JPH0193389A - Ink jet recording method - Google Patents

Abstract

PURPOSE:To enhance the density of printed images and prevent nozzles from being clogged, by adhering an oxidizing agent-containing liquid to parts to which an ink containing a reduction-type compound is to be adhered. CONSTITUTION:Immediately before an ink containing a reduction-type compound of a dye showing solubility in a reduced state and becoming insoluble upon being oxidized is adhered to a recording material, a liquid containing an oxidizing agent is adhered to parts to which the ink is to be adhered. The oxidizing agent-containing liquid augments a precipitating action of the dye. By this, it is possible to enhance clearness, resolution, sharpness and density of images. Since the insolubilization of the dye is performed on the recording medium and the dye is maintained in a high solubility state in a recorder, nozzles are prevented from being clogged.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to an inkjet recording method, and more particularly, to an inkjet recording method that uses an ink containing a reduced compound of a dye that is soluble in a reduced state and insoluble when oxidized. The present invention relates to an inkjet recording method in which ink is injected from a nozzle to oxidize and insolubilize a recording material.

[Prior Art] The inkjet recording method has the following advantages: (a) High-speed recording is possible; (b) Since it is non-contact with the recording medium, various materials including plain paper can be used as the recording medium; and (c) It has been widely used in recent years due to its advantages such as the ability to record in color.

On the other hand, this inkjet recording method still has the problem of nozzle clogging. To solve this,
In addition to adding innovation to the shape and structure of the nozzle tip,
It is required that dyes with high solubility in solvents be used in inks. However, when dyes with high solubility are used in ink, the durability of images obtained (
When the solvent is water, water resistance tends to deteriorate.

As a means to eliminate these defects, (1) coat the recording paper with a material for fixing the dye in advance (Japanese Patent Application Laid-open No. 56-86789, JP-A No. 55-144172@,
(described in publications such as JP-A-56-84992), (2)
It has been proposed to apply a waterproofing agent that forms a dye and lake to the printed image (as described in Japanese Patent Application Laid-Open No. 150396/1983). However, in the method (1) above, it is necessary to use a specific recording paper as the recording medium. Although method (2) above solves the problem of water resistance, it has no or only slight effect on the dryness of the image after printing, the resolution of the image, the image density, etc., so it is not suitable for use as a recording medium. What can be applied is quite limited.

In addition, when printing on recording paper (recording media) used in general offices with the ink used in conventional inkjet recording methods, drying time is slow, and background stains and smear occur due to offset in the recording paper supply system. Particularly in the case of color recording, the amount of ink applied per unit area of the recording paper (recording medium) is large (due to overlapping of multiple colors), so ink flows to unnecessary areas and the image is damaged. It has the disadvantage that it smears.

(3) As a means to solve such drying problems
(4) Paper containing no sizing agent or a reduced amount of sizing agent is used as a recording medium (described in JP-A-52-74340); paper provided with a coated layer is used as a recording medium (JP-A-52-53012, JP-A-56-
89594@), (5) Adding a compound such as a surfactant to the ink to increase the permeability of the ink to lower the surface tension of the ink (Japanese Unexamined Patent Publication No. 55-6
5269], (6) use of an ink mainly composed of an organic solvent such as alcohol or ketone, which has an inherently low surface tension, (7) use of an ink mainly composed of a volatile solvent (Japanese Patent Application Laid-open No. 5269) 55-66976], etc. have been proposed.

However, methods (3) and (4) above require the use of a specific recording medium, similar to (1) above. (5) above
Although method (6) does improve the drying performance, the dye in the ink also penetrates considerably along with the ink medium (carrier), so the dye easily penetrates deep into the recording paper, reducing the image density. There are disadvantages such as the sharpness of the image tends to decrease and the clarity of the image tends to decrease. Further, due to the improved wettability of the recording surface, there are other disadvantages such as feathering and a decrease in resolution (the ink spreads in the direction of the surface and the dot diameter increases). Said (7
In method (6), the ink penetrates into the recording paper faster and at the same time, the solvent tends to evaporate from the surface of the recording paper, ensuring quick drying. However, in addition to the same disadvantages as in (6) above, , clogging is likely to occur due to evaporation of the solvent in the nozzle.

Furthermore, as a means to improve the sharpness of printed images (
8) A method has been proposed in which a solution of a polymer such as carboxymethyl cellulose, polyvinyl alcohol, polyvinyl acetate, etc. is sprayed onto a recording medium in advance and then printed (described in JP-A-56-89595). This (8)
Although the method described above can improve sharpness,
Since the polymer solution has a high viscosity, the drying properties of the solution itself are poor, and in addition, the drying properties of the printed ink are not significantly improved compared to when printing on ordinary paper.

In view of these circumstances, it is desired to improve inkjet recording methods that do not cause the above-mentioned defects.

[Purpose] The present invention meets these demands, and improves the dryness, water resistance, resolution, clarity, sharpness, etc. of images after printing, and further increases the density of the images after printing, and prevents nozzle clogging. An object of the present invention is to provide an inkjet recording method that prevents problems and improves printer reliability.

In order to achieve the above object, the present invention creates an image by ejecting an ink containing a reduced compound of a dye that exhibits solubility in a reduced state and becomes insoluble when oxidized from a nozzle. Provided is an inkjet recording method in which a liquid containing an oxidizing agent is applied to a portion to which the ink is to be applied immediately or immediately after the ink is applied to a recording material. It is something.

Typical examples of dyes that exhibit solubility in a reduced state and become insoluble when oxidized include those known as vat dyes and sulfur dyes.

Also, those known as soluble vat dyes are preferably used. A more specific example is C, 1, Vat Yellow; 2.4, 10, 20
,22,33.35C,1,Vat Orange;
1.2.3.5.7.9, 13.15C, 1, Solubilized Vat Orange; 3C, 1, Vat Red
; 1.2. to, 13, 15, 16, 31, 52, 6
1C, 1, Solubilized Vat Red; IC, 1, Vat Violet; 1.2.9, 13.
21C, 1, Vat Blue; 1.3.4.5
．． 8.8,12,14. t8゜19, 20.29.35
．． 41.42.43.56.64°66,67,72 C,1, solubilized vat 131LIe; 1.5.6.
41C, 1, Vat Green; 1.2.3.8
．． 9,13,43,44,45C,1, Solubilized Vat
Green; IC, 1, vat Br0Wn; 1.
3,22,35,39,41,44,46,57゜68
, 72.73 C,1, solubilized vat Br0Wn; IC,1, Vat
Black; 8.9, 13, 14, 20, 25,
27,29,36°56,57.59.60 C,1, Solubilized Vat Black; IC,1,5ul
phur Yellow; 4°C, 1, solubilization 5ulp
hur Yellow;2C51,5tJlphUr 0
ran(le; 1,3C,1, solubilized 5ulfur
Orange; IC, L 5ulfur Red;
2.3.5.7C, 1, Solubilized 5ulfur Red
;7C,1,5ulfur Blue; 2.3.4
．． 6.7.9.13C,1, Solubilization 5ulfur B
lue; 2.4.7, 10.15C, 1.5ulph
ur Green; 1.2.3.6,11,14.2
7C, 1, Solubilized 5ulfur Green; 2.
3.27C, 1.5ulphur Brown; 7
．． 8,10,12,15,26.31C,1,Solubilized 5ulfur Brown; 8,12.51C,
1.5ulphur Black; 1.2.5.6,
10,11.15C,1,Solubilized 5ulfur Bl
ack; 1.5 is mentioned. Among these dyes, C,1,Vat Ye is preferred for use in the present invention.
low 20, 22, C, 1, solubilized Vat, Red
1, Vat; Red 2, 13.1B, 31, Vat
Blue 4.5, 12, 29, 41, Solubilized Vat
Blue 5, 8 and solubilized Vat Black 1 are included.

Among the above dyes, except those which have already been reduced and solubilized, Na2S, Na25z04. Na2S2O
It is reduced using a reducing agent such as 3°H2S, LiAlH4, NaBH4, CO, or alkali metals and used in ink. After the reduction is completed, these reducing agents are removed as necessary by a method such as dialysis in order to prevent clogging in the nozzle portion. Reduction can also be achieved by blowing in hydrogen. At this time, catalysts such as I'd-C and Ni can be used, but these are solids that do not dissolve in water, and there is no need to remove the reducing agent in this method.

In addition, the DH value of the ink is preferably adjusted to DH10 or more in order to provide sufficient solubility to the dye, and furthermore, in order to increase the drying speed of the ink on the recording paper, p) (
It can be 12 or more. In order to adjust the pH value of the ink to such a range, ioH, Na0tl,
KOH, LizCO3, K2CO3, Na2SO3゜(
CH3)4NOH, (C2H5)4NOH, (C2H4
0H)4NOt1, etc. are used, but particularly preferred alkaline agents to increase the solubility of the dye are NaOH, Li0l, etc.
1, (CH3)4NO1, and other quaternary ammonium hydroxides.

In order to prevent the dye in the ink from oxidizing during storage, the ink can contain a reducing agent that is highly soluble and has a weak reducing effect. Examples of these reducing agents include sugars such as glucose and sucrose, ascorbic acid, oxalic acid, Na2SO3, and the like.

Compounds that can be further added to the ink include compounds used in conventional inkjet inks. For example, temperature regulators include ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, propylene glycol, dipropylene glycol, polyethylene glycol 200-1500, polyhydric alcohols such as glycerin, ethylene glycol monomethyl ether, diethylene glycol monoethyl ether, etc. Examples include ethers of alcohols, and cyclic amides such as N-methyl-pyrrolidone and 1,3-dimethylimidazolidinone.

As preservatives, salts of dehydroacetic acid, sorbate, benzoate, pentachlorophenol salt, 2-pyridinethiol-1-oxide salt, 2,4-dimethyl-6-acetoxy-m-dioxane, 1.2- Benzthiazoline
Compounds such as 3-one' can be added.

It is preferable that the ink has a surface tension of 50 dye/cm or less in order to speed up its absorption into the recording material.

Examples of compounds that reduce surface tension and improve permeability include the following compounds. Namely, polyoxyethylene alkyethers, polyoxyethylene alkylphenyl ethers, polyoxyethylene alkyl esters, polyoxyethylene alkyl sorbitan esters, polyoxyethylene alkyl amines, glycerin fatty acid esters, sorbitan fatty acid esters, propylene glycol fatty acid esters,
Nonionic surfactants such as polyoxyethylene glycol fatty acid esters, alkyl sulfates, polyoxyethylene alkyl ether sulfates, polyoxyethylene alkyl ether acetates, alkylbenvin sulfonates, N-acylamino acid salts, alkyl sulfosuccinates Anionic surfactants such as acid salts and alkyl phosphates, cationic surfactants such as quaternary amines such as Benly'ruconium salts, perfluoroalkyl phosphates, perfluoroalkyl carboxylates, Use fluorine-based surfactants such as perfluoroalkyl betaines.

Among these, more specific and preferable penetrating agents are diethylene glycol monobutyl ether, diethylene glycol monophenyl ether, propylene glycol monobutyl ether, and fluorine-based surfactants, which have a large effect of increasing the penetrating property.

On the other hand, as an oxidizing agent used in a solution containing an oxidizing agent, tl
Peroxides such as zOz, Naz02, (CH3CO)202, HCO3tl, C) bcOOH, C5H
4(COOtl) Beroxo acids such as CO3H, Na2C
rO4, chromic acids such as NaCr03Cl, NaMnO
Permanganic acids such as 4, NaClO3, NaCl0. N
aBr0, NaCl0a, Na103. NaB
rO3, Nal0aW oxygen acids, FeCl3. C.O.
3O4, CtJ(CH3COO)z, CLICI2
, 5nC14, and other metal salts.

The strength of the oxidizing action of these oxidizing agents is determined based on the ease with which the dye becomes insolubilized by oxidation, the ease with which the dye fades due to oxidation, and the oxidizing agent used when washing with water after printing, such as in textile printing. Factors such as whether or not it is possible to remove water by washing must be taken into consideration.

The amount of the oxidizing agent added must also be determined in consideration of the above factors. The amount of addition should be such that 1710 to 20, preferably 172 to 2, of the oxidizing agent adheres to the dye that adheres to the same portion of the recording material.

By adding an acidic substance to a liquid containing an oxidizing agent, the precipitation effect of the dye can be strengthened. Examples of acidic substances include acetic acid, succinic acid, and lactic acid.

Wetting agents and penetrating agents that can be added to the inks described above can also be added to the liquid containing the oxidizing agent.

Applying a liquid containing an oxidizing agent to the area to which the ink is to be applied can provide sufficient water resistance to the image either before or after forming the image with the ink. However, if a liquid containing an oxidizing agent is applied immediately before printing an image, an insoluble compound of the dye is formed immediately when the ink is applied, so the dye tends to remain near the surface of the recording material, resulting in a higher concentration. A clear image can be obtained.

Methods for applying the liquid containing the oxidizing agent to the recording material include methods such as spraying, applying it to the entire recording material using a roller, and immersing the recording material in the oxidizing agent-containing liquid and then squeezing out the excess liquid using a squeeze roller or the like. Although there are several methods available, the most preferred method is an inkjet method, which allows a certain amount of the oxidizing agent-containing liquid to be selectively deposited only on the areas where the ink is to be deposited.

However, even when applying an oxidizing agent-containing solution by an inkjet method, if the diameter of the dot formed by one drop of the oxidizing agent-containing solution on the recording medium is approximately equal to the diameter of the dot formed by one drop of ink, the oxidizing agent When selectively depositing the oxidizing agent-containing solution, the position where the oxidizing agent-containing solution is deposited and the position where the ink is deposited must completely match, making it difficult to adjust the injection positions of both solutions. Therefore (a)
(b) When the viscosity of the oxidizing agent-containing solution is made lower than the viscosity of the ink and the oxidizing agent-containing solution is ejected under the same conditions as the ink. The dot diameter of the oxidizing agent-containing solution on the recording medium is compared with the dot diameter of the ink by a method such as making the diameter of the oxidizing agent-containing solution droplet larger than the ink droplet. It is preferable to keep it large. Or (C) If it is difficult to make a difference in the dot diameter between the oxidizing agent-containing solution and the ink, by processing the ink print signal, the ink can be printed by one dot around the image. A method in which an oxidizing agent-containing solution is applied in excess to the surface is preferred.

The liquid containing the oxidizing agent is preferably colorless or light-colored. One reason for this is that the oxidizing agent-containing solution also adheres to the periphery of the image formed by the ink adhesion. Another reason why the oxidizing agent-containing solution must be colorless or light-colored is so that the image (formed) that is desired to be printed is nearly identical to that printed with ink alone.

Therefore, the oxidizing agent-containing solution may be substantially colorless or light-colored as long as these do not cause problems.In other words, the oxidizing agent-containing solution should be substantially colorless or light-colored, so long as the oxidizing agent-containing solution is not recognizable around the image, especially for color images. It is sufficient that the color is colorless or light-colored to the extent that color reproduction is not poor when formed.

In a method in which an oxidizing agent-containing solution is applied prior to printing with ink, the time between applying the oxidizing agent-containing solution to the recording medium and subsequently applying the ink is an important factor that affects print quality (image quality). It is. This time is set within an appropriate range depending on factors such as the matrix of the oxidizing agent-containing solution and the ink droplets, the flying speed of the droplets, the permeation speed of the oxidizing agent-containing solution into the recording medium, and the surface tension of the ink.

If the oxidizing agent-containing solution remains on the surface of the recording medium when ink droplets are attached, the ink may scatter, causing stains around the image, or the ink may migrate to the oxidizing agent-containing solution, causing image bleeding. easy.

On the other hand, if too much time has passed since the oxidizing agent-containing solution was attached, the oxidizing agent-containing solution will penetrate into the recording material.
Because the oxidation reaction does not occur quickly, the expected clarity of the image may not be obtained.

Furthermore, the oxidizing agent may be decomposed by components within the recording material.

In order to control the adhesion state of the oxidizing agent-containing solution when the ink adheres, it is necessary to adjust the relative position of the head that ejects the oxidizing agent-containing solution and the head that ejects the ink in the printer, and to infiltrate the oxidizing agent-containing solution. The amount of agent added may be adjusted.

Various proposed inkjet methods can be used to apply the oxidizing agent-containing solution and ink to the recording medium. Regarding these methods, for example, see the Journal of the Society of Television Engineers 37 (7) 540 (proposed by Junji Maeda).
1983). A typical method is a charge control type continuous injection method; an on-day method such as Kaiser type, Gould type, bubble jet type, or Stenme type.

Example: Add C,1 to 95g of water in which Na0tl and NazS were dissolved.
, vatYet low 20. 3 g was gradually added with stirring to obtain an aqueous solution of reduced dye 1. After removing the oxidized reducing agent and the unreacted reducing agent by dialysis, Naou was further added to adjust the DH of the aqueous solution to 12.5. Using this aqueous dye solution, an ink having the following formulation was prepared and filtered through a filter with a pore size of 0.1 μm to obtain a test ink.

Dye 1.5wt% glycerin 10//ethylene glycol 151/diethylene glycol
20j/N-methyl-2-pyrrolidone 4
〃Diethylene glycol monobutyl ether 4 〃 2-pyridinethiol-1-oxitona!・Rium salt 0.4n water
C as residual red dye
, 1, Vat Red 2 is used to convert the previous Vat Yel
A red ink was obtained by performing the same treatment, preparation, and filtration as in low 20.

Using C,1, solubilized Vat Blue 5 as a blue dye, a mixture was prepared by replacing Vat Yellow 20 in the above formulation with this dye, and filtered to obtain a blue ink for testing.

C,1 as black dye, solubilized Vat Black 1
Using this dye, the dye was substituted for vat ye++ow 20 in the above formulation and filtered to obtain a black ink for testing.

The surface tension of these inks is 40-43 dyne/cm
Met.

The following formulation was prepared as an oxidizing agent-containing solution.

NazOz 0.5wt%
Glycerin 10.0//Ethylene glycol 15.0 #Diethylene glycol 10.0 l/Diethylene glycol monobutyl ether 8, Q 7/Amber! 4.0 Sodium dehydroacetate O65 Water
A printing test was conducted using these remaining test liquids.

The outline of the printer is as follows.

Kaiser type on-day inkjet printer Five heads each having a nozzle with a diameter of 60 μm, an ink chamber, and nine exciters are prepared, and each jets an oxidizing agent-containing solution, yellow ink, magenta ink, cyan ink, and black ink. used. FIG. 1 is a plan view of the printer cartridge, FIG. 2 is a side view of the carriage, and FIG. 3 is a front view of one head. The Killer Ridge 1 is scanned over the shuttle 2 (scanned in the direction of the arrow shown in FIG. 1), and an oxidizing agent-containing solution is supplied to its head portion 31P from an oxidizing agent-containing solution cartridge 3P provided on the carriage 1. In addition, ink cartridge 3Y
, 3M, 3C, and 3Bg, ink is supplied to the respective head sections 31Y, 31M, 31C, and 318g,
A voltage is applied to an electrostrictive element (not shown) attached to the head in accordance with the image signal, and an image is formed on the recording paper (recording medium) 4.

In the figure, 5 is a platen.

The heads 31P for jetting the oxidizing agent-containing solution are the ink heads 31Y, 31M, and 31C of the carriage 1.
and 318N, and the recording medium 4
is scanned upward, so the oxidizing agent-containing salt solution is relatively designed to be deposited on the recording medium 4 before the ink. Further, the oxidizing agent-containing solution is ejected in correspondence with the portion where any one of yellow (Y), magenta (H), cyan (C), and black (Bρ) images is to be printed.

When the above printer was used to print on commercially available high-quality paper, clear images with no image bleeding were obtained. Furthermore, even when the obtained image was immersed in water, there was no change in the image at all.

Comparative Example In the example, the same image as in the example was obtained by ejecting only the ink without applying the oxidizing agent-containing solution.

The clarity and image density of this image were inferior to those of the Examples. Also, when it was immersed in water, the image was dissolved in the water. In particular, cyan and black images have almost disappeared.

[Effects] It provides an image with excellent water resistance even when printed on plain paper, fabric, clothing, etc., and by applying the oxidizing agent-containing solution before printing with ink, the image clarity, resolution,
Sharpness and density can also be improved. Furthermore, since a clear image can be obtained even if the ink has a large penetrating effect, it is possible to speed up the drying of the image. In addition, the insolubilization of the dye is carried out in the form of a recording medium, and the dye is kept in a highly soluble state within the recording device, which prevents nozzle clogging.
Printer reliability can be improved.

[Brief explanation of the drawing]

FIG. 1 is a plan view of the printer cartridge of an inkjet recording apparatus used to carry out the inkjet recording method of the present invention, FIG. 2 is a side view of the carriage section, and FIG. 3 is a view of the head (one head). It is a front view. 1... Killeridge 2... Shuttle 3P0.・
Cartridges for oxidizing agent-containing solutions 3Y, 3M, 3C, 38
ρ...Ink cartridge

Claims (1)

[Claims] An inkjet recording method in which an image is formed by ejecting an ink containing a reduced compound of a dye that is soluble in a reduced state and becomes insoluble when oxidized from a nozzle, and the ink is applied to a recording material. An inkjet recording method, characterized in that a liquid containing an oxidizing agent is applied to the portion to which the ink is to be applied, immediately before or after the ink is applied.