Record receiver having plural interactive leaves or a colorless – Having plural interactive leaves
Reexamination Certificate
2001-03-09
2002-12-24
Hess, Bruce H. (Department: 1774)
Record receiver having plural interactive leaves or a colorless
Having plural interactive leaves
C428S195100
Reexamination Certificate
active
06498123
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a thermal transfer sheet used in a thermal transfer printer using heating means such as a thermal head, and, more particularly, to a thermal transfer sheet in which a transfer ink layer capable of being melted and sublimated under heat is disposed on one surface of a substrate film and a backface layer is structured of a specific material on the other surface of the substrate film which surface is brought into contact with a thermal head to prevent refuses from adhering to the thermal head so that it has high printing stability and running stability.
2. Description of the Related Art
When a plastic film which is not heat-resistant is used as a substrate of a thermal transfer sheet, this poses the problem that a film sticks to a thermal head and refuses adhere to the thermal head during printing whereby the peeling ability and the slip characteristics are impaired and the substrate film is broken. For this, a method is proposed in which a heat-resistant layer made of a heat-curable resin having high heat resistance is formed. This method improves the heat-resistance but does not serve to improve the slip characteristics. Also, because it is necessary to use a hardener such as a cross-linking agent in this method, the coating solution is a two-solution type resultantly. Further, since the substrate is the plastic thin film which cannot be treated at high temperatures, it is necessary to carry out heat treatment (aging) at relatively low temperatures for a long time over several tense hours after the film is applied to obtain a film which is sufficiently cured. This gives rise to the problem that not only the aging is complicated from the processing point of view but also wrinkles appear during heat treatment and the coating surface is stuck to the backface causing blocking if strict temperature control is not made.
It is proposed to add a lubricant having a relatively low melting point such as silicone oil, low-melting point wax and a surfactant. However, because these lubricants have a low melting point, there are the problems that these lubricants are carried to the backface when the thermal transfer sheet is rolled and the thermal head is contaminated with these lubricants during printing. There are methods of adding a filler to remove these adsorbed materials. However, when an unsuitable material is used, this poses the problem that the coefficient of fiction with the thermal head increases causing wrinkles during printing and the thermal head is worn by the material.
In order to solve these problems, a backface layer made of a silicone polyurethane is proposed in the publication of Japanese Patent Application Laid-Open (JP-A) No. 61-184717 and JP-A No. 62-220385, a heat-resistant protective layer made of a polysiloxane/polyamide type block copolymer is proposed in the publication JP-A No. 5-229271 and a heat resistant protective layer comprising a silicone modified polyimide resin is proposed in the publication of JP-A No. 5-229272. However, each of these resins has low heat resistance and therefore has the drawback that sticking is caused in high energy printing and productivity and environmental adaptability are impaired because a specific solvent is used. Also, a polyamideimide resin composition is proposed in the publication of JP-A No. 8-113647 and the publication of JP-A No. 8-244369 and a heat resistant protective layer made of a polyamideimide resin containing a lubricant is proposed in the publication of JP-A No. 10-297124. All of these materials have insufficient heat resistance, giving rise to the problem that refuses adhere to the head, bringing some influence on the printed image.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to solve the aforementioned problems of the conventional technologies and to provide a thermal transfer sheet provided with a backface layer having high heat resistance and slip characteristics, the backface layer being formed using a one-solution type coating solution using an environmentally acceptable general solvent without requiring any heat treatment such as aging.
The present invention resides in a thermal transfer sheet provided with a transfer ink layer which is melted or sublimated by heating on one surface of a substrate and a backface layer on the other surface of the substrate film which surface is brought into contact with a thermal head, wherein the backface layer comprises a binder which comprises a polyamideimide resin and a polyamideimide silicone resin each having a grass transition temperatures of 200° C. or more based on differential thermal analysis at a specified mixing ratio, a polevalent metal salt of alkyl phosphate and filler at a specified mixing ratio. If Tg of the aforementioned polyamideimide resin and polyamideimide silicone resin on the basis of differential thermal analysis is less than 200° C., the thermal transfer sheet has inferior heat resistance.
Also, in the present invention, the aforementioned polyamideimide resin and polyamideimide silicone resin are used by mixing the both in a mixing ratio ranging from preferably 1:5 to 5:1 and particularly preferably 1:2 to 2:1. If the ratio of the polyamideimide silicone resin is larger than 1:5, only unsatisfactory heat resistance is obtained, leading to easy production of head refuses. On the other hand, if the ratio of the polyamideimide silicone resin is 5:1 or less, only insufficient lubricity is obtained, causing sticking.
The polyamideimide silicone resin is a copolymer of a polyamideimide resin and a polyfunctional silicone compound having a molecular weight of 1000 to 6000 with a copolymerizing ratio of 0.01 to 0.3 per 1 of the polyamideimide resin by weight. The polyamideimide silicone resin is a modified product of a polyamideimide resin with a polyfunctional silicone compound having a molecular weight of 1000 to 6000 with a modification ratio of 0.01 to 0.3 per 1 of the polyamideimide resin by weight. When the amount of the copolymer or modified product is too small, sufficient lubricity is not obtained in the aforementioned mixing ratio, leading to easy occurrence of sticking. On the other hand when the amount of the copolymer or modified product is too large, the heat resistance and the film strength are decreased.
The polyvalent metal salt of alkyl phosphate is preferably a compound represented by the structural formula 1, wherein R represents an alkyl group having 12 or more carbon atoms, M represents an alkali earth metal, zinc or aluminum and n denotes the valence of M.
[Compound 1]
A polyvalent metal salt of alkylcarboxylic acid is preferably mixed in a specified amount with the polyvalent metal salt of alkyl phosphate.
The mixing ratio of the polyvalent metal salt of alkylcarboxylic acid to the polyvalent metal salt of alkyl phosphate is preferably 1:9 to 9:1.
The polyvalent metal salt of alkylcarboxylic acid is preferably a compound represented by the structural formula 2, wherein R represents an alkyl group having 11 or more carbon atoms, M represents an alkali earth metal, zinc, aluminum or lithium and n denotes the valence of M.
[Compound 2]
The proportion of the polyvalent metal salt of alkyl phosphate is preferably 1 to 100 parts by weight and particularly preferably 5 to 20 parts by weight per 100 parts by weight of the binder. If the amount of the polyvalent metal salt of alkyl phosphate to be used is less than the above range, only insufficient releasability can be obtained during thermal printing, so that refuses tend to adhere to a thermal head. On the other hand, if the amount of the polyvalent metal salt of alkyl phosphate exceeds the above range, the physical strength of the backface layer is reduced and therefore such an amount is undesirable.
Also, the filler is preferably a talc.
Further, the talc is preferably mixed in a proportion of 2 to 20 parts by weight per 100 parts by weight of the binder. A proportion in the above range brings about good balance between the lubricity and heat
Fukui Daisuke
Ieshige Munenori
Suzuki Taro
Dai Nippon Printing Co. Ltd.
Hess Bruce H.
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