JP2008068558A - Inkjet recording sheet with printing and printing method thereof - Google Patents

Abstract

【Task】
There is obtained a printed inkjet recording sheet that can achieve good printability without causing various problems at the time of printing without fear of lowering the inkjet printability.
[Solution]
An ink jet recording sheet in which at least one ink receiving layer 4 is provided on a support 5 has a lower printing layer 3 cured by ultraviolet rays on a part of the ink receiving layer 4, and the lower printing layer 3. Since the UV curable ink which has the main printing layer 2 on the ink jet layer 4 and soaks into the ink jet receiving layer 4 and constitutes the lower printing layer 3 is cured by UV, a printing layer whose surface strength is reinforced is formed. Further, it is possible to prevent paper smearing when the main printing layer 2 is printed on the lower printing layer.
[Selection] Figure 1

Description

  The present invention relates to an inkjet recording sheet with printing and a printing method thereof, and more particularly to an inkjet recording sheet in which a printing layer is applied on an ink receiving layer.

  Inkjet recording method is a method in which liquid ink is ejected from a fine nozzle onto a recording body to form images, characters, etc. on the recording body, and there is little noise during recording, colorization is easy, and high-speed recording is possible. In addition, since it is cheaper than other printing apparatuses, it is widely spread and used in various applications. In this specification, recording various information by ink jet recording is referred to as ink jet printing in this specification. On the other hand, with the rapid spread of the ink jet recording method, ink jet recording sheets have been used for various purposes, and it is particularly useful for labels to print characters, pictures, or patterns on specific parts of the ink jet recording sheet in advance. Etc. have come to be widely performed.

  Therefore, in performing such partial printing, Patent Document 1 focuses on the problem of picking that occurs during offset printing, and proposes an idea of providing an ink jet receiving layer using a specific pigment in order to improve the problem. Disclosure.

JP 2001-30619 A

  An object of the present invention is to solve the problem at the time of printing an ink jet recording sheet. As a result of repeated trials and examinations on the problems during printing, the present inventors have found that there are mainly the following two problems. That is, one of them is “paper scraping”, which is a phenomenon in which a part of the paper surface is peeled off due to insufficient surface strength in printing on an ink receiving layer of an inkjet recording sheet. The other is “blanket piling”, which is a phenomenon that makes it impossible to continue printing because the peeled pieces removed by the paper scrap are accumulated on the blanket. However, with respect to such a problem during printing, Patent Document 1 discloses that a specific pigment is contained in the ink receiving layer of the ink jet recording sheet against powder falling that is a cause of picking that occurs during offset printing. Although it is disclosed to obtain an ink jet recording paper having an excellent coating layer strength without powder falling off, until such a modification of the ink jet receiving layer is achieved, until the printing problem in offset printing is solved However, there is a risk that the ink absorbability, which is one of the ink jet printing suitability, is deteriorated or the printing density is lowered.

  As described above, the present invention is a method for printing an inkjet recording sheet that can achieve good printing aptitude without causing various problems during printing to occur without causing a decrease in inkjet printing aptitude in the inkjet recording sheet as described above. It is an object of the present invention to provide a printed inkjet recording sheet on which such printing has been performed.

  As a result of intensive studies to solve the above problems, the present inventors have provided a lower printing layer that is cured by ultraviolet rays (hereinafter abbreviated as UV) on a part of the ink receiving layer of the ink jet recording sheet. Furthermore, the present inventors have found that the problem can be solved by providing a main printing layer on the lower printing layer and printing an ink jet recording sheet. That is, the present invention provides an inkjet recording sheet in which at least one ink receiving layer is provided on a support, and has a lower printing layer cured by UV on a part of the ink receiving layer, and further the lower printing layer The present invention provides a printed ink-jet recording sheet having the present printing layer thereon and a printing method thereof.

  According to the present invention, a printing method for an ink jet recording sheet capable of achieving good printability that does not cause various problems during printing practically, and that does not cause a decrease in ink jet printability, and such printing have been achieved. A printed inkjet recording sheet was obtained.

  FIG. 1 shows an example of an inkjet recording sheet with printing according to an embodiment of the present invention. FIG. 1 is a cross-sectional view of a printing portion of a printed inkjet recording sheet according to the present invention. On the support 5, the ink receiving layer 4 is formed by coating and drying with a coater to obtain an ink jet recording sheet. Next, the lower printing layer 3 cured by UV is formed on a part of the ink receiving layer 4 by a printing machine, and the printing layer 2 is further formed on the lower printing layer 3 by a printing machine. An ink jet recording sheet with such a structure is obtained. Here, the lower printing layer 3 indicates a printing portion or a printing layer printed under a character, a picture, or a pattern that is the main printing. In addition, the print layer 2 also indicates a print portion or print layer of characters, designs, or designs. In addition, the ink receiving layer 4 may be provided with a glossy layer as necessary in a layer that absorbs and retains water-based ink, a layer that passes through and transports it to a lower absorption layer, or an upper layer.

  The support to be used is not particularly limited as long as it can be used as a normal ink jet recording sheet, and paper, synthetic paper, plastic film and the like are used. The thickness of the support used in the present invention is not particularly limited, but when a resin film, resin-coated paper, synthetic paper or the like is used as the support, a thickness of about 10 to 200 μm is preferable from the viewpoint of handling properties.

  When using paper as a support used in the present invention, commonly used paper can be used. As the pulp constituting the paper, natural pulp, recycled pulp, synthetic pulp or the like is used alone or in combination of two or more. This paper is mixed with additives such as a sizing agent, a paper strength enhancer, a filler, an antistatic agent, a fluorescent whitening agent, and a dye generally used in papermaking. Furthermore, hydrophilic resins such as starch and polyvinyl alcohol, surface sizing agents, surface paper strength enhancers, fluorescent whitening agents, antistatic agents, dyes, anchor agents, and the like may be coated on the surface.

In addition, the paper may be a paper whose surface smoothness is improved by making a compression process by applying a pressure with a calendar or the like during or after paper making, or after providing a treatment layer with a size press on the surface. The basis weight is preferably 30 to 300 g / m ² . More preferably, it is 50-200 g / m < ² >.

  As the ink receiving layer of the ink jet recording sheet, a known ink receiving layer can be used. For example, the ink receiving layer has a pigment and an adhesive, and a cationic polymer is blended as necessary. That is, as the pigment used in the ink receiving layer, one or more known white pigments can be used. For example, light calcium carbonate, heavy calcium carbonate, kaolin, talc, calcium sulfate, barium sulfate, titanium dioxide, zinc oxide, zinc sulfide, zinc carbonate, satin white, silicate is luminium, diatomaceous earth, calcium silicate, magnesium silicate, synthesis Amorphous silica, colloidal silica, colloidal alumina, pseudoboehmite, aluminum hydroxide, alumina, lithopone, zeolite, hydrous halloysite, magnesium carbonate, magnesium hydroxide and other inorganic pigments, styrene plastic pigments, acrylic plastic pigments, polyethylene, Organic pigments such as microcapsules, urea resins, and melamine resins can be used. Among the above-mentioned pigments, porous inorganic pigments are preferable, and examples include porous amorphous synthetic silica, porous magnesium carbonate, and porous alumina, and porous synthetic amorphous silica having a large porous volume is particularly preferable.

Further, it is preferable to use silica having an average primary particle diameter of 30 nm or less and a specific surface area of 200 m ² / g or more by the BET method because a high-quality image can be obtained. The lower limit of the primary particles is not particularly limited, but is preferably 1 nm or more, and the upper limit of the specific surface area is not particularly limited, but is preferably 500 m ² / g or less.

  The amount of pigment used in the ink receiving layer is about 20 to 90% by weight, preferably about 30 to 80% by weight, based on the solid content of the ink receiving layer.

  Furthermore, as the cationic polymer, it is possible to use a polymer that dissociates and exhibits cationic properties when dissolved or emulsified in water. Examples of such cationic polymers include polydiallyldimethylammonium chloride, polyammonium diallyldimethyl acrylamide copolymer, diallyldimethylammonium chloride / sulfur dioxide copolymer, polyallylamine hydrochloride, N-vinylacrylamidine hydrochloride, Acrylamide copolymers, and the like.

  Adhesives such as polyvinyl alcohol, vinyl acetate, oxidized starch, etherified starch, carboxymethylcellulose, cellulose derivatives such as hydroxyethylcellulose, casein, gelatin, soy protein, silyl-modified polyvinyl alcohol, etc .; maleic anhydride resin, styrene-butadiene copolymer Conjugated diene copolymer latex such as methyl methacrylate-butadiene copolymer; polymer or copolymer of acrylic acid ester and methacrylic acid ester, acrylic polymer such as polymer or copolymer of acrylic acid and methacrylic acid Polymer latex; vinyl polymer latex such as ethylene vinyl acetate copolymer; or functional group-modified polymer latex with functional group-containing monomers such as carboxyl groups of these various polymers; melamine resin, urea resin, etc. Thermosetting synthetic tree Aqueous adhesives such as polymethyl methacrylate, polyurethane resins, unsaturated polyester resins, vinyl chloride-vinyl acetate copolymers, polyvinyl butyral, alkyd resins, and other synthetic resin adhesives. Used. These adhesives are generally used in the range of about 5 to 80 parts by weight, preferably about 10 to 60 parts by weight with respect to 100 parts by weight of the pigment.

Various devices such as various blade coaters, roll coaters, air knife coaters, bar coaters, die coaters, rod blade coaters, curtain coaters, short dwell coaters, size presses, sprayers, etc. The device can be used on-machine or off-machine. Further, after coating the ink receiving layer, it may be finished using a calendar such as a machine calendar, a TG calendar, a super calendar, or a soft calendar. The coating amount of the ink receiving layer provided on the support is usually 4 to 30 g / m ² in terms of dry solid content.

  A gloss layer can be further provided on the ink receiving layer described above. This gloss layer can contain a resin as a main component, and can also be constituted by containing a pigment and a resin. The glossy layer is preferably porous or liquid-permeable so long as it does not interfere with the glossy layer so that ink can pass or be absorbed quickly. In order to do this, it is preferable to select a drying condition in which the resin does not completely form a film within a range where gloss is not lowered.

  Since the gloss layer is excellent in ink absorption and transparency, when a cationic compound is blended, the ink dye is efficiently fixed on the gloss layer, and the gloss density tends to be extremely excellent in combination with transparency. Examples of the gloss layer resin include water-soluble resins (eg, polyvinyl alcohols such as polyvinyl alcohol, cation-modified polyvinyl alcohol, and silyl-modified polyvinyl alcohol, cellulose derivatives such as casein, starch, carboxymethylcellulose, and methylcellulose), styrene-butadiene copolymer Water-dispersed resins such as polymers, conjugated diene polymer latexes such as methyl methacrylate-butadiene copolymer, vinyl copolymer latexes such as styrene-vinyl acetate copolymer, aqueous acrylic resins, aqueous polyurethane resins, aqueous polyester resins, etc. In addition, various publicly known resins are generally used alone or in combination in the coated paper field.

  In the case of forming a gloss layer mainly composed of a resin, a polymer or copolymer (hereinafter collectively referred to as a polymer) obtained by polymerizing a monomer having an ethylenically unsaturated bond (hereinafter referred to as an ethylenic monomer) is used. It is preferable to be configured as a main component. Furthermore, substituted derivatives of these polymers may be used. In addition, an ethylenic monomer is polymerized in the presence of colloidal silica, and a complex is formed by a Si-OR (R: polymer component) bond, or a functional group that reacts with colloidal silica such as SiOH group in the polymer. It is also possible to use it in the form of a complex formed by reacting with colloidal silica. When this composite is used, it tends to be excellent in gloss and ink absorbability.

  Furthermore, in the aspect which obtains a glossy layer by the casting method using a heating mirror surface drum, there are three methods of wet, rewet and gel methods. In the wet method, while the glossy layer coated on the base paper is in a wet state, the glossy layer is pressed against the heated mirror drum surface to perform a high gloss finish. In the gelation method, while the glossy layer coated on the base paper is in a wet state, the glossy layer is brought into contact with a gelling agent bath, and the gelled glossy layer is pressed against the heated drum surface to obtain a high gloss finish. Is to do. In the rewetting method, a glossy layer in a wet state is once dried and then brought into contact with a wetting liquid again, and then pressed against the surface of a heated drum to perform a high gloss finish.

The coating amount of the glossy layer, 0.2 to 30 g / m ² on a dry solids, preferably 0.5 to 20 g / m ^2.

  Further, the ink receiving layer is provided on at least one side of the support, but on the surface on which the ink receiving layer is not formed, an undercoat layer or a back surface coating layer for the purpose of preventing curling, imparting barrier properties, preventing charging, adjusting color tone, etc. May be formed. The inkjet recording sheet is a known process such as a so-called adhesive process in which an adhesive layer and a release sheet are laminated on the back side, a so-called magnetic process in which a magnetic recording layer is formed on the back side, a so-called card process to be laminated on a card substrate. Those with the mark are also effective.

  The printing of the lower printing layer and the main printing layer in the present invention includes various printing methods such as sheet-fed offset printing, offset rotary printing, gravure rotary printing, flexographic printing, screen printing, waterless printing, and letterpress printing. In the method of providing the main printing layer after printing the lower printing layer in, typographic printing in which curing is performed with UV is the most suitable printing method for carrying out the printing. Further, UV curing type flexographic printing is effective.

The printing ink used for normal printing includes various oil-based inks such as planographic ink, letterpress ink, letterpress rotary ink, rubber letterpress ink, tinplate ink, gravure ink, special gravure ink, newspaper ink, flexographic ink, etc. The ink used for the lower printing layer is a curable ink by UV, and is composed mainly of a polymer, oligomer, monomer and photopolymerization initiator of a photosensitive resin as a composition. The ink for the lower printing layer is preferably a color ink that does not interfere with the design of the printing layer, and is preferably transparent or white. In consideration of the efficiency of ink drying and continuous printing, it is more preferable to use the same UV curable ink as that of the lower printing layer. Further, the ink amount of the lower printing layer is preferably provided so as to be in the range of 0.3 to 4 g / m ² after drying.

  In addition, when printing the lower printing layer in this invention, according to the intensity | strength of an inkjet receptive layer, you may adjust the tack | tuck of an ink, a viscosity, etc. with the viscosity adjusting agent called a dewaxing agent, a compound, etc. In this case, the tack value, which is a measure of the viscosity of the ink, is 2 or more as measured by an incometer according to JIS K-5701 (SEV type 3 manufactured by Hoy Devices, measurement conditions: 400 rpm, 1 minute value at 30 ° C.) It is preferable to adjust to 8 or less. If it exceeds 8, paper smear will occur, and if it is less than 2, the amount of ink adhering is small and the desired surface strength cannot be obtained.

  Incidentally, when printing is performed without providing the underprint layer of the present invention, normal ink has a high ink tack, and paper smearing occurs in the ink receiving layer of the inkjet recording sheet. Even when printing is performed with a viscosity modifier that lowers tack, even if the occurrence of paper blemishes cannot be suppressed or even the occurrence of paper blemishes can be prevented, the print density will decrease, and this causes the amount of ink to adhere. As a result, the workability is lowered and the printing is blurred.

  In the present invention, the printing area of the lower printing layer is preferably larger than the printing area of the present printing layer to the extent that printing during inkjet printing is not hindered. This is because if the printing area is smaller than the printing area of the main printing layer, the main printing layer is printed in a place where there is no lower printing layer, so that paper smearing occurs.

  The effect of the printing of the lower printing layer performed in the present invention is further exhibited if the surface strength of the ink receiving layer of the ink jet recording sheet is 80% or less. Incidentally, the ink jet recording sheet having a surface strength exceeding 80% does not necessarily require the underprint layer of the present invention. Here, if the surface strength of the ink receiving layer is less than 30%, the generation of paper dust at the time of cutting increases, and the characteristics as an ink jet recording sheet in which print peeling occurs after printer printing is impaired. The surface strength of the ink receiving layer is more preferably 30% or more. Here, the evaluation of the surface strength is based on the evaluation method in the following examples.

  The printing method in the present invention is to enable printing while covering the weak surface strength of the ink receiving layer of the ink jet recording sheet. The reason for this is that the UV curable ink that constitutes the lower printing layer soaks into the inkjet receiving layer having a weak surface strength, and a printing layer having a reinforced surface strength is formed by curing with UV, Further, it is presumed that paper smear at the time of actual printing on the lower printing layer can be prevented.

  Examples of the present invention will be described below, but the present invention is not limited to these examples. In the examples, “parts” and “%” indicate parts by mass and mass% unless otherwise specified.

The evaluation methods and printing methods in the examples are shown below.
<Surface strength evaluation>
Using a Gakushin type testing machine described in JIS L-0849 (manufacturer: Suga test machine, model FR-2), a black paper of 20 × 50 mm is fixed to the friction element of the testing machine, and the load arm is 200 g. The weight of the black paper was measured by a Macbeth densitometer (model: Gretag Macbeth RD-19), and the ratio to the black paper density before processing was calculated as a percentage. The lower the value, the weaker the surface strength.
<Paper scale evaluation>
After printing the lower printing layer on the inkjet receptive layer, the solid-printed portion (60 mm × 20 mm) of this printing layer is 0.08 mm ² or more defined by the dust test method described in JIS P-8145. The number of white spots having an area was visually counted. Here, the white spot indicates a state where the ink jet recording surface is whitened due to paper blur, and the higher the numerical value, the more paper blur is present.
<Printing method>
Six printing units and two printing units of a UV letterpress rotary label printing machine (manufactured by Sanki: SKP-250A) having an ultraviolet irradiation device after each printing unit are used. After printing, the film was prepared by UV irradiation. After the main printing layer was printed on the lower printing layer by the second printing unit, continuous printing was performed by UV irradiation. The printing speed was 50 m / min. In addition, the ink is UV white ink (UV VNL Conk White: manufactured by TOKA) for underprinting, Dicure Hibright Red Ink (made by DIC) for main printing, and UV Contex (T & K TOKA as a scouring agent). Used).

<Production of support>
A pulp slurry consisting of 80 parts of LBKP (450 ml / CSF) and 20 parts of NBKP (480 ml / CSF), 10 parts of light calcium carbonate (trade name: TP-121, manufactured by Okutama Kogyo Co., Ltd.) as filler, 0.5 part of sulfate band, alkyl Add 0.05 parts of ketene dimer type sizing agent (trade name: size pine K903, manufactured by Arakawa Chemical Industries) and use polyvinyl alcohol (trade name: PVA117, manufactured by Kuraray Co., Ltd.) and starch (trade name: ace) in a size press. A, manufactured by Oji Cornstarch Co., Ltd.) 4: 1 mixed solution 5% and a size press solution containing 0.5% alkyl ketene dimer (trade name: SKP-287, manufactured by Arakawa Chemical Industries) as an external sizing agent A high-quality paper having a basis weight of 70 g / m ² and a Steecht sizing degree of 15 seconds produced by a net paper machine was prepared.

<Preparation of ink receiving layer coating liquid>
90 parts of amorphous silica (trade name: Fine Seal X-45, manufactured by Tokuyama Co., Ltd.) and 10 parts of amorphous silica (trade name: Silojet P-407, manufactured by Grace Devison Co., Ltd.) were mixed with silyl-modified polyvinyl alcohol (trade name). : Kuraray Poval R-1130, manufactured by Kuraray Co., Ltd.) and dispersed in 300 parts of a 10% aqueous solution while stirring, and then 25 parts of a cationic polymer (trade name: Unisense CP-105, manufactured by Senka Co.) and acrylic resin 10 parts of an emulsion (trade name: Yodosol CE60, NS & C) was added to prepare a coating solution having a concentration of 18%.

Example 1
Using the off-machine air knife coating machine, 12 g / m ² (one side) of the ink receiving layer coating solution was applied to the above-prepared fine paper and dried to prepare an ink jet recording sheet as an ink receiving layer. . At this time, the surface strength of the ink receiving layer was 75%. The inkjet recording sheet thus produced was printed by the above-described printing method with a roll having a width of 200 mm to obtain a printed inkjet recording sheet. The evaluation results are shown in Table 1. FIG. 1 is a cross-sectional view of the inkjet with printing according to the present invention, and the printing area of the lower printing layer is larger than the area of the printing layer.

Example 2
Printing was performed in the same manner as in Example 1 except that 200 parts of a 10% aqueous solution of silyl-modified polyvinyl alcohol (trade name: Kuraray Poval R-1130, manufactured by Kuraray Co., Ltd.) was used as the ink-receiving layer coating liquid. A sheet was obtained. At this time, the surface strength of the ink receiving layer was 60%. The evaluation results are shown in Table 1.

Example 3
In the ink-receptive layer coating liquid, 100 parts of a 10% aqueous solution of silyl-modified polyvinyl alcohol (trade name: Kuraray Poval R-1130, manufactured by Kuraray Co., Ltd.) is used. Printing was performed in the same manner as in Example 1 except that 20 parts were added and the tackiness of the ink was adjusted to obtain a printed inkjet recording sheet. At this time, the surface strength of the ink receiving layer was 50%. The evaluation results are shown in Table 1.

Example 4
In the ink-receiving layer coating solution, 50 parts of a 10% aqueous solution of silyl-modified polyvinyl alcohol (trade name: Kuraray Poval R-1130, manufactured by Kuraray Co., Ltd.) is used. Printing was performed in the same manner as in Example 1 except that 50 parts were added and the tackiness of the ink was adjusted to obtain a printed inkjet recording sheet. At this time, the surface strength of the ink jet receiving layer was 35%. The evaluation results are shown in Table 1.

<Preparation of glossy layer coating liquid>
Composite emulsion of colloidal silica and acrylic resin (trade name: Elsard 740, manufactured by Lion Corporation, weight ratio of colloidal silica and acrylic resin = 80: 20, average particle size of composite 50 nm), 3 parts of casein and thickener A 25% coating solution in which 2 parts were mixed was prepared.

Example 5
Using the inkjet recording sheet prepared in Example 1, the glossy layer coating solution was further coated with 6 g / m ² by wet casting, and heated to a drum temperature of 85 ° C. to give a glossy layer. A sheet was produced. Otherwise, printing was performed in the same manner as in Example 1 to obtain a printed inkjet recording sheet. At this time, the surface strength of the ink receiving layer was 75%. The evaluation results are shown in Table 1.

Comparative Example 1
In Example 1, printing was performed in the same manner as in Example 1 except that the lower printing layer was not provided and the main printing was performed only with the main printing ink, to obtain a printed inkjet recording sheet. The evaluation results are shown in Table 1.

Comparative Example 2
In Comparative Example 1, printing was performed in the same manner as in Example 1 using an ink in which 50 parts of UV tex was added to 100 parts of the main printing ink to lower the tack of the main printing ink. An ink jet recording sheet was obtained. The evaluation results are shown in Table 1.

Comparative Example 3
Printing was performed in the same manner as in Example 1 except that the lower printing layer was printed without UV irradiation, to obtain a printed inkjet recording sheet. The results are shown in Table 1.

  From Table 1, in contrast to Example 1 and Comparative Example 1, by providing a lower printing layer cured by UV, an obvious effect was observed on paper smearing during printing. Moreover, since the same effect was recognized also in the inkjet recording sheet of Example 4 with low surface strength, a favorable inkjet recording sheet with printing could be obtained by the printing method of the present invention.

It is sectional drawing of the printing part of the sheet | seat for inkjet recording with printing which is one Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Inkjet recording sheet with printing 2 Lower printing layer 3 Main printing layer 4 Inkjet receiving layer 5 Support body

Claims (4)

  An ink jet recording sheet having at least one ink receiving layer provided on a support, and having a lower printing layer cured by ultraviolet light on a part of the ink receiving layer, and further, a main printing layer on the lower printing layer A sheet for inkjet recording with printing, comprising:   The sheet for inkjet recording with printing according to claim 1, wherein the lower printing layer is a transparent or white printing layer.   The sheet for inkjet recording with printing according to claim 1 or 2, wherein an area of the lower printing layer is larger than an area of the main printing layer.   Before printing this printing layer on an inkjet recording sheet having at least one ink-receiving layer provided on a support, underprinting that is cured by ultraviolet rays in a region wider than this region, including the region of this printing layer A method for printing an inkjet recording sheet, in which a layer is printed and then the printed layer is printed.

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