JP2581132B2 - Biaxially oriented polyester film for thermal transfer foil - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a heat-sensitive transfer foil used for a thermal printer or the like, that is, a biaxially oriented polyester film suitable for a base material of a heat-sensitive transfer ribbon or a heat-sensitive transfer sheet. It is.

[Prior art] A color material layer (a heat-meltable or sublimable ink layer) is applied on one side of a thin polyester film, and on the other side,
A heat-sensitive transfer foil coated with a heat-resistant resin layer such as a silicone resin is well known in JP-A-56-155794 and 58-13359. Further, as for the polyester film used as the base material of the heat-sensitive transfer foil, mechanical properties, surface roughness and the like are specified (JP-A-60-217194, 62-193889).
And a film in which a mixture layer of an aqueous polymer and a lubricant is applied to one side of a film (Japanese Patent Application Laid-Open No. Sho 60-192633).

[Problems to be Solved by the Invention] An object of the present invention is to provide a base material suitable for obtaining a heat-sensitive transfer foil which is less likely to cause dropout (missing printing of an image) and a hot stick (a trouble that the thermal head sticks to the foil). Material film. The principle of thermal transfer is that the heat supplied from the thermal head is transmitted to the thermal transfer foil and the ink layer on the surface is transferred onto the recording paper to record images and characters, but the ink is originally transferred. Sometimes there is no ink or a thin part of ink at the right place, which is called dropout. In this dropout, there is almost no case in which most of the image or the character is dropped, and in many cases, a small portion of the image or a spot-like drop is generated in the image. Such a dropout often occurs when the ink layer has a partial omission or when the heat transfer from the thermal head becomes uneven for some reason. An object of the present invention is to provide a base film for producing a heat-sensitive transfer foil which is less likely to cause such a dropout and hardly causes a hot stick, and which is satisfied by the above-described prior art. That was not.

[Means for Solving the Problems] The present invention has a thickness of 1 to 10 μm and an average surface roughness of 0.06 to 0.25.
A layer of a mixture of a thermoplastic and / or thermosetting resin and an organopolysiloxane is applied on one side of a μm film, and the charge potential on the opposite surface is 50 to 1500 V
The biaxially oriented polyester film for a heat-sensitive transfer foil, which is characterized by being within the range, is used as the gist.

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 described above, more preferably 95 mol% or more has ethylene terephthaleo as a repeating unit, but within this limited amount range, a part of the acid component and / or the glycol component is combined with the third component as described below. May be replaced.

-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.
The intrinsic viscosity of PET as described above (measured in orthochlorophenol at 25 ° C) is between 0.40 and 1.20, preferably between 0.
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 film of the present invention needs to be in the range of 1 to 10 μm, and this range is suitable as a substrate for a heat-sensitive transfer foil. If the film is thinner than this, the workability at the time of handling the film is significantly inferior, and the heat-sensitive transfer foil using this as a base material is too weak mechanically to be practically used. Conversely, with a thicker film, the thermal conductivity is inferior, so that the printing speed is significantly reduced. Next, the average surface roughness (Ra) of the film surface of the present invention is 0.06 to 0.25 μm,
Preferably, it must be within the range of 0.07 to 0.20 μm. If the value of Ra is smaller than this, adhesion (called a hot stick) is likely to occur between the back surface of the thermal transfer foil and the thermal head, and in many cases dropouts are caused due to this. On the other hand, if the value of Ra is larger than the above range, not only the occurrence of dropout due to poor heat transfer will increase, but also the recorded image or character will have low gloss and the recording quality will be degraded. The value of Ra is
The value may be the same on both surfaces of the film, or the values of Ra on the front and back may be different within the above range. Front and back
When the value of Ra is different, it is better to apply a mixture of a thermoplastic and / or thermosetting resin and an organopolysiloxane described later to the surface having the larger value of Ra. The value of Ra of the film depends on the type, amount,
It can be controlled by the particle size and the like. The particles may be so-called precipitated particles which precipitate during the polyester polymerization step, or may be particles obtained by adding inorganic or organic fine particles to the polyester. Further, even with a polyester containing the same particles, the value of Ra can be changed depending on various conditions at the time of forming a film, for example, extrusion conditions, stretching temperature, stretching ratio, heat treatment conditions and the like.

Next, the film of the present invention needs to have a mixture of a thermoplastic and / or thermosetting resin and an organopolysiloxane applied to one surface thereof. When coated as a heat-sensitive transfer foil, this coating surface is on the back side (the side opposite to the color material layer and the side facing the thermal head). This greatly reduces the occurrence.

The thermoplastic resin mentioned here is not particularly limited, but typical ones include the following. Polyolefin resins, especially modified polyolefin resins modified with acrylic acid, chlor, etc., polyester resins, especially water-soluble or water-dispersible polyesters in which 0.5 to 15 mol% of sulfonic acid or a sulfonic acid metal base-containing dicarboxylic acid component is copolymerized. , acrylic resins, in particular _{-COOH, -CONR 4 R 5, -NR} 4 R 5, -OH, An acrylic resin, a methacrylic resin, a copolymer thereof, or a perfluoro group having a group selected from —COOCO— (where R ₄ and R ₅ are hydrogen or an aliphatic hydrocarbon group having 1 to 4 carbon atoms); Acrylic resins, acrylonitrile styrene copolymer resins, fluororesins such as fluoroethylene copolymers, thermoplastic polyurethane resins, vinyl acetate resins, or copolymers or blends thereof.

In addition, super-cooling of these thermoplastic resins such as polyethylene glycol, dicyclohexyl phthalate, diphenyl phthalate, triphenyl phosphate, dimethyl fumarate, benzotriazole, 2,4-dihydroxybenzophenone, tribenzylamine, benzyl, vanillin and phthalophenone, which are solids at room temperature. Substances, or anionic surfactants, cationic surfactants, amphoteric surfactants, nonionic surfactants, fluorine-based surfactants, organic carboxylic acids and derivatives thereof, higher aliphatic alcohols,
Paraffin, wax, surfactant and wax are often added in an amount of 1 to 50 parts by weight, preferably 3 to 25 parts by weight, based on the thermoplastic resin.

Among the above-mentioned thermoplastic resins, those particularly suitable for the present invention are acrylic acid and methacrylic acid copolymers whose terminals have been hydrophilized, and thermoplastic polyurethane resins.

The above-mentioned thermosetting resin is not particularly limited, but typical examples thereof include a silane coupling agent, a polycondensable organometallic compound such as a titanium coupling agent, hydroxyl, carboxyl, and amide. , Amine, nitrile, acrylate having a crosslinkable functional group such as epoxy, methacrylate or a copolymer or blend thereof, epoxy resin, alkyd resin,
Amine, melamine, diazine, urea, cyclic ethylene urea, cyclic propylene urea, alkyl melamine, aryl melamine, benzoguanamine, guanamine, aldehyde, isocyanate, etc., or crosslinked polyester copolymer or urethane resin, etc. Alternatively, a mixture thereof can be mentioned, and particularly preferred in the present invention is a crosslinked polyester copolymer or a crosslinked polyurethane resin. Examples of the aforementioned organopolysiloxane include silicone oil and modified silicone oil into which various functional groups are introduced. Representative examples of the organopolysiloxane are represented by the following general formulas (a) to (c).

[However, X, Y, and Z are integers of 1 to 5000, and R has 1 to 1 carbon atoms.
100 alkyl groups or hydroxyl groups, R 'has 1 to 10 carbon atoms
Alkylene group, phenylene group, cyclohexylene group,
Selected from ether groups, R ″ is hydrogen, having 1 to 1 carbon atoms
100 alkyl groups, an epoxy group, an amino group, a carboxyl group, a phenyl group, a hydroxyl group, a mercapto group, a polyoxyylene alkyl group, those selected from alkyl groups containing halogen, R is an alkyl group having 1 to 100 carbon atoms, Shown are those selected from polyoxyalkylene alkyl groups, hydroxyl groups, and halogen-containing alkyl groups. ]. Specific examples include dimethylpolysiloxane oil, amino-modified silicone oil, epoxy-modified silicone oil, epoxy / polyether-modified silicone oil, carboxyl-modified silicone oil, polyether-modified silicone oil,
Alcohol-modified silicone oil, alkyl- and alkyl-aralkyl-modified silicone oil, alkyl-aralkyl-polyether-modified silicone oil, fluorine-modified silicone oil, alkyl-higher alcohol ester-modified silicone oil, methyl hydrogen polysiloxane oil, phenylmethyl silicone and these Can be exemplified. Particularly preferred in the present invention are dimethyl polychiroxane oil, epoxy-modified silicone oil, epoxy / polyether-modified silicone oil, polyether-modified silicone oil, amino-modified silicone oil, and emulsions thereof. Also, two or more of these may be mixed and used at any ratio. Further, it is particularly preferable to use various crosslinking agents which react with the reactive groups of the silicone oil.

Organopolysiloxanes suitable for this application have a viscosity measured at 25 ° C. of 100 centistokes (hereinafter, centistokes is abbreviated as C · S) to 5,000,000 C · S, preferably 2,000 C · S to 3,000,000. Those below C · S are preferred.

The mixture of the thermoplastic and / or thermosetting resin and the organopolysiloxane as described above is applied to the back surface of the film. The composition ratio of the resin and the organopolysiloxane in this coating layer is determined by the weight of the resin. When 100, the organopolysiloxane is 5 to 50, particularly 10 to 40.
Is preferably within the range. Hot sticks and dropouts tend to be poor when the amount of organopolysiloxane is increased or decreased from this range. Known additives such as inorganic or organic fine particles (particle diameter of about 0.1 to 1 μm), plasticizers, lubricants, surfactants, and antistatic agents may be added to the mixture layer. . The mixture layer applied to the back of the film is desirably subjected to a heat treatment at 180 ° C. or higher, preferably 200 ° C. or higher for 1 to 10 seconds. By receiving such a high temperature thermal history, hot sticks and dropouts are greatly improved. Such a high-temperature heat treatment is extremely difficult with a normal coating technique of applying a coating agent to a biaxially oriented polyester film and performing a dry heat treatment (the film used in the present invention is usually about 1 to 10 μm thick, The film shrinks when exposed to temperatures as high as 180 ° C or more because it is thin. Therefore, in the process of producing a biaxially oriented polyester film, it is preferable to apply the above mixture, and then stretch and heat-treat. With this method, high-temperature heat treatment such as 180 ° C or higher, preferably 200 ° C or higher,
It can be implemented without any problems. The thickness of the mixture layer applied to the back of the film is 0.02-0.8 μm,
Preferably, it is in the range of 0.03 to 0.5 μm. Hot sticks and dropouts tend to be worse, thicker or thinner than this range.

Next, the electrostatic potential of the polyester-side surface of the film of the present invention (that is, the surface on which the color material layer is applied) is 50 to 1500.
V, preferably in the range of 100-1200V. The charge potential is the amount of static charge on the film surface expressed in volts, and both the positive potential and the negative potential are expressed in absolute values. Regardless of whether the charge potential is higher or lower than the above range, the number of dropouts increases when a heat-sensitive transfer foil is prepared using the base as a base. This tendency is particularly remarkable when the coloring material layer is dissolved in an organic solvent and applied. The control of the electrostatic potential on the film surface is controlled by the type of roll (metal roll, rubber roller,
Plastic rolls, conductive rubber rolls, etc.), humidity in the atmosphere, whether or not a contact or non-contact type static eliminator is installed, installation conditions, or film winding conditions (speed, tension, torque, surface pressure, etc.) Can be.

Next, a specific example of the method for producing the thermal transfer foil of the present invention will be described. According to a conventional method, PET containing so-called precipitated particles and inorganic fine particles (for example, colloidal silica having a particle diameter of 1 μm) precipitated during the polymerization process is dried, melt-extruded, and the extruded sheet-like melt is cooled and solidified. Make a stretched PET film. This film is heated to 80 to 120 ° C and stretched 2.5 to 5 times in the longitudinal direction to obtain a uniaxially oriented film.
One surface of the film is subjected to corona discharge treatment in a carbon dioxide gas atmosphere, and an emulsion, suspension or solution in which a thermoplastic and / or thermosetting resin and an organopolysiloxane are mixed is applied to the treated surface. Next, the coated film was stretched 3 to 4.5 times in the width direction while being heated to 90 to 130 ° C., and subsequently, 180 to 240 times.
C. and heat-treated for 1 to 10 seconds.
During this heat treatment, it is better to perform a 3 to 12% relaxation treatment in the width direction. The heat-treated film is gradually cooled through an intermediate cooling zone, and when it reaches room temperature, it is wound up by a winder to form a mill roll. Ionized air is blown onto the contact portion between the film and the roll of the mill roll winding section to control charging. Next, this mill roll is slitted into a film product roll having a desired width and length.
When the product roll is wound up with a slitter, the material of the roll that comes into contact with the non-coating side of the film (that is, the side of the polyester side on which the color material layer is coated) and the amount of The amount of spraying controls the charge potential on this surface. For example, when a rubber roll covered with a Teflon tube is used, the charge potential increases, and when a conductive rubber roll is used, the charge potential decreases. When the amount of ionized air sprayed is increased, the charge position is lowered.

Since the potential on the film surface tends to decrease somewhat with the passage of time, the potential immediately after the slit is
It may be slightly higher than the range of the present invention (of course, immediately after slitting, when applying a color material layer to make a thermal transfer foil, it is necessary to put the charged position within the range of the present invention at that time. is there).

On the non-coated side of the film thus obtained, a hot-melt type or heat-sublimation type color material layer is applied, and if necessary, a top coat layer for release is further applied thereon, and then Slit to the required width of a serial or line type printer to make a thermal transfer foil.

Thermal transfer foils made in this way are available in both monochromatic (black) and color ink colors, word processors, fax machines, printers for personal computers,
It is used for printing out characters or images such as video printers, barcode ticketing machines, typewriters, plain paper copiers and the like.

[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) Average surface roughness (Ra) It was measured according to Jis-B0601-1976. The cutoff value is
It was 0.25 mm.

(2) Charge potential on the film surface After rewinding about 10 m of the surface layer from the polyester film product roll and cutting it off, rewinding about 1 m starting from the new film end, and this 1 m hangs right below the film roll. Shape. The charge position of the polyester side surface (that is, the non-coated surface) at the center of the hanging film (at a position about 50 cm upward from the end of the film) is divided into 10 points in the film width direction (the entire width of the film is divided into 10 equal parts Then, each of the equal parts was defined as one point at the center). Measurement of charged voltage is performed by Trek Inc.'s Electrostatic
Using a Voltmeter Model 344, the distance between the film surface and the probe was about 6 mm. All measured charged voltages are treated as absolute values (that is, minus 500 V
Even if it is 500 V, treat it as 500 V), add up the 10 measured values, and divide this by 10 to obtain the average of the absolute values of the charged voltages. This value was taken as the surface charge potential of this film.

(3) Evaluation of hot stick and dropout Sublimation of the following composition on the opposite surface of a biaxially oriented PET film coated with a mixture layer of a thermoplastic and / or thermosetting resin and an organopolysiloxane on one side. After applying the hydrophilic ink as a color material layer and drying it, it was slit into an appropriate width to prepare a heat-sensitive transfer foil.

Disperse Dye KST-B-136: 0.4 parts by weight (Nippon Kayaku) Ethyl hydroxyethyl cellulose: 0.6 メ チ ル Methyl ethyl ketone: 4.5 〃 Toluene: 4.5 被 The thermal transfer foil is applied to a thermal printer to record the dye receiving amount. Printing was performed on paper with a thermal head. At this time, the degree of adhesion between the heat-sensitive transfer foil and the thermal head is comprehensively determined from visual judgment and the degree of sound generation, and the level of the hot stick is determined to be excellent,
Judgment was made in four stages: good, acceptable and unacceptable. The dropout level was determined in four stages of excellent, good, acceptable and unacceptable by comprehensively judging the occurrence of partial omission of printing and occurrence of shading.

[Examples] The present invention will be described based on examples.

Example 1 PET pellets containing 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 0.2% by weight of calcium carbonate particles having a particle diameter of about 1.5 μm (intrinsic viscosity of 0.
63dl / g) is sufficiently vacuum-dried and then fed to an extruder.
The mixture was melt-extruded at 280 ° C., passed through a 10 μm-cut metal sintered filter, extruded from a T-shaped die into a sheet, wound around a cooling drum having a surface temperature of 50 ° C., and solidified by cooling. In order to improve the adhesion between the sheet and the surface of the cooling drum during this time, a wire electrode was arranged on the sheet side, and a DC voltage of 6000 V was applied thereto. 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 the following water-based coating agent was applied to the treated surface by a rod coat method.

(Production of water-based coating agent) The following three components were mixed so that the solid content weight ratio of (A) / (B) / (C) was 65/20/15, and water was added thereto to solidify. Diluted to a concentration of 8% by weight, and further added a fluorine-based surfactant in an amount corresponding to 1.2% based on the total solid weight,
The mixture was uniformly stirred and mixed to prepare a water-based coating composition having a viscosity of 10 centipoise at 20 ° C.

(A). Water-soluble polyester copolymer having a reactive acrylic group on the side chain (B). Water-soluble amino-modified silicone oil (C). Blocked isocyanate of the following structure The uniaxially stretched film coated on one side was preheated at 98 ° C., and then stretched 3.9 times in the width direction while heating at 105 ° C. Then, the film is introduced into hot air at 225 ° C., and is heat-strained for 1 second, and then allowed to shrink by 8% of the original film width in the width direction in the same temperature atmosphere. Inside, heat-strain for about 1 second, then gradually cool through each zone of 180 ° C, 150 ° C, 100 ° C, finally cool down to room temperature, lead it to the winder, It was rolled up to a mill roll. In this winding process, all rolls that come into contact with the non-coated side of the film are grounded metal rolls, and ionized air is flowed through the contact section and the mill roll winding section to prevent strong electrification. did. Next, this mill roll was slit into a film width of 600 mm to form a film product roll. At the time of this slit, a conductive rubber roll is used as a conductive rubber roll to adjust the winding hardness of the product roll, and the non-coated surface of the film is applied. Was controlled on the non-coated side. The thus obtained film having a thickness of about 6 μm has a coating layer of about 0.2 μm applied on one side (A side) and the opposite surface (B
The charged potential of the (surface) was 320 V one week after slitting. The average surface roughness of both surfaces of this film is
A side (measured including the coating layer) is 0.10μm, B side is 0.12μm
m. On the side B of this film, a sublimable ink was applied by the method described above so as to have a dry coating amount of 1 g / m ² ,
A thermal transfer foil was made. As a result of evaluating this heat-sensitive transfer foil by the evaluation method described above, both the hot stick and the dropout were excellent, and the level was “excellent”.

Example 2 A thermoplastic polyurethane emulsion and an amino-modified silicone emulsion were mixed so that the solid content weight ratio was 90/10, and water was added thereto to adjust the solid content concentration to 8% by weight. Fluorine surfactant was added thereto in an amount of 1.2% based on the total solid weight, and the mixture was uniformly mixed and stirred to prepare an aqueous coating composition having a viscosity of 8 centipoise at 20 ° C. This coating material was applied to a uniaxially stretched film in the same manner as in Example 1, and 600 mm
A film product roll of width was made. The thickness of this film is about 6 μm, a coating layer of about 0.1 μm is applied on one side (A side), and the charged potential on the opposite side (B side) is 240 V after 10 days from the slit. Was. The average surface roughness of this film was 0.11 on the A side (measured including the coating layer).
μm and the surface B was 0.12 μm. The heat-sensitive transfer foil made in the same manner as in Example 1 using this film was excellent in both hot stick and dropout, and the level was “excellent”.

Comparative Example By changing the mill roll winding conditions and the slitting conditions in Example 1, films of 1920 V and 8 V having a charged potential on the side B one week after slitting were produced. Using these films, a heat-sensitive transfer foil was prepared in the same manner as in Example 1, and the hot stick and drop-out thereof were evaluated. As a result, the hot stick level was “excellent” for any of the films using any of the films, but the dropout was much worse. The dropout level used a 1920V film. "No" for those who have a film, "OK" for those who use 8V film
Was the result.

[Effects of the Invention] The present invention applies a specific coating agent to one surface of a biaxially oriented polyester film having a specific thickness and an average surface roughness,
Further, by setting the charge potential on the opposite surface to a specific range, the effect of reducing dropouts and hot sticks of the heat-sensitive transfer foil using this film as a base material is exhibited. The film of the present invention can be widely used for both sublimation type and heat melting type thermal transfer ribbons or sheets.

Claims (1)

(57) [Claims] 1. A thickness of 1 to 10 μm and an average surface roughness of 0.06 to 0.25.
A layer of a mixture of a thermoplastic and / or thermosetting resin and an organopolysiloxane is applied on one side of a μm film, and the charge potential on the opposite surface is 50 to 1500 V
A biaxially oriented polyester film for a heat-sensitive transfer foil.