JPH0550627A - Thermal head - Google Patents

Abstract

PURPOSE:To provide a thermal head reduced in power consumption and capable of performing high speed printing. CONSTITUTION:By laminating a heat accumulating layer 7 made of a polyimide resin to the insulating substrate 1 of a thermal head, Joule heat at the time of the generation of heat is accumulated and the transmission efficiency of energy is enhanced. Radiation after the generation of heat is fastened to increase a printing speed. By constituting the insulating substrate 1 of a glass substrate, the surface of the substrate is made smooth and the contact of the substrate with thermal paper is made uniform to eliminate printing irregularity.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal head for use in a thermal recording type facsimile apparatus or a thermal recording apparatus such as a thermal printer.

[0002]

2. Description of the Related Art In recent years, thermal heads have been widely used in various recording devices such as printers for facsimiles and word processors, and these devices are required to be small in size, light in weight and low in price.

Under such circumstances, in the conventional thermal head,
As shown in FIG. 13, a glazed ceramic substrate in which a glaze layer 102 for heat storage is formed on a ceramic substrate 101 made of Al ₂ O ₃ having a purity of 90% or more is used,
A plurality of heating resistors 2 are arranged in a line in the main scanning direction thereon, and individual wiring electrodes 4 for electrically connecting one end of each heating resistor 2 and the heating resistor driving control element 3 to each other.
And a common electrode 6 for electrically connecting the other end of the heat generating resistor 2 to each other, and further provided with a protective film 9 for preventing the heat generating resistor 2, the individual wiring electrodes 4 and the common electrode 6 from wear deterioration and the like. ing.

Then, after connecting the control element 3 to the individual wiring electrode 4 of the substrate through the solder bump, the control element 3
To protect the resin mold 103, and then press-contact the double-sided flexible circuit board 104 to which the thermistor, the connector 107, the capacitor, etc. are soldered, and the head cover 1
The thermal head is completed by performing an assembly step of fixing the 05 and the heat sink 106 with screws.

[0005]

However, in the thermal head shown in FIG. 13, since the energy applied to the heating resistor for printing is large, in order to save energy, the glaze layer as the heat storage layer should be thicker. There is a need to. However, when the glaze layer is thickened, low energy driving is possible, but since the amount of heat stored in the glaze layer is large, a so-called trailing phenomenon occurs in which the thermal paper is colored even when the application pulse is stopped.

In order to reduce the applied energy and eliminate the tailing phenomenon, the period of the applied pulse may be made sufficiently long to allow the heat accumulated in the glaze layer to escape to the ceramic substrate, but the printing speed becomes slow. A problem has occurred, and conventional thermal heads cannot achieve both low power consumption and high speed.

Further, since an expensive glaze ceramic is used as a substrate, it is an obstacle to lowering the cost of the thermal head.

In view of the above, it is an object of the present invention to provide a thermal head which is inexpensive, has low power consumption and is capable of high-speed printing.

[0009]

1 to 12, a plurality of heating resistors 2 are arranged on an insulating substrate 1 in the scanning direction, and each heating resistor is arranged in the scanning direction. An individual wiring electrode 4 electrically connecting one end of the body 2 and the heating resistor driving control element 3 and a common electrode 6 electrically connecting the other end of each heating resistor 2 in common are provided. In the thermal head, the insulating substrate 1 is composed of a glass substrate, and a heat dissipation layer 11 made of a metal film formed on the insulation substrate 1 and a heat storage layer 7 made of a polyimide resin for covering the heat dissipation layer 11 are laminated. It was done.

[0010]

In the above means for solving the problem, when printing the thermal paper, the heating resistor 2 is caused to generate heat. At this time, when a current is passed through the heating resistor 2, the heating resistor 2 generates heat, but if the current state is kept, the heat of the heating resistor 2 is diffused and a large capacity is required to reach a predetermined temperature. Need power.
However, in the present invention, since the heat storage layer 7 is located below the heat generation resistor 2, the Joule heat generated in the heat generation resistor 2 is accumulated in the heat storage layer 7 and the amount of heat transferred to the thermal paper increases. Moreover, since the heat storage layer 7 uses the polyimide having a lower thermal diffusion coefficient than the conventional glaze ceramic, the heat storage property is further enhanced.

After printing, the heat of the heat storage layer 7 is diffused from the heat dissipation layer 11 having a high heat diffusion coefficient below the heat generating resistor 2. As a result, the tailing phenomenon that occurs when the grace layer is thickened in order to achieve low power consumption in the related art does not occur, and the printing speed of the thermal head can be improved.

Furthermore, since an inexpensive glass substrate is used as the substrate 1, since the warpage is small, the area can be easily increased, and the number of heads to be taken from one sheet can be increased, so that the cost of the thermal head can be reduced. Become.

[0013]

1 is a diagram showing the structure of a thermal head according to one embodiment of the present invention, FIG. 2 is a diagram showing a state in which a metal layer is formed on the surface of a glass substrate in the same manufacturing process, and FIG. 3 is also a metal. The figure which shows the state which patterned the layer as a heat dissipation layer, FIG. 4 is the figure which similarly shows the state which formed the heat storage layer, FIG.
Is a diagram showing a state in which an inorganic layer is formed on the heat storage layer,
FIG. 6 is a diagram showing a state where a heating resistor layer, individual wiring electrodes, a common electrode, etc. are laminated on the inorganic material layer, FIG. 7 is a diagram showing a state where the common electrode is patterned, and FIG. 8 is also a bonding electrode. FIG. 9 is a diagram showing a state where the heating resistor layer on the side is patterned, FIG. 9 is a diagram showing a state where the heating resistor layer on the side of the heat dissipation layer is also patterned, and FIG. 10 is a diagram showing a state before mounting the driver IC, FIG. 11 is a diagram showing the relationship between the print density and the distance from the writing start position in 1-line printing, and FIG. 12 is a diagram showing the relationship between the applied power and the print density. The same functional components as those of the conventional technique and the prior art shown in FIG. 13 are designated by the same reference numerals.

In FIG. 1, 1 is a thermal decomposition starting temperature 350.
It is a glass substrate as an insulating substrate having a temperature of about 1 mm and a temperature of about 1 mm. Borosilicate glass is used here. The maximum processing temperature in the manufacturing process of the present embodiment is 400 ° C., as described later, so if it has more heat resistance and satisfies the flatness required for the thermal head, Other types of glass may be used.

Here, it is conceivable to use a heat-resistant epoxy resin or the like as the insulating substrate, but the glass substrate is
Compared with heat-resistant epoxy resin, in terms of manufacturing, (1) substrate cost is low, (2) substrate warpage and waviness do not occur,
Automation line is easy. (3) In the case of a resin substrate, the gas is released from the substrate, so the degree of vacuum may drop and the film formation may vary. However, in the case of a glass substrate, it may be released into a vacuum with a sputtering device or the like. Stable deposition is possible with less gas,
(4) Since the substrate can be divided by scribing, there is an advantage that the glass can be easily broken by scribing and applying force. Also in terms of performance, (1) excellent surface smoothness, uniform contact with thermal paper, no print unevenness, and (2) thermal conductivity of 1 × 10 ⁻⁷ kca of resin substrate.
2.6 × 10 ⁻⁷ kcal / mm compared to 1 / mm ° C
The glass substrate is used in this embodiment instead of the resin substrate because it has the advantages of excellent heat dissipation and good print quality because the temperature is good in ° C.

On the surface of the glass substrate 1, a metal layer such as Cu, Al having a high thermal diffusion coefficient is formed. If the adhesion between the metal layer and the glass substrate 1 poses a problem, an adhesive metal layer such as Cr may be interposed between them. When Cu (11A in FIGS. 4 to 10) is used as the metal layer,
The NiP layer 11B is formed on the surface of the Cu film 11A by an electroless plating method in order to prevent Cu from being oxidized and to secure adhesion strength with a polyimide resin described later. In this way, the metal layer formed on the entire surface of the glass substrate 1 is patterned as the heat dissipation layer 11 by photolithography.

The entire surface of the heat dissipation layer 11 is covered with the heat storage layer 7
Is covered by. The heat storage layer 7 is formed of a polyimide resin, and the thermal diffusivity of this polyimide resin is 0.1 (mm ² / sec), and the thermal diffusivity of the conventionally used glass glaze is 0.45 (mm ² / sec)
1/4 of that of the glass substrate 1
The heat lost to the side is reduced and the ratio of the thermal energy transmitted to the thermal paper is increased, so that energy can be saved.

On the polyimide heat storage layer 7, there are laminated a plurality of heating resistors 2 arranged in a line in the main scanning direction with an inorganic layer 8 interposed therebetween.

The inorganic layer 8 is formed of a SIALON film formed thinner than the heat storage layer 7. The SIALON film is an insulating material and has a thermal diffusion coefficient about 8 times larger than that of polyimide, and has an effect of quickly diffusing heat in a two-dimensional direction. Therefore, it has a function of flattening the temperature distribution inside the heating resistor, and thereby a thermal head with good printing quality can be obtained.

Further, due to the effect of quickly diffusing heat in the two-dimensional direction as described above, even if the printing pulse is applied without the contact of thermal paper or the like with the thermal head, the printing state can be improved. It is possible to prevent the heat transferred to the thermal paper from being accumulated in the heat-generating resistor 2 and to prevent the temperature of the heat-generating resistor 2 from rising more than necessary, and the heat-generating resistor 2 exceeds the heat resistant temperature of the polyimide resin of the heat-storage layer 7. Can be prevented from being destroyed.

Further, this SIALON film has excellent mechanical strength, and in the thermal head of this embodiment using a soft polyimide resin as the heat storage layer 7, by forming the SIALON film on the polyimide heat storage layer 7, the SIALON film is later formed. The thermal head due to the crack of the heating resistor 2 generated when the mechanical strength of the heating resistor 2 formed above is reinforced and foreign matter such as dust is caught between the thermal paper and the thermal head during printing of the thermal head. It works to prevent defects.

The heating resistor 2 provided on the inorganic layer 8 is
An individual wiring electrode 4 made of a TaSiO ₂ film and electrically connected to the heating resistor driving control element 3 at one end,
At the other end, a common electrode 6 that is electrically connected to another heating resistor 2 is arranged.

The control element 3 is provided on the end of the individual wiring electrode 4.
Control element connection (Face down) for electrically connecting the drive control element 3 and the individual wiring electrode 4 with solder at the time of connection (Face down bonding) of the metal (NiCu-Au). Bonding electrodes 5 are formed.

A protective film 9 is formed on the heating resistor 2, the common electrode 6, the individual wiring electrodes 4 and the polyimide heat storage layer 7 except for the face-down bonding electrode portion 5, and this protective film 9 is formed. Functions as a moisture-resistant, oxidation-resistant, and abrasion-resistant film.

On the back surface of the heat resistant printed wiring board 1,
The heat sink 106 is bonded via the back surface metal layer 10. The heat sink 106 is made of a metal having a high thermal diffusion coefficient (aluminum plate in this embodiment) and diffuses heat of the thermal head substrate.

Next, a method of manufacturing the thermal head will be described with reference to FIGS.

First, as shown in FIG. 2, for example, a Cu layer 11A and a NiP layer 11B are formed on the surface of a glass substrate 1 which is an insulating substrate by a method such as vapor deposition, sputtering, and plating.

Next, as shown in FIG. 3, the heat dissipation layer 11 is formed by patterning the metal layers 11A and 11B on the surface of the glass substrate 1 so as to extend in a predetermined portion, that is, under the heating resistor 2 in the main scanning direction. Therefore, the resist film is formed by photolithography and the etching resist film of the metal film is peeled off sequentially.

Next, the heat storage layer 7 is formed on the entire surface of the glass substrate 1 with a polyimide resin. In this method, a polyimide precursor is applied by a roll coating method or a spin coating method, and heat treatment is performed to imidize and cure the polyimide precursor to form a polyimide heat storage layer 7.
This state is shown in FIG.

Then, on the polyimide heat storage layer 7, as shown in FIG.
As described above, the inorganic layer 8 made of SIALON is formed by spattering.

Next, on the inorganic layer 8, TaSiO ₂ of the heating resistor layer ₂ and the individual wiring electrodes 4, the common electrode 6 and the Al layers 4A, T of the face-down bonding electrode 5 are formed.
The i layer 4B and the CuNi layers 5A and 6A are sequentially laminated by sputtering. This state is shown in FIG.

Then, the common electrode 6 and the CuNi layers 5A and 6A as the electrodes 5 for face-down bonding are formed by HN.
Patterning is performed by photolithography using an O ₃ -based etching solution. This state is shown in FIG. At this time, the Ti layer 4B under the CuNi layers 5A and 6A is made of HNO ₃
Since it is insoluble in the system etching liquid, the CuNi layer 5A,
It is possible to form a pattern of 6A only.

In this step, the common electrode 6 and the face-down bonding electrode 5 are patterned at the same time, so that the step is shortened.

The Au layer 5B is selectively formed by electroless plating on the pattern of the CuNi layer 5A thus formed to secure the solder wettability of the face-down bonding electrode 5. This state is shown in FIG.

Next, in order to separate the individual heating resistors 2, the AlSi layer 4A, the Ti layer 4B of the individual wiring electrodes 4 and the TaSiO ₂ of the heating resistor layer 2 are patterned by photolithography. This state is shown in FIG.

Etching of Ti and TaSiO ₂ is performed by dry etching using a HF-based etching liquid and a mixed gas of CF ₄ and O _2, and H ₃ PO ₄ -based etching liquid is used for etching the AlSi layer. Use.

Then, the AlSi layer 4A and the Ti layer 4B of the individual wiring electrode 4 are patterned in one line in the sub-scanning direction of the thermal head by photolithography to form the heating resistor 2 of the thermal head.

Then, the heating resistor 2, the individual wiring electrode 4,
A protective film 9 for protecting the common electrode 6 from oxidation, corrosion, and abrasion is formed by a sputtering method, a plasma CVD method, or the like,
The first half of the thermal head process is completed. This state is shown in Figure 1.
It shows in 0.

Next, the thermal head substrate is divided into a predetermined size by the dicing method. Then, as shown in FIG.
A heating resistor driving control element (driver IC chip) 3 is die-bonded on the divided substrate 1 by a face-down bonding method to form a face-down bonding electrode 5.
And driver IC3 are connected. Further, after the reflow, the driver IC 3 is molded with the epoxy resin 103.

Next, the double-sided flexible circuit board 10 to which the thermistor, the connector 107, the capacitor and the like are soldered
4 and the thermal head substrate 1 are partially overlapped with each other, sandwiched between the head cover 105 and the heat sink 106, and fixed with screws to connect the thermal substrate and the double-sided flexible circuit substrate 104.

By performing the above steps, the thermal head having the structure shown in FIG. 1 is completed.

In this way, the thermal head insulating substrate 1
Since the heat storage layer 7 made of a polyimide resin is laminated on the heat storage layer, it is possible to store the heat generated during the heat generation and improve the energy transfer efficiency.

Further, since the heat dissipation layer 11 made of copper, which has a heat diffusion coefficient three orders of magnitude higher than that of polyimide, is formed under the heat generating resistor 2, heat dissipation after heat generation can be accelerated and printing speed can be increased. ..

Further, since the glass substrate is used as the insulating substrate, rather than using the resin substrate as shown in FIG.
Since the surface is smooth, uneven printing in one line can be reduced, and a thermal head with excellent printing quality can be provided. As shown in FIG. 12, although the power saving property is slightly inferior to that of the resin substrate, the print density superior to that of the glaze ceramic substrate can be obtained.

The present invention is not limited to the above embodiments, and it goes without saying that many modifications and changes can be made to the above embodiments within the scope of the present invention.

[0046]

As is apparent from the above description, according to claim 1 of the present invention, a heat storage layer is provided below the heat-generating resistor and a heat dissipation layer is provided below the heat storage layer, thereby reducing power consumption.
Printing speed can be increased.

Further, since the glass substrate is used as the insulating substrate, there is an excellent effect that it is possible to provide a thermal head which is inexpensive, can be easily automated, and has good printing quality.

[Brief description of drawings]

FIG. 1 is a diagram showing a structure of a thermal head according to an embodiment of the present invention.

FIG. 2 is a view showing a state in which a metal layer is formed on the surface of a glass substrate in the same manufacturing process.

FIG. 3 is a view showing a state in which the metal layer is similarly patterned to be a heat dissipation layer.

FIG. 4 is a view showing a state in which a heat storage layer is similarly formed.

FIG. 5 is a view showing a state in which an inorganic layer is similarly formed on the heat storage layer.

FIG. 6 is a view showing a state in which a heating resistor layer, individual wiring electrodes, a common electrode, etc. are similarly laminated on the inorganic layer.

FIG. 7 is a view showing a state in which common electrodes and the like are also patterned.

FIG. 8 is a view showing a state in which the heating resistor layer on the bonding electrode side is also patterned.

FIG. 9 is a view showing a state in which the heating resistor layer on the heat dissipation layer side is also patterned.

FIG. 10 is a diagram similarly showing a state before mounting a driver IC.

FIG. 11 is a diagram showing a relationship between a distance from a writing start position and print density in 1-line printing.

FIG. 12 is a diagram similarly showing a relationship between applied power and print density.

FIG. 13 is a diagram showing a structure of a conventional thermal head.

[Explanation of symbols]

 1 Insulating Substrate 2 Heating Resistor 3 Control Element 4 Individual Wiring Electrode 5 Control Element Connecting Electrode 6 Common Electrode 7 Heat Storage Layer 11 Heat Dissipation Layer

Claims (1)

[Claims] 1. A plurality of heating resistors are arranged in the scanning direction on an insulating substrate, and individual wiring electrodes for electrically connecting one end of each heating resistor and a heating resistor drive control element, In a thermal head provided with a common electrode that electrically connects the other ends of the heating resistors in common, the insulating substrate is a glass substrate, and a heat dissipation layer made of a metal film is formed on the insulating substrate. And a heat storage layer made of a polyimide resin that covers the heat dissipation layer.