JPH03182366A - Thick film-type thermal head - Google Patents

Abstract

PURPOSE:To form a dot close to rectangular thereby to define the border of dots clearly by setting the sectional area and thermal conductivity of an electrode and the sectional area and thermal conductivity lambdaR of a heat generating resistance body to hold a specific relation when the band-shaped heat generating resistance body is formed stretching over the electrode which is formed on a glaze layer on an insulative substrate. CONSTITUTION:A glass glaze layer 3 is formed as a heat accumulating layer on an insulative substrate 2. A resinate gold paste is printed and burnt on the glass glaze layer 3 to form a conductive film. Then, the conductive film is patterned by application of photolithography, thereby forming a common electrode 4 and an independent electrode 5. Further, a resistance body paste is printed and burnt in a band shape on the glass glaze layer 3 to stretch over the electrodes 4, 5. Accordingly, a heat generating resistance body 6 is formed. In this case, the sectional area SE and thermal conductivity lambdaE of each electrode 4, 5 in an X direction, and the sectional area SR and thermal conductivity lambdaR of the heat generating resistance body 6 in a Y direction are so set as to hold the relation (SEXlambdaE)/(SRXlambdaR)>=3.529.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application This invention relates to a thick film thermal head, and more specifically, to a thick film thermal head that can clearly color dots on heat-sensitive recording paper.

(B) Prior Art A conventional thick film thermal head will be described below with reference to FIGS. 5 and 7. Reference numeral 12 denotes an insulating substrate made of a material such as ceramic, on the surface of which a glass glaze layer 13 is formed as a heat storage layer (see FIG. 7).

On this glass glaze J1113, a common electrode 14 and individual electrodes 15 are formed using gold (Au) paste.

As shown in FIG. 5, the electrodes 14, 15 are arranged in a comb-teeth shape and interlock with each other.

Furthermore, a heating resistor 16 is formed on the glaze layer 13. This heat generating resistor 16 is in the form of a band that straddles the electrodes 14.15, and the portion sandwiched between adjacent common electrodes 14.14 corresponds to one dot. Reference numeral 17 denotes a wear-resistant layer, which protects the heating resistor 16 and electrodes 14 and 15 from mechanical friction with the heat-sensitive recording paper.

In this thick film type thermal head, when a voltage is applied between the common electrode 14 and the individual electrodes 15, current flows through the heating resistor 16 and generates heat. This heat is transmitted to the heat-sensitive recording paper through the abrasion-resistant layer 17, causing color dots to develop on the heat-sensitive recording paper.

(c) Problems to be Solved by the Invention In the above-mentioned conventional thick-film thermal head, the heating resistor 16
Ruthenium oxide (RuO
The resistor paste is formed by screen printing a resistor paste containing t) or glass and firing this resistor paste, and its film thickness is usually about 10 μm. For this reason, the heat conduction of the heating resistor 16 itself cannot be ignored, and the dots do not become rectangular as shown in FIG. 6(a), but instead the dots are shaped like heating resistors at both ends as shown in FIG. 6(b). 6 It becomes a shape that bulges in the stretching direction. With such a shape, there is a problem that the boundaries between adjacent dots become unclear.

In particular, this problem becomes even more pronounced in the case of a thermal head for printing barcodes.

The present invention has been made in view of the above, and an object of the present invention is to provide a thick-film thermal head in which the dots can be approximated to rectangular shapes and the boundaries between the dots can be made clear.

(d) Means and operation for solving the problems In order to solve the above problems, the thick film thermal head of the present invention forms a glaze layer on an insulating substrate, forms electrodes on this glaze layer, and In a device formed by forming a band-shaped heating resistor spanning an electrode, the cross-sectional area SE of the electrode, thermal conductivity λE, and the cross-sectional area sll of the heating resistor, thermal conductivity λ
7, S, l×λ, respectively.

It is set so that the relationship holds true.

If the relationship in equation (1) above is satisfied, it can be said that thermal diffusion by the electrodes is superior to thermal diffusion by the heating resistor itself. Therefore, the colored dots on the thermosensitive recording paper become more rectangular, and the boundaries between the dots can be made clearer.

(E) Embodiment An embodiment of the present invention will be described below with reference to FIGS. 1 to 4.

FIG. 1 is a diagram illustrating the arrangement of the electrodes 4.5 and the heating resistor 6 of the thick-film thermal head according to the embodiment, and FIGS. 2 and 3 are the lines ■-■ and If-■ in FIG. FIG. 3 is an enlarged cross-sectional view along the dlr line.

2 is an insulating substrate made of a material such as ceramic. A glass glaze layer 3 is formed on this insulating substrate 2 as a heat storage layer. This glass glaze layer 3 is obtained by printing a glass paste on the insulating substrate 2 and firing it.

On the glass glaze layer 3, a resinate gold paste is printed and fired to form a conductive film, and then the conductive film is patterned using photolithography to form a common electrode 4,
Individual electrode 5 is used.

Furthermore, a resistor paste is printed and fired on the glass glaze layer 3 so as to span the electrodes 4.5 in a band shape, thereby forming a heat generating resistor 6. A portion of the heating resistor 6 sandwiched between adjacent common electrodes 4.4 corresponds to one dot.

A glass paste is printed on the insulating substrate 2 so as to cover the electrodes 4.5 and the heating resistor 6, and is fired to form the protective glass N7. This protective glass layer 7 covers the electrodes 4.
5. The heating resistor 6 is protected from friction with thermal recording paper (not shown).

Now, the cross-sectional area S6 of the electrode 4.5 in U-H2S (X direction), the thermal conductivity λt, the cross-sectional area Sll of the heating resistor 6 in the ■-■ line (Y direction), and the thermal conductivity λE are as follows. (
1) It is determined to satisfy the relationship of formula.

SR×λ.

If the thickness t4 of the electrode 4.5 is 0.6 x 10-4C and the width (in the X direction) is 2.5 x 10-'cm, the cross-sectional area S7 will be 1.5 x 10-'cm2. In addition, its thermal conductivity λE is 0.708 (caf/cm-s-
deg).

On the other hand, the thermal conductivity λ6 of the heating resistor 6 is set to 0.0033 (
cal/cm・s-deg), then from equation (1), the cross-sectional area S, l is 9. l2 x 10-'cm2
The following is true. The width of the heating resistor 6 (Y direction) is 2.40X
If 1.0-2c+o, the thickness tR is as follows (2)
It is necessary to satisfy the formula.

240X (tR-tE)X2XIO-'≦9.12
X10-b...(2) ko(D(Ltr tt) 4.t is the thickness of the heating resistor 6 on the electric field w14.5.11 is 0.6X
Since 10-'c+a, tR is 2.5 x 10-
' cm (2.5 μm) or less.

FIG. 4 shows Example J! J, film type thermal head, comparative example thick film type thermal head (only the thickness of the heating resistor differs)
This figure shows the state of color development of dots, and in this figure, 0.3 mJ of energy is applied to each dot. In FIG. 4, (a) shows an example thick film type thermal head (t*
=2.5 um) and (bHc) are the comparative example thick film thermal head ■ and II (ti =3,0
71 m and 3.5 μm).

In the example original model thermal head, the average width of the dots in the X direction was 125 μm, and in the comparative example thick film type thermal head I,
In both cases, the average width of the dots in the X direction is 139 μm, and it can be confirmed that the dots of the thick film type thermal head of the example are more rectangular.

Note that the specific numerical values shown in this example are just one example, and (
1) The design can be changed as appropriate within the range that satisfies the second relationship.

(f) As described in detail, the thick-film thermal head of the present invention has the following characteristics: ( Since the relationship of SE Xλt)/(S*XλE) ≧3.529 is given, the shape of the dots approaches a rectangular shape and has the advantage that the boundaries between adjacent dots are clear. This advantage is particularly evident in thermal heads for barcode printing.

[Brief explanation of drawings]

FIG. 1 is a diagram illustrating the arrangement of electrodes and heat generating resistors of a thick film thermal head according to an embodiment of the present invention, and FIGS. 2 and 3 are main parts of the same thick film thermal head, respectively. The enlarged cross-sectional view, FIG. 4(a), is a diagram showing the dot coloring state of the same thick film type thermal head, FIG. 4(b), and FIG.
C) is a diagram showing the dot coloring state of a comparative example thick-film thermal head, FIG. 5 is a diagram explaining the arrangement of electrodes and heating resistors of a conventional 11-film thermal head, and FIG.
Figure (a) shows a desirable dot shape (part 6)
7 is a diagram showing an actual dot shape of the conventional thick film type thermal head, and FIG. 7 is a sectional view of a main part of the conventional thick film type thermal head. 2: Insulating substrate, 3 Niglass glass layer, 4: Common electrode, 5: Individual electrode, 6: Heat generating resistor.

Claims (1)

[Claims] (1) A thick-film thermal head in which a glaze layer is formed on an insulating substrate, electrodes are formed on the glaze layer, and a band-shaped heating resistor is formed spanning these electrodes, in which: The cross-sectional area S_E, the thermal conductivity λ_E, and the cross-sectional area S_R and the thermal conductivity λ_R of the heating resistor are respectively (
A thick-film thermal head characterized in that the following relationship is established: S_E×λ_E)/(S_R×λ_R)≧3.529.