JPS61290084A - Ink jet recording method - Google Patents

Abstract

PURPOSE:To enhance contrast and obtain excellent resolution and gradation properties, by specifying the relationships between the diameter of ink droplets, the thickness of an ink-receiving layer of a recording material, ink absorptivity of the ink-receiving layer and the like. CONSTITUTION:In an ink jet recording method in which recording is conducted by adhering ink droplets to a recording material comprising a base and an ink-receiving layer provided on the base, the diameter d1 of ink droplets and the thickness d2 of the ink-receiving layer are so set as to satisfy the Formula (1), wherein B is the void ratio of the ink-receiving layer, and S is the rate of swelling of the ink-receiving layer with an ink. For example, yellow, magenta, cyan and black color inks are used, and the voltage to be applied to a head is varied to thereby vary the diameter d1 of the ink droplets, thereby producing gradations. Conversely, the thickness d4d2 of the ink-receiving layer, the void ratio B and the rate of swelling S of the layer with the ink are previously set in predetermined ranges, and the jetting pressure of an ink jet recorder, the diameter of a nozzle or the like is varied to conform the diameter d1 of the ink droplets to the inequality (1).

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 that provides a recorded image with excellent resolution, high contrast, and excellent gradation.

(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 heats the ink to foam it. This method utilizes the pressure to generate and fly ink droplets, and some or all of them adhere to a recording material such as paper to perform recording, but it generates less noise. It is attracting attention as a recording method that allows high-speed printing and multicolor 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. Main ingredients are used, and polyhydric alcohols and the like are often added to prevent nozzle clogging and improve ejection stability.

In addition, as recording materials used in inkjet recording methods, conventionally used are ordinary paper and recording materials called inkjet recording paper, which are formed by providing a porous ink-receiving layer on paper. However, as the performance of ink jet recording apparatuses increases and becomes more widespread, such as faster recording speeds and multi-color recording, more sophisticated and wide-ranging properties are being required of recording materials.

That is, it is necessary that the ink be absorbed as quickly as possible and that the ink bleed be appropriate. 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 excellent image storage stability, durability, water resistance, light resistance, and the like.

In addition, in order to make a recorded image by an inkjet recording method excellent in gradation and resolution like a photograph, it is necessary to determine the diameter of the ink droplet applied to the recording material according to the image signal, that is, the amount of ink. It is necessary to change the density (0, D,) of the recorded image by changing the amount of ink printed on the recorded area using a dithering method or the like.

To change the amount of ink, image processing is performed, such as changing the amount of ink ejected by changing the voltage applied to the recording head that ejects ink, or printing two or more ink on the same location. ing.

(The problem that the invention is trying to solve) However,
The reality is that there is still no known recording method that provides a recorded image that satisfies all of these required performances.

In particular, in order to obtain a recorded image with high contrast and excellent resolution and gradation, various image processing methods such as those described above are required. In other words, there is no linear relationship between density and density, and in areas where particularly high density is required, the amount of ink applied is large, and the ink cannot be absorbed by the ink receiving layer in time, causing ink to flow out or other ink dots to form. As a result, a recorded image with high resolution and fine gradation could not be obtained.

Therefore, an object of the present invention is to provide an inkjet recording method that provides a recorded image with high contrast, excellent resolution, and excellent gradation.

As a result of intensive research to solve the above-mentioned drawbacks of the conventional technology, the present inventor found that in order to achieve the above-mentioned object in an inkjet recording method, it is impossible to simply change the amount of ink as in the past. The present invention has been made possible by finding that this is possible by establishing a specific relationship between the diameter of the ink droplet, the thickness of the ink-receiving layer of the recording material, the ink-absorbing property of the ink-receiving layer, etc. completed.

(Disclosure of the Invention) That is, the present invention provides an inkjet recording method in which recording is performed by depositing small droplets of ink on a recording material consisting of a base material and an ink receiving layer provided on the Omura. This inkjet recording method is characterized in that the diameter (d1) of the droplet and the thickness (d2) of the ink receiving layer are within the range expressed by the following formula (1).

However, B in the above formula (1) represents the porosity of the ink-receiving layer, and S represents the swelling rate of the ink-receiving layer due to ink. Further, in a location where two or more n dots are recorded in the same location, a value expressed by the following equation (2) is used as dl.

To explain the present invention in more detail, the present invention is characterized in that when carrying out an inkjet recording method, it not only changes the ink ejection amount of the recording device and the properties of the ink, but also changes the recording material selected according to the ink ejection amount. The relationship between the diameter of the ink droplet and the thickness of the ink-receiving layer of the recording material can be determined by changing the ink ejection amount of the recording device and the properties of the ink according to the properties of the recording material. The object of the present invention is achieved for the first time with such a configuration.

The recording material used in the present invention generally consists of a base material as a support and a recording surface provided on the surface of the base material, that is, an ink receiving layer, and is generally a transparent or opaque base material. It can be obtained by forming an ink-receiving layer made of a water-soluble to hydrophilic polymer.

The water-soluble polymeric hydrophilic polymer used to form the ink-receiving layer of the recording material in the present invention may be any conventionally known water-soluble to hydrophilic polymer.

Examples of such water-soluble to hydrophilic polymers include:
Albumin, gelatin, casein, starch, cationic starch, gum arabic, natural resins such as sodium alginate, polyvinyl alcohol, polyacrylamide, polyvinylpyrrolidone, quaternized polyvinylpyrrolidone, polyethyleneimine, polyvinylbilicylium halide, melamine resin, polyacetic acid Partially hydrolyzed vinyl, partially or fully saponified copolymers of vinyl acetate and other monomers, polyvinyl ether, copolymers of vinyl ethers such as methyl vinyl ether and other monomers, polymers of vinyl carboxylic acids such as acrylic acid, or vinyl Copolymers of carboxylic acids and other monomers, water-soluble celluloses such as hydroxyethyl cellulose and carboxymethyl cellulose, water-soluble polyurethanes, polyamides,
It is a synthetic resin such as polyester. The water solubility of these ~
By selecting and combining hydrophilic polymers, the porosity and swelling rate of the formed ink-receiving layer can be adjusted.

Furthermore, in order to reinforce the strength of the ink-receiving layer and/or improve the adhesion with the base material, and further to change the porosity and swelling ratio of the ink-receiving layer, SBR latex or NBR latex may be added as necessary. , polyvinyl formal, polymethyl methacrylate, polyvinyl butyral, polyacrylonitrile, polyvinyl chloride, polyvinyl acetate, phenol resin, alkyd resin, and other hydrophobic resins may be used in combination.

In addition, various fillers such as silica, clay, talc, diatomaceous earth, calcium carbonate, calcium sulfate, barium sulfate, etc. Fillers such as , aluminum silicate, synthetic zeolites, alumina, zinc oxide, lithopone, satin white, etc. can also be included.

In the present invention, the base material used as a support for the ink-receiving layer made of the above-mentioned water-soluble to hydrophilic polymers is as follows:
Any conventionally known base material, such as transparency or opacity, can be used.

Suitable examples of transparent substrates include films such as polyester resins, diacetate resins, triacetate resins, acrylic resins, polycarbonate resins, polyvinyl chloride resins, polyimide resins, cellophane, celluloid, etc. Examples include plates and glass plates.

If such a transparent base material is used and the ink-receiving layer is also formed to be transparent, it becomes a translucent recording material used for observing a projected image using an OHP (overhead projector) or the like.

It is desirable that such a light-transmitting recording material has a linear transmittance of at least 2%, preferably 10% or more.

In addition, due to opacity, (preferred materials include:
For example, in addition to general paper, cloth, wood, metal plates, synthetic paper, etc.
Examples include those obtained by processing the above-mentioned transparent base material to make it opaque by known means.

If such an opaque base material is used, it becomes a recording material used for observing a surface image.

A method for forming an ink-receiving layer on at least one surface of such a base material is to prepare a coating liquid by dissolving or dispersing the above-mentioned water-soluble to hydrophilic polymers alone or in a mixture in an appropriate solvent. and a method in which the coating liquid is applied onto the substrate by a known method such as a roll coating method, a rot bar coat ink method, an air knife coating method, a spray coating method, etc., and then quickly dried, or A single ink-receiving layer may be formed from the above-mentioned materials by a known method such as a heat stretching method or a T-die method, and the ink-receiving layer may be used so as to have the function of a support. The ink-receiving layer may be formed on the substrate by, for example, laminating the sheet onto the substrate or hot-melt coating the polymer material.

The thickness of the ink receiving layer formed as described above can be arbitrarily changed from O, OI ILm to several hundred 7 tm by a conventionally known method.

In addition, in the present invention, the "porosity (B)" of the ink receiving layer is
' means a lever that changes the apparent volume of the ink-receiving layer by ■2 and the true volume by ■1, B = (V2- V+ )/
It is represented by V2.

Specifically, an ink-receiving layer is formed on the surface of a substrate 1 that does not absorb solvents, such as a glass plate or aluminum foil, the apparent volume 2 is measured from the thickness and area, and then the ink-receiving layer is It can be obtained by measuring the true volume v1 of the ink-receiving layer using an inert solvent (eg, benzene, ethanol, etc.).

In addition, the "swelling rate (S)" of the ink receiving layer in the present invention is
)" refers to a binder component that excludes non-swellable materials (e.g., pigments) from the constituent components of the ink-receiving layer. An ink-receiving layer with a size of 5#Lm was formed, a 10cm square frame was placed on top of this, and 20ml of ink was placed inside.The ink was removed after 1 minute, and the ink adhering to the surface was removed. It can be calculated from the following formula.

In the above formula, W represents the amount of weight increase, and ρ represents the density (specific gravity) of the ink.

The thickness, porosity, and swelling rate of the ink-receiving layer of the recording material described above can be easily changed by selecting and combining the polymers used, or by using various additives when forming the ink-receiving layer. I can do it.

In the method of the present invention, the components of the aqueous ink applied to the recording material as described above by the inkjet recording method may be any known components.

For example, dyes include water-soluble dyes such as direct dyes, acid dyes, basic dyes, reactive dyes, and food colorings, which are particularly suitable as inks for inkjet recording methods and are compatible with the above-mentioned recording materials. Examples of combinations of C, 1, Direct Black 17.19.32.51.
71.108.146; C, 1, Direct Blue 6.22.25.71.86
．． 90,106.199: C,1, Direct Red l, 4.17.28.83; C,1, Direct Yellow 12.24.26.86.9
8.142; C, 1, Direct Orange 34.39.44°46.
60; C, 1, Direct Violet 47.48; C, 1,
Direct Brown 109; C,1, direct dye such as Direct Green 59, C,1
, Acid Black 2.7.24.26.31.52.
63.112.118; C, r, acid blue 9, 22.40.59.93.
102.104.113.117.120.167.2
29.234; C, 1, Acid Red l, 6.32.37.51.5
2.80.85.87.92.94.115.180.
256.317.315;C,! , acid yellow 11
．． Acidic dyes such as 17.23.25.29.42.61.71; C,1, Acid Orange 7.19; C,1, Acid Violet 49 are preferred; others, (, I, Basic Black 2; C, 1, Basic Blue l, 3.5.7.9.24.
25.26.28.29; C, 1, Basic Red 1.2.9.12.13.1
4,37; C,1, Basic Violet 7.14.27C,1
, food blank 1.2, etc. can also be used.

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 a proportion of about 0.1 to 20% by weight in conventional inks, and this range may also be used in the present invention.

The solvent used in the ink used in the present invention is a mixed solvent of water and a water-soluble organic solvent, and a particularly preferred one contains a polyhydric alcohol-based organic solvent that has an effect of preventing drying of the ink as a water-soluble organic solvent. It is something to do.

Further, as water, it is preferable to use deionized water rather than ordinary water containing various ions.

Examples of water-soluble organic solvents used in combination with water include methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, 5ec-butyl alcohol, tert-butyl alcohol, and isobutyl alcohol. carbon number 1~
4 Alkyl alcohols Amides such as dimethylformamide and dimethylacetamide; Ketones or keto alcohols such as acetone and diacetone alcohol; Ethers such as tetrahydrofuran and dioxane; Polyalkylene glycols such as polyethylene glycol and polypropylene glycol 1 ethylene Alkylene glycols in which the fullkylene group contains 2 to 6 carbon atoms, such as glycol, propylene glycol, butylene gelcol, triethylene glycol, 1,2,6-hexandriol, thiodiglycol, hexylene glycol, diethylene glycol; Glycerin; lower alkyl ethers of polyhydric alcohols such as ethylene glycol methyl (or ethyl) ether, diethylene glycol methyl (or ethyl) ether, 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 alcohol-based organic solvents such as diethylene glycol and lower alkyl ethers of polyhydric alcohol-based organic solvents such as triethylene glycol monomethyl (or ethyl) ether are preferred.

In addition to the above-mentioned components, the ink used in the present invention may contain various additives such as a surfactant, a viscosity modifier, and a surface tension modifier, if necessary.

The ink used in the present invention is as described above, but in the present invention, by changing the composition of the above-mentioned ink and variously changing its surface tension, viscosity, etc. Diameter (d
1) can be adjusted to some extent.

The inkjet recording method for performing recording by applying the above-mentioned ink to the recording material in the method of the present invention applies the ink to the recording material, which is a projectile object, by effectively releasing the ink from a nozzle. Any method may be used as long as it obtains the information, and representative methods include, for example,
IEEE Tra Axions on Industry Applications (IEEE Tra
ns actions on Industry
Applications) Vol, JA-13,
No. 1 (February/March 1977 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. There is a method in which a strong electric field is applied between the ink particles and the nozzle, and the ink is drawn out one after another from the nozzle, and an information signal is given to the deflection electrodes while the drawn ink flies between the deflection electrodes to record the ink particles. There is a method of ejecting ink droplets in response to an information signal without deflection, and both methods are effective for the method of the present invention.

The second method is to forcibly eject minute ink particles by applying high pressure to the ink with a small pump and mechanically vibrating the nozzle with a crystal oscillator. 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 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 appropriate values, and two types of ink droplets, large and small, are ejected from the nozzle tip. Only small and medium diameter droplets are generated and used for recording. The feature of this method is that it is possible to obtain a group of minute droplets even with a nozzle diameter as large as conventional ones.

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, rather than 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.

As described above, the conventionally known inkjet recording methods and devices are capable of achieving
The diameter (d1) of the ejected ink droplets can be adjusted.

In the above inkjet recording method, the diameter (small) of the ejected ink droplets is generally 110-100
The thickness (d2) of the ink receiving layer can be set arbitrarily within the range of 1 L, and the thickness (d2) of the ink receiving layer in the recording material is 0.01 Bm.
to several hundred 7 tm, the porosity CB) is 0 to 0.9. The w side car (S) can be set arbitrarily from 0 to about 500. However, in the present invention, in order to obtain a recorded image having excellent resolution and excellent gradation, inkjet recording must be performed within a range that satisfies the relationship of equation (1) above.

For example, in a full-color inkjet recording method, the diameter (d1) of the ink droplets is changed by using four colors of ink: yellow, magenta, tan, and black, and the voltage applied to the head is changed to create gradation. ,
The ei of each color is changed in the range of 30 to 654 m, and for red, green, and blue, mackerel≠2 colors are printed in layers.

Therefore, the dot diameter is 30 to 82I according to the above formula (2).
It changes up to Lm. Therefore, in a recording material consisting of a porous ink-receiving layer with no swelling property, the porosity of the ink-receiving layer (
When B) is 0-4, the thickness of the ink-receiving layer must be 13 μm or more according to the above formula (1).

In the example below, the diameter (d1) of the ink droplet ejected in the inkjet recording method is used as the standard, and the properties of the ink receiving layer of the recording material are adapted to this. First, the thickness (d2), porosity (B), and swelling rate (S) of the ink-receiving layer are set within predetermined ranges, and the ejection pressure of the inkjet recording device, the diameter of the nozzle, etc. are varied. It goes without saying that the diameter (d,) of the ejected ink droplet may be adapted to the above equation (1).

According to the present invention as described above, the diameter (d1) of the ejected ink droplet, the thickness (d2) of the ink receiving layer of the recording material,
By performing inkjet recording in a specific relationship between the porosity (B) of the ink-receiving layer and the swelling rate (S) of the ink-receiving layer due to ink, the amount of ink applied to the ink-receiving layer and the resulting amount can be determined. The density of the recorded image has a substantially proportional relationship, and as a result, a recorded image with high contrast, excellent resolution, and fine gradation can be obtained.

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

Example 1 Art paper (OK Art Post (trade name), manufactured by Tamako Paper Industries) was used as a base material, and the following composition was applied thereon to a dry film thickness of 8.
Coat by bar coater method so that pLm is 80
Dry at °C for 10 minutes, porosity (B) = 0.3,
Recording material 1 with a swelling ratio (S) of -0.5 was obtained.

Hydrophilic polyurethane (Tricoat G, manufactured by Taihohe Industries) 10 parts Talc
30 parts Methyl ethyl ketone 60 parts An on-demand inkjet recording head that ejects ink using a piezoelectric vibrator (discharge orifice diameter 45gm, piezoelectric vibrator drive voltage 60cm, frequency 2KHz) using an ink having the following composition on the recording material 1 A 16-gradation pattern was recorded using a 4×4 dot matrix with an ink droplet diameter (d,) of 60 gm using a recording device having an ink droplet diameter (d) of 60 gm.

Drumsmith Yno (Composition) C, 1, Direct Yellow 86 2 parts Glycerin 15 parts Triethylene glycol 5 parts Polyethylene glycol 940
0 3 parts water
75 parts Grave El (composition) (:, 1. Acid Red 35 2 parts Glycerin 15 parts Triethylene glycol 5 parts Polyethylene glycol #4
00 3 parts water
75 parts Li21 (composition) C, 1, Direct Blue 86 2 parts glycerin 15 parts triethylene glycol 5 parts polyethylene glycol #40
0 3 parts water
75 parts Ri ink (composition) C, 1, food black 2 2 parts glycerin 15 parts triethylene glycol 5 parts polyethylene glycol #4
00 3 parts water
The images obtained on 75 copies had smooth gradation and there was no ink overflow even in the high density region, resulting in a clear image.

Example 2 The same procedure as in Example 1 was carried out except that the following recording material 2 was used instead of recording material 1 in Example 1.

(Recording material 2) (Using a PET film (thickness 100#m, Lumirror #100T, manufactured by Toshi) as the material, apply the composition F on it using a percoater so that the dry film thickness is 5 gm. The porosity (
A recording material 2 with B)=0 and swelling ratio (S)=2.5 was obtained.

The resulting image had smooth gradation and was clear even in the high density region.

Polyvinyl alcohol (PVA-117, manufactured by Kuraray) 2 parts Polyvinyl alcohol (PVA 5-33, manufactured by Kuraray) 8 parts water
9
Part 0 Example 3 In Example 1, the following recording material 3 was used instead of the recording material L, the piezoelectric vibrator drive voltage was 80 V, and the diameter (d,) of the ink droplet was 80 lm. The same procedure as in Example 1 was carried out except for the following.

(Recording material 3) Art paper (OK Art Post (trade name), manufactured by Tamako Paper Industries) was used as a base material, and the following composition was applied thereon by a bar coater method so that the dry film thickness was 154 m. death,
Dry at 120°C for 5 minutes to obtain a porosity (B) of 0.4.
A recording material 3 having a swelling ratio (S)=O was obtained.

Silica (Thyroid 620, manufactured by Fuji Davison) 10 parts Polyvinyl alcohol (PVA-HC, manufactured by Kuraray) 2 parts Water
The images obtained in 88 copies were as good as in Example 1.

Comparative Example 1 The same procedure as in Example 3 was carried out, except that the coating composition of Recording Material 2 was applied to a dry film thickness of 2 #Lm as the recording material. .

Comparative Example 2 Example 3 was carried out in the same manner as in Example 3, except that the recording material was coated with the coating composition of recording material 1 so that the dry film thickness was 81 parts m. Ta.

In both Comparative Examples 1 and 2, the ink overflowed in the high density area, disrupting the one-tone gradation (the gradation was saturated in the high density area), and the gradation decreased and the clarity was impaired.

Patent applicant: Canon Co., Ltd. −′1

Claims (1)

[Claims] (1) In an inkjet recording method in which recording is performed by attaching ink droplets to a recording material consisting of a base material and an ink receiving layer provided on the base material, the diameter (d_1) of the ink droplet is and the thickness (d_2) of the ink-receiving layer are within the range represented by the following formula (1). d_1/{d_2(B^1^/^2+S-B^1^/^
2S)}≦10(1) [However, in the above formula (1), B represents the porosity of the ink-receiving layer, and S represents the swelling rate of the ink-receiving layer due to the ink. ]