JP3649423B2 - Inkjet recording sheet - Google Patents

Description

【００４５】
【発明の効果】
上記のように、インク受容層を構成する樹脂成分が、多孔質親水性ポリウレタン樹脂又は多孔質親水性ポリウレア樹脂又は多孔質親水性Ｖポリウレタン−ポリウレア樹脂からなるインクジェット用記録シートは、インクの吸収性及び発色性に優れ、安定した高品位な印字画像を与え、更にはインク受容層及び印字画像の搬送性、ブロッキング性、耐水性及び耐湿性に優れる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an ink jet recording sheet, and particularly for an ink jet having an ink-receiving layer that is excellent in water-based ink absorbability, provides a stable and high-quality printed image, and is excellent in transportability, blocking property, water resistance, and moisture resistance. It relates to a recording sheet.
[0002]
[Prior art]
The ink jet recording method is based on various operating principles, for example, an electrostatic suction method, a method of applying mechanical vibration or displacement to the ink using a piezoelectric element, a method of heating and foaming the ink, and utilizing the pressure of the ink. This is a recording method that allows high-quality printing and multi-color printing with less high-speed printing and noise generation, and recording images, characters, etc. It is rapidly spreading to various applications.
[0003]
In such a recording sheet used for ink jet recording, the ink adhering to the recording sheet does not cause bleeding or flow, and the print quality is not impaired, so that the base sheet such as paper quickly absorbs ink, In order to form clear ink dots, recording sheets with an ink receiving layer mainly composed of various pigments and resins, or recording sheets in which a porous pigment is rubbed into paper itself have been proposed. Yes.
[0004]
For example, Japanese Patent Application Laid-Open No. 57-82085 discloses an ink receiving layer composed of a water-soluble polymer using an inorganic pigment and an organic pigment as pigments. It is disclosed that an ink-receiving layer made of a powdered silica and a polyvinyl alcohol copolymer having a silanol group is provided.
[0005]
However, as the performance of inkjet recording devices such as higher speed, higher definition, or full color is improved and applications are expanded, it is required that inkjet recording sheets also have the following advanced characteristics. Became.
(1) fast ink absorption and large absorption capacity;
(2) High color developability of the ink,
(3) the surface strength of the ink receiving layer is high;
(4) The support has water resistance, and the ink does not cause irregularities or curls on the support,
(5) The ink receiving layer has good image storability such as water resistance and ozone resistance after image printing, and (6) the ink receiving layer does not change with time.
[0006]
Conventionally, a porous pigment or a water-soluble polymer having excellent ink absorbability is used as a component of an ink receiving layer provided on an ink jet recording sheet to satisfy these requirements, or water resistance of the ink receiving layer is improved. It has been practiced and studied to use latex for the substrate, and to use synthetic paper or plastic having water resistance for the support itself.
[0007]
However, a paper using a support or using only a water-based polymer as an ink receiving layer has poor water resistance of the ink receiving layer, bleeding of a printed portion, and poor image sharpness. On the other hand, those using synthetic paper or plastic film for the support or using latex for the resin of the ink receiving layer have problems in the adhesion between the ink receiving layer and the support, the ink absorbability and the drying property.
[0008]
[Problems to be solved by the invention]
The present invention relates to an ink jet recording sheet, and in particular, is excellent in water-based ink absorbability, sharp in ink shape, excellent in color development of ink, gives a stable and high-quality printed image, and further has transportability and blocking properties. An object of the present invention is to provide an ink jet recording sheet having an ink receiving layer excellent in water resistance and moisture resistance.
[0009]
[Means for Solving the Problems]
The above object is achieved by the present invention described below. That is, the present invention is on one side of the substrate sheet used in the inkjet recording, an inkjet recording sheet provided with an ink receiving layer of at least one layer, the ink receiving layer, the hydrophilic polyurethane resin or a hydrophilic polyurea resin or hydrophilic sex polyurethane - using polyurea resin, and characterized by having upper Symbol resin was emulsified (O / W or W / O), the porous of the resin formed by the method for applying and deposited on the base sheet This is an inkjet recording sheet.
[0010]
In general, the resolution of a print image on an inkjet recording sheet depends on the amount of ink absorbed. If the ink absorbency is too high, the print image density decreases, and the resolution is reduced due to a decrease in sharpness and color development. Become inferior. On the other hand, if the ink absorptivity is too low, the print density becomes high, but there are drawbacks that the quality of the printed image is lowered and the ink drying time is prolonged due to density unevenness and bleeding.
[0011]
In order to solve the problems of the conventional inkjet recording sheet as described above, the present inventors have made various studies, and as a result, the water-based ink has excellent absorbability and the shape of the ink dots is sharp. It has been found that an ink jet recording sheet having an ink-receiving layer that is excellent in color developability, gives a stable and high-quality printed image, and further has excellent transportability, blocking property, water resistance, and moisture resistance can be obtained.
According to the present invention, by using a porous hydrophilic resin in the ink receiving layer, the water-absorbing property of the water-based ink is increased by a capillary phenomenon, giving a high-quality printed image, and excellent in transportability, blocking property, etc. An ink jet recording sheet having high performance is provided.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Next, the present invention will be described in more detail with reference to preferred embodiments.
In the ink jet recording sheet of the present invention, the resin component constituting the ink receiving layer is a porous hydrophilic polyurethane resin, a porous hydrophilic polyurea resin, or a porous hydrophilic polyurethane-polyurea resin.
[0013]
In the present invention, the hydrophilic polyurethane resin, hydrophilic polyurea resin or hydrophilic polyurethane-polyurea resin forming the porous ink receiving layer can be obtained according to a conventionally known method.
When these preferable things are demonstrated more concretely, a hydrophilic polyurethane resin, a hydrophilic polyurea resin, and a hydrophilic polyurethane-polyurea resin are obtained by making a polyol and / or polyamine and polyisocyanate react.
[0014]
Preferred polyols and polyamines in the present invention are hydrophilic compounds having a hydroxyl group or amino group at the end group and a molecular weight in the range of 200 to 8,000.
As the terminal having a hydroxyl group and having hydrophilicity, for example,
Polyethylene glycol,
Polyethylene glycol / polytetramethylene glycol copolymer polyol,
Polyethylene glycol / polypropylene glycol copolymer polyol,
Polyethylene glycol adipate,
Polyethylene glycol succinate,
And polyethylene glycol / poly-ε-caprolactone copolymer polyol and polyethylene glycol / poly-valerolactone copolymer polyol.
[0015]
As a compound having a terminal amino group and hydrophilicity, for example,
Polyethylene oxide diamine,
Polyethylene oxide, propylene oxide diamine,
Polyethylene oxide triamine,
Examples include polyethylene oxide, propylene oxide triamine, and the like.
[0016]
However, when synthesizing a hydrophilic polyurethane resin, hydrophilic polyurea resin or hydrophilic polyurethane-polyurea resin, other polyols or polyamines having no hydrophilic chain in order to maintain the water resistance of the ink receiving layer to be formed, and Silicone polyols, perfluoroalkyl polyols, and the like can be copolymerized.
[0017]
As the organic isocyanate to be reacted with the polyol, any conventionally known one can be used, or a urethane prepolymer obtained by reacting these organic polyisocyanate with a low molecular weight polyol or polyamine so as to be a terminal isocyanate. Can of course also be used. The chain extender includes any conventionally known low molecular diol, low molecular amine and the like.
The preferred molecular weight of the hydrophilic polyurethane resin or hydrophilic polyurea resin or hydrophilic polyurethane-polyurea resin obtained from the above materials is 10,000 to 500,000, and most preferably 20,000 to 200,000.
[0018]
In the present invention, as a method for obtaining a porous ink receiving layer, a coating liquid containing the above-mentioned hydrophilic polyurethane resin, hydrophilic polyurea resin or hydrophilic polyurethane-polyurea resin is prepared, and this is applied to a substrate and formed into a film. A method is mentioned. As a method for preparing a coating liquid containing the above resin and forming an ink receiving layer, the following typical methods are exemplified.
[0019]
(1) A method of emulsifying (O / W or W / O) the resin and applying and forming a film on a substrate sheet ,
(2) A method in which the resin has a partially dissolved portion and a non-dissolved portion in an organic solvent, and a resin dispersion is formed by a difference in solubility due to the organic solvent, and this is applied to a base sheet and formed into a film,
(3) A method in which a solution obtained by dissolving the resin in an organic solvent having affinity for water is applied to a base sheet, and the base sheet is immersed in water to remove the solvent and form a film .
[0020]
As the base material of the ink jet recording sheet of the present invention, paper, plastic film, glass, cloth, wood, metal and the like are used. Examples of the paper include high quality paper, medium quality paper, coated paper, cast coated paper, and the like. Examples of the plastic film include sheets of 50 to 250 μm such as polyester, cellulose triacetate, polycarbonate, polyvinyl chloride, polypropylene, polyamide, polystyrene, polyethylene, and polymethyl methacrylate. Further, if necessary, a primer layer for imparting adhesion to the substrate or a back surface of the substrate sheet on the non-receptive layer side may be provided with an anti-curl layer or a slipping layer for improving the friction coefficient.
[0021]
The resin component constituting the ink receiving layer may be the aforementioned resin alone, but a water-soluble polymer may be used in order to further impart or adjust hydrophilicity and / or water absorption depending on the composition of the inkjet ink. You may use it in combination. Examples of the water-soluble polymer used here include polyvinyl alcohol, modified polyvinyl alcohol, hydroxyethyl cellulose, CMC, cellulose derivatives, polyvinyl pyrrolidone, starch, cationic starch, gelatin, casein, and acrylic acid polymers. .
[0022]
Further, for the purpose of further imparting water resistance and durability to the ink receiving layer and the printed image, a hydrophobic polymer may be used in combination with the resin. Examples of the hydrophobic polymer used here include polyester resin, polyvinyl chloride resin, polystyrene resin, polymethyl methacrylate resin, polycarbonate resin, polyurethane resin, vinyl chloride-vinyl acetate copolymer resin, acrylonitrile-styrene copolymer resin, Examples thereof include synthetic resins generally used such as polyvinyl butyral resin, polyamide resin, epoxy resin, urea resin, melamine resin and the like.
[0023]
Furthermore, inorganic or organic pigments or resin particles can be added for the purpose of improving the ink absorbability, fixability, color development, blocking property, and water resistance of the ink receiving layer. Examples of pigments and resin particles used include kaolin, delaminated kaolin, aluminum hydroxide, silica, diatomaceous earth, calcium carbonate, talc, titanium oxide, calcium sulfate, barium sulfate, zinc oxide, alumina, calcium silicate, magnesium silicate, Mineral pigments such as colloidal silica, zeolite, bentonite, sericite, lithopone, porous pigments and polystyrene resin, urea resin, acrylic resin, melamine resin, benzoguanamine resin, polyurethane resin, other fine particles such as organic pigment, porous fine particles, Among the known pigments such as hollow particles and resin particles, one or two or more are appropriately used according to the quality design of the recording sheet for inkjet.
In this case, the amount of these pigments and resin particles used is 0 to 95% by weight, preferably 10 to 90% by weight, based on the total solid content of the resin composition.
[0024]
Furthermore, if necessary, in the ink receiving layer, in addition to resins and pigments, thickeners, mold release agents, penetrating agents, wetting agents, thermal gelling agents, sizing agents, antifoaming agents, foam suppressors, foaming Agent, colorant, optical brightener, ultraviolet absorber, antioxidant, quencher agent, preservative, antistatic agent, crosslinking agent, dispersant, lubricant, plasticizer, pH adjuster, fluidity improver, solidification Various auxiliaries such as accelerators and water-proofing agents can be appropriately blended.
[0025]
The ink jet recording sheet of the present invention can be obtained by application to a base material or lamination by a method for forming a porous ink receiving layer. The thickness of the formed porous ink layer is preferably 1 to 2,000 μm. If the thickness is less than 1 μm, ink absorption is insufficient, and a high-quality printed image cannot be obtained. If the thickness is 2,000 μm or more, the density decreases due to the thickness, the ink receiving layer breaks, curls, etc. Problems are likely to occur.
[0026]
【Example】
Next, the present invention will be described more specifically with reference to examples and comparative examples. In the text, “%” or “%” is based on weight.
Example 1
(Method by emulsification: O / W type)
76 parts of water-added MDI was added to 70 parts of polytetramethylene glycol (molecular weight: 1,970), 230 parts of polyethylene glycol (molecular weight 2,040) and 2 parts of trimethylolpropane, and reacted at 90 ° C. for 5 hours to obtain terminal isocyanate. Of a prepolymer was obtained. When the free isocyanate group of the obtained product was quantified, the theoretical value was 2.65%, while the measured value was 2.44%.
[0027]
To 100 parts of the obtained prepolymer, 30 parts of toluene and 2 parts of a surfactant (Emulgen; manufactured by Kao) were added and dissolved uniformly, and then an aqueous solution in which 3.4 parts of isophoronediamine was dissolved in 30 parts of water, The solution is added slowly at room temperature (24 ° C.) with high speed stirring at about 6,000 rpm. After completion of the addition, 370 parts of water was added under high-speed stirring with a homomixer to obtain a milky white polyurethane-polyurea resin dispersion having an average molecular weight of about 120,000.
[0028]
A dispersion obtained by adding 1 part of an anionic foam stabilizer (manufactured by San Nopco) to 100 parts of this dispersion and stirring the mixture with a homomixer to form uniform bubbles by air is used as a synthetic paper (product of 80 μm thickness). Name: YUPO FPG-80 / manufactured by Oji Oil & Chemical Co., Ltd.) The present invention has a uniform porous ink-receptive layer that is coated and dried with a bar coater so that the solid content is 30 g / m ^2. An inkjet recording sheet was obtained.
[0029]
Example 2
(Method by emulsification: W / O type)
50 parts of polytetramethylene glycol (molecular weight; 1020), 150 parts of polyethylene glycol (molecular weight 2,040) and 6 parts of ethylene glycol are dissolved in 350 parts of methyl ethyl ketone, and 54 parts of diphenylmethane diisocyanate are added with good stirring at 70 ° C. . After completion of the addition, 257 parts of methyl ethyl ketone was further added and reacted at 80 ° C. for 6 hours to obtain a polyurethane resin solution having an average molecular weight of 98,000 and a solid content of 30%.
[0030]
Next, 16 parts of a urethane emulsifier and 172 parts of toluene were added, and 690 parts of water was added under high speed stirring with a homomixer to obtain a milky white polyurethane resin dispersion. This dispersion was coated on a synthetic paper (trade name: YUPO FPG-80 / Oji Oil Chemical Co., Ltd.) having a thickness of 80 μm with a bar coater so that the solid content was 30 g / m ² . The ink-jet recording sheet of the present invention having a uniform porous ink receiving layer was obtained by first drying at 60 ° C. and then drying at 130 ° C.
[0031]
Reference example 3
(Method by difference in solubility)
200 parts of polyethylene glycol (molecular weight 2,040) and 15 parts of 1,4-butanediol are dissolved in 250 parts of toluene and 250 parts of methyl ethyl ketone, and 66 parts of diphenylmethane diisocyanate are added with good stirring at 70 ° C. After completion of the addition, 340 parts of methyl ethyl ketone is further added and reacted at 80 ° C. for 6 hours. As the reaction proceeds, the solution becomes milky white. Then, it cooled to normal temperature, stirring, and obtained the milky white polyurethane resin solution in which the microparticles | fine-particles of 1-3 micrometers with a solid content of 25% were disperse | distributed uniformly. In the same manner as in Example 1, this solution was applied and dried so as to have a solid coating amount of 30 g / m ² to obtain an ink jet recording sheet of the present invention having a uniform porous ink receiving layer.
[0032]
Reference example 4
(Method by immersion in water)
Dissolve 200 parts of polyethylene oxide (Texacochemical, Jeffamine ED; molecular weight 2,000) and 10 parts of propylenediamine in 350 parts of dimethylformamide, and adjust the internal temperature to 0 to 5 ° C while stirring well. Was dissolved dropwise in 280 parts of dimethylformamide and allowed to react. After completion of the dropwise addition, the internal temperature was gradually raised, and when the temperature reached 50 ° C., the reaction was further continued for 5 hours to obtain a pale yellow transparent polyurea resin solution having an average molecular weight of 120,000 and a solid content of 30%. In the same manner as in Example 1, this solution was coated on a synthetic paper with a bar coater so as to have a solid coating amount of 30 g / m ^2, and placed in a 40 ° C. dimethylformamide / water (= 1/1) bath. The ink jet recording sheet of the present invention having a uniform porous ink receiving layer was obtained by dipping and drying.
[0033]
Reference Example 5
40 parts of polytetramethylene glycol (molecular weight; 1,020), 160 parts of polyethylene glycol (molecular weight 2,040), 8 parts of 1,4-butanediol and 52 parts of diphenylmethane diisocyanate were bulk polymerized. The resulting flat and average molecular weight: 70,000 35 parts 8,000 of thermoplastic polyurethane resin and stearyl alcohol 65 parts, the diameter ([Phi) continuously 400mm wide with kneading at 190 ° C. in an extruder of 35 mm, a die gap 1mm A sheet having a thickness of 80 μm was obtained by extrusion from a T die. The obtained sheet is immersed in a mixed solution of water / dimethylformamide (= 3/7) to remove stearyl alcohol in the sheet, and then the synthetic paper and polyester paper adhesive (Polyester; manufactured by Nippon Synthetic Chemical) The ink jet recording sheet of the present invention having a uniform porous ink receiving layer with a film thickness of 30 μm was obtained by one-side heat treatment with a heating roller having a bonding surface temperature of 130 ° C.
[0034]
Comparative Example 1
A polyurethane-polyurea resin dispersion obtained by the same formulation as in Example 1 was applied on a synthetic paper without forming bubbles and dried under conditions of 130 ° C./2 minutes to form a transparent ink receiving layer. A recording sheet was obtained.
[0035]
Comparative Example 2
A pale yellow transparent polyurethane resin solution was obtained in the same manner as in Reference Example 3 except that the solvent, methyl ethyl ketone, was replaced with dimethylformamide.
This solution was applied onto synthetic paper and dried to obtain an ink jet recording sheet on which a transparent ink receiving layer was formed.
[0036]
Comparative Example 3
After the polyurea resin solution of Reference Example 4 was applied on synthetic paper, it was dried as it was at 130 ° C./3 minutes without being immersed in a dimethylformamide / water bath to obtain an ink jet recording sheet on which a transparent ink receiving layer was formed. .
[0037]
Comparative Example 4
Inkjet recording in which the thermoplastic polyurethane resin obtained by bulk polymerization of Reference Example 5 was laminated with synthetic paper on a sheet obtained by T-die processing without adding stearyl alcohol to form a transparent ink receiving layer A sheet was obtained.
[0038]
The nine types of sheets obtained as described above were printed and recorded using four colors of yellow, magenta, cyan, and black with an ink jet printer that recorded and recorded with water-soluble dye ink, and the following items were evaluated. Went.
“Blocking”
An untreated polyethylene terephthalate film was left on the ink receiving layer at a load of 0.29 MPa and a temperature of 40 ° C. for 1 day, and then the blocking property was evaluated.
○: No blocking property Δ: Slightly blocking property ×: Blocking property [0039]
"Printer transportability"
The printer transportability during printing and recording with an inkjet printer was evaluated.
○: Good transportability △: Slightly abnormal noise ×: Poor transportability [0040]
"Ink absorbability"
The ink absorption was evaluated by measuring the number of seconds until the printed ink was dried.
○: 5 seconds or less Δ: 6 to 10 seconds ×: 11 seconds or more
"Color clarity"
The color sharpness was visually observed with respect to the color sharpness of the obtained color image after printing the color image with the printer.
○: Good △: Normal ×: Bad [0042]
"Bleeding"
The degree of bleeding was visually observed for the degree of ink bleeding and flow out at the overlapping printing boundary portion of magenta and cyan.
○: Good △: Normal ×: Bad [0043]
"Water resistance of ink receiving layer"
Water was applied to the ink receiving layer, and the peeled state of the ink receiving layer when the water was wiped off with a constant finger pressure was evaluated.
○: No change △: Slight change ×: Peel
[Table 1]

[0045]
【The invention's effect】
As described above, an ink jet recording sheet in which the resin component constituting the ink receiving layer is composed of a porous hydrophilic polyurethane resin, a porous hydrophilic polyurea resin, or a porous hydrophilic V polyurethane-polyurea resin has an ink absorptivity. In addition, it has excellent color developability and gives a stable and high-quality printed image, and further has excellent transportability, blocking property, water resistance and moisture resistance of the ink receiving layer and the printed image.

Claims (1)

On at least one surface of the base sheet, the ink-jet recording sheet provided with an ink receiving layer of at least one layer, the ink receiving layer, the hydrophilic polyurethane resin or a hydrophilic polyurea resin or hydrophilic polyurethane - using polyurea resin, the upper Symbol emulsifying the resin (O / W or W / O) is, ink-jet recording sheet characterized by comprising a porous aforementioned resin formed by the method for applying and deposited on the substrate sheet.