JP2581125B2 - Transferr for thermal recording - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a transfer member for thermal recording (ink ribbon, ink sheet, etc.) of a current transfer type.

[Prior Art] In recent years, a recording method based on thermal transfer has been used in addition to an electrophotographic, ink-jet, and electrostatic recording method. An energization method has been proposed as one of the thermal transfer methods. In this method, instead of applying thermal energy to the ink layer by a thermal head, an electric current is passed through a conductive film having a certain electric resistance, and the ink layer is melted or sublimated by Joule heat generated there.
For example, according to Japanese Patent Application Laid-Open No. 54-58511, carbon black is mixed into polycarbonate and used as a film substrate of this type. According to JP-A-56-121786, carbon black is mixed into a polyester resin and used as a base material of this system. However, polycarbonate and polyester have poor heat resistance and mechanical properties.
Use of aromatic polyamide resins such as 2-39288 has begun.

In this energization method, heat energy is effectively transmitted to the ink layer by generating heat in the film itself, so that high-speed printing and energy saving can be achieved. In particular, the use of a heat resistant resin such as an aromatic polyamide is highly effective in increasing the speed and improving the print quality.

[Problems to be Solved by the Invention] However, the printing speed of the energization method is still inferior to the impact method which is currently frequently used. One of the causes is that the contact resistance between the transfer body and the energizing head is large. For this reason, the amount of current that flows even when a voltage is applied to the head is small, and heat is generated at the contact portion between the transfer body and the head, so that heat escapes to the head side and contributes little to the heating of the ink layer. There is.

The present invention solves such a problem and provides a thin thermal transfer medium having high energy efficiency.

[Means for Solving the Problems] The present invention relates to an aromatic polyamide film containing 10 to 40% by weight of carbon black or a transfer body for thermal recording in which an ink layer is provided on one side of an aromatic polyimide film. The surface roughness Ra (μm) and glossiness L of one surface on the head side are in the range of the following formula (1), and the number of coarse projections having a height of 1 μm or more is 1 / mm.
A transfer member for thermal recording, wherein the number of transfer members is 0 or less.

3.500 ≦ L / Ra ≦ 35,000 (1) The aromatic polyamide of the present invention is a repeating unit represented by the general formula HN—Ar ₁ —NHOC—Ar ₂ —CO
Those composed of a polymer containing at least 70 mol% are preferred.

Here, Ar ₁ and Ar ₂ contain at least one aromatic ring and may be the same or different, and representative examples thereof include the following.

Also, part of the hydrogen on these aromatic rings are halogen (especially chlorine), a nitro group, an alkyl group of C ₁ -C ₃ (especially methyl), such as alkoxy groups C ₁ -C ₃ Also includes those substituted with a substituent. Also, X is _{-O -, - CH 2 -,} - SO 2 -, - S -, - CO- , and the like. These are included in the form of homopolymer or copolymer.

The aromatic polyimide in the present invention is one containing at least one aromatic ring and at least one imide ring in the repeating unit of the polymer, and has the general formula Those containing 70 mol% or more of the repeating unit represented by are preferred.

Here, Ar ₃ and Ar ₅ contain at least one aromatic ring, and two carbonyl groups forming the imide ring are bonded to adjacent carbon atoms on the aromatic ring. This Ar ₃ is derived from an aromatic tetracarboxylic acid or its anhydride. Representative examples include the following.

Here, Y is _{-O -, - CO-, CH 2} -, - S-, SO 2
-And so on.

Ar ₅ is derived from tricarboxylic acid or its anhydride.

Ar ₄ and Ar ₆ contain at least one aromatic ring and are derived from aromatic diamines and aromatic diisocyanates. Further, it may contain an amide bond, a urethane bond, or the like. Ar ₄ , A
Typical examples of r ₆ include the following.

Here, some of the hydrogens on these aromatic rings are halogen group, a nitro group, an alkyl group of C ₁ -C _3, even those substituted with substituents such as alkoxy groups C ₁ -C ₃ Including. Z is
—O—, CH ₂ —, —S—, SO ₂ —, —CO— and the like.
These are included in the form of homopolymer or copolymer.

Further, the aromatic polyamide and the aromatic polyimide of the present invention may be blended with a lubricant, an antioxidant, other additives, and other polymers to the extent that the physical properties of the film are not impaired.

The carbon black in the present invention is not particularly limited as long as it has conductivity, but is preferably furnace black or acetylene black. Carbon black which has been subjected to a surface treatment for improving electric conductivity may be used. Further, these carbon blacks preferably have a specific surface area of 5 m ² / g to 1000 m.
² / g, particularly preferably from 10m ² / g~950m ² / g, average primary particle size of preferably 5 nm to 500 nm, especially 10mμ~100
mμ is preferable, and carbon purity is preferably 90% or more, more preferably 97% or more.

The addition amount of carbon black is 10 to 40 wt%, preferably
It is 15 to 35 wt%. If it is less than 10 wt%, the conductivity will be low and the film will not generate heat. Conversely, if it exceeds 40 wt%, the conductivity will be too high and it will be difficult to convert to Joule heat in the film, the film temperature will not rise, the mechanical properties of the film will deteriorate, and the film will be broken and wrinkled frequently, making it practical for use. Become intolerable.

Further, at least one surface on the head side of the film of the present invention needs to have the glossiness L and the surface roughness in the range of the expression (1). The surface characteristics of the film vary depending on the surface shape in addition to the average roughness Ra. When the relationship between the glossiness L representing the surface shape and the surface roughness Ra falls within the range of the expression (1), the present invention is not limited to the above. The goal can be achieved.
Preferably, 5,000 ≦ L / Ra ≦ 30,000. If L / Ra is less than 3,500, the contact resistance with the head increases, and the heat generated at the contact portion escapes to the head side, so that energy loss increases and transfer efficiency decreases. Further, although different depending on the material of the head, there is a problem that the transfer body is shaved or the head is shaved. In particular, when increasing the resolution with a transfer body that does not have an intermediate layer such as Al, it is necessary to set the forward and return electrodes closely, but the film and electrode shavings accumulate between the electrodes. Short circuit may occur. Furthermore, L / Ra of the film on the ink layer side is 3,
If it is less than 500, the contact with the image receiving paper is deteriorated and the print quality is reduced.

On the other hand, if L / Ra is greater than 35,000, the surface properties of the transfer body become too smooth, causing problems such as sticking and running failure in the running system. In addition, workability deteriorates during the production of the transfer body. Here, the surface roughness Ra is preferably 0.01 μm or more, more preferably 0.02 μm or more, from the viewpoint of improving running properties and sticking.

Further, at least 1 μm of one surface on the head side
The number of coarse projections having the above height needs to be 10 or less per 1 mm. The number is preferably 5 or less. This is determined by measuring the surface roughness and writing it on a chart from a roughness curve corresponding to 1 mm of the film. If the number is more than 10, the contact between the head and the transfer member becomes poor, so that the transfer efficiency of the ink layer is reduced, and coarse protrusions and the head are scraped.

The thickness of the film of the present invention is preferably from 1 to 20 μm, more preferably from 2 to 10 μm. If it is thinner than 1 μm, the strength is reduced, and it is not practical. On the other hand, when the thickness is more than 20 μm, the heat diffusion becomes large, so that the local heating of the ink cannot be performed and clear printing cannot be performed, or the energy for printing increases, which is not suitable for high-speed printing.

Further, the surface resistivity Rs (KΩ) of the film is preferably 2 ≦ Rs × t ≦ 500, more preferably 2 ≦ Rs × t ≦ 100, where t (μm) is the film thickness. If Rs × t is smaller than the above range, the conductivity becomes too high and the calorific value of the film decreases. Conversely, if Rs × t exceeds the above range, the conductivity decreases and the film does not generate heat. When the surface resistivity varies depending on the dispersion state of carbon black, metal powder may be added to stabilize the film so that the physical properties of the film are not impaired.

Further, the film of the present invention has a strength in at least one of the longitudinal direction or the transverse direction of 12 kg / mm ² or more, more preferably 15 kg / mm ² or more.
It is preferably at least Kg / mm ² . If the strength is less than 12 kg / mm ^2, problems such as wrinkling or breakage tend to occur when processing a film or when using as a transfer body.
Further, the elongation in at least one direction is 10% or more, more preferably 15 to 100%, and the Young's modulus is preferably 400 kg / mm ² .

The moisture absorption of the film (measured after standing at 25 ° C. and 75% RH for 48 hours) is preferably 4% by weight or less, more preferably 2% by weight or less. If it is more than 4 wt%, the resistance value changes depending on the humidity, the printing quality changes depending on the environmental conditions used, and the film foams due to heating.

Further, the heat shrinkage of the film of the present invention at 250 ° C. is preferably 5% or less, more preferably 3% or less.

Next, the heat-sensitive transfer ink layer in the present invention is not particularly limited, but specific examples include a meltable ink and a sublimable ink. The ink contains a coloring component and a binder component as main components, and if necessary, a softener, a flexible agent,
A leveling agent, a dispersing agent, a surface forming agent, and the like are configured as additional components. The thickness of the ink layer is 0.2-20 μm, preferably 0.5
1010 μm.

As the binder component, well-known waxes such as carnauba wax, paraffin wax, and ester wax, cellulose-based resins, vinyl-based resins, and various polymers having a low melting point are useful. Organic or inorganic pigments or dyes may be used, but are not limited thereto.

Next, the production method of the present invention will be described, but is not limited thereto. In order to achieve the present invention, carbon black is present in a solution of aromatic polyamide, aromatic polyimide, or polyamic acid (polyimide precursor), and the solution is formed by forming a film.

First, an aromatic polyamide, in the case of acid chloride and diamine, N-methylpyrrolidone (NMP),
It is synthesized by solution polymerization in an aprotic organic polar solvent such as dimethylacetamide (DMAc) or dimethylformamide (DMF), or by interfacial polymerization using an aqueous medium. When acid chloride and diamine are used as monomers, hydrogen chloride is produced as a monomer in the polymer solution.In order to neutralize this, an inorganic neutralizing agent such as calcium hydroxide, calcium carbonate, lithium carbonate, or ethylene oxide is used. , An organic neutralizing agent such as ammonia and triethylamine.

The reaction between the isocyanate and the carboxylic acid is performed in an aprotic organic polar solvent in the presence of a catalyst.
These polymer solutions may be used as a stock solution for forming a film, or the polymer may be isolated once and then redissolved in the above-mentioned solvent to prepare a stock solution. In some cases, an inorganic salt such as calcium chloride, magnesium chloride, or lithium chloride is added as a dissolution aid to the film forming stock solution. The polymer concentration in the membrane forming solution is preferably about 2 to 40% by weight.

On the other hand, a solution of aromatic polyimide or polyamic acid is obtained as follows. That is, polyamic acid is N-
It can be prepared by reacting tetracarboxylic dianhydride with an aromatic diamine in an aprotic organic polar solvent such as methylpyrrolidone, dimethylacetamide and dimethylformamide. The aromatic polyimide can be prepared by heating a solution containing the above-mentioned polyamic acid or adding an imidizing agent such as pyridine to obtain a polyimide powder, which is dissolved in a solvent again. The polymer concentration in the film forming solution is preferably about 5 to 40% by weight.

The kneading of carbon black and polymer includes the following methods, but is not limited thereto.

(1) Carbon black is dispersed in a solvent in which the polymer is soluble, and then added to the polymer solution, or the isolated polymer is added to the dispersion and dispersed.

(2) Polymerization is performed after carbon black is dispersed in a polymerization solvent before polymerization.

(3) Carbon black is added to the polymer solution as powder or together with a solvent and dispersed.

Examples of the dispersing device include a colloid mill, a three-roll mill, a kneader, an ultrasonic dispersing machine, a sand mill, and a ball mill, and the ultrasonic dispersing device is more preferable from the viewpoint of dispersibility.

Further, when the surface of the film is too smooth only by adding carbon black, it is preferable to keep particles in the film forming stock solution. Here, the particles are not particularly limited, but SiO ₂ , TiO ₂ , ZnO, Al ₂ O ₃ , CaSO ₄ , BaSO ₄ , CaCO ₃ ,
Inorganic, such as zeolite, silicone particles, Teflon particles,
Organic ones are used. The particle size is preferably 0.1 to 10 μm, and the amount added is preferably 0.1 to 5% by weight.

The film-forming stock solution prepared as described above is formed into a film by a so-called solution film-forming method such as a wet method, a dry-wet method, and a dry method.

When a film is formed by a wet method, a method is employed in which the undiluted solution is directly extruded from a die into a film-forming bath, or once extruded onto a support such as a drum and the support is introduced into the wet bath. This bath is generally composed of an aqueous medium, and may contain an organic solvent, an inorganic salt or the like in addition to water. In the wet bath, an organic solvent, an inorganic salt and the like are extracted, and the film is stretched in the longitudinal direction. Next, drying, transverse stretching, and heat treatment are performed.
500500 ° C., 1 second to 30 minutes.

When a film is formed by a dry-wet method, the undiluted solution is transferred from a die to a drum,
Extruded onto a support such as an endless belt to form a thin film,
Next, the solvent is scattered from the thin film layer and dried until the thin film has a self-holding property. Drying conditions are in the range of room temperature to 300 ° C. within 60 minutes. The film after the dry process is peeled from the support and introduced into the wet process, desalting and desolvation are performed in the same manner as in the above wet process, and further stretched, dried,
Heat treatment is performed to form a film.

When a dry process is employed, a film which has been dried on a drum or an endless belt or the like and has self-holding properties is peeled off from these supports and stretched in the longitudinal direction of the film. Further, drying, stretching, and heat treatment for removing the residual solvent are performed, and these treatments are performed at 150 to 500 ° C. for 1 second to 30 minutes.

The film formed as described above is stretched during the film-forming process, and the stretching ratio is 0.9 to 3.0 in area ratio (the area ratio is the area of the film after stretching divided by the area of the film before stretching). It is preferable to be within the range of 1) or less in order to improve conductivity and maintain mechanical properties and thermal properties. 3.0 magnification
If it is larger, the mechanical properties are improved, but the conductivity is remarkably deteriorated, which is not preferable.

As a method for adjusting the surface properties of the film, there are controls such as the type and amount of carbon black added, the dispersion method, and the film forming conditions. In the dry method and the dry-wet method, a film having a smooth surface can be obtained by increasing the polymer concentration at the time of peeling from a drum or an endless belt. In addition, by applying pressure with a nip roll during the film forming process, a film that is smooth on one side or both sides can be obtained. Further, the coarse protrusions can be removed depending on the dispersion conditions of the carbon black or the excessive amount.

Next, an ink layer is formed on the base film of the present invention obtained as described above. If necessary, a pretreatment such as a corona treatment or a glow treatment may be performed. The inks include those described above, and can be formed by hot melt coating on one side of the film or a general coating method such as gravure, reverse, or a slit die as a solution dissolved in a solvent. .

The substrate structure of the transfer body for thermal recording of the present invention comprises the above-mentioned base film and ink layer, and a conductive layer such as Al, Au, A between the film and the ink layer (referred to as an intermediate layer).
g, Ni, Cr, Co, Zn, Sn, Mo, W, or an alloy, oxide, or nitride thereof at 200 to 5000 Å, preferably 400 to 30
00 ° may be provided. Further, the present invention does not obstruct the present invention even if a layer other than the conductive layer, such as a release layer, a lubricant layer, or a heat-resistant layer, is provided as the intermediate layer together with or without the conductive layer.

[Effect of the Invention] Since the transfer body of the present invention is based on a film mainly composed of carbon black and aromatic polyamide or aromatic polyimide, it has good heat resistance and mechanical properties, and can be used in a large amount even with a thin transfer body. Energy can be added. Also, despite the excellent smoothness of the surface of the film on the head side, there is no sticking during printing or running failure in the running system. Furthermore, good contact between the head and the transfer member effectively generates heat in the film, and less heat is scattered to the head side, so that the applied energy is effectively used for transferring the ink layer. As a result, it is possible to further increase the speed and improve the print quality, and to realize an energy-saving and compact printer.

When the film surface on the ink layer side is also smooth, the adhesion to the image receiving paper is improved, the printing quality is further improved, and the effect is very large.

[Measurement method of characteristics] (1) Surface roughness Ra, number of coarse protrusions Using a surface roughness measuring instrument of SE-3E manufactured by Kosaka Laboratories, measuring a measurement length of 4 mm with a cutoff value of 0.08 mm, and measuring the center line Find the average roughness Ra. Further, the number of protrusions having a height of 1 μm or more from the center line of the roughness curve chart is counted, and the number of protrusions corresponding to 1 mm of the film is obtained. The film is measured by fixing the film to a glass cylinder having an outer diameter of 80 mm with cellophane tape.

(2) Gloss L Using a variable angle gloss meter VG-107 manufactured by Nippon Denshoku Industries, aluminum is deposited at 1000 to 1500 ° and measured at an angle of 60 °. The mirror gloss varies slightly with the thickness of the glass, but is around 800.

(3) Surface resistivity Rs A circular main electrode with a diameter of 16 mm and a ring-shaped counter electrode with an inner diameter of 30 mm and an outer diameter of 34 mm are fixed so that the center of each circle is the same, and a 1 kg load is applied to the film surface. And read the resistance value when a current was passed through it, and calculated by the following equation.

Rs = (P / g) × R where Rs: Surface resistivity (KΩ) P: Effective circumference of electrode (7.23 cm) g: Distance between electrodes (0.7 cm) R: Actual measured value of resistance (KΩ) EXAMPLES Hereinafter, the present invention will be described based on examples, but the present invention is not limited thereto.

Example 1 65 mol% of 2-chloroparaphenylenediamine and 4,
Polymerization was carried out in NMP using 35 mol% of 4'-diaminodiphenyl ether as an amine component and 100 mol% of 2-chloroterephthalic acid chloride as an acid component, which was poured into water, washed with water and dried to isolate a polymer. . 15Kg of this polymer and NM
Disperse P200Kg, and carbon black 5Kg with a kneader,
A homogeneous solution was obtained. This was passed through a filter of 10 μm cut, uniformly cast on a metal drum, and dried at 120 ° C. until it had a self-holding property. After that, the film is peeled off from the drum and stretched 1.1 times in the machine direction (MD direction), then introduced into a tenter and stretched 1.1 times in the width direction (TD direction) at 300 ° C. to a thickness of 8 μm.
Was obtained. As shown in Table 1, the characteristics of this film are such that the surface property of the support surface (surface B) is very excellent.

A mixture having the following composition was applied to the non-supporting surface (side A) of this film to form a 4 μm thick ink layer to obtain a transfer ribbon.

Carbon black 15 parts Paraffin wax 35 parts Ester wax 40 parts Polytetrahydrofuran 10 parts Using this transfer ribbon, a 20 μm / mm energizing head with a diameter of 30 μm and a return electrode at a position of 100 μm from this are used to apply a voltage of 10 V. When printing was performed on plain paper, dots having a diameter of 40 μm were printed sharply.
No sticking or dirt on the head was observed.

Example 2 A film was obtained in the same manner as in Example 1 except that the film was passed twice between two metal nip rolls mirror-finished to 0.1S in the film forming process of Example 1. As shown in Table 1, this film had very excellent surface properties on both the A side and the B side.

A transfer ribbon was prepared by providing an ink layer on the surface A in the same manner as in Example 1, and a printing test was performed in the same manner as in Example 1. As a result, dots having a diameter of 50 μm were printed sharply. Energy efficiency was confirmed. In addition, it was good without sticking.

Example 3 30 mol% of paraphenylenediamine and 70 mol% of 3,4'-diaminodiphenyl ether were used as an amine component, and 100 mol% of terephthalic acid chloride was used as an acid component to polymerize with NMP.
This was poured into water to isolate the polymer. With this polymer
NMP is added to the kneader, LiBr is added at 10 wt% per polymer,
Further, carbon black was added to the concentration shown in Table 1 to obtain a uniform solution. This was cast on a metal drum through a 10 μm cut filter, dried, and then introduced into water. It was stretched 1.2 times in the MD direction in water, and a roll polished to 0.1S on the B side and a 1S polished roll on the A side was used as a nip roll and passed between them.
Thereafter, the film was introduced into a tenter and stretched 1.2 times in the TD direction at 330 ° C. to obtain an 8 μm film. Table 1 shows the properties of the film.

An ink layer was formed on the surface A in the same manner as in Example 1, and a transfer ribbon was obtained. A printing test was performed in the same manner as in Example 1. As a result, 35 μm dots were printed sharply. No sticking or dirt on the head was observed.

Example 4 Carbon black was added to a DMAc solution of a polyamic acid synthesized from 4,4'-diaminodiphenyl ether and pyromellitic anhydride to a concentration shown in Table 1 to obtain a uniform solution. This was cast on a metal drum through a 10 μm-cut filter, dried and subjected to the same pressure as in Example 3. Furthermore, this is introduced into a tenter and
Heat treatment was performed for 0 minutes. The stretching ratio is 1.0 for both MD and TD.

A transfer ribbon was prepared by providing an ink layer on the A side of the film in the same manner as in Example 1, and a printing test was performed in the same manner as in Example 1. As a result, sharp dots of 40 μm were obtained. No sticking or dirt on the head was observed.

Comparative Example 1 A printing test was performed in the same manner as in Example 1 except that the film of Example 1 was used and an ink layer was provided on the B side. As a result, the printed dot diameter was 20 μm, and only dots smaller than those in Example 1 were obtained. When the voltage was increased to obtain the same dot diameter as in Example 1, a dot having the same diameter was finally obtained at 25 V. However, it was necessary to input larger energy than in Example 1. In addition, a portion that could not be printed came out as the printing was repeated, and the head portion was observed. As a result, shavings of the head were accumulated between the current-carrying head and the return electrode. This was because the head was scraped because the film surface was rough.

Comparative Example 2 A film was formed in the same manner as in Example 2 except that the nip roll was passed 10 times, and an ink layer was provided on the A side to obtain a transfer ribbon. The properties of the film were as shown in Table 1, and the head side (B side) had a very smooth surface. When a printing test was carried out in the same manner as in Example 2, sticking occurred and printing was not possible.

Comparative Example 3 A film was made in the same manner as in Example 4 except that a filter was not passed during film formation, and a transfer ribbon was manufactured. This film has many coarse projections as shown in Table 1.

Using this ribbon, a printing test was carried out in the same manner as in Example 1, but the dot diameter was large, ranging from 10 μm to 20 μm, and only dots smaller than Example 4 were obtained. After the printing test, a large amount of film shavings adhered to the head.

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-62-286788 (JP, A) JP-A-62-37191 (JP, A) JP-A-62-286789 (JP, A) JP-A 62-286789 193889 (JP, A) JP-A-62-244691 (JP, A) JP-A-62-286790 (JP, A) JP-A-62-286791 (JP, A)

Claims (1)

(57) [Claims] 1. A transfer member for thermal recording wherein an ink layer is provided on one surface of an aromatic polyamide film or an aromatic polyimide film containing 10 to 40% by weight of carbon black. The surface roughness Ra (μm) and the glossiness L are in the range of the following formula (1), and the number of coarse protrusions having a height of 1 μm or more is 1 / mm.
Thermal transfer sheet for thermal recording characterized by being 0 or less 3,500 ≦ L / Ra ≦ 35,000 (1)