JPH0761116A - Ink jet recording method - Google Patents

Abstract

PURPOSE:To provide an ink jet recording method capable of forming a recording image especially excellent in transparency and surface glossiness using a recording medium satisfying various characteristics in good balance at the same time. CONSTITUTION:Ink whose surface tension is 25-35 dynes/cm is used while a recording medium consisting of a base material and the coating layer based on a copolymer consisting of vinyl pyrrolidone and a vinyl monomer having a hydrophobic group and polyalkylene oxide or a derivative thereof provided on the base material is used.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet recording method capable of providing an image having a high color density and a high resolution, and particularly to a recorded image excellent in translucency or surface glossiness. Inkjet recording method suitable for

[0002]

2. Description of the Related Art Conventionally, as a recording medium for forming an image used in an ink jet recording method, for example, Japanese Patent Publication No.
Japanese Patent Publication No. 3-2535, which has a coating layer containing a finely divided silica and a water-soluble binder such as polyvinyl alcohol on a base paper as described in Japanese Patent Publication No. 26665.
A glossy paper as described in JP-A No. 2-9, which has a film containing polyvinyl alcohol having a degree of saponification of 50 to 90 mol% and a cross-linking agent formed on one surface of a cast coated paper as an ink receiving layer, and further, JP A saponification degree of 7 on a polyester film as described in JP-A-60-220750.
Recording sheets for overhead projectors (OHP) have been used in which an ink receiving layer is provided with a hydrophilic film composed of 0 to 90 mol% of water-soluble polyvinyl alcohol.

[0003]

In recent years, speeding up of recording,
Along with the improvement in the performance of inkjet recording apparatuses such as multicolor printing, more advanced and broader characteristics are required for inkjet recording media. In particular, (1) high ink absorption capacity (large absorption capacity, fast absorption time). (2) The optical density of the ink dots is high, and the area around the dots is not blurred. (3) The shape of the ink dots is close to a perfect circle, and the area around the dots is smooth. (4) Changes in characteristics are small due to changes in temperature and humidity. No curling (5) It is required to simultaneously satisfy the characteristics such as blocking. Further, (6) the image formed on the recording medium is stable and does not deteriorate in long-term storage (especially under high temperature and high humidity environment) (7) the recording medium itself is stable and does not deteriorate in long-term storage (especially high temperature and high humidity) Preservability such as in a moist environment) is also required.

Further, by using the ink jet recording method,
It is also required to form an image having excellent transparency that can be used for OHP and an image having high gloss on the surface, and a recording medium having excellent translucency and a recording medium having gloss on the surface (glossy paper) are required. is necessary. These recording media require a transparent coating layer to be provided as much as possible in order to suppress the diffuse reflection of incident light on the recording surface. Therefore, a hydrophilic resin such as polyvinyl alcohol is formed on the substrate such as the film described above. It has been formed by providing an ink receiving layer as a main component.

In the ink jet recording method for forming such a translucent image or surface glossy image, as the recording speed increases, the image density increases, and the color increases,
The deterioration of image quality due to poor ink fixation of the recording medium has become a serious problem. That is, since the recording surface of these recording media does not have a porous structure like that of conventional coated paper or plain paper, the ink absorption capacity is insufficient, and therefore, the portion where the image density is high, that is, the amount of ejected ink is large. Image stains caused by ink spilling out in areas, and uneven density (beading) such as unfixed ink droplets condensing on the recording surface.
In particular, in the case of forming a color image, color smear (boundary blur) due to color mixture at the boundary portion of different colors occurs.
These phenomena significantly reduce the sharpness of the image.

For example, in a recording sheet provided with an ink receiving layer composed mainly of polyvinylpyrrolidone described in Japanese Patent Publication No. 3-29596, the ink absorbing capacity is relatively good at room temperature and normal humidity, but at high temperature. Since the ink dries very slowly under high humidity, blocking is likely to occur, and the mechanical strength of the recording surface is weak and scratches are likely to occur.

Particularly, in the recording method using the recording sheet having the above-mentioned light-transmitting property or surface glossiness, an attempt to improve the problem of beading or boundary bleeding, which is a remarkable problem, from the side of the recording medium has been successful. However, a sufficiently effective recording medium has not been obtained. Further, almost no studies have been made to solve these problems from both aspects of the ink recording medium.

An object of the present invention is to provide an ink jet recording method using a recording medium which simultaneously satisfies the above-mentioned various characteristics in a well-balanced manner. In particular, it has high density, high resolution, transparency and surface gloss. An object of the present invention is to provide an inkjet recording method capable of forming a recorded image having excellent properties.

[0009]

The above object of the present invention is to form a recorded image on a recording medium by ejecting a droplet of ink from an orifice of a recording head in accordance with a recording signal and adhering it to the recording medium. In the inkjet recording method, the ink has a surface tension of 25 to 35 dy.
An ink in the range of ne / cm is used, and as the recording medium, a substrate and a copolymer of vinylpyrrolidone and a vinyl monomer having a hydrophobic group, which is provided on the substrate, and a polyalkylene. An ink jet recording method, characterized by using a recording medium comprising a coating layer mainly containing oxide or a derivative thereof.

In the above method of the present invention, preferably, four kinds of ink, cyan, magenta, yellow and black inks are used as the ink, and a color recorded image is formed on the recording medium.

As a preferred embodiment of the present invention,
In the above inkjet recording method, the coating layer constituting the recording medium contains a hydrophilic acrylic resin made of a copolymer of a vinyl group monomer having a cationic group and a vinyl group monomer having a hydrophobic group, the recording medium A coating layer containing 0.5% by weight or more of an epoxy compound, and / or the base material of the recording medium is a plastic film.

Further, as another embodiment of the present invention, in the above ink jet recording method, the liquid medium component of the ink is mainly composed of water and a water-miscible glycol or glycol ether. To form an image by having two or more orifices for ejecting ink for each color and ejecting two or more ink droplets of the same color at the same time, ejecting a small ink droplet at a frequency of at least 3 KHz, Has a maximum recording density of 6
There is provided a method characterized by being nl / mm ² or more, or by ejecting ink by thermal energy.

The inventors of the present invention have described a method of forming a light-transmitting image that can be used in, for example, an overhead projector or the like, or an image having a high glossy surface comparable to a silver salt photograph, by using an ink jet recording method. Consider
By performing inkjet recording on a recording medium having a coating layer of the specific composition using an ink having a surface tension in the specific range, it is possible to form a recorded image satisfying the required performance. In particular, it was a remarkable problem when forming a recorded image as described above,
The inventors have found that it is possible to form a high-quality recorded image without the occurrence of beading or boundary bleeding, and have completed the present invention.

According to the findings of the present inventors, the problem of beading and boundary bleeding is not only the problem due to insufficient ink absorbability of the recording medium as described above, but also the problem of adhesion to the recording sheet. It is also a problem related to the wettability between the ink and the surface of the recording medium. That is, if the wettability of the ink with respect to the surface of the recording medium is insufficient in solid printing, or a portion where recording is performed in the vicinity of the solid printing, a slight deviation in the position where the ink droplets land on the recording medium surface, etc. Unfixed ink droplets of adjacent pixels on the surface of the medium gather together in an irregularly connected form in units of several to several tens, and become an isolated state. Seeming beading phenomenon occurs.
On the other hand, when the wettability is good, almost all unfixed ink droplets are uniformly connected to form an aggregated state, so that the recording portion looks uniform without uneven density. On the other hand, when the wettability is excessively high, this occurs at a boundary portion recorded with inks of different colors, which causes color mixing and causes a problem of boundary blurring in which the boundary is unclear. As described above, it has been found that these problems are problems in which it is difficult to obtain a sufficient solution even if the improvement is made only on the recording medium side.

Adjusting the surface tension of the ink so as to optimize the wettability of the ink on the recording medium is one means for solving the above problems. However,
According to the results of the study by the present inventors, not only the preferable range of the surface tension of the ink described above varies depending on the material forming the recording medium surface, but also the preferable range is extremely narrow, or there is no range in which both are compatible. It was also found that the image quality level when optimized was different. From the results of such studies, the present inventors selected a specific material as a recording medium forming material in consideration of the synergistic effect of the combination with ink, and further selected the most suitable surface strength for the material. The inventors have found that it is possible to form a high-quality light-transmitting image and surface glossy image that could not be obtained by combining the inks with the inks of the present invention, and arrived at the present invention.

The term "translucency" as used in the present invention means that the linear transmittance of the recording medium is 30% or more. Here, the linear transmittance (T%) means that the light is vertically incident on the sample, passes through the sample, passes through the light-receiving slit on the extension line of the incident light path at a distance of at least 8 cm from the sample, and is transmitted to the detector. The spectral transmittance of the received linear light is measured by using, for example, a 323 type Hitachi self-recording spectrophotometer (manufactured by Hitachi Ltd.), and the Y value of the tristimulus value of the color is calculated from the measured spectral transmittance. It is a value calculated from the following equation based on these values.

T = (Y / Y0) × 100 T; linear transmittance Y; sample Y value Y0; blank Y value Further, the excellent surface gloss recording sheet referred to in the present invention is
At least one surface of the recording medium has a 60-degree specular gloss of 30% or more. What is 60 degree specular gloss?
It is a value measured based on IS-Z-8741.

The present invention will be described in detail below with reference to preferred embodiments.

The first feature of the present invention is to provide a specific material as an ink receiving layer on a substrate, that is, a copolymer of vinylpyrrolidone and a vinyl monomer having a hydrophobic group, and a polyalkylene oxide or a derivative thereof. The point is to use a recording medium provided with a coating layer mainly composed of.

Recording media per se having a coating layer containing polyvinylpyrrolidone, a homopolymer of vinylpyrrolidone, are known as already mentioned. In the present invention,
The copolymer of the first component constituting the coating layer can be obtained by copolymerizing vinylpyrrolidone and the following vinyl-based monomer having a hydrophobic group by a known method.

Examples of vinyl monomers having a hydrophobic group include alkyl acrylates such as methyl acrylate and ethyl acrylate, methacrylic acid alkyl esters such as methyl methacrylate and ethyl methacrylate,
Examples thereof include styrene, vinyltoluene, vinyl acetate, ethylene and the like. The copolymerization ratio of vinylpyrrolidone and these monomers is preferably in the range of 4/6 to 9/1 (molar ratio). Outside the above range, problems such as beading and boundary bleeding may occur. Moreover, you may contain other hydrophilic monomers, such as 2-hydroxyethyl acrylate and 2-hydroxyethyl methacrylate, as needed.

On the other hand, the second component constituting the coating layer, polyalkylene oxide, is a polyhydroxy compound obtained by adding ethylene oxide and / or propylene oxide to a compound having two or more active hydrogen groups. . Examples of the compound having two or more active hydrogen groups include ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, 1,4-butanediol, 1,6-
Hexanediol, tetraethylene glycol, polyethylene glycol, polypropylene glycol, propylamine, butylamine, octylamine, cyclohexylamine, bisphenol A, glycerin, trimethylolpropane, pentaerythritol, monoethanolamine, diethanolamine, triethanolamine, isopropanolamine, etc. Can be mentioned.

Similarly, examples of the polyalkylene oxide derivative constituting the coating layer include reaction products of the above polyhydroxy compounds and compounds having reactivity with them. It is desirable that these have a weight average molecular weight of at least 20,000 or more. Those having a low molecular weight have strong adhesiveness even after the ink receiving layer is formed, and are likely to cause blocking and the like.

Particularly preferred polyalkylene oxide compounds include the following. That is, the above polyhydroxy compound has a weight average molecular weight of 1,000.
A polymer having a weight average molecular weight of 20,000 or more obtained by reacting the above with a polycarboxylic acid, an acid anhydride thereof, or a lower alkyl ester thereof. Specific examples of the polycarboxylic acid to be reacted with the polyhydroxy compound include malonic acid, maleic acid, succinic acid, fumaric acid, itaconic acid, phthalic acid, isophthalic acid, terephthalic acid, adipic acid, sebacic acid, dimer acid and pyrol. Examples thereof include meritic acid and trimellitic acid. Examples of the lower alkyl ester include monomethyl, dimethyl, monoethyl, diethyl, monopropyl, dipropyl, monobutyl, dibutyl ester and the like. The reaction of such a polyhydroxy compound with a polycarboxylic acid, an acid anhydride thereof, or a lower alkyl ester thereof is dehydrated or dealcoholized (transesterification) under reduced pressure of 0.001 to 20 mmHg under heating at 80 to 250 ° C., for example. It is obtained by carrying out the reaction for 30 minutes to 10 hours. When the molecular weight of the polymer compound obtained here is less than 20,000, the film strength is weak and the blocking resistance may be unsatisfactory.

According to the recording medium having the above-mentioned coating layer mainly composed of two components as the ink receiving layer, when used in combination with an ink having a specific surface tension, beading, It is possible to form an image with excellent uniformity without causing image unevenness such as joining stripes, etc. Further, it is possible to form a clear image with excellent ink absorbency and less occurrence of boundary bleeding.

Further, there is an advantage that the above performance can be maintained in any environment such as low temperature and low humidity and high temperature and high humidity.

In the method of the present invention, in the coating layer of the recording medium, in addition to the above two components, a hydrophilic acrylic resin which is a copolymer of a vinyl monomer having a cationic group and a vinyl monomer having a hydrophobic group. A resin can be blended. The hydrophilic acrylic resin is, for example, a copolymer having at least one monomer selected from the following two groups as a constituent unit. Examples of the monomer having a cationic group include dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate, diethylaminoethyl acrylate, diethylaminoethyl methacrylate, methylethylaminoethyl acrylate, dimethylaminostyrene, diethylaminostyrene, methylethylaminostyrene, and the like. Examples thereof include those having a primary to tertiary amine or quaternary ammonium base in the side chain, such as quaternized compounds. Examples of the monomer having a hydrophobic group include alkyl acrylates such as methyl acrylate and ethyl acrylate, methacrylic acid alkyl esters such as methyl methacrylate and ethyl methacrylate, styrene, vinyltoluene, vinyl acetate and ethylene. To be The copolymer composition of the copolymer is preferably in the range of monomer having a cationic group / monomer having a hydrophobic group = 1/9 to 9/1 (molar ratio). Such a copolymer may contain another hydrophilic monomer such as 2-hydroxyethyl acrylate or 2-hydroxyethyl methacrylate as a constituent unit, if necessary.

As described above, in the recording medium used in the method of the present invention, a copolymer of vinylpyrrolidone and a vinyl monomer having a hydrophobic group and a polyalkylene oxide are provided on at least one surface of the substrate. Alternatively, if a coating layer (ink receiving layer) containing the hydrophilic acrylic resin is provided in addition to the derivative thereof, all the required properties for the inkjet recording medium are well balanced, and the recording medium itself and the image are exposed to high temperature and high humidity. It is preferable because the deterioration of the recording medium itself and the image can be suppressed as much as possible when left in the environment for a long time. This is due to the synergistic effect of the above three components.

In the recording medium of the above preferred embodiment,
The polyalkylene oxide (particularly polyethylene oxide) or its derivative is preferably contained in the coating layer (in the ink receiving layer) in an amount of 2 to 10% by weight.
When the amount is less than the lower limit of the above range, deterioration of the recording medium itself (decrease in ink absorbency) is likely to occur particularly when the recording medium is left in a high temperature and high humidity environment for a long time. When the amount is more than the upper limit of the above range, even if a hydrophilic acrylic resin which is a copolymer of a vinyl monomer having a cationic group and a vinyl monomer having a hydrophobic group is used in combination, the temperature is kept high in a high temperature and high humidity environment for a long time. Deterioration when the image is left (dots bleed over time,
Image sharpness is reduced. ) Is likely to occur.

When a hydrophilic acrylic resin, which is a copolymer of a vinyl monomer having a cationic group and a vinyl monomer having a hydrophobic group, is contained in the ink receiving layer, the content of the hydrophilic acrylic resin is at least polyalkylene oxide. Or it is desirable that it is larger than its derivative. The hydrophilic acrylic resin, which is a copolymer of a vinyl group-containing monomer having a cationic group and a vinyl group-containing monomer having a hydrophobic group in the above aspect, is contained in the ink receiving layer in an amount of 10 to 40.
It is preferably contained in a weight percentage. When the amount is less than the lower limit of the above range, bleeding of an image with time may occur in a high temperature and high humidity environment even if the polyalkylene oxide or its derivative is contained in the above range. When the content exceeds the upper limit of the above range, unevenness occurs on the image, which is not preferable.

Further, in the present invention, in the above recording medium, the mechanical properties of the recording surface are improved by containing the epoxy compound in the coating layer in an amount of 0.5% by weight or more, preferably 0.5 to 5% by weight. It is possible to further improve the strength. Specific examples of epoxy compounds include ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, neopentyl alcohol diglycidyl ether, glycerol polyglycidyl ether, trimethylolpropane polyglycidyl ether. , Diglycerol polyglycidyl ether and the like.

The recording medium used in the method of the present invention is a coating layer (ink receiving layer) formed by coating the composition containing the above components on at least one surface of the substrate.
Various binders and filler additives may be used in combination with this composition within a range that does not impair the achievement of the object of the present invention. As an example of the binder, conventionally known starch,
Cationized starch, casein, gelatin, acrylic resin, maleic anhydride resin, melamine resin, urea resin, S
Examples include, but are not limited to, BR latex, sodium alginate, polyvinylpyrrolidone, carboxymethyl cellulose, hydroxyethyl cellulose, polyvinyl alcohol and the like. Examples of the filler include silica, alumina, aluminum silicate, magnesium silicate, basic magnesium carbonate, talc, clay, hydrotalcite, calcium carbonate, titanium oxide, inorganic pigments such as zinc oxide, and polyethylene, polystyrene, polyacrylate. , But not limited to such plastic pigments. Specific examples of additives include various surfactants, dye fixing agents (waterproofing agents),
Examples thereof include antifoaming agents, antioxidants, fluorescent whitening agents, ultraviolet absorbers, dispersants, viscosity adjusting agents, pH adjusting agents, antifungal agents and plasticizers. These additives may be arbitrarily selected from known compounds according to the purpose.

As the substrate constituting the recording medium used in the method of the present invention, for example, high-quality paper, medium-quality paper, art paper, bond paper, recycled paper, baryta paper, cast coated paper, cardboard paper and the like, and polyethylene. Film or plate made of plastics such as terephthalate, diacetate, triacetate, cellophane, celluloid, polycarbonate, polyimide, polyvinyl chloride, polyvinylidene chloride, polyacrylate, polyethylene, polypropylene, or cotton, rayon,
Cloths such as acrylic, nylon, silk and polyester can be used. It is appropriately selected from the above-mentioned base materials depending on the recording purpose of the recording medium, the use of the recorded image, or various conditions such as adhesion to the composition coated on the upper side thereof.
When a transparent recording sheet or a surface glossy recording sheet is prepared, a plastic film is preferable.

The recording medium used in the method of the present invention can be prepared as follows.

That is, first, the composition for forming the coating layer (ink receiving layer) is dissolved or dispersed in water, alcohol, or another suitable organic solvent together with other additives, if necessary, to prepare a coating solution. Prepare.

Subsequently, the obtained coating liquid is applied, for example, by a roll coater method, a blade coater method, an air knife coater method, a gate roll coater method, a size press method, a spray coat method, a gravure coater method, a curtain coater method or the like. Apply to the surface of the substrate. Then, for example, it is dried by using a hot air drying oven, a heating drum or the like to obtain a recording medium. If necessary, the surface of the coating layer may be subjected to a super calendar treatment or the like.

The total coating amount of the ink receiving layer is 0.2 to 50 g / m ² , more preferably 1 to 30 g / m ² .
It is within the range of m ² . When the coating amount is small, a part of the base material may be exposed on the surface. Also, the coating amount is 0.2g
/ M ² is less effective in terms of color development of the dye than when the ink receiving layer is not provided, while
When the amount is more than 50 g / m ² , curling may occur remarkably in a low temperature and low humidity environment, which is not preferable. The thickness of the coating layer is preferably in the range of 0.5 to 100 μm.

The second feature of the ink jet recording method of the present invention is to perform recording on the above-described recording medium using an ink having a surface tension in the range of 25 to 35 dyne / cm. When an ink having a surface tension of more than 35 dyne / cm is used, beading in a recorded image formed is remarkable even when the recording medium is used, which is not preferable. Further, if it is 25 dyne / cm or less, an image without beading can be obtained, but the blurring at the boundary becomes worse. The surface tension referred to in the present invention is 25.
It is a value measured according to a conventional method at ° C.

The ink used in the present invention generally contains a dye (recording agent) for forming an image and a liquid medium for dissolving or dispersing the dye as essential components, and various kinds are added as necessary. It is prepared by adding a dispersant, a surfactant, a viscosity adjusting agent, a specific resistance adjusting agent, a pH adjusting agent, an antifungal agent, a dissolution (or dispersion) stabilizer of a recording agent, and the like.

Examples of the recording agent used in the ink include linear dyes, acid dyes, basic dyes, reactive dyes, food dyes, disperse dyes, oil dyes and various pigments. It can be used without restriction. The content of such a dye is determined depending on the type of liquid medium component, the characteristics required for the ink, etc., but is generally preferably about 0.1 to 20% by weight.

In the ink used in the present invention, the liquid solvent for dissolving or dispersing the dye as described above may be water or a mixed solvent of water and a water-soluble organic solvent, and particularly preferable ones are It is a mixed solvent of water, a water-soluble organic solvent, and contains, as a water-soluble organic solvent, a polyhydric alcohol having an ink drying preventing effect.

Examples of the organic solvent usable for the ink include alkyl alcohols such as methanol, ethanol, isopropyl alcohol, n-butanol, and the like;
Amides such as dimethylformamide and dimethylacetamide; ketones such as acetone and acetone alcohol; reto alcohols; ethylene glycol, propylene glycol, triethylene glycol, thiodiglycol, diethylene glycol, 1,2,6-hexanetriol, polyethylene glycol, etc. Alkyl ethers of polyhydric alcohols such as (di) ethylene glycol monomethyl (or ethyl) ether and triethylene glycol mono (or di) methyl (or ethyl) ether; sulfolane, n
-Methyl-2-hirolidone, 1,3-dimethyl-2-imidazolidinone and the like. These are 1 or 2
Used in the form of a mixture of one or more species.

The ink is adjusted to have a surface tension within the predetermined range by using the above materials and further adding a surfactant or the like if necessary.

Examples of the surfactant include polyoxyethylene alkyl ethers such as polyoxyethylene lauryl ether and polyoxyethylene cetyl ether; polyoxyethylene alkyl such as polyoxyethylene nonylphenyl ether and polyoxyethylene octylphenyl ether. Phenyl ethers; sorbitan monooleate, sorbitan tristearate and other sorbitan fatty acid esters; glyceryl monostearate, glyceryl monooleate and other glycerine fatty acid esters; polyoxyethylene alkylamines, polyoxyethylene alkylamides, polyoxy Ethylene fatty acid esters, polyglycerin fatty acid esters, propylene glycol fatty acid esters, pentaerythritol fatty acid esters, acetyl Nonionic surfactants such as glycol, acetylene alcohol, and fluorine-based surfactants can be used. In addition to these, alkyl sulfates, polyoxyethylene alkyl ether sulfates, polyoxyethylene alkyl ether phosphates, alkylbenzenes, etc. Examples thereof include anionic surfactants such as sulfonates and alkylsulfosuccinates, and cationic surfactants such as benzalkonium chloride and quaternary ammonium salts of cetyltrimethylammonium chloride. It is not limited to Of these, particularly preferable surfactants include acetylene glycol and acetylene alcohol.

As an example of the ink containing the above-mentioned acetylene glycol and acetylene alcohol, there is disclosed in JP-A-63 / 1988.
The inks described in JP-A-139964 are listed. However, the preferable range of the surface tension of the ink described in this publication is 35 to 65 dyne / cm, which is different from the preferable range of the surface tension of the ink in the method of the present invention. As described above, in the present invention, a special material; a recording sheet having a polyvinyl acetal having an aromatic ring and a polyalkylene oxide or a derivative thereof, and an ink having a low surface tension, which has hitherto not been relatively preferable. By carrying out ink jet recording using, beading that could not be achieved by the conventional technology,
It enables the formation of high-quality translucent images and surface gloss images that do not cause boundary bleeding.

The ink jet recording method of the present invention may be any method as long as it can effectively separate the ink from the nozzle and apply the ink to the recording medium as a range. Particularly preferably, in the method described in Japanese Patent Laid-Open No. 54-59936, the ink subjected to the action of thermal energy causes a rapid volume change, and the action force due to this state change causes the ink to be ejected from the nozzle. The inkjet method can be effectively used.

An example of an ink jet recording apparatus which can be preferably used in the ink jet recording method of the present invention,
A description will be given with reference to the drawings.

First, the structure of the recording head, which is the main part of the apparatus, will be described with reference to FIGS.

FIG. 1 is a longitudinal sectional view of the recording head taken along the ink flow path, and FIG. 2 is a transverse sectional view taken along the line AB of FIG.

The recording head 13 in FIG.
A glass, ceramics, or plastic plate having a groove 14 for passing 1 and a heating head 15 used for thermal recording
(The head is shown in the figure, but not limited to this). The heating head 15 includes a protective film 16 made of silicon oxide, aluminum electrodes 17-1 and 17-2, a heating resistor layer 18 made of nichrome, a heat storage layer 19, and a substrate having good heat dissipation such as alumina. It is composed of twenty.

The ink 21 has a discharge orifice (fine hole) 2
2, the meniscus 23 is formed by the pressure P.

Here, when an electric signal (recording signal) is applied to the electrodes 17-1 and 17-2, the area indicated by n of the heating head 15 rapidly generates heat and bubbles are generated in the ink 21 in contact with the area. Occurs. The pressure of the bubbles causes the meniscus 23 to project and the ink 21 to be ejected, and the orifice 22
The recording droplets 24 are further formed and fly toward the recording sheet 25.

Subsequently, the small droplets 24 adhere to the ink receiving layer 26 of the recording sheet 25 to form a recorded image.

FIG. 3 is a perspective view showing the structure of a multi-head in which a large number of recording heads having the structure shown in FIG. 1 are arranged side by side. In the figure, the multi-head 27 is a multi-groove 2
Glass plate 29 having 8 and the heating head 15 shown in FIG.
A heating head 30 similar to the above is closely attached.

Next, an ink jet recording apparatus equipped with the recording head shown in FIG. 1 will be described with reference to FIG.

In the figure, reference numeral 61 denotes a blade as a wiping member, one end of which is held by a blade holding member (not shown) to become a fixed end, which is in the form of a cantilever. The blade 61 is arranged at a position adjacent to the recording area of the recording head 65, but in the case of this example, it is held in a protruding form in the movement path of the recording head 65. Reference numeral 62 denotes a cap, which is arranged at a home position adjacent to the blade 61, and has a configuration in which it moves in a direction perpendicular to the moving direction of the recording head 65 and contacts the ejection port surface to perform capping. Further, 63 is an ink absorber provided adjacent to the blade 61, and like the blade 61, is held in a form protruding in the movement path of the recording head 65. The blade 61, the cap 62, the absorber 63
The ejection recovery unit 64 is configured by the blade 61 and the absorber 63, and moisture, dust, and the like on the ink ejection port surface are removed.

The recording head 65 has an ejection energy generating means, ejects ink to a recording material facing the ejection port surface where the ejection ports are arranged to perform recording, and is mounted on the carriage 66 and moved as described below. To do. That is, the carriage 66 is slidably engaged with the guide shaft 67, and a part of the carriage 66 is connected (not shown) to a belt 69 driven by a motor 68. As a result, the carriage 66 can move along the guide shaft 67, and the recording head 65 can move the recording area and its adjacent area.

On the other hand, the recording medium as described above is inserted into the paper feeding section 51, and is conveyed to a position facing the ejection opening surface of the recording head 65 by the paper feeding roller 52 driven by a motor (not shown). . Then, the recording medium is sent to the outside by the paper discharge roller 53 as the recording progresses.

In the ink jet recording apparatus having the above structure, when the recording head 65 returns to the home position after the recording is completed or the like, the cap 62 of the ejection recovery section 64 is covered by the recording head 6.
Although the blade 61 is retracted from the movement route of No. 5, the blade 61 is projected in the movement route. As a result, the ejection port surface of the recording head 65 is wiped. When the cap 62 comes into contact with the ejection surface of the recording head 65 to perform capping, the cap 62 moves so as to project into the moving path of the recording head.

Further, 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 above-mentioned position at the time of wiping. As a result, even in this movement, the recording head 65
The discharge port surface of is wiped.

The above-described movement of the recording head 65 to the home position is not limited to the end of recording or the recovery of ejection.
That is, while the recording head 65 moves in the recording area for recording, it moves to a home position adjacent to the recording area at a predetermined interval. Along with this movement, the wiping is performed.

As described above, in the present invention, in particular, in forming a translucent recorded image or a recorded image excellent in surface gloss by using the ink jet recording system, the recording speed is increased, the recording density is increased, and the color is formed. Its main purpose is to solve the problems of beading and boundary blurring that accompany the above. Therefore, the inkjet recording method of the present invention,
Inkjet recording at high speed such that a droplet of each color ink is ejected from the orifice of the recording head at a driving frequency of at least 3 KHz or more, and at least two orifices for ejecting each color ink are provided. A recording method using an inkjet recording device capable of forming a recorded image by simultaneously ejecting two or more ink droplets of the same color using the recording head provided, and the maximum recording density of each color ink is 6 nl / mm ² or more. It is preferable to apply it to the inkjet recording method.

The maximum recording density in the present invention is the maximum number of single-color ink droplets that can be deposited per unit area when the recording system is used, multiplied by the volume of the ejected ink droplet. It is a thing.

[0064]

The present invention will be described in more detail with reference to the following examples. In the text, “part” or “%” is based on weight unless otherwise specified.

(Preparation of Recording Sheet) A coating liquid for forming a coating layer having the following composition was applied to a polyethylene terephthalate film (thickness 100 μm; made by Lumirror Toray) using a wire bar so that the coating thickness after drying was 20 μm. Then, it was dried at 100 ° C. for 10 minutes to prepare recording sheets for the present invention and for comparison.

Composition of coating solution Sheet 1 1/1 copolymer of vinylpyrrolidone and vinyl acetate (manufactured by Rubiscol 55E GA F) 10 parts Polyethylene oxide (Alcox R-40 manufactured by Meisei Chemical Co., Ltd.) 1 part Water / methanol mixed solvent 89 parts Sheet 2 7/3 copolymer of vinylpyrrolidone and vinyl acetate (manufactured by Rubiscol 73E GA F) 10 parts Polyethylene oxide (Alcox R-40 manufactured by Meisei Chemical Co., Ltd.) 0.5 part Water / methanol mixed solvent 89.5 Part Sheet 3 Copolymer of vinylpyrrolidone and styrene (Antara 450 GAF) 10 parts Polyethylene oxide (Alcox R-40 Meisei Chemical Co., Ltd.) 1 part Water / butanol mixed solvent 89 parts Sheet 4 Vinylpyrrolidone and vinyl acetate 1 / 1 copolymer (manufactured by Rubiscol 55E GA F) 14 parts Polyene Renoxide (Alcox R-40 manufactured by Meisei Chemical Co., Ltd.) 1 part Hydrophilic acrylic resin (Jurimer SP-50 manufactured by Nippon Pure Chemical Co., Ltd.) which is a copolymer of methyl methacrylate and an acrylic quaternary ammonium salt compound 5 parts Water / isopropyl Alcohol mixed solvent 80 parts Sheet 5 Polyvinyl alcohol having a saponification degree of 98 to 99% and a polymerization degree of about 1700 (made by PVA-117 Kuraray) 10 parts Water 90 parts Sheet 6 Polyvinylpyrrolidone (made of PVPK-90 GAF) 10 parts Polyethylene Oxide (Alcox R-40 manufactured by Meisei Chemical Co., Ltd.) 1 part Water / methanol mixed solvent 89 parts

The base film used for the preparation of the above recording sheet was used as it was to form a sheet 7.

A sheet 8 was prepared in the same manner as the sheet 1 except that a white polyethylene terephthalate film (manufactured by Melinex ICI) was used as the substrate, and a sheet 4 was prepared in the same manner as the sheet 4 except that art paper was used as the substrate. 9 was prepared.

(Examples 1-10, Comparative Examples 1-8, Inkjet recording) Recording sheets 1-9 prepared as described above,
Color recording was performed under the following conditions by using inks A to F having the following compositions and an inkjet recording device equipped with a mechanism for ejecting the ink by foaming the ink with thermal energy. The combinations of recording sheet and ink used in each example are shown in Table 1 below.

Ink composition Dye 4 parts Glycerin 10 parts 1,2,6-Hexanetriol 6 parts Urine 4 parts Acetylene glycol (trade name; Surfynol 104 Nisshin Chemical Co., Ltd.) x parts Water 76-x parts Dye Y: C. I. Direct Yellow # 86 M: C.I. I. Acid Red # 23 C: C.I. I. Direct Blue # 199 Bk: C.I. I. Hood Black # 2 Ink A x = 0.3 Surface tension = 43 dyne / cm Ink B x = 1 Surface tension = 28 dyne / cm Ink C x = 3 Surface tension = 26 dyne / cm Ink D x = 10 Surface tension = 20 dyne / cm Ink Ex = 1 Surface tension = 30 dyne / cm
Use acetylene alcohol (trade name; Surfynol 61 manufactured by Nisshin Chemical Co., Ltd.) instead of acetylene glycol. Ink F x = 1.5 Surface tension = 33 dyne / cm
Instead of acetylene glycol, polyoxyethylene nonylphenyl ether (trade name; Neugen EA-5
0 Daiichi Kagaku) is used.

Recording conditions Discharge frequency: 5 KHz Discharge droplet capacity: 47 pl Recording density: 360 DPI Single color maximum recording density: 9.4 nl / mm ²

The following items were evaluated for the obtained color print sample (recorded image).

(Evaluation Items) (1) Image Density Solid printing (200% Duty) using the above recording device.
The image density of black (Bk) of the printed matter, when it is a translucent image, Macbeth transmission densitometer TD-904,
In other cases, evaluation was performed using a Macbeth densitometer RD-918. (2) Image unevenness was evaluated for the following two items.

(I) Beading In the solid printing portion of each of red, green, and blue, which is a mixed color of two single-color inks of a printed material solidly printed by using the above recording apparatus, uneven density is not recognized. Was marked with ◯, a mark that could be visually confirmed from a distance of 25 cm between the printed matter and the eye was marked with x, and a medium mark was marked with Δ.

(Ii) Border Bleed In the solid print portion where red, green and blue, which are mixed colors of two single color inks of the solid print on the solid print using the above recording apparatus, are adjacent to each other, Was marked with ◯ when the boundary line was clearly visible from a distance of 25 cm away, x was marked with color mixing and could not be recognized as one line, and Δ was the middle one. (3) Comprehensive evaluation In the case of a translucent recorded image, it is a projected image when projected by an overhead projector (model number: CL-308 Lion). evaluated.

The results of the above evaluations are also shown in Table 1 below.

[0077]

[Table 1]

[0078]

As described in detail above, according to the present invention,
A high-density, high-quality, high-fine, translucent recorded image that can be applied to applications such as projecting a recorded image by OHP, etc., and a record with a high-gloss surface comparable to ordinary silver salt photographs. An ink jet recording method capable of forming an image can be provided.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view showing the configuration of a recording head of an inkjet recording apparatus used in a method of the present invention.

FIG. 2 is a cross-sectional view taken along the line AB of FIG.

3 is a perspective view showing a configuration of a multi-head in which a plurality of recording heads of FIG. 1 are arranged.

FIG. 4 is a perspective view showing the configuration of an inkjet recording apparatus used in the method of the present invention.

[Explanation of symbols]

 13 recording head 14 groove 15 heating head 16 protective film 17-1, 17-2 aluminum electrode 18 heating resistor layer 19 heat storage layer 20 substrate 21 ink 22 ejection orifice 23 meniscus 24 recording droplet 25 recording sheet 26 ink receiving layer 27 multi Head 28 Multi-groove 29 Glass plate 30 Heating head 51 Paper feed section 52 Paper feed roller 53 Paper ejection roller 61 Blade 62 Cap 63 Absorber 64 Discharge recovery section 65 Recording head 66 Carriage 67 Guide shaft 68 Motor 69 Belt

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Keiichi Suzuki 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc.

Claims (10)

[Claims] 1. An ink jet recording method for forming a recorded image on a recording medium by ejecting a small droplet of ink from an orifice of a recording head in accordance with a recording signal and adhering the recording medium onto the recording medium, wherein the surface tension of the ink is 25 to 25. 35 dyne / cm
Using an ink within the range, and as the recording medium, a substrate and a copolymer of vinylpyrrolidone and a vinyl-based monomer having a hydrophobic group provided on the substrate,
An inkjet recording method comprising using a recording medium comprising a coating layer mainly containing polyalkylene oxide or a derivative thereof. 2. The ink includes cyan, magenta, and
The inkjet recording method according to claim 1, wherein a color recording image is formed on the recording medium by using four kinds of yellow ink and black ink. 3. The coating layer of the recording medium further contains a hydrophilic acrylic resin made of a copolymer of a vinyl monomer having a cationic group and a vinyl monomer having a hydrophobic group. The inkjet recording method according to claim 1. 4. The inkjet recording method according to claim 1, wherein the coating layer of the recording medium contains an epoxy compound in an amount of 0.5% by weight or more. 5. The ink jet recording method according to claim 1, wherein the base material of the recording medium is a plastic film. 6. The ink jet recording method according to claim 1, wherein the liquid medium component of the ink is composed mainly of water and a water-miscible glycol or glycol ether. 7. A recording image is formed by using a recording head having two or more orifices for ejecting ink for each color, and ejecting two or more ink droplets of the same color at the same time. 1. The inkjet recording method according to 1 or 2. 8. A small drop of ink is ejected at a frequency of at least 3 KHz or higher.
Inkjet recording method described. 9. The maximum recording density of the ink is 6 nl / m.
The inkjet recording method according to claim 1, wherein the inkjet recording method is m ² or more. 10. The inkjet recording method according to claim 1, wherein the ink is ejected by thermal energy.