Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41M—PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING
  • B41M5/00—Duplicating or marking methods; Sheet materials for use therein
  • B41M5/50—Recording sheets characterised by the coating used to improve ink, dye or pigment receptivity, e.g. for ink-jet or thermal dye transfer recording
  • B41M5/502—Recording sheets characterised by the coating used to improve ink, dye or pigment receptivity, e.g. for ink-jet or thermal dye transfer recording characterised by structural details, e.g. multilayer materials
  • B41M5/506—Intermediate layers
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41M—PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING
  • B41M2205/00—Printing methods or features related to printing methods; Location or type of the layers
  • B41M2205/12—Preparation of material for subsequent imaging, e.g. corona treatment, simultaneous coating, pre-treatments
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41M—PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING
  • B41M2205/00—Printing methods or features related to printing methods; Location or type of the layers
  • B41M2205/38—Intermediate layers; Layers between substrate and imaging layer

Definitions

• the present invention relates to a recording medium suitable for recording with a liquid ink, particularly to a recording medium suitable for ink-jet recording.
• the present invention relates also to a process for producing the recording medium, and a process of image formation employing the recording medium.
• the ink-jet recording system conducts recording by ejecting fine ink droplets and depositing the ink droplets onto a recording medium like a paper sheet to record a picture or letters.
• the ink-jet recording system has advantages of high speed printing with less noise generation, ease of multicolor printing, versatility in recording patterns, needlessness of development and fixation of images, and so forth. Therefore, the ink-jet recording system has come to be widely employed for image-recording in many applications such as information apparatuses.
• a multicolor ink-jet system is capable of recording an image comparable with multicolor printing using plates, or color photography, and is capable of recording images at a lower cost than that of conventional multicolor printing and color photograph when the number of copies is small.
• the multicolor ink-jet system is coming to be employed widely in full-color image recording.
• Japanese Patent Application Laid-Open No. 56-5830 discloses an ink-jet recording paper sheet which has an ink-absorbent coating layer on a base sheet; Japanese Patent Application Laid-Open No. 55-51583 employs amorphous silica as a pigment in a coating layer.
• U.S. Patents 4,879,166 and 5,104,730, and Japanese Patent Application Laid-Open Nos. 2-276670, 3-215082, and 3-281383 disclose recording sheets having a porous ink-receiving layer containing alumina hydrate of a pseudo-boehmite structure. These disclosed ink-jet recording sheets are excellent in the quality and gloss of the recorded image. However, such an ink-receiving layer comprising alumina hydrate has disadvantages that its surface can be scratched readily, and that the recorded matter can be damaged by simple rubbing with cloth or paper.
• Japanese Patent Application Laid-Open Nos. 3-67685, 6-183131, 7-76162, 7-101142, 7-117335, 8-2087, 8-2091, 8-2093, 8-183242, 9-66663, 10-129122, 10-166715, and so forth disclose a surface layer comprising silica, silica-alumina, or a fine particulate organic matter provided on an ink-receiving layer.
• the above methods have disadvantages as follows:
• the present invention has been accomplished to solve the above problems.
• the present invention intends to provide a recording medium which gives a high image density, high ink absorption rate, high gradation of printing, high resistance against scratching, high deliverability without causing beading and printing irregularity, good transparency, and no blocking at a high temperature under high humidity.
• the present invention intends also to provide an image formation process employing the above recording medium.
• the present invention intends further to provide a process for producing the recording medium in which the coating liquid has high stability of the dispersion, and high productivity in the coating process.
• the recording medium of the present invention comprises at least a base member, an ink-receiving layer containing alumina hydrate of a boehmite structure formed on the base member, and a porous layer containing particles and an alcohol-soluble organic polymer resin formed further thereon.
• the image formation process of the present invention comprises ejecting ink droplets through a fine nozzle onto the above recording medium.
• the process for producing a recording medium of the present invention having a porous ink-receiving layer formed on a base member, and a porous layer formed thereon comprises applying a liquid dispersion containing an alumina hydrate of a boehmite structure and a binder on a base member to form at least one porous ink-receiving layer followed by drying, and further applying another liquid dispersion containing an alcohole-soluble organic polymer resin and a particulate material dissolved in a solvent containing at least alcohol followed by drying to form a porous layer.
• a recording medium of the invention gives a high image density, high ink absorption rate, high gradation of printing, high resistance against scratching, high deliverability without causing bending and printing irregularity, good transparency, and no blocking at a high temperature under high humidity. Furthermore, the coating has high stability of the dispersion, and high productivity in the coating process.
• the ink-receiving layer of the recording medium of the present invention is formed as a porous layer comprising an alumina hydrate of a boehmite structure and a binder.
• the porous ink-receiving layer should have functions of receiving ink droplets ejected and deposited thereon by ink-jet recording, absorbing the solvent of the ink, and fixing the coloring matter such as a dye; should have high absorbency for preventing ink running and ink bleeding; and should have uniform layer quality for obtaining an image of photographic tone.
• the most suitable ink-receiving layer for formation of the porous layer thereon has a special fine porous structure containing a boehmite-structured alumina and a binder. This structure is suitable for high ink absorbency of the ink-receiving layer after forming the porous layer.
• the alumina hydrate for the recording medium of the present invention is preferred as the material for the ink-receiving layer because the alumina hydrate is electrically positively charged to give high dye fixability to form images with high color developability and does not cause browning of a black ink, or lack of light-fastness.
• the alumina hydrate contained in the ink-receiving layer of the recording medium of the present invention has preferably a boehmite structure as measured by X-ray diffraction in consideration of dye adsorption, ink absorption, and transparency.
• the alumina hydrate is generally defined by the general formula below: Al 2 O 3-n (OH) 2n ⁇ mH 2 O where n is an integer from 0 to 3, and m is a number from 0 to 10, preferably from 0 to 5; mH 2 O represents usually water component not participating in formation of the crystal lattice and being releasable; m may not be an integer; and m and n are not simultaneously zero.
• the process for production of the alumina hydrate of the boehmite structure to be contained in the ink-receiving layer of the present invention is not specially limited. Any process which is capable of producing the alumina hydrate may be employed, including Beyer process, and an alum pyrolysis process.
• an aluminum alkoxide of a long chain is hydrolyzed by addition of an acid: an alkoxide having 5 or more carbon atoms.
• the alkoxides having 12-22 carbon atoms are preferred further, since the alcohol component can be removed readily and the shape of the boehmite-structured alumina hydrate can be controlled readily.
• the above processes are advantageous in that impurities like ions are less liable to cause contamination.
• the aluminum alkoxide of long chains is advantageous in comparison with an alkoxide of short chains like aluminum isopropoxide, since the alcohol can readily be removed completely from the alumina hydrate after the hydrolysis.
• the alumina hydrate prepared by the above process may be subjected to hydrothermal synthesis for particle growth, or may be dried into a powdery alumina hydrate.
• the alumina hydrate crystal having a boehmite structure is a layered compound having the (020) plane as a giant plane, exhibiting a characteristic diffraction peak in the X-ray diffraction pattern.
• the boehmite structure includes the perfect boehmite structure and so-called pseudo-boehmite structures, the latter containing excess water between the layers of the (020) plane.
• the pseudo-boehmite exhibits a diffraction peak broader than that of the perfect boehmite.
• the perfect boehmite and the pseudo-boehmite cannot definitely be differentiated, so that the boehmite-structured alumina hydrate in the present invention includes the both type of boehmite, unless otherwise mentioned.
• the alumina hydrate has its crystallinity ranging preferably from 15 to 80. Within this crystallinity range, the optical density of the printed portion is high, and ink running, ink beading, and ink crawling are less liable to occur.
• the crystallinity thus obtained is a physical quantity corresponding to the ratio of the crystalline portion to the noncrystalline portion of the alumina hydrate in the recording medium.
• "Running of ink” in the present invention signifies the spreading (expansion) of the area of a dyed portion of a prescribed solid print area.
• Beading signifies irregularity in a granular shape in density caused by coalescence of the ink droplets in the solid print area.
• “Crawling” signifies occurrence of non-colored portion in the solid print area.
• the degree of parallelization between the microcrystal of the boehmite-structured alumina hydrate and the plane direction of the ink-receiving layer is preferably not less than 1.5.
• the degree of parallelization is defined in Example described later under the heading of "crystallinity”.
• the circularity of the printed dots is good at the parallelization degree of not less than 1.5, whereas it is poor at the parallelization degree of less than 1.5.
• the shape of the boehmite-structured alumina hydrate particles can be observed by transmission electron microscopy with a test sample prepared by dropping a dispersion of the alumina hydrate in water, alcohol, or the like onto a collodion film.
• pseudo-boehmite is known to include a cilium-shaped type, and the other types as shown in a report (Rocek J., et al: Applied Catalysis, vol.74, pp.29-36, 1991). In the present invention, either the cilium-shaped type or plate type can be used.
• the shape of the alumina hydrate particles can be measured by transmission electron microscopy with a test sample prepared by dropping a dispersion of the alumina hydrate in deionized water onto a collodion film.
• the alumina hydrate in a flat plate shape is preferred to the one in a hair bundle shape (cilium shape), since the alumina hydrate in a flat plate shape has higher dispersibility in water, gives a larger pore volume by random orientation of the alumina hydrate particles in the formed ink-receiving layer, and gives a broader distribution of the pore size.
• Hair bundle shape herein signifies a state of assemblage of needle-shaped alumina hydrate particles in a shape of hair bundle with their side faces contacting together.
• the aspect ratio is a ratio of the diameter to the thickness of a particle.
• the aspect ratio of the plate-shaped particle can be measured by the method defined in Japanese Patent Publication No. 5-16015.
• the diameter herein is a diameter of a circle having an area equal to the projected area of a particle in observation of the alumina hydrate by an optical or electron microscope.
• the length/breadth ratio is a ratio of the largest diameter to the smallest diameter when observed in the same manner as the aspect ratio.
• the aspect ratio of the hair bundle shape can be obtained by measuring the diameters and the lengths at the ends of a needle-shaped particle of individual alumina hydrate as a column, and taking the ratio of the length to the diameter.
• the alumina hydrate in a flat plate shape has preferably an average aspect ratio ranging from 3 to 10 and an average particle diameter ranging from 1 to 50 nm; the aluminum hydrate in a hair bundle shape has preferably an aspect ratio ranging from 3 to 10 and an average particle diameter ranging from 1 to 50 nm.
• interstices are formed between particles in formation of an ink-receiving layer or on addition into a fibrous material, thereby a porous structure being readily formed with broad distribution of the pore radius.
• porous structure can be formed with a large pore volume.
• the pore diameter distribution in the ink-receiving layer will be narrow, whereas at the average aspect ratio higher than the upper limit of the above range, alumina hydrate cannot be prepared with uniform particle diameter.
• the pore diameter distribution tends to be narrow, whereas at the value larger than the above upper limit, the absorbency for the printed dye tends to be low.
• the pore properties of the alumina hydrate can be adjusted in the production process.
• the alumina hydrate preferably has a pore volume ranging from 0.1 to 1.0 cm 3 /g.
• the alumina hydrate having a larger pore above the range volume tends to cause cracking or powder-falling, whereas the alumina hydrate having a smaller pore volume below the range tends to cause a decrease in ink absorbency, ink running, and feathering of the image, in particular, in multicolor printing.
• the BET specific surface area of the alumina hydrate ranges preferably from 40 to 500 m 2 /g.
• a smaller BET specific surface area, below the range, of the alumina hydrate tends to increase haze in the ink-receiving layer to cause white fogging of the image.
• a larger BET specific surface area above the range tends to cause cracking in the ink-receiving layer.
• the pore volume of the ink-receiving layer ranges preferably from 0.1 to 1.0 cm 3 /g.
• a larger pore volume, above the range, of the ink-receiving layer is liable to cause cracking or powder-falling of the layer and to decrease its transparency to lower the image density.
• a smaller pore volume, below the range, of the ink-receiving layer tends to decrease the ink absorbency of the layer to cause ink running, and feathering of the image, in particular, in multicolor printing.
• the BET specific surface area ranges preferably from 20 to 450 m 2 /g.
• a smaller BET specific surface area below the range tends to increase haze in the ink-receiving layer to cause fogging of the image.
• a larger BET specific surface area above the range tends to cause cracking in the ink-receiving layer.
• the BET specific surface area and the pore volume mentioned above is measured by adsorption and desorption of nitrogen with a sample having been deaerated at 120°C for 24 hours.
• the pore structure of the ink-receiving layer can be measured by a nitrogen absorption method or a mercury pressure-penetration method.
• the pore radius distribution has a maximum peak preferably in the range from 2.0 to 20.0 nm. Within this range, both the ink absorption rate and the dye fixation rate can be raised without occurrence of running or bleeding of the ink. With the maximum peak radius exceeding the above range, the dye fixation rate may be decreased to cause ink running or to lower the circularity of the printed dots. With the maximum peak radius less than the above range, the ink absorption rate may be low.
• Japanese Patent Publication No. 7-2430 discloses a recording medium having an ink-receiving layer comprising pseudo-boehmite in which the total volume of the pores within the range from 10 to 100 nm is not more than 0.1 cc/g.
• Japanese Patent No. 2714352 discloses a recording medium having an ink-receiving layer having an average pore radius ranging from 2.0 to 20.0 nm and the half breadth of the pore radius distribution ranging from 2.0 to 15.0 nm.
• Japanese Patent No. 2714350 discloses a recording medium having pore radius distribution peaks at a radius of not more than 10.0 nm and in the radius range from 10.0 to 20.0 nm.
• Japanese Patent Application Laid-Open No. 5-323037 discloses a recording medium having a ink-receiving layer of two-layered pseudo-boehmite structure constituted of a lower layer having an average pore diameter ranging from 2 to 8 nm and a thickness ranging from 5 to 60 ⁇ m and an upper layer having an average pore diameter ranging from 4 to 15 nm and a thickness ranging from 2 to 30 nm.
• Japanese Patent Application Laid-Open No. 9-66664 discloses a recording medium having an ink-receiving layer which has cavities inside communicating through a small pores with the surface of the ink-receiving layer.
• the above disclosed pore structure of the porous layer when employed in the present invention as the ink-receiving layer, will respectively be effective in broadening of the ink selection range, increase of the transparency, increase of the ink absorbency, prevention of ink running, prevention of blurring of the prints, improvement of absorbency in multicolor printing, and so forth. Furthermore, the porous layer formed thereon enables further improvement of the above effects.
• the pore structure of the ink-receiving layer does not depend on the properties of the alumina hydrate employed, but depends on the production conditions such as the type and the amount of the binder; the concentration, viscosity and dispersion state of the coating liquid; the coating apparatus; the coating head; the coating amount; the flow rate, temperature, and flow direction of the drying air flow; and so forth. Therefore, the production conditions should be controlled to be in the optimum range to obtain the desired properties of the ink-receiving layer in the present invention.
• the recording medium in the present invention may contain an additive as necessary.
• the additive may be selected arbitrarily from metal oxides, salts of divalent or higher valent metal, and cationic organic compounds.
• the metal oxides preferably include titanium dioxide and silica as described in Japanese Patent No. 2714351, boria, silica-boria, magnesia, silica-magnesia, zirconia, and zinc oxide, and hydroxides.
• the divalent or higher valent metal salts preferably includes salts such as calcium carbonate, and barium sulfate; halide salts such as magnesium chloride, potassium bromide, calcium iodide, zinc chloride, zinc bromide, and zinc iodide; calcium nitrate; kaolin; and talc.
• the cationic organic compounds preferably include quaternary ammonium slats, polyamines, and alkylamines.
• the amount of the additive to be contained is preferably not more than 20% by weight of the alumina hydrate.
• the binder may be selected arbitrarily from water-soluble polymers and water-dispersible polymers.
• the polymers preferably include water-soluble polymers such as modified or unmodified polyvinyl alcohols, modified or unmodified starch, modified or unmodified gelatin, modified or unmodified casein, gum arabic, cellulose derivatives like carboxymethylcellulose, polyvinylpyrrolidone, maleic anhydride or copolymers thereof, and acrylate ester copolymers; and water-dispersible polymers such as conjugate diene type copolymer latexes like SBR latexes, and vinyl type copolymer latexes like functional-group-modified polymer latexes and an ethylene-vinyl acetate latex.
• polyvinyl alcohols are widely used in view of the water absorbency and the transparency.
• the resin emulsion can be used suitably in view of the dispersion of the alumina hydrate and the water absorbency and water resistance of the recording medium as mentioned in Japanese Patent Application Laid-Open Nos. 8-325992 and 10-94754.
• the mixing ratio of the alumina hydrate to the binder ranges preferably from 1:1 to 30:1 by weight. Within this range, the ink absorption rate of the medium is high, and the optical density of the printed portion is high. With the amount of the binder less than that, the mechanical strength of the ink-receiving layer is not sufficient, tending to cause cracking or powder-fall. With the amount of the binder more than that, the pore volume may be small to cause drop of the ink absorbency. In consideration of the ink absorbency and the less tendency of cracking on bending, the above amount of the binder is more preferably in the range from 3:1 to 20:1.
• the ink-receiving layer may contain, in addition to the alumina hydrate and the binder, an additive such as a pigment dispersant, a thickening agent, a pH-controlling agent, a lubricant, a fluidity modifier, a surfactant, an anti-foaming agent, a waterproofing agent, a foam-inhibitor, a releasing agent, a foaming agent, a penetrating agent, a coloring dye, a fluorescent whitener, a UV absorber, an antioxidant, an antiseptic agent, and a mildew-proofing agent.
• an additive such as a pigment dispersant, a thickening agent, a pH-controlling agent, a lubricant, a fluidity modifier, a surfactant, an anti-foaming agent, a waterproofing agent, a foam-inhibitor, a releasing agent, a foaming agent, a penetrating agent, a coloring dye, a fluorescent whitener,
• suitably used are melamine type materials and aldehyde type materials for raising the surface tension of the liquid dispersion or for promoting the film formation; crosslinking agents such as boric acid, and borates for crosslinking the binder; solvents having a boiling point in the range from 100°C to 180°C higher than that of the dispersion medium, such as methylcellosolve, ethylcellosolve, propylene glycol monomethyl ether, DMF, and ethylene glycol and propylene glycol and esters thereof.
• water-proofing agent quaternary ammonium halides, quaternary ammonium salt polymers can be used without limitation.
• the base member for formation of the ink-receiving layer in the present invention includes paper sheets such as suitably sized paper sheets, non-sized paper sheets, and resin-coated paper sheets coated with polyethylene of the like; and thermoplastic resin films, without limitation.
• the thermoplastic resin film includes transparent sheets of polyester, polystyrene, polyvinyl chloride, polymethyl methacrylate, cellulose acetate, polyethylene, and polycarbonate; and opaque sheet made opaque by filling of a filler or by fine foaming.
• the recording medium of the present invention can be produced by any conventional process for alumina hydrate coating, without special limitation.
• the alumina hydrate is dispersed in water and is applied onto a base member. If necessary, a heat treatment may be additionally conducted as described in Japanese Patent Application Laid-Open No. 9-86035.
• the dispersion treatment of the liquid dispersion containing the boehmite-structured alumina hydrate and the binder can be conducted by any of conventional dispersion processes.
• a suitably used machine includes a grinding type of dispersion machines such as a ball mill and a sand mill, and an agitation type of dispersion machines such as a homomixer and a homodisperser.
• the porous layer of the recording medium of the present invention is provided for modifying the surface properties of the ink-receiving layer not only to improve the deliverability and the anti-blocking properties, but to allow the ink components of the deposited recording ink to permeate quickly into the porous layer to be absorbed by the ink-receiving layer without impairing the recording properties of the ink-receiving layer, to improve the image density, the color tone, and the resolution, and to prevent beading.
• the porous layer should have high transparency and high ink permeability.
• the particle employed in the present invention is preferably dispersible and suspendible in a colloidal state in the liquid medium, and is capable of forming, in the coating film, pores for securing the ink permeability with less light-scattering.
• the diameter of the particles ranges preferably from 10 nm to 100 nm.
• the particles having a diameter smaller than the above range may plug the pores on the surface to decrease the pore volume and the pore radius of the entire recording medium to retard the ink permeation and to cause ink running, ink bleeding, beading, and so forth.
• the particles having a diameter larger than the above range may decrease the transparency of the surface layer to cause white fogging of the printed image, or may reduce the image definition to decrease the sharpness of the image.
• the shape of the particles is preferably spherical.
• the spherical particles serve to improve surface slip properties and to retard tacking, thereby making the recording medium resistant to scratching on rubbing, decreasing the static friction between the piled sheets in cassette type feeding of the paper sheets without delivery failure or double-sheet feeding.
• the nonspherical particles are liable to form sharp protrusions on the outermost surface of the sheet to increase the static friction of the surface, making less resistant to scratching, or causing sheet delivery failure.
• the particles employed in the present invention are preferably dispersible stably in alcohol.
• the particles stable only in water will convert the entire liquid dispersion into a large gel when an alcohol-soluble organic polymer resin of the present invention is added thereto as a binder, thereby making impracticable the formation of the coating film.
• the particulate material includes inorganic pigments such as colloidal silica, colloidal alumina, titania sol, zirconia sol, and zinc oxide sol; organic particulate pigments which do not melted together during the coating film formation, including pigments containing a polymer such as polystyrene, polymethyl methacrylate, styrene-butadiene copolymers, methyl methacrylate-butadiene copolymers, acrylate ester-methacrylate ester copolymers, styrene-acrylate ester copolymers, microcapsules, and beads of resins, e.g., urea resins, and melamine resins.
• inorganic pigments such as colloidal silica, colloidal alumina, titania sol, zirconia sol, and zinc oxide sol
• organic particulate pigments which do not melted together during the coating film formation, including pigments containing a polymer such as polystyrene, poly
• colloidal silica more specifically organosilica sol, and water-dispersible silica sol which is not destroyed by addition of an alcohol: for example, acidic silica sol, composite silica sol modified on the surface with an aluminum oxide, particulate silica modified at the surface by introduction of organic group by use of a coupling agent, a chelating agent, or a metal alkoxide, and so forth, since they combine well with the alcohol-soluble organic polymer resin to form a hard surface film and to retard the particle-falling or powder-falling owing to insufficient bonding properties of the binder.
• an alcohol for example, acidic silica sol, composite silica sol modified on the surface with an aluminum oxide, particulate silica modified at the surface by introduction of organic group by use of a coupling agent, a chelating agent, or a metal alkoxide, and so forth, since they combine well with the alcohol-soluble organic polymer resin to form a hard surface film and to retard the particle-falling or powder-falling owing
• the binder preferably used for the porous layer in the present invention includes alcohol-soluble organic polymer resins, since the alcohol-soluble organic polymer resin is effective in improving the water-resistance and preventing the beading.
• the alcohol-soluble organic polymer resin is effective in improving the water-resistance and preventing the beading.
• the water-resistance of the layer is lowered by the solubleness of the coating layer, the printed dots are spread owing to the water contained as the major portion of the ink to promote ink-running, and beading is liable to ba caused in solid print.
• the alcohol-soluble organic polymer resin is water-resistant, and is capable of giving sharp dots without running of the ink without beading.
• the ink contains alcohols such as isopropyl alcohol, glycerin, and ethylene glycol for prevention of nozzle clogging and for stable ink ejection.
• the alcohols which is contained in the ink at a content much lower than that of the water, cannot dissolve the surface layer.
• the use of the alcohol-soluble organic polymer resin is effective in increasing the affinity with the ink to improve the ink permeability, and in improving the anti-blocking property under high temperature and high humidity.
• the surface portion can be swollen by the moisture in the air to result in tackiness of the surface, whereby the sheets may be blocked to prevent the separation of the sheets when stored under high temperature and high humidity like in the summer or the rainy season.
• the blocking of the sheets can be prevented by providing on the outermost portion a matting agent having a large particle size.
• this method is not advantageous since the transparency of the ink-receiving layer is impaired, and the image density and the image definition are lowered by this method.
• the use of the alcohol-soluble organic polymer resin scarcely causes swelling of the layer by air moisture, not causing sheet blocking.
• the liquid dispersion of particles dispersed in alcohol and an alcohol-soluble organic polymer resin can be dried quickly on coating on the ink-receiving layer to form a porous layer, thereby coating speed being raised to improve the productivity remarkably.
• the particles are less liable to agglomerate together, and the dispersion forms the coating layer containing the particles dispersed uniformly without cracking.
• the extremely quick drying in the coating process evaporate a large amount of the solvent to form many communication holes in the interstices between particles from the ink-receiving layer to the surface of the porous layer to promote the ink permeability, giving a recording medium excellent in ink absorption rate and anti-beading property.
• the particles when a liquid dispersion containing particles dispersed in water and a water-soluble polymer resin is applied on the ink-receiving layer, the particles can agglomerate together in the liquid dispersion or during the film formation, which can cause cracking in the coating film, or can cause migration of the binder to the outermost surface to retard the formation of the communication holes in the porous layer on the surface.
• This binder migration can decrease substantially the pore radius and the pore volume in the entire layers including the ink-receiving layer to decrease the ink permeability or the ink absorption capacity disadvantageously.
• the alcohol-soluble organic polymer resin employed for the above purpose is not limited specially, provided that it is soluble in alcohol, specifically including alcohol-soluble nylon and copolymers thereof, polyvinylacetal, polyvinylbutyral, polyvinyl acetate and copolymers thereof, polyacrylic resins and copolymers thereof, methylcellulose, ethylcellulose, ethylene-vinyl copolymer, polyacrylic ester and copolymer thereof.
• One or more resins may be selected from the above resin group.
• the solvent may be a simple alcohol or a mixed solvent of an alcohol and water or another organic solvent.
• the mixing ratio of the alcohol to the other solvent is decided suitably depending on the solubility of the binder and dispersibility of the particles, and is not limited specially.
• the alcohol is preferably contained in the mixed solvent at a content of not less than 30% by weight based on the entire mixed solvent.
• the type of the alcohol is not limited specially, provided that the alcohol is capable of dissolving the binder resin: specifically including alkyl alcohols having 1-6 carbon atoms such as methyl alcohol; ketone alcohols such as diacetone alcohol; polyalkylene glycols such as polyethylene glycol; alkylene glycols of 2-6 carbon alkylene group such as ethylene glycol: glycerin; and lower alkyl ethers of a polyhydric alcohol such as ethylene glycol methyl ether.
• alkyl alcohols having 1-6 carbon atoms such as methyl alcohol
• ketone alcohols such as diacetone alcohol
• polyalkylene glycols such as polyethylene glycol
• alkylene glycols of 2-6 carbon alkylene group such as ethylene glycol: glycerin
• lower alkyl ethers of a polyhydric alcohol such as ethylene glycol methyl ether.
• One or more of the above solvents may be suitably used arbitrarily.
• the mixing ratio of the particles and the binder ranges preferably from 1:1 to 30:1 by weight. Within this range, the surface of the porous layer has satisfactory slip properties and less tackiness, and is less liable to cause beading. With the amount of the binder less than the above range, the mechanical strength of the porous layer is insufficient, and cracking and powder-falling are liable to occur. With the amount of the binder more than the above range, the voids in the porous layer may become smaller to result in lower ink permeability. In consideration of the high ink permeation rate and the high surface hardness, the above ratio is more preferably in the range from 3:1 to 20:1.
• the porous layer may contain, in addition to the particles and the binder, an additive such as a pigment dispersant, a thickening agent, a pH-controlling agent, a lubricant, a fluidity modifier, a surfactant, an anti-foaming agent, a waterproofing agent, a foam-inhibitor, a releasing agent, a foaming agent, a penetrating agent, a coloring dye, a fluorescent whitener, a UV absorber, an antioxidant, an antiseptic agent, and a mildew-proofing agent.
• an additive such as a pigment dispersant, a thickening agent, a pH-controlling agent, a lubricant, a fluidity modifier, a surfactant, an anti-foaming agent, a waterproofing agent, a foam-inhibitor, a releasing agent, a foaming agent, a penetrating agent, a coloring dye, a fluorescent whitener, a UV absorber, an antioxidant,
• the liquid dispersion containing the particles and the binder may be prepared in any of conventional dispersion method.
• Specific examples of the dispersion apparatuses include attrition type dispersion machines such as ball mills and sand mills, and agitation type dispersion machines such as homomixer and homodisperser.
• the application of the coating liquid for formation of the porous layer and the ink-receiving layer may be conducted by use of a conventional apparatus such as a blade coater, an air knife coater, a roll coater, a brush coater, a curtain coater, a bar coater, a gravure coater, a die coater, and a sprayer.
• a conventional apparatus such as a blade coater, an air knife coater, a roll coater, a brush coater, a curtain coater, a bar coater, a gravure coater, a die coater, and a sprayer.
• the amount of the application of the liquid dispersion is in the range preferably from 0.5 to 60 g/m 2 in terms of solid content in view of the ink absorption capacity, more preferably from 5 to 45 g/m 2 in view of higher ink absorption rate and prevention of cracking and powder-falling.
• the amount of the application of the liquid dispersion is in the range preferably from 0.05 to 20 g/m 2 in terms of solid content for keeping the transparency and imparting the slip properties and anti-blocking properties, and more preferably from 0.5 to 15 g/m 2 for improving the ink permeability and prevention of bronze-like gloss irregularity.
• the porous layer of the present invention is made from particles and an alcohol-soluble organic polymer resin. Thereby, many communication holes are formed through the porous layer from the outermost surface to the ink-receiving layer with the high transparency retained to achieve high ink permeation rate. Further, the porous layer provided on the ink-receiving layer improves the recording medium in scratch resistance, anti-blocking properties, deliverability, and water-resistance.
• the recording medium produced as above should be capable of absorbing the ink in a larger amount at a higher absorption rate to meet the requirements for the ink-jet printer for high-quality printing as the silver salt photograph.
• This type of ink-jet printer conducts image formation at a high dot density by overlapping dots of inks of different dye concentrations to obtain smooth gradation from highlight to shadow portions.
• a larger amount of ink is applied in a high density in one scan by decreasing the number of the paths of the multi-path.
• the recording medium should be capable of absorbing the ink at a high speed in a large amount. In particular, after printing in one scanning with the head, the ink component should be completely absorbed before the subsequent scanning for printing.
• the ink applied at a resolution of 600dpi ⁇ 600dpi and a density of 5.0 ⁇ 10 -3 mL/inch 2 should be absorbed within one second. If the ink absorption time of the recording medium is longer than the time mentioned above, the ink remains unabsorbed on the recording medium during the printing to cause mixing of the ink on the surface, resulting in beading, and bleeding of the ink, and making the gradation less smooth, and further, streaking irregularity corresponding to the head scanning is liable to be caused.
• the recording medium of the present invention has communication holes formed as described above in the porous layer.
• These communication holes allow the ink to penetrate at a high speed and to fix in the ink-receiving layer, and serves to diffuse and evaporate the solvent component. Therefore, the communication holes are not filled by the ink, thereby keeping the permeability and enabling high-speed ink absorption.
• the total pore volume in the entire of the porous layer and the ink-receiving layer ranges preferably from 0.1 to 1.0 cm 3 /g.
• the pore volume larger than the above range will decrease the transparency to cause white fogging of the image or decrease of resolution or sharpness of the image after recording.
• the pore volume smaller than the above range will lower the ink absorption rate remarkably and tends to allow the ink to run to cause feathering of the image, especially in multicolor printing.
• the ratio (PV2/PV1) of the overall pore volume (PV2) of the ink-receiving layer and the porous layer to the pore volume (PV1) of the ink-receiving layer ranges preferably from 0.6 to 1.5.
• the pore volume ratio larger than the above range may decrease the transparency to result in a low image density after printing, or may cause ink running.
• the pore volume smaller than the above range may decrease the ink absorbency to cause crawling of the ink or deformation of the circular dot shape.
• the maximum peak of the pore radius distribution of the entire layers including the porous layer and the ink-receiving layer ranges preferably from 2.0 to 20.0 nm.
• the peak radius larger than the above range may cause light scattering in the layers to increase the haze, resulting in white fogging of the image.
• the fine peak radius smaller than that may lower the ink absorption rate to cause beading, or bleeding in the image border.
• the ink used in the image formation in the present invention composed mainly of a coloring agent (dye or pigment), a water-soluble organic solvent, and water.
• the dye is preferably a water-soluble dye such as direct dyes, acid dyes, basic dyes, reactive dyes, and food dyes, but is not specially limited thereto provided that the dye has required properties for fixability, color-developability, sharpness, stability, light-fastness, and other properties in combination with the above recording medium.
• the water-soluble dye is used as a solution in a solvent composed generally of water or water and a water-soluble organic solvent.
• the solvent is preferably a mixture of water and a water-soluble organic solvent.
• the water content is preferably adjusted to be in the range from 2.0 to 90% by weight of the ink.
• the useful water-soluble organic solvent includes alcohols having 1-4 carbon atoms such as methyl alcohol; amides such as dimethylformamide; ketones and ketone alcohols such as acetone; ethers such as tetrahydrofuran; polyalkylene glycols such as polyethylene glycol; alkylene glycols having an alkylene group of 2-6 carbon atoms such as ethylene glycol; glycerin; lower alkyl ethers of a polyhydric alcohol such as ethylene glycol methyl ether.
• polyhydric alcohols such as diethylene glycol; lower alkyl ethers of polyhydric alcohol such as triethylene glycol monomethyl ether, and triethylene glycol monoethyl ether.
• Polyhydric alcohols are particularly preferred since they are effective as a lubricant for preventing clogging of nozzles owing to deposition of the water-soluble dye by evaporation of water in the ink.
• a solubilizer may be added to the ink.
• Typical solubilizers are nitrogen-containing heterocyclic ketones.
• the solubilizer is used to improve remarkably the solubility of the water-soluble dye in the solvent.
• N-methyl-2-pyrrolidone, and 1,3-dimethyl-2-imidazolidinone are preferred as the solubilizer.
• other additives may be added for improving the properties of the ink.
• the additives include surfactants for raising permeability of the ink component into a plain paper sheet, viscosity-controllers, surface tension controlling agents, and resistivity controlling agents.
• Image formation is conducted on the above recording medium with the above ink by an ink-jet recording system.
• Any ink-jet system may be employed which discharge ink effectively through a nozzle to deposit the ink on a recording medium.
• the ink-jet system disclosed in Japanese Patent Application Laid-Open No. 54-59936 is useful in which the ink is ejected through a nozzle by a driving force generated by quick volume change of the ink by thermal energy.
• Printing was conducted with Ink composition 1 by means of the aforementioned ink-jet printer with ink ejection density of 5.0 ⁇ 10 -3 mL/inch 2 . Thereby the time for complete absorption of the ink was measured.
• the recording medium which absorbs the ink completely within one second was evaluated as "A” (good absorbency).
• the recording medium which absorbs the ink not completely within one second was evaluated as "C” (poor absorbency).
• Solid image was printed of the respective colors with Ink compositions 1 by means of the aforementioned ink-jet printer with the amount of the ink of 100% (monocolor).
• the transmitted image density was measured by a densitometer 310TR (X-Rite Co.).
• Solid image was printed with Ink compositions 1 by means of the aforementioned ink-jet printer with the amount of the ink changing from 100% (monocolor) to 400% (four colors).
• the presence of the defects of running, bleeding, beading, crawling, and streaking were examined visually.
• the recording medium was evaluated as "AA" (very good).
• the recording medium was evaluated as "A" (good).
• the recording medium is evaluated as "B” (fair).
• the recording medium is evaluated as "C” (poor).
• Running is a measure of image resolution of the recording medium, and denotes the phenomenon that a solid print in a prescribed area spreads or the printed area becomes larger than the originally dyed area.
• Bleeding denotes the phenomenon that the ink runs at the border in multi-color solid printing and the unfixed dyes comes to mix together.
• Beading denotes the phenomenon that the deposited ink droplets on the recording medium coalesce into a larger liquid drop in the precess of absorption: visually, it is recognized as color irregularity in a visual size of a bead.
• Crawling denotes the occurrence of a non-dyed portion in a solid print.
• Streaking denotes the occurrence of streak-shaped irregularity having a breadth of the printing ink head in a solid print.
• Solid image was printed of the respective colors with Ink compositions 1 by means of the aforementioned ink-jet printer with the amount of the ink of 100% (monocolor).
• the image densities of the solid images of the respective colors were measured by a densitometer 310TR (X-Rite Co.).
• the recording mediums were immersed in still water for three minutes, and left in the air for drying for one day. Thereafter, the image densities were measured in the same manner as above.
• the remaining ratio of the image density of the respective colors was derived according to the equation below, and the minimum value of the ratio was taken for the respective color. The larger the minimum value, the higher the water resistance is.
• Remaining ratio (%) [1 - ⁇ (Density before test - Density after test)/ (Density before test) ⁇ ] ⁇ 100
• Aluminum dodexide was prepared by the method described in U.S.Patent 4,242,271.
• the aluminum dodexide was hydrolyzed by the method described in U.S.Patent 4,202,870 to prepare an alumina slurry.
• Water was added to this alumina slurry to adjust the concentration of the alumina hydrate having the boehmite structure to 7.9% in terms of a solid content.
• the alumina slurry had pH of 9.4.
• the pH was adjusted by addition of 4% nitric acid solution to obtain fractions of solutions, and the solutions were aged under the conditions shown in Table 1 to obtain colloidal sols.
• the colloidal sol was spray-dried to produce powdery alumina hydrate having the boehmite structure.
• the alumina hydrate had the crystal structure of boehmite, and the particles were in a flat plate shape.
• the properties of the alumina hydrate products were measured in the aforementioned methods respectively. Table 1 shows the results.
• a portion of 110 parts by weight of alumina hydrate A was added to 390 parts by weight of deionized water.
• the mixture was stirred at 1500 rpm for 30 minutes with a mixer (Portable Homomixer A510 with DS impeller blade, Satake Kagaku Kikai K.K.). While the stirring was further continued at 2500 rpm, 157 parts by weight of aqueous 10% solution of polyvinyl alcohol (Gohsenol GH17, The Nippon Synthetic Chemical Industry Co.) was added thereto.
• the mixture was stirred further for 30 minutes to obtain a coating liquid containing the alumina hydrate and the polymer at a weight ratio of 7/1 at a solid matter concentration of 19.1% by weight.
• the coating liquid was applied onto a transparent PET film of 100 ⁇ m thick (Lumirror, Toray Industries, Inc.) by gravure coating at a coating speed of 10 m/min with simultaneous corona discharge treatment.
• the applied coating was dried at 120°C.
• an ink-receiving layer was formed with the dried coating thickness of 40 ⁇ m.
• the properties thereof were measured according to the method shown in the above Item of "Properties of Ink-Receiving Layer". Table 2 shows the results.
• Ink-receiving layers were formed in the same manner as in "Production Example 1 of Ink-Receiving Layer" except that Alumina Hydrate A was replaced by Alumina Hydrate B in Production Example 2, by Alumina Hydrate C in Production Example 3, and by Alumina Hydrate D in Production Example 4.
• the evaluations were conducted in the same manner. Table 2 shows the results.
• An ink-receiving layer was formed in the same manner as in "Production Example 1 of Ink-Receiving Layer" except that Alumina Hydrate A was replaced by silica (Mizuka Sil P-78A, Mizusawa Kagaku Kogyo K.K.; BET specific surface area: 350 m 2 /g, BET pore volume: 1.53 mL/g, and average particle diameter: 2.0 ⁇ m). The properties were measured in the same manner. Table 2 shows the results.
• the mixture was stirred at 1500 rpm for 30 minutes with a mixer (Portable Homomixer A510 with DS impeller blade, Satake Kagaku Kikai K.K.).
• To this liquid dispersion was added 34.2 parts by weight of 10% solution of alcohol-soluble nylon (Toresin MF-30, N-methoxymethylated polyamide resin, Teikoku Kagaku Sangyo K.K.) in methanol as a binder.
• the mixture was further stirred for 30 minutes to obtain a coating liquid containing colloidal silica and an alcohol-soluble polymer at a weight ratio (P/B) of 7/1, solid matter concentration of 7.0% by weight.
• the coating liquid was applied on the ink-receiving layer of "Example 1 of Ink-Receiving Layer Production” by gravure coating at a coating rate of 20 m/min, and was dried at 120°C to form a porous layer of dried coating thickness of 5 ⁇ m.
• the coated sheet was cut into an A-4 size (297mm ⁇ 210mm) to obtain a recording medium.
• the properties were measured according to the methods described in the above Item "Properties of Recording Medium”. Table 3 shows the measurement results.
• Recording mediums were produced in the same manner as in Example 1 except that the ink-receiving layer was replaced by the one produced in "Production Example 2 of Ink-Receiving Layer" in example 18, by the one produced in "Production Example 3 of Ink-Receiving Layer” in example 19, and by the one produced in "Production Example 4 of Ink-Receiving Layer” in Example 20.
• the measurement and evaluation were conducted in the same manner. Table 4 shows the results.
• a recording mediums was produced in the same manner as in Example 1 except that the ink-receiving layer was replaced by the one produced in "Production Example 5 of Ink-Receiving Layer". The measurement and evaluation were conducted in the same manner. Table 4 shows the results.
• P/B weight ratio
• the coating liquid was applied on the ink-receiving layer of "Example 1 of Ink-Receiving Layer Production” by gravure coating at a coating rate of 10 m/min, and was dried at 120°C to form a porous layer of dried coating thickness of 5 ⁇ m.
• the coated sheet was cut into an A-4 size (297mm ⁇ 210mm) to obtain a recording medium.
• the properties were measured according to the methods described in the above Item "Properties of Recording Medium”. Table 4 shows the measurement results.
• a recording medium was prepared in the same manner as example 1 except that the spherical colloidal silica and the amount of the addition thereof were changed to 160 parts by weight of linear colloidal silica, Snowtex OUP (Nissan Chemical Industries, Ltd.; particle size: 40-100 nm, solid matter content: 15%). The measurement and evaluation were conducted in the same manner. Table 4 shows the results.
• the recording medium of the present invention absorbs ink at a high absorption rate to form high density of printed images with excellent density gradation in variable density printing without beading or streaking or the like defects of printed image.
• the recording medium of the present invention is excellent in surface scratch resistance, deliverability, and transparency.
• the coating liquid is stable and the productivity is high.
• S-LEC KS-8 4 Polyvinylbutyral Sekisui Chemical Co.
• S-LEC BX-1 5 Ethylene-vinylalcohol copolymer Nippon Synth.Chem.Ind.Co. SOANOL 30T 6
• SMR-30L 7 Ethylcellulose Shin-Etsu Chemical Co.
• a recording medium comprising at least a base member, an ink-receiving layer containing alumina hydrate of a boehmite structure formed on the base member, and a porous layer containing particles and an alcohol-soluble organic polymer resin formed further on the ink-receiving layer.

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• Ink Jet Recording Methods And Recording Media Thereof (AREA)
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• Ink Jet (AREA)
• Transition And Organic Metals Composition Catalysts For Addition Polymerization (AREA)
• Macromolecular Compounds Obtained By Forming Nitrogen-Containing Linkages In General (AREA)

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• 1998
  • 1998-12-28 JP JP10373140A patent/JP2000190629A/ja not_active Withdrawn
• 1999
  • 1999-12-27 EP EP99126018A patent/EP1016543B1/fr not_active Expired - Lifetime
  • 1999-12-27 AT AT99126018T patent/ATE263033T1/de not_active IP Right Cessation
  • 1999-12-27 DE DE69916000T patent/DE69916000T2/de not_active Expired - Lifetime

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