Etching a substrate: processes – Masking of a substrate using material resistant to an etchant
Reexamination Certificate
2001-04-02
2003-05-06
Chen, Kin-Chan (Department: 1765)
Etching a substrate: processes
Masking of a substrate using material resistant to an etchant
C216S072000, C347S203000
Reexamination Certificate
active
06558563
ABSTRACT:
The present invention relates to methods of fabricating thermal heads which are used in thermal recording apparatus such as various types of printers, plotters, facsimile machines, recorders and the like. Particularly, the present invention relates to a method of fabricating a thermal head which can enhance efficiency of etching processing to be performed on a lower protective layer using a mask in order to improve adhesion thereof to a carbon protective film, prior to forming the carbon protective layer having an excellent wear resistance.
Thermal recording materials comprising a thermal recording layer on a substrate of a film or the like are commonly used to record, for example, images produced in diagnosis by ultrasonic scanning.
This recording method, also referred to as thermal recording, eliminates the need for wet processing and offers several advantages including convenience in handling. Hence, in recent years, use of the thermal recording is not limited to small-scale applications such as images produced in diagnosis by ultrasonic scanning and an extension to those areas of medical diagnoses such as CT, MRI and X-ray photography where large and high-quality images are required is under review.
As is well known, thermal recording involves the use of a thermal head having a glaze, in which heating elements comprising heat generating resistors (hereinafter referred to as heaters) and electrodes, used for heating the thermal recording layer of the thermal recording material to record an image are arranged in one direction (main scanning direction) and, with the glaze urged at a small pressure against the thermal recording layer of the thermal recording material (hereinafter referred to simply as thermal recording layer), the two members are moved relative to each other in an auxiliary scanning direction perpendicular to the main scanning direction, energy is applied to the heaters of the respective pixels in the glaze in accordance with image data to be recorded which were supplied from an image data supply source such as MRI or CT in order to heat the thermal recording layer thereby accomplishing image reproduction.
A protective film is formed on the surface of the glaze of the thermal head in order to protect the heaters for heating the thermal recording material, the associated electrodes and the like. Therefore, it is this protective film that contacts She thermal recording material during thermal recording and the heaters heat the thermal recording material through this protective film so as to perform thermal recording.
The above-described protective film is usually made of wear-resistant ceramics and the like; however, during thermal recording, the surface of the protective film is heated and kept in sliding contact with the thermal recording material, so it will gradually wear and deteriorate upon repeated recording.
If the resultant wear of the protective film progresses, density unevenness will occur on the thermal image or a desired protective strength can not be maintained and, hence, the ability of the film to protect the heaters and the like is impaired to such an extent that the intended image recording is no longer possible (the head has lost its function).
Particularly in the applications such as the aforementioned medical use which require multiple gradation images of high quality, a trend is toward ensuring a desired high image quality by adopting thermal films with highly rigid substrates such as polyester films and also increasing setting values of recording temperature (energy applied) and of pressure at which the thermal head is urged against the thermal recording material.
Under these circumstances, as compared with a conventional thermal recording system, a greater dynamic stress and more heat are exerted on the protective film of the thermal head, permitting wear and corrosion (or wear due to corrosion) more likely to progress. Further, in a thermal film using a polyester film and the like as the substrate thereof, a substance which causes the corrosion of the protective film such as water contained in the thermal recording layer does not penetrate into the substrates and sticks on the surface of the thermal head, namely, the protective layer thereof so that a concentration of a corrosive substance on the surface of the protective layer is likely to be increased thereby causing a further progress of corrosion.
With a view to preventing the wear of the protective film on such a thermal head and improving its durability, a number of techniques to perform improvement of the protective film, improvement of the thermal recording material, improvement of a recording condition or the like have been proposed or practically executed.
Among the above-described improvements, the improvement of the thermal recording material primarily intends to reduce a quantity of a component which will cause wear or corrosion; however, in this case, an adverse effect such as dust deposition on the head, sticking of the head or the like may occurs at the same time whereupon a sufficient wear resistant effect may not be obtained.
On the other hand, the improvement of the recording condition intends to reduce a maximum temperature or recording pressure of thermal recording, but this method sometimes has an effect on an image quality of the recording image, in particular, in an application in which a high-quality image is required, a sufficient effect can not be obtained in some cases.
Therefore, in order to prevent wear of the protective film on the thermal head, a multiplicity of techniques to enhance performance of the protective film has been studied.
As a method to enhance the wear resistance of the protective film as described above, Unexamined Published Japanese Patent Application No. 62-227763 discloses use of a diamond thin film as a protective film.
Further, it has been proposed that a thermal head having an excellent durability can be realized by enhancing the wear resistance of the protective film by means of provision of a plurality of layers of the protective films.
For example, Unexamined Published Japanese Patent Application (Kokai) No. 7-132628 discloses a thermal head which has a dual protective film comprising a lower silicon-based compound layer and an overlying diamond-like carbon layer (DLC layer, hereinafter also referred to simply as “carbon layer”) whereby the potential wear and breakage of the protective film are significantly reduced to ensure that high-quality images can be recorded over an extended period of time.
When a thermal head having such a dual-layer structure is produced, in order to enhance adhesion between the lower silicon-based compound layer (for example, silicon nitride layer, hereinafter referred to as “silicon nitride layer”) and the overlying carbon layer, the overlying carbon layer is formed after a surface of the lower silicon nitride layer is subjected to etching processing by plasma and the like. Namely, smear on the surface of the lower silicon nitride layer is removed by etching processing to have the surface cleaned.
On this occasion, the carbon layer is formed in a limited area such as a portion just above the heater and the like so that, when the surface of the silicon nitride layer is cleaned by the above-described etching processing, the etching processing is performed after other areas than the portion where the above-described carbon layer is formed is shielded with a mask. As an example of the mask, a structure composed of a stainless steel (SUS) material and the like is ordinarily repeatedly used.
After the etching processing is performed, the carbon layer is formed by a method such as sputtering or the like. On this occasion, when the mask composed of the above-described stainless steel material is used, there occurred a problem that the processing was not always stabilized. Namely, in some cases, the carbon layer having good adhesion was able to be formed; in other cases, the formed carbon layer had insufficient adhesion thereby peeling off while in use.
SUMMARY OF THE INVENTION
The present invention has been a
Kashiwaya Makoto
Nakada Junji
Chen Kin-Chan
Fuji Photo Film Co. , Ltd.
LandOfFree
Method of fabricating thermal head does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method of fabricating thermal head, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method of fabricating thermal head will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3076015