JP2006142497A - Thermal head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a thermal head realizing high image quality and high speed printing. <P>SOLUTION: The thermal head comprises a plurality of heating resistors generating heat upon conduction, an insulating barrier layer covering each heating resistor entirely, and an electrode layer conducting to the opposite ends of each heating resistor in the longitudinal direction thereof wherein a metal film for transmitting heat generated from the heating resistor is provided on the insulating barrier layer without touching the electrode layer. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a thermal head mounted on a thermal transfer printer.

In general, a thermal head has a plurality of heating resistors that generate heat when energized on a heat-dissipating substrate having a heat storage layer, an electrode layer for energizing the plurality of heating resistors, and the plurality of heating resistors and electrodes. And a protective layer that protects a part of the layer, and a heating operation is performed by bringing the heat generating resistor that has generated heat into pressure contact with an ink ribbon and a substrate to be printed wound around a platen roller. In such a thermal head, in recent years, the printing speed has been increased. In order to achieve high-speed printing, in order to ensure the print density above a certain level, the current supply time to the heating resistor is shortened while the supply power is increased to reduce the unit time of the heating resistor. It is necessary to increase the amount of heat generated per hit.
JP-A-57-61585 JP 57-61586 A JP-A-5-318796 JP 2001-96784 A

  However, in the thermal head having the conventional structure, when the heating resistor is energized along the resistance length direction, the temperature rise at the center portion in the resistance width direction orthogonal to the energization direction is larger than that at the peripheral portion in the resistance width direction. The temperature distribution (heat generation distribution) is large as shown in FIG. For this reason, if the amount of heat generation per unit time to the heating resistor is increased for the purpose of speeding up printing, the temperature rise of the heating resistor also increases, and the peak temperature of the heating resistor exceeds the softening point of the ink ribbon. Is a problem. The peak temperature of the heating resistor may exceed 600 ° C. depending on conditions. On the other hand, an ink ribbon that has been widely used in the past is mainly composed of PET (polyethylene terephthalate), and when the temperature of the heating resistor greatly exceeds the softening point of the ink ribbon, the ink ribbon that is in pressure contact with the heating resistor. Is damaged, ribbon breaks and printing is not possible. On the other hand, if the amount of heat generation per unit time of the heating resistor is suppressed so that the peak temperature of the heating resistor does not exceed the softening point of the ink ribbon, the energization time for the heating resistor will be shortened. The concentration will be lighter. Further, an ink ribbon formed of a material having a softening point at a high temperature can be used in place of the ink ribbon made of a PET main component, but this is not preferable because the cost increases.

  SUMMARY An advantage of some aspects of the invention is that it provides a thermal head capable of realizing high-speed printing.

  In the present invention, the local heat concentration of the heating resistor is alleviated, and if the region of high temperature (increased heat generation) is expanded in the resistance length direction without causing the ink ribbon to break, the print quality is not deteriorated. This is because the printing speed can be increased.

  That is, the present invention includes a plurality of heating resistors that generate heat when energized, an insulating barrier layer that covers the entire heating resistors, and electrode layers that are electrically connected to both ends of each heating resistor in the resistance length direction. The thermal head is characterized in that a heat transfer metal film for uniformly transmitting the heat generated by the heating resistor is provided on the insulating barrier layer in a non-contact manner with the electrode layer.

  According to the above aspect, since the region covered with the heat transfer metal film is uniformly heated, the ink ribbon is not cut even when the power supplied to the heating resistor per unit time is increased. A high temperature region can be obtained.

  Since the traveling direction of the ink ribbon is the resistance length direction of the heating resistor, the heat transfer metal film is preferably formed in a rectangular shape that is long in the resistance length direction. According to this aspect, a uniform high temperature region can be expanded in the resistance length direction of the heating resistor.

  The heat transfer metal film needs to be formed of a metal material having a melting point higher than the maximum heat generation temperature of the heating resistor. Specifically, a refractory metal material containing at least one of Cr, Ti, Ta, Mo, and W, one of Al and Cu, an alloy material containing the refractory metal material, or an alloy containing Al or Cu It is preferable that it is formed of a material. Furthermore, the heat transfer metal film is preferably formed of the same metal material as the electrode layer. When the heat transfer metal film and the electrode layer are made of the same metal material, the heat transfer metal film and the electrode layer can be formed at the same time, which facilitates the manufacturing process.

  According to the present invention, it is possible to obtain a thermal head that is excellent in printing quality and can realize high-speed printing.

  1 to 3 show a thermal head 1 according to a first embodiment of the present invention. FIG. 1 is a plan view showing a thermal head 1 (a state before forming a wear-resistant protective layer), and FIG. 2 is a sectional view taken along line II-II in FIG. The thermal head 1 is mounted on a thermal transfer printer and performs printing by applying heat generated by the heating resistor 4 to thermal paper or an ink ribbon.

The thermal head 1 has a heat storage layer 3 made of a heat insulating material such as glass on a substrate 2 made of Si, a ceramic material, a metal material or the like and having excellent heat dissipation, and the heat storage layer 3 shown in FIG. A plurality of heating resistors 4 arranged in a line at a minute interval in the left-right direction are provided. Each heating resistor 4 is a part of a resistor layer 4 ′ formed entirely on the heat storage layer 3 using a cermet material such as Ta ₂ N or Ta—SiO ₂ , and the surface thereof is an insulating barrier layer 5. Covered by. The insulating barrier layer 5 is made of an insulating material such as SiO ₂ , SiON, or SiAlON, for example, and defines the planar size (length dimension L, width dimension W) of each heating resistor 4. Between adjacent heating resistors 4, there is a gap region γ where the substrate 2 is exposed.

  Electrode layers 6 are conductively connected to both end portions of each heating resistor 4 in the resistance length direction. The resistance length direction of the heating resistor 4 is parallel to the running direction of the ink ribbon. The electrode layer 6 is formed on the resistor layer 4 ′ over the entire surface, and is formed by opening an opening 6c that exposes the surface of each heating resistor 4. Through the opening 6c, all the heat is generated. A common electrode 6 a commonly connected to the resistor 4 and a plurality of individual electrodes 6 b independently connected to each heating resistor 4 are separated. A gap region γ exists between the common electrode 6a and the individual electrode 6b, and the width dimension of the common electrode 6a and the individual electrode 6b is defined to be the same as the width dimension W of the heating resistor 4 by the gap region γ. . This electrode layer 6 is made of a refractory metal material such as Cr, Ta, Mo, W, Ti, Al, Cu, an alloy material containing the refractory metal material, or an alloy material containing Al or Cu. Can be formed. The electrode layer 6 of this embodiment is made of Al, and is used for high-speed printing operation in which a large current is applied with a very short period of about several hundreds μs to turn on (energize) / off (non-energize) the heating resistor 4. It can be supported.

On the insulating barrier layer 5, the common electrode 6a, and the individual electrode 6b, a wear-resistant protective layer 7 made of a wear-resistant material such as SiAlON or Ta ₂ O ₅ is formed. The wear-resistant protective layer 7 protects the insulating barrier layer 5, the common electrode 6a, and the individual electrode 6b from friction generated during head operation. In FIG. 1, the wear-resistant protective layer 7 is not shown. Although not shown, the thermal head is also provided with a drive IC, a printed circuit board, and the like for controlling energization to the plurality of heating resistors 4.

  In the thermal head 1 configured as described above, the heat transfer metal film 10 that uniformly transmits the heat generated by the heating resistor 4 is provided on the insulating barrier layer 5 in a non-contact manner with the electrode layer 6. The heat transfer metal film 10 has a rectangular shape that is long in the resistance length direction of the heating resistor 4, and the length L1 in the resistance length direction is about 100 μm, and the width dimension W1 is about 70 μm. Further, the distance d in the resistance length direction between the heat transfer metal film 10 and the electrode layer 6 is about 50 μm.

  The heat transfer metal film 10 is made of a metal material that is excellent in thermal conductivity and has a melting point higher than the maximum heat generation temperature of the heating resistor 4, and specifically includes at least one of Cr, Ti, Ta, Mo, and W. It is preferably formed of a refractory metal material, one of Al and Cu, an alloy material containing the refractory metal material, or an alloy material containing Al or Cu. The heat transfer metal film 10 of the present embodiment is made of Al, which is the same material as the electrode layer 6, and is formed simultaneously with the electrode layer 6 in the manufacturing process for forming the electrode layer 6. Specifically, when an Al conductor film is formed on the entire surface of the resistor layer 4 ′ and the insulating barrier layer 5 and the opening 6 c exposing the surface of the insulating barrier layer 5 is formed, the insulating barrier layer 5 is formed. The upper Al conductor film is left as the heat transfer metal film 10. The heat transfer metal film 10 may be a single layer film or a multilayer film.

  FIG. 3 is a schematic diagram illustrating the temperature distribution in the resistance length direction of the heating resistor 4. When the heating resistor 4 is energized in the resistance length direction via the electrode layer 6 (common electrode 6a, individual electrode 6b), the heat generated by the heating resistor 4 is transferred to the heat transfer metal film 10 via the insulating barrier layer 5. Since it is transmitted and uniformly spread by the heat transfer metal film 10, the temperature rise at the center of the heating resistor 4 is alleviated. As shown in FIG. 3, in the heating resistor 4, the region covered with the heat transfer metal film 10 becomes a substantially uniform high temperature region. As described above, since the heat transfer metal film 10 has a rectangular shape that is long in the resistance length direction, the high-temperature region is also long in the resistance length direction.

According to the above embodiment, since the heating resistor 4 has a temperature distribution without a peak temperature in the resistance length direction (travel direction of the ink ribbon), the amount of heat generated per unit time (feeding power) to the heating resistor 4 ), A high temperature region can be obtained in a range not exceeding the softening point of the ink ribbon, and high quality and high speed printing can be realized.

It is a top view which shows the thermal head by one Embodiment of this invention. It is sectional drawing which follows the II-II line | wire of FIG. It is a schematic diagram explaining the temperature distribution of a heating resistor. It is a schematic diagram explaining the temperature distribution of the heating resistor in the thermal head of the conventional structure.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Thermal head 4 Heating resistor 5 Insulation barrier layer 6 Electrode layer 6a Common electrode 6b Individual electrode 6c Opening part 10 Heat transfer metal film L Resistance length direction dimension W Resistance width direction dimension γ Gap region

Claims (4)

In a thermal head comprising a plurality of heating resistors that generate heat by energization, an insulating barrier layer that covers the entire heating resistors, and electrode layers that are electrically connected to both ends in the resistance length direction of the heating resistors,
A thermal head, wherein a heat transfer metal film for uniformly transmitting heat generated by the heating resistor is provided on the insulating barrier layer in a non-contact manner with the electrode layer. 2. The thermal head according to claim 1, wherein the heat transfer metal film is formed in a rectangular shape that is long in the resistance length direction. 3. The thermal head according to claim 1, wherein the heat transfer metal film is a refractory metal material containing at least one of Cr, Ti, Ta, Mo, and W, Al and Cu, or the refractory metal. A thermal head formed of an alloy material containing a material or an alloy material containing Al or Cu. 4. The thermal head according to claim 1, wherein the heat transfer metal film and the electrode layer are formed of the same refractory metal material. 5.

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