TWI902814B - Optical laminated polyester film - Google Patents

Abstract

The present invention addresses the problem of providing an optical laminated polyester film with high transparency, anti-blocking properties, and excellent adhesion to hard coating layers, light diffusing layers, lens layers, anti-glare layers, and transparent conductive layers. The optical laminated polyester film of the present invention comprises an easily adhesive polyester film having a coating layer on at least one side of a polyester film substrate. The laminated layer includes at least one optical functional layer selected from hard coating layers, light diffusing layers, lens layers, anti-glare layers, and transparent conductive layers, and the aforementioned coating layer has a specific composition.

Description

Optical laminated polyester film

This invention relates to an optical laminated polyester film with excellent adhesion and transparency. More specifically, it relates to an optical laminated polyester film on which optical functional films such as hard coatings, light diffusing sheets, lens sheets, transparent conductive films, and anti-glare films are laminated on an easily adhesive polyester film coating layer.

Generally speaking, the substrates used for optical functional films in components of various displays such as liquid crystal displays are transparent thermoplastic resin films composed of polyethylene terephthalate (PET), acrylic acid, polycarbonate (PC), triacetyl cellulose (TAC), polyolefins, etc.

When using the aforementioned thermoplastic resin film as the substrate for various optical functional films, functional layers corresponding to various applications are laminated. For example, in liquid crystal displays, functional layers such as protective films (hard coatings) to prevent surface damage, prism layers for focusing or diffusing light, and light diffusing layers to enhance brightness can be listed. Among such substrates, polyester films are widely used as substrates for various optical functional films, especially due to their excellent transparency, dimensional stability, chemical resistance, and relatively low cost.

Generally speaking, the surface of biaxially oriented polyester films is highly crystalline and aligned, thus lacking good adhesion to various coatings, adhesives, etc. Therefore, various methods have been proposed to impart easy adhesion to the surface of biaxially oriented polyester films.

Previously, it was known that a technique was used to impart easy adhesion to hard coating processes, prism lens processing, etc., by using copolymerized polyester resins and urethane resins as coatings (see, for example, Patent 1). However, this prior art has the problem that the anti-blocking properties of the easy-adhesive polyester film are not excellent.

Furthermore, it is known that techniques using urethane resins and end-capped isocyanates in coatings can impart good adhesion, particularly to hard coating processes used in the manufacture of front panels for solar cells (see, for example, Patent 2). However, this prior art suffers from low transparency in the easily adhered polyester film. Additionally, it is known that techniques using urethane resins and end-capped isocyanates in coatings can improve adhesion to the lens layer (see, for example, Patent 3). However, this prior art suffers from insufficient adhesion to the lens layer. [Prior Art Documents] [Patent Documents]

[Patent Document 1] Japanese Patent Application Publication No. 2000-229355. [Patent Document 2] Japanese Patent Application Publication No. 2016-015491. [Patent Document 3] Japanese Patent Application Publication No. 2014-221560.

[The problem the invention aims to solve]

This invention addresses the problems of the prior art. Specifically, the purpose of this invention is to provide an optical laminated polyester film that uses an easily bondable polyester film. This easily bondable polyester film has high transparency, anti-blocking properties, and good adhesion to various optical resin compositions. [Means for Solving the Problem]

In order to solve the above-mentioned problems, the inventors conducted research on the causes of the problems and discovered that when a coating layer containing a crosslinking agent, a polycarbonate structure, and a polyester resin is provided on at least one side of a polyester film substrate, and the nitrogen atom ratio in the coating layer and the OCOO bond ratio on the surface of the coating layer opposite to the polyester film substrate meet specific conditions, the problems of the present invention can be solved, thereby completing the present invention.

The aforementioned problems can be solved using the following methods. 1. An optically laminated polyester film, comprising the aforementioned coating layer of an adhesive polyester film having a coating layer on at least one side of a polyester film substrate, the laminate having at least one optical functional layer selected from a hard coating layer, a light diffusion layer, a lens layer, an anti-glare layer, and a transparent conductive layer, wherein the aforementioned coating layer is formed by curing a composition containing an urethane resin having a polycarbonate structure, a crosslinking agent, and a polyester resin, and the nitrogen atom distribution curve of the coating layer in the depth direction determined by X-ray photoelectron spectroscopy is such that the nitrogen atoms on the surface of the coating layer opposite to the polyester film substrate are... When the ratio is set to A (at%), the maximum value of the nitrogen atom ratio is set to B (at%), the etching time for the maximum nitrogen atom ratio B (at%) is set to b (seconds), and the etching time for the nitrogen atom ratio to become 1/2 B (at%) after b (seconds) is set to c (seconds), the following equations (i) to (iii) are satisfied. Furthermore, in the surface analysis spectrum measured by X-ray photoelectron spectroscopy, when the sum of the peak areas originating from each bond in the C1s spectral region is set to 100 (%), and the peak area originating from the OCOO bond is set to X (%), the following equation (iv) is satisfied. (i) 0.5≦B－A(at%)≦3.0 (ii) 30≦b(seconds)≦180 (iii) 0≦c－b(seconds)≦300 (iv) 2.0≦X(%)≦10.0 2. The optical laminated polyester film as described in section 1 above, wherein the fog level of the aforementioned easily bondable polyester film is 1.5% or less. [Invention Benefits]

The easily adhesive polyester film of this invention has high transparency, anti-blocking properties, and good adhesion to various optical resin compositions. Therefore, the optical laminated polyester film of this invention using the aforementioned easily adhesive polyester film exhibits excellent adhesion between the coating layer and various functional layers, making it suitable for use in optical components such as displays.

[Polyester Film Substrate] The polyester resin constituting the polyester film substrate in this invention is polyethylene terephthalate, polybutylene terephthalate, polyethylene 2,6-naphthalenedicarboxylate, polypropylene terephthalate, etc., and copolymerized polyester resins in which a portion of the diol or dicarboxylic acid component of the aforementioned polyester resin is replaced with copolymerizing components as described below. Examples of copolymerizing components include: diethylene glycol, neopentyl glycol, 1,4-cyclohexanediol, polyalkylene glycol, etc., and dicarboxylic acid components such as adipic acid, sebacic acid, phthalic acid, isophthalic acid, 5-sodium isophthalic acid, 2,6-naphthalenedicarboxylic acid, etc.

The polyester resins suitable for use in this invention are mainly selected from polyethylene terephthalate, polyethylene terephthalate, polyethylene butylene terephthalate, and polyethylene 2,6-naphthalate. Among these polyester resins, polyethylene terephthalate is the best in terms of balance between physical properties and cost. In addition, the polyester film substrate composed of these polyester resins is preferably a biaxially oriented polyester film, which can improve chemical resistance, heat resistance, and mechanical strength.

The catalyst used for condensation polymerization in the manufacture of polyester resins is not particularly limited; antimony trioxide is suitable due to its low cost and excellent catalytic activity. Germanium or titanium compounds are also preferred. More desirable condensation polymerization catalysts include: catalysts containing aluminum and/or its compounds and phenolic compounds; catalysts containing aluminum and/or its compounds and phosphorus compounds; and catalysts containing aluminum salts of phosphorus compounds. It is particularly advantageous to use a catalyst containing aluminum and/or its compounds and phosphorus compounds, as this can improve the transparency of the film.

In addition, the polyester film substrate in this invention can be a single-layer polyester film, or it can be composed of two layers with different compositions, or it can be a polyester film substrate having an outer layer and an inner layer and consisting of at least three layers.

[Explanation of Characteristic Values in the Invention] The easily adhesive polyester film of the present invention preferably has a coating layer on at least one side of the polyester film substrate as described above. The aforementioned coating layer is formed by curing a composition containing a polycarbonate-structured urethane resin, a crosslinking agent, and a polyester resin. The phrase "formed by curing a composition" is used here because it is extremely difficult to accurately describe the chemical composition of the polycarbonate-structured urethane resin, crosslinking agent, and polyester resin in a state where they are cured by forming a crosslinked structure through the crosslinking agent. Furthermore, when the maximum value of the nitrogen element distribution curve, determined based on the elemental distribution along the depth direction of the aforementioned coating layer, is located near the surface of the coating layer opposite to the polyester film substrate, improved transparency, anti-blocking properties, and adhesion to hard coating layers, anti-glare layers, and transparent conductive layers are achieved, which is therefore preferable. Moreover, the presence of an appropriate amount of polycarbonate structure on the coating layer surface opposite to the polyester film substrate further enhances adhesion to lens layers, light diffusion layers, etc., which is also preferable.

The characteristics of the coating layer in the aforementioned easily adhesive polyester film are explained. First, the nitrogen element distribution curve was determined by plotting the elemental distribution along the depth direction of the coating layer using X-ray photoelectron spectroscopy (ESCA). Specifically, spectral collection was performed every 30 seconds until the etching time of 120 seconds, and then every 60 seconds thereafter. Then, as shown in Figure 2, the etching time (in seconds) from the coating surface is used as the horizontal axis, and the ratio of nitrogen atoms to the total amount of carbon, oxygen, nitrogen, and silicon atoms (nitrogen atom ratio, in at%) is used as the vertical axis. The nitrogen atom ratio of the coating surface opposite to the polyester film substrate is set as A (at%), the maximum nitrogen atom ratio is set as B (at%), the etching time for the maximum nitrogen atom ratio B (at%) is set as b (seconds), and the etching time when the nitrogen atom ratio becomes 1/2 B (at%) after b (seconds) is set as c (seconds). B-A (at%) and c-b (seconds) are calculated based on the read data. The nitrogen atom ratio A (at%) on the coating surface opposite to the polyester film substrate is the nitrogen atom ratio at etching time 0 (seconds).

Furthermore, when the characteristic values read from the nitrogen element distribution curve determined based on the elemental distribution along the depth direction of the aforementioned coating layer fall within the following relationships, an easily bondable polyester film with excellent transparency, anti-blocking properties, and adhesion to hard coating layers, light diffusion layers, lens layers, anti-glare layers, and transparent conductive layers can be obtained. (i) 0.5≦B－A(at%)≦3.0 (ii) 30≦b(seconds)≦180 (iii) 30≦c－b(seconds)≦300

The lower limit of B-A is preferably 0.5 at%, more preferably 0.6 at%, further preferably 0.7 at%, especially preferably 0.8 at%, and most preferably 0.9 at%. If it is above 0.5 at%, the amount of highly resilient urethane resin is sufficient to achieve anti-blocking properties, which is therefore preferable. In addition, the adhesion to the hard coating layer, anti-glare layer, and transparent conductive layer is also improved, which is also preferable. The upper limit of B-A is preferably 3.0 at%, more preferably 2.9 at%, further preferably 2.8 at%, especially preferably 2.7 at%, and most preferably 2.5 at. If it is below 3.0 at%, low haze and transparency are achieved, which is therefore preferable.

The lower limit of b is preferably 30 seconds. If it is above 30 seconds, the toughness of the coating surface opposite to the polyester film substrate is maintained, and anti-blocking properties are obtained, which is preferable. The upper limit of b is preferably 180 seconds, more preferably 120 seconds, further preferably 90 seconds, and especially preferably 60 seconds. If it is below 180 seconds, the toughness of the coating surface opposite to the polyester film substrate is maintained, and anti-blocking properties become good, which is preferable. In addition, the adhesion to the hard coating layer, anti-glare layer, and transparent conductive layer is improved, which is preferable.

The upper limit of c-b is preferably 300 seconds, more preferably 240 seconds, and even more preferably 180 seconds. If it is below 300 seconds, the urethane resin component in the coating will not become excessive, resulting in low fog and transparency, which is therefore preferable. The lower limit of c-b is above 30 seconds, based on the relationship that the spectral collection is performed every 30 seconds from the start of the measurement up to an etching time of 120 seconds.

In this invention, it is preferable that most of the polycarbonate structure portion of the urethane resin in the coating layer constituting the easily bondable polyester film is located on the coating surface opposite to the polyester film substrate. This is because the presence of an appropriate amount of polycarbonate structure portion on this surface improves adhesion to the lens layer and light diffusion layer. On the other hand, it has also been found that the presence of polycarbonate structure portion on this surface sometimes increases flexibility but may not necessarily result in sufficient anti-blocking properties. Therefore, as described above, when the characteristic values read from the nitrogen element distribution curve determined based on the elemental distribution along the depth direction of the coating are within the following relationships, an easily bondable polyester film with excellent transparency, anti-blocking properties, and adhesion to the hard coating, anti-glare layer, and transparent conductive layer can be obtained. (i) 0.5≦B－A(at%)≦3.0 (ii) 30≦b(seconds)≦180 (iii) 30≦c－b(seconds)≦300

As a means to make the easily adhesive polyester film of the present invention satisfy the above-mentioned formulas (i) to (iii), examples can be listed: when synthesizing and polymerizing an amino carbamate resin having a polycarbonate structure to form a coating layer, the synthesis and polymerization includes a polycarbonate polyol component and a polyisocyanate component, the mass ratio of the polycarbonate polyol component to the polyisocyanate component is in the range of 0.5 to 2.5, the molecular weight of the polycarbonate polyol component is 500 to 1800, and when the total solid components of the polyester resin, amino carbamate resin and crosslinking agent in the coating liquid are set to 100% by mass, the content of the solid components of the crosslinking agent is 10% by mass to 50% by mass. Furthermore, as a crosslinking agent, a capped isocyanate is used, specifically a capped isocyanate with three or more functions and an isocyanate group, thereby enabling efficient regulation of B-A.

Furthermore, as described above, it is preferable that most of the polycarbonate structure portion of the urethane resin in the coating layer of the present invention exists in a certain proportion on the coating surface opposite to the polyester film substrate. In the present invention, in the surface analysis spectrum measured by X-ray photoelectron spectroscopy, the sum of the peak areas originating from each type of bond in the C1s spectral region is set as 100 (%), and the peak area originating from the OCOO bond (as a polycarbonate structure) is set as X (%), expressed as a percentage of the OCOO bond.

The ratio X (%) of the OCOO bonds (as part of the polycarbonate structure) in the surface region was evaluated using X-ray photoelectron spectroscopy (ESCA). Figures 5 and 6 are examples of graphs showing the analytical results of the C1s spectra of the surface regions of the easily bondable polyester films of Example 6 and Experimental Example 1, respectively, described later. The gray solid line represents the measured data of the C1s spectrum. The peaks of the obtained measured spectrum were separated into multiple peaks, and the bond types corresponding to each peak were identified according to their position and shape. Furthermore, curve fitting was performed using the peaks derived from each bond type to calculate the peak area. The coating layer of this invention contains a polycarbonate structure urethane resin, a crosslinking agent represented by a three-functional or higher isocyanate-terminated isocyanate group, and a polyester resin. In the case of this coating layer, the peaks of the bonds in Table 1 (1) to (6) can be detected. The bonds in Table 1 (1) to (6) are not necessarily only those shown in Table 1, and sometimes also contain a small number of similar bonds. Here, in Figure 5 of Example 6, the C=O bond peak of (3) and the π-π* bond peak of (6) in Table 1 do not appear. In addition, in Figure 6 of Experimental Example 1, the C=O bond peak of (3) and the OCOO bond peak of (5) in Table 1 do not appear. The ratio X (%) of the OCOO bonds in the surface area can be expressed as a percentage (%) representing the area ratio of the peak (5) when the area of the peaks (1) to (6) is set to 100%.

[Table 1] Keys (1) Black two-dot chain CC key (2) Black dotted line CO key, CN key (3) Black three-point chain C=O key (4) Black single-dot chain COO key (5) Black dots and lines OCOO key (6) Black solid line π-π* key

The suitable range for the peak area X (%) derived from the OCOO key is as follows. The lower limit of X is preferably 2.0%, more preferably 2.5%, further preferably 3.0%, especially preferably 3.5%, and best 4.0%. A value above 2.0% effectively satisfies the adhesion requirements to the lens layer and light diffusion layer, and is therefore preferred. The upper limit of X is preferably 10.0%, more preferably 9.0%, further preferably 8.0%, especially preferably 7.5%, and best 7%. A value below 10.0% prevents excessively high surface softness and facilitates the acquisition of anti-blocking properties, and is therefore preferred.

As a method for manufacturing the easily bondable polyester film of the present invention, since the X characteristic value based on the aforementioned C1s spectral region can be effectively achieved in the range of 2.0% to 10.0%, it is preferable that when synthesizing and polymerizing the polycarbonate structure of the urethane resin to form the coating layer, the mass ratio of the polycarbonate polyol component to the polyisocyanate component is 0.5 or more, and when the total solid components of the polyester resin, the polycarbonate structure of the urethane resin and the crosslinking agent in the coating liquid are set to 100% by mass, the urethane resin content is 5% to 50% by mass.

[Coating Layer] The easily adhesive polyester film of this invention preferably has a coating layer on at least one side to improve adhesion to the hard coating layer, the lens layer, and the light diffusion layer. The coating layer is formed from a composition containing a polycarbonate-structured urethane resin, a crosslinking agent, and a polyester resin. The coating layer can be disposed on both sides of the polyester film, or it can be disposed on only one side of the polyester film, with a different type of resin coating disposed on the other side.

The components of the coating layer are described in detail below. [Carbamate Resin] The carbamate resin with a polycarbonate structure in this invention has at least carbamate bond portions derived from polycarbonate polyol and polyisocyanate components, and may further include chain extenders as needed.

The lower limit of the mass ratio of polycarbonate polyol to polyisocyanate (mass of polycarbonate polyol/mass of polyisocyanate) in the synthesis and polymerization of the polycarbonate-structured urethane resin of the present invention is preferably 0.5, more preferably 0.6, further preferably 0.7, even more preferably 0.8, and most preferably 1.0. If it is 0.5 or higher, the ratio X of OCOO bonds on the coating surface can be efficiently adjusted to 2% or higher, which is therefore preferred. The upper limit of the mass ratio of polycarbonate polyol to polyisocyanate in the synthesis and polymerization of the polycarbonate-structured urethane resin of the present invention is preferably 2.5, more preferably 2.2, further preferably 2.0, even more preferably 1.7, and most preferably 1.5. If the value is below 2.5, the ratio X of OCOO bonds on the coating surface can be efficiently adjusted to below 10%, which is preferable. Furthermore, in the nitrogen distribution curve based on the depth-direction elemental distribution measurement by X-ray photoelectron spectroscopy, B-A can be effectively adjusted to above 0.5 at%, and c-b can be effectively adjusted to below 300 seconds.

The polycarbonate polyol used in the synthesis and polymerization of the polycarbonate-structured urethane resin of this invention preferably contains an aliphatic polycarbonate polyol with excellent heat resistance and hydrolysis resistance. Examples of aliphatic polycarbonate polyols include aliphatic polycarbonate diols and aliphatic polycarbonate triols, with aliphatic polycarbonate diols being a suitable candidate. Regarding the aliphatic polycarbonate diols used for the synthesis and polymerization of the polycarbonate-structured urethane resins of the present invention, examples include aliphatic polycarbonate diols obtained by reacting one or more of the following diols, such as ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, 1,9-nonanediol, 1,8-nonanediol, neopentanediol, diethylene glycol, and dipropylene glycol, with carbonates such as dimethyl carbonate, ethyl carbonate, and carbohydrate.

The number average molecular weight of the aforementioned polycarbonate polyol in this invention is preferably 500 to 1800. More preferably, it is 600 to 1700, and most preferably, it is 700 to 1500. If it is 500 or higher, the ratio X of OCOO bonds on the surface of the coating layer can be effectively adjusted to 10% or less. If it is 1800 or less, in the nitrogen distribution curve determined by depth-direction elemental distribution by X-ray photoelectron spectroscopy, B-A can be effectively adjusted to 0.5 or more, and c-b can be effectively adjusted to 300 seconds or less.

The polyisocyanates used in the synthesis and polymerization of the polycarbonate-structured urethane resins of this invention include, for example, aromatic aliphatic diisocyanates such as phenyl dimethyl diisocyanate, isoflavone diisocyanate and 4,4-dicyclohexylmethane diisocyanate, alicyclic diisocyanates such as 1,3-bis(methyl isocyanate)cyclohexane, aliphatic diisocyanates such as hexamethylene diisocyanate and 2,2,4-trimethylhexamethylene diisocyanate, or polyisocyanates formed by pre-addition of one or more of these compounds with trimethylolpropane, etc. When using the aforementioned aromatic aliphatic diisocyanates, cycloaliphatic diisocyanates, or aliphatic diisocyanates, there is no yellowing problem, which is therefore preferable. In addition, the coating does not become too hard and can alleviate the stress caused by the thermal shrinkage of the polyester film substrate, resulting in good adhesion, which is also preferable.

Examples of chain extenders include: ethylene glycol, diethylene glycol, 1,4-butanediol, neopentyl glycol and 1,6-hexanediol, glycerol, trimethylolpropane and neopentyl tetrol, ethylenediamine, hexamethylenediamine and piperazine, monoethanolamine and diethanolamine, thiodiols such as thiodiethanolamine and thiodiol, or water.

The coating layer in this invention is preferably made using an aqueous coating solution, applied via an in-line coating method described later. Therefore, the carbamate resin of this invention is preferably water-soluble or water-dispersible. Furthermore, the aforementioned "water-soluble or water-dispersible" means dispersed in an aqueous solution containing less than 50% by mass of water or a water-soluble organic solvent.

To impart water dispersibility to urethane resins, sulfonic acid (salt) groups or carboxylic acid (salt) groups can be introduced (copolymerized) into the urethane molecular backbone. To maintain moisture resistance, weakly acidic carboxylic acid (salt) groups are preferable. Alternatively, nonionic groups such as polyoxyalkylene groups can also be introduced.

To introduce carboxylic acid (salt) groups into urethane resins, polyol compounds with carboxylic acid groups, such as dihydroxymethylpropionic acid and dihydroxymethylbutyric acid, which are polyol components, are introduced as copolymerizing agents, and then neutralized using salifying agents. Specific examples of salifying agents include: trialkylamines such as ammonia, trimethylamine, triethylamine, triisopropylamine, tri-n-propylamine, and tri-n-butylamine; N-alkylformaldehydes such as N-methyl-M-Folin and N-ethyl-M-Folin; and N-dialkylalkanolamines such as N-dimethylethanolamine and N-diethylethanolamine. These salifying agents can be used alone or in combination of two or more.

When using a polyol compound with a carboxylic acid (salt) group as a copolymer component to impart water dispersibility, if the total polyisocyanate content of the carboxylic acid (salt) group in the carboxylic acid (salt) group of the carboxylic acid (salt) group in the carboxylic acid (salt) group of the carboxylic acid (salt) group of the carboxylic acid (salt) group of the carboxylic acid (car ...

The carbamate resin of this invention may also have end-capped isocyanates bonded at the ends to improve hardness.

[Crosslinking Agent] In this invention, the crosslinking agent contained in the composition used to form the coating layer is preferably a capped isocyanate, more preferably a capped isocyanate with three or more functions, and even more preferably a capped isocyanate with four or more functions. These crosslinking agents improve anti-blocking properties and enhance adhesion to hard coatings, anti-glare layers, and transparent conductive layers. If a capped isocyanate crosslinking agent is used, the nitrogen distribution curve based on the depth-direction elemental distribution determined by X-ray photoelectron spectroscopy can be effectively adjusted to 0.5 at% or more, which is therefore preferable.

The lower limit of the boiling point of the capping agent for the aforementioned capped isocyanate is preferably 150°C, more preferably 160°C, further preferably 180°C, particularly preferably 200°C, and most preferably 210°C. The higher the boiling point of the capping agent, the more its volatilization is suppressed by the heat load during the drying process after coating or during film manufacturing using in-line coating methods. This further suppresses the formation of minute coating surface irregularities and improves film transparency. The upper limit of the boiling point of the capping agent is not particularly limited; from a production perspective, it is considered to be around 300°C. Since boiling point is related to molecular weight, in order to increase the boiling point of the capping agent, it is preferable to use a capping agent with a large molecular weight, preferably 50 or higher, more preferably 60 or higher, and even more preferably 80 or higher.

The upper limit of the dissociation temperature of the capping agent is preferably 200°C, more preferably 180°C, further preferably 160°C, particularly preferably 150°C, and most preferably 120°C. The capping agent dissociates from the functional groups due to the heat load during the drying step after coating or during film manufacturing steps using in-line coating methods, thereby generating regenerated isocyanate groups. Therefore, crosslinking reactions with carbamate resins, etc., proceed, and adhesion is improved. When the dissociation temperature of the capping isocyanate is below the above-mentioned temperature, the dissociation of the capping agent proceeds sufficiently, thus adhesion, especially resistance to damp heat, becomes good.

End-capping agents used in the end-capped isocyanates of this invention, with a dissociation temperature below 120°C and a boiling point above 150°C, include: sulfite compounds such as sodium bisulfite; pyrazole compounds such as 3,5-dimethylpyrazole, 3-methylpyrazole, 4-bromo-3,5-dimethylpyrazole, 4-nitro-3,5-dimethylpyrazole; and active methylene compounds such as malonate diesters (dimethyl malonate, diethyl malonate, di-n-butyl malonate, di(2-ethylhexyl) malonate), methyl ethyl ketone, etc. Triazole compounds include 1,2,4-triazole, etc. Among these, pyrazole compounds are preferred in terms of resistance to damp heat and yellowing.

The polyisocyanates that serve as precursors to the end-capped isocyanates of this invention can be obtained by introducing diisocyanates. Examples include: carbamate-modified diisocyanates, urea-modified diisocyanates, urea-modified diurea-modified diurea-modified diurea-modified diurea-dione-modified diurea-modified diisocyanates, isocyanurate-modified diisocyanates, carbodiimide-modified diisocyanates, etc.

Examples of diisocyanates include: 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, 2,2'-diphenylmethane diisocyanate, 1,5-naphthalene diisocyanate, 1,4-naphthalene diisocyanate, phenyl diisocyanate, tetramethylphenyl diisocyanate, 4,4'-diphenyl ether diisocyanate, 2-nitrobiphenyl-4,4'-diisocyanate, 2,2'-diphenylpropane-4,4'-diisocyanate, 3,3'- Aromatic diisocyanates such as dimethyl diphenylmethane-4,4'-diisocyanate, 4,4'-diphenylpropane diisocyanate, and 3,3'-dimethoxybiphenyl-4,4'-diisocyanate; aromatic aliphatic diisocyanates such as phenyl dimethyl diisocyanate; isoflavone diisocyanate and 4,4-dicyclohexylmethane diisocyanate; alicyclic diisocyanates such as 1,3-bis(methyl isocyanate)cyclohexane; hexamethylene diisocyanate; and aliphatic diisocyanates such as 2,2,4-trimethylhexamethylene diisocyanate. In terms of transparency, adhesion, and resistance to humidity and heat, aliphatic, cycloaliphatic isocyanates or their modified forms are preferred for optical applications requiring non-yellowing and high transparency.

Regarding the capped isocyanates in this invention, in order to impart water solubility or water dispersibility, a hydrophilic group can be introduced into the polyisocyanate used as a precursor. Examples of hydrophilic groups include: (1) quaternary ammonium salts of dialkylamino alcohols or dialkylaminoalkylamines, (2) sulfonates, carboxylates, phosphates, etc., and (3) polyethylene glycol, polypropylene glycol, etc., which are single-terminated with alkoxy groups. When a hydrophilic site is introduced, it becomes (1) cationic, (2) anionic, or (3) nonionic. Among these, since most other water-soluble resins are anionic resins, it is preferable to be anionic or nonionic, which can be easily miscible. In addition, anionic resins have excellent compatibility with other resins, while nonionic resins do not have ionic hydrophilic groups, which also improves their resistance to humidity and heat, making them superior.

As anionic hydrophilic groups, they are preferably hydroxyl groups for introducing up to a maximum of isocyanates, or carboxylic acid groups for imparting hydrophilicity. Examples include: glycolic acid, lactic acid, tartaric acid, citric acid, hydroxybutyric acid, hydroxyvalerate, hydroxytrimethylacetic acid, dihydroxymethylacetic acid, dihydroxymethylpropionic acid, dihydroxymethylbutyric acid, and polycaprolactone containing carboxylic acid groups. To neutralize the carboxylic acid groups, organic amine compounds are preferred. Examples include: ammonia, methylamine, ethylamine, propylamine, isopropylamine, butylamine, 2-ethylhexylamine, cyclohexylamine, dimethylamine, diethylamine, dipropylamine, diisopropylamine, dibutylamine, trimethylamine, triethylamine, triisopropylamine, tributylamine, ethylenediamine, and other linear or branched primary, secondary, or tertiary amines with 1 to 20 carbon atoms; cyclic amines such as methylphenol, N-alkylmethylphenol, and pyridine; monoisopropanolamine, methylethanolamine, methylisopropanolamine, dimethylethanolamine, diisopropanolamine, diethanolamine, triethanolamine, diethylethanolamine, and triethanolamine containing hydroxyl groups.

As a nonionic hydrophilic group, the number of repeating units of ethylene oxide and/or propylene oxide in polyethylene glycol and polypropylene glycol with single-terminal alkoxy end-capped structures is preferably 3 to 50, more preferably 5 to 30. With fewer repeating units, the compatibility with the resin may sometimes decrease, and the fogging may increase; with more repeating units, adhesion under high temperature and humidity may sometimes decrease. Regarding the end-capped isocyanates of this invention, nonionic, anionic, cationic, or amphoteric surfactants can be added to improve water dispersibility. Examples include: nonionic surfactants such as polyethylene glycol and polyol fatty acid esters; anionic surfactants such as fatty acid salts, alkyl sulfates, alkylbenzene sulfonates, sulfosuccinates, and alkyl phosphates; cationic surfactants such as alkylamine salts and alkyl betaine; and surfactants such as carboxylic acid amine salts, sulfonate amine salts, and sulfate ester salts.

In addition to water, it may also contain water-soluble organic solvents. For example, the organic solvent used in the reaction may be used, or the organic solvent may be removed and another organic solvent may be added.

[Polyester Resin] The polyester resin used to form the coating layer in this invention can also be a linear polyester resin, but it is more preferably a polyester resin composed of dicarboxylic acids and branched alkyldiols. Regarding the dicarboxylic acids mentioned here, their main components, in addition to terephthalic acid, isophthalic acid, or 2,6-naphthalenedicarboxylic acid, include: aliphatic dicarboxylic acids such as adipic acid and sebacic acid, and aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, phthalic acid, and 2,6-naphthalenedicarboxylic acid. In addition, branched alkyl glycols are diols with branched alkyl groups, such as: 2,2-dimethyl-1,3-propanediol, 2-methyl-2-ethyl-1,3-propanediol, 2-methyl-2-butyl-1,3-propanediol, 2-methyl-2-propyl-1,3-propanediol, 2-methyl-2-isopropyl-1,3-propanediol, 2-methyl-2-n-hexyl-1,3-propanediol, 2,2-diethyl-1,3-propanediol, 2-ethyl-2-n-butyl-1,3-propanediol, 2-ethyl-2-n-hexyl-1,3-propanediol, 2,2-di-n-butyl-1,3-propanediol, 2-n-butyl-2-propyl-1,3-propanediol, and 2,2-di-n-hexyl-1,3-propanediol, etc.

Regarding polyester resins, the branched alkyldiol component, as a preferred form as described above, is preferably contained in the total alkyldiol composition at a rate of 10 mol% or more, and more preferably at a rate of 20 mol% or more. Ethylene glycol is the most preferred alkyldiol component other than the aforementioned compounds. If in small quantities, diethylene glycol, propylene glycol, butanediol, hexanediol, or 1,4-cyclohexanediethanol may also be used.

Regarding the dicarboxylic acid that forms part of the aforementioned polyester resin, terephthalic acid or isophthalic acid is preferred. If in small quantities, other dicarboxylic acids, especially aromatic dicarboxylic acids such as diphenylcarboxylic acid and 2,6-naphthalenedicarboxylic acid, may be added to copolymerize them. In addition to the aforementioned dicarboxylic acids, to impart water dispersibility to the copolymerized polyester resin, it is preferable to copolymerize 5-sulfonoisophthalic acid in the range of 1 mol% to 10 mol%, for example: sulfonoterephthalic acid, 5-sulfonoisophthalic acid, 4-sulfononaphthaleneisophthalic acid-2,7-dicarboxylic acid, 5-(4-sulfophenoxy)isophthalic acid and its salts, etc.

When the total solid content of polyester resin, polycarbonate-structured urethane resin, and crosslinking agent in the coating solution is set to 100% by mass, the lower limit of the crosslinking agent content is preferably 5% by mass, more preferably 7% by mass, further preferably 10% by mass, and most preferably 12% by mass. If the lower limit of the crosslinking agent content is 5% by mass or more, it is easier to adjust B-A to 0.5 at% or more in the nitrogen distribution curve based on the depth-direction elemental distribution determined by X-ray photoelectron spectroscopy, which is therefore preferable. The upper limit of the crosslinking agent content is preferably 50% by mass, more preferably 40% by mass, further preferably 35% by mass, and most preferably 30% by mass. If the lower limit of the crosslinking agent content is less than 50% by mass, then in the nitrogen distribution curve determined by depth-direction elemental distribution by X-ray photoelectron spectroscopy, it is easy to adjust c-b to less than 300 seconds, which is therefore better.

When the total solid content of polyester resin, polycarbonate-structured urethane resin, and crosslinking agent in the coating liquid is set to 100% by mass, the lower limit of the content of polycarbonate-structured urethane resin is preferably 5% by mass. If the content of polycarbonate-structured urethane resin is 5% by mass or more, it is easier to adjust the ratio X of OCOO bonds on the surface of the coating layer to 2.0% or more, which is therefore preferable. The upper limit of the content of polycarbonate-structured urethane resin is preferably 50% by mass, more preferably 40% by mass, further preferably 30% by mass, and most preferably 20% by mass. If the content of the carbamate resin is less than 50% by mass, it is easier to adjust the ratio X of OCOO bonds on the coating surface to less than 10.0%, which is therefore better.

When the total solid content of polyester resin, carbamate resin, and crosslinking agent in the coating solution is set to 100% by mass, the lower limit of the polyester resin content is preferably 10% by mass, more preferably 20% by mass, further preferably 30% by mass, particularly preferably 35% by mass, and most preferably 40% by mass. If the polyester resin content is 10% by mass or more, the adhesion between the coating layer and the polyester film substrate becomes good, which is therefore preferred. The upper limit of the polyester resin content is preferably 70% by mass, more preferably 67% by mass, further preferably 65% by mass, particularly preferably 62% by mass, and most preferably 60% by mass. If the polyester resin content is below 70% by mass, the hard coating film after hard coating process will have good resistance to moisture and heat, and is therefore better.

[Additives] To the coating layer of this invention, known additives may be added, to a extent that they do not impair the effects of the invention, such as surfactants, antioxidants, heat stabilizers, weather stabilizers, UV absorbers, organic lubricants, pigments, dyes, organic or inorganic particles, antistatic agents, nucleating agents, etc.

In this invention, adding particles to the coating layer is a preferred method to improve its anti-blocking properties. In this invention, the particles contained in the coating layer include, for example, titanium oxide, barium sulfate, calcium carbonate, calcium sulfate, silicon dioxide, aluminum oxide, talc, kaolin, clay, or mixtures thereof. Other common inorganic particles can also be listed, such as calcium phosphate, mica, lithium bentonite, zirconium oxide, tungsten oxide, lithium fluoride, calcium fluoride, and inorganic particles combined with other inorganic particles, or styrene-based, acrylic-based, melamine-based, benzo[a]melamine-based, polysiloxane-based, and other organic polymer particles.

The average particle size of the particles in the coating layer (average particle size based on the number of particles measured using a scanning electron microscope (SEM), the same applies below) is preferably from 0.04 μm to 2.0 μm, more preferably from 0.1 μm to 1.0 μm. If the average particle size of the inert particles is 0.04 μm or more, it becomes easier to form unevenness on the film surface, thus improving the film's slip and winding properties, and improving processability during bonding, which is therefore preferable. On the other hand, if the average particle size of the inert particles is 2.0 μm or less, particle shedding is less likely to occur, which is also preferable. The particle concentration in the coating layer is preferably from 1% to 20% by mass of the solid composition.

The average particle size was determined by observing the particles in the cross-section of the easily bondable polyester film using a scanning electron microscope. Thirty particles were observed, and the average particle size was taken as the average particle size.

The shape of the particles is not particularly restricted as long as it meets the purpose of this invention; spherical particles and amorphous non-spherical particles can be used. The particle size of amorphous particles can be calculated using the equivalent circle diameter. The equivalent circle diameter is obtained by dividing the observed particle area by π, taking the square root, and then multiplying it by 2.

[Manufacturing of Easy-Adhesive Polyester Film] The manufacturing method of the easy-adhesive polyester film of this invention is illustrated by using an example of a polyethylene terephthalate (PET) film substrate, but is not limited to this example.

After the PET resin is thoroughly vacuum dried, it is fed to an extruder, where molten PET resin at approximately 280°C is extruded from a T-die onto a rotating cooling roller to form a sheet. The sheet is then cooled and solidified by applying electrostatic discharge to obtain an unstretched PET sheet. The aforementioned unstretched PET sheet can be a single layer or a multi-layered structure formed by co-extrusion.

The unstretched PET sheet is crystalline and oriented by performing uniaxial or biaxial stretching. For example, in the case of biaxial stretching, a uniaxially stretched PET film is obtained by stretching the film 2.5 to 5.0 times its length using rollers heated to 80°C to 120°C. The film is then clamped at its ends and introduced into a hot air zone heated to 80°C to 180°C, where it is stretched 2.5 to 5.0 times its width. Alternatively, in the case of uniaxial stretching, the film is stretched 2.5 to 5.0 times its width in a tenter frame. After stretching, the film is further introduced into a heat treatment zone for heat treatment, thereby completing the crystalline orientation.

The lower limit of the temperature in the heat treatment zone is preferably 170°C, and more preferably 180°C. If the temperature in the heat treatment zone is above 170°C, the hardening becomes sufficient, and the adhesion in the presence of liquid water becomes good, thus eliminating the need for a longer drying time. On the other hand, the upper limit of the temperature in the heat treatment zone is preferably 230°C, and more preferably 200°C. If the temperature in the heat treatment zone is below 230°C, there is no risk of a decrease in the physical properties of the film, which is therefore preferable.

The coating can be applied after or during the film manufacturing process. In particular, for the sake of productivity, it is preferable to apply the coating solution to at least one side of the PET film after it has been unstretched or uniaxially stretched to form the coating at any stage of the film manufacturing process.

The method for applying the coating liquid to the PET film can be any known method. Examples include: reverse roller coating, gravure coating, touch coating, mold coating, roller brush coating, spray coating, air knife coating, wire rod coating, tube doctor blade coating, dip coating, and curtain coating. These methods can be applied individually or in combination.

In this invention, the thickness of the coating layer can be appropriately set in the range of 0.001 μm to 2.00 μm, but to balance processability and adhesion, it is preferably in the range of 0.01 μm to 1.00 μm, more preferably 0.02 μm to 0.80 μm, and even more preferably 0.05 μm to 0.50 μm. If the coating layer thickness is 0.001 μm or more, the adhesion is good, and therefore it is preferred. If the coating layer thickness is less than 2.00 μm, adhesion is less likely to occur, and therefore it is preferred.

The upper limit of the haze of the easily bondable polyester film of this invention is preferably 1.5%, more preferably 1.3%, further preferably 1.2%, and even more preferably 1.0%. If the haze is below 1.5%, the transparency is better, making it suitable for use in optical films requiring transparency. Low haze is preferred, but it can also be above 0.1%.

[Laminated Polyester Film for Optical Applications] It is preferable to provide a functional layer on the coating layer of the easily adhesive polyester film of this invention. The functional layer refers to a layer with functional properties such as a hard coating layer, anti-glare layer, light diffusion layer, and transparent conductive layer, which serves to prevent reflection or suppress glare, suppress iris unevenness, and suppress scratches. Various functional layers known in the art can be used, and there are no particular limitations on the type of functional layer. The following describes each functional layer.

[Hard Coating] When forming the hard coating, any known hard coating material can be used without particular limitation. Resin compounds that polymerize and/or react through drying, heat, chemical reaction, or irradiation with electron beams, radiation, or ultraviolet light can be used. Examples of such curing resins include melamine-based, acrylic-based, polysiloxane-based, and polyvinyl alcohol-based curing resins. However, for achieving high surface hardness or optical design, photocurable acrylic-based curing resins are preferred. As such acrylic curable resins, multifunctional (meth)acrylate monomers or acrylate oligomers can be used. Examples of acrylate oligomers include: polyester acrylates, epoxy acrylates, urethane acrylates, polyether acrylates, polybutadiene acrylates, and polysiloxane acrylates. By mixing reaction diluents, photopolymerization initiators, sensitizers, etc., with these acrylic curable resins, coating compositions for forming the aforementioned optical functional layer can be obtained.

The aforementioned hard coating layer preferably contains inorganic particles. These inorganic particles are formulated to increase the hardness of the hardened film. Examples include silica, alumina, zirconium oxide, titanium oxide, zinc oxide, and tin oxide, which can be used alone or in combination of two or more. Among these, silica and alumina are preferred in terms of having minimal impact on optical properties. When using silica, to improve dispersibility in the coating, it is preferable to use silica that has been surface-treated with a silane coupling agent or an organic compound with reactive functional groups such as (meth)acrylic acid. However, when using alumina, the presence or absence of surface treatment has little impact on dispersibility, so it can be used without problems regardless of surface treatment.

The average particle size of the aforementioned inorganic particles is preferably from 5 nm to 200 nm, more preferably from 10 nm to 100 nm, and even more preferably from 20 nm to 60 nm. By setting the average particle size of the inorganic particles to 5 nm or more, an improvement in film hardness can be expected; by setting the average particle size of the inorganic particles to 200 nm or less, the impact on optical properties such as fog can be reduced. Furthermore, the amount of the inorganic particles relative to the total solid content is preferably from 0.5 wt% to 10 wt%, more preferably from 1 wt% to 8 wt%. By setting it to 0.5 wt% or more, an improvement in hardness can be expected; by setting it to 10 wt% or less, the impact on optical properties such as fog can be reduced. Furthermore, regarding the average particle size, in the case of silicon dioxide, it is set as the median particle size (d50) measured by the BET (Brunauer-Emmett-Teller) method, and in other cases including alumina, it is set as the median particle size (d50) measured by the laser diffraction scattering method according to JIS Z8825-1.

The aforementioned hard coating can also possess an anti-glare function that scatters external light. This anti-glare function can be achieved by creating an uneven surface on the hard coating. Ideally, the film's fog level should be between 0% and 50%, more preferably between 0% and 40%, even more preferably between 0% and 30%, and most preferably below 1.5%. The lower limit can also be above 0.1%.

[Light Diffusion Layer] From a practical standpoint as a substrate film for light diffusion sheets, the upper limit of its thickness is preferably 250 μm. A particularly preferred upper limit is 200 μm, similar to that of a typical TAC film. Preferably, at least one side of the substrate has a bead coating layer primarily composed of acrylic resin beads and an adhesive, and the fog level of the light diffusion sheet is 80% or higher. A fog level of 80% or higher results in enhanced brightness without causing color unevenness, which is therefore preferable. A more preferred lower limit is 85%.

Secondly, a method for forming a bead coating layer on a polyester film substrate as a light-diffusing sheet will be described, but the invention is not limited thereto. Adhesives used as the bead coating layer include acrylic resins such as PMMA (polymethyl methacrylate), polyester resins, polyvinyl chloride, polyurethane, and polysiloxane resins. Acrylic resins are particularly suitable due to their excellent transparency.

The beads contained in the bead coating layer are preferably made of acrylic resin, but beads made of other resins can also be used. Examples of other resins include: polysiloxane resin, nylon resin, urethane resin, styrene resin, polyethylene resin, silica particles, polyester resin, and various other resins. There is no particular limitation on the particle size of these beads; beads with an average particle size of 1 μm to 50 μm are suitable. Furthermore, when spherical beads are used as the aforementioned beads, these spherical beads act as lenses, enabling a more effective light diffusion effect.

The aforementioned beads are mixed in an appropriate amount in the aforementioned adhesive to prepare a coating liquid. The coating liquid is then uniformly applied to the surface of the coating layer of the easily adhesive polyester film manufactured as described above, and allowed to dry, thereby forming a bead coating layer in which the beads are uniformly dispersed in the adhesive. There is no particular limitation on the proportion of beads to the adhesive, but considering light diffusion properties, it is preferably about 10 to 60 parts by weight relative to 100 parts by weight of the adhesive. As a coating method, various methods can be used, such as roller coating, dip coating, spray coating, swirl coating, lamination, and flow coating, but there are no particular limitations.

The backlight of the liquid crystal display device using the light-diffusing sheet of this invention has good brightness, with little change in brightness over angle and minimal brightness unevenness. Therefore, it can help to achieve higher brightness, higher quality, and lower cost of liquid crystals.

[Transparent Conductive Layer] Examples of the transparent conductive film in this invention include: indium oxide, tin oxide, zinc oxide, indium-tin composite oxide, tin-antimony composite oxide, zinc-aluminum composite oxide, and indium-zinc composite oxide. Among these, indium-tin composite oxide is suitable from the viewpoint of environmental stability or circuit processability. In this invention, a transparent conductive film layer is laminated, and the surface resistance of the transparent conductive laminated film is preferably set to 50Ω/□ to 2000Ω/□, and more preferably 100Ω/□ to 1500Ω/□, thereby enabling it to be used as a transparent conductive laminated film in touch panels, etc. When the surface resistance is between 50Ω/□ and 2000Ω/□, the touch panel's position recognition accuracy is good, therefore it performs better.

The thickness of the transparent conductive film is preferably in the range of 4 nm to 30 nm, and more preferably in the range of 10 nm to 25 nm. When the thickness of the transparent conductive film is 4 nm or more, it is easier to form the film continuously and obtain good conductivity, which is therefore preferable. On the other hand, when the thickness of the transparent conductive film is 30 nm or less, the difference in optical properties between the portions with and without the transparent conductive layer is smaller when the transparent conductive layer is patterned, which is also preferable.

The structure of the transparent conductive layer can be a single layer or a multilayer structure with two or more layers. In the case of a transparent conductive film with two or more multilayer structures, the aforementioned metal oxides constituting each layer can be the same or different.

As for the methods for forming the transparent conductive thin film of this invention, known methods include vacuum evaporation, sputtering, CVD (Chemical Vapor Deposition), ion deposition, and spraying. The aforementioned methods can be used appropriately according to the required film thickness. Alternatively, a transparent conductive layer can be deposited on a coating layer by coating a conductive material such as aniline-based compounds, thiol-based compounds, pyrrole-based compounds, or carbon nanotubes into an adhesive resin. For example, in the case of sputtering, conventional sputtering using an oxide target or reactive sputtering using a metal target can be used. At this time, oxygen, nitrogen, or other reactive gases can be introduced, or ozone can be added, plasma irradiation can be used, or ion-assisted methods can be employed. In addition, bias voltages such as DC, AC, and high frequency can be applied to the substrate without compromising the purpose of this invention.

The optically laminated polyester film with a transparent conductive layer of this invention is particularly suitable as a resistive or electrostatic capacitive electrode film for touch panels. Furthermore, when the aforementioned hard coating layer is deposited on the coating layer of the easily bondable polyester film, and the transparent conductive layer is deposited on the hard coating layer, the oligomer precipitation of the easily bondable polyester film can be suppressed, thus representing a particularly superior state.

[Transparent Layer] Backlight from a liquid crystal panel is directed in all directions. To improve the brightness of a display device, a transparent layer is used to concentrate the light towards the viewing side. As lens sheets, depending on the shape of the lens processed on the surface, the following types can be listed: cylindrical or prismatic lenses, biconvex lenses (one-axis focusing type with light focused in only one direction), rectangular tapered lenses or deformed rectangular tapered lenses with a longer ridge in one direction (two-axis focusing type with light focused in two orthogonal directions), triangular or hexagonal tapered lenses (three-axis focusing type), octagonal or larger multi-axis types, and even smaller hemispherical or semi-elliptical microlenses, Fresnel lenses, etc. Any of these types can be used. Lens sheets can be processed with lenses on both sides instead of just one side, and the shape of the lens can also be different on both sides. A single-axis focusing lens can also be processed on both sides with the focusing axes orthogonal. Among these, two-axis, three-axis, multi-axis, and microlens types offer high focusing efficiency and are considered particularly superior lens shapes.

The lens layer of this invention can be obtained, for example, by applying a composition containing a thermoplastic resin or a reaction-curing resin with suitable hardness and shaping properties onto a coating layer of an easily adhesive polyester film. The composition containing a thermoplastic resin or a reaction-curing resin with shaping properties can be applied to various materials, such as the various curing resins described in the description of hard coatings, with UV-curing acrylic resins as a representative example. Alternatively, a composition containing monomers or oligomers for forming UV-curable acrylic resin can be cast into a mold with a lens pattern, so that the coating surface of the easily bondable polyester film is the resin side and is closely bonded to the resin. Ultraviolet light is irradiated from the easily bondable polyester film side to harden the composition, thereby forming a lens layer.

Regarding lens sheets, examples include: methods for embossing the surface of a transparent substrate using a mold with a specific pattern, and methods for coating an easily adhesive polyester film with UV-curing resins such as acrylic and then curing it with UV light while it is in contact with a mold with a specific pattern, as mentioned above.

As a lens layer, its shape is not particularly limited; for example, it can be used with prism lenses, Fresnel lenses, microlenses, etc.

Based on the above, the optical laminated polyester film of this invention is primarily suitable for all optical films, namely, base films for optical components such as prism lenses, AR (Anti-Reflection) films, hard coatings, diffusers, shatterproof films, etc., in LCD (Liquid Crystal Display) or flat-panel TVs (televisions), CRT (Cathode Ray Tubes), etc.; near-infrared absorption filters for front panel components of plasma displays; and transparent conductive films such as touch panels or electroluminescent films. [Example]

Secondly, the invention is described in detail using embodiments and experimental examples, but the invention is not limited to the embodiments described below.

[Manufacturing of Polyester Resin Granules P-1] High-purity terephthalic acid and ethylene glycol in an amount equal to two moles of the high-purity terephthalic acid were loaded into a 2-liter stainless steel autoclave equipped with a mixer. 0.3 moles of triethylamine were added relative to the acid component. While the system was being distilled at 250°C under a pressure of 0.25 MPa, an esterification reaction was carried out to obtain a mixture of bis(2-hydroxyethyl) terephthalate and oligomers with an esterification rate of approximately 95% (hereinafter referred to as the BHET mixture). Next, while stirring the BHET mixture, an ethylene glycol solution of antimony trioxide as a polymerization catalyst was added relative to the acid component in the polyester at an antimony atom concentration of 0.04 moles. The mixture was then stirred for 10 minutes at atmospheric pressure and 250°C under a nitrogen atmosphere. Subsequently, the temperature was increased to 280°C over 60 minutes, and the pressure of the reaction system was slowly reduced to 13.3 Pa (0.1 Torr), thereby carrying out a polycondensation reaction at 280°C and 13.3 Pa. After releasing the pressure, the slightly pressurized resin is sprayed in a stream into cold water for rapid cooling. After remaining in the cold water for 20 seconds, it is then cut to obtain cylindrical particles approximately 3 mm in length and 2 mm in diameter.

The polyester granules obtained by melt polymerization were subjected to depressurization drying (below 13.3 Pa, 80°C, 12 hours) followed by crystallization treatment (below 13.3 Pa, 130°C, 3 hours, then below 13.3 Pa, 160°C, 3 hours). While maintaining the system at below 13.3 Pa and 215°C, the cooled polyester granules were subjected to solid-state polymerization in a solid-state polymerization reactor to obtain polyester granules (P-1) with an intrinsic viscosity of 0.62 dl/g.

[Preparation of Polyester P-2 Granules] [Preparation of Aluminum Compound] A 20 g/L aqueous solution of basic aluminum acetate (hydroxyaluminate diacetate; manufactured by Aldrich) and an equal volume (by volume) of ethylene glycol were placed in a flask. The mixture was stirred at room temperature for 6 hours, then stirred under reduced pressure (133 Pa) at 90°C to 110°C for several hours while water was removed by autodistillation. This yielded a 20 g/L ethylene glycol solution of the aluminum compound. The aforementioned basic aluminum acetate was prepared by heating at 80°C for 2 hours with stirring, and the peak position of the 27Al-NMR spectrum showed a chemical shift towards the lower magnetic field side.

[Preparation of Phosphorus Compound] Irganox 1222 (manufactured by Ciba Specialty Chemicals) and ethylene glycol were placed together in a flask. The solution was heated at 160°C for 25 hours under nitrogen purging with stirring to prepare a 50 g/L ethylene glycol solution of the phosphorus compound. 31P-NMR spectroscopy confirmed that approximately 60 mol% was converted to hydroxyl groups.

[Preparation of a mixture of aluminum compound and phosphorus compound solutions in ethylene glycol] The ethylene glycol solutions obtained from the preparation of the aluminum compound and the phosphorus compound described above were placed in a flask. Aluminum and phosphorus atoms were mixed at room temperature in a molar ratio of 1:2, and stirred for one day to prepare a catalyst solution. Chemical shifts were confirmed in both the 27Al-NMR and 31P-NMR spectra of this mixed solution under different conditions.

[Manufacturing of P-2 Particles] Using a mixture of ethylene glycol solutions of the aforementioned aluminum compound and phosphorus compound as a condensation catalyst, the acid components in the polyester were added at 0.014 mol% aluminum atoms and 0.028 mol% phosphorus atoms, respectively. Otherwise, the same procedures as for manufacturing polyester particles P-1 were performed. Polyester particles (P-2) with an intrinsic viscosity of 0.65 dl/g were obtained.

[Polymerization of urethane resin A-1 with a polycarbonate structure] 32 parts by mass of 1,3-cyclohexyl diisocyanate, 7 parts by mass of dihydroxymethylpropionic acid, 58 parts by mass of polyhexamethylene carbonate diol with a number average molecular weight of 800, 3 parts by mass of neopentyl glycol, and 84.00 parts by mass of acetone as solvent were added to a four-necked flask equipped with a stirrer, a Deutsche condenser, a nitrogen inlet, a silicone drying tube, and a thermometer. The mixture was stirred at 75°C for 3 hours under a nitrogen atmosphere until the desired amine equivalent was achieved. Next, the reaction mixture was cooled to 40°C, and 5.17 parts by mass of triethylamine were added to obtain a polyurethane prepolymer solution. Next, 450g of water was added to a reaction vessel equipped with a homogenizer capable of high-speed stirring, and the temperature was adjusted to 25°C. While stirring and mixing for 2000 ^min⁻¹ , a polyurethane prepolymer solution was added to disperse the solution in water. Then, under reduced pressure, a portion of the acetone and water was removed, thereby preparing a water-dispersible polyurethane resin solution (A-1) with a solid content of 34%.

[Polymerization of urethane resin A-2 with a polycarbonate structure] 38 parts by mass of 4,4-dicyclohexylmethane diisocyanate, 9 parts by mass of dihydroxymethylpropionic acid, 53 parts by mass of polyhexamethylene carbonate diol with a number average molecular weight of 1000, and 84.00 parts by mass of acetone as solvent were added to a four-necked flask equipped with a stirrer, a Deutsche condenser, a nitrogen inlet, a silicone drying tube, and a thermometer. The mixture was stirred at 75°C for 3 hours under a nitrogen atmosphere until the desired amine equivalent was achieved. Next, the reaction mixture was cooled to 40°C, and 5.17 parts by mass of triethylamine were added to obtain a polyurethane prepolymer solution. Next, 450g of water was added to a reaction vessel equipped with a homogenizer capable of high-speed stirring, and the temperature was adjusted to 25°C. While stirring and mixing for 2000 ^min⁻¹ , a polyurethane prepolymer solution was added to disperse the solution in water. Then, under reduced pressure, a portion of the acetone and water was removed, thereby preparing a water-dispersible polyurethane resin solution (A-2) with a solid content of 35% by mass.

[Polymerization of urethane resin A-3 with a polycarbonate structure] In a four-necked flask equipped with a stirrer, a Deutsche condenser, a nitrogen inlet, a silicone drying tube, and a thermometer, 30 parts by mass of 4,4-dicyclohexylmethane diisocyanate, 16 parts by mass of polyethylene glycol monomethyl ether with a number average molecular weight of 700, 50 parts by mass of polyhexamethylene carbonate glycol with a number average molecular weight of 1200, 4 parts by mass of neopentyl glycol, and 84.00 parts by mass of acetone as a solvent were added. The mixture was stirred at 75°C for 3 hours under a nitrogen atmosphere until the desired amine equivalent was achieved. Next, the reaction solution was cooled to 40°C to obtain a polyurethane prepolymer solution. Next, 450g of water was added to a reaction vessel equipped with a homogenizer capable of high-speed stirring, and the temperature was adjusted to 25°C. While stirring and mixing for 2000 ^min⁻¹ , a polyurethane prepolymer solution was added to disperse the solution in water. Then, under reduced pressure, a portion of the acetone and water was removed, thereby preparing a water-dispersible polyurethane resin solution (A-3) with a solid content of 35% by mass.

[Polymerization of urethane resin A-4 with a polycarbonate structure] 24 parts by mass of 4,4-dicyclohexylmethane diisocyanate, 4 parts by mass of dihydroxymethylbutyric acid, 71 parts by mass of polyhexamethylene carbonate glycol with a number average molecular weight of 2000, 1 part by mass of neopentyl glycol, and 84.00 parts by mass of acetone as solvent were added to a four-necked flask equipped with a stirrer, a Deutsche condenser, a nitrogen inlet, a silicone drying tube, and a thermometer. The mixture was stirred at 75°C for 3 hours under a nitrogen atmosphere until the reaction solution reached the predetermined amine equivalent. Next, the reaction solution was cooled to 40°C, and 8.77 parts by mass of triethylamine were added to obtain a polyurethane prepolymer solution. Next, 450g of water was added to a reaction vessel equipped with a homogenizer capable of high-speed stirring, and the temperature was adjusted to 25°C. While stirring and mixing for 2000 ^min⁻¹ , a polyurethane prepolymer solution was added to disperse the solution in water. Then, under reduced pressure, a portion of the acetone and water was removed, thereby preparing a water-dispersible polyurethane resin solution (A-4) with a solid content of 34% by mass.

[Polymerization of Ammonium Carbamate Resin A-5 without Polycarbonate Polyol Components] Using a polyether polyol, an organic polyisocyanate, and diethylene glycol as a chain extender, a multi-stage isocyanate addition method was employed, reacting at a temperature of 70°C to 120°C for 2 hours. The obtained ammonium carbamate prepolymer was mixed with an aqueous solution of hydrogen sulfite, and the mixture was stirred thoroughly for approximately 1 hour to achieve end-capping. The reaction temperature was set below 60°C. Then, the mixture was diluted with water to prepare a 20% by weight thermally reactive, water-dispersible ammonium carbamate resin solution (A-5).

[Polymerization of urethane resin A-6 with a polycarbonate structure] In a four-necked flask equipped with a stirrer, a Deutsche condenser, a nitrogen inlet, a silicone drying tube, and a thermometer, 54 parts by mass of 4,4-dicyclohexylmethane diisocyanate, 16 parts by mass of polyethylene glycol monomethyl ether with a number average molecular weight of 700, 18 parts by mass of polyhexamethylene carbonate glycol with a number average molecular weight of 1200, 12 parts by mass of neopentyl glycol, and 84.00 parts by mass of acetone as a solvent were added. The mixture was stirred at 75°C for 3 hours under a nitrogen atmosphere until the desired amine equivalent was achieved. Next, the reaction solution was cooled to 40°C, and 8.77 parts by mass of triethylamine were added to obtain a polyurethane prepolymer solution. Next, 450g of water was added to a reaction vessel equipped with a homogenizer capable of high-speed stirring, and the temperature was adjusted to 25°C. While stirring and mixing for 2000 ^min⁻¹ , a polyurethane prepolymer solution was added to disperse the solution in water. Then, under reduced pressure, a portion of the acetone and water was removed, thereby preparing a water-dispersible polyurethane resin solution (A-6) with a solid content of 34% by mass.

The following two items are shown in Table 2. A. Mass ratio of polycarbonate polyol to polyisocyanate components during the synthesis and polymerization of the urethane resin to form the coating (polycarbonate polyol component / polyisocyanate component) B. Molecular weight of the polycarbonate polyol component

[Table 2] A. Mass ratio (polycarbonate polyol content / polyisocyanate content) B. Molecular weight of polycarbonate polyol components A-1 1.8 800 A-2 1.4 1000 A-3 1.7 1200 A-4 3 2000 A-5 0 - A-6 0.3 1200

[Polymerization of End-Capped Isocyanate Crosslinker B-1] In a flask equipped with a stirrer, thermometer, and reflux condenser, 66.04 parts by weight of a polyisocyanate compound (Asahi Kasei Chemicals, Durnate TPA) with an isocyanurate structure, using hexamethylene diisocyanate as a raw material, and 17.50 parts by weight of N-methylpyrrolidone were added dropwise at 70°C for 1 hour under a nitrogen atmosphere. Then, 5.27 parts by weight of dihydroxymethylpropionic acid were added dropwise. The infrared spectrum of the reaction solution was measured. After confirming the disappearance of absorption by the isocyanate groups, 5.59 parts by mass of N,N-dimethylethanolamine and 132.5 parts by mass of water were added to obtain a 40% by mass aqueous dispersion of the capped polyisocyanate (B-1). The functional group number of this capped isocyanate crosslinker is 4.

[Polymerization of Terminal-Capped Isocyanate Crosslinker B-2] A flask equipped with a stirrer, thermometer, and reflux condenser was filled with 100 parts by weight of a polyisocyanate compound (Asahi Kasei Chemicals, Durnate TPA) with an isocyanurate structure, using hexamethylene diisocyanate as a raw material; 55 parts by weight of propylene glycol monomethyl ether acetate; and 30 parts by weight of polyethylene glycol monomethyl ether (average molecular weight 750). The mixture was kept at 70°C for 4 hours under a nitrogen atmosphere. Then, the temperature of the reaction solution was lowered to 50°C, and 47 parts by weight of methyl ethyl ketone oxime were added dropwise. The infrared spectrum of the reaction solution was measured, and the absorption of the isocyanate groups disappeared, yielding an oxime-terminated isocyanate crosslinker (B-2) with a solid content of 40% by weight. The terminal isocyanate crosslinker has a functional group of 3.

[Polymerization of carbodiimide B-3] 168 parts by mass of hexamethylene diisocyanate and 220 parts by mass of polyethylene glycol monomethyl ether (M400, average molecular weight 400) were placed in a flask equipped with a stirrer, thermometer, and reflux condenser. The mixture was stirred at 120°C for 1 hour. Then, 26 parts by mass of 4,4'-dicyclohexylmethane diisocyanate and 3.8 parts by mass of 3-methyl-1-phenyl-2-phosphacyclopentene-1-oxide (2 by mass relative to all isocyanates) were added as a catalyst for carbodiimide polymerization. The mixture was stirred at 185°C for 5 hours under nitrogen. The infrared spectrum of the reaction solution was measured, confirming the disappearance of absorption in the wavelength range of 220 ^cm⁻¹ to 2300 ^cm⁻¹ . After cooling to 60°C, 567 parts by mass of ion-exchanged water were added to obtain a carbodiimide aqueous resin solution (B-3) with a solid content of 40% by mass.

[Polyester Resin Polymerization C-1] A stainless steel high-pressure reactor equipped with a mixer, thermometer, and partial reflux condenser was charged with 194.2 parts by weight of dimethyl terephthalate, 184.5 parts by weight of dimethyl isophthalate, 14.8 parts by weight of sodium sodium 5-sulfoisophthalate, 233.5 parts by weight of diethylene glycol, 136.6 parts by weight of ethylene glycol, and 0.2 parts by weight of tetrabutyl titanate. An ester exchange reaction was carried out at a temperature ranging from 160°C to 220°C for 4 hours. The temperature was then raised to 255°C, and the reaction system was slowly depressurized. The reaction was then carried out at a reduced pressure of 30 Pa for 1 hour and 30 minutes to obtain a copolymerized polyester resin (C-1). The obtained copolymerized polyester resin (C-1) was pale yellow and transparent. The reducing viscosity of the copolymerized polyester resin (C-1) was measured to be 0.70 dl/g. The glass transition temperature measured by DSC was 40℃.

[Preparation of Polyester Aqueous Dispersion] 15 parts by weight of polyester resin (C-1) and 15 parts by weight of ethylene glycol n-butyl ether were added to a reactor equipped with a mixer, thermometer, and reflux device. The mixture was heated at 110°C and stirred to dissolve the resin. After the resin was completely dissolved, 70 parts by weight of water were slowly added to the polyester solution while stirring. After adding water, the liquid was cooled to room temperature while stirring, thus preparing a milky white polyester aqueous dispersion (Cw-1) with a solid content of 15% by weight.

[Example 1] (1) Preparation of the coating solution The following coating agent is mixed with a mixed solvent of water and isopropanol to prepare a coating solution with a solids content of 25/26/49 for the components of carbamate resin solution (A-1)/crosslinker (B-1)/polyester aqueous dispersion (Cw-1). Carbamate resin solution (A-1) 3.55 parts by weight Crosslinker (B-1) 3.16 parts by weight Polyester aqueous dispersion (Cw-1) 16.05 parts by weight Particles 0.47 parts by weight (Dry-processed silica with an average particle size of 200 nm and a solids concentration of 3.5%) Particles 1.85 parts by weight (Silica sol with an average particle size of 40 nm to 50 nm and a solids concentration of 30% by weight) Surfactant 0.30 parts by weight (Polysiloxane-based, solids concentration of 10% by weight)

(2) Manufacturing of Easy-to-Adhere Polyester Film Polyester granules (P-1), used as the film raw material polymer, were dried at 135°C for 6 hours under reduced pressure of 133 Pa. Then, they were fed to an extruder and melt-extruded into a sheet at approximately 280°C. The sheet was then rapidly cooled and solidified on rotating cooling metal rollers with the surface temperature maintained at 20°C to obtain an unstretched PET sheet.

The unstretched PET sheet is heated to 100°C using a heated roller assembly and an infrared heater, and then stretched 3.5 times along the length direction using a roller assembly with a circumferential speed difference to obtain a uniaxially stretched PET film.

Next, the aforementioned coating solution, which had been left to stand at room temperature for at least 5 hours, was applied to one side of the PET film using a roller coating method, and then dried at 80°C for 20 seconds. Furthermore, the final (after biaxial stretching) dried coating amount was adjusted to 0.15 g/ ^m² (dried coating thickness 150 nm). The film was then stretched 4.0 times its original width at 120°C using a tenter frame, and heated at 230°C for 5 seconds while maintaining a fixed length in the width direction. Following this, a 3% relaxation treatment in the width direction was performed at 100°C for 10 seconds to obtain a 100 μm easily bondable polyester film.

(3) Manufacturing of optical laminated polyester film

[Optical laminated polyester film with hard coating (1)] Using a #5 wire bar, a hard coating forming solution of the following composition was applied to the coating layer of an easily bondable polyester film, and dried at 80°C for 1 minute to remove the solvent. Then, the film with the hard coating was irradiated with 300 mJ/ ^cm² ultraviolet light using a high-pressure mercury lamp to obtain an optical laminated polyester film (1) with a hard coating. [Coating Solution for Hard Coating Formation] • Neopentyl terephthalate triacrylate PETA 39.10% by weight (Manufactured by Toa Synthetic Co., Ltd., trifunctional acrylic UV-curing resin, 100% solids, refractive index 1.49) • Zirconium oxide particles 3.40% by weight (Manufactured by Nippon Catalyst, ZP-153, average particle size 11nm, 70% solids, refractive index 1.53) • Photopolymerization initiator 3.50% by weight (Omnirad 184 manufactured by IGM Resins BV) • Photopolymerization initiator 2.00% by weight (Omnirad 907 manufactured by IGM Resins BV) • Solvent 52.00% by weight (Methyl ethyl ketone (MEK)/propylene glycol monomethyl ether (PGM))

[Optical laminated polyester film with hard coating (2)] Using a #5 wire bar, a hard coating forming solution of the following composition was applied to the coating layer of the easily bondable polyester film, and dried at 80°C for 1 minute to remove the solvent. Then, the film with the hard coating was irradiated with 300 mJ/ ^cm² of ultraviolet light using a high-pressure mercury lamp to obtain an optical laminated polyester film (2) with a hard coating. [Coating Solution for Hard Coating Formation] • Neopentyl terephthalate triacrylate PETA 34.2% by weight (Manufactured by Toa Synthetic Co., Ltd., trifunctional acrylic UV-curing resin, 100% solids, refractive index 1.49) • Nano-silica 4.30% by weight (Manufactured by Nissan Chemical Co., Ltd., average particle size 80nm, MEK-AC-5140Z, 32% solids) • Photopolymerization initiator 3.50% by weight (Omnirad 184 manufactured by IGM Resins BV) • Photopolymerization initiator 2.00% by weight (Omnirad 907 manufactured by IGM Resins BV) • Solvent 56.00% by weight (Propylene glycol monomethyl ether (PGM))

[Optical laminated polyester film with a lens layer of light-curing urethane/acrylate resin] Approximately 5g of the light-curing urethane/acrylate coating solution is placed on a clean, 1mm thick SUS plate (SUS304). The coating layer of the easily bondable polyester film is overlapped with the light-curing urethane/acrylate coating solution in contact. The light-curing urethane/acrylate coating solution is pressed onto the easily bondable polyester film in an extended manner using a manual, 10cm wide, 4cm diameter weighted rubber roller. The easily adhesive polyester film side was irradiated with 300 mJ/ ^cm² ultraviolet light using a high-pressure mercury lamp to cure the photocurable urethane/acrylate resin. A film sample with a 50 μm thick photocurable urethane/acrylate layer was peeled from the SUS plate to obtain an optical laminated polyester film with a photocurable urethane/acrylate layer (in its state before shaping). [Light-curing urethane/acrylic coatings] Light-curing acrylic resin 20.00% by weight (Blemmer 650, manufactured by Shin-Nakamura Chemicals) Light-curing methacrylate resin 40.00% by weight (BPE-500, manufactured by Shin-Nakamura Chemicals) Light-curing urethane/acrylic resin 29.00% by weight (U-6HA, manufactured by Shin-Nakamura Chemicals) Light-curing acrylic resin 8.00% by weight (AMP-10G, manufactured by Shin-Nakamura Chemicals) Photopolymerization initiator 3.00% by weight (Irgacure 184, manufactured by Ciba Specialty Chemicals)

[Optical laminated polyester film with a lens layer of photocurable acrylic resin] The photocurable urethane/acrylic coating solution of the optical laminated polyester film with a photocurable urethane/acrylic layer was changed to the following photocurable acrylic coating solution, and the ultraviolet irradiation dose was changed to 100 mJ/cm ^2. Otherwise, an optical laminated polyester film with a lens layer of photocurable acrylic resin (state before shaping processing) was obtained in the same manner. [Light-curing acrylic coating liquid] Light-curing acrylic resin 77.00% by weight (A-BPE-4 manufactured by Shin-Nakamura Chemicals) Light-curing acrylic resin 22.00% by weight (AMP-10G manufactured by Shin-Nakamura Chemicals) Photopolymerization initiator 1.00% by weight (Irgacure 184 manufactured by Ciba Specialty Chemicals)

[Optical laminated polyester film with light diffusion layer] Using a #5 wire rod, a coating liquid for forming a light diffusion layer of the following composition is applied to a coating layer of an easily adhesive polyester film. The film is then dried and heat-cured at 160°C for 60 seconds to obtain an optical laminated polyester film with a light diffusion layer. [Coating for Light Diffusion Layer Formation] Acrylic polyol (50% solids): 150 parts by weight (Acrydic A-807: Dai Nippon Ink & Chemical Co., Ltd.) Isocyanate (60% solids): 30 parts by weight (Takenate D11N: Takeda Pharmaceutical Co., Ltd.) Methyl ethyl ketone: 200 parts by weight Butyl acetate: 200 parts by weight Acrylic resin particles: 40 parts by weight (MX-1000, average particle size 10.0 μm: Soken Chemical Co., Ltd.)

[Optical laminated polyester film with anti-glare layer] Using a #5 wire rod, an anti-glare layer forming coating solution of the following composition was applied to the coating layer of an easily adhesive polyester film, and dried at 70°C for 1 minute to remove the solvent. Then, the film with the anti-glare layer was irradiated with 300 mJ/ ^cm² ultraviolet light using a high-pressure mercury lamp to obtain an optical laminated polyester film with an anti-glare layer thickness of 5 μm. • Anti-glare coating solution: Toluene 34 parts by weight, neopentyl terephthalol triacrylate 50 parts by weight, silica (average particle size 1 μm) 12 parts by weight, polysiloxane (leveling agent) 1 part by weight, photopolymerization initiator 1 part by weight (Irgacure 184 manufactured by Ciba Specialty Chemicals).

[Example 2] The urethane resin was changed to (A-2), but otherwise, an easily bondable polyester film and various optical laminated polyester films were obtained in the same manner as in Example 1.

[Example 3] The urethane resin was changed to (A-3), but otherwise, easily bondable polyester films and various optical laminated polyester films were obtained in the same manner as in Example 1.

[Example 4] The crosslinking agent is changed to (B-2), otherwise, easily bondable polyester films and various optical laminated polyester films are obtained in the same manner as in Example 1.

[Example 5] The following coating agent was mixed with a mixed solvent of water and isopropanol, with the solid content ratio of urethane resin solution (A-1)/crosslinker (B-1)/polyester aqueous dispersion (Cw-1) changed to 22/10/68. Otherwise, an easily bondable polyester film and various optical laminated polyester films were obtained in the same manner as in Example 1. Carbamate resin solution (A-1) 2.71 parts by weight Crosslinker (B-1) 1.00 parts by weight Polyester aqueous dispersion (Cw-1) 19.05 parts by weight Particles 0.47 parts by weight (Dry-processed silica with an average particle size of 200 nm and a solids concentration of 3.5%) Particles 1.85 parts by weight (Silica sol with an average particle size of 40 nm to 50 nm and a solids concentration of 30% by weight) Surfactant 0.30 parts by weight (Polysiloxane-based, solids concentration of 10% by weight)

[Example 6] The urethane resin was changed to (A-2), but otherwise, an easily bondable polyester film and various optical laminated polyester films were obtained in the same manner as in Example 5.

As shown in Table 5, in Examples 1 to 6, "B-A", "b", and "c-b" respectively meet the following ranges, and the fogging, hard coating adhesion, and anti-blocking performance are sufficient to meet the requirements. (i) 0.5≦B-A(at%)≦3.0 (ii) 30≦b(seconds)≦180 (iii) 30≦c-b(seconds)≦300 In addition, "X" meets the following formula, and the adhesion performance of various optical functional layers is sufficient to meet the requirements. (iv) 2.0≦X(%)≦10.0

[Example 7] As the membrane raw material polymer, the polyester particles are changed to (P-2). Otherwise, an easily bondable polyester film and various optical laminated polyester films are obtained in the same manner as in Example 1.

As shown in Table 5, in Example 7, "B-A", "b", and "c-b" respectively satisfy the ranges of the following formulas, thus meeting the requirements for adhesion and anti-blocking properties of various optical functional layers. (i) 0.5≦B-A(at%)≦3.0 (ii) 30≦b(seconds)≦180 (iii) 30≦c-b(seconds)≦300 Furthermore, "X" satisfies the following formula, meeting the requirements for adhesion properties of various optical functional layers. (iv) 2.0≦X(%)≦10.0 Furthermore, it was confirmed that compared with Examples 1 to 6 using polyester particles P-1, the haze value was smaller, and the transparency of the film was improved.

[Example 8] To vacuum expose the easily bondable polyester film obtained in Example 1, a dewinding process was performed in a vacuum chamber. The pressure was 0.002 Pa, and the exposure time was set to 10 minutes. The temperature of the center roller was set to 40°C. Next, a transparent conductive film composed of indium tin oxide was formed on the hard coating layer of the hard coating film. The pressure before sputtering was set to 0.0007 Pa, and a DC (Direct Current) power of 2 W/ ^cm² was applied using indium oxide (manufactured by Mitsui Metals Industry, density 7.1 g/ ^cm³ ) containing 5% by mass of tin oxide as a target. Furthermore, Ar gas was flowed at a flow rate of 130 sccm and _O2 gas at a flow rate of 10 sccm, and a film was formed using DC magnetron sputtering at an atmosphere of 0.4 Pa. In this manner, a transparent conductive film consisting of an indium tin oxide layer with a thickness of 22 nm and a surface resistivity of 250 Ω was obtained. The adhesion performance of the transparent conductive layer met the requirements.

[Example 9] To expose the hard coating film (1) obtained in Example 1 under vacuum, a dewinding process was performed in a vacuum chamber. Subsequent steps were performed in the same manner as in Example 8, thereby obtaining a transparent conductive film composed of an indium tin oxide layer with a thickness of 22 nm and a surface resistivity of 250 Ω. The adhesion performance of the transparent conductive layer met the requirements.

[Experimental Example 1] The following coating agent was mixed with a mixed solvent of water and isopropanol, with the solids ratio of the urethane resin solution (A-5) to the polyester aqueous dispersion (Cw-1) changed to 29/71. Otherwise, easily bondable polyester films and various optical laminated polyester films were obtained in the same manner as in Example 1. Carbamate Resin Solution (A-5) 6.25 parts by weight Polyester Aqueous Dispersion (Cw-1) 20.00 parts by weight Elastron Catalyst 0.50 parts by weight Particles 1.02 parts by weight (Dry-processed silica with an average particle size of 200 nm and a solids concentration of 3.5%) Particles 2.15 parts by weight (Silica sol with an average particle size of 40 nm and a solids concentration of 20% by weight) Surfactant 0.30 parts by weight (Fluorine-based, solids concentration of 10% by weight)

As shown in Table 5, in Experiment 1, "X" did not reach 2.0%, therefore the adhesion of the lens layer could not be met. In addition, "b" exceeded 180 seconds, therefore the anti-adhesion performance also could not be met.

[Experimental Example 2] The urethane resin was changed to (A-4), and otherwise, easily bondable polyester films and various optical laminated polyester films were obtained in the same manner as in Example 1.

[Experimental Example 3] By changing the urethane resin to (A-4) and the crosslinking agent to (B-2), otherwise, easy-to-adhere polyester films and various optical laminated polyester films were obtained in the same manner as in Example 1.

As shown in Table 5, in Experimental Examples 2 and 3, "B-A" did not reach 0.5at%, therefore the hard coating adhesion sometimes cannot fully meet the requirements.

[Experimental Example 4] The following coating agent was mixed with a mixed solvent of water and isopropanol, with the solids ratio of urethane resin solution (A-4)/crosslinker (B-1) changed to 70/30. Otherwise, an easily bondable polyester film and an optically laminated polyester film were obtained in the same manner as in Example 1. Carbamate resin solution (A-4) 9.03 parts by weight Crosslinking agent (B-1) 3.38 parts by weight Particles 0.52 parts by weight (Dry-processed silica with an average particle size of 200 nm and a solids concentration of 3.5%) Particles 1.80 parts by weight (Silica sol with an average particle size of 40 nm and a solids concentration of 30% by weight) Surfactant 0.30 parts by weight (Polysiloxane-based, solids concentration of 10% by weight)

As shown in Table 5, in Experiment 4, "c-b" exceeded 300 seconds, so the fog level could not meet the requirements.

[Experimental Example 5] The following coating agent was mixed with a mixed solvent of water and isopropanol, with the solids ratio of urethane resin solution (A-4)/crosslinker (B-1) changed to 20/80. Otherwise, easily bondable polyester films and various optical laminated polyester films were obtained in the same manner as in Example 1. Carbamate resin solution (A-4) 2.58 parts by weight Crosslinking agent (B-1) 9.00 parts by weight Particles 0.52 parts by weight (Dry-processed silica with an average particle size of 200 nm and a solids concentration of 3.5%) Particles 1.80 parts by weight (Silica sol with an average particle size of 40 nm and a solids concentration of 30% by weight) Surfactant 0.30 parts by weight (Polysiloxane-based, solids concentration of 10% by weight)

As shown in Table 5, in Experiment 5, "c-b" exceeded 300 seconds, so the fog level could not meet the requirements.

[Experimental Example 6] By changing the urethane resin to (A-2) and the crosslinking agent to (B-3), otherwise, easy-to-adhere polyester films and various optical laminated polyester films were obtained in the same manner as in Example 5.

As shown in Table 5, in Experimental Example 6, "B-A" did not reach 0.5 at%, therefore the anti-adhesion and hard coating adhesion sometimes could not fully meet the requirements.

[Experimental Example 7] The urethane resin was changed to (A-6), and otherwise, an easily bondable polyester film and an optically laminated polyester film were obtained in the same manner as in Example 5.

As shown in Table 5, in Experiment 7, "X" did not reach 2.0%, therefore the adhesion of the lens layer sometimes could not fully meet the requirements.

The evaluation methods used in this invention will be explained below.

(1) Fog The fog level of the easily bondable polyester film was measured using a turbidity meter (Nippon Denshoku Manufacturing Co., Ltd., NDH5000) according to JIS K 7136:2000.

(2) Anti-adhesion Two film samples were overlapped with their coated surfaces facing each other. A load of 98 kPa was applied, and the two film samples were kept in close contact at 50°C for 24 hours. Then, the films were peeled off, and their peeling status was determined according to the following criteria: ○: No coating transfer; easily peelable. △: Coating maintained, but some surface layer of the coating has partially transferred to the opposite surface. ×: The two films are adhered and cannot be peeled off, or although peelable, the film substrate cracks.

(3) Adhesion Using a cutter guide with 2mm spacing, 100 square cuts were made on the optical functional layer of the obtained optical laminated polyester film, penetrating the optical functional layer to the substrate film. Then, celluloid adhesive tape (manufactured by Nichiban Corporation, No. 405; width 24mm) was attached to the square cut surfaces, and the tape was rubbed with an eraser to ensure complete adhesion. Then, the celluloid adhesive tape is vertically peeled off the optical functional layer of the optical laminated polyester film. This process is repeated five times. The number of squares where the optical functional layer has peeled off is visually counted, and the adhesion between the optical functional layer and the film substrate is calculated using the following formula. Furthermore, partially peeled squares are also counted as peeled squares. Adhesion is considered acceptable at 95%. Adhesion (%) = (1 - Number of peeled squares / 100) × 100

(4) Depth-Oriented Elemental Distribution Measurement: The depth-oriented elemental distribution of the coating layer was measured using X-ray photoelectron spectroscopy (ESCA). An Ar cluster, which is low-damage to organic materials, was used as the ion source for etching. The sample was rotated during etching to ensure uniform etching. To minimize damage from X-ray irradiation, spectral collection at each etching time was performed in a snapshot mode for short-term evaluation. Furthermore, for ease of evaluation, spectral collection was performed every 30 seconds until the etching time reached 120 seconds, and then every 60 seconds thereafter. Details of the measurement conditions are shown below. Furthermore, the Shirley method was used to remove the background during analysis. • Apparatus: K-Alpha ⁺ (manufactured by Thermo Fisher Scientific) • Measurement Conditions: Excitation X-rays: Monochromatic Al Kα rays; X-ray output: 12kV, 2.5mA; Photoelectron extraction angle: 90°; Spot size: 200μmφ; Through energy: 150 eV (Snapshot mode); Ion gun accelerating voltage: 6kV; Cluster size: Large; Etching rate: 10nm/min (converted from polystyrene) ^※ Sample rotation during etching: Yes (The etching rate was calculated using a 155nm thick sample prepared by spin coating of monodisperse polystyrene with a molecular weight Mn: 91000 (Mw/Mn = 1.05) dissolved in toluene on a silicon wafer).

Based on the data from this evaluation, a nitrogen distribution curve was plotted with the etching time from the coating surface as the horizontal axis and the ratio of the amount of nitrogen atoms to the total amount of carbon, oxygen, nitrogen, and silicon atoms (nitrogen atom ratio) as the vertical axis. The nitrogen distribution curves of the easily adhesive polyester film samples (Example 2, Example 5, and Experimental Example 6) are shown in Figures 1, 3, and 4, respectively. Based on the nitrogen distribution curve of Example 2 shown in Figure 1, Figure 2 is used to illustrate the method for calculating the characteristic values of the present invention. As shown in Figure 2, the nitrogen atom ratio on the coating surface opposite to the polyester film substrate is set as A (at%), the maximum nitrogen atom ratio is set as B (at%), the etching time when the nitrogen atom ratio reaches the maximum value B (at%) is set as b (seconds), and the etching time when the nitrogen atom ratio becomes 1/2 B (at%) after b (seconds) is set as c (seconds). The values are then read, and B - A (at%) and c - b (seconds) are calculated. The nitrogen atom ratio on the coating surface opposite to the polyester film substrate refers to the nitrogen atom ratio at etching time 0 (seconds) in the figure. (Furthermore, in Figures 1 to 4, the "s" in "etching time s" on the horizontal axis refers to the unit "second".)

(5) Determination of the OCOO bond ratio in the surface region: The OCOO bond ratio (X) in the surface region was evaluated by X-ray photoelectron spectroscopy (ESCA). The apparatus used was K-Alpha ⁺ (manufactured by Thermo Fisher Scientific). Details of the measurement conditions are shown below. Furthermore, the Shirley method was used to remove the background during analysis. In addition, X was calculated as the average of the measurement results from at least three locations. • Measurement conditions: Excitation X-ray: Monochromatic Al Kα radiation; X-ray output: 12kV, 6mA; Photoelectron extraction angle: 90°; Spot size: 400μmφ; Passing energy: 50eV; Step size: 0.1eV; Energy decomposition energy: FWHM of Ag3d(5/2) spectrum = 0.75eV. Figures 5 and 6 are curves showing the resolution results of the C1s spectrum of the surface region of the easily bondable polyester film of Example 6 and Experimental Example 1, respectively. The gray solid line represents the measured data of the C1s spectrum. The peaks of the obtained measured spectrum were separated into multiple peaks, and the corresponding bonds were identified according to the position and shape of each peak. Furthermore, curve fitting is performed using the peaks derived from each key type to calculate the peak area. The key types of each possible peak (1) to peak (6) are shown in Table 3.

[Table 3] Keys (1) Black two-dot chain CC key (2) Black dotted line CO key, CN key (3) Black three-point chain C=O key (4) Black single-dot chain COO key (5) Black dots and lines OCOO key (6) Black solid line π-π* key

The total peak area of the C1s spectral region derived from each key type refers to the total peak area of peaks (1) to (6), and the peak area derived from the OCOO key refers to the peak area of peak (5). When the total peak area of the C1s spectral region derived from each key type is set to 100%, X (%) is the percentage (%) of the area of peak (5).

The peak areas of peaks (1) to (6) in Example 6 and Experiment 1 are calculated and shown in Table 4. As mentioned above, the percentage data of peak (5) is X (%). Peaks (3) and (6) in Example 6, and peaks (3) and (5) in Experiment 1 did not appear.

[Table 4] Implementation Example 6 Experimental Example 1 (1) 63.5% 64.4% (2) 23.1% 20.9% (3) - - (4) 7.5% 12.7% (5) 5.9% - (6) - 2.0%

(6) Method for Determining the Number Average Molecular Weight of Polycarbonate Polyols When measuring urethane resins with a polycarbonate structure using proton nuclear magnetic resonance spectroscopy (1H-NMR), a peak originating from methylene groups adjacent to the OCOO bond was observed near 4.1 ppm. Additionally, a peak originating from methylene groups adjacent to the urethane bond generated by the reaction between the polyisocyanate and the polycarbonate polyol was observed at a magnetic field approximately 0.2 ppm higher. The number average molecular weight of the polycarbonate polyol was calculated based on the integral values of these two peaks and the molecular weight of the monomers constituting the polycarbonate polyol.

Table 5 summarizes the evaluation results of each implementation example and experimental example.

[Table 5] [Industry Availability]

The easily bondable polyester film of this invention has excellent adhesion to hard coatings, light diffusion layers, lens layers, anti-glare layers, and transparent conductive layers, making it particularly suitable for optical applications. It is suitable as a substrate film for optical functional films such as hard coatings for displays and lens sheets using this film.

[Figure 1] is the nitrogen element distribution curve determined by X-ray photoelectron spectroscopy (XPS) of the easy-to-bond polyester film of Example 2, based on the depth-direction elemental distribution. [Figure 2] is an explanatory diagram used to determine B-A, b, and c-b based on the nitrogen element distribution curve determined by XPS. [Figure 3] is the nitrogen element distribution curve determined by XPS of the easy-to-bond polyester film of Example 5, based on the depth-direction elemental distribution. [Figure 4] is the nitrogen element distribution curve determined by XPS of the easy-to-bond polyester film of Example 6, based on the depth-direction elemental distribution. [Figure 5] is a graph showing the analytical results of the C1s spectrum of the surface region of the coating layer of the easy-to-adhere polyester film of Example 6. [Figure 6] is a graph showing the analytical results of the C1s spectrum of the surface region of the coating layer of the easy-to-adhere polyester film of Example 1.

without.

Claims (2)

An optically laminated polyester film comprises an easily adhesive polyester film having a coating layer on at least one side of a polyester film substrate. The laminate includes at least one optical functional layer selected from a hard coating layer, a light diffusing layer, a lens layer, an anti-glare layer, and a transparent conductive layer. The coating layer is formed by curing a composition containing a polycarbonate-structured urethane resin, a crosslinking agent, and a polyester resin. The polyester resin further contains sulfonyl (-SO₃ ₎ groups. The aromatic dicarboxylic acid H), based on the nitrogen element distribution curve determined by X-ray photoelectron spectroscopy of the coating layer in the depth direction, when the nitrogen atom ratio on the coating surface opposite to the polyester film substrate is set to A (at%), the maximum nitrogen atom ratio is set to B (at%), the etching time for the maximum nitrogen atom ratio B (at%) is set to b (seconds), and the etching time when the nitrogen atom ratio becomes 1/2 B (at%) after b (seconds) is set to c (seconds), satisfies the following conditions. Equations (i) to (iii) below, and in the surface analysis spectra measured by X-ray photoelectron spectroscopy, when the sum of the peak areas originating from each bond in the C1s spectral region is set to 100 (%) and the peak area originating from the OCOO bond is set to X (%), satisfy the following equation (iv): (i) 0.5≦B－A(at%)≦3.0 (ii) 30≦b(seconds)≦180 (iii) 30≦c－b(seconds)≦300 (iv) 2.0≦X(%)≦10.0. The optical laminated polyester film described in claim 1, wherein the haze of the aforementioned easily bondable polyester film is 1.5% or less.