JP3058236B2 - Inkjet recording method - Google Patents

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 more particularly to a recorded image excellent in light transmission or surface gloss. The present invention relates to an ink jet recording method suitable for performing the method.

[0002]

2. Description of the Related Art As a recording medium for forming an image used in a conventional ink jet recording method, for example, Japanese Patent Publication No.
No. 26665, a recording paper having a coating layer containing a finely divided silica and a water-soluble binder such as polyvinyl alcohol on a base paper, or Japanese Patent Publication No. 3-25352.
Glossy paper as an ink receiving layer by forming a film containing polyvinyl alcohol having a saponification degree of 50 to 90 mol% and a crosslinking agent on one surface of a cast coated paper as described in A saponification degree of 70 to 9 on a polyester film as described in JP-A-220750
Overhead projector (OHP) recording sheets provided with a hydrophilic coating made of 0 mol% of water-soluble polyvinyl alcohol and used as an ink receiving layer have been used.

[0003]

In recent years, the speed of recording has been increased,
With the improvement of the performance of the ink jet recording apparatus such as multi-color printing, higher and wider characteristics are also required for the ink jet recording medium. In particular, (1) the ink absorption capacity is high (the absorption capacity is large and the absorption time is fast) (2) the optical density of the ink dots is high and the periphery of the dots is not blurred (3) the ink dot shape is a perfect circle Close and smooth surroundings (4) Changes in characteristics are small due to changes in temperature and humidity, and curl does not occur. (5) Blocking does not occur. (6) The image formed on the recording medium is stable and does not deteriorate during long-term storage (particularly in a high-temperature, high-humidity environment). (7) The recording medium itself is stable and does not deteriorate during long-term storage (in particular, high-temperature, high-humidity). (Under environmental conditions).

Further, using an ink jet recording method,
It is also required to form an image having excellent transparency and an image having high gloss on the surface, which can be used for OHP, and a recording medium having excellent translucency and a recording medium having glossy surface (glossy paper) are required. is necessary. In these recording media, in order to control the diffuse reflection of incident light on the recording surface, it is necessary to provide a transparent coating layer as much as possible, so that a hydrophilic resin such as polyvinyl alcohol is coated on the above-described base material such as a film. It has been formed by providing a main ink receiving layer.

[0005] In the ink jet recording method for forming such a translucent image or a surface glossy image, as the recording speed is increased, the image density is increased, and the colorization is advanced.
Deterioration of image quality due to poor fixing of ink on a recording medium is a serious problem. That is, since the recording surface of these recording media does not have a porous structure such as conventional coated paper or plain paper, the ink absorbing ability is insufficient, so that a portion having a high image density, that is, a large amount of ink is applied. Image stains due to overflow of ink in parts, density unevenness such as unfixed ink droplets agglomerated on the recording surface (beading)
In particular, in the case of forming a color image, color contamination (bleeding of a boundary) is caused by mixing colors at the boundary between different colors.
These phenomena significantly reduce the sharpness of the image.

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

In particular, in the above-mentioned recording method using a recording sheet having a light-transmitting property or a surface gloss, an attempt has been made to improve the problem of beading and boundary bleeding which are remarkable problems from the recording medium side. However, a sufficiently effective recording medium has not been obtained. Also, almost no studies have been made to solve these problems in terms of both ink and 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 properties in a well-balanced manner, and in particular, has high density, high resolution, transparency or surface gloss. An object of the present invention is to provide an ink jet recording method capable of forming a recorded image having excellent properties.

[0009]

SUMMARY OF THE INVENTION It is an object of the present invention to provide 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 attaching the droplet to a recording medium. In the recording method, the ink has a surface tension of 25 to 35 dyne.
/ Cm and the recording medium is mainly composed of an aromatic polyvinyl acetal resin and a polyalkylene oxide or a derivative thereof.
This is achieved by an ink-jet recording method, characterized in that a material having a coating layer containing 0% by weight on a substrate is used.

In the above method of the present invention, preferably, four types of inks of cyan, magenta, yellow, and black inks are used to form a color recording image on a recording medium.

Further, as a preferred embodiment of the present invention,
In the above ink jet recording method, the coating layer constituting the recording medium contains a hydrophilic acrylic resin composed of a copolymer of a vinyl monomer having a cationic group and a vinyl monomer having a hydrophobic group, wherein the recording medium Wherein the coating layer contains 0.5% by weight or more of an epoxy compound and / or the substrate 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. Forming a recorded image by discharging two or more ink droplets of the same color at the same time and discharging two or more ink droplets of the same color at the same time; discharging small ink droplets at a frequency of at least 3 KHz; Maximum recording density is 6
There is proposed a method characterized by being equal to or more than nl / mm ² , or by performing ink ejection by thermal energy.

The present inventors have proposed a method for forming a translucent image which can be used for, for example, an overhead projector, and an image having a high gloss on the surface comparable to a silver halide photograph using an ink jet recording method. To study,
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, when forming a recorded image as described above, was a significant problem,
It has been found that a high-quality recorded image can be formed without occurrence of beading or boundary bleeding, and the present invention has been completed.

According to the findings of the present inventors, the problems of beading and boundary bleeding are caused not only by the insufficient ink absorbency of the recording medium as described above, but also by the adhesion to the recording sheet. This is a problem related to the wettability between the ink and the recording medium surface. That is, in the portion where the solid printing or the recording close to the recording is performed, if the wettability of the ink to the recording medium surface is insufficient, a slight displacement of a position where the ink droplet lands on the recording medium surface is a cause. Unfixed ink droplets of pixels adjacent to each other on the medium surface are gathered in an irregularly connected form in units of several to tens of units to be in an isolated state. A beading phenomenon that appears to occur.
On the other hand, when the wettability is good, almost all of the unfixed ink droplets are connected uniformly to form an aggregated state, so that the recording portion appears to be in a uniform state without generation of density unevenness. On the other hand, if the wettability is excessively high, this occurs at a boundary portion recorded with inks of different colors, causing color mixing and causing a problem of blurring at the boundary where the boundary becomes unclear. As described above, it has been found that these problems are difficult to obtain a sufficient solution even if improvements are 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 problem. However,
According to the study results of the present inventors, the preferable range of the surface tension of the above-described ink is not only different depending on the material constituting the recording medium surface, but also the preferable range is extremely narrow, or there is no range in which both are compatible. In addition, it was also found that the level of image quality at the time of optimization was different. From the results of these studies, the present inventors selected a specific material in consideration of the synergistic effect of the combination with ink as a recording medium forming material, and furthermore, determined the most suitable surface tension for the material. The present inventors have found that it is possible to form a high-quality translucent image and a surface glossy image, which could not be obtained conventionally, by combining the ink with the ink of the present invention.

The translucency (transparency) in the present invention means that the recording medium has a linear transmittance of 30% or more. Here, the linear transmittance (T%) means that the light is perpendicularly incident on the sample, passes through the sample, passes through the light receiving slit on the extension of the incident optical path at a distance of at least 8 cm from the sample, and passes through the detector. The spectral transmittance of the received linear light is measured using, for example, a 323 type Hitachi automatic recording spectrophotometer (manufactured by Hitachi, Ltd.), and the Y value of the tristimulus value of the color is determined from the measured spectral transmittance. It is a value obtained from the following equation based on these values.

T = (Y / Y0) × 100 T; linear transmittance Y; Y value of sample Y0; Y value of blank

The excellent surface gloss recording sheet referred to in the present invention is a recording medium in which at least one surface has a 60-degree specular gloss of 30% or more. The 60-degree specular gloss is a value measured based on JIS-Z-8741.

Hereinafter, the present invention will be described in detail with reference to preferred embodiments.

A first feature of the present invention is that a composition mainly containing a specific material as an ink receiving layer, that is, an aromatic polyvinyl acetal resin and a polyalkylene oxide or a derivative thereof, is provided on a substrate. The point is that a recording medium provided with a coating layer is used.

The aromatic polyvinyl acetal resin as the first component constituting the coating layer is obtained, for example, by reacting (condensing) aldehyde with polyvinyl alcohol as a raw material to form an acetal.

The raw material polyvinyl alcohol is a homopolymer of vinyl acetate or vinyl acetate, for example, vinyl chloride, ethylene, maleic acid, itaconic acid, acrylic acid, dimethylaminoethyl methacrylate, or a quaternary product thereof. To a predetermined degree of saponification with an acid or an alkali.

On the other hand, the aldehyde to be condensed with polyvinyl alcohol is an aromatic aldehyde. Specific examples thereof include alkyl-substituted benzaldehydes such as benzaldehyde and 2-methylbenzaldehyde; halogen-substituted benzaldehydes such as chlorobenzaldehyde; phenyl-substituted alkylaldehydes such as phenylacetaldehyde and β-phenylpropionaldehyde; And aldehydes having a condensed aromatic ring such as naphthaldehyde and anthraldehyde.

As a method for acetalization, conventionally known methods such as a dissolution method, a precipitation method, and a homogeneous method are employed.

The preferred range of the degree of saponification of polyvinyl alcohol as a raw material is in the range of 75 to 98 mol%. When a recording medium using a coating layer obtained by acetalizing polyvinyl alcohol outside this range is used in the method of the present invention, the ink absorption capacity is low, and the image quality such as beading and boundary bleeding tends to deteriorate. Not preferred. The preferred range of the degree of polymerization of polyvinyl alcohol is 5
It is about 00 to 4500. The preferred range of the degree of acetalization in the polyvinyl acetal resin is 2 to 4
The range is 0 mol%. If less than 2 mol%,
There is not much difference from the case of using normal polyvinyl alcohol,
Problems such as beading and boundary bleeding may occur on the image, which is not preferable. If it exceeds 40 mol%, the ink absorbency may be reduced and the image quality may be deteriorated.

On the other hand, the polyalkylene oxide as the second component constituting the coating layer 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. No.

Similarly, examples of the polyalkylene oxide derivative constituting the coating layer include a reaction product of the above polyhydroxy compound and a compound having reactivity with the above polyhydroxy compound. 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 or the like.

Particularly preferred polyalkylene oxide compounds include the following. That is, the above polyhydroxy compound having a weight average molecular weight of 1000
A polymer having a weight average molecular weight of 20,000 or more obtained by reacting the above with a polyvalent carboxylic 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 pyrroic acid. Examples include melitic 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 the polyhydroxy compound with a polycarboxylic acid, an acid anhydride thereof, or a lower alkyl ester thereof is performed, for example, by dehydration or dealcoholation (ester exchange) under heating at 80 to 250 ° C. under reduced pressure of 0.001 to 20 mmHg. It is obtained by performing the reaction for 30 minutes to 10 hours. When the molecular weight of the polymer compound obtained here is less than 20,000, the coating strength is weak and the blocking resistance may be unsatisfactory.

According to a recording medium having a coating layer mainly composed of two components as an ink receiving layer as described above, when used in combination with an ink having a specific surface tension as described later, beading, An image with excellent uniformity can be formed without generating image unevenness such as a connecting streak, and a clear image with excellent ink absorptivity, less occurrence of boundary bleeding can be formed.

Further, there is an advantage that the above performance can be maintained in any environment such as low temperature, 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 acryl copolymer which is a copolymer of a vinyl monomer having a cationic group and a vinyl monomer having a hydrophobic group is used. A resin can be blended. The hydrophilic acrylic resin is, for example, a copolymer containing at least one or more monomers selected from the following two groups as constituent units. Examples of the monomer having a cationic group include, for example, dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate, diethylaminoethyl acrylate, diethylaminoethyl methacrylate, methylethylaminoethyl acrylate, dimethylaminostyrene, diethylaminostyrene, methylethylaminostyrene, and the like. Examples of the quaternized compound include those having a primary to tertiary amine to a quaternary ammonium base in the side chain. Examples of the monomer having a hydrophobic group include methyl acrylate, alkyl acrylate such as ethyl acrylate, methyl methacrylate, alkyl methacrylate such as ethyl methacrylate, styrene, vinyl toluene, vinyl acetate, and ethylene. Can be The copolymer composition of such a 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, as necessary, another hydrophilic monomer such as 2-hydroxyethyl acrylate or 2-hydroxyethyl methacrylate as a structural unit.

As described above, the recording medium used in the method of the present invention contains the above-mentioned hydrophilic acrylic resin in addition to the above-mentioned polyvinyl acetal resin and polyalkylene oxide or its derivative on at least one surface of the substrate. The provision of the coating layer (ink receiving layer) satisfies all the required characteristics of the ink jet recording medium in a well-balanced manner, and furthermore, the recording medium itself when the image is left in a high temperature and high humidity environment for a long time. , And deterioration of the image can be minimized. This is due to the synergistic effect of the three components.

In the recording medium according to the above preferred embodiment,
Polyalkylene oxide (especially polyethylene oxide) or a derivative thereof is contained in the coating layer (in the ink receiving layer) at a ratio of 2 to 10% by weight. If the amount is less than the lower limit of the above range, the quality of the recording medium itself (i.e., a decrease in ink absorbency) tends to occur particularly when the recording medium is left for a long time in a high-temperature, high-humidity environment. When the amount is larger 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, it may be used for a long time under a high temperature and high humidity environment. When the image is left as it is, deterioration (dots bleed over time and the sharpness of the image is reduced) is likely to occur.

Heretofore, it has been known that polyvinyl acetal and polyalkylene oxide sometimes have poor compatibility, and when they are mixed to form a film on an arbitrary substrate, they may separate with time and become cloudy. I have. However, in the above embodiment, by using in combination with a hydrophilic acrylic resin which is a copolymer of a vinyl monomer having a cationic group and a vinyl monomer having a hydrophobic group, it can be sufficiently used as an OHP recording sheet. It is possible to prepare a recording medium having excellent transparency.

In view of this point, 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 is as follows: , At least larger than polyalkylene oxide or a derivative thereof. In the above embodiment, the hydrophilic acrylic resin which is a copolymer of the vinyl monomer having a cationic group and the vinyl monomer having a hydrophobic group is contained in the ink receiving layer at a ratio of 10 to 40% by weight. Is preferred.
When the amount is less than the lower limit of the above range, even if the polyalkylene oxide or its derivative is contained in the above range, bleeding of an image with time in a high-temperature and high-humidity environment may occur. Exceeding the upper limit of the above range is not preferable because unevenness occurs on the image.

Further, in the present invention, in the recording medium, an epoxy compound is contained in the coating layer in a proportion of 0.5% by weight or more, preferably 0.5 to 5% by weight, so that the mechanical property of the recording surface is improved. 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, and trimethylolpropane polyglycidyl ether. And diglycerol polyglycidyl ether.

The recording medium used in the method of the present invention is a composition in which the composition containing the above components is applied to at least one surface of a substrate to form a coating layer (ink receiving layer).
In the composition, various binders and filler additives can be used in combination as long as the object of the present invention is not hindered. 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, polyvinyl pyrrolidone, carboxymethyl cellulose, hydroxyethyl cellulose, polyvinyl alcohol, and the like. Examples of fillers include inorganic pigments such as silica, alumina, aluminum silicate, magnesium silicate, basic magnesium carbonate, talc, clay, hydrotalcite, calcium carbonate, titanium oxide, zinc oxide, and polyethylene, polystyrene, and polyacrylate. , And the like, but not limited thereto. Specific examples of additives include various surfactants, dye fixatives (waterproofing agents), defoamers, antioxidants, fluorescent brighteners, ultraviolet absorbers, dispersants, viscosity adjusters, and pH adjusters. , A fungicide, a plasticizer and the like. These additives may be arbitrarily selected from known compounds according to the purpose.

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

The recording medium used in the method of the present invention can be prepared as follows. That is, first, the coating layer (ink receiving layer) forming composition is dissolved or dispersed in water, an alcohol, or another appropriate organic solvent, if necessary, together with other additives to prepare a coating liquid. .

Subsequently, the obtained coating liquid is subjected to, for example, a roll coater method, a blade coater method, an air knife coater method, a gate roll coater method, a bar coater method, a size press method, a spray coat method, a gravure coater method,
Coating on the substrate surface by curtain coater method or the like. Thereafter, for example, using a hot air drying furnace, a hot drum, and the like,
Obtain a recording medium. Further, if necessary, the surface of the coating layer may be subjected to a super calendar treatment or the like.

Here, 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 .
m ² . When the coating amount is small, a part of the substrate may be exposed on the surface. The coating amount is 0.2g
/ M ² , there is no effect in terms of the color development of the paint as compared with the case where the ink receiving layer is not provided.
In particular, when the amount is more than 50 g / m ² , the curl may be significantly generated in a low-temperature and low-humidity environment. The thickness of the coating layer is preferably in the range of 0.5 to 100 μm.

A second feature of the ink jet recording method of the present invention resides in that recording is performed 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, even if the recording medium is used, beading in a formed recorded image is remarkable, which is not preferable. When the density is 25 dyne / cm or less, an image free from beating can be obtained, but the bleeding of the boundary is deteriorated. 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 comprises, as essential components, a dye (recording agent) for forming an image and a liquid medium for dissolving or dispersing the dye. It is prepared by adding a dispersing agent, a surfactant, a viscosity adjusting agent, a specific resistance adjusting agent, a pH adjusting agent, a fungicide, a dissolution (or dispersion) stabilizing agent for a recording agent, and the like.

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

In the ink used in the present invention, examples of the liquid solvent for dissolving or dispersing the above-described dye include water or a mixed solvent of water and a water-soluble organic solvent. A mixed solvent of water, a water-soluble organic solvent, and a water-soluble organic solvent containing a polyhydric alcohol having an ink drying prevention effect.

The organic solvent usable for the ink includes, for example, alkyl alcohols such as methanol, ethanol, isopropyl alcohol and n-butanol;
Amides such as dimethylformamide and dimethylacetamide; ketones such as acetone and acetone alcohol; keto alcohols; ethylene glycol, propylene glycol, triethylene glycol, thiodiglycol, diethylene glycol, 1,2,6-hexanetriol, polyethylene glycol and the like Alkylene glycols; glycerins; 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-pyrrolidone, 1,3-dimethyl-2-imidazolidinone and the like. These are one or two
It is used in the form of a mixture of more than one species.

The ink is adjusted to a surface tension within the above-mentioned predetermined range by using the above materials and further adding a surfactant or the like as needed.

Examples of the surfactant include polyoxyethylene alkyl ethers such as polyoxyethylene lauryl ether and polyoxyethylene cetyl ether; polyoxyethylene alkyl such as polyoxyethylene nonyl phenyl ether and polyoxyethylene octyl phenyl ether. Phenyl ethers; sorbitan fatty acid esters such as sorbitan monooleate and sorbitan tristearate; glycerin fatty acid esters such as glyceryl monostearate and glyceryl monooleate; polyoxyethylene alkylamines, polyoxyethylene alkylamides and polyoxy Ethylene fatty acid esters, polyglycerin fatty acid esters, propylene glycol fatty acid esters, pentaerythritol fatty acid esters, acetyl Glycols, acetylene alcohols, nonionic surfactants such as fluorine-based surfactants, etc. Other than these, alkyl sulfates, polyoxyethylene alkyl ether sulfates, polyoxyethylene alkyl ether phosphates, alkylbenzenes Examples include anionic surfactants such as sulfonates and alkyl sulfosuccinates, and cationic surfactants such as benzalkonium chloride and quaternary ammonium salts of cetyltrimethylammonium chloride. It is not limited to. Among these, particularly preferred surfactants include acetylene glycol and acetylene alcohol.

Examples of the above-mentioned inks containing acetylene glycol and acetylene alcohol are disclosed in
And JP-A-139964. However, the preferred range of the surface tension of the ink described in this publication is 35 to 65 dyne / cm, which is different from the preferred 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 heretofore been relatively unfavorable. By performing inkjet recording using, beading that could not be achieved with the conventional technology,
It is possible to form a high-quality translucent image and a surface glossy image that do not cause border bleeding.

The ink jet recording method of the present invention may be any method as long as the ink can be effectively released from the nozzles and the ink can be applied to the recording medium which is the target. Particularly preferably, according to the method described in JP-A-54-59936, the ink subjected to the action of thermal energy causes a sudden change in volume, and the ink is ejected from the nozzles by the action force due to this state change. The ink jet system can be used effectively.

One example of an ink jet recording apparatus which can be suitably used in the ink jet recording method of the present invention is as follows.
This will be described with reference to the drawings.

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

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

The recording head 13 in FIG.
A glass, ceramics or plastic plate having a groove 14 through which a recording medium 1 passes, and a heating head 15 used for thermal recording.
(A head is shown in the figure, but is not limited to this). The heating head 15 includes a protective film 16 made of silicon oxide or the like, aluminum electrodes 17-1 and 17-2, a heating resistor layer 18 made of nichrome or the like, a heat storage layer 19, and a substrate 20 having good heat dissipation such as alumina. It is composed of

The ink 21 has a discharge orifice (fine hole) 2
2, and 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 of the heating head 15 indicated by n rapidly generates heat, and bubbles are generated in the ink 21 in contact with the relevant location. Occurs. With the pressure of this bubble, meniscus 2
3 protrudes, the ink 21 is discharged, and a recording droplet 24 is formed from the orifice 22 and flies 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 configuration of a multi-head in which a number of recording heads having the structure shown in FIG. 1 are arranged. In the figure, the multi-head 27 is a multi-groove 2
8 and the heating head 15 shown in FIG.
The heating head 30 similar to that described 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 serving as a wiping member, one end of which is held by a blade holding member (not shown) and serves as a fixed end, forming a cantilever. Although the blade 61 is disposed at a position adjacent to the recording area by the recording head 65, in the case of this example, it is held in a form protruding into the movement path of the recording head 65. Reference numeral 62 denotes a cap, which is provided at a home position adjacent to the blade 61 and has a configuration in which the cap moves in a direction perpendicular to the direction in which the recording head 65 moves and comes into contact with the ejection port surface to perform capping. Further, an ink absorber 63 is provided adjacent to the blade 61 and is held in a form protruding into the movement path of the recording head 65, similarly to the blade 61. Above blade 61, cap 62, absorber 63
Constitutes an ejection recovery section 64, and the blade 61 and the absorber 63 remove moisture, dust, and the like from the ink ejection port surface.

The recording head 65 has ejection energy generating means, performs recording by ejecting ink on a recording medium facing the ejection port surface where ejection ports are arranged, and is mounted on a carriage 66 and moves as described below. . 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 the 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 the 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 face of the recording head 65 by a paper feed roller 52 driven by a motor (not shown). . Subsequently, the recording medium is sent to the outside by the discharge roller 53 as the recording proceeds.

In the ink jet recording apparatus having the above-described configuration, when the recording head 65 returns to the home position at the end of recording or the like, the cap 62 of the ejection recovery section 64 is attached to the recording head 6.
5, but the blade 61 protrudes into the movement path. As a result, the ejection port surface of the recording head 65 is wiped. When capping the cap 62 by abutting the protruding surface of the recording head 65, the cap 62 moves so as to protrude into the moving path of the recording head.

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 position at the time of wiping described above. As a result, the ejection port surface of the recording head 65 is also wiped during this movement.

The movement of the print head 65 to the home position described above is not limited to when printing is completed or when ejection is recovered.
That is, the recording head 65 moves to a home position adjacent to the recording area at a predetermined interval while moving in the recording area for recording. The wiping is performed along with this movement.

As described above, the present invention is particularly useful for forming a translucent recorded image or a recorded image having excellent surface gloss using an ink jet recording method, by increasing the recording speed, increasing the density, and increasing the color density. Its main purpose is to solve the problem of beading and boundary bleeding that has occurred in conjunction with. Therefore, the inkjet recording method of the present invention,
For high-speed ink-jet recording in which recording is performed by discharging small droplets of each color ink from the orifice of the recording head at a driving frequency of at least 3 KHz, and at least two orifices per color for discharging at least each color ink are provided. Ink droplets of the same color
It is preferable to apply the present invention to a recording method using an ink jet recording apparatus capable of forming a recorded image by discharging droplets or more, and an ink jet recording method in which the maximum recording density of each color ink is 6 nl / mm ² or more.

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

[0068]

The present invention will be described in more detail with reference to the following examples. In the following description, parts or% are based on weight unless otherwise specified.

(Synthesis of Polyvinyl Acetal Resin) Polyvinyl alcohol 3 having a saponification degree of 88% and a polymerization degree of 1700
50 parts were dissolved in 3000 parts of water by heating, cooled, and 170 parts of 35% by weight hydrochloric acid and 77 parts of phenylacetaldehyde were appropriately added and reacted at 10 ° C. for 5 hours. The resulting precipitate was washed with water and neutralized to remove the catalyst and unreacted aldehyde, and then dried to obtain polyvinylphenylacetoacetal. The degree of acetalization of this resin was 14 mol%. (This resin is referred to as polyvinyl acetal resin a)

Further, polyvinylphenylacetoacetal having an acetalization degree of 5 mol% was synthesized in the same manner as described above. (Polyvinyl acetal resin b) In the above method, acetaldehyde was used instead of phenylacetaldehyde, and the acetalization degree was 4
0 mol% of polyvinyl acetoacetal was synthesized.
(Polyvinyl acetal resin c.)

(Preparation of Recording Sheet) Using a wire bar, a coating liquid for forming a coating layer having the following composition was applied to a polyethylene terephthalate film (thickness: 100 μm; manufactured by Lumirror Toray Co., Ltd.) so that the coating thickness of the dryer became 20 μm. , And dried at 100 ° C. for 10 minutes to prepare recording sheets of the invention and comparative examples.

Coating liquid composition Sheet 1 Polyvinyl acetal resin a 10 parts Polyethylene oxide (Alcox R-40 manufactured by Meisei Chemical) 1 part Water / butanol mixed solvent 89 parts Sheet 2 Polyvinyl aryl acetal (Eslek KK-1 Sekisui Chemical) 10 parts Polyethylene oxide (Alcox R-40 manufactured by Meisei Chemical) 1 part Water / butanol mixed solvent 89 parts Sheet 3 polyvinyl acetal resin b 10 parts Polyethylene oxide (Alcox R-40 manufactured by Meisei Chemical) 1 part Water / butanol mixed solvent 89 parts Sheet 4 Polyvinyl aryl acetal (Eslek KK-1 manufactured by Sekisui Chemical) 14 parts Polyethylene oxide (Alcox R-40 manufactured by Meisei Chemical) 1 part Copolymer of methyl methacrylate and acrylic quaternary ammonium salt compound Hydrophilic acrylic resin (Julima SP-50 manufactured by Nippon Pure Chemical) 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 (PVA-117 Kuraray) 10 parts Water 90 parts Sheet 6 Polyvinyl acetal resin c 10 parts Polyethylene oxide (Alcox R-40 manufactured by Meisei Chemical Co.) 1 part Water / butanol mixed solvent 89 parts The base film used in the preparation of the above recording sheet was used as it is. To make sheet 7.

The 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 base material, and the sheet 8 was formed in the same manner as the sheet 4 except that the art paper was used as the base material. 9 was prepared.

(Examples 1 to 10, Comparative Examples 1 to 8, Inkjet Recording) The recording sheets 1 to 9 prepared as described above,
Color recording was performed under the following conditions using inks A to F having the following compositions and an ink jet recording apparatus equipped with a mechanism for foaming the ink by thermal energy and discharging the ink.

Table 1 below shows combinations of recording sheets and inks used in each example.

Ink Composition Dye 4 parts Glycerin 10 parts 1.2.6-Hexanetriol 6 parts Urea 4 parts Acetylene glycol (trade name: Surfynol 104 manufactured by Nissin Chemical) x part water 76-x part

Dye Y: C.I. I. Direct Yellow # 86 M: C.I. I. Acid Red # 23 C: C.I. I. Direct Blue # 199 Bk: C.I. I. Food 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 Instead of acetylene glycol, acetylene alcohol (trade name: Surfynol 61 manufactured by Nissin Chemical Co., Ltd.) was used.

Ink Fx = 1.5 Surface tension = 33 dy
ne / cm Instead of acetylene glycol, polyoxyethylene nonylphenyl ether (trade name: Neugen EA-50 manufactured by Daiichi Kagaku) is used.

Recording conditions Ejection frequency: 5 KHz Ejected droplet capacity: 47 pl Recording density: 360 DPI Maximum recording density of a single color: 9.4 n1 / mm ²

The following items were evaluated for the obtained color print samples (recorded images).

(1) Image Density Solid printing (200% duty) using the above recording apparatus
The image density of black (Bk) of the printed material thus obtained, and a Macbeth transmission densitometer TD-904 for a translucent image,
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 solid printed by the above-described recording apparatus, no unevenness of density is observed. Was evaluated as ○, x was visually observed from a distance of 25 cm between the printed matter and the eyes, and x was a medium one.

(Ii) Border bleeding In a solid printing portion where red, green, and blue, which are a mixture of two single-color inks of a solid printed by the above-described recording apparatus, are adjacent to each other, Were visually recognized from a distance of 25 cm, and those which could not be clearly recognized as one line due to color mixing were evaluated as x, and those in the middle were evaluated as Δ.

(3) Comprehensive Evaluation In the case of a translucent recorded image, the projected image was projected with an overhead projector (model number: CL-303 Lion), and the surface gloss recorded image was visually observed. Was evaluated comprehensively.

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

[0088]

[Table 1]

[0089]

As described in detail above, according to the present invention,
It has a high optical density, high quality, high definition, and has a translucent recorded image that can be used for applications such as projecting recorded images by OHP or the like, and has a high gloss surface comparable to ordinary silver halide photography An inkjet recording method capable of forming a recorded image can be provided.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a configuration of a recording head of an inking jet recording apparatus used in a method of the present invention.

FIG. 2 is a transverse sectional view taken along the line AB in FIG. 1;

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 ink jet recording apparatus used in the method of the present invention.

[Explanation of symbols]

 DESCRIPTION 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 unit 52 Paper feed roller 53 Paper discharge roller 61 Blade 62 Cap 63 Absorber 64 Discharge recovery unit 65 Recording head 66 Carriage 67 Guide shaft 68 Motor 69 Belt

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Shaichi Suzuki 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (56) References JP-A-63-221077 (JP, A) JP-A-4 JP-A-78570 (JP, A) JP-A-2-55184 (JP, A) JP-A-5-64954 (JP, A) JP-A-5-262028 (JP, A) JP-A-5-221112 (JP, A) JP-A-7-1828 (JP, A) JP-A-4-214382 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B41M 5/00

Claims (16)

(57) [Claims] 1. An ink jet recording method in which a small droplet of ink is ejected from an orifice of a recording head in accordance with a recording signal and adheres to a recording medium to form a recorded image on the recording medium, wherein the ink has a surface tension of 25 to 35 dyne / c
using an ink which is in the range of m, as and the recording medium, a main component and an aromatic polyvinyl acetal resin, and a polyalkylene oxide or a derivative thereof, said port
2- to 10-fold alkylene oxide or its derivative
An ink jet recording method, characterized by using a coating layer having a coating layer containing an amount of% on a substrate . 2. The ink according to claim 1, wherein the ink is cyan, magenta,
2. The ink jet recording method according to claim 1, wherein a color recording image is formed on a recording medium using four types of yellow and black inks. 3. The ink jet recording method according to claim 1, wherein the polyalkylene oxide is a polyhydroxy compound obtained by adding ethylene oxide or propylene oxide to a compound having two or more active hydrogen groups. 4. The compound having two or more active hydrogen groups is ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, 1,4-butanediol, 1,6-hexanediol, or tetraethylene glycol. The polyethylene glycol, polypropylene glycol, propylamine, butylamine, octylamine, cyclohexylamine, bisphenol A, glycerin, trimethylolpropane, pentaerythritol, monoethanolamine, diethanolamine, triethanolamine and isopropanolamine. Inkjet recording method. 5. The ink jet recording method according to claim 3, wherein the polyalkylene oxide is a polymer obtained by reacting a polyhydroxy compound with a polyvalent carboxylic acid, an acid anhydride thereof or a lower alkyl ester thereof. 6. The polycarboxylic acid is malonic acid, maleic acid, succinic acid, fumaric acid, itaconic acid, phthalic acid, isophthalic acid, terephthalic acid, adipic acid, sebacic acid, dimer acid, pyromellitic acid and trimellitic acid. The inkjet recording method according to claim 5, wherein the inkjet recording method is selected from acids. 7. The recording medium according to claim 1, wherein the coating layer further comprises a hydrophilic acrylic resin comprising 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. 8. The ink jet recording method according to claim 1, wherein the coating layer of the recording medium contains 0.5% by weight or more of an epoxy compound. 9. The ink jet recording method according to claim 1, wherein the base material of the recording medium is a plastic film. 10. The recording medium according to claim 1, wherein the recording medium is translucent.
The ink-jet recording method as described above. 11. The recording medium according to claim 6, wherein the 60-degree specular gloss is 3
2. The ink jet recording method according to claim 1, wherein the content is 0% or more. 12. The ink jet recording method according to claim 1, wherein the liquid medium component of the ink is mainly composed of water and a water-miscible glycol or glycol ether. 13. A recording image is formed by using a recording head having two or more orifices for discharging ink for each color and discharging two or more ink droplets of the same color at the same time. 2. The ink jet recording method according to 1. 14. The ink jet recording method according to claim 1, wherein the ink droplets are ejected at a frequency of at least 3 KHz. 15. A maximum recording density of the ink is 6 nl /
2. The ink jet recording method according to claim 1, wherein the diameter is not less than mm2. 16. The ink jet recording method according to claim 1, wherein the ink is ejected by thermal energy.