JPS61118285A - Ink jet recording system - Google Patents

Abstract

PURPOSE:To obtain picture excellent in clearness and storability of dye colors by using a recording material containing less than a specific amount of active acids to be stayed in recorded pictures for ink jet recording. CONSTITUTION:When dyes containing water-soluble or hydrophilic groups, e.g., sulfonic acid, carboxyl, amino, hydroxyl, or salts of these, which are used in ink, are used for printing on recording materials, if the recording face of the recording material contains too much acids, the water-soluble or hydrophilic groups of the dye are affected. In short, the electron density of the chromophores of dye is changed, and the color-forming property of the dye is damaged to cause discoloration or fading. In forming ink-receiving layers on plastics as base materials for this reason, neutral or basic water-soluble or hydrophilic resins containing no sulfonic acid or carboxylic acid group and used, and these are neutralized as needed to lower their acidity.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an inkjet recording method that provides recorded images with excellent color development, sharpness, storage stability, etc.

(Prior Art) Inkjet recording methods include various ink (recording liquid) ejection methods, such as an electrostatic suction method, a method that applies mechanical vibration or displacement to the ink using a piezoelectric element, and a method that causes the ink to foam by heating it. , by using a method that utilizes the pressure, small droplets of ink are generated and made to fly, and some or all of them adhere to a recording material such as paper to perform recording, but it does not generate noise. It is attracting attention as a recording method that allows high-speed printing and multi-color printing.

Ink for inkjet recording is mainly composed of a water-soluble dye as a recording agent and a liquid medium.

Water-soluble dyes, preferably acidic dyes or direct dyes, are used as recording agents in terms of safety, light resistance, recording properties, etc., while water is mainly used as liquid media in terms of safety and recording properties. The main component is used, and polyhydric alcohols and the like are often added to prevent nozzle clogging (I) and to improve ejection stability. In addition, the recording material used in the inkjet recording method has conventionally been a recording material consisting of a base material called ordinary paper or inkjet recording paper on which a porous ink-receiving layer is provided. . However, as the performance of inkjet recording apparatuses improves and becomes more widespread, such as faster recording speeds and multicolor recording, more sophisticated and wide-ranging properties are being required of recording materials.

That is, ink absorption is as quick as possible;
It is necessary that the ink bleeds appropriately. Furthermore, in order to carry out color inkjet recording using color inks, a recording material that is particularly excellent in color development and sharpness of the dye used as the recording agent and provides high chromaticity is required.

Furthermore, recorded images recorded by inkjet recording are required to have good image storage stability, durability, and the like.

(The problem that the invention is trying to solve) However,
The reality is that a recording method that satisfies all of these required performances and provides a recorded image is not yet known.

Most of the recording materials used in conventional inkjet recording methods have a porous ink-receiving layer on the surface of the base material, such as paper or plastic film, and the ink is absorbed into the porous voids to absorb the dye. A method of fixation is used.

When inkjet recording is performed on such recording materials, there are drawbacks such as in some cases the dye changes and the color development is reduced, and in extreme cases the hue of the dye changes or the color disappears completely. .

Further, even if good printing is possible during recording, there are still drawbacks such as discoloration or fading when the recorded matter is stored for a long period of time.

Therefore, an object of the present invention is to provide an inkjet recording method that uses a water-soluble dye as a recording agent, and that provides an image that is particularly excellent in dye color development and clarity, and also has excellent storage stability. be.

The inventors of the present invention have conducted intensive studies on phenomena such as decreased color development, discoloration, and fading of dyes during inkjet recording and after recording, and have found that these phenomena are caused by active acids present in the recording material. The present invention was obtained based on the knowledge that this is caused by the above.

(Disclosure of the Invention) That is, the present invention provides an inkjet recording method in which an ink containing a water-soluble dye is used as a recording agent, and recording is performed by attaching small droplets of the ink to a recording material. Recording materials.

This inkjet recording method is characterized in that the recording material contains 0.01 gram equivalent or less of active acid per 1 m' of recording surface.

To explain the present invention in more detail, the main feature of the present invention is that when obtaining a recorded image by inkjet recording,
The point is to use a recording material in which the amount of active acid present on the recording surface is below a specific value.

That is, according to the knowledge of the present inventor, conventional recording materials,
For example, in the case of paper, fillers such as various sizing agents are contained, and in the case of recording materials with ink receiving layers provided on paper or plastic films, those ink receiving layers are
It is made of water-soluble or wood-philic resins with acidic groups, and various additives are added to it, and the acidic components in these water-soluble or wood-philic resins and additives are As a result, various problems such as the coloring property of the dye, discoloration, fading, etc., as mentioned above, occur.

The specific recording material used in the present invention and which mainly characterizes the present invention is the coloring property of the dye of the ink applied by the inkjet recording method.

It does not cause problems such as discoloration or fading in the long term,
These excellent properties are achieved when the recording material is paper.
This is achieved by neutralizing the acidity of the surface, and by using a plastic film such as paper, polyester, or acetate as the base material, and adding the necessary additives to the surface with a water-soluble or hydrophilic resin as the main component. In addition, when an ink-receiving layer is formed, the amount of active acid contained in the ink-receiving layer is 0.01 gram equivalent or less, preferably 0.0
This can be achieved by setting the amount to 0.05 gram equivalent or less, more preferably 0.001 gram equivalent or less. Specifically, when forming an ink-receiving layer on a plastic base material, a neutral or basic water-soluble or wood-philic resin that does not have sulfonic acid groups or carboxylic acid groups is used; A method that does not use an acidic substance as an agent, a method that when using a resin having an acidic group as described above, a method that reduces the acidity by neutralizing it as necessary before use, or a method that reduces the acidity of the ink-receiving layer. A method can be adopted in which the calendar is formed and then neutralized with ammonia gas or the like.

The amount of active acid referred to in the present invention was measured by the following method. Cut 1 m' of recording surface of the recording material into small pieces of about 1 c, and disperse them in ti pure water using zero-order NaOH.
, 0.01 gram equivalent of a strong alkali such as KOH is added.

After adding the alkali, measure the pH after stirring for several hours (until there is no pH change), and if the final pH is 8.5 or higher, the active acid concentration per 1 m'' of recording surface of the recording material is determined. The amount is assumed to be 0.01 gram equivalent or less. According to this measurement method, it is possible to measure not only the amount of water-soluble acid but also the amount of solid acid in the filler and water-insoluble organic acid in the resin.

The recording material for inkjet recording as described above used in the method of the present invention may be prepared by any conventionally known method, except for taking into account the above points.For example, paper called inkjet recording paper or various Any known recording material such as a recording material having an ink absorbing layer provided on a support can be used. 1
As an example, to further explain the recording material having an ink-receiving layer, as a base material that can be used as a support, any conventionally known base material such as transparent or opaque can be used. Suitable examples include polyester resins, diacetate resins, triacetate resins, and acrylic resins.

Examples include films or plates of polycarbonate resins, polyvinyl chloride resins, polyimide resins, cellophane, celluloid, and glass plates. Preferred opaque substrates include, for example, general paper, cloth,
In addition to wood, metal plate 1, synthetic paper, etc., the above-mentioned transparent substrates may be made opaque by known means. Preferably, such substrates have a thickness in the range of about lθ to 200 pm.

The ink-receiving layer provided on the base material is mainly formed from a hydrophilic material that can accept water-based ink, and preferred examples of such materials include albumin, gelatin, casein, starch, and cationic starch. , natural resins such as gum arabic, sodium alginate, polyamide, polyacrylamide, polyvinylpyrrolidone,
Quaternized polyvinylpyrrolidone, polyethyleneimine, polyvinylpyricillium halide, melamine resin, polyurethane, carboxymethyl cellulose, polyvinyl alcohol, cation-modified polyvinyl alcohol, polyester, polyacrylic acid, acrylic acid copolymer, maleic acid copolymer, etc. One of these materials is synthetic resin.
More than one species may be used as desired.

Furthermore, in order to reinforce the strength of the ink-receiving layer and/or improve the adhesion with the base material, SBR latex, NOR latex, polyvinyl formal, polymethyl methacrylate, polyvinyl butyral, polyacrylonitrile, polyvinyl chloride may be added as necessary. , polyvinyl acetate, phenol resin, alkyd resin, etc. may be used in combination.

In addition, in order to improve the ink absorbency of the ink-receiving layer, various fillers such as silica, clay, etc. are added to the ink-receiving layer.
Fillers such as talc, diatomaceous earth, calcium carbonate, calcium sulfate, barium sulfate, aluminum silicate, synthetic zeolites, alumina, zinc oxide, lithopone, satin white, and the like can also be dispersed in the ink-receiving layer.

As a method for forming such an ink-receiving layer, a coating liquid is prepared by dissolving or dispersing the above-mentioned polymers alone or in a mixture in an appropriate solvent, and the coating liquid is coated by, for example, a roll coating method, It is preferable to apply the coating onto the substrate by a known method such as the Rottbar coat ink method, the air knife coating method, or the spray coating method, and then dry it immediately. A single ink-receiving layer is formed by a known method such as the T-die method, and the ink-receiving layer is used to have the function of a support, or
The ink-receiving layer may be formed on the substrate by laminating the sheet onto the substrate, or by hot/h melt coating the polymer material.

The thickness of the ink-receiving layer formed in this way may be within a range capable of receiving ink, and although it depends on the amount of ink to be recorded, there is no particular limitation as long as it is 0.1 gm or more. For practical purposes, a range of 0.5 to 30 gm is suitable.

In the method of the present invention, the ink itself applied to the above-mentioned specific recording material by the inkjet recording method may be any known ink. Examples include direct dyes, acid dyes, basic dyes, reactive dyes, etc. It is a water-soluble dye,
Inks that are particularly suitable as inks for inkjet recording systems and that, in combination with the above-mentioned recording materials, provide images that satisfy the required performance such as color development, clarity, stability, and luminosity include, for example: C, 1, Direct Black 17.19.32.51.71.108.146, C,
1, Direct Blue 6.22.25.71.86.9
0.106.199;C.

■, Direct Red 1.4.17.28.83;c,
1. Direct Niro 12.24.26.86.98.
L42. C, 1, Direct Orange 34.39.44
．． 46.60; C, I, Gyleft Violet 47
．． 48; C, 1, Direct Brown 109. c.1.
Direct Green 59. C, 1, acid black 2
．． 7.24.26.31.52.63.112.118
;C, 1, acid blue 9.22, 40.59.93
．． 102.104.113.117.120.167.
229.234. C, 1, Acid Red 1, 6.32
．． 37.51.52.80.85.87.92.94,
115,180.25 '6.317.315. C
, 1, Acid Yellow 11.17.23.25.29.
42.61.71, C, 1, Acid-2 Orange 7.1
9; C, I.

Examples include direct dyes and acid dyes such as Acid Violet 49, and others such as C, 1, Basic Black 2. C
, 1, Basic Blue 1.3.5.7.9.24.2
5.26.28.29; C, 1, Basic Red 1.
2,9.12.13.14.37. Examples include C,1, Basic Violet 7.14.27; C,1, Food Black 1°2. The above examples of dyes are particularly preferable for inks applicable to the recording method of the present invention, but dyes for inks used in the present invention are not limited to these dyes.

Such water-soluble dyes are generally used in conventional inks in proportions ranging from about 0.1 to 20% by weight.

The solvent used in the ink composition used in the present invention is water or a mixed solvent of water and a water-soluble organic solvent, and a particularly preferable one is a mixed solvent of water and a water-soluble organic solvent. It contains a polyhydric alcohol which has the effect of preventing ink from drying. In addition, as water, it is preferable to use deionized water rather than ordinary water containing various ions.As for the water-soluble organic solvent used in combination with water, for example, methyl alcohol, ethyl alcohol, etc. , C1-4 alkyl alcohols such as n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, 32C-butyl alcohol, tert-butyl alcohol, and isobutyl alcohol; amides such as dimethylformamide and dimethylacetamide; Ketones or keto alcohols such as acetone alcohol: Ethers such as tetrahydrofuran and dioxane: Polyalkylene glycols such as polyethylene glycol and polypropylene glycol: ethylene glycol, propylene glycol, butylene gelicol, triethylene glycol, 1.2.6- Alkylene glycols in which the alkylene group contains 2 to 6 carbon atoms, such as hexandriol, thiodiglycol, hexylene glycol, diethylene glycol; glycerin; ethylene glycol methyl (or ethyl) diter, diethylene glycol methyl (or ethyl) Examples include lower alkyl ethers of polyhydric alcohols such as ether and triethylene glycol monomethyl (or ethyl) ether: N-methyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, and the like. Among these many water-soluble organic solvents, polyhydric alcohols such as diethylene glycol and lower alkyl ethers of polyhydric alcohols such as triethylene glycol monomethyl (or ethyl) ether are preferred.

The content of the water-soluble organic solvent in the ink is generally in the range of 0 to 95% by weight, preferably 10 to 80% by weight, and more preferably 20 to 50% by weight based on the total weight of the ink. be.

In addition to the above-mentioned components, the ink used in the present invention may optionally contain a surfactant, a viscosity modifier, a surface tension modifier, and the like.

In the method of the present invention, the inkjet recording method for performing recording by applying the above-mentioned ink to the above-mentioned specific recording material is such that the ink composition is effectively released from the nozzle and onto the recording material, which is a projectile object. Any method may be used as long as it can apply ink, and representative methods include, for example, IEEE Transaction
s on Industry Application
ons Vol, JA-13, No. 1 (1977
(February/March issue), Nikkei Electronics.

The methods described above are suitable for the method of the present invention.To explain some of them, there is an electrostatic attraction method, which uses a nozzle and an accelerating electrode placed in front of the nozzle. There is a method in which a strong electric field is applied between the ink particles and the ink is drawn out one after another from a nozzle, and an information signal is given to the deflection electrodes while the drawn ink composition flies between the deflection electrodes to record the ink particles. There is a method of ejecting ink particles in response to an information signal without deflection, and either method is effective for the textile printing method of the present invention.

The second method is to apply high pressure to the ink with a small pump and mechanically vibrate the nozzle with a crystal oscillator, etc. to forcibly eject minute ink particles, and the ejected ink particles At the same time as the injection, it is charged according to the information signal. When the charged ink particles pass between the deflection electrode plates, they are deflected according to the amount of charge. Another method using this method is called the microdot inkjet method. In this method, ink pressure and excitation conditions are kept within a certain range of values, and two types of ink droplets, large and small, are produced from the nozzle tip. is generated, and only these medium- and small-diameter droplets are used for recording. The feature of this method is that it is possible to obtain a group of minute droplets even with a conventionally large nozzle diameter.

A third method is a piezo element method, in which a piezo element is used as a pressure means for applying pressure to the ink, instead of a mechanical means such as a pump as in other methods.

This method applies an electric signal to a piezo element to cause mechanical displacement, thereby applying pressure to the ink and ejecting it from a nozzle.

In addition, an inkjet method is disclosed in Japanese Patent Application Laid-Open No. 54-51837, in which ink subjected to the action of thermal energy undergoes a sudden change in volume, and the acting force due to this state change causes the ink to be ejected from a nozzle. can also be used effectively.

According to the method of the present invention as described above, when recording is performed with an ink using a water-soluble dye, particularly an acid dye or a direct dye in a conventional inkjet recording method, the applied dye develops color during or after recording. However, according to the present invention, by using a specific recording material, the recording material is The dye in the ink applied to the recording material does not inhibit color development, change color, or fade unlike conventional recording materials, and provides recorded images with excellent clarity and storage stability. 0 Such WJ in the present invention can be
It is believed that the remarkable effects are achieved for the following reasons.

In other words, dyes used in inks often contain sulfonic acid groups, carboxyl groups, amino groups, hydrophilic groups, or other water-soluble or wood-philic groups in the dye molecules. When a dye is applied to a recording material and the recording surface of this recording material contains an excessive amount of acid or base, especially an acid, these water-soluble or hydrophilic groups are affected by these acids and their This is because the electron density of the chromophore and auxochrome of the dye changes as a result, and in the present invention, by using the specific recording material of the present invention, it is possible to prevent the above change in the electron density of the dye. It is something that

Next, the present invention will be explained in more detail with reference to Examples. In the text, parts or percentages are based on weight.

Example 1 General high-quality paper (Kusankan, manufactured by Dezumi Kokusaku Pulp) was used as a base material, and the following composition was applied using a bar coater method to a dry film thickness of 10 JLm, and dried at 100°C for 15 minutes. It was used as a recording material.

1.1 Inbutylene/maleic anhydride copolymer resin (Inpan 10: manufactured by Clarei Soprene Chemical) 5 parts NaOH
(90% of the neutralization amount of the above resin) 2.2 parts silica, Pusil E200 manufactured by Nippon Silica) 20 parts water

738B On-demand inkjet recording head (discharge orifice diameter: 60 l, piezoelectric vibrator drive voltage: 70V, frequency 2
Inkjet recording was performed using a recording device having a high frequency (KHz).

Yellow ink (composition) C, 1, Direct Yellow 86 2 parts diethylene glycol 20 parts polyethylene glycol #2
00 10 parts water
70 parts Red ink (composition) c, r, acid red 35 2 parts diethylene glycol 20 parts polyethylene glycol #
200 10 parts water
7 part o Blue ink (composition) c, r, direct blue 86 2 parts diethylene glycol 20 parts polyethylene glycol #2
00 10 parts water
70 parts Black ink (composition) C, 1, Acid Black 26 2 parts diethylene glycol 20 parts polyethylene glycol #2
00 10 parts water
70 copies The evaluation results of the above recording material are shown in Table 1.

Each evaluation item in Table 1 was measured according to the following method.

(1) Ink fixation time was measured by measuring the time required for the ink to dry and stop adhering to the finger when touching the recorded image after recording.

(2) Dot density is determined using Sakura Microdensidometer PD by applying JISK75Q5 to printed microdots.
The black dots were measured using M-5 (manufactured by Konishiroku Photo Industry).

(3) The amount of active acid in the recording surface 1rrr' of the recording material is determined to be Na0HO by the method described in this specification.

It is indicated by the pH when 0.01 gram equivalent is added.

(4) Color development is determined by visually comparing the color of the ink when it is dropped onto a white tile and the color when it is recorded on the recording material, and the hue is markedly different, or
A case where the coloring property clearly decreased was given as X, a case where there was almost no change was given as o, and a case between O and × was given as Δ.

Example 2 Using a PET film (Q80: manufactured by Toshi) as a base material, the following composition was coated by a bar coater method to a dry film thickness of 6 JLm, and dried at 100°C for 10 minutes to form a recording material. It was used as a material.

Methyl vinyl ether/maleic anhydride copolymer resin (GANTREZ AN-149, manufactured by GAF) 5
Part NaOH (neutralization amount of the above resin) 2.5 parts Water
92.5 copies of this recording material was subjected to recording in the same manner as in Example 1 to perform recording according to the present invention. The evaluation results are shown in Table 1.

Comparative Example 1 The same procedure as in Example 1 was conducted except that the following composition was used as the coating composition.

Isopan lOS part Nibcil E200 20 parts DMF
75 parts Comparative Example 2 The same procedure as in Example 2 was carried out except that the following composition was used as the coating composition in Example 2.

GANTREZ AN-1495 part water
95 copies (margins below) List-U Niman Catfish L J! L

Claims (2)

[Claims] (1) In an inkjet recording method in which an ink containing a water-soluble dye is used as a recording agent and recording is performed by attaching small droplets of the ink to a recording material, the recording material has a recording surface of 1 m^ An inkjet recording method characterized in that the recording material contains an active acid of 0.01 gram equivalent or less per 2 grams. (2) The method according to claim (1), wherein the water-soluble dye is an acid dye and/or a direct dye.