JPS6356873B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an inkjet recording material (hereinafter also referred to as recording paper) used for recording characters, figures, etc. using a recording liquid. 2. Description of the Related Art Conventionally, recording with recording liquid, that is, ink, has been widely performed using writing instruments such as pens, fountain pens, and felt pens. Also, recently, the so-called
An inkjet recording system has also appeared, and recording liquid is also used here. Incidentally, this inkjet recording method uses various ink ejection methods (for example, an electrostatic suction method, a method that applies mechanical vibration or displacement to the ink using a piezoelectric element, a method that heats the ink to foam it, and uses the pressure applied at that time. ), the method using
Recording is performed by forming ink droplets and attaching some or all of them to a recording material such as paper. In this way, when recording using liquid ink, it is generally necessary that the ink does not bleed onto the surface of the recording paper and cause the print to become blurry, and that the ink is used as quickly as possible after recording. It is desirable that the ink does not dry and accidentally contaminate the paper surface, and that the pigment in the ink fixed on the paper does not discolor. In particular, in the inkjet recording method, the recording liquid (ink) must be absorbed quickly into the recording paper, especially when performing multicolor or full color recording.
Even if ink dots overlap, make sure that the later ink does not disturb or spill out the earlier ink, and that the ink droplets spread on the recording paper and the diameter of the ink dot becomes larger than necessary on the recording paper. The shape of the ink dot must be close to a perfect circle, and the area around it must be smooth. The density of the ink dot must be high and the area around the dot must not be blurred. The color of the recording paper must be white and the contrast with the ink dot must be high. be large, the color of the ink does not change depending on the type of recording paper, there is little scattering of ink drops around the ink dots, and there is no dimensional variation in the recording paper (e.g. wrinkles, spread).
It is necessary to satisfy various requirements such as having a small amount of data before and after recording. but,
Conventionally, it has been understood that meeting these requirements largely depends on the characteristics of the recording paper used, but in reality, plain paper and processed paper meet the above requirements. There is still no recording paper that can meet the requirements. For example, the processed paper for inkjet recording described in JP-A-52-74340 is
Although ink absorption is fast, the ink dots tend to have large diameters, the periphery of the dots tends to blur, and the size of the paper changes significantly after recording. Therefore, the main purpose of the present invention is to
The purpose of this invention is to satisfy the problems that the prior art could not solve in the technical field mentioned above. In particular, it is an object of the present invention to provide a high-performance recording material (recording paper) that satisfies almost all of the above-mentioned requirements for writing instruments or recording using liquid ink using an inkjet recording method. It is said that Therefore, the recording material of the present invention that achieves the above object has both a hydrophilic structural part and a hydrophobic structural part, and the weight ratio of the monomer units forming the hydrophilic structural part is 2 to 40% by weight. % of a polymer and porous inorganic particles is provided on a substrate, the surface of this coating layer is partitioned by formed irregular cracks, and the size of the partitioned portion is:
It is characterized in that it is in the range of 10 μm×10 μm to several hundred μm×several hundred μm. Hereinafter, the present invention will be explained in detail with reference to illustrated examples and examples. First, the configuration of the present invention will be outlined using the schematic diagram of FIG. In the figure, reference numeral 1 denotes a liquid-absorbing substrate, which is made of a porous material such as paper or cloth. 2 is a covering layer which receives ink. This coating layer 2 is basically composed of a film-forming resin paint, but the paint contains as main components:
It contains a polymer and porous inorganic particles that have both a hydrophilic structural part and a hydrophobic structural part that has an affinity with paint. Such polymers are mainly polymers of monomers having addition-polymerizable vinyl groups, and hydrophilic structural moieties such as carboxylic acid groups, sulfonic acid groups, and sulfuric acid ester groups are bonded to a predetermined amount of acrylic acid. Acid, methacrylic acid, crotonic acid, itaconic acid, itaconic acid monoester, maleic acid, maleic acid monoester, fumaric acid, fumaric acid monoester, vinyl sulfonic acid, sulfoethyl methacrylate, sulfopropyl methacrylate,
α,β-unsaturated monomers such as sulfonated vinylnaphthalenes are used to incorporate into the polymer structure. On the other hand, monomer units for introducing hydrophobic structural moieties having affinity with dyes include, for example, acrylonitrile, vinylidene chloride, α,
β-ethylenically unsaturated carboxylic acid ester, vinyl acetate, vinyl chloride, acrylamide, methacrylamide, hydroxyethyl methacrylate, hydroxypropyl methacrylate, glycidyl methacrylate, N-methylolacrylamide,
N-butoxymethylacrylamide and the like are most preferred. In addition to the above monomer units, styrene, styrene derivatives, vinylnaphthalene, vinylnaphthalene derivatives, _C8 to _C18 aliphatic alcohol esters of α,β-ethylenically unsaturated carboxylic acids, etc. can be used. . Incidentally, in the present invention, it is necessary to form a salt of the polymer in order to solubilize or disperse the polymer in the solvent of the paint in the form of a colloid. Examples of partners for forming salts with the above polymer include alkali metals such as Na and K, as well as mono-, di-,
Or aliphatic amines such as tri-(methylamine), mono-, di- or tri-(ethylamine), mono-,
Alcohol amines such as di- or tri-(ethanolamine), mono-, di- or tri-(propanolamine) methylethanolamine, dimethylethanolamine, morpholine, N-methylmorpholine, etc. are included. In the above polymer, the ratio of monomer units forming hydrophilic structural parts is particularly important. In other words, when the weight ratio of monomer units forming hydrophilic structural moieties such as carboxyl groups, sulfonic acid groups, or sulfuric ester groups exceeds approximately 40% by weight, the substrate 1
The so-called sizing effect on the coating layer 2 decreases, and the degree of bleeding of the recording liquid (ink) attached to the coating layer 2 becomes excessive, and the dyed area decreases, resulting in a decrease in the color density of the print. On the other hand, when this weight ratio is less than 2% by weight, the bonding force between the coating layer 2 and the substrate 1 decreases, resulting in a disadvantage that the coating layer 2 and the substrate 1 are easily peeled off. Therefore, a more preferable ratio of the hydrophilic structure portion in the above polymer is about 25 to 40 by weight.
%. Also, if the molecular weight of this polymer is too low,
Generally, it is desirable to use a polymer having a molecular weight of about 2,000 or more, since this may lead to deterioration of film-forming properties. Such a polymer can be produced according to the following method. For example, by mixing essential monomer components in a predetermined ratio, solution polymerization method, emulsion polymerization method,
A polymer having a desired molecular weight is synthesized by a method such as a suspension polymerization method (using a polymerization regulator if necessary). Separately, polymers containing acid anhydrides, esters, nitrile groups, hydroxyl groups, etc. are prepared first, and these groups are subsequently added to the polymer by hydrolysis, saponification, sulfate esterification, or sulfonation. A method of generating a carboxyl group or the like can also be adopted. The amine salt, etc. may be formed at any time; for example, any method may be used, such as polymerization using an amine salt, etc. of the carboxylic acid monomer, or adding an amine, etc. after polymerization or after the above-mentioned hydrolysis, etc. can also be adopted. In addition, the porous inorganic particles used in combination with the polymer are components that can adsorb and capture pigments (for example, dyes) in the ink in the coating layer 2 mainly through physical action. In some cases, it is actively used. As such a component, a white inorganic pigment that is porous and has ionicity on the particle surface can be particularly effectively used in the present invention. in particular,
Natural zeolite, synthetic zeolite (e.g., molecular sieve [manufactured by Union Carbide]), diatomaceous earth, finely divided silica (average particle size, 1μ or less),
Silica (average particle size, 20μ or less), synthetic mica [general formula: M.Mg2.5 (Si ₄ .O ₁₀ ), where M is a hydrogen atom or a metal atom. ], etc. can be used. In the present invention, these polymers and particles (...
Particle size generally from several hundred millimicrons to several microns]
A coating layer paint is prepared by dissolving or dispersing each of these as a single component or in combination in a paint solvent.
At this time, if the film-forming ability of the polymer is poor, other binder resins may be used in combination. As such a resin, either water-soluble or organic solvent-soluble resin can be used. For example, water-soluble resins include polyvinyl alcohol, starch, casein, gum arabic, gelatin, polyacrylamide, carboxymethyl cellulose, sodium polyacrylate, sodium alginate, etc., and organic solvent-soluble resins include polyvinyl butyral, polyvinyl chloride, etc. , polyvinyl acetate, polyacrylonitrile, polymethyl methacrylate, polyvinyl formal, melamine resin,
These include polyamide resins, phenolic resins, polyurethane resins, alkyd resins, etc. Further, as a solvent for preparing the paint, water alone or a mixture of water and a water-soluble organic solvent may be used. Examples of water-soluble organic solvents include methyl alcohol, ethyl alcohol, n-propyl alcohol, iso-propyl alcohol, n-butyl alcohol, sec-butyl alcohol, tert-butyl alcohol, iso-butyl alcohol, furfuryl alcohol, and tetrahydrofuryl alcohol. Alcohols such as furyl alcohol; ketone or keto alcohols such as acetone, methyl ethyl ketone, and diacetone alcohol; ethers such as tetrahydrofuran and dioxane; esters such as ethylene carbonate and propylene carbonate; N,N'-dimethylformamide, N, Examples include nitrogen-containing solvents such as N'-dimethylacetamide, N-methyl-2-pyrrolidone, and diethanolamine. To form the coating layer 2, generally 1 g/m ² to 10 g/m 2 is coated on the substrate 1 by a known method (for example, roll coating method, rod bar coating method, spray coating method).
Apply the above paint in an amount of about ² m2. Practically speaking, it is preferable to apply the coating at a rate of about 2 g/m ² to 5 g/m ² . After such a coating layer is provided, the coating layer is dried as soon as possible. The coating layer 2 obtained in this way has a partial area 2.
As shown in the partial enlarged view 2L drawn at 50 times magnification, irregularly shaped cracks 4 (...most of these cracks 4 are
It has even reached the surface of the base 1. ) A large number of fine scale-like films 3 are arranged in a two-dimensional arrangement in close proximity to each other. The size of one scaly film 3 is not particularly limited, but is approximately 10 μm x 10 μm to several hundred μm x several hundred μm.
m is generally used, and the width of the crack 4 is also not particularly limited in the present invention, but is usually about several μm. Incidentally, the individual size and shape of the scale-like film 3, the width of the cracks 4, etc. can be determined by adjusting or controlling the composition or film-forming conditions of the paint, especially the drying conditions after coating. It can be changed arbitrarily within the above range. When ink adheres to the coating layer 2 described above, the pigment (for example, dye) in the ink may cause ionic bonds, hydrogen bonds, etc. with the polymer constituting the coating 3, or may form physical bonds with the porous inorganic particles. and is selectively adsorbed and captured by the film 3. On the other hand, after the solvent in the ink passes through the cracks 4, it is quickly absorbed into the substrate 1. In this way, in the present invention, the coloring matter in the ink is captured almost at the outermost surface area of the recording paper, so that the color development is extremely good. Furthermore, since the solvent in the ink quickly migrates to the underlying substrate through the cracks, an apparent dry state can be quickly achieved on the surface of the recording paper. Furthermore, the scale-like film 3 is particularly effective in preventing ink dots from becoming unnecessarily large on the recording paper, the dot density being high, and the area around the dots not being blurred. This is because the pigments in the ink are intensively adsorbed.
The quality of this adsorption ability is mainly determined by the chemical properties of the polymer (for example, ionicity) and the surface physical properties of the particles (for example, porosity). In the present invention, it is undesirable that the area occupied by the scale-like film 3 in the coating layer 2 is extremely reduced, and that the area occupied by the cracks 4 is extremely increased. In other words, in the former case, there is a drawback that the dye capture rate is lowered and the coloration and density of the dots are reduced. In the latter case, the amount of ink transferred to the substrate increases, resulting in the so-called ink strike-through phenomenon and deterioration of the dot shape. Therefore, it is desirable to avoid these aspects in the present invention. Here, more detailed examples will be described to illustrate the effects of the present invention. In addition, prior to Examples, synthesis examples of polymers which are the main components according to the present invention and examples of commercially available polymers are illustrated below. (All parts in the synthesis examples are parts by weight.) *Synthesis Example 1 50% water in a four-fluid separable flask equipped with a stirrer
1 part, 30 parts of isopropyl alcohol, 0.5 part of sodium dodecylbenzenesulfonate, and 0.5 part of ammonium persulfate are mixed and heated to 60°C. Separately, a mixed solution of 5 parts of styrene, 9 parts of acrylic acid, and 5 parts of butyl acrylate was placed in a separating funnel and gradually added dropwise over 60 minutes. After dropping, raise the temperature to 80℃ and add 2 more times.
Polymerization was carried out by stirring for hours. The molecular weight of the obtained polymer was approximately 50,000. Example 2 In a flask similar to Example 1, 8 parts of methyl methacrylate, 5 parts of styrene, 15 parts of itaconic acid, 1 part of benzoyl peroxide, 1 part of lauryl mercabutane, 50 parts of diacetone alcohol, and 20 parts of ethylene glycol were charged, and nitrogen gas was added. Polymerization was carried out for 6 hours while passing through. The molecular weight of the obtained polymer was approximately 30,000. A polymer was obtained from the following raw materials in the same manner as in Example 2. Example 3 Styrene 10 parts Acrylonitrile 5 Methacrylic acid 10 Hydroxyethyl methacrylate 5 Azobisisobutyronitrile 1 Ethylene glycol monomethyl ether 19 Butanol 50 (Molecular weight: approx. 15,000) Example 4 Vinylnaphthalene 10 parts Dimethylamino methacrylate 5 Maleic anhydride 10 Methyl ethyl ketone peroxide 1 Isopropyl alcohol 60 Triethanolamine 14 (Molecular weight: approx. 20,000) Example 5 Styrene 10 parts Maleic anhydride 10 parts Diethanolamine 2 Azobisisobutyro Nitrile 1 Ethyl acrylate 5 Ethyl carbitol 23 Ethylene glycol monomethyl ether 50 (Molecular weight: approx. 30,000) Example 6 Styrene 5-part itaconic acid monoethyl ester 5 Methacrylic acid 10 2-ethylhexyl methacrylate 10 Benzoyl bar Oxide 1〃 Thiomalic acid 1〃 N-propyl alcohol 48〃 Ethylene glycol 20〃 (Molecular weight: approx. 8,000) Commercial product example a Sodium naphthalene sulfonate formalin condensate Product name: Demol N [Kao Atlas Co., Ltd.] b Diisobutylene-maleic acid copolymer product name: Demol EP [Kao Atlas Co., Ltd.] c Sodium polyacrylate product name: Nobucosanto R [San Nobuco Co., Ltd.] d Ammonium polyacrylate product name: Nobucosanto RFA [San Nobuco Co., Ltd.] e Sodium polymethacrylate product name: Primal 850 [Rohm & Haas Co., Ltd.] f Styrene-maleic acid copolymer (monoester ammonium salt) Product name ;SMA resin 1440H [Alcochemical
(KK)〕 g PEG product name; Macrogol 1500 [NOF Corporation] h PEG-PPG block polymer product name; UNILUBE 40DP-50B [NOF Corporation] Example 1 Polymer obtained in Synthesis Example 6 (30 parts by weight) ), silica (50 parts by weight), and water (150 parts by weight) are thoroughly stirred.
A slurry was obtained by mixing. The slurry was applied to 5 sheets of base paper (basis weight, 60 g/m ² ).
Each was coated on one side of the paper so that the dry solid content was approximately 4 g/m ² . Next, these were dried under the following conditions to prepare recording paper samples. *Drying conditions Sample: Naturally dried by leaving. Sample: 2 hours in oven (60℃). Sample: 30 minutes with 90℃ hot air. Sample: 1 minute with 110℃ hot air. Sample: 2 hours with 180℃ hot air. The surface condition of each of the above samples is shown in electron micrographs (X200) in FIGS. 2 to 6. Table 1 below summarizes the results of a comparative study of the characteristics in inkjet recording of each of the samples thus obtained. In addition, in Table 1 below, the dot density was measured using a Sakura microdensitometer PDM-5 (manufactured by Konishiroku Photo Industries Co., Ltd.), with a slit width of 30μ in width and 30μ in height, and a slit width in the X-axis direction. Electric speed 10μ/sec, chart feed speed 1mm/
The feeding speed ratio of the sample to the sec chart is the result of measurement at 100 times magnification. The dot diameter was determined by measuring the diameter of the printed dot using a stereomicroscope. The fixing time can be determined by using a device in which a rubber roller is placed a certain distance from the inkjet head used, and the paper feeding speed is varied to change the time it takes for the ink dot to contact the rubber roller. The time taken from when ink dots were generated to when ink no longer adhered to the roller was measured. In addition, the ink ejection opening diameter (orifice diameter) of the inkjet recording device used here was 50μ,
The ink used had the following composition. Water Black 187L (manufactured by Orient Co., Ltd.) 10 parts by weight diethylene glycol 30 〃 Water 60 〃 Ink physical properties: Viscosity 3.8 cps (measured with Tokyo Keiki E-type rotational viscometer) Surface tension 52.4 dyne/cm (Kyowa Kagaku hanging plate type surface tension) (measured with a meter)

[Table] Example 2 The polymer obtained in Synthesis Example 3 (50 parts by weight), diatomaceous earth (70 parts by weight), water (110 parts by weight) and ethanol (50 parts by weight) were thoroughly stirred and mixed. Created slurry. This slurry was applied to the surface of a base paper having a basis weight of 65 g/m ² so that the dry solid content was 4 g/m ² and dried with hot air at 180° C. for several seconds to prepare a recording paper. When an electron micrograph was taken of the surface of this coating layer, a photograph almost equivalent to that shown in FIG. 6 was obtained. Further, when inkjet recording was performed on this recording paper in the same manner as in Example 1, the results were almost the same as in the case of the sample of Example 1. Example 3 The polymer obtained in Synthesis Example 4 (80 parts by weight), synthetic zeolite (130 parts by weight), polyvinyl alcohol (20 parts by weight), water (250 parts by weight), and methanol (100 parts by weight) were sufficiently mixed. After stirring and mixing to prepare a slurry, the same procedure as in Example 2 was carried out to obtain substantially the same results. Examples 4 and 5 Inkjet recording was performed on the same sample as that obtained in Example 2 in the same manner as in Example 1 using the inks shown in Table 2 below, and the results are shown in Table 2 below. It was hot.

All numerical values, codes, etc. in [Table] are based on Example 1.
Example 6 Full-color recording was performed using cyan, magenta, yellow, and black inks using the same sample as in Example 3, and the fixing time, dot density, and dot diameter were almost the same as in Example 1. An equivalent product was obtained, and a full-color photograph with each color extremely clear and with good color reproducibility was also reproduced. Example 7 When printing was performed using a commercially available fountain pen on the recording paper obtained in Example 2, there was no smearing, the ink was absorbed quickly, and very clean characters were written. As mentioned above, in the present invention, the attached recording liquid (ink) is quickly absorbed into the inside of the recording liquid (ink).
Even when recording liquid of different colors is repeatedly deposited on the same spot within a short period of time, there is no phenomenon of recording liquid flowing out or seeping out, and the ink coloration is good. It is possible to provide a recording material that is particularly suitable for multicolor inkjet recording, in which the sharpness of the image can be suppressed to a level that does not impair the sharpness of the image.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of the configuration of the present invention, and FIGS. 2 to 6 are diagrams showing electron micrographs of the surface of recording paper. In the figure, 1 is a base, 2 is a coating layer, 3 is a scale-like film, and 4 is a crack.

Claims (1)

[Scope of Claims] 1. A polymer having both a hydrophilic structural part and a hydrophobic structural part, in which the weight ratio of monomer units forming the hydrophilic structural part is 2 to 40% by weight, and porous inorganic particles. The surface of the coating layer is partitioned by formed irregular cracks, and the size of the partitioned portion is as follows:
A recording material for an inkjet having a size ranging from 10 μm x 10 μm to several hundred μm x several hundred μm. 2. The recording material for an inkjet according to claim 1, wherein the width of the crack is several μm. 3. The recording material for an inkjet according to claim 1, wherein the cracks reach the substrate.