JPH081979A - Thermal head - Google Patents

Abstract

(57) [Summary] [Object] An object of the present invention is to provide a thermal head which is low in cost, can perform high-speed printing, can be driven with low power consumption, and has high reliability. A heating portion 2 defined in a predetermined area on an insulating substrate 1, electrodes 3 and 3'formed on the insulating substrate 1 with the heating portion 2 interposed therebetween, a heating portion 2 and an electrode 3, 3'consisting of a resistor 4 continuously covering the resistor 4 and an anodized film 5 obtained by anodizing the surface of the resistor 4, and the width W ₁ of the resistor 4 near the heat generating portion and the electrodes 3, 3 '. Is W ₂ , the width of the heat generating portion 2 is W ₃ , the length of the heat generating portion 2 is L, the end portion of W ₃ and W ₁
When the difference in the lengthwise direction from the end portion on the heat generating portion side is defined as ΔL, (1) W ₁ ≧ W ₃ ≧ W ₂ and W ₁ / W ₂ ≦ 1.
30 relationships, (2) 0.96 W ₁ > W ₃ ≧ W ₂ and W ₁
/ W ₂ ≦ 1.20 and ΔL / L ≦ 0.30, at least one of which is satisfied.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal head used in an ink jet printer, a thermal transfer printer, or a thermal printer.

[0002]

2. Description of the Related Art Conventionally, this type of thermal head is disclosed in Japanese Patent Laid-Open No. 61-260604, and FIG.
FIG. 3 is a sectional view showing the structure of the thermal head and the roller. In FIG. 14, this thermal head has a substrate 3
The low antibody 32 is formed on top of which the heat generating part 3 is formed.
The conductor 34 is formed in a portion other than the portion to be 3. Further, the surface of the low antibody 32 at the heat generating portion 33 is the anodic oxide film 3
5, the anodic oxide film 35 and the conductor 34 are further covered with a protective layer 36. Thermal paper 37 is rubber roller 3
8 is pressed against the protective layer 36 on the heat generating portion 33 and recorded.

In the thermal head having such a structure, when the conductor 34 is energized, the low antibody 3 at the heat generating portion 33 is generated.
2 is heated and dots are printed on the thermal paper.

Another conventional thermal head is disclosed in Japanese Patent Application Laid-Open No. 60-109850, which is shown in FIG.
FIG. 3 is a sectional view showing the structure of the thermal head.

In FIG. 15, this thermal head is
The heat insulating layer 42, the low antibody 43 and the conductor 44 are formed on the silicon substrate 41, the conductor 44 on the portion to be the heat generating portion 45 is removed, and the low antibody 43 and the conductors 44 and 44 'are anodized to form the surface. The tantalum pentoxide 46 and the aluminum oxides 47, 47 'are formed on the substrate. In addition, a barrier 49, via an adhesive layer 48, 48 'on the thermal head,
49 'and the orifice plates 50, 50' are adhered.

In the thermal head having such a structure, when the conductors 44 and 44 'are energized, the low antibody 43 at the heat generating portion 45 is heated, the ink (not shown) on the thermal head is boiled, and the ink is discharged. It comes out from the orifice 51,
Dots are printed on a printing paper (not shown).

[0007]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
In the thermal head described in Japanese Patent No. 0604, the low antibody 3
2. Since the conductor 34 and the protective layer 36 are formed by sputtering, three sputtering processes are required. This sputtering process has a problem that the cost is high because the equipment and the sputtering target are expensive.

Although the thermal head used in the thermal printer has been described as an example, the thermal head of the ink jet printer has the same structure. In the case of an inkjet printer, the thermal head is placed in an ink atmosphere. The conductor 34 is made of aluminum, copper, or the like, which corrodes when it comes into contact with ink. Therefore, the protective layer 36 needs to prevent ink from entering. The protective layer 36 is formed by sputtering, but the sputtering film is microscopically porous, and it is necessary to increase the film pressure in order to use the sputtering film as the protective layer. Therefore, since the conventional thermal head has a thick protective layer, the thermal capacity of the protective layer is large and the thermal response is poor,
There is a problem that not only the printing speed cannot be increased but also the input power must be increased, resulting in high power consumption.

For example, in the case of the thermal head having the above structure, in order to eliminate the influence of the pinhole in the protective layer, 1.
A protective layer with a thickness of 5 μm is required. At this time, a silicon wafer with a thermal oxide film of 1.35 μm is used as a substrate,
When silicon nitride was used as the protective layer, the thermal responsiveness was about 10 kHz, and the input power to the heat generating portion required 1000 W / mm 2 to generate bubbles.

Further, in the thermal head described in JP-A-60-109850, the sputtering process is performed twice with the low antibody 43 and the conductor 44, and the cost is low, but there are the following problems. It was That is, the surface of the thermal head is covered with tantalum pentoxide 46 and aluminum oxide 47, 47 ', but since they are different substances and are not chemically bonded, microslits are generated at their boundary portions B, B'. In addition, since thermal stress is generated at the boundary portion when the thermal head is driven, ink invasion from the boundary portion or destruction of the boundary portion occurs, and durability is short.

Further, since the low antibody 43 and the conductors 44 and 44 'are different substances, the optimum anodic oxidation conditions are different for each, but in the case of this thermal head, tantalum pentoxide 46 is used.
Since the anodic oxidation is performed at the same time to form the aluminum oxide 47 and the aluminum oxide 47, there is a problem that it is difficult to form an anodic oxide film that is optimal for both. For example, in the case of the thermal head having this structure, the durability was about 10 6 pulses, and the breakage occurred at the boundary portions B and B ′ between the two.

Therefore, the present invention solves such a problem, and provides a thermal head which improves the durability of the thermal head, is inexpensive, consumes less power, and can perform high-speed printing. The purpose is to

[0013]

In order to solve the above-mentioned problems, a thermal head according to the present invention has a heat generating portion defined in a predetermined region on an insulating substrate and an insulating substrate sandwiching the heat generating portion. It includes a formed electrode, a low antibody that continuously covers the heat generating portion and the electrode, and a protective layer obtained by anodizing the surface of the low antibody, and the width of the resistor that covers the electrode near the heat generating portion is W ₁ , When the electrode width near the portion is W ₂ , the heating portion width W ₃ , the heating portion length is L, and the difference in the length direction between the end portion of W _{3 and} the end portion of W _{1 on} the heating portion side is defined as ΔL, (1) W ₁
The relation of ≧ W ₃ ≧ W ₂ and W ₁ / W ₂ ≦ 1.30, (2)
It is characterized in that at least one of the relations of 0.96W ₁ > W ₃ ≧ W ₂ and W ₁ / W ₂ ≦ 1.20 and ΔL / L ≦ 0.30 holds. By satisfying this relationship, the ratio Pmax / PO between the heat generation amount Pmax at the heat generation peak portion and the heat generation amount PO at the center of the heat generation portion becomes 2.00 or less, and there is no thermal breakdown and even when used for a long time. Reliability does not deteriorate.

[0014]

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

FIG. 1 is a plan view showing a thermal head showing a typical embodiment of the present invention, and FIG. 2 is a sectional view taken along the line AA 'of the thermal head of FIG.

In the figure, conductor electrodes 3 and 3 ′ are formed on the surface of a silicon substrate 1, and the electrodes 3 and 3 ′ are covered with a low antibody 4. The heat generating part 2 is formed between the electrodes 3 and 3 ', and only the low antibody 4 is formed in the heat generating part, not a conductor. The surface of the low antibody 4 is anodized, and an anodized film 5 is formed as a protective layer. The boundary surfaces of the electrodes 3 and 3'with the heat generating portion 2 are inclined.

In the present embodiment, the shapes of the heat generating portion 2, the electrodes 3, 3 ′ around the heat generating portion 2 and the low antibody 4 influence the heat generation distribution of the heat generating portion 2. This will be described later. A method of manufacturing the example thermal head will be described.

First, 0.5 μm of aluminum is formed as a conductor material by sputtering on a silicon substrate 1 having a thermal oxide film with a thickness of 1.35 μm on its surface. next,
By the photolithography process, the portion to be the heat generating portion 2 and the portion between the adjacent conductors are removed by an etching solution to form the electrodes 3 and 3 ′. The electrodes 3 and 3'are the electrode patterns in the area surrounded by the broken line in FIG.

Next, tantalum as a resistor material is formed into a film of 0.26 μm by sputtering, and a photolithography process is performed so as to continuously cover the electrodes 3 and 3'and the heat generating portion 2 and the adjacent low antibody. Is removed and low antibody 4 is formed. The low antibody 4 has a low antibody pattern in a region surrounded by a solid line in FIG.

Next, 147 V is applied to the surface of the low antibody 4 in a 0.1% phosphoric acid aqueous solution with the low antibody 4 as an anode to anodize the surface of the low antibody 4 to form an anodized film 5 of 0.3 μm tantalum pentoxide.
Is formed. Low antibody 4 that was not anodized at this time
Has a thickness of 0.1 μm.

As a material for forming the electrodes 3 and 3 ', aluminum or aluminum alloy such as aluminum-copper or aluminum-silicon having high electric conductivity can be used. In addition, as a material for forming the low antibody 4, tantalum, tantalum nitride, or the like, which has a volume resistivity of a certain size and excellent heat resistance, can be used.

In the thermal head having such a structure, when a voltage is applied between the electrodes 3 and 3 ', the heating portion 2 has no electrodes and is composed of only low antibody, so that the resistance value becomes high. Therefore, the heat generating portion 2 generates heat.

Here, in the embodiment of the present invention, the sputtering rig process is performed twice, that is, the conductors 3, 3'and the resistor 4, which is inexpensive. Moreover, the input power to the heat generating portion required to generate bubbles is 650 W / mm 2, which is low power consumption.

Furthermore, a low antibody tantalum anodic oxide film 5
Has a stoichiometric amount of tantalum pentoxide (Ta205) and is extremely dense. Therefore, the membrane pressure of the low antibody 4 that has not been anodized is 0.1 μm or more, and can be made extremely thin. As a result, it can be driven at a high speed of 20 kHz or more.

Further, since the material which participates in the anode is only tantalum which is the resistor material, it can be performed under the optimum conditions suitable for this, and the surfaces of the conductors 3 and 3'and the heating portion 2 are anodized. It is continuously covered with low antibody and has no discontinuity, thus improving durability. In the case of this embodiment,
A thermal head having a durability of about 107 pulses was obtained. This is about 10 times more durable than the conventional thermal head.

In the thermal head of this embodiment, the heat generating portion 2
It was found that the heat generation distribution of 1 is greatly affected by the shape of the heat generating portion 2. FIG. 11 is a heat generation distribution calculated by a simulation based on the Laplace equation regarding the potential distribution of the low antibody for the resistor shape of the thermal head shown in FIG. Here, since the resistor shape shown in FIG. 10 is vertically and horizontally symmetrical, it is sufficient to show the heat generation distribution only in the lower left ¼ region of FIG. 10, as shown in FIG. The conditions used for the simulation were that the input voltage was 5.8 V, the membrane pressure of the low antibody 4 was 0.1 μm, and the low antibody 4 was 4.
Has a resistivity of 1.55 μΩm. From FIG. 11, the heat generating part 2
It is confirmed that the peak of heat generation is generated in the narrowed part. At this time, the heat generation amount PP at the central position of the heat generating portion 2
Ratio Pma of heat generation amount Pmax of heat generation peak portion to O
x / PO is 2.66. In this case, when the thermal head is driven, a large thermal shock is applied to 7, 7'having a heat generation amount of Pmax in the area of the heat generating portion 2, and when the thermal head is driven for a long period of time, destruction occurs from there.
As a result, the reliability of the thermal head is greatly reduced.

FIG. 3 is a thermal head of Example 1, which shows a resistor shape in which local current concentration is reduced when the thermal head is driven. This shape is based on the Laplace equation regarding the potential distribution of low antibody. This is an example determined from the heat generation distribution calculated by simulation. As parameters for determining the shape, the width W 1 of the low antibody 4 covering the electrodes 3, 3 ′, the width W ₂ of the electrodes 3, 3 ′, the width W of the heat generating portion 2
₃ , four differences ΔL in the length direction between the end portion of the width W ₃ of the heat generating portion 2 and the end portion of the width W ₁ of the low antibody 4 on the heat generating portion side with respect to the length L of the heat generating portion 2 are raised.

FIGS. 4 to 6 are characteristic diagrams showing the influence of four parameters on the heat generation distribution. Here, the effect on the heat generation distribution is that the heat generation distribution of the heat generation part 2 becomes more uniform as the ratio Pmax / PO of the heat generation amount Pmax of the heat generation peak part to the heat generation amount PO at the central position of the heat generation part 2 approaches 1.00. Can be said to be close to. On the other hand, as a result of trial manufacture and evaluation of a thermal head having a heat generating part with various heat generation distributions, it was found that if the ratio Pmax / PO is 2.00 or less, the life of the thermal head is not significantly affected. Therefore, the value of Pmax / PO is preferably 2.00 or less.

FIG. 4 is a diagram showing changes in the ratio Pmax / PO when the width W ₁ of the low antibody 4 is changed with respect to the width W ₂ of the electrodes 3, 3 '. In FIG. 4, W ₁ / W ₂ is 1.
When it exceeds 30, the width of the low antibody that does not cover the electrode (W ₁ -W
It is confirmed that the current wraparound occurs due to the increase in the area of ₂ ), causing local current concentration. Since W ₁ / W ₂ is in the 1.30 or less is Pmax / PO is 2.00 or less, W ₁ / W ₂ is preferably 1.30 or less. Further, when W ₁ / W ₂ becomes 1.20 or less, Pmax / PO becomes as small as 1.50 or less. Therefore, if there are no restrictions on the manufacturing conditions due to the alignment accuracy at the time of forming the low antibody pattern, W ₁ / W ₂ is 1.2 or less.
A heat distribution of 0 or less can be further homogenized.

FIG. 5 shows the width W of the low antibody 4 covering the electrodes 3 and 3 '.
Pma when the width W ₃ of the heat generating portion 2 with respect to 1 is changed
It is a figure which shows the change of x / PO. In FIG. 5, W ₃ /
When W ₁ exceeds 1.00, the heating part 2 width W ₃ is low antibody 4
A current sneak occurs in a region exceeding the width W1, causing local current concentration. Therefore, W ₃ / W ₁ is preferably 1.00 or less. Also, W ₃ / W ₁
Is preferably 1.00 or less. Also, W ₃ / W
_{When 1} is 0.89 or more (W ₃ / W ₂ is greater than 1.0) and 0.96 or less, Pmax / PO is 1.50 or less, so the heat generation distribution is more uniform.

FIG. 6 shows 0.96 W ₁ > W ₃ ≧ W ₂ and W ₂
When ≦ 1.20, the current of the current is increased between the end portion of the width W ₃ of the heat generating portion 2 and the end portion of the low antibody 4 width W _{1 on} the heat generating portion side which is the length L of the heat generating portion 2. Since the wraparound extends to the vicinity of the center of the heat generating portion 2, the value of Pmax / PO rapidly increases. When ΔL / L is 0.30 or less, Pmax /
Since PO is 1.50 or less, the heat generation distribution is more uniform, which is desirable.

The thermal head shown in FIG. 3 has a resistor shape in consideration of the above four parameters. The shape of the resistor of the thermal head shown in FIG. 3 is W ₃ = 0.92W ₁ > W
₂ , W ₁ / W ₂ = 1.13 and ΔL / L = 0.05. FIG. 7 shows the heat generation distribution calculated by a simulation based on the Laplace equation regarding the potential distribution of the low antibody at this time. Here, since the shape of the resistor of the thermal head in FIG. 3 is vertically and horizontally symmetrical,
FIG. 7 shows the heat generation distribution in the area of No. 4. The conditions used for the simulation were that the input voltage was 5.8 V, low antibody 4
Film thickness of 0.1μm, low antibody 4 resistivity is 1.55μΩ
m. As is apparent from comparison with the cases of FIGS. 12 and 13, the peak of heat generation in the narrowed portion is relaxed, and Pmax / PO at this time is 1.19. As a result, the load of low antibody is reduced, and the power resistance is improved.

FIG. 8 shows a second embodiment (second embodiment) of the present invention.
FIG. 3 is a partial plan view of the thermal head of FIG. The shape of the resistor of the thermal head shown in FIG. 8 is W ₃ = W ₁ > W ₂ , W ₁ /
W ₂ = 1.13 and ΔL = 0. FIG. 9 is a plan view showing a heat generation distribution calculated by a simulation based on the Laplace equation regarding the potential distribution of the low antibody for this resistor shape. Since the resistor shape of the thermal head shown in FIG. 8 is vertically and horizontally symmetrical,
Shows the heat generation distribution in the lower left quarter region of FIG. The conditions used for the simulation are as follows: input voltage 5.8V, low antibody 4 film thickness 5.8V, resistor 4 film thickness 0.1 μm,
The low antibody 4 has a resistivity of 1.55 μΩm. 12, 1
Compared with No. 3, the thermal head of FIG. 8 does not have a narrowed portion, so a peak of heat generation can be seen near the power 3, 3 ′, but Pmax / PO is 1.75, which is improved compared to the case of FIG. ing. As a result, the addition of low antibody is reduced, and the power resistance is improved.

Table 1 shows various characteristics of Examples 3, 4, 5 of the thermal head having a resistor shape in consideration of the four parameters in the same manner as Examples 1 and 2 described above. Two resistance meter shapes are shown as comparative examples. Table 1 also shows the data of Pmax / PO in each resistor shape and the breakdown power value of the prototype in which tantalum is applied to the resistor 4. Pmax in the data of all materials
Since the breakdown power value increases as the value of / PO approaches 1.00, the validity of the simulation is confirmed.

In all the embodiments, (1) W ₁ ≧ W ₃ ≧ W
₂ and W ₁ / W ₂ ≦ 1.30, (2)
0.96W ₁ / W ₂ ≦ 1.20 and ΔL / L ≦ 0.30
Meet the relationship. At least one of (1) and (2) may be satisfied. Since the relationship (2) includes the relationship (1), the resistor shape satisfying the relationship (2) also satisfies the relationship (1). Examples 1, 3,
Nos. 4 and 5 are examples having a resistor shape satisfying the relationship of (2) and satisfying only Examples 2 and 6 (1).

On the other hand, Comparative Example 1 is an example having a resistor shape in which W ₁ = W ₃ which does not satisfy only (1), and Comparative Example 2 is one of (1) and (2). It is an example having a resistor shape in which W ₁ > W _{3 in} which the above relationship is not satisfied. Also, the shape of the resistor in the thermal head shown in FIG. 10 does not satisfy any of the relationships (1) and (2).

As a result, in FIG. 10 and Comparative Examples 1 and 2, Pm
While the value of ax / PO is 2.00 or more,
In all the examples, it is less than 2.00. Therefore, since the addition of the resistor is reduced, the breakdown power value is increased and the reliability is improved.

The values of Pmax / PO in Examples 1, 3, 4, and 5 satisfying the relationship of (2) are higher than those of Examples 2 and 6 satisfying only (1). The value is close to 1.00. Therefore, by applying the resistor shape satisfying the relationship of (2), the heat generation distribution was made more uniform, the breakdown power value was increased, and the reliability was further improved.

[0039]

[Table 1]

[0040]

As described above, according to the present invention,
Sputtering is done in two steps at low cost, and because the thickness of the resistor can be made thin, high-speed printing is possible and low power consumption drive is possible, and reliability that can guarantee a long life depending on the conditions of (1) or (2). A high thermal head can be obtained.

[Brief description of drawings]

FIG. 1 is a plan view showing a thermal head of a typical embodiment of the present invention.

FIG. 2 is a sectional view taken along line A-A 'of FIG.

FIG. 3 is a plan view showing a part of the thermal head according to the first embodiment of the present invention.

FIG. 4 is a diagram showing changes in a heat generation distribution ratio Pmax / PO when the resistance body width W ₁ is changed with respect to the electrode width W ₂ .

FIG. 5 is a diagram showing changes in Pmax / PO when the heating portion width W ₃ is changed with respect to the resistor width W ₁ .

FIG. 6 is a longitudinal difference Δ between the end portion of the heating portion width W _{3 and} the end portion of the resistor width W _{1 on} the heating portion side with respect to the heating portion length L.
It is a figure which shows the change of Pmax / PO when L is changed.

FIG. 7 is an enlarged view showing the heat generation distribution calculated by simulation for the resistor shape used in Example 1 of the present invention.

FIG. 8 is a plan view showing a part of a thermal head according to a second embodiment of the present invention.

FIG. 9 is an enlarged view showing the heat generation distribution calculated by simulation for the resistor shape used in Example 2 of the present invention.

FIG. 10 is a plan view showing an example of a thermal head for comparison.

FIG. 11 is an enlarged view showing a heat generation distribution calculated by simulation for the resistor shape used in the example of FIG.

FIG. 12 is a cross-sectional view showing a conventional thermal head.

FIG. 13 is a sectional view showing another conventional thermal head.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 Heat generating part 3,3 'Electrode 4,4' Resistor 5,5 'Anodized film 6 Region of resistor not covering electrodes 7,7' Local region in heat generating part 2

Claims (2)

[Claims] 1. A low-antibody that continuously covers the heat-generating portion and the electrode, the heat-generating portion defined in a predetermined region on the insulating substrate, the electrode formed on the insulating substrate with the heat-generating portion interposed therebetween. And a protective layer obtained by anodizing the resistor surface,
If the width of the low antibody covering the electrode near the heat generating portion is defined as W ₁ , the electrode width near the heat generating portion is defined as W ₂ and the width of the heat generating portion is defined as W ₃ , then W ₁ ≧ W ₃ ≧ W ₂ Relationship and W ₁ / W ₂
A thermal head characterized by satisfying a relationship of ≤1.30. 2. The width W _{1 of the} low antibody and the width W of the heat generating portion.
_{When 3} has a relation of W ₁ > W ₃ , the length of the heat generating portion is L, the end portion of the width W ₃ of the heat generating portion and the width W of the low antibody.
_When ΔL is defined as the difference in the lengthwise direction from the end portion on the heat generating portion side of 0.9, 0.96W ₁ > W ₃ ≧ W ₂ and W ₁ / W ₂ ≦
1. A thermal head characterized by satisfying the relationship of 1.20 and ΔL / L ≦ 0.30.