JPS61141585A - Ink jet recording method - Google Patents

Abstract

PURPOSE:To enable excellent recording characteristics to be displayed in a wide range of surface tension of a recording liquid and enable to record full- color images with excellent clearness and surface luster, by providing a recording material with a minutely rugged surface and specifying the surface tension of a recording liquid. CONSTITUTION:A support base for an ink-receiving layer consists of a transparent base formed of a polyester resin, a diacetate resin or the like or an opaque base such as a paper, a cloth, a wood sheet, a metallic sheet, a synthetic paper or the like. The ink-receiving layer is formed from polyvinyl alcohol, gelatine, a phenol resin, an alkyd resin or the like. The ink-receiving layer is provided by a method wherein a resin and a filler are dissolved or dispersed in an appropriate solvent to prepare a coating liquid, which is applied to the base, and is dried. The minutely rugged pattern is provided by, for example, embossing by a boarding roll or an embossing means to obtain a height difference between recessed parts and projected parts of 15-200mum. The recording liquid comprises a recording agent such as a dye and a liquid medium component, and is so adjusted to have a surface tension of 20-60dyn/cm at 20 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an inkjet recording method, and particularly to an inkjet recording method using a recording material whose surface is patterned.

[Prior art]

The inkjet recording method uses various ink (recording liquid) ejection methods, such as an electrostatic suction method, a method of applying mechanical vibration or displacement to the recording liquid using a piezoelectric element, and a method of heating the recording liquid to generate temperature and pressure. By using methods such as using
This method is used to record by adhering it to a recording material such as '', but it is attracting attention as a recording method that generates little noise and can perform high-speed printing and multicolor printing.

Inks for inkjet recording are mainly water-based from the standpoint of safety and recording characteristics, and polyhydric alcohols are sometimes added to prevent nozzle clogging and improve ejection stability. many.

Conventionally, the recording material used in this inkjet recording method is a recording material called ordinary paper or inkjet recording paper, which has a porous ink-receiving layer provided thereon. However, as the performance of inkjet recording apparatuses improves and becomes more widespread, such as faster recording and multi-color recording, recording materials are increasingly required to have more sophisticated and wide-ranging properties. In other words, the recording material for inkjet recording to obtain high-resolution, high-quality recorded images must (1) be able to receive ink as quickly as possible on the recording material, and (2) have overlapping ink dots. (3) Ink droplets do not spread on the recording material and the diameter of the ink dot does not become larger than necessary, (4) ) The shape of the ink dot should be close to a perfect circle and its circumference should be smooth; (5) The ink dot should have a high 00 (optical density) and the periphery of the dot should not be blurred. There is.

Furthermore, in order to obtain high-resolution recorded image quality comparable to color recording using multicolor inkjet recording, in addition to the above-mentioned performance requirements, (6) the coloring components of the ink must have excellent coloring properties; (7) ) A glossy surface; (8) A high degree of whiteness.

[Problem that the invention seeks to solve]

However, the reality is that there is still no known recording material that satisfies all of these required performances.

In addition, many of the conventional recording materials for surface image observation have a porous ink receiving layer on the surface, and a method is used in which the recording liquid is received in the porous voids and the recording agent is fixed.
The clarity was low because the recording agent penetrated deeply into the ink-receiving layer.

On the other hand, when the surface of the ink-receiving layer is non-porous, non-volatile components such as polyhydric alcohol 1 in the ink remain on the surface of the recording material for a long time after recording, and the drying and fixing time of the ink increases. Because of their long length, they have the disadvantage that if they come into contact with a recorded image, they stain clothing or damage the recorded image.

An object of the present invention is to provide a novel inkjet recording method that can exhibit excellent recording characteristics (clearness of recorded images) over a wide surface tension range of recording liquid.

Another object of the present invention is to provide an inkjet recording method for recording full-color images with excellent clarity and surface gloss.

[Means for solving problems]

The above and other objects are achieved by the invention as follows.

That is, the present invention provides an inkjet recording method in which recording is performed by attaching small droplets of recording liquid to a recording material, wherein the recording material has a finely uneven shape on its surface; This inkjet recording method is characterized in that the surface tension of the recording liquid at 20° C. is 20 to 60 dyn/cm.

[Effect]

The recording material used in the method of the present invention generally consists of a base material as a support and an ink receiving layer provided on the surface of the base material,
A particularly preferred embodiment is (1) an embodiment in which both the base material and the ink-receiving layer are opaque and the surface has fine irregularities.

(2) An embodiment in which the base material is transparent, the ink-receiving layer is opaque, and the surface has fine irregularities; (3) The base material is opaque, the ink-receiving layer is transparent, and the surface has fine irregularities. Examples include aspects, and the like.

In each embodiment, the ink-receiving layer may also have the function of a support.The base material used as the support for the ink-receiving layer in the present invention may be a conventionally known material such as transparency or opacity. Any of the base materials can be used, and examples of suitable transparent base materials include polyester resins, diacetate resins, triacetate resins,
Examples include films or plates of acrylic resin, polycarbonate resin, polyvinyl chloride resin, polyimide resin, cellophane, celluloid, and glass plates. Preferred examples of the opaque base material include general paper, cloth, wood, metal plate 1 synthetic paper, and the above-mentioned transparent base materials treated to make them opaque by known means.

In addition, the ink receiving layer in the present invention is made of a material that has an affinity for water and polyhydric alcohol, which are liquid components of the ink, such as polyvinyl alcohol, albumin, gelatin, casein, starch, cationic starch, gum arabic, and sodium alginate. Natural resin, polyimide, polyvinylpyrrolidone, quaternized polyvinylpyrrolidone, polyethyleneimine, polyvinylpyricillium/Xride, melamine resin, polyurethane, carboxymethylcellulose,
Polyester, SBR latex, NBR latex,
Synthetic resins such as polyvinyl formal, polymethyl tamacrylate, polyvinyl butyral, polyacrylonitrile, polyvinyl chloride, polyvinyl acetate, phenolic resins, and alkyd resins can be mentioned, and one or more of these materials can be used as desired.

Further, in order to further improve the ink receptivity of the ink receptive layer or to make it opaque, for example, silica, clay, talc, diatomaceous earth may be used.

Fillers such as 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.

The mixing ratio of the resin and filler is filler/resin=3
/2 to 0 is suitable. If this ratio is 0, mode (3)
If this ratio exceeds 372, the gloss will decrease, and the sharpness and contrast will decrease, which is not preferable.

In order to form such an ink-receiving layer, a coating solution is prepared by dissolving or dispersing the above-mentioned resin and, if necessary, a filler in a suitable solvent.

The coating liquid may be applied by one method, for example, a roll coating method.

Rod bar coating method, spray coating method,
It is preferable to apply the mixture onto a substrate by a known method such as air knife coating and then dry it immediately. Other methods may also be used, such as forming a sheet for use in advance and laminating the sheet to the base material.

Furthermore, as a method for providing the unique fine unevenness shape, the molding may be performed by roll or embossing, or by photoetching using a photosensitive resin.

Furthermore, the molding may be performed either before or after the drying step.

The difference in height between the concave portion and the convex portion provided in this way is 1
The range is preferably 5 to 200 ILm, more preferably 20 to 1100 ILm. The difference is 15p
If it is less than m, the effect of unevenness cannot be obtained, and if it is more than 200 pm, the dot shape on the surface becomes poor.

In the present invention as described above, the thickness of the ink receiving layer formed on the base material is usually about 1 to 200 pm, preferably about 5 to 1100 pm.

The blood nose observation has been explained above by exemplifying typical aspects of the recording material used in the present invention, but of course the recording material used in the present invention is not limited to these aspects. In either embodiment, the ink receiving layer contains a dispersant and a fluorescent dye.

Various known additives such as pH adjusters, antifoaming agents, lubricants, preservatives, and surfactants can be included.

On the other hand, the recording liquid used in the method of the present invention is as follows.

It consists of a recording agent such as a dye and a liquid medium component. Generally, when recording using a recording liquid, it is important to match the liquid physical properties of the recording material and the recording liquid, and in particular, select a recording liquid that has good wettability to the recording material. need to use. That is, the critical surface tension of the recording material mentioned above is.

Note that it is better to use a recording liquid with a surface tension close to this value, which is within the range of 40 to 50 dyn/cm; therefore, the recording liquid used in the method of the present invention is
20-60 dyn/cm at 0°C, preferably 35
~55ciyn/cm, particularly preferably 40-50dy
It is necessary to have a surface tension within the range of n/cm. When printing is performed using a recording liquid with a surface tension lower than this range, the wettability to the recording material is good, but the spread of the printed dots increases. Furthermore, when recording with such a recording liquid on a recording material with fine irregularities, the recording liquid runs (bleeds) along the grooves (grooves) on the surface.
The recorded image is distorted in an unexpected way.

On the other hand, when a recording liquid having a surface tension higher than the above-mentioned surface tension range is used, the wettability to the recording material becomes poor, resulting in a decrease in the absorbency and dot density of the recording liquid, which is undesirable.

As the liquid medium component of the recording liquid used in the method of the present invention, not only water units but also preferably a mixture of water and various water-soluble organic solvents are used within a range that satisfies the surface tension of the recording liquid. be done.

Examples of the water-soluble organic solvent include methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, 5ec.
-Butyl alcohol.

Alkyl alcohols having 1 to 4 carbon atoms such as tert-butyl alcohol and isobutyl alcohol; amides such as dimethylformamide and dimethylacetamide;
Ketones or ketone alcohols such as a7tone and diacetone alcohol; ethers such as tetrahydrofuran and dioxane; polyalkylene glycols such as polyethylene glycol and polypropylene glycol; ethylene glycol, propylene glycol, 1,2.6-hexandriol, Alkylene glycols in which the alkyl group has 2 to 6 carbon atoms, such as thiodiglycol, hexylene glycol, diethylene glycol: glycerin, ethylene glycol methyl ether, diethylene glycol methyl (or ethyl) ether, triethylene glycol monomethyl (or ethyl) Examples include lower alkyl ethers of polyhydric alcohols such as ethers.

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. Polyhydric alcohols are particularly preferred because they are highly effective as wetting agents to prevent nozzle clogging caused by evaporation of water in the recording liquid and precipitation of the recording agent.

In order to adjust the surface tension of the recording liquid containing such liquid medium components within the above range, surface tension adjusting agents such as various cationic, anionic or nonionic surfactants, jetanolamine, triethanolamine, etc. are used. can be added.

A solubilizer can also be added to the recording liquid.

Typical solubilizers are nitrogen-containing heterocyclic ketones, whose purpose is to dramatically improve the solubility of recording agents, typically dyes, in solvents. For example, N- Methyl-2-pyrrolidone, 1,3-dimethyl-2
-imidazolidinone is preferably used.

A recording liquid prepared from these components has its own recording characteristics (signal response, droplet formation stability, ejection stability, long-term continuous recording, ejection stability after a long recording pause). properties), storage stability.

Although it has excellent fixing properties to recording materials, it may further contain various additives to further improve these properties. For example, polyvinyl alcohol, cellulose, etc.
Examples include viscosity regulators such as water-soluble resins; pH regulators using buffer solutions.

Further, in order to prepare a recording liquid used in an inkjet recording method of the type in which the recording liquid is charged, a resistivity adjuster such as S-type salts such as lithium chloride, heptammonium chloride, and sodium chloride is added. Note that when applying to an inkjet method that ejects recording liquid by the action of thermal energy, thermal physical property values (e.g. specific heat,
(thermal expansion coefficient, thermal conductivity, etc.) may be adjusted.

Hereinafter, the present invention will be explained in more detail according to Examples.

Example 1 As a base material, NK emboss (matte finish, uneven height difference 40
, cm; manufactured by Nippon Kako Paper Industries), the following composition was applied onto this substrate by air spray so that the dry film thickness was 5 pm, and dried at 80° C. for 10 minutes to obtain a recording material. Ta.

Using the following eight types of ink on the above recording material,
On-demand inkjet recording head that ejects ink using a piezo vibrator (ejection orifice diameter 60I)
Ltx, piezo vibrator drive voltage 70V, frequency 2KHz
) Inkjet recording was carried out using a recording device having:

Ink No., A: Surface tension is approximately 80 d 11 n /
Cm (composition) Ethylene glycol 30j4i [1 water

70//C, 1, Direct Blue 86 2//Ink No., B: Surface tension is approximately 55 dyn/c
m (composition, composition) ethylene glycol 30 parts water
7 o
〃Acetyl/-, II/EH (10% water) 0.0
5 // (Surfactant; manufactured by Yoken Fine Chemical Co., Ltd.)
C, 1, Direct Blue 86 2//Ink No.
, C: Surface tension is approximately 50 dyn/cm (composition) Ethylene glycol 30 parts by weight Water
70//
Acetinol EHO, 07// C, 1, Direct Blue 86 2// Ink No.
, D: surface tension of approximately 45 dyn/cm (
Composition) Ethylene glycol 30 parts by weight Water
70
〃Acetinol EH (10% water) 0.5//C,
1, Direct Blue 86 2 Ink No. E:
Surface tension is approximately 40 dyn/cm (composition) Ethylene glycol 30 parts by weight Water
70
//Acetinol EH (10% water) 1,17/C
, 1, Direct Blue 862// Ink No., F: Surface tension is approximately 35 d yn /
cm (composition) Propylene glycol monoethyl ether 30 parts by weight water
701I Acetinol EH (10% water) 1.0/
/C, 1, Direct Blue 862// Ink No., G: Surface tension is approximately 30 d yn /
cm (composition) Propylene glycol monoethyl ether 50 parts by weight water
50//Acetinol EH (10% water) 0.1
//C, 1, Direct Blue 862// Ink No., H: Surface tension is approximately 65 d yn /
cm (composition) C, 1, Direct Blue 86 2 parts by weight water
100//Example 2 As a base material, SK emboss (wire type, uneven height difference 20
A recording material was obtained in the same manner as in Example 1, except that JLm (manufactured by Sanyo Kokusaku Pulp) was used, and inkjet recording was performed.

Example 3 As a base material, KS emboss (grain type, height difference of unevenness 30
Example 1 except that pm; Kanzaki Paper Industries Co., Ltd.) was used.
A recording material was obtained in the same manner as above, and inkjet recording was performed.

Example 4 OK Coat (manufactured by Tamago Paper Co., Ltd.) was used as a base material, and the following composition was applied onto this base material using a bar coater method so that the dry film thickness was 10 μm, and the mixture was heated at 100°C for 5 minutes. After drying, a mesh pattern was formed on the surface using a roll to obtain a recording material having an uneven height difference of 801 Lin.

Polyvinyl alcohol (PVA-220; manufactured by Kuraray) 8 parts Titanium oxide (Tie Bake W-10, manufactured by Ishiya Sangyo) 2 parts water
90
Inkjet recording was performed on this recording material in the same manner as in Example 1.

Comparative Example 1 A recording material was obtained in the same manner as in Example 4, except that the molding was not performed using a roll, and inkjet recording was performed.

Comparative Example 2 Inkjet recording was performed using the OK coated paper used in Example 4 as a recording material.

The evaluation results of the above Examples and Comparative Examples are shown in Tables 1 to 5. Each evaluation item in Tables 1 to 5 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 was measured for black dots using Sakura Microdensidometer PDM-5 (manufactured by Konishiroku Photo Industry Co., Ltd.) by applying JIS K 7505 to printed microdots.

(3) The dot shape is determined by observing the printed dot under a microscope.
A perfectly round shape was designated as 0, a shape with a jagged edge due to feathering etc. was designated as ×, and a value in between was designated as Δ.

(4) The panel test was conducted as a comprehensive image evaluation.

A 1010x20 illustration was printed and the test was conducted by 8 men and 7 women.The following two questions were asked, and if 10 or more people answered "yes", it was marked as 0, otherwise it was marked as ×.

■Visual observation: ``Contrast and brightness'' (@Can you feel a warm, unique texture to the touch?) Table 1 (Ink fixing time) Table 2 (Dot density) Table 3 (Dot shape) [Effects] According to the inkjet recording method of the present invention, even if the recorded images are overlapped immediately after printing, there is point contact, so there is no staining due to clothing, etc., and different colored recording liquid is removed within a short time. Even if the recording liquid adheres to the same spot repeatedly, there is no flow out or seepage phenomenon of the recording liquid, and images with clear and excellent color development can be obtained.Furthermore, it can be applied over a wide range depending on the recording liquid ejection method, recording purpose, etc. Even when a recording liquid having surface tension is used, these excellent properties can be exhibited at all times, making it an excellent inkjet recording method for color recording.

Claims (2)

[Claims] (1) In an inkjet recording method in which recording is performed by attaching small droplets of recording liquid to a recording material, the recording material has a finely uneven shape on its surface, and the recording material An inkjet recording method characterized in that the surface tension of the liquid at 20°C is 20 to 60 dyn/cm. (2) The inkjet recording method according to claim 1, wherein the height difference between the concave and convex portions of the unevenness on the surface of the recording material is 15 to 200 μm.