JPH0420576A - Ink for ink jet recording - Google Patents

Abstract

PURPOSE:To prevent the occurrence of blotting due to bleeding and the clogging of a delivery port by using a visualizing agent for forming a recorded image and a polar aprotic substance as the constituents. CONSTITUTION:A visualizing agent for forming a recorded image, comprising, e.g. a (fluorescent) dye (e.g. C.I. Solvent Black 3) is mixed with a phase changing agent comprising a polar aprotic substance (e.g. 1,3-propane sultone) having a melting point of 45 deg.C or higher and, if necessary, a thermoplastic polymer, a tackifier, a plasticizer comprising an ester, a chlorinated paraffin, an antioxidant, a mildewproofing agent, etc.

Description

[Detailed description of the invention] 〔Technical field〕 The present invention relates to an inkjet recording ink.

[Prior art]

In the normal inkjet recording method, liquid ink such as water-based or oil-based ink stored in a liquid chamber is applied pressure by a piezoelectric element that is sensitive to an image signal, or the ink is moved from the print head by the action of heat, electric field, etc. This method, in which the head is ejected and printed on a recording material such as paper, has been put into practical use in recent years because the head can be manufactured relatively easily.

However, with this method of using liquid ink, it is not possible to record on so-called plain paper regardless of the paper type.

It is difficult to obtain clear images due to the tendency to bleed, poor drying properties, and poor color reproducibility in the case of color.In effect, the above disadvantages can be overcome by applying special processed paper for inkjet recording. I was making up for it.

On the other hand, a method of heating ink that is solid at room temperature to a liquid state and ejecting it is described in USP, No. 3,653,932, US
P, 4, 390, No. 369, JP-A-55-5436
No. 8, JP-A-61-83268, JP-A-62-487
No. 74, etc. The method using such ink has the feature that it is possible to obtain clear monochromatic or color images on most materials such as plain paper, plastic film, woven fabric, wood chips, or metal surfaces. However, in all conventional heat-melting inks, dyes, pigments, and coloring materials are dispersed in specific media, often waxes, so there is a tendency for recording color removal materials to bleed from specific media. The dispersion of the coloring material described above poses difficulties in purifying and providing reliability to the ink ejected from the nozzle, causing clogging.

〔the purpose〕

An object of the present invention is to provide an inkjet recording ink that does not cause bleeding due to bleeding and does not cause clogging of ejection ports, which is likely to occur after a pause.

〔composition〕

The present invention provides (i) a visualization agent that forms a recorded image;
The present invention relates to an inkjet recording ink whose main component is i) a polar aprotic substance having a melting point of 45° C. or higher.

The ink of the present invention takes a liquid state by heating in the print head according to the composition (ii) above, is ejected from a nozzle, is received on a recording material, and is solidified and fixed by cooling. Since solidification occurs through a uniform liquid phase due to the dissolving power of the proton solvent, various problems mentioned above can be improved.

Furthermore, since it is effective in optimizing the viscosity of the ejected liquid, a stable ejected state can be maintained on the general-purpose recording member.

The polar aprotic substances of the present invention include ethyl-phenylsulfone, dimethylsulfoxide, sulfolanesulfolene, 1,3-propanesultone, dimethylaminoacetophenone, 4-dimethylaminopyridine, quinoxaline, inquinoline, diethylbenzamide, and tributylphosphate. , tricresyl phosphate, diisopropylidene acetone, 1,3-dimethylbarbital acid,
N,N-dimethylbenzamide, 4,4'-dimethylbenzophenone, 1,3-dimethyl-4-chlorouracil, N,N-diethyl-N, N'-diphenylurea, 2
, 4-difluorobenzonitrile, 4,4'-difluorobenzophenone, 4,6-difluoro-m-dinitrobenzene, P,P'-difluorodiphenylsulfone,
Diveratryle ether, piperonyl nitrile, quinazoline, etc. can be mentioned, and all of these have 45 to 11
It is a compound with a melting point of 0°C.

In the present invention, at least one or two or more of these substances may be used, and if necessary, additives described below may be added to achieve a suitable combination for ejection.

The ink of the present invention may also contain dyes, fluorescent dyes, etc. as visualization agents.5For example, among the dyes classified as oil-based or disperse dyes in the color index, they dissolve in the phase change agent made of the polar aprotic substance when heated. The visualization agent selected is not particularly limited.

Although the polar aprotic substance is the main component, the solution forming temperature or open time is optimized, adhesive strength to the recording member is improved, cohesive force is improved, and heat resistance is achieved.

For the purpose of adjusting environmental resistance such as cold resistance, thermoplastic polymers such as beer chloride-vinyl acetate copolymer and polyester polymer can be appropriately selected and added.

Further, in order to impart initial tackiness upon melting and residual tackiness upon solidification, terpene resins, butyral resins, esterified rosins, hydrogenated rosins, and the like can be appropriately selected and added as tackifiers.

In addition, an ester plasticizer, chlorinated paraffin, etc. can be added as appropriate to improve heat fluidity and wetting to the recording member.

Furthermore, due to the nature of the composition of the present invention, it may be exposed to an environment susceptible to oxidation, such as being kept in a molten state for a certain period of time, or may be kept at temperature conditions favorable for microorganisms depending on the composition of the ink. It is effective to appropriately select and add an antioxidant stabilizer and a fungicide containing phosphorus.

Next, an inkjet recording method using the coloring composition of the present invention will be described. The coloring composition of the present invention can be applied to any inkjet recording method proposed so far. An example of a typical method is PZT
This is a pulse-on-demand method in which a pulse voltage according to the image is applied to a piezoelectric element, applying pressure to the ink in the ink chamber and pushing the ink out of the nozzle. This is an electrostatic suction method in which charges are induced in the ink by applying a pulse voltage according to the image to the electrodes, and the ink is absorbed from the nozzle toward the recording paper side. The specific methods of these inkjet methods are described in, for example, the Journal of the Television Society 37 (7) 540 (1).
983) etc. Among these inkjet methods, methods that collect and reuse ink, such as methods that continuously form ink droplets and control the amount of charge, are difficult to use when using the ink of the present invention, which is solid or highly viscous at room temperature. It is also necessary to maintain the ink at a low viscosity by heating in the ink recovery section. Therefore, it is more preferable to use the ink of the present invention in a drop-on-demant type recording device.

〔Example〕

Example I C, I Solvent Black 3: ht%1.
A mixture consisting of 3-propane sultone 70% vinyl chloride-vinyl acetate copolymer 7% purified candelilla wax 20% by weight was heated to 90°C to form a solution, and then a Teflon filter with a pore size of 0.5μ was used. The ink was prepared by hot filtration.

This ink was filled into an inkjet recording apparatus as shown in FIG. 1, and an image was recorded.

In FIG. 1, 6 is a print head, and the ink was heated to about 80° C. by a heater (not shown) in the head. The ink filled in the head is moved by a piezoelectric element (
(not shown) applies pressure according to the image signal,
The ink flies in the direction of the platen 12 and is printed on the recording paper supplied onto the platen. Recording paper 1 is fed to paper feed roller 3. The paper is supplied onto the platen by the paper guides 4 and 5, and is conveyed to the paper discharge tray 16 by the rollers 9 and 10 and the separation claw 11. The print head 6 is scanned in a reciprocating manner on the guide shafts 7 and 8. Also, platen 12
There is an infrared lamp 13 inside the platen.
It is heated to ℃. 14 is a sensor for detecting the temperature of the platen, and 15 is a controller for feeding back the detected temperature and correspondingly changing the output of the lamp so that the temperature of the platen is constant. be.

The maximum printing frequency is 4KHz, and the printing density is 8 dots/
m m, droplet diameter is approximately 100μm, droplet speed is approximately 4m
/sec, and the distance between the nozzle and the printing surface was approximately 1 mm.

Under the above conditions, commercially available high-quality paper, bond paper, medium-quality paper, OH
Printing was carried out on P sheets, and on all recording media, the images were pure black, had high density, and were clear and free from bleeding. The obtained image was stored at 30° C. for 3 months, but no change was observed in the image.

In addition, we conducted continuous operation tests for 1,000 hours and 2 months of rest using the above-mentioned device, and stable discharge characteristics were obtained in both tests, and images as clear as the initial ones were obtained. .

Comparative Example 1 Instead of the ink formulation of Example 1, an ink with the following formulation was prepared in the same manner as in Example 1, and then filled into the same apparatus and printed in the same manner.

Density wax 35-t% Candelilla wax 62 t% Oil black 3-t% The obtained image was as clear as the image in Example 1, and the image did not change upon storage. After the print stopped for several months, no ink was ejected from the nozzle, making it impossible to print.

Example 2 C,I Solvent Blue 673t% Sulfolane 25t% Sulfolene 60t% Tricresyl Phosphate 10υt% After heating the above mixture to 100°C, an ink was prepared in the same manner as in Example 1. The liquefaction melting temperature of this ink was 48-64°C. Printing was performed using the same device as in Example 1, and a clear blue image was obtained without blurring, and the same reliability as in Example 1 was obtained.

Comparative Example 2 C, I Solvent Blue 67 3wt% candelilla wax 60wt% paraffin
Wax 37wt% The above mixture was prepared in Example 1.
After adjusting according to the above, the same device was filled and printing was performed in the same manner. The obtained blue image was clear and did not change during storage, but after the print was stopped for two months, ink could not be ejected from the nozzle and printing could not be performed.

Example 3 C, I Direct Black 154 3wt%4
．． 4'-Difluorobenzophenone 3 (ht% diisopropylidene acetone 40wt% purified candelilla wax 20υt% saturated polyester resin
'ht% The above mixture was heated to 90°C, and an ink was prepared as a solution in the same manner as in Example 1, and printing was performed using the same apparatus. A clear black image was obtained without blur, and stable ejection characteristics were obtained in the same manner as in Example 1.

〔effect〕

When the ink of the present invention is used, it is possible to form clear images on a wide variety of recording materials without bleeding due to bleeding.

Further, when the ink of the present invention is used, the ejection ports will not be clogged even when the ink is not used for a long period of time.

[Brief explanation of drawings]

FIG. 1 shows an example of an inkjet recording device that can use the ink of the present invention. 1... Recording paper for printing 2... Printed recording paper 3
...Paper feed roller 4,5...Paper guide roller...Print head 7,8...Guide shaft 9.10
... Roller 11 ... Separation paper 12 ... Platen 13 ... Infrared lamp 14 ... Sensor 15 ... Controller 16 ... Print paper tray 17 ... Supply paper receiver

Claims (1)

[Claims] 1. An inkjet recording ink whose main components are (i) a visualization agent that forms a recorded image, and (ii) a polar aprotic substance having a melting point of 45° C. or higher.