JPS6067195A - Thermal transfer printing method - Google Patents

Abstract

PURPOSE:To enable to inexpensively print with high accuracy while using a small-type device and without wasting a toner, by a method wherein a toner uniformly adhered to a base film by electrostatic forces is selectively melted by heating, and the melted toner is transferred onto a transfer printing material. CONSTITUTION:The base film 12 (an insulating film with smooth surfaces having a volume resistivity of not lower than about 10<8>OMEGA.cm and a thickness of about several mum - several tens mum) fitted in a loop form to a metallic roller 13 and guide rollers 15, 15 is turned in the direction of arrows, and an electrostatically charged toner 7 contained in a storing tank 8 is uniformly adhered to the film 2 by electrostatic forces through a developing roller 9 impressed with a bias voltage (about 600V). On the other hand, a printing paper 5 is synchronously moved between a platen roller 14 and the base film 12, and the toner selectively melted by heating by a thermal head 4 is transferred onto the paper 5, and is fixed, thereby performing predetermined printing.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improved thermal transfer printing method, and particularly aims to provide a thermal transfer printing method useful for various printing devices such as computers and facsimiles.

Conventionally, these various printing devices have been desired to be non-impact type for the purpose of preventing noise during printing, etc.
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Other methods are becoming popular. In addition, thermal printing methods generally use processed paper coated with a special thermal recording material, but because of the high price and insufficient quality and shelf life of the printed matter, thermal transfer printing methods have recently become available for printing on plain paper. is being used.

FIG. 1 shows the main parts of a conventionally used thermal transfer printing device. In FIG. 1, ■ indicates an ink film formed by coating a base film with hot-melt ink, ■ indicates a supply reel, and ■ indicates a take-up reel.

The ink film is closely overlapped with the printing paper and guided onto the platen roller. At this time, the thermal film was placed in close contact with the back side of the ink film ■.
When a printing command is issued to the RAD (2), the ink film (2) is partially heated, and the ink on the base film that is melted by the heating is transferred onto the printing paper to perform printing.

In this type of printing method, although only a small amount of ink is required for the actual printing, the ink film requires approximately the same area as the paper being printed on, and most of the ink film is used for the actual printing. are not used and are thrown away. Furthermore, it was necessary to replace the ink film, which was inefficient from an economical and operational standpoint. Therefore, hot-melt ink is stored in a tank or the like and heated and melted, and a base film arranged in an endless belt is sequentially passed into the tank, and the molten ink is applied to the base film to form an ink film. However, proposals have also been made to perform the above printing. Although this method prevents ink and ink film from being wasted, it is difficult to apply ink uniformly on the base film, and printing quality deteriorates due to uneven ink film thickness. Moreover, it was extremely difficult to control the heating of the ink melting reservoir.

On the other hand, a method has also been proposed in which magnetic toner used in fields such as electrophotography and electrostatic recording is thermally transferred onto printing paper without using the above-mentioned ink film. The main parts of the apparatus for carrying out this method are shown in FIG. In FIG. 2, ■ represents a magnetic toner, ■ represents a magnetic toner storage box, ■ represents a developing roller, [phase] represents a magnetic rotor, and ■ represents an outer cylindrical shell made of a material with low magnetic permeability. When the magnetic toner is supplied from the storage box to the developing roller, the toner is arranged and held in a chain around the outer cylindrical shell by the action of a magnetic field. On the other hand, it is brought close to the developing roller. Then, when a print command is issued to the thermal head, the thermal energy from the thermal head melts the magnetic toner at the tip arranged in a chain shape through the printing paper, and the thermally melted magnetic toner is transferred to the printing paper. Printing is performed by However, even with this method, the holding force of the magnet Rogue, the adjustment of the gap between the developing roller and the printing paper, and the adjustment of the heat amount of the thermal head depending on the type and thickness of the printing paper are extremely complicated and difficult. . If these adjustments are not sufficient, the magnetic toner/7'''
If the thermal energy is large, it may melt more magnetic toner than necessary, resulting in a significant drop in print quality, or as a result of melting more toner than necessary. This deteriorated the stable supply and fluidity of the magnetic toner.

As a result of intensive research to solve the above-mentioned problems in conventional thermal transfer printing methods, the inventors of the present invention have developed a method using a type of ink film that evenly holds toner on a base film using electrostatic force. The present invention was achieved by discovering the fact that a transfer printing method solves the various problems mentioned above.

In other words, in the final FIA, toner is uniformly adhered and coated using electrostatic force onto a heat-resistant and insulating base film arranged in the shape of an endless belt, and heat from a heating element is applied to the base film to cause the toner to be applied. Provides a method for performing thermal transfer printing characterized by heating and melting and transfer printing onto a printing material. ^J - 1 lotus 1 set - Hereinafter, the method according to the present invention will be explained in detail with reference to the drawings. FIG. 3 shows an example of a schematic diagram of a device for carrying out the method according to the present invention, where ■ is a developer, ■ is a storage box thereof, ■ is a developing roller, and 0 is an endless belt consisting of a base film. , [Phase] is a metal roller, ■ is a platen roller, and ■ is indicated.

In Figure 3, the base film is 0 and the metal roller is 0.
and a guide roller ■, which is tightly stretched like an endless belt.
It circulates in a certain direction.

On the other hand, the developer (2) is held on the developing roller from the storage box (2). Here, when a two-component developer consisting of a chargeable toner and an iron powder carrier is used as the developer,
Due to frictional charging with the carrier on the developing roller,
The toner is charged to Φ.

As shown between the developing roller ■ and the metal roller O,
For example, if a bias potential of ■600■ is provided, the base film 0 passing between the developing roller ■ and the metal roller 0
The toner, which is also charged to (1) under the action of the above-mentioned electric field, adheres to the insulating base film circulating on the metal roller O by electrostatic force.

The base film with toner attached to its surface is circulated by a guide roller to the platen roller ■, while between the platen roller and the base film, the printing paper ■ approaches or contacts the base film near the graden roller ■. As shown in the figure, when a printing command is given to the thermal head, which is a heat generating element provided on the back side of the base film at a position facing the platen roller, the toner on the base film is printed. .

Here, the base film needs to be an insulating film having a volume resistivity of at least 108 Ω・a, more preferably at least 10 12 Ω・σ, and if it is less than that, the toner adhesion and retention properties are poor. It will be enough. Further, it is necessary that the material does not deform upon contact with a heating element such as a thermal head, and it is necessary that it has continuous heat resistance of 120° C. or higher, more preferably 150° C. or higher. In addition, from the viewpoint of high-speed printing suitability and print quality, the thickness of the base film is * p
It is necessary to have a thickness of 10 μm and a highly smooth surface.The thicker the base film, the more natural energy and time required to melt the toner, making it difficult to print at high speeds. If smoothness is not obtained, and if the smoothness is poor, the transfer efficiency and print quality will deteriorate.Specific examples of these base films and various films such as polyester film, polyimide film, fluorine GT + fat film, etc. Can be used.

Note that using a film with aluminum vapor deposited on the back side of the base film not only makes electrical contact with the metal roll easier and enables uniform toner adhesion, but also makes it possible to use materials such as rubber instead of the metal roll. It is also possible to use an insulating or ≧reliable roller to provide a bias potential between the aluminum vapor deposited portion and the developing roller portion.

Further, as the toner, a two-component toner used together with a carrier or a one-component magnetic toner containing a magnetic material can be used. As a two-component toner,
Materials that can be charged either (i) or (e) can be used, and they can be used together with a carrier such as iron powder or glass beads, and developed by a developing method such as the magnetic law method, magnetic brush method, or cascade method, or with the carrier. The toner can be attached onto the base film by a developing method such as the Bakugou Fluct method. Further, when using a -component type magnetic toner, it can be carried out using a magnetic a-ra type or the like. Regarding the setting of the bias potential, consider the charging characteristics of the toner, and if the toner is charged, the
In the case of charging, it is necessary to set the e potential in the range of aOO to tooov, preferably 400 to 600V.

When the purpose is to uniformly adhere the toner, it is also possible to further provide a metal phase between the developing roller (1) and the base film on the metal roller 0 to form a bias potential between the respective rollers.

(As shown in FIG. 4) As another method, a corona charging device (2) may be provided to apply an electric charge to the base film, and the charge may be discharged at a pressure of 4 to eKVtvN to cause the charge to be deposited on the base film. A specific example of this case is shown in FIG. 5, in which the toner can be attached by the aforementioned developing means. Even when a corona charging device is used, it is preferable to provide a bias potential to form an electric field of 100 to 400 V for the purpose of more uniform toner adhesion.

Further, although not shown, it is also possible to electrostatically adhere the adhesive to a base film that is not attached to the base film using a similar developing means.

As a cleaning means, after Vc on the base film and AC corona discharge if necessary, a fur brush or a magnetic brush may be used to generate dirt that causes paste fill. In this case, toner can be removed.

A thermal head is generally used as the heating element for melting and transferring the adhered toner on the PACE-Y film, and its printing accuracy is 5 to 10 dots/rm.

Heating time is 3-20m5. The heating temperature is 2o.

It is preferable to use one with a temperature of ~450°C.

Further, as the heating element, a heat beam such as a cobalt laser or a Reitz'-1 YAG laser can be used. In this case, the laser beam can be applied from the back side of the base film like a thermal head, but depending on the material and transparency of the base film, the thermal energy is absorbed by the base film, and the high output laser is applied by thermally melting the toner. It may be necessary. By irradiating the toner-adhering surface of the base film with a laser beam, it becomes possible to thermally melt the toner with a relatively low-power laser beam. In this case, it is necessary to adjust the laser beam irradiation position, and immediately after the toner on the base film has been melted by the laser irradiation, the porch film and the printing paper are brought into close contact with each other using a pressure roller or the like.
By transferring the fused toner, desired printing can be achieved.

Note that the toner used in the tub transfer printing method according to the present invention preferably has a particle size in the range of 1 to 80 μm from the viewpoint of printing accuracy, and from the relationship of printing speed and heating energy of the heating element, It is preferable to have a softening point or melting point in the range of 50 to 150°C. If the temperature is 050°C or lower, the toner may aggregate at the ambient temperature of the printing device, which is not preferable because it may be necessary to satisfy fluidity and supplyability.

As explained above, the thermal transfer printing method according to the present invention has the following effects compared to conventional methods.

■ The toner is attached by electrostatic force without using a conventional ink film 0 ■ The toner is not transferred directly from the developing roller to the printing paper, but the toner is held on the base film once, and the toner is transferred to the base film. Since the image is transferred from the printer, it is not subject to structural limitations of the printing device and can be made smaller.

Also, it must be easy to adjust the gap between the printing paper, platen roller, developing roller, heating element, etc.

In addition, since a base film of a constant material and thickness can be used, especially when applying heat energy from the back side, the energy of the heating element only needs to be constant at all times, and the influence of changes in the material of the printing medium is avoided. Don't accept it.

(2) Since the toner is attached to the PACE 7 ilm using electrostatic force, uniform adhesion is possible and toner scattering is less likely to occur, allowing for improved printing speed. In addition, by adjusting the bias potential and amount of corona charge, the amount of toner adhesion can be controlled.
It is possible to improve printing quality and accuracy.

■ It is easy to replace toner and color printing is possible. It is easy to change the structure of the guide roller of the twisted base film, and a printing section made of a plurality of base films can be installed without greatly improving the device, so that multicolor printing is possible.

[Brief explanation of the drawing]

FIG. 1 is a drawing showing the main parts of a conventional thermal transfer printing apparatus using an ink film. FIG. 2 is a drawing showing the main parts of a thermal transfer printing device using magnetic toner. Figures 3 to 5 show the main parts of an apparatus for carrying out the method according to the present invention. Figure 8 shows a type of apparatus in which toner is attached using a bias potential, and Figure 4 shows a developing roller and A type in which a metal roller is further provided between the metal rollers and the toner is more evenly deposited is shown in Fig. 5.
Each type of device uses a corona charging device to charge the base film. Note that the reference numeral 5j in the figure indicates the following. G... Ink film 10... Magnet rotor 2... Supply reel 11...
External cylindrical shell 3...Take-up reel +2.
...Base film 4...Tsumaruhet +3...Metal roller 5...Coating
Printing paper 14...Platen roller 8...
... Storage box 17 ... Corona charging device 9 ... Developing roller box 1 Seed 3 Low @ Gourd V

Claims (1)

[Claims] ■ Toner is uniformly adhered by electrostatic force onto a heat-resistant and insulating base film arranged in the shape of an endless belt, and a heating element is applied to the toner on the base film. A thermal transfer printing method characterized by applying heat energy to heat-melt the toner and transfer printing onto the printing material ■ A patent in which the base film is an insulating film having a volume resistance of 1 (111Ω・α or more) Thermal transfer printing method according to claim 1 (2) When the toner is adhered to the base film by electrostatic force, in order to promote the toner adhesion between the developing roller and the metal roller, an amount of 1-00 to 1.0 OOV is applied. During the thermal transfer according to claim 1, characterized in that a bias potential in the range of is provided. 18 Thermal transfer printing method according to the thermal transfer printing according to claim 1, characterized in that the toner is transferred to the printing material by cleaning with a 71-brush or magnetic brush method to remove unnecessary toner. The thermal transfer printing method according to claim 1, characterized in that: