Optical laminated polyester film

Abstract

 The present invention addresses the problem of providing a laminated polyester film for optical use, which is highly transparent, has an antiblocking property, and exhibits excellent adhesion to hard coat layers, light diffusing layers, lens layers, antiglare layers, and transparent conductive layers. The laminated polyester film for optical use according to the present invention includes a readily adhesive polyester film having a coated layer disposed at least on one surface of a polyester film base material, and at least one optical function layer that is laminated on said coated layer and that is selected from among hard coat layers, light diffusing layers, lens layers, antiglare layers, and transparent conductive layers. The coated layer has a specific compositional makeup.

Description

[Technical Field]

[0001] The present invention relates to an optical laminated polyester film with excellent adhesion and transparency. More specifically, it relates to an optical laminated polyester film in which an optically functional film such as a hard coat film, a light diffusion sheet, a lens sheet, a transparent conductive film, or an anti-glare film is laminated on a coating layer of an easily adhesive polyester film. [Background technology]

[0002] Generally, transparent thermoplastic resin films made of polyethylene terephthalate (PET), acrylic, polycarbonate (PC), triacetylcellulose (TAC), polyolefin, etc. are used as substrates for optical functional films used as components for various displays such as liquid crystal displays.

[0003] When the aforementioned thermoplastic resin film is used as a substrate for various optical functional films, functional layers are laminated according to the application. For example, in liquid crystal displays, functional layers include a protective film (hard coat layer) to prevent surface scratches, a prism layer used for light focusing and diffusion, and a light diffusion layer to improve brightness. Among such substrates, polyester film is particularly widely used as a substrate for various optical functional films because it has excellent transparency, dimensional stability, and chemical resistance, and is relatively inexpensive.

[0004] Generally, biaxially oriented polyester film surfaces have a disadvantage in that they have poor adhesion to various paints and adhesives due to their highly crystalline orientation. For this reason, various methods have been proposed to impart easy adhesion to the surface of biaxially oriented polyester film.

[0005] Conventionally, a technique has been known to provide easy adhesion for hard coating, prism lens processing, etc., by using copolymerized polyester resin and urethane resin as a coating layer (see, for example, Patent Document 1). However, this conventional technique had the problem that the blocking resistance of the easily adhesive polyester film was not good.

[0006] Furthermore, a technique was known in which urethane resin and blocked isocyanate were used in the coating layer to provide easy adhesion to hard coat processing, particularly used in the manufacture of front sheets for solar cells (see, for example, Patent Document 2). However, this conventional technique had the problem of low transparency of the easily adhesive polyester film. Also, a technique was known in which urethane resin and blocked isocyanate were used in the coating layer to improve adhesion to the lens layer (see, for example, Patent Document 3). However, this conventional technique had the problem of insufficient adhesion to the lens layer. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2000-229355 [Patent Document 2] Japanese Patent Publication No. 2016-015491 [Patent Document 3] Japanese Patent Publication No. 2014-221560 [Overview of the Initiative] [Problems that the invention aims to solve]

[0008] This invention was made against the backdrop of the problems of the prior art. Specifically, the object of this invention is to provide an optical laminated polyester film using an easily adhesive polyester film that has high transparency, blocking resistance, and good adhesion to various optical resin compositions. [Means for solving the problem]

[0009] In order to solve the above problems, the inventors, in the process of investigating the causes of the above problems, discovered that the problems of the present invention can be solved when a coating layer containing a crosslinking agent, a urethane resin having a polycarbonate structure, and a polyester resin is provided on at least one side of a polyester film substrate, and when 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 satisfy specific conditions, the inventors have completed the present invention.

[0010] The aforementioned problems can be solved by the following means. 1. An optical laminated polyester film having an easy-to-adhere polyester film having a coating layer on at least one surface of a polyester film substrate, wherein at least one optical functional layer selected from a hard coat layer, a light diffusion layer, a lens layer, an anti-glare layer, and a transparent conductive layer is laminated on the coating layer, wherein the coating layer is made of a composition containing a urethane resin having a polycarbonate structure, a crosslinking agent, and a polyester resin, which is cured, and in the nitrogen element distribution curve based on the elemental distribution measurement in the depth direction by X-ray photoelectron spectroscopy of the coating layer, when the nitrogen atom ratio on the surface of the coating layer opposite to the polyester film substrate is A (at%), the maximum value of the nitrogen atom ratio is B (at%), the etching time at which the nitrogen atom ratio shows the maximum value B (at%) is b (seconds), and the etching time at which the nitrogen atom ratio becomes 1 / 2B (at%) after b (seconds) is c (seconds), the following equations (i) to (iii) are satisfied, and measured by X-ray photoelectron spectroscopy In a defined surface analysis spectrum, when the sum of peak areas originating from each bond type in the C1s spectral region is set to 100%, and the peak area originating from the OCOO bond is set to X, an optical laminated polyester film that satisfies the following equation (iv). (i) 0.5 ≤ BA(at%) ≤ 3.0 (ii) 30 ≦ b(seconds) ≦ 180 (iii) 30 ≦ cb(sec) ≦ 300 (iv) 2.0 ≤ X(%) ≤ 10.0 2. The optical laminated polyester film according to the first aspect, wherein the haze of the easily adherable polyester film is 1.5 (%) or less.

Advantages of the Invention

[0011] The easily adherable polyester film in the present invention has high transparency, blocking resistance, and good adhesion to various optical resin compositions. Therefore, the optical laminated oil ester film of the present invention using the easily adherable polyester film is excellent in adhesion between the coating layer and various functional layers, and is suitable as an optical member such as a display.

Brief Description of the Drawings

[0012] [Figure 1] It is a distribution curve of nitrogen element based on the measurement of the elemental distribution in the depth direction by X-ray photoelectron spectroscopy for the easily adherable polyester film of Example 2. [Figure 2] It is an explanatory diagram for obtaining B-A, b, and c-b from the distribution curve of nitrogen element based on the measurement of the elemental distribution in the depth direction by X-ray photoelectron spectroscopy. [Figure 3] It is a distribution curve of nitrogen element based on the measurement of the elemental distribution in the depth direction by X-ray photoelectron spectroscopy for the easily adherable polyester film of Example 5. [Figure 4] It is a distribution curve of nitrogen element based on the measurement of the elemental distribution in the depth direction by X-ray photoelectron spectroscopy for the easily adherable polyester film of Experimental Example 6. [Figure 5] It is a graph showing the analysis result of the C1s spectrum of the coating layer surface region of the easily adherable polyester film of Example 6. [Figure 6] It is a graph showing the analysis result of the C1s spectrum of the coating layer surface region of the easily adherable polyester film of Experimental Example 1.

Embodiments for Carrying Out the Invention

[0013] (Polyester Film Substrate) In the present invention, the polyester resin constituting the polyester film substrate is polyethylene terephthalate, polybutylene terephthalate, polyethylene-2,6-naphthalate, polytrimethylene terephthalate, etc., as well as a copolymerized polyester resin in which a part of the diol component or dicarboxylic acid component of the above-mentioned polyester resin is replaced with the following copolymer components. For example, the copolymer components can include diol components such as diethylene glycol, neopentyl glycol, 1,4-cyclohexanedimethanol, and polyalkylene glycol, and dicarboxylic acid components such as adipic acid, sebatic acid, phthalic acid, isophthalic acid, 5-sodium isophthalic acid, and 2,6-naphthalenedicarboxylic acid.

[0014] The polyester resins preferably used in the present invention are mainly selected from polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate, and polyethylene-2,6-naphthalate. Among these polyester resins, polyethylene terephthalate is the most preferred in terms of the balance between physical properties and cost. Furthermore, the polyester film substrate composed of these polyester resins is preferably a biaxially oriented polyester film, which can improve chemical resistance, heat resistance, mechanical strength, and other properties.

[0015] While there are no particular limitations on the catalyst used for polycondensation in the production of polyester resins, antimony trioxide is preferred because it is inexpensive and has excellent catalytic activity. Germanium compounds or titanium compounds are also preferred. More preferred polycondensation 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. Particularly preferred is the use of a catalyst containing aluminum and / or its compounds and phosphorus compounds, which can improve the transparency of the film.

[0016] Furthermore, the polyester film substrate in the present invention may be a single-layer polyester film, a two-layer structure with different components, or a polyester film substrate consisting of at least three layers, including an outer layer and an inner layer.

[0017] (Explanation of characteristic values ​​in the present invention) In the present invention, the easily adhering polyester film preferably has a coating layer on at least one surface of the polyester film substrate as described above. The coating layer is formed by curing a composition containing a urethane resin having a polycarbonate structure, a crosslinking agent, and a polyester resin. The expression "formed by curing a composition" is used here because it is extremely difficult to accurately describe the chemical composition of the urethane resin having a polycarbonate structure, the crosslinking agent, and the polyester resin in the state after they have formed a crosslinked structure with the crosslinking agent and been cured. Furthermore, it is preferable that the maximum value of the nitrogen element distribution curve based on elemental distribution measurement in the depth direction of the coating layer is located near the surface of the coating layer opposite to the polyester film substrate, as this improves transparency, blocking resistance, and adhesion to hard coat layers, anti-glare layers, transparent conductive layers, etc. In addition, it is preferable that an appropriate amount of polycarbonate structure is present on the surface of the coating layer opposite to the polyester film substrate, as this improves adhesion to lens layers, light diffusion layers, etc.

[0018] The characteristics of the coating layer in the above-mentioned easily adhering polyester film are described below. First, the nitrogen element distribution curve based on the elemental distribution measurement in the depth direction of the coating layer is plotted using X-ray photoelectron spectroscopy (ESCA). Specifically, spectrum collection is performed every 30 seconds until the etching time reaches 120 seconds, and every 60 seconds thereafter. As shown in Figure 2, the etching time from the surface of the coating layer (in seconds) is plotted on the horizontal axis, and the ratio of the amount of nitrogen atoms to the total amount of carbon atoms, oxygen atoms, nitrogen atoms, and silicon atoms (nitrogen atom ratio, in at%) is plotted on the vertical axis. The nitrogen atom ratio on the surface of the coating layer opposite the polyester film substrate is A (at%), the maximum value of the nitrogen atom ratio is B (at%), the etching time at which the nitrogen atom ratio reaches the maximum value B (at%) is b (seconds), and the etching time at which the nitrogen atom ratio becomes 1 / 2B (at%) after b (seconds) is c (seconds). BA (at%) and cb (seconds) are calculated from the data read. The nitrogen atom ratio A (at%) on the surface of the coating layer opposite the polyester film substrate is the nitrogen atom ratio at etching time 0 (seconds).

[0019] Furthermore, when the following relationship is observed between the characteristic values ​​read from the nitrogen element distribution curve based on the elemental distribution measurement in the depth direction of the above-mentioned coated layer, an easily adhering polyester film with excellent transparency, blocking resistance, and adhesion to the hard coat layer, light diffusion layer, lens layer, anti-glare layer, and transparent conductive layer can be obtained. (i) 0.5 ≤ BA(at%) ≤ 3.0 (ii) 30 ≦ b(seconds) ≦ 180 (iii) 30 ≦ cb(sec) ≦ 300

[0020] The lower limit of BA is preferably 0.5 at%, more preferably 0.6 at%, even more preferably 0.7 at%, particularly preferably 0.8 at%, and most preferably 0.9 at%. A value of 0.5 at% or higher is preferable because it satisfies the amount of tough urethane resin component, resulting in good blocking resistance. It is also preferable because it improves adhesion with the hard coat layer, anti-glare layer, and transparent conductive layer. The upper limit of BA is preferably 3.0 at%, more preferably 2.9 at%, even more preferably 2.8 at%, particularly preferably 2.7 at%, and most preferably 2.5 at%. A value of 3.0 at% or lower is preferable because it results in low haze and transparency.

[0021] The lower limit of b is preferably 30 seconds, and if it is 30 seconds or more, the toughness of the coated layer surface on the opposite side of the polyester film substrate is maintained, and blocking resistance is obtained, which is preferable. The upper limit of b is preferably 180 seconds, more preferably 120 seconds, even more preferably 90 seconds, and particularly preferably 60 seconds. If it is 180 seconds or less, the toughness of the coated layer surface on the opposite side of the polyester film substrate is maintained, and blocking resistance is good, which is preferable. Also, adhesion with the hard coat layer, anti-glare layer, and transparent conductive layer is improved, which is preferable.

[0022] The upper limit of cb is preferably 300 seconds, more preferably 240 seconds, and even more preferably 180 seconds. A value of 300 seconds or less is preferable because it prevents excess urethane resin components in the coating layer, resulting in low haze and transparency. The lower limit of cb is 30 seconds or more, because spectrum acquisition is performed every 30 seconds from the start of measurement until the etching time of 120 seconds.

[0023] In the present invention, it is preferable that a large portion of the polycarbonate structural portion in the urethane resin of the coating layer constituting the easily adhesive polyester film is localized on the surface of the coating layer opposite to the polyester film substrate. This is because the presence of an appropriate amount of polycarbonate structural portion on this surface improves adhesion to the lens layer and the light diffusion layer. On the other hand, it has also been found that the presence of polycarbonate structural portion on this surface increases flexibility, and blocking resistance may not always be sufficient. Therefore, as described above, when the characteristic values ​​read from the nitrogen element distribution curve based on elemental distribution measurement in the depth direction of the coating layer have the following relationship, an excellent easily adhesive polyester film can be obtained that also possesses transparency, blocking resistance, and adhesion to the hard coat layer, anti-glare layer, and transparent conductive layer. (i) 0.5 ≤ BA(at%) ≤ 3.0 (ii) 30 ≦ b(seconds) ≦ 180 (iii) 30 ≦ cb(sec) ≦ 300

[0024] In the easily adhering polyester film of the present invention, the above formulas (i) to (iii) are satisfied. As a means to achieve this, when synthesizing and polymerizing the urethane resin having a polycarbonate structure that forms the coating layer, it is synthesized and polymerized containing 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 content of the polyester resin, urethane resin, and crosslinking agent in the coating solution is taken as 100% by mass, the solid content of the crosslinking agent is 10 to 50% by mass. Furthermore, by using a blocked isocyanate as the crosslinking agent, and by using a blocked isocyanate having three or more functional isocyanate groups, efficient adjustment of BA becomes possible.

[0025] Furthermore, as described above, it is preferable that a certain proportion of the polycarbonate structure portion in the urethane resin in the coating layer of the present invention is present on the surface of the coating layer opposite to the polyester film substrate. In the present invention, in the surface analysis spectrum measured by X-ray photoelectron spectroscopy, the total peak area derived from each bond species in the C1s spectral region is set to 100 (%), and the peak area derived from the OCOO bond (which is the polycarbonate structure) is set to X (%), and expressed as a percentage.

[0026] Here, the ratio X (%) of OCOO bonds in the surface region (which is a polycarbonate structure) is evaluated by X-ray photoelectron spectroscopy (ESCA). Figures 5 and 6 are examples of graphs showing the analysis results of the C1s spectra of the surface region of the easily adhering polyester film in 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 are separated into multiple peaks, and the bond species corresponding to each peak is identified from the position and shape of each peak. Furthermore, curve fitting is performed on the peaks derived from each bond species, and the peak area can be calculated. The coating layer in the present invention is a urethane resin having a polycarbonate structure, and a blocked isocyanate having three or more functional isocyanate groups. It contains representative crosslinking agents and polyester resins, and in the case of such a coating layer, peaks of the bonding species (1) to (6) in Table 1 may be detected. The bonding species of peaks (1) to (6) in Table 1 do not necessarily include only the bonding species shown in Table 1, but may also include small amounts of similar bonding species. Here, in Figure 5 relating to Example 6, the C=O bond peak (3) and the π-π* bond peak (6) in Table 1 are not present. Also, in Figure 6 relating to Experimental Example 1, the C= (3) in Table 1 is not present. The O bond peak and the OCOO bond peak in (5) are not visible. Ratio of OCOO bonds in the surface region. The rate X (%) is the area of ​​peak (5) when the total peak area of ​​peaks (1) to (6) is set to 100%. It can be described as an area ratio expressed as a percentage (%).

[0027] [Table 1]

[0028] The preferred range for the peak area X (%) derived from OCOO bonding is as follows: The lower limit of X is preferably 2.0%, more preferably 2.5%, even more preferably 3.0%, particularly preferably 3.5%, and most preferably 4.0%. A value of 2.0% or higher is preferable as it effectively satisfies the adhesion to the lens layer and the light diffusion layer. The upper limit of X is preferably 10.0%, more preferably 9.0%, even more preferably 8.0%, particularly preferably 7.5%, and most preferably 7%. A value of 10.0% or lower is preferable as it prevents the surface layer from becoming too flexible and makes it easier to obtain blocking resistance.

[0029] In the method for producing the easily adhering polyester film according to the present invention, when synthesizing and polymerizing the urethane resin having a polycarbonate structure to form the coating layer, it is preferable that the mass ratio of the polycarbonate polyol component to the polyisocyanate component is 0.5 or more, and that when the total solid content of the polyester resin, the urethane resin having a polycarbonate structure, and the crosslinking agent in the coating solution is 100% by mass, the urethane resin content is 5% to 50% by mass, in order to effectively achieve an X characteristic value in the range of 2.0 to 10.0% based on the C1s spectral region.

[0030] (Coated layer) In the present invention, to improve adhesion to the hard coat layer, lens layer, and light diffusion layer, it is preferable that the easily adhering polyester film has a coating layer laminated on at least one side thereof, which is formed from a composition containing a urethane resin having a polycarbonate structure, a crosslinking agent, and a polyester resin. The coating layer may be provided on both sides of the polyester film, or it may be provided on only one side of the polyester film, with a different type of resin coating layer on the other side.

[0031] The following provides a detailed explanation of the composition of each coating layer. (urethane resin) The urethane resin having a polycarbonate structure in the present invention has a urethane bonding portion derived from at least a polycarbonate polyol component and a polyisocyanate component, and further includes a chain extender as needed.

[0032] In the present invention, when synthesizing and polymerizing a urethane resin having a polycarbonate structure, the lower limit of the mass ratio of the polycarbonate polyol component to the polyisocyanate component (mass of polycarbonate polyol component / mass of polyisocyanate component) is preferably 0.5, more preferably 0.6, even more preferably 0.7, particularly preferably 0.8, and most preferably 1.0. A ratio of 0.5 or higher is preferable because it allows for efficient adjustment of the OCOO bond ratio X on the surface of the coated layer to 2% or higher. In the present invention, when synthesizing and polymerizing a urethane resin having a polycarbonate structure, the upper limit of the mass ratio of the polycarbonate polyol component to the polyisocyanate component is preferably 2.5, more preferably 2.2, even more preferably 2.0, particularly preferably 1.7, and most preferably 1.5. A ratio of 2.5 or lower is preferable because it allows for efficient adjustment of the OCOO bond ratio X on the surface of the coated layer to 10% or lower. Furthermore, in the nitrogen distribution curve based on elemental distribution measurements in the depth direction using X-ray photoelectron spectroscopy, BA can be effectively adjusted to 0.5 at% or higher, and cb can be effectively adjusted to 300 seconds or lower.

[0033] The polycarbonate polyol component used to synthesize and polymerize the urethane resin having a polycarbonate structure in the present invention preferably contains an aliphatic polycarbonate polyol that has excellent heat resistance and hydrolysis resistance. Examples of aliphatic polycarbonate polyols include aliphatic polycarbonate diols and aliphatic polycarbonate triols, but aliphatic polycarbonate diols can be preferably used. Examples of aliphatic polycarbonate diols used to synthesize and polymerize the polycarbonate structure urethane resin in the present invention include aliphatic polycarbonate diols obtained by reacting one or more 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, neopentyl glycol, diethylene glycol, and dipropylene glycol with carbonates such as dimethyl carbonate, ethylene carbonate, and phosgene.

[0034] The number-average molecular weight of the polycarbonate polyol in the present invention is preferably 500 to 1800. More preferably 600 to 1700, and most preferably 700 to 1500. A number-average molecular weight of 500 or more is preferable because it effectively adjusts the proportion X of OCOO bonds on the surface of the coated layer to 10% or less. A number-average molecular weight of 1800 or less is preferable because it effectively adjusts the nitrogen distribution curve based on elemental distribution measurement in the depth direction by X-ray photoelectron spectroscopy to BA of 0.5 or more and cb of 300 sec or less.

[0035] Examples of polyisocyanates used in the synthesis and polymerization of urethane resins having a polycarbonate structure in the present invention include aromatic aliphatic diisocyanates such as xylylene diisocyanate, alicyclic diisocyanates such as isophorone diisocyanate and 4,4-dicyclohexylmethane diisocyanate and 1,3-bis(isocyanate-methyl)cyclohexane, aliphatic diisocyanates such as hexamethylene diisocyanate and 2,2,4-trimethylhexamethylene diisocyanate, or polyisocyanates obtained by pre-adding these compounds, either individually or in combination, with trimethylolpropane or the like. When using the aforementioned aromatic aliphatic diisocyanates, alicyclic diisocyanates, or aliphatic diisocyanates, there is no problem of yellowing, which is preferable. Furthermore, the coating film does not become too hard, which is preferable as it can relieve stress due to thermal shrinkage of the polyester film substrate and provides good adhesion.

[0036] Examples of chain extenders include glycols such as ethylene glycol, diethylene glycol, 1,4-butanediol, neopentyl glycol, and 1,6-hexanediol; polyhydric alcohols such as glycerin, trimethylolpropane, and pentaerythritol; diamines such as ethylenediamine, hexamethylenediamine, and piperazine; amino alcohols such as monoethanolamine and diethanolamine; thiodiglycols such as thiodiethylene glycol; or water.

[0037] In the present invention, the coated layer is preferably provided using an aqueous coating solution by the in-line coating method described later. Therefore, it is desirable that the urethane resin of the present invention be water-soluble or water-dispersible. The above-mentioned "water-soluble or water-dispersible" means that it is dispersed in water or an aqueous solution containing less than 50% by mass of a water-soluble organic solvent.

[0038] To impart water dispersibility to urethane resin, sulfonic acid (salt) groups or carboxylic acid (salt) groups can be introduced (copolymerized) into the urethane molecular backbone. To maintain moisture resistance, it is preferable to introduce weakly acidic carboxylic acid (salt) groups. Nonionic groups such as polyoxyalkylene groups can also be introduced.

[0039] To introduce carboxylic acid (salt) groups into urethane resin, for example, a polyol compound having carboxylic acid groups, such as dimethylolpropanoic acid or dimethylolbutanoic acid, is introduced as a copolymer component and neutralized with a salt-forming agent. Specific examples of salt-forming agents include ammonia, trialkylamines such as trimethylamine, triethylamine, triisopropylamine, tri-n-propylamine, and tri-n-butylamine, N-alkylmorpholines such as N-methylmorpholine and N-ethylmorpholine, and N-dialkylalkanolamines such as N-dimethylethanolamine and N-diethylethanolamine. These can be used individually or in combination of two or more.

[0040] When a polyol compound having a carboxylic acid (salt) group is used as a copolymer component to impart water dispersibility, the molar ratio of the polyol compound having a carboxylic acid (salt) group in the urethane resin is preferably 3 to 60 mol%, and more preferably 5 to 40 mol%, when the total polyisocyanate component of the urethane resin is considered to be 100 mol%. If the molar ratio is less than 3 mol%, water dispersibility may become difficult. Furthermore, if the molar ratio exceeds 60 mol%, water resistance may decrease, which may lead to a decrease in heat and humidity resistance.

[0041] The urethane resin of the present invention may have blocked isocyanates bonded to its ends to improve its rigidity.

[0042] (Crosslinking agent) In the present invention, a blocked isocyanate is preferred as the crosslinking agent contained in the coating layer forming composition, a trifunctional or more functional blocked isocyanate is more preferred, and a tetrafunctional or more functional blocked isocyanate is particularly preferred. This improves blocking resistance and adhesion to the hard coat layer, anti-glare layer, and transparent conductive layer. When a blocked isocyanate crosslinking agent is used, it is preferable that the BA can be effectively adjusted to 0.5 at% or more in the nitrogen distribution curve based on elemental distribution measurement in the depth direction by X-ray photoelectron spectroscopy.

[0043] The lower limit of the boiling point of the blocking agent, the blocked isocyanate, is preferably 150°C, more preferably 160°C, even more preferably 180°C, particularly preferably 200°C, and most preferably 210°C. The higher the boiling point of the blocking agent, the more effectively the volatilization of the blocking agent is suppressed by the heat applied during the drying process after coating the coating solution or, in the case of the in-line coating method, during the film formation process. This suppresses the occurrence of minute surface irregularities on the coated surface and improves the transparency of the film. There is no particular upper limit to the boiling point of the blocking agent, but from the viewpoint of productivity, it is thought that the upper limit is around 300°C. Since the boiling point is related to the molecular weight, it is preferable to use a blocking agent with a large molecular weight in order to raise the boiling point of the blocking agent. The molecular weight of the blocking agent is preferably 50 or more, more preferably 60 or more, and even more preferably 80 or more.

[0044] The upper limit of the dissociation temperature of the blocking agent is preferably 200°C, more preferably 180°C, even more preferably 160°C, particularly preferably 150°C, and most preferably 120°C. The blocking agent dissociates from the functional groups due to the heat added during the drying process after application of the coating solution or, in the case of the in-line coating method, during the film formation process, generating regenerated isocyanate groups. As a result, the crosslinking reaction with urethane resin and the like proceeds, improving adhesion. If the dissociation temperature of the blocked isocyanate is below the above temperature, the dissociation of the blocking agent proceeds sufficiently, resulting in good adhesion, especially resistance to heat and humidity.

[0045] Examples of blocking agents used in the blocked isocyanates of the present invention that have a dissociation temperature of 120°C or lower and a boiling point of 150°C or higher include: bisulfite compounds: such as sodium bisulfite; pyrazole compounds: such as 3,5-dimethylpyrazole, 3-methylpyrazole, 4-bromo-3,5-dimethylpyrazole, 4-nitro-3,5-dimethylpyrazole; active methylene compounds: such as malonic acid diesters (dimethyl malonate, diethyl malonate, di-n-butyl malonate, di-2-ethylhexyl malonate), methyl ethyl ketone, etc.; and triazole compounds: such as 1,2,4-triazole. Among these, pyrazole compounds are preferred in terms of resistance to humid heat and yellowing.

[0046] The polyisocyanates, which are precursors to the blocked isocyanates of the present invention, are obtained by introducing diisocyanates. Examples include urethane-modified diisocyanates, allophanate-modified diisocyanates, urea-modified diisocyanates, biuret-modified diisocyanates, uretoidion-modified diisocyanates, uretoimine-modified diisocyanates, isocyanurate-modified diisocyanates, carbodiimide-modified diisocyanates, and the like.

[0047] Examples of diisocyanates include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4′-diphenylmethane diisocyanate, 2,4′-diphenylmethane diisocyanate, 2,2′-diphenylmethane diisocyanate, 1,5-naphthylene diisocyanate, 1,4-naphthylene diisocyanate, phenylene diisocyanate, tetramethylxylylene diisocyanate, 4,4′-diphenyl ether diisocyanate, 2-nitrodiphenyl-4,4′-diisocyanate, 2,2′-diphenylpropane-4,4′-diisocyanate, and 3,3′-diphenyl Examples include aromatic diisocyanates such as 4,4'-diphenylmethane-4,4'-diisocyanate, 4,4'-diphenylpropane-diisocyanate, and 3,3'-dimethoxydiphenyl-4,4'-diisocyanate; aromatic aliphatic diisocyanates such as xylylene diisocyanate; alicyclic diisocyanates such as isophorone diisocyanate and 4,4-dicyclohexylmethane diisocyanate, and 1,3-bis(isocyanate-methyl)cyclohexane; hexamethylene diisocyanate; and aliphatic diisocyanates such as 2,2,4-trimethylhexamethylene diisocyanate. From the viewpoint of transparency, adhesion, and resistance to moisture and heat, aliphatic and alicyclic isocyanates and their modified forms are preferred, and are preferred for optical applications where high transparency without yellowing is required.

[0048] In the present invention, the blocked isocyanate can be made water-soluble or water-dispersible by introducing hydrophilic groups into the precursor polyisocyanate. Examples of hydrophilic groups include (1) quaternary ammonium salts of dialkylamino alcohols and quaternary ammonium salts of dialkylaminoalkylamines, (2) sulfonates, carboxylates, phosphates, etc., and (3) polyethylene glycol and polypropylene glycol with one end sealed by an alkoxy group. When hydrophilic moieties are introduced, the properties become (1) cationic, (2) anionic, or (3) nonionic. Among these, anionic and nonionic properties are preferred because many other water-soluble resins are anionic, allowing for easy compatibility. Furthermore, anionic properties offer excellent compatibility with other resins, and nonionic properties are preferred for improving heat and humidity resistance because they do not have ionic hydrophilic groups.

[0049] As anionic hydrophilic groups, those having a hydroxyl group for introduction into the polyisocyanate and a carboxylic acid group for imparting hydrophilicity are preferred. Examples include glycolic acid, lactic acid, tartaric acid, citric acid, oxybutyric acid, oxyvaleric acid, hydroxypivalic acid, dimethylolacetic acid, dimethylolpropanoic acid, dimethylolbutanoic acid, and polycaprolactone having a carboxylic acid group. Organic amine compounds are preferred for neutralizing the carboxylic acid group. Examples include linear, branched, primary, secondary, or tertiary amines having 1 to 20 carbon atoms, such as ammonia, methylamine, ethylamine, propylamine, isopropylamine, butylamine, 2-ethylhexylamine, cyclohexylamine, dimethylamine, diethylamine, dipropylamine, diisopropylamine, dibutylamine, trimethylamine, triethylamine, triisopropylamine, tributylamine, and ethylenediamine; cyclic amines such as morpholine, N-alkylmorpholine, and pyridine; and hydroxyl-containing amines such as monoisopropanolamine, methylethanolamine, methylisopropanolamine, dimethylethanolamine, diisopropanolamine, diethanolamine, triethanolamine, diethylethanolamine, and triethanolamine.

[0050] The nonionic hydrophilic group preferably has 3 to 50 repeating units of ethylene oxide and / or propylene oxide of polyethylene glycol or polypropylene glycol, with one end sealed with an alkoxy group, and more preferably 5 to 30. If the repeating units are small, the compatibility with the resin will be poor and the haze will increase, and if they are large, the adhesion under high temperature and high humidity may decrease. Nonionic, anionic, cationic, and amphoteric surfactants can be added to the blocked isocyanate of the present invention to improve its water dispersibility. Examples include nonionic surfactants such as polyethylene glycol and polyhydric alcohol fatty acid esters, anionic surfactants such as fatty acid salts, alkyl sulfate esters, alkylbenzene sulfonates, sulfosuccinates, and alkyl phosphates, cationic surfactants such as alkylamine salts and alkyl betaines, and surfactants such as carboxylic acid amine salts, sulfonic acid amine salts, and sulfate ester salts.

[0051] Furthermore, the mixture can contain water-soluble organic solvents other than water. For example, the organic solvent used in the reaction can be removed, and another organic solvent can be added.

[0052] (Polyester resin) The polyester resin used to form the coating layer in the present invention may be linear, but more preferably it is a polyester resin composed of a dicarboxylic acid and a branched glycol. The dicarboxylic acid referred to here may be terephthalic acid, isophthalic acid, or 2,6-naphthalenedicarboxylic acid as its main component, as well as 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. Furthermore, branched glycols are diols having branched alkyl groups, and examples include 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.

[0053] In the polyester resin, the branched glycol component, which is the more preferred embodiment described above, is preferably contained in a proportion of 10 mol% or more, and more preferably 20 mol% or more, of the total glycol component. Among the glycol components other than the above compounds, ethylene glycol is the most preferred. In small amounts, diethylene glycol, propylene glycol, butanediol, hexanediol, or 1,4-cyclohexanedimethanol may also be used.

[0054] The most preferred dicarboxylic acid as a component of the polyester resin is terephthalic acid or isophthalic acid. In small amounts, other dicarboxylic acids, particularly aromatic dicarboxylic acids such as diphenylcarboxylic acid and 2,6-naphthalenedicarboxylic acid, may be added and copolymerized. In addition to the above dicarboxylic acid, it is preferable to copolymerize 5-sulfoisophthalic acid in a range of 1 to 10 mol% to impart water dispersibility to the copolymerized polyester resin. Examples include sulfoterephthalic acid, 5-sulfoisophthalic acid, 4-sulfonaphthaleneisophthalic acid-2,7-dicarboxylic acid, 5-(4-sulfophenoxy)isophthalic acid and their salts.

[0055] When the total solid content of the polyester resin, the urethane resin having a polycarbonate structure, and the crosslinking agent in the coating solution is 100% by mass, the lower limit of the crosslinking agent content is preferably 5% by mass, more preferably 7% by mass, even more preferably 10% by mass, and most preferably 12% by mass. A content of 5% by mass or more is preferable as it makes it easier to adjust BA to 0.5 at% or more in the nitrogen distribution curve based on elemental distribution measurement in the depth direction by X-ray photoelectron spectroscopy. The upper limit of the crosslinking agent content is preferably 50% by mass, more preferably 40% by mass, even more preferably 35% by mass, and most preferably 30% by mass. A content of 50% by mass or less is preferable as it makes it easier to adjust cb to 300 seconds or less in the nitrogen distribution curve based on elemental distribution measurement in the depth direction by X-ray photoelectron spectroscopy.

[0056] When the total solid content of the polyester resin, the urethane resin having a polycarbonate structure, and the crosslinking agent in the coating solution is 100% by mass, the lower limit of the content of the urethane resin having a polycarbonate structure is preferably 5% by mass. A content of 5% by mass or more is preferable because it makes it easier to adjust the OCOO bond ratio X on the surface of the coating layer to 2.0% or more. The upper limit of the content of the urethane resin having a polycarbonate structure is preferably 50% by mass, more preferably 40% by mass, even more preferably 30% by mass, and most preferably 20% by mass. A urethane resin content of 50% by mass or less is preferable because it makes it easier to adjust the OCOO bond ratio X on the surface of the coating layer to 10.0% or less.

[0057] When the total solid content of polyester resin, urethane resin, and crosslinking agent in the coating solution is 100% by mass, the lower limit of the polyester resin content is preferably 10% by mass, more preferably 20% by mass, even more preferably 30% by mass, particularly preferably 35% by mass, and most preferably 40% by mass. A polyester resin content of 10% by mass or more is preferable because it results in good adhesion between the coating layer and the polyester film substrate. The upper limit of the polyester resin content is preferably 70% by mass, more preferably 67% by mass, even more preferably 65% ​​by mass, particularly preferably 62% by mass, and most preferably 60% by mass. A polyester resin content of 70% by mass or less is preferable because it results in good moisture and heat resistance of the hard coat film after hard coat processing.

[0058] (Additives) In the coating layer of the present invention, known additives such as surfactants, antioxidants, heat stabilizers, weather stabilizers, ultraviolet absorbers, organic lubricants, pigments, dyes, organic or inorganic particles, antistatic agents, nucleating agents, etc., may be added, as long as they do not impair the effects of the present invention.

[0059] In the present invention, it is also preferable to add particles to the coating layer in order to further improve the blocking resistance of the coating layer. Examples of particles to be contained in the coating layer in the present invention include titanium dioxide, barium sulfate, calcium carbonate, calcium sulfate, silica, alumina, talc, kaolin, clay, or mixtures thereof, as well as other general inorganic particles such as calcium phosphate, mica, hectorite, zirconia, tungsten oxide, lithium fluoride, calcium fluoride, etc., used in combination with other inorganic particles, and organic polymer particles such as styrene-based, acrylic-based, melamine-based, benzoguanamine-based, and silicone-based particles.

[0060] The average particle size of the particles in the coating layer (average particle size based on the number of particles measured by a scanning electron microscope (SEM); the same applies hereinafter) is preferably 0.04 to 2.0 μm, and more preferably 0.1 to 1.0 μm. An average particle size of 0.04 μm or more for inert particles is preferable because it facilitates the formation of irregularities on the film surface, improving handling properties such as film slipperiness and windability, and resulting in good processability during lamination. On the other hand, an average particle size of 2.0 μm or less for inert particles is preferable because particle shedding is less likely to occur. The particle concentration in the coating layer is preferably 1 to 20% by mass of the solid components.

[0061] The average particle size was measured by observing the particles in a cross-section of an easily adhesive polyester film using a scanning electron microscope. Thirty particles were observed, and the average value was used as the average particle size.

[0062] The shape of the particles is not particularly limited as long as it satisfies the objectives of the present invention, and spherical particles or irregularly shaped non-spherical particles can be used. The particle size of irregularly shaped particles can be calculated as the equivalent diameter of a circle. The equivalent diameter of a circle is obtained by dividing the area of ​​the observed particle by π, calculating the square root, and multiplying by 2.

[0063] (Manufacturing of easily adhesive polyester film) The method for producing an easily adhesive polyester film according to the present invention will be explained using an example with a polyethylene terephthalate (hereinafter sometimes abbreviated as PET) film substrate, but it is not limited to this.

[0064] After thoroughly vacuum-drying the PET resin, it is supplied to an extruder, and the molten PET resin at approximately 280°C is melt-extruded from the T-die onto a rotating cooling roll in a sheet shape. The molten PET resin is then cooled and solidified by electrostatic application to obtain an unstretched PET sheet. The unstretched PET sheet may be a single-layer structure or a multi-layer structure obtained by co-extrusion.

[0065] The obtained unstretched PET sheet is subjected to uniaxial or biaxial stretching to achieve crystal orientation. For example, in the case of biaxial stretching, the sheet is stretched 2.5 to 5.0 times in the longitudinal direction on a roll heated to 80 to 120°C to obtain a uniaxially oriented PET film. Then, the ends of the film are held with clips and guided into a hot air zone heated to 80 to 180°C, where it is stretched 2.5 to 5.0 times in the width direction. In the case of uniaxial stretching, it is stretched 2.5 to 5.0 times in a tenter. After stretching, it is then guided into a heat treatment zone and heat treatment is performed to complete the crystal orientation.

[0066] The lower limit of the heat treatment zone temperature is preferably 170°C, and more preferably 180°C. A temperature of 170°C or higher in the heat treatment zone is preferable because it ensures sufficient curing and good blocking properties in the presence of liquid water, eliminating the need for a long drying time. On the other hand, the upper limit of the heat treatment zone temperature is preferably 230°C, and more preferably 200°C. A temperature of 230°C or lower in the heat treatment zone is preferable because it does not risk degrading the physical properties of the film.

[0067] The coating layer can be applied after the film is manufactured or during the manufacturing process. In particular, from the viewpoint 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, thereby forming the coating layer.

[0068] Any known method can be used to apply this coating solution to the PET film. Examples include the reverse roll coating method, gravure coating method, kiss coating method, die coater method, roll brush method, spray coating method, air knife coating method, wire bar coating method, pipe doctor method, impregnation coating method, curtain coating method, and the like. These methods can be used individually or in combination.

[0069] In the present invention, the thickness of the coating layer can be appropriately set within the range of 0.001 to 2.00 μm, but to achieve both processability and adhesion, the range of 0.01 to 1.00 μm is preferable, more preferably 0.02 to 0.80 μm, and even more preferably 0.05 to 0.50 μm. A coating layer thickness of 0.001 μm or more is preferable because it provides good adhesion. A coating layer thickness of 2.00 μm or less is preferable because it is less likely to cause blocking.

[0070] The upper limit of the haze of the easily adhering polyester film in the present invention is preferably 1.5%, more preferably 1.3%, even more preferably 1.2%, and particularly preferably 1.0%. A haze of 1.5% or less is preferable in terms of transparency, and the film can be suitably used in optical films where transparency is required. While a low haze is preferable, it may be 0.1% or more.

[0071] (Laminated polyester film for optical applications) In the present invention, it is preferable to provide a functional layer on the coated layer of the easily adhering polyester film. A functional layer is a layer having functionality such as a hard coat layer, an anti-glare layer, a light-diffusing layer, and a transparent conductive layer, for purposes such as preventing reflections, suppressing glare, suppressing rainbow unevenness, and suppressing scratches. Various types of functional layers known in the art can be used, and there are no particular limitations on their type. The following describes each functional layer.

[0072] (Hard coat layer) For forming the hard coat layer, known hard coat layer materials can be used, and are not particularly limited, but resin compounds that polymerize and / or react by drying, heat, chemical reaction, or irradiation with electron beams, radiation, or ultraviolet light can be used. Examples of such curable resins include melamine-based, acrylic-based, silicone-based, and polyvinyl alcohol-based curable resins, but photocurable acrylic-based curable resins are preferred in terms of obtaining high surface hardness or optical design. Examples of such acrylic-based curable resins include polyfunctional (meth)acrylate monomers and acrylate-based oligomers, and examples of acrylate-based oligomers include polyester acrylate, epoxy acrylate, urethane acrylate, polyether acrylate, polybutadiene acrylate, and silicone acrylate. By mixing these acrylic-based curable resins with a reaction diluent, a photopolymerization initiator, a sensitizer, etc., a coating composition for forming the optical functional layer can be obtained.

[0073] The hard coat layer preferably contains inorganic particles. Fine particles are added to increase the hardness of the cured film. Examples include silica, aluminum oxide, zirconium oxide, titanium oxide, zinc oxide, and tin oxide, which can be used individually or in combination of two or more. Among these, silica and aluminum oxide are preferred because they have little effect on optical properties. When using silica, it is preferable to treat the surface with a silane coupling agent or an organic compound having a reactive functional group such as a (meth)acryloyl group to improve dispersibility in the paint, but when using aluminum oxide, the presence or absence of surface treatment has little effect on dispersibility, so either can be used without any problems.

[0074] The average particle size of the inorganic particles is preferably 5 to 200 nm, more preferably 10 to 100 nm, and particularly preferably 20 to 60 nm. A particle size of 5 nm or more is expected to improve film hardness, while a particle size of 200 nm or less can reduce the impact on optical properties such as haze. The amount of inorganic particles relative to the total solid content is preferably 0.5 to 10% by weight, and more preferably 1 to 8% by weight. A particle size of 0.5% by weight or more is expected to improve hardness, while a particle size of 10% by weight or less can reduce the impact on optical properties such as haze. The average particle size is the median diameter (d50) measured by the BET method in the case of silica, and by the laser diffraction / scattering method in accordance with JIS Z 8825-1 for other materials including aluminum oxide.

[0075] The hard coat layer described above may have an anti-glare function that scatters ambient light. The anti-glare function is obtained by forming irregularities on the surface of the hard coat layer. In this case, the haze of the film is ideally preferably 0 to 50%, more preferably 0 to 40%, particularly preferably 0 to 30%, and most preferably 1.5% or less. The lower limit may be 0.1% or more.

[0076] (Light Diffusion Layer) From the viewpoint of practicality as a base film for light diffusion sheets, the upper limit of thickness is preferably 250 μm. A particularly preferred upper limit of thickness is 200 μm, which is about the same as that of a typical TAC film. It is preferable that at least one surface of the base material has a bead coating layer consisting mainly of acrylic resin beads and a binder, and that the haze of the light diffusion sheet is 80% or more. A haze of 80% or more of the light diffusion sheet is preferable because it provides a brightness improvement effect and prevents color unevenness. A more preferred lower limit is 85%.

[0077] Next, a method for forming a bead coating layer on a polyester base film as a light-diffusing sheet will be described, but the present invention is not limited thereto. Various resins can be used as binders for the bead coating layer, including acrylic resins such as PMMA (polymethyl methacrylate), polyester resins, polyvinyl chloride, polyurethane, and silicone resins, but acrylic resins are particularly preferred due to their excellent transparency.

[0078] Acrylic resin beads are preferred for the bead coating layer, but other resins can also be used in combination. Examples of other resins include silicone resin, nylon resin, urethane resin, styrene resin, polyethylene resin, silica particles, and polyester resin. The particle size of such beads is not particularly limited, but beads with an average particle size of 1 μm to 50 μm are preferably used. Furthermore, if spherical beads are used, these spherical beads act as a kind of lens, providing an even more effective light diffusion effect.

[0079] A coating solution is prepared by mixing the above-mentioned beads with the binder in an appropriate proportion. This coating solution is then uniformly applied to the surface of the coating layer of the easily adhesive polyester film manufactured as described above, and dried to form a bead-coated layer in which the beads are uniformly dispersed in the binder. The proportion of beads to the binder is not particularly limited, but considering the light diffusion performance, approximately 10 to 60 parts by weight per 100 parts by weight of binder is preferred. Various coating methods can be used, such as roll coating, dipping, spray coating, spooling, lamination, and pouring, but are not particularly limited.

[0080] The backlight of a liquid crystal display device using the light-diffusing sheet of the present invention exhibits good brightness, minimal brightness variation with respect to angle, and small brightness variations. Therefore, it can contribute to higher brightness, higher quality, and lower cost of liquid crystals.

[0081] (Transparent conductive layer) Examples of transparent conductive thin films in the present 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. Of these, indium-tin composite oxide is preferred from the viewpoint of environmental stability and circuit processability. In the present invention, by laminating transparent conductive thin film layers and setting the surface resistance of the transparent conductive laminated film to preferably 50 to 2000 Ω / □, and more preferably 100 to 1500 Ω / □, it can be used as a transparent conductive laminated film for touch panels and the like. When the surface resistance is 50 Ω / □ or more and 2000 Ω / □ or less, the position recognition accuracy of the touch panel is good and therefore preferable.

[0082] The thickness of the transparent conductive thin film is preferably in the range of 4 to 30 nm, and more preferably 10 to 25 nm. When the thickness of the transparent conductive thin film is 4 nm or more, continuous thin film formation is easy, and good conductivity can be obtained, which is preferable. On the other hand, when the thickness of the transparent conductive thin film is 30 nm or less, when the transparent conductive layer is patterned, the difference in optical properties between the part with the transparent conductive layer and the part without the transparent conductive layer is small, which is preferable.

[0083] The structure of the transparent conductive layer may be a single layer or a laminated structure of two or more layers. In the case of a transparent conductive thin film having a laminated structure of two or more layers, the metal oxides constituting each layer may be the same or different.

[0084] Known methods for forming transparent conductive thin films in the present invention include vacuum deposition, sputtering, CVD, ion plating, and spraying, and these methods can be appropriately used depending on the required film thickness. Furthermore, a transparent conductive layer can also be laminated on a coated layer by incorporating conductive substances such as aniline compounds, thiol compounds, pyrrole compounds, and carbon nanotubes into a binder resin and coating it. For example, in the case of sputtering, conventional sputtering using an oxide target or reactive sputtering using a metal target can be used. In this case, oxygen, nitrogen, etc., may be introduced as a reactive gas, or ozone addition, plasma irradiation, ion assistance, etc., may be used in combination. Additionally, a bias such as DC, AC, or high frequency may be applied to the substrate, as long as it does not impair the objectives of the present invention.

[0085] The optical laminated polyester film having a transparent conductive layer of the present invention is particularly suitable as an electrode film for resistive or capacitive touch panels. Furthermore, laminating the hard coat layer on a coating layer of an easily adhesive polyester film, and then laminating the transparent conductive layer on the hard coat layer, is a particularly preferred embodiment because it can suppress oligomer deposition of the easily adhesive polyester film.

[0086] (Lens layer) In liquid crystal panels, light from the backlight is directed in various directions, but it is known that a lens sheet is preferable to concentrate this light toward the viewer and increase the brightness of the display device. Examples of lens sheets include uniaxial focusing types that concentrate light in only one direction, such as cylindrical lenses, prism lenses, and lenticular lenses; biaxial focusing types that concentrate light in two orthogonal directions, such as square pyramidal shapes and deformed square pyramidal shapes with an elongated apex in one direction; triaxial focusing types such as triangular pyramidal shapes and hexagonal pyramidal shapes; multiaxial types such as octagonal pyramidal shapes and larger; and even small hemispherical or elliptical hemispherical microlens types and Fresnel lens types, all of which can be used. The lens sheet may have lenses processed on both sides, not just one side, and the lens shapes may differ on both sides. A uniaxial focusing type lens may be processed so that the focusing axes are orthogonal on both sides. Among these, biaxial, triaxial, multiaxial, and microlens types have high focusing effects and are particularly preferred lens shapes.

[0087] The lens layer in the present invention can be obtained, for example, by coating and molding a composition containing a thermoplastic resin or reaction-curing resin having appropriate hardness and formability onto a coated layer of an easily adhesive polyester film. Various materials can be used for the composition containing a thermoplastic resin or reaction-curing resin with formability, but examples include various curable resins as described in the hard coat layer description, with UV-curing acrylic resin being a typical example. Alternatively, a composition containing monomers or oligomers for forming UV-curing acrylic resin can be poured into a mold with a lens pattern, and an easily adhesive polyester film can be placed on top with the coated surface facing the resin. The composition can then be cured by irradiating it with ultraviolet light from the easily adhesive polyester film side to form the lens layer.

[0088] Lens sheets can also be manufactured by methods such as embossing the surface of a transparent substrate using a mold with a specific pattern, or by applying an ultraviolet-curing resin such as acrylic to an easily adhesive polyester film and curing it with ultraviolet light while in contact with a mold with a specific pattern, as described above.

[0089] The shape of the lens layer is not particularly limited, but for example, prism-shaped lenses, Fresnel-shaped lenses, and microlenses are suitably applied.

[0090] Based on the above, the optical laminated polyester film of the present invention can be used for a wide range of optical films, and is suitable for use as a base film for optical components such as LCDs, flat-screen TVs, and CRTs, such as prism lens sheets, AR (anti-reflection) films, hard coat films, diffusers, and shatterproof films; as well as for near-infrared absorption filters used as front panels for plasma displays; and as transparent conductive films for touch panels and electroluminescence. [Examples]

[0091] Next, the present invention will be described in detail using examples and experimental examples, but the present invention is not limited to the following examples.

[0092] [Manufacturing of polyester resin pellets P-1] In a 2-liter stainless steel autoclave equipped with a stirrer, high-purity terephthalic acid and twice its molar volume of ethylene glycol were charged. Triethylamine was added at a concentration of 0.3 mol% relative to the acid component, and the esterification reaction was carried out at 250°C under a pressure of 0.25 MPa while distilling off the water from the system. This was carried out to obtain a mixture of bis(2-hydroxyethyl) terephthalate and oligomer (hereinafter referred to as the BHET mixture) with an esterification rate of approximately 95%. Next, while stirring this BHET mixture, an ethylene glycol solution of antimony trioxide was added as a polymerization catalyst so that the antimony atoms amounted to 0.04 mol% relative to the acid component in the polyester, and the mixture was continued to be stirred at 250°C for 10 minutes under atmospheric pressure and a nitrogen atmosphere. After that, the temperature was raised to 280°C over 60 minutes while gradually lowering the pressure of the reaction system to 13.3 Pa (0.1 Torr), and then further heated to 28 The polycondensation reaction was carried out at 0°C and 13.3 Pa. Following the release of pressure, the resin was extruded in strand form into cold water under slight pressure and rapidly cooled. After being held in cold water for 20 seconds, it was cut to obtain cylindrical pellets approximately 3 mm in length and 2 mm in diameter.

[0093] Polyester pellets obtained by melt polymerization were dried under reduced pressure (13.3 Pa or less, 80°C, 12 hours), followed by crystallization treatment (13.3 Pa or less, 130°C, 3 hours, and then 13.3 Pa or less, 160°C, 3 hours). After cooling, these polyester pellets were subjected to solid-phase polymerization in a solid-phase polymerization reactor while maintaining the system temperature at 13.3 Pa or less and 215°C to obtain polyester pellets (P-1) with an intrinsic viscosity of 0.62 dl / g.

[0094] [Manufacturing of Polyester Pellet P-2] (Preparation of aluminum compounds) Prepared by heating at 80°C for 2 hours under stirring, and the peak position of the 27Al-NMR spectrum A 20 g / l aqueous solution of basic aluminum acetate (hydroxyaluminum diacetate; manufactured by Aldrich), in which a chemical shift towards a lower magnetic field was confirmed, was combined with an equal volume (by volume) of ethylene glycol in a flask. After stirring at room temperature for 6 hours, water was removed from the system under reduced pressure (133 Pa) at 90-110°C for several hours while stirring, to prepare a 20 g / l ethylene glycol solution of the aluminum compound.

[0095] (Preparation of phosphorus compounds) Irganox 1222 (manufactured by Ciba Specialty Chemicals) is used as a phosphorus compound in ethylene The phosphorus compound was placed in a flask with glycol and heated at 160°C for 25 hours while stirring under nitrogen purging to prepare a 50 g / l ethylene glycol solution of phosphorus compounds. 31P-NMR Spectrometer Measurement of the Toll confirmed that approximately 60 mol% was converted to hydroxyl groups.

[0096] (Ethylene glycol solution of aluminum compounds / Ethylene glycol solution of phosphorus compounds) Preparation of the mixture) The ethylene glycol solutions obtained from the preparation of the aluminum compound and the phosphorus compound were placed in flasks and mixed at room temperature so that the molar ratio of aluminum atoms to phosphorus atoms was 1:2. The mixture was then stirred for one day to prepare the catalyst solution. Chemical shifts were observed in the 27Al-NMR spectrum and 31P-NMR spectra of the mixed solution in both cases.

[0097] (Manufacturing of Pellet P-2) As a polycondensation catalyst, the above aluminum compound is used as an ethylene glycol solution / phosphorus compound The same procedure as for the production of polyester pellet P-1 was followed, except that a mixture of ethylene glycol solution was added to the acidic component in the polyester so that it amounted to 0.014 mol% and 0.028 mol% of aluminum and phosphorus atoms, respectively. A polyester pellet (P-2) with an intrinsic viscosity of 0.65 dl / g was obtained.

[0098] (Polymerization of urethane resin A-1 having a polycarbonate structure) In a four-necked flask equipped with a stirrer, a Liebig condenser, a nitrogen inlet tube, a silica gel drying tube, and a thermometer, 32 parts by mass of 1,3-cyclohexyl diisocyanate, 7 parts by mass of dimethylolpropanoic 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 a solvent were added. The mixture was stirred under a nitrogen atmosphere at 75°C for 3 hours, and it was confirmed that the reaction solution reached the predetermined amine equivalent. Next, the reaction solution was cooled to 40°C, and 5.17 parts by mass of triethylamine was added to obtain a polyurethane prepolymer solution. Next, 450 g of water was added to a reaction vessel equipped with a homodisperser capable of high-speed stirring, and the temperature was adjusted to 25°C for 2000 min. -1 While stirring and mixing, the polyurethane prepolymer solution was added and dispersed in water. Then, under reduced pressure, a water-dispersible urethane resin solution (A-1) with a solid content of 34% was prepared by removing some of the acetone and water.

[0099] (Polymerization of urethane resin A-2 having a polycarbonate structure) In a four-necked flask equipped with a stirrer, a Liebig condenser, a nitrogen inlet tube, a silica gel drying tube, and a thermometer, 38 parts by mass of 4,4-dicyclohexylmethane diisocyanate, 9 parts by mass of dimethylolpropanoic 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 a solvent were added. The mixture was stirred under a nitrogen atmosphere at 75°C for 3 hours, and it was confirmed that the reaction solution reached the predetermined amine equivalent. Next, the reaction solution was cooled to 40°C, and 5.17 parts by mass of triethylamine was added to obtain a polyurethane prepolymer solution. Next, in a reaction vessel equipped with a homodisperser capable of high-speed stirring, 450 g of water was added, the temperature was adjusted to 25°C, and the mixture was stirred for 2000 min. -1 While stirring and mixing, the polyurethane prepolymer solution was added and dispersed in water. Then, under reduced pressure, a water-dispersible urethane resin solution (A-2) with a solid content of 35% was prepared by removing some of the acetone and water.

[0100] (Polymerization of urethane resin A-3 having a polycarbonate structure) In a four-necked flask equipped with a stirrer, a Liebig condenser, a nitrogen inlet tube, a silica gel 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 diol 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 under a nitrogen atmosphere at 75°C for 3 hours, and it was confirmed that the reaction solution reached the predetermined amine equivalent. Next, the reaction solution was cooled to 40°C to obtain a polyurethane prepolymer solution. Then, in a reaction vessel equipped with a homodisperser capable of high-speed stirring, 450 g of water was added, the temperature was adjusted to 25°C, and the mixture was stirred for 2000 min. -1 While stirring and mixing, the polyurethane prepolymer solution was added and dispersed in water. Then, under reduced pressure, a water-dispersible urethane resin solution (A-3) with a solid content of 35% was prepared by removing some of the acetone and water.

[0101] (Polymerization of urethane resin A-4 having a polycarbonate structure) In a four-necked flask equipped with a stirrer, a Liebig condenser, a nitrogen inlet tube, a silica gel drying tube, and a thermometer, 24 parts by mass of 4,4-dicyclohexylmethane diisocyanate, 4 parts by mass of dimethylolbutanoic acid, 71 parts by mass of polyhexamethylene carbonate diol with a number average molecular weight of 2000, 1 part 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 under a nitrogen atmosphere for 3 hours, and it was confirmed that 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 was added to obtain a polyurethane prepolymer solution. Next, in a reaction vessel equipped with a homodisperser capable of high-speed stirring, 450 g of water was added, the temperature was adjusted to 25°C, and the mixture was stirred for 2000 min. -1 While stirring and mixing, the polyurethane prepolymer solution was added and dispersed in water. Then, under reduced pressure, a water-dispersible urethane resin solution (A-4) with a solid content of 34% by mass was prepared by removing some of the acetone and water.

[0102] (Polymerization of urethane resin A-5 that does not contain polycarbonate polyol components) A multi-stage isocyanate polyaddition method using polyether polyol, organic polyisocyanate, and diethylene glycol as a chain extender was carried out at a temperature of 70-120°C for 2 hours. The resulting urethane prepolymer was mixed with an aqueous solution of bisulfite and prepared for approximately 1 The reaction was allowed to proceed for a period of time with good stirring until it formed a block. The reaction temperature was kept below 60°C. Afterwards, it was diluted with water to prepare a heat-reactive, water-dispersible urethane resin solution (A-5) with a solid content of 20% by mass.

[0103] (Polymerization of urethane resin A-6 having a polycarbonate structure) In a four-necked flask equipped with a stirrer, a Liebig condenser, a nitrogen inlet tube, a silica gel 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 diol 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 under a nitrogen atmosphere for 3 hours, and it was confirmed that 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 was added to obtain a polyurethane prepolymer solution. Next, 450 g of water was added to a reaction vessel equipped with a homodisperser capable of high-speed stirring, and the temperature was adjusted to 25°C for 2000 min. -1 While stirring and mixing, the polyurethane prepolymer solution was added and dispersed in water. Then, under reduced pressure, a water-dispersible urethane resin solution (A-6) with a solid content of 34% by mass was prepared by removing some of the acetone and water.

[0104] The following two items are shown in Table 2. I. The mass ratio of polycarbonate polyol component to polyisocyanate component when synthesizing and polymerizing the urethane resin that forms the coating layer (polycarbonate polyol component / polyisocyanate component) b. Molecular weight of polycarbonate polyol component

[0105] [Table 2]

[0106] (Polymerization of blocked isocyanate crosslinking agent B-1) In a flask equipped with a stirrer, thermometer, and reflux condenser, 66.04 parts by mass of a polyisocyanate compound having an isocyanurate structure derived from hexamethylene diisocyanate (Duranate TPA, manufactured by Asahi Kasei Chemicals) and 17.50 parts by mass of N-methylpyrrolidone were added dropwise to 25.19 parts by mass of 3,5-dimethylpyrazole (dissociation temperature: 120°C, boiling point: 218°C). The mixture was held at 70°C for 1 hour under a nitrogen atmosphere. Subsequently, 5.27 parts by mass of dimethylolpropanoic acid were added dropwise. The infrared spectrum of the reaction solution was measured to confirm the disappearance of absorption of the isocyanate group. Then, 5.59 parts by mass of N,N-dimethylethanolamine and 132.5 parts by mass of water were added to obtain a block polyisocyanate aqueous dispersion (B-1) with a solid content of 40% by mass. The number of functional groups of this block isocyanate crosslinking agent is 4.

[0107] (Polymerization of blocked isocyanate crosslinking agent B-2) In a flask equipped with a stirrer, thermometer, and reflux condenser, 100 parts by mass of a polyisocyanate compound having an isocyanurate structure derived from hexamethylene diisocyanate (Duranate TPA, manufactured by Asahi Kasei Chemicals), 55 parts by mass of propylene glycol monomethyl ether acetate, and 30 parts by mass of polyethylene glycol monomethyl ether (average molecular weight 750) were charged and held at 70°C for 4 hours under a nitrogen atmosphere. The reaction mixture temperature was then lowered to 50°C, and 47 parts by mass of methyl ethyl ketoxime were added dropwise. The infrared spectrum of the reaction mixture was measured, and the disappearance of the isocyanate group absorption was confirmed, yielding an oxime-blocked isocyanate crosslinking agent (B-2) with a solid content of 40% by mass. This blocked isocyanate crosslinking agent has 3 functional groups.

[0108] (Polymerization of carbodiimide B-3) In a flask equipped with a stirrer, thermometer, and reflux condenser, 168 parts by mass of hexamethylene diisocyanate and 220 parts by mass of polyethylene glycol monomethyl ether (M400, average molecular weight 400) were charged and 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-phosphorene-1-oxide (2% by mass relative to the total isocyanate) were added as a carbodiimide catalyst, and the mixture was stirred for a further 5 hours at 185°C under a nitrogen stream. The infrared spectrum of the reaction solution was measured, with wavelengths ranging from 220 to 2300 cm⁻¹. -1 It was confirmed that the absorption had disappeared. The mixture was allowed to cool to 60°C, and 567 parts by mass of deionized water was added to obtain a carbodiimide aqueous resin solution (B-3) with a solid content of 40% by mass.

[0109] (Polyester resin polymerization C-1) In a stainless steel autoclave equipped with a stirrer, thermometer, and partial reflux condenser, 194.2 parts by mass of dimethyl terephthalate, 184.5 parts by mass of dimethyl isophthalate, 14.8 parts by mass of dimethyl-5-sodium sulfoisophthalate, 233.5 parts by mass of diethylene glycol, 136.6 parts by mass of ethylene glycol, and 0.2 parts by mass of tetra-n-butyl titanate were charged, and a transesterification reaction was carried out at a temperature of 160°C to 220°C for 4 hours. The temperature was then raised to 255°C, the reaction system was gradually depressurized, and the reaction was carried out under a reduced pressure of 30 Pa for 1 hour and 30 minutes to obtain copolymerized polyester resin (C-1). The obtained copolymerized polyester resin (C-1) was pale yellow and transparent. The reduced viscosity of copolymerized polyester resin (C-1) was measured to be 0.70 dl / g. The glass transition temperature determined by DSC was 40°C.

[0110] (Preparation of polyester aqueous dispersion) In a reactor equipped with a stirrer, thermometer, and reflux device, 15 parts by mass of polyester resin (C-1) and 15 parts by mass of ethylene glycol n-butyl ether were added and heated at 110°C, stirring to dissolve the resin. After the resin was completely dissolved, 70 parts by mass of water were gradually added to the polyester solution while stirring. After the addition, the liquid was cooled to room temperature while stirring to prepare a milky white polyester aqueous dispersion (Cw-1) with a solid content of 15% by mass.

[0111] (Example 1) (1) Preparation of the coating solution A coating solution was prepared by mixing the following coating agents with a mixed solvent of water and isopropanol, resulting in a solid content mass ratio of urethane resin solution (A-1) / crosslinking agent (B-1) / polyester aqueous dispersion (Cw-1) of 25 / 26 / 49. Urethane resin solution (A-1) 3.55 parts by mass Crosslinking agent (B-1) 3.16 parts by mass Polyester aqueous dispersion (Cw-1) 16.05 parts by mass Particles 0.47 parts by mass (Dry-processed silica with an average particle size of 200 nm, solid content concentration of 3.5%) Particles 1.85 parts by mass (Silica sol with average particle size of 40-50 nm, solid content concentration of 30% by mass) Surfactant 0.30 parts by mass (Silicone-based, solid content concentration 10% by mass)

[0112] (2) Manufacturing of easily adhesive polyester film As a film raw material polymer, polyester pellets (P-1) were dried at 135°C for 6 hours under reduced pressure of 133 Pa. Then, they were fed into an extruder and melt-extruded into a sheet at approximately 280°C. The sheet was then rapidly cooled and solidified on a rotating, cooled metal roll maintained at a surface temperature of 20°C to obtain an unstretched PET sheet.

[0113] This unstretched PET sheet was heated to 100°C using a heated roll group and an infrared heater, and then stretched 3.5 times in the longitudinal direction using a roll group with different peripheral speeds to obtain a uniaxially oriented PET film.

[0114] Next, the coating solution, which had been left to stand at room temperature for more than 5 hours, was applied to one side of the PET film by roll coating, and then dried at 80°C for 20 seconds. The final coating amount after drying (after biaxial stretching) was 0.15 g / m². 2 The film was adjusted to have a coating layer thickness of 150 nm after drying. Subsequently, it was stretched 4.0 times in the width direction at 120°C using a tenter, and with the length in the width direction of the film fixed, it was heated at 230°C for 5 seconds, and then subjected to a 3% widthwise relaxation treatment at 100°C for 10 seconds to obtain a 100 μm easy-to-adhere polyester film.

[0115] (3) Manufacturing of laminated polyester films for optical use

[0116] (1) Optical laminated polyester film having a hard coat layer A hard coat layer forming solution with the following composition was applied to the coating layer of an easily adhering polyester film using a #5 wire bar, dried at 80°C for 1 minute, and the solvent was removed. Then, the film with the hard coat layer was subjected to a high-pressure mercury lamp at a pressure of 300 mJ / cm². 2 UV rays Irradiation was performed to obtain an optical laminated polyester film (1) having a hard coat layer. (Coating solution for forming a hard coat layer) Pentaerythritol triacrylate PETA 39.10% by mass (Manufactured by Toagosei Co., Ltd., trifunctional acrylic UV-curing resin, 100% solids content, refractive index 1.49) • Zirconia particles 3.40% by mass (Manufactured by Nippon Shokubai, ZP-153, average particle size 11nm, solid content 70%, refractive index 1.53) • Photopolymerization initiator 3.50% by mass (IGM Resins BV Omnirad184) • Photopolymerization initiator 2.00% by mass (IGM Resins BV Omnirad907) • Solvent 52.00% by mass (Methyl ethyl ketone (MEK) / propylene glycol monomethyl ether (PGM))

[0117] (Optical laminated polyester film (2) having a hard coat layer) On the coating layer of the easy-adhesive polyester film, a coating liquid for forming a hard coat layer having the following composition was applied using a #5 wire bar, dried at 80 °C for 1 minute, and the solvent was removed. Next, ultraviolet rays of 300 mJ / cm 2 were irradiated onto the film coated with the hard coat layer using a high-pressure mercury lamp to obtain an optical laminated polyester film (2) having a hard coat layer. (Coating liquid for forming a hard coat layer) · Pentaerythritol triacrylate PETA 34.2 mass% (Manufactured by Toagosei Co., Ltd., trifunctional acrylic ultraviolet curable resin, solid content 100%, refractive index 1.49) · Nanoscale silica 4.30 mass% (Manufactured by Nissan Chemical Industries, Ltd., average particle size 80 nm, MEK-AC-5140Z, solid content 32%) · Photoinitiator 3.50 mass% (Omnirad184 manufactured by IGM Resins B.V.) · Photoinitiator 2.00 mass% (Omnirad907 manufactured by IGM Resins B.V.) · Solvent 56.00 mass% (Propylene glycol monomethyl ether (PGM)

[0118] (Optical laminated polyester film having a lens layer of a photocurable urethane / acrylic resin) ​Approximately 5g of the following light-curing urethane / acrylic coating solution was placed on a clean, 1mm thick SUS304 stainless steel plate. The coating layer of an easy-to-adhere polyester film was then placed on top of the plate so that it was in contact with the light-curing urethane / acrylic coating solution. The light-curing urethane / acrylic coating solution was then pressed and stretched out from the easy-to-adhere polyester film using a 10cm wide, 4cm diameter manual load rubber roller. A high-pressure mercury lamp was used to apply a pressure of 300mJ / cm² from the easy-to-adhere polyester film side. 2 The photocurable urethane / acrylic resin is cured by irradiating it with ultraviolet light. A film sample having a 50 μm thick photocurable urethane / acrylic layer was peeled from a SUS plate to obtain an optical laminated polyester film (before shaping) having a photocurable urethane / acrylic layer. (Photocurable urethane / acrylic coating solution) Light-curing acrylic resin 20.00% by mass (Bremmer 650 manufactured by Shin-Nakamura Chemical) Photocurable methacrylate resin 40.00% by mass (Shin Nakamura Chemical BPE-500) Light-curing urethane / acrylic resin 29.00% by mass (Shin Nakamura Chemical U-6HA) Light-curing acrylic resin 8.00% by mass (Shin Nakamura Chemical AMP-10G) Photopolymerization initiator 3.00% by mass (Irgacure 184, manufactured by Ciba Specialty Chemicals)

[0119] (Laminated polyester film for optical applications having a lens layer made of photocurable acrylic resin) The above-mentioned photocurable urethane / acrylic coating solution for an optical laminated polyester film having a photocurable urethane / acrylic layer was changed to the following photocurable acrylic coating solution, and the UV irradiation dose was set to 100 mJ / cm². 2 Except for the change, the process was the same, and the lens layer of light-curing acrylic resin was modified. A laminated polyester film for optical use (before shaping) was obtained. (Photocurable acrylic coating solution) Light-curing acrylic resin 77.00% by mass (Shin Nakamura Chemical A-BPE-4) Light-curing acrylic resin 22.00% by mass (Shin Nakamura Chemical AMP-10G) Photopolymerization initiator 1.00% by mass (Irgacure 184, manufactured by Ciba Specialty Chemicals)

[0120] (Laminated polyester film for optical applications with a light-diffusing layer) A light-diffusing layer-forming coating solution with the following composition was applied to a coated layer of an easily adhesive polyester film using a #5 wire bar, and the film was dried and heat-cured at 160°C for 60 seconds to obtain an optical laminated polyester film having a light-diffusing layer. (Coating solution for forming a light-diffusing layer) Acrylic polyol (50% solids content) 150 parts by mass (Acrydic A-807: Dainippon Ink and Chemicals Co., Ltd.) Isocyanate (60% solids content) 30 parts by mass (Takenate D11N: Takeda Pharmaceutical Company Limited) Methyl ethyl ketone 200 parts by mass 200 parts by mass of butyl acetate 40 parts by mass of acrylic resin particles (MX-1000, average particle size 10.0μm: Soken Kagakusha)

[0121] (Laminated polyester film for optical applications with an anti-glare layer) A coating solution for forming an anti-glare layer, with the following composition, was applied to the coating layer of an easily adhering polyester film using a #5 wire bar, dried at 70°C for 1 minute, and the solvent was removed. Next, the film coated with the anti-glare layer was irradiated with 300 mJ / cm2 ultraviolet light using a high-pressure mercury lamp, resulting in a thickness of 5 μm. An optical laminated polyester film having an anti-glare layer of m was obtained. • Coating solution for forming an anti-glare layer Toluene 34 parts by mass Pentaerythritol triacrylate 50 parts by mass Silica (average particle size 1μm) 12 parts by mass Silicone (leveling agent) 1 part by mass Photopolymerization initiator: 1 part by mass (Irgacure 184, manufactured by Ciba Specialty Chemicals)

[0122] (Example 2) An easy-to-adhere polyester film and various optical laminated polyester films were obtained in the same manner as in Example 1, except that the urethane resin was changed to (A-2).

[0123] (Example 3) An easy-to-adhere polyester film and various optical laminated polyester films were obtained in the same manner as in Example 1, except that the urethane resin was changed to (A-3).

[0124] (Example 4) An easily adhesive polyester film and various optical laminated polyester films were obtained in the same manner as in Example 1, except that the crosslinking agent was changed to (B-2).

[0125] (Example 5) An easily adhering polyester film and various optical laminated polyester films were obtained in the same manner as in Example 1, except that the following coating agent was mixed with a mixed solvent of water and isopropanol, and the solid content mass ratio of the urethane resin solution (A-1) / crosslinking agent (B-1) / polyester aqueous dispersion (Cw-1) was changed to 22 / 10 / 68. Urethane resin solution (A-1) 2.71 parts by mass Crosslinking agent (B-1) 1.00 parts by mass Polyester aqueous dispersion (Cw-1) 19.05 parts by mass Particles 0.47 parts by mass (Dry-processed silica with an average particle size of 200 nm, solid content concentration of 3.5%) Particles 1.85 parts by mass (Silica sol with average particle size of 40-50 nm, solid content concentration of 30% by mass) Surfactant 0.30 parts by mass (Silicone-based, solid content concentration 10% by mass)

[0126] (Example 6) An easy-to-adhere polyester film and various optical laminated polyester films were obtained in the same manner as in Example 5, except that the urethane resin was changed to (A-2).

[0127] As shown in Table 5, in Examples 1 to 6, "BA", "b", and "cb" each satisfied the range of the following formula, and the haze, hard court adhesion, and blocking resistance were satisfactory. (i) 0.5 ≤ BA(at%) ≤ 3.0 (ii) 30 ≦ b(seconds) ≦ 180 (iii) 30 ≦ cb(sec) ≦ 300 Furthermore, "X" satisfies the following equation, and its adhesion to various optical functional layers was satisfactory. (iv) 2.0 ≤ X(%) ≤ 10.0

[0128] (Example 7) An easily adhesive polyester film and various optical laminated polyester films were obtained in the same manner as in Example 1, except that the polyester pellets were changed to (P-2) as the film raw material polymer.

[0129] As shown in Table 5, in Example 7, "BA", "b", and "cb" each satisfy the range of the following formula, and the adhesion to various optical functional layers and blocking resistance were satisfactory. (i) 0.5 ≤ BA(at%) ≤ 3.0 (ii) 30 ≦ b(seconds) ≦ 180 (iii) 30 ≦ cb(sec) ≦ 300 Furthermore, "X" satisfies the following equation, and its adhesion to various optical functional layers was satisfactory. (iv) 2.0 ≤ X(%) ≤ 10.0 Furthermore, compared to Examples 1-6 which used polyester pellets P-1, we confirmed that the haze value was smaller and the transparency of the film was improved.

[0130] (Example 8) In Example 1, the easily adhering polyester film obtained was subjected to a rewinding process in a vacuum chamber for vacuum exposure. The pressure at this time was 0.002 Pa, and the exposure time was 10 minutes. The temperature of the center roll was 40°C. Next, a transparent conductive thin film made of indium tin oxide was deposited on the hard coat layer of the hard coat film. At this time, the pressure before sputtering was 0.0007 Pa, and indium oxide containing 5% by mass of tin oxide (manufactured by Mitsui Mining & Smelting Co., Ltd., density 7.1 g / cm³) was used as the target. 3 Using ), 2W / cm 2 A DC power was applied. Furthermore, Ar gas was flowed at a flow rate of 130 sccm and O2 gas at 10 sccm, and the film was deposited in an atmosphere of 0.4 Pa using the DC magnetron sputtering method. In this manner, a transparent conductive film having a transparent conductive layer made of 22 nm thick indium tin oxide with a surface resistance of 250 Ω was obtained. The adhesion of the transparent conductive layer was satisfactory.

[0131] (Example 9) To expose the hard coat film (1) obtained in Example 1 to vacuum, a vacuum chamber was used. A rewinding process was performed inside. The subsequent steps were the same as in Example 8, and a transparent conductive film having a transparent conductive layer made of indium tin oxide with a thickness of 22 nm and a surface resistance of 250 Ω was obtained. The adhesion of the transparent conductive layer was satisfactory.

[0132] (Experimental Example 1) An easily adhering polyester film and various optical laminated polyester films were obtained in the same manner as in Example 1, except that the following coating agent was mixed with a mixed solvent of water and isopropanol, and the solid content ratio of the urethane resin solution (A-5) / polyester aqueous dispersion (Cw-1) was changed to 29 / 71. Urethane resin solution (A-5) 6.25 parts by mass Polyester aqueous dispersion (Cw-1) 20.00 parts by mass Catalyst for Elastron: 0.50 parts by mass Particles 1.02 parts by mass (Dry-processed silica with an average particle size of 200 nm, solid content concentration of 3.5%) Particles 2.15 parts by mass (Silica sol with average particle size of 40 nm, solid content concentration of 20% by mass) Surfactant 0.30 parts by mass (Fluorine-based, solid content concentration 10% by mass)

[0133] As shown in Table 5, in Experimental Example 1, the adhesion to the lens layer was not satisfactory because "X" was less than 2.0%. Also, the blocking resistance was not satisfactory because "b" exceeded 180 seconds.

[0134] (Experimental Example 2) An easy-to-adhere polyester film and various optical laminated polyester films were obtained in the same manner as in Example 1, except that the urethane resin was changed to (A-4).

[0135] (Experimental Example 3) An easily adhesive polyester film and various optical laminated polyester films were obtained in the same manner as in Example 1, except that the urethane resin was changed to (A-4) and the crosslinking agent to (B-2).

[0136] As shown in Table 5, in experimental examples 2 and 3, the "BA" was less than 0.5 at%, resulting in unsatisfactory hard court adhesion.

[0137] (Experimental Example 4) An easily adhering polyester film and an optical laminated polyester film were obtained in the same manner as in Example 1, except that the following coating agent was mixed with a mixed solvent of water and isopropanol, and the solid content ratio of the urethane resin solution (A-4) / crosslinking agent (B-1) was changed to 70 / 30. Urethane resin solution (A-4) 9.03 parts by mass Crosslinking agent (B-1) 3.38 parts by mass Particles 0.52 parts by mass (Dry-processed silica with an average particle size of 200 nm, solid content concentration of 3.5%) Particles 1.80 parts by mass (Silica sol with average particle size of 40 nm, solid content concentration of 30% by mass) Surfactant 0.30 parts by mass (Silicone-based, solid content concentration 10% by mass)

[0138] As shown in Table 5, in Experimental Example 4, the haze was not satisfactory because "cb" exceeded 300 seconds.

[0139] (Experimental Example 5) An easily adhering polyester film and various optical laminated polyester films were obtained in the same manner as in Example 1, except that the following coating agent was mixed with a mixed solvent of water and isopropanol, and the solid content ratio of the urethane resin solution (A-4) / crosslinking agent (B-1) was changed to 20 / 80. Urethane resin solution (A-4) 2.58 parts by mass Crosslinking agent (B-1) 9.00 parts by mass Particles 0.52 parts by mass (Dry-processed silica with an average particle size of 200 nm, solid content concentration of 3.5%) Particles 1.80 parts by mass (Silica sol with average particle size of 40 nm, solid content concentration of 30% by mass) Surfactant 0.30 parts by mass (Silicone-based, solid content concentration 10% by mass)

[0140] As shown in Table 5, in Experiment Example 5, the haze was not satisfactory because "cb" exceeded 300 seconds.

[0141] (Experimental Example 6) An easily adhesive polyester film and various optical laminated polyester films were obtained in the same manner as in Example 5, except that the urethane resin was changed to (A-2) and the crosslinking agent to (B-3).

[0142] As shown in Table 5, in Experimental Example 6, the "BA" content was less than 0.5 at%, resulting in unsatisfactory blocking resistance and hard court adhesion.

[0143] (Experimental Example 7) An easy-to-adhere polyester film and an optical laminated polyester film were obtained in the same manner as in Example 5, except that the urethane resin was changed to (A-6).

[0144] As shown in Table 5, in Experiment Example 7, the percentage of "X" was less than 2.0%, indicating that the adhesion to the lens layer was not entirely satisfactory.

[0145] The evaluation method used in this invention is described below.

[0146] (1) Hayes The haze of the obtained easy-to-adhere polyester film was measured using a turbidimeter (NDH5000, manufactured by Nippon Denshoku) in accordance with JIS K 7136:2000.

[0147] (2) Blocking resistance Two film samples were placed on top of each other with their coated surfaces facing each other, a load of 98 kPa was applied, and they were left in contact for 24 hours in a 50°C atmosphere. After that, the films were peeled off, and the peeling state was judged according to the following criteria. ○: The coating layer does not shift and can be easily peeled off. △: The coating layer is maintained, but the surface layer of the coating layer has partially transferred to the mating surface. ×: Two films are stuck together and cannot be separated, or even if they can be separated, the film substrate is cleaved.

[0148] (3) Adhesion Using a cutter guide with a 2mm gap spacing, 100 grid-like cuts were made in the optical functional layer of the obtained optical laminated polyester film, penetrating the optical functional layer and reaching the base film. Next, cellophane adhesive tape (Nichiban, No. 405; 24mm wide) was applied to the grid-like cut surfaces and rubbed with an eraser to ensure complete adhesion. After that, the cellophane adhesive tape was peeled vertically from the optical functional layer surface of the optical laminated polyester film five times. The number of grids that peeled off from the optical functional layer surface of the optical laminated polyester film was then visually counted, and the adhesion between the optical functional layer and the film base was calculated using the following formula. Note that grids that are only partially peeled off are also counted as peeled grids. An adhesion of 95% is considered acceptable. Adhesion (%) = (1 - number of peeled squares / 100) × 100

[0149] (4) Measurement of elemental distribution in the depth direction The elemental distribution in the depth direction of the coated layer was measured by X-ray photoelectron spectroscopy (ESCA). An Ar cluster, which is expected to cause 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 acquisition at each etching time was performed in snapshot mode, which allows for short-duration evaluation. For evaluation purposes, spectral acquisition was performed every 30 seconds up to 120 seconds of etching, and every 60 seconds thereafter. Details of the measurement conditions are shown below. Background removal was performed using the Shirley method during analysis. ·Equipment: K-Alpha + (Manufactured by Thermo Fisher Scientific) • Measurement conditions Excitation X-rays: Monochromatized Al Kα rays X-ray output: 12 kV, 2.5 mA Photoelectron escape angle: 90° Spot size: 200 μmφ Path energy: 150 eV (Snapshot mode) Ion gun acceleration voltage: 6kV Cluster size: Large Etching rate: 10 nm / min (polystyrene equivalent) ※ Sample rotation during etching: Yes (For the etching rate calculation, monodisperse polystyrene with a molecular weight Mn:91000 (Mw / Mn=1.05) was dissolved in toluene, and then a 155 nm thick film was fabricated on a silicon wafer by spin coating.)

[0150] Based on the data evaluated in this way, a nitrogen distribution curve is drawn with the etching time from the coated layer surface on the horizontal axis and the ratio of the amount of nitrogen atoms to the total amount of carbon atoms, oxygen atoms, nitrogen atoms, and silicon atoms (nitrogen atom ratio) on the vertical axis. The nitrogen distribution curves for the easily adhering polyester film samples (Examples 2, 5, and Experimental Example 6) are shown in Figures 1, 3, and 4, respectively. The method for determining the characteristic values ​​of the present invention will be explained using Figure 2, based on the nitrogen distribution curve of Example 2 shown in Figure 1. As shown in Figure 2, the nitrogen atom ratio on the coated layer surface opposite to the polyester film substrate is read as A (at%), the maximum value of the nitrogen atom ratio is read as B (at%), the etching time at which the nitrogen atom ratio reaches the maximum value B (at%) is read as b (seconds), and the etching time at which the nitrogen atom ratio becomes 1 / 2B (at%) after b (seconds) is read as c (seconds), and BA (at%) and cb (seconds) are calculated. The nitrogen atom ratio on the coated layer surface opposite to the polyester film substrate refers to the nitrogen atom ratio at etching time 0 (seconds) in the figure. (Note that the "s" in "etching time s" on the horizontal axis in Figures 1-4 represents the unit "second".)

[0151] (5) Measurement of the OCOO bond ratio in the surface region The ratio of OCOO bonding in the surface region (X) was evaluated by X-ray photoelectron spectroscopy (ESCA). Place K-Alpha + (Thermo Fisher Scientific) was used. Details of the measurement conditions are as follows: The results were shown. Background noise was removed using the Shirley method during the analysis. Furthermore, X was calculated as the average of three or more measurement results. • Measurement conditions Excitation X-rays: Monochromatized Al Kα rays X-ray output: 12 kV, 6 mA Photoelectron escape angle: 90° Spot size: 400 μmφ Pass energy: 50 eV Step: 0.1eV Energy resolution: FWHM = 0.75 eV for Ag3d(5 / 2) spectrum Figures 5 and 6 are graphs showing the analysis results of the C1s spectra of the surface regions of the easily adhering polyester films in Example 6 and Experimental Example 1, respectively. The solid gray lines represent the measured C1s spectra. The peaks of the obtained measured spectra were separated into multiple peaks, and the bond species corresponding to each peak were identified from the position and shape of each peak. Furthermore, curve fitting was performed on the peaks derived from each bond species, and the peak area was calculated. The bond species of each peak (1) to (6) that may appear are shown in Table 3.

[0152] [Table 3]

[0153] The sum of the peak areas derived from each coupling species in the C1s spectral region refers to the sum of the peak areas of peaks (1) to (6), while the peak area derived from the OCOO coupling refers to the sum of the peak areas of peak (5). This refers to the peak area. When the sum of the peak areas derived from each binding species in the C1s spectral region is taken as 100%, X(%) represents the percentage of the area of ​​peak (5).

[0154] Table 4 shows the peak area calculation results for peaks (1) to (6) in Example 6 and Experimental Example 1. As mentioned above, the percentage data for peak (5) is X(%). Peaks (3) and (6) in Example 6, and peaks (3) and (5) in Experimental Example 1 did not appear.

[0155] [Table 4]

[0156] (6) Method for measuring the number-average molecular weight of polycarbonate polyols When a urethane resin with a polycarbonate structure is measured by proton nuclear magnetic resonance spectroscopy (1H-NMR), a peak originating from a methylene group adjacent to the OCOO bond is observed around 4.1 ppm. Furthermore, at a magnetic field approximately 0.2 ppm higher than this peak, a peak originating from a methylene group adjacent to the urethane bond formed by the reaction between polyisocyanate and polycarbonate polyol is observed. The number-average molecular weight of the polycarbonate polyol was calculated from the integral values ​​of these two peaks and the molecular weights of the monomers constituting the polycarbonate polyol.

[0157] Table 5 summarizes the evaluation results for each example and experimental case.

[0158] [Table 5] [Industrial applicability]

[0159] The easily adhering polyester film of the present invention exhibits excellent adhesion to hard coat layers, light diffusion layers, lens layers, anti-glare layers, and transparent conductive layers, making it particularly suitable for optical applications. It is also suitable as a base film for optical functional films such as hard coat films and lens sheets using the film, which are mainly used in displays and the like.

Claims

1. An optical laminated polyester film having an easy-to-adhere polyester film having a coating layer on at least one surface of a polyester film substrate, wherein at least one optical functional layer selected from a hard coat layer, a light diffusion layer, a lens layer, an anti-glare layer, and a transparent conductive layer is laminated on the coating layer, The coating layer is formed by curing a composition containing a urethane resin having a polycarbonate structure, a crosslinking agent, and a polyester resin. The urethane resin having the polycarbonate structure contains a polycarbonate polyol. The number-average molecular weight of polycarbonate polyols is 500 to 1800. The polyester resin is a copolymerized polyester resin containing an aromatic dicarboxylic acid component, wherein the aromatic dicarboxylic acid component includes a component selected from sulfoterephthalic acid, 5-sulfoisophthalic acid, 4-sulfonaphthalene-2,7-dicarboxylic acid, 5-(4-sulfophenoxy)isophthalic acid, and salts thereof. In the nitrogen element distribution curve based on depth-direction elemental distribution measurements of the coated layer by X-ray photoelectron spectroscopy, when A (at%) is the nitrogen atom ratio on the coated layer surface opposite the polyester film substrate, B (at%) is the maximum nitrogen atom ratio, b (seconds) is the etching time at which the nitrogen atom ratio reaches the maximum value B (at%), and c (seconds) is the etching time at which the nitrogen atom ratio becomes 1 / 2B (at%) after b (seconds), the following equations (i) to (iii) are satisfied, and, An optical laminated polyester film that satisfies the following equation (iv) when the total peak area originating from each bond type in the C1s spectral region is set to 100% and the peak area originating from the OCOO bond is set to X% in the surface analysis spectrum measured by X-ray photoelectron spectroscopy. (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

2. The optical laminated polyester film according to claim 1, wherein the haze of the easily adhering polyester film is 1.5% or less.

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