CN114902097A

CN114902097A - Polarizing plate with phase difference layer and image display device

Info

Publication number: CN114902097A
Application number: CN202080090733.2A
Authority: CN
Inventors: 新地真规子; 加藤芽实; 中岛淳
Original assignee: Nitto Denko Corp
Current assignee: Nitto Denko Corp
Priority date: 2019-12-27
Filing date: 2020-12-18
Publication date: 2022-08-12
Also published as: KR20220118403A; JPWO2021132068A1; WO2021132068A1; TW202132824A

Abstract

The invention provides a polarizing plate with a phase difference layer, which inhibits damage traces. The polarizing plate with a retardation layer of the present invention comprises: the polarizing plate comprises a polarizing plate (10) comprising a polarizer (11) and a protective layer (12) provided at least on the viewing side of the polarizer (11), and a phase difference layer (30) bonded to the side of the polarizing plate (10) opposite to the viewing side via an adhesive layer (20). The polarizer has a thickness of 12 μm or less, and the adhesive layer has a residual depth of 11 μm or less when a 3N load is applied.

Description

Polarizing plate with phase difference layer and image display device

Technical Field

The present invention relates to a polarizing plate with a retardation layer and an image display device.

Background

In image display devices (for example, liquid crystal display devices, organic EL display devices, and quantum dot display devices), a polarizing plate is often disposed on at least one side of an image display unit due to the image forming system. For the polarizing plate disposed on the viewing side of the image display device, a retardation film (polarizing plate with a retardation layer) may be laminated on the image display unit side for the purpose of preventing reflection of external light, reflection of a background, improving a color, and the like. As image display devices are made thinner, there is a strong demand for thinner polarizing plates with retardation layers. In order to meet such a demand, the polarizer is being thinned. However, a polarizing plate with a retardation layer including a thin polarizer is difficult to handle, and for example, a mark of damage (typically, a plurality of minute cracks in a certain region) may be generated by an external force due to a handling error of an operator.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2013-200445

Disclosure of Invention

Problems to be solved by the invention

The present invention has been made to solve the above problems, and a main object of the present invention is to provide a polarizing plate with a retardation layer in which damage traces are suppressed.

Means for solving the problems

The polarizing plate with a retardation layer according to an embodiment of the present invention includes: the polarizing plate comprises a polarizer and a protective layer provided at least on the visible side of the polarizer, and a retardation layer bonded to the side of the polarizing plate opposite to the visible side via an adhesive layer. The polarizer has a thickness of 12 μm or less, and the adhesive layer has a residual depth of 11 μm or less when a 3N load is applied.

In one embodiment, the adhesive layer has a thickness of 6 to 15 μm.

In one embodiment, the thickness of the protective layer on the visible side is 30 μm or more.

In one embodiment, the retardation layer exhibits a refractive index characteristic of nx > nz > ny. In one embodiment, the Nz coefficient of the retardation layer is 0.3 to 0.7. In one embodiment, the retardation layer has an in-plane retardation Re (550) of 250 to 350nm, a thickness of 150 μm or less, and a photoelastic coefficient of 1.0X 10 ^-12 m ² More than/N. In one embodiment, the retardation layer includes a cyclic olefin resin.

In one embodiment, an angle formed by the slow axis of the retardation layer and the absorption axis of the polarizer is substantially orthogonal or substantially parallel.

According to other aspects of the present invention, an image display device may be provided. The image display device includes the above polarizing plate with a retardation layer.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the embodiment of the present invention, a retardation layer-equipped polarizing plate in which scratches are suppressed can be realized by using a pressure-sensitive adhesive layer having a specific residual depth in the retardation layer-equipped polarizing plate including a thin polarizer.

Drawings

Fig. 1 is a schematic cross-sectional view of a polarizing plate with a retardation layer according to an embodiment of the present invention.

Description of the symbols

10 polarizing plate

11 polarizer

12 protective layer

20 adhesive layer

30 phase difference layer

100 polarizing plate with phase difference layer

Detailed Description

Embodiments of the present invention will be described below, but the present invention is not limited to these embodiments.

(definitions of wording and symbols)

The terms and symbols in the present specification are defined as follows.

(1) Refractive index (nx, ny, nz)

"nx" is a refractive index in a direction in which the in-plane refractive index is maximized (i.e., the slow axis direction), "ny" is a refractive index in a direction orthogonal to the slow axis in the plane (i.e., the fast axis direction), and "nz" is a refractive index in the thickness direction.

(2) In-plane retardation (Re)

"Re (. lamda)" is an in-plane retardation measured at 23 ℃ with light having a wavelength of. lamda.nm. For example, "Re (550)" is an in-plane retardation measured at 23 ℃ with light having a wavelength of 550 nm. When the thickness of the layer (film) is d (nm), the following formula can be used: re (λ) was obtained as (nx-ny) × d.

(3) Retardation in thickness direction (Rth)

"Rth (λ)" is a phase difference in the thickness direction measured at 23 ℃ with light having a wavelength of λ nm. For example, "Rth (550)" is a phase difference in the thickness direction measured at 23 ℃ with light having a wavelength of 550 nm. When the thickness of the layer (film) is d (nm), the following formula can be used: rth (λ) is obtained as (nx-nz) × d.

(4) Coefficient of Nz

The Nz coefficient is obtained by Nz ═ Rth/Re.

(5) Angle of rotation

In the present specification, when referring to an angle, the angle includes both clockwise and counterclockwise with respect to the reference direction. Thus, for example, "45" means ± 45 °.

(6) Substantially orthogonal or substantially parallel

In the present specification, the expressions "substantially orthogonal" and "substantially orthogonal" include a case where the angle formed by the 2 directions is 90 ° ± 7 °, preferably 90 ° ± 5 °, and more preferably 90 ° ± 3 °. The expressions "substantially parallel" and "substantially parallel" include the case where the angle formed by the 2 directions is 0 ° ± 7 °, preferably 0 ° ± 5 °, and more preferably 0 ° ± 3 °. In the present specification, the term "orthogonal" or "parallel" may include a substantially orthogonal state or a substantially parallel state.

A. Integral constitution of polarizing plate with phase difference layer

Fig. 1 is a schematic cross-sectional view of a polarizing plate with a retardation layer according to an embodiment of the present invention. The polarizing plate 100 with a retardation layer illustrated in the figure has a polarizing plate 10 and a retardation layer 30. The polarizing plate 10 includes a polarizer 11 and a protective layer (visible-side protective layer) 12 provided at least on the visible side of the polarizer 11. In the illustrated example, only the visible-side protective layer 12 is provided, but another protective layer (inner protective layer) may be provided on the side opposite to the visible side. The retardation layer 30 is attached to the side opposite to the viewing side of the polarizing plate 10 via the adhesive layer 20. The retardation layer 30 has a slow axis because it has an in-plane retardation. Typically, the slow axis of the retardation layer 30 is substantially orthogonal or substantially parallel to the absorption axis of the polarizer 11. In actual use, another adhesive layer (not shown) is provided on the side of the retardation layer 30 opposite to the polarizing plate 10 (i.e., as the outermost layer on the side opposite to the viewing side), and the polarizing plate with the retardation layer can be attached to the image display unit. Further, it is preferable to temporarily attach a separator (not shown) to the surface of the other adhesive layer until the polarizing plate with the retardation layer is used. By temporarily attaching the separator, it is possible to protect the other adhesive layer and form a roll of the polarizing plate with the retardation layer.

In the embodiment of the present invention, the remaining depth of the pressure-sensitive adhesive layer 20 when a 3N load is applied is 11 μm or less, preferably 10.8 μm or less. The lower the remaining depth is, the more preferable, the lower limit thereof may be, for example, 10 μm. The remaining depth can be measured, for example, as follows: (1) adhering the adhesive sheet to the glass plate; (2) the surface of the adhesive sheet was scratched while applying a load thereto by a small load automatic scratch tester. (3) The depth of penetration when scraping was performed with a load of 3N was measured by a displacement sensor and used as the remaining depth. By optimizing the remaining depth of the pressure-sensitive adhesive layer, the trace of damage (typically, a plurality of minute cracks in a certain region) can be significantly suppressed. Typically, the trace of the damage is generated due to external factors (e.g., impact and/or pressing force) resulting from a processing error of the operator. In addition, in a polarizing plate with a retardation layer having an adhesive layer on one surface of a polarizer, damage marks are typically generated in the polarizer. The damage mark is conspicuous in a thin polarizer, and also in a polarizing plate with a retardation layer for a large-sized image display device (for example, a television) which is more difficult to handle. The present inventors have found that, at first glance, the cause of damage traces of an aggregate of microcracks is completely different from cracks, and therefore damage traces cannot be suppressed by a crack suppression method (for example, adjustment of the storage modulus of the pressure-sensitive adhesive layer), and as a result of repeated attempts, it has been found that it is effective to optimize the residual depth (that is, the recovery after application of an external force to the pressure-sensitive adhesive layer). That is, the effect of suppressing the damage trace by optimizing the remaining depth can solve a newly discovered problem of the damage trace and is an unexpected excellent effect obtained by repeated attempts corresponding to the problem.

In the embodiment of the present invention, the thickness of the polarizer 11 is 12 μm or less. As described above, the damage mark is conspicuous in the thin polarizer, and is a problem substantially unique to the thin polarizer.

The polarizing plate 100 with a retardation layer may further have any suitable functional layer (not shown) on the side of the retardation layer 30 opposite to the polarizer 10 (image display unit side) according to the purpose. Typical examples of the functional layer include other retardation layers and conductive layers. The kind, number, combination, arrangement position, and characteristics (for example, optical characteristics of other retardation layers: specifically, refractive index characteristics, in-plane retardation, thickness direction retardation, and Nz coefficient) of the functional layers can be appropriately set according to the purpose. By further providing the polarizing plate with a retardation layer with a conductive layer, the polarizing plate with a retardation layer can be suitably used for an in-cell touch panel type input display device.

Hereinafter, the constituent elements of the polarizing plate with retardation layer will be described in more detail.

B. Polarizing plate

B-1 polarizer

Typically, the polarizer 11 is made of a resin film containing a dichroic material.

As the resin film, any appropriate resin film that can be used as a polarizer can be used. Typically, the resin film is a polyvinyl alcohol resin (hereinafter referred to as "PVA-based resin") film.

As the PVA-based resin forming the PVA-based resin film, any suitable resin may be used. Examples thereof include polyvinyl alcohol and ethylene-vinyl alcohol copolymers. Polyvinyl alcohol can be obtained by saponifying polyvinyl acetate. The ethylene-vinyl alcohol copolymer is obtained by saponifying an ethylene-vinyl acetate copolymer. The saponification degree of the PVA-based resin is usually 85 mol% to 100 mol%, preferably 95.0 mol% to 99.95 mol%, and more preferably 99.0 mol% to 99.93 mol%. The degree of saponification can be determined in accordance with JIS K6726-1994. By using the PVA-based resin having such a saponification degree, a polarizer having excellent durability can be obtained. If the degree of saponification is too high, gelation may occur.

The average polymerization degree of the PVA-based resin may be appropriately selected depending on the purpose. The average polymerization degree is usually 1000 to 10000, preferably 1200 to 4500, and more preferably 1500 to 4300. The average polymerization degree can be determined in accordance with JIS K6726-.

Examples of the dichroic material contained in the resin film include: iodine, organic dyes, and the like. These may be used alone or in combination of two or more. Iodine is preferably used.

The resin film may be a single-layer resin film or a laminate of two or more layers.

A specific example of the polarizer made of a single-layer resin film is a polarizer obtained by subjecting a PVA-based resin film to a dyeing treatment with iodine and a stretching treatment (typically uniaxial stretching). The dyeing with iodine is performed by, for example, immersing the PVA-based film in an aqueous iodine solution. The stretching ratio of the uniaxial stretching is preferably 3 to 7 times. The stretching may be performed after the dyeing treatment, or may be performed while dyeing. In addition, dyeing may be performed after stretching. The PVA-based resin film is subjected to swelling treatment, crosslinking treatment, washing treatment, drying treatment, and the like as necessary. For example, by immersing the PVA-based resin film in water and washing it with water before dyeing, not only dirt and an anti-blocking agent on the surface of the PVA-based film can be washed but also the PVA-based resin film can be swollen to prevent uneven dyeing and the like.

Specific examples of the polarizer obtained using the laminate include a laminate using a resin substrate and a PVA type resin layer (PVA type resin film) laminated on the resin substrate, and a polarizer obtained using a laminate of a resin substrate and a PVA type resin layer formed on the resin substrate by coating. A polarizer obtained by using a laminate of a resin substrate and a PVA-based resin layer formed on the resin substrate by coating can be produced by the following method: for example, a laminate of a resin base and a PVA type resin layer is obtained by applying a PVA type resin solution to a resin base and drying the solution to form a PVA type resin layer on the resin base; the laminate was stretched and dyed to prepare a polarizer from the PVA type resin layer. In the present embodiment, the stretching typically includes immersing the laminate in an aqueous boric acid solution to perform stretching. Further, the stretching may further include stretching the laminate in a gas atmosphere at a high temperature (for example, 95 ℃ or higher) before the stretching in the aqueous boric acid solution, as necessary. The obtained resin base material/polarizer laminate may be used as it is (that is, the resin base material may be used as a protective layer for the polarizer), or the resin base material may be peeled off from the resin base material/polarizer laminate and an arbitrary appropriate protective layer according to the purpose may be laminated on the peeled surface. Details of such a method for producing a polarizer are described in, for example, japanese patent laid-open nos. 2012 and 73580 and 6470455. The entire disclosures of these publications are incorporated herein by reference.

As described above, the thickness of the polarizer is 12 μm or less, preferably 1 to 12 μm, more preferably 3 to 10 μm, and still more preferably 3 to 8 μm. When the thickness of the polarizer is in such a range, the curling during heating can be favorably suppressed, and favorable durability of the appearance during heating can be obtained.

The polarizer preferably exhibits dichroism of absorption at any wavelength of 380nm to 780 nm. The polarizer has a single transmittance of, for example, 41.5% to 46.0%, preferably 43.0% to 46.0%, and more preferably 44.5% to 46.0%. The degree of polarization of the polarizer is preferably 97.0% or more, more preferably 99.0% or more, and still more preferably 99.9% or more.

B-2 protective layer

The visible-side protective layer 12 and the inner protective layer (if present) may be formed of any appropriate films that can be used as protective layers for polarizers, respectively. Specific examples of the material that becomes the main component of the film include cellulose resins such as Triacetylcellulose (TAC), polyesters, polyvinyl alcohols, polycarbonates, polyamides, polyimides, polyethersulfones, polysulfones, polystyrenes, polynorbornenes, polyolefins, (meth) acrylic acids, and transparent resins such as acetates. Further, there may be mentioned a heat-curable resin such as (meth) acrylic resins, carbamates, (meth) acrylic carbamates, epoxy resins, silicone resins, and ultraviolet-curable resins. In addition, for example, a glassy polymer such as a siloxane polymer is also included. Further, the polymer film described in Japanese patent application laid-open No. 2001-343529 (WO01/37007) may be used. As a material of the film, for example, a resin composition containing a thermoplastic resin having a substituted or unsubstituted imide group in a side chain and a thermoplastic resin having a substituted or unsubstituted phenyl group and a nitrile group in a side chain can be used, and examples thereof include: a resin composition having an alternating copolymer of isobutylene and N-methylmaleimide, and an acrylonitrile-styrene copolymer. The polymer film may be, for example, an extrusion molded product of the above resin composition.

The polarizing plate with a retardation layer is typically disposed on the viewing side of the image display device, and the viewing-side protective layer 12 is disposed on the viewing side. Therefore, the visible-side protective layer 12 may be subjected to surface treatment such as hard coating treatment, antireflection treatment, anti-sticking treatment, and antiglare treatment, as necessary. In addition, or alternatively, in the case of performing visual recognition by polarized sunglasses, the 1 st protective layer 12 may be subjected to a process for improving the visual recognition (typically, imparting a (elliptical) polarization function, imparting an ultra-high retardation) as necessary. By performing such processing, excellent visibility can be achieved even when the display screen is viewed through a polarizing lens such as a polarizing sunglass. Therefore, the polarizing plate with a retardation layer is also suitable for an image display device that can be used outdoors.

The thickness of the visible-side protective layer is preferably 30 μm or more, more preferably 30 μm to 100 μm, and still more preferably 30 μm to 60 μm. When the thickness of the protective layer is in such a range, the damage mark can be more remarkably suppressed by the synergistic effect with the residual depth of the pressure-sensitive adhesive layer. When the surface treatment layer is formed by subjecting the visible-side protective layer to surface treatment, the thickness of the visible-side protective layer is a thickness including the surface treatment layer.

The inner protective layer (where present) is preferably optically isotropic. In the present specification, "optically isotropic" means that the in-plane retardation Re (550) is 0 to 10nm and the retardation Rth (550) in the thickness direction is-10 to +10 nm. The thickness of the inner protective layer is preferably 5 to 80 μm, more preferably 10 to 40 μm, and still more preferably 10 to 30 μm. From the viewpoint of thinning, it is preferable that the protective layer be omitted. In the embodiment of the present invention, it is preferable that the retardation layer 30 simultaneously functions as an inner protective layer.

C. Adhesive layer

As the adhesive for forming the adhesive layer 20, any appropriate adhesive may be used as long as the desired residual depth can be achieved. Examples of the base resin of the binder include: acrylic resin, styrene resin, silicone resin, urethane resin, and rubber resin. From the viewpoints of chemical resistance, adhesion for preventing the penetration of a treatment liquid during immersion, freedom of an adherend, and the like, an acrylic resin is preferable. That is, the pressure-sensitive adhesive layer 20 may preferably be composed of an acrylic pressure-sensitive adhesive (acrylic pressure-sensitive adhesive composition). Typically, the acrylic adhesive composition contains a (meth) acrylic polymer as a main component. The (meth) acrylic polymer may be contained in the adhesive composition in a proportion of, for example, 50% by weight or more, preferably 70% by weight or more, and more preferably 90% by weight or more, of the solid content of the adhesive composition. The (meth) acrylic polymer contains, as a main component, an alkyl (meth) acrylate as a monomer unit. The term (meth) acrylate refers to an acrylate and/or a methacrylate. Examples of the alkyl group of the alkyl (meth) acrylate 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. Examples of the monomer constituting the (meth) acrylic polymer include, in addition to the alkyl (meth) acrylate: a carboxyl group-containing monomer (e.g., (meth) acrylic acid), a hydroxyl group-containing monomer (e.g., hydroxyethyl acrylate), an amide group-containing monomer (e.g., acrylamide), an aromatic ring-containing (meth) acrylate (e.g., benzyl acrylate), a heterocyclic ring-containing (meth) acrylate (e.g., acryloylmorpholine), a (meth) acrylate having a bridged ring structure (e.g., dicyclopentyl (meth) acrylate), and the like. The (meth) acrylic polymer preferably has a carboxyl group-containing monomer unit and a hydroxyl group-containing monomer unit. The content of the carboxyl group-containing monomer unit in the (meth) acrylic polymer is preferably 3 to 7% by weight, and the content of the hydroxyl group-containing monomer unit is preferably 0.05 to 0.1% by weight. With such a configuration, a desired residual depth can be achieved. The acrylic adhesive composition may preferably contain a silane coupling agent and/or a crosslinking agent. Examples of the silane coupling agent include: an epoxy group-containing silane coupling agent. Examples of the crosslinking agent include: isocyanate crosslinking agents and peroxide crosslinking agents. By appropriately combining the monomer unit of the (meth) acrylic polymer, the silane coupling agent, and the crosslinking agent, an acrylic pressure-sensitive adhesive having desired characteristics (as a result, a pressure-sensitive adhesive layer) can be obtained. The details of the pressure-sensitive adhesive layer or the acrylic pressure-sensitive adhesive composition are described in, for example, Japanese patent application laid-open Nos. 2007-138147, 2016-190996, and 2018-028573, and the descriptions of these publications are incorporated herein by reference.

The thickness of the pressure-sensitive adhesive layer 20 is preferably 6 to 25 μm, more preferably 6 to 15 μm, and still more preferably 10 to 15 μm. If the thickness of the pressure-sensitive adhesive layer is in such a range, bubbles can be suppressed when the polarizer and the retardation layer are bonded.

The creep value of the adhesive layer 20 is preferably 30 μm/h to 50 μm/h, more preferably 35 μm/h to 45 μm/h. If the creep value of the adhesive layer is in such a range, the damage mark can be remarkably suppressed. The creep value can be measured, for example, as follows. An adhesive composition is applied to a protective layer of a polarizing plate including the protective layer and a polarizer to form an adhesive layer, thereby producing a polarizing plate with an adhesive layer. The polarizing plate thus obtained was cut into a width of 10mm by a length of 50 mm. The cut polarizing plate with an adhesive layer was adhered to a stainless steel plate with the adhesive layer interposed therebetween at a width of 10mm × a length of 10mm, treated in an autoclave (50 ℃ C., 5 atm) for 15 minutes, and then allowed to stand at room temperature for 1 hour. After the sheet was left, the end of the pressure-sensitive adhesive layer-attached polarizing plate on the side not to be bonded to the stainless steel plate was subjected to a load (tensile load) of 500g at 23 ℃ for 1 hour, and the amount of displacement (amount of deformation) of the pressure-sensitive adhesive layer after the application of the load was measured using a laser creep tester, whereby the creep value of the pressure-sensitive adhesive layer could be measured.

D. Retardation layer

As described above, the retardation layer 30 has an in-plane retardation and has a slow axis. As described above, the retardation layer also serves as a protective layer for the polarizer and a retardation layer (or an optical compensation layer). With such a configuration, since it is not necessary to separately provide a protective layer and an optical compensation layer, it is possible to greatly contribute to the reduction in thickness of the image display device. The in-plane retardation Re (550) of the retardation layer is preferably 250 to 350nm, more preferably 270 to 330nm, and still more preferably 290 to 310 nm. If the in-plane retardation Re (550) of the retardation layer is in such a range, the moving distance on the poincare sphere is short, and therefore, excellent hue and luminance characteristics can be realized, and the color shift of the image display panel and the variation due to the retardation component of the TFT are also small.

For the phase difference layer, it is preferable that the refractive index characteristic shows a relationship of nx > nz > ny. By providing the retardation layer with such refractive index characteristics, the hue in the oblique direction of an image display device to which the polarizing plate with the retardation layer is applied can be favorably improved. In addition, since such an improvement in the color tone in the oblique direction can be performed without separately providing a retardation layer and a layer for performing optical compensation in the oblique direction, it is possible to contribute to a reduction in the thickness of the polarizing plate with a retardation layer (as a result, the image display device).

The Nz coefficient of the retardation layer is preferably 0.3 to 0.7, more preferably 0.4 to 0.6, and further preferably 0.45 to 0.55. If the Nz coefficient is in such a range, the hue in the oblique direction can be further improved favorably.

The phase difference layer may exhibit an inverse dispersion wavelength characteristic in which a phase difference value increases according to the wavelength of the measurement light, a positive wavelength dispersion characteristic in which a phase difference value decreases according to the wavelength of the measurement light, or a flat wavelength dispersion characteristic in which a phase difference value does not substantially vary according to the wavelength of the measurement light. Typically, the retardation layer exhibits flat wavelength dispersion characteristics.

The absolute value of the photoelastic coefficient of the retardation layer is preferably 15 × 10 ^-12 m ² A value of less than or equal to N, more preferably 10X 10 ^-12 m ² The ratio of the nitrogen to the nitrogen is less than N. The lower limit of the absolute value of the photoelastic coefficient may be, for example, 1.0 × 10 ^-12 m ² and/N. If the absolute value of the photoelastic coefficient of the phase difference layer is in such a range, display unevenness of the image display device can be favorably suppressed.

The retardation layer is typically a retardation film formed of any appropriate resin capable of achieving the above-described characteristics. Examples of the resin for forming the retardation film include: cyclic olefin resins, polyarylates, polyamides, polyimides, polyesters, polyaryletherketones, polyamideimides, polyesterimides, polyvinyl alcohols, polyfumarates, polyethersulfones, polysulfones, polycarbonate resins, cellulose resins, and polyurethanes. These resins may be used alone or in combination. Preferred are cyclic olefin resins. As a typical example of the cyclic olefin resin, a norbornene resin can be given.

The norbornene-based resin is obtained by polymerizing a norbornene-based monomer as a polymerization unit. Examples of the norbornene-based monomer include: norbornene, and alkyl and/or alkylidene substituents thereof, for example: polar group-substituted compounds such as 5-methyl-2-norbornene, 5-dimethyl-2-norbornene, 5-ethyl-2-norbornene, 5-butyl-2-norbornene and 5-ethylidene-2-norbornene, and halogen thereof; dicyclopentadiene, 2, 3-dihydrodicyclopentadiene, and the like; dimethyl octahydronaphthalene, alkyl and/or alkylidene substituents thereof, and polar group substituents such as halogen, for example: 6-methyl-1, 4:5, 8-dimethylbridge-1, 4,4a,5,6,7,8,8 a-octahydronaphthalene, 6-ethyl-1, 4:5, 8-dimethylbridge-1, 4,4a,5,6,7,8,8 a-octahydronaphthalene, 6-ethylidene-1, 4:5, 8-dimethylbridge-1, 4,4a,5,6,7,8,8 a-octahydronaphthalene, 6-chloro-1, 4:5, 8-dimethylbridge-1, 4,4a,5,6,7,8,8 a-octahydronaphthalene, 6-cyano-1, 4:5, 8-dimethylbridge-1, 4,4a,5,6,7,8,8 a-octahydronaphthalene, 6-pyridyl-1, 4:5, 8-dimethylbridge-1, 4,4a,5,6,7,8,8 a-octahydronaphthalene, 6-methoxycarbonyl-1, 4:5, 8-dimethylbridge-1, 4,4a,5,6,7,8,8 a-octahydronaphthalene, etc.; 3-4 mers of cyclopentadiene, for example: 4,9:5, 8-dimethyl-3 a,4,4a,5,8,8a,9,9 a-octahydro-1H-benzindene, 4,11:5,10:6, 9-trimethyl-3 a,4,4a,5,5a,6,9,9a,10,10a,11,11 a-dodecahydro-1H-cyclopenta anthracene, and the like. The norbornene-based resin may be a copolymer of a norbornene-based monomer and another monomer.

The retardation layer (retardation film) is a stretched film of a film formed of the above resin. As a method for producing the stretched film, any suitable method can be used. Typically, a shrinkable film is laminated on one or both surfaces of the resin film, and the resultant film is heated and stretched. The shrinkable film is used to impart a shrinking force in a direction orthogonal to the stretching direction during heat stretching. By applying such a shrinking force, nz can be increased, and as a result, a Z film can be produced. Examples of the material for the shrinkable film include: polyester, polystyrene, polyethylene, polypropylene, polyvinyl chloride, polyvinylidene chloride, and the like. From the viewpoint of excellent shrinkage uniformity and heat resistance, a polypropylene film is preferably used.

As the stretching method, any suitable stretching method may be employed as long as it can apply a tensile force in the stretching direction of the resin film and a contractive force in the direction perpendicular to the stretching direction in the film plane. The stretching temperature is preferably not less than the glass transition temperature (Tg) of the resin film. This is because the retardation value of the obtained stretched film is likely to be uniform, and the film is less likely to be crystallized (cloudy). The stretching temperature is more preferably from Tg +1 to Tg +30 ℃, still more preferably from Tg +2 to Tg +20 ℃, particularly preferably from Tg +3 to Tg +15 ℃, and most preferably from Tg +5 to Tg +10 ℃ of the polymer film. By setting the stretching temperature in such a range, uniform heating stretching can be performed. Further, it is preferable that the stretching temperature is constant in the film width direction. This is because a stretched film having good optical uniformity with little variation in phase difference value can be produced.

The stretching ratio in the stretching may be set to any appropriate value. Preferably 1.05 to 2.00 times, more preferably 1.10 to 1.50 times, and particularly preferably 1.20 to 1.40 times. By setting the stretching ratio in such a range, a stretched film having less shrinkage in the film width and excellent mechanical strength can be obtained.

The thickness of the retardation layer is preferably 80 to 200. mu.m, more preferably 90 to 150. mu.m, and still more preferably 110 to 150. mu.m. With such a thickness, a desired in-plane retardation value can be obtained.

E. Image display device

The polarizing plate with a retardation layer according to the embodiment of the present invention can be applied to an image display device. Typically, the polarizing plate with a retardation layer is disposed on the viewing side of the image display device so that the polarizing plate is on the viewing side. Typical examples of the image display device include a liquid crystal display device, an organic Electroluminescence (EL) display device, and a quantum dot display device. The liquid crystal display device is preferably an IPS mode liquid crystal display device. This is because the hue improvement in the oblique direction is more remarkable. The image display device is preferably a large-sized (for example, 27 inches or more for a television) image display device. This is because the effect of suppressing the damage trace by optimizing the remaining depth of the adhesive layer is remarkable.

Examples

The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. The evaluation methods in the examples are as follows. Unless otherwise specified, "parts" and "%" in the examples are based on weight.

(1) Depth of survival

An adhesive sheet was formed from the adhesive prepared in the manufacturing example. The obtained adhesive sheet was stuck to a glass plate, and the surface of the adhesive sheet was scratched while applying a load thereto by a micro-load automatic scratch tester. The depth of penetration when scraping was performed with a 3N load was measured by a displacement sensor and taken as the remaining depth.

(2) Damage trace

The polarizing plates with retardation layers obtained in examples and comparative examples were cut into 50mm in the longitudinal direction and 25mm in the transverse direction to obtain measurement samples. The measurement sample was attached to the glass plate via a usual acrylic adhesive (corresponding to the other adhesive layer). The measurement sample adhered to the glass plate was reciprocated in the longitudinal direction by a slide tester in a state in which the guitar pick with the weight attached thereto was pressed against the adhesive sheet with a load of 3N. The number of reciprocations was set to 1, 5,10, 50 and 70. Then, the measurement sample was put into an oven at 95 ℃ for 1 hour. The measurement sample taken out of the oven was evaluated by the following criteria, with no damage trace being observed with a microscope.

Excellent: no damage mark was confirmed even after 70 cycles

Good: no damage mark was observed after 50 reciprocations, but damage marks were observed after 70 reciprocations

Unqualified: no damage mark was observed after 10 passes, but damage marks were observed after 50 passes

Difference: the trace of the damage was confirmed by 1, 5 or 10 reciprocations

(3) Appearance of the product

The polarizing plates with a retardation layer obtained in examples and comparative examples were evaluated by visually observing the state of bubbles between the polarizer and the retardation layer at the time of production (at the time of bonding the polarizer and the retardation layer) according to the following criteria.

Good: no bubble was observed

It is permissible that: a small amount of bubbles was observed, but the display characteristics were not affected

Unqualified: confirming that the degree of influence on display characteristics is high

The appearance evaluation was performed in two evaluations.

Production example 1: preparation of adhesive constituting adhesive layer

100 parts of butyl acrylate, 5 parts of acrylic acid, 0.075 part of 2-hydroxyethyl acrylate, and 0.3 part of 2, 2' -azobisisobutyronitrile were added to a reaction vessel equipped with a condenser tube, a nitrogen inlet tube, a thermometer, and a stirrer together with ethyl acetate to prepare a solution. Then, the solution was stirred while blowing nitrogen gas, and reacted at 60 ℃ for 4 hours to obtain a solution containing an acrylic polymer having a weight average molecular weight of 220 ten thousand. Ethyl acetate was further added to the acrylic polymer-containing solution to obtain an acrylic polymer solution (a1) having a solid content concentration of 30%.

The obtained acrylic polymer solution (a1) was mixed with a crosslinking agent containing 0.6 part of a compound having an isocyanate group as a main component (product name "Coronate L" from japan polyurethane corporation) as a crosslinking agent and 0.075 part of γ -glycidoxypropyltrimethoxysilane (product name "KMB-403" from shin-Etsu chemical corporation) as a silane coupling agent in this order with respect to 100 parts of the solid content of the acrylic polymer solution (a1) to prepare a pressure-sensitive adhesive a. The remaining depth of the adhesive layer (adhesive sheet) formed by the adhesive A was 10.7 mm.

Production example 2: preparation of adhesive constituting adhesive layer

99 parts of butyl acrylate, 1.0 part of 4-hydroxybutyl acrylate and 0.3 part of 2, 2' -azobisisobutyronitrile were added together with ethyl acetate to a reaction vessel equipped with a condenser tube, a nitrogen inlet tube, a thermometer and a stirrer, and reacted at 60 ℃ for 4 hours under a nitrogen stream. Subsequently, ethyl acetate was added to the reaction solution to obtain a solution (solid content concentration 30%) containing an acrylic polymer having a weight average molecular weight of 165 ten thousand. To the resulting acrylic polymer solution, 0.15 part of dibenzoyl peroxide (trade name: NYPER BO-Y, manufactured by Nippon oil and fat Co., Ltd.), 0.08 part of trimethylolpropane xylylene diisocyanate (trade name: Takenate D110N, manufactured by Mitsui Kogyo chemical Co., Ltd.) and 0.2 part of a silane coupling agent (trade name: A-100, manufactured by Sukikai chemical Co., Ltd., acetoacetyl group-containing silane coupling agent) were added to prepare an adhesive B. The remaining depth of the adhesive layer (adhesive sheet) formed by the adhesive B was 12.5 mm.

[ example 1]

1. Manufacture of polarizer

As the resin base material, a long-sized amorphous isophthalic acid copolymerized polyethylene terephthalate (IPA copolymerized PET) film (thickness: 100 μm) having a water absorption of 0.75% and a Tg of 75 ℃ was used. One surface of the substrate was subjected to corona treatment, and an aqueous solution containing polyvinyl alcohol (polymerization degree 4200, saponification degree 99.2 mol%) and acetoacetyl-modified PVA (polymerization degree 1200, acetoacetyl-modification degree 4.6%, saponification degree 99.0 mol% or more, manufactured by japan synthetic chemical industries co., ltd., trade name "GOHSEFIMER Z200") at a ratio of 9:1 was applied to the corona-treated surface at 25 ℃ and dried to form a PVA-based resin layer having a thickness of 11 μm, thereby producing a laminate.

The obtained laminate was subjected to free-end uniaxial stretching (auxiliary stretching in a gas atmosphere) of 2.0 times in the longitudinal direction (longitudinal direction) in an oven at 120 ℃ between rolls having different peripheral speeds.

Next, the laminate was immersed in an insolubilization bath (an aqueous boric acid solution prepared by mixing 4 parts by weight of boric acid with 100 parts by weight of water) at a liquid temperature of 30 ℃ for 30 seconds (insolubilization treatment).

Next, in a dyeing bath at a liquid temperature of 30 ℃, immersion was performed while adjusting the iodine concentration and immersion time so that the polarizing plate could have a predetermined transmittance. In this example, an aqueous iodine solution prepared by adding 0.2 parts by weight of iodine and 1.5 parts by weight of potassium iodide to 100 parts by weight of water was immersed for 60 seconds (dyeing treatment).

Subsequently, the substrate was immersed in a crosslinking bath (an aqueous boric acid solution prepared by mixing 3 parts by weight of potassium iodide with 100 parts by weight of water and boric acid) at a liquid temperature of 30 ℃ for 30 seconds (crosslinking treatment).

Then, the laminate was immersed in an aqueous boric acid solution (aqueous solution prepared by mixing 4 parts by weight of boric acid and 5 parts by weight of potassium iodide with respect to 100 parts by weight of water) at a liquid temperature of 70 ℃ and uniaxially stretched (stretched in an aqueous solution) between rolls having different peripheral speeds so that the total stretching ratio was 5.5 times in the longitudinal direction (longitudinal direction).

Then, the laminate was immersed in a cleaning bath (aqueous solution containing 4 parts by weight of potassium iodide per 100 parts by weight of water) at a liquid temperature of 30 ℃ (cleaning treatment).

Finally, the laminate was dried to obtain a laminate having a polarizer formed on a resin base. The polarizer had a thickness of 5 μm and a monomer transmittance of 42.3%.

2. Attachment of protective layer

An acrylic resin film (thickness: 40 μm) containing a lactone ring structure was bonded as a protective layer to the polarizer surface of the laminate obtained in the above item 1 via an ultraviolet-curable adhesive. Specifically, the curable adhesive was applied so that the total thickness became 1.0 μm, and was bonded using a roll machine. Then, UV light is irradiated from the protective layer side to cure the adhesive. Next, the resin base material was peeled off, and a laminate having a protective layer (acrylic resin film)/polarizer was obtained.

3. Production of retardation layer (retardation film)

A shrinkable film having a thickness of 60 μm (trade name "TORAYFAN BO 2873" manufactured by Toray corporation) was laminated on both sides of a norbornene-based resin film having a thickness of 130 μm via an acrylic pressure-sensitive adhesive layer (thickness 15 μm) "]. Then, the film was stretched in the air circulation type oven at 146 ℃ by a factor of 1.38 while keeping the film length direction by a roll stretcher, and after stretching, the shrinkable film was peeled off together with the acrylic pressure-sensitive adhesive layer to prepare a retardation film. The obtained retardation film exhibited refractive index characteristics of nx > Nz > ny, Re (550) was 280nm, Nz coefficient was 0.52, and photoelastic coefficient was 4.0X 10 ^-12 m ² and/N, the thickness is 138 μm.

4. Production of polarizing plate with retardation layer

The retardation film (retardation layer) obtained in the above 3 was bonded to the polarizer surface of the laminate obtained in the above 2 via the adhesive a (thickness 12 μm) obtained in production example 1. Thus, a polarizing plate with a retardation layer having a structure of a protective layer, a polarizer, an adhesive layer, and a retardation layer was obtained. The obtained polarizing plate with a retardation layer was subjected to the evaluations (2) and (3). The results are shown in Table 1.

[ example 2]

A polarizing plate with a retardation layer was obtained in the same manner as in example 1, except that the thickness of the adhesive a was changed to 23 μm. The obtained polarizing plate with a retardation layer was subjected to the same evaluation as in example 1. The results are shown in Table 1.

[ example 3]

A polarizing plate with a retardation layer was obtained in the same manner as in example 1, except that the thickness of the adhesive a was changed to 5 μm. The obtained polarizing plate with a retardation layer was subjected to the same evaluation as in example 1. The results are shown in Table 1.

Comparative example 1

A polarizing plate with a retardation layer was obtained in the same manner as in example 1, except that an adhesive B (thickness 12 μm) was used instead of the adhesive a. The obtained polarizing plate with a retardation layer was subjected to the same evaluation as in example 1. The results are shown in Table 1.

Comparative example 2

A polarizing plate with a retardation layer was obtained in the same manner as in example 1, except that an adhesive B (thickness 20 μm) was used instead of the adhesive a. The obtained polarizing plate with a retardation layer was subjected to the same evaluation as in example 1. The results are shown in Table 1.

[ reference example 1]

1. Manufacture of polarizer

A polyvinyl alcohol resin film having an average polymerization degree of 2400, a saponification degree of 99.9 mol% and a thickness of 50 μm was prepared. The polyvinyl alcohol film was stretched 2.4 times in the transport direction between rolls having a peripheral speed ratio different from that of each other while being swollen by immersing it in a swelling bath (water bath) at 20 ℃ for 30 seconds (swelling step), and then, was immersed and dyed in a dyeing bath (aqueous solution having an iodine concentration of 0.03 wt% and a potassium iodide concentration of 0.3 wt%) at 30 ℃ so that the monomer transmittance after final stretching became a desired value, and was stretched 3.7 times in the transport direction based on the original polyvinyl alcohol film (polyvinyl alcohol film which was not stretched at all in the transport direction) (dyeing step). The immersion time was about 60 seconds. Next, the dyed polyvinyl alcohol film was stretched 4.2 times in the transport direction based on the original polyvinyl alcohol film while being immersed in a crosslinking bath (aqueous solution having a boric acid concentration of 3.0 wt% and a potassium iodide concentration of 3.0 wt%) at 40 ℃. Further, the obtained polyvinyl alcohol film was immersed in a stretching bath (an aqueous solution having a boric acid concentration of 4.0 wt% and a potassium iodide concentration of 5.0 wt%) at 64 ℃ for 50 seconds, stretched 6.0 times in the carrying direction based on the original polyvinyl alcohol film (stretching step), and then immersed in a cleaning bath (an aqueous solution having a potassium iodide concentration of 3.0 wt%) at 20 ℃ for 5 seconds (cleaning step). The washed polyvinyl alcohol film was dried at 30 ℃ for 2 minutes to prepare a polarizer (thickness: 20 μm).

2. Polarizing plate and production of polarizing plate with retardation layer

An acrylic resin film (thickness: 40 μm) containing a lactone ring structure was bonded as a protective layer to the surface of the polarizer obtained in the above 1. in the same manner as in example 1, to obtain a laminate having a structure of protective layer (acrylic resin film)/polarizer. The subsequent steps were carried out in the same manner as in example 1 to obtain a polarizing plate with a retardation layer. The obtained polarizing plate with a retardation layer was subjected to the same evaluation as in example 1. The results are shown in Table 1.

[ Table 1]

[ evaluation ]

As is clear from table 1, according to the examples of the present invention, the damage trace can be significantly suppressed. Further, according to the reference example, such a damage mark is a problem unique to a thin polarizer.

Industrial applicability

The polarizing plate with a retardation layer of the present invention can be suitably used as an image display device such as a liquid crystal display device, an organic EL display device, or a quantum dot display device, and particularly can be suitably used as a liquid crystal display device.

Claims

1. A polarizing plate with a retardation layer, comprising:

a polarizing plate comprising a polarizer and a protective layer provided at least on the viewing side of the polarizer, and

a retardation layer bonded to the side of the polarizing plate opposite to the visible side via an adhesive layer,

the polarizer has a thickness of 12 μm or less,

the adhesive layer has a residual depth of 11 [ mu ] m or less when a 3N load is applied.

2. The polarizing plate with a phase difference layer according to claim 1,

the thickness of the adhesive layer is 6-15 μm.

3. The polarizing plate with a phase difference layer according to claim 1 or 2,

the thickness of the protective layer on the visible side is 30 [ mu ] m or more.

4. The polarizing plate with a retardation layer according to any one of claims 1 to 3,

the phase difference layer exhibits a refractive index characteristic of nx > nz > ny.

5. The polarizing plate with a phase difference layer according to claim 4,

the Nz coefficient of the phase difference layer is 0.3-0.7.

6. The polarizing plate with a phase difference layer according to claim 4 or 5,

the retardation layer has an in-plane retardation Re (550) of 250 to 350nm, a thickness of 150 [ mu ] m or less, and a photoelastic coefficient of 1.0X 10 ^-12 m ² More than/N.

7. The polarizing plate with a retardation layer according to any one of claims 4 to 6,

the phase difference layer contains a cyclic olefin resin.

8. The polarizing plate with a retardation layer according to any one of claims 1 to 7,

the slow axis of the retardation layer is at an angle substantially orthogonal or substantially parallel to the absorption axis of the polarizer.

9. An image display device comprising the polarizing plate with a retardation layer according to any one of claims 1 to 8.