JPH0655757A - Thermal head - Google Patents

Abstract

PURPOSE:To obtain a thermal head whose installation area is small and which can be manufactured at low cost by determining the pressure contact angle of the head to be large, with another advantage of sharp print which can be obtained by extending an ink ribbon stripping distance. CONSTITUTION:The subject thermal head has a glass glaze 2 formed near the one end surface of a substrate 1, and thermal elements 3 formed in such a manner that the elements are offset to the end surface from the center of the glass glaze 2. In addition, the end surface 12 is machined so that a stepped part consisting of more than one step is formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The thermal head of the present invention relates to a thermal transfer printer head used in computers, word processors, facsimiles and the like. In particular, it is an object to provide a thermal head, which has been in high demand in recent years, with high printing quality on plain paper at low cost.

[0002]

[Prior art]

(Conventional Example 1) FIG. 4 shows a structure of a general thermal head.

A general thermal head is provided with a glass glaze 2 formed on a substrate 1, a plurality of heating elements 3 formed near the center of the glass glaze 2, and individually connected to each heating element. Heating element 3 independently according to the signal
A segment electrode 4 for driving, a common electrode 5 commonly connected to the heating element, a heating element 3, a segment electrode 4,
It comprises a protective film 6 for protecting the common electrode 5.

The width L of the common electrode 5 is determined in consideration of the resistance value of the common electrode 5 when a plurality of heating elements 3 are driven at the same time, and usually needs to be about 0.5 mm.

The influence of the resistance value of the common electrode 5 will be further described.

For example, when the resistance value of the plurality of heating elements 3 is Rh, the number n of the heating elements 3 is the driving voltage V, and the resistance value of the common electrode 5 is Rc, the combined resistance R can be expressed by the equation 1.

R = Rh / n + Rc = Rh + n × Rc Equation 1 Therefore, the current value ic flowing through the common electrode 5 can be expressed by Equation 2.

Ic = V / (Rh + n × Rc) Equation 2 From this, the voltage drop Vc of the common electrode 5 is given by Equation 3.

Vc = ic × Rc = V × Rc / (Rh + n × Rc) Equation 3 In this case, the voltage Vr applied to the heating element 3 is Equation 4.

Vr = V-Vc = V * Rh / (Rh + n * Rc) Equation 4 At this time, the current value ir flowing through one heating element 3 is as shown in Equation 5.

Ir = Vr / Rh = V / (Rh + n × Rc) Equation 5 Therefore, the power Wr consumed by the heating element 3 can be expressed by Equation 6.

Wr = ir ² × Rh = V ² × Rh / (Rh + n × Rc) ² Equation 6 Here, for example, V = 24 [Volt], Rh = 500
Assuming that [Ω] and Rc = 5 [Ω], Wr = 1.13 [Watt] since n = 1 when the number of the heating elements 3 to be driven simultaneously is one.

However, the number n of the heating elements 3 driven simultaneously is n.
In the case of driving 48 heating elements at the same time, if n = 48, then Wr = 0.53 [Watt].

This indicates that even if the heating elements 3 are driven at the same voltage, the energy obtained by one heating element 3 varies depending on the number of driving of the heating elements 3.

The most appropriate means for solving such a problem is to lower Rc. Therefore, the common electrode 5, which is generally formed of a thin film, needs to have a width L greater than a certain level.

(Prior art example 2) Further, in the prior art, for example, Japanese Patent Laid-Open No.
A thermal head as described in JP-A-3-95963 has been known.

FIG. 5 shows a sectional view of a thermal head obtained by obliquely polishing the end portion of the substrate in this case. The thermal head of FIG.
The glass glaze 2 is formed in the vicinity of the boundary between the sloped surface 7 and the substrate surface by polishing the sloped surface 7 at an angle of 60 degrees.

(Prior art example 3) Further, for example, JP-A-61-2
A thermal head as described in Japanese Patent No. 37662 has been known.

As shown in FIG. 6, the common electrode 5 is formed on the substrate 1.
And the glass glaze 2 is formed on the common electrode 5.

[0020]

However, in the case of the thermal head as in the prior art example 1, when the thermal head 11 is pressed against the platen 8 via the printing paper 9 and the ink ribbon 10 as shown in FIG. , End 12 of the thermal head
Therefore, there is a problem that the press contact angle 13 cannot be set too large. The fact that the press contact angle 13 cannot be made large means that when the flexible cable 14 connected to the thermal head 11 is mounted, as shown in FIG.
Must be provided on the end face in the direction perpendicular to the end face on which the glass glaze 2 is formed. Therefore, the area of the thermal head 11 increases due to the width of the mounting portion 15, which leads to an increase in cost.

In the case of the conventional example 2, as shown in FIG. 9, the pressure contact angle 13 can be increased by polishing the end face of the substrate 1. As a result, the flexible cable 14 connected to the thermal head 11 can be connected to the end surface on which the glass glaze 2 is formed and the opposite end surface. Therefore, there is an advantage that the area of the thermal head 11 can be reduced and the installation space can be reduced.

However, in the case of the conventional example 2, since it is necessary to polish the end face of the substrate 1, as shown in FIG. 10, only two thermal heads 11 can be formed on at most one substrate. Become. Normally, in the manufacture of thermal heads, multiple thermal heads are created on one substrate,
Although the cost can be reduced by dividing, in the case of the conventional example 2 as shown in FIG. 10, the cost is considerably high.

Further, in the case of the conventional example 3, as shown in FIG. 11, since the glass glaze 2 is formed near the end face of the substrate 1, it is possible to make the press contact angle 13 large and polish the end face. Since there is no need to do so, many thermal heads that can be made with one substrate can be provided, and there is no problem such as high cost.

However, in the case of Conventional Example 3, as shown in FIG. 12, the platen 8 is provided with the ink ribbon 10 and the printing paper 1.
1. The pressure contact portion 16 of the thermal head 11 pressed against
The ink L on the ink ribbon 10 is melted and transferred to the printing paper 9, and the distance L2 until the ink ribbon 10 is peeled off from the ink 17 becomes extremely short. This shortens the time until the ink ribbon 10 is peeled from the melted ink 17 (ink ribbon peeling time). When the peeling time is short, the ink is peeled off in a low viscosity state, and the melted ink drops like a starch syrup and is transferred. (A state in which the syrup is transferred in the form of a starch syrup is referred to as poor print quality) Therefore, there is a problem in that the print quality is degraded.

An object of the present invention is to obtain a head with good print quality at low cost.

[0026]

A substrate, a glass glaze formed on the substrate, a plurality of heating elements formed on the glass glaze, and an electrode portion connected to the heating element and supplying electric power to the heating element. In a thermal head having and, the glass glaze is formed near one end surface of the substrate, the plurality of heating elements are formed to be displaced from the center of the glass glaze in the end surface direction, and the end surface is It is characterized by being processed into one or more steps. Also,
It is characterized in that a step portion between the step-shaped surface processed into the step shape and the substrate surface is formed at an angle of 20 to 70 degrees from the step-shaped surface.

[0027]

Embodiments of the thermal head of the present invention will be described with reference to the drawings.

FIG. 1 is a sectional view of the thermal head of the present invention during printing. Reference numeral 1 is a substrate, 2 is a glass glaze, and 8 is a glass glaze.
Is a platen, 9 is printing paper, 10 is an ink ribbon, 11
Is a thermal head, 12a is a stepped portion, 13 is a contact angle of 1
Reference numeral 4 is a flexible cable, and 15 is a mounting portion. In the case of the thermal head of the present invention, since one end face of the substrate 1 is processed like the stepped portion 12a, the distance L until the ink ribbon is peeled off from the pressure contact portion 16 of the thermal head.
2 will be big enough. For this reason, the ink as described in Conventional Example 3 is not spread and transferred in the form of a starch syrup, and high-quality printing with good sharpness can be obtained.

Further, since the press contact angle 13 can be made large, the flexible cable 14 can be mounted by mounting the mounting portion 15 on the substrate end opposite to the substrate end on which the glass glaze 2 is formed. Become. Therefore, the thermal head 11 having a smaller installation area can be obtained, and the cost can be further reduced.
FIG. 2 is a perspective view showing a method of forming the stepped portion of the thermal head according to the present invention, in which 18 is a blade.

A machine tool such as a dicing saw is used for the substrate 1 to form the stepped portion 12a.
The blade 18 is preferably a diamond tooth that rotates at high speed, and forms the stepped portion 12a while gradually moving in the direction of the arrow in FIG.

At this time, the surface of the substrate 1 and the stepped portion 12a
The angle of the step portion 12b with respect to will be described.

FIG. 3 is a step portion 1 of the thermal head of the present invention.
It is sectional drawing explaining the influence of the angle of 2b, Comprising:
9 is the angle of the step portion 12b, 20 is the cut amount of the stepped portion 12a, and 21 is the length of the step portion 19 in the substrate plane direction.

The thermal head of the present invention comprises a stepped portion 12
After forming a, the glass glaze 2 is printed and fired. In the glass glaze 2, a glass frit in which glass powder is usually dispersed in a solvent is printed on the substrate 1 by a general screen printing method, and then baked in a high temperature baking furnace to evaporate a solvent component and melt the glass. It is formed by

After that, a heating element layer for forming the heating element 3 and an electrode layer for forming the segment electrode 4 and the common electrode 5 are formed by a general method such as sputtering.

The patterning method using the heating element layers as the plurality of heating elements 3 and the electrode layers as the segment electrodes 4 and the common electrodes 5 is based on the photolithography method which is generalized in the manufacturing process of ICs.

At this time, if the angle 19 of the step portion 12b is large, there is a problem that photoresist is accumulated in the vicinity of the tangent line between the stepped portion 12a and the step portion 12b, resulting in frequent pattern short-circuiting and disconnection. Therefore, the angle 19 of the step portion 12b is limited to about 70 degrees.

Next, a problem when the angle 19 of the step portion 12b is small will be described.

As described above, when forming the stepwise portion 12a, a machine tool such as a dicing saw is used for processing, but the thickness of the substrate 1 usually varies by about ± 50 μm. Therefore, if the cut amount 20 of the stepped portion 12a is set to, for example, 100 μ, the cut amount is 50.
It will vary in the range of μ to 150 μ.

At this time, the angle 19 of the step portion 12a is θ, the cut amount 20 is z, and the distance 21 in the plane direction of the step portion a is L.
When it is set to 3, the calculated value of L3 is represented by Expression 7. L3 = z / tan (θ) ... Equation 7 Here, in the case where the value of z is 50 to 150, θ
= 20 and 45, when θ = 45, the range of L3 is 50 to 150, and the variation of L3 is ± 50. When θ = 20, the range of L3 is 1
37.4 to 412.1, and the variation of L3 is ± 13
It turns out that it will be 7.4.

Such a variation has a problem that when the glass glaze 2 is formed later, the positional accuracy of the glass glaze 2 is not obtained and the yield of the substrate is lowered.

Therefore, it is desirable that the angle 19 of the step portion 12a is about 20 degrees or more.

[0042]

As described above, by processing the end face of the substrate of the thermal head in a stepwise manner, the ink ribbon peeling distance can be lengthened and a head with good print quality can be obtained. Further, since the head can have a large pressure contact angle, it is possible to obtain a low-cost thermal head with a small installation area.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a thermal head of the present invention during printing.

FIG. 2 is a perspective view showing a method of forming a stepped portion of a thermal head according to the present invention.

FIG. 3 is a cross-sectional view explaining the influence of the angle of the step portion 12b of the thermal head of the present invention.

FIG. 4 is a diagram showing a structure of a general thermal head.

FIG. 5 is a cross-sectional view of a conventional thermal head obtained by obliquely polishing an end portion of a substrate.

FIG. 6 is a cross-sectional view of a conventional thermal head in which a common electrode is arranged on a substrate and a glass glaze is formed on the common electrode.

FIG. 7 is a cross-sectional view of a thermal head of Conventional Example 1 during printing.

FIG. 8 is a plan view of a thermal head of Conventional Example 1.

FIG. 9 is a sectional view of a thermal head of Conventional Example 2 during printing.

FIG. 10 is a plan view of the manufacturing process of the thermal head of Conventional Example 2.

FIG. 11 is a sectional view of a thermal head of Conventional Example 3 during printing.

FIG. 12 is a cross-sectional view showing a problem at the time of printing the thermal head of Conventional Example 3.

[Explanation of symbols]

 1 Substrate 2 Glass Glaze 3 Heating Element 4 Segment Electrode 5 Common Electrode 6 Protective Film 7 Slope 8 Platen 9 Printing Paper 10 Ink Ribbon 11 Thermal Head 12 End Face 12a Stair Step 12b Step 13 Pressing Angle 14 Flexible Cable 15 Mounting Part 16 Pressure contact part 17 Ink 18 Blade 19 Angle of step part 20 Cut amount of step part 21 Length of step part in the plane direction of the substrate

Claims (2)

[Claims] 1. At least a substrate, a glass glaze formed on the substrate, a plurality of heating elements formed on the glass glaze, and an electrode portion connected to the heating element and supplying electric power to the heating element. In the thermal head, the glass glaze is formed in the vicinity of one end surface of the substrate, and the plurality of heating elements are formed so as to be offset from the center of the glass glaze in the end surface direction, and the end surface has one or more steps. The thermal head is characterized by being processed into a stepped shape. 2. A step portion between the step-like surface processed into the step-like shape and the substrate surface is formed at an angle of 20 to 70 degrees from the step-like surface. The described thermal head.