JPH06127004A - Thermal head - Google Patents

Abstract

PURPOSE:To conduct heat generated by heating resistors concentratedly only toward printing paper by coating the heating elements of a thermal head with a protective film having an anisotropism in thermal conductivity. CONSTITUTION:Heating resistors 2a, 2b, 2c, and 2d of a heating resistor layer are coated with a protective layer 7 in five directions other than their bottoms. An arrow thetaa shown near the heating resistor 2c indicates a flux of heat directed upward in the cross section (toward printing paper). Arrows thetab represent fluxes of heat direction obliquely in the cross section toward the other heating resistors 2b and 2c. In addition, an arrow thetac indicates a flux of heat directed downward in the cross section (toward a glazing layer 3). It is required that the protective film 7 is made of a material having an anisotropism in thermal conductivity, such as a material increasing the magnitude of the heat flux indicated by the arrow thetaa and decreasing the magnitude of the heat flux indicated by the arrow thetab. In this manner, the heat efficiency for printing is enhanced, and energy can be saved as a whole.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal transfer method for thermally transferring a sublimable dye applied to an ink ribbon onto photographic paper in order to print a still image of various images such as an image picked up by a video camera and a television image. Regarding the head.

[0002]

2. Description of the Related Art Conventionally, for printing a still image of various images such as an image picked up by a video camera, a television image, etc. on a printing paper, an ink jet method, a thermal transfer method using molten wax, and a projection on a cathode ray tube. A CRT method for taking an instant image of an existing image, a thermal transfer method using a sublimable dye, and the like are used.

Among them, in the thermal transfer system using a sublimable dye, a sublimable ink ribbon coated with a sublimable dye is superposed on photographic paper, and electric energy corresponding to image information is applied to a thermal head. This is a method in which the sublimable dye on the ink ribbon is sublimated and transferred onto the printing paper by the thermal energy generated from the thermal head.

The sublimable ink ribbon is prepared by dissolving a sublimable dye in an acetate or polyester solution and adding a dispersant to form a colloidal solution to form an ink, which is mixed with a binder and applied to a base paper. It is made by.

The photographic printing paper usually comprises a photographic printing paper base and a receiving layer made of a thermal transfer recording material formed on the photographic printing paper base. As the above-mentioned thermal transfer material, conventionally, a dye resin such as a polyester resin or a polycarbonate resin to which an additive such as a lubricant is added has been used.

The thermal head is an element that converts electric energy into heat energy. That is,
It is an element that causes the dye to be sublimated from the sublimable ink ribbon by Joule heat generated by passing an electric current through the heating resistor and transferred to the printing paper.

Here, as a thermal head used in the thermal transfer system, for example, a so-called flat type thermal head is known in which a printing paper is pressed by a platen on the surface of a substrate on which a heating resistor is formed for printing. That is, this flat type thermal head is mounted on a printing device so that the heating resistors formed in a line on the substrate are pressed against the platen, and the printing paper is placed between the main surface of the substrate and the platen. It is to sandwich and print.

[0008]

By the way, conventionally, the heating resistor of the planar thermal head is covered with a protective film made of one material. It is desired that this protective film has excellent abrasion resistance.
Further, it is desired that this protective film suppresses thermal interference to an adjacent heating resistor to a minimum source and improves unidirectional conduction of heat in the direction toward the printing paper.

That is, this protective film improves the thermal conductivity in the direction toward the printing paper and deteriorates the thermal conductivity in the direction toward another adjacent heating resistor. Must be demonstrated.

The present invention has been made in view of the above circumstances, and provides a thermal head having a protective film capable of centrally conducting the amount of heat generated by the heating resistor only in the direction toward the printing paper. To aim.

[0011]

A thermal head according to the present invention is a thermal head in which heat from a heating element is applied to an ink ribbon and a printing paper to transfer a sublimable dye to the printing paper. The above problem is solved by being characterized by being covered with a protective film having anisotropic property.

Here, the above-mentioned protective film has a poor thermal conductivity.
And a second material having good thermal conductivity. That is, the protective film may be formed by combining the respective materials so that the cross section of the first material and the cross section of the second material are arranged parallel to the desired heat conduction direction. At this time, the cross sections of the respective materials in the direction perpendicular to the heat conduction direction do not have to be particularly parallel. It is effective to use glass as the first material and copper as the second material.

[0013]

In the thermal head according to the present invention, the heating resistor is protected by the protective film formed of the material that improves the thermal conductivity only in the direction toward the printing paper and deteriorates the thermal conductivity in the other directions. Therefore, the efficiency of heat quantity for printing can be improved,
Energy saving can be achieved comprehensively.

[0014]

Embodiments of the thermal head according to the present invention will be described below with reference to the drawings. The first embodiment is shown in FIG.
As shown in FIG. 2, it is roughly divided into a heating unit 17 and a driving unit 18.
The heating unit 17 is a unit that heats the ink ribbon and the printing paper coated with the sublimable dye. Especially for printing
It is the main part that thermally transfers the sublimable dye from the ink ribbon to the printing paper. The drive unit 18 is a unit including a circuit for driving the heating unit 17 and the like.

First, the heating part 17 is formed on the first main surface 1a of the first substrate 1 so as to partially cover the glaze layer 3 for thermal insulation.
The heat-generating resistor layer 2 is provided through. The heating resistor layer 2 generates heat by the current supplied from the electrode layers 5a and 5b provided on the upper portion thereof. In addition, this heating resistor layer 2
Through the glaze layer 3, which is a heat insulating layer,
A thin film is formed on the substrate 1. This first substrate 1
Are bonded to the heat dissipation substrate 13 by the adhesive layer 11. The heat dissipation board 13 is connected to the heat dissipation fins 14 by screws (not shown) or the like. Here, the heating resistor layer 2 and the electrode layers 5 a and 5 b are protected by a protective film 7. Further, the common electrode layer 6 is provided between the protective film 7 and the electrode layer 5b.

Next, the drive unit 18 is connected to the second substrate 12
The driving IC circuit 4 for driving the heating unit 17 is provided on the upper main surface 12a. The drive IC circuit 4 is connected by a bonding wire 8 to an electrode pattern (not shown) formed on the one main surface 12a of the second substrate 12 and the electrode layer 5a. Also, this drive I
A sealing agent 9 is filled on the C circuit 4, and the driving IC circuit 4 is packaged by the sealing agent 9. Furthermore, the upper portion of the packaged driving IC circuit 4 is covered with a cover 10. The second substrate 12 is also adhered to the heat dissipation substrate 13 adhered to the first substrate 1 with an adhesive tape or the like not shown. This drive unit 1
The radiating board 13 on the 8th side is also connected to the radiating fins 14 similarly to the heating section 17 side. Further, to the drive section 18, a connector section 15 to which power and a drive input signal to the drive IC circuit 4 and the like are supplied is connected to the second substrate 12.

The first substrate 1 of the heating unit 17 is preferably made of a material having an excellent insulating property, for example, an alumina substrate. A glass glaze layer is suitable for the glaze layer 3. Further, the heating resistor layer 2 is formed by a usual thin film forming technique using PolySi, for example. Further, Al (aluminum), for example, is used for the electrode layers 5a and 5b and the common electrode layer 6. In addition, the protective film 7 is excellent in abrasion resistance as well as the direction toward the photographic paper (platen direction).
Has good thermal conductivity, other adjacent heating resistors
It is made of a material with poor thermal conductivity. The adhesive layer 11 is made of, for example, a silicone resin used as a so-called chip adhesive.

The second substrate 12 of the driving unit 18 is
An electrode pattern is provided on one main surface 12a, for example, Cu
It is formed by a glass excimer substrate. The bonding wire 8 is made of Au, for example. The encapsulant 9 is made of, for example, IC coating resin. The cover 10 is for preventing the drive unit 18 from coming into contact with the platen 16, the printing paper, and the ink ribbon, and is made of, for example, SUS or the like.

The first embodiment constructed as described above is as follows:
The protective film 7 formed on the heating resistor layer 2 formed in a line on the substrate 1 is attached to the printing apparatus main body so as to be pressed against the platen 16, and the protective film 7 and the platen 1 are attached.
Printing is performed by sandwiching a printing paper between 6 sheets.

Next, the heating part 17 which is the main part of the first embodiment will be described with reference to FIGS. 2 and 3. First, FIG. 2 is a perspective view showing the appearance of the heating unit 17 of the first embodiment shown in FIG. In this FIG.
The heating resistor layer 2 is formed by the heating resistors 2a, 2b, 2c and 2d which are arranged in a line on the first substrate 1 with the glaze layer 3 partially interposed therebetween.

That is, the heating unit 1 shown in FIG.
FIG. 3 shows a cross section taken along the ABCD plane surrounding 7 by an alternate long and short dash line (a cross section of the main part of the heating part where the heat generated in the heating resistor is concentrated). In FIG. 3, the heat generating resistors 2a, 2b, 2c and 2d of the heat generating resistor layer 2 are shown.
Are covered with the protective film 7 in five directions except the bottom.

Here, these heating resistors 2a, 2b, 2
The heat flux (cal / mm ² ) generated by c and 2d will be described by taking the heating resistor 2c as an example.

For example, an arrow θ _a shown near the heating resistor 2 c indicates a heat flux toward the upper portion of the cross section (direction of the printing paper), and an arrow θ _b indicates another heating resistor 2 b such as a diagonal direction of the cross section.
And the heat flux toward the 2d direction, and the arrow θ _c indicates the heat flux toward the lower section (the glaze layer 3 direction).

The protective film 7 for protecting the heating resistors 2a, 2b, 2c and 2d having such a heat flux efficiently transfers the heat from the heating resistor 2c to the ink ribbon and the printing paper, for example. On the other hand, it is necessary to prevent the heat from being transmitted to the adjacent heating resistors 2b and 2d. That is, it is desirable that the protective film 7 be formed of a material having anisotropy in thermal conductivity. For example, in the example of FIG. 3, it is a material that increases the heat flux indicated by the arrow θ _a and decreases the heat flux indicated by the arrow θ _b .

A specific structure of the protective film 7 will be described with reference to FIGS. 4 and 5. First, FIG. 4 is configured by combining a first material 22 having poor thermal conductivity and a second material 21 having good thermal conductivity. That is, the protective film 7 shown in FIG. 4 is configured to surround the four lateral surfaces of the second material 21 having good thermal conductivity with the first material 22 having poor thermal conductivity. Therefore, the protective film 7 also concentrates the heat transferred laterally in the upper direction, thereby improving the efficiency of the amount of heat for printing.

Next, FIG. 5 also comprises a combination of a first material 24 having poor thermal conductivity and a second material 23 having good thermal conductivity. That is, the protective film shown in FIG. 5 is configured by arranging the second material 23 having good thermal conductivity and the first material 24 having poor thermal conductivity in a stripe shape.

Here, in the protective film 7, the cross sections of the first materials 22 and 24 and the cross sections of the second materials 21 and 23 are arranged parallel to a desired heat conduction direction (vertical direction in FIGS. 4 and 5). Is formed by combining the respective materials. At this time, the cross sections of the respective materials in the direction perpendicular to the heat conduction direction do not have to be particularly parallel.

Therefore, in the first embodiment, the heat which is transferred laterally is also transferred in the upper direction by the protective film 7 (since the substrate 2 having poor heat conductivity is provided in the lower part, the upper direction). Therefore, the efficiency of the amount of heat for printing is improved.

Here, for example, glass can be used as the first material having poor thermal conductivity shown in FIGS. 4 and 5. Further, for example, copper can be used as the second material having good thermal conductivity.

FIG. 6 is a sectional view showing the structure of the heating portion of the second embodiment of the thermal head according to the present invention. In the second embodiment, the glaze layer 32, which is a heat insulating layer, is provided over the lower front surface of the heating resistor layer 33. Also,
The electrode layers 34 a and 3 are formed on the heating resistor layer 33.
4b are stacked. In addition, the electrode layers 34a and 3
An anti-oxidation film 35 is laminated on a part of the surface of 4b and the heating resistor 33. A protective film 36 is laminated on the antioxidant film 35. A substrate 31 is provided below the glaze layer 32.

The heating resistor layer 33 of the heating portion is formed of, for example, a Ta-based or re-met type material. The electrode layers 34a and 34b are formed of, for example, Al (aluminum). The antioxidant film 35 is formed of, for example, SiO ₂ . The substrate 31 is formed of, for example, a ceramic substrate.

Similarly to the first embodiment, the protective film 36 of the second embodiment is also an abrasion resistant film and has different thermal conductivity in different directions. That is, it can be formed by a combination of a material having poor thermal conductivity and a material having good thermal conductivity as shown in FIGS.

Therefore, the protective film 3 is also used in the second embodiment.
6, the heat transferred to the side can also be concentratedly transferred in the upper direction, so that the efficiency of the amount of heat for printing can be improved.

The thermal head according to the present invention is not limited to the above embodiment, and for example, a crystal having anisotropic heat conductivity may be used for the protective film.

The material forming each of the above layers is not limited to that in the above embodiment.

Further, the material forming the protective film is not limited to copper as a material having good thermal conductivity and glass as a material having poor thermal conductivity.

[0037]

The thermal head according to the present invention is a protective film formed of a material that improves the thermal conductivity only in the direction toward the photographic paper and deteriorates the thermal conductivity in the other directions, and the heating resistor is Since it is protected, the amount of heat generated by the heating resistor can be concentrated and conducted only in one direction, and the efficiency of the amount of heat for printing can be improved. Therefore, energy saving can be achieved comprehensively. Further, it is possible to reduce the heat radiation rate for radiating the released ineffective heat, and it is possible to reduce the heat radiation area and the air volume of the heat radiation fan.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing the structure of a first embodiment.

FIG. 2 is a perspective view showing an outline of a main part (heating part) of the first embodiment.

FIG. 3 is a sectional view of a main part (heating part) of the first embodiment shown in FIG.

FIG. 4 is a diagram showing a specific structural example of a protective film.

FIG. 5 is a diagram showing another specific example of the structure of the protective film.

FIG. 6 is a cross-sectional view of a heating unit according to a second embodiment.

[Explanation of symbols]

 1 ... First substrate 2 ... Heating resistor layer 3 ... Glaze layer 4 ... Driving IC circuit 5a, 5b / electrode layer 6 ... Common electrode layer 7 ... Protective film 8 ... Bonding wire 9 ... Sealant 10 ... Cover 12 ... Second substrate 13 ... Heat dissipation substrate 14 ... Radiation fin 15 ... Connector

Claims (3)

[Claims] 1. A thermal head for applying heat from a heating element to an ink ribbon and a printing paper to transfer a sublimable dye to the printing paper, wherein the heating element is covered with a protective film having anisotropy in thermal conductivity. The thermal head is characterized by 2. The thermal head according to claim 1, wherein the protective film is formed of a first material having poor thermal conductivity and a second material having good thermal conductivity. 3. The thermal head according to claim 1, wherein the first material and the second material are glass and copper.