JP2000141473A - Biaxially oriented polyethylene-2,6-naphthalate film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a film excellent in productivity, good in flatness and suitable for a thermal transfer ribbon by obtaining a film reduced in deformation at a time of heating, obtaining a transfer image excellent in gradation properties and made uniform in physical properties in a lateral direction by reducing a bowing phenomenon. SOLUTION: In a biaxially oriented polyester film containing polyethylene-2,6- naphthalate as a main component, the angle of orientation of this film in its lateral direction is 75-105 deg., the Young's modulus (YMD, kg/mm2) in the longitudinal direction of the film and the Young's modulus (YTD, kg/mm2) in the lateral direction thereof satisfy expression (1): 700<=YMD, expression (2): 500<=YTD and expression (3): 1.1<=YMD/YTD<=1.4 and the heat shrinkage factor (SMD, %) of the film in the longitudinal direction thereof after heat treatment at 200 deg.C for 10 min and the heat shrinkage factor (STD, %) in the lateral direction thereof satisfy expression (4):0.8<=SMD/STD<=13.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a biaxially oriented polyethylene-2,6-naphthalate film suitably used for a base film of a thermal transfer ribbon, and more particularly to a method of printing at high speed without causing ink blurring. A film suitably used for a thermal transfer ribbon excellent in printing performance which does not cause wrinkling of the ribbon due to rubbing with a head, comprising biaxially oriented polyethylene-2 having uniform properties in the width direction and improved productivity. , 6-naphthalate film.

[0002]

2. Description of the Related Art Two types of thermal transfer recording systems, a heat-melting type and a sublimation type, have been put to practical use. Among them, the sublimation type thermal transfer recording system is a recording system capable of easily outputting a high-quality full-color image. In recent years, it has become very popular. The sublimation-type thermal transfer method uses a thermal transfer ribbon having a configuration in which a thermal transfer ink layer having a composition in which a thermal sublimable dye is dispersed in a binder is laminated on a base film, and is supplied with thermal energy from a thermal head. In this method, only a part of the heat sublimable dye is sublimated by heat and transferred to an image receiving surface of a transfer material (printing paper, film, etc.) to form a gradation image.

In recent years, as the printing speed has been required to be higher, the temperature of the thermal head at the time of printing has increased, resulting in an increase in the amount of heat received by the thermal transfer ribbon. Cannot be neglected, and the printing becomes unclear at the time of printing, wrinkles are generated on the thermal transfer ribbon, and in extreme cases, there is a problem that printing becomes impossible.

As such a base film, a polyester film having a specified surface roughness is disclosed in JP-A-62-299.
No. 389. In many cases, a polyester film used as a base film is prepared by first producing a wide raw film, slitting the raw film into a predetermined width, and processing into a thermal transfer ribbon. Therefore, in order to improve the productivity of the thermal transfer ribbon, it is necessary to increase the film forming speed, but on the other hand, the shrinkage rate when the film is heated may increase, and the increase in the film forming speed is limited. is there. As another method of improving productivity, there is a method of increasing the yield in the width direction of the formed raw film, but there are variations in physical properties in the width direction of the film as described below, and only the center portion of the film is a product. Therefore, there is a limit to increase the yield. That is, physical property variations in the width direction of the film occur due to the distortion of the main orientation axis and the bowing phenomenon accompanying the transverse stretching of the film. In particular, variations in physical properties in the width direction of the film are considered to be caused by the bowing phenomenon, and various countermeasures have been studied.
For example, as described in "Molding" (Vol. 4, No. 5, pp. 312-317, published by The Japan Society of Plastics Processing), the Boeing phenomenon refers to, for example, drawing straight in the width direction at the entrance of a tenter. The bowed line warps in a bow shape when it comes out of the tenter. This distortion causes variations in physical properties in the width direction of the film, and improvement has been desired.

[0005]

SUMMARY OF THE INVENTION The present invention has been made to solve these problems, and can provide a transferred image having a small deformation of a film upon heating and excellent in gradation. An object of the present invention is to provide a film suitable for a thermal transfer ribbon having excellent flatness and excellent productivity by obtaining a film having uniform physical properties.

[0006]

The present invention relates to a biaxially oriented polyester film containing polyethylene-2,6-naphthalate as a main component, wherein the film has an orientation angle in the width direction of 75 ° or more and 105 ° or less. Yes, Young's modulus in the vertical direction (YMD, kg / mm ² ) and Young's modulus in the width direction (YT
D, kg / mm ² ) satisfy the following expressions (1) to (3), and 2
Heat shrinkage in the longitudinal direction after heat treatment at 00 ° C for 10 minutes (SMD,
%) And a heat shrinkage in the width direction (STD,%) satisfy the following formula (4): a biaxially oriented polyethylene-2,6-naphthalate film. 700 ≦ YMD (1) 500 ≦ YTD (2) 1.1 ≦ YMD / YTD ≦ 1.4 (3) 0.8 ≦ SMD / STD ≦ 1.3 (4)

[Polyethylene-2,6-naphthalate]
The polyethylene-2,6-naphthalate constituting the film of the present invention contains at least 80 mol% of all repeating units.
Is preferably ethylene-2,6-naphthalate. Ethylene-
If it is at least 80 mol% of the total repeating units of 2,6-naphthalate, the film will have little dimensional change at high temperatures without extremely losing the original properties of polyethylene-2,6-naphthalate.

Suitable copolymerization components other than the polymer component having ethylene-2,6-naphthalate as a repeating unit include compounds having two ester-forming functional groups, such as oxalic acid, adipic acid, phthalic acid, and the like. Sebacic acid, dodecanedicarboxylic acid, succinic acid, isophthalic acid, 5-sodium sulfoisophthalic acid, terephthalic acid, 2-potassium sulfoterephthalic acid, 2,7-naphthalenedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 4,4 ′ Diphenyldicarboxylic acid, phenylindanedicarboxylic acid, diphenyletherdicarboxylic acid and lower alkyl esters thereof; oxycarboxylic acids such as p-oxyethoxybenzoic acid and lower alkyl esters thereof; propylene glycol, 1,2-propanediol, 3- Butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,2-cyclohexanedimethanol,
1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, p-xylylene glycol, ethylene oxide adduct of bisphenol A, ethylene oxide adduct of bisphenol S, triethylene glycol, polyethylene oxide glycol, polytetramethylene oxide Glycol, neopentyl glycol and the like.

Further, polyethylene-2,6-naphthalate is obtained by blocking a part or all of the terminal hydroxyl group and / or carboxyl group with a monofunctional compound such as benzoic acid or methoxypolyalkylene glycol. Alternatively, it may be modified with a very small amount of an ester-forming compound having three or more functions such as glycerin and pentaerythritol within a range where a substantially linear polymer can be obtained.

[Additives] The biaxially oriented polyethylene-2,6-naphthalate film of the present invention may optionally contain additives such as stabilizers, dyes, lubricants, ultraviolet absorbers, and flame retardants. it can.

In particular, in order to impart favorable lubricity to the film, it is preferable to contain a small proportion of inert particles. Such inert particles include, for example, spherical silica,
Porous silica, calcium carbonate, silica alumina, alumina, titanium dioxide, kaolin clay, barium sulfate,
Examples thereof include inorganic particles such as zeolite, or organic particles such as silicon resin particles and crosslinked polystyrene particles. The inorganic particles are preferably synthetic products rather than natural products for reasons such as uniform particle size, and inorganic particles of any crystal form, hardness, specific gravity, and color can be used.

The inert particles have an average particle size of 0.05 to
It is preferably in the range of 5.0 μm, and 0.1 to 3.0 μm.
More preferably, it is 0 μm.

The content of the inert particles is 0.001 to
1.0% by weight, preferably 0.03 to 0.5%.
More preferably, it is% by weight.

The inert particles to be added to the film may be a single component selected from those exemplified above, or may be a multi-component containing two or more components.

The timing of adding the inert particles is not particularly limited as long as it is a stage before the formation of the copolymerized polyethylene-2,6-naphthalate. For example, the inert particles may be added at the polymerization stage. May be added.

By adding a lubricant in this way, a biaxially oriented polyester film having an average surface roughness of 0.01 to 0.2 μm can be obtained. When the average surface roughness of the film is smaller than 0.01 μm, sufficient slip properties cannot be obtained, and it becomes difficult to wind the film. On the other hand, if the average surface roughness is larger than 0.2 μm, the heat transfer becomes poor when printing at high speed with a thermal transfer printer, and the printing becomes unclear. If the particle size of the inorganic or organic lubricant to be added is smaller than 0.05 μm, a sufficiently large surface roughness cannot be obtained, and the winding property is reduced, and the productivity is reduced. When it is larger than 5.0 μm, the film is likely to be broken in the stretching step.

As a method of eliminating the surface defects of the film and improving the uniformity of the thickness, a wire-shaped extruder and a surface of the rotary cooling drum are provided on the surface of the extrusion die and the rotary cooling drum in order to increase the adhesion between the film-like melt and the surface of the rotary cooling drum. There is known a method in which an electrode is provided to generate an electrostatic charge on the surface of a film-like molten material, and the film is rapidly cooled while being in close contact with the surface of a cooling drum. When using this method, 0.1 to 40 mmol% of an ester based on the bifunctional carboxylic acid component of polyethylene-2,6-naphthalate is used in order to efficiently deposit an electrostatic charge on the film surface and reduce the volume resistance. By adding a quaternary phosphonium salt of a sulfonic acid having a forming functional group before polymerization, or by adding it as a simple substance simultaneously with a polyethylene-2,6-naphthalate chip before forming a film, the value of the AC volume resistivity of the molten film is increased. It is preferably 6 × 10 ⁸ Ω · cm or less, because the adhesion between the film-like molten material and the surface of the rotary cooling drum is further enhanced, and a film having a uniform thickness can be obtained without surface defects of the film.
Preferred examples of the quaternary phosphonium salt of a sulfonic acid having an ester-forming functional group include tetrabutylphosphonium 3,5-dicarboxybenzenesulfonate and tetraphenylphosphonium 3,5-dicarboxybenzenesulfonate.

[Young's Modulus] The biaxially oriented polyethylene-2,6-naphthalate film of the present invention has a Young's modulus (YMD) in the longitudinal direction of 700 kg / mm ² or more, preferably 7 kg / mm ² or more.
50 kg / mm ² or more, more preferably 780 kg / mm ²
mm ² or more and Young's modulus in the width direction (YTD)
Is 500 kg / mm ² or more, preferably 550 kg / mm ²
mm ² or more, more preferably 600 kg / mm ² or more. In addition, it is necessary to satisfy the following expression in relation to the Young's modulus in both directions. 1.1 ≦ YMD / YTD ≦ 1.4

If the Young's modulus in the vertical direction is smaller than 700 kg / mm ² , wrinkles are likely to occur due to the tension applied to the ribbon during printing, which is not preferable. On the other hand, if the Young's modulus in the width direction is less than 500 kg / mm ² , the print head and the platen roll cannot bear the shear, and wrinkles occur. In severe cases, the ribbon is broken and jamming may occur, which is not preferable.

If the ratio of the Young's modulus in both directions satisfies the above expression, the ribbon is stretched in a well-balanced manner against the tension in the longitudinal direction of the ribbon and the shear in the width direction received from the platen roll. preferable.
If the Young's modulus ratio is out of the above range, wrinkles are likely to occur in the direction of a low Young's modulus, which is not preferable.

[Thermal Shrinkage] The biaxially oriented polyethylene-2,6-naphthalate film of the present invention was prepared at 200.degree.
The ratio (SMD / STD) of the heat shrinkage ratio (SMD) in the longitudinal direction and the heat shrinkage ratio (STD) in the width direction after the partial heat treatment is from 0.8 to 1.3, preferably from 0.9 to 1.2. It is.
When the ratio of the heat shrinkage ratio is within this range, the base can shrink in a well-balanced manner against the longitudinal tension applied to the ribbon when the base receives heat from the head during printing, and thus it is preferable that wrinkles are hardly generated. On the other hand, if the ratio is out of the above range, the balance of the thermal shrinkage with respect to the tension is deteriorated, and the film is stretched in a direction in which the thermal shrinkage is small.

Further, it is preferable to set the heat shrinkage ratio under the following heat treatment conditions in the following range, since it is possible to prevent the shrinkage of the film due to the rubbing between the film and the thermal head and change in dimensions. 1. The heat shrinkage after heat treatment at 150 ° C. for 30 minutes is 3% or less in the longitudinal and width directions, and further 2% or less. 2. The heat shrinkage after heat treatment at 200 ° C. for 10 minutes is 6% or less in the longitudinal and width directions, and further 5% or less. 3. The heat shrinkage after heat treatment at 230 ° C. for 10 minutes is 10% or less in the longitudinal and width directions, and further 6% or less.

[Orientation Angle] The biaxially oriented polyethylene-2,6-naphthalate film of the present invention has the following characteristic conditions A
Needs to be satisfied. Further, as a raw film for producing the film of the present invention, the following characteristic conditions B1
And B2 are preferably satisfied. A. The orientation angle in the width direction is 75 ° or more and 105 ° or less, preferably 80 ° or more and 100 ° or less, more preferably 8 ° or more.
5 ° or more and 95 °. B1. The change amount of the orientation angle in the width direction is 0 ° or more and 10 ° or less per 1 m of the length. B2. The orientation angle of the entire remaining portion except for 100 mm each from the ends of both widths is 75 ° or more and 105 ° or less, and further 80 °
Not less than 100 ° and not more than 85 ° and not more than 95 °. In addition,
The orientation angles of A and B are values measured by a molecular orientation meter, and are 0 ° in the width direction.

If the above characteristic condition B1 is not satisfied, the orientation of the principal axis is greatly different from the tension (longitudinal direction) applied to the ribbon at the time of printing, and the problem that the wrinkle is liable to be inclined tends to occur. In the characteristic condition B1, it is most desirable that the amount of change in the orientation angle is close to 0 ° because the orientation direction is uniform in the width direction. Further, the change amount of the orientation angle does not become less than 0 °.

When a film is transversely stretched using a tenter,
The edge of the film pinched by the clip of the tenter is not sufficiently biaxially oriented. The end of the film is called an edge, and is separated from a portion to be a raw film between the time when the film exits the tenter and the time when the film is wound, and is often pulverized and collected again as a raw material.

However, the original film obtained by separating the edges also has a distribution in the direction of the main orientation axis in the entire width. Therefore, it is necessary to increase the Young's modulus in the longitudinal direction when producing a thin film to reduce the thickness of the thermal transfer ribbon. As a result, the film of the present invention does not satisfy the above characteristic condition A. If the raw film does not satisfy the above-mentioned characteristic condition B2, the generation of wrinkles is not improved even though the Young's modulus is increased, and the center of the raw film is slightly reduced in order to obtain a film free of wrinkles. Only a part can be made into a product, which is not preferable because productivity is reduced.

The biaxially oriented polyethylene-2,6- of the present invention
It is preferable that the naphthalate film is obtained from the remaining portion of the raw film except for 100 mm each from both ends.

[Space Factor] The biaxially oriented polyethylene-2,6-naphthalate film of the present invention preferably has a space factor of 1% to 23%. If this value is less than 1%, the slipperiness of the film,
Workability (handling) is insufficient, while 23%
If it exceeds, the surface becomes too rough, which may cause breakage, which is not preferable. The space factor within the above range can be achieved by setting the type, average particle size, and amount of the inert particles to be added to the above-mentioned polyethylene-2,6-naphthalate within the above-mentioned ranges.

[Thickness] Biaxially oriented polyethylene of the present invention
The thickness of the 2,6-naphthalate film is 0.5 to 10 μm
m is preferred. When the thickness exceeds 10 μm, it takes time to conduct heat from the thermal head, which is not suitable for high-speed printing. On the other hand, if the thickness is less than 0.5 μm, the strength is low, the workability is poor, and the strength required as a ribbon is poor, which is not preferable.

[Refractive Index] The biaxially oriented polyethylene-2,6-naphthalate film of the present invention has a refractive index (nz) in the thickness direction of 1.493 or more, more preferably 1.495 or more.
It is preferably 1.505 or less, more preferably 1.500 or less. If the refractive index in the thickness direction is smaller than 1.493, the film has poor slitting properties and is easily broken, which is not preferable. 1.5
If it is larger than 05, the slitting property is good, but the thickness unevenness becomes large and the flatness becomes poor, which is not preferable.

[Endothermic Peak] The biaxially oriented polyethylene-2,6-naphthalate film of the present invention has an endothermic peak at the time of film formation other than the melting point measured by a differential scanning calorimeter of 225.
It is preferably present at a temperature of at least C. Such a temperature range is
230 ° C or higher, especially 235 ° C or higher, most 240 ° C
The above is preferred. However, the peak existing around 240 ° C. may become a shoulder because it overlaps with the peak of the polymer melting point. In this case, the peak observed when the background of the melting point peak is subtracted is regarded as the endothermic peak. . When the film of the present invention is heated, physical properties are stably maintained up to the endothermic peak temperature, and dimensional stability is improved. When the above-mentioned endothermic peak is present only at a temperature lower than 225 ° C., when heat above that temperature is applied to the film, the thermal dimensional stability is deteriorated, which is not preferable as a thermal transfer ribbon. Although the upper limit of the endothermic subpeak temperature is not particularly defined, it is preferably 248 ° C or lower. Above this temperature,
It is not preferable because flatness is lost. Furthermore, the amount of relaxation of the highly oriented molecular chains is increased by stretching, and the strength is reduced. When used as a ribbon, the ribbon cannot withstand the tension of the printer and may be broken, which is not preferable.

[Density] Biaxially oriented polyethylene of the present invention
The 2,6-naphthalate film has a density of 1.35.
200 g / cm ³ or more 1.3599g / cm ³ or less, preferably 1.353g / cm ³ or more 1.3596g / cm ³ or less. If the density is lower than this range, the film will have low crystallinity and poor thermal dimensional stability. On the other hand, if the density is higher than this range, the degree of crystallinity is too large, causing thickness unevenness, and poor flatness, which is not preferable.

[Easy Adhesive Layer] By providing a thermal transfer ink layer on one side of the biaxially oriented polyethylene-2,6-naphthalate film of the present invention, a thermal transfer ribbon can be manufactured. In that case, it is preferable to provide an easily adhesive layer between the base film and the thermal transfer ink layer for the purpose of improving the adhesiveness between them.

This easily adhesive layer is preferably a coating layer composed of at least one water-soluble or water-dispersible resin selected from the group consisting of urethane resins, polyester resins, acrylic resins and vinyl resin-modified polyester resins. .

As the urethane resin constituting the easily adhesive layer, the following polyvalent hydroxy compound, polyvalent isocyanate compound, chain extender,
Crosslinking agents and the like can be exemplified. That is, as the polyvalent hydroxy compound, polyoxyethylene glycol, polyoxypropylene glycol, polyethers such as polyoxytetramethylene glycol, polyethylene adipate, polyethylene-butylene adipate, polyesters such as polycaprolactone, polycarbonates, Acrylic polyols, castor oil and the like can be used. As polyvalent isocyanate compounds, tolylene diisocyanate, phenylene diisocyanate,
4,4'-diphenylmethane diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, isophorone diisocyanate, and the like can be used. Examples of the chain extender or the crosslinking agent include ethylene glycol, propylene glycol, diethylene glycol, trimethylolpropane, hydrazine, ethylenediamine, diethylenetriamine, ethylenediamine-sodium acrylate adduct, 4,4′-diaminodiphenylmethane, and 4,4′- Diaminodicyclohexylmethane, water and the like can be used. One or more of these compounds are appropriately selected, and a urethane resin is synthesized by a conventional polycondensation-crosslinking reaction.

The polyester resin constituting the easily adhesive layer can be exemplified by the following polyvalent carboxylic acids and polyvalent hydroxy compounds as constituent components. That is, as the polycarboxylic acid, terephthalic acid, isophthalic acid, orthophthalic acid, 4,4′-diphenyldicarboxylic acid, 2,5
-Naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 2-potassium sulfoterephthalic acid, 5-sodium sulfoisophthalic acid, adipic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid, glutaric acid , Succinic acid, trimellitic acid, trimesic acid, trimellitic anhydride, phthalic anhydride, p-hydroxybenzoic acid, monopotassium trimellitic acid and their ester-forming derivatives and the like can be used, and polyhydric hydroxy compounds can be used. Are ethylene glycol, 1,2-propylene glycol, 1,3
-Propylene glycol, 1,4-butanediol,
1,6-hexanediol, 2-methyl-1,5-pentanediol, neopentyl glycol, 1,4-cyclohexanedimethanol, p-xylylene glycol,
Bisphenol A-ethylene glycol adduct, bisphenol A-1,2-propylene glycol adduct, diethylene glycol, triethylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, polytetramethylene oxide glycol, dimethylolpropionic acid, glycerin,
Trimethylolpropane, sodium dimethylolethylsulfonate, potassium dimethylolpropionate and the like can be used. One or more of these compounds are appropriately selected, and a polyester resin is synthesized by a conventional polycondensation reaction. In addition to the above, a composite polymer having a polyester component such as a polyester polyurethane obtained by chain-extending a polyester polyol with an isocyanate is also included in the polyester resin referred to in the present invention.

The acrylic resin constituting the easy-adhesion layer preferably contains an alkyl acrylate or an alkyl methacrylate as a main component.
It is a water-soluble or water-dispersible resin containing 0 to 10 mol% of a copolymerizable vinyl monomer component having a functional group. Vinyl monomers having a functional group copolymerizable with an alkyl acrylate or an alkyl methacrylate have a carboxyl group or a salt thereof, an acid anhydride group, a sulfonic acid group or a salt thereof, an amide group or an alkylol group as a functional group. It is a vinyl monomer having an amide group, an amino group (including a substituted amino group) or an alkylolated amino group or a salt thereof, a hydroxyl group, an epoxy group and the like. Of these, particularly preferred are a carboxyl group or a salt thereof, an acid anhydride group, and an epoxy group. Two or more of these groups may be contained in the resin. Examples of the alkyl group of the alkyl acrylate and the alkyl methacrylate include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, and an n-
Examples thereof include a butyl group, an isobutyl group, a t-butyl group, a 2-ethylhexyl group, a lauryl group, a stearyl group, and a cyclohexyl group.

As the vinyl monomer having a functional group copolymerizable with an alkyl acrylate or an alkyl methacrylate, the following compounds having a functional group such as a reactive functional group, a self-crosslinkable functional group and a hydrophilic group can be used. . Examples of the compound having a carboxyl group or a salt thereof, and an acid anhydride group include acrylic acid, methacrylic acid, itaconic acid, maleic acid, metal salts of these carboxylic acids with sodium, ammonium salts, maleic anhydride, and the like. . Examples of the compound having a sulfonic acid group or a salt thereof include vinyl sulfonic acid, styrene sulfonic acid, metal salts of these sulfonic acids with sodium and the like, and ammonium salts. Examples of the compound having an amide group or an alkylolated amide group include acrylamide, methacrylamide, N-methylmethacrylamide, methylolated acrylamide, methylolated methacrylamide, ureido vinyl ether, β-ureido isobutyl vinyl ether, ureido ethyl acrylate, and the like. No. Examples of the compound having an amino group or an alkylolated amino group or a salt thereof include diethylaminoethyl vinyl ether, 2-aminoethyl vinyl ether, 3-aminopropyl vinyl ether, 2-aminobutyl vinyl ether, dimethylaminoethyl methacrylate, and dimethylaminoethyl. Vinyl ethers, those whose amino groups are methylolated,
Examples thereof include those quaternized with an alkyl halide, dimethyl sulfate, sultone, or the like. As the compound having a hydroxyl group, β-hydroxyethyl acrylate, β
-Hydroxyethyl methacrylate, β-hydroxypropyl acrylate, β-hydroxypropyl methacrylate, β-hydroxyethyl vinyl ether, 5-hydroxypentyl vinyl ether, 6-hydroxyhexyl vinyl ether, polyethylene glycol monoacrylate, polyethylene glycol monomethacrylate, polypropylene glycol monoacrylate, Examples of the compound having an epoxy group, such as polypropylene glycol monomethacrylate, include glycidyl acrylate and glycidyl methacrylate. Other compounds having a functional group include vinyl isocyanate and allyl isocyanate.
Further, olefins such as ethylene, propylene, methylpentene, butadiene, styrene, α-methylstyrene, vinyl methyl ether, vinyl ethyl ether, vinyl trialkoxysilane, acrylonitrile,
Methacrylonitrile, vinylidene chloride, vinyl chloride, vinylidene fluoride, ethylene tetrafluoride, vinyl acetate, and the like are also examples of the vinyl monomer compound.

The vinyl resin-modified polyester resin constituting the easily adhesive layer can be synthesized by polymerizing the vinyl resin in a water-soluble or water-dispersible polyester resin. Examples of the components constituting the polyester include the following polybasic acids or their ester-forming derivatives and polyols or their ester-forming derivatives. That is, polybasic acid components include terephthalic acid, isophthalic acid, phthalic acid, phthalic anhydride, 2,6-naphthalenedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, adipic acid, sebacic acid, trimellitic acid, and pyromellitic acid And dimer acid. A copolymerized polyester resin is synthesized using two or more of these acid components. Also, it is possible to use a small amount of an unsaturated polybasic acid component such as maleic acid, itaconic acid and the like, and hydroxycarboxylic acids such as p-hydroxybenzoic acid and the like. As the polyol component, ethylene glycol, 1,4-
Butanediol, diethylene glycol, dipropylene glycol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, xylene glycol, dimethylolpropane, poly (ethylene oxide) glycol, poly (tetramethylene oxide) glycol and the like. Two or more of these can be used. Further, vinyl-based monomers such as those exemplified below are exemplified. As the vinyl monomer,
Alkyl acrylate, alkyl methacrylate (as the alkyl group, methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, t
-Butyl group, 2-ethylhexyl group, cyclohexyl group, etc.); hydroxy-containing monomers such as 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate; acrylamide, methacrylamide, N- Alkyl acrylamide, N-alkyl methacrylamide, N, N-dialkyl acrylamide, N, N-dialkyl methacrylate (as the alkyl group, methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, t-butyl group, 2-ethylhexyl group, cyclohexyl group, etc.), N
-Alkoxyacrylamide, N-alkoxymethacrylamide, N, N-dialkoxyacrylamide, N,
Amides such as N-dialkoxy methacrylamide (alkoxy groups include methoxy, ethoxy, butoxy, isobutoxy, etc.), N-methylolacrylamide, N-methylolmethacrylamide, N-phenylacrylamide, N-phenylmethacrylamide, etc. Epoxy group-containing monomers such as glycidyl acrylate, glycidyl methacrylate and allyl glycidyl ether; acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid, styrene sulfonic acid and salts thereof (sodium salt, potassium salt) , Ammonium salts, tertiary amine salts, etc.) and monomers containing a galoxy group or a salt thereof; maleic anhydride, itaconic anhydride and other acid anhydride monomers; vinyl isocyanate,
Allyl isocyanate, styrene, α-methylstyrene, vinyl methyl ether, vinyl ethyl ether, vinyl trialkoxysilane, alkyl maleic acid monoester, alkyl fumaric acid monoester, alkyl itaconic acid monoester, acrylonitrile, methacrylonitrile, vinylidene chloride, Examples include monomers such as ethylene, propylene, vinyl chloride, vinyl acetate, and butadiene. In addition, these monomers are exemplified, but not limited thereto. These monomers can be copolymerized using one kind or two or more kinds.

The coating solution constituting the easily adhesive layer may contain a small amount of organic solvent as long as it does not affect the resin and other additives. This coating solution is an anionic surfactant,
A required amount of a surfactant such as a cationic surfactant or a nonionic surfactant can be added and used. As such a surfactant, the surface tension of the aqueous coating solution is 40 dyne / cm.
Those which can be reduced to the following and promote wetting to the polyester film are preferable, for example, polyoxyethylene alkylphenyl ether, polyoxyethylene-fatty acid ester, sorbitan fatty acid ester, glycerin fatty acid ester, fatty acid metal soap, alkyl sulfate, alkyl sulfone Acid salts, alkyl sulfosuccinates, quaternary ammonium chloride salts, alkylamine hydrochloride, betaine-type surfactants, and the like.

In the easily adhesive layer of the present invention, an isocyanate-based compound, an epoxy-based compound, an oxazoline-based compound, or a cross-linking agent is used for improving adhesion (blocking property), water resistance, solvent resistance, and mechanical strength. It may contain an aziridine compound, a melamine compound, a silane coupling agent, a titanium coupling agent, a zirco-aluminate coupling agent, or the like. If the resin component of the easily adhesive layer has a crosslinking reaction point, a reaction initiator such as a peroxide or an amine, or a sensitizer may be contained in a photosensitive resin or the like.
In order to improve the sticking property and the sliding property, silica, silica sol, alumina, alumina sol, zirconium sol, kaolin, talc, calcium carbonate, calcium phosphate, titanium oxide, barium sulfate, carbon black are used as inorganic fine particles in the easily adhesive layer. , Molybdenum sulfide, antimony oxide sol, etc., as organic fine particles, polystyrene,
It may contain polyethylene, polyamide, polyester, polyacrylate, epoxy resin, silicone resin, fluorine resin and the like. Further, if necessary, an antifoaming agent, a coating improver, a thickener, an antistatic agent, an organic lubricant, an antioxidant, a foaming agent, a dye, a pigment and the like may be contained.

The coating solution for forming the easily adhesive layer is preferably applied to one or both surfaces of the film before the completion of the crystal orientation in the film production process. Coating may be performed separately from the film manufacturing process, but in this case, dust and dirt are likely to be involved, and that portion becomes a defect at the time of printing, and a clean atmosphere is desirable. From these points, coating during the manufacturing process is preferable. At that time, the solid content concentration of the coating solution is usually 0.1 to 30% by weight, more preferably 1 to 10% by weight.
The coating amount is preferably 0.5 to 50 g per 1 m ^{2 of the} running film.

[Anti-fusing Layer] It is preferable to provide an anti-fusing layer on the surface of the thermal transfer ribbon opposite to the thermal transfer ink layer in order to prevent sticking of the thermal head. As the anti-fusing layer, silicone resin, acrylate having a crosslinkable functional group, methacrylate or its polyester copolymer isocyanate,
Epoxy, crosslinked with melamine, fluorine resin,
It is preferably made of silicone oil, mineral oil or the like. The anti-fusion layer can be formed by applying a coating solution containing the above components, but the coating may be performed on the film before the completion of the crystal orientation or may be performed off-line after the biaxial film formation. . By doing so, the heat history at the time of processing into a transfer ribbon can be reduced, and a film with less wrinkles can be obtained.

A known method can be applied as a coating method. For example, roll coating, gravure coating, roll brushing, spray coating, air knife,
An impregnation method, a curtain coating method, or the like may be applied alone or in combination.

[Film Production Method] The biaxially oriented polyethylene-2,6-naphthalate film of the present invention can be produced by biaxially stretching an unstretched film obtained by a usual method and heat-setting. . The heat setting treatment is preferably performed by the following method. That is, the heat fixing zone (X1, X2,...) Divided into two or more sections is used, and the temperature of the first heat fixing zone (X1) is set to the stretching temperature (T
(SD, ° C) (TSD + 40) ° C or more (TSD +
100) C. or lower, and further, among the heat setting zones after the first zone, zones having a temperature higher than the temperature of the first zone are provided, and the film is set in the heat setting zones by 4 to 3
Heat set with 5% elongation. At this time, the temperature of the maximum temperature heat fixing zone is preferably 225 ° C. or more, preferably 235 ° C. or more and 250 ° C. or less, and it is preferable that the relaxation treatment and the tension treatment are not performed after the zone where the maximum temperature is reached.

Further preferred production conditions will be described below. That is, polyethylene-2,6-naphthalate is melted and extruded from a slit die into a cooled rotating drum to produce an unstretched film, which is then polyethylene-
The glass transition temperature (Tg, ° C) of 2,6-naphthalate is not lower than (Tg + 50) ° C and is 3.8 to 6.
0 times, preferably 4.1 to 5.5 times, more preferably 4.6 to 5.2 times, 2.1 to 4.5 times, preferably 2.8 to 4.0 times stretching in the transverse direction. After biaxial stretching at the magnification,
Heat fixing zone (X1, X2,
..) In the first zone (X1) at a temperature of (lateral stretching temperature + 40) ° C. to (lateral stretching temperature + 100) ° C.
Preferably (lateral stretching temperature + 45) ° C. to (lateral stretching temperature + 1)
(00) Heat set at a temperature of 1 ° C. for 1 to 50 seconds, and the heat set is continued in the remaining heat set section. At this time, the film is heat-set while the film is stretched so that the width of the exit of the final section becomes wider by 4 to 35% as compared with the width of the entrance of the first section (X1) of the heat-setting zone. At this time, the film may be stretched only in the first one zone, or may be stretched in two or more continuous zones or intermittently.

When the relaxation treatment is performed, it is preferable to perform the relaxation treatment in a zone before the maximum heat setting temperature. However, the relaxation treatment method is to reduce the tenter width in the middle of the heat fixing zone and to reduce the width by -5 to 5% in the film width direction. Is preferred.

From the raw film obtained under the above manufacturing conditions, the biaxially oriented polyethylene-2,6-polyethylene according to the present invention is further slit to a predetermined width except for both ends as necessary.
Naphthalate films can be produced. The film of the present invention satisfies the aforementioned Young's modulus, heat shrinkage, refractive index in the thickness direction, endothermic peak temperature other than the melting point measured by a differential scanning calorimeter, density, and orientation angle. And
A thermal transfer ribbon can be manufactured by providing the above-described thermal transfer ink layer and the anti-fusing layer on the film and slitting the film to a predetermined width.

[0049]

The present invention will be described in more detail with reference to the following examples. (1) Degree of orientation by molecular orientation meter (change of orientation angle, orientation angle in width direction) Using a molecular orientation meter MOA-2001A manufactured by Shin-Oji Paper Co., Ltd., plot of orientation ellipsoid of microwave intensity of film. Get. At this time, the width direction is set to 0 °, and the angle formed by the minor axis of the alignment ellipsoid is defined as the alignment angle. The change in the orientation angle is measured at a portion excluding 100 mm from each end of both widths of the raw film, and is expressed as a change per 1 m of the width. The entire part except for 100 mm is measured and expressed by the maximum and minimum orientation angles.

(2) Young's modulus The film was cut into a sample having a width of 10 mm and a length of 15 cm. The film was cut with a chuck of 100 mm and pulled at a tensile speed of 10 mm / min and a chart speed of 500 mm / min using an universal tensile tester of Instron type. The Young's modulus is calculated from the tangent line at the top of the obtained load-elongation curve.

(3) Heat Shrinkage Rate Each set time (150 ° C. is 30) in an oven set at each temperature (150, 200, 230 ° C.) without tension.
The film is held for 10 minutes at 200 ° C. and 230 ° C. for 10 minutes), and the dimensional change before and after the heat treatment is calculated as the heat shrinkage ratio by the following equation. Heat shrinkage% = ((L0−L) / L0) × 100 L0: distance between gauges before heat treatment L: distance between gauges after heat treatment

(4) Refractive Index Using an Abbe refractometer, the refractive index (nz) in the direction perpendicular to the film surface is determined using sodium D line (589 nm) as a light source.

(5) Endothermic peak 10 mg of the film was subjected to a thermal analysis system (differential scanning calorimeter) SSC5200, DSC22 manufactured by Seiko Electronic Industry Co., Ltd.
The film was heated at a rate of 20 ° C./min in a nitrogen stream, and the endothermic behavior of the film was analyzed by first and second derivatives to determine the temperature at which the film exhibited a peak. Temperature. At this time, the endothermic sub-peak is not a peak of the melting point but a peak resulting from partial melting of the structure formed by heat setting.

(6) Density This is a value measured by a flotation method at 25 ° C. in a density gradient tube using an aqueous solution of calcium nitrate.

(7) Thickness When the width of the sample film is W (cm), the length is 1 (cm), the weight is G (g), and the density is d (g / cm ³ ), the film thickness t (μm) ) Is calculated by the following equation. t = G / (W × 1 × d) × 10000

(8) Space Factor (SF) Film weight w (g) and density d (g) of 100 cm ² sample
/ Cm ³ ) by the gravimetric thickness t1 (μm), 10
Ten sample films of cm square are stacked, and the thickness of one sample film determined using a micrometer is defined as t2 (μ
m), it is calculated from the following equation. SF (%) = 100−t1 / t2 × 100

(9) Printability The image receiving sheet VY · 200 (a standard paper product name of Hitachi, Ltd.) is added to the printer Hitachi VY · 200.
(Product name, manufactured by Hitachi, Ltd.) was printed to maximize the optical density. With respect to the produced thermal transfer ribbon, printability and wrinkles generated on the ribbon were evaluated according to the following criteria. ：: The image is printed clearly. Δ: Printing density is not uniform. X: The ribbon is wrinkled and the print is disturbed.

Example 1 To a mixture of 100 parts by weight of dimethyl 2,6-naphthalenedicarboxylate and 60 parts of ethylene glycol, 0.03 part of manganese acetate tetrahydrate was added.
The transesterification reaction was performed while gradually raising the temperature from 50 ° C to 240 ° C. On the way, when the reaction temperature reached 170 ° C., 0.024 parts of antimony trioxide was added, and 0.4 parts by weight of spherical silica particles having an average particle diameter of 1.2 μm were added, and then the temperature reached 220 ° C. At this time, a mixture of 0.042 parts (corresponding to 2 mmol%) of 3,5-dicarboxybenzenesulfonic acid tetrabutylphosphonium salt and 0.124 parts of ethylene glycol was added as a solution heated to 40 ° C. Subsequently, a transesterification reaction is carried out, and after the transesterification reaction is completed, trimethyl phosphate is dissolved in ethylene glycol at 135 ° C for 5 hours at 1.1 to 1.6 kg / c.
A solution heat-treated under a pressure of m ² (0.023 parts in terms of trimethyl phosphate) was added. Thereafter, the reaction product was transferred to a polymerization reactor, and the temperature was raised to 290 ° C.
g under a high vacuum of 25 ° C.
-A polyethylene-2,6-naphthalate polymer having an intrinsic viscosity of 0.62 as measured in -chlorofinol.
Using this polymer, melt extrude it into a sheet with an extruder and a T-die, and apply 37.5 m to a water-cooled casting drum.
/ Minute, and the mixture was solidified by cooling to obtain an unstretched sheet. This unstretched film was stretched 4.5 times at 144 ° C. by a high-speed roll at 150 m / min in the longitudinal direction (machine axis direction) by roll stretching. On the side of the longitudinally stretched film where the ink layer is not applied, a coating of the following composition 1 is applied as a fusion preventing layer with a gravure coater so that the coating thickness after drying is 0.5 μm. The coating having a thickness of 0.1 μm after drying a coating composition of the following composition 2 as an easily adhesive layer on the side where
m with a gravure coater. afterwards,
In the transverse direction (width direction), the first heat-fixing zone is stretched by a factor of 3.2 at 140 ° C. and stretched at 180 ° C. so that the outlet width increases by 25% with respect to the entrance width of the first heat-fixing zone. In the second and third heat fixing zones, the inlet width and the outlet width were kept the same at 240 and 180 ° C., respectively, and the thickness was 5.1.
A μm raw film was obtained. <Coating composition 1> Acrylic acid ester 14.0% by weight Amino-modified silicone 5.9% by weight Isocyanate 0.1% by weight Water 80.0% by weight <Coating composition 2 (acryl + polyester + epoxy)
> The composition of the coating material 2 is configured as follows. The acrylic resin is methyl methacrylate 65 mol% / ethyl acrylate 28 mol% / 2-hydroxyethyl methacrylate 2
Mol% / N-methylol acrylamide 5 mol%, solid content 42% by weight, polyester resin 35 mol% of terephthalic acid / 13 mol% of isophthalic acid / 5 mol of 5-sodium sulfoisophthalic acid as an acid component The glycol component is composed of ethylene glycol 45 mol% / diethylene glycol 5 mol%, the solid content is 42 wt%, and N, N, N
N ', N'-tetraglycidyl-m-xylylenediamine is 6% by weight on a solid basis, and lauryl polyoxyethylene as a wetting agent is 10% by weight on a solid basis. With respect to the obtained biaxially oriented film, the orientation angle, Young's modulus, heat shrinkage, refractive index, endothermic peak, density, thickness and space factor were determined. Table 1 shows the results. Next, a transfer ink having the following composition was applied to the raw film, and the coating film thickness was 1.
The coating was applied to the surface opposite to the anti-fusing layer with a gravure coater so as to have a thickness of 0 μm, and slit to a predetermined width to prepare a thermal transfer ribbon. <Composition of thermal transfer ink> Magenta dye (MSRedG) 3.5% by weight Polyvinyl acetoacetal resin 3.5% by weight Methyl ethyl ketone 46.5% by weight Toluene 46.5% by weight Ink adhesion and printability of prepared thermal transfer ribbon Was evaluated. Table 1 shows the evaluation results.

[Examples 2 to 4 and Comparative Examples 1 to 3] An original film was prepared in the same manner as in Example 1 except that the film forming conditions were changed as shown in Table 1, and then the same as in Example 1 was performed. A thermal transfer ribbon was made by the method. Table 1 shows the properties of the raw film and the thermal transfer ribbon.

Comparative Example 4 In place of polyethylene-2,6-naphthalate, spherical silica particles having an intrinsic viscosity of 0.61 and a particle size of 1.2 μm measured in o-chlorophenol at 25 ° C. A raw film was prepared in the same manner as in Example 1 except that the film forming conditions were changed as shown in Table 1 using polyethylene terephthalate containing 4% by weight, and then a thermal transfer ribbon was formed in the same manner as in Example 1. Created. Table 1 shows the properties of the raw film and the thermal transfer ribbon.

[0061]

[Table 1]

[0062]

According to the present invention, it is possible to obtain a transfer image having a small deformation of the film upon heating and excellent in gradation, and to further reduce the bowing phenomenon to obtain a film having uniform physical properties in the width direction. Thereby, a biaxially oriented polyethylene-2,6-naphthalate film suitable for a thermal transfer ribbon having excellent productivity and good flatness can be obtained.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI theme coat ゛ (reference) // B29K 67:00 B29L 7:00 F term (reference) 2H111 AA01 AA27 BB06 BB08 4F071 AA45 AA82 AA87 AF06Y AF20Y AF31Y AF54Y AF61Y AH16 BB08 BC01 BC11 4F210 AA26 AB17 AE01 AG01 QA03 QC06 QD08 QG01 QG11 QG15 QG18 4F213 AA26 AB17 AE01 AG01 WA10 WA58 WB02 4J002 CF081 FD170 FD200 GK03

Claims (3)

[Claims] 1. A biaxially oriented polyester film containing polyethylene-2,6-naphthalate as a main component, wherein the orientation angle in the width direction of the film is 75 ° or more and 105 ° or more.
The Young's modulus in the longitudinal direction (YMD, kg / mm ² ) and the Young's modulus in the width direction (YTD, kg / mm ² ) are expressed by the following formula (1).
To (3), and the heat shrinkage (SMD,%) in the longitudinal direction and the heat shrinkage (STD,%) in the width direction after heat treatment at 200 ° C. for 10 minutes satisfy the following expression (4). A biaxially oriented polyethylene-2,6-naphthalate film. 700 ≦ YMD (1) 500 ≦ YTD (2) 1.1 ≦ YMD / YTD ≦ 1.4 (3) 0.8 ≦ SMD / STD ≦ 1.3 (4) 2. The film has a refractive index (nz) in the thickness direction of 1.493 or more and 1.505 or less, an endothermic peak other than a melting point measured by a differential scanning calorimeter at 225 ° C. or more,
The heat shrinkage after heat treatment at 150 ° C. for 30 minutes is 3% or less in both the vertical and width directions, and the heat shrinkage after heat treatment at 200 ° C. for 10 minutes is 6% or less in both the vertical and width directions, 230 ° C., 10
Thermal shrinkage after partial heat treatment is 10% in both longitudinal and width directions
Hereinafter, the density is 1.3500 g / cm ³ or more and 1.3599.
g / cm ³ or less and a space factor of 1%
The biaxially oriented polyethylene-2,6-naphthalate film according to claim 1, which is not less than 23%. 3. The amount of change in the orientation angle in the width direction of the raw film is 0 ° or more and 10 ° or less per 1 m length, and the width of the raw film is 0 °, and the remaining amount excluding 100 mm from both ends of the width. 3. The biaxially oriented polyethylene-2 according to claim 1 or 2, obtained from the remaining portion of the raw film having an orientation angle of 75 ° or more and 105 ° or less excluding 100 mm each from both width ends. 6-naphthalate film.