JP5924933B2 - Protective sheet for inkjet recording image - Google Patents

Description

  According to the present invention, after forming a desired inkjet recording image on a recording medium, and providing the image on the recording surface, the inkjet can protect the recorded image in a good state without causing image degradation due to lamination. The present invention relates to a protective sheet (protective film) for recorded images.

  Conventionally, a transparent sheet is laminated on a recorded image formed on a recording medium in order to protect the image. The functions required for the transparent sheet include a function of blocking an oxidizing gas that causes image deterioration, and a function of preventing the image from fading and discoloration due to ultraviolet rays by providing the sheet with an ultraviolet absorbing ability. It is done. In addition to the purpose of laminating a transparent sheet for image protection, the purpose of the image is to prevent the ink forming the image from moving to an article containing various plasticizers such as an eraser in contact with the image. A wide range of applications, including the addition of plasticizer resistance and the provision of wear resistance and sebum resistance.

  Regarding a method for laminating such a protective sheet for a recorded image to a recorded image, a method of thermocompression bonding to a protected image surface using a heat roller, or an adhesive resin is used to adhere to a protected image surface at room temperature. Methods are known. Also, a transfer type image protection sheet in which an image protection layer is laminated on a base sheet is prepared, and the image protection layer of the transfer type image protection sheet is thermally transferred to a protected image, whereby the image protection layer is recorded on the recording image surface. A method of laminating is also known. Furthermore, there is a proposal for forming an ink receiving layer on the adhesive surface side of a protective sheet for a recorded image, and corresponding to an inkjet recording method using water-based ink (see Patent Document 1). Further, in the case of laminating a protective sheet on a recording portion printed by an ink jet recording method by laminating a protective layer having a surface layer and an adhesive layer on a heat-resistant substrate, the protective sheet has a configuration. It is disclosed that even if bending is performed, it is possible to prevent the protective layer from being cracked along the fine cracks of the recording portion (Patent Document 2).

  When the above-described protective sheet for recording images is used, only the portion that has been overheated during thermal transfer is laminated on the protected image, so that the recording medium can be prevented from curling after lamination. In addition, when an integrated ink ribbon in which an ink receiving layer and image protection are sequentially formed is used, it is possible to laminate an image protection layer on the image following the formation of the image inside the thermal transfer recording apparatus. Become. Further, if a protective sheet having an ink receiving layer on the adhesive surface of the protective sheet is used, it is possible to perform lamination with an ink jet recording apparatus using liquid ink.

  According to Patent Document 3, the surface of the protective paper is smoothed and the surface of the protective paper is better than that of the recording medium. However, by using a soft sheet with a low density of protective paper and low rigidity, the image recorded with the pigment ink is protected from rubbing and scratching, and the deterioration of the image is well prevented.

  Furthermore, in Patent Document 4, an image protective liquid containing a base material and a protective sheet for images provided with a transfer layer containing a thermoplastic resin and a lubricant component on the base material, or containing a resin emulsion and a lubricant component is used. Is applied to the ink jet recording image portion to provide an image protective layer formed of pigment ink, thereby forming an ink jet recording material having a protective layer that is not easily scratched on the surface of the ink jet recording material.

Japanese Patent Laid-Open No. 10-324054 JP 2005-161810 A JP 2002-52815 A JP 2004-1446 A

  Here, in a recording medium conventionally used for forming an image by a sublimation type thermal transfer method using a thermoplastic resin, since a water-based ink is difficult to be absorbed in the recording medium, an image protection sheet is bonded. Therefore, a method for imparting writing properties to water-based stamps and water-based inks has been taken. However, in an ink jet recording method in which image formation is performed by ejecting aqueous ink onto a recording medium from a recording nozzle using an electric field, heat, pressure, or the like as a drive source, the amount of liquid necessary for image formation is usually higher than that of an aqueous stamp. Therefore, the above-described image protection sheet cannot absorb water-based ink, and there is a problem that it is difficult to form an image and to secure adhesion of the protection sheet to a recording medium. In recent years, the use of the ink jet recording method has been remarkably expanded in offices and homes, and it is also desired to use a recording medium and a protective sheet used in the sublimation thermal transfer method.

  The present invention is intended to solve the above-described problems of the prior art, and the object thereof is to protect the protected image by pasting it on the protected image, and further, if necessary. Accordingly, it is possible to form an image with the water-based ink of the ink jet recording system on the protective sheet in that state, and the water-based ink forming the recording image to be protected is in an unabsorbed state on the surface of the recording medium. Another object of the present invention is to provide a protective sheet for an ink jet recording image having an adhesive layer capable of preventing the occurrence of image deterioration without causing floating due to blocking water-based ink at the time of bonding.

The above object is achieved by the present invention described below. That is, the present invention is an ink jet recording image protective sheet for protecting an ink jet recording image formed on a recording medium, wherein an ink receiving layer and an adhesive layer are laminated on a base film, The ink receiving layer is made of a resin composition mainly comprising a hydrophilic resin, the adhesive layer is made of a resin composition mainly containing a thermoplastic resin or an adhesive resin, and the ink receiving layer is partially Provided is a protective sheet for inkjet recording images, wherein an adhesive layer is provided so as to form the same surface in an exposed state.

  Preferred forms of the protective sheet for inkjet recording images of the present invention include the following. An adhesive layer having a discontinuous lattice shape or dot shape and an effective thickness of 0.2 to 5 μm is laminated on a part of the surface of the ink receiving layer, and the adhesive layer is partially exposed. A protective sheet for inkjet recording images, on which is formed. A protective sheet for inkjet recording images, wherein an area ratio of the adhesive layer to the ink receiving layer is 30% to 80%. The hydrophilic resin is at least one selected from the group consisting of a resin obtained by polymerizing a monomer containing an acetal compound of vinyl alcohol, a cellulose resin, a polyvinyl pyrrolidone resin, a polyvinyl alcohol resin, and a polyamide resin. A protective sheet for an inkjet recording image. The ink receptive layer has the same or similar degree of ink bleeding that occurs when it is absorbed in contact with the recording ink as the ink receptive layer constituting the recording medium on which the ink jet recording image is formed. A protective sheet for inkjet recording images. A protective sheet for an inkjet recording image, wherein the inkjet recording image formed on the recording medium is cast-coated paper using a porous synthetic resin film. A protective sheet for inkjet recording images, wherein an ink receiving layer made of a resin composition mainly comprising a hydrophilic resin is formed on the opposite side of the surface of the base film on which the ink receiving layer and the adhesive layer are laminated. .

  The ink bleeding rate in the above is “the diameter of dots formed when one ink droplet discharged from a recording nozzle lands on the surface of an ink receiving layer of a recording medium / per one shot discharged from a recording nozzle. Ink droplet diameter ".

The protective sheet for ink-jet recording images of the present invention has an integral surface on which one of the protective sheets has the functions of the “adhesive layer” and the “ink receiving layer” and has both functions. According to the present invention, even if there is unabsorbed recording ink on the surface of the ink receiving layer of the recording medium on which the ink jet recording image is formed, the adhesive surface of the protective sheet is formed. When the ink receiving layer provided in an exposed state quickly absorbs the ink and bonds the protective sheet, it is possible to form a surface protective layer exhibiting desired characteristics without losing its adhesion. Become.
The ink jet recording method is remarkable for increasing the recording speed by utilizing the characteristics of non-contact printing and has applications such as a display label and an ID card. According to the present invention, the recording ink is applied immediately after image formation. Since the protective sheet can be attached in spite of the state remaining on the surface of the recording medium, that is, the so-called unfixed state, it is possible to reduce the time required for generating the recorded matter. For this reason, although it is an inkjet recording image, it can also be used for outdoor applications that require high fastness (abrasion resistance, light resistance, oxidation resistance gas), automobiles, aircraft, etc. that use heat engines. A thing is obtained.

It is a schematic diagram which shows the state which has affixed the protection sheet of this invention on the recording medium in which the image imaged by inkjet recording was formed. It is the schematic diagram which looked at the state which bonded the protection sheet of this invention on the recording medium from the side.

  Below, the protective sheet and protective sheet of this invention are demonstrated in detail based on the preferable embodiment. First, the protective sheet of the present invention will be described. FIG. 1 is a perspective view showing an outline of the protective sheet of the present invention and a usage form of the protective sheet. FIG. 2 is a schematic diagram for explaining a state in which the protective sheet of the present invention is attached to the image forming surface of the recording medium.

  As shown in FIG. 1, the protective sheet of the present invention is for the purpose of protecting the image forming surface of a recorded material after forming an image on a recording medium by an ink jet recording method. As shown in FIG. 2, the protective sheet of the present invention is formed by laminating the ink receiving layer 2 and the adhesive layer 3 on the base film 10, and the ink receiving layer is partially exposed. In this state, the adhesive layer 3 is provided so as to form substantially the same surface as the ink receiving layer 2. In FIG. 1, an adhesive layer having a dot shape (halftone dot shape) is laminated on a part of the surface of the ink receiving layer so that the ink receiving layer is partially exposed. Thus, since the adhesive layer 3 is laminated so that the ink receiving layer 2 is partially exposed, the recording ink forming the recording image is the ink receiving layer provided in the substrate 1 of the recording medium. 4, even if it is present in an unabsorbed state, the unabsorbed recording ink can be quickly absorbed by the ink receiving layer 2 of the protective sheet and can be bonded in a good state. It is possible to effectively prevent the occurrence of image deterioration when a protective sheet is pasted in a state where the toner is not fixed.

The protective sheet of the present invention is based on the basis weight of the base film from the viewpoint of maintaining the strength of the sheet and preventing the influence of the weight of the sheet itself when the protective sheet is bonded to the recording medium. Is preferably about 10 to 100 g / m ² .

  Hereinafter, the material for forming the protective sheet of the present invention and the recording medium to be protected will be described. The protective sheet of the present invention comprises an ink receiving layer 4 for protecting an image forming surface after an image is formed on a recording medium having an ink receiving layer 4 formed on a substrate 1 of an ink jet recording medium. The ink receiving layer 2 and the adhesive layer 3 are laminated on the base film 10.

  As a configuration of the recording medium on which the protective sheet of the present invention is bonded, any recording medium that is used for conventional inkjet recording can be used. A superior effect is also exhibited when cast-coated paper having a lower ink absorbability than plain paper or the like using a porous film) is used. Hereinafter, the structure of the cast coat paper which can bond the protective sheet of this invention and can protect a recorded image in a favorable state is demonstrated. Examples of porous films include polyolefin resin polymers such as polyethylene, polypropylene, polybutene, polystyrene, ethylene / propylene copolymers, ethylene / butylene copolymers, and fluororesin polymers such as polyvinylidene fluoride and polytetrafluoroethylene. Further, polyurethane, phenolic polyether, cellulose acetate, acrylonitrile polymer, amide resin, polyester resin, or the like produced by stretching a single or mixed film in a uniaxial or biaxial direction can be used.

  In addition, in a film made of the above-described materials, inorganic fillers such as calcium carbonate, kaolin, talc, titanium oxide, silica, diatomaceous earth, and zinc oxide, polyamides such as 6-nylon and 6,6 nylon, and polytetrafluorocarbons are used. Fluorine resin such as ethylene fluoride, tetrafluoroethylene-hexafluoropropylene copolymer, polyimide, silicone resin, phenol resin, benzoguanamine resin, or styrene, acrylic acid, methacrylic acid, methyl acrylate, methyl methacrylate, etc. A combination of single or plural synthetic resin particles such as a copolymer with a crosslinking agent such as divinylbenzene is also useful. Among these, those using silica as a filler have the effect of increasing the ink jet printing density and are more preferably used. Further, it is preferable to form an ink receiving layer on the corona discharge machining.

  In general, the pore size of the porous film is adjusted by the degree of stretching and the particle size of the filler, but the pore size is not particularly limited. For example, an average pore diameter of 0.2 μm to 3 μm can be exemplified. These fine holes have a portion penetrating from the front surface to the back surface of the porous film, and need to have air permeability. That is, moisture is vaporized and transmitted from the front surface to the back surface during the casting process described later, and is evaporated and dried. The porous film used as a support in the present invention is characterized by good air permeability as described above, and the air permeability according to JIS P-8117 is required to be 200 seconds or less. When the air permeability exceeds 200 seconds, the evaporation of moisture due to drying is not sufficiently performed through the pores during the casting process, so that not only is it difficult to peel off from the cast drum, but also the ink permeation of the ink jet becomes slow. The problem of delaying drying of the product occurs. The air permeability is preferably 120 seconds or less, and there is no particular lower limit. However, commercially available products are currently up to about 30 seconds. In general, the air permeability can be adjusted to be low by a production method such as increasing the amount of inorganic filler added.

  Next, the heat shrinkage rate which is an important property of the base material 1 of the cast coated paper used in the present invention will be described. The heat shrinkage ratio is determined by letting the substrate sample (about 50 cm × 50 cm) stand in air at 80 ° C. for 10 minutes, and then changing the length of the film in a direction parallel to the flow direction of the film manufacturing machine (vertical direction). ) And a perpendicular direction (horizontal direction), and the degree of contraction is expressed in%. In general, the heat shrinkage rate is larger in the vertical direction than in the horizontal direction. In the present invention, the heat shrinkage rate is the larger of the shrinkage rates in the vertical direction and the horizontal direction. For example, when the heat shrinkage rate is 10% or less, the heat shrinkage rate in the vertical direction and the heat shrinkage rate in the horizontal direction are measured, and the heat shrinkage rate in the larger direction (usually the vertical direction) is selected to be 10% or less. . The heat shrinkage rate is required to be 10% or less, preferably 0 to 5%. When the thermal shrinkage rate exceeds 10%, curling after casting becomes remarkable, causing a conveyance trouble when printing with an ink jet printer. The heat shrinkage rate can be adjusted by the type of resin and the degree of stretching.

  Next, the configuration of the undercoat layer on the base material 1 of the cast coated paper will be described. First, as the pigment, kaolin, clay, calcined kaolin, amorphous silica, zinc oxide, aluminum oxide, aluminum hydroxide, calcium carbonate, satin white, aluminum silicate, magnesium silicate, magnesium carbonate, plastic pigment, etc. should be used as appropriate. However, amorphous silica, aluminum oxide, calcined kaolin and the like having good ink jet printing suitability are particularly preferably used.

  Examples of the adhesive used in combination with the pigment include proteins such as casein, soybean protein, and synthetic protein, various starches such as starch and oxidized starch, cellulose derivatives such as polyvinyl alcohol, carboxymethylcellulose and methylcellulose, and styrene-butadiene copolymer. Conventionally used for coated paper such as polymer, conjugated diene polymer latex of methyl methacrylate-butadiene copolymer, acrylic polymer latex, vinyl polymer latex such as ethylene-vinyl acetate copolymer, etc. Known adhesives may be used alone or in combination of two or more. In addition, the compounding quantity of an adhesive agent is adjusted in the range of 5 to 50 weight% with respect to a pigment, More preferably, it is 10 to 30 weight%.

  In the present invention, those obtained by adding a cationic resin to the undercoat layer can also be used, thereby improving water resistance and printing color density. Examples of the cationic resin used in this case include polyalkylene polyamines such as polyethylene polyamine and polypropylene polyamine, or derivatives thereof, acrylic resins having tertiary amino groups and quaternary ammonium groups, and diacrylamines. Are used together as appropriate. The addition amount of the cationic resin is not particularly limited, but is adjusted in the range of about 1 to 30% by weight, preferably 5 to 20% by weight with respect to the pigment. In addition, various auxiliary agents such as a dispersant, a thickener, an antifoaming agent, a colorant, an antistatic agent, and an antiseptic used in the production of general coated paper can be appropriately added.

The composition for the undercoat layer composed of the above materials is generally adjusted to a solid content concentration of about 1 to 65% by weight, and is preferably ^{2 to} 30 g / m ² by dry weight on the support made of the porous film described above, preferably blade coater so is about 5 to 10 g / m ^2, an air knife coater, roll coater, brush coater, champflex coater, bar coater coating, the various coating devices such as a gravure coater, dried, the primed sheet obtain. Furthermore, if necessary, after the undercoat layer is dried, a smoothing process such as super calendering or brushing can be performed.

  The ink receiving layer as the surface layer provided on the base material 1 of the cast coated paper is usually formed on one side of the base material 1 but may be formed on both sides as desired. When an ink receiving layer is provided on both surfaces of the substrate 1, an anti-curl effect can be obtained. When an ink receiving layer is formed only on one side of the substrate 1, an anti-curl layer made of another material may be provided on the opposite side.

  The ink receiving layer can be formed by, for example, a resin composition containing a polymer having a glass transition point of 40 ° C. or higher obtained by polymerizing a monomer having an ethylenically unsaturated bond. Examples of the polymer obtained by polymerizing a monomer having an ethylenically unsaturated bond (hereinafter referred to as ethylenic monomer) include methyl acrylate, ethyl acrylate butyl acrylate, 2 ethyl hexyl acrylate, lauryl acrylate, 2-hydroxyethyl acrylate, and glycidyl acrylate. Methacrylic acid having 1 to 18 alkyl groups such as acrylic acid ester having 1 to 18 alkyl groups such as methyl methacrylate, ethyl methacrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, glycidyl methacrylate, etc. Ester, styrene, α-methylstyrene, vinyl toluene, acrylonitrile, vinyl chloride, vinylidene chloride, vinyl acetate, vinyl propionate, acrylamide, N Methylol acrylamide, ethylene, ethylene monomer and polymerized to obtain a polymer of butadiene and the like.

  In addition, the polymer in this case may be a copolymer using two or more kinds of ethylenic monomers in combination as necessary, or may be a substituted derivative of these polymers or copolymers. Examples of the substituted derivative include those obtained by carboxylation, and those obtained by making them alkali-reactive. It is also possible to polymerize the monomer having an ethylenically unsaturated bond in the presence of colloidal silica and use it in the form of a complex by Si—O—R (R: polymer component) bond. . The polymer obtained by polymerizing the above ethylenic monomer preferably has a glass transition point of 40 ° C. or higher.

  That is, in the production of the conventional cast coated paper, in order to obtain an excellent surface gloss, the resin component in the coating composition was sufficiently formed during casting to obtain a high gloss. However, according to such a conventional method, the porosity of the surface of the cast coat layer is reduced, and as a result, the ink absorbability at the time of ink jet recording is lowered, and a cast coated paper having desirable ink jet recording aptitude can be obtained. Can not. In order not to reduce the absorbability of the ink, it is preferable to use a polymer having a high glass transition point and perform the cast finish in a state where the polymer does not completely form a film. By doing in this way, since the porosity of the coating layer surface is maintained effectively, it is possible to obtain a cast coated surface having good adhesive paste absorbability and an excellent glossy surface.

  On the other hand, if the glass transition point of the polymer is less than 40 ° C., the heat on the surface of the cast drum makes it easier for the resin to form a film than necessary, and as a result, the porosity of the surface of the cast coat layer decreases. Although the surface gloss value is high, it is not preferable because the adhesive paste absorbability is lowered.

  In addition, in the coating composition for casting, in order to adjust whiteness, viscosity, fluidity, etc., pigments used in general printing coated papers and ink jet recording papers (including the pigments in the undercoat layer described above) are used. ), Dispersing agents, thickeners, antifoaming agents, colorants, antistatic agents, preservatives and the like can be added as appropriate.

The coating solution for cast coating thus obtained is variously known on the sheet provided with the above-mentioned undercoat layer, such as a blade coater, an air knife coater, a roll coater, a brush coater, a champlex coater, a bar coater, and a gravure coater. As described above, while the coating layer is in a wet state, it is pressed against a heated mirror drum, dried and cast to obtain an ink jet recording medium. The coating amount of the cast coating liquid in this case is 0.2 to 30 g / m ² , preferably 1 to 10 g / m ² in terms of dry solid content.

  Next, the material for forming the protective sheet of the present invention in which the ink receiving layer and the adhesive layer are laminated on the base film will be described. As the substrate film, a film substrate such as a polyester film (for example, PET film), a polyolefin film (for example, PE film, PP film) or synthetic paper can be used. Two or more layers of these may be laminated, or paper or a metal vapor deposition layer may be laminated. For example, assuming that the recorded material using the protective sheet of the present invention is used in a PET bottle, the material for forming an adhesive layer, which will be described later, is excellent in the permeability of the cleaning liquid and is dissolved or swollen in the cleaning liquid. If the thing which has the performance to do is used, the base film which does not have water permeability can be used. In particular, the use of a base film that does not have heat-shrinkability is excellent in heat resistance, and the label is formed by heat during storage of the bottle sterilization process, contents filling process, distribution process, and cleaning process. This is preferable because there is no deformation due to unintended shrinkage. In addition, the film without heat shrinkability here is a film having an expansion / contraction ratio at 80 ° C. of 10% or less. A PP film preferably having no heat shrinkability is excellent because it can be separated from PET in specific gravity in the PET bottle recovery process.

  The ink receiving layer constituting the protective sheet of the present invention may be formed from a resin composition mainly composed of a hydrophilic resin. The hydrophilic resin includes at least one selected from the group consisting of a resin obtained by polymerizing a monomer containing an acetal compound of vinyl alcohol, a cellulose resin, a polyvinyl pyrrolidone resin, a polyvinyl alcohol resin, and a polyamide resin. These may be used, and they may be formed by a conventionally known method. For the formation of the ink receiving layer, the components for forming the ink receiving layer of the recording medium described above may be appropriately selected and used. However, since it is a protective sheet, its transparency needs to be ensured. .

  The adhesive layer that is laminated on the above-described ink receiving layer and that constitutes the protective sheet of the present invention will be described. The adhesive layer is made of a resin composition mainly composed of a thermoplastic resin or an adhesive resin. Since it is a protective sheet, the resin composition used for forming the adhesive layer is also preferably substantially transparent, and it is preferable to use a material that does not discolor over time. The adhesive layer is provided so as to form substantially the same surface as the ink receiving layer with the ink receiving layer partially exposed. More specifically, an adhesive layer having a discontinuous lattice shape or dot shape with an effective thickness of 0.2 to 5 μm is laminated on a part of the surface of the ink receiving layer, and the ink receiving layer is partially exposed. It is preferable that the adhesive layer is formed in such a state. Hereinafter, a method for forming a lattice-shaped adhesive layer will be described. A resin composition that forms an adhesive layer may be used on the ink-receiving layer, and the adhesive layer may be provided so as to have a grid-like printed pattern of 30 to 320 lines, for example.

  That is, in the present invention, it is important that the ink receiving layer is exposed, and the adhesive layer is not provided over the entire area. However, if the proportion of the adhesive layer is too small, the adhesive strength is reduced, and when the protective sheet is used while being bonded, unintentional peeling or sheet lifting occurs. The area ratio of the adhesive layer to the ink receiving layer is preferably 30% to 80%. If the area ratio is lower than 30%, the adhesive force is poor, and conversely if the area ratio is higher than 80%, the absorption of unabsorbed ink in the ink receiving layer may be insufficient, which is not preferable. The area ratio here means the area ratio of the portion where the adhesive layer is provided on the surface of the ink receiving layer.

  “Discontinuous” as described above means that a continuous print pattern is not included. Among discontinuities, when the pattern is selected from a houndstooth pattern or a dot pattern (which may be independent in any shape such as a circle or a rectangle), stable adhesiveness and ink absorbency are obtained. Since it is exhibited in a balanced state, it is preferable.

  The “printed pattern of 30 to 320 lines” described above refers to the number of lines per inch or the number of halftone dots per inch. In general, the smaller the number of lines, the larger the printed pattern, and the larger the number, the finer the printed pattern. If the number of printed patterns is less than 30, the printed pattern is large, so that the blocks of the adhesive portion and the ink absorbing portion are enlarged. If it becomes too large, for example, when a label using the protective sheet of the present invention is used on a PET bottle, unintended peeling occurs, or the protective sheet originally floats off the recording medium. Or the appearance may be impaired. On the other hand, if the number of printed patterns is more than 320, the printed adhesive layer has a fine pattern, so that the ink receiving layer is likely to be insufficiently exposed, and the ink receiving layer does not absorb the unabsorbed ink sufficiently. There is a risk of becoming.

  As a printing method used for forming the adhesive layer, a method generally used for label printing can be applied. Specific examples include letterpress printing, letterpress offset printing, planographic printing, engraving intaglio printing, gravure printing, screen printing, flexographic printing, and the like. Of these, letterpress printing, gravure printing and screen printing are particularly suitable. The resin composition for the adhesive layer used for printing may be any transparent composition that does not become colored after printing. Details will be described later. In addition, when the protective sheet of the present invention is bonded, a material having a configuration in which drying and curing treatment are performed and bonded by heating with a drying oven or the like or ultraviolet irradiation with an ultraviolet irradiation device may be used.

  The adhesive layer constituting the protective sheet of the present invention is preferably formed of a transparent resin composition, and the protective sheet has a haze value of less than 7%, or the protective sheet is attached to a PET film. It is preferable that the later haze value be less than 7%. The haze value mentioned here refers to the haze value, and is a value measured with a haze meter (model HGM-2K, manufactured by Suga Test Instruments Co., Ltd.). The larger the numerical value, the more clouded, that is, the smaller the numerical value. It means that it is transparent. If the haze value is 7% or more, the transparency is impaired, and therefore, when the protective sheet of the present invention is bonded, the quality of the recorded image is considered to be adversely affected.

  The coating amount of the adhesive layer is preferably adjusted in the range of 0.2 to 5 μm, preferably 0.5 to 3 μm in terms of effective thickness. If the thickness is less than 0.2 μm, the adhesive strength may not be sufficiently exhibited. On the other hand, if the thickness exceeds 5 μm, the amount of the adhesive may be too large, and transparency may be lowered. Absent.

  As an adhesive forming the adhesive layer constituting the protective sheet of the present invention, it is possible to disperse or dissolve in alkaline hot water and / or hot water when considering using a label using the protective sheet of the present invention for a PET bottle. Preferably there is. It is desirable to be resistant to cold water.

Examples of the adhesive having the above-described properties include resin compositions composed of materials and blends as listed below. Specifically, (a-1) carboxyl group-containing vinyl monomer: 20 to 100% by weight, (a-2) general formula CH ₂ = CR ₂ COOR ₃ (where R ₂ is H or CH ₃ , R ₃ represents a straight-chain or branched alkyl group having 1 to 12 carbon atoms): (meth) acrylic acid ester monomer: 0 to 50% by weight, (a-3) an unsaturated monomer having a functional group Mer: 0 to 5% by weight, (a-4) (meth) acrylic acid ester monomer other than (a-4) and (a-2) wherein R ₂ or R ₃ is glycol is 0 to 20% by weight (B-1) Surfactant with respect to 100 parts by weight of the polymer solution obtained by copolymerizing the monomer comprising the above (a-1) to (a-4) in an organic medium : 0.1 to 50 parts by weight, (b-2) Hydroxides containing monovalent cations that can be neutralized (saponified) in (a-1): 1 to 10 Parts (b-1) to (b-) of parts by weight, (b-3) crosslinking agent or curing agent: 0.1 to 30 parts by weight, (b-4) tackifier and plasticizer: 0 to 50 parts by weight. The resin composition obtained by mixing the additive which consists of 4) can be illustrated.

  Examples of the carboxyl group-containing polymerizable vinyl monomer (a-1) include acrylic acid, methacrylic acid, maleic acid, maleic anhydride, fumaric acid, fumaric anhydride, itaconic acid, and crotonic acid. Of these, acrylic acid and methacrylic acid are preferred. In particular, a homopolymer of acrylic acid or a copolymer of acrylic acid and methacrylic acid exhibits excellent performance with respect to detergency of warm water or alkaline water.

The monomer (a-2) is a (meth) acrylic acid ester represented by the general formula CH ₂ ═CR ₂ COOR _3, where R ₂ is hydrogen or a methyl group, and R ₃ is carbon. A linear or branched alkyl group of 1 to 12 and examples of such a group R ₃ include a methyl group, an ethyl group, an i-propyl group, an n-butyl group, an i-butyl group, and an n-hexyl group. 2-ethylhexyl group, n-octyl group, i-octyl group, n-nonyl group, i-nonyl group, n-decyl group, n-dodecyl group and the like. Specific examples of such (meth) acrylic acid esters include methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, i-butyl (meth) acrylate, and n-hexyl (meth) acrylate. 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, i-octyl (meth) acrylate, n-nonyl (meth) acrylate, i-nonyl (meth) acrylate, n-decyl (meth) acrylate, etc. It can be illustrated.

  On the other hand, examples of the monomer containing the functional group (a-3) include acrylics having 1 to 3 carbon atoms of alkyl groups such as methyl acrylate, ethyl acrylate, n-propyl acrylate, i-propyl acrylate, and the like. Methacrylic acid esters such as acid esters, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, i-butyl methacrylate, dimethyl malate, di-n-butyl malate, di-2-ethylhexyl malate, di-n-octylma Maleate or fumarate esters such as rate, dimethyl fumarate, di-n-butyl fumarate, di-2-ethylhexyl fumarate, di-n-octyl fumarate, vinyl acetate, vinyl propionate, vinyl versatate Saturated fatty acid vinyl esters such as Monomer selected from styrene, vinyl toluene, acrylonitrile, or acrylamide, methacrylamide, N, N-dimethylmethacrylamide, N-methylacrylamide, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 4-hydroxybutyl acrylate 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, aminoethyl acrylate, N, N-dimethylaminoethyl acrylate, N, N-diethylaminoethyl acrylate, aminoethyl methacrylate, N, N-dimethylaminoethyl methacrylate, N, N -Diethylaminoethyl methacrylate, glycidyl acrylate, glycidyl methacrylate, vinyl mercaptan, allyl mercaptan, (poly Ethylene glycol diacrylate, neopentyl glycol diacrylate, trimethylolpropane triacrylate, 1,6-hexanediol diacrylate, allyl acrylate, triallyl cyanurate, triallyl isocyanurate, diallyl phthalate, divinylbenzene, (poly) ethylene glycol Amide group or substituted amide group such as dimethacrylate, trimethylolpropane trimethacrylate, 1,6-hexanediol dimethacrylate, allyl methacrylate, amino group or substituted amino group, hydroxyl group, epoxy group, mercapto group, radical polymerizable unsaturated group The monomer (a-1) or (a-2) which is an unsaturated monomer containing at least one functional group such as Except These functional monomers can also be used as required. In addition, it does not restrict | limit especially as a monomer (a-3), A various unsaturated monomer can be used suitably in the range which does not impair the effect of this invention.

Further, (meth) acrylic acid ester monomers other than (a-2) wherein R ₂ or R ₃ in the above general formula is glycol include, for example, polyethylene glycol monomethacrylate, polypropylene glycol monomethacrylate, ethylene glycol diester (Meth) acrylic acid ester monomers containing glycols such as methacrylate, 1,3 butylene glycol dimethacrylate, neopentyl glycol dimethacrylate (NPGDMA), diethylene glycol dimethacrylate (DEGDMA), triethylene glycol dimethacrylate (TEGDMA) In addition, monomers other than those described above can be used as necessary.

  As the surfactant (b-1), a nonionic surfactant and an anionic surfactant can be used alone or in combination. From the viewpoint of conflicting properties that the obtained protective sheet is water-resistant and easily dissolved in a high-temperature cleaning solution, and reduced adhesive properties (adhesive strength, tack, holding power), nonionic surfactants are used. It is preferable to use more.

  Examples of nonionic surfactants include polyoxyethylene alkyl ethers such as polyoxyethylene lauryl ether and polyoxyethylene stearyl ether; for example, polyoxyethylene octyl phenyl ether and polyoxyethylene nonyl phenyl ether Ethylene alkyl phenyl ethers; for example, sorbitan higher fatty acid esters such as sorbitan monolaurate, sorbitan monostearate, sorbitan trioleate; for example, polyoxyethylene sorbitan higher fatty acid esters such as polyoxyethylene sorbitan monolaurate; Glycerin higher fatty acid esters such as oleic acid monoglyceride and stearic acid monoglyceride; for example, polyoxyethylene polyoxypropylene Block copolymers; etc. may be exemplified.

  Examples of the anionic surfactant include higher fatty acid salts such as sodium oleate; alkyl aryl sulfonates such as sodium dodecylbenzene sulfonate; alkyl sulfate esters such as sodium lauryl sulfate; Polyoxyethylene alkyl ether sulfates such as ethylene lauryl ether sulfate; for example, polyoxyethylene alkyl aryl ether sulfates such as polyoxyethylene nonylphenyl ether sulfate; monooctylsulfosuccinate, dioctylsulfosuccinate, poly Examples thereof include alkyl sulfosuccinic acid ester salts such as sodium oxyethylene lauryl sulfosuccinate and derivatives thereof;

  Examples of the hydroxide containing a monovalent cation that can be neutralized (saponified) to (a-1) of (b-2) include monovalent cations (alkali metal ions such as sodium and potassium, and ammonium). Ion)) (for example, sodium hydroxide, potassium hydroxide, ammonia, etc.).

  Hydrophobic carboxyl groups contained in adhesives by neutralizing carboxyl groups contained in adhesives with hydroxides containing monovalent cations (alkali metal ions such as sodium and potassium and ammonium ions) The contained polymer is saponified and also exhibits hydrophilicity. Further, by leaving a part of the carboxyl group in the adhesive, the remaining carboxyl group reacts with alkaline water (such as an aqueous sodium hydroxide solution) at the time of cleaning, and becomes easy to be adapted to the cleaning liquid.

  Examples of the (b-3) crosslinking agent or curing agent include isocyanate crosslinking agents, chelating crosslinking agents, oxazoline crosslinking agents, polyglycidyl compounds having epoxy groups, glycidyl ethers of polyhydric alcohols, hydrazide crosslinking agents, Examples thereof include ionic crosslinking agents including polycarbodiimide crosslinking agents, metal chelate compounds, and the like. These cross-linking agents are intended to improve the adhesion of the adhesive layer to the recording medium in addition to adjusting the molecular weight of the adhesive, that is, to increase the cohesive force of the adhesive and the anchoring force of the adhesive and the recording medium. Used for purposes.

  The cross-linking agents listed above are not particularly limited as long as they have two or more groups in one molecule that react with the functional groups contained in the adhesive as described above. It is not preferable that the curing agent is added to the product, and after a while, it reacts with the adhesive to gel and thicken or generate aggregates. That is, the cross-linking agent is chemically stable before forming the adhesive layer (before coating), and the cross-linking reaction is irreversibly after the dispersion medium volatilizes or the adhesive composition is dried at the time of applying the adhesive. It is desirable to progress. Such a combination of a crosslinking agent and a functional group may be the above-mentioned known one.

  The (b-4) tackifier and plasticizer are plasticizers or tackifiers having a Tg of −70 ° C. to 10 ° C. For example, naphthenic process oil, oil such as paraffinic oil, plasticizer such as dioctyl phthalic acid, stabilized rosin glycerin ester, β-pinene resin, terpene resin polymerized with α-pinene resin, C5 petroleum resin, C9 Also includes petroleum resins.

  As a polymerization initiator used for the polymerization of the acrylic resin, benzoyl peroxide, lauroyl peroxide, diisopropyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, t-butyl peroxybivalate, t-butyl peroxy Oxybenzoate, t-butylperoxy-2-ethylhexanoate, 2,2′-azobisisobutyronitrile, 2,2′-azobis-2-methylbutyronitrile, 2,2′-azobis-2 Oil-soluble polymerization initiators such as 2,4-dimethylvaleronitrile, 2,2′-azobis-4-methoxy-2,4-dimethylvaleronitrile, 2,2′-azobismethylisobutyrate, or sodium persulfate , Persulfates such as potassium persulfate and ammonium persulfate, organic peroxides as described above Chain transfer of water-soluble polymerization initiators such as hydrogen peroxide, reducing agents such as n-dodecyl mercaptan, t-dodecyl mercaptan, n-butyl mercaptan, 2-mercaptoethanol, 2-ethylhexyl thioglycolate, trichlorobromomethane An agent etc. can be mentioned.

  The acrylic resin can be obtained by, for example, a monomer mixture as described in detail above by an arbitrary method such as a bulk polymerization method or a solution polymerization method. In order to prevent the adhesive layer from becoming clouded when the obtained protective sheet is immersed in water, the acrylic monomer mixture is more preferably solvent-polymerized. Specifically, the monomer mixture such as acrylic acid is one or more kinds selected from organic solvents represented by methyl alcohol, ethyl alcohol, isopropyl alcohol, t-butanol, acetone, toluene, ethyl acetate and the like. A base polymer can be obtained by performing a polymerization reaction in a solvent.

  The molecular weight is controlled by a known method such as the use of a catalyst amount, a polymerization regulator, the rate of temperature increase during polymerization, and the adjustment of the reaction temperature, and is obtained from the balance of various properties such as tackiness and holding power of the protective sheet. The molecular weight of the adhesive composition is preferably 200,000 to 1,500,000 in terms of polystyrene.

The protective sheet of the present invention is preferably laminated with a release sheet in order to protect the adhesive layer until the adhesive sheet is used. As the release sheet, a commonly used one can be used. As the base material of the release sheet, for example, laminated paper of thermoplastic resin such as polyethylene, glassine paper, clay coat paper, or high-quality paper, for example, casein, dextrin, starch and derivatives thereof, carboxymethylcellulose, Natural such as methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, polyvinyl alcohol, styrene-butadiene copolymer, methyl methacrylate-butadiene copolymer, ethylene-vinyl chloride copolymer, ethylene-vinyl acetate copolymer, acrylate copolymer Or a base paper, a PET film, a polyethylene film, a polypropylene film, a synthetic paper, a non-woven fabric provided with a sealing layer mainly composed of a synthetic resin and / or a pigment with a dry weight of about 0.1 to 10 g / m ² Etc. Beam base material and the like. When importance is attached to transparency, it is desirable to use a highly smooth film substrate such as a PET film. Examples of the pigment include kaolin, calcium carbonate, clay, talc, calcined kaolin, deramikaolin, titanium dioxide, aluminum hydroxide, silica, white carbon and other inorganic pigments, polystyrene resin fine particles, urea-formalin resin fine particles, fine particles Organic synthetic pigments such as hollow particles can be used. As the release agent, a general release agent can be used. For example, a water-dispersed, solvent-type or solvent-free type silicone resin, fluorine resin, or the like can be used, and the release substrate has a dry weight of 0.05 to 3 g / m ^2. After the coating, the release layer is formed by heat curing, ultraviolet curing, ionizing radiation curing, etc., and a release sheet can be obtained.

  Although the manufacturing method of the protection sheet of this invention is not specifically limited, The following methods are mentioned. For example, the adhesive layer coating liquid composed of the resin composition as described above on the release agent coating layer of the release sheet is applied in a lattice shape or dot shape as described above, and an adhesive layer is provided. Next, a method of adhering this to the surface of the base film on which the ink receiving layer is formed (so-called transfer method), and the coating liquid for the adhesive layer on the surface of the base film on which the ink receiving layer is formed are described above. It is finished by a method (a so-called direct method) in which it is applied in a lattice shape or a dot shape, dried and provided with an adhesive layer, and then bonded to a release sheet release agent coating layer.

  Next, as an apparatus for applying the coating liquid for the adhesive layer of the present invention to the surface of the base film on which the ink receiving layer is formed or to an object to be coated such as a release sheet, for example, a roll coater, a reverse roll coater, General coating devices such as knife coaters, air knife coaters, bar coaters, slot die coaters, lip coaters, gravure coaters, reverse gravure coaters, spray sprayers, etc. can be mentioned, and they are also produced by printing machines such as screen printing and gravure printing. be able to.

The coating amount of the adhesive layer is adjusted in the range of about 3 to 30 g / m ² by dry weight. If it is less than 3 g / m ² , the adhesion performance of the resulting protective sheet to the coating will be insufficient, while if it exceeds 30 g / m ² , it will be saturated in quality, which is not preferable from an economic point of view.

  The recorded image on the recording medium protected by the protective sheet of the present invention having the above-described configuration was formed using any ink composition including a pigment as a colorant or a dye as a colorant. It may be a thing. The effect of the present invention becomes more prominent when the image is a recorded image formed with an ink containing a pigment as a colorant, particularly an image formed on cast coated paper having poor permeability.

  In the case of a pigment ink containing a pigment as a colorant, the pigment is not particularly limited, and either an inorganic pigment or an organic pigment can be used. As the inorganic pigment, in addition to titanium oxide and iron oxide, carbon black produced by a known method such as a contact method, a furnace method, or a thermal method can be used. Organic pigments include azo pigments (including azo lakes, insoluble azo pigments, condensed azo pigments, chelate azo pigments), polycyclic pigments (for example, phthalocyanine pigments, perylene pigments, perinone pigments, anthraquinone pigments, quinacridone pigments, dioxazines). Pigments, thioindigo pigments, isoindolinone pigments, quinofullerone pigments, etc.), dye chelates (for example, basic dye chelate, acid dye chelate, etc.), nitro pigments, nitroso pigments, aniline black, and the like.

  In the present invention, these pigments can be added to the ink as a pigment dispersion obtained by dispersing the pigment in an aqueous medium with a dispersant or a surfactant. That is, as the ink used in the present invention, a conventionally known ink obtained by dispersing the above-described pigment in an aqueous medium with a dispersant or a surfactant can be used. As the dispersant, a dispersant commonly used for preparing a pigment dispersion, for example, a polymer dispersant can be used. The surfactant and the aqueous medium can be used without particular limitation as long as they are usually used in this type of ink composition. Further, the composition ratio of each component may be in the same range as that of a normal ink composition.

  The protective sheet of the present invention is used on the image forming surface of a recording medium to which the protective sheet is applied, but the ink for forming the image to be protected may contain a dye as a colorant. Although this dye is not specifically limited, For example, the water-soluble acidic dye, the direct dye, the basic dye, and the reactive dye which are described in the color index (COLOR INDEX) can be used preferably. In the present invention, the ink composition may be a black ink or a color ink. The ink composition can also contain a glycol ether. By adding these, the penetrability of the ink composition into the recording medium can be increased, and printing with less bleeding can be expected on various recording media.

  Further, the combination of the recording medium and the ink composition for forming the image to be protected, to which the protective sheet of the present invention is applied, is not particularly limited, and other than the cast coated paper mentioned above. It is also suitably used for a recording medium. For example, it is useful and preferably used for protecting a recording image formed by a combination of a recording medium having an ink-receiving layer for pigment ink and an ink containing a pigment as a colorant. Particularly preferred combinations include the following recording media and ink combinations.

Recording medium; plain paper as a support (especially “Marshmallow” manufactured by Oji Paper); and an ink receiving layer provided on the support, and silica (particularly, manufactured by Tokuyama) in the ink receiving layer. “X37B”), polyvinyl alcohol (particularly “PVA217” manufactured by Kuraray Co., Ltd.), and a cationic polymer (particularly Sumirez resin “1001” manufactured by Sumitomo Chemical Co., Ltd.).
Ink composition; an ink composition described in WO99 / 05230, specifically, an ink composition comprising at least a colorant, water, a water-soluble dispersant, and a penetrant, wherein the colorant C. I. Pigment Blue 15: 3 is 2 to 4% by weight, C.I. I. Pigment Red 122 3 to 5% by weight, C.I. I. Pigment Yellow 74 3 to 5% by weight, Carbon Black 2 to 5% by weight, C.I. I. Pigment orange 43 or C.I. I. Pigment orange 36, or C.I. I. Pigment Green 7 or C.I. I. Pigment Green 36, 0.1 to 5% by weight of an acetylene glycol compound as a penetrant, and the water-soluble dispersant is a styrene- (meth) acrylic acid-based water-soluble resin, the styrene- ( An ink composition comprising a (meth) acrylic acid-based water-soluble resin in a proportion of 0.1 to 1 part by weight with respect to the pigment in terms of solid content.

  Then, as shown in FIG. 1, the protective sheet A of the present invention overlaps the surface of the protective sheet A on which the adhesive layer is formed so as to cover the image recording surface on which the image is recorded on the recording medium 1. Can be used. As shown in FIG. 1, the protective sheet A is overlaid and bonded to the ink receiving layer 4 of the recording medium on which the image is formed. As a result, when the recorded image is stored, it is possible to prevent the image from being deteriorated by rubbing or being damaged.

  As a method for forming a recorded image, there are known recording methods such as an ink jet recording method, an electrophotographic recording method, a thermal recording method, and a thermal transfer recording method. However, the protective sheet of the present invention is not yet determined by an ink jet recording method. It is particularly suitable for protecting the recorded image surface on which the deposited ink exists. Recording is also possible from single color to full color. Different recording methods can be used on the same surface, and different recording methods can be used on the front and back surfaces. In the case of a heat-applied recording method, the amount of heat may be adjusted so that the substrate does not shrink due to heat during recording. Alternatively, after recording on another sheet, the recorded image may be transferred to the base material, or a recording image recorded on another display sheet may be attached to the base material and laminated. The ink jet recording method is a preferable recording method because it does not require heat that causes the base material to thermally shrink, and can be recorded directly on a recording medium. However, it is a method that forms an image by ejecting liquid droplets. Therefore, there is a problem that the image is deteriorated particularly when there is unabsorbed ink that is not rapidly absorbed by the recording medium and a protective sheet is provided on the recording image surface. The present invention solves this problem by the protective sheet having the configuration described above.

Hereinafter, the present invention will be described more specifically with reference to production examples, examples, and comparative examples, but the present invention is not limited thereto. Further, “parts” and “%” in the examples indicate parts by mass and mass%, respectively, unless otherwise specified.
First, cast coated paper was produced as follows as a recording medium for forming the ink jet recording images used in the examples and comparative examples.

<Manufacturing>
[Production Example 1-Production of cast coated paper]
100 parts of amorphous silica (Fine Seal X-37: manufactured by Tokuyama) as a pigment, 10 parts of polyvinyl alcohol (PVA117: manufactured by Kuraray) as an adhesive, and 15 parts of polyethylene polyamine resin (Neofix E-117: as a cationic resin) (Manufactured by Nikka Chemical), 0.5 part of sodium polyphosphate was added as a dispersant to prepare an undercoat coating solution having a solid content of 18%. This undercoat coating solution is applied to a polypropylene-based porous film (NF sheet NG: manufactured by Tokuyama, 120 μm thick, air permeability 50 sec / 100 cc, calcium carbonate used as a filler, heat shrinkage 4.0%) Further, a sheet having an undercoat layer was obtained by coating with an air knife coater so that the dry weight was 8 g / m ² .

On the other hand, as a coating solution for cast coating, the solid content concentration of 30% of styrene-2methylhexyl acrylate copolymer having a glass transition point of 70 ° C., 50 parts of colloidal silica, and 2 parts of zinc stearate as a release agent is 30%. A coating solution for cast coating was prepared. After applying this coating liquid onto the above-mentioned undercoat sheet using a roll coater, it is immediately pressed against a mirror drum having a surface temperature of 70 ° C., dried and then released to obtain a cast coated paper which is an ink jet recording medium. It was. The coating amount at this time was 7 g / m ² in terms of solid content.

[Production Example 2-Production of cast coated paper]
In production example 1, except that the base material is a polypropylene porous film (NF sheet NS: Tokuyama thickness 140 μm product, air permeability 100 sec / 100 cc, silica used as filler, heat shrinkage 2.5%) Produced a cast coated paper for ink jet recording in the same manner as in Production Example 1. However, the coating amount of the coating solution used for forming the undercoat layer at this time was 7 g / m ² in terms of solid content, and the coating amount of the coating solution for cast coat coating was 6 g / m ² .

[Production Example 3]
In Production Example 1, the base material was a polypropylene-based porous film (NF sheet NG: manufactured by Tokuyama, thickness 190 μm, air permeability 50 sec / 100 cc, calcium carbonate used as a filler, heat shrinkage 2.0%) Except that, a cast coated paper for inkjet recording was obtained in the same manner as in Production Example 1. The coating amount of the coating solution used for forming the undercoat layer at this time was 5 g / m ² in terms of solid weight, and the coating amount of the coating solution for cast coat coating was 6 g / m ² .

[Production Example 4]
As a coating solution for cast coating, a coating solution having a solid content concentration of 35% comprising 100 parts of a styrene-methyl acrylate copolymer having a glass transition point of 50 ° C. and 5 parts of ammonium stearate as a release agent was prepared. After applying this coating solution on the undercoat sheet obtained in Production Example 1 using a roll coater, it was immediately pressed against a mirror drum having a surface temperature of 70 ° C., dried, and released to obtain an ink jet recording sheet. It was. However, the coating amount of the coating solution for cast coating at this time was 3 g / m ² in terms of solid content.

[Production Example 5]
100 parts of a composite of styrene-methyl acrylate copolymer and colloidal silica having a glass transition point of 70 ° C. (mass ratio of copolymer to colloidal silica 60:40) as a coating liquid for cast coating, oleic acid as a release agent A coating solution comprising 3 parts of ammonium and having a solid content concentration of 40% was prepared. After applying this coating liquid on the undercoat sheet obtained in Production Example 1 using a roll coater, it was immediately pressed against a heated mirror drum having a surface temperature of 70 ° C., dried and released, and an ink jet recording sheet. Got. However, the coating amount at this time was 6 g / m ² in terms of solid content.
<Preparation of protective sheet>
[Example 1]
(Manufacture of coating solution for adhesive layer for protective sheet)
300 parts of ethyl acetate and 200 parts of toluene are added to a reactor equipped with a thermometer, a stirrer, a nitrogen introduction tube and a reflux condenser, and the temperature is raised while stirring. When the internal temperature reaches about 70 ° C., nitrogen purge is performed. Replacement was performed. Next, a solution in which 192 parts of acrylic acid, 106 parts of butyl acrylate, 6 parts of β-hydroxyethyl acrylate or β-hydroxyethyl methacrylate, 16 parts of diethylene glycol dimethacrylate (DEGDMA) and 1.2 parts of benzoyl peroxide were dissolved for 3 hours. Dripped over. The polymerization reaction was maintained at 80 ° C. and was completed in 15 hours after the dropping of the monomer to obtain a resin composition for an adhesive layer having a solid content concentration of 40.0%. For 100 parts of the resulting resin composition, 30 parts of polyoxyethylene lauryl ether as a surfactant, 27.7 parts of potassium hydroxide as a neutralizing agent, 10 parts of aluminum trisacetylacetonate as a crosslinking agent, As a fire, 10 parts of hydrogenated rosin resin (trade name; KR-610, manufactured by Arakawa Chemical Co., Ltd.) having a softening point of 85 ° C. was blended to obtain a coating solution for an adhesive layer having a neutralization rate of 60%.

(Formation of ink receiving layer)
As the base film, a PET (polyethylene terephthalate) film having a transparent ink receiving layer mainly composed of polyvinyl alcohol on the surface was used. Specifically, a transparent PET film having a thickness of 100 μm is used as a base material, and a transparent ink receiving layer having a thickness of about 20 μm is applied on one surface thereof. Specifically, as a resin composition for an ink receiving layer on a substrate made of a transparent PET film, polyvinyl alcohol and polyvinyl acetal, starch, casein, cellulose derivatives, acrylic, polyurethane, polyester, vinyl acetate, ethylene-acetic acid A vinyl or styrene-butadiene copolymer containing either of them was used, and a combination of at least one coagulant selected from boric acid or borax was applied and dried to form an ink receiving layer.

(Formation of adhesive layer)
The ink-receiving layer obtained above is peeled off as a transparent adhesive paste on a letterpress rotary printing machine (manufactured by Copac International) on the ink-receiving layer of a transparent PET film provided on one side. Using OP Varnish K-1.8 (trade name: manufactured by T & K TOKA), an adhesive layer having a structure in which the ink receiving layer was partially exposed was formed by the following method. That is, the number of lines / 60 lines, printed patterns / dots (circular with a diameter of 0.32 μm), and effective application of adhesive paste using a resin printing plate so that the area ratio of the formed adhesive layer is 50%. Printing was performed so that the work thickness was 1 μm. After printing, this was dried and cured with an ultraviolet irradiation device to obtain a protective sheet provided with an adhesive layer.

[Example 2]
In the formation of the adhesive layer, a protective sheet on which an adhesive layer having a structure in which the ink receiving layer is partially exposed was formed in the same manner as in Example 1 except that a printing plate having 150 lines was used. It was.

[Example 3]
In the formation of the pressure-sensitive adhesive layer, except that a printing plate having an area ratio of 35% was used, a protective sheet with an adhesive layer having a configuration in which the ink receiving layer was partially exposed was obtained in the same manner as in Example 1. .

[Example 4]
In the formation of the pressure-sensitive adhesive layer, except that a printing plate having an area ratio of 70% was used, a protective sheet having an adhesive layer having a configuration in which the ink receiving layer was partially exposed was obtained in the same manner as in Example 1. .

[Comparative Example 1]
A protective sheet was obtained in the same manner as in Example 1 except that the adhesive layer was not formed.

[Comparative Example 2]
In the formation of the adhesive layer, a protective sheet was obtained in the same manner as in Example 1 except that the adhesive layer was solid-printed.

[Example 5]
In the formation of the adhesive layer, a protective sheet was obtained in the same manner as in Example 1 except that the printed pattern was in a staggered pattern (one side 0.3 μm).

[Reference Example 1]
In the formation of the adhesive layer, a protective sheet was obtained in the same manner as in Example 1 except that the area ratio was 10%.

[Reference Example 2]
In the formation of the adhesive layer, a protective sheet was prepared in the same manner as in Example 1 except that the adhesive paste was printed so that the effective coating thickness was 6 μm, dried and cured with an ultraviolet irradiation device, and provided with an adhesive layer. Obtained.

<Evaluation>
Each of the protective sheets obtained above was used to form a recorded image on the previously prepared cast-coated paper by the ink jet recording method, and then the protective sheet was quickly bonded to protect the recording surface.

[Example of use]
On each cast-coated paper produced in Production Examples 1 to 5, the same images having many solid coating portions as shown in FIG. 1 were formed using an ink jet recording apparatus using an aqueous pigment ink. And immediately after forming an image, each protective sheet of the Example, the comparative example, and the reference example which were prepared previously was bonded together. Then, the recorded image was visually observed and the contour portion was observed with a magnifying glass, and whether or not the image was deteriorated was relatively evaluated in three stages of ○, Δ, and X. In addition, relative evaluation was performed in three stages of ○, Δ, and × to determine whether floating occurred in the bonded state. Further, after immersing the recorded material in warm water at 40 ° C. for 1 hour, the recorded image was visually observed and the contour portion was observed with a magnifying glass to determine whether the image was blurred. Relative evaluation was performed in three stages. Table 1 shows the evaluation results obtained.

  In contrast to the thermal transfer recording method and thermal sublimation recording method that are the most representative printing methods in the past, the inkjet recording method is remarkable for speeding up the recording speed by utilizing the characteristics of non-contact printing. There are uses such as ID cards. According to the present invention, it is possible to attach a protective sheet regardless of the state in which the recording ink remains on the surface of the recording medium immediately after image formation, that is, the so-called unfixed state. It is possible to shorten the time required for the generation of methane, so it can be used for applications such as outdoors and heat engines that require high fastness (abrasion resistance, light resistance, oxidation resistance gas), and automobiles, aircraft, etc. It is.

1 A substrate of a recording medium for ink jet recording.
2 This is an ink receiving layer of the protective sheet of the present invention.
3 is an adhesive layer of the protective sheet of the present invention.
4 An ink receiving layer of a recording medium for inkjet recording.
5 A recording medium for inkjet recording.
6 This is a protective sheet of the present invention.
10 A base film of the protective sheet of the present invention.

Claims (6)

An inkjet recording image protective sheet for protecting a recording image formed on a recording medium, wherein an ink receiving layer and an adhesive layer are laminated on a base film, and the ink receiving layer is hydrophilic. The resin layer is mainly composed of a resin composition, and the adhesive layer is composed of a resin composition mainly composed of a thermoplastic resin or an adhesive resin, and the ink receiving layer is partially exposed. A protective sheet for inkjet recorded images.   An adhesive layer having a discontinuous lattice shape or dot shape and an effective thickness of 0.2 to 5 μm is laminated on a part of the surface of the ink receiving layer, and the adhesive layer is partially exposed. The protective sheet for inkjet recording images according to claim 1, wherein:   The protective sheet for inkjet recording images according to claim 1 or 2, wherein an area ratio of the adhesive layer to the ink receiving layer is 30% to 80%.   The hydrophilic resin is at least one selected from the group consisting of a resin obtained by polymerizing a monomer containing an acetal compound of vinyl alcohol, a cellulose resin, a polyvinyl pyrrolidone resin, a polyvinyl alcohol resin, and a polyamide resin. The protective sheet for inkjet recording images according to any one of claims 1 to 3. The protective sheet for inkjet recording images according to any one of claims 1 to 4 , wherein the recording medium is cast-coated paper using a porous synthetic resin film. On the opposite side of the surface where the ink-receiving layer of the base film and the adhesive layer is laminated, one of the claims 1 to 5 for ink receiving layer comprising a resin composition mainly comprising a hydrophilic resin are formed Item 2. A protective sheet for inkjet recording images according to item 1.

Images