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
  • B41M5/508—Supports
• • 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
  • B41M5/52—Macromolecular coatings
• • 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
  • B41M5/52—Macromolecular coatings
  • B41M5/5218—Macromolecular coatings characterised by inorganic additives, e.g. pigments, clays

Definitions

• the present invention relates to an ink jet recording sheet, more particularly an ink jet recording sheet comprising a substrate made of paper composed mainly of natural pulp and an ink-receiving layer formed on the substrate, which permits formation of images of high quality by an ink jet recording method using aqueous ink, has slight waviness after recording, and has excellent characteristics.
• the ink jet recording method performs recording of letters or images by allowing ink droplets ejected by various working principles to deposit on a recording sheet such as paper.
• the ink jet recording has such favorable features that it makes high-speed recording possible, that it produces little noise, that it can easily perform multi-color recording, that there is no limitation as to kind of patterns, and that it requires no developing-fixing.
• the ink jet recording is rapidly becoming widespread as devices for recording various characters including kanji and color images.
• the images formed by the multi-color ink jet recording method are by no means inferior to those printed by a multi-color press or those obtained by a color-photography.
• use of the ink jet recording extends to a field of full-color image recording where the number of copies is not so large, since it entails less costs per copy than employment of the photographic process.
• the recording sheets are required to have the following properties: the image density of printed ink dots is high and their hue characteristics are bright and appealing; the ink absorbing speed is so high that the ink applied does not bleed or spread even if the recorded dots are put over additionally; the diffusion of the recorded dots in the plane direction is not greater than needed and the circumference of dots is sharp and demarcating; and the quality of images is not changed with time or by circumstances, for example, the recording sheets are excellent in light resistance, water resistance, ozone resistance, etc.
• ink jet printers have become inexpensive and have come to permit easy formation of images excellent in image reproducibility and color reproducibility, for example, sharpness and hue characteristics even by means of a personal computer. Accordingly, the ink jet printers have changed to generally used recording devices from special recording devices used by special persons. Since they can give images equal in quality to those of printed matters and photographs, they have come to be used also as printers for personally produced picture postcards or digital photographs. In this case, the same texture and feel as those of the picture postcards or photographic prints have come to be required.
• ink jet recording sheets With diversification of uses of ink jet recording sheets, they have come to be used as posters or POP arts. In addition, they have come to be used also as labels such as labels for price marking, labels for commodity indication (bar codes), labels for quality indication, labels for weight indication, labels (stickers) for advertisement, etc. by forming an adhesive layer on the reverse side of the sheet. Furthermore, since these ink jet recording labels adhere sufficiently to various adherends and hence are easy to attach, they can be attached to, for example, sheets with heat-sensitive properties, magnetic properties and offset printability through an adhesive layer to impart combined functions thereto. Therefore, their employment in railroad tickets, commutation tickets, various cards, etc. is becoming widespread.
• Inks are classified into solvent-based inks and aqueous inks.
• the aqueous inks are more than the solvent-based inks because of their price, safety, ease of handling, etc.
• the aqueous inks involve important problems such as the prevention of bleeding of the ink caused by the contact of water to a printed surface, and the reduction of waviness of the sheet caused by water which has reached the base paper. No sufficient measure to counter these problems, however, is taken, and the problems are especially important and have to be promptly solved in ink jet recording sheets obtained by using as their medium a support composed mainly of natural pulp having a function as an ink absorber.
• Ink jet recording sheets can be roughly classified according to their form into those of plain paper type represented by so-called fine papers ⁇ bond papers and those of coated type which comprise a support such as paper (e.g. fine paper), synthetic paper or synthetic resin film and an ink-receiving layer provided on the support.
• a support such as paper (e.g. fine paper), synthetic paper or synthetic resin film
• an ink-receiving layer provided on the support.
• various characteristics of the ink-receiving layer formed by coating directly affect the printing quality. Accordingly, there have been investigated the specific surface area and particle shape of pigments in view of absorption capacity; the transparency and refractive index of pigments in view of hue characteristics and color reproducibility; and coating layer structure, surface profile, etc. in view of quality of image.
• the present invention is intended to provide an ink jet recording sheet which can give high-quality ink jet images excellent in hue characteristics and sharpness and is attractive with slight waviness after image recording when the sheet is used in an ink jet recording method using aqueous ink.
• the present invention is also intended to provide an ink jet recording sheet which is excellent in the coating properties of a coating solution for the ink-receiving layer, is free from nonuniformity of coating of the ink-receiving layer, and has a warm feel like paper.
• the present inventors earnestly investigated and consequently suceeded in preventing the waviness of an ink jet recording sheet after image recording by forming an ink-receiving layer on a paper substrate having a density higher than that of ordinary coated base paper or fine paper.
• the present inventors found that an ink jet recording sheet which is excellent in image sharpness and free from waviness after recording can be obtained by forming an ink-receiving layer on a paper substrate having a water absorption in a specific range.
• the present inventors considered that the improvement of smoothness of the paper substrate is the most preferable means for obtaining a uniform ink-receiving layer.
• the present inventors have invented an ink jet recording sheet which is excellent in the coating properties of a coating solution for its ink-receiving layer, is free from nonuniformity of coating of the ink-receiving layer, is excellent in image sharpness, gives high-quality ink jet images, and has a warm feel like paper.
• the first aspect of the present invention is directed to an ink jet recording sheet comprising a substrate made of paper composed mainly of natural pulp and an ink-receiving layer coated on at least one side of the substrate, wherein the ink-receiving layer is formed on the substrate having a density of sheet of 1.01 g/cm 3 or more as measured by the method prescribed in JIS P8118.
• the second aspect of the present invention is directed to an ink jet recording sheet comprising a substrate made of paper composed mainly of natural pulp and an ink-receiving layer coated on at least one side of the substrate, wherein the ink-receiving layer is formed on the substrate having a Cobb sizing degree of 1.0 g/m 2 to 15.0 g/m 2 as measured by the water absorption test by Cobb sizing degree method prescribed in JIS P8140.
• the third aspect of the present invention is directed to an ink jet recording sheet comprising a substrate made of paper composed mainly of natural pulp and an ink-receiving layer coated on at least one side of the substrate, wherein the substrate has an unevenness in thickness in machine direction specified hereinafter (Rpy) (hereinafter referred to as unevenness index) of 150 mV or less and a center plane average roughness in machine direction in the whole wavelength region (SRa) of 1.6 ⁇ m or less as measured with a tracer type three-dimensional surface roughness meter.
• Ra unevenness index
• SRa center plane average roughness in machine direction in the whole wavelength region
• the ink jet recording sheet according to the first aspect of the invention comprises a substrate made of paper composed mainly of natural pulp and an ink-receiving layer coated on at least one side of the substrate, said paper having a density of sheet of 1.01 g/cm 3 or more as measured by the method prescribed in JIS P8118.
• the substrate used in the first aspect of the invention has a density of sheet of 1.01 g/cm 3 or more, preferably 1.03 g/cm 3 or more, more preferably 1.05 g/cm 3 or more. Investigation by the present inventors made it clear that specifically, the substrate having a density of sheet of 1.01 g/cm 3 or more can be obtained by adopting any of, preferably a combination of two or more of, the following methods (1) to (6).
• the ink jet recording sheet according to the second aspect of the invention comprises a substrate made of paper composed mainly of natural pulp and an ink-receiving layer coated on at least one side of the substrate, said paper having a Cobb sizing degree (at a contact time with pure water of 30 seconds) of 1.0 g/m 2 to 15.0 g/m 2 as measured by the water absorption test by Cobb sizing degree method prescribed in JIS P8140.
• the substrate used in the second aspect of the invention has a Cobb sizing degree of 1.0 g/m 2 to 15.0 g/m 2 , preferably 2.0 g/m 2 to 13.0 g/m 2 , more preferably 2.0 g/m 2 to 11.0 g/m 2 .
• a Cobb sizing degree of 1.0 g/m 2 to 15.0 g/m 2 , preferably 2.0 g/m 2 to 13.0 g/m 2 , more preferably 2.0 g/m 2 to 11.0 g/m 2 .
• the ink jet recording sheet according to the third aspect of the invention comprises a substrate made of paper composed mainly of natural pulp and an ink-receiving layer coated on at least one side of the substrate, said paper having an unevenness index Rpy of 150 mV or less as measured under the conditions described hereinafter and a center plane average roughness in machine direction in the whole wavelength region (SRa) of 1.6 ⁇ m or less as measured with a tracer type three-dimensional surface roughness meter.
• a sample is let run between a pair of spherical tracers, and by using a film thickness meter which measures the variation of thickness of the sample as an electrical signal through an electrical micrometer, the variation of thickness of the sample in the machine direction is measured by scanning the sample in the machine direction at a constant rate of 1.5 m/min after adjustment of the zero point, under the condition that the sensitive range of the electrical micrometer is ⁇ 15 ⁇ m/ ⁇ 3 V.
• the hanning window and FFT are applied to the electrical signal by FFT analyzer, followed by averaging of 128 times of integration, whereby the power spectrum (unit: mV 2 ) is obtained.
• the obtained power value is integrated from 2 to 25 Hz, multiplied by 2/3 and then raised to the one-half power.
• the thus determined value (unit: mV) is the unevenness index (Rpy).
• Rpy is determined as follows. The sample is let run between a pair of spherical tracers, about 5 mm in diameter, with a measuring pressure of about 30 g/stroke, and the viriation of thickness of the sample is measured by scanning the sample in the machine direction at a constant rate of 1.5 m/min after adjustment of the zero point, under the condition of sensitivity range of electrical micrometer of ⁇ 15 ⁇ m/ ⁇ 3 V, by using a film thickness meter mfd. by Anritsu Corp. which measures the thickness variation as an electrical signal through an electrical micrometer.
• the power spectrum is obtained by the electrical signal applying hanning window and FFT by the FFT analyzer CF-300 mfd. by Ono Sokki K.K.
• Data processing in the X-axis direction is carried out by sampling at 500 points, and scanning in the Y-axis direction is carried out in 17 lines or more.
• the substrate used in the third aspect of the invention has an unevenness index Rpy specified above of 150 mV or less, preferably 140 mV or less, more preferably 130 mV or less. Investigation by the present inventors made it clear that specifically, the substrate having an unevenness index Rpy of 150 mV or less can be obtained by adopting any of, preferably a combination of two or more of, more preferably a combination of three or more of, most preferably a combination of four or more of, the methods (1) to (4) and (6) described above as to the first aspect of the invention.
• the substrate used in the third aspect of the invention has a center plane average roughness SRa defined by the equation 1 of 1.6 ⁇ m or less, preferably 1.4 ⁇ m or less, more preferably 1.2 ⁇ m or less. Investigation by the present inventors made it clear that specifically, the substrate having a center plane average roughness SRa of 1.6 ⁇ m or less can be obtained by adopting any of, preferably a combination of two or more of, more preferably a combination of three of more of, the following methods.
• natural pulp properly selected as described above is advantageously used.
• wood pulp such as softwood pulp, hardwood pulp or a mixture thereof, which has been subjected to a conventional bleaching treatment with chlorine, hypochlorite, chlorine dioxide or the like, alkali extraction or alkali treatment, and optionally oxidation bleaching with hydrogen peroxide, oxygen or the like, or a combination of these treatments.
• Various pulps such as craft pulp, sulfite pulp, soda pulp, etc. can be used.
• additives may be incorporated into the substrate used for carrying out the present invention, in the preparation of a pulp slurry. It is advantageous to incorporate, for example, the following additives in proper combination: sizing agents such as fatty acids and/or metallic salts of fatty acids, the alkyl ketene dimer emulsion or epoxidized higher fatty acid amides described or exemplified in Japanese Patent Kokoku No.
• alkenyl- or alkylsuccinic anhydride emulsions, rosin derivatives, etc. dry strength agents such as anionic, cationic or ampholytic polyacrylamide, polyvinyl alcohols, cationized starch, vegetable galactomannan, etc.; wet strength agents such as polyamine-polyamido-epichlohydrin resin, etc.; fillers such as clay, kaolin, calcium carbonate, titanium oxide, etc.; fixing agents such as water-soluble aluminum salts (e.g.
• a composition consisting of any of various water-soluble polymers, hydrophilic colloids or polymer latices, an antistatic agent and other additives may be incorporated into or applied on the substrate used for carrying out the present invention, by, for example, sizing press, tab-sizing press, blade coating, or air knife coating. It is advantageous to incorporate the following in proper combination: water-soluble polymers or hydrophilic colloides, such as the starch-based polymes described or exemplified in Japanese Patent Kokai No.
• polyvinyl alcohol-based polymers such as polyvinyl alcohol-based polymers, gelatin-based polymers, polyacrylamide-based polymers, cellulose-based polymers, etc.; emulsions and latices, such as petroleum resin emulsions, emulsions or latices of the copolymers having as components at least ethylene and acrylic acid (or methacrylic acid) which are described or exemplified in Japanese Patent Kokai Nos.
• antistatic agents such as alkali metal salts (e.g. sodium chloride and potassium chloride), alkaline earth metal salts (e.g. calcium chloride and barium chloride), colloidal metal oxides (e.g. colloidal silica), organic antistatic agents (e.g.
• polystyrene sulfonates etc.
• fillers such as clay, kaolin, calcium carbonate, talc, barium sulfate, titanium oxide, etc.
• pH adjustors such as hydrochloric acid, phosphoric acid, citric acid, sodium hydroxide; and the above-exemplified color pigments, dyes, fluorescent brighteners.
• the thickness of the substrate used for carrying out the present invention is not particularly limited.
• the basis weight of the substrate may be properly chosen in the range of 20 to 300 g/m 2 , preferably 80 to 280 g/m 2 , more preferably 100 to 250 g/m 2 .
• the ink jet recording sheet of the present invention is of a coated type and comprises the above-mentioned substrate and an ink-receiving layer formed thereon.
• the term "ink-receiving layer" used in the present specification means, for example, a layer composed mainly of at least one pigment and at least one binder and having voids into which a solvent contained in ink penetrates and holds or absorbs the solvent, a layer composed mainly of at least one high-molecular weight substance which dissolves or swells in a solvent contained in ink.
• Each of these layers may be composed of a single layer, two or more layers, or a combination of a pigment layer and a polymer layer without any problem, as the ink-receiving layer used in the present invention.
• the ink-receiving layer when the ink-receiving layer is formed on the substrate used in the third aspect of the invention, it can be made smooth and uniform.
• ink when ink is deposited on the ink-receiving layer surface by means of an ink jet printer, a recorded dot close to a true circle can be obtained because the ink-receiving layer surface formed by coating is uniform, so that the ink spreads uniformly in the direction of the ink-receiving layer surface.
• the reason is guessed as follows: the surplus ink penetrates uniformly in the direction of thickness of the substrate from the ink-receiving layer surface.
• the ink-receiving layer surface tends to have non-uniformity of coating, so that ink spreads in the direction of the recording surface in a nonuniform proportion. Consequently, a recorded dot unlike a true circle is obtained, and the sharpness of images is not sufficient because the spread of the ink is different in different places. Moreover, the penetration of the ink into the substrate becomes irregular, so that the circumference of dots are not sharp, resulting in a deteriorated sharpness of images.
• the pigment may be any conventional pigment.
• the pigment includes, for example, inorganic or organic pigments such as silicas (e.g. colloidal silica and amorphous silica), aluminas or alumina hydrates (e.g.
• alumina sol colloidal alumina, cationic aluminium oxide or hydtates thereof, and pseudo-boehmite
• aluminum silicate magnesium silicate, magnesium carbonate, light calcium carbonate, heavy calcium carbonate, kaolin, talc, calcium sulfate, barium sulfate, titanium dioxide, zinc oxide, zinc sulfide, zinc carbonate, satin white, diatomaceous earth, calcium silicate, aluminum hydroxide, lithopone, zeolite, hydrated halloysite, magnesium hydroxide, styrene plastic pigments, acrylic plastic pigments, polyethylenes, microcapsules, urea resins, melamine resins, etc.
• porous inorganic pigments such as porous synthetic amorphous silica, porous magnesium carbonate, porous alumina, etc. are preferable.
• porous synthetic amorphous silica or porous alumina hydrate which has a large capacity of pore.
• Non-porous inorganic pigments can also be used as the pigment for the ink-receiving layer used in the present invention because particles of the non-porous inorganic pigment are aggregated during preparation of a coating solution and further aggregated during coating and drying to form a porous coating surface.
• the porous inorganic pigments and the non-porous inorganic pigments may be used at the same time without any problem.
• the binder includes, for example, polyvinyl alcohols and derivatives thereof, polyvinyl acetates, oxidized starch, etherified starch, cellulose derivatives (e.g. carboxymethyl cellulose and hydroxyethyl cellulose), casein, gelatin, soybean protein, silyl-modified polyvinyl alcohols, maleic anhydride resins, latices of conjugated diene type copolymers (e.g. styrene-butadiene copolymers and methyl methacrylate-butadiene copolymers), latices of acrylic polymers (e.g.
• polymethyl methacrylates polyurethane resins, unsaturated polyester resins, vinyl chloride-vinyl acetate copolymers, polyvinyl butyrals, and alkyd resins).
• binders may be used singly or as a mixture thereof.
• conventional cationic resins may be used in combination with the binders.
• the total amount of the binder(s) used can be properly adjusted depending on characteristics of a desired ink jet recording sheet. It is usually 5 to 60 parts by weight per 100 parts by weight of the pigment(s).
• the ink-receiving layer may properly contain other additives such as pigment dispersants, thickening agents, fludity improvers, defoaming agents, foam-inhibitors, mold release agents, foaming agents, penetrating agents, color pigments, dyes, fluorescent brighteners, ultraviolet absorbers, anti-oxidants, antiseptics, mildew-proofing agents, water-proofing agents, wet strength agents, dry strength agents, etc.
• the high-molecular weight substance includes, for example, polyvinyl alcohols, polyvinyl acetates, oxidized starch, etherified starch, gelatin and its derivatives, cellulose derivatives (e.g. carboxymethyl cellulose and hydroxyethyl cellulose), various ink-absorbing polymers (e.g. polyvinyl pyrrolidones, polyethylene oxides, acrylic polymers, and vinyl acetal polymers), etc.
• These high-molecular weight substances may be used singly or as a mixture thereof.
• a multi-layer structure containing the high-molecular weight substances may also be used as the ink-receiving layer used in the present invention.
• various coating equipments such as blade coater, roll coater, air-knife coater, bar coater, rod coater, gate roll coater, curtain coater, short-dwell coater, gravure coater, flexo-gravure coater, sizing press, slide hopper type equipments, etc. can be used in on-machine or off-machine coating.
• finishing may be carried out with a calender such as a machine calender, thermal calender, supercalender, soft calender or the like.
• a calender such as a machine calender, thermal calender, supercalender, soft calender or the like.
• the thickness of the ink-receiving layer is not particularly limited, the coating amount is preferably 0.5 g/m 2 to 60 g/m 2 .
• various back coat layers may be formed in order to improve the antistatic properties, sheet feed ability, curl-preventing properties, writability, starchability, etc.
• the back coat layers may contain a proper combination of inorganic antistatic agents, organic antistatic agents, hydrophilic binders, latices, hardening agents, pigments, lubricants, matting agents, surfactants, etc.
• the ink referred to in the present specification is a recording liquid comprising at least one coloring agent, at least one liquid medium and other additives.
• the coloring agent includes, for example, water-soluble dyes and disperse dyes, such as direct dyes, acid dyes, basic dyes, reactive dyes, food dyes, etc.; color pigments; and carbon black.
• the solvent in the ink includes, for example, water and water-soluble various organic solvents, e.g., alkyl alcohols having 1 to 4 carbon atoms, such as methanol, ethanol, n-propanol, isopropanol, n-butanol, sec-butanol, tert-butanol, isobutanol, etc.; amides such as dimethylformamide, dimethylacetamide, etc.; ketones or ketone alcohols, such as acetone, diacetone alcohols, etc.; ethers such as tetrahydrofuran, dioxane, etc.; polyalkylene glycols such as polyethylene glycols, polypropylene glycols, etc.: alkylene glycols having 2 to 6 alkylene groups, such as ethylene glycol, propylene glycol, butylene glycol, triethylene glycol, 1,2,6-hexanetriol, thiodiglycol, hexylene glycol
• polyhydric alcohol e.g. diethylene glycol
• lower alkyl ethers of polyhydric alcohols e.g. triethylene glycol monomethyl ether and triethylene glycol monoethyl ether
• the other additives include, for example, pH adjustors, sequestering agents, mildew-proofing agents, viscosity adjustors, surface tension adjustors, wetting agents, surfactants, and rust preventives.
• the ink jet recording sheet of the present invention can be used not only as an ink jet recording sheet for aqueous ink but also as any recording sheet for ink which is liquid at the time of recording.
• a recording sheet includes, for example, receiving sheets for heat transfer recording which are used by heating an ink-coated sheet obtained by applying heat-meltable ink composed mainly of, for example, a heat-meltable substance and a dye or pigment on a thin support (e.g.
• ink jet recording sheets for performing recording by heat-melting heat-meltable ink into droplets and ejecting the droplets; ink jet recording sheets for ink obtained by dissolving an oil-soluble dye in a solvent; ink jet recording sheets for ink obtained by dispersing a color pigment in an organic solvent; and image-receiving sheets suitable for light-sensitive and pressure-sensitive donor sheets obtained by using micro-capsules containing a photopolymerizable monomer and a coloress or color dye or pigment.
• ink is liquid at the time of recording.
• the liquid ink penetrates or diffuses into the ink-receiving layer of the recording sheet in the direction of depth or the horizontal direction before hardening, solidification or fixing.
• the above-exemplified various recording sheets are required to have absorbing properties suitable for each method, and the ink jet recording sheet of the present invention may be used as any of the above-exemplified various recording sheets without any limitation.
• the ink jet recording sheet of the present invention may be used as a recording sheet for heating and fixing a toner for electrophotographic recording which is widely used in copying machines, printers, etc.
• a pulp slurry was prepared by adding 3 parts by weight of cationized starch, 0.2 part by weight of anionized polyacrylamide, 0.4 part by weight (in terms of ketene dimer) of an alkylketene dimer emulsion, and 0.4 part by weight of a polyamidoepichlorohydrin resin to 100 parts by weight of the beaten mixed pulp.
• the pulp slurry was formed into a web with a Fourdrinier machine, and the web was subjected to three-platen wet pressing and then treatment with a smoothing roll in the wet part, subjected to two-platen wet re-press in the subsequent dry part, and then dried.
• a size press liquor containing 5% by weight of a carboxy-modified polyvinyl alcohol was size pressed at a rate of 20 g/m 2 , and the resulting product was dried so that the water content of the finally obtained paper based on bone dry weight might be 8% by weight.
• the thus obtained paper was subjected to machine calendering at the linear pressure shown in Table 1, to obtain a substrate for ink jet recording sheet which had a basis weight of 150 g/m 2 and the density shown in Table 1. All the substrates thus obtained had a Cobb sizing degree of 15 to 16 g/m 2 .
• the web was subjected to two-platen wet pressing but not treatment with a smoothing roll in the wet part, and dried without wet re-press in the subsequent dry part.
• a size press liquor containing 5% by weight of a carboxy-modified polyvinyl alcohol was size pressed at a rate of 20 g/m 2 , and the resulting product was dried so that the water content of the finally obtained paper based on bone dry weight might be 8% by weight.
• the obtained paper was subjected to machine calendering at the linear pressure shown in Table 1.
• substrates of Comparative Examples 1 to 3 each having a basis weight of 150 g/m 2 and the density shown in Table 1.
• a coating solution having a solid content of about 10% and consisting of 5 parts by weight (in terms of solids) of alumina sol AS-3 (pseudo-boehmite, mfd. by Catalysts and Chemicals Industry Co., Ltd.), 1 part by weight (in terms of solids) of a polyvinyl alcohol MA-26 (mfd. by Shin-etsu Chemical Co. Ltd.) and water was prepared as a composition for forming an ink-receiving layer.
• the coating solution was applied on each substrate produced in the manner described above, with a bar coater so that the dry coating amount might be 15 g/m 2 . Then, the substrate was dried to produce an ink jet recording sheet.
• Waviness after image recording was evaluated by forming high-definition photographic images having wide hue and lightness ranges, allowing the images to stand for 24 hours, and visually evaluating the waviness of the recording surface after drying in the following five grades:
• a pulp slurry was prepared by adding 3 parts by weight of cationized starch, 0.2 part by weight of anionized polyacrylamide, 0.2 part by weight (Example 6), 0.3 part by weight (Example 7), 0.4 part by weight (Example 8) or 0.5 part by weight (Example 9) (in terms of ketene dimer) of an alkylketene dimer emulsion, and 0.4 part by weight of a polyamido-epichlorohydrin resin to 100 parts by weight of the beaten mixed pulp.
• the pulp slurry was formed into a web with a Fourdrinier machine, and the web was subjected to three-platen wet pressing and then treatment with a smoothing roll in the wet part, subjected to two-platen wet re-press in the subsequent dry part, and then dried.
• a carboxy-modified polyvinyl alcohol solution was size pressed to adjust the amount of the solution adhered to 2.0 g/m 2 in terms of solids.
• the resulting product was dried so that the water content of the finally obtained paper based on bone dry weight might be 8% by weight.
• the thus obtained paper was subjected to machine calendering at a linear pressure of 60 kg/cm to obtain a substrate for ink jet recording sheet which had a basis weight of 150 g/m 2 and the Cobb sizing degree shown in Table 2. All the substrates thus obtained had a density of 0.98 to 1.00 g/m 3 .
• Substrates for ink jet recording sheet which each had the Cobb sizing degree shown in Table 2 were produced in the same manner as in Example 8 except for using a liquor consisting of 5 parts by weight of carboxy-modified polyvinyl alcohol and 0.10 part by weight of a surface sizing agent composed of a styrene/acrylic acid copolymer (KN-500, mfd. by Harima Chemicals, Inc.), in place of the size press solution used in Example 8, and adjusting the amount of the liquor adhered to 1.0 g/m 2 (Example 10), 2.0 g/m 2 (Example 11) or 3.0 g/m 2 (Example 12). All the substrates had a density of 0.98 to 1.00 g/m 3 .
• a liquor consisting of 5 parts by weight of carboxy-modified polyvinyl alcohol and 0.10 part by weight of a surface sizing agent composed of a styrene/acrylic acid copolymer (KN-500, m
• a coating solution having a solid content of about 10% and consisting of 5 parts by weight (in terms of solids) of alumina sol AS-3 (pseudo-boehmite, mfd. by Catalysts and Chemicals Industry Co., Ltd.), 1 part by weight (in terms of solids) of a polyvinyl alcohol MA-26 (mfd. by Shin-etsu Chemical Co. Ltd.) and water was prepared as a composition for forming an ink-receiving layer.
• the coating solution was applied on each substrate produced in the manner described above, with a bar coater so that the dry coating amount might be 15 g/m 2 . Then, the substrate was dried to produce an ink jet recording sheet. In the substrate of Comparative Example 9, the ink-receiving layer peeled off, so that the ink jet recording sheet obtained by using this substrate could not be evaluated.
• Sharpness of image was evaluated by forming a high-definition photographic image and visually observing the overflow and run of ink.
• An excellent ink jet recording sheet was rated as (marked by) ⁇ , an ink jet recording sheet equal to a conventional one as ⁇ , and an unusable ink jet recording sheet as X.
• Waviness after image recording was evaluated by forming high-definition photographic images having wide hue and lightness ranges, allowing the images to stand for 24 hours, and visually evaluating the waviness of the recording surface after drying in the following five grades:
• a pulp slurry was prepared by adding 3 parts by weight of cationized starch, 0.2 part by weight of anionized polyacrylamide, 0.4 part by weight (in terms of ketene dimer) of an alkylketene dimer emulsion, 0.4 part by weight of a polyamido-epichlorohydrin resin and proper amounts of a fluorescent brightener, a blue dye and a red dye to 100 parts by weight of the beaten mixed pulp.
• the pulp slurry was formed into a web with a Fourdrinier machine, and the web was subjected to three-platen wet pressing and then treatment with a smoothing roll in the wet part, subjected to two-platen wet re-press in the subsequent dry part, and then dried.
• a size press liquor consisting of 4 parts by weight of a carboxy-modified polyvinyl alcohol, 0.05 part by weight of a fluorescent brightener, 4 parts by weight of sodium chloride and 92 parts by weight of water was size pressed at a rate of 20 g/m 2 , and the resulting product was dried so that the water content of the finally obtained paper based on bone dry weight might be 8% by weight.
• the thus obtained paper was subjected to machine calendering at the linear pressure shown in Table 3. Then, the paper was either subjected or not to thermal soft calendering at a temperature or 200°C and a linear pressure of 200 kg/cm in accordance with the instruction given in Table 3, to obtain a substrate for ink jet recording sheet which had a basis weight of 150 g/m 2 and the unevenness index Rpy value and center plane average roughness SRa value shown in Table 3.
• Substrates of Comparative Examples 10 to 15 each having a basis weight of 150 g/m 2 and the unevenness index Rpy value and center plane average roughness SRa value shown in Table 3 were produced by treatments under the conditions shown in Table 3, in the same manner as in Examples 13 to 21 except for using mixed pulp consisting of 90% by weight of hardwood bleached kraft pulp and 10% by weight of softwood bleached kraft pulp, in place of the mixed pulp used in Examples 13 to 21.
• a coating solution having a solid content of about 10% and consisting of 5 parts by weight (in terms of solids) of alumina sol AS-3 (pseudo-boehmite, mfd. by Catalysts and Chemicals Industry Co., Ltd.), 1 part by weight (in terms of solids) of a polyvinyl alcohol PVA117 (mfd. by Kuraray Co., Ltd.) and water was prepared as a composition for forming an ink-receiving layer.
• the coating solution was applied on each substrate produced in the manner described above, with a bar coater so that the dry coating amount might be 15 g/m 2 . Then, the substrate was dried to produce an ink jet recording sheet.
• Uniformity of coating layer was evaluated by visually judging the nonuniformity of coating of a surface printed with 50% dots of 720 dpi black ink, in the following four grades:
• a pulp slurry was prepared by adding 3 parts by weight of cationized starch, 0.2 part by weight of anionized polyacrylamide, 0.4 part by weight (in terms of ketene dimer) of an alkylketene dimer emulsion, 0.4 part by weight of a polyamido-epichlorohydrin resin and proper amounts of a fluorescent brightener, a blue dye and a red dye to 100 parts by weight of the beaten mixed pulp.
• the pulp slurry was formed into a web with a Fourdrinier machine, and the web was subjected to three-platen wet pressing and then treatment with a smoothing roll in the wet part, subjected to two-platen wet re-press in the subsequent dry part, and then dried.
• a size press liquor consisting of 8 parts by weight of a carboxy-modified polyvinyl alcohol, 0.05 part by weight of a fluorescent brightener, 4 parts by weight of sodium chloride and 88 parts by weight of water was size pressed at a rate of 25 g/m 2 , and the resulting product was dried so that the water content of the finally obtained paper based on bone dry weight might be 8% by weight.
• the thus obtained paper was subjected to machine calendering at the linear pressure shown in Table 4. Then, the paper was either subjected or not to thermal soft calendering at a temperature or 200°C and a linear pressure of 200 kg/cm in accordance with the instruction given in Table 4, to obtain a substrate for ink jet recording sheet which had a basis weight of 150 g/m 2 and the values of density, Cobb sizing degree, unevenness index Rpy and center plane average roughness SRa which are shown in Table 4.
• a coating solution having a solid content of about 10% and consisting of 5 parts by weight (in terms of solids) of alumina sol AS-3 (pseudo-boehmite, mfd. by Catalysts and Chemicals Industry Co., Ltd.), 1 part by weight (in terms of solids) of a polyvinyl alcohol PVA117 (mfd. by Kuraray Co., Ltd.) and water was prepared as a composition for forming an ink-receiving layer.
• the coating solution was applied on each substrate produced in the manner described above, with a bar coater so that the dry coating amount might be 15 g/m 2 . Then, the substrate was dried to produce an ink jet recording sheet.
• an ink jet recording sheet obtained by coating an ink-receiving layer on the substrate for ink jet recording sheet used in the first aspect of the invention i.e., the substrate having a density of 1.01 g/cm 3 or more is an excellent coated type ink jet recording sheet having no waviness even after image recording and drying.
• an ink jet recording sheet obtained by coating an ink-receiving layer on the substrate for ink jet recording sheet used in the second aspect of the invention i.e., the substrate having a Cobb sizing degree of 1.0 g/m 2 to 15.0 g/m 2 is an excellent coated type ink jet recording sheet which is excellent in image sharpness and has no waviness even after image recording and drying.
• an ink jet recording sheet obtained by coating an ink-receiving layer on the substrate for ink jet recording sheet used in the third aspect of the invention i.e., the substrate having an unevenness in thickness in machine direction (Rpy) of 150 mV or less and a center plane average roughness in machine direction in the whole wavelength region (SRa) of 1.6 ⁇ m or less as measured with a tracer type three-dimensional surface roughness meter, is an excellent coated type ink jet recording sheet which has no nonuniformity of coating of the ink-receiving layer surface and is excellent in quality of image.
• an ink jet recording sheet obtained by coating an ink-receiving layer on a substrate for ink jet recording sheet which satisfies the conditions specified in the above three aspects of the invention i.e., a substrate having a density of 1.01 g/cm 3 or more, a Cobb sizing degree of 1.0 g/m 2 to 15.0 g/m 2 , an unevenness in thickness in machine direction (Rpy) of 150 mV or less and a center plane average roughness in machine direction in the whole wavelength region (SRa) of 1.6 ⁇ m or less as measured with a tracer type three-dimensional surface roughness meter, is an excellent coated type ink jet recording sheet which is excellent in image sharpness, has no waviness even after image recording and drying, has no nonuniformity of coating of the ink-receiving layer surface, and is excellent in quality of image.

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• 1998
  • 1998-06-23 EP EP98111534A patent/EP0887199B1/fr not_active Expired - Lifetime
  • 1998-06-23 DE DE69822707T patent/DE69822707T2/de not_active Expired - Lifetime

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