JP6658219B2 - Polyester resin for primer, polyester-based aqueous liquid for primer, polyester film with primer layer, laminated film, and method for producing polyester resin for primer - Google Patents

Description

  The present invention relates to a polyester-based resin for a primer, a polyester-based aqueous liquid for a primer, a polyester film with a primer layer, a laminated film, and a method for producing a polyester-based resin for a primer. It relates to a polyester resin for a primer that has excellent adhesion to both of the hard coat layers, especially excellent in wet heat and heat adhesion, and that can form a coating having a high refractive index, and also has excellent aqueous liquid stability. is there.

  Conventionally, polyester films have been used in various industrial fields such as packaging materials, magnetic cards, and printing materials. As the polyester film, for example, a thermoplastic polyester such as polyethylene terephthalate (PET) or a copolymer of these, and other resins mixed with other resins, if necessary, is melt-extruded and molded, and then biaxially stretched. A heat-fixed one is used. Such a polyester film is excellent in various physical properties such as mechanical strength, heat resistance, chemical resistance and the like, but its surface is highly crystallographically oriented, for example, adhesion to paints, adhesives, inks, etc. There is a problem of poor sex.

  For this reason, conventionally, an aqueous liquid (solution or dispersion) of a polyester-based resin is applied to the surface of a polyester film, and a film formed by forming a film is provided as a primer layer to improve adhesion to a paint or the like. Improvements have been made.

  When used as such a primer layer, water resistance, solvent resistance, wet heat resistance and the like are required. For example, Patent Document 1 does not contain isophthalic acid as an acid component, and does not contain terephthalic acid. An aqueous dispersion of a polyester resin containing 95 to 100 mol% of an acid and 25 to 80 mol% of an alkylene oxide derivative of a bisphenol as an alcohol component is disclosed. In addition to water resistance and solvent resistance, bending resistance is disclosed. It is described that a film having excellent properties can be obtained.

JP 2012-072308 A

  However, since terephthalic acid has high crystallinity, the water solubility or water dispersibility of the polyester-based resin is reduced depending on the composition in the technique of Patent Document 1, and the resin may be precipitated.

  Further, a hard coat film obtained by laminating a hard coat layer on a polyester film is used for optical applications and the like because of its excellent hardness and scratch resistance. Although a primer layer is provided between the polyester film and the hard coat layer also in such a hard coat film, when a primer layer is formed using a polyester resin having poor stability when used as an aqueous liquid, It was difficult to use such a hard coat film in optical applications, because the transparency of the obtained film was lowered, and the film was uneven and the visibility was lowered. Furthermore, in the hard coat film, there is a problem that iris-like reflection occurs due to a difference between the refractive index of the primer layer and the refractive index of the polyester film and the hard coat layer, thereby hindering visibility. .

  Under such circumstances, the present invention has excellent adhesion to both a polyester film and a hard coat layer formed from, for example, an active energy ray-curable resin composition, particularly in a high humidity heat environment. It is an object of the present invention to provide a polyester resin for a primer, which has excellent adhesion even underneath, has a high refractive index, has good visibility, and has excellent stability of an aqueous liquid.

  However, the present inventor has conducted intensive studies in view of such circumstances, and as a result, in a polyester resin comprising a polyvalent carboxylic acid component (A) and a polyol component (B), terephthalic acid (a1) is indispensable as a polyvalent carboxylic acid. By containing a large amount of a glycol compound (b1) having a bisphenol skeleton as a polyol and controlling the acid value within a specific range, the wet heat and heat resistance can be maintained without lowering the refractive index. Was improved, and it was found that a polyester resin for a primer which solved the above problem was obtained, and the present invention was completed.

That is, the gist of the present invention is a polyester resin comprising a polyvalent carboxylic acid component (A) and a polyol component (B), wherein terephthalic acid (a1) is added to the entire polyvalent carboxylic acid component (A). 20 to 80 mol% or more, and based on the whole polyol component (B), the glycol compound (b1) having a bisphenol skeleton is contained in an amount of 60 mol% or more, and the acid value is 15 mgKOH / g or more. The present invention relates to a characteristic polyester resin for a primer.

  Further, in the present invention, a polyester-based aqueous liquid for the primer, wherein the polyester-based resin for the primer is dissolved or dispersed in an aqueous solvent, a polyester film with a primer layer, a polyester film, a primer layer, and a hard coat layer were laminated. It also provides a method for producing a laminated film and a polyester resin for a primer.

  According to the present invention, when used as a primer, the polyester film and, for example, excellent adhesion to both the hard coat layer formed from the active energy ray-curable resin composition, particularly excellent in wet heat resistance, In addition, a polyester resin and a polyester aqueous liquid capable of forming a coating having a high refractive index can be obtained. Therefore, it is very useful as a primer resin for providing a hard coat layer on a polyester resin substrate such as a polyester film.

  Hereinafter, the present invention will be described in detail, but these are merely examples of desirable embodiments. In the present invention, the term "carboxylic acid" includes carboxylic acid salts, carboxylic acid anhydrides, carboxylic acid halides, carboxylic acid esters, and the like.

<Polyester resin>
The polyester resin for a primer of the present invention is obtained by copolymerizing a copolymer component containing a polyvalent carboxylic acid component (A) and a polyol component (B).

[Polyvalent carboxylic acid component (A)]
The polycarboxylic acid component (A) used in the present invention contains terephthalic acid (a1) as an essential component.

Specific examples of terephthalic acid (a1) include, for example, terephthalic acid and its ester-forming derivative. These can be used alone or in combination of two or more.
Of these, terephthalic acid is preferably used from the viewpoint of reactivity.

  In the present invention, it is necessary to contain the terephthalic acid (a1) in the range of 20 to 80 mol%, preferably 25 to 70 mol%, and more preferably 30 to 80 mol% based on the whole polyvalent carboxylic acid component (A). ６５65 mol%, especially 35-60 mol%. If the content of terephthalic acid (a1) is too small relative to the entire polyvalent carboxylic acid component (A), the wet heat adhesion to the hard coat layer is reduced, and the object of the present invention cannot be achieved. If the amount is too large, the stability of the aqueous liquid of the obtained polyester resin is lowered, and the object of the present invention cannot be achieved.

Examples of the divalent carboxylic acid component other than terephthalic acid (a1) that can be used in the present invention include:
Aromatic dicarboxylic acids such as isophthalic acid, benzylmalonic acid, diphenic acid and 4,4'-oxydibenzoic acid;
Malonic acid, dimethylmalonic acid, succinic acid, glutaric acid, adipic acid, trimethyladipic acid, pimelic acid, 2,2-dimethylglutaric acid, azelaic acid, sebacic acid, fumaric acid, maleic acid, itaconic acid, thiodipropionic acid Dicarboxylic acids such as diglycolic acid;
Alicyclics such as 1,3-cyclopentanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid, 1,3-cyclopentanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 2,5-norbornanedicarboxylic acid, and adamantanedicarboxylic acid Dicarboxylic acid;
And their salts, ester-forming derivatives, acid anhydrides and the like.
These can be used alone or in combination of two or more.
Among these, it is preferable to use an aromatic carboxylic acid from the viewpoint of the refractive index, particularly preferably an aromatic dicarboxylic acid, and more preferably isophthalic acid from the viewpoint of stability when used as an aqueous liquid.

  The content ratio of the divalent carboxylic acid component other than the terephthalic acid (a1) in the polyvalent carboxylic acid component (A) is preferably 10 to 70 mol%, more preferably 10 to 70 mol%, based on the entire polyvalent carboxylic acid component (A). Preferably it is 20 to 60 mol%. If the content of the other divalent carboxylic acid is too small, the polyester resin tends to gel easily in the production process.

  Incidentally, for the purpose of increasing the branch point in the polyester resin, a trivalent or higher polycarboxylic acid can be used in a small amount, and as the trivalent or higher carboxylic acid, trimellitic acid, pyromellitic acid, adamantane tricarboxylic acid, Trimesic acid and the like, and salts, ester-forming derivatives and acid anhydrides thereof.

  Further, in the present invention, a polyvalent carboxylic acid component in that it has a function as a chain extender, a function as a hydrophilicity imparting agent, and a function of forming a reaction point with a crosslinking agent described later in the polyester resin. As (A), it is preferable to contain a carboxylic anhydride (a2) having two or more carboxylic anhydride structures (hereinafter sometimes referred to as “carboxylic anhydride (a2)”).

  The carboxylic anhydride (a2) having two or more carboxylic anhydride structures may be any one having at least two carboxylic anhydride structures.

Specific examples of the carboxylic anhydride (a2) include, for example,
1,2,4,5-benzenetetracarboxylic dianhydride (pyromellitic anhydride), 3,3 ′, 4,4′-benzophenonetetracarboxylic dianhydride, 4,4-oxydiphthalic dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, ethylene glycol bistrimellitate dianhydride, 2,2 ', 3,3' Aromatic carboxylic anhydrides such as diphenyltetracarboxylic dianhydride, 2,2 ', 3,3'-diphenylsulfonetetracarboxylic anhydride and thiophene-2,3,4,5-tetracarboxylic dianhydride object;
1,2,3,4-cyclobutanetetracarboxylic dianhydride, 5- (2,5 dioxotetrahydrofuryl) -3-methyl-3-cyclohexene-1,2-dicarboxylic anhydride, 5- (2 Alicyclic carboxylic anhydrides such as 5-dioxotetrahydrofuryl) -3-cyclohexene-1,2-dicarboxylic anhydride, cyclopentanetetracarboxylic dianhydride;
Aliphatic carboxylic anhydrides such as ethylenetetracarboxylic dianhydride, 1,2,3,4-butanetetracarboxylic dianhydride, 1,2,3,4-pentanetetracarboxylic dianhydride; No.
These can be used alone or in combination of two or more.

  Among these, tetracarboxylic dianhydride is preferred because it is unlikely to cause gelation during resin production. Among them, 1,2,4,5-benzenetetracarboxylic dianhydride (pyromellitic anhydride) and 5-carboxylic acid are preferred. (2,5-dioxotetrahydrofuryl) -3-methyl-3-cyclohexene-1,2-dicarboxylic anhydride, 5- (2,5-dioxotetrahydrofuryl) -3-cyclohexene-1,2-dicarboxylic acid Acid anhydrides and the like are preferably used.

  The content ratio of the carboxylic acid anhydride (a2) in the polyvalent carboxylic acid component (A) is preferably 3 to 25 mol%, particularly preferably 4 to 20%, based on the whole polyvalent carboxylic acid component (A). It is preferably from 5 to 15 mol%, more preferably from 6 to 10 mol%. If the content is too low, the water dispersibility of the obtained polyester resin tends to decrease, and if the content is too high, gelation occurs during the manufacturing process or the wet heat resistance to the hard coat layer decreases. Tend to.

  In the present invention, it is preferable not to use a polyvalent carboxylic acid having a sulfonic acid group from the viewpoint of wet heat resistance.

  Further, from the viewpoint of improving the water dispersibility, a small amount of a polycarboxylic acid having a sulfonic acid group may be contained. It is preferably at most 10 mol%, more preferably at most 5 mol%, further preferably at most 3 mol%, particularly preferably at most 1 mol%. Examples of the polyvalent carboxylic acid having a sulfonate group include 5-sulfoisophthalic acid, 2-sulfoisophthalic acid, 4-sulfoisophthalic acid, sulfoterephthalic acid, 4-sulfonaphthalene-2,6-dicarboxylic acid, and these. Alkali metal salts are mentioned. One kind selected from these polycarboxylic acids having a sulfonate group may be used, or two or more kinds may be used in combination. From the viewpoint of availability, 5-sulfoisophthalic acid, dimethyl 5-sulfoisophthalate and alkali metal salts thereof are preferred.

[Polyol component (B)]
The polyol component (B) used in the present invention contains a glycol compound (b1) having a bisphenol skeleton as an essential component.

  Specific examples of the glycol compound (b1) having a bisphenol skeleton include, for example, bisphenol A, bisphenol B, bisphenol E, bisphenol F, bisphenol AP, bisphenol BP, bisphenol P, bisphenol PH, bisphenol S, bisphenol Z, 4,4 '-Dihydroxybenzophenone and their ethylene oxide and propylene oxide adducts. These can be used alone or in combination of two or more.

  Among these, it is preferable to use those not having a carbon-oxygen double bond such as a carbonyl group or a sulfur-oxygen double bond such as a sulfonyl group from the viewpoint of wet heat adhesion, and further, bisphenol A from the viewpoint of the refractive index. , Bisphenol E, bisphenol F, bisenol AP, bisphenol BP, and bisphenol PH are preferably 2 to 3 moles of ethylene oxide adduct, and particularly preferably bisphenol A is 2 mol of ethylene oxide adduct.

  In the present invention, it is necessary to contain the glycol compound (b1) having a bisphenol skeleton in an amount of 60 mol% or more based on the whole polyol component (B), preferably 70 to 100 mol%, particularly preferably 80 to 98. Mol%, more preferably 90 to 97 mol%. If the content of the glycol compound (b1) having a bisphenol skeleton with respect to the whole polyol component (B) is too small, a sufficient refractive index cannot be obtained or the wet heat resistance decreases, thereby achieving the object of the present invention. Can not.

  In the present invention, in order to further improve the refractive index, as the glycol compound (b1) having a bisphenol skeleton, a compound having a fluorene ring, for example, bisphenoxyethanol fluorene can be used. The content of the glycol compound having a bisphenol skeleton having a fluorene ring is preferably 50 mol% or less, and more preferably 40 mol% or less, based on the entire glycol compound having a bisphenol skeleton (b1) from the viewpoint of resistance to wet heat. It is preferably at most 35 mol%, more preferably at most 30 mol%.

  In the present invention, in addition to the above-mentioned glycol compound (b1) having a bisphenol skeleton, another polyol component having two or more valences may be further contained as the polyol component (B).

Examples of the polyol component (B) other than the glycol compound having a bisphenol skeleton (b1) that can be used in the present invention include:
Ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, 1,3-propanediol, 2,4-dimethyl-2-ethylhexane-1,3-diol, 2-methyl-1,3-propanediol 2,2-dimethyl-1,3-propanediol (neopentyl glycol), 2-ethyl-2-butyl-1,3-propanediol, 2-ethyl-2-isobutyl-1,3-propanediol, , 3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, 2,2,4-trimethyl-1,6- Aliphatic diols such as hexanediol;
1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, spiroglycol, tricyclodecanedimethanol, adamantanediol, 2,2,4,4-tetramethyl-1,3 Alicyclic diols such as cyclobutanediol;
4,4'-thiodiphenol, 4,4'-methylenediphenol, 4,4'-dihydroxybiphenyl, o-, m- and p-dihydroxybenzene, 2,5-naphthalenediol, p-xylenediol and the like And dihydric alcohols such as ethylene oxide and propylene oxide adducts.
These can be used alone or in combination of two or more.

  Among these, from the viewpoints of reactivity, refractive index, and wet heat resistance, aliphatic diols such as ethylene glycol, 1,3-propanediol, 2-methyl-1,3-propanediol, neopentyl glycol, It is preferable to use 4-butanediol, 1,5-pentanediol, 1,6-hexanediol, and alicyclic diols such as 1,2-cyclohexanedimethanol, 1,3cyclohexanedimethanol, and 1,4cyclohexanedimethanol. And more preferably an aliphatic diol, particularly preferably ethylene glycol, 1,6-hexanediol or neopentyl glycol.

  Further, the above trihydric or higher polyhydric alcohols can also be used. Examples of the trihydric or higher polyhydric alcohol include pentaerythritol, dipentaerythritol, tripentaerythritol, glycerin, trimethylolpropane, trimethylolethane, , 3,6-hexanetriol, adamantanetriol and the like.

  In the present invention, it is preferable to use a glycol compound (b1) having a bisphenol skeleton and another divalent or higher polyol component in combination from the viewpoint of reactivity when producing a polyester resin.

  The content ratio of the polyol component (B) in the polyol component (B) other than the glycol compound (b1) having a bisphenol skeleton is preferably from 0 to 40 mol%, more preferably from 2 to 20 mol%, based on the entire polyol component (B). Mol%, particularly preferably 3 to 10 mol%. If the content of the polyol component other than the glycol compound having a bisphenol skeleton (B1) is too large, a sufficient refractive index cannot be obtained, or the wet heat resistance to the hard coat layer tends to be reduced.

(Production method of polyester resin)
The polyester resin for a primer of the present invention is obtained by copolymerizing a copolymer component containing the above-mentioned polyvalent carboxylic acid component (A) and polyol component (B), and the production method is not particularly limited. Is obtained by copolymerizing a hydroxyl group-containing prepolymer obtained by copolymerizing a polyvalent carboxylic acid component (A) excluding a carboxylic anhydride (a2) having two or more carboxylic anhydride structures and a polyol component (B) with a carboxylic acid. It is preferable to produce by a method of extending a chain with a carboxylic anhydride (a2) having two or more anhydride structures.

  In this case, first, a predetermined amount of the polycarboxylic acid component (A) excluding the carboxylic anhydride (a2) and the polyol component (B) are mixed without solvent. At this time, the mixing ratio (molar ratio) of the polyvalent carboxylic acid component (A) excluding the carboxylic anhydride (a2) and the polyol component (B) was such that the polyol (B) was mixed with 1 mol of the polyol (A). Component (B) is preferably used in an amount of 1.03 to 1.3 mol, particularly preferably 1.05 to 1.15 mol, and more preferably 1.06 to 1.1 mol.

  This mixture is charged into an appropriate reactor, and is usually heated to 170 to 260 ° C., so that an esterification reaction or a transesterification reaction is allowed to proceed while distilling off water or methanol as a by-product. Produce a polymer.

  Furthermore, a polyester resin can be obtained by extending the chain of the hydroxyl-containing prepolymer by a ring-opening addition reaction using a carboxylic anhydride (a2).

  When the hydroxyl group-containing prepolymer is chain-extended with a carboxylic anhydride (a2) having two or more carboxylic anhydride structures, it is usually 230 ° C or lower, preferably 150 to 210 ° C, particularly preferably 165 to 200 ° C. The reaction can be carried out at ℃. A solvent is not necessarily required for the above reaction, but if the viscosity of the reactant at the above temperature is too high, an appropriate solvent can be used as appropriate to facilitate stirring.

  Examples of such a solvent include ketone solvents such as acetone, methyl ethyl ketone and methyl isobutyl ketone; aromatic solvents such as benzene, toluene, xylene, mesitylene and pseudocumene; amide solvents such as dimethylformamide and dimethylacetamide. . In addition, it is preferable not to use a solvent that may react with the polyester resin, such as an ester solvent and an alcohol solvent.

In the above reaction, an esterification catalyst, a transesterification catalyst, other polymerization catalysts and the like can be appropriately blended, and for example, tetrabutoxytitanium can be used. Further, various additives such as other stabilizers may be used.
Thus, the polyester resin of the present invention can be obtained by the above-described method.

The number average molecular weight of the polyester resin thus obtained is preferably 4,000 to 20,000, more preferably 4,500 to 17,000, and particularly preferably 5,000 to 15,000. If the number average molecular weight of the polyester-based resin is too large, the initial adhesion to the polyester-based resin base material or the hard coat layer tends to be reduced, and water dispersion tends to be difficult. On the other hand, when the number average molecular weight is too small, the wet heat resistance to the hard coat layer tends to decrease.
The weight-average molecular weight is a weight-average molecular weight in terms of standard polystyrene molecular weight, and the column: TSKgel SuperMultipore HZ-M (exclusion limit molecular weight: 2) was applied to high-performance liquid chromatography (“HLC-8320GPC” manufactured by Tosoh Corporation). × 10 ⁶ , theoretical plate number: 16,000 plates / strand, filler material: styrene-divinylbenzene copolymer, filler particle size: 4 μm).

The glass transition temperature (Tg) of the polyester resin used in the present invention is preferably from 60 to 110 ° C, more preferably from 65 to 100 ° C, and particularly preferably from 70 to 90 ° C. If the glass transition temperature is too high, the initial adhesion to the hard coat layer and the resistance to wet heat are reduced, or a resin aqueous solution is applied to a polyester film, cracks occur during drying and during stretching of the polyester film with the resin coating. It tends to occur and cause haze. On the other hand, if the glass transition temperature is too low, the refractive index, the initial adhesion to the hard coat layer and the wet heat resistance tend to decrease.
The glass transition temperature (Tg) of the polyester resin is measured using a differential scanning calorimeter DSC Q20 manufactured by TA Instruments.

The acid value of the polyester resin used in the present invention must be 15 mgKOH / g or more, preferably 15 to 40 mgKOH / g, more preferably 15 to 35 mgKOH / g, particularly 17 to 30 mgKOH / g, Particularly, it is preferably 18 to 25 mgKOH / g. If the acid value is too low, the water dispersibility decreases, or the wet heat resistance to the hard coat layer decreases due to insufficient crosslinking points with the crosslinking agent, and the object of the present invention cannot be achieved. On the other hand, when the acid value is too high, the hydrophilicity is increased, and the wet heat resistance to the hard coat layer tends to decrease.
The acid value of the polyester resin is determined by dissolving 0.5 g of the polyester resin in a mixed solvent of 7/3 (toluene / methanol (volume ratio)) of toluene and methanol, and performing a neutralization titration based on JIS K0070. It is.

The refractive index of the polyester resin used in the present invention is preferably 1.58 or more, particularly preferably 1.585 to 1.615, and further preferably 1.59 to 1.605. If the refractive index is too high, there is a tendency that the wet heat resistance decreases, cracks occur during application and drying of the aqueous resin solution on the polyester film, and when the polyester film with the resin film is stretched, resulting in haze. On the other hand, if it is too low, iris-like reflection due to the difference between the refractive index of the polyester film and the refractive index of the hard coat layer occurs when the hard coat is laminated, and the visibility tends to decrease.
In addition, the refractive index mentioned here is a refractive index with respect to a D line (589 nm) at 20 ° C., and is measured using an Abbe refraction system DR-M4 manufactured by Atago Co., Ltd.

  The polyester-based resin of the present invention may contain, if necessary, an antioxidant such as a hindered phenol, a heat stabilizer, a glass fiber, an inorganic or organic filler, a colorant, a flame retardant, a softener, a dispersant, and a wetting agent. An agent, an emulsifier, a gelling agent, an antifoaming agent, another thermoplastic resin, and the like can be blended to such an extent that the effects of the present invention are not impaired, and used as a polyester resin composition.

<Polyester-based aqueous liquid>
The polyester-based aqueous liquid for a primer of the present invention is obtained by dissolving or dispersing the polyester-based resin obtained as described above in an aqueous solvent. Hereinafter, dissolving or dispersing in an aqueous solvent is referred to as “water dissolution or dispersion”.
In general, a method in which a polyester-based resin is neutralized with a neutralizing agent and dissolved or dispersed in an aqueous solvent to obtain a polyester-based aqueous liquid is preferable.

  The neutralizing agent is not particularly limited as long as it can neutralize the carboxyl group of the polyester resin. For example, lithium hydroxide, potassium hydroxide, metal hydroxide such as sodium hydroxide; ethylamine; Diethylamine, triethylamine, propylamine, isopropylamine, iminobispropylamine, 3-ethoxypropylamine, 3-diethylaminopropylamine, diethanolamine, triethanolamine, N, N-diethylethanolamine, N, N-dimethylethanolamine, amino Organic amines such as ethanolamine, morpholine, N-methylmorpholine and N-ethylmorpholine; and ammonia. One kind selected from these neutralizing agents may be used, or two or more kinds may be used in combination.

  Among these neutralizing agents, those having a boiling point of 150 ° C. or lower are preferred from the viewpoint of easy volatilization by drying and the water resistance of the obtained film. In particular, ammonia, diethylamine, and triethylamine are preferable in terms of high versatility, low boiling point, and easy volatilization during drying, and triethylamine and ammonia are particularly preferable in that the dispersion stability of the polyester resin is particularly excellent.

  Examples of the aqueous solvent include water or a mixture of water and a suitable hydrophilic organic solvent. Examples of the hydrophilic organic solvent include ketones such as acetone; alcohols such as methanol, ethanol, and isopropyl alcohol; glycol ethers such as ethylene glycol monomethyl ether, ethylene glycol monobutyl ether, and ethylene glycol monotertiary butyl ether; What can be mixed with water is mentioned. In particular, it is preferable to use ethylene glycol monobutyl ether, ethylene glycol monotertiary butyl ether, and isopropyl alcohol. When a hydrophilic organic solvent is used, the proportion of the polyester-based aqueous liquid to the whole is appropriately set. For example, it can be set in the range of 0 to 20% by weight, but the ratio of the hydrophilic organic solvent to the whole aqueous liquid is not limited to the above range. One kind selected from these aqueous solvents may be used, or two or more kinds may be used in combination.

  In the present invention, it is preferable that a polyester-based aqueous liquid contains a crosslinking agent from the viewpoint of improving adhesion. Such a crosslinking agent may be any compound containing a functional group having a reactivity with a functional group contained in the polyester resin, and for example, containing a functional group having a reactivity with a hydroxyl group or a carboxyl group in the polyester resin. Is used.

  The cross-linking agent may be any compound containing a functional group having reactivity with a functional group contained in the polyester-based resin, such as a compound having an epoxy group, an oxazoline group, a carbodiimide group, an amino group, or an isocyanate group. , Aziridine compounds, melamine compounds and the like. Among them, a compound having a carbodiimide group and an isocyanate group and a melamine compound are preferable.

  Examples of the compound having an epoxy group include bisphenol A / epichlorohydrin type epoxy resin and sorbitol polyglycidyl ether (for example, “Denacol EX-611”, “Denacol EX-612”, and “Denacol EX-” manufactured by Nagase ChemteX Corporation). 614 "," Denacol EX-614B "," Denacol EX-622 ", etc.), polyglycerol polyglycidyl ether (for example," Denacol EX-512 "," Denacol EX-521 "manufactured by Nagase ChemteX Corporation), pentane Erythritol polyglycidyl ether (eg, “Denacol EX-411” manufactured by Nagase ChemteX Corporation), diglycerol polyglycidyl ether (eg, “Denacol EX-421” manufactured by Nagase ChemteX Corporation), glycerol po Glycidyl ether (for example, "Denacol EX-313", "Denacol EX-314", manufactured by Nagase ChemteX Corporation), and trimethylolpropane polyglycidyl ether (for example, "Denacol EX-321" manufactured by Nagase ChemteX Corporation) Resorcinol diglycidyl ether (eg, “Denacol EX-201” manufactured by Nagase ChemteX Corporation), neopentyl glycol diglycidyl ether (eg, “Denacol EX-211” manufactured by Nagase ChemteX Corporation), 1,6 -Hexanediol diglycidyl ether (for example, "Denacol EX-212" manufactured by Nagase ChemteX Corporation), hydrogenated bisphenol A diglycidyl ether (for example, "Denacol EX-252" manufactured by Nagase ChemteX Corporation) , D Lenglycol diglycidyl ether (for example, "Denacol EX-810", "Denacol EX-811" manufactured by Nagase ChemteX Corporation), diethylene glycol diglycidyl ether (for example, "Denacol EX-850" manufactured by Nagase ChemteX Corporation), "Denacol EX-851"), polyethylene glycol diglycidyl ether (for example, "Denacol EX-821", "Denacol EX-830", "Denacol EX-832", "Denacol EX-841" manufactured by Nagase ChemteX Corporation) , "Denacol EX-861" or the like), propylene glycol diglycidyl ether (for example, "Denacol EX-911" manufactured by Nagase ChemteX Corporation), or polypropylene glycol diglycidyl ether (for example, manufactured by Nagase ChemteX Corporation) "Denacol EX-941", "Denacol EX-920", "Denacol EX-931" and the like. Among them, an aqueous type is preferred.

  Examples of the compound having an oxazoline group include addition-polymerizable 2-oxazoline (for example, 2-isopropenyl-2-oxazoline) having a substituent having an unsaturated carbon-carbon bond at the 2-position carbon and other unsaturated compounds. Copolymers with monomers and the like, and as commercial products, “Epocross WS-500”, “Epocross WS-700”, “Epocross K-2010E”, “Epocross K-2020E”, "Epocross K-2030E" and the like.

  The compound having a carbodiimide group may be a compound containing at least two or more carbodiimide groups. For example, "Carbodilite V-02", "Carbodilite V-02-L2", and "Carbodilite SV-" manufactured by Nisshinbo Chemical Inc. 02, "carbodilite V-10", "carbodilite V-04", "carbodilite V-06", "carbodilite E-01", "carbodilite E-02", "carbodilite E-04" and the like.

  Examples of the compound having an amino group include hexamethylenediamine, triethanolamine and the like.

  Examples of the compound having an isocyanate group include, for example, toluylene diisocyanate, 4,4′-diphenylmethane diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, metaxylylene diisocyanate, 1,5-naphthalene diisocyanate, hydrogenated diphenylmethane diisocyanate, hydrogenated toluene Isocyanate compounds such as diisocyanate, hydrogenated xylylene diisocyanate, isophorone diisocyanate, tetramethyl xylene diisocyanate and their blocked isocyanate compounds, “Aquanate 100”, “Aquanate 110”, “Aquanate 200”, “Aquanate 210” ( Self-emulsifying water such as Nippon Polyurethane Co., Ltd., "Elastron BN-77" (Daiichi Kogyo Seiyaku Co., Ltd.) Dispersed polyisocyanate compounds and the like can be mentioned. Among them, an aqueous dispersion type and a blocked isocyanate compound are preferred.

  The aziridine-based compound only needs to contain at least two or more aziridine groups, and examples thereof include "Chemiteite PZ-33" and "Chemiteite DZ-22E" (manufactured by Nippon Shokubai Co., Ltd.).

  Examples of the melamine-based compound include hexamethoxymethylol melamine and “Nikalac MW-30M”, “Nikarac MW-30”, “Nikarac MW-22”, “Nikarac MS-11”, “Nikarac MS-11” manufactured by Sanwa Chemical Co., Ltd. Methylated melamine resins such as “MS-011”, “Nicalak MX-730”, “Nicalak MX-750”, “Nicalack MX-706”, and “Nicalack MX-035”, “Nicalack MX-45”, “Nicalack MX-” 410 "and the like.

  As the crosslinking agent, one kind selected from these may be used, or two or more kinds may be used in combination.

  The content of the crosslinking agent can be appropriately selected depending on the amount of the functional group contained in the polyester-based resin, the molecular weight of the polyester-based resin, and the purpose of use. It is preferably from 50/50 to 90/10, particularly preferably from 60/40 to 85/15, more preferably from 65/35 to 75/25 parts by weight. If the proportion of the crosslinking agent is too large, the refractive index and the wet heat resistance to the hard coat layer tend to decrease, and if it is too small, the initial adhesion and the wet heat resistance to the hard coat layer tend to decrease.

The polyester-based aqueous liquid of the present invention may contain an anionic surfactant, a nonionic surfactant, and the like, if necessary. By blending the surfactant, the wettability to the polyester resin base material when applying the polyester aqueous liquid to the polyester resin base material such as a polyester film can be improved. Any appropriate surfactant can be used as the surfactant, for example, polyoxyethylene alkyl phenyl ether, polyoxyethylene fatty acid ester, sorbitan fatty acid ester, glycerin fatty acid ester, fatty acid metal soap, alkyl sulfate, alkyl sulfonate, Alkyl sulfosuccinate, dodecylbenzene sulfonate and the like can be mentioned. One type selected from these surfactants may be used, or two or more types may be used in combination.
In addition, it is preferable not to add a surfactant from the viewpoint of initial and wet heat resistance to the polyester resin base material and the hard coat layer.

  Further, the polyester-based aqueous liquid of the present invention may further contain an antistatic agent, a filler, an ultraviolet absorber, a lubricant, a coloring agent, and the like, if necessary.

  The concentration of the solid content of the polyester-based aqueous liquid of the present invention is appropriately adjusted so as to ensure good dispersibility of the polyester-based resin and to form a good film by coating and film formation. % By weight, particularly preferably 5 to 20% by weight.

  A polyester-based aqueous liquid containing the above-mentioned polyester-based resin is applied to a polyester-based resin base material such as a polyester film, and dried by heating to form a film (primer layer). A resin substrate can be obtained. The polyester film with the primer layer may be further stretched.

  As the polyester film, conventionally known appropriate ones can be used, and examples thereof include polyethylene terephthalate, polyethylene-2,6-naphthalate, polybutylene terephthalate, and copolymers obtained by copolymerizing other copolymer components with these. Films may be mentioned. This polyester film may be either unstretched or stretched, but it is preferable to use a stretched film, and it is particularly preferable to use a biaxially stretched film.

As the polyester film, a film manufactured by a conventionally known appropriate method can be used. For example, an unstretched polyester film can be obtained by melting and extruding a polyester as a raw material into a sheet and cooling it with a cooling drum.
Further, the unstretched polyester film is stretched in a uniaxial direction or a biaxial direction, and then heat-fixed, and if necessary, subjected to a heat relaxation treatment to obtain a uniaxially stretched film or a biaxially stretched film.

  An appropriate method can be adopted for coating and forming a polyester-based aqueous liquid on a polyester film. At this time, for example, on one or both sides of the unstretched film or the uniaxially stretched film, a polyester-based aqueous liquid is applied by an appropriate method such as kiss coat, reverse coat, gravure coat, die coat, etc. This film can be stretched into a biaxially stretched film. Alternatively, a polyester-based aqueous liquid may be applied to the secondary stretched film by an appropriate method, and then heated and dried to form a film. At this time, the coating amount of the polyester-based aqueous liquid is appropriately set, and for example, the thickness of the dried coating film is preferably 0.01 to 5 μm, particularly 0.01 to 2 μm, more preferably 0.01 to 1 μm, and particularly preferably 0.01 to 1 μm. Is preferably in the range of 0.05 to 0.15 μm.

  The thus-obtained polyester film with a primer layer is excellent in initial and wet heat and heat adhesion to a hard coat layer formed from, for example, an active energy ray-curable resin composition, has a high refractive index, and is used for optical applications. It also has good visibility when used.

  Examples of the hard coat layer provided on the polyester film via the primer layer include a polyfunctional (meth) acrylate compound, a urethane (meth) acrylate compound, and a mixture thereof.

The hard coat layer can be formed, for example, by applying an active energy ray-curable resin composition on the primer layer, drying it as necessary, and then irradiating it with an active energy ray to cure.
Examples of the coating method include a wet coating method such as spray, shower, gravure, dipping, roll, spin, screen printing and the like.
As the active energy rays, for example, light rays such as far ultraviolet rays, ultraviolet rays, near ultraviolet rays, and infrared rays, electromagnetic waves such as X-rays and γ-rays, as well as electron rays, proton rays, and neutron rays can be used.
The thickness of the hard coat layer (thickness after curing) is usually preferably 1 from the viewpoint of light transmission for uniformly reacting the photopolymerization initiator as an active energy ray-curable coating film and visibility. To 15 μm, particularly preferably 2 to 10 μm, and more preferably 3 to 5 μm.

  As described above, a laminated film having a layer structure of a polyester film, a primer layer containing a polyester resin for a primer, and a hard coat layer obtained by curing an active energy ray-curable resin composition can be obtained.

  The polyester resin for a primer of the present invention thus obtained has an initial and wet heat resistance to both the polyester resin substrate and the hard coat layer formed from, for example, the active energy ray-curable resin composition. It is very useful as a material for forming a primer layer having an excellent and high refractive index. Further, the polyester film with a primer layer is useful, for example, as a label sheet or a printing sheet, particularly a hard coat film, and various films and sheets that are used by providing a print layer or a hard coat layer on the film or sheet. It has good visibility especially when used for optical applications, and is useful as a base material for a protective film or an ITO film.

Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples as long as the gist of the present invention is not exceeded. In the examples, “%” and “parts” mean on a weight basis.
The number average molecular weight, glass transition temperature, acid value, and refractive index of the polyester-based resin were measured according to the methods described above.

<Example 1>
[Production of polyester resin [I-1] and its aqueous liquid]
116.2 parts (0.699 mol) of terephthalic acid, 77.4 parts (0.466 mol) of isophthalic acid, 381.2 parts (1.206 mol) of an ethylene oxide 2 mol adduct of bisphenol A, ethylene glycol 6 parts (0.058 mol) and 0.1 part of tetrabutoxytitanium as a catalyst were charged into a transesterification reactor, and the temperature was raised from 200 ° C. to 275 ° C. over 1 hour and 30 minutes in a nitrogen atmosphere. The esterification reaction was carried out at 275 ° C. until the addition was completed.
Next, after cooling to 190 ° C., 21.6 parts (0.099 mol) of pyromellitic anhydride were charged and reacted at 190 ° C. for 1 hour to obtain a polyester resin [I-1].
Table 1 shows the composition and physical properties of the obtained polyester resin.
In addition, in Table 1, the numerical value of each compound in the column of the polyvalent carboxylic acid component (A) and the polyol (B) indicates a mole fraction of the compound with respect to the component (A) or the component (B).
Next, 60 parts of the obtained polyester resin [I-1], 306 parts of water, 28 parts of n-butyl cellosolve, and 6 parts of 25% ammonia water are charged into a reactor, and the mixture is heated to 95 ° C. and dissolved with stirring. A polyester-based aqueous liquid having a solid content of 15% was prepared.

  The stability of the polyester-based aqueous liquid thus obtained was evaluated according to the following method. The results are shown in Table 1.

(Aqueous liquid stability)
The polyester-based aqueous liquid having a solid content of 15% adjusted as described above was allowed to stand at room temperature, and the stability of the aqueous liquid was evaluated by the number of days until the aqueous liquid became turbid.
The evaluation criteria were as follows, and ◎ and ○ were regarded as having good stability.
(Evaluation criteria)
◎: no turbidity occurred after 90 days passed ○: turbidity occurred in 60 days or more and less than 90 days Δ: turbidity occurred in 30 days or more and less than 60 days ×: turbidity occurred in less than 30 days did

<Example 2>
[Production of polyester resin [I-2] and its aqueous liquid]
As shown in Table 1, a polyester-based resin [I-2] and an aqueous liquid thereof were produced in the same manner as in Example 1 except that the copolymer components and the ratio thereof were changed, and the stability of the aqueous liquid was evaluated.

<Comparative Examples 1 to 3>
[Production of polyester-based resins [I'-1] to [I'-3] and their aqueous liquids]
As shown in Table 1, polyester resins [I'-1] to [I'-3] and their aqueous liquids were produced in the same manner as in Example 1 except that the copolymerization components and the proportions thereof were changed. The stability of the aqueous liquid was evaluated. In addition, since the aqueous liquid of the polyester resin [I'-1] of Comparative Example 1 was inferior in stability, no further evaluation was performed.

The abbreviations shown in Table 1 represent the following compounds.
TPA: Terephthalic acid IPA: Isophthalic acid PMAn: Pyromellitic anhydride

BisA-2EO: 2-mol ethylene oxide adduct of bisphenol A EG: ethylene glycol

<Examples 3 and 4, Comparative Examples 4 and 5>
Using aqueous liquids of the polyester resins [I-1] to [I-2] and [I'-2] to [I'-3] obtained in Examples 1 and 2 and Comparative Examples 2 to 3, According to the following methods, the initial adhesion to the hard coat layer and the wet heat resistance were evaluated. Table 2 shows the results.

[Adhesion (initial)]
Water was added to the aqueous polyester solution prepared in Examples 1 and 2 and Comparative Examples 1 to 3 to dilute the solid content to 7%, and then a crosslinking agent was blended in the ratio shown in Table 2 to obtain a polyester aqueous solution for a primer. Was adjusted. The obtained polyester-based aqueous liquid for a primer was coated on a PET film (manufactured by Toray Industries, Lumilar T60, thickness 100 μm) with a bar coater No. 6 and dried at 150 ° C. for 3 minutes to form a 0.5 μm thick primer layer.
In Table 2, the numerical values in the column of parts by weight of the polyester resin and the crosslinking agent represent values converted into the solid content of the polyester resin and the active ingredient of the crosslinking agent.

Next, 35 parts of urethane acrylate compound "UV-7610B" for hard coat (manufactured by Nippon Synthetic Chemical Industry Co., Ltd.), 65 parts of ethyl acetate, 1.4 g of photopolymerization initiator "Irgacure-184" (manufactured by Ciba Specialty Chemicals) 1.4. Part was blended with a bar coater No. on the primer layer. 10 and dried at 60 ° C. for 3 minutes. Subsequently, ultraviolet rays were irradiated at 450 mJ / cm ² using a high-pressure mercury lamp having an irradiation intensity of 80 W / cm set at a height of 13 cm from the application surface to cure the ultraviolet-curable resin composition, and the thickness of the resin composition was 4 μm. A hard coat layer was formed.

After 100 crosscuts of 1 mm ² were put in the hard coat layer thus formed, Nichiban Cellotape (registered trademark) was stuck thereon, and the tape was rubbed with a plastic eraser so that the tape was sufficiently adhered. The adhesiveness was evaluated based on the number of the hard coat layers that were rapidly peeled off in the direction of 90 °.
The evaluation criteria were as follows, and ◎ and ○ were regarded as good adhesiveness.
(Evaluation criteria)
：: 95/100 or more (remaining number / measured number)
：: 90/100 or more, 94/100 or less Δ: 70/100 or more, 89/100 or less ×: 69/100 or less

[Adhesion (after wet heat resistance test)]
In the same manner as in the evaluation of the initial adhesion, the film on which the primer layer and the hard coat layer were laminated was cut into a size of 5 cm × 13 cm and immersed in boiling water for 3 hours and 6 hours. Thereafter, the film was wiped off, allowed to stand at room temperature for 1 hour, and then subjected to a cross cut and tape peeling test in the same manner as in the evaluation of the initial adhesion.
The evaluation criteria were as follows, and ◎ and ○ were regarded as good adhesiveness.
：: 95/100 or more (remaining number / measured number)
：: 90/100 or more, 94/100 or less Δ: 70/100 or more, 89/100 or less ×: 69/100 or less

The crosslinking agents II-1 and II-2 shown in Table 2 are as follows.
II-1: Melamine-based cross-linking agent "Nikarac MW-30M" (manufactured by Sanwa Chemical Co., Ltd.)
II-2: Carbodiimide-based crosslinking agent “carbodilite V-04” (manufactured by Nisshinbo Chemical Inc.)

  From the above results, an example in which a polyhydric carboxylic acid containing a specific amount of terephthalic acid (a1) and a polyol component containing a specific amount of a glycol component (b1) having a bisphenol structure and satisfying a specific acid value are used. The polyester resins of Examples 1 and 2 have a high refractive index, are excellent in stability of an aqueous liquid, and are used. The primer layers of Examples 3 and 4 are hard coat layers both at the initial stage and after a heat and moisture resistance test. It can be seen that the adhesiveness with the adhesive is excellent.

  On the other hand, the polyester resin of Comparative Example 1 in which the content of terephthalic acid (a1) was more than 80 mol% was inferior in the stability of the aqueous liquid. Further, a comparison was made using the aqueous liquids of Comparative Example 2 in which the content of terephthalic acid (a1) was less than 20 mol% and Comparative Example 3 in which the content of the polyol component (b1) having a bisphenol structure was less than 60 mol%. The primer layers of Examples 4 and 5 had poor adhesion to the hard coat layer after the heat and moisture resistance test.

  The polyester resin for a primer of the present invention can be suitably used as a primer for a polyester film on which a hard coat layer or the like is laminated. In particular, since it is possible to form a primer layer having excellent adhesion between both the polyester resin base material and the hard coat layer, particularly excellent wet heat resistance, and having a high refractive index, it is possible to suppress iris-like reflection. It can be suitably used for applications where visibility and design are required, particularly as a primer for protective films and ITO films.

Claims (7)

  A polyester resin comprising a polyvalent carboxylic acid component (A) and a polyol component (B), which contains terephthalic acid (a1) in an amount of 20 to 80 mol% or more based on the entire polyvalent carboxylic acid component (A). A polyester resin for a primer, comprising a glycol compound (b1) having a bisphenol skeleton in an amount of 60 mol% or more based on the whole polyol component (B), and having an acid value of 15 mgKOH / g or more.   The polyester resin for a primer according to claim 1, wherein the polycarboxylic acid component (A) contains a carboxylic anhydride (a2) having two or more carboxylic anhydride structures.   The polyester resin for a primer according to claim 1 or 2, wherein the refractive index is 1.58 or more.   4. A polyester-based aqueous liquid for a primer, wherein the polyester-based resin for a primer according to any one of claims 1 to 3 is dissolved or dispersed in an aqueous solvent.   A polyester film having a primer layer, comprising a primer layer containing the polyester resin for a primer according to any one of claims 1 to 3 on the polyester film.   A laminated film comprising a hard coat layer formed by curing an active energy ray-curable resin composition on the primer layer of the polyester film having a primer layer according to claim 5. The method for producing a polyester resin for a primer according to any one of claims 1 to 3, wherein the polycarboxylic acid component (A) and the polyol are a polycarboxylic acid component (a2) excluding a carboxylic acid anhydride (a2) having two or more carboxylic acid anhydride structures. Production of a polyester resin for a primer, wherein a hydroxyl group-containing prepolymer obtained by copolymerizing the component (B) is chain-extended with a carboxylic anhydride (a2) having two or more carboxylic anhydride structures. Method.