JP6205255B2 - Polarizer protective film, polarizing plate, and image display device - Google Patents

Description

  The present invention relates to a polarizer protective film, a polarizing plate, and an image display device. Specifically, the present invention is a polarizer protective film having a polyester film and an easy-adhesion layer containing at least two types of blocked isocyanate, and has excellent adhesion to the polarizer and improved blocking resistance. It is related with the made polarizer protective film.

  A liquid crystal display (LCD), a plasma display (PDP), an electroluminescence display (OELD or IELD), a field emission display (FED), a touch panel, electronic paper, and the like are used as image display devices. In such an image display device, a polarizing plate is disposed on the display screen side of the image display panel, and the polarizing plate is provided with protective films on both surfaces of the polarizer. Furthermore, an optical laminate having functions such as antireflection and hard coat properties is provided on the outermost surface of the image display device.

  Conventionally, a film made of a cellulose ester typified by triacetyl cellulose has been used as a protective film provided on both surfaces of a polarizer. This is because the retardation value of the cellulose ester is low, so that it has little influence on the display quality of the image display device and has an appropriate water permeability. Therefore, when producing a polarizing plate using an optical laminate, a polarizer This is because the moisture remaining in the film can be dried through the optical laminate. In addition, the cellulose ester film has a merit that it is relatively inexpensive.

  In addition, attempts have been made to use polyester films such as polyethylene terephthalate having low water permeability instead of cellulose ester films. For example, Patent Documents 1 and 2 disclose that a polyester film is used as a protective film, and a laminated film in which an easy-adhesion layer is provided on the polyester film in order to bond the polyester film to a polarizer or the like. Is disclosed. In Patent Document 1, in order to improve the adhesion between the polarizer protective film and the polarizer, a specific polyester resin and polyvinyl alcohol resin are used for the easy-adhesion layer, and further, a crosslinking agent such as isocyanate is used. It has been proposed to increase the adhesion with the child. In Patent Document 2, it is proposed to use two or more kinds of crosslinking agents for the easy-adhesion layer, and it is preferable to use an oxazoline compound and an epoxy compound in combination as the crosslinking agent.

Japanese Patent No. 5109094 JP 2013-1000049 A

As described above, by using a polyester film such as polyethylene terephthalate having low water permeability, attempts have been made to improve polarizing functions such as resistance to moisture and heat, polarization function and hue under high temperature and high humidity environment, and the like. Yes.
However, even in the conventional laminated polyester film, the adhesiveness with the polarizer is not sufficient, and the present inventors have a problem that the end face is liable to peel off at the time of punching, inspection process, or panel bonding. It became clear by examination.
In addition, when a cross-linking agent is used for the easy-adhesive layer, blocking (a phenomenon in which the films adhere to each other and become difficult to slip or peel off) may occur when the laminated film is rolled up. It has been a problem that adhesion marks remain on the film or that the easy-adhesion layer is peeled off due to the contact between the easy-adhesion layers.

  Therefore, in order to solve such problems of the prior art, the present inventors are polarizer protective films having excellent adhesion to the polarizer, and suppressing the occurrence of blocking when wound into a roll. A study was conducted for the purpose of providing a polarizer protective film.

As a result of intensive studies to solve the above problems, the present inventors have obtained a polyester protective film having a polyester film and an easy-adhesion layer, and the gel fraction of the easy-adhesion layer is 70% or more. A polarizer protective film is produced by stretching a laminated film in which an easy-adhesion layer is laminated on an unstretched or longitudinally stretched polyester film containing two types of blocked isocyanates having different temperatures when stretched in the width direction. Thus, it was found that a polarizer protective film having excellent adhesion to a polarizer and having blocking resistance can be obtained.
Specifically, the present invention has the following configuration.

[1] A polarizer protective film having a polyester film and an easy adhesion layer,
The easy adhesion layer includes a polyester resin, a polyvinyl alcohol resin, a first blocked isocyanate, and a second blocked isocyanate, and the first blocked isocyanate has a temperature of 90% when the gel fraction becomes 70%. The second blocked isocyanate has a temperature at which the gel fraction becomes 70% is higher than 90 ° C., and the polarizer protective film is an unstretched or longitudinally stretched polyester film. The polarizer protective film manufactured by extending | stretching the laminated film which laminated | stacked the easily bonding layer in the width direction.
[2] The polarizer protective film according to [1], wherein the polarizer protective film is produced by stretching a laminated film in which an easy-adhesion layer is laminated on an unstretched polyester film in the width direction. .
[3] The total content of the first blocked isocyanate and the second blocked isocyanate is 0.6 to 70% by mass with respect to the total mass of the easy-adhesion layer, as described in [1] or [2]. Polarizer protective film.
[4] The polarizer according to any one of [1] to [3], wherein the content of the first blocked isocyanate is 0.1 to 30% by mass with respect to the total mass of the easy-adhesion layer. Protective film.
[5] The polarizer according to any one of [1] to [4], wherein the content of the second blocked isocyanate is 0.5 to 40% by mass with respect to the total mass of the easy-adhesion layer. Protective film.
[6] The polarizer protective film according to any one of [1] to [5], in which a mass ratio of the first blocked isocyanate to the second blocked isocyanate is 1: 4 to 10: 1.
[7] The polarizer protective film according to any one of [1] to [6], wherein the easy adhesion layer is provided on one side of the polyester film and on the polarizer side.
[8] The ratio (NCO / OH group amount) of the NCO group amount (mmol) of the first blocked isocyanate and the OH group amount (mmol) of the polyvinyl alcohol resin is 0.001 to 0.23. 7]. The polarizer protective film of [7].
[9] The polarizer protective film according to [7] or [8], wherein the content of the polyester-based resin is 10 to 80% by mass with respect to the total mass of the easy-adhesion layer.
[10] The polarizer protective film according to any one of [7] to [9], wherein the content of the polyvinyl alcohol-based resin is 5 to 45% by mass with respect to the total mass of the easy-adhesion layer.
[11] The polarizer protective film according to any one of [1] to [10], wherein the polyester film contains an ultraviolet absorber.
[12] An easy-adhesion layer is laminated on an unstretched or longitudinally stretched polyester film to obtain a laminated film, and a step of stretching the laminated film in the width direction. 1 block isocyanate and a 2nd block isocyanate, The said 1st block isocyanate has a temperature when a gel fraction will be 70%, 90 degrees C or less, The said 2nd block isocyanate is a gel A method for producing a polarizer protective film, wherein the temperature when the fraction becomes 70% is higher than 90 ° C.
[13] The polarizer protection according to [12], wherein in the step of obtaining the laminated film, the easy adhesion layer is laminated by coating, and the coating amount of the coating liquid for forming the easy adhesion layer is 1 to 30 g / m ^2. A method for producing a film.
[14] The method for producing a polarizer protective film according to [12] or [13], wherein a corona discharge treatment is performed on the easy-adhesion layer provided on the side laminated with the polarizer.
[15] The polarizer protection according to any one of [12] to [14], wherein the easy-adhesion layer provided on the side laminated with the polarizer is subjected to a corona discharge treatment and then wound into a roll form. A method for producing a film.
[16] A polarizing plate comprising the polarizer protective film according to any one of [1] to [11] and a polarizer.
[17] The polarizing plate according to [16], further comprising a protective film and a hard coat layer.
[18] The polarizing plate according to [17], wherein the polarizer protective film has a polarizer-side easy-adhesion layer and a hard coat layer-side easy-adhesion layer.
[19] An image display device comprising the polarizing plate according to any one of [16] to [18].

  According to this invention, the polarizer protective film excellent in adhesiveness with a polarizer can be obtained. Moreover, since the polarizer protective film of this invention is excellent in blocking resistance, generation | occurrence | production of blocking is suppressed even when it winds up in roll shape. For this reason, the handleability of a polarizer protective film at the time of panel bonding etc. can be improved.

FIG. 1 is a cross-sectional view showing the configuration of the polarizer protective film of the present invention. FIG. 2 is a cross-sectional view showing an example of the configuration of the polarizing plate of the present invention.

  Hereinafter, the present invention will be described in detail. The description of the constituent elements described below may be made based on representative embodiments and specific examples, but the present invention is not limited to such embodiments. In the present specification, a numerical range expressed using “to” means a range including numerical values described before and after “to” as a lower limit value and an upper limit value.

(Polarizer protective film)
The present invention relates to a polarizer protective film having a polyester film and an easy adhesion layer. Here, an easily bonding layer contains polyester-type resin, polyvinyl alcohol-type resin, 1st block isocyanate, and 2nd block isocyanate. The first blocked isocyanate has a temperature of 90 ° C. or less when the gel fraction is 70%, and the second blocked isocyanate has a temperature of 90% or less when the gel fraction is 70%. It is expensive. Moreover, the polarizer protective film of this invention is manufactured by extending | stretching in the width direction the laminated | multilayer film which laminated | stacked the easily bonding layer on the polyester film unstretched or extended | stretched to the vertical direction.
The “width direction” refers to a direction (TD direction) perpendicular to the casting direction (MD direction) of a strip-like (long shape) film. In addition, when the laminated film which laminated the easy-adhesion layer on the polyester film is a cut film, the laminated film may be stretched in any one direction, and the polyester film is stretched in one direction The film may be stretched in a direction perpendicular to the one direction.
The gel fraction is defined as follows. First, as an easy-adhesive layer, an applicator with a solid content concentration of 30%, in which the ratio of the main agent and each blocked isocyanate was adjusted so that the NCO / OH ratio was 0.3, and the film thickness after drying was 40 μm. After use and coating, the film is dried at 60 ° C. to 140 ° C. every 10 ° C. for 30 minutes to produce a dry coating film. After the coating film is immersed in acetone at 20 ° C. for 24 hours, the coating film is taken out and the weight is measured.

  FIG. 1 shows a configuration example of the polarizer protective film of the present invention. As shown in FIG. 1A, the polarizer protective film has a polyester film 10 and an easy adhesion layer 12. In the polarizer protective film of the present invention, the easy adhesion layer may be provided only on one surface of the polyester film as shown in FIG. 1 (a), and both of the polyester film as shown in FIG. 1 (b). It may be provided on the surface. In addition, when the easily bonding layer 12 is provided only in one side of the polyester film 10, it is preferable that the easily bonding layer 12 is provided in the polarizer side. Moreover, when the easily bonding layers 12 and 14 are provided in both surfaces of the polyester film 10, the structure of the easily bonding layer 12 and the easily bonding layer 14 may be the same, and may differ.

  The polyester film used for the production of the polarizer protective film may be an unstretched or longitudinally stretched polyester film, but is preferably an unstretched polyester film. That is, the polarizer protective film of the present invention is preferably produced by stretching a laminated film in which an easy-adhesion layer is laminated on an unstretched polyester film in the width direction. In addition, when the polyester film used for manufacture of a polarizer protective film is a polyester film extended | stretched to the vertical direction, the draw ratio of the vertical direction before laminating | stacking an easily bonding layer may be 1.1-5. Preferably, it is 1.1-4.

The polarizer protective film may be a sheet-like film or a roll-like film. Since the polarizer protective film of this invention is excellent in blocking resistance, even if it is a roll-shaped film, handling property is favorable. Moreover, even if it is stored in a roll shape for a long time, quality and the like do not deteriorate.
Moreover, it is also preferable that the polarizer protective film of the present invention is subjected to corona discharge treatment on an easy-adhesion layer provided on the side laminated with the polarizer. Furthermore, the polarizer protective film of the present invention is preferably wound into a roll after being subjected to a corona discharge treatment on an easy-adhesion layer provided on the side laminated with the polarizer.

(Block isocyanate)
The blocked isocyanate has a structure in which an isocyanate group is masked with a blocking agent, and is used as a heat-crosslinking type curing agent. Examples of the blocking agent for blocked isocyanate include phenolic compounds such as bisulfites, phenol, cresol, and ethylphenol, alcoholic compounds such as propylene glycol monomethyl ether, ethylene glycol, benzyl alcohol, methanol, and ethanol, dimethyl malonate, and malon. Active methylene compounds such as diethyl acid, methyl acetoacetate, ethyl acetoacetate and acetylacetone, mercaptan compounds such as butyl mercaptan and dodecyl mercaptan, lactam compounds such as ε-caprolactam and δ-valerolactam, diphenylaniline, aniline, ethylene Imine, diisopropylamine, diisobutylamine, di (2-butylamine), di (t-butyl) amine, dicyclohexylamine, N- Examples include amine compounds such as t-butylcyclohexylamine, acetanilide, acid amide compounds of acetic acid amide, oxime compounds such as formaldehyde, acetaldoxime, acetone oxime, methyl ethyl ketone oxime, and cyclohexanone oxime, and these may be used alone or in combination of two or more. It may be used in combination.

  Examples of the isocyanate include aromatic isocyanates such as tolylene diisocyanate, xylylene diisocyanate, methylene diphenyl diisocyanate, phenylene diisocyanate, and naphthalene diisocyanate, and aromatic rings such as α, α, α ′, α′-tetramethylxylylene diisocyanate. Aliphatic isocyanates such as methylene diisocyanate, methylene diisocyanate, propylene diisocyanate, lysine diisocyanate, trimethylhexamethylene diisocyanate, hexamethylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate, 2,2,4 trimethyl 1,6 diisocyanatohexane, etc. , Cyclohexane diisocyanate, methylcyclohexane diisocyanate, isophor Cycloisocyanate, methylenebis (4-cyclohexylisocyanate), isopropylidenedicyclohexyldiisocyanate, 1,3-bis (isocyanatomethyl) -cyclohexane, 4,4'-dicyclohexylmethane diisocyanate, norbornene diisocyanate, hydrogenated xylylene diisocyanate, etc. Group isocyanate and the like are exemplified. Further, polymers and derivatives such as burettes, isocyanurates, uretdiones, and carbodiimide modified products of these isocyanates are also included. These may be used alone or in combination. Among the above isocyanates, aliphatic isocyanates or alicyclic isocyanates are more preferable than aromatic isocyanates in order to avoid yellowing due to ultraviolet rays.

  When forming the easy-adhesion layer containing block isocyanate, the process of apply | coating an easy-adhesion layer coating liquid and the process (preheating part) to dry are provided. In this drying step, the group derived from the blocking agent is dissociated from the blocked isocyanate compound, whereby the urethanization reaction proceeds between the NCO group derived from the blocked isocyanate compound and the OH group in the system, and the crosslinking density. Can be improved.

  The number average molecular weight of the blocked isocyanate of the present invention is preferably 500 to 10,000. The lower limit is more preferably 300, more preferably 500, and most preferably 700. Further, the upper limit is further preferably 9,000, more preferably 8,500, and most preferably 8,000.

<First blocked isocyanate>
The first blocked isocyanate is a blocked isocyanate having a temperature of 90 ° C. or lower when the gel fraction is 70%. The temperature at which the gel fraction becomes 70% may be 90 ° C. or less.
The temperature during stretching of the polyester film substrate suitably used in the present invention generally needs to be Tg (glass transition temperature) to Tg + 30 ° C. of the unstretched polyester film resin. It is difficult to obtain a transparent base film due to crystallization. Therefore, the temperature at which the coating solution is dried needs to be equal to or lower than the above temperature. As a specific example, since the stretching temperature when applied to an unstretched polyethylene terephthalate film is 80 to 100 ° C, the drying temperature is preferably about 90 ° C. When the block of the first blocked isocyanate is dissociated and reacts at a temperature lower than this temperature, it is possible to form a crosslinked film before stretching, and the strength of the coated film is improved.
The temperature at which the gel fraction of the first blocked isocyanate is 70% is lower than the temperature at which the gel fraction of the second blocked isocyanate described later is 70%. It can also be called blocked isocyanate.

  The content of the first blocked isocyanate is preferably 0.1 to 30% by mass, more preferably 0.5 to 20% by mass, and 1 to 15% by mass with respect to the total mass of the easy-adhesion layer. % Is more preferable. By making the content rate of 1st blocked isocyanate into the said range, it becomes possible to improve the adhesiveness of an easily bonding layer and a polarizer effectively.

  As the first blocked isocyanate, for example, hexamethylene diisocyanate and isophorone diisocyanate, or both are preferably used, and as the blocking agent, malonic acid diester is particularly preferably used as an active methylene type, among which diethyl malonate, Dimethyl malonate is more preferably used. As the amine system, a chain secondary amine is preferably used, and among them, diisopropylamine, diisobutylamine, di (2-butylamine), and di (t-butyl) amine are more preferable. Furthermore, it is more preferable to use an active methylene type and an amine type in combination.

The effective NCO group mass% here is used to quantify the amount of blocked isocyanate groups that can participate in the crosslinking reaction present in the blocked polyisocyanate composition after the blocking reaction, and is expressed as mass% of isocyanate groups. Expressed by the following formula.
{(Solid content (mass%) of blocked isocyanate composition) x (mass isocyanate used in reaction x isocyanate group content% of precursor isocyanate)} / (resin mass of blocked isocyanate composition after blocking reaction)
When diluted with a solvent or the like, the value in the diluted state is described.
In addition, when the diluted components such as the solvent were removed, it was described as effective NCO group mass (solid)%.
The effective NCO group mass% contained in the first blocked isocyanate is not particularly limited.

<Second blocked isocyanate>
The second blocked isocyanate is a blocked isocyanate having a temperature higher than 90 ° C. when the gel fraction is 70%. The temperature at which the gel fraction becomes 70% may be higher than 90 ° C, preferably 100 ° C or higher, more preferably 110 ° C or higher, and further preferably 120 ° C or higher. Since the temperature when the gel fraction of the second blocked isocyanate is 70% is higher than the temperature when the gel fraction of the first blocked isocyanate is 70%, in the present invention, the high temperature blocked isocyanate is used. Can also be called.

  The content of the second blocked isocyanate is preferably 0.5 to 40% by mass, more preferably 0.5 to 30% by mass, and more preferably 0.5 to 30% by mass with respect to the total mass of the easy-adhesion layer. More preferably, it is 20 mass%. By making the content rate of 2nd blocked isocyanate in the said range, the blocking resistance of a polarizer protective film can be improved, improving the adhesiveness of an easily bonding layer and a polarizer.

  As the second blocked isocyanate, for example, hexamethylene diisocyanate or isophorone diisocyanate is preferably used. As the blocking agent, bisulfites, phenolic compounds, alcohol compounds, active methylene compounds, lactam compounds, amines are used. Compounds, oxime compounds and the like are preferably used, and bisulfites are particularly preferably used. Moreover, you may have in the inside the frame | skeleton of the copolymer polyurethane which superposed | polymerized dicarboxylic acid and a diol component beforehand.

  The total content of the first blocked isocyanate and the second blocked isocyanate is preferably 0.6 to 70% by mass and more preferably 1 to 50% by mass with respect to the total mass of the easy-adhesion layer. More preferably, it is 1.5-35 mass%. By setting the total content of the first blocked isocyanate and the second blocked isocyanate within the above range, the crosslink density of the easy-adhesion layer can be set within an appropriate range.

  The mass ratio of the first blocked isocyanate and the second blocked isocyanate contained in the easy-adhesion layer is preferably 1: 4 to 10: 1, more preferably 1: 3 to 10: 1. : 3 to 2: 1 is more preferable.

(Easily adhesive layer)
The easily bonding layer which comprises the polarizer protective film of this invention contains a polyester-type resin and a polyvinyl alcohol-type resin, and also contains the 1st block isocyanate and the 2nd block isocyanate which were mentioned above. The easy-adhesion layer may contain a plurality of first blocked isocyanates or a plurality of second blocked isocyanates.

<Polyester resin>
The main components of the polyester resin contained in the easy-adhesion layer are, for example, the following polyvalent carboxylic acids and polyvalent hydroxy compounds. Examples of the polyvalent carboxylic acid include terephthalic acid, isophthalic acid, orthophthalic acid, phthalic acid, 4,4′-diphenyldicarboxylic acid, 2,5-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, and 2,6-naphthalene. Dicarboxylic acid, 2,7-naphthalenedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 2-sodium sulfoterephthalic acid, 2-potassium sulfoterephthalic acid, 4-sodium sulfoisophthalic acid, 4-potassium sulfoisophthalic acid, 5 -Sodium sulfoisophthalic acid, 5-potassium sulfoisophthalic acid, adipic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid, glutaric acid, succinic acid, trimellitic acid, trimesic acid, pyromellitic acid, trimellitic anhydride, anhydrous Pyromellitic acid, phthalic anhydride, p-hydroxy Cibenzoic acid, trimellitic acid monopotassium salt and ester-forming derivatives thereof can be used. Examples of the polyvalent hydroxy compound include ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, 2-methyl-1 , 5-pentanediol, neopentyl glycol, 1,4-cyclohexanedimethanol, p-xylylene glycol, bisphenol A-ethylene glycol adduct, diethylene glycol, triethylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, poly Tetramethylene oxide glycol, dimethylolpropionic acid, glycerin, trimethylolpropane, sodium dimethylolethylsulfonate, potassium dimethylolethylsulfonate, dimethylo Or the like can be used potassium Rupuropion acid. One or more of these compounds may be appropriately selected, and a polyester resin may be synthesized by a conventional polycondensation reaction.

  Further, the number average molecular weight of the polyester resin is preferably 5000 or more, more preferably 8000 or more, and further preferably 10,000 or more. By setting the number average molecular weight of the polyester within the above range, adhesion with the polyester base material is improved.

  The content of the polyester resin-derived compound in the easy adhesion layer is preferably 10 to 80% by mass, more preferably 15 to 75% by mass, and further preferably 30 to 75% by mass. . By making the content rate of the compound derived from a polyester resin into the said range, the adhesiveness of an easily bonding layer and a polarizer and an easily bonding layer and a polyester film can be improved.

<Polyvinyl alcohol resin>
The polyvinyl alcohol resin contained in the easy-adhesion layer has a polyvinyl alcohol moiety. For example, conventionally known polyvinyl alcohol can be used, including modified compounds partially acetalized or butyralized with respect to polyvinyl alcohol. The degree of polymerization of polyvinyl alcohol is not particularly limited, but is usually 100 or more, preferably 300 to 40,000. By using a polymer having a polymerization degree within the above range, the water resistance of the easy adhesion layer can be increased.

The saponification degree of polyvinyl alcohol is not particularly limited, but is preferably 70 mol% or more, and a polyvinyl acetate saponified product in a range of 70 to 99.9 mol% is practically used.

  The ratio (NCO / OH group amount) of the NCO group amount (mmol) of the first blocked isocyanate and the OH group amount (mmol) of polyvinyl alcohol is preferably 0.001 to 0.23, More preferably, it is 0.2, and it is still more preferable that it is 0.005-0.17. By making the ratio of the NCO group amount (mmol) of the first blocked isocyanate and the OH group amount (mmol) of polyvinyl alcohol within the above range, it is possible to protect the polarizer while improving the adhesion between the easy adhesion layer and the polarizer. The blocking resistance of the film can be increased.

  The content of the compound derived from polyvinyl alcohol in the polarizer-side easy-adhesion layer is preferably 5 to 45% by mass, more preferably 15 to 45% by mass, and 15 to 40% by mass. Further preferred. By making content rate of the compound derived from polyvinyl alcohol into the said range, the adhesiveness of an easily bonding layer and a polarizer and an easily bonding layer and a polyester film can be improved.

  The easy adhesion layer may contain a crosslinking agent other than the first blocked isocyanate or the second blocked isocyanate. Examples of the crosslinking agent include melamine compounds, epoxy compounds, oxazoline compounds, isocyanate compounds, carbodiimide compounds, and the like. These cross-linking agents may be used alone or in combination of two or more. Furthermore, when consideration is given to application to in-line coating, it is preferable to have water solubility or water dispersibility.

  Moreover, in an easily bonding layer, you may contain particle | grains in order to improve the blocking property and slipperiness of an easily bonding layer. Examples of the particles include inorganic particles such as silica, alumina, and metal oxide, or organic particles such as crosslinked polymer particles.

  Furthermore, within the range that does not impair the gist of the present invention, the easy-adhesion layer includes an antifoaming agent, a coating property improver, a thickener, an organic lubricant, an antistatic agent, an ultraviolet absorber, an antioxidant, as necessary. Foaming agents, dyes, pigments and the like may be contained. In addition, the coating composition for an easy-adhesion layer used in the present invention may contain a surfactant, a dispersant, a thickener, a film forming aid, an antiblocking agent, and the like as necessary. In addition, the analysis of the various components in an easily bonding layer can be performed by surface analysis, such as TOF-SIMS, for example.

<Polarizer side easy adhesion layer>
It is preferable that the easily bonding layer which comprises the polarizer protective film of this invention is a polarizer side easily bonding layer provided in the polarizer side. The polarizer-side easy-adhesion layer is a layer for improving the adhesiveness with various polarizers, and in order to improve the adhesiveness with various adhesives used to bond the polarizer and the polyester film together. Can be used.

  When the easy-adhesion layer constituting the polarizer protective film is a polarizer-side easy-adhesion layer, the polarizer-side easy-adhesion layer comprises a polyester-based resin, a polyvinyl alcohol-based resin, a first blocked isocyanate, and a second blocked isocyanate. Including. Furthermore, the polarizer-side easy-adhesion layer may contain an acrylic resin, a urethane resin, or the like.

<Acrylic resin>
The acrylic resin is a polymer composed of a polymerizable monomer having a carbon-carbon double bond, as typified by acrylic and methacrylic monomers. These may be either a homopolymer or a copolymer. Moreover, the copolymer of these polymers and other polymers (for example, polyester, polyurethane, etc.) is also included. For example, a block copolymer or a graft copolymer. Alternatively, a polymer (possibly a mixture of polymers) obtained by polymerizing a polymerizable monomer having a carbon-carbon double bond in a polyester solution or a polyester dispersion is also included. Similarly, a polymer (in some cases, a mixture of polymers) obtained by polymerizing a polymerizable monomer having a carbon-carbon double bond in a polyurethane solution or polyurethane dispersion is also included. Similarly, a polymer obtained by polymerizing a polymerizable monomer having a carbon-carbon double bond in another polymer solution or dispersion (in some cases, a polymer mixture) is also included.

  The polymerizable monomer having a carbon-carbon double bond is not particularly limited, but particularly representative compounds include, for example, acrylic acid, methacrylic acid, crotonic acid, itaconic acid, fumaric acid, maleic acid, citracone. Various carboxyl group-containing monomers such as acids, and salts thereof; 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, monobutyl hydroxyl fumarate, Various hydroxyl group-containing monomers such as monobutylhydroxy itaconate; various monomers such as methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, lauryl (meth) acrylate ( (Meth) acrylic acid esters; Various nitrogen-containing compounds such as meth) acrylamide, diacetone acrylamide, N-methylolacrylamide or (meth) acrylonitrile; various styrene derivatives such as styrene, α-methylstyrene, divinylbenzene, vinyltoluene, vinyl propionate Various vinyl esters such as: Various silicon-containing polymerizable monomers such as γ-methacryloxypropyltrimethoxysilane, vinyltrimethoxysilane, etc .; Phosphorus-containing vinyl monomers; Various such as vinyl chloride and biridene chloride And various conjugated dienes such as butadiene.

<Urethane resin>
A urethane resin is a high molecular compound which has a urethane resin in a molecule | numerator. Usually, urethane resin is prepared by reaction of polyol and isocyanate. Examples of the polyol include polycarbonate polyols, polyester polyols, polyether polyols, polyolefin polyols, and acrylic polyols. These compounds may be used alone or in combination.

  Polycarbonate polyols are obtained from a polyhydric alcohol and a carbonate compound by a dealcoholization reaction. Examples of the polyhydric alcohols include ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentane. Diol, 1,6-hexanediol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decane Diol, neopentyl glycol, 3-methyl-1,5-pentanediol, 3,3-dimethylol heptane and the like can be mentioned. Examples of the carbonate compound include dimethyl carbonate, diethyl carbonate, diphenyl carbonate, and ethylene carbonate. Examples of polycarbonate polyols obtained from these reactions include poly (1,6-hexylene) carbonate, poly (3- And methyl-1,5-pentylene) carbonate.

  Polyester polyols include polycarboxylic acids (malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, sebacic acid, fumaric acid, maleic acid, terephthalic acid, isophthalic acid, etc.) or their acid anhydrides. Product and polyhydric alcohol (ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 2-methyl-1,3-propanediol, 1,5-pentanediol, neopentyl glycol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, 2-methyl-2,4-pentanediol 2-methyl-2-propyl-1 3-propanediol, 1,8-octanediol, 2,2,4-trimethyl-1,3-pentanediol, 2-ethyl-1,3-hexanediol, 2,5-dimethyl-2,5-hexanediol 1,9-nonanediol, 2-methyl-1,8-octanediol, 2-butyl-2-ethyl-1,3-propanediol, 2-butyl-2-hexyl-1,3-propanediol, cyclohexane Diol, bishydroxymethylcyclohexane, dimethanolbenzene, bishydroxyethoxybenzene, alkyl dialkanolamine, lactone diol, bisphenol A, bisphenol A ethylene glycol adduct, etc.).

  Examples of polyether polyols include polyethylene glycol, polypropylene glycol, polyethylene propylene glycol, polytetramethylene ether glycol, polyhexamethylene ether glycol, and the like.

  Among the above polyols, polycarbonate polyols are more preferably used in order to improve the adhesiveness with various adhesive layers.

  Examples of the polyisocyanate compound used for obtaining the urethane resin include aromatic diisocyanates such as tolylene diisocyanate, xylylene diisocyanate, methylene diphenyl diisocyanate, phenylene diisocyanate, naphthalene diisocyanate, and tolidine diisocyanate, α, α, α ′, α ′. -Aliphatic diisocyanates having aromatic rings such as tetramethylxylylene diisocyanate, aliphatic diisocyanates such as methylene diisocyanate, propylene diisocyanate, trimethylhexamethylene diisocyanate, hexamethylene diisocyanate, cyclohexane diisocyanate, methylcyclohexane diisocyanate, isophorone diisocyanate, dicyclohexyl Methanzi Cyanate, alicyclic diisocyanates such as isopropylidene dicyclohexyl diisocyanates. These may be used alone or in combination.

  A chain extender may be used when synthesizing the urethane resin, and the chain extender is not particularly limited as long as it has two or more active groups that react with an isocyanate group. Alternatively, a chain extender having two amino groups can be mainly used.

  Examples of the chain extender having two hydroxyl groups include aliphatic glycols such as ethylene glycol, propylene glycol and butanediol, aromatic glycols such as xylylene glycol and bishydroxyethoxybenzene, and esters such as neopentyl glycol hydroxypivalate. And glycols such as glycols. Examples of the chain extender having two amino groups include aromatic diamines such as tolylenediamine, xylylenediamine, and diphenylmethanediamine, ethylenediamine, propylenediamine, hexanediamine, 2,2-dimethyl-1,3- Propanediamine, 2-methyl-1,5-pentanediamine, trimethylhexanediamine, 2-butyl-2-ethyl-1,5-pentanediamine, 1,8-octanediamine, 1,9-nonanediamine, 1,10- Aliphatic diamines such as decane diamine, 1-amino-3-aminomethyl-3,5,5-trimethylcyclohexane, dicyclohexylmethanediamine, isoprobilitincyclohexyl-4,4′-diamine, 1,4-diaminocyclohexane, 1 , 3-Bisaminomethylcyclohexane Alicyclic diamines, and the like of.

  The urethane resin in the present invention may use a solvent as a medium, but preferably uses water as a medium. In order to disperse or dissolve the urethane resin in water, there are a forced emulsification type using an emulsifier, a self-emulsification type in which a hydrophilic group is introduced into the urethane resin, and a water-soluble type. In particular, a self-emulsification type in which an ionic group is introduced into a skeleton of a urethane resin to form an ionomer is preferable because it is excellent in the storage stability of the liquid and the water resistance, transparency, and adhesion of the easily adhesive layer obtained. Examples of the ionic group to be introduced include various groups such as a carboxyl group, sulfonic acid, phosphoric acid, phosphonic acid, quaternary ammonium salt, and the like, and a carboxyl group is preferable. As a method for introducing a carboxyl group into a urethane resin, various methods can be taken in each stage of the polymerization reaction. For example, there are a method of using a carboxyl group-containing resin as a copolymer component during prepolymer synthesis, and a method of using a component having a carboxyl group as one component such as polyol, polyisocyanate, and chain extender. In particular, a method in which a desired amount of carboxyl groups is introduced using a carboxyl group-containing diol depending on the amount of this component charged is preferred. For example, dimethylolpropionic acid, dimethylolbutanoic acid, bis- (2-hydroxyethyl) propionic acid, bis- (2-hydroxyethyl) butanoic acid and the like are copolymerized with a diol used for polymerization of a urethane resin. Can do. The carboxyl group is preferably in the form of a salt neutralized with ammonia, amine, alkali metal, inorganic alkali or the like. Particularly preferred are ammonia, trimethylamine and triethylamine. In such a polyurethane resin, a carboxyl group from which the neutralizing agent has been removed in the drying step after coating can be used as a crosslinking reaction point by another crosslinking agent. Thereby, it is possible to further improve the durability, solvent resistance, water resistance, blocking resistance and the like of the easy-adhesive layer obtained in addition to excellent stability in a liquid state before coating.

  The polarizer-side easy-adhesion layer can be used in combination with a binder polymer other than a polyester-based resin, a urethane-based resin, an acrylic resin, or polyvinyl alcohol in order to improve the coating surface state and transparency.

  In the present invention, the “binder polymer” is a number average molecular weight (Mn) measured by gel permeation chromatography (GPC) according to a polymer compound safety evaluation flow scheme (sponsored by the Chemical Substance Council in November 1985). It is defined as a polymer compound of 1000 or more and having a film-forming property.

  Specific examples of the binder polymer include polyvinyl (polyvinyl chloride, polyvinyl pyrrolidone, vinyl chloride vinyl acetate copolymer, etc.), polyalkylene glycol, polyalkyleneimine, methylcellulose, hydroxycellulose, starches and the like.

  The polarizer-side easy-adhesion layer may contain a material such as an ultraviolet absorber or fine particles for adjusting the refractive index.

<Hard coat layer side easy adhesion layer>
The easy adhesion layer can be provided on both sides of the polyester film, and the one easy adhesion layer may be a hard coat layer side easy adhesion layer. In this case, the hard coat layer side easy-adhesion layer is bonded to the hard coat layer provided on the side opposite to the side where the polarizer is provided.

  The hard coat layer-side easy-adhesion layer may be the same as or different from the polarizer-side easy-adhesion layer described above. As for the resin, binder polymer, crosslinking agent, etc. used in the hard coat layer side easy-adhesion layer, those used in the polarizer-side easy adhesive layer can be exemplified in the same manner, but the combination of resin and cross-linking agent May be different from the polarizer-side easy-adhesion layer.

  In the hard coat layer side easy-adhesion layer, when a clear surface functional layer such as a hard coat layer is formed, a material that adjusts the refractive index may be used in order to reduce interference unevenness due to external light. Is possible. Specifically, the material for adjusting the refractive index is a high refractive index material in the present invention. Examples of the high refractive index material include metal compounds, aromatic-containing organic compounds, sulfur atoms, bromine atoms and the like.

  Examples of the metal compound include titanium oxide, zinc oxide, tin oxide, antimony oxide, yttrium oxide, zirconium oxide, indium oxide, cerium oxide, ATO (antimony / tin oxide), and ITO (indium / tin oxide). Aluminum such as metal oxide, aluminum acetylacetonate, hydroxyaluminum diacetate, dihydroxyaluminum acetate; tetranormal butyl titanate, tetraisopropyl titanate, butyl titanate dimer, tetra (2-ethylhexyl) titanate, tetramethyl titanate, titanium acetylacetate Nato, titanium tetraacetylacetonate, polytitanium acetylacetonate, titanium octylene glycolate, titanium lactate, titanium triethanolamine Titanium such as iron acetate and titanium ethyl acetoacetate; Iron such as iron acetylacetonate and iron acetate; Cobalt such as cobalt acetylacetonate; Copper acetate, copper acetate monohydrate, copper acetate multihydrate, copper acetyl Coppers such as acetonate; zincs such as zinc acetate, zinc acetate dihydrate, zinc acetylacetonate hydrate; zirconium acetate, zirconium normal propylate, zirconium normal butyrate, zirconium tetraacetylacetonate, zirconium monoacetylacetate Examples thereof include organic compounds having a metal element such as zirconium and zirconium compounds such as narate and zirconium bisacetylacetonate. These may be used alone or in combination of two or more.

  Among the organic compounds having the metal element, an organic compound having a titanium element or a zirconium element is preferable in terms of particularly good coatability and transparency, and more preferably water-soluble when considering application to in-line coating. Titanium chelate compounds, water-soluble zirconium chelate compounds and the like are preferably used.

  Examples of aromatic-containing organic compounds include compounds having a high proportion of benzene rings such as condensed polycyclic aromatic compounds, bisphenol A compounds, biphenyl compounds, and fluorene compounds, which can be exemplified by naphthalene rings and anthracene rings. Examples thereof include compounds, ultraviolet absorber-containing compounds such as benzophenone and benzotriazole, and various heteroaromatic ring compounds. These may be used alone or in combination of two or more. An aromatic compound is effective because it can be incorporated into a polyester resin, acrylic resin, or urethane resin contained in the hard coat layer side easy-adhesion layer. Among these, polyester resins can easily use many aromatic compounds because of their structures. Among the aromatic compounds, naphthalene rings and bisphenol A compounds are useful because they can efficiently increase the refractive index of the easily adhesive layer. A melamine compound that can be used as a crosslinking agent is a compound having a high ratio of heteroaromatic rings, and is also a compound effective for increasing the refractive index.

(Polyester film)
The polyester film used for the polarizer protective film of the present invention is a film containing polyester as a main component. The polyester film may be a single layer film or a multilayer film. Moreover, the surface treatment may be performed on both surfaces or one surface of these single layer films or multilayer films, and this surface treatment is performed by corona treatment, saponification treatment, heat treatment, ultraviolet irradiation, electron beam irradiation, or the like. Modification may be sufficient, and thin film formation by application | coating, vapor deposition, etc. of a polymer, a metal, etc. may be sufficient. The mass ratio of the polyester to the whole polyester film is usually 50 mass% or more, preferably 70 mass% or more, more preferably 90 mass% or more.

  Examples of the polyester include polyethylene terephthalate, polyethylene isophthalate, polyethylene 2,6-naphthalate, polybutylene terephthalate, and 1,4-cyclohexanedimethylene terephthalate, and two or more of them may be used as necessary. . Of these, polyethylene terephthalate is preferably used.

  Polyethylene terephthalate is a polyester having a structural unit derived from terephthalic acid as a dicarboxylic acid component and a structural unit derived from ethylene glycol as a diol component, and 80 mol% or more of all repeating units are preferably ethylene terephthalate. The structural unit derived from other copolymerization components may be included. Other copolymer components include isophthalic acid, p-β-oxyethoxybenzoic acid, 4,4′-dicarboxydiphenyl, 4,4′-dicarboxybenzophenone, bis (4-carboxyphenyl) ethane, adipic acid , Dicarboxylic acid components such as sebacic acid, 5-sodium sulfoisophthalic acid, 1,4-dicarboxycyclohexane, propylene glycol, butanediol, neopentyl glycol, diethylene glycol, cyclohexanediol, ethylene oxide adduct of bisphenol A, polyethylene glycol And diol components such as polypropylene glycol and polytetramethylene glycol. These dicarboxylic acid components and diol components can be used in combination of two or more if necessary. It is also possible to use an oxycarboxylic acid such as p-oxybenzoic acid in combination with the carboxylic acid component or diol component. As another copolymer component, a dicarboxylic acid component and / or a diol component containing a small amount of an amide bond, a urethane bond, an ether bond, a carbonate bond, or the like may be used. Polyethylene terephthalate can be produced by a direct polymerization method in which terephthalic acid and ethylene glycol and, if necessary, other dicarboxylic acid and / or other diol are directly reacted, dimethyl ester of terephthalic acid and ethylene glycol, and necessary Depending on the above, any production method such as a so-called transesterification method in which a dimethyl ester of another dicarboxylic acid and / or another diol is transesterified can be applied.

  The polyester film used for the production of the polarizer protective film is a polyester film that has not been stretched or has been stretched in the machine direction. The laminated film in which the easy-adhesion layer as described above is laminated on this polyester film is then stretched in the width direction. A polarizer protective film is manufactured through such a process. That is, the polyester film constituting the polarizer protective film is stretched at least in the width direction.

The in-plane retardation Re (retardation value) of the stretched polyester film is preferably 4000 to 30000 nm. By setting the retardation Re in the in-plane direction of the polyester film within the above range, coloring from the front tends to be inconspicuous. The in-plane retardation value Re of the polyester film is represented by the following formula (1).
Re = (na−nb) × d (1)
Here, na is the refractive index in the in-plane slow axis direction of the stretched polyester film, and nb is the in-plane fast axis direction (the direction perpendicular to the in-plane slow axis direction) of the stretched polyester film. , D is the thickness of the stretched polyester film.

The thickness direction retardation Rth of the polyester film is preferably in the range where the ratio to Re (Re / Rth) is 0.6 to 1.2. The retardation Rth in the thickness direction of the polyester film and the retardation (Rth) in the thickness direction are defined by the following formula (2).
Rth = {(na + nb) / 2−nc} × d (2)
Here, na is the refractive index in the in-plane slow axis direction of the stretched polyester film, and nb is the in-plane fast axis direction (the direction perpendicular to the in-plane slow axis direction) of the stretched polyester film. , Nc is the refractive index in the thickness direction of the stretched polyester film, and d is the thickness of the stretched polyester film.

  The thickness of the polyester film is preferably 10 to 250 μm, and more preferably 10 to 100 μm. By making the thickness of the polyester film within the above range, the polarizing plate can be made thin while improving the handling property.

  The polyester film preferably has a melting sub-peak temperature (Tsm) of 140 to 220 ° C, more preferably 150 ° C or higher and lower than 220 ° C, and further preferably 150 ° C or higher and lower than 210 ° C. It is particularly preferable that the temperature is less than 150 ° C and 200 ° C or less. By setting the melting sub-peak temperature within the above range, it is possible to suppress changes in the thermal dimension and to suppress the occurrence of cracks in the laminated hard coat layer.

  The polyester film may be blended with known additives as necessary. Examples thereof include ultraviolet absorbers, particles, lubricants, antiblocking agents, heat stabilizers, antioxidants, antistatic agents, and light resistance. Agents, impact modifiers, lubricants, dyes, pigments and the like. However, when a polyester film is used as a base film for an antiglare film, transparency is generally required, so it is preferable to keep the additive amount to a minimum.

  The polyester film preferably contains an ultraviolet absorber in order to prevent the liquid crystal of the liquid crystal display from being deteriorated by ultraviolet rays. The ultraviolet absorber is not particularly limited as long as it is a compound having ultraviolet absorbing ability and can withstand the heat applied in the production process of the polyester film.

  As the ultraviolet absorber, there are an organic ultraviolet absorber and an inorganic ultraviolet absorber. From the viewpoint of transparency, an organic ultraviolet absorber is preferable. Although it does not specifically limit as an organic type ultraviolet absorber, For example, a benzotriazole type, a cyclic imino ester type, a benzophenone type etc. are mentioned. From the viewpoint of durability, benzotriazole and cyclic imino ester are more preferable. It is also possible to use two or more ultraviolet absorbers in combination.

  Examples of the benzotriazole-based ultraviolet absorbers include, but are not limited to, 2- [2′-hydroxy-5 ′-(methacryloyloxymethyl) phenyl] -2H-benzotriazole, 2- [2 '-Hydroxy-5'-(methacryloyloxyethyl) phenyl] -2H-benzotriazole, 2- [2'-hydroxy-5 '-(methacryloyloxypropyl) phenyl] -2H-benzotriazole, 2- [2'- Hydroxy-5 '-(methacryloyloxyhexyl) phenyl] -2H-benzotriazole, 2- [2'-hydroxy-3'-tert-butyl-5'-(methacryloyloxyethyl) phenyl] -2H-benzotriazole, 2 -[2'-hydroxy-5'-tert-butyl-3 '-(methacryl Yloxyethyl) phenyl] -2H-benzotriazole, 2- [2′-hydroxy-5 ′-(methacryloyloxyethyl) phenyl] -5-chloro-2H-benzotriazole, 2- [2′-hydroxy-5 ′ -(Methacryloyloxyethyl) phenyl] -5-methoxy-2H-benzotriazole, 2- [2'-hydroxy-5 '-(methacryloyloxyethyl) phenyl] -5-cyano-2H-benzotriazole, 2- [2 '-Hydroxy-5'-(methacryloyloxyethyl) phenyl] -5-tert-butyl-2H-benzotriazole, 2- [2'-hydroxy-5 '-(methacryloyloxyethyl) phenyl] -5-nitro-2H -Benzotriazole and the like.

  Moreover, as a commercial item, a benzotriazole type | system | group ultraviolet absorber can be mentioned, for example, It can be used as it is disperse | distributed to water as it is, using an emulsifier as needed. In addition, New Coat UVA-204W (trade name, manufactured by Shin-Nakamura Chemical Co., Ltd.), SE-2538E (trade name, manufactured by Taisei Fine Chemical Co., Ltd.) and the like can be exemplified as water-based benzotriazole ultraviolet absorbers.

  Examples of the cyclic imino ester-based ultraviolet absorber include, but are not limited to, 2-methyl-3,1-benzoxazin-4-one, 2-butyl-3,1-benzoxazine-4, for example. -One, 2-phenyl-3,1-benzoxazin-4-one, 2- (1- or 2-naphthyl) -3,1-benzoxazin-4-one, 2- (4-biphenyl) -3, 1-benzoxazin-4-one, 2-p-nitrophenyl-3,1-benzoxazin-4-one, 2-m-nitrophenyl-3,1-benzoxazin-4-one, 2-p-benzoyl Phenyl-3,1-benzoxazin-4-one, 2-p-methoxyphenyl-3,1-benzoxazin-4-one, 2-o-methoxyphenyl-3,1-benzoxazin-4-one, -Cyclohexyl-3,1-benzoxazin-4-one, 2-p- (or m-) phthalimidophenyl-3,1-benzoxazin-4-one, N-phenyl-4- (3,1-benzoxazine -4-On-2-yl) phthalimide, N-benzoyl-4- (3,1-benzoxazin-4-one-2-yl) aniline, N-benzoyl-N-methyl-4- (3,1- Benzoxazin-4-one-2-yl) aniline, 2- (p- (N-methylcarbonyl) phenyl) -3,1-benzoxazin-4-one, 2,2′-bis (3,1-benzo Oxazin-4-one), 2,2′-ethylenebis (3,1-benzoxazin-4-one), 2,2′-tetramethylenebis (3,1-benzoxazin-4-one), 2, 2'-Decame Renbis (3,1-benzoxazin-4-one, 2,2 '-(1,4-phenylene) bis [4H-3,1-benzoxazin-4-one] [In addition, 2,2'-p- Phenylenebis (3,1-benzoxazin-4-one)], 2,2′-m-phenylenebis (3,1-benzoxazin-4-one), 2,2 ′-(4,4 ′) -Diphenylene) bis (3,1-benzoxazin-4-one), 2,2 '-(2,6- or 1,5-naphthylene) bis (3,1-benzoxazin-4-one), 2, 2 '-(2-methyl-p-phenylene) bis (3,1-benzoxazin-4-one), 2,2'-(2-nitro-p-phenylene) bis (3,1-benzoxazine-4 -One), 2,2 '-(2-chloro-p-phenylene) bis (3 , 1-benzoxazin-4-one), 2,2 ′-(1,4-cyclohexylene) bis (3,1-benzoxazin-4-one), 1,3,5-tri (3,1- Benzoxazin-4-on-2-yl) benzene, 1,3,5-tri (3,1-benzoxazin-4-on-2-yl) naphthalene, 2,4,6-tri (3,1- Benzoxazin-4-one-2-yl) naphthalene, 2,8-dimethyl-4H, 6H-benzo (1,2-d; 5,4-d ′) bis (1,3) -oxazine-4,6 -Dione, 2,7-dimethyl-4H, 9H-benzo (1,2-d; 4,5-d ') bis (1,3) -oxazine-4,9-dione, 2,8-diphenyl-4H , 8H-Benzo (1,2-d; 5,4-d ′) bis (1,3) -oxazine-4,6-dio 2,7-diphenyl-4H, 9H-benzo (1,2-d; 4,5-d ′) bis (1,3) -oxazine-4,6-dione, 6,6′-bis (2- Methyl-4H, 3,1-benzoxazin-4-one), 6,6′-bis (2-ethyl-4H, 3,1-benzoxazin-4-one), 6,6′-bis (2- Phenyl-4H, 3,1-benzoxazin-4-one), 6,6′-methylenebis (2-methyl-4H, 3,1-benzoxazin-4-one), 6,6′-methylenebis (2- Phenyl-4H, 3,1-benzoxazin-4-one), 6,6′-ethylenebis (2-methyl-4H, 3,1-benzoxazin-4-one), 6,6′-ethylenebis ( 2-phenyl-4H, 3,1-benzoxazin-4-one), 6,6′- Tylene bis (2-methyl-4H, 3,1-benzoxazin-4-one), 6,6′-butylene bis (2-phenyl-4H, 3,1-benzoxazin-4-one), 6,6′- Oxybis (2-methyl-4H, 3,1-benzoxazin-4-one), 6,6′-oxybis (2-phenyl-4H, 3,1-benzoxazin-4-one), 6,6′- Sulfonylbis (2-methyl-4H, 3,1-benzoxazin-4-one), 6,6′-sulfonylbis (2-phenyl-4H, 3,1-benzoxazin-4-one), 6,6 '-Carbonylbis (2-methyl-4H, 3,1-benzoxazin-4-one), 6,6'-carbonylbis (2-phenyl-4H, 3,1-benzoxazin-4-one), 7 , 7'-methylenebis (2 -Methyl-4H, 3,1-benzoxazin-4-one), 7,7'-methylenebis (2-phenyl-4H, 3,1-benzoxazin-4-one), 7,7'-bis (2 -Methyl-4H, 3,1-benzoxazin-4-one), 7,7'-ethylenebis (2-methyl-4H, 3,1-benzoxazin-4-one), 7,7'-oxybis ( 2-methyl-4H, 3,1-benzoxazin-4-one), 7,7′-sulfonylbis (2-methyl-4H, 3,1-benzoxazin-4-one), 7,7′-carbonyl Bis (2-methyl-4H, 3,1-benzoxazin-4-one), 6,7′-bis (2-methyl-4H, 3,1-benzoxazin-4-one), 6,7′- Bis (2-phenyl-4H, 3,1-benzoxazine-4 ON, 6,7′-methylenebis (2-methyl-4H, 3,1-benzoxazin-4-one), 6,7′-methylenebis (2-phenyl-4H, 3,1-benzoxazin-4-one) ) And the like.

  Among the above compounds, when considering the color tone, a benzoxazinone-based compound which is difficult to be yellowed is preferably used. As an example thereof, a compound represented by the following general formula (1) is more preferably used. It is done.

In the general formula (1), R represents a divalent aromatic hydrocarbon group, and X ¹ and X ² are each independently selected from hydrogen or the following functional group group, but are not necessarily limited thereto. Absent.

  Functional group: alkyl group, aryl group, heteroaryl group, halogen, alkoxyl group, aryloxy group, hydroxyl group, carboxyl group, ester group, nitro group.

  Among the compounds represented by the general formula (1), 2,2 ′-(1,4-phenylene) bis [4H-3,1-benzoxazin-4-one] is particularly preferable in the present invention.

  It is preferable that the addition rate of the ultraviolet absorber contained in a polyester film is 10.0 mass% or less with respect to the total mass of a polyester film, and it is more preferable that it is 0.3-3.0 mass%. By making the addition rate of an ultraviolet absorber into the said range, the adhesive fall of a polyester film and the deterioration of surface functionality can be prevented.

  Further, in the case of a polyester film having a multilayer structure, a film having at least a three-layer structure is preferable, and the ultraviolet absorber is preferably blended in the intermediate layer. By blending an ultraviolet absorber in the intermediate layer, the compound can be prevented from bleeding out to the film surface, and as a result, properties such as film adhesion can be maintained.

  If the polyester film prevents the deterioration of the liquid crystal due to ultraviolet rays, as a guide, the light transmittance of the polyester film at a wavelength of 380 nm is preferably 15% or less, more preferably 10% or less, and still more preferably. 5% or less.

  Particles may be blended in the polyester film for the main purpose of imparting slipperiness and preventing scratches in each step. The kind of the particle to be blended is not particularly limited as long as it is a particle capable of imparting slipperiness. Specific examples thereof include silica, calcium carbonate, magnesium carbonate, barium carbonate, calcium sulfate, calcium phosphate, and phosphoric acid. Examples of the particles include magnesium, kaolin, aluminum oxide, and titanium oxide. Further, the heat-resistant organic particles described in JP-B-59-5216, JP-A-59-217755 and the like may be used. Examples of other heat-resistant organic particles include thermosetting urea resins, thermosetting phenol resins, thermosetting epoxy resins, benzoguanamine resins, and the like. Furthermore, it is also possible to use precipitated particles in which a part of a metal compound such as a catalyst is precipitated and finely dispersed during the polyester film manufacturing process.

  On the other hand, the shape of the particles to be used is not particularly limited, and any of a spherical shape, a block shape, a rod shape, a flat shape, and the like may be used. Moreover, there is no restriction | limiting in particular also about the hardness, specific gravity, a color, etc. These series of particles may be used in combination of two or more as required.

  Moreover, the average particle diameter of the particle | grains to be used is 0.01-3 micrometers normally, Preferably it is the range of 0.1-2 micrometers. If the average particle size is less than 0.01 μm, sufficient slipperiness cannot be imparted, or the particles may aggregate, resulting in insufficient dispersibility, which may reduce the transparency of the polyester film. . On the other hand, when the thickness exceeds 3 μm, the surface roughness of the polyester film becomes too rough, and a problem may occur when a functional layer such as a prism layer or a light diffusion layer is formed in a subsequent process.

  Furthermore, the particle content in the polyester film is usually in the range of 0.001 to 5 mass%, preferably 0.005 to 3 mass%. When the particle content is less than 0.001% by mass, the slipperiness of the film may be insufficient. On the other hand, when the content exceeds 5% by mass, the transparency of the polyester film is insufficient. There are cases.

  The method for adding particles to the polyester film is not particularly limited, and a conventionally known method can be adopted. For example, it can be added at any stage for producing the polyester constituting each layer, but it is preferably added after completion of esterification or transesterification.

  Also, a method of blending a slurry of particles dispersed in ethylene glycol or water with a vented kneading extruder and a polyester raw material, or a blending of dried particles and a polyester raw material using a kneading extruder. It is done by methods.

  Further, in order to impart haze to the polyester film, inorganic fine particles or organic fine particles may be blended in the polyester film. Inorganic fine particles include calcium carbonate, barium sulfate, titanium oxide, aluminum hydroxide, silica, glass, talc, mica, white carbon, magnesium oxide, zinc oxide, and other inorganic particles, and these inorganic particles are surface treated with fatty acids. What has been applied can be cited as a representative one. The organic fine particles include melamine beads (refractive index 1.57), polymethyl methacrylate beads (refractive index 1.49), methyl methacrylate / styrene copolymer resin beads (refractive index 1.50 to 1.59). ), Polycarbonate beads (refractive index 1.55), polyethylene beads (refractive index 1.53), polyvinyl chloride beads (refractive index 1.46), silicone resin beads (refractive index 1.46) and the like are used. be able to.

<Method for producing polarizer protective film>
A polarizer protective film has the process of laminating | stacking an easily bonding layer on the polyester film unstretched or extended | stretched to the vertical direction, and obtaining the laminated | multilayer film, and the process of extending | stretching a laminated | multilayer film to the width direction. Here, the easy-adhesion layer includes a first blocked isocyanate and a second blocked isocyanate, and the first blocked isocyanate has a temperature when the gel fraction becomes 70%, which is 90 ° C. or less. The blocked isocyanate of 2 has a temperature higher than 90 ° C. when the gel fraction is 70%.

  When producing a polarizer protective film, first, a polyester-based resin is melt-extruded into a film and cooled and solidified with a casting drum to obtain an unstretched polyester film. If necessary, the unstretched polyester film may be subjected to longitudinal stretching. When performing longitudinal stretching, it is preferable to stretch the polyester film 1.1 to 5 times in the longitudinal direction at a temperature of Tg to (Tg + 60) ° C.

  An easy-adhesion layer coating solution is applied to the unstretched polyester film or the longitudinally stretched polyester film. When providing an easy-adhesion layer by in-line coating, the above-mentioned series of compounds is applied as an aqueous solution or water dispersion, and a coating solution adjusted to a solid content concentration of about 0.1 to 50% by mass is applied onto the polyester film. It is preferable to produce a polyester film as described above. Moreover, in the range which does not impair the main point of this invention, a small amount of organic solvents may be contained in the coating liquid for the purpose of improving dispersibility in water, improving film-forming properties, and the like. Only one type of organic solvent may be used, or two or more types may be used as appropriate.

The coating amount of the adhesive layer coating solution is preferably from 1 to 30 g / m ^2, more preferably 1 to 25 g / m ^2, further preferably from 1 to 20 g / m ^2. Moreover, it is preferable that the film thickness of an easily bonding layer is 0.002-1.0 micrometer, It is more preferable that it is 0.02-0.5 micrometer, It is further more preferable that it is 0.03-0.2 micrometer. . By setting the coating amount and film thickness of the easy-adhesion layer coating solution within the above ranges, the appearance and transparency can be improved and the blocking resistance can be improved.

  In the present invention, a method for providing an easy-adhesion layer may be a conventionally known coating method such as reverse gravure coating, direct gravure coating, roll coating, die coating, bar coating, or curtain coating. As for the coating method, there is a description example in “Coating method” published by Yoji Harasaki in 1979.

  In this invention, although it does not necessarily limit about the drying conditions at the time of forming an easily bonding layer on a polyester film, Usually, it is preferable to heat-process for 3 to 300 second as a standard at 70-100 degreeC.

  Further, irrespective of off-line coating or in-line coating, heat treatment and active energy ray irradiation such as ultraviolet irradiation may be used in combination as required. The polyester film constituting the polarizer protective film in the present invention may be subjected to surface treatment such as corona treatment or plasma treatment in advance.

  Next, the laminated film coated with the easy-adhesion layer coating solution is stretched so as to be 3 to 10 times, preferably 3 to 5 times in the width direction. The polyester film is preferably uniaxially stretched in the width direction from the viewpoint of greatly expressing the in-plane retardation Re. Furthermore, since the adhesiveness of an easily bonding layer and a polyester film can also be improved, it is preferable. In addition, since it is preferable that a polarizer protective film is uniaxially stretched in the width direction, it is preferable that the polyester film used for manufacture of a polarizer protective film is an unstretched polyester film.

  Next, the laminated film that has been stretched in the width direction is preferably subjected to heat treatment (herein referred to as heat setting) at 140 ° C. to 220 ° C. for 1 to 60 seconds. The heat setting temperature is more preferably 150 ° C. or higher and 220 ° C. or lower, and particularly preferably 150 ° C. or higher and lower than 220 ° C.

  Furthermore, it is preferable to perform reheat treatment (referred to as relaxation treatment) while shrinking 0 to 20% in the width direction at a temperature 10 to 20 ° C. lower than the heat setting temperature. In this method, since the film is less likely to come into contact with the roll, minute scratches and the like are less likely to occur on the film surface than in the method described above, which is advantageous for application to optical applications. The glass transition temperature of the film is expressed as Tg. When the heat setting temperature is 150 ° C. or higher and lower than 220 ° C., the deviation in the orientation direction of the polyester is small and the thermal dimensional change is also small. Therefore, when a hard coat layer or a polarizer is laminated, peeling or cracking is difficult to occur. Become.

  When the polarizer protective film obtained as described above is bonded to the polarizer, the polarizer is bonded to the easy adhesion layer side of the polarizer via an adhesive. As the adhesive, conventionally known ones can be used, for example, acrylic compounds such as polyvinyl alcohol, polyvinyl butyral and polybutyl acrylate, and epoxy having an alicyclic epoxy group exemplified by glycidyl group and epoxycyclohexane. System compounds and the like.

For example, polyvinyl alcohol which is uniaxially stretched and dyed with iodine or the like is preferably laminated as a polarizer on the prepared adhesive layer. A polarizing plate can be obtained by laminating a protective film or a retardation film on the opposite side of the polarizer.
In the manufacturing method of the polarizer protective film of this invention, it is preferable to perform a corona discharge process on the easily bonding layer provided in the side laminated | stacked with a polarizer. A method for performing the corona discharge treatment on the easy-adhesion layer provided on the side laminated with the polarizer will be described in the description of the polarizing plate described later.
In the manufacturing method of the polarizer protective film of this invention, after performing a corona discharge process on the easily bonding layer provided in the side laminated | stacked with a polarizer, it is preferable to wind up in a roll form.

(Polarizer)
The present invention relates to a polarizing plate comprising a polarizer protective film and a polarizer as described above. The polarizing plate preferably further includes a hard coat layer and a protective film. FIG. 2 is a cross-sectional view showing an example of the aspect of the polarizing plate of the present invention. As shown in FIG. 2, the polarizing plate may have a polarizer protective film having a polyester film 10 and easy-adhesion layers 12 and 14, a polarizer 20, a protective film 30, and a hard coat layer 40. preferable. Here, the easy adhesion layer 12 is a polarizer side easy adhesion layer, and the easy adhesion layer 14 is a hard coat layer side easy adhesion layer.

  The polarizer used in the polarizing plate of the present invention preferably contains polyvinyl alcohol and is made of polyvinyl alcohol. Although there is no restriction | limiting in particular as a manufacturing method of a polarizer, Usually, the process of uniaxially stretching a polyvinyl alcohol-type resin film by a well-known method, and dyeing a polyvinyl alcohol-type resin film with a dichroic dye, It is manufactured through a step of adsorbing water, a step of treating a polyvinyl alcohol resin film adsorbed with a dichroic dye with an aqueous boric acid solution, and a step of washing with water after the treatment with an aqueous boric acid solution.

A polarizing plate can be produced by bonding a polarizer and a polyester film used for the polarizer protective film with a polyvinyl alcohol water paste, UV resin, or the like. Moreover, it is preferable to surface-treat such as a corona treatment on the polarizer-side easy-adhesion layer of the polyester film when bonding. By performing the surface treatment at an intensity of 10 to 100,000 J / m ² , components such as surface hydroxyl groups and carboxylic acid groups can be introduced only on the surface. Therefore, when polyvinyl alcohol and isocyanate on the polarizer-side easy-adhesion layer are reacted to create a strong crosslink, the amount of hydroxyl groups on the surface decreases according to the reaction. Components can be introduced, and the surface can be modified while maintaining the internal cross-linked structure. In particular, it is suitably used for bonding with a polyvinyl alcohol-based water, and mainly improves the wettability immediately after bonding. The corona treatment may be performed immediately before the polarizer is bonded, or may be performed in advance. In general, corona treatment is said to have no stability over time, but the combined use of polyvinyl alcohol and two blocked isocyanates in the polarizer-side easy-adhesion layer improves the surface functional group introduction rate and stability over time. Can also be maintained.
In the case of producing the polarizing plate of the present invention, it includes a step of bonding a polarizer and a polarizer protective film, but it is easy to be provided on the polarizer side before the step of bonding the polarizer and the polarizer protective film. It is preferable to perform a corona discharge treatment on the adhesive layer. In the case of producing the polarizing plate of the present invention, before the step of laminating the polarizer and the polarizer protective film, after performing the corona discharge treatment on the easy-adhesion layer provided on the polarizer side, the roll form It is preferable to wind it up.

  The hard coat layer is preferably provided on the surface of the polarizing plate in order to impart physical strength. As a method for forming the hard coat layer, a known method can be adopted, but in the polarizing plate of the present invention, the hard coat layer is preferably formed by coating. The hard coat layer is preferably formed using a composition for hard coat layer containing an ionizing radiation curable resin which is a resin curable by ultraviolet rays and a photopolymerization initiator.

  Examples of the ionizing radiation curable resin include a compound having one or more unsaturated bonds such as a compound having an acrylate functional group, and the polarizing plate of the present invention includes a hard coat layer containing an acrylate. It is preferable from the viewpoint of improving the adhesion between the polyester film as the polarizer protective film and the hard coat layer laminated on the polyester film after wet heat aging. Examples of the compound having one unsaturated bond include ethyl (meth) acrylate, ethylhexyl (meth) acrylate, styrene, methylstyrene, N-vinylpyrrolidone and the like. Examples of the compound having two or more unsaturated bonds include polymethylolpropane tri (meth) acrylate, tripropylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (Meth) acrylate, dipentaerythritol hexa (meth) acrylate, dipentaerythritol penta (meth) acrylate, 1,6-hexanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, and the like, and ethylene oxide ( A polyfunctional compound modified with EEO), or a reaction product of the polyfunctional compound and (meth) acrylate (for example, poly (meth) acrylate ester of polyhydric alcohol). It is possible. In the present specification, “(meth) acrylate” refers to methacrylate and acrylate.

  In addition to the above compounds, polyester resins, polyether resins, acrylic resins, epoxy resins, urethane resins, alkyds having a relatively low molecular weight (number average molecular weight of 300 to 80,000, preferably 400 to 5000) having an unsaturated double bond. Resins, spiroacetal resins, polybutadiene resins, polythiol polyene resins, and the like can also be used as the ionizing radiation curable resin. The resin in this case includes all dimers, oligomers, and polymers other than monomers.

Preferred compounds as the acrylate include compounds having 3 or more unsaturated bonds. When such a compound is used, the crosslink density of the hard coat layer to be formed can be increased, and the coating hardness can be improved.
Specifically, in the present invention, pentaerythritol triacrylate, pentaerythritol tetraacrylate, polyester polyfunctional acrylate oligomer (3 to 15 functional), urethane polyfunctional acrylate oligomer (3 to 15 functional) and the like are used in appropriate combination. Is preferred.

  The ionizing radiation curable resin should be used in combination with a solvent-drying resin (such as a thermoplastic resin that can be used as a coating only by drying the solvent added to adjust the solid content during coating). You can also. By using the solvent-drying resin in combination, film defects on the coated surface can be effectively prevented. The solvent dry resin that can be used in combination with the ionizing radiation curable resin is not particularly limited, and a thermoplastic resin can be generally used.

  The thermoplastic resin is not particularly limited. For example, styrene resin, (meth) acrylic resin, vinyl acetate resin, vinyl ether resin, halogen-containing resin, alicyclic olefin resin, polycarbonate resin, polyester resin. And polyamide resins, cellulose derivatives, silicone resins and rubbers or elastomers. The thermoplastic resin is preferably amorphous and soluble in an organic solvent (particularly a common solvent capable of dissolving a plurality of polymers and curable compounds). In particular, from the viewpoints of film forming properties, transparency, and weather resistance, styrene resins, (meth) acrylic resins, alicyclic olefin resins, polyester resins, cellulose derivatives (cellulose esters, etc.) and the like are preferable.

  Moreover, the composition for hard-coat layers may contain the thermosetting resin. The thermosetting resin is not particularly limited. For example, phenol resin, urea resin, diallyl phthalate resin, melamine resin, guanamine resin, unsaturated polyester resin, polyurethane resin, epoxy resin, aminoalkyd resin, melamine-urea cocondensation resin , Silicon resin, polysiloxane resin, and the like.

  The photopolymerization initiator is not particularly limited and known ones can be used. For example, specific examples of the photopolymerization initiator include acetophenones, benzophenones, Michler benzoylbenzoate, α-amyloxime ester. Thioxanthones, propiophenones, benzyls, benzoins, acylphosphine oxides. In addition, it is preferable to use a mixture of photosensitizers, and specific examples thereof include n-butylamine, triethylamine, poly-n-butylphosphine, and the like.

  As the photopolymerization initiator, acetophenones, benzophenones, thioxanthones, benzoin, benzoin methyl ether, etc. may be used alone or in combination when the ionizing radiation curable resin is a resin system having a radical polymerizable unsaturated group. Is preferred. When the ionizing radiation curable resin is a resin system having a cationic polymerizable functional group, the photopolymerization initiator may be an aromatic diazonium salt, an aromatic sulfonium salt, an aromatic iodonium salt, a metallocene compound, a benzoin sulfonate ester. Etc. are preferably used alone or as a mixture.

  As the photopolymerization initiator, in the case of an ionizing radiation curable resin having a radical polymerizable unsaturated group, 1-hydroxy-cyclohexyl-phenyl-ketone is compatible with the ionizing radiation curable resin, and yellowing is also caused. It is preferable for the reason that there are few.

  The content of the photopolymerization initiator in the hard coat layer composition is preferably 1 to 10 parts by mass with respect to 100 parts by mass of the ionizing radiation curable resin. If it is less than 1 part by mass, the hardness of the hard coat layer in the optical laminate of the first invention may not be in the above-described range, and if it exceeds 10 parts by mass, up to the deep part of the coated film. This is because the ionizing radiation does not reach and internal curing is not promoted, and there is a risk that the pencil hardness of 3H or higher on the surface of the target hard coat layer may not be obtained.

  The minimum with more preferable content of a photoinitiator is 2 mass parts, and a more preferable upper limit is 8 mass parts. When the content of the photopolymerization initiator is in this range, a hardness distribution does not occur in the film thickness direction, and uniform hardness is likely to occur.

  The hard coat layer can also serve as an antiglare layer (described later) provided with particles having an average particle size of 0.2 to 10 μm to provide an antiglare function (antiglare function).

  The film thickness of the hard coat layer can be appropriately designed depending on the application. The film thickness of the hard coat layer is preferably 0.2 to 10 μm, more preferably 0.5 to 7 μm.

  The hardness of the hard coat layer is preferably H or more, more preferably 2H or more, and most preferably 3H or more in a pencil hardness test according to JIS K-5400. Alternatively, the scratch resistance of the docoat layer is preferably as the wear amount of the test piece provided with the hard coat layer before and after the test is smaller in the Taber test according to JIS K-5400.

[Image display device]
The image display device of the present invention includes the polarizing plate of the present invention. Examples of the image display device include a liquid crystal display (LCD), a plasma display (PDP), an electroluminescence display (OELD or IELD), a field emission display (FED), a touch panel, and electronic paper. These image display devices preferably include the polarizing plate of the present invention on the display screen side of the image display panel.

<Liquid crystal display device>
The liquid crystal display device preferably includes the polarizing plate of the present invention and a liquid crystal display element. Here, the liquid crystal display element is typically a liquid crystal panel having a liquid crystal cell in which liquid crystal is sealed between upper and lower substrates and displaying an image by changing the alignment state of the liquid crystal by applying a voltage. The polarizing plate of the present invention can be applied to various known displays such as a display panel, a CRT display, and an organic EL display. In the liquid crystal display device, it is preferable that the polarizing plate of the present invention is disposed on the visual recognition side with respect to the liquid crystal display element with the hard coat layer side facing outside. The polyester film may be directly bonded to the surface of the liquid crystal display element. When the liquid crystal panel is used as a liquid crystal display element, for example, as described above, the polyester film is bonded to the surface of the liquid crystal panel via a polarizer. You can also. Thus, when the polarizing plate of the present invention having a polyester film is applied to a liquid crystal display element, the polyester film and the hard coat layer are excellent in adhesion durability after wet heat aging, and a conventional protective film is used. The strength of the liquid crystal display element is reinforced more than the case, and the warpage of the liquid crystal display element can be prevented.

The features of the present invention will be described more specifically with reference to examples and comparative examples. The materials, amounts used, ratios, processing details, processing procedures, and the like shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the specific examples shown below. In the following, Example 5 is to be read as Reference Example 5 respectively.

Example 1
-Formation of an easy adhesion layer-
(1) Coating liquid for hard coat layer side easy-adhesion layer The following compounds were mixed in the following ratio to prepare a coating liquid (1) for the hard coat layer side easy-adhesion layer.

Coating liquid for hard coat layer side easy adhesion layer (1)
Acrylic resin: AS563-A (manufactured by Daicel Finechem Co., Ltd.) (solid content 28% by mass) 21.4 parts by mass Carbodiimide-based crosslinking agent: Carbodilite V-02-L2 (manufactured by Nisshinbo Co., Ltd.) (solid content 40 %) 3 parts by mass / surfactant 1: NAROACTY CL-95 (manufactured by Sanyo Chemical Industries) (100% solids) 0.1 part by mass / surfactant 2: Rapisol A-90 (NOF ( Co., Ltd.) (100% solid content)
0.1 parts by mass / particle: Snowtex XL (Nissan Chemical Industries, Ltd.) (solid content 40%)
0.4 parts by mass / lubricant: Cerosol 524 (manufactured by Chukyo Yushi Co., Ltd.) (solid content 30%) 1.0 part by mass / others: water adjusted so that the total mass part is 100

(2) Formation of polarizer-side easy-adhesion layer The following compounds were mixed at the following ratios to prepare a coating solution for polarizer-side easy-adhesion.

(2-1-1) Preparation of aqueous polyvinyl alcohol solution (P1)
90 parts by mass of water was added, and 10 parts by mass of polyvinyl alcohol resin (PVA-505 made by Kuraray) having a saponification degree of 73% and a polymerization degree of 500 was gradually added while stirring. After the addition, the solution was heated to 95 ° C. while stirring to dissolve the resin. After dissolution, the mixture was cooled to room temperature with stirring to prepare a polyvinyl alcohol aqueous solution having a solid content of 10% by mass.

(2-1-2) Preparation of aqueous polyvinyl alcohol solution (P2)
90 parts by weight of water was added, and 10 parts by weight of polyvinyl alcohol resin (PVA-405 made by Kuraray) having a saponification degree of 82% and a polymerization degree of 500 was gradually added while stirring. After the addition, the solution was heated to 95 ° C. while stirring to dissolve the resin. After dissolution, the mixture was cooled to room temperature with stirring to prepare a polyvinyl alcohol aqueous solution having a solid content of 10% by mass.

(2-1-3) Preparation of aqueous polyvinyl alcohol solution (P3)
90 parts by mass of water was added, and 10 parts by mass of a polyvinyl alcohol resin (PVA-205 made by Kuraray) having a saponification degree of 88% and a polymerization degree of 500 was gradually added while stirring. After the addition, the solution was heated to 95 ° C. while stirring to dissolve the resin. After dissolution, the mixture was cooled to room temperature with stirring to prepare a polyvinyl alcohol aqueous solution having a solid content of 10% by mass.

(2-1-4) Preparation of polyvinyl alcohol aqueous solution (P4)
90 parts by mass of water was added, and 10 parts by mass of a carboxylic acid-modified polyvinyl alcohol resin (KL-506 manufactured by Kuraray) having a saponification degree of 77% and a polymerization degree of 600 was gradually added while stirring. After the addition, the solution was heated to 95 ° C. while stirring to dissolve the resin. After dissolution, the mixture was cooled to room temperature with stirring to prepare a polyvinyl alcohol aqueous solution having a solid content of 10% by mass.

(2-2) Production of first blocked isocyanate (low-temperature blocked isocyanate) compound A four-necked flask equipped with a stirrer, thermometer, reflux condenser, and nitrogen blowing tube was put in a nitrogen atmosphere, and 1000 parts by mass of HDI, 3 22 parts by mass of trimethylolpropane (molecular weight 134) which is a monohydric alcohol was charged, and urethanization was carried out while maintaining the temperature in the reactor at 90 ° C. for 1 hour with stirring. Thereafter, the temperature of the reaction solution was kept at 60 ° C., an isocyanuration catalyst trimethylbenzylammonium hydroxide was added, and phosphoric acid was added when the conversion rate reached 48% to stop the reaction. Then, after filtering a reaction liquid, unreacted HDI was removed with the thin film distillation apparatus.
The obtained polyisocyanate had a viscosity at 25 ° C. of 25,000 mPa · s, an isocyanate group content of 19.9% by mass, a number average molecular weight of 1080, and an average number of isocyanate groups of 5.1. Thereafter, the presence of urethane bond, allophanate bond and isocyanurate bond was confirmed by NMR measurement.
A 4-necked flask equipped with a stirrer, thermometer, reflux condenser, nitrogen blowing tube, and dropping funnel was placed in a nitrogen atmosphere, and 100 parts by mass of the polyisocyanate obtained above and methoxypolyethylene glycol having a number average molecular weight of 400. 3 parts and 76.6 parts of dipropylene glycol dimethyl ether were charged and kept at 80 ° C. for 6 hours. Thereafter, the reaction temperature was cooled to 60 ° C., 72 parts by mass of diethyl malonate and 0.88 part by mass of a 28% methanol solution of sodium methylate were added and maintained for 4 hours, and then 0.86 parts by mass of 2-ethylhexyl acid phosphate. Was added.
Subsequently, 43.3 parts by mass of diisopropylamine was added, and the mixture was held at a reaction solution temperature of 70 ° C. for 5 hours. This reaction solution was analyzed by gas chromatography, and it was confirmed that the reaction rate of diisopropylamine was 70%. Thus, a first block polyisocyanate compound having a solid content concentration of 70% by mass was obtained. (Effective NCO base mass 5.3%)

(2-3) Preparation of second blocked isocyanate (high temperature blocked isocyanate) compound A 34 parts by mass of hexamethylene diisocyanate was added to 200 parts by mass of polyester of ethylene oxide adduct of bisphenol A and maleic acid, and reacted. Then, 73 parts by mass of a 30% by mass aqueous sodium bisulfite solution was added and stirred. Then, it diluted with water and obtained the 2nd block polyisocyanate compound. (Solid content 27%, effective NCO base mass 1%)

(2-4-1) Polyester aqueous dispersion (E1)
A sulfonic acid aqueous dispersion of a polyester resin copolymerized with a monomer having the following composition was obtained.
Monomer composition: (acid component) terephthalic acid / isophthalic acid / 5-sodium sulfoisophthalic acid // (diol component) ethylene glycol / triethylene glycol / diethylene glycol = 66/30/4 // 40/30/30 (mol%) ), Tg = 45 ° C., molecular weight 15000

(2-4-2) Polyester aqueous dispersion (E2)
A sulfonic acid aqueous dispersion of a polyester resin copolymerized with a monomer having the following composition was obtained.
Monomer composition: (acid component) terephthalic acid / isophthalic acid / 5-sodium sulfoisophthalic acid // (diol component) ethylene glycol / neopentyl glycol = 44/52/4 // 50/50 (mol%), Tg = 67 ° C, molecular weight 15000 (contains 10% n-butyl cellosolve as solvent)

(2-4-3) Polyester aqueous dispersion (E3)
A sulfonic acid aqueous dispersion of a polyester resin copolymerized with a monomer having the following composition was obtained.
Monomer composition: (acid component) terephthalic acid / isophthalic acid / phthalic acid / 5-sodium sulfoisophthalic acid // (diol component) ethylene glycol / diethylene glycol = 44/42/4/10 // 82/18 (mol%) , Tg = 61 ° C., molecular weight 20000 (containing 10% t-butyl cellosolve as a solvent)

(2-5) Polarizer side easy-adhesion coating solution The following coating agent is mixed, and polyester resin (E1) / polyvinyl alcohol resin (P1) / first blocked isocyanate compound / second blocked isocyanate compound A coating solution for easily adhering to the polarizer, which has a mass ratio of A of 60/30/10/10, was prepared.

Polyester aqueous dispersion (solid content 25% by mass) 17.5 parts by mass Polyvinyl alcohol aqueous solution (solid content 10% by mass) 21.9 parts by mass First block isocyanate compound (solid content 70% by mass) 0 part by mass / second blocked isocyanate compound A (solid content 27%) 2.7 parts by mass / particle: Snowtex ZL (manufactured by Nissan Chemical Industries, Ltd.) (solid content 40%)
1.8 parts by mass / catalyst (organotin-based compound solid content 10% by mass) 0.6 parts by mass / surfactant NAROACTY CL-95 (manufactured by Sanyo Chemical Industries, Ltd.) (solid content 100%)
0.1 parts by mass, sodium bicarbonate 0.01 parts by mass, sodium carbonate monohydrate 0.02 parts by mass, water: adjusted so that the total mass of water is 100

(3) Application of easy-adhesion layer on both sides of polyester film By the bar coat method, the coating solution for the hard coat layer-side easy-adhesion layer is applied to one side of the unstretched polyester film, and the other side is applied to the polarizer side. the coating solution for the adhesive coating weight after drying, respectively, 0.10g / m ^2, while adjusting so that 0.12 g / m ^2, was coated.

(4) Transverse stretching process (preheating part)
The preheating temperature was 90 ° C., and the mixture was heated to a temperature at which stretching was possible. Moreover, the temperature of the film surface was measured in this process, and it was confirmed that the moisture in the coating film had evaporated.

(Extension part)
The unstretched polyester film coated with pre-adhesive layer and preheated is guided to a tenter (transverse stretching machine), and the end of the film is held with a clip, while the TD direction (film width direction, lateral Direction) under the following conditions to obtain a 2 m wide film. The stretching conditions are as follows.
-Transverse stretching temperature: 90 ° C
・ Horizontal stretch ratio: 4 times

(Heat fixing part)
Next, a heat setting treatment was performed while controlling the film surface temperature of the polyester film within the following range. The heat setting conditions are as follows.
・ Heat setting temperature: 160 ℃
・ Heat setting time: 20 seconds

(Heat relaxation part)
The polyester film after heat setting was heated to the following temperature to relax the film. The thermal relaxation conditions are as follows.
-Thermal relaxation temperature: 160 ° C
-Thermal relaxation rate: TD direction (film width direction, lateral direction) 0.5%

(Cooling section)
Next, the polyester film after heat relaxation was cooled at a cooling temperature of 50 ° C., and the polarizer protective film of Example 1 was produced.

(Examples 2 to 20)
Table 1 shows the mass ratio of the polyester-based resin (E1) / polyvinyl alcohol-based resin (P1) / first blocked isocyanate compound / second blocked isocyanate compound A in the polarizer-side easy-adhesion layer coating solution and the compounds used. Except having changed into, it carried out similarly to Example 1, and created the polarizer protective film of Examples 2-20.

(Example 21)
Table 1 shows the mass ratio of the polyester-based resin (E1) / polyvinyl alcohol-based resin (P1) / first blocked isocyanate compound / second blocked isocyanate compound A in the polarizer-side easy-adhesion layer coating solution and the compounds used. The polarizer protective film of Example 21 was changed in the same manner as in Example 1 except that the following longitudinal stretching step was added before the transverse stretching step, and the temperature of the transverse stretching was changed to 120 ° C. Produced.
Longitudinal stretching process (stretching part)
The unstretched polyester film was longitudinally stretched in the MD direction (film stretching direction, longitudinal direction) under the following conditions under the following method and conditions. The stretching conditions are as follows.
-Longitudinal stretching temperature: 90 ° C
-Longitudinal stretch ratio: 2 times

(Comparative Examples 1 and 2)
Other than changing the mass ratio of the polyester resin (E1) / polyvinyl alcohol resin (P1) / first blocked isocyanate compound / second blocked isocyanate compound A in the polarizer-side easy-adhesion layer coating solution as shown in Table 1 Made the polarizer protective films of Comparative Examples 1 and 2 in the same manner as in Example 1.

(Comparative Example 3)
The mass ratio of the polyester resin (E1) / polyvinyl alcohol resin (P1) / first blocked isocyanate compound / second blocked isocyanate compound A in the polarizer-side easy-adhesion layer coating solution was changed as shown in Table 1, And the polarizer protective film of the comparative example 3 was carried out similarly to Example 1 except having apply | coated the polyester film biaxially in the vertical direction and the width direction before apply | coating the polarizer side easily bonding layer coating liquid to a polyester film. Created.

(Comparative Example 4)
(1) Preparation of second blocked isocyanate (high temperature blocked isocyanate) compound B The inside of a four-necked flask equipped with a stirrer, thermometer, reflux condenser, and nitrogen blowing tube was put in a nitrogen atmosphere, and HDI: 1000 parts by mass, 3 22 parts by mass of trimethylolpropane (molecular weight 134) which is a monohydric alcohol was charged, and urethanization was carried out while maintaining the temperature in the reactor at 90 ° C. for 1 hour with stirring. Thereafter, the temperature of the reaction solution was kept at 60 ° C., an isocyanuration catalyst trimethylbenzylammonium hydroxide was added, and phosphoric acid was added when the conversion rate reached 48% to stop the reaction. Then, after filtering a reaction liquid, unreacted HDI was removed with the thin film distillation apparatus.
The obtained polyisocyanate had a viscosity at 25 ° C. of 25,000 mPa · s, an isocyanate group content of 19.9% by mass, a number average molecular weight of 1080, and an average number of isocyanate groups of 5.1. Thereafter, the presence of urethane bond, allophanate bond and isocyanurate bond was confirmed by NMR measurement.
A 4-necked flask equipped with a stirrer, thermometer, reflux condenser, nitrogen blowing tube, and dropping funnel was placed in a nitrogen atmosphere, and 100 parts by mass of the polyisocyanate composition obtained in Production Example 2, n-butyl acetate 92. 9 parts by mass was charged and maintained at 40 ° C. Thereafter, 42.5 parts by mass of methyl ethyl ketoxime was dropped from the dropping funnel. After completion of dropping, the mixture was stirred for 1 hour, and then the infrared spectrum was measured. As a result, disappearance of the isocyanate group was confirmed, and a block polyisocyanate composition having a solid content concentration of 60% by mass was obtained. (Effective NCO base mass 8.2%)
23 parts by mass of the obtained block polyisocyanate composition, 27 parts by mass of water, 3 parts by mass of sodium dialkylsulfosuccinate (trade name “New Coal 290M” of Nippon Emulsifier Co., Ltd., solid content of 70% by mass) were added. Mix with a mixer. After mixing, a milky white second block polyisocyanate compound B aqueous dispersion was obtained. (Solid content 30%)

(2) Polarizer-side easy-adhesion coating solution Polarizer-side easy-adhesion layer coating solution polyester-based resin (E1) / polyvinyl alcohol-based resin (P1) / first blocked isocyanate compound / second blocked isocyanate compound A A polarizer protective film was prepared in the same manner as in Example 1 with the mass ratio of the second blocked isocyanate compound B as shown in Table 1.

(Comparative Examples 5 and 6)
Other than changing the mass ratio of the polyester resin (E1) / polyvinyl alcohol resin (P1) / first blocked isocyanate compound / second blocked isocyanate compound A in the polarizer-side easy-adhesion layer coating solution as shown in Table 1 Produced the polarizer protective films of Comparative Examples 5 and 6 in the same manner as in Example 1.

(Measurement of gelation temperature)
Acrylic polyol (Bernock WE-301 (manufactured by DIC) 45% solids, hydroxyl value 36 mgKOH / g (solid)) is used as the main agent, and the NCO / OH ratio is 0.3 so that the NCO / OH ratio is 0.3. The ratio was adjusted. The ratio is calculated as follows.
[Block isocyanate amount] / [Main agent amount]
= [Hydroxyl value] / [Effective NCO group mass%] / 561 × 42 × [NCO / OH ratio]

After the adjustment, each coating solution was diluted with water so that the total solid content was 30%.
Each coating solution was applied using an applicator so that the film thickness after drying was 40 μm, and a dried coating film was prepared by drying from 60 ° C. to 140 ° C. every 10 ° C. for 30 minutes. After immersing this coating film in acetone at 20 ° C. for 24 hours, the coating film was taken out and weighed, and the value (gel fraction) relative to the weight before immersion was measured. Further, the temperature at which the gel fraction exceeded 70% was defined as the minimum gelation temperature.
The minimum gelation temperature of each blocked isocyanate was as follows.
First block polyisocyanate composition 70 ° C.
Second block polyisocyanate A 140 ° C.
Second block polyisocyanate B 130 ° C.

  When the polarizer protective film of the present invention is produced, the temperature at the time of drying (preheating part) of the easy-adhesion layer-forming coating solution is 90 ° C., so the first gel having a minimum gelation temperature of 90 ° C. or lower is used. The blocked isocyanate (low-temperature blocked polyisocyanate) having a temperature exceeding 90 ° C. was defined as the second blocked isocyanate (high-temperature blocked polyisocyanate).

(Evaluation)
(Adhesion (peeling force))
About each film sample, the delamination force was measured by the 90 degree peeling test method. Specifically, it is as follows.
<Polarizer production>
A commercially available cellulose acetate film (ZRD40, manufactured by Fuji Film Co., Ltd.) was prepared as a polarizing plate protective film, and continuously passed through a 1.5 N aqueous sodium hydroxide solution and immersed at 55 ° C. for 2 minutes. It wash | cleaned in the room temperature water-washing tub, and neutralized using 0.1 N sulfuric acid at 30 degreeC. Again, it was washed in a water bath at room temperature and further dried with hot air at 100 ° C. In this way, the surface of the cellulose acetate film was saponified.
Subsequently, a roll-shaped polyvinyl alcohol film having a thickness of 80 μm was continuously stretched 5 times in the conveying direction in an aqueous iodine solution and dried to obtain a polarizer having a thickness of 20 μm.
<Implementation of corona treatment>
Regarding Examples 1 to 18 and Comparative Examples 1 to 6, corona treatment was performed on the polarizer-side easy-adhesion layer so as to have an intensity of 16 KJ / m ² . In Examples 19 to 21, the corona treatment was not performed and the following steps were performed.
<Bonding of polarizer and film>
Using a 3% aqueous solution of polyvinyl alcohol (Pura-117H made by Kuraray) as an adhesive, the polyvinyl alcohol film side (B layer) of the polarizer and the polarizer-side easy-adhesive layer (A layer) of each film sample are bonded together, and 80 ° C. for 10 minutes. Dried.
<Fixing to glass>
Each film sample was bonded to the hard coat layer side of each film sample and a glass plate via an adhesive. The size of each film sample was 2.5 cm wide × 15 cm long, and the length of the bonded portion was 7 cm.
At the interface between the A layer and the B layer, the interface layer was advanced by pulling the B layer in the 90 ° direction, and only the film edge was peeled off. The load at this time was measured, and this value was defined as the delamination force (N / 25 mm). At that time, Tensilon (RTG-1310, manufactured by A & D Co., Ltd.) was used, and the peeling rate was 300 mm / min.

(Blocking resistance)
Cut each film sample into 3.5cm □ (vertical x horizontal 3.5cm each) and stack two sheets so that the polarizer-side easy-adhesive layer and hard-coat side easy-adhesive layer of each sample are in contact with each other. The sample is left in an environment of 30 ° C. and 80% for 1 day with a pressure of 0.5 MPa applied in a direction perpendicular to the surface. Thereafter, the sample was taken out and the two samples were peeled off, and the state of each film was evaluated from the following viewpoints.
A: The two films peeled off without applying force, and no adhesion marks or the like were observed.
B: When peeling two films, a slight load is felt, but no adhesion mark or the like is seen.
C: When peeling two films, a strong load is felt, and in some cases, adhesion marks or peeling of the film occurs.

As can be seen from Table 1, in Examples 1 to 21, it can be seen that the peeling force when peeling the polarizer protective film from the polarizer is large, and the adhesion between the polarizer and the polarizer protective film is excellent. Moreover, it turns out that blocking resistance is also favorable.
On the other hand, in Comparative Examples 1-6, it turns out that peeling force is remarkably inferior and the adhesiveness of a polarizer and a polarizer protective film is not favorable. Further, it can be seen that Comparative Examples 1, 4 and 5 have poor blocking resistance.

  In Comparative Examples 1 and 4, since the low-temperature reaction type first blocked isocyanate is not used, the reaction with the hydroxyl group of polyvinyl alcohol in the film does not proceed sufficiently before the film stretching process. For this reason, it is presumed that the film breaks at the time of stretching and the respective components are divided, a sufficient reaction does not occur even in the heat setting process, a large amount of hydroxyl groups remain, and the blocking property deteriorates. In addition, since Comparative Example 5 does not have a polyester resin component that is hydrophobic and has good adhesion to the polyester film of the base material in the easy-adhesion layer, the hydrophobicity of the surface proceeds due to the mixed structure with the polyvinyl alcohol layer. It is estimated that the blocking properties deteriorate.

  According to this invention, the polarizer protective film excellent in adhesiveness with a polarizer can be obtained. Moreover, since the polarizer protective film of this invention is excellent in blocking resistance, generation | occurrence | production of blocking is suppressed even when it winds up in roll shape. The polarizer protective film of the present invention is preferably used for a polarizing plate, an image display device, and the like, and has good industrial applicability because the handleability of the polarizer protective film during panel bonding is good.

10 Polyester film 12 Easy adhesive layer 14 Easy adhesive layer 20 Polarizer 30 Protective film 40 Hard coat layer

Claims (14)

A polarizer protective film having a polyester film and an easy adhesion layer,
The easy adhesion layer includes a polyester resin, a polyvinyl alcohol resin, a first blocked isocyanate and a second blocked isocyanate,
The first blocked isocyanate has a temperature of 90 ° C. or less when the gel fraction is 70%, and the second blocked isocyanate has a temperature of 90% or less when the gel fraction is 70%. high,
The mass ratio of the first blocked isocyanate and the second blocked isocyanate is 1: 4 to 10: 1,
The said polarizer protective film is a polarizer protective film which is a width direction stretched film of the laminated film which consists of an unstretched polyester film or a longitudinal direction stretched polyester film, and an easily bonding layer. The polarizer protective film according to claim 1, wherein the polarizer protective film is a width direction stretched film of a laminated film composed of an unstretched polyester film and an easy adhesion layer. The polarizer protective film according to claim 1 or 2, wherein a total content of the first blocked isocyanate and the second blocked isocyanate is 0.6 to 70% by mass with respect to a total mass of the easy-adhesion layer. . The polarizer protective film according to claim 1, wherein a content of the first blocked isocyanate is 0.1 to 30% by mass with respect to a total mass of the easy-adhesion layer. The polarizer protective film according to any one of claims 1 to 4, wherein a content of the second blocked isocyanate is 0.5 to 40% by mass with respect to a total mass of the easy-adhesion layer. The polarizer layer according to any one of claims 1 to 5, wherein the easy adhesion layer is provided on one side of the polyester film and on the polarizer side. The ratio (NCO / OH group amount) of the NCO group amount (mmol) of the first blocked isocyanate and the OH group amount (mmol) of the polyvinyl alcohol resin is 0.001 to 0.23. The polarizer protective film of description. The polarizer protective film according to claim 6 or 7, wherein the content of the polyester resin is 10 to 80% by mass with respect to the total mass of the easy-adhesion layer. The polarizer protective film according to any one of claims 6 to 8, wherein a content of the polyvinyl alcohol-based resin is 5 to 45 mass% with respect to a total mass of the easy-adhesion layer. The polarizer protective film according to claim 1, wherein the polyester film contains an ultraviolet absorber. The polarizing plate containing the polarizer protective film of any one of Claims 1-10, and a polarizer. The polarizing plate according to claim 11 , further comprising a protective film and a hard coat layer. The polarizing plate according to claim 12 , wherein the polarizer protective film has a polarizer-side easy-adhesion layer and a hard coat layer-side easy-adhesion layer. An image display device comprising a polarizing plate according to any one of claims 11 to 13.

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