JP3545947B2 - Manufacturing method of glazed ceramic substrate for thermal head - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for manufacturing a glazed ceramic substrate used as a supporting base material for supporting a circuit pattern of a thermal head.
[0002]
[Prior art]
Conventionally, a glazed ceramic substrate has been widely used as a supporting base material for supporting a circuit pattern of a thermal head.
[0003]
Such a conventional glazed ceramic substrate has a structure in which a colorless and transparent glass layer is adhered and formed to a thickness of 30 to 100 μm so as to form a mountain-shaped cross section on the upper surface of a ceramic substrate made of, for example, alumina ceramic having a purity of about 99%. Have.
[0004]
When a circuit pattern of a thermal head is formed on such a glazed ceramic substrate, a conventionally known thin film method, specifically, a sputtering method, a photolithography technology, an etching technology, or the like is employed on the upper surface of the ceramic substrate and the glass layer. Then, the heating resistor, the electrode wiring, and the like are finely processed into a predetermined pattern.
[0005]
The glass layer not only functions as a heat storage layer for storing and dissipating heat generated by the heating resistor inside to maintain good thermal response characteristics of the thermal head, but also protruding the heating resistor upward. In addition, it also has a role of improving the contact of thermal paper and the like during printing.
[0006]
Recently, a so-called double partial type glazed ceramic substrate has been proposed in which a convex portion is further provided near the top of the glass layer in order to further improve the paper contact of the thermal head.
[0007]
Such a glazed ceramic substrate is manufactured, for example, by the following steps (1) to (4).
Process ▲ 1 ▼
First, a predetermined glass paste obtained by adding and mixing an appropriate organic solvent, an organic binder, and the like to the powder of the high softening point glass is printed and applied to a predetermined region of the upper surface of the ceramic substrate by a conventionally known screen printing method or the like. This is baked at a temperature of about 1200 ° C. to form a glass layer having a mountain-like cross section.
[0008]
Next, the outer shape of the glass layer is processed into a predetermined shape by a photolithography and etching process.
[0009]
Process ▲ 2 ▼
The photolithography process includes an exposure process and a subsequent development process. In the first exposure process, a positive photoresist 13 formed in a liquid state is applied to the glass layer 12 as shown in FIG. After drying, a photomask 14 having a predetermined pattern 15 is disposed at a predetermined distance on the glass layer 12 having the photoresist 13, and ultraviolet light having a predetermined wavelength is irradiated through the photomask 14. Then, the photoresist 13 in the region irradiated with the ultraviolet rays is photolyzed.
[0010]
In the next developing step, the ceramic substrate 11 is immersed in a predetermined developing solution while the photoresist 13 is adhered, and the photo-decomposed photoresist 13 is dissolved in the developing solution, so that the ultraviolet light is not irradiated. Only the photoresist 13 in the region that has been left is left on the glass layer 12.
[0011]
Process ▲ 3 ▼
Then, in the next etching step, the ceramic substrate 11 on which the glass layer 12 and the photoresist 13 are formed is immersed in an etching solution for a predetermined time, and the surface of the glass layer in the region where the photoresist 13 is not present has a depth of, for example, 2 to 10 μm. Erod up to.
[0012]
Process ▲ 4 ▼
Finally, the ceramic substrate 11 is immersed in a predetermined stripping solution to peel off the photoresist 13 from the surface of the glass layer, whereby a glazed ceramic substrate having a predetermined convex portion on the top of the glass layer 12 is completed.
[0013]
[Problems to be solved by the invention]
However, according to the conventional method of manufacturing a glazed ceramic substrate, when the glass layer 12 is externally processed in a photolithography process, a part of the ultraviolet light applied to the photoresist 13 passes through the photoresist 13 and is transparent and colorless. It enters the glass layer 12 and causes irregular reflection inside the glass layer 12 and on the upper surface of the ceramic substrate 11. A part of the ultraviolet light that has caused the irregular reflection as described above is irradiated to the photoresist 13 from the lower surface side (glass layer side) of the photoresist 13, so that it is impossible to pattern the photoresist 13 into a desired shape. In addition, there is a disadvantage that the width and height dimensions of the projections formed through the subsequent etching process vary.
[0014]
[Means for Solving the Problems]
The present invention has been devised in view of the above drawbacks, and a method of manufacturing a glazed substrate for a thermal head according to the present invention comprises applying a glass layer to at least a part of the surface of a ceramic substrate and forming a light-shielding layer on the glass layer. A step of applying, a step of applying a photoresist on the light-shielding layer, a step of processing the photoresist into a predetermined pattern by exposure and development, and a part of the light-shielding layer and the glass layer in a region where the photoresist does not exist. Etching and then removing the photoresist.
It becomes possible.
[0015]
Further, in the method for manufacturing a glazed ceramic substrate for a thermal head according to the present invention, the light shielding layer has an ultraviolet transmittance of 10% or less.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a cross-sectional view of a thermal head manufactured using a glazed ceramic substrate obtained by the manufacturing method of the present invention.
[0017]
The glazed ceramic substrate obtained by the manufacturing method of the present invention is formed by sequentially applying a glass layer 2 and a light-shielding layer 3 on the upper surface of a ceramic substrate 1, and a heat-resistant layer 4 on the glass layer 2 and the light-shielding layer 3. A thermal head is manufactured by applying and forming a predetermined thermal head circuit pattern composed of a heating resistor 5, an electrode wiring 6, and the like.
[0018]
The ceramic substrate 1 of the glazed ceramic substrate is made of, for example, alumina ceramics having a purity of 99% or more. When the ceramic substrate 1 is made of alumina ceramics, alumina (Al ₂ O ₃ ), silica (SiO ₂ ), magnesia (MgO), or the like is used. A ceramic green sheet is obtained by adding and mixing an appropriate organic solvent and a solvent to the ceramic raw material powder to form a slurry, and employing a conventionally known doctor blade method or the like to obtain a ceramic green sheet. Is punched into a predetermined shape and fired at a high temperature (about 1600 ° C.).
[0019]
The glass layer 2 on the ceramic substrate 1 is made of colorless and transparent glass, and the glass layer 2 is partially applied to a predetermined region of the upper surface of the ceramic substrate so as to form a mountain-shaped cross section.
[0020]
The glass layer 2 is composed of a base layer portion 2a having a gentle mountain shape and a convex portion 2b provided near the top of the base layer portion 2a. The base layer portion 2a has a width of 400 to 2000 μm, for example. The projection 2b is formed, for example, with a width of 50 to 350 μm and a height of 2 to 30 μm.
[0021]
The glass layer 2 accumulates and dissipates the heat generated by the heat generating resistor 3 of the thermal head internally when a thermal head is manufactured by attaching the heat generating resistor 5 and the electrode wiring 6 thereon. Of the thermal head as a heat storage layer for maintaining good thermal response characteristics, and the heat generating resistor 3 is attached to the convex portion 2b so as to protrude upward, so that the thermal head contacts the thermal paper or the like (printing pressure). Has the effect of effectively increasing the The method for forming the glass layer 2 will be described later.
[0022]
A light-shielding layer 3 having an ultraviolet transmittance of 10% or less is formed on the upper surface of the convex portion of the glass layer 2.
[0023]
The light-shielding layer 3 is formed by depositing titanium (Ti), tantalum (Ta), chromium (Cr), or the like to a predetermined thickness, and the light-shielding layer 3 is formed by forming a glass layer 2 by using a well-known photolithography and etching technique. When the convex portion 2b is formed near the top portion by processing, the entire surface of the glass layer is covered in the exposure step, thereby effectively preventing ultraviolet rays from entering the glass layer 2. Note that a part of the light shielding layer 3 used for shielding the ultraviolet light in the photolithography step is removed from the ceramic substrate 1 together with a part of the glass layer 2 in a subsequent etching step. Therefore, the glazed ceramic substrate as a product has a shape in which the light shielding layer 3 remains only on the upper surface of the projection.
[0024]
The ultraviolet transmittance of the light-shielding layer 3 can be measured by using a predetermined illuminometer.
[0025]
On the upper surface of the glazed ceramic substrate 1, that is, on the glass layer 2 and the light shielding layer 3, as described above, the circuit pattern of the thermal head including the heating resistor 5 and the electrode wiring 6 via the heat resistant layer 4. Is deposited and formed thereon, and a protective film 7 is further deposited thereon.
[0026]
The heat-resistant layer 4 is made of a silicon nitride (Si ₃ N ₄ ) or sialon (Si—Al—O—N) or the like formed by a well-known sputtering method or the like. The heat-resistant layer 4 is formed by finely processing a heat-generating resistor 5 and an electrode wiring 6 to be described later into a predetermined pattern by a conventionally known photolithography and etching technique. In this case, the glass layer 2 is effectively prevented from being eroded by over-etching or the like, and at the time of use of the thermal head, the heat generated by the heating resistor 5 is effectively prevented from being oxidized and corroded by the heating resistor itself. To act. When the light-shielding layer 3 is formed of a conductive material such as a metal, the heat-resistant layer 4 also functions as an insulating layer for preventing an electrical short circuit between the light-shielding layer 3 and the heating resistor 5.
[0027]
The heating resistor 5 is made of a TaSiO-based resistance material, a TiSiO-based resistance material, a TaN-based resistance material, or the like, and is provided so as to be located on the convex portion 2b of the glass layer 2. Since the heating resistor 5 itself has a predetermined electric resistivity, when power supply power is applied via an electrode wiring 6 described later, Joule heat is generated and a print is formed on a thermal paper or the like. (200-300 ° C.) required for the above.
[0028]
The electrode wiring 6 is made of a conductive material such as aluminum (Al) or copper (Cu), and is electrically connected to both ends of the heating resistor 5 to apply a predetermined power to the heating resistor 5. Make
[0029]
The heating resistor 5 and the electrode wiring 6 are formed by applying a conventionally known thin film technique, specifically, a sputtering method, a photolithography technique, an etching technique, or the like, to deposit a TaSiO-based resistance material, aluminum, or the like in a predetermined pattern. Formed by
[0030]
The protective film 7 deposited on the heating resistor 5 and the electrode wiring 6 is made of an electrically insulating material having excellent abrasion resistance and sealing properties, such as silicon nitride (Si ₃ N ₄ ). Is formed by applying a thickness of 3.0 to 12.0 μm by a conventionally known sputtering method or the like.
[0031]
When the thermal head is used, the protective film 7 has a function of protecting the heating resistor 5 and the electrode wiring 6 from abrasion due to sliding contact of thermal paper or the like due to contact with moisture or the like contained in the atmosphere. .
[0032]
Next, a method of forming the glass layer 2 will be described in detail with reference to FIGS.
[0033]
Process ▲ 1 ▼
First, a predetermined ceramic substrate 1 is prepared, and then, as shown in FIG. 2 (a), a glass layer 2 'is applied to at least a part of the surface of the ceramic substrate 1 and, for example, an ultraviolet transmittance is formed on the glass layer 2'. 10% or less of the light shielding layer 3 is applied.
[0034]
The glass layer 2 ′ contains 50 wt% of silicon oxide (SiO ₂ ), 6 wt% of aluminum oxide (Al ₂ O ₃ ), 12 wt% of calcium oxide (CaO), and 25 wt% of barium oxide (BaO). A glass paste obtained by adding and mixing an appropriate organic solvent, an organic binder, and the like to a softening point glass powder (average particle size: 1 to 4 μm) is formed into a band on a predetermined region of the upper surface of a ceramic substrate by a conventionally known screen printing method or the like. It is formed so as to form a gentle mountain shape by printing and coating on the surface and baking it at a temperature of 1100 to 1200 ° C.
[0035]
The light shielding layer 3 is formed so as to cover the entire glass layer by applying titanium (Ti), tantalum (Ta), chromium (Cr) or the like to a predetermined thickness by a conventionally known sputtering method or the like. For example, when the light-shielding layer 3 is made of tantalum, the thickness of the light-shielding layer 3 is set to 50 ° or more, and when it is made of chromium, the thickness of the light-shielding layer 3 is set to 100 ° or more. it can.
[0036]
Process ▲ 2 ▼
Next, a photoresist 8 is applied on the light shielding layer 3, and the photoresist 8 is processed into a predetermined pattern.
[0037]
As the photoresist 8, for example, a positive type photoresist is used. The photoresist 8 is formed into a liquid state and adjusted to a predetermined viscosity, and is applied onto the light-shielding layer 3 by a conventionally known roll coating method or the like. The photoresist 8 is dried by heating the applied photoresist 8 at a temperature of 80 to 100 ° C. for a predetermined time.
[0038]
Subsequent patterning is performed by a conventionally known photolithography technique.
This photolithography includes an exposure step and a subsequent development step. In the first exposure step, as shown in FIG. 2B, a predetermined distance is formed on the glass layer 2 ′ having the photoresist 8 at a certain distance. Then, a photomask 9 having a predetermined pattern 10 is disposed, and in this state, ultraviolet rays of a predetermined wavelength (wavelengths: 365 nm, 405 nm, and 436 nm) are irradiated through the photomask 9 using a high-pressure mercury lamp. Photo-resist of the photoresist 8 in the set area.
[0039]
At this time, since the light-shielding layer 3 is interposed between the photoresist 8 and the glass layer 2 ', even if a part of the ultraviolet light passes through the photoresist 8 and tries to enter the colorless and transparent glass layer 2'. The ultraviolet rays are satisfactorily shielded by the light-shielding layer 3, and unnecessary ultraviolet rays are irradiated to the photoresist 8 from the lower surface side (glass layer side) of the photoresist 8 due to irregular reflection in the glass layer 2 ′. It can be effectively prevented. Therefore, the photoresist 8 can be exposed according to the pattern corresponding to the photomask 9, and the photoresist 8 can be photolyzed only in a desired region.
[0040]
If the light transmittance of the light-shielding layer 3 is more than 10%, the light-shielding effect of the ultraviolet light becomes insufficient, and when the photoresist 8 is irradiated with the ultraviolet light in the above-mentioned exposure step, There is a possibility that a desired pattern cannot be obtained because the amount of ultraviolet light transmitted through the light shielding layer 3 is increased. Therefore, the ultraviolet transmittance of the light shielding layer 3 is preferably set to 10% or less.
[0041]
Then, in the next development step, the ceramic substrate 1 is immersed in a predetermined developing solution while the photoresist 8 is adhered thereto, and the photodegraded photoresist 8 is dissolved in the developing solution to be decomposed. The photoresist 8 thus removed is removed from the ceramic substrate 1, thereby leaving only the photoresist 8 in a region not irradiated with the ultraviolet rays on the glass layer 2 ′, as shown in FIG. 2C. Here, since only the desired area of the photoresist 8 is photolyzed as described above, the photoresist 8 on the glass layer 2 'is patterned with extremely high precision.
[0042]
Process ▲ 3 ▼
Next, as shown in FIG. 2D, a part of the light-shielding layer 3 and the glass layer 2 ′ in a region where the photoresist layer 8 is not present is removed by etching, and the projection is formed on the glass layer 2 immediately below the photoresist layer 8. The part 2b is formed.
[0043]
This etching is performed by immersing the ceramic substrate 1 in a hydrofluoric / nitric acid solution having a predetermined concentration to continuously etch the light-shielding layer 3 and a part of the glass layer 2 ′ in a region where the photoresist layer 8 does not exist. As a result, the glass layer 2 'is eroded from the surface thereof to a depth region of, for example, 2 to 30 [mu] m to form the glass layer 2 composed of the base layer 2a and the projections 2b on the base layer 2a.
[0044]
At this time, since the photoresist 8 is patterned with high precision as described above, there is almost no variation in the width, height, and the like of the convex portion 2b, whereby the glass layer 2 is precisely formed to a predetermined size. The manufacturing yield of the glazed ceramic substrate formed and the thermal head using the substrate as a supporting base material can be remarkably improved.
[0045]
Process ▲ 4 ▼
Finally, the photoresist 8 is removed from the upper surface of the light shielding layer 3, and the entire glass layer is heat-treated.
[0046]
The removal of the photoresist 8 is performed using a predetermined stripper (remover). Specifically, the ceramic substrate 1 obtained in the step (3) is immersed in a stripping solution as it is, and the photoresist 8 is stripped from the surface of the light-shielding layer on the projection 2b.
[0047]
The heat treatment of the glass layer 2 is performed by reheating in a furnace maintained at a temperature of 800 to 850 ° C., whereby the angular portion of the surface of the glass layer becomes smooth, and a thermal head as a product is produced. The finished glazed ceramic substrate is completed.
[0048]
Note that the present invention is not limited to the above-described embodiment, and various changes, improvements, and the like can be made without departing from the gist of the present invention.
[0049]
For example, in the above-described embodiment, the glass layer 2 is formed partially on the upper surface of the ceramic substrate 1, but the glass layer may be formed over the entire upper surface of the ceramic substrate instead. In this case, the base layer portion of the glass layer has a substantially constant thickness, and only the convex portions protrude.
[0050]
In the above-described embodiment, only one convex portion 2b is provided near the top of the glass layer 2. However, instead of this, a plurality of convex portions 2b are provided corresponding to the heating resistor, or at the top of the convex portion 2a. Still another projection may be provided.
[0051]
【The invention's effect】
According to the method of manufacturing a glazed ceramic substrate for a thermal head of the present invention, when processing a photoresist into a predetermined pattern in performing an outer shape processing of a glass layer, a part of ultraviolet rays pass through the photoresist in an exposure step and the glass layer is formed. Even if it tries to enter, the ultraviolet rays are well shielded by the light-shielding layer deposited on the glass layer, and unnecessary ultraviolet rays are irradiated to the photoresist from the lower surface side (glass layer side) of the photoresist. Is effectively prevented. Therefore, the photoresist can be exposed and developed according to a predetermined pattern, thereby making it possible to precisely process the outer shape of the glass layer.
[Brief description of the drawings]
FIG. 1 is a sectional view of a thermal head manufactured using a glazed ceramic substrate obtained by a manufacturing method of the present invention.
FIGS. 2A to 2D are cross-sectional views for explaining respective steps of the manufacturing method of the present invention.
FIG. 3 is a cross-sectional view in an exposure step for explaining a conventional method for manufacturing a glazed ceramic substrate.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Ceramic substrate, 2, 2 '... Glass layer, 2b ... Convex part, 3 ... Light shielding layer, 8 ... Photoresist

Claims (2)

A step of applying a glass layer on at least a part of the surface of the ceramic substrate and applying a light-shielding layer on the glass layer,
Applying a photoresist on the light-shielding layer, processing the photoresist into a predetermined pattern by exposure and development,
Etching a portion of the light-shielding layer and the glass layer in a region where the photoresist is not present, and then removing the photoresist, the method comprising the steps of: 2. The method according to claim 1, wherein the light shielding layer has an ultraviolet transmittance of 10% or less.

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