JPH09201992A - Thermal head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably obtain an image free from density irregularity while preventing the abrasion and contamination of a thermal head. SOLUTION: Partial glaze 32 is provided on a substrate 31 and a resistor film 33, two electrodes 34, 35 and a protective layer 36 are provided on the partial glaze 32. A heating element 37 is positioned between two electrodes 34, 35. This partial glaze 32 has a radius of curvature of 0.7-4.0cm and can set head pressure to a specified value and the abrasion and contamination of a thermal head are prevented and an image free from density irragularity can be stably obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal head of a thermal printer, and more particularly, to a thermal head having a partial glaze on a substrate, which prevents abrasion of the thermal head and contamination of the head, and provides stable image density. The present invention relates to a thermal head suitable for obtaining an image.

[0002]

2. Description of the Related Art Generally, a thermal head comprises a substrate, heating elements arranged in a dot pattern on the substrate, an introduction pattern for supplying a current to the heating element, and a common pattern. Using the thermal head having such a structure, the thermosensitive recording paper is pressed toward the thermal head side by the platen roll to drive the heating resistor of a predetermined image to generate heat, thereby performing the printing operation.

In this case, since the thermal head is in surface contact with the thermosensitive recording paper, uneven printing density is likely to occur. Also,
When the pressing force between the thermal head and the thermal recording paper is increased to prevent uneven printing density, the frictional force applied to the thermal head increases, the surface of the thermal head wears, and the surface of the thermal head becomes dirty. Occurs.

Therefore, attempts have been made to improve the structure of the thermal head. For example, in FIG. 4, in this thermal head, a heating element 42 is formed on a substrate 41, a pattern 43 is formed on the heating element 42, and a protective layer 44 is formed so as to cover the heating element 42 and the pattern 43. Has been done. A partial glaze 45 is formed in a portion corresponding to the heating element 42A. Since only the protrusion due to the partial glaze 45 comes into contact with the thermosensitive recording paper, it is possible to obtain an image without print density unevenness.

On the other hand, in recent years, ultrasonic scanners, C
Along with the computerization of medical devices such as T-scanners and X-rays, transparent heat-sensitive recording materials that can directly record these digital images have been developed. In this case, in general, when diagnosing by a doctor or the like, the image recorded on the thermosensitive recording material is exposed to light such as a fluorescent lamp from behind (a device that illuminates such light is called a sheer curtain) and is supported so as not to damage the image. Observe from the body side.

A film used as a support for a heat-sensitive recording material used in such an application is thicker than a film used as a support for a heat-sensitive recording material used for other purposes, and has a property of being less likely to bend or deform. Have. When thermal recording is performed on the thermal recording material for such an application by using the thermal head having the above-mentioned partial glaze, contact between the thermal head and the thermal recording material is poor and printing blur occurs. Therefore, the platen roll pressure is set higher than in the conventional case. As a result, the head pressure per unit area becomes high, head wear, head contamination, etc. occur, and the load on the film conveying motor becomes large, causing problems such as a loud film conveying noise.

In order to solve these problems, it is absolutely necessary to reduce the head pressure.

An object of the present invention is to prevent head wear and head contamination in a thermal head even for a heat-sensitive recording material having a highly rigid film as a support, and to perform recording without image unevenness for a long time. It is to provide a thermal head capable of

In order to achieve the above-mentioned object, the thermal head of the present invention has a partial glaze on a substrate, and in the thermal head in which a plurality of heating elements are arranged, the heating element is provided. The radius of curvature of the sectional shape of the partial glaze is 0.7 cm or more and 4 cm or less.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail. First, the relationship between the radius of curvature of the partial glaze of the thermal head and the head pressure was examined. The outline of this test is shown in FIG. In FIG. 1, reference numeral 1 denotes a thermal head, and 1A is a partial glaze thereof. The head pressure when the platen roll 3 was pressed against the heat sensitive film 2 and the thermal head 1 while the heat sensitive film 2 was sandwiched was calculated.

FIG. 2 shows the results of this test. In FIG. 2, the horizontal axis indicates the head position (μm) when the radius of curvature of the partial glaze 1A is changed, and the vertical axis indicates the head pressure ( kg / cm ²⁾ in and, in the figure, □ corresponds to the radius of curvature of the partial glaze in a conventional thermal head curvature radius (r) is at 0.53 cm, in the figure, + is the radius of curvature (r) is 1cm of Partial glaze, Δ is a partial glaze with a radius of curvature (r) of 2 cm.

From FIG. 2, it can be seen that the head pressure can be reduced significantly as the radius of curvature (r) of the partial glaze of the thermal head increases. This is because the contact area between the thermal film and the head could be increased. However, if the curvature radius of the partial glaze is larger than 4 cm, the head pressure becomes too low and print unevenness (image density unevenness) is likely to occur. If the radius of curvature of the partial glaze is smaller than 0.7 cm, the head pressure is too large and the surface of the thermal head is abraded, and the resistance of the thermal head is easily broken. The components are likely to adhere to the head and stain the head. Therefore, the radius of curvature of the partial glaze of the thermal head is 0.7 from the viewpoint of preventing unevenness in printing (unevenness in image density), minimizing wear of the surface of the thermal head, and preventing contamination of the thermal head.
cm or more and 4 cm or less.

FIG. 3 is a sectional view showing an embodiment of the thermal head of the present invention. In FIG. 3, a partial glaze 32 having a radius of curvature of 0.7 cm or more and 4 cm or less is formed on a base 31, and a resistor film 33, two electrodes 34, 35 and a protective layer are formed on the partial glaze 32. 36 is sequentially covered, and a heating element 37 is formed between the two electrodes 34 and 35. The entire surface of the heating element 37 is in contact with the heat-sensitive recording paper, and printing is usually performed while the thermal head is moving.

When the thermal head having the above-mentioned partial glaze is used, printing unevenness (image density unevenness) does not occur even on a thermal recording material having a film having relatively high rigidity, and the surface of the thermal head is worn. Can be reduced as much as possible to prevent the thermal head from being soiled.

In addition, with respect to the thermal head of the present invention,
When using a film having a support made of a film having relatively high rigidity such as polyethylene terephthalate,
It is desirable to provide an intermediate layer between the support and the thermosensitive recording layer so that the intermediate layer has a predetermined tensile elastic modulus.

The tensile modulus of elasticity of the intermediate layer is JIS K
The tensile elastic modulus defined by 7127 is 1 × 10 ⁸ dyn
It is preferable to use e / cm ² or more and 1 × 10 ¹⁰ dyne / cm ² or less. This tensile modulus indicates the ratio of the tensile stress within the tensile proportional limit and the corresponding strain, and when the tensile stress-strain curve has no straight line portion, it is due to the inclination of the tangent line of the inclination at the deformation start point.

The tensile modulus of elasticity of this intermediate layer is 1 × 10 ⁸ dy.
When it is less than ne / cm ^{2, the} thermal recording layer formed in the intermediate layer is less likely to hit the thermal head, and a predetermined image cannot be obtained particularly in the case of a thermal recording material having a high recording transmission density. In addition, the tensile elastic modulus is 1 × 10 ¹⁰ dyne /
If it is larger than cm ² , the head pressure to the thermal head of the heat-sensitive recording layer formed in the intermediate layer becomes high, head wear easily occurs, and the life of the thermal head is shortened.

When the intermediate layer has the above tensile modulus,
A transparent thermosensitive recording material that can directly record digital images of medical devices such as ultrasonic scanners, CT scanners, and X-rays with a support. Etc. can be maintained, and there is no hindrance in the handling of the thermal recording material on which an image is formed. Therefore, from this viewpoint, it is possible to select a resin having a higher tensile elastic modulus than the resin film forming the intermediate layer.

Therefore, when the thermal recording material of the present invention is used and the intermediate layer has an intermediate layer having a tensile elastic modulus in the above range, the thermal recording material can be used for medical purposes. In addition, it is possible to stably obtain an image having no recording density unevenness while preventing abrasion of the thermal head and contamination of the thermal head.

[0020]

【Example】

Example 1 (Preparation of thermosensitive recording material) 16 g of 2-anilino-3-methyl-6-N-ethyl-N-butyl-aminofluorane as a capsule, Takenate D-110N (capsule wall of Takeda Pharmaceutical Co., Ltd.) 10 g of the agent (trade name) was added to a solvent of 20 g of ethyl acetate and 5 g of methylene chloride and dissolved. The resulting solution was mixed with 400 g of an aqueous 8% by weight polyvinyl alcohol solution, 15 g of water, and 0.5 g of a 2% by weight aqueous solution of a sodium salt of dioctyl sulfosuccinate (surfactant), and then mixed with an ace homogenizer ( 1000r using Nippon Seiki Co., Ltd.
The emulsion was emulsified for 5 minutes at pm. 7 more in the obtained emulsion.
After adding 0 g of water, the capsule-capsulation reaction was performed at 40 ° C. for 3 hours to prepare a capsule liquid having an average particle size of 0.7 μm. In addition, all the average particle diameters used the value of 50% volume average particle diameter measured using the laser diffraction particle size distribution measuring device by Horiba, Ltd.

(Preparation of color developer emulsion dispersion) 4 g of the developer represented by the following structural formula (1).

Embedded image And 2 g of a color developer represented by the following structural formula (2)

Embedded image And a developer 15 represented by the following structural formula (3)
g

Embedded image

4 g of 1-phenyl-1-xylylethane
And 15 g of ethyl acetate were added to and dissolved in a mixed solution. The obtained solution was used as an 8 wt% polyvinyl alcohol aqueous solution 4
After mixing with 0 g, 15 g of water, and 0.5 g of sodium dodecylbenzenesulfonate, the mixture was mixed with an aqueous phase, and then 100 using an ace homogenizer (manufactured by Nippon Seiki Co., Ltd.).
The emulsification was carried out at 0 rpm so that the average particle size was 0.5 μm.

(Preparation of Protective Layer Solution) 20 g of 10 wt% carboxy-modified polyvinyl alcohol aqueous solution (KM618 manufactured by Kuraray Co., Ltd.) was added to 30 g of water, and 0.3 g of 2 wt% dioctyl sulfosuccinate sodium salt (surfactant) aqueous solution. 3 g of kaolin dispersion obtained by mixing 100 g of 3 wt% polyvinyl alcohol (PVA205, Kuraray Co., Ltd.) and kaolin 35 in advance, and dispersing with a ball mill, 30 wt% zinc stearate dispersion (Z-Kyoto Yushi Co., Ltd. 7-30) 0.5 g was mixed to prepare a protective layer liquid.

A solution of 5.0 g of the capsule liquid, 10.0 g of the color developer emulsion dispersion and 5 g of water with stirring was mixed with polyethylene terephthalate (P) having a thickness of 175 μm.
The ET) film was subjected to corona discharge treatment, and then coated and dried so that the solid content was 15 g / m ² to form a thermosensitive recording layer. Next, the protective layer solution was applied and dried on the formed thermal recording layer so that the thickness after drying was 2 μm to prepare a thermal recording material.

The heat-sensitive recording material having a width of 257 mm obtained as described above was applied to a thermal head having a partial glaze with a radius of curvature of 0.7 cm and a platen roll (iron core diameter 28
mm, rubber part diameter 36 mm, rubber hardness 70 degrees, length 25
7 mm, roll pressure 7 kg) so that the thermal recording layer of the thermal recording material is on the thermal head side, the recording energy is 100 mJ / mm ² , and the running speed is 5.5 mm / s.
A recording running test was conducted at.

As a result, at the time when the running distance exceeded 3 km, an unrecorded portion, which was considered to be a disconnection of the thermal head resistor, occurred. Further, the head was contaminated, which was considered to be due to the sticking of the thermal recording layer to the thermal head.

Example 2 A thermosensitive recording material was prepared by forming a thermosensitive recording layer and a protective layer in the same manner as in Example 1. A recording running test was conducted on this thermosensitive recording material in the same manner as in Example 1 except that a thermal head having a partial glaze with a radius of curvature of 4.0 cm was used. As a result, at the time when the running distance exceeded 10 km, an unrecorded portion which was considered to be a disconnection of the thermal head resistor was generated.
Further, the head was contaminated, which was considered to be due to the sticking of the thermal recording layer to the thermal head. Almost no uneven density was observed.

Comparative Example 1 A thermosensitive recording material was prepared by forming a thermosensitive recording layer and a protective layer in the same manner as in Example 1. This thermal recording material was subjected to a recording running test in the same manner as in Example 1 except that a thermal head (KGT-260-12MP8-FF manufactured by Kyocera Corporation) having a partial glaze with a radius of curvature of 0.53 cm was used. As a result, at the time when the running distance exceeded 2 km, there was already an unrecorded portion that was considered to be a break in the thermal head resistor. Further, the head contamination, which is considered to be caused by the sticking of the thermal recording layer to the thermal head, was extremely severe.

Comparative Example 2 A thermosensitive recording material was prepared by forming a thermosensitive recording layer and a protective layer in the same manner as in Example 1. This thermal recording material has a radius of curvature of 5
A recording running test was conducted in the same manner as in Comparative Example 1 except that a thermal head having a partial glaze of cm was used. As a result, recording density unevenness occurred in which the recording density was faint depending on the location.

[0030]

As described above, according to the present invention, by setting the radius of curvature of the partial glaze within a specific range,
It is possible to prevent abrasion of the thermal head and stain of the head, and it is possible to obtain a stable image without unevenness in image density.

[Brief description of drawings]

FIG. 1 is a conceptual diagram for investigating a relationship between a radius of curvature of a partial glaze of a thermal head and a head pressure.

FIG. 2 is a graph showing a radius of curvature of a partial glaze of a thermal head and a head pressure according to a head position.

FIG. 3 is a schematic sectional view showing an embodiment of the thermal head of the present invention.

FIG. 4 is a schematic cross-sectional view showing a partial glaze of a conventional thermal head.

[Explanation of symbols]

 1 Substrate 1A Partial Glaze 2 Thermosensitive Film 3 Platen Roll 31 Substrate 32 Partial Glaze 33 Resistor 34, 35 Electrode 36 Protective Layer 37 Heating Element

Claims (1)

[Claims] 1. A thermal head having a partial glaze on a substrate and a plurality of heating elements arranged in the partial glaze, wherein the partial glaze having the heating element has a cross-sectional radius of curvature of 0.7 cm or more. And a thermal head of 4 cm or less.