KR0163272B1 - Recording medium, recording method using the same and production of printing matter - Google Patents

Abstract

The present invention has a surface layer having an ink permeability and an ink holding layer, the volume of the voids corresponding to the peak of 100 nm or less of the pore diameter distribution curve is 0.015 cc / g or less, the void corresponding to one or more peaks exceeding 100 nm The recording medium has a volume of 0.015 cc / g or more and a pH of the surface layer of 8 or more.

Description

Recording medium, recording method using the same, and method for manufacturing recorded material

Fig. 1 is a longitudinal sectional view of a configuration example of a head of an inkjet recording apparatus suitable for use in performing recording on a recording medium according to the present invention, taken along the flow path of ink.

FIG. 2 is a cross-sectional view of the head shown in FIG. 1 taken along line 2-2. FIG.

3 is a perspective view of the appearance of an exemplary multihead.

4 shows an example of an ink jet recording apparatus in which a head is to be inserted.

* Explanation of symbols for main parts of the drawings

13: head 14: groove

15,28: heat generating head 16: protective film

17-1, 17-2: aluminum electrode 18: heat generating resistor layer

19: heat storage layer 20: substrate

21: Ink 22: Orifice

23: main scus 25: recording medium

61: blade 62: cap

63: ink absorber 64: discharge recovery portion

65: recording head 66: carriage

67: guide shaft

The present invention relates to a recording medium excellent in absorbency of an ink, chromaticity, gloss and durability of an image, a recording method using the recording medium, and a manufacturing method of the recording material.

The inkjet recording method is attracting attention because it is easy to speed up recording, full multicoloring, and high density, and recording apparatuses utilizing the inkjet recording method are widely used. As a recording paper applied to such an inkjet recording system, the exclusive coated paper described in Japanese Patent Laid-Open No. 59-35977 is mentioned, for example.

However, since such an exclusive coated paper is observed on the recording surface of the ink as the image formed on the recording paper is configured so that the recording agent in the ink remains as much as possible on the surface of the absorbing layer, there is a disadvantage in that the durability and storage property of the formed image and the like are poor. .

Therefore, in order to improve the recording performance such as the ink absorbency, the color developing property of the recording agent, the image quality of the recorded image, the resolution, the chromaticity, the recording optical density or the gloss, it is described in Japanese Patent Laid-Open No. 62-140878. A recording medium having different recording planes and observation planes is proposed. This recording medium is a lamination of a holding layer of ink and a porous surface layer on a transparent substrate, recording on the surface side, and observing an image recorded on the substrate side.

In the inkjet recording system, those which are dissolved in various water-soluble dyes in water or a mixture of water and an organic solvent are used as the ink. However, in the case of an ink using such a water-soluble dye, since these water-soluble dyes are inherently poor in light resistance, poor light resistance of a recorded image is often a problem.

In addition, since the ink is water-soluble, the water resistance of the recorded image is often a problem. In other words, when rain, sweat, or beverages get on the recorded image, the recorded image may be blurred or blurred.

On the other hand, writing instruments using a dye such as a ballpoint pen have the same problem, and various aqueous pigment inks for writing instruments have been proposed in order to solve the problems of light resistance and water resistance. For practical application of water-based pigment inks, Japanese Patent Laid-Open No. 58-80368, Japanese Patent Application Laid-Open No. 61-A, as an example of studies on dispersion stability, prevention of ink solidification at the tip of a pen, and prevention of abrasion of ball points of a ballpoint pen 20082, 61-247774, 61-272278, 62-568, 62-101671, 62-101672, Japanese Patent Publication No. 1-249869 No. 1-301760, etc. may be mentioned. In recent years, ballpoint pens or markers using an aqueous pigment ink have been commercially available. Further, pigment inks using a specific water-soluble solvent and a polymer dispersant have been proposed as the ink jet ink using an aqueous pigment ink, such as Japanese Patent Laid-Open No. 56-147859 and Japanese Patent No. 56-147860.

Thus, many proposals regarding the pigment ink for inkjet are made | formed.

In recent years, with the improvement of the performance of inkjet recording apparatuses such as high speed recording and multicoloring, more highly extensive characteristics are required for inkjet recording media. More specifically, it is required to simultaneously satisfy the following characteristics.

(1) performing proper color mixing without causing color modulation from the original color tone of the dye,

(2) the absorption ability of the ink is increased (the absorption capacity is large and the absorption time is short),

(3) The optical density of the dot is high, and to sharpen the periphery of the dot,

(4) the dot shape is close to a circle, and its surroundings are smooth;

(5) There is little change of characteristic by change of temperature, humidity and does not cause curl,

(6) not causing blocking,

(7) the burns formed on them are stable to long-term storage and do not deteriorate (especially under high temperature and high humidity environment),

(8) The recording medium itself is stable for long term storage and is not altered (especially under high temperature and high humidity environment).

As described above, in recent years, a number of methods using pigment ink for inkjet printing have been reported to improve the water resistance and light resistance of an image formed on a recording medium.

However, when the pigment ink is used for the recording medium in which the recording surface and the viewing surface are opposed to each other as described above, there is a problem that the density of the image observed on the viewing surface is low and the color development is poor.

The object of the present invention is that when the recording surface and the observation surface are different from each other, and the above-described characteristics are satisfactorily balanced at the same time, and recorded on the recording surface using a pigment ink expressing durability such as water resistance and light resistance, the optical density is high and The present invention proposes a recording medium excellent in color development, a recording method using the same, and a manufacturing method of a recording material.

The above object can be achieved by the following invention.

According to the present invention, a volume having a surface layer and an ink holding layer having liquid permeability and corresponding to a peak of 100 nm or less of the pore diameter distribution curve has a volume of 0.015 cc / g or less and corresponds to one or more peaks exceeding 100 nm. A recording medium is provided in which the void volume is 0.015 cc / g or more and the pH of the surface layer is 8 or more.

Further, according to the present invention, there is provided a recording method comprising applying ink containing pigment particles each having an average particle diameter of 100 nm to 500 nm to the recording medium from a discharge orifice in a liquid crystal state in accordance with a recording signal.

According to the present invention, a method for producing a recording material, wherein ink containing pigment particles each having an average particle diameter of 100 nm to 500 nm is applied to the surface layer of the recording medium by an inkjet method to form an image on the ink holding layer through the surface layer. This is provided.

The present invention is characterized in that, using an ink containing a pigment as a main component of a recording agent, unlike a conventional recording medium in which the recording surface and the observation surface are the same, recording is performed on the recording medium in which the recording surface and the observation surface face each other.

More specifically, according to the present invention, recording is performed by applying ink to the surface layer on the recording side, and the recorded image is observed on the ink holding layer side on the observation side.

Thus, the surface layer has excellent liquid permeability, that is, a function of rapidly absorbing and permeating ink imparted to the surface thereof.

At this time, the surface layer should have high affinity for the liquid medium in the ink and at the same time low affinity for the pigment as the recording agent, and should be configured to allow the pigment to pass through the pores in the surface layer. If the pore diameter is smaller than the particle size of the pigment, the pigment cannot pass through the void and remains on the recording surface side, and when the image is observed from the observation surface, the optical density is low and color development is poor.

Therefore, the surface layer should be configured such that the pore diameter is larger than the particle size of the pigment by selecting a material that does not have properties such as wetting, penetration, diffusion, etc. with respect to the liquid medium in the ink, and the pH of the surface layer, It must be adjusted to an appropriate pH (within a stable pH range) where the pigment in the ink does not aggregate when passed.

On the other hand, the ink holding layer must have a stronger ink absorbing power than the surface layer in order to absorb and capture the ink temporarily absorbed in the surface layer.

Therefore, the ink holding layer should have high affinity not only for the liquid medium in the ink but also for the recording agent in the ink. The pH of the ink holding layer is more preferably within a pH region where the pigments in the ink are not aggregated (lower than the pH in the stable pH region), because the water resistance and moisture resistance of the formed image are further improved in that region. . In the present invention, the pH of the surface layer and the ink holding layer is a value measured according to the Surface pH Measurement of Paper (J. TAPPI Test Methods for Paper and Pulp, No. 6-A) described in the literature.

The present invention will be described in detail based on the following embodiments.

The recording medium of the present invention directly receives and substantially includes ink formed on a substrate as a support, an ink holding layer formed on the support and substantially absorbing and capturing ink or a recording agent, and formed on the ink holding layer. It consists of a surface layer which does not leave ink in it. Further, the volume of the voids corresponding to the peak of 100 nm or less of the pore diameter distribution curve of the recording medium is 0.015 cc / g or less, and the volume of the voids corresponding to one or more peaks exceeding 100 nm is 0.015 cc / g or more.

In the above configuration, when the surface layer or the ink holding layer serves as a substrate, the substrate is not necessarily required. As a base material used for this invention, a conventionally well-known thing can be used, A specific example thereof is a polyester resin, diacetate resin, triacetate resin, polystyrene resin, polyethylene resin, polycarbonate resin, polymethacrylate resin, And light-transmitting substrates such as plastic films, sheets or plates, and glass sheets or plates, such as cellophane, celluloid, polyvinyl chloride resins, and polyimide resins.

As described above, the present invention observes the recorded image from the opposite side to the recording side, so that the substrate may be processed as long as the substrate maintains good light transmittance. For example, the substrate may be imparted with a desired pattern or gloss, such as a suitable gloss or silk treated pattern, to the substrate material.

It is also possible to impart water resistance, abrasion resistance and blocking resistance to the base material.

The surface layer constituting the recording medium of the present invention needs to have good liquid permeability.

Liquid permeability in the present invention refers to a property that allows ink to pass quickly and does not substantially leave the recording agent in the ink in the surface layer. A preferred aspect for improving liquid permeability is to have a porous structure with cracks or communicating pores inside the surface layer.

In addition, since the average particle diameter of the pigment particle in the ink used by this invention is generally 100-500 nm, the volume of the space | gap corresponding to the peak of 100 nm or less of the pore diameter distribution curve of a recording medium is 0.015 cc / g or less, The volume of the pores corresponding to at least one peak exceeding 100 nm should be at least 0.015 cc / g. When the volume of the voids corresponding to the peak of 100 nm or less exceeds 0.015 cc / g, pigment particles in the ink remain in the surface layer, and an image with sufficient density and brightness cannot be formed. Likewise, the diameter of the pores corresponding to the peaks exceeding 100 nm of the pore diameter distribution curve should be larger than the average particle diameter of the pigment particles.

On the other hand, when the volume of the voids corresponding to the peak exceeding 100 nm is 0.015 cc / g or less, the liquid permeability of the formed recording medium deteriorates, and the optical density and brightness are lowered.

Incidentally, the pore diameter distribution curve mentioned in the present invention is measured by mercury intrusion. As an apparatus used for such a measurement, the porosimeter poresizer 9320 (brand name, the product made by Shimadzu Corporation) is mentioned.

In addition, as described above, in the present invention, since the reflection recording image is observed from the opposite side of the recording surface, it is preferable that the surface layer has good light diffusivity.

The surface layer for supplementing the above properties mainly consists of resin particles and a binder.

As the resin particles used in the present invention, organic pigments such as thermoplastic resins and thermosetting resins which are non-adsorbable to the recording agent, for example, polyethylene, polymethacrylate, elastomer, ethylene vinyl acetate copolymer, styrene acrylic acid copolymer, polyester At least one of resin powders and emulsions of, polyacrylate and polyvinyl ether is preferably used.

In addition, the resin particles used in the present invention are not limited to the resin particles as described above, and any known material may be used as long as they are non-adsorbent with respect to the recording agent.

The particle size of the resin particles is preferably 0.3 to 20 µm, more preferably 0.5 to 12 µm. If the particle diameter is less than the lower limit of the above range, the permeability of the pigment particles in the ink becomes insufficient, and it is difficult to form an image having a sufficient optical density. When the particle diameter exceeds the upper limit of the above range, the circularity of the dots formed on the surface layer tends to be damaged, thereby providing a rough feeling.

The binder used in the present invention has a function of bonding the resin particles to each other and / or the ink holding layer and needs to be non-adsorbable to the recording agent like the resin particles.

Preferred materials for the binder may be any of conventionally known materials as long as they have the above functions. For example, polyvinyl alcohol, acrylic resin, styrene-acrylic acid copolymer, ethylene-vinyl acetate copolymer, starch, polyvinyl buty At least one of ral, gelatin, casein, ionomer, gum arabic acid, carboxymethylcellulose, polyvinyl pyrrolidone, polyacrylamide, phenolic resin, melamine, epoxy and styrene-butadiene rubber may be preferably used.

Such materials are used to adjust the pH of the surface layer to at least 8, preferably from 8 to 10. If the pH of the surface layer is less than 8, the pigment in the ink tends to aggregate in the surface layer, and the density of the formed image becomes insufficient when observed from the side of the ink holding layer. If pH is too high, the color development property of the formed image will fall easily.

If the desired pH cannot be obtained only with the above materials, various cationic or anionic surfactants, various cationic or anionic polymers or oligomers, and various pH adjusting agents may be used in combination.

As long as the molecule contains an anionic moiety, the anionic compound is not particularly limited.

Examples of the anionic surfactants include alkylbenzenesulfonates, alkyl sulfates, alkylnaphthalenesulfonates, alkylphosphates, alkylsulfosuccinates, naphthalene sulfonic acid-formalin condensates, and salts of polyoxyethylene alkylphosphates. Amphoteric surfactants such as alkylbetaines, imidazolinium betaines and alanine-based surfactants containing anionic moieties may also be included.

Examples of the anionic polymers or oligomers include those having sulfonic acid groups, carboxyl groups, sulfate groups, phosphate groups, phenolic hydroxyl groups, alcoholic hydroxyl groups and the like. Carboxyl terminal-terminated polyesters obtained by reacting all polymers and oligomers having a sulfonic acid group, a carboxyl group, a sulfate group, a phosphate group, a phenolic hydroxyl group, an alcoholic hydroxyl group and the like, for example, a polycarboxylic acid and a polyhydric alcohol; Acid cellulose derivatives modified with various polycarboxylic acids; Homopolymers such as vinyl ether ester monomers of polycarboxylic acids or copolymers with other common monomers; Homopolymers such as methacrylic acid or copolymers with other common monomers; Copolymers of α, β-unsaturated vinyl monomers such as maleic anhydride and itaconic acid with homopolymers or other common monomers; Sulfonic acid modified polymers obtained by modifying polyvinyl alcohol or vinyl alcohol copolymers with sulfonic acid compounds; Compounds having hydroxyl groups such as ethyl cellulose, benzyl cellulose, hydroxyethyl cellulose and hydroxypropyl cellulose can be preferably used.

As long as the molecule contains a cationic moiety, the cationic compound is not particularly limited.

Examples of cationic surfactants include quaternary ammonium salt based cationic surfactants such as monoalkylammonium chloride, dialkylammonium chloride, tetramethylammonium chloride, trimethylphenylammonium chloride and ethylene oxide-added ammonium chloride; And amine salt cationic surfactants. Amphoteric surfactants such as alkylbetaines, imidazolinium betaines and alanine-based surfactants containing cationic moieties may also be included.

Cationic polymers or oligomers include cation modified products of polyacrylamides, acrylamides and cationic monomers, polyallylamines, polyamine-sulfones, polyvinylamines, polyethylene-amines, polyamide-epichlorohydrin resins and polyvinyl And copolymers with pyridinium halides.

Copolymers of vinylpyrrolidone-based monomers with homopolymers or other common monomers; Copolymers of vinyloxazolidone monomers with homopolymers or other common monomers; Homopolymers or copolymers of vinylimidazole-based monomers with other common monomers may be preferably used.

Examples of common monomers include methacrylate, acrylate, acrylonitrile, vinyl ether, vinyl acetate, ethylene and styrene. Cation modified polyvinyl alcohol, cellulose and the like may be used. Cationic materials are not limited to these surfactants and polymers or oligomers.

Examples of pH adjusting agents include ammonia, various organic amines such as diethanolamine and triethanolamine, inorganic alkalizing agents such as alkali metal hydroxides such as sodium hydroxide, lithium hydroxide and potassium hydroxide, organic acids and inorganic acids. .

Two or more kinds of various compounds may be used simultaneously.

If necessary, various additives such as surfactants, surfactants, crosslinking agents and the like may be added to the surface layer in order to improve the function of the surface layer.

The weight mixing ratio of the resin particles to the binder is preferably 1: 2 to 50: 1, more preferably 3: 1 to 20: 1.

If the mixing ratio is less than 1: 2, the cracks or communication pores of the formed surface layer are small, so that the ink adsorption effect is reduced. When the mixing ratio is more than 50: 1, the resin particles cannot sufficiently bond with each other and / or the ink holding layer, thereby failing to form the surface layer.

The thickness of the surface layer may vary depending on the amount of ink droplets to be imparted, but is preferably 1 to 200 m, more preferably 3 to 50 m.

An ink retaining layer that substantially captures ink or recording agent is one that absorbs and captures ink that has passed through the surface layer to hold substantially permanently.

The ink holding layer needs to have stronger ink absorption than the surface layer. The reason is that when the absorbing power of the ink holding layer is weaker than the absorbing power of the surface layer, the ink applied to the surface of the surface layer partially remains in the surface layer when passing through the surface layer and the leading end portion of the ink reaches the ink holding layer, so that the surface layer and the ink At the interface of the holding layer, ink penetrates and diffuses in the transverse direction in the surface layer. As a result, the resolution of the recorded image is lowered and it is impossible to form a high quality image. In addition, as described above, since the formed image is observed from the side opposite to the recording surface, the ink holding layer needs to have good light transmittance.

It is preferable that the ink holding layer that satisfies the above-mentioned requirements is made of a light-transmissive cationic resin that adsorbs the recording agent and / or a light-transmissive hydrophilic resin having good solubility and swelling property with respect to the ink.

In addition, the material constituting the ink holding layer is not particularly limited as long as it has a function of absorbing and capturing ink and excellent brightness.

The thickness of the ink holding layer may be sufficient to absorb and capture the ink. However, the thickness varies depending on the amount of droplets of the ink to be applied, but is preferably 1 to 50 µm, more preferably 3 to 20 µm.

The pH of the ink holding surface is preferably 6 or less, more preferably 4 to 6. If the pH of the ink holding layer is within this range, the pigment reaching the ink holding layer will cause proper aggregation on the surface of or inside the ink holding layer, thereby forming an image excellent in water resistance and moisture resistance with little bleeding. can do.

If the desired pH cannot be obtained only by the above materials, the various cationic or anionic surfactants, various cationic or anionic polymers or oligomers, and various pH adjusting agents may be used in combination.

A method of forming an ink retaining layer and a surface layer on a substrate, wherein each of the above substances is separately dispersed in a suitable solvent to prepare a coating liquid, and the coating liquid is a known method such as a roll coating method, a rod bar coating method, and a spray. The method of apply | coating on a board | substrate by a coating method or an air knife coating method, and then rapidly drying is preferable. The hot melt coating method, or a method of forming an individual single sheet from the material and laminating the sheet on a substrate may also be used.

However, when the ink holding layer is provided on the substrate, it is necessary to strengthen the adhesion between the substrate and the ink holding layer to eliminate the space.

The presence of a space between the substrate and the ink holding layer is undesirable because irregular reflection occurs on the surface of the recorded image, which substantially reduces the optical density of the image.

In the recording method of the present invention, since the recording surface and the observation surface are opposed to each other, it is necessary to use an apparatus capable of printing the reflected image characters unlike in the prior art when printing characters.

Although the pigment ink for inkjets used by this invention is not specifically limited, The outline is demonstrated below.

In the present invention, the amount of the pigment contained in the pigment ink is preferably used in the range of 1 to 20% by weight, preferably 2 to 12% by weight, based on the total weight of the ink. Any pigment may be used for the present invention, but for example, carbon black used in black ink is carbon black manufactured by a furnace method or a channel method, and has a primary particle diameter of 15 to 40 nm and a BET method. The specific surface area measured was 50 to 300 m ² / g, and the oil absorption measured using DBP was 40 to 150 ml / 100 g, the volatile matter was 05. to 10%, and the pH had 2 to 9. For example, No. 2300, No. 990, MCF 88, No. 33, No. 40, no. 45, No. 52, MA7, MA8, No. 2200B (trade name, manufactured by Mitsubishi Chemical Industried Limited), RAVEN 1255 (trade name, manufactured by Columbian Carbon Japan Limited), REGAL 400R, REGAL 330R, REFAL 660R, and MOGUL L (trade name, manufactured by Cabot Company), Color Black FW1, Color Black FW18, Color Black S170, Color Black S150, Printex 35 and Printex U (trade name, manufactured by Degussa) may be used. Examples of pigments used in yellow, magenta, and cyan inks are CI Pigment Yellow 1, CI Pigment Yellow 2, CI Pigment Yellow 3, CI Pigment Yellow 13, CI Pigment Yellow 16, and CI Pigment Yellow, respectively. 83; CI Pigment Red 5, CI Pigment Red 7, CI Pigment Red 12, CI Pigment Red 48 (Ca), CI Pigment 48 (Mn), CI Pigment Red 57 (Ca), CI Pigment Red 112 and CI Pigment Red 122; And CI Pigment Blue 1, CI Pigment Blue 2, CI Pigment Blue 3, CI Pigment Blue 15: 3, CI Pigment Blue 16, CI Pigment Blue 22, CI Bat Blue 4 and CI Bat Blue 6 can be given. However, it is not limited only to these pigments. In addition to the pigments, freshly prepared ones may also be used for practicing the present invention.

As the dispersant for the pigment contained in the ink used in the present invention, a resin may be used without particular limitation as long as it is a water-soluble resin. However, those having a molecular weight of 1,000 to 30,000, more preferably 3,000 to 15,000 can be preferably used. Examples of such dispersants include styrene, styrene derivatives, vinylnaphthalene, vinylnaphthalene derivatives, aliphatic alcohol esters of α, β-ethylenically unsaturated carboxylic acids, acrylic acid, acrylic acid derivatives, maleic acid, maleic acid derivatives, itaconic acid derivatives, itaconic acid derivatives, Block copolymers, random copolymers and graft copolymers composed of two or more monomers (at least one hydrophilic monomer) selected from the group consisting of fumaric acid and fumaric acid derivatives, and salts of these copolymers. These resins are alkali-soluble resins dissolved in an aqueous solution of a base. In addition, homopolymers composed of hydrophilic monomers, or salts thereof, may be used. Water-soluble resins such as polyvinyl alcohol, carboxymethyl cellulose and naphthalenesulfonic acid-formaldehyde condensates can also be used.

N, N-dimethylaminoethyl methacrylate, N, N-dimethylaminoethyl acrylate, N, N-dimethylaminoacrylamide, N, N-dimethylaminomethacrylamide, N, N-dimethylaminopropylacrylamide, Cationic dispersants such as acrylic acid copolymers containing monomer units quaternized with N, N-dimethylaminopropylmethacrylamide and the like with methyl chloride, dimethyl sulfuric acid, benzyl chloride, epichlorohydrin and the like may be used.

In addition, it is preferable that the ink of the present invention is adjusted to be neutral or alkaline, because the solubility of the water-soluble resin can be improved and the ink can be provided as an ink having excellent long-term storage property. However, in this case, if the alkalinization degree is too high, it is more preferable to adjust the pH to 7 to 10 because various components used in the inkjet recording apparatus cause corrosion.

The pigment and water-soluble resin are dispersed or dissolved in an aqueous medium.

Suitable aqueous media for use in the inks of the present invention are mixed solvents of water and aqueous organic solvents. As water, it is preferable to use ion-exchanged water, such as deionized water, instead of tap water containing various ions.

In addition, examples of the water-soluble organic solvent used in combination with water include alkyl having 1 to 4 carbon atoms such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol and tert-butyl alcohol. Alcohols; Amides such as dimethylformamide and dimethylacetamide; Ketones and keto-alcohols such as acetone and diacetone alcohol; Ethers such as tetrahydrofuran and dioxane; Polyalkylene glycols such as polyethylene glycol and polypropylene glycol; Alkylene glycols having 2 to 6 carbon atoms in the alkylene component, such as ethylene glycol, propylene glycol, butylene glycol, triethylene glycol, thiodiglycol, hexylene glycol and diethylene glycol; 1,2,6-hexanetriol; Glycerol; Lower alkyl ethers of polyhydric alcohols, such as ethylene glycol monomethyl (or monoethyl) ether, diethylene glycol methyl (or ethyl) ether and triethylene glycol monomethyl (or monoethyl) ether; N-methyl-2-pyrrolidone; 2-pyrrolidone; And 1,3-dimethyl-2-imidazolidinone.

The content of the water-soluble organic solvent in the ink of the present invention is generally 3 to 50% by weight, preferably 3 to 40% by weight based on the total weight of the ink, and the content of water used is 10 to based on the total weight of the ink. 90% by weight, preferably 30 to 80% by weight.

The ink of the present invention is produced as follows, respectively. First, the pigment is added to an aqueous solution containing at least a water-soluble resin as a dispersant and water, and the mixture is stirred. Dispersion is performed by the following dispersing means and centrifuged to obtain a desired dispersion. Any additive component which can be used in the present invention is added to this dispersion and the resulting mixture is stirred to prepare the ink.

It is more effective to premix the aqueous solution containing the pigment for at least 30 minutes before dispersion treatment. This premixing improves the wettability of the pigment surface and facilitates the adsorption of the dispersion onto the pigment surface.

Any disperser commonly used may be used in the present invention. Examples thereof include ball mills, roll mills, and sand mills.

Among these mills, high speed sand mills can be preferably used. Examples include Super Mill, Sand Grinder, Beads Mill, Agitator Mill, Grain Mill, Dyno Mill, Pearl Mill. Mill and Coball Mill (brand name) are mentioned.

As a method for obtaining a pigment having a desired particle size distribution, a technique for making the grinding media of the disperser smaller, a technique for making the grinding media faster, a longer processing time, a technique for slowing the discharging speed, and grinding Later, a technique for classifying with a filter, a centrifuge, or the like can be given. These methods can also be used together.

The average particle diameter of the pigment particle in the pigment ink of this invention is 100-500 nm, Preferably it is 100-200 nm as aggregate of a primary particle. The average particle diameter of the pigment particles can be measured by conventionally known methods such as centrifugal precipitation, X-ray transmission, laser diffraction or sieving.

An example of an inkjet recording apparatus suitable for recording with a recording medium according to the present invention will be described later. The structure of the head, which is the main part of the device, is shown in FIGS. 1, 2 and 3. Referring to FIG. 1, the head 13 has a heat generating head 15 for use in thermal recording using glass, ceramic or plastic plates having a groove 14 through which ink will pass (the head is illustrated in the drawing, The present invention is not limited thereto. The heat generating head 15 is formed of a heat resistant resistor layer 18, a heat storage layer 19, alumina, etc. formed of a protective film 16 made of silicon, etc., aluminum electrodes 17-1 and 17-2, nichrome, or the like. It consists of the board | substrate 20 with which the heat dissipation was performed. The ink 21 comes to the discharge orifice (micropore) and forms the main scus 23 due to the pressure P.

Now, when an electrical signal is applied to the electrodes 17-1 and 17-2, the heat generating head 15 rapidly generates heat in the region indicated by n, and bubbles are generated in the ink 21 in contact therewith. At this pressure, the main scus 23 of the ink protrudes, and the ink 21 is ejected from the orifice 22 and directed to the recording medium 25 in the form of fine droplets 24. 3 shows an external view of a multi-head in which a plurality of heads shown in FIG. 2 are arranged. The multi head is manufactured by bringing a glass plate 27 having a plurality of grooves 26 into close contact with a heat generating head 28 similar to the head illustrated in FIG.

1 is a cross-sectional view of the recording head 13 cut along the ink flow path, and FIG. 2 is a cross-sectional view taken along the line A-B in FIG.

4 shows an example of an inkjet recording apparatus in which such a head is incorporated. In FIG. 4, reference numeral 61 denotes a blade provided as a wiping member, one end of which is a fixed end held by the blade holding member, and forms a contiever. The blade 61 is disposed at a position adjacent to the recording area in which the recording head operates, and in the present example, is held in a protruding form during the movement path of the recording head. Reference numeral 62 denotes a cap, which is provided at a home position adjacent to the blade 61, and is configured to move in a direction perpendicular to the moving direction of the recording head and to contact the discharge spherical surface to cap it. Incidentally, reference numeral 63 denotes an ink absorber provided adjacent to the blade 61, and is maintained in the form protruding in the movement path of the recording head, which is shaped like the blade 61. The discharge recovery part 64 is comprised by the said blade 61, the cap 62, and the absorber 63, and the blade 61 and the absorber 63 remove water, dust, etc. from the ink discharge opening. All.

Reference numeral 65 denotes a recording head which has discharge energy generating means and discharges ink to a recording medium opposite to the discharge opening surface on which the discharge openings are arranged, for recording. Reference numeral 66 denotes the recording head 65. Reference is made to a carriage in which the recording head 65 can be moved. The carriage 66 is slidably engaged with the guide shaft 67, and a part of the carriage 66 is connected (not shown) to the belt 69 driven by the motor 68. Therefore, the carriage 66 can be moved along the guide shaft 67, and the recording head 65 can be moved from the recording area to the area adjacent thereto.

Reference numeral 51 denotes a paper feed unit for separately inserting recording media, and reference numeral 52 denotes a paper feed roller driven by a motor (not shown). With this configuration, the recording medium is supplied to a position opposite to the discharge opening surface of the recording head 65, and is discharged from the discharge end face in which the discharge roller 53 is arranged at the time of recording progress.

In the above configuration, the recording head 65 returns to the home position after the recording is completed, for example, the cap 62 of the recovery portion 64 of the head is removed from the moving flow path of the recording head 65, and the blade 61 is removed. ) Protrudes in the moving passage. As a result, the ejection opening surface of the recording head 65 is wiped. In addition, when the cap 62 is capped in contact with the discharge opening surface of the recording head 65, the cap 62 is moved to protrude in the movement flow path of the recording head 65.

When the recording head 65 moves from the home position to the recording start position, the cap 62 and the blade 61 are at the same position as the wiping position described above. As a result, the ejection opening surface of the recording head 65 is wiped at this time.

The above-described movement of the recording head 65 to the home position is made not only at the end of recording or when the recording head is recovered for ejection, but also between the recording head 65 moving between the recording areas following the recording, in the meantime. It moves to a home position adjacent to the recording area at predetermined intervals, and the ejection opening surface is wiped in accordance with this movement.

Hereinafter, the present invention will be described in more detail with reference to the following examples. All parts and percentages used in the examples which follow are mean parts by weight and% by weight unless otherwise indicated.

Example 1

[Production of Pigment Dispersion]

The components were mixed and warmed to 70 ° C. in a water bath to completely dissolve the resin components therein. 10 parts by weight of C.I. Pigment Red 112 and 1 part by weight of isopropyl alcohol were added and premixed for 30 minutes. Thereafter, the formed preliminary mixture was subjected to dispersion treatment under the following conditions.

The dispersion was further centrifuged (16,000 rpm, 20 minutes) to remove coarse particles to make a dispersion.

The above ingredients were mixed to prepare a pigment ink of magenta color.

The average particle diameter of the pigment particles in the ink was measured with a coulter counter and found to be 120 nm.

The stable pH range for this pigment ink was 7.2 or more.

The stable pH region for the pigment ink was determined by changing the pH of the pigment ink maintained in good dispersion using monoethanolamine and hydrochloric acid to measure the pH region where the pigment does not precipitate or aggregate.

[Production of Cyan Ink]

Pigment is C.I. Except for changing to Pigment Blue 22, a cyan color pigment ink was prepared in the same manner as in magenta ink. The stable pH range measured by the same method as above was 7.4 or more.

The average particle diameter of the pigment particles in the ink was measured with a coulter counter, and found to be 130 nm.

[Production of Yellow Ink]

Pigment is C.I. A yellow color pigment ink was prepared in the same manner as in magenta ink, except that the pigment yellow 13 was changed. The stable pH range measured by the same method as above was 8.0 or more.

The average particle diameter of the pigment particles in the ink was measured with a Coulter counter and found to be 125 nm.

[Production of Black Ink]

A black color pigment ink was prepared in the same manner as in magenta ink except that the pigment was changed to carbon black (MCF 88, trade name, manufactured by Mitsubishi Chemical Industried Limited).

The average particle diameter of the pigment particles in the ink was measured with a coulter counter, and found to be 100 nm. The pH range measured by the same method as above was 7.8 or more.

[Manufacture of Recording Medium 1]

Using a polyethylene terephthalate film (thickness; 100 μm, manufactured by Toray Industries, Inc.) as the light transmitting substrate, the following composition A was coated by a bar coating method to have a dry thickness of 8 μm, and then 5 to 120 ° C. in a drying oven. Dry for minutes.

In addition, on the coating layer thus formed, the following composition B was coated by a bar coating method to have a dry thickness of 15 μm, and then dried at 80 ° C. for 10 minutes in a drying oven. The pH of the surface layer formed was 5.4.

The recording medium thus obtained was white opaque. The pH of the surface layer formed was 8.3.

Example 2

Using the same polyethylene terephthalate as used in Example 1 as the light transmitting substrate, the following composition C was coated by a bar coating method to have a dry thickness of 5 μm, and then dried at 110 ° C. for 10 minutes in a drying oven.

In addition, the following composition D was coated on the coating layer thus formed by a bar coating method to have a dry thickness of 20 μm, and then dried at 80 ° C. for 10 minutes in a drying oven. The pH of the surface layer formed was 4.6.

The recording medium thus obtained was white opaque and had a pH of 8.2.

Example 3

Using the same polyethylene terephthalate as used in Example 1 as the light transmitting substrate, the next composition E (adjusting the pH to 5.8 by adding acetic acid) was coated by a bar coating method to have a dry thickness of 10 μm, followed by a drying oven Dried at 100 ° C. for 12 minutes.

In addition, on the coating layer thus formed, the following composition F was coated by a bar coating method to have a dry thickness of 10 μm, and then dried at 70 ° C. for 10 minutes in a drying oven.

A brand name, product of Kao Corporation)

The recording medium thus obtained was white opaque. The pH of the surface layer formed was 8.7.

Example 4

Except for changing the crosslinked polymethyl methacrylate in composition F used in Example 3 to benzoguanamine resin (Epostar S, trade name, Nippon Shokubai Kagaku Kogyo Co., Ltd., particle diameter; 0.3 μm) A white opaque recording medium was produced in the same manner as in Example 3. The pH of the surface layer formed was 8.6.

Example 5

After the same compositions E and F as used in Example 3 were applied to the Teflon membrane in the same manner as in Example 3, the white opaque recording medium was obtained by separating the Teflon membrane.

Comparative Example 1

Using the same polyethylene terephthalate membrane as used in Example 1 as the light transmitting substrate, the following composition G was coated by a bar coating method to have a dry thickness of 6 μm, and then dried in a drying oven at 120 ° C. for 5 minutes.

In addition, on the coating layer thus formed, the following composition H was coated by a bar coating method to have a dry thickness of 25 μm, and then dried at 80 ° C. for 10 minutes in a drying oven.

The recording medium thus obtained was white opaque.

Comparative Example 2

White in the same manner as in Comparative Example 1, except that the urea-formalin resin in Composition H used in Comparative Example 1 was changed to synthetic silica (Sylysia, trade name, Fuji Silysia KK primary particle diameter: 0.02 to 0.03 μm). An opaque recording medium was obtained.

The pore diameter distribution of the recording medium obtained above was measured by mercury intrusion porosimetry, and the results are shown in Table 1.

Using the ink having the respective compositions, recording was performed on each recording medium under the following conditions by an inkjet recording apparatus in which ink was bubbled by thermal energy to eject ink from the orifice, and the recording medium was evaluated for the aircraft items. .

Evaluation item:

(1) optical density

For each recording obtained by performing beta recording (100% efficiency), the optical density of the beta recording surface of magenta (M) color was measured with a Macbeth densitometer RD-918 from the translucent base side.

The evaluation results are collectively shown in Table 1.

As described above, in the recording medium in which the recording surface and the observation surface are opposed to each other in the recording medium having the surface layer and the ink-retaining layer having liquid permeability according to the present invention, each particle has a specific range of particle diameters, such as water resistance and light resistance. By using a pigment ink expressing durability and using a recording medium having a peak of a pore diameter distribution curve corresponding to the particle diameter of the forcing particles, an inkjet recording method capable of providing an image having high optical density and excellent color development Implementation becomes possible.

While the invention has been described in terms of what is considered to be the preferred embodiments, it is to be understood that the invention is not limited to the embodiments disclosed herein. Rather, the invention is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims. The scope of the following claims is to be accorded the widest scope of interpretation and includes all such modifications and equivalent structures and functions.

Claims (22)

It has a liquid permeable surface layer and an ink holding layer, the volume of the voids corresponding to the peak of 100 nm or less of the pore diameter distribution curve is 0.015 cc / g or less, and the volume of the voids corresponding to one or more peaks exceeding 100 nm. 0.015 cc / g or more, wherein the pH of the surface layer is 8 or more. A recording medium according to claim 1, wherein the ink holding layer has a pH of 6 or less. The recording medium according to claim 1, wherein the ink holding layer and the surface layer are laminated on the substrate. A recording medium according to claim 1, wherein the substrate has good light transmittance. The recording medium of claim 1, wherein the surface layer is porous. The recording medium of claim 1, wherein the surface layer mainly consists of resin particles and a binder. A recording medium according to claim 1, wherein the ink holding layer is transparent. The recording medium of claim 1, wherein the ink holding layer mainly consists of a cationic resin and / or a hydrophilic polymer. A recording medium according to claim 1, wherein the surface layer has good light diffusing property, and the ink holding layer has better light transmittance than the surface layer. The recording medium of claim 1, wherein the ink holding layer has a stronger ink absorption than the surface layer. The recording medium of claim 1, wherein the surface layer has communication voids. The recording medium of claim 1, wherein the recording medium has a crack in the surface layer. A recording method comprising discharging ink containing pigment particles each having an average particle diameter of 100 nm to 500 nm from a discharge orifice in the form of droplets to a recording medium according to any one of claims 1 to 12 in accordance with a recording signal. . The recording method according to claim 13, wherein ink is applied to the surface layer of the recording medium to perform recording. The recording method according to claim 13, wherein four color inks of yellow, magenta, cyan and black colors are used as the ink. The recording method according to claim 13, wherein ink is applied by an inkjet method. The recording method according to claim 16, wherein the inkjet method is a method of discharging ink by applying thermal energy to the ink. The recording method according to claim 13, wherein the diameter of the voids corresponding to the peaks exceeding 100 nm of the pore diameter distribution curve of the recording medium is larger than the average particle diameter of the aggregated particles of the pigment in each ink. The recording method according to claim 13, wherein the pH of the surface layer of the recording medium is equal to or larger than the pH in the stable pH region for each pigment ink. The recording method according to claim 13, wherein the pH of the ink holding layer of the recording medium is smaller than any pH within a stable pH region for each pigment ink. Inks containing pigment particles each having an average particle diameter of 100 nm to 500 nm are imparted to the surface layer of the recording medium according to any one of claims 1 to 12 in an inkjet manner so that an image is formed on the ink holding layer through the surface layer. A method of producing a recording comprising forming the same. 22. The method of claim 21, wherein the inkjet method is a method of ejecting ink by applying thermal energy to the ink.