Incremental printing of symbolic information – Thermal marking apparatus or processes – Specific resistance recording element type
Reexamination Certificate
1998-07-22
2001-02-06
Tran, Huan (Department: 2861)
Incremental printing of symbolic information
Thermal marking apparatus or processes
Specific resistance recording element type
Reexamination Certificate
active
06184913
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a thermal head comprising a protection layer having a printing surface which is brought into contact with a heat sensitive record medium, a heat generating section which includes heat generating resistors and electrodes connected to the heat generating resistors and generates heat transferred to said heat sensitive record medium through said protection layer, and a driving circuit connected to said electrodes for supplying a heating electric power to the electrodes.
The present invention also relates to a method of manufacturing the thermal head of the kind mentioned above.
2. Related Art Statement
The thermal head of the kind described in the preamble has been used in simple and low cost printers using heat sensitive papers and heat transfer papers which do not require a supply of inks. In printers using such a thermal head, a high image quality and high printing speed have been required. For instance, in a heat transfer type color printer or an index printer installed in an automatic mini-laboratory, a thermal head having a very high resolution such as 600 dpi to 1200 dpi has been required.
However. in such a thermal head, an excellent heating up and cooling down property is required in order to raise a temperature of the heat generating section within a very short time and to dissipate heat at a high rate. Such a high speed heating up and cooling down property is particularly required for avoiding undesired blur in an printed image. In order to attain a prompt heating up, it is required that a generated heat does not escape from the heat generating section, and in order to effect the rapid heat dissipation, a generated heat has to be dissipated as soon as possible. For attaining a desired heating up and cooling down property, these two contradictory problems have to be solved simultaneously.
Various requirements for the thermal head may be summarized as follows.
1) small size, light weight, simple structure
2) low price
3) large image size covering A3 size
4) low power consumption
5) high printing speed
6) high density and high resolution
7) uniform image quality without irregular color
In order to attain one or more of the above mentioned characteristics, there have been proposed various thermal heads. For instance. in Japanese Patent Kokai Hei 5-64905, there is proposed a known thermal head shown in FIG,
1
. In this known thermal head, a printing surface is formed to be flat, and therefore a space is hardly formed between the printing surface and a heat sensitive record medium and a thermal efficiency is improved. As shown in
FIG. 1
, on a flat surface of a preliminary substrate
30
, a pealing-off layer
31
, a wear and abrasion resistance layer
32
, a protection layer
33
, a heat generating resistance layer
34
, an electrode layer
35
and a heat storage layer
36
made of polyimide resin are successively applied. After cementing the assembly to a substrate
38
by means of an adhesive layer
37
, the preliminary substrate
30
is removed by means of the pealing-off layer
31
. In this manner, a flat printing surface
40
can be obtained.
However, in the known thermal head illustrated in
FIG. 1
, in which the heat storage layer
36
is made of a resin material such as polyimide resin and the printing surface
40
constituted by a portion of the wear and abrasion resistance layer
32
is formed to be flat, has the following problem.
A record paper is urged against the thermal head with a very strong force by means of a press roller, but since the printing surface is flat, the roller is brought into contact with the thermal head over a larger area and thus the pressing force is decreased. This results in that an influence of the roller deformation and abrasion might occur.
In order to mitigate the above problem, the inventors have proposed a thermal head, in which a printing surface is curved outwardly or is protruded from one surface of a protection layer and a driving IC is provided on the other surface of the protection layer. However. a thickness of assembly besides the protruded printing surface becomes small, and therefore a mechanical strength is decreased and a reliability of the thermal head is reduced.
SUMMARY OF THE INVENTION
The present invention has for its object to provide a novel and useful thermal head having a large mechanical and a high reliability.
According to the invention, a thermal head comprises:
a protection layer having mutually opposed first and second surfaces. said first surface including a printing surface which is brought into contact with a heat sensitive record medium and is protruded from the remaining portion of the first surface of the protection layer;
a heat generating section provided on said second surface of the protection layer at said protruded printing surface and including heat generating resistors and electrodes connected to the heat generating resistors for generating heat to be transferred to said heat sensitive record medium through said printing surface of the protection layer;
a driving circuit connected to said electrodes of the heat generating section for supplying a heating electric power to the electrodes; and
a reinforcing layer made of a material different from a material of said protection layer and provided on said first surface of the protection layer except for said printing surface such that a surface of said reinforcing layer is not higher than said first surface of the protection layer at said protruded printing surface.
In a preferable embodiment of the thermal head according to the invention, said protection layer has a groove formed in the second surface at a portion corresponding to said protruded printing surface, and said heat generating section is provided in said groove.
According to the invention, said thermal head further comprises a heat control section for controlling the heat generated by said heat generating section, said heat control section being provided in said groove such that the heat control section is brought into contact with a side of said heat generating section remote from said protection layer.
In a preferable embodiment of the thermal head according to the invention, said heat control section comprises a heat storage layer, which may be made of a glass having a low melting point or a heat resistant synthetic resin such as epoxy resin and polyimide resin. In case of using the heat resistant synthetic resin, ceramic fillers or powders such as alumina and silica and/or metal powders may be added for adjusting a thermal conductance and thermal expansion of the heat storage layer.
In a preferable embodiment of the thermal head according to the invention, said heat control section further comprises a heat conduction member for dissipating a heat stored in the heat storage layer. By suitably constructing said heat storage layer and heat conduction member, the heat control can be performed optimally.
According to the invention, said heat conduction member may be made of a metal or an alumina based ceramic coating agent. In case of forming the metal heat conduction member, a metal rod may be advantageously used.
According to the invention, an assembly of the protection layer, heat generating section, heat control section and driving IC may be supported by a supporting member. This supporting member may be formed by a heat resistant synthetic resin or a metal plate. In case of using the heat resistant synthetic resin, the driving IC may be embedded in the supporting member, and in case of using a metal substrate plate, the driving IC may be provided in a recess formed in the metal substrate plate. According to the invention, it is also possible to provide said driving IC in a recess formed in the second surface of the reinforcing layer.
According to the invention, said reinforcing layer is preferably made of a glass such as borosilicate glass. Further, said protection layer is preferably made of a material selected from the group consisting of SiC compounds, SiB compounds, SiN compounds, AIN compounds and
Hagiwara Jun
Hirabayashi Jun
Nagano Katsuto
Saita Yoshio
Susukida Masato
Oliff & Berridg,e PLC
TDK Corporation
Tran Huan
LandOfFree
Thermal head and method of manufacturing the same does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Thermal head and method of manufacturing the same, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Thermal head and method of manufacturing the same will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2611028