JP3257253B2 - Laminated polyester film for thermal transfer material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminated polyester film, and more particularly to a base film suitable for a thermal transfer material.

[0002]

2. Description of the Related Art In recent years, with the development of office automation, various recording systems have been developed. Among them, a heat-sensitive recording system, which has low noise during printing and is easy to operate, attracts attention. Have been. In the thermal recording method, a thermal recording device such as a thermal printer is used to bring a recording paper into contact with a thermal ink layer of a thermal transfer material, and a film is selectively heated by a pulse signal from a heating head opposite to the ink layer. As a result, the ink heated through the film is melted or sublimated and transferred to the recording paper. As this thermal transfer material, a thin-leaf plastic film is generally used in order to increase thermal efficiency.

However, in general, when a plastic film is used as a base film of a thermal transfer material, a phenomenon appears in which the film is partially fused to the thermal head due to the amount of heat given by the thermal head. This phenomenon is called a stick phenomenon, and when this phenomenon occurs, not only does the thermal transfer material not run smoothly, but also there is a problem that the thermal head is significantly contaminated and print clarity is impaired.

To prevent this sticking, it has been proposed to provide a heat-resistant protective layer on the surface of the base film opposite to the ink layer. In the thermal transfer method, a molten ink layer mainly composed of a low-melting wax and a pigment or dye is provided on one side of the base film. However, depending on storage conditions, the ink layer and the heat-resistant protective layer are blocked, and the ink layer is peeled off. Problem may occur. recent years,
The ink layer tends to have a low melting point for the purpose of high-speed printing, and this phenomenon is becoming more and more remarkable.

Hitherto, in order to avoid the sticking, various heat-resistant protective layers have been proposed on the surface of the plastic film which comes into contact with the thermal head. For example, a device provided with a heat-resistant protective layer of silicon, melamine, phenol, epoxy, polyimide or the like (Japanese Patent Application Laid-Open No. 55-7467), a stick-preventing layer made of a highly lubricious inorganic pigment and a resin having high heat resistance. Some are provided (JP-A-56-1
55794). Further, those provided with a layer comprising a water-soluble or water-dispersible silicone and a resin (Japanese Patent Application Laid-Open No.
192628), provided with a layer composed of a water-dispersible fluorine-based resin and an aqueous polymer (JP-A-60-19263).
No. 0), and those obtained by coating or transferring a wax and / or a liquid or paste-like substance at room temperature (Japanese Patent Application Laid-Open Nos. 59-14897 and 60-56583).
There is.

[0006]

However, those provided with the heat-resistant protective layer such as silicon or melamine do not slide well with the head, so that a printer having a low pulse width or a platen drive type printer has a thermal transfer ribbon. The running property is poor, and there is a drawback that printing stops or running stops in extreme cases. In addition, a pigment containing an inorganic pigment has a problem in that the life of the head is shortened due to friction with the thermal head and the surface is roughened, so that thermal conductivity is poor and clear printing cannot be obtained. Laminates of silicone resin or fluorine resin are likely to transfer to the surface to which ink is applied after winding on a roll, which causes repelling during ink application and peeling due to poor ink adhesion. And so on. Laminated film obtained by applying wax etc. to plastic film and drying it is
Although it has an excellent lubricating effect on the round head, it has the disadvantage that the melting point of the heat-resistant protective layer is low and that the composition is similar to the ink layer, so that blocking tends to occur. In particular, in recent years, thermal transfer printers have tended to have higher printing speeds, and the development of thermal transfer materials capable of responding to this trend has been desired. An object of the present invention is to eliminate the above-mentioned disadvantages, such as a word processor, a facsimile, and a bar code printer provided with a heat-resistant protective layer which does not generate sticks and does not block the low melting point ink layer. It is an object of the present invention to provide a laminated polyester film suitable as a base film for a thermal transfer material which can be suitably used in a wide range from a low pulse width region to a high pulse width region such as a video printer.

[0007]

According to the present invention, there is provided a laminated film mainly composed of a wax-based composition and a metal salt of a higher fatty acid having a melting point of 105 ° C. or more on the surface opposite to the surface on which the ink layer of the polyester film is provided. The main feature thereof is a multilayer polyester film for a thermal transfer material characterized by the following.

The term "polyester film" as used in the present invention is a generic term for a polymer film having an ester bond as a main bonding chain of a main chain. Particularly, as a base film for a thermal transfer material, polyethylene terephthalate, Films such as polyethylene-2,6-naphthalate, polyethylene α, β-bis (2-chlorophenoxy) ethane 4,4, -dicarboxylate and polybutylene terephthalate, among which quality and economy In consideration of the properties, polyethylene terephthalate film (hereinafter polyethylene terephthalate is abbreviated as PET),
Polyethylene-2,6-naphthalate film (hereinafter polyethylene-2,6-naphthalate is abbreviated as PEN) is particularly preferred. In particular, when a PEN film is used as the base film for the thermal transfer material intended for the present invention, even when high energy is applied for high-speed printing, wrinkling of the base film hardly occurs, so that printing accuracy is reduced. Good and preferred. Of course, PEN / PET, PEN / PET / P
A two-layer or three-layer base film such as EN is also an example of a preferable configuration. Here, polyethylene terephthalate is a resin in which 80 mol% or more, preferably 90 mol% or more, and more preferably 95 mol% or more has ethylene terephthalate as a repeating unit. Some of the components may be replaced with a third component as described below.

-Acid component- Isophthalic acid, 2,6-naphthalenedicarboxylic acid, 1,
5-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, 4,4, -diphenyldicarboxylic acid, 4,
4, -diphenylsulfonedicarboxylic acid, 4,4, -diphenyletheredicarboxylic acid, p-β-hydroxyethoxybenzoic acid, adipic acid, azelaic acid, sebacic acid, hexahydroterephthalic acid, hexahydroisophthalic acid, ε- Oxycaproic acid, trimellitic acid, trimesic acid, pyromellitic acid, α, β-bisphenoxyethane-4,4, -dicarboxylic acid, α, β-bis (2-chlorophenoxy) ethane-4,4, -dicarboxylic acid Acid, 5-
Sodium sulfoisophthalic acid and the like.

-Glycol component- propylene glycol, butylene glycol, hexamethylene glycol, decamethylene glycol, neopentylene glycol, 1,1-cyclohexanedimethanol
1,4-so-hexanehexanemethanol, 2,2-bis (4-β-hydroxyethoxyphenyl) propane,
Bis (4-β-hydroxyethoxyphenyl) sulfone, diethylene glycol, triethylene glycol,
Pentaerythritol, trimethylolpropane, polyethylene glycol, polytetramethylene glycol and the like.

In addition, known additives such as heat stabilizers, oxidation stabilizers, weather stabilizers, ultraviolet absorbers, organic lubricants, pigments, dyes, organic or inorganic fine particles, are added to the base polyester film. A filler, an antistatic agent, a nucleating agent and the like may be blended. Particularly, inorganic and / or organic fine particles are added, and the average surface roughness of the polyester film after biaxial orientation is 0.03 to 0.4 μm, preferably 0.03 to 0.4 μm.
When the thickness is 5 to 0.2 μm, the running property of the present invention can be further improved.

The intrinsic viscosity of the above polyester (measured in orthochlorophenol at 25 ° C.) is 0.40 to 1.2.
0 dl / g, preferably 0.50 to 0.80 dl / g,
More preferably, those in the range of 0.5 to 0.75 dl / g are suitable for the content of the present invention.

The polyester film is preferably biaxially oriented in view of mechanical strength and dimensional stability. A biaxially oriented polyester film is obtained by stretching a non-stretched PET sheet about 2.5 to 5.0 times each in a so-called biaxial direction in a longitudinal direction and a width direction, and heat-setting to complete crystal orientation. It is a product which shows a biaxial orientation pattern in wide-angle X-ray diffraction.

The thickness of the polyester film is not particularly limited, but when the laminated polyester film of the present invention is used as a substrate film for a thermal transfer material, the thickness is 0.5 μm or more.
It is preferably 0 μm or less, more preferably 1 μm or more and 10 μm or less from the viewpoint of heat transferability and mechanical strength.

In the present invention, the surface opposite to the surface on which the ink layer of the polyester film is provided has a laminated film mainly composed of a wax-based composition and a metal salt of a higher fatty acid having a melting point of 105 ° C. or more. Here, the main component means that the weight ratio in the laminated film composition is 50% or more, preferably 60% or more. Wax compounds are various commercially available waxes, for example, petroleum wax, vegetable wax,
Mineral waxes, animal waxes, low molecular weight polyolefins and the like can be used and are not particularly limited, but in the present invention, petroleum waxes and vegetable waxes are preferred in terms of stick resistance. . Examples of the petroleum-based wax include paraffin wax, microcrystalline wax, and oxidized wax, and among these, use of oxidized wax is particularly preferable in view of projection forming properties for imparting lubricity. Examples of the vegetable wax include candelilla wax, carnauba wax, wood wax, ocicle wax, sugarcane wax, and rosin-modified wax. In the present invention, a composition comprising the following compounds is particularly preferable. That is, rosin or disproportionated rosin, or hydrogenated rosin α
β-substituted ethylene (α-substituent: carboxyl, β-substituent: hydrogen or methyl or carboxyl) adduct
It is preferable to use an ester adduct of an alkyl or alkenyl (each having 1 to 8 carbon atoms) poly (repeating unit: 1 to 6) alcohol in terms of slipperiness and releasability. More preferably, it is used in a system.

The melting point of the laminated film of the present invention is 105 ° C.
Or more, preferably 120 ° C. or more, more preferably 135 ° C.
It is necessary to contain a higher fatty acid metal salt having a temperature of not less than ° C. When the higher fatty acid metal salt having a melting point of 105 ° C. or more is coexisted with the wax composition in the laminated film, when used as the back surface treatment layer of the thermal transfer material, the low melting point ink layer can be used without impairing the sticking prevention effect. This has the effect of preventing blocking from occurring.
Higher fatty acid metal salts having a melting point of 105 ° C. or higher
Metal salts of 0 or more higher fatty acids can be suitably used. As higher fatty acids having 10 or more carbon atoms, lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, behenic acid, and the like can be given. As the metal salt, lithium, sodium, potassium, calcium, zinc, Examples include barium, cadmium, lead, magnesium, aluminum, and composite salts of two or more of these. Of these, higher fatty acid metal salts that can be particularly preferably used are stearic acid, zinc laurate,
Calcium and barium salts.

The content of the higher fatty acid metal salt in the laminated film is not particularly limited, but is preferably 15 to 90% by weight, more preferably 25 to 85% by weight, particularly preferably 40 to 90% by weight.
80% by weight.

That is, the coexistence of the wax-based composition and the higher fatty acid metal salt in the laminated film withstands a wide range of loads, imparts good print running properties, and has the heat resistance of the heat-sensitive transfer material without blocking with the ink layer. It has been found that a protective layer is obtained.

Further, in the present invention, when a mixture of the above-mentioned laminated film composition and an oily substance showing fluidity or paste at room temperature is further added, the printing runability in a high pulse width region is further improved. It can be. Examples of the oily substance include vegetable oils, fats and oils, mineral oils, and synthetic lubricating oils. Vegetable oils include linseed oil, kaya oil, safflower oil, soybean oil, cinnamon oil, sesame oil, corn oil, rapeseed oil, nuka oil, cottonseed oil, olive oil, sasanqua oil, tsubaki oil, castor oil, peanut oil, bamboo oil -Oil,
Palm oil and the like. Fats and oils include beef tallow, pork oil, sheep oil, cocoa oil and the like, and mineral oils include machine oil, insulating oil, turbine oil, motor oil, gear oil, cutting oil, liquid paraffin and the like. . As the synthetic lubricating oil, those satisfying the requirements described in the Chemical Dictionary (Kyoritsu Shuppan) can be arbitrarily used, and examples thereof include olefin polymerized oil, diester oil, and polyalkylene glycol oil. Among these, mineral oils and synthetic lubricating oils having good running properties in a high pulse width region are preferable. Further, a mixed system of these may be used. The oily substance is contained in the laminated film composition in an amount of 1 to 30% by weight, more preferably 2 to 20% by weight.
It is preferred that the content be contained by weight.

Various additives can be used in the above composition within a range not to impair the effects of the present invention. For example, antistatic agents, heat-resistant agents, antioxidants, organic and inorganic particles, pigments and the like can be mentioned. Further, various additives such as a dispersing aid, a surfactant, a preservative, and an antifoaming agent may be added to the paint for the purpose of improving dispersibility in water or improving applicability.

Further, in the present invention, in order to improve the slipperiness and the anti-sticking effect, it is necessary to form a long and narrow projection having a ratio of 3 or more on the surface of the laminated film on the surface of the laminated film.
It is effective to use a surface having at least 100 μm ² . Such protrusions can be obtained by applying the mixed aqueous coating composition of the above-mentioned laminated film composition to a polyester film before the completion of the crystal orientation, and then stretching it in one direction.
A preferred composition in terms of projection formation is a petroleum wax, and it is particularly effective to use an oxidized wax. Accordingly, it is preferable to use a method of applying the laminated film of the present invention in the film production process (in-line coating method) in view of the formation of projections on the surface by the composition. For this purpose, it is preferable to use the laminated film forming coating agent dissolved, emulsified or suspended in water from the viewpoint of explosion proof property and environmental pollution prevention. For example, an aqueous dispersion of a wax composition can be obtained by a conventionally known method (for example, JP-A-59-90625). The thickness of the laminated film is not particularly limited, but is 0.005 μm from the viewpoint of preventing sticking and preventing contamination of the thermal head.
It is desirably from m to 0.3 μm, preferably from 0.01 μm to 0.15 μm. The coating method can be performed using various coating apparatuses, for example, a roll coater, a gravure coater, a reverse coater, a kiss coater, a bar coater and the like. .

Next, as a specific example of the method for producing a laminated polyester film of the present invention, a laminated polyester film for a thermal transfer material will be described as a typical example. The PET containing so-called precipitated particles and inorganic particles (eg, silica having an average particle diameter of 1 μm) precipitated in the polymerization step is dried by a conventional method, melt-extruded, and the extruded sheet-like molten material is cooled and solidified. Make a stretched PET film. This film is heated to 80 to 120 ° C., and is heated to 2.0 to 5.0 in the longitudinal direction.
The film is stretched twice to obtain a uniaxially oriented film. One surface of the film is subjected to a corona discharge treatment in an air atmosphere, and an aqueous dispersion coating solution containing a wax-based composition diluted to a predetermined concentration and a metal salt of a higher fatty acid is applied to the treated surface. Next, the coated film is stretched 3 to 5 times in the width direction while being heated to 90 to 140 ° C., and subsequently guided into a heat treatment zone at 140 to 240 ° C., where heat treatment is performed for 1 to 10 seconds. During this heat treatment, a relaxation treatment of 3 to 12% may be performed in the width direction as necessary. The film thus obtained is slit into an appropriate width to obtain a biaxially oriented laminated polyester film for a thermal transfer material. When this film is used as a heat-sensitive transfer material, it can be obtained by applying a hot-melt type or heat-sublimation type ink on the non-coated side and slitting it to a desired width.

The thus obtained biaxially stretched laminated polyester film for a thermal transfer material is provided with an ink layer according to the intended use, so that various thermal transfer materials, such as word processors, facsimile machines, printers for personal computers, video cameras, etc. Printers, barcode printers, typewriters, plain paper copiers, etc., used for printing out characters or images, and in particular, high load energy is applied to them. It is suitable for a printer.

[0024]

[Method for measuring characteristics and method for evaluating effects] The method for measuring characteristics and the method for evaluating effects in the present invention are as follows.

(1) Lamination Thickness A cross section of a biaxially oriented polyester film provided with a coating layer was cut out and actually measured from an electron microscope observation photograph at a magnification of 100,000.
The thickness was defined as the average of the maximum thickness and the minimum thickness in one visual field, and the average value of 30 measurement points was defined as the laminated thickness.

(2) Formability of protrusion on laminated surface The surface of the laminated surface is photographed with an electron microscope at a magnification of 10,000 times or more.
The projection shape is determined from the photograph, and the length (long direction) and width (short direction) of the elongated projection are determined. The number of the elongated projections was obtained from the photograph per unit area and converted into (pieces / mm ² ).

(3) Hot stick property-1 The following hot-melt ink was applied to the laminated biaxially oriented polyester film on the opposite side of the laminated surface by 3-4 μm by a hot melt method.
m to form a thermal transfer material.

[Hot-melt ink composition] Carnauba wax 100 parts by weight Microcrystalline wax 30 parts by weight Vinyl acetate / ethylene copolymer 15 parts by weight Carbon black 20 parts by weight A thermal transfer printer BC-8MK manufactured by Autonics was evaluated.
Using II, the applied voltage was changed with a thermal head having a head resistance of 500Ω and printing was performed with a pulse width of 0.5 msec.
An applied voltage of 10 V or higher was regarded as good stick resistance. In addition, when the voltage was less than 10 V, sticking occurred in the case of [×]. Note that plain paper was used as the transfer paper.

(4) Hot Stick Property-2 A sublimation ink having the following composition was applied to the surface opposite to the lamination surface, dried, and then slit to an appropriate width to prepare a heat-sensitive transfer material.

[0030] This heat-sensitive transfer material was run under normal use conditions through a sublimation type printer (SharpColor Video Printer-GZ-P11W), and was judged according to the following criteria (good).

：: No sticking at all, extremely good runnability ：: Normal print is possible without any problem in runnability, but a slight stick sound is generated in the solid print portion. △: Readable level Normal printing cannot be performed. ×: Stick is extremely illegible. (5) Hot stick property-3 A high-speed thermal transfer printer (KM705A manufactured by Anritsu Co., Ltd.) using the thermal transfer material prepared in (2) above. Use 1
Observe the state of stick generation when printing at a speed of 20 mm / sec. If the stick is not generated and normal printing is possible (（), the stick sounds while running, but the print is discolored or misaligned. Was evaluated as (x), and the one with poor running caused by the stick was evaluated as (x).

(6) Head Contamination and Abrasion After printing was performed for 3000 m under the conditions of (2) above, the thermal head was removed, and the contaminated state and the worn state of the head were observed with a 100 × optical microscope. . When the contaminated area of the head portion was less than 30%, it was evaluated as [O]. When it was less than 30%, it was evaluated as [X]. The occurrence of scratches on the thermal head was observed, and those with no scratches were marked with [○], and those with scratches were marked with [x].

(7) Inking Property, Ink Adhesion Property Another polyester film is superposed on the biaxially oriented polyester film provided with the laminated film so as to be in contact with the laminated film surface, and a load of 5 kg / 100 cm ² is applied at 70 ° C. Leave for 24 hours. Next, the two films were peeled off, and the ink of the above (2) was applied to the surface where the other polyester film was in contact with the surface of the laminated film, and the degree of cissing was observed. The application of the ink is performed by the hot melt method, and the coating thickness is 3 to 4 μm.
And Those without repelling were marked with [○], and those with slight repelling were marked with [x]. In addition, the ink layer is 20 g /
The case where the peeling area when peeled with a tape having an adhesiveness of cm ² was less than 20% was evaluated as [［], and the case where the peeled area was 20% or more was evaluated as [x]. (8) Ink blocking property The ink layer surface of the thermal transfer material prepared in (2) above and the laminated film (heat-resistant protective layer) surface were brought into contact with each other and superimposed.
It was stored for 24 hours under a condition of 50 ° C. and 85% RH under a load of 100 cm ² . After taking out, release the load and
The transfer area of the ink layer to the laminated film side when the character is peeled off is 10
% Or less was regarded as good.

(9) Wrinkled state of thermal transfer material after printing In the evaluation of (5) above, the wrinkled state of the thermal transfer material after printing was visually observed and judged according to the following criteria.

◎: A level at which no wrinkles are generated. ：: A level at which fine wrinkles are present but has no effect on a printed image. Δ: A level at which large wrinkles are formed and printing is affected.

[0036]

Next, the present invention will be described with reference to examples, but is not necessarily limited thereto.

Example 1 0.15% by weight of precipitated particles having a particle diameter of 0.5 to 1.5 μm (particles precipitated during the polymerization step) and an average particle diameter of 1.5
PE containing 0.2% by weight of μm calcium carbonate particles
T pellets (intrinsic viscosity: 0.63 dl / g) were sufficiently dried by heating under vacuum, then supplied to an extruder and melted at 280 ° C.
After filtering through a 0 μm-cut metal sintered filter, the mixture was extruded from a T-shaped die into a film, and the surface temperature was 30 ° C.
And cooled and solidified. In order to improve the adhesion between the film and the surface of the cooling drum during this time, a wire electrode was arranged on the film side, and a DC voltage of 6 KV was applied. The unstretched PET film thus obtained was
The film was heated at 5 ° C. and stretched 3.5 times in the longitudinal direction to obtain a uniaxially stretched film. One side of this film was subjected to corona discharge treatment in air, and the treated surface was coated with a water-dispersed paint having the following composition by a gravure coat method after biaxial stretching to a thickness of 0.05 μm.
m.

“Coating composition” (a) 40% by weight of oxidized wax aqueous dispersion (solid content ratio) (b) 60% by weight of zinc stearate (melting point: 128 ° C.) aqueous dispersion (solid content ratio) The coating liquid has a total solid content weight ratio of 1.0%.
It was prepared by diluting with water so that

The coated uniaxially stretched film is gripped with a clip and guided into a tenter. After drying the water in a 110 ° C. preheating step, the film is stretched 4.5 times in the width direction while being heated to 120 ° C. Subsequently, heat treatment was performed at 225 ° C. for 5 seconds to obtain a laminated polyester film having a thickness of 0.05 μm and a film thickness of 5 μm. A heat-sensitive transfer material was prepared from this laminated polyester film according to the above-described evaluation method and evaluated.
The results are shown in Tables 1 and 2.

Examples 2 to 5 and Comparative Examples 1 and 2 Laminated polyester films were prepared in the same manner as in Example 1 except that the mixing ratio of the coating compositions (a) and (b) in Example 1 was changed as shown in Table 1. And a thermal transfer material was prepared. The results are shown in Tables 1 and 2.

Comparative Example 3 The coating composition (b) of Example 1 was replaced with stearic acid (melting point: 56
° C) to prepare a laminated polyester film in the same manner as in Example 1. A thermal transfer material using this laminated polyester film was prepared and evaluated. The results are shown in Tables 1 and 2.

Examples 6 and 7, Comparative Example 4 A laminated polyester film and a heat-sensitive transfer material were prepared in the same manner as in Example 1 except that the component (b) of the coating composition of Example 1 was changed as shown in Table 1. evaluated. The results are shown in Tables 1 and 2.

Example 8 The procedure of Example 1 was repeated except that 20 parts by weight of polyethylene glycol oil was added to 100 parts by weight of the solid content of the coating composition of Example 1 to obtain a 3% by weight aqueous coating composition. To produce a laminated polyester film. The results are shown in Tables 1 and 2.

Example 9 The PET pellets of Example 1 were prepared using PEN (intrinsic viscosity 0.61).
dl / g) A laminated polyester film was prepared in the same manner as in Example 1 except that pellets were used. The results are shown in Tables 1 and 2.

[0045]

[Table 1]

[Table 2]

[0046]

According to the present invention, there is provided an ink for a polyester film.
The wax composition and the melting point of 10
By providing a laminated film containing a higher fatty acid metal salt of 5 ° C. or higher as a main component, it has excellent hot stick resistance when used as a thermal transfer material, and has no repelling or blocking with an ink layer during inking, Head pollution,
Head wear can be reduced.

Claims (5)

(57) [Claims] An ink layer of a polyester film is provided.
A laminated polyester film having a wax-based composition and a higher fatty acid metal salt having a melting point of 105 ° C. or higher as a main component, on the opposite side to the laminated surface . 2. A method of forming a fluid or a paste at room temperature in a laminated film.
2. The laminated polyester film for a thermal transfer material according to claim 1, further comprising an oily substance having a strike shape. 3. The laminated polyester film for a thermal transfer material according to claim 1, wherein the content of the higher fatty acid metal salt in the laminated film is 15 to 90% by weight. 4. The laminated film according to claim 1, wherein the surface of the laminated film has 20/100 μm ² or more elongated projections having a ratio of a longitudinal direction / a short direction of 3 or more. A laminated polyester film for a thermal transfer material as described in the above. 5. The laminated polyester for a thermal transfer material according to claim 1, wherein the polyester film is a film containing polyethylene terephthalate or polyethylene naphthalate as a main component. Film.