JP2540054B2 - Ink for stencil printing - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a stencil printing ink, and more particularly to a heat-sensitive stencil printing ink.

[Prior art]

As is well known, the stencil printing method uses a stencil printing base paper, and by moving the ink from one side of the base paper to the other side through a perforation portion of the base paper, printing is performed on the surface of a substrate such as paper. It is something to do.

The perforated portion of the stencil printing base paper used for this stencil printing is, for example, a method of applying an impact force like a typewriter base paper, a method of applying a frictional force with a writing brush such as a wax base paper, or electrical energy such as electric discharge destruction. It is formed by the method used.

Since the perforated portion formed by such a perforation method has a relatively small opening area, in order to achieve the required movement of ink through the perforated portion, the ink is relatively soft as a copy ink. It was necessary to use a fluid ink.

By the way, in recent years, stencil printing base papers using heat-sensitive energy of a flash or a thermal head have been actively produced.

In such an apparatus, for example, an ink kneading roller is arranged in a drum unit, ink for stencil printing is stored between the rollers, and an electrode for ink detection is provided in contact with the ink. Then, the method of detecting the presence of the ink is adopted by the capacitance of the ink existing between the electrode and the ink roller. For this reason, the amount of ink supplied to the ink storage portion depends on the magnitude of the electrostatic capacity of the stored ink, and it has been strongly desired to adjust this value within a certain range.

〔Purpose〕

An object of the present invention is to provide a stencil printing ink having excellent ink detection property.

〔Constitution〕

According to the present invention, a stencil printing ink comprising at least a colorant, an emulsifier and water dispersed in mineral oil or vegetable oil, which is measured under the conditions of an electrode distance of 16 mm, an electrode length of 5 mm and a frequency of 100 KHz. There is provided a stencil printing ink having a capacitance of 5 to 25 pF.

Generally, in the method of detecting the ink amount by using the electrostatic capacity of the ink, if the electrostatic capacity of the ink is too large, the amount of the ink remaining in the ink reservoir is small, but "the ink remains sufficiently. The detection circuit will give a signal "I am doing". Even if the detection circuit functions and the ink supply device starts to supply ink to the ink reservoir, it is said that "the ink has been replenished to the ink reservoir" before the ink supply amount reaches a certain amount. A signal is emitted. For this reason, the ink storage portion is always in a state of lack of ink. For example, when a printed material having a large image area is produced, the image portion is out of ink, and the image portion suffers from blurring or blank areas.

On the contrary, if the electrostatic capacity is small, the detection circuit gives a signal "ink is exhausted" even though the ink is fully retained in the ink reservoir, and the detection circuit functions. However, even if the ink supply device starts to supply the ink to the reservoir and the ink reservoir is replenished with a sufficient amount of ink, a signal "the ink has not been replenished yet" is given. For this reason, the ink is always excessively supplied, and the ink flows out from the ink storage portion, and the inside of the printing machine is contaminated, and the ink contamination of the obtained printed material is remarkably generated.

The present inventors have created various stencil printing inks in order to eliminate these drawbacks, as a result of diligent study of the relationship between the capacitance and ink detectability, as a result, at least a colorant in mineral oil or vegetable oil. And water dispersed, distance between electrodes 16mm,
The inventors have found that an ink having an electrostatic capacity of 5 to 25 pF measured under the condition of an electrode length of 5 mm and a frequency of 100 KHz can accurately grasp the ink amount by an ink amount detection circuit, and completed the present invention.

 Hereinafter, the present invention will be described in more detail.

The stencil printing ink of the present invention has a capacitance of 5 to 5 measured under the conditions of an electrode distance of 16 mm, an electrode length of 5 mm, and a frequency of 10 KHz.
It should be 25 pF, preferably 10-15 pF.

If the electrostatic capacity is less than 5 pF, the ink spills out of the ink reservoir and contaminates the inside of the drum, and if it exceeds 25 pF, the ink supply becomes insufficient and the image density becomes uneven, thereby achieving the intended purpose of the present invention. I can't.

Further, as a capacitance measuring device, a commercially available device such as a model 4332 manufactured by Tanagawa Hewlett-Packard Co.
A etc. are used.

Examples of the mineral oil used in the present invention include liquid paraffin, spindle oil, light oil, kerosene, machine oil, lubricating oil, and the like, and vegetable oils include olive oil, rapeseed oil, castor oil, soybean oil, and the like. Particularly, it is preferable to use a so-called low-viscosity oil having a viscosity at room temperature (20 ° C.) of 300 mPa or less, preferably 1 to 100 mPa.

As the coloring pigment, any conventionally known one can be arbitrarily used, and for example, inorganic pigments such as carbon black, red iron oxide, ocher, ultramarine blue and navy blue, and organic pigments such as Hansa yellow, cyanine blue, phthalocyanine blue and lake red are used. .

The emulsifier has an HLB value of 1 to 8.0, preferably 2
Anion type, cation type,
Any of the nonion type can be used. Examples of such a surfactant are shown below.

In the present invention, in addition to the above essential components, auxiliary components usually used in this type of stencil printing ink can be used. Examples of such auxiliary components include rosin, rosin-modified alkyd resin, and rosin-modified. Phenolic resin,
Examples thereof include resins such as rosin-modified maleic acid resin.
Further, in the present invention, a thickener such as organic bentonite may be used in combination within a range that does not impair the purpose.

The stencil printing ink of the present invention is characterized by having a capacitance of 5 to 25 pF as described above. An ink having such a characteristic value is, for example, 10 to 40 parts by weight of mineral oil or vegetable oil. Parts, colorant 2-10 parts by weight, emulsifier 2-10
It is prepared by adding 2 parts by weight, and optionally 2 to 10 parts by weight of other auxiliary ingredients.

〔effect〕

Since the stencil printing ink of the present invention has the above-mentioned constitution and its electrostatic capacity is within a specific range, its amount is accurately measured by an ink amount detection circuit. It has many advantages such as being able to solve problems such as excessive supply.

〔Example〕

 The present invention will be described below with reference to the present invention.

Examples 1-14, Comparative Examples 1-2 The stencil printing inks having the composition shown in Table 1 were uniformly dispersed, and then dispersed with a three-roll mill. A W / O emulsion was dispersed to prepare an ink for stencil printing.

The capacitance of each stencil printing ink thus prepared was measured. The results are shown in Table-1.

Next, the ink detectability of each stencil printing ink was evaluated. Those of Examples 1 to 14 show good ink detectability,
In practice, problems such as lack of ink and excess ink did not occur. On the other hand, the ink of Comparative Example 1 was short of ink, and the ink of Comparative Example 2 was excessive in ink, and normal printing could not be performed.

Claims (1)

(57) [Claims] 1. A stencil printing ink comprising at least a colorant, an emulsifier and water dispersed in a mineral oil or a vegetable oil, which is measured under the conditions of an electrode distance of 16 mm, an electrode length of 5 mm and a frequency of 100 KHz. Ink for stencil printing, which has a capacitance of 5 to 25 pF.