JPS6341577A - Semisolid ink - Google Patents

Abstract

PURPOSE:To obtain the title semisolid ink that contains carbon black with a specific oil absorption value in a specific amount, thus being useful in image processors, electronic typewriters, facsimile and other purposes. CONSTITUTION:The objective semisolid ink contains 0.5-40wt% of carbon black with an oil absorption value of 40-180cc/100g and is used in the filmless heat transfer recording where the ink is heat-melted, allowed to flow out of the nozzle and transfer to the recording medium. The semisolid ink is produced, e.g., by melting a hot-melting binder such as wax or a thermoplastic resin, preferably at 100-200 deg.C, adding the carbon black, a softening agent and other additives to the melt and dispersing the components thoroughly by mixing.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a semi-solid ink, particularly for use in recording devices to which a filmless thermal transfer recording method is applied, such as image processors, electronic typewriters, facsimile machines, and various bulletin boards. It relates to semi-solid inks.

[Conventional technology]

Currently, thermal transfer recording methods generally use an ink film, and the ink film is usually interposed between a recording medium such as paper and a thermal head, and the ink film is heated by the thermal head to form the heated area. Recording is performed by melting ink and applying it to a recording medium (=1). However, in the thermal transfer recording method using the above ink film, it is necessary to install an ink film feeding mechanism in the recording device applied to the method. Not only is the device configuration complicated, but the running cost is high because the ink film must be disposable, and furthermore, the processing of the used ink film is complicated.

In order to improve the above-mentioned drawbacks, a filmless thermal transfer recording method that does not use an ink film has been proposed, for example, as disclosed in Japanese Patent Application Laid-Open Nos. 59-+18'193 and 59-225990. , is attracting attention. Basically, instead of holding ink on an ink film, this method holds semi-solid ink in a recording head that has passage holes, heats and melts the ink, causes it to flow out through the passage holes, and transfers it to paper or other paper. Transfer recording is performed by attaching it to a recording medium.

Figure 1 shows this kind of filmless heat transfer? An example of a recording head used in the j' recording method is shown.

As shown, the recording head 6 holds b. Here, 3 is an ink container, and 1 is a heating element for heating and melting the semi-solid ink. heating element 1
is a passage hole 7 for flowing out the heated and melted ink 2a.
have. 4 is recording paper as a recording medium, 5
is a platen roller for conveying the recording paper 4. Note that a pressure 8 is applied to the raw national ink 2 as desired for the purpose of facilitating outflow and replenishment of the ink 2.

Further, as the heating element 1, carbon steel, ruthenium oxide, or the like is usually used.

1- In the configuration described above, when heat is generated in the heating element 1,
The semi-solid ink 2 near the heating element is melted and softened to reduce its viscosity, and this molten ink 2a flows out from the passage hole 7. The passage holes 7 are provided in each of the heating elements 1 of the recording head 6 formed in an array, and a heating signal is selectively applied to each heating element 1 to record desired characters, images, etc. on the recording paper 4. It forms an image. During this recording, depending on the type of semi-solid ink, the semi-solid ink may not be supplied smoothly immediately after the ink is melted and transferred, resulting in a temporary ink shortage near the heating element. For example, as illustrated in FIG. 1, by applying a pressure 8 to the ink, it is possible to easily replenish the ink immediately. Therefore, it is preferable to use a semi-solid ink that does not melt when heated, does not flow out from the passage hole before heating, and has a fluidity of +1 that makes it easy to replenish the ink. is a connoisseur. The heating temperature during recording is usually 40
The temperature is said to be about 120°C.

Filmless thermal transfer recording methods that use such semi-solid inks have the advantage of not consuming ink film compared to normal thermal transfer recording methods, and are more energy efficient because the ink is heated directly without using a film. has.

By the way, when a black semi-solid ink is desired, carbon black is usually used as a coloring agent. In order to record a high rate of ◇ in which the black color of carbon black is maintained for 1 minute,
It is desirable that the dispersed state of carbon black be maintained well during ink storage, melt transfer, and subsequent solidification process of the ink.

However, it is usually not easy to uniformly disperse carbon black in ink compared to other dyes and pigments, and its dispersion state changes during ink storage or use, resulting in changes in ink properties and color changes. may occur.

For this reason, problems such as a decrease in recording sensitivity and unclear formation of images occur.

[Problem that the invention seeks to solve]

The present invention has been made in view of the above-mentioned points, and an object of the present invention is to solve the drawbacks and problems of the conventional example mentioned above, to be able to record with high sensitivity, and to obtain clearer images. The object of the present invention is to provide a semi-solid ink for use in a filmless thermal transfer recording method which is particularly excellent in carbon black dispersibility and storage stability.

[Failure to solve the problem]

The above objects of the present invention are achieved by the present invention as follows.

A semi-solid ink used in a filmless thermal transfer recording method in which semi-solid ink is melted by heating and flows out from a passage hole, and the flowed out semi-solid ink is transferred and recorded on a recording medium,
The semi-solid ink has an oil absorption of 40 to 180 by DBP method.
A semi-solid ink characterized by containing 0.5 to 40% by weight of cc/long carbo black.

Here, the oil absorption amount measured by the DBP method is the amount of oil required to fill the voids in carbon black. (DBP
It refers to the oil absorption amount obtained by measuring with an absorptomet, er), and is adopted in the A 57M test method.

Generally, the larger the value, the larger the surface area and the higher the ink viscosity.

(Function) The semi-solid ink of the present invention obtained using carbon black having the above-mentioned oil absorption amount is not limited to the dispersion state of the carbon black during the ink production, as well as during storage, melt transfer, and subsequent solidification process of the ink. is maintained well, exhibits excellent storage stability, and does not cause changes in ink viscosity or color changes, making it possible to perform highly sensitive and clear recording.

If the oil absorption amount of carbon black is less than 40cc/100g, the dispersibility in the ink will decrease, and the uniformity of the black ink will deteriorate during the ink melt transfer and subsequent solidification process during ink production or recording. is not maintained, resulting in uneven ink density and deterioration of storage stability.

On the other hand, if the oil absorption exceeds 180 cc/g/g or if the carbon black content exceeds 40% by weight, the viscosity of the ink will increase, causing problems in recording. In addition, the carbon black content is 0.5%
If the amount is less than 1, the amount of carbon black in the ink is too small to obtain a clear recorded image on the recording medium.

Specifically, such carbon blacks include, for example, #30, #32, #33, manufactured by Tamabishi Kasei Co., Ltd. as commercially available products.
#40, #44, #45, #50, #52, MA7, M
AR1# 2200B, # 2300, # 235
0, CF9, Monarch manufactured by Cabot, USA (MONA
RCI+) 700.800.880, 900,
+000.1100, l300, REGAI
, ) 500R1fi60, 66OR, 5RF-5, Elftex (1+THX) 11, 12, etc., but of course it is not limited to these. The above carbon blacks can be used alone or in combination.

The semi-solid ink of the present invention is prepared by appropriately combining carbon black as described above with a heat-melting binder, a softener, or other additives.

Examples of the heat-melting binder that can be used in the semi-solid ink of the present invention include wood wax, spermaceti wax, beeswax, lanolin,
Natural waxes such as carnauba wax, candelilla wax, montan wax, ceresin wax, petroleum waxes such as paraffin wax, microcrystalline wax, synthetic waxes such as petrolatum oxide, oxidized wax, ester wax, low molecular weight polyethylene, Fischer-Tropsch wax, laurin acids, higher fatty acids such as myristic acid, palmitic acid, stearic acid, behenic acid, higher alcohols such as sudearyl alcohol and behenyl alcohol, esters such as sucrose fatty acid ester, sorbitan fatty acid ester, amides such as oleylamide , polyamide resin, polyester resin, epoxy resin, polyurethane resin,
Elastomers such as cellulose resin, polyvinyl alcohol resin, petroleum resin, phenol resin, polystyrene resin, natural rubber, styrene butadiene rubber, isoprene rubber, chloroprene rubber, rice wax,
Examples include osichelite and hydrogenated castor oil. These can be used alone or in combination of two or more.

Examples of softeners for these binders include paraffinic hydrocarbons, naphthenic hydrocarbons, halogenated hydrocarbons, ethers, acetals, ketones, and derivatives thereof, which are liquid at room temperature. In addition to these softeners, solvents such as various nitrogen compounds and phenols, plasticizers, or oils such as mineral oil, vegetable oil, and animal oil may be selected and used as appropriate to improve the melting point or softening point of the semisolid ink, melt viscosity, etc. The viscosity and the like at room temperature may be adjusted as appropriate.

The method for producing the semi-solid ink of the present invention is not particularly limited.
It is preferable to heat and melt the mixture at 00 to 200°C, add carbon black field and the above-mentioned softeners and additives as appropriate, mix and disperse for 1 minute, and cool to room temperature without leaving or stirring. .

Although not specifically explained above, the present invention is also suitable as a semi-solid ink for a rotary recording head used in a filmless transfer recording method previously proposed by the applicant in Japanese Patent Application No. 81-16747. It is something. It can also be used as a releasable ink for recording and erasing various bulletin boards.

〔Example〕

EXAMPLES Hereinafter, the present invention will be specifically explained using Examples, but these are not intended to limit the present invention in any way.

Example 1 Beeswax (manufactured by Noda Wax Co., Ltd., bleached beeswax, melting point 60°C
) 30 parts by weight, 60 parts by weight of liquid paraffin (manufactured by Esso Oil Co., Ltd., Kustol 70), and carbon black (manufactured by Mitsubishi Kasei Corporation, #40, oil absorption 110 cc/long)
(DBP method) 5 parts by weight were added to a mono-tube Santo mill kept at 140°C together with glass beads with a diameter of 1.5 mmφ, and after dispersing and mixing at 2000 rpm for 30 minutes, the beads were separated and cooled. A semi-solid ink was made.

The recording characteristics of this ink were evaluated by performing transfer recording on recording paper using the recording head illustrated in FIG. Recording was performed by using a carbon sheet as the heating element of the recording head, and applying a potential pulse of 5 to 30 V to an electrode connected to the carbon sheet to generate Joule heat in the heating element to heat and melt the ink in the vicinity. When recording,
0.1 to 2.0 kg/crn' in the direction of the ink passage hole
The pressure was applied constantly or in synchronization with the potential pulse. When recording was performed in this manner, recording dots were recorded in response to potential pulses with high sensitivity.

In addition, this ink maintains the dispersibility of carbon black well during the manufacturing process and the subsequent recording process.
No color change or density unevenness was observed in the recorded image, and high-quality recording was possible.

Furthermore, the storage stability of this ink was evaluated by leaving it for 10 days, and the dispersibility of carbon black was maintained well even after leaving it, and no change in ink viscosity or color change was observed. It had excellent storage stability. These results are summarized in Table 1.

Example 2 The carbon black of Example 1 (manufactured by Mitsubishi Kasei Corporation, #40,
Carbon black (manufactured by Cabot, USA, Monarch <MONAI'IC1+) 880, oil absorption 11
A semi-solid ink was obtained in the same manner as in Example 1 except that 5 cc/100 g (DBP method)) was used.

The recording properties and storage stability of this ink were evaluated in the same manner as in Example 1. The results are shown in Table 1.

Example 3 Carbon black of Example 1 (manufactured by Mitsubishi Kasei Corporation, #40,
The same procedure as in Example 1 was carried out except that carbon black (manufactured by Mitsubishi Kasei Corporation, M to 7, oil absorption 65 cc/100 g (DBP method)) was used instead of 110 cc/100 g (DBP method)). A solid ink was obtained.

The recording properties and storage stability of this ink were evaluated in the same manner as in Example 1. The results are shown in Table 1.

Comparative Example 1 The carbon black in Example 1 was manufactured by Columbia Carbon Co., Ltd. (7) RAVEN MT-PB.
EADS (Oil absorption amount 36[:C/100g (DBP
A semi-solid ink was obtained in the same manner as in Example 1 except for the following steps.

When the dispersibility of carbon black was observed for this ink immediately after cooling after mixing, a sedimentation phenomenon of carbon black was observed, and a difference in density was observed in the degree of blackness between the first layer portion and the lower layer portion.

Further, when the recording properties of this ink were evaluated in the same manner as in Example 1, uneven density was observed in the recorded image obtained, and it was of low quality, non-uniform and unclear. These results are summarized in Table 1.

Comparative Example 2 The carbon black in Example 1 was replaced with CONDIICTEX manufactured by Columbia Carbon Co., Ltd.
40-220 (Oil absorption amount 260 cc/100g (D
A semi-solid ink was prepared in the same manner as in Example 1 except that the BP method)) was used.

The viscosity of this ink was considerably higher than that of the ink of Example 1 when it was cooled after mixing.

An attempt was made to evaluate the recording properties of this ink using the same method as in Example 1, but almost no ink was transferred onto the recording paper, and no recorded image could be formed.

This is because the ink viscosity was too high and the ink could not be supplied.

Table 1 ■ Dispersibility of carbon black ○ Good, Δ Slightly poor, X Bad Ink storage stability 0 Good, Δ Slightly poor, , ×
Solid or liquid *4 Recorded image quality: Good, △ Slightly poor, X Poor -1- As is clear from the examples and comparative examples, DB
The semi-solid ink of the present invention using carbon black having an oil absorption of 40 to 180 cc/l00g by the P method had good carbon black dispersibility and was excellent in storage stability and recording quality.

〔Effect of the invention〕

The effects brought about by the semi-solid ink for filmless thermal transfer of the present invention include those listed below.

■It is a highly sensitive ink with excellent thermal responsiveness and excellent dispersibility of carbon black, and it is possible to obtain clear recorded images without density unevenness or color change.

■Even during long-term storage, the dispersion state of carbon black does not change, resulting in excellent storage stability.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view illustrating an example of a recording head used in a filmless thermal transfer recording method.

Claims (1)

[Claims] (1) A semi-solid ink used in a filmless thermal transfer recording method in which semi-solid ink is melted by heating and flows out from a passage hole, and the semi-solid ink that flows out is transferred and recorded on a recording medium, wherein the semi-solid ink is DBP. Oil absorption amount by method 40-1
A semi-solid ink characterized by containing 0.5 to 40% by weight of 80cc/100g of carboblack.