KR20230145362A - Manufacturing method of laminate and image display panel - Google Patents

Abstract

The present invention provides a laminate that includes a thin polarizing plate with a retardation layer and is excellent in workability in the manufacturing process of an image display panel. The laminate according to an embodiment of the present invention is a laminate comprising a surface protection film, a polarizing plate including a polarizer and a protective layer, a retardation layer, an adhesive layer, and a release film in this order, from the polarizing plate to the above The thickness of the laminated portion up to the adhesive layer is 70 μm or less, the thickness of the release film is 40 μm or more, the peel force Fr of the release film with respect to the adhesive layer is 0.04 N / 25 mm or less, and the The peeling force Fp of the surface protection film is greater than the above Fr and is 0.1 N/25 mm or less.

Description

Manufacturing method of laminate and image display panel

The present invention relates to a method of manufacturing a laminate and an image display panel.

Image display devices represented by liquid crystal displays and electroluminescence (EL) display devices (eg, organic EL display devices and inorganic EL display devices) are rapidly becoming popular. Polarizing plates and retardation plates are typically used in image display panels mounted on image display devices. In practical terms, a polarizing plate with a retardation layer that integrates a polarizing plate and a retardation plate is widely used (for example, patent document 1). In recent years, there has been an increasing demand for thinner image display devices. Additionally, the possibility of curving, bending, folding, and winding the image display device is being examined. As a polarizing plate with a retardation layer used in such an image display device, a thin polarizing plate with a retardation layer is desired. However, when bonding such a polarizing plate with a retardation layer to the image display panel main body, workability may be poor.

Japanese Patent Publication No. 3325560

The present invention was made to solve the above-described conventional problems, and its main purpose is to provide a laminate that includes a thin polarizing plate with a retardation layer and is excellent in workability in the manufacturing process of an image display panel.

According to an embodiment of the present invention, a laminate is provided. This laminate is a laminate comprising a surface protection film, a polarizing plate including a polarizer and a protective layer, a retardation layer, an adhesive layer, and a release film in this order, and the laminated portion from the polarizing plate to the adhesive layer. The thickness of the release film is 40 μm or more, the peeling force Fr of the release film with respect to the adhesive layer is 0.04N/25mm or less, and the peeling force of the surface protection film with respect to the polarizing plate is 0.04N/25mm or less. Fp is larger than Fr and is 0.1 N/25 mm or less.

In one embodiment, the thickness of the surface protection film is 60 μm or more.

In one embodiment, the thickness of the surface protection film is greater than the thickness of the laminated portion.

In one embodiment, a protective layer is disposed on the polarizing plate only on the side of the polarizer on which the retardation layer is not disposed.

In one embodiment, the thickness of the polarizer is 8 μm or less.

In one embodiment, the retardation layer is an alignment solidification layer of a liquid crystal compound.

In one embodiment, the warpage of the laminate is 5% or less.

According to another embodiment of the present invention, a method for manufacturing an image display panel is provided. This manufacturing method includes preparing the laminate, peeling the release film from the adhesive layer, bonding the laminate to the image display panel main body, and peeling the surface protection film from the polarizing plate in this order. Includes as follows.

According to an embodiment of the present invention, workability in the manufacturing process of an image display panel is significantly improved by using a laminate containing a surface protection film and a release film that satisfy a predetermined peel force for a polarizing plate with a retardation layer. You can do it.

1 is a schematic cross-sectional view showing the schematic configuration of a laminate according to one embodiment of the present invention.
Figure 2 is a cross-sectional view showing an example of the bending state of the laminate precursor.
FIG. 3A is a diagram showing an example of a manufacturing process for an image display panel according to one embodiment.
FIG. 3B is a diagram following FIG. 3A.
FIG. 3C is a diagram following FIG. 3B.
FIG. 3D is a diagram following FIG. 3C.
FIG. 3E is a diagram following FIG. 3D.

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

(Definition of terms and symbols)

The definitions of terms and symbols 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), and '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 phase difference measured with light with a wavelength of λ nm at 23°C. For example, 'Re(550)' is the in-plane phase difference measured with light with a wavelength of 550 nm at 23°C. Re(λ) can be obtained by the formula: Re(λ)=(nx-ny)×d, when the thickness of the layer (film) is d (nm).

(3) Phase difference in the thickness direction (Rth)

'Rth(λ)' is the phase difference in the thickness direction measured with light with a wavelength of λ nm at 23°C. For example, 'Rth(550)' is the phase difference in the thickness direction measured with light with a wavelength of 550 nm at 23°C. Rth(λ) can be obtained by the formula: Rth(λ)=(nx-nz)×d, when the thickness of the layer (film) is d (nm).

(4) Nz coefficient

The Nz coefficient can be obtained by Nz=Rth/Re.

(5) angle

When an angle is mentioned herein, the angle includes both clockwise and counterclockwise directions with respect to the reference direction. Therefore, for example, '45°' means ±45°.

A. Laminate

1 is a schematic cross-sectional view showing the schematic configuration of a laminate according to one embodiment of the present invention. The laminate 100 includes a surface protection film 30, a polarizing plate 10, a retardation layer 20, an adhesive layer 40, and a release film (separator) 50 in this order. The polarizing plate with a retardation layer obtained by the laminate 100 is typically arranged so that the polarizing plate 10 is on the viewing side rather than the retardation layer 20.

The surface protection film 30 includes a base material 31 and an adhesive layer 32 formed on one side of the base material 31, and is bonded to the polarizing plate 10 in a peelable manner. The phase difference layer 20 includes a laminated structure including the first phase difference layer 21 and the second phase difference layer 22. In the illustrated example, the polarizing plate 10 includes a polarizer 11 and a protective layer 12 disposed on the viewing side of the polarizer 11 (the side on which the retardation layer 20 is not disposed), and the polarizer ( No protective layer is disposed between 11) and the phase difference layer 20. According to this form, for example, the thickness of the polarizing plate with a retardation layer and the thickness of the polarizing plate described later can be achieved satisfactorily. The release film 50 is bonded to the adhesive layer 40 in a peelable manner and can protect the adhesive layer 40 . By using the release film 50, roll formation of the laminate 100 becomes possible, for example.

Although not shown, a protective layer may be additionally included on the other side of the polarizer 11 (between the polarizer 11 and the retardation layer 20). Additionally, unlike the illustrated example, the retardation layer 20 may be a single layer or may have a laminated structure of three or more layers.

Although not shown, the laminate may additionally include other functional layers. The type, characteristics, number, combination, arrangement, etc. of functional layers that the laminate may include can be appropriately set depending on the purpose. For example, the laminate may further include a conductive layer or an isotropic base material with a conductive layer. A conductive layer or an isotropic base material with a conductive layer is typically disposed between the retardation layer 20 and the adhesive layer 40. Additionally, a laminate (polarizing plate with a retardation layer) containing a conductive layer or an isotropic substrate with a conductive layer is applied to, for example, an image display device with a touch sensor built into the image display panel. As another example, the laminate may further include another phase difference layer. Other optical properties (eg, refractive index properties, in-plane retardation, Nz coefficient, photoelastic coefficient), thickness, arrangement, etc. of the retardation layer can be set appropriately depending on the purpose. As a specific example, it is included in the polarizer 10, and on the viewer side of the polarizer 11, there is another phase difference layer (typically, a (other) circularly polarized light function that provides improved visibility when viewed through polarized sunglasses). layer, a layer that provides an ultra-high phase difference) may be provided. By including such a layer, excellent visibility can be achieved even when the display screen is viewed through polarized lenses such as polarized sunglasses. Therefore, the obtained polarizing plate with a retardation layer can also be suitably applied to an image display device that can be used outdoors.

Each member constituting the laminate may be laminated via any appropriate adhesive layer (not shown). Specific examples of the adhesive layer include an adhesive layer and an adhesive layer. For example, the retardation layer 20 is bonded to the polarizing plate 10 through an adhesive layer (preferably using an active energy ray-curable adhesive). As shown in the illustration, when the retardation layer 20 has a laminated structure of two or more layers, each retardation layer is bonded through an adhesive layer (preferably using an active energy ray-curable adhesive).

The thickness of the laminated portion from the polarizing plate 10 to the adhesive layer 40 (sometimes simply referred to as the ‘thickness of the polarizing plate with a retardation layer’) is 70 μm or less, preferably 60 μm or less, and more preferably is 50㎛ or less. On the other hand, the thickness of the polarizing plate with a retardation layer is, for example, 25 μm or more. Additionally, the thickness of the polarizing plate with a retardation layer also includes the thickness of the adhesive layer.

A-1. polarizer

The polarizing plate includes a polarizer and a protective layer. The thickness of the polarizing plate may depend on the number of protective layers included, but is preferably 20 μm or more, and more preferably 25 μm or more. On the other hand, the thickness of the polarizing plate is preferably 40 μm or less, more preferably 36 μm or less, and even more preferably 33 μm or less. In addition, the thickness of the polarizing plate does not include the thickness of the adhesive layer (for example, adhesive layer) when laminating the polarizer and the protective layer.

The polarizer is typically a resin film containing a dichroic material (eg, iodine). Examples of the resin film include hydrophilic polymer films such as polyvinyl alcohol (PVA)-based films, partially formalized PVA-based films, and ethylene/vinyl acetate copolymer-based partially saponified films.

The thickness of the polarizer is preferably 15 μm or less, more preferably 12 μm or less, further preferably 10 μm or less, and particularly preferably 8 μm or less. Meanwhile, the thickness of the polarizer is preferably 1 μm or more.

The polarizer preferably exhibits absorption dichroism at any wavelength from 380 nm to 780 nm. The single transmittance of the polarizer is, for example, 41.5% to 46.0%, preferably 42.0% to 46.0%, and more preferably 44.5% to 46.0%. The polarization degree of the polarizer is preferably 97.0% or more, more preferably 99.0% or more, and even more preferably 99.9% or more.

The protective layer can be formed from any suitable film that can be used as a protective layer for a polarizer. Specific examples of materials that become the main component of the film include cellulose-based resins such as triacetylcellulose (TAC), polyester-based, polyvinyl alcohol-based, polycarbonate-based, polyamide-based, polyimide-based, polyethersulfone-based, and polyester. Resins such as sulfone-based, polystyrene-based, cycloolefin-based such as polynorbornene, polyolefin-based, (meth)acrylic-based, and acetate-based resins can be mentioned.

The polarizing plate with a retardation layer obtained by the embodiment of the present invention is typically placed on the viewer's side of the image display device, and the protective layer 12 is placed on the viewer's side. Therefore, the protective layer 12 may be subjected to surface treatment such as hard coat (HC) treatment, anti-reflection treatment, anti-sticking treatment, or anti-glare treatment as necessary.

The thickness of the protective layer 12 is preferably 5 μm to 80 μm, more preferably 10 μm to 40 μm, and still more preferably 10 μm to 30 μm. In addition, when the above surface treatment is performed, the thickness of the protective layer 12 is a thickness including the thickness of the surface treatment layer.

In one embodiment, the protective layer (not shown) disposed between the polarizer 11 and the retardation layer 20 is preferably optically isotropic. In this specification, 'optically isotropic' means that the in-plane phase difference Re(550) is 0 nm to 10 nm and the thickness direction phase difference Rth(550) is -10 nm to +10 nm. The thickness of the protective layer disposed between the polarizer 11 and the retardation layer 20 is preferably 5 μm to 80 μm, more preferably 10 μm to 40 μm, and even more preferably 10 μm to 30 μm. am.

The polarizer may be manufactured by any suitable method. Specifically, the polarizing plate may contain a polarizer produced from a single-layer resin film, or may contain a polarizer obtained using a laminate of two or more layers.

The method of manufacturing a polarizer from the above-mentioned single-layer resin film typically includes subjecting the resin film to dyeing treatment and stretching treatment with a dichroic substance such as iodine or a dichroic dye. As the resin film, as described above, hydrophilic polymer films such as polyvinyl alcohol (PVA)-based films, partially formalized PVA-based films, and ethylene-vinyl acetate copolymer-based partially saponified films are used. The method may further include insolubilization treatment, swelling treatment, crosslinking treatment, etc. A polarizing plate can be obtained by laminating a protective layer on at least one side of the obtained polarizer. Since this manufacturing method is well-known and common in the industry, detailed description is omitted.

Specific examples of the polarizer obtained by using the above two or more layered 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 PVA-based resin layer coated and formed on the resin substrate and the resin substrate. A polarizer obtained by using a laminated body of resin layers can be mentioned. A polarizer obtained by using a laminate of a resin substrate and a PVA-based resin layer formed by applying it to the resin substrate is, for example, applied to the resin substrate, dried, and formed to form a PVA-based resin layer on the resin substrate. Obtaining a laminate of PVA-based resin layers; It can be produced by stretching and dyeing the laminate and using the PVA-based resin layer as 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. In addition, stretching may further include air stretching the laminate at a high temperature (eg, 95°C or higher) before stretching in an aqueous boric acid solution, if necessary. In addition, in this embodiment, the laminate is preferably subjected to dry shrinkage treatment to shrink the laminate by 2% or more in the width direction by heating while conveying in the longitudinal direction. Typically, the manufacturing method of this embodiment includes performing aerial auxiliary stretching treatment, dyeing treatment, underwater stretching treatment, and dry shrink treatment on the laminate in this order. By introducing auxiliary stretching, even when PVA is applied on a thermoplastic resin, it becomes possible to increase the crystallinity of PVA and achieve high optical properties. Moreover, by simultaneously increasing the orientation of PVA in advance, problems such as a decrease in orientation or dissolution of PVA when immersed in water in the subsequent dyeing process or stretching process can be prevented, making it possible to achieve high optical properties. It becomes. Additionally, when the PVA-based resin layer is immersed in a liquid, the disruption of the orientation of polyvinyl alcohol molecules and the decrease in orientation can be suppressed compared to the case where the PVA-based resin layer does not contain a halide. Thereby, the optical properties of the polarizer obtained through a treatment process performed by immersing the laminate in a liquid, such as dyeing treatment and underwater stretching treatment, can be improved. Additionally, optical properties can be improved by shrinking the laminate in the width direction through dry shrinkage treatment. The obtained resin substrate/polarizer laminate may be used as is (i.e., the resin substrate may be used as a protective layer of the polarizer), or on the peeling surface where the resin substrate is peeled from the resin substrate/polarizer laminate, or on the peeling surface. It may be used by laminating any appropriate protective layer depending on the purpose on the side opposite to the above. Details of the manufacturing method of such a polarizer are described in, for example, Japanese Patent Application Laid-Open No. 2012-73580 and Japanese Patent Application Publication No. 6470455. The entire description of these publications is incorporated herein by reference.

A-2. phase contrast layer

The thickness of the retardation layer may depend on its structure (whether it has a single layer or a laminated structure), but is preferably 10 μm or less, more preferably 8 μm or less, and even more preferably 5 μm or less. Meanwhile, the thickness of the retardation layer is, for example, 1 μm or more. Additionally, when the retardation layer has a laminated structure, 'thickness of the retardation layer' means the sum of the thicknesses of each retardation layer. Specifically, the 'thickness of the phase difference layer' does not include the thickness of the adhesive layer (eg, adhesive layer).

As the phase difference layer, an alignment-fixed layer of a liquid crystal compound (liquid-crystal alignment-fixed layer) is preferably used. By using a liquid crystal compound, the difference between nx and ny of the obtained retardation layer can be significantly increased compared to a non-liquid crystal material, and therefore the thickness of the retardation layer for obtaining the desired in-plane retardation can be significantly reduced. Therefore, it is possible to realize significant thinning of the polarizing plate with a retardation layer. In this specification, the term 'alignment-fixed layer' refers to a layer in which a liquid crystal compound is aligned in a predetermined direction within the layer and the alignment state is fixed. In addition, the 'alignment solidified layer' is a concept that includes an alignment hardened layer obtained by curing a liquid crystal monomer, as will be described later. In the phase contrast layer, typically, rod-shaped liquid crystal compounds are oriented in a line in the slow axis direction of the phase contrast layer (homogeneous orientation).

The liquid crystal alignment solidification layer applies an orientation treatment to the surface of a predetermined substrate, applies a coating liquid containing a liquid crystal compound to the surface, orients the liquid crystal compound in a direction corresponding to the orientation treatment, and maintains the orientation state. It can be formed by fixing . As the orientation treatment, any appropriate orientation treatment may be employed. Specifically, mechanical alignment treatment, physical alignment treatment, and chemical alignment treatment can be mentioned. Specific examples of mechanical orientation treatment include rubbing treatment and stretching treatment. Specific examples of physical alignment treatment include magnetic field alignment treatment and electric field alignment treatment. Specific examples of chemical alignment treatment include oblique vapor deposition and photo-alignment treatment. The treatment conditions for various orientation treatments may be any appropriate conditions depending on the purpose.

The alignment of the liquid crystal compound is achieved by treatment at a temperature that exhibits a liquid crystal phase depending on the type of the liquid crystal compound. By performing such temperature treatment, the liquid crystal compound assumes a liquid crystal state, and the liquid crystal compound is aligned according to the orientation treatment direction of the substrate surface.

In one embodiment, the alignment state is fixed by cooling the liquid crystal compound aligned as described above. When the liquid crystal compound is a polymerizable monomer or a crosslinkable monomer, the alignment state is fixed by subjecting the liquid crystal compound oriented as described above to polymerization treatment or crosslinking treatment.

Specific examples of the liquid crystal compound and details of the method for forming the alignment solidification layer are described in Japanese Patent Application Laid-Open No. 2006-163343. The description in this publication is incorporated herein by reference.

As described above, the retardation layer 20 may be a single layer or may have a laminated structure of two or more layers.

Unlike the illustrated example, in one embodiment where the phase difference layer 20 is a single layer, the phase difference layer 20 can function as a λ/4 plate. Specifically, Re(550) of the retardation layer is preferably 100 nm to 180 nm, more preferably 110 nm to 170 nm, and still more preferably 110 nm to 160 nm. The thickness of the retardation layer can be adjusted to obtain the desired in-plane retardation of the λ/4 plate. When the retardation layer is the above-mentioned liquid crystal alignment solidification layer, its thickness is, for example, 1.0 μm to 2.5 μm. In this embodiment, the angle formed by 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 44° to 46°. . In this embodiment, the phase difference layer preferably exhibits inverse dispersion wavelength characteristics in which the phase difference value increases depending on the wavelength of the measurement light. In addition, in this embodiment, the laminate further includes a layer (other phase difference layer, not shown) disposed between the retardation layer 20 and the adhesive layer 40 and exhibiting refractive index characteristics of nz>nx=ny. can do.

In another embodiment where the phase difference layer 20 is a single layer, the phase difference layer 20 may function as a λ/2 plate. Specifically, Re(550) of the retardation layer is preferably 200 nm to 300 nm, more preferably 230 nm to 290 nm, and still more preferably 230 nm to 280 nm. The thickness of the retardation layer can be adjusted to obtain the desired in-plane retardation of the λ/2 plate. When the retardation layer is the above-mentioned liquid crystal alignment solidification layer, its thickness is, for example, 2.0 μm to 4.0 μm. In this embodiment, the angle formed by the slow axis of the retardation layer and the absorption axis of the polarizer is preferably 10° to 20°, more preferably 12° to 18°, and even more preferably 12° to 16°. .

As shown in FIG. 1, when the retardation layer 20 has a laminated structure, the retardation layer 20 includes, for example, a first retardation layer (H layer) 21 and a second retardation layer (Q layer) in order from the polarizer side. ) (22) has a two-layer stacked structure. The H layer can typically function as a λ/2 plate, and the Q layer can typically function as a λ/4 plate. Specifically, Re(550) of the H layer is preferably 200 nm to 300 nm, more preferably 220 nm to 290 nm, and still more preferably 230 nm to 280 nm; Re(550) of the Q layer is preferably 100 nm to 180 nm, more preferably 110 nm to 170 nm, and still more preferably 110 nm to 150 nm. The thickness of the H layer can be adjusted to obtain the desired in-plane retardation of the λ/2 plate. When the H layer is the above-mentioned liquid crystal alignment solidification layer, its thickness is, for example, 2.0 μm to 4.0 μm. The thickness of the Q layer can be adjusted to obtain the desired in-plane retardation of the λ/4 plate. When the Q layer is the above-mentioned liquid crystal alignment solidification layer, its thickness is, for example, 1.0 μm to 2.5 μm. In this embodiment, the angle formed by the slow axis of the H layer and the absorption axis of the polarizer is preferably 10° to 20°, more preferably 12° to 18°, and still more preferably 12° to 16°. ; The angle formed between the slow axis of the Q layer and the absorption axis of the polarizer is preferably 70° to 80°, more preferably 72° to 78°, and even more preferably 72° to 76°. When the phase difference layer 20 has a laminated structure, each layer (e.g., H layer and Q layer) may exhibit inverse dispersion wavelength characteristics in which the phase difference value increases depending on the wavelength of the measurement light, and the phase difference value may be the wavelength of the measurement light. It may exhibit positive wavelength dispersion characteristics that become smaller depending on the wavelength, or it may exhibit flat wavelength dispersion characteristics in which the phase difference value hardly changes depending on the wavelength of the measurement light.

The refractive index characteristics of the retardation layer 20 (each layer when it has a laminated structure) typically exhibit the relationship nx>ny=nz. Additionally, 'ny=nz' includes not only the case where ny and nz are completely the same, but also the case where they are substantially the same. Therefore, there may be cases where ny > nz or ny < nz within the range that does not impair the effect of the present invention. The Nz coefficient of the phase difference layer is preferably 0.9 to 1.5, and more preferably 0.9 to 1.3.

As mentioned above, the retardation layer is preferably a liquid crystal alignment solidification layer. Examples of the liquid crystal compound include a liquid crystal compound (nematic liquid crystal) whose liquid crystal phase is a nematic phase. As such a liquid crystal compound, for example, a liquid crystal polymer or a liquid crystal monomer can be used. The mechanism for expressing liquid crystallinity of the liquid crystal compound may be lyotropic or thermotropic. The liquid crystal polymer and liquid crystal monomer may be used individually or in combination.

When the liquid crystal compound is a liquid crystal monomer, the liquid crystal monomer is preferably a polymerizable monomer or a crosslinkable monomer. This is because the alignment state of the liquid crystal monomer can be fixed by polymerizing or crosslinking (i.e., curing) the liquid crystal monomer. After aligning the liquid crystal monomers, for example, by polymerizing or crosslinking the liquid crystal monomers, the alignment state can be thereby fixed. Here, polymers are formed by polymerization and a three-dimensional network structure is formed by crosslinking, but these are non-liquid crystalline. Therefore, the formed retardation layer does not transition into a liquid crystal phase, a glass phase, or a crystal phase due to temperature changes peculiar to liquid crystalline compounds, for example. As a result, the phase difference layer becomes a phase difference layer that is not affected by temperature changes and has extremely excellent stability.

The temperature range in which a liquid crystal monomer exhibits liquid crystallinity varies depending on its type. Specifically, the temperature range is preferably 40°C to 120°C, more preferably 50°C to 100°C, and most preferably 60°C to 90°C.

As the liquid crystal monomer, any suitable liquid crystal monomer may be employed. For example, described in Japanese Patent Application Publication No. 2002-533742 (WO00/37585), EP358208 (US5211877), EP66137 (US4388453), WO93/22397, EP0261712, DE19504224, DE4408171, and GB2280445. polymerizable mesogenic compounds, etc. can be used. there is. Specific examples of such polymerizable mesogenic compounds include, for example, BASF's trade name LC242, Merck's trade name E7, and Wacker-Chem's trade name LC-Sillicon-CC3767. As the liquid crystal monomer, a nematic liquid crystal monomer is preferable.

A-3. surface protection film

The base material of the surface protection film may be formed of any suitable material. Specific examples of forming materials include polyester polymers such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), and polybutylene terephthalate (PBT); Cellulose-based polymers such as diacetylcellulose and triacetylcellulose; polycarbonate-based polymer; (meth)acrylic polymers such as polymethyl methacrylate; Cycloolefin-based polymers such as polynorbornene can be mentioned. These may be used individually, or may be used in combination of two or more types.

The thickness of the base material of the surface protection film is, for example, 10 μm or more and 100 μm or less, preferably 15 μm or more and 90 μm or less, and more preferably 25 μm or more and 80 μm or less.

As the adhesive layer of the surface protection film, any appropriate structure may be adopted. Specific examples include acrylic adhesives, rubber adhesives, silicone adhesives, polyester adhesives, urethane adhesives, epoxy adhesives, and polyether adhesives. By adjusting the type, number, combination and mixing ratio of monomers forming the base resin of the adhesive, the amount of crosslinking agent, reaction temperature, reaction time, etc., an adhesive having desired properties according to the purpose can be prepared. The base resin of the adhesive may be used individually or in combination of two or more types. The base resin is preferably an acrylic resin (specifically, the adhesive layer is preferably made of an acrylic adhesive). The thickness of the adhesive layer is, for example, 5 μm to 15 μm. The storage modulus of the adhesive layer at 25°C is, for example, 1.0×10 ⁵ Pa to 1.0×10 ⁷ Pa.

The thickness of the surface protection film is, for example, 40 μm or more, preferably 50 μm or more, more preferably 60 μm or more, and even more preferably 70 μm or more. In one embodiment, the thickness of the surface protection film is greater than the thickness of the polarizing plate with a retardation layer. According to such a surface protection film, a thin polarizing plate with a retardation layer can be sufficiently protected from external stress. Specifically, it is possible to prevent external problems such as scratches from occurring in the obtained polarizing plate with a retardation layer due to external stress. Additionally, workability when peeling the release film from the laminate, which will be described later, can be further improved. On the other hand, the thickness of the surface protection film is preferably 100 μm or less.

A-4. adhesive layer

The thickness of the adhesive layer 40 is preferably 10 μm to 20 μm. Details of the adhesive constituting the adhesive layer 40 are the same as those of the adhesive layer included in the surface protection film.

A-5. release film

The release film may be comprised of any suitable plastic film. Specific examples of plastic films include polyethylene terephthalate (PET) film, polyethylene film, and polypropylene film. The release film can function as a separator. Specifically, as a release film, a plastic film whose surface is coated with a release agent is preferably used. Specific examples of the release agent include silicone-based release agents, fluorine-based release agents, and long-chain alkyl acrylate-based release agents.

The thickness of the release film is 40 μm or more, and is preferably 45 μm or more. According to such a release film, a thin polarizing plate with a retardation layer (especially the adhesive layer 40) can be protected from external stress. Specifically, it is possible to prevent external problems such as scratches from occurring in the obtained polarizing plate with a retardation layer due to external stress. On the other hand, the thickness of the release film is preferably 80 μm or less.

A-6. Relationship between peel force

The peeling force Fp of the surface protection film 30 with respect to the polarizing plate 10 is greater than the peeling force Fr of the peeling film 50 with respect to the adhesive layer 40. Fr is 0.04N/25mm or less, preferably 0.03N/25mm or less, and more preferably 0.02N/25mm or less. According to this relationship between peel forces, workability in the manufacturing process of the image display panel described later can be significantly improved. This effect can be significantly achieved when the peeling film is thick. Specifically, a thin polarizing plate with a retardation layer tends to have low stiffness, and the peelability of a thick (e.g., 40 μm or more) release film bonded to a thin polarizing plate with a retardation layer tends to be low. As a result, workability in the manufacturing process of the image display panel deteriorates, which may be a cause of lowering the yield. By satisfying the relationship of peeling force, even when a thick peeling film is bonded to a thin polarizing plate with a retardation layer, the peeling property can be excellent. Additionally, Fp is 0.1N/25mm or less, preferably 0.07N/25mm or less, and more preferably 0.05N/25mm or less. With such peeling force, workability in the manufacturing process of an image display panel can be significantly improved. Specifically, the peelability of the surface protection film may be excellent.

The Fr is preferably 0.005N/25mm or more, and preferably 0.01N/25mm or more. The Fp is preferably 0.02N/25mm or more, and preferably 0.03N/25mm or more. In addition, Fr can be adjusted, for example, by appropriately selecting the structure of the adhesive layer 40 and the type of the release film 50. Fp can be adjusted, for example, by appropriately selecting the type of surface protection film 30.

A-7. Fabrication of laminates

The laminate 100 can be obtained, for example, by stacking the polarizer 10 and the retardation layer 20 to produce a laminate precursor, and then laminating the surface protection film 30 and the release film 50 on the obtained laminate precursor. there is.

The polarizer 10 and the retardation layer 20 are laminated, for example, while rolling them (so-called roll-to-roll). Lamination is typically accomplished by transferring the liquid crystal alignment solidification layer formed on the substrate. As in the illustrated example, when the retardation layer has a laminated structure, each retardation layer may be sequentially laminated (transferred) on a polarizing plate, or the laminated product of the retardation layer may be laminated (transferred) on a polarizing plate.

The transfer is performed using, for example, an active energy ray-curable adhesive. The thickness (thickness of the adhesive layer) after curing of the active energy ray-curable adhesive is, for example, 0.2 μm to 3.0 μm, preferably 0.4 μm to 2.0 μm, and more preferably 0.6 μm to 1.5 μm. For example, due to the adhesive used for laminating the polarizing plate and the retardation layer (specifically, shrinkage upon curing of the active energy ray-curable adhesive), the laminate precursor obtained by laminating the polarizing plate 10 and the retardation layer 20 Warping may occur.

Figure 2 is a cross-sectional view showing an example of the bent state of the laminate precursor. Additionally, in Figure 2, hatching is omitted for the cross-section of the laminate precursor to make the diagram easier to see. In the example shown in FIG. 2, the laminate precursor 90 has a convex bend on the polarizing plate 10 side. Bending tends to occur along the absorption axis direction of the polarizer 10 (polarizer 11).

The lamination of the polarizer 10 and the retardation layer 20 is preferably performed in an environment where the amount of water vapor is 10.2 g/m ³ or less. The amount of water vapor in lamination is more preferably 6.0 g/m ³ to 10.0 g/m ³ , and even more preferably 8.0 g/m ³ to 9.5 g/m ³ . By performing lamination in an environment where the amount of water vapor is within this range, for example, the effect of humidification treatment described later becomes significant. This amount of water vapor in the laminate can be realized, for example, by changing the relative humidity depending on the temperature in the range of 18°C to 25°C. The amount of water vapor can be realized by setting the relative humidity to 65% RH or less, for example, when the temperature is 18°C; Also, for example, when the temperature is 20°C, it can be realized by setting the relative humidity to 55% RH or less; Also, for example, when the temperature is 23°C, it can be realized by setting the relative humidity to 45% RH or less. Additionally, the lower limit of relative humidity may be, for example, 30% RH.

As described above, when the laminate further includes other functional layers (e.g., conductive layers, other retardation layers), the functional layers may be laminated or formed at predetermined positions by any appropriate method.

The surface protection film 30 and the release film 50 are laminated on the laminate precursor including at least the polarizing plate 10 and the retardation layer 20. Here, the surface protection film 30 is disposed so that the adhesive layer 32 is on the laminate precursor side. The release film 50 is laminated on the laminate precursor with the adhesive layer 40 interposed therebetween. In the laminate obtained in this way, bending (for example, convex bending on the side of the release film 50) may occur. Warping of the laminate may affect workability in the manufacturing process of the image display panel (for example, workability when peeling a release film from the laminate, which will be described later). The warpage of the laminate is preferably 7% or less, more preferably 5% or less, and even more preferably 3% or less. The method of measuring warpage (%) will be described later.

B. Manufacturing method of image display panel

Typically, the above laminate is used to manufacture image display panels. 3A to 3E are diagrams showing an example of a manufacturing process for an image display panel according to one embodiment. 3A to 3E, the laminated structure of the polarizing plate 10, the retardation layer 20, and the adhesive layer 40 is simplified and described as the polarizing plate 110 with a retardation layer.

FIG. 3A shows a state in which the release film 50 is peeled from the laminate 100. After attaching the peeling tape T1 to the lowermost surface (release film 50) of the laminate 100 adsorbed on the suction plate A, in a direction of 180° from the end of the release film 50 (in the direction of the arrow) ), the release film 50 is peeled from the laminate 100 by pulling the release tape T1. As described above, the peeling force Fp of the surface protection film 30 with respect to the polarizing plate 10 is greater than the peeling force Fr of the peeling film 50 with respect to the adhesive layer 40, and Fr is 0.04 N/25 mm or less. . By satisfying this relationship, the peelability of the release film 50 can be excellent. Specifically, when peeling the release film 50 from the laminate 100, the polarizing plate 110 with a retardation layer can be prevented from being peeled off from the surface protection film 30.

FIG. 3B shows a state in which the laminate 100 from which the release film 50 has been peeled is bonded to the surface of the image display panel (e.g., organic EL panel) main body 70 adsorbed on the suction plate B, and FIG. 3C shows After the laminate 100 is bonded to the image display panel main body 70, the suction plate A is removed from the laminate 100.

FIG. 3D shows a state in which the surface protection film 30 is peeled from the laminate 100. After attaching the peeling tape T2 to the top surface of the laminate 100 (surface protection film 30) bonded to the surface of the image display panel main body 70, The surface protection film 30 is peeled from the laminate 100 by pulling the peeling tape T2 in the direction (direction of the arrow). As described above, Fp is 0.1N/25mm or less. By satisfying this relationship, the peelability of the surface protection film 30 can be excellent. Specifically, when peeling the surface protection film 30 from the laminate 100, the surface protection film 30 does not peel off from the laminate 100, and the image display panel main body 70 is separated from the suction plate B. It can prevent it from falling out. In this way, the image display panel 80 shown in Fig. 3E is obtained. Specifically, an image display panel 80 is obtained in which a polarizing plate 110 with a retardation layer is bonded to an image display panel main body 70.

[Example]

Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited to these examples. In addition, the thickness is a value measured by the following measurement method. Additionally, unless otherwise specified, 'part' and '%' in Examples and Comparative Examples are based on weight.

<Thickness>

The thickness of 10 μm or less was measured using a scanning electron microscope (manufactured by Nippon Electronics, product name ‘JSM-7100F’). Thickness exceeding 10㎛ was measured using a digital micrometer (manufactured by Anritsu, product name 'KC-351C').

[Example 1]

(Production of polarizer)

As a thermoplastic resin substrate, an amorphous isophthalic copolymerization polyethylene terephthalate film (thickness: 100 μm) with a long shape and a Tg of about 75°C was used, and corona treatment was performed on one side of this resin substrate.

100 parts by weight of PVA-based resin mixed with polyvinyl alcohol (polymerization degree 4200, saponification degree 99.2 mol%) and acetoacetyl-modified PVA (manufactured by Japan Synthetic Chemical Industry Co., Ltd., brand name 'Kosefaimer') at a ratio of 9:1, potassium iodide 13 The added weight was dissolved in water to prepare a PVA aqueous solution (coating solution).

The PVA aqueous solution was applied to the corona-treated surface of the resin substrate and dried at 60°C to form a PVA-based resin layer with a thickness of 13 μm, thereby producing a laminate.

The obtained laminate was uniaxially stretched 2.4 times in the longitudinal direction (longitudinal direction) in an oven at 130°C (air auxiliary stretching treatment).

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

Next, in a dyeing bath (iodine aqueous solution obtained by mixing iodine and potassium iodide at a weight ratio of 1:7 with respect to 100 parts by weight of water) at a liquid temperature of 30°C, the final single transmittance (Ts) of the polarizer obtained is the desired value. It was immersed for 60 seconds while adjusting the concentration to achieve this (dyeing treatment).

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

Thereafter, the laminate was immersed in an aqueous boric acid solution (boric acid concentration: 4% by weight, potassium iodide concentration: 5% by weight) at a liquid temperature of 70°C, and the total stretching ratio was stretched in the longitudinal direction (longitudinal direction) between rolls with different circumferential speeds. Uniaxial stretching was performed to make this 5.5 times larger (underwater stretching treatment).

Thereafter, the laminate was immersed in a washing bath (aqueous solution obtained by mixing 4 parts by weight of potassium iodide with respect to 100 parts by weight of water) at a liquid temperature of 20°C (washing treatment).

Afterwards, it was dried in an oven maintained at about 90°C and brought into contact with a heating roll made of SUS whose surface temperature was maintained at about 75°C (dry shrink treatment).

In this way, a polarizer with a thickness of about 5 μm was formed on the resin substrate, and a laminate having a resin substrate/polarizer configuration was obtained.

An acrylic film (thickness 20 μm) was bonded to the polarizer side of the obtained laminate as a protective layer through an ultraviolet curing adhesive. Next, the resin substrate was peeled from the polarizer to obtain a polarizing plate having the structure of an acrylic film (protective layer)/polarizer.

(Production of phase contrast layer)

10 g of a polymerizable liquid crystal displaying a nematic liquid crystalline phase (manufactured by BASF, brand name 'Paliocolor LC242', expressed in the formula below), and a photopolymerization initiator for the polymerizable liquid crystal compound (manufactured by BASF, brand name ' 3 g of Irgacure 907') was dissolved in 40 g of toluene to prepare a liquid crystal composition (coating solution).

The surface of the polyethylene terephthalate (PET) film (thickness 38 μm) was rubbed using a rubbing cloth, and orientation treatment was performed. The direction of the orientation treatment was set to be 15° when viewed from the viewer's side with respect to the direction of the absorption axis of the polarizer when bonding to the polarizing plate. The liquid crystal coating liquid was applied to this alignment treated surface using a bar coater, and the liquid crystal compound was aligned by heating and drying at 90°C for 2 minutes. The liquid crystal layer formed in this way was irradiated with light of 1 mJ/cm2 using a metal halide lamp, and the liquid crystal layer was cured to form a liquid crystal alignment solidification layer A (H layer) on the PET film. The thickness of the liquid crystal alignment solidification layer A was 2.5 μm, and the in-plane retardation Re(550) was 270 nm. In addition, the liquid crystal alignment solidification layer A showed a refractive index characteristic of nx>ny=nz.

Liquid crystal alignment solidification layer B (Q layer) was formed on the PET film in the same manner as above except that the coating thickness was changed and the orientation treatment direction was 75° when viewed from the visual side with respect to the direction of the absorption axis of the polarizer. formed. The thickness of the liquid crystal alignment solidification layer B was 1.5 μm, and the in-plane retardation Re(550) was 140 nm. In addition, the liquid crystal alignment solidification layer B showed a refractive index characteristic of nx>ny=nz.

(Production of laminate)

The obtained liquid crystal orientation fixed layer A (H layer) and liquid crystal orientation fixed layer B (Q layer) were transferred to the polarizer side of the obtained polarizing plate in this order. At this time, transfer (lamination) was performed so that the angle between the absorption axis of the polarizer and the slow axis of the alignment-fixed layer A was 15°, and the angle between the absorption axis of the polarizer and the slow axis of the orientation-fixed layer B was 75°. . The transfer of the liquid crystal alignment solidification layer A (H layer) was performed through an ultraviolet curing adhesive (thickness 0.5 μm). The transfer of the liquid crystal alignment solidification layer B (Q layer) was performed through an ultraviolet curing adhesive (thickness of 1.5 μm). In this way, a laminate precursor was obtained. In addition, transfer was performed while roll conveying. In addition, the transfer was performed in an environment with a water vapor amount of 9.3 g/m3 (23°C and 45% RH).

On the protective layer side of the polarizing plate of the obtained laminate precursor, a surface protection film with a thickness of 90 μm (PPF-911, manufactured by Fujimori Industries, Ltd., base material (PET) thickness of 75 μm, adhesive layer thickness of 15 μm) was roll-conveyed. It was joined together. Additionally, on the liquid crystal alignment solidification layer B (Q layer) side of the laminate precursor, an acrylic pressure-sensitive adhesive layer (15 μm thick) was rolled while conveying a 50 μm thick release film (MHE50, PET-based film, manufactured by Mitsubishi Chemical Corporation). were bonded together through an interposition to obtain a laminate.

The thickness of the laminated portion from the polarizing plate to the adhesive layer of the obtained laminate (thickness of the polarizing plate with retardation layer) was 46 μm.

[Example 2]

Except that a surface protection film (manufactured by Nitto Denko, 'RP109F', base material (PET) thickness of 38 μm, adhesive layer thickness of 10 μm) with a thickness of 48㎛ was bonded to the protective layer side of the polarizing plate of the laminate precursor. A laminate was obtained in the same manner as in Example 1.

[Example 3]

A laminate was obtained in the same manner as in Example 1 except that the tension applied to the surface protection film was changed when bonding the surface protection film.

[Comparative Example 1]

A laminate was prepared in the same manner as in Example 1, except that a 38-μm-thick release film (MHE38, PET-based film, manufactured by Mitsubishi Chemical Corporation) was bonded to the liquid crystal alignment layer B (Q layer) side of the laminate precursor. got it

[Comparative Example 2]

A laminate was prepared in the same manner as in Example 1, except that a 50-μm-thick release film (Mitsubishi Chemical Company, 'MRF50', PET-based film) was bonded to the liquid crystal alignment solidification layer B (Q layer) side of the laminate precursor. got it

[Comparative Example 3]

Except that a surface protection film with a thickness of 48 ㎛ (RP1010M' manufactured by Nitto Denko, base material (PET) thickness of 38 ㎛, adhesive layer thickness of 10 ㎛) was bonded to the protective layer side of the polarizing plate of the laminate precursor. A laminate was obtained in the same manner as in Example 1.

<Evaluation>

1. Peel force

A sample of the obtained laminate was cut to a size of 25 mm in width and 50 mm in length, left in an environment of 23°C The peeling force (N/25mm) when peeled was measured. Specifically, the peeling force Fr of the release film to the adhesive layer and the peeling force Fp of the surface protection film to the polarizing plate were measured. In addition, the measurement was conducted under an environment of 23°C x 50% RH.

2. Bending

A test piece measuring 171 mm x 127 mm was cut from the obtained laminate. At this time, the polarizer was cut so that the absorption axis direction was in the long side direction. When the cut test piece was placed on a flat surface so that the release film side was on the flat surface, the height of the highest part from the flat surface was measured to determine the amount of deflection. Here, the case where the bending was convex towards the stationary surface was called 'negative (-)', and the case where the bend was convex towards the side opposite to the stationary surface was called 'positive (+)'. In addition, the values (unit: %) shown in Table 1 are values obtained according to the amount of deflection (mm)/long side (171 mm) x 100.

3. Peel test

The obtained laminate was cut into a size of 171 mm x 127 mm, and a sheet-shaped laminate was obtained. At this time, the polarizer was cut so that the absorption axis direction was 45° with respect to the long side.

As shown in FIG. 3, the release film and the surface protection film were peeled from the obtained sheet-like laminate, the polarizing plate with a retardation layer was bonded to the organic EL panel main body, and the presence or absence of peeling defects was confirmed.

[Table 1]

It can be seen that the peelability can be excellent in each example even in a state where negative bending (e.g., 1% or more) occurs in the laminate.

In the laminate of Comparative Example 1, many marks were confirmed on the adhesive layer (adhesive) disposed between the retardation layer and the release film.

In Comparative Example 2, the release film did not peel from the adhesive layer at the time of peeling of the release film, and peeling occurred between the surface protection film and the polarizing plate. In Comparative Example 3, when the surface protection film was peeled off, the surface protection film did not peel off from the polarizing plate, and the organic EL panel main body fell off from the suction plate.

[Industrial applicability]

The polarizing plate with a retardation layer obtained from the laminate according to one embodiment of the present invention can be used as a polarizing plate with a retardation layer in an image display device, and can be particularly suitably used in an image display device that is curved or can be bent, folded, or rolled. You can. Representative image display devices include liquid crystal display devices, organic EL display devices, and inorganic EL display devices.

10: Polarizer
11: Polarizer
12: protective layer
20: Phase contrast layer
21: First phase difference layer (H layer)
22: Second phase difference layer (Q layer)
30: Surface protection film
40: Adhesive layer
50: release film
70: Image display panel body
80: Image display panel
90: Laminate precursor
100: Laminate
110: Polarizer with phase contrast layer

Claims (8)

A laminate comprising a surface protection film, a polarizing plate including a polarizer and a protective layer, a retardation layer, an adhesive layer, and a release film in this order,
The thickness of the laminated portion from the polarizing plate to the adhesive layer is 70 μm or less,
The thickness of the release film is 40㎛ or more,
The peeling force Fr of the release film with respect to the adhesive layer is 0.04N/25mm or less,
The peeling force Fp of the surface protection film with respect to the polarizing plate is greater than the Fr and is 0.1 N/25 mm or less,
Laminate. According to paragraph 1,
A laminate wherein the surface protection film has a thickness of 60 μm or more. According to claim 1 or 2,
A laminate wherein the surface protection film has a thickness greater than the thickness of the laminated portion. According to any one of claims 1 to 3,
A laminate in which a protective layer is disposed on the polarizing plate only on the side of the polarizer on which the retardation layer is not disposed. According to any one of claims 1 to 4,
A laminate wherein the thickness of the polarizer is 8 μm or less. According to any one of claims 1 to 5,
A laminate wherein the retardation layer is an alignment solidification layer of a liquid crystal compound. According to any one of claims 1 to 6,
A laminate with a warpage of 5% or less. Preparing the laminate according to any one of claims 1 to 7,
bonding the laminate obtained by peeling the release film from the adhesive layer to the image display panel main body, and
Peeling off the surface protection film from the polarizing plate
A method of manufacturing an image display panel comprising in this order.