Polarizing plate manufacturing method

Abstract

To provide a method for manufacturing a one-side protected polarizing plate with suppressed poor appearance.SOLUTION: A polarizing plate manufacturing method includes: a first step of pasting a protective film 20 to one surface of a polarizing film 5 via an aqueous adhesive layer, and laminating a release film 10 on the other surface of the polarizing film via volatile liquid; and a second step of drying the aqueous adhesive layer by heating, and evaporating the volatile liquid. A maximum height Rz on the polarizing film-side surface of the release film that is stipulated in JIS B0601-2001 is 70 nm or less.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a method for producing a polarizing plate in which a protective film is attached to one surface of a polarizing film. [Background technology]

[0002] Polarizing plates are widely used as polarized light supplying elements and polarized light detecting elements in display devices such as liquid crystal display devices. Polarizing plates generally have a structure in which a protective film is attached to a polarizing film using an adhesive.

[0003] In response to market demands for thinner and lighter polarizing plates, various polarizing plate configurations have been proposed that can achieve this, and one representative example is a single-sided protected polarizing plate in which a protective film is attached to only one side of the polarizing film (e.g., Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-109860 Summary of the Invention [Problem to be solved by the invention]

[0005] In manufacturing a single-side-protected polarizing plate, a protective film is bonded to one side of a polarizing film via an adhesive layer, and a peelable release film is laminated on the other side of the polarizing film, on which the protective film is not bonded, in order to temporarily protect the other side. This release film is peeled and removed, for example, in the process of bonding the single-side-protected polarizing plate to a liquid crystal cell.

[0006] However, a polarizing plate from which the release film has been peeled has a problem in that defects such as dents occur on the surface where the release film was laminated, resulting in poor appearance. An object of the present invention is to provide a method for producing a single-side-protected polarizing plate in which poor appearance is suppressed. [Means for solving the problem]

[0007] The present invention provides a method for producing a polarizing plate and a single-side-protected polarizing plate, as exemplified below. [1] A first step of laminating a protective film on one side of a polarizing film via an aqueous adhesive layer and laminating a release film on the other side of the polarizing film via a volatile liquid; a second step of drying the aqueous adhesive layer and volatilizing the volatile liquid by heating, The method for producing a polarizing plate, wherein the release film has a maximum height Rz of 70 nm or less on the surface on the polarizing film side as defined in JIS B0601-2001. [2] The method for producing a polarizing plate according to [1], wherein the release film has a coating layer formed on the surface thereof facing the polarizing film. [3] The method for producing a polarizing plate according to [2], wherein the coating layer of the release film has a thickness of 30 μm or less. [4] The method for producing a polarizing plate according to [2] or [3], wherein the coating layer of the release film is made of a cured product of a (meth)acrylic resin. [5] At least one of the protective film and the release film has a moisture permeability of 400 g / m 2 The method for producing a polarizing plate according to any one of [1] to [4], wherein the process lasts for 24 hours or longer. [6] The method for producing a polarizing plate according to any one of [1] to [5], wherein the thickness of the aqueous adhesive layer is 10 nm or more and 1 μm or less. [7] The method for producing a polarizing plate according to any one of [1] to [6], wherein the protective film has a thickness of 1 μm or more and 90 μm or less. [8] The method for producing a polarizing plate according to any one of [1] to [7], wherein the polarizing film has a thickness of 1 μm or more and 40 μm or less. [9] The method for producing a polarizing plate according to any one of [1] to [8], further comprising a third step of peeling the release film from the polarizing film.

[10] The method for producing a polarizing plate according to [9], wherein in the third step, the peeling force between the polarizing film and the release film is 0.01 N / 25 mm or more and 2.0 N / 25 mm or less.

[11] A polarizing film and a protective film attached to one side of the polarizing film, The polarizing film is a single-sided protected polarizing plate, in which the maximum height Rz of the surface opposite to the protective film as defined in JIS B0601-2001 is 60 nm or less.

[12] A polarizing film and a protective film attached to one side of the polarizing film, The polarizing film has 10 depressions per m2 with a width of 0.5 mm or more and 2.0 mm or less and a depth of 0.1 μm or more and 1.0 μm or less on the surface opposite to the protective film. 2 Below is a single-sided protective polarizer. [Effects of the Invention]

[0008] According to the present invention, it is possible to produce a single-side protected polarizing plate in which defects in appearance are suppressed. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic cross-sectional view showing the basic layer structure of a single-side protected polarizing plate. [Figure 2] FIG. 10 is a schematic cross-sectional view showing another example of a single-sided protected polarizing plate. [Figure 3] FIG. 10 is a schematic cross-sectional view showing another example of a single-sided protected polarizing plate. [Figure 4] FIG. 1 is a schematic cross-sectional view showing the layer structure of a double-sided protected polarizing plate that can be obtained using a single-sided protected polarizing plate. [Figure 5] 1 is a side view schematically illustrating an example of a method for producing a single-side-protected polarizing plate according to the present invention and a production apparatus used therein. [Figure 6] 1 shows atomic force microscope images of the surface of the polarizing film on the side opposite to the protective film in the single-sided protected polarizing plate of Example 1. (A) is a plan view of the surface, and (B) is a three-dimensional shape diagram of the surface. [Figure 7]1 shows atomic force microscope images of the surface of the polarizing film on the side opposite to the protective film in the single-sided protected polarizing plate of Comparative Example 1. (A) is a plan view of the surface, and (B) is a three-dimensional shape diagram of the surface. DETAILED DESCRIPTION OF THE INVENTION

[0010] <Polarizing Plate Manufacturing Method> The present invention relates to a method for manufacturing a single-sided protected polarizing plate. In the present invention, a "single-sided protected polarizing plate" refers to a polarizing plate in which a protective film is bonded to only one side of a polarizing film, and this protective film is usually bonded to the polarizing film via an adhesive layer. The basic structure of a single-sided protected polarizing plate is shown in FIG. 1. Like the single-sided protected polarizing plate 1 shown in FIG. 1, the single-sided protected polarizing plate according to the present invention basically comprises a polarizing film 5 and a first protective film 20 bonded to one side of the polarizing film via a first adhesive layer 25.

[0011] As will be described in detail later, the manufacturing method according to the present invention includes a first step of bonding a protective film (first protective film) to one surface of a polarizing film via an aqueous adhesive layer and laminating a release film to the other surface via a volatile liquid, and a second step of drying the aqueous adhesive layer and volatilizing the volatile liquid by heating. The single-sided protected polarizing plate obtained through these first and second steps further includes a release film 10 laminated on the other surface of the polarizing film 5, as in the single-sided protected polarizing plate 2 with a release film shown in FIG.

[0012] The release film 10 is a film that can be peeled off from the polarizing film 5, and is peeled off and removed when necessary (for example, when the single-sided protected polarizing plate is to be attached to a liquid crystal cell) to obtain the single-sided protected polarizing plate 1 shown in Fig. 1. For example, in order to be attached to a liquid crystal cell, the single-sided protected polarizing plate according to the present invention can further include an adhesive layer 30 laminated on the other side of the polarizing film 5, as in the single-sided protected polarizing plate 3 with an adhesive layer shown in Fig. 3.

[0013] In addition, the single-sided protected polarizing plate 1 and the single-sided protected polarizing plate 2 with a release film of the present invention can also be suitably used as manufacturing intermediates for double-sided protected polarizing plates in which protective films are bonded to both sides of a polarizing film.Referring to Figure 4, a double-sided protected polarizing plate 4 can be obtained by bonding a second protective film 21 to the side of the polarizing film 5 opposite to the first protective film 20 via a second adhesive layer 26.

[0014] The release film 10 has a maximum height Rz, as defined in JIS B0601-2001, of 70 nm or less, preferably 50 nm or less, more preferably 30 nm or less, and even more preferably 20 nm or less, on the surface facing the polarizing film 5. When the surface roughness of the release film 10 laminated to the polarizing film 5 in the first step is within the above-mentioned range, the produced single-sided protected polarizing plate 1 has reduced depressions on the surface facing the polarizing film 5, and a single-sided protected polarizing plate with reduced appearance defects can be obtained. By reducing appearance defects in the single-sided protected polarizing plate, a decrease in the yield in the production of single-sided protected polarizing plates can be suppressed.

[0015] Hereinafter, the method for producing a single-sided protected polarizing plate according to the present invention will be described in detail with reference to an embodiment with reference to Fig. 5. The method for producing a single-sided protected polarizing plate according to the present invention comprises the following steps: (1) a first step of bonding a first protective film to one surface of a polarizing film via a water-based adhesive layer and laminating a release film to the other surface of the polarizing film via a layer made of a volatile liquid; (2) a second step of drying the aqueous adhesive layer and volatilizing the volatile liquid by heating; Includes:

[0016] Fig. 5 is a side view schematically showing an example of a method for producing a single-sided protected polarizing plate according to the present invention and a production apparatus used therein. Generally, polarizing plates such as single-sided protected polarizing plates can be continuously produced as long products by continuously unwinding and transporting a long film while performing treatments in each step, as shown in Fig. 5. However, the production method of the present invention is not limited to continuous production using such a long film, and may also be a method using a sheet film.

[0017] (1) First step Referring to FIG. 5, in this process, first, a roll (wound product) of a long polarizing film 5, a roll of a long first protective film 20, and a roll of a long release film 10 are prepared, and these are continuously unwound using an unwinding device (not shown) to transport the films. Each film is transported so that its longitudinal direction is the transport direction. Guide rolls 60 that support the running film are appropriately provided along the film transport path. The arrows in FIG. 5 indicate the film transport direction or the rotation direction of the various rolls. Typically, the transport direction of the polarizing film 5 (film longitudinal direction), the transport direction of the first protective film 20 (film longitudinal direction), and the transport direction of the release film 10 (film longitudinal direction) are parallel to each other.

[0018] In this step, a first protective film 20 is bonded to one surface of the polarizing film 5 via a first adhesive layer 25 (not shown in FIG. 5 ), which is an aqueous adhesive layer, and a release film 10 is laminated to the other surface of the polarizing film 5 via a layer made of a volatile liquid 50. The bonding of the first protective film 20 and the lamination of the release film 10 can be carried out by overlapping the first protective film 20, polarizing film 5, and release film 10 so that their longitudinal directions (conveyance directions) are parallel, passing them between a pair of laminating rolls 40, 40, and pressing the laminated films from above and below with the laminating rolls 40, 40, as shown in FIG.

[0019] In this case, before passing between the laminating rolls 40, 40, injection devices 80, 81 are used to inject a water-based adhesive 55 between the polarizing film 5 and the first protective film 20, and a volatile liquid 50 is injected between the polarizing film 5 and the release film 10, thereby interposing a layer of the water-based adhesive 55 (first adhesive layer 25) and a layer of the volatile liquid 50 between these films, respectively.

[0020] The device for interposing the layer made of the water-based adhesive 55 (first adhesive layer 25) and the layer made of the volatile liquid 50 is not limited to the injection devices 80, 81 as shown in FIG. 5 , and depending on the viscosity and other factors of the water-based adhesive 55 and the volatile liquid 50, a coating method such as a doctor blade method, wire bar coating method, die coating method, comma coater method, gravure coating method, dip coating method, or casting method may be appropriately selected to coat the water-based adhesive 55 and the volatile liquid 50 on the bonding surface of at least one of the films to be superimposed.

[0021] In conventional methods for producing single-sided protected polarizing plates, a release film is directly laminated on the polarizing film surface without any special layer interposed therebetween, which has led to the problem that the polarizing film is prone to breakage during the process of producing a single-sided protected polarizing plate. When a protective film is attached to one surface of a polarizing film via an aqueous adhesive layer, a step of drying the aqueous adhesive layer is required to obtain a single-sided protected polarizing plate, but in conventional production methods, the polarizing film is prone to breakage particularly during this drying step.

[0022] In contrast, according to the manufacturing method of the present invention in which a layer of volatile liquid 50 is interposed between polarizing film 5 and release film 10 and release film 10 is laminated to polarizing film 5, breakage of polarizing film 5 can be effectively suppressed even in the step (second step) of drying the layer of aqueous adhesive 55 (first adhesive layer 25). Furthermore, interposing a layer of volatile liquid 50 between polarizing film 5 and release film 10 also has the effect of suppressing the occurrence of wrinkles in the single-sided protected polarizing plate during the process of manufacturing the single-sided protected polarizing plate.

[0023] Since the intervening volatile liquid 50 can be evaporated during the step of drying the first adhesive layer 25 (second step), the manufacturing method of the present invention does not require a separate step for volatilizing and removing the volatile liquid 50.

[0024] When bonding the first protective film 20 to the polarizing film 5, the bonding surface of the polarizing film 5 and / or the first protective film 20 may be subjected to an adhesion-facilitating treatment such as plasma treatment, corona treatment, ultraviolet irradiation treatment, flame (flame) treatment, or saponification treatment to improve adhesion. Among these, plasma treatment, corona treatment, or saponification treatment is preferred. For example, when the first protective film 20 is made of a cyclic polyolefin resin, the bonding surface of the first protective film 20 may be subjected to plasma treatment or corona treatment. Furthermore, when the first protective film 20 is made of a cellulose ester resin, the bonding surface of the first protective film 20 may be subjected to saponification treatment. Examples of saponification treatment include a method of immersing in an alkaline aqueous solution such as sodium hydroxide or potassium hydroxide.

[0025] [Polarizing film] The polarizing film 5 can be a uniaxially stretched polyvinyl alcohol resin film to which a dichroic dye is adsorbed and aligned. The polyvinyl alcohol resin constituting the polyvinyl alcohol resin film can be a saponified polyvinyl acetate resin. Examples of polyvinyl acetate resins include polyvinyl acetate, which is a homopolymer of vinyl acetate, and copolymers of vinyl acetate with other monomers copolymerizable therewith. Examples of other monomers copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and (meth)acrylamides having an ammonium group.

[0026] In this specification, "(meth)acrylic" means at least one selected from acrylic and methacrylic. The same applies to "(meth)acryloyl" and "(meth)acrylate".

[0027] The saponification degree of the polyvinyl alcohol resin can be in the range of 80.0 to 100.0 mol%, preferably in the range of 90.0 to 99.5 mol%, and more preferably in the range of 94.0 to 99.0 mol%. If the saponification degree is less than 80.0 mol%, the water resistance and moist heat resistance of the resulting single-sided protected polarizing plate will be reduced. If a polyvinyl alcohol resin with a saponification degree of more than 99.5 mol% is used, the dyeing speed will be slow, productivity will be reduced, and a polarizing film 5 with sufficient polarizing performance may not be obtained.

[0028] The degree of saponification is the ratio of acetate groups (acetoxy groups: -OCOCH3) contained in polyvinyl acetate resin, which is the raw material for polyvinyl alcohol resin, that are converted to hydroxyl groups during the saponification process, expressed as a unit ratio (mol %), and is calculated using the following formula: Saponification degree (mol%) = 100 × (number of hydroxyl groups) / (number of hydroxyl groups + number of acetate groups) The degree of saponification can be determined in accordance with JIS K 6726 (1994). A higher degree of saponification indicates a higher proportion of hydroxyl groups, and therefore a lower proportion of acetate groups that inhibit crystallization.

[0029] The average degree of polymerization of the polyvinyl alcohol resin is preferably 100 to 10,000, more preferably 1,500 to 8,000, and even more preferably 2,000 to 5,000. The average degree of polymerization of the polyvinyl alcohol resin can also be determined in accordance with JIS K 6726 (1994). If the average degree of polymerization is less than 100, it is difficult to obtain favorable polarizing performance, and if it exceeds 10,000, solubility in solvents deteriorates, making it difficult to form a polyvinyl alcohol resin film.

[0030] The polarizing film 5 can be produced through the steps of uniaxially stretching a polyvinyl alcohol-based resin film; dyeing the polyvinyl alcohol-based resin film with a dichroic dye to adsorb the dichroic dye; treating the polyvinyl alcohol-based resin film with the adsorbed dichroic dye with an aqueous boric acid solution; and washing the film with water after the treatment with the aqueous boric acid solution.

[0031] The polyvinyl alcohol-based resin film is produced by forming the above-mentioned polyvinyl alcohol-based resin. The film-forming method is not particularly limited, and known methods such as melt extrusion and solvent casting can be used. The thickness of the polyvinyl alcohol-based resin film is, for example, about 1 to 150 μm.

[0032] The uniaxial stretching of the polyvinyl alcohol-based resin film can be performed before, simultaneously with, or after dyeing with a dichroic dye. When the uniaxial stretching is performed after dyeing, the uniaxial stretching may be performed before or during the boric acid treatment. Alternatively, the uniaxial stretching may be performed in a plurality of these stages.

[0033] In the uniaxial stretching, the film may be stretched uniaxially between rolls with different peripheral speeds, or may be stretched uniaxially using a heated roll. The uniaxial stretching may be dry stretching in which stretching is performed in the atmosphere, or wet stretching in which the polyvinyl alcohol-based resin film is stretched in a swollen state using a solvent. The stretching ratio is usually about 3 to 8 times.

[0034] As a method for dyeing a polyvinyl alcohol-based resin film with a dichroic dye, for example, a method of immersing the polyvinyl alcohol-based resin film in an aqueous solution (dyeing solution) containing the dichroic dye is adopted. The polyvinyl alcohol-based resin film is preferably subjected to a water immersion treatment (swelling treatment) before the dyeing treatment.

[0035] The dichroic dye contained (adsorbed and oriented) in the polarizing film 5 can be iodine or a dichroic organic dye. When iodine is used as the dichroic dye, a method of dyeing a polyvinyl alcohol resin film by immersing it in an aqueous solution containing iodine and potassium iodide is usually employed. The iodine content in this aqueous dye solution is usually about 0.01 to 1 part by weight per 100 parts by weight of water. The potassium iodide content is usually about 0.5 to 20 parts by weight per 100 parts by weight of water. The temperature of the aqueous dye solution is usually about 20 to 40°C. The immersion time in the aqueous dye solution (dyeing time) is usually about 20 to 1,800 seconds.

[0036] On the other hand, when a dichroic organic dye is used as the dichroic pigment, a method of dyeing a polyvinyl alcohol resin film by immersing it in a dyeing aqueous solution containing a water-soluble dichroic organic dye is usually adopted. The content of the dichroic organic dye in the dyeing aqueous solution is usually 1 × 10 per 100 parts by weight of water. -4 ~10 parts by weight, 1×10 -3 The amount of the aqueous dye solution is preferably about 1 part by weight to 1 part by weight. This aqueous dye solution may contain an inorganic salt such as sodium sulfate as a dyeing assistant. The temperature of the aqueous dye solution is usually about 20 to 80°C. The immersion time in the aqueous dye solution (dyeing time) is usually about 10 to 1800 seconds.

[0037] The boric acid treatment after dyeing with a dichroic dye can be carried out by immersing the dyed polyvinyl alcohol-based resin film in an aqueous solution containing boric acid.

[0038] The amount of boric acid in the boric acid-containing aqueous solution is usually about 2 to 15 parts by weight, preferably 5 to 12 parts by weight, per 100 parts by weight of water. When iodine is used as the dichroic dye, the boric acid-containing aqueous solution preferably contains potassium iodide. The amount of potassium iodide in the boric acid-containing aqueous solution is usually about 0.1 to 15 parts by weight, preferably about 5 to 12 parts by weight, per 100 parts by weight of water. The immersion time in the boric acid-containing aqueous solution is usually about 60 to 1200 seconds, preferably about 150 to 600 seconds, and more preferably about 200 to 400 seconds. The temperature of the boric acid-containing aqueous solution is usually 50°C or higher, preferably 50 to 85°C, and more preferably 60 to 80°C.

[0039] After the boric acid treatment, the polyvinyl alcohol-based resin film is usually washed with water. The washing can be carried out, for example, by immersing the boric acid-treated polyvinyl alcohol-based resin film in water. The temperature of the water used in the washing is usually about 1 to 40°C. The immersion time is usually about 1 to 120 seconds.

[0040] After rinsing with water, the film is dried to obtain polarizing film 5. Various drying methods are available, including blowing hot air, contacting a heated roll, and heating with an IR heater, and any of these methods can be used. Contacting a heated roll to dry is advantageous because it improves drying efficiency, shortens the drying time, and suppresses shrinkage in the width direction of the film, allowing for wider widths. The drying temperature in the drying process refers to the ambient temperature inside the drying oven in the case of a method using blowing hot air or an IR heater, or the surface temperature of the heated roll in the case of contact-type drying equipment such as a heated roll. The drying temperature is typically about 30 to 100°C, preferably 50 to 80°C. The drying time is typically about 60 to 600 seconds, preferably 120 to 600 seconds.

[0041] The drying treatment reduces the moisture content of the polarizing film 5 to a practical level. The moisture content is usually adjusted to 5 to 45% by weight, and more preferably 8 to 40% by weight. If the moisture content is lower than 5% by weight, the polarizing film 5 loses its flexibility and may be damaged or break after drying. If the moisture content is higher than 45% by weight, it becomes difficult to achieve sufficient adhesion to the protective film, which can lead to problems such as poor appearance or the film breaking in the production line, contaminating the process.

[0042] The thickness of the polarizing film 5 is usually about 1 to 40 μm, preferably 2 to 20 μm, and more preferably 2 to 10 μm. The polarizing film 5 is preferably thin from the viewpoint of thinning the polarizing plate, but as the polarizing film 5 becomes thinner, defects in appearance caused by depressions that occur in the polarizing film 5 tend to become more pronounced. According to the present invention, defects in appearance that occur in the polarizing plate can be suppressed even when a thin polarizing film is used.

[0043] [First protective film] The first protective film 20 can be a transparent resin film made of a thermoplastic resin, for example, a polyolefin resin such as a linear polyolefin resin (such as a polypropylene resin) or a cyclic polyolefin resin (such as a norbornene resin); a cellulose ester resin such as cellulose triacetate or cellulose diacetate; a polyester resin such as polyethylene terephthalate, polyethylene naphthalate, or polybutylene terephthalate; a polycarbonate resin; a (meth)acrylic resin such as a polymethyl methacrylate resin; or a mixture, copolymer, or the like of these.

[0044] Examples of linear polyolefin resins include homopolymers of linear olefins such as polyethylene resins and polypropylene resins, as well as copolymers of two or more linear olefins. More specific examples include polypropylene resins (polypropylene resins which are homopolymers of propylene and copolymers mainly composed of propylene) and polyethylene resins (polyethylene resins which are homopolymers of ethylene and copolymers mainly composed of ethylene).

[0045] Cyclic polyolefin resin is a general term for resins polymerized using cyclic olefins as polymerization units, and examples thereof include resins described in JP-A-1-240517, JP-A-3-14882, JP-A-3-122137, etc. Specific examples of cyclic polyolefin resins include ring-opening (co)polymers of cyclic olefins, addition polymers of cyclic olefins, copolymers (typically random copolymers) of cyclic olefins with chain olefins such as ethylene and propylene, graft polymers modified with unsaturated carboxylic acids or their derivatives, and hydrogenated products thereof. Among these, norbornene resins using norbornene monomers such as norbornene or polycyclic norbornene monomers as the cyclic olefin are preferred.

[0046] Cellulose ester resins are esters of cellulose and fatty acids. Specific examples of cellulose ester resins include cellulose triacetate, cellulose diacetate, cellulose tripropionate, and cellulose dipropionate. Copolymers of these resins and those in which some of the hydroxyl groups have been modified with other substituents can also be used. Among these, cellulose triacetate (triacetyl cellulose: TAC) is particularly preferred.

[0047] Polyester resins are resins having ester bonds, and are generally composed of polycondensates of polycarboxylic acids or their derivatives with polyhydric alcohols. Examples of polycarboxylic acids or their derivatives include dicarboxylic acids or their derivatives, such as terephthalic acid, isophthalic acid, dimethyl terephthalate, and dimethyl naphthalenedicarboxylate. Examples of polyhydric alcohols include dihydric diols, such as ethylene glycol, propanediol, butanediol, neopentyl glycol, and cyclohexanedimethanol. Examples of suitable polyester resins include polyethylene terephthalate.

[0048] Polycarbonate resins are engineering plastics made of polymers in which monomer units are bonded via carbonate groups, and have high impact resistance, heat resistance, flame retardancy, and transparency. The polycarbonate resins may be modified polycarbonates, in which the polymer skeleton is modified to reduce the photoelastic coefficient, or copolymer polycarbonates with improved wavelength dependency.

[0049] The (meth)acrylic resin is a resin whose main constituent monomer is a compound having a (meth)acryloyl group. Specific examples of the (meth)acrylic resin include poly(meth)acrylic acid esters such as polymethyl methacrylate; methyl methacrylate-(meth)acrylic acid copolymers; methyl methacrylate-(meth)acrylic acid ester copolymers; methyl methacrylate-acrylic acid ester-(meth)acrylic acid copolymers; methyl (meth)acrylate-styrene copolymers (MS resins, etc.); and copolymers of methyl methacrylate and compounds having alicyclic hydrocarbon groups (e.g., methyl methacrylate-cyclohexyl methacrylate copolymers, methyl methacrylate-norbornyl (meth)acrylate copolymers, etc.). Preferably, poly(meth)acrylic acid C such as polymethyl (meth)acrylate is used. 1-6 A polymer containing an alkyl ester as a main component is used, and more preferably, a methyl methacrylate-based resin containing methyl methacrylate as a main component (50 to 100% by weight, preferably 70 to 100% by weight) is used.

[0050] The first protective film 20 may also be a protective film having optical functions such as a retardation film and a brightness enhancement film. For example, a retardation film having an arbitrary retardation value can be obtained by stretching (uniaxially or biaxially stretching, etc.) a transparent resin film made of the above-mentioned material or by forming a liquid crystal layer or the like on the film.

[0051] A surface treatment layer (coating layer) such as a hard coat layer, an antiglare layer, an antireflection layer, an antistatic layer, or an antifouling layer may be formed on the surface of the first protective film 20 opposite to the polarizing film 5. The method for forming a surface treatment layer on the surface of the protective film is not particularly limited, and known methods can be used.

[0052] The thickness of the first protective film 20 is preferably 1 to 90 μm, more preferably 1 to 60 μm, and even more preferably 1 to 50 μm.

[0053] At least one of the first protective film and the release film described later has a moisture permeability of 400 g / m 2 The moisture permeability of the first protective film 20 is preferably 400 g / m 2 24 hours or more is preferable, 420 g / m 2 If the moisture permeability is in this range, the layer made of the water-based adhesive 55 can be dried efficiently in the subsequent second step, thereby increasing productivity.

[0054] [Water-based adhesive] The aqueous adhesive 55 forming the first adhesive layer 25 is an adhesive component dissolved or dispersed in water. A preferred aqueous adhesive is, for example, an adhesive composition using a polyvinyl alcohol resin or a urethane resin as the main component. The thickness of the first adhesive layer 25 formed from the aqueous adhesive is usually 10 nm to 1 μm or less.

[0055] When a polyvinyl alcohol resin is used as the main component of the adhesive, the polyvinyl alcohol resin may be a partially saponified polyvinyl alcohol, a fully saponified polyvinyl alcohol, or a modified polyvinyl alcohol resin such as a carboxyl group-modified polyvinyl alcohol, an acetoacetyl group-modified polyvinyl alcohol, a methylol group-modified polyvinyl alcohol, or an amino group-modified polyvinyl alcohol. The polyvinyl alcohol resin may be a vinyl alcohol homopolymer obtained by saponifying polyvinyl acetate, which is a homopolymer of vinyl acetate, or a polyvinyl alcohol copolymer obtained by saponifying a copolymer of vinyl acetate and another monomer copolymerizable therewith.

[0056] A water-based adhesive containing a polyvinyl alcohol resin as an adhesive component is usually an aqueous solution of the polyvinyl alcohol resin. The concentration of the polyvinyl alcohol resin in the adhesive is usually 1 to 10 parts by weight, preferably 1 to 5 parts by weight, per 100 parts by weight of water.

[0057] To improve adhesion, adhesives composed of aqueous solutions of polyvinyl alcohol-based resins preferably contain curing components or crosslinking agents, such as polyaldehydes, melamine compounds, zirconia compounds, zinc compounds, glyoxal, or water-soluble epoxy resins. Examples of water-soluble epoxy resins include polyamidepolyamine epoxy resins obtained by reacting epichlorohydrin with polyamidoamines obtained by reacting polyalkylene polyamines, such as diethylenetriamine or triethylenetetramine, with dicarboxylic acids, such as adipic acid. Commercially available polyamidepolyamine epoxy resins include Sumirez Resin 650 (manufactured by Taoka Chemical Co., Ltd.), Sumirez Resin 675 (manufactured by Taoka Chemical Co., Ltd.), and WS-525 (manufactured by Nippon PMC Corporation). The amount of these curing components or crosslinking agents (the total amount when both are added as a curing component and a crosslinking agent) added is typically 1 to 100 parts by weight, preferably 1 to 50 parts by weight, per 100 parts by weight of polyvinyl alcohol-based resin. If the amount of the curable component or crosslinking agent added is less than 1 part by weight per 100 parts by weight of polyvinyl alcohol-based resin, the effect of improving adhesion tends to be small, and if the amount of the curable component or crosslinking agent added is more than 100 parts by weight per 100 parts by weight of polyvinyl alcohol-based resin, the adhesive layer tends to become brittle.

[0058] Furthermore, when a urethane resin is used as the main component of the adhesive, an example of a suitable adhesive composition is a mixture of a polyester ionomer urethane resin and a compound having a glycidyloxy group. A polyester ionomer urethane resin is a urethane resin having a polyester skeleton into which a small amount of an ionic component (hydrophilic component) has been introduced. Such an ionomer urethane resin is suitable as an aqueous adhesive because it can be directly emulsified in water to form an emulsion without the use of an emulsifier.

[0059] [Release film] The release film 10 is a film that can be peeled off at a desired timing after being laminated on the polarizing film 5. "Peelable" means that the polarizing film 5 and the release film 10 can be separated without damaging or damaging the polarizing film 5 or the release film 10.

[0060] In consideration of handleability, transparency, low cost, etc., the release film 10 can be a transparent resin film made of, for example, a linear polyolefin resin such as a polyethylene resin or a polypropylene resin; a cellulose ester resin such as cellulose triacetate or cellulose diacetate; a polyester resin such as polyethylene terephthalate, polyethylene naphthalate, or polybutylene terephthalate; a (meth)acrylic resin such as a polymethyl methacrylate resin, or a mixture or copolymer thereof. A film formed from one or more of these resins in a single layer or multilayer configuration can also be used as the release film 10. Among these, films made from polyethylene terephthalate, cellulose triacetate, or a polymethyl methacrylate resin are preferably used.

[0061] The peeling force between the polarizing film 5 and the release film 10 is, for example, 0.01 N / 25 mm to 2.0 N / 25 mm, and preferably 0.01 N / 25 mm to 0.5 N / 25 mm. When the peeling force is 0.01 N / 25 mm or more, partial peeling between the polarizing film 5 and the release film 10 can be prevented. When the peeling force is 2.0 N / 25 mm or less, the release film 10 can be easily peeled from the polarizing film 5 in the third step described below.

[0062] The peel force is determined by cutting a single-sided protected polarizing plate laminated with release film 10 into a 25 mm width to obtain a measurement sample, and then using a precision universal testing machine "Autograph AGS-50NX" manufactured by Shimadzu Corporation, gripping the release film 10 and the single-sided protected polarizing plate of the measurement sample and measuring the force required to peel them off in a 180° direction. The peel force is measured at a peel rate of 300 mm / min in an environment of a temperature of 23±2°C and a relative humidity of 50±5%.

[0063] The thickness of the release film 10 is, for example, about 5 to 100 μm, preferably about 10 to 80 μm, and more preferably 10 to 60 μm.

[0064] The moisture permeability of the release film 10 is preferably 400 g / m 2 24 hours or more, preferably 420 g / m 2 24 hours or more, preferably 450 g / m 2 24 hours or more, even more preferably 500g / m 2 If the moisture permeability is within this range, the volatile liquid 50 can be efficiently removed by evaporation in the subsequent second step, thereby preventing quality problems such as deterioration of optical properties and poor appearance due to insufficient drying.

[0065] The shrinkage rate (heat shrinkage rate) of the release film 10 when heated at 80°C for 5 minutes is preferably 0.15% or less, and more preferably 0.1% or less. If the heat shrinkage rate of the release film 10 is large, wrinkles are more likely to occur in the release film 10 during the heat treatment in the second step, and as a result, wrinkles are more likely to occur in the single-sided protected polarizing plate. Examples of resin materials with heat shrinkage rates within the above range include polyethylene terephthalate, cellulose triacetate, and polymethyl methacrylate resins. "A heat shrinkage rate of 0.15% or less" means that both the MD shrinkage rate and the TD shrinkage rate are 0.15% or less.

[0066] Setting the contact angle of the release film 10 on the surface facing the polarizing film 5 to the volatile liquid 50 to 50 to 80°, preferably 50 to 75°, is advantageous in that it keeps the peel force between the polarizing film 5 and the release film 10 within the above range, making the release film 10 relatively easy to peel. For the same reason, the contact angle of the polarizing film 5 on the surface facing the release film 10 to the volatile liquid 50 is preferably 50 to 110°, more preferably 50 to 100°. The contact angle can be measured, for example, by the following method. A measurement sample is prepared by attaching the polarizing film or release film to a glass substrate with an adhesive, with the surface to be measured (the surface of the polarizing film facing the release film or the surface of the release film facing the polarizing film) facing outward. The measurement sample is placed horizontally in a contact angle meter (image processing contact angle meter: FACE CA-X model, manufactured by Kyowa Interface Science Co., Ltd.) with the surface to be measured facing up. One microliter of the volatile liquid is dropped on the surface to be measured, and the contact angle with the volatile liquid is measured.

[0067] The release film 10 may have a coating layer formed on the surface facing the polarizing film 5. By forming a coating layer on the surface of the release film 10, a release film with low surface roughness can be easily obtained. Since minute foreign matter (additives, film scraps, etc.) originating from the release film is likely to adhere to the surface of the release film, this can cause dents on the polarizing film surface. However, by covering these foreign matter with a coating layer, dents on the polarizing film surface can be suppressed. Furthermore, the release film 10 on which the coating layer is formed has a good peel strength with respect to the polarizing film 5, and this peel strength is, for example, 0.01 N / 25 mm to 2.0 N / 25 mm, preferably 0.05 N / 25 mm to 0.5 N / 25 mm. The coating layer may be formed on both sides of the release film.

[0068] The coating layer is, for example, a cured layer of an ultraviolet-curable resin. Examples of ultraviolet-curable resins include (meth)acrylic resins, silicone resins, polyester resins, urethane resins, amide resins, and epoxy resins. The coating layer may contain an additive to improve hardness. The additive is not limited, and examples include inorganic fine particles, organic fine particles, and mixtures thereof.

[0069] The thickness of the coating layer of the release film is preferably 1 μm or more and 30 μm or less, more preferably 1 μm or more and 20 μm or less, and even more preferably 1 μm or more and 15 μm or less. When the coating layer is 1 μm or more thick, depressions on the surface of the polarizing film caused by foreign matter on the release film are easily suppressed. If the coating layer is too thick, the moisture permeability is likely to decrease, so from the viewpoint of obtaining a release film with good moisture permeability, the thickness of the coating layer is preferably 30 μm or less.

[0070] [Volatile liquid] The volatile liquid 50 interposed between the polarizing film 5 and the release film 10 is a liquid that can be evaporated by the heat treatment in the second step and preferably does not adversely affect the polarizing film 5. An antistatic agent may be added as long as it does not adversely affect the polarizing film 5. Examples of the volatile liquid 50 that can be used in the present invention include water and mixtures of water and hydrophilic liquids. The hydrophilic liquid is preferably one that does not remain after the heat treatment in the second step, and examples thereof include methanol, ethanol, 1-butanol, tetrahydrofuran, acetone, acetonitrile, N,N-dimethylformamide, dimethyl sulfoxide, formic acid, and acetic acid.

[0071] (2)Second process This step is a step in which the first adhesive layer 25, which is an aqueous adhesive layer, is dried by heating, and the volatile liquid 50 is volatilized and removed. By this heat treatment, the release film 10 is laminated directly onto the surface of the polarizing film 5 with an appropriate adhesive force.

[0072] 5, the heat treatment can be carried out by introducing the laminated film consisting of the first protective film 20, the polarizing film 5, and the release film 10, which has passed between laminating rolls 40, 40, into a drying device 70. This produces a single-sided protected polarizing plate 2 with a release film. The drying device 70 is not particularly limited, and a hot air dryer, a far-infrared heater, or the like can be used.

[0073] The drying temperature is preferably 30 to 90°C. If the temperature is lower than 30°C, the first protective film 20 in the obtained single-sided protected polarizing plate 2 with a release film tends to be easily peeled off from the polarizing film 5. If the drying temperature exceeds 90°C, the heat may deteriorate the polarization performance of the polarizing film 5. The drying time can be about 10 to 1000 seconds, and from the viewpoint of productivity, it is preferably 60 to 750 seconds, and more preferably 150 to 600 seconds.

[0074] (3) Other processes After the second step, the adhesive may be cured at room temperature or higher for at least half a day, usually for several days or more, to obtain sufficient adhesive strength. This curing is typically performed in a rolled state. The curing temperature is preferably in the range of 30 to 50°C, more preferably 35 to 45°C. If the curing temperature exceeds 50°C, the adhesive is likely to become "tightened" in the rolled state. The humidity during curing is not particularly limited, but it is preferable to select a relative humidity in the range of about 0 to 70% RH. The curing time is usually about 1 to 10 days, preferably about 2 to 7 days.

[0075] After the second step, a third step of peeling and removing the release film 10 from the polarizing film 5 of the release-film-attached single-sided protected polarizing plate 2, and a fourth step of laminating a pressure-sensitive adhesive layer 30 on the surface of the polarizing film 5 where the release film 10 was previously laminated, can be carried out to produce the pressure-sensitive adhesive layer-attached single-sided protected polarizing plate 3 shown in Fig. 3. This pressure-sensitive adhesive layer 30 can be used to attach the single-sided protected polarizing plate to a liquid crystal cell.

[0076] The adhesive used in the adhesive layer 30 can be any suitable adhesive known in the art, such as (meth)acrylic adhesives, urethane adhesives, silicone adhesives, polyester adhesives, polyamide adhesives, polyether adhesives, fluorine-based adhesives, and rubber adhesives. Among these, (meth)acrylic adhesives are preferred from the viewpoints of transparency, adhesive strength, reliability, and reworkability. The adhesive layer 30 can be formed, for example, by applying an adhesive in the form of an organic solvent solution to the polarizing film 5 using a die coater or gravure coater, followed by drying. Alternatively, the adhesive layer 30 can be formed by transferring a sheet of adhesive formed on a release-treated plastic film (called a "separate film") to the polarizing film 5. In either method, it is preferable that a separate film be attached to the surface of the adhesive layer 30. The thickness of the adhesive layer 30 can be, for example, 2 to 40 μm.

[0077] Alternatively, instead of performing the fourth step, a double-sided protected polarizing plate 4 can be obtained by laminating a second protective film 21 via a second adhesive layer 26 to the surface of the polarizing film 5 on which the release film 10 was previously laminated. The second adhesive layer 26 may be an aqueous adhesive layer, like the first adhesive layer 25, or may be a layer made of another adhesive. Examples of other adhesives include active energy ray-curable adhesives that can be cured by exposure to active energy rays such as ultraviolet light, visible light, electron beams, and X-rays. In this case, the second adhesive layer 26 is a layer of the cured product of the adhesive.

[0078] The second protective film 21 may also be a protective film having optical functions such as a retardation film or a brightness enhancement film. The double-sided protected polarizing plate 4 can be attached to a liquid crystal cell using a pressure-sensitive adhesive layer 30 laminated on the outer surface of the first protective film 20 or the second protective film 21.

[0079] Among these, the adhesive for forming the second adhesive layer 26 is preferably an active energy ray-curable adhesive containing an epoxy compound that cures by cationic polymerization as a curing component, and even more preferably an ultraviolet-curable adhesive containing such an epoxy compound as a curing component. Here, the term "epoxy compound" refers to a compound having an average of one or more, preferably two or more, epoxy groups in the molecule. The epoxy compounds may be used alone or in combination of two or more.

[0080] Examples of epoxy compounds that can be suitably used include hydrogenated epoxy compounds (glycidyl ethers of polyols having alicyclic rings) obtained by reacting epichlorohydrin with an alicyclic polyol obtained by hydrogenating the aromatic rings of an aromatic polyol; aliphatic epoxy compounds such as polyglycidyl ethers of aliphatic polyhydric alcohols or their alkylene oxide adducts; and alicyclic epoxy compounds, which are epoxy compounds having one or more epoxy groups bonded to an alicyclic ring in the molecule.

[0081] The active energy ray-curable adhesive may further contain a radically polymerizable (meth)acrylic compound as a curable component. Examples of the (meth)acrylic compound include (meth)acryloyloxy group-containing compounds such as (meth)acrylate monomers having at least one (meth)acryloyloxy group in the molecule, and (meth)acrylate oligomers obtained by reacting two or more functional group-containing compounds and having at least two (meth)acryloyloxy groups in the molecule.

[0082] When the active energy ray-curable adhesive contains an epoxy compound that cures by cationic polymerization as a curable component, it preferably contains a photocationic polymerization initiator. Examples of the photocationic polymerization initiator include aromatic diazonium salts; onium salts such as aromatic iodonium salts and aromatic sulfonium salts; and iron-allene complexes. Furthermore, when the active energy ray-curable adhesive contains a radically polymerizable curable component such as a (meth)acrylic compound, it preferably contains a photoradical polymerization initiator. Examples of the photoradical polymerization initiator include acetophenone-based initiators, benzophenone-based initiators, benzoin ether-based initiators, thioxanthone-based initiators, xanthone, fluorenone, camphorquinone, benzaldehyde, and anthraquinone.

[0083] When an active energy ray-curable adhesive is used, a curing step is carried out to cure the adhesive layer made of the adhesive. The adhesive layer can be cured by irradiating it with active energy rays. The active energy rays are preferably ultraviolet rays.

[0084] The light source of the active energy rays is not particularly limited, but active energy rays having an emission distribution of wavelengths of 400 nm or less are preferred. Specifically, low-pressure mercury lamps, medium-pressure mercury lamps, high-pressure mercury lamps, ultra-high-pressure mercury lamps, chemical lamps, black light lamps, microwave-excited mercury lamps, metal halide lamps, etc. are preferably used.

[0085] The intensity of irradiation of active energy rays to the adhesive layer made of an active energy ray-curable adhesive is determined appropriately depending on the composition of the adhesive, but the irradiation intensity in the wavelength range effective for activating the polymerization initiator is 0.1 to 6000 mW / cm. 2 It is preferable that the irradiation intensity is set to 0.1 mW / cm. 2 If the reaction time is not too long, the output will be 6000mW / cm 2 If it is below this value, there is little risk of yellowing of the adhesive layer or deterioration of the polarizing film 5 due to heat radiated from the light source and heat generated when the adhesive is cured.

[0086] The irradiation time of the active energy rays is also determined appropriately depending on the composition of the adhesive, but the cumulative light amount expressed as the product of the irradiation intensity and the irradiation time is 10 to 10,000 mJ / cm 2 It is preferable that the integrated light amount is set to 10 mJ / cm 2 When the irradiation amount is 10,000 mJ / cm or more, a sufficient amount of active species derived from the polymerization initiator can be generated to more reliably progress the curing reaction, and 2 When the irradiation time is not too long, good productivity can be maintained.

[0087] The material and configuration of the second protective film 21 are described above with reference to the first protective film 20. The first protective film 20 and the second protective film 21 may be the same type of film or different types of films.

[0088] <Single-sided protective polarizing plate> A single-sided protected polarizing plate 1 according to one embodiment of the present invention comprises a polarizing film 5 and a protective film 20 bonded to one side of the polarizing film 5. The polarizing film 5 has a maximum height Rz, as defined in JIS B0601-2001, on the surface opposite to the protective film 20 of 60 nm or less, preferably 50 nm or less, more preferably 30 nm or less, and even more preferably 20 nm or less. Such a single-sided protected polarizing plate has reduced appearance defects. A single-sided protected polarizing plate can be produced according to the above-described method for producing a polarizing plate.

[0089] A single-sided protected polarizing plate 1 according to one embodiment of the present invention has a polarizing film 5 and a protective film 20 attached to one side of the polarizing film 5. The polarizing film 5 has, on the surface opposite to the protective film 20, 10 dents / m 2 each having a width of 0.5 mm or more and 2.0 mm or less and a depth of 0.1 μm or more and 1.0 μm or less. 2 More preferably, 5 particles / m 2The following is an example. Such a single-sided protected polarizing plate suppresses appearance defects. A single-sided protected polarizing plate can be produced according to the above-mentioned polarizing plate production method. The width of the recess refers to the maximum length in the plane direction of the polarizing film. The depth of the recess refers to the maximum depth from the surface of the polarizing film (the length in the direction perpendicular to the polarizing film). [Example]

[0090] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these. The moisture permeability, thickness, peel strength and surface roughness in the examples were measured according to the following methods.

[0091] (1) Moisture permeability of protective film and release film Moisture permeability (g / m) at 40°C in accordance with JIS Z0208-1976 2 24 hours) was measured.

[0092] (2) Layer thickness The thickness of the film was measured using a contact film thickness measuring device (manufactured by Nikon Corporation: MS-5C), and the thickness of the adhesive layer was measured using a laser microscope (manufactured by Olympus Corporation: OLS3000).

[0093] (3) Peel strength between the polarizing film and the release film The peel strength was determined by cutting a single-sided protected polarizing plate laminated with a release film to a width of 25 mm to obtain a measurement sample, and then measuring the force required to peel the sample off in a 180° direction using an Autograph AGS-50NX precision universal testing machine manufactured by Shimadzu Corporation. The peel strength was measured at a peel rate of 300 mm / min in an environment with a temperature of 23±2°C and a relative humidity of 50±5%.

[0094] (4) Surface roughness The surface roughness (maximum height Rz defined in JIS B0601-2001) of the polarizing film and release film was measured using an atomic force microscope (AFM, manufactured by Shimadzu Corporation: SPM-9700HT).

[0095] (5) Measurement of unevenness on the surface of polarizing film Using an optical microscope (Keyence Corporation: Model No. VHX-6000), the number of depressions with a width of 0.5 mm to 2.0 mm and a depth of 0.1 μm to 1.0 μm on the surface of the polarizing film was counted.

[0096] Example 1 (A) Preparation of polarizing film A 20 μm-thick polyvinyl alcohol film with an average degree of polymerization of approximately 2400 and a saponification degree of 99.9 mol% or greater was uniaxially stretched approximately four times its original size using a dry stretching method. While still under tension, the film was then immersed in pure water at 40°C for 1 minute, followed by immersion in an aqueous solution of iodine / potassium iodide / water in a weight ratio of 0.1 / 5 / 100 at 28°C for 60 seconds. This was followed by immersion in an aqueous solution of potassium iodide / boric acid / water in a weight ratio of 10.5 / 7.5 / 100 at 68°C for 300 seconds. The film was then washed with pure water at 5°C for 5 seconds and dried at 70°C for 180 seconds to obtain a polarized film in which iodine was adsorbed and aligned on the uniaxially stretched polyvinyl alcohol film. The polarized film had a thickness of 8 μm.

[0097] (B) Preparation of water-based adhesive Polyvinyl alcohol powder (trade name "KL-318" manufactured by Kuraray Co., Ltd., average degree of polymerization 1800) was dissolved in hot water at 95°C to prepare a 3 wt% aqueous polyvinyl alcohol solution. A crosslinker (trade name "Sumirez Resin 650" manufactured by Taoka Chemical Co., Ltd.) was mixed with the resulting aqueous solution in a ratio of 1 part by weight to 2 parts by weight of the polyvinyl alcohol powder to prepare a water-based adhesive.

[0098] (C) Protective film The protective film used was a cyclic polyolefin resin (COP) film with a thickness of 27 μm. The moisture permeability of the protective film was 5.5 g / m 2 It was 24 hours.

[0099] (D) Release film The release film used was a 42 μm-thick triacetyl cellulose (TAC) film with a 4 μm-thick coating layer of a cured methacrylic resin (HC-TAC). The moisture permeability of the release film was 540 g / m 2 It was 24 hours.

[0100] (E) Preparation of a single-sided protected polarizing plate with a release film and a single-sided protected polarizing plate A single-sided protected polarizing plate with a release film was fabricated using the same polarizing plate manufacturing apparatus as shown in Figure 5, following the procedure below. The polarizing film obtained in (A) above was continuously transported, while the protective film was continuously unwound from the protective film roll and the release film was continuously unwound from the release film roll. Next, the aqueous adhesive obtained in (B) above was injected between the polarizing film and the protective film, and pure water was injected between the polarizing film and the release film. The film was then passed between laminating rolls 40, 40 to form a laminated film consisting of the protective film / aqueous adhesive layer / polarizing film / pure water / release film (Step 1). The laminated film was then transported and passed through a drying device 70, where it was heated at 80°C for 300 seconds. This dried the aqueous adhesive layer and volatilized and removed the pure water between the polarizing film and the release film, yielding a single-sided protected polarizing plate with a release film (Step 2). The thickness of the aqueous adhesive layer was 75 nm. The release film was then peeled off and removed from the polarizing film to obtain a single-sided protected polarizing plate (Step 3).

[0101] During the production of the single-sided protected polarizing plate with a release film, no breakage of the polarizing film or wrinkles of the polarizing plate occurred. The measurement results of the thickness, peel strength, and surface roughness of the polarizing film, protective film, and release film used in the production of the polarizing plate of Example 1 are shown in Table 1.

[0102] <Comparative Examples 1 and 2> Single-sided protected polarizing plates of Comparative Examples 1 and 2 were produced in the same manner as in Example 1, except that the type of release film was changed. In Comparative Example 1, a 60 μm thick TAC film without a coating layer was used as the release film. In Comparative Example 2, a 25 μm thick TAC film without a coating layer was used as the release film. The measurement results for the thickness, peel strength, and surface roughness of the protective film and release film are shown in Table 1.

[0103] The maximum height and depressions on the polarizing film surface of the side opposite to the protective film of the produced single-sided protected polarizing plate were measured. The results are shown in Table 1.

[0104] [Table 1]

[0105] The single-sided protected polarizing plate produced in Example 1 had less depressions on the polarizing film surface opposite the protective film than the single-sided protected polarizing plates of Comparative Examples 1 and 2. Images of the surfaces of the single-sided protected polarizing plates of Example 1 and Comparative Example 1 from which the release film had been peeled off, observed with an atomic force microscope (SPM-9700HT, manufactured by Shimadzu Corporation) are shown in Figures 6 and 7, respectively.

[0106] <Reference example 1> A single-sided protected polarizing plate of Reference Example 1 was produced in the same manner as in Example 1, except that the type of release film was changed. In Reference Example 1, a 60 μm thick polymethyl methacrylate (PMMA) film without a coating layer was used as the release film. The moisture permeability of the release film was 60 g / m 2 It was 24 hours.

[0107] The single-sided protected polarizing plate produced in Example 1 had better optical properties than the single-sided protected polarizing plate of Reference Example 1. This is presumably because the release film of Example 1 had higher moisture permeability than the release film of Reference Example 1. [Explanation of symbols]

[0108] 1 Single-sided protected polarizing plate, 2 Single-sided protected polarizing plate with release film, 3 Single-sided protected polarizing plate with adhesive layer, 4 Double-sided protected polarizing plate, 5 Polarizing film, 10 Release film, 20 First protective film, 21 Second protective film, 25 First adhesive layer, 26 Second adhesive layer, 30 Adhesive layer, 40 Laminating roll, 50 Volatile liquid, 55 Water-based adhesive, 60 Guide roll, 70 Drying device, 80, 81 Injection device.

Claims

1. a first step of bonding a protective film to one surface of a polarizing film via an aqueous adhesive layer and laminating a release film to the other surface of the polarizing film via a volatile liquid; a second step of drying the aqueous adhesive layer and volatilizing the volatile liquid by heating, The thickness of the polarizing film is 2 μm or more and 8 μm or less, the release film has a maximum height Rz of 20 nm or less on the polarizing film side surface as defined in JIS B0601-2001; the release film has a coating layer formed on the polarizing film side surface, The coating layer of the release film has a thickness of more than 1 μm; the contact angle of the release film on the polarizing film side surface to a volatile liquid is 50 to 80°; The release film has a moisture permeability of 500 g / m ２ A method for producing a polarizing plate, the method lasting 24 hours or more.

2. The method for producing a polarizing plate according to claim 1 , wherein the coating layer of the release film has a thickness of 30 μm or less.

3. The method for producing a polarizing plate according to claim 1 or 2, wherein the coating layer of the release film is made of a cured product of a (meth)acrylic resin.

4. The protective film has a moisture permeability of 400 g / m ２ The method for producing a polarizing plate according to any one of claims 1 to 3, wherein the time is 24 hours or more.

5. 5. The method for producing a polarizing plate according to claim 1, wherein the thickness of the aqueous adhesive layer is 10 nm or more and 1 μm or less.

6. 6. The method for producing a polarizing plate according to claim 1, wherein the protective film has a thickness of 1 μm or more and 90 μm or less.

7. The method for producing a polarizing plate according to any one of claims 1 to 6, further comprising a third step of peeling the release film from the polarizing film.

8. The method for producing a polarizing plate according to claim 7 , wherein in the third step, a peeling force between the polarizing film and the release film is 0.01 N / 25 mm or more and 2.0 N / 25 mm or less.

Images