the weight average molecular weight Mw is less than 1 million, crack suppression may be insufficient. If the weight average molecular weight Mw exceeds 3 million, the viscosity may increase and/or gelation may occur during the polymerization process of the polymer.

Representative examples of conductive components include inorganic cation salts and organic cation salts.

Inorganic cation salts are specifically inorganic cation-anion salts. Typically, cations constituting the cationic part of the inorganic cation salt include alkali metal ions. Specific examples include lithium ions, sodium ions and potassium ions. Preferably lithium ion. Therefore, the preferred inorganic cation salt is the lithium salt.

Examples of anions constituting the anion part of the inorganic cation salt include Cl ^- , Br ^- , I ^- , AlCl ₄ ^- , Al ₂ Cl ₇ ^- , BF ₄ ^- , PF ₆ ^- , ClO ₄ ^- , NO ₃ ^- and CH ₃ COO ^- , CF ₃ COO ^- , CH ₃ SO ₃ ^- , CF ₃ SO ₃ ^- , (CF ₃ SO ₂ ) ₃ C ^- , AsF ₆ ^- , SbF ₆ ^- , NbF ₆ ^- , TaF ₆ ^- , (CN) ₂ N ^- , C ₄ F ₉ SO ₃ ^- , C ₃ F ₇ COO ^- , (CF ₃ SO ₂ )(CF ₃ CO)N ^- , ^- O ₃ S(CF ₂ ) ₃ SO ₃ ^- and the following general formula (1) ~Anions shown in (4): (1): (C _n F _{2n ＋ 1} SO ₂ ) ₂ N ^- (n is an integer from 1 to 10); (2): CF ₂ (C _m F _2m SO ₂ ) ₂ N ^- (m is an integer from 1 to 10); (3): ^- O ₃ S(CF ₂ ) _l SO ₃ ^- (l is an integer from 1 to 10); (4): (C _p F _{2p + 1} SO ₂ )N ^- (C _q F _{2q + 1} SO ₂ ) (p and q are integers from 1 to 10). Fluoride-containing anions are preferred, and fluoride-containing imine anions are even more preferred.

Examples of the fluorinated acyl imine anion include those having a perfluoroalkyl group. Specific examples include the above-mentioned (CF ₃ SO ₂ )(CF ₃ CO)N ^- and anions represented by the following general formulas (1), (2) and (4): (1): (C _n F _{2n + 1} SO ₂ ) ₂ N ^- (n is an integer from 1 to 10); (2): CF ₂ (C _m F _2m SO ₂ ) ₂ N ^- (m is an integer from 1 to 10); (4): (C _p F _{2p + 1} SO ₂ )N ^- (C _q F _{2q + 1} SO ₂ ) (p and q are integers from 1 to 10). It is preferably (perfluoroalkylsulfonyl)imide represented by the general formula (1) of (CF ₃ SO ₂ ) ₂ N ^- , (C ₂ F ₅ SO ₂ ) ₂ N ^-, etc., and more preferably (CF ₃ SO ₂ ) ₂ N ^- Bis(trifluoromethanesulfonyl)imide. Therefore, a preferred inorganic cation salt that can be used in embodiments of the present invention is lithium bis(trifluoromethanesulfonyl)imide.

The organic cation salt is specifically an organic cation-anion salt. Typically, the cation constituting the cation part of the organic cation salt is, for example, an organic onium substituted with an organic group to form an onium ion. Examples of the organic onium include nitrogen-containing onium, sulfur-containing onium, and phosphorus-containing onium. Preferred are nitrogen-containing onium and sulfur-containing onium. Examples of nitrogen-containing onium include ammonium cation, piperidinium cation, pyrrolidinium cation, pyridinium cation, cation with pyrroline skeleton, cation with pyrrole skeleton, imidazolium cation, tetrahydropyrimidinium cation, dihydropyrimidinium cation, pyrazolinium cation, pyrazolinium cation. Examples of sulfonium-containing compounds include sulfonium cations. Examples of phosphonium-containing compounds include phosphonium cations. Examples of the organic group in the organonium include alkyl group, alkoxy group, and alkenyl group. Specific examples of preferred organonium include tetraalkylammonium cations (for example, trimethylbutylammonium cations), alkylpiperidinium cations, and alkylpyrrolidinium cations. The anions constituting the anionic portion of the organic cationic salt are described in the same manner as the anions constituting the anionic portion of the inorganic cation. The preferred organic cation salts that can be used in the embodiment of the present invention are methylpropylpyrrolidinium bis(trifluoromethanesulfonyl)imide and 1-ethyl-3-methylimidazolium bis(fluorosulfonyl) ) acyl imine, trimethylbutylammonium bis(trifluoromethanesulfonyl) acyl imine.

Inorganic cation salts and organic cation salts can also be used in combination.

The conductive component can be solid or liquid (ie, ionic liquid).

The content of the conductive component in the adhesive composition is preferably 5 to 15 parts by weight, more preferably 8 to 12 parts by weight relative to 100 parts by weight of the base polymer. If the content of the conductive component is within this range, the desired surface resistance value can be obtained without adversely affecting other characteristics.

Typically, the adhesive composition contains a silane coupling agent and/or a cross-linking agent. Representative examples of the silane coupling agent include functional group-containing silane coupling agents. Examples of functional groups include epoxy group, mercapto group, amine group, isocyanate group, isocyanate group, vinyl group, styrene group, acetyl acetyl group, urea group, thiourea group, and (meth)acrylyl group. , heterocyclic group, acid anhydride group and combinations thereof. Silane coupling agents containing functional groups can be used alone or in combination. Examples of the cross-linking agent include isocyanate-based cross-linking agents and peroxide-based cross-linking agents. Cross-linking agents can also be used alone or in combination.

The adhesive composition may contain additives. Specific examples of additives include colorants, powders such as pigments, dyes, surfactants, plasticizers, tackifiers, surface lubricants, leveling agents, softeners, antioxidants, anti-aging agents, and light stabilizers. , UV absorbers, polymerization inhibitors, inorganic or organic fillers, metal powders, particles or foils. In addition, within a controllable range, a redox system including a reducing agent can also be used. The type, quantity, combination, content, etc. of additives can be appropriately set according to the purpose.

F.Image display device The polarizing plate according to the embodiment of the present invention can be applied to an image display device. Therefore, the image display device is also included in the embodiments of the present invention. Examples of image display devices include liquid crystal display devices, organic electroluminescence (EL) display devices, and quantum dot display devices. 2 is a schematic cross-sectional view of main parts of a portion near a through hole of a polarizing plate in an image display device according to an embodiment of the present invention. The image display device 200 in the illustrated example has: an image display unit 120; a polarizing plate 100, which is attached to the viewing side of the image display unit 120 through an adhesive layer 40; and another adhesive layer 140, which is disposed on the polarizing plate. 100 points of view. The polarizing plate 100 is the polarizing plate according to the embodiment of the present invention described in the above-mentioned items A to E. In the embodiment of the present invention, the through hole 50 of the polarizing plate 100 is filled with adhesive that constitutes another adhesive layer 140 . The image display device in the illustrated example may further have a cover glass 160 on the viewing side of another adhesive layer 140 if necessary. The cover glass 160 can be laminated on the image display device (essentially the polarizing plate 100) through another adhesive layer 140. In one embodiment, the image display device has a camera unit (not shown) at a position corresponding to the through hole 50 of the polarizing plate 100 . With this structure, adverse effects on the photography performance of the camera can be prevented. As for the structure of the image display unit on the side opposite to the viewing side, any appropriate structure can be adopted according to the type of the image display device, so detailed description is omitted.

As for the adhesive constituting the other adhesive layer 140, any suitable adhesive can be used. Specific examples of adhesives include acrylic adhesives, rubber adhesives, silicone adhesives, polyester adhesives, urethane adhesives, epoxy adhesives and polyether adhesives. agent. It can be prepared by adjusting the monomer type, quantity, combination and blending ratio, cross-linking agent blending amount, additive type, quantity, combination and blending ratio, reaction temperature and reaction time of the base polymer forming the adhesive. To produce an adhesive with the desired properties suitable for the purpose. The base polymer of the adhesive can be used alone or in combination of two or more types. From the viewpoint of transparency, processability, durability, etc., an acrylic adhesive is suitable.

The storage elastic modulus of the other adhesive layer before hardening at 60°C is preferably 1.0×10 ³ Pa to 1.0×10 ⁶ Pa, more preferably 1.0×10 ⁴ Pa to 1.0×10 ⁵ Pa. The storage elastic modulus of the other adhesive layer at 25°C after hardening is preferably 1.0×10 ⁴ Pa to 1.0×10 ⁷ Pa, more preferably 1.0×10 ⁵ Pa to 1.0×10 ⁷ Pa. If the storage elastic modulus of the other adhesive layer is within this range, it will be soft during bonding and its resistance to external stress after hardening will be enhanced, as will be described later through the synergistic effect with the effects of the embodiments of the present invention. , even if the thickness is thin, bubbles in the through-hole part can still be suppressed.

The thickness of the other adhesive layer is preferably 150 μm or less, more preferably 120 μm or less, more preferably 100 μm or less, especially 75 μm or less. According to the embodiment of the present invention, even if the thickness of the other adhesive layer is so thin, bubbles in the through-hole portion can still be suppressed, and the reliability under high-temperature and high-humidity environments is excellent, and conduction can be suppressed when applied to an image display device. Polarizing plate in bad condition. In addition, for example, the thickness of the other adhesive layer may be 50 μm or more. Example

The present invention will be specifically described below through examples, but the present invention is not limited to these examples. The evaluation items in the examples are as follows. In addition, unless otherwise stated, "parts" and "%" in the examples are based on weight.

(1) Bubbles in the through hole part The polarizing plates obtained in the examples and comparative examples were cut into 150 mm × 70 mm, and a through hole with a diameter of 3 mm was formed so that the upper part of the through hole would be located 3 mm from the upper end in the longitudinal direction. Attach this polarizer to the glass plate. Through the optical adhesive, use a vacuum laminator (pressure 0.3MPa, temperature 60°C, 10 minutes) to place the optical adhesive on the cover glass (another adhesive layer, thickness 100μm, "CEF7104" manufactured by 3M Company) The laminate is bonded to the polarizing plate/glass plate laminate, and the through-hole portion of the polarizing plate is filled with optical adhesive. Observe the bubbles in the through-hole part visually and evaluate based on the following criteria. ○(Good): No bubbles were observed × (Defect): Bubbles are observed

(2) Changes in polarization degree under high-temperature and high-humidity environments. The polarizing plates obtained in Examples and Comparative Examples were bonded to an alkali-free glass plate to serve as measurement samples. For this measurement sample, the degree of polarization P ₀ was measured using an ultraviolet-visible spectrophotometer (LPF-200, manufactured by Otsuka Electronics). The measurement sample was further subjected to a 500-hour durability test at 65°C and 90%RH, and the polarization degree P ₅₀₀ after the test was measured. ΔP=P ₀ -P ₅₀₀ was calculated and evaluated based on the following standards. ○ (Good): ΔP is less than 0.02% × (Bad): ΔP is 0.02% or more

(3) Surface resistance value and surface resistance stability of the adhesive layer Hiresta UP MCP HT450 (Mitsubishi Chemical Analytech Co., Ltd.) was used to measure the surface resistance value of the adhesive layer of the polarizing plates obtained in the examples and comparative examples. In addition, once the surface resistance value exceeds 2×10 ⁹ Ω/□, the occurrence of conduction failure in the image display device increases. Therefore, when the value is less than this value, the conductivity is judged to be good. Furthermore, the polarizing plate was subjected to a 500-hour durability test at 60°C and 90% RH, and the surface resistance value of the adhesive layer after the test was measured, and the stability of the surface resistance value was evaluated according to the following standards. ○ (Good): The surface resistance value is 2×10 ⁹ Ω/□ or less × (Bad): The surface resistance value is more than 2×10 ⁹ Ω/□

(4) Polarizing plate peeling in high temperature and high humidity environment The polarizing plates obtained in Examples and Comparative Examples were cut into 300 mm × 220 mm, bonded to an alkali-free glass plate, and used as measurement samples. The measurement sample was subjected to a durability test for 500 hours at 60°C and 90%RH. The state of the polarizing plate after the test was observed and evaluated according to the following standards. ○(Good): No peeling is observed, or the peeling at the end is less than 0.3mm × (Defect): Peeling of more than 0.3mm is observed at the edge

(5) Cracks near the through hole The polarizing plates obtained in the examples and comparative examples were cut into 150 mm × 70 mm, and a through hole with a diameter of 3 mm was formed so that the upper part of the through hole would be located 3 mm from the upper end in the longitudinal direction. This polarizing plate was bonded to an alkali-free glass plate to serve as a measurement sample. The measurement sample was subjected to a thermal shock test in which the environment was repeatedly changed between 85°C and -40°C for 200 cycles. The cracks in the through-hole part after the test were observed and evaluated according to the following standards. ○ (Good): The maximum size of cracks near the through hole is 300 μm or less × (Defect): The maximum size of cracks near the through hole is greater than 300μm

<Manufacturing Example 1: Preparation of adhesive layer> Put 80.3 parts of butyl acrylate, 16 parts of phenoxyethyl acrylate, and 3 parts of N-vinyl-2-pyrrolidone (NVP) into a 4-neck flask equipped with a stirring blade, a thermometer, a nitrogen inlet pipe, and a cooler. , a monomer mixture of 0.3 parts of acrylic acid and 0.4 parts of 4-hydroxybutyl acrylate. Further, to 100 parts of the monomer mixture (solid content), 0.1 part of 2,2'-azobisisobutyronitrile used as a polymerization initiator was fed together with 100 parts by weight of ethyl acetate, and nitrogen gas was introduced while slowly stirring. , after nitrogen purging, the liquid temperature in the flask was maintained at around 55°C and the polymerization reaction was carried out for 8 hours to prepare an acrylic polymer solution with a weight average molecular weight (Mw) of 1.5 million. To 100 parts of the solid content of the obtained acrylic polymer solution, EMI-FSI (1-ethyl-3-methylimidazolium bis(trifluorosulfonyl)imide) used as a conductive agent (antistatic agent) was blended. , ionic liquid manufactured by Daiichi Industrial Pharmaceutical Co., Ltd.) 8.5 parts, and further blended with 0.2 parts of isocyanate cross-linking agent (trade name: TAKENATE D160N, trimethylolpropane hexamethylene diisocyanate, manufactured by Mitsui Chemicals Co., Ltd.) , 0.25 parts of benzoyl peroxide (trade name: NYPER BMT 40SV, manufactured by Nippon Oils & Fats Co., Ltd.), 0.2 parts of silane coupling agent (made by Soken Chemical Co., Ltd.: A-100) and antioxidant (trade name: Irganox 1010 , hindered phenol system, manufactured by BASF JAPAN Co., Ltd.) 0.3 parts to obtain adhesive composition I.

Next, the adhesive composition I was coated on a polyethylene terephthalate film treated with a polysiloxane release agent so that the thickness of the adhesive layer would become 15 μm after drying (separator film: Mitsubishi Chemical Polyethylene MHE38 (manufactured by Ester Film Co., Ltd.) was dried at 155°C for 1 minute on one side, and an adhesive layer A with a thickness of 15 μm was formed on the surface of the separator film.

<Manufacturing Example 2: Preparation of adhesive layer> The adhesive layer B with a thickness of 10 μm was formed on the surface of the separator film in the same manner as in Production Example 1 except that the coating thickness of the adhesive composition I was changed.

<Manufacturing Example 3: Preparation of adhesive layer> The same procedure as Production Example 1 is used except that 20 parts of TBMA-TFSI (tributylmethylammonium bis(trifluoromethane)sulfonimide, ionic liquid manufactured by 3M Company, FC-4400) is used instead of 8.5 parts of EMI-FSI. Adhesive composition II was prepared in the same manner. An adhesive layer C having a thickness of 15 μm was formed on the surface of the separator film in the same manner as in Production Example 1 except that the adhesive composition II was used.

<Manufacturing Example 4: Preparation of adhesive layer> The adhesive layer D with a thickness of 20 μm was formed on the surface of the separator film in the same manner as in Production Example 1 except that the coating thickness of the adhesive composition I was changed.

<Manufacturing Example 5: Preparation of adhesive layer> Adhesive composition III was produced in the same manner as in Production Example 1 except that the blending amount of EMI-FSI was changed from 8.5 parts to 6.0 parts. The adhesive layer E with a thickness of 20 μm was formed on the surface of the separator film in the same manner as in Production Example 1 except that the adhesive composition III was used and the coating thickness was changed.

<Manufacture Example 6: Preparation of resin composition for hard coat layer formation> 50 parts by weight (solid content conversion) of ultraviolet curable acrylic resin (manufactured by Shin-Nakamura Chemical Co., Ltd., trade name "A-DCP", solid content 100%), ultraviolet curable acrylic resin (Mitsubishi Chemical Co., Ltd. Made, trade name "UV-1700TL", solid content 80%) 50 parts by weight (solid content conversion), photopolymerization initiator (manufactured by BASF, trade name "OMNIRAD907") 5 parts by weight and leveling agent (Kyoeisha Chemical Co., Ltd., trade name "LE-303", solid content 40%) 0.1 part by weight was mixed. The mixture was diluted with a methyl isobutyl ketone (MIBK)/cyclopentanone mixed solvent (weight ratio 60/40) so that the solid content concentration would be 30%, to prepare a resin composition for forming a hard coat layer (coat layer). cloth liquid)A. In addition, "A-DCP" is tricyclodecane dimethanol dimethacrylate, and "UV-1700TL" is 10-functional urethane acrylate. The hard coat layer formed from the coating liquid A is called hard coat layer A.

<Manufacture Example 7: Preparation of resin composition for hard coat layer formation> 40 parts by weight of ultraviolet curable acrylate resin (manufactured by Toagosei Co., Ltd., trade name "M-920", solid content 100%), ultraviolet curable acrylate resin (manufactured by Mitsubishi Chemical Co., Ltd., trade name "UV -1700TL", solid content 80%) 60 parts by weight, photopolymerization initiator (manufactured by BASF, trade name "OMNIRAD907") 3 parts by weight and leveling agent (manufactured by Kyeisha Chemical Co., Ltd., trade name "LE- 303", solid content 40%) 0.2 parts by weight are mixed. This mixture was diluted with a MIBK/cyclopentanone mixed solvent (weight ratio 70/30) so that the solid content concentration would be 30%, and a resin composition (coating liquid) B for forming a hard coat layer was prepared. In addition, "M-920" is glyceryl triacrylate. The hard coating layer formed by coating liquid B is called hard coating layer B.

<Production Example 8: Preparation of resin composition for hard coat layer formation> 100 parts by weight of ultraviolet curable urethane acrylate (manufactured by DIC Co., Ltd., trade name "UNIDIC 17-806", solid content 80%), photopolymerization initiator (manufactured by BASF, trade name "OMNIRAD907" )3 parts by weight and 0.01 part by weight of leveling agent (manufactured by DIC Co., Ltd., trade name "PC4100", solid content 40%). The mixture was diluted with propylene glycol monomethyl ether (PGM)/cyclopentanone mixed solvent (weight ratio 63/37) so that the solid content concentration would be 36%, to prepare a resin composition (coating liquid) for forming a hard coat layer )C. The hard coat layer formed by the coating liquid C is called hard coat layer C.

<Example 1> For the thermoplastic resin base material, a long amorphous isophthalic acid copolymer polyethylene terephthalate film (thickness: 100 μm) with a Tg of about 75°C is used, and the resin base material is coated on one side. Corona treatment. A PVA system composed of polyvinyl alcohol (degree of polymerization 4200, degree of saponification 99.2 mol%) and acetyl-acetyl modified PVA (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name "GOHSEFIMER") in a ratio of 9:1 13 parts by weight of potassium iodide was added to 100 parts by weight of the resin, and the added product was dissolved in water to prepare a PVA aqueous solution (coating liquid). The above-mentioned PVA aqueous solution was applied to the corona-treated surface of the resin base material and dried at 60°C to form a PVA-based resin layer with a thickness of 13 μm, thereby producing a laminate. The obtained laminate was uniaxially extended to 2.4 times in the longitudinal direction (air-assisted stretching treatment) in an oven at 130°C. Next, the laminated body was immersed in an insolubilization bath (a boric acid aqueous solution obtained by mixing 4 parts by weight of boric acid into 100 parts by weight of water) with a liquid temperature of 40° C. for 30 seconds (insolubilization treatment). Then, it was placed in a dyeing bath with a liquid temperature of 30°C (an iodine aqueous solution obtained by mixing iodine and potassium iodide in a weight ratio of 1:7 to 100 parts by weight of water) to determine the single transmittance (Ts) of the final polarizer. Soak it for 60 seconds (dyeing process) while adjusting the concentration so that it becomes the desired value. Next, it was immersed in a crosslinking bath with a liquid temperature of 40°C (a boric acid aqueous solution obtained by mixing 3 parts by weight of potassium iodide and 5 parts by weight of boric acid to 100 parts by weight of water) for 30 seconds (crosslinking treatment). Thereafter, the laminated body was immersed in a boric acid aqueous solution with a liquid temperature of 70° C. (boric acid concentration 4% by weight, potassium iodide concentration 5% by weight), while being placed between rollers with different circumferential speeds, with a total extension ratio in the longitudinal direction (longitudinal direction) of Uniaxial stretching (water stretching treatment) at 5.5 times. Thereafter, the laminated body was immersed in a cleaning bath (an aqueous solution obtained by mixing 4 parts by weight of potassium iodide into 100 parts by weight of water) with a liquid temperature of 20° C. (washing treatment). Thereafter, it was dried in an oven maintained at about 90° C. while keeping the contact surface temperature of the SUS heated roller at about 75° C. (drying shrinkage treatment). In this way, a polarizer with a thickness of about 5 μm was formed on the resin base material, and a laminate having a resin base material/polarizer structure was obtained.

A triacetylcellulose (TAC) film (thickness 25 μm) was prepared as the resin film of the first protective layer. The TAC film was coated with the coating liquid A of Production Example 6, and the coating film was heated at 60° C. for 1 minute and dried, and then irradiated with ultraviolet rays with a cumulative light intensity of 260 mJ/cm ² using a high-pressure mercury lamp to harden the coating film to form a thickness 3μm hard coating (HC) layer A. In this way, the HC-TAC film used as the first protective layer was prepared. The HC-TAC film used as the first protective layer is bonded to the polarizer surface (the surface opposite to the resin base material) of the laminate obtained above. In addition, the HC-TAC film is laminated so that the TAC film becomes the polarizer side. Next, the resin base material was peeled off, and a cyclic olefin resin (COP) film (thickness: 13 μm) serving as a second protective layer was bonded to the peeled surface. The adhesive layer A (thickness 15 μm) of Production Example 1 was further transferred to the surface of the COP film. In this way, a polarizing plate having a structure of first protective layer (HC layer A/TAC film)/polarizer (5 μm)/second protective layer (COP film)/adhesive layer A was produced. The obtained polarizing plate was subjected to the evaluation of (1) to (5) above. The results are shown in Table 1.

<Example 2> A long polyvinyl alcohol (PVA)-based resin film containing iodine was uniaxially stretched in the longitudinal direction (MD direction) to produce a polarizer (thickness: 12 μm). Except using this polarizing element, it carried out similarly to Example 1, and produced the polarizing plate in which the through hole was formed. The obtained polarizing plate was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

＜Comparative Examples 1~9＞ Make a polarizing plate with the structure shown in Table 1. The obtained polarizing plate was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

[Table 1]

In Table 1, the thickness unit is "μm" and the moisture permeability unit is "g/m ² ·24h".

As can be clearly seen from Table 1, the polarizing plate of the embodiment of the present invention is thin, has suppressed air bubbles in the through-hole part, and has excellent reliability in high temperature and high humidity environments (specifically, small change in polarization degree, adhesive layer The change in surface resistance value is small and the phenomenon of peeling off from the image display unit is suppressed). Furthermore, it can be seen from the surface resistance value of the adhesive layer that when the polarizing plate of the embodiment of the present invention is used in an image display device, it can suppress poor conduction. industrial availability

The polarizing plate according to the embodiment of the present invention is suitable for use in an image display device, and is particularly suitable for use in an image display device having a camera unit, such as a smartphone, a tablet PC, and a smart watch.

10:Polarizer 20: 1st protective layer 21:Resin film 22:Hard coating 30: 2nd protective layer 40:Adhesive layer 50:Through hole 100:Polarizing plate 120:Image display unit 140: Another adhesive layer 160: cover glass 200:Image display device

FIG. 1 is a schematic cross-sectional view of main parts of a portion near a through hole in a polarizing plate according to an embodiment of the present invention. 2 is a schematic cross-sectional view of main parts of a portion near a through hole of a polarizing plate in an image display device according to an embodiment of the present invention.

10:Polarizer

20: 1st protective layer

21:Resin film

22:Hard coating

30: 2nd protective layer

40:Adhesive layer

50:Through hole

100:Polarizing plate

Claims (8)

A polarizing plate having: a polarizer; a first protective layer arranged on one side of the polarizer and including a resin film and a hard coating layer formed on the opposite side of the resin film to the polarizer; and a second protective layer , which is disposed on the other side of the polarizer; and an adhesive layer, which is disposed on the side of the second protective layer opposite to the polarizer; and the total thickness of the polarizer is 70 μm or less and is formed with through holes, The thickness of the polarizer is less than 12 μm, the thickness of the first protective layer is less than 29 μm and the moisture permeability is 200g/m ² ‧24h to 500g/m ² ‧24h, and the moisture permeability of the second protective layer is less than 100g/m ² ‧24h, the thickness of the adhesive layer is 12μm~17μm and the surface resistance value is 1.0×10 ⁸ Ω/□ to 2.0×10 ⁹ Ω/□; the thickness of the hard coating layer is less than 5 μm; the hard coating layer is resin The hardened layer of the composition includes a resin composition containing more than six functional urethane acrylates, tricyclodecane dimethanol dimethacrylate and a photopolymerization initiator. The polarizing plate of claim 1, wherein the resin composition contains the above-mentioned hexafunctional or above urethane acrylate and the above-mentioned tricyclic ring in a ratio of 60/40 (weight ratio) to 40/60 (weight ratio). Decane dimethanol dimethacrylate. The polarizing plate of claim 1 or 2, wherein the resin film of the first protective layer is a cellulose triacetate film, and the second protective layer is composed of a cycloolefin resin film. The polarizing plate of claim 1 or 2, wherein the diameter of the through hole is 5 mm or less. An image display device has: an image display unit; For example, the polarizing plate of any one of claims 1 to 4 is bonded to the viewing side of the image display unit through the aforementioned adhesive layer; and another adhesive layer is disposed on the viewing side of the polarizing plate. ; Furthermore, the through-hole of the polarizing plate is filled with the adhesive constituting the other adhesive layer. The image display device of claim 5, wherein the thickness of the other adhesive layer is 120 μm or less. The image display device of claim 5 or 6 further has a cover glass on the viewing side of the other adhesive layer. The image display device according to claim 5 or 6 has a camera portion at a position corresponding to the through hole of the polarizing plate.

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