JP7664759B2 - Manufacturing method for image display panel and polarizing plate with surface protective film - Google Patents

Description

The present invention relates to a method for manufacturing an image display panel, a surface protective film, and a polarizing plate with a surface protective film.

Image display panels, such as liquid crystal display devices and electroluminescence (EL) display panels (e.g., organic EL display devices, inorganic EL display devices), are rapidly becoming popular. In image display panels, a polarizing plate is typically disposed on the viewing side of the image display panel. During the manufacture (including inspection) of the image display panel, for example, in order to prevent the image display panel surface (e.g., the polarizing plate surface) from being scratched, a surface protective film is usually attached to the polarizing plate side of the image display panel. However, during the manufacture (including inspection) of the image display panel, there is a problem in that the manufacturing efficiency decreases due to the quality of the surface protective film.

JP 2017-149923 A

The present invention has been made to solve the above-mentioned problems in the conventional art, and its main objective is to provide a manufacturing method for an image display panel that suppresses a decrease in manufacturing efficiency, and to provide a surface protection film that contributes to suppressing a decrease in the manufacturing efficiency of an image display panel.

A manufacturing method for an image display panel in an embodiment of the present invention is a manufacturing method for an image display panel that uses a surface protective film that is attached to the viewing side of a polarizing plate that is arranged on the viewing side of the image display panel main body, and includes a substrate having opposing first and second main surfaces and an adhesive layer that is arranged on the second main surface side of the substrate, wherein the surface resistance value of the first main surface side of the surface protective film is 1.0 x 10 ⁸ Ω/□ or more, and the peel strength of the surface protective film with respect to the polarizing plate is 0.03 N/25 mm or more.
In one embodiment, the production method includes preparing a polarizing plate with a surface protective film, the polarizing plate having the polarizing plate and the surface protective film attached to one side of the polarizing plate.
In one embodiment, the reflectance of the viewing side of the polarizing plate is 2.5% to 3.0%.
In one embodiment, the water contact angle of the viewing side of the polarizing plate is 95° or more.
In one embodiment, the image display panel body includes a touch panel.

According to another aspect of the present invention, there is provided a surface protection film. The surface protection film in an embodiment of the present invention includes a substrate and a pressure-sensitive adhesive layer, the substrate has a first main surface and a second main surface opposed to each other, a pressure-sensitive adhesive layer is disposed on the second main surface side of the substrate, the surface resistance value of the first main surface side of the surface protection film is 1.0×10 ⁸ Ω/□ or more, the pressure-sensitive adhesive layer includes an acrylic pressure-sensitive adhesive, the acrylic pressure-sensitive adhesive includes a (meth)acrylic polymer having a polar functional group, and the content of the monomer component having the polar functional group is 1.0 to 10.0 parts by weight relative to 100 parts by weight of the monomer forming the (meth)acrylic polymer.
In one embodiment, the surface protective film further includes a treatment layer, and the treatment layer is formed on the first main surface side of the base material.
In one embodiment, the treatment layer comprises a quaternary ammonium cation-containing polymer.
In another embodiment, there is provided a polarizing plate with a surface protective film. This polarizing plate with a surface protective film includes the above polarizing plate and the above surface protective film on the viewing side of the polarizing plate.

According to an embodiment of the present invention, in a manufacturing method for an image display panel, a surface protective film is used that is attached to the viewing side of a polarizing plate that is arranged on the viewing side of the image display panel main body, and includes a substrate having opposing first and second main surfaces and an adhesive layer that is arranged on the second main surface side of the substrate, and the surface resistance value of the first main surface side of the surface protective film is 1.0 x 10 ⁸ Ω/□ or more, and the peel strength of the surface protective film with respect to the polarizing plate is 0.03 N/25 mm or more, thereby suppressing a decrease in the manufacturing efficiency of the image display panel.

According to another aspect of the present invention, a surface protective film includes a substrate and an adhesive layer, the substrate having opposing first and second main surfaces, an adhesive layer disposed on the second main surface side of the substrate, the surface resistance value of the first main surface side of the surface protective film is 1.0 x 10 ⁸ Ω/□ or more, the adhesive layer includes an acrylic adhesive, the acrylic adhesive includes a (meth)acrylic polymer having a polar functional group, and the content of the monomer component having the polar functional group is 1.0 part by weight to 10.0 parts by weight relative to 100 parts by weight of monomers forming the (meth)acrylic polymer, thereby contributing to suppression of a decrease in the manufacturing efficiency of image display panels.

1 is a schematic cross-sectional view showing a general configuration of an example of an image display panel of the present invention. FIG. 1 is a schematic cross-sectional view showing a schematic configuration of one example of a polarizing plate constituting an image display panel of the present invention. FIG. 2 is a schematic cross-sectional view showing an example of a functional layer constituting the polarizing plate of the present invention. FIG. 2 is a schematic cross-sectional view showing an example of a surface protective film constituting the image display panel of the present invention.

The following describes embodiments of the present invention, but the present invention is not limited to these embodiments.

(Definition of terms and symbols)
The definitions of terms and symbols used in this specification are as follows.
(1) Refractive index (nx, ny, nz)
"nx" is the refractive index in the direction in which the in-plane refractive index is maximum (i.e., the slow axis direction), "ny" is the refractive index in the direction perpendicular to the slow axis in the plane (i.e., the fast axis direction), and "nz" is the refractive index in the thickness direction.
(2) In-plane phase difference (Re)
"Re(λ)" is the in-plane retardation measured with light having a wavelength of λ nm at 23° C. For example, "Re(550)" is the in-plane retardation measured with light having a wavelength of 550 nm at 23° C. Re(λ) is calculated by the formula: Re(λ)=(nx−ny)×d, where d (nm) is the thickness of the layer (film).
(3) Retardation in the thickness direction (Rth)
"Rth(λ)" is the retardation in the thickness direction measured with light having a wavelength of λ nm at 23° C. For example, "Rth(550)" is the retardation in the thickness direction measured with light having a wavelength of 550 nm at 23° C. Rth(λ) is calculated by the formula: Rth(λ)=(nx-nz)×d, where d (nm) is the thickness of the layer (film).
(4) Nz Coefficient The Nz coefficient is calculated by Nz=Rth/Re.
(5) Angle When referring to an angle in this specification, the angle includes both clockwise and counterclockwise angles with respect to a reference direction. Thus, for example, "45°" means ±45°.

A. Manufacturing method of image display panel The manufacturing method of the image display panel according to the embodiment of the present invention uses a surface protective film that is attached to the viewing side of a polarizing plate arranged on the viewing side of an image display panel body. Fig. 1 is a schematic cross-sectional view showing the outline of an example of an image display panel obtained by the manufacturing method of the image display panel according to the embodiment of the present invention. In Fig. 1, an organic EL panel is taken as an example of the image display panel.

The image display panel (organic EL panel) 100 comprises an image display panel (organic EL panel) main body 50 and a polarizing plate 200 with a surface protective film. The polarizing plate 200 with a surface protective film comprises a polarizing plate 20 and a surface protective film 10 bonded to one side of the polarizing plate 20. In the illustrated example, the polarizing plate 200 with a surface protective film comprises a retardation layer 30 and an adhesive layer 40 arranged on the other side of the polarizing plate 20. The surface protective film 10 may be peeled off during the manufacturing process of the final product (e.g., an image display device), or may be mounted directly on the final product.

The manufacturing method of the image display panel according to the embodiment of the present invention preferably includes preparing a polarizing plate with a surface protective film having a polarizing plate and a surface protective film laminated to one side of the polarizing plate. Specifically, the polarizing plate with a surface protective film 200 is laminated to the organic EL panel body 50 to obtain the organic EL panel 100. In the example shown in FIG. 1, the polarizing plate with a surface protective film 200 includes a retardation layer 30 and an adhesive layer 40, but may include other members. In practical use, a separator is temporarily attached to the adhesive layer 40 side of the polarizing plate with a surface protective film 200 in a peelable manner (not shown). By temporarily attaching the separator, the adhesive layer is protected until the polarizing plate with a surface protective film is used, and the polarizing plate with a surface protective film can be rolled. Furthermore, any suitable adhesive layer (not shown) is used for laminating each layer constituting the image display panel of the present invention.

The components of an image display panel according to an embodiment of the present invention are described in more detail below.

B. Image display panel body The image display panel (organic EL panel) body 50 typically includes a substrate, a circuit layer including thin film transistors (TFTs) and the like, organic light emitting diodes (OLEDs), and an upper structure layer including a sealing film for sealing the OLEDs (none of which are shown). The image display panel body 50 may further include a touch panel (not shown). The touch panel typically includes a conductive layer.

The conductive layer can be formed by forming a metal oxide film on any suitable substrate by any suitable film forming method (e.g., vacuum deposition, sputtering, CVD, ion plating, spraying, etc.). Examples of metal oxides include indium oxide, tin oxide, zinc oxide, indium-tin composite oxide, tin-antimony composite oxide, zinc-aluminum composite oxide, and indium-zinc composite oxide. Among these, indium-tin composite oxide (ITO) is preferred.

When the conductive layer contains a metal oxide, the thickness of the conductive layer is preferably 50 nm or less, more preferably 35 nm or less. The lower limit of the thickness of the conductive layer is preferably 10 nm.

The conductive layer may be patterned as necessary. By patterning, conductive portions and insulating portions may be formed. As a result, electrodes may be formed. The electrodes may function as touch sensor electrodes that detect contact with the touch panel. Any appropriate method may be used as the patterning method. Specific examples of patterning methods include wet etching and screen printing.

C. Polarizing Plate with Surface Protective Film As shown in Fig. 1, the polarizing plate with a surface protective film 200 includes a polarizing plate 20 and a surface protective film 10 bonded to one side of the polarizing plate 20. As described above, the polarizing plate with a surface protective film 200 may further include a retardation layer 30 and a pressure-sensitive adhesive layer 40. The components of the polarizing plate with a surface protective film will be described in more detail below.

C-1. Polarizing Plate FIG. 2 is a schematic cross-sectional view showing an example of a polarizing plate constituting the image display panel shown in FIG. 1. FIG. 3 is a schematic cross-sectional view showing an example of a functional layer constituting the polarizing plate shown in FIG. 2. As shown in FIG. 2, the polarizing plate 20 includes a polarizer 21 and a protective layer 22. If necessary, a protective layer may be further provided on the image panel body side of the polarizer 21 (not shown). Furthermore, the polarizing plate 20 according to one embodiment of the present invention includes a functional layer 23 on the viewing side of the protective layer 22. The components of the polarizing plate will be described in detail below.

C-1-1. Polarizer Any appropriate polarizer may be used as the polarizer. For example, the resin film forming the polarizer may be a single-layer resin film. The polarizer may also be formed using a laminate of two or more layers.

Specific examples of polarizers made of a single-layer resin film include hydrophilic polymer films such as polyvinyl alcohol (PVA)-based films, partially formalized PVA-based films, and partially saponified ethylene-vinyl acetate copolymer films that have been dyed with iodine or a dichroic substance such as a dichroic dye and stretched, and polyene-based oriented films such as dehydrated PVA and dehydrochlorinated polyvinyl chloride. Preferably, a polarizer obtained by dyeing a PVA-based film with iodine and stretching it uniaxially is used because of its excellent optical properties.

The dyeing with iodine is carried out, for example, by 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 carried out after the dyeing process, or may be carried out while dyeing. Alternatively, the film may be stretched and then dyed. If necessary, the PVA-based film may be subjected to a swelling process, a crosslinking process, a washing process, a drying process, or the like. For example, by immersing the PVA-based film in water and washing it with water before dyeing, it is possible to wash off dirt and anti-blocking agents on the surface of the PVA-based film, and also to swell the PVA-based film and prevent uneven dyeing.

Specific examples of polarizers obtained using a laminate include a laminate of a resin substrate and a PVA-based resin layer (PVA-based resin film) laminated on the resin substrate, or a polarizer obtained using a laminate of a resin substrate and a PVA-based resin layer coated on the resin substrate. A polarizer obtained using a laminate of a resin substrate and a PVA-based resin layer coated on the resin substrate can be produced, for example, by applying a PVA-based resin solution to a resin substrate and drying the substrate to form a PVA-based resin layer on the resin substrate to obtain a laminate of the resin substrate and the PVA-based resin layer; stretching and dyeing the laminate to make the PVA-based resin layer into a polarizer. In this embodiment, a polyvinyl alcohol-based resin layer containing a halide and a polyvinyl alcohol-based resin is preferably formed on one side of the resin substrate. Stretching typically involves immersing the laminate in an aqueous boric acid solution and stretching it. Furthermore, the stretching may further include air-stretching the laminate at a high temperature (e.g., 95°C or higher) before stretching in the boric acid aqueous solution, as necessary. In addition, in this embodiment, the laminate is preferably subjected to a drying shrinkage treatment in which the laminate is heated while being conveyed in the longitudinal direction, thereby shrinking the laminate by 2% or more in the width direction. Typically, the manufacturing method of this embodiment includes subjecting the laminate to an air-assisted stretching treatment, a dyeing treatment, an underwater stretching treatment, and a drying shrinkage treatment in this order. By introducing the auxiliary stretching, it is possible to increase the crystallinity of PVA even when PVA is applied onto a thermoplastic resin, and it is possible to achieve high optical properties. At the same time, by increasing the orientation of PVA in advance, problems such as a decrease in the orientation of PVA or dissolution can be prevented when the PVA is immersed in water in the subsequent dyeing step or stretching step, and it is possible to achieve high optical properties. Furthermore, when the PVA-based resin layer is immersed in a liquid, the disorder of the orientation of polyvinyl alcohol molecules and the decrease in orientation can be suppressed compared to when the PVA-based resin layer does not contain a halide. This can improve the optical properties of the polarizer obtained by immersing the laminate in a liquid in a treatment process such as a dyeing process and an underwater stretching process. Furthermore, the optical properties can be improved by shrinking the laminate in the width direction by a drying shrinkage process. The obtained resin substrate/polarizer laminate may be used as it is (i.e., the resin substrate may be used as a protective layer for the polarizer), or the resin substrate may be peeled off from the resin substrate/polarizer laminate and any suitable protective layer according to the purpose may be laminated on the peeled surface. Details of the manufacturing method of such a polarizer are described in, for example, JP-A-2012-73580 (Patent No. 5414738) and Japanese Patent No. 6470455. The entire disclosures of these publications are incorporated herein by reference.

The thickness of the polarizer is preferably 10 μm or less, more preferably 8 μm or less, and even more preferably 6 μm or less. The lower limit of the thickness of the polarizer can be, for example, 1 μm.

The polarizer preferably exhibits absorption dichroism at any wavelength between 380 nm and 780 nm. The single transmittance of the polarizer is, for example, 41.5% to 46.0%, preferably 43.0% to 46.0%, and 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 even more preferably 99.9% or more.

C-1-2. Protective layer The protective layer is formed of any suitable film. Specific examples of the material that is the main component of the film include cellulose-based resins such as triacetyl cellulose (TAC), polyester-based, polyvinyl alcohol-based, polycarbonate-based, polyamide-based, polyimide-based, polyethersulfone-based, polysulfone-based, polystyrene-based, polynorbornene-based, polyolefin-based, (meth)acrylic-based, acetate-based, and other transparent resins. In addition, examples include thermosetting resins or ultraviolet-curing resins such as (meth)acrylic-based, urethane-based, (meth)acrylic urethane-based, epoxy-based, and silicone-based resins. In addition, examples include glassy polymers such as siloxane-based polymers. In addition, the polymer films described in JP-A-2001-343529 (WO01/37007) can also be used. As the material for this film, for example, a resin composition containing a thermoplastic resin having a substituted or unsubstituted imide group in the side chain and a thermoplastic resin having a substituted or unsubstituted phenyl group and a nitrile group in the side chain can be used, for example, a resin composition containing an alternating copolymer of isobutene and N-methylmaleimide, and an acrylonitrile-styrene copolymer. The polymer film is, for example, an extrusion molded product of the above resin composition.

The thickness of the protective layer is preferably 45 μm or less, more preferably 40 μm or less, and even more preferably 35 μm or less. The lower limit of the thickness of the protective layer is, for example, 10 μm.

The protective layer disposed on the viewing side of the polarizing plate is subjected to surface treatment such as hard coat treatment, anti-reflection treatment (low reflection treatment), anti-sticking treatment, and anti-glare treatment as necessary, to form a functional layer. Note that, when a functional layer is formed, the thickness of the protective layer includes the thickness of the functional layer.

The polarizing plate according to the embodiment of the present invention is typically disposed on the viewing side of the image display panel body. Furthermore, as described above, the protective layer is disposed on the viewing side of the polarizing plate. Here, for example, when an organic EL panel (OLED) is used as a mobile device, a glass plate may not be disposed on the viewing side for the purpose of reducing weight, etc. In such cases, a surface treatment may be applied to the viewing side of the image display panel (i.e., the viewing side of the polarizing plate).

The reflectance of the viewing side of the polarizing plate is preferably 2.5% to 3.0%, and more preferably 2.6% to 2.9%. Having the reflectance of the viewing side of the polarizing plate in this range improves visibility for the user.

The water contact angle of the viewing side of the polarizing plate is preferably 95° or more, more preferably 96° or more, and even more preferably 97° or more. When the water contact angle of the viewing side of the polarizing plate is in this range, the antifouling function of the viewing side of the polarizing plate is improved.

As shown in FIG. 2, the polarizing plate according to the embodiment of the present invention has a functional layer 23 formed by the above-mentioned surface treatment on the viewing side. The functional layer 23 is, for example, a layer formed by applying a hard coat treatment and an anti-reflection treatment to the protective layer 22. The functional layer 23 reduces the reflectance by, for example, utilizing the interference of light.

In one embodiment of the present invention, the functional layer 23 includes a resin layer 23a and an anti-reflection layer 23b as shown in FIG. 3. The resin layer 23a is formed, for example, by applying a coating liquid containing a resin, a filler, and a solvent to a polarizing plate to form a coating film, and then removing the solvent from the coating film. Examples of the resin include a thermosetting resin and an ionizing radiation curable resin that is cured by ultraviolet light or light. As the resin, a commercially available thermosetting resin or ultraviolet curable resin can also be used.

As the thermosetting resin or ultraviolet curing resin, for example, a curing compound having at least one of an acrylate group and a methacrylate group that is cured by heat, light (ultraviolet light, etc.), or an electron beam, etc., can be used. Examples of such a curing compound include silicone resin, polyester resin, polyether resin, epoxy resin, urethane resin, alkyd resin, spiroacetal resin, polybutadiene resin, polythiolpolyene resin, oligomers or prepolymers of acrylates or methacrylates of polyfunctional compounds such as polyhydric alcohols, etc. One type of these may be used alone, or two or more types may be used in combination. Preferably, a silicone resin can be used. This is because the use of a silicone resin can ensure that the water contact angle on the viewing side of the polarizing plate falls within the above range, thereby ensuring anti-fouling function.

The anti-reflection layer 23b is obtained by applying a coating liquid for forming an anti-reflection layer. The coating liquid for forming an anti-reflection layer may contain, for example, a resin, a fluorine-containing additive, hollow particles, solid particles, a dilution solvent, etc., and may be produced, for example, by mixing these. The hollow particles and solid particles may be, for example, silica particles.

By having the above-described configuration of the functional layer 23, it is possible to reduce the weight of the image display panel while improving the visibility for the user and further improving the anti-soiling function of the viewing side of the polarizing plate. The functional layer is described in JP 2020-030363 A, which is incorporated herein by reference.

C-1-3. Retardation Layer The retardation layer 30 may be a single layer, or may have a laminated structure (substantially a two-layer structure).

When the retardation layer 30 is a single layer, it typically functions as a λ/4 plate. The retardation layer is typically provided to impart anti-reflection properties to the image display panel. The retardation layer typically exhibits a refractive index characteristic of nx>ny=nz. The in-plane retardation Re(550) of the retardation layer is preferably 100 nm to 190 nm, more preferably 110 nm to 170 nm, and even more preferably 120 nm to 160 nm. Note that "ny=nz" here includes not only the case where ny and nz are completely equal, but also the case where they are substantially equal. Therefore, there may be cases where ny>nz or ny<nz within a range that does not impair the effects of the present invention.

The Nz coefficient of the retardation layer is preferably 0.9 to 1.5, and more preferably 0.9 to 1.3. By satisfying this relationship, an image display panel with excellent reflection hue can be obtained.

When the retardation layer is a single layer, the retardation layer preferably exhibits an inverse dispersion wavelength characteristic in which the retardation value increases according to the wavelength of the measurement light. In this case, Re(450)/Re(550) of the retardation layer is preferably 0.8 or more and less than 1, and more preferably 0.8 or more and 0.95 or less. With such a configuration, it is possible to realize very excellent anti-reflection properties.

The angle between the slow axis of the retardation layer and the absorption axis of the polarizer is preferably 40° to 50°, more preferably 42° to 48°, and even more preferably about 45°. If the angle is in this range, an image display panel with very good anti-reflection properties can be obtained by using a λ/4 plate as the retardation layer as described above.

The retardation layer may be made of any suitable material as long as it satisfies the above-mentioned characteristics. Specifically, the retardation layer may be a stretched resin film or a layer of liquid crystal compound alignment and solidification (hereinafter, liquid crystal alignment and solidification layer).

When the retardation layer is a stretched resin film, a representative example of the resin constituting the resin film is a polycarbonate-based resin or a polyester carbonate-based resin (hereinafter, sometimes simply referred to as a polycarbonate-based resin). As the polycarbonate-based resin, any appropriate polycarbonate-based resin can be used as long as the desired moisture permeability is obtained. For example, the polycarbonate-based resin contains a structural unit derived from a fluorene-based dihydroxy compound, a structural unit derived from an isosorbide-based dihydroxy compound, and a structural unit derived from at least one dihydroxy compound selected from the group consisting of an alicyclic diol, an alicyclic dimethanol, a di-, tri- or polyethylene glycol, and an alkylene glycol or a spiro glycol. Preferably, the polycarbonate resin comprises a structural unit derived from a fluorene dihydroxy compound, a structural unit derived from an isosorbide dihydroxy compound, a structural unit derived from an alicyclic dimethanol, and/or a structural unit derived from a di-, tri- or polyethylene glycol; more preferably, the structural unit derived from a fluorene dihydroxy compound, a structural unit derived from an isosorbide dihydroxy compound, and a structural unit derived from a di-, tri- or polyethylene glycol. The polycarbonate resin may comprise a structural unit derived from other dihydroxy compounds as required. The retardation layer is formed by stretching the film composed of the above-mentioned polycarbonate resin under any suitable stretching conditions. Details of the polycarbonate resin and the method of forming the retardation layer are described in, for example, JP 2014-10291 A, JP 2014-26266 A (Patent No. 5528606), JP 2015-212816 A (Patent No. 6189355), JP 2015-212817 A (Patent No. 6823899), JP 2015-212818 A, JP 2017-54093 A (Patent No. 6360821), and JP 2018-60014 A (Patent No. 6321107). The descriptions in these publications are incorporated herein by reference.

When the retardation layer is a liquid crystal alignment solidified layer, the difference between nx and ny of the retardation layer obtained can be significantly increased by using a liquid crystal compound compared to non-liquid crystal materials, so that the thickness of the retardation layer to obtain the desired in-plane retardation can be significantly reduced. As a result, a polarizing plate with a surface protection film (and, as a result, an image display panel) can be made thinner. In this specification, the term "alignment solidified layer" refers to a layer in which the liquid crystal compound is aligned in a predetermined direction within the layer and the alignment state is fixed. The term "alignment solidified layer" is a concept that includes an alignment hardened layer obtained by hardening a liquid crystal monomer. In this embodiment, typically, rod-shaped liquid crystal compounds are aligned in the slow axis direction of the retardation layer (homogeneous alignment). Specific examples of liquid crystal compounds and details of the method for forming the liquid crystal alignment solidified layer are described, for example, in JP-A-2006-163343 and JP-A-2006-178389. The descriptions in these publications are incorporated herein by reference.

The thickness of the retardation layer is typically set to a thickness that allows it to function appropriately as a λ/4 plate. When the retardation layer is a stretched resin film, the thickness of the retardation layer is, for example, 10 μm to 60 μm. When the retardation layer is a liquid crystal alignment solidified layer, the thickness of the retardation layer is, for example, 1 μm to 5 μm.

When the retardation layer 30 has a laminated structure, the retardation layer typically has a two-layer structure of a first liquid crystal alignment solidified layer and a second liquid crystal alignment solidified layer. In this case, either the first liquid crystal alignment solidified layer or the second liquid crystal alignment solidified layer can function as a λ/2 plate, and the other can function as a λ/4 plate. Here, a case is described in which the first liquid crystal alignment solidified layer can function as a λ/2 plate and the second liquid crystal alignment solidified layer can function as a λ/4 plate, but these may be reversed. The thickness of the first liquid crystal alignment solidified layer can be adjusted to obtain the desired in-plane retardation of the λ/2 plate, and can be, for example, 2.0 μm to 4.0 μm. The thickness of the second liquid crystal alignment solidified layer can be adjusted to obtain the desired in-plane retardation of the λ/4 plate, and can be, for example, 1.0 μm to 2.5 μm. The in-plane retardation Re (550) of the first liquid crystal alignment solidified layer is preferably 200 nm to 300 nm, more preferably 230 nm to 290 nm, and even more preferably 250 nm to 280 nm. The in-plane retardation Re (550) of the second liquid crystal alignment solidified layer is, as described above, preferably 100 nm to 190 nm, more preferably 110 nm to 170 nm, and even more preferably 120 nm to 160 nm. The angle between the slow axis of the first liquid crystal alignment solidified layer and the absorption axis of the polarizer is preferably 10 ° to 20 °, more preferably 12 ° to 18 °, and even more preferably about 15 °. The angle between the slow axis of the second liquid crystal alignment solidified layer and the absorption axis of the polarizer is preferably 70 ° to 80 °, more preferably 72 ° to 78 °, and even more preferably about 75 °. With such a configuration, it is possible to obtain characteristics close to ideal reverse wavelength dispersion characteristics, and as a result, it is possible to realize very excellent antireflection characteristics.

C-2. Surface protective film Fig. 4 is a schematic cross-sectional view showing an example of a surface protective film constituting the image display panel shown in Fig. 1. As shown in Fig. 4, the surface protective film 10 in one embodiment of the present invention includes a substrate 11 and a pressure-sensitive adhesive layer 12 of the surface protective film, the substrate 11 has a first main surface 11a and a second main surface 11b facing each other, and the pressure-sensitive adhesive layer 12 of the surface protective film is disposed on the second main surface 11b of the substrate 11. Preferably, the surface protective film 10 further includes a treatment layer 13, and the treatment layer 13 is formed on the first main surface 11a of the substrate 11.

In one embodiment of the present invention, the surface resistance value of the first main surface side of the surface protective film is 1.0×10 ⁸ Ω/□ or more, preferably 1.0×10 ⁹ Ω/□ or more. By using such a surface protective film, the occurrence of touch panel sensor errors can be suppressed, and the manufacturing efficiency of the image display panel can be improved. Specifically, when the image display panel is used as a mobile device, suppression of touch panel sensor errors can be important. The touch panel sensor error is a phenomenon in which the screen does not respond or does not respond easily when touched with a finger during the manufacturing (particularly in the inspection process) of the image display panel (image display device) when checking the operability of the touch panel. When the above surface protective film is applied to the image display panel and the visible side of the surface protective film is touched with a finger, if the above surface resistance value is 1.0×10 ⁸ Ω/□ or more, a change in the charge of the touched portion can be detected. That is, the occurrence of the above touch panel sensor errors is suppressed during the manufacturing of the mobile device, particularly in the inspection process, and the suppression of the decrease in the manufacturing efficiency of the image display panel can be realized. The surface resistance is, for example, 1.0×10 ¹³ Ω/□ or less, preferably 1.0×10 ¹² Ω/□ or less, more preferably 1.0×10 ¹¹ Ω/□ or less. If the surface resistance is a certain value or more, problems such as blocking with other films may occur. Here, for a film having a surface resistance value of a certain value or more, it is necessary to perform a surface treatment to make the surface resistance value a certain value or less. On the other hand, if the surface resistance value of the film is a certain value or less, the above-mentioned touch panel sensor error may occur. Therefore, the present invention is excellent in solving the above two problems by forming a treatment layer containing a specific antistatic agent on the surface protective film.

In one embodiment of the present invention, the peeling force of the surface protective film against the polarizing plate is 0.03 N/25 mm or more, preferably 0.04 N/25 mm or more, more preferably 0.05 N/25 mm or more, and even more preferably 0.06 N/25 mm or more. By using such a surface protective film, the surface protective film can be prevented from peeling off from the polarizing plate during the production of the image display panel, thereby improving the production efficiency of the image display panel. In one embodiment of the present invention, a functional layer is formed on the viewing side of the polarizing plate as described above. The functional layer typically contains a silicone resin to ensure an anti-soiling function. In a functional layer containing a silicone resin, the surface free energy of the functional layer is low, and the adhesion to the adhesive is low. If the adhesion between the polarizing plate and the surface protective film is low, the surface protective film tends to peel off easily during the production process. In addition, for practical purposes, a separator is temporarily attached to the adhesive layer side of the surface protective film in a releasable manner. In the process of peeling the separator from such a polarizing plate with a surface protective film, the surface protective film side is fixed with a vacuum plate or the like, so the peeling force of the surface protective film needs to be greater than the peeling force of the separator. By having the peeling force of the surface protective film from the polarizing plate of 0.03 N/25 mm or more, the surface protective film is prevented from peeling off from the polarizing plate, and a decrease in the manufacturing efficiency of the image display panel is suppressed. The upper limit of the peeling force is, for example, 0.50 N/25 mm.

The thickness of the surface protection film is preferably 15 μm to 200 μm, more preferably 20 μm to 150 μm, even more preferably 30 μm to 100 μm, and particularly preferably 40 μm to 60 μm.

The components of the surface protection film are explained in more detail below.

C-2-1. Substrate Examples of materials for forming the substrate include ester-based resins such as polyethylene terephthalate-based resins, cycloolefin-based resins such as norbornene-based resins, olefin-based resins such as polypropylene, polyamide-based resins, polycarbonate-based resins, and copolymer resins thereof. Ester-based resins (particularly polyethylene terephthalate-based resins) are preferred.

The thickness of the substrate is preferably 10 μm to 150 μm, more preferably 20 μm to 100 μm, and even more preferably 30 μm to 50 μm.

C-2-2. Pressure-sensitive adhesive layer of surface protective film The pressure-sensitive adhesive layer of the surface protective film contains an acrylic pressure-sensitive adhesive. The acrylic pressure-sensitive adhesive typically contains a (meth)acrylic polymer having a polar functional group. The (meth)acrylic polymer having a polar functional group typically contains a polymer of an alkyl (meth)acrylate and a monomer having a polar functional group. Here, (meth)acrylate refers to acrylate and/or methacrylate.

The content of the monomer component having a polar functional group is preferably 1.0 to 10.0 parts by weight, and more preferably 2.0 to 8.0 parts by weight, relative to 100 parts by weight of the monomer forming the (meth)acrylic polymer. If the content of the monomer component having a polar functional group is within the above range, the polar functional group can form hydrogen bonds with, for example, a functional layer formed on the viewing side of the polarizing plate, thereby improving adhesion.

Examples of the alkyl (meth)acrylate include linear or branched alkyl groups having 1 to 18 carbon atoms. Examples of the alkyl group include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, amyl, hexyl, cyclohexyl, heptyl, 2-ethylhexyl, isooctyl, nonyl, decyl, isodecyl, dodecyl, isomyristyl, lauryl, tridecyl, pentadecyl, hexadecyl, heptadecyl, and octadecyl groups. The alkyl (meth)acrylates can be used alone or in combination. The average number of carbon atoms in the alkyl group is preferably 3 to 10. Of the alkyl groups, the 2-ethylhexyl group is preferred.

The content of the alkyl (meth)acrylate is, for example, 20.0 to 80.0 parts by weight, preferably 30.0 to 70.0 parts by weight, per 100 parts by weight of the monomer that forms the (meth)acrylic polymer.

Examples of monomers having a polar functional group include carboxyl group-containing monomers and hydroxyl group-containing monomers, and preferably carboxyl group-containing monomers. Monomers having a polar functional group can be used alone or in combination.

The carboxyl group-containing monomer is a compound that contains a carboxyl group in its structure and a polymerizable unsaturated double bond such as a (meth)acryloyl group or a vinyl group. Examples of the carboxyl group-containing monomer include (meth)acrylic acid, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, itaconic acid, maleic acid, fumaric acid, and crotonic acid. Among these, acrylic acid is preferred. The acrylic polymer may preferably contain a polymer of an alkyl (meth)acrylate and a carboxyl group-containing monomer, more preferably a polymer of an alkyl (meth)acrylate and an acrylic acid.

In one embodiment, the acrylic polymer contains structural units derived from other copolymerizable monomers. Examples of the other copolymerizable monomers include vinyl esters such as vinyl acetate and vinyl propionate, and preferably vinyl acetate. The other copolymerizable monomers can be used alone or in combination.

The content of the other copolymerizable monomer is, for example, 1.0 to 20.0 parts by weight, preferably 3.0 to 15.0 parts by weight, per 100 parts by weight of the monomer that forms the (meth)acrylic polymer.

The weight average molecular weight Mw of the (meth)acrylic polymer is, for example, 300,000 to 600,000, and preferably 400,000 to 500,000.

The crosslinking agent is capable of reacting with a portion of the polar functional groups possessed by the (meth)acrylic polymer. As the crosslinking agent, an organic crosslinking agent, a polyfunctional metal chelate, or the like can be used. As the organic crosslinking agent, for example, an isocyanate crosslinking agent, a peroxide crosslinking agent, an epoxy crosslinking agent, or an imine crosslinking agent can be mentioned. In the polyfunctional metal chelate, a polyvalent metal is covalently bonded or coordinately bonded to an organic compound. When the pressure-sensitive adhesive composition is a radiation curing type, a polyfunctional monomer can be used as the crosslinking agent. The crosslinking agents can be used alone or in combination.

The amount of crosslinking agent is, for example, 1.0 to 20.0 parts by weight, preferably 3.0 to 15.0 parts by weight, per 100 parts by weight of (meth)acrylic polymer (base polymer).

The adhesive may contain any suitable additives as necessary. Examples of such additives include initiators, tackifiers, plasticizers, pigments, dyes, fillers, antioxidants, conductive materials, antistatic agents, UV absorbers, light stabilizers, release regulators, softeners, surfactants, flame retardants, and antioxidants.

The thickness of the adhesive layer of the surface protection film is preferably 3 μm to 100 μm, more preferably 4 μm to 60 μm, even more preferably 5 μm to 40 μm, and particularly preferably 10 μm to 25 μm.

C-2-3. Treatment layer The surface protective film 10 may further include a treatment layer 13 on the first main surface 11a of the substrate 11 as shown in FIG. 4. The treatment layer is formed by diluting an antistatic agent or the like with a solvent such as an organic solvent or water, and applying the resulting coating liquid to the substrate layer and drying it. Examples of the antistatic agent include a quaternary ammonium cation-containing polymer and a polyaniline sulfonic acid-based antistatic agent, and preferably a quaternary ammonium cation-containing polymer can be used.

Examples of the quaternary ammonium cation contained in the quaternary ammonium cation-containing polymer include trimethylammonium cation, triethylammonium cation, tripropylammonium cation, methyldiethylammonium cation, ethyldimethylammonium cation, methyldipropylammonium cation, dimethylbenzylammonium cation, diethylbenzylammonium cation, methyldibenzylammonium cation, and ethyldibenzylammonium cation. Among these, trimethylammonium cation is particularly preferred. These quaternary ammonium cation-containing polymers containing quaternary ammonium cations have hydrophilic and lipophilic groups in the molecule, and the hydrophilic groups absorb moisture in the air, thereby achieving excellent antistatic effects.

The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. The methods for measuring each property are as follows. Note that "parts" and "%" in the examples and comparative examples are by weight unless otherwise specified.

(1) Thickness Thicknesses of 10 μm or less were measured using an interference film thickness meter (manufactured by Otsuka Electronics Co., Ltd., product name "MCPD-3000"), and thicknesses of more than 10 μm were measured using a digital micrometer (manufactured by Anritsu Co., Ltd., product name "KC-351C").
(2) Peeling Force The second main surface side of the surface protection film obtained in the Examples and Comparative Examples was bonded to the functional layer side of a polarizing plate MCIG1465CUZZ10Y (manufactured by Nitto Denko Corporation) to prepare a rectangular side of 25 mm x 100 mm. The surface protection film on the rectangular side obtained was peeled off at 180° peel speed of 300 mm/min.
Good: peeling force is 0.03 N/25 mm or more. Bad: peeling force is less than 0.03 N/25 mm. (3) Surface Resistance Value. Using the surface protection films obtained in the examples and comparative examples, the surface resistance values were measured by an eddy current method using a non-contact surface resistance meter (product name "EC-80") manufactured by Napson Co., Ltd. The measurement temperature was 23°C.
Good: the surface resistance is 1.0×10 ⁸ Ω/□ or more. Bad: the surface resistance is less than 1.0×10 ⁸ Ω/□.

[Production Example 1] Preparation of adhesive composition A A monomer composition containing 100 parts by weight of 2-ethylhexyl acrylate, 80 parts by weight of vinyl acetate, and 5 parts by weight of acrylic acid was polymerized to obtain an acrylic polymer. 100 parts by weight of the obtained acrylic polymer was mixed with 10.0 parts by weight of 1,3-bis(N,N-diglycidylaminomethyl)dichlorohexane (manufactured by Mitsubishi Gas Chemical Company, product name "TETRAD-C") as a crosslinking agent to prepare adhesive composition A.

[Production Example 2] Preparation of adhesive composition B An acrylic polymer was obtained by polymerizing a monomer composition containing 100 parts by weight of 2-ethylhexyl acrylate and 4 parts by weight of 2-hydroxyethyl acrylate. 100 parts by weight of the obtained acrylic polymer was mixed with 5 parts by weight of aliphatic polyisocyanate (manufactured by Tosoh, product name "Coronate HX") as a crosslinking agent, 0.03 parts by weight of dioctyltin dilaurate (manufactured by Tokyo Fine Chemical, product name "Envirizer OL-1") as a crosslinking assistant, and 0.3 parts by weight of polyoxyethylene alkylpropenyl phenyl ether ammonium sulfate (manufactured by Daiichi Kogyo Seiyaku, product name "Aqualon HS-10") as a peeling assistant to prepare adhesive composition B.

[Preparation Example 3] Preparation of Adhesive Composition C Adhesive composition C was prepared in the same manner as in Preparation Example 2, except that no release aid was added.

[Production Example 4] Preparation of adhesive composition D Adhesive composition D was prepared in the same manner as in Production Example 2, except that 3 parts by weight of aromatic polyisocyanate (manufactured by Tosoh, product name "Coronate L") as a crosslinking agent, 0.02 parts by weight of dioctyltin dilaurate (manufactured by Tokyo Fine Chemical, product name "Embilizer OL-1") as a crosslinking aid, and 0.5 parts by weight of polyoxypropylene glycol (manufactured by Sanyo Chemical, product name "Sannyx PP-3000") as a peeling aid were mixed.

[Production Example 5] Formation of treated layer A On the antistatic treated surface of a polyethylene terephthalate film with an antistatic treatment layer, "Diafoil T100N38" (manufactured by Mitsubishi Chemical), 17% alkyl acetalized polyvinyl alcohol (manufactured by Sekisui Chemical Co., Ltd., product name "S-LEC K KW-10") and 83% octadecyl isocyanate (manufactured by Ohara Palladium Chemical Co., Ltd., product name "R-NCO") were mixed and diluted with a solvent such as xylene to a base of 0.3%, and a coating liquid was applied thereto. The coating liquid was then dried by heating at 130°C for 1 minute to form a layer with a thickness of 40 to 60 nm, forming treated layer A.

[Production Example 6] Formation of treated layer B A coating liquid was mixed with 74% PEDOT-based conductive coating agent (manufactured by Chukyo Yushi, product name "T-670"), 8% PEDOT-based conductive coating agent curing agent (manufactured by Chukyo Yushi, "P-795"), 9% polyaniline sulfonic acid-based antistatic agent (manufactured by Mitsubishi Rayon, product name "aquaPASS-F15P"), and 9% antistatic agent additive (manufactured by Mitsubishi Rayon, product name "aquaPASS-A01") on a polyethylene terephthalate film "Diafoil T100C38" (manufactured by Mitsubishi Chemical), and diluted to 0.35% with a solvent such as methanol. The coating liquid was then applied and dried at 130°C for 1 minute to form a layer with a thickness of 40 to 60 nm, forming treated layer B.

[Example 1]
The adhesive composition A prepared in Production Example 1 was applied to the side of a polyethylene terephthalate film with an antistatic treatment layer (manufactured by Mitsubishi Chemical, product name "Diafoil T100F38") on which the antistatic layer was not formed, and heated at 130°C for 1 minute. Furthermore, a treatment layer A was formed on the opposite side of the PET film according to Production Example 5 to obtain a surface protection film. The obtained surface protection film was subjected to the evaluations of (2) and (3) above. The antistatic treatment layer contains a quaternary ammonium cation-containing polymer. The results are shown in Table 1.

[Example 2]
A pressure-sensitive adhesive layer was formed on one side of a polyethylene terephthalate film (manufactured by Mitsubishi Chemical, product name "Diafoil T100C38") in the same manner as in Example 1 to obtain a surface protection film. The obtained surface protection film was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

[Comparative Example 1]
A surface protective film was obtained in the same manner as in Example 1, except that a polyethylene terephthalate film with an antistatic treatment layer in which the treatment layer A was formed according to Production Example 5 was used. The obtained surface protective film was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

[Comparative Example 2]
A surface protective film was obtained in the same manner as in Example 1, except that the pressure-sensitive adhesive composition B prepared according to Production Example 2 was used. The obtained surface protective film was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

[Comparative Example 3]
A surface protective film was obtained in the same manner as in Example 1, except that the pressure-sensitive adhesive composition C prepared according to Production Example 3 was used, and the polyethylene terephthalate film on which the treatment layer B was formed according to Production Example 6 was used. The obtained surface protective film was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

[Comparative Example 4]
A surface protective film was obtained in the same manner as in Example 2, except that the pressure-sensitive adhesive composition D prepared according to Production Example 4 was used. The obtained surface protective film 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, when the surface protective film in the examples was used, both the peel strength and the surface resistance were good. Therefore, when the surface protective film was applied to an image display panel, a decrease in the manufacturing efficiency of the image display panel can be suppressed.

The surface protection film of the present invention is suitable for use in image display panels.

Reference Signs List 10: Surface protection film 11: Substrate 11a: First main surface 11b: Second main surface 12: Pressure-sensitive adhesive layer of surface protection film 13: Treatment layer
20 Polarizing plate 21 Polarizer 22 Protective layer 23 Functional layer 23a Resin layer 23b Anti-reflection layer 30 Retardation layer 40 Pressure-sensitive adhesive layer 50 Image display panel body 100 Image display panel (organic EL panel)
200 Polarizing plate with surface protection film

Claims (7)

A method for producing an image display panel using a surface protective film that is attached to a viewing side of a polarizing plate that is arranged on the viewing side of an image display panel body, the surface protective film including a substrate having a first main surface and a second main surface that face each other, and a pressure-sensitive adhesive layer that is arranged on the second main surface side of the substrate,
preparing a polarizing plate with a surface protective film, the polarizing plate having the polarizing plate and the surface protective film bonded to one side of the polarizing plate;
the polarizing plate is provided on a viewing side thereof with a functional layer including a resin layer including a silicone resin and an antireflection layer,
The polarizing plate with a surface protective film is
a pressure-sensitive adhesive layer located on the opposite side of the polarizing plate from the surface protective film;
A separator temporarily and releasably attached to the pressure-sensitive adhesive layer,
The surface resistivity of the first main surface of the surface protective film is 1.0×10 ⁸ Ω/□ or more;
The peel strength of the surface protective film to the functional layer is greater than the peel strength of the separator to the pressure-sensitive adhesive layer, and is 0.03 N/25 mm or more.
A method for manufacturing an image display panel. The method according to claim 1 , wherein the reflectance of the viewing side of the polarizing plate is 2.5% to 3.0%. The method according to claim 1 , wherein the polarizing plate has a water contact angle of 95° or more on the viewing side. The manufacturing method according to claim 1 , wherein the image display panel body further comprises a touch panel. A polarizing plate with a surface protective film, comprising: a polarizing plate; a surface protective film located on a viewing side of the polarizing plate; a pressure-sensitive adhesive layer located on a side opposite to the surface protective film with respect to the polarizing plate; and a separator temporarily and releasably attached to the pressure-sensitive adhesive layer,
The surface protective film includes a substrate and a pressure-sensitive adhesive layer,
the substrate has a first main surface and a second main surface opposed to each other, and a pressure-sensitive adhesive layer is disposed on the second main surface side of the substrate;
the surface resistivity of the first main surface side of the surface protective film is 1.0×10 ⁸ Ω/□ or more;
the pressure-sensitive adhesive layer comprises an acrylic pressure-sensitive adhesive, the acrylic pressure-sensitive adhesive comprises a (meth)acrylic polymer having a polar functional group, and a content of a monomer component having a polar functional group is 1.0 part by weight to 10.0 parts by weight relative to 100 parts by weight of a monomer forming the (meth)acrylic polymer,
the polarizing plate is provided on a viewing side thereof with a functional layer including a resin layer including a silicone resin and an antireflection layer,
The peel strength of the surface protective film to the functional layer is greater than the peel strength of the separator to the pressure-sensitive adhesive layer, and is 0.03 N/25 mm or more.
Polarizing plate with surface protection film. The polarizing plate with a surface protective film according to claim 5 , further comprising a treated layer, the treated layer being formed on the first main surface side of the base material. The polarizing plate with a surface protective film according to claim 6 , wherein the treatment layer contains a polymer containing a quaternary ammonium cation.

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