Thermal head and controller for controlling the same

Details Thermal head and controller for controlling the same Thermal head and controller for controlling the same

2001-03-08

2004-11-23

Tran, Huan (Department: 2861)

Incremental printing of symbolic information

Thermal marking apparatus or processes

Specific resistance recording element type

C347S202000, C347S207000

Reexamination Certificate

active

06822665

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a thermal head capable of printing two lines at the same time using two lines of heating elements, and to a thermal head capable of performing preheating using one of two lines of heating elements while performing printing using the other one of two lines of heating elements thereby achieving a high-speed printing operation.
The present invention also relates to a thermal head controller, and more particularly, to a thermal head controller for controlling a thermal head including a preheating heater and a printing heater.
2. Description of the Related Art
FIG. 23
illustrates a thermal head disclosed in Japanese Unexamined Patent Application Publication No. 64-58566, wherein
FIG. 23A
is a top view of the thermal head and
FIG. 23B
is a cross-sectional view taken along line XXIIIB of FIG.
23
A. In
FIG. 23
, reference numerals
501
a
and
501
b
denote ceramic substrates, and reference numeral
517
denotes a common electrode formed of a bulk material.
FIG. 24
illustrates a thermal head disclosed in Japanese Unexamined Patent Application Publication No. 10-151784, wherein
FIG. 24A
is a top view of the thermal head and
FIG. 24B
is a cross-sectional view taken along line XXIVB of FIG.
24
A. In
FIG. 24
, reference numeral
602
denotes a metal substrate having a projection
603
, and reference numerals
608
and
611
denote heating resistors.
FIG. 25
illustrates a conventional thermal head, wherein
FIG. 25A
is a top view of the thermal head and
FIG. 25B
is a cross-sectional view taken along line XXVB of FIG.
25
A. In
FIG. 25
, reference numeral
701
denotes a substrate formed of single silicon crystal, and reference numeral
707
denotes a common electrode. Reference numeral
702
denotes a through-hole formed in the common electrode
707
, wherein the inner surface of the through-hole is plated with a conductive metal
703
. Reference numerals
704
and
705
denote heating resistors.
FIG. 26
illustrates another conventional thermal head, wherein
FIG. 26A
is a top view of the thermal head and
FIG. 26B
is a cross-sectional view taken along line XXVIB of FIG.
26
A. In
FIG. 26
, reference numerals
858
,
854
,
863
and
864
denote heating resistors, and reference numeral
852
denotes glaze glass.
In the case of the thermal head shown in
FIG. 23
, there is a difference in thermal expansion coefficient between the common electrode
517
and the substrate
501
a
or
501
b
, and the difference in thermal expansion coefficient can cause partial removal of the common electrode
517
. Thus, performance degradation occurs as the thermal head is used for a long period of time.
In the case of the thermal head shown in
FIG. 24
, the substrate
602
is heated by a common current flowing through the projection
603
which is a part of the substrate
602
. As a result, thermal interference occurs between the heating element
608
and the heating element
611
. This makes it difficult to control the heating elements
608
and
611
independently of each other.
In the case of the thermal head shown in
FIG. 25
, a complicated process is needed to form the through-hole
702
through the substrate of single silicon crystal.
In the case of the thermal head shown in
FIG. 26
, if the heating resistors
853
and
854
are located very close to the heating resistors
863
and
864
, interference due to heat storage in a partial glaze occurs because the heating resistors
853
,
854
,
863
and
864
are formed on the same partial glaze. The interference can cause the thermal head to become thermally uncontrollable. Although the above problem can be avoided by increasing the distance between two lines of heating resistors, the contact condition between the thermal head and a platen roller (not shown) which urges print paper against the thermal head becomes poor. To improve the contact condition, it is needed to increase the diameter of the platen roller or increase the force applied to the platen roller.
In the conventional thermal head, the thermal head heater is continuously energized until a needed intensity of color is obtained each time a line is printed. In this technique, the printed color intensity increases as the temperature (amount of heat) of the thermal head increases.
When respective colors of yellow, magenta, and cyan are printed on paper, no color appears during a particular period after turning on the thermal head, wherein the period in which no color appears varies depending upon the color. If, each time a line is printed, the thermal head is energized during a period in which no color appears plus a period needed to obtain a desired intensity of color, a long printing time is needed, that is, the printing speed becomes low.
One technique to avoid the above problem is to preheat paper using a preheating heater (preheater) to a temperature which is very close to but lower than a minimum temperature needed to develop a color. In this technique, a printing thermal head heater is used to further heat the paper to develop a color. Thus, color is developed with no delay and thus the problem of the reduction in the printing speed is avoided.
Although most of the heat generated by the preheater is consumed to preheat print paper, the heat is partially accumulated in the preheater and parts in the vicinity of the preheater. As a result, when the same amount of heat is generated by the thermal head heater over the entire surface of paper, the printed color intensity is low at a line (first line) at which the printing is started and the printed color intensity increases as the printing operation advances toward a final line as shown in FIG.
27
. That is, nonuniformity in printed color density occurs.
Furthermore, the preheating can cause a color to be developed in a white-data area in which any color should not appear. In the case where the intensity specified by print data varies across print paper, the preheating can cause a deviation in color intensity from the specified intensity.
In the case where printing is performed using both a printing thermal head and a preheating heater, if the printing and the preheating are performed at the same time, a high-capacity power supply capable of supplying a high current with a high voltage is needed to drive the thermal head, and a complicated configuration is needed.
SUMMARY OF THE INVENTION
In view of the above, it is an object of the present invention to provide a thermal head which is formed of a material which does not cause removal, which can be produced without needing complicated processing, and which has less thermal interference.
It is another object of the present invention to provide a controller for controlling a thermal head, capable of controlling the thermal head without producing nonuniformity in color intensity caused by preheating using a preheater and without needing a high-voltage/high-current power supply for driving the thermal head.
According to an aspect of the present invention, there is provided a thermal head comprising: a metal substrate; an insulating layer formed on the surface of the metal substrate; a plurality of heating elements disposed on the surface of the insulating layer, the heating elements being arranged with a predetermined pitch along a plurality of lines in a main scanning direction, the plurality of lines being spaced from each other in a paper feeding direction perpendicular to the main scanning direction; and a heat radiating element projecting from the surface of the metal substrate to the side where the insulating layer is disposed. Note that the heat radiating element does not include a member serving as a path for supplying a current to the heating elements.
In this structure, although most of heat generated by the respective heating elements is transferred to an ink ribbon or print paper, residual partial heat is absorbed by heat radiating means via the insulating layer and radiated into the atmosphere. This suppresses thermal interference among the heating elements.
In this therma

Affiliated with

Also associated with

Rating

Thermal head and controller for controlling 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 controller for controlling the same, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Thermal head and controller for controlling the same will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3278890