JP2569761B2 - Polyester film for thermal transfer material - Google Patents

Description

The present invention relates to a heat-sensitive transfer material used for a thermal printer or the like, that is, a polyester film suitable as a base material of a heat-sensitive transfer ribbon or a heat-sensitive transfer sheet.

[Prior Art] A heat-sensitive transfer material comprising a biaxially oriented polyester film having a colorant layer applied on one side and a heat-resistant protective layer such as a silicone resin or a melamine resin applied on the other side is disclosed in These are well-known in JP-A-55-7467, JP-A-58-13359, and JP-A-60-24995. Further, polyester films as a base material of such a thermal transfer material are also disclosed in JP-A-60-217194 and 60-1926.
28, 62-193889 and 62-233227.

[Problems to be Solved by the Invention] However, various problems have arisen as recent thermal transfer technology shifts toward high-speed printing, that is, high thermal energy printing. For example, the problem of sticking between the thermal head and the back of the thermal transfer material (this problem is called sticking), contamination of the thermal head due to poor adhesion between the protective layer and the substrate, and guide plates and guides stored in thermal printers This is due to running problems due to poor lubrication between the roll and the thermal transfer material, and when the thermal transfer material and film according to the prior art described above are used as the thermal transfer material, there is one of the above disadvantages. Was.

An object of the present invention is to provide a heat-sensitive transfer material which does not have the above-mentioned disadvantages when used as a heat-sensitive transfer material, that is, has no sticking even under high printing energy, and has no trouble such as contamination of a thermal head or poor running property. It is to provide a film.

[Means for Solving the Problems] The present invention relates to a biaxially oriented polyester film having a laminated film provided with a substantially one-layer protective layer on one surface thereof, which is attributed to the bifunctional siloxane in the protective layer.
The polyester film for a thermal transfer material is characterized in that the Si / C atomic ratio is 0.15 to 0.40 in the outer layer of the protective layer and 0.05 or less in the inner layer of the protective layer.

Here, the inner layer of the protective layer refers to the surface layer of the biaxially oriented polyester in the protective layer, and the outer layer of the protective layer refers to the surface layer on the opposite side.

As used herein, the polyester is a generic term for polymers having an ester bond as a main bonding chain, and particularly preferable polyesters are polyethylene terephthalate, polyethylene 2,6-naphthalate, and polyethylene α, β-bis ( 2-chlorophenoxy) ethane 4,4'-
Examples thereof include dicarboxylate and polybutylene terephthalate. Of these, polyethylene terephthalate is most preferable in consideration of quality, economy, and the like. Therefore, hereinafter, description will be made with polyethylene terephthalate as a representative of polyester.

In the present invention, polyethylene terephthalate (hereinafter referred to as PET)
Is abbreviated as 80 mol% or more, preferably 90 mol%
As mentioned above, more preferably 95 mol% or more has ethylene terephthalate as a repeating unit, but within this limited amount range, a part of the acid component and / or the glycol component is replaced with the third component as described below. Is also good.

-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'-diphenyletherdicarboxylic 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 Acid, α, β-bis (2-chlorophenoxy) ethane-4,4′-dicarboxylic acid, 5-sodium sulfoisophthalic acid-glycol component-propylene glycol, butylene glycol, hexamethylene glycol, decamethylene glycol, neopentylene Glycol, 1,1-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, 2,2-bis (4
-Β-hydroxyethoxyphenyl) propane, bis (4-β-hydroxyethoxyphenyl) sulfone, diethylene glycol, triethylene glycol, pentaerythritol, trimethylolpropane, polyethylene glycol and the like.

In addition, known additives in the PET, such as heat stabilizers, oxidation stabilizers, weather stabilizers, ultraviolet absorbers, organic lubricants, pigments, dyes, organic or inorganic fine particles, fillers, and release agents. Molding agents, antistatic agents, nucleating agents and the like may be blended.
As described above, the ultimate mortality of PET (measured in orthochlorophenol at 25 ° C) is 0.40 to 1.20, preferably 0.1 to 0.20.
Those in the range of 50 to 0.80, more preferably 0.55 to 0.75 dl / g are suitable for the present invention.

Next, the biaxially oriented polyester film referred to in the present invention refers to a polyester sheet or film in an unstretched state, in a longitudinal direction and a width direction, so-called biaxial directions.
It is made by stretching about 2.5 to 5 times, and wide angle X
It refers to one that shows a biaxially oriented pattern in line diffraction.

The thickness of the biaxially oriented polyester film is not particularly limited, but is usually 0.5 μm or more and 40 μm or less, preferably 1 μm or less.
When it is not less than m and not more than 10 μm, it is suitable as a substrate film of a thermal transfer material.

Also, the average surface roughness of the biaxially oriented polyester film is not particularly limited, and is usually preferably from 0.04 to 0.4 μm, and more preferably from 0.07 to 0.2 μm.

In the present invention, in the protective layer provided on one side of the biaxially oriented polyester film Si / C attributed to bifunctional siloxane
The atomic ratio is 0.15 to 0.40 in the outer layer of the protective layer, preferably
0.18 to 0.35, more preferably 0.20 to 0.30, and 0.05 or less, preferably 0.03 or less, more preferably 0.01 or less in the inner layer of the protective layer. Here, the bifunctional siloxane is a general formula R is an alkyl group having 1 to 100 carbon atoms, a hydroxyl group,
It is selected from hydrogen, an epoxy group, an amino group, a carboxyl group, a phenyl group, a mercapto group, and an alkyl group containing a halogen. When R is a methyl group, the effect of the present invention is more remarkable, and thus it is preferable. . When the Si / C atomic ratio in the outer layer of the protective layer is less than 0.15, the improvement of sticking and running properties is insufficient. When the ratio exceeds 0.40, the effect of improving sticking and running properties is recognized, but the protection layer is The strength of the outer layer is insufficient, and contamination of the thermal head occurs. When the Si / C atomic ratio exceeds 0.05 in the protective layer, the adhesion between the base polyester film and the protective layer is insufficient, and the thermal head is contaminated by the falling off of the protective layer.

Good characteristics are exhibited only when the Si / C atomic ratio is within the range of the present invention.

The thickness of the protective layer is not particularly limited, but is usually 0.03 μm to 1 μm.
m, preferably 0.05 μm to 0.3 μm.

Examples of the bifunctional siloxane-containing substance include various organosiloxane monomers, oligomers, and polymers, but it is preferable to use a polymer from the viewpoint of the toughness of the coating film. Preferred representative examples for achieving the effects of the present invention include organopolysiloxanes containing dimethylpolysiloxane as a component, and further include dimethylpolysiloxane and organopolysiloxanes into which various other functional groups have been introduced. Is more preferred. Here, the dimethylsiloxane unit in the organopolysiloxane (general formula However, n shows the integer of 1-5000. ) And organosiloxane units other than dimethylsiloxane (general formula Wherein R 'is a reactive group other than a methyl group, a non-reactive group, m
Represents an integer of 1 to 5000. )), The dimethylsiloxane content represented by n / (n + m) of 0.30 or more and 0.95 or less, preferably 0.50 or more and 0.80 or less is particularly suitable for obtaining the protective layer of the present invention. Such organopolysiloxanes include dimethylpolysiloxane, amino-modified silicone, amino-glycol-modified silicone, epoxy-modified silicone, epoxy-polyether-modified silicone, carboxy-modified silicone, alcohol-modified silicone, alkyl- and aralkyl-modified silicone, and alkyl-aralkyl. Examples include polyether-modified silicone, alkyl-higher alcohol-modified silicone-modified silicone, fluorine-modified silicone, methylhydrogenpolysiloxane, methylphenylpolysiloxane, mercapto-modified silicone, chloroalkyl-modified silicone, and vinyl-containing silicone. . Two or more of these may be used in combination.

These organopolysiloxanes can be used by dissolving or dispersing in any solvent. However, it is more preferable to use those which are dissolved, emulsified, or suspended in water from the viewpoint of avoiding environmental pollution and inflammable explosion in the production process. The organopolysiloxane may be used alone as the protective layer, but is usually preferably used in combination with a thermoplastic or thermosetting resin because the film-forming properties and adhesion of the coating film are insufficient. Thermoplastic resin,
The thermosetting resin is not particularly limited, but preferably has good adhesion to the base polyester film, and more preferably has a crosslinked structure by reacting with an organopolysiloxane having a functional group. Specific examples include polyester-based resins, urethane-based resins, acrylic resins, epoxy-based resins, amide-based resins and the like, and it is particularly preferable that the resin itself has reactivity. These may be used as a mixture of two or more kinds, and if necessary, a crosslinking catalyst may be used in combination. These thermoplastic and thermosetting resins can be used by dissolving or dispersing them in any solvent. preferable.

The content of the organopolysiloxane in the protective layer is not particularly limited as long as it satisfies the constitutional requirements of the present invention, but from the viewpoint of the toughness of the coating film, it is 10 to 50% by weight, preferably 15% by weight.
Preferably it is 4040% by weight.

The effect of the present invention can be obtained by applying the mixed coating liquid of the organopolysiloxane and the resin to the polyester film before the completion of the crystal orientation, and stretching and heat-treating the mixture under the conditions of the characteristics. . That is, after applying a coating liquid obtained by mixing an organopolysiloxane and a thermoplastic, thermosetting resin, it is preferable to stretch in a state where no solvent is present in the coating film in a stretching process,
For this purpose, it is effective to increase the concentration of the solvent, take a sufficiently long preheating temperature, increase the stretching temperature or increase the stretching speed in a range where defects such as film breakage and neck stretching do not occur. is there. Specifically, the coating solution concentration is 2 to 20 wt%, preferably 3 to 10 wt%, and the stretching temperature is 98 to 180 ° C, preferably 110 to 150 ° C. The stretching speed is appropriately selected depending on the stretching temperature. For example, about 10,000% / minute to about 400000% / minute is preferable.

It is also important that moisture be present in the stretching process atmosphere. Specifically, it is achieved by stretching in pressurized water or in the presence of steam during the stretching step. The temperature at this time needs to be 10% RH or more, preferably 25% RH or more, as a value on the surface layer of the film to be stretched. After the stretching, it is necessary to perform a heat treatment at 180 to 250 ° C. That is, no moisture is present in the coating film, but moisture is present only in the surface layer of the coating film at the time of stretching, and then the heat treatment is performed at a high temperature, whereby the structure of the protective layer of the present invention is achieved.

Next, a typical method for producing a polyester film for a thermal transfer material of the present invention will be described in which polyethylene terephthalate (hereinafter abbreviated as PET) is used as a typical example of polyester, but is not limited thereto.

PE containing so-called precipitated particles and inorganic fine particles (for example, colloidal silica having a particle size of 1 μm) precipitated during the polymerization process.
T is dried and melt-extruded according to a conventional method, and the extruded sheet-like melt is cooled and solidified to produce an unstretched PET film. The film is heated to 80-120 ° C.,
The film is stretched up to 5 times to obtain a uniaxially oriented film. One surface of the film is subjected to corona discharge treatment in a carbon dioxide gas atmosphere, and a mixed coating liquid of a thermoplastic or thermosetting resin and euganopolysiloxane is applied to the treated surface. Then, after drying in the preheating step, humidify with pressurized steam at 98-180 ° C.
It is stretched 6 times in the width direction. Subsequently, the heat treatment is conducted to a heat treatment zone of 180 to 250 ° C. for 1 to 10 seconds. During this heat treatment, it is better to perform a relaxation treatment of 3 to 12% in the width direction. If necessary, the film may be stretched 1.1 to 1.7 times in the longitudinal direction again.

The method of applying is not particularly limited, and an extrusion lamination method, a melt coating method may be used, but a coating liquid dispersed in water or various solvents is gravure coated, reverse coated, because a thin film can be coated at a high speed,
Spray coating, kiss coating, die coating and bar coating are preferred.

The polyester film for the heat-sensitive transfer material thus obtained is coated with a color material layer, then cut into appropriate widths, and processed into word processors, facsimile machines, personal computer printers, video printers, bar code printers, typewriters, It is used for printing out characters or images such as plain paper copiers.

[Method for Measuring Characteristics and Method for Evaluating Effect] The method for measuring characteristics and the method for evaluating effect in the present invention are as follows.

(1) Atomic ratio of Si / C attributed to bifunctional siloxane of outer layer and inner layer of protective layer Measured by the ESCA method under the following conditions.

Apparatus: Shimadzu Corporation ESCA750 Excitation X-ray: MgKα _1,2 line (hν = 1253.6 eV) Energy correction: binding energy of C1s main peak (B;
E) The value was adjusted to 284.6 eV.

Photoelectron escape angle: 30 ° to sample surface (detection depth: surface to
50Å) The atomic ratio Si / C was determined from the peak area of the photoelectron peak thus determined.

Si attributable to the bifunctional siloxane was identified from the Si2p peak position.

The Si / C atomic ratio of the outer layer of the protective layer was measured from the surface of the protective layer by the above method. For the inner layer of the protective layer, a section of the protective layer was cut out by a freezing method, and the position of the section closest to the base film side was measured. 2 if measurement in this section is not possible
Secondary ion mass spectrometer (SIMS)
²⁸ Si ^{- 28} of the protective layer deepest portion corresponds strength to 1/10 of the coating thickness seek Si ^- intensity and the value of the protective layer lining the. The thickness of the protective layer was measured by enlarging a cross section cut by a freezing method by 100,000 times. The measurement was performed at 10 points each in the longitudinal direction and the width direction, and the average value was obtained. ESCA calculated ²⁸ Si ^- strength obtained by SIMS method
The ²⁸ Si ^- strength obtained by extrapolation from the known values measured by the SIMS method and the SIMS method was converted to Si / C by the ESCA method. The measurement conditions of the SIMS method are as follows.

Apparatus: Secondary ion mass spectrometer (SIMS) A-DIDA3000 manufactured by ATOMIKA, West Germany Primary ion species: Cs ⁺ Primary ion acceleration voltage: 12 kV Primary ion current: 30 nA Raster area: 400 μm mouth Analysis area: Gate 30% measurement Vacuum degree: 1 × 10 ^-8 Torr HQH: # 12 (2) Hot stick property Sublimation ink of the following composition is applied to the other side of a biaxially oriented polyester film having a protective layer on one side and dried. After being sewn, a thermal transfer material was prepared by slitting to an appropriate width.

[Sublimation ink layer composition] Disperse dye KST-B-136 (manufactured by Nippon Kayaku Co., Ltd.) 4 parts by weight Ethyl hydroxyethyl cellulose 6 parts by weight Methyl ethyl ketone 45 parts by weight Toluene 45 parts by weight The thermal transfer material was applied to the following printer. The voltage when the hot stick was generated was measured by changing the applied voltage. The vehicle was run under normal use conditions except that the applied voltage was changed.

Sublimation type printer: Sharp color video printer GZ
-P11W (3) Contamination of thermal head A hot-melt ink layer of the following composition is applied to the other side of a biaxially oriented polyester film provided with a protective layer on one side by a hot melt method and slit to an appropriate width to form a thermal transfer material. made.

[Hot-melt ink layer 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 This thermal transfer material was subjected to the following thermal printer,
After traveling 1000 m under normal use conditions, the thermal head was observed at a magnification of 100 using an optical microscope, and the contamination state was determined according to the following criteria.

Thermal printer: Mitsubishi line thermal color printer G500F-10 type ◎: No contaminants attached ○: Almost no contamination (contaminated area less than 10%) △: Considerable contamination (contaminated area 10% or more 30) %: ×: Significant contamination.

(Contamination area 30% or more) (3) Runnability The runnability of the guide roll and guide plate was measured by measuring the static friction coefficient (μs) and dynamic friction coefficient (μd) between the protective layer surface and the mirror-finished hard chrome plate at 80 ° C. 0.25 for both μs and μd
The following was defined as [good], and the case exceeding it was defined as [poor]. The measurement was performed with a slip tester according to ASTM-D-1894B-63.

[Effects of the Invention] In the present invention, a protective layer is provided on one surface of a biaxially oriented polyester film, and the ratio of the number of Si / C atoms attributed to the bifunctional siloxane in an outer layer and an inner layer of the protective layer is set to a specific range. A polyester film for a heat-sensitive transfer material is obtained, in which sticking hardly occurs, prevention of contamination of the thermal head due to falling off of the protective layer, and improvement in running property due to improvement in lubricity with a guide plate or a guide roll.

[Examples] Next, the present invention will be described based on examples.

Example 1 PET pellets containing 0.15% by weight of precipitated particles having a particle size of 0.5 to 1.5 μm (particles precipitated during the polymerization step) and 0.2% by weight of calcium carbonate particles having a particle size of about 1.5 μm (intrinsic viscosity)
0.63dl / g) after being sufficiently vacuum dried and fed to an extruder
The mixture was melt-extruded at 280 ° C., filtered through a 10 μm-cut metal sintered filter, extruded into a sheet shape from a T-shaped die, wound around a cooling drum having a surface temperature of 50 ° C., and cooled and solidified. In order to improve the adhesion between the sheet and the surface of the cooling drum during this time, a wire electrode
A DC voltage of V was applied. The unstretched PET film thus obtained was heated to 95 ° C. and stretched 3.5 times in the longitudinal direction to obtain a uniaxially stretched film. One surface of this film was subjected to a corona discharge treatment in a carbon dioxide gas atmosphere, and an aqueous paint having the following composition was applied to the treated surface by a gravure coating method so that the applied thickness after biaxial stretching was 0.1 μm.

[Coating composition] Thermoplastic acrylic resin emulsion (methyl methacrylate / ethyl acrylate (50/50) mol%, molecular weight 30
10,000 parts) 67 parts by weight Epoxy / polyether-modified silicone (dimethylsiloxane content 0.82 viscosity 2000 centipoise) 30 parts by weight Ammonium dihydrogen phosphate 3 parts by weight This is diluted with water to a solid concentration of 5% by weight, and further coated. Fluorosurfactant as modifier for all solids
1.2 parts by weight were added and uniformly stirred and mixed to prepare a water-based paint having a viscosity of 4 centipoise at 20 ° C.

After the application, the moisture is sufficiently dried in a preheating step at 110 ° C., and then the ambient temperature is heated and humidified to 140 ° C. with raw steam, stretched 4.5 times in the width direction in a tenter, and then
Heat treatment was performed at 10 ° C. for 5 seconds to obtain a polyester film for a thermal transfer material having a protective layer thickness of 0.1 μm and a base film thickness of 6 μm. The atomic ratio of Si / C attributed to the bifunctional siloxane in the protective layer of this film was 0.23 in the outer layer of the protective layer and 0.01 in the inner layer of the protective layer. An ink layer was applied to the surface of the film opposite to the protective layer to prepare a thermal transfer material.
This thermal transfer material is used at the normal working voltage of 14.5
Sticking did not occur up to 16.5V exceeding V.
In addition, the contamination state of the thermal head was at the level of “○”, and the running property was at the level of “good”.

Comparative Example 1 A polyester film for a thermal transfer material was prepared in the same manner as in Example 1 except that the stretching conditions in the width direction and the heat treatment conditions used in Example 1 were changed. That is, the applied coating material was stretched in the width direction while not sufficiently dried in the preheating step, and the heat treatment temperature was set to 160 ° C. The Si / C atomic ratio of the protective layer of this film is 0.12 in the outer layer and 0.
It was 10. A thermal transfer material was prepared from this film in the same manner as in Example 1. This heat-sensitive transfer material was sticky at a voltage of 12 V which is lower than a normal use voltage of a sublimation type printer. In addition, due to poor adhesion of the protective layer, the thermal head was significantly contaminated, and the runnability was "poor".

Comparative Example 2 5% by weight of the coating material used in Example 1 was applied to a commercially available biaxially oriented polyester film, dried, and the protective layer thickness was 0.1 μm.
m was obtained. Si / C of the protective layer of this film
The atomic ratio was 0.11 in the outer layer and 0.13 in the inner layer.

A thermal transfer material was prepared from this film in the same manner as in Example 1. However, the sticking generation voltage was 11.5 V, the thermal head contamination [x], and the running property [poor] were obtained.

Comparative Example 3 A polyester film for a thermal transfer material was prepared in the same manner as in Example 1, except that the coating composition was changed as follows.

[Coating Composition] Dimethylpolysiloxane Emulsion 100 parts by weight This coating was diluted with water in the same manner as in Example 1 and applied so that the coating thickness after biaxial stretching was 0.1 μm. The Si / C atomic ratio of the protective layer of the film obtained in this way is 0.
50 and 0.50 in the inner layer. When this film was evaluated as a thermal transfer material, the thermal stick resistance was good, but the contamination of the thermal head was at the level of [x].

Claims (1)

(57) [Claims] 1. A laminated film comprising a biaxially oriented polyester film having a substantially one-layer protective layer provided on one side thereof, which is attributed to the bifunctional siloxane in the protective layer.
A polyester film for a thermal transfer material, wherein the Si / C atomic ratio is 0.15 to 0.40 in the outer layer of the protective layer and 0.05 or less in the inner layer of the protective layer.