JPH0419953B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a multi-print type pressure-sensitive transfer recording medium used for overstrike and multi-strike in impact typewriters and printers. [Prior Art] Conventionally, this type of multi-printing type pressure-sensitive transfer recording medium uses porous powder and mutual bonding, as shown in Japanese Patent Laid-Open No. 58-29694, for example. A structure is known in which a microporous layer composed of a binder agent is provided on the surface of a base material, and a liquid ink paste incompatible with the binder agent is contained in the microporous layer. There is. In this type of conventional technology, the lower the viscosity of the liquid ink paste and the less residual ink paste, the lower the coloring power and the smearing of prints, so it is necessary to keep the viscosity above a certain level (4000 cP or more). It was said that there was. [Problems to be Solved by the Invention] Although such conventional techniques have been able to improve the initial density, they have the drawback that the print density changes greatly due to repeated printing, which tends to cause unevenness in printing.
Furthermore, the number of times that the same location can be printed continuously is only about 10 times at most. [Means for Solving the Problems] In order to solve these problems, the present invention improves the liquid ink paste, in which the colorant is a pigment and an oil-soluble dye dissolved in a liquid fatty acid. The viscosity of the entire ink paste at room temperature is less than 4000 cP,
It adopts a configuration that is adjusted to 300 cp or more. [Function] By using a solution in which an oil-soluble dye is dissolved in liquid fatty acid, the coloring power can be significantly improved without excessive penetration into the recording paper. Furthermore, by using such a specific colorant, printing does not bleed even with a low viscosity ink paste, so by using such a low viscosity ink paste, it is possible to sufficiently penetrate into the porous powder. This has made it possible to hold and hold it, and when it oozes out due to the printing pressure of the impact, it no longer oozes out in large amounts at once. [Effects of the Invention] Because of this effect, the change in print density due to repeated printing becomes much gentler than in the past, and even and clear printing can be performed more times than in the past. [Example] Next, an example of the present invention will be described. First, an overview of the ink preparation method will be explained. An oil-soluble dye and a liquid fatty acid are mixed, this mixture is heated to dissolve the dye in the fatty acid, and this dye solution is mixed with liquid ink paste components such as pigments, wetting agents, and viscosity modifiers. Porous layer components such as porous powder and binder are kneaded and mixed with a volatile solvent and the like. Then, the dispersion obtained in this manner is applied to a base material using a coater and dried to coat the porous layer composed of the porous powder and binder with the dye solubility, pigment, and wetting agent. A layer containing a liquid ink paste consisting of a viscosity modifier and having a coating weight of about 15 to 30 g/m ² after drying is formed on one side of the substrate. The component compositions of each example thus obtained are shown in Tables 1 and 3. Table 3 shows examples of changes in the components of the porous layer, and the printing performance of each porous layer component prepared using the ink paste of each example shown in Table 1. were investigated, but each ink paste showed similar performance, and there was almost no influence by the structure of the porous layer. Using each of the examples shown in Table 1 and the comparative example having the same composition as the conventional example shown in Table 2, an AP 500 electronic typewriter manufactured by Canon Inc. was used, The ribbons of the above examples and comparative examples were fixed to the ribbon cassette of this typewriter, and the same ribbon was printed on this recording paper with the same printing image while changing its position relative to the recording paper (high-quality paper). The PCS value (VIS) of the obtained impression was measured using a Guitar 082 OCR tester. The results are shown in the graph of FIG. As is clear from this graph, in the example of the present invention, the attenuation of print density is extremely gradual compared to the conventional case, and the number of times that printing with a PCS value of 0.6 or more can be performed is about twice that of the conventional case. The liquid fatty acid may be oleic acid, isostearic acid, or a liquid fatty acid similar to these.
A mixture of two or more types can be used, and it is preferable to mix the ink paste in an amount of 1 to 30% by weight based on the total amount of the ink paste. As the oil-soluble dye, nigrosine base, spirit black, special black, Victoria blue base, methyl violet base, etc. can be used alone or in mixtures, and they can be blended in an amount of 1 to 10% by weight based on the total amount of the ink paste. is preferred. As the pigment, Printex 25
(trade name of carbon black for color manufactured by Degussa), Mogul L (trade name of carbon black for color manufactured by Kayabot), Raven 1255 (trade name of carbon black for color manufactured by Columbia & Carbon), Black Toner, etc. A species or multiple species can be used appropriately, making up 20 to 40 of the total amount of ink paste.
It is preferable to mix it within a range of % by weight. As the wetting agent, one or more of sorbitan fatty acid esters such as sorbitan monoisostearate and sorbitan monooleate, lecithin, or similar substances can be appropriately used.
It is preferable to mix the ink paste in an amount of 3 to 30% by weight (especially 5 to 25% by weight) based on the total amount of the ink paste. The viscosity modifiers include vegetable oils such as rapeseed oil, soybean oil and castor oil, mineral oils such as vitoria oil and diet oil, di(2-ethylhexyl) adipate (hereinafter referred to as DOA), di(2-ethylhexyl) sebacate ( (hereinafter referred to as DOS), di(2-ethylhexyl) azelate (hereinafter referred to as DOZ)
One or more types of cold-resistant plasticizers such as (denoted as (3600 cP or less), an appropriate amount may be used to achieve a value of 300 cP or more, but it is particularly preferable to blend the ink paste in an amount of 20 to 50% by weight of the total amount of the ink paste. The binder may be a porous powder that is incompatible with the liquid ink paste component, such as vinyl chloride-vinyl acetate copolymer, polyester resin, or cellulose acetate butyrate resin, and is compatible with the following volatile solvent, and the following: One or more resins having adhesive properties to the body can be used as appropriate, and it is appropriate to use 1 to 5 parts by weight (in particular 2 to 3 parts by weight) to 10 parts by weight of the liquid ink paste. be. Examples of the porous powder include inorganic porous powders such as diatomaceous earth, zeolite, porous silica, and activated carbon, foamed urethane powder, etc., with a porosity of 50 to 97% (60 to 93%) and a particle size of 1 to 20μ. One or more organic porous powders can be used as appropriate, and the amount is suitably 1 to 4 parts by weight (especially 2 to 3 parts by weight) per 10 parts by weight of the liquid ink paste. The volatile solvent may be one or more of methyl ethyl ketone (hereinafter referred to as MEK), acetone, methyl isobutyl ketone, toluene, IP solvent (trade name of isoparaffinic hydrocarbon oil manufactured by Idemitsu Petrochemical Co., Ltd.), etc. can be used appropriately. As the base material, a film made of polyester, polypropylene, polyamide, etc. and having a thickness of about 3 to 50 microns can be used satisfactorily.

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【table】 [Brief explanation of drawings]

FIG. 1 is a graph showing changes in PCS values of print images on recording paper between the examples shown in Table 1 and the comparative examples shown in Table 2, with the vertical axis representing the PCS value and the horizontal axis representing the same value. Indicates the number of times a part is printed.

Claims (1)

[Claims] 1. A microporous layer composed of porous powder and a binder agent that binds the porous powder to each other is provided on the surface of the base material, and a liquid ink paste that is incompatible with the binder agent is applied to the microporous layer. In the multi-printing type pressure-sensitive transfer recording medium, the colorant of the liquid ink paste is composed of a pigment and a solution of an oil-soluble dye dissolved in a liquid fatty acid, and the colorant of the liquid ink paste is composed of a pigment and a solution of an oil-soluble dye dissolved in a liquid fatty acid, and A multi-print pressure-sensitive transfer recording medium whose viscosity at room temperature is adjusted to less than 4000 cP and more than 300 cP.