JP2012213958A - Inkjet recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent curl and warpage occurring in a transport process while extracting an inkjet recording medium from a roll-like recording medium and performing inkjet printing thereon, in an inkjet recording medium.SOLUTION: This inkjet recording medium is provided with an ink reception layer on a surface of a base material. The inkjet recording medium includes, on a surface opposite to a surface formed with the ink reception layer, a resin layer having moisture evaporating capability higher than that of the ink reception layer.

Description

  The present invention occurs in a process of curling in a dry atmosphere until the ink head is drawn out from a state where it is not in contact with the outside air, for example, a roll wound in multiple layers and conveyed to the inkjet head. The present invention relates to an ink jet recording medium that prevents curling.

  In recent years, the ink jet recording system has been used for printing a wide variety of products in a very wide range of fields, and depending on the application, a substrate for an ink jet recording medium having a very thin thickness has been increasingly used.

For packaging various molded products such as PET bottles and plastic cases, heat-shrinkable films utilizing the property of shrinking by heating are also widely used.
The heat-shrinkable film forms a cylindrical body with a heat-shrinkable base material and covers a molded product such as a plastic bottle or a plastic case, or is attached to the molded product as an adhesive label, and heats the molded product. Thus, the heat-shrinkable base material is shrunk and adhered to the molded product.
A heat-shrinkable inkjet recording medium for performing image processing on these heat-shrinkable films has been proposed. In the field of heat-shrinkable films, particularly thin substrates are required.

As described above, in recent years, an opportunity for using a thin substrate having a thickness of 100 μm or less is increasing in the ink jet recording medium.
In particular, in the case of a heat-shrinkable ink jet recording medium, there is a strong demand for a thin material, and the thickness of the substrate is usually 60 μm or less in many cases.

When the substrate is thin, it is easily affected by the exchange of moisture in the air of the ink receiving layer provided on the substrate surface. Exposure to water fluctuates the moisture in the ink receiving layer, causing warping and curling of the recording medium.
In such a case, a solution method is conceivable in which an ink receiving layer or a resin layer having a similar formulation is provided on the opposite side of the receiving layer (Patent Document 1).

However, even if such a method is adopted, it is still insufficient for preventing curling.
For example, in the case of a roll, it is usually wound with the ink receiving layer on the outside, but the time required to be exposed to the outside air on the outer side and the inner side of the ink receiving layer in the process of drawing out from the roll for ink printing. A difference in length of approximately three times the diameter of the roll occurs. In the dry situation in a heated atmosphere in winter, moisture evaporation from the ink receiving layer and the like is unexpectedly large, and even between the above-mentioned time differences, those between the inner layer and the outer layer are An unexpected problem arises in that the difference in the amount of water contained causes warping or curling of the recording medium.
This can also occur in the case of a cut sheet that is not rolled. Even in the case of single-cut paper, a usage form in which a plurality of sheets are stacked and set in a printing machine is common, and the time of exposure to the outside air differs between the front and back, and the same problem arises.
In particular, in the case of a thin base material, it is easy to occur even in a light dry state of the outside air.

JP-A-10-138629

  The problem of the present invention occurs in the transport process from when the inkjet recording medium is brought out of contact with outside air (for example, the state of the medium other than the outermost periphery during storage in a roll state) until inkjet printing is performed. It is to improve the state of curling and warping.

The above problems are solved by the following invention.
(Invention 1) An ink jet recording medium in which an ink receiving layer is provided on the surface of a base material, and having a resin layer having a higher water evaporation ability than the ink receiving layer on a surface opposite to the surface having the ink receiving layer. An inkjet recording medium.
(Invention 2) The inkjet recording medium according to Invention 1, wherein the substrate is a heat shrinkable substrate.
(Invention 3) The inkjet recording medium according to Invention 1 or Invention 2, wherein the thickness of the substrate is 60 μm or less.
(Invention 4) The ink jet according to any one of Invention 1 to Invention 3, wherein a resin layer having a higher water transpiration capability than the ink receiving layer is provided by transferring a resin layer previously prepared on the surface of another substrate. recoding media.

It is a conceptual diagram when a roll-shaped inkjet recording medium is pulled out and moves to an ink head.

  Moisture transpiration capacity means a decrease in moisture from the layer when entering a dry atmosphere with low humidity from a high humidity atmosphere. The present invention is characterized in that the moisture evaporation capacity of the resin layer provided on the surface of the substrate opposite to the surface having the ink receiving layer is larger than that of the ink receiving layer. This means that the water loss is larger than that of the ink receiving layer.

FIG. 1 shows an example of an embodiment of an inkjet recording medium of the present invention. The ink jet recording medium 1 shown in FIG. 1 has a base 11 and an ink receiving layer 21 on one surface of the base 11 and a resin layer 31 on the other surface, and is wound around a core in a roll shape. is there. In FIG. 1, the layers constituting the ink jet recording medium 1 are not shown.
As shown in FIG. 1, the ink jet recording medium 1 is wound in a roll shape with the surface 2 provided with the ink receiving layer 21 facing outward (outside air side). When the inkjet recording medium 1 passes a point a before one round of winding, the ink receiving layer 21 outside the inkjet recording medium 1 is exposed to the outside air. On the other hand, the surface 3 opposite to the ink receiving layer 21 of the ink jet recording medium 1 starts to be exposed to the outside air when leaving the roll, and starts to be exposed to the outside air one lag behind the surface 2 provided with the ink receiving layer. The time for exposure to the outside air is longer for the ink receiving layer 21 by the time required for the inkjet recording medium 1 to move one round. In many recent ink jet printers, although it depends on the diameter of the roll-shaped recording medium, the fixed position of the roll-shaped recording medium and the distance to the head, in many cases, the outside air contact time on the outside of the roll is about twice that on the inside of the roll. There are many things.
The ink jet recording medium 1 may be provided with a resin layer 31 having a composition close to that of the ink receiving layer 21 on the side 3 opposite to the ink receiving layer 21 in order to prevent curling. However, when the time of exposure to dry air is long, moisture evaporation increases correspondingly, and the ink receiving layer 21 on the side 2 of the ink jet recording medium 1 provided with the ink receiving layer has less water, and the dry air When the difference in exposure time increases, curling occurs with the ink receiving layer 21 inside. If the moisture transpiration capacity of the resin layer 31 is increased, the moisture content of the resin layer 31 increases and reaches the print head 4 in the process in which the medium is separated from the point a and both surfaces are exposed to the outside air. The amount is almost the same, and the curl can be reduced.

  In order to increase the water evaporation capacity of the resin layer, it is possible to make the surface area of the resin layer larger than that of the ink receiving layer. In order to increase the surface area, particles having large diameters such as alumina are added to the resin layer 31, or the resin layer is laminated on a roughened substrate as described in Japanese Patent No. 3517047. A resin layer 31 having a surface area larger than that of the ink receiving layer 21 is obtained by providing a resin layer having a surface of the ink receiving layer 21 on the substrate and then transferring only the resin layer to the surface opposite to the surface having the ink receiving layer of the ink jet recording medium. Can be formed.

  The resin layer 31 is preferably a composition used for the ink receiving layer 21. Alternatively, the above-described means for increasing the moisture transpiration ability by bringing the composition closer works efficiently. Resins that can be used in the ink receiving layer 21 described below can be preferably used as the binder of the resin layer 31.

  The ink receiving layer 21 in the present invention includes, for example, polyamide, polyacrylamide, polyvinyl pyrrolidone, polyethylene imine, polyvinyl pyridium halide, melamine resin, polyurethane, carboxymethyl cellulose, hydroxyethyl cellulose, hydroxymethyl cellulose, polyvinyl acetal, polyvinyl alcohol, polyester, poly Hydrophilic synthetic polymers such as sodium acrylate, hydrophilic natural polymers such as gelatin, starch, cellulose derivative cellulose, casein, chitin and chitosan, superabsorbent resins such as polyethylene oxide and copolymers thereof, vinyl chloride-acetic acid It is formed from vinyl copolymer, vinyl chloride-vinylidene chloride copolymer, acrylic resin, epoxy resin, polycarbonate resin, phenol resin, etc. Those can be used.

  Among them, it is preferable to use a dispersion resin such as urethane or acrylic, which is known for creating an ink receiving layer having good ink absorbability, water resistance, and transparency, and the dispersion resin such as urethane or acrylic is crosslinked with carbodiimide. What was made can also be used more preferably. In particular, urethane resin is widely used as the resin.

As such an ink receiving layer 21, for example, one having the following configuration is known.
Ink-receiving layer as disclosed in JP-A-2003-166183, which includes a resin obtained by crosslinking a polyurethane resin having a silanol group with a crosslinking agent selected from polyisocyanate, polyethyleneimine, and carbodiimide resin. 75% by weight of polyurethane resin emulsion in Example 5 (Takelac XW-75-X35 (solid content 30% by weight) manufactured by Takeda Pharmaceutical Co., Ltd.) and 15% by weight of carbodiimide resin (Carbodilite V-02 manufactured by Nisshinbo Industries, Ltd.) % Ink receiving layer,
Ink-receiving layer described in JP-A No. 2004-345110 containing an acrylic polymer and a compound having a carbodiimide group,
An ink receiving layer containing a dispersion resin such as polyester urethane latex and acrylic silicone latex described in JP-A-2009-125958 and carbodiimide.
Further, an ink receiving layer containing two types of water-based urethane resin and water-based acrylic resin described in JP-A-2005-74880 and a crosslinking agent can also be used.
Furthermore, it seems that the dispersion resin and the urethane resin are cross-linked like a combined system of a dispersion resin such as a cationic acrylic silicon emulsion resin having a hydrolyzable silyl group as a crosslinking component and a cationic urethane resin. Those described in JP-A-2006-88341 are also preferable.

Examples of the urethane resin include polyesters and polyethers. Cationic polyether urethane resins are preferred.
Examples of the cationic urethane-based resin include polyester-based and polyether-based resins, but a cationic polyether-based urethane resin is preferable.
The acrylic resin is an acrylic polymer resin such as a polymer or copolymer of acrylic acid ester and methacrylic acid ester, or ethylene such as ethylene-vinyl acetate, ethylene-acryl-vinyl acetate, ethylene-vinyl chloride-vinyl acetate. -Vinyl acetate copolymer resin, acrylic-styrene copolymer resin, etc. can be illustrated. Cationic acrylic / styrene copolymer resins are preferred.
The weight percent of the cationic acrylic silicone emulsion resin and the cationic urethane resin in the solid content of the ink receiving layer is 5 to 25% for the cationic acrylic silicone emulsion resin and 75 to 95% for the cationic urethane resin. Are preferred.
Furthermore, it is preferable that the cationic acrylic silicone emulsion resin is 10 to 20% and the cationic urethane resin is 80 to 90%.

As the crosslinking agent, those selected from polyisocyanate, polyethyleneimine, and carbodiimide resin are used.
The carbodiimide resin is a water-soluble or water-dispersible carbodiimide compound obtained by sealing a terminal isocyanate group of a condensation reaction product obtained by decarbonization condensation of diisocyanates or diisocyanates and triisocyanates with a hydrophilic group. .
As diisocyanates and triisocyanates, any of alicyclic isocyanate, aliphatic isocyanate, and aromatic isocyanate may be used, and those having at least two, particularly two, isocyanate groups in the molecule are suitable. Examples of such isocyanates include 4,4′-dicyclohexylmethane diisocyanate (HMDI), tetramethylxylylene diisocyanate (TMXDI), isophorone diisocyanate (is an isocyanate compound having no isocyanate group bonded to a carbon atom of a methylene group in the molecule. IPDI), 2,4,6-triisopropylphenyl diisocyanate (TIDI), 4,4′-diphenylmethane diisocyanate (MDI), tolylene diisocyanate (TDI), hydrogenated tolylene diisocyanate (HTDI), etc. Hexamethylene diisocyanate (HDI) and hydrogenated xylylene diisocyanate for alicyclic, aliphatic and aromatic isocyanates having two or more isocyanate groups bonded to carbon atoms of the methylene group H6XDI), xylylene diisocyanate (XDI), 2,2,4-trimethylhexamethylene diisocyanate (TMHDI), 1,12-diisocyanate dodecane (DDI), norbornane diisocyanate (NBDI), and 2,4-bis- (8- And isocyanate octyl) -1,3-dioctylcyclobutane (OCDI).
The compound that seals the terminal isocyanate group is a water-soluble or water-dispersible organic compound having a group capable of reacting with an isocyanate group, and is a monofunctional water-dispersible organic compound such as polyethylene glycol or polypropylene glycol. Examples include alkyl esters or monoalkyl ethers, or monofunctional organic compounds having a cationic functional group (for example, a group containing nitrogen) or an anionic functional group (for example, a group containing a sulfonyl group). Glycol monomethyl ether and polypropylene glycol monomethyl ether are preferred.

  As the substrate 11 used in the present invention, a polyester film, a polyolefin film, a cellulose film, a polyamide film, an aramid film, or the like can be suitably used. Among these, polyethylene terephthalate is particularly desirable.

  In the present invention, a heat shrinkable substrate can also be used as the substrate 11. A heat-shrinkable substrate means a material that has the ability to shrink by heating, such as olefin resin such as polyethylene or polypropylene, vinyl chloride resin, vinylidene chloride resin, polystyrene resin, polyester resin, polyamide resin, nylon resin and other resins. And a film formed by stretching at least a uniaxial direction. What extended | stretched to the biaxial direction may be used.

  Although there is no restriction | limiting in particular as the thickness of the base material 11, About 10-300 micrometers is suitable, and when setting it as a heat-shrinkable base material, 10-60 micrometers is more preferable.

  When the substrate 11 is a heat-shrinkable substrate, the heat shrinkage rate is preferably about 5 to 80% when the heat-shrinkable substrate is contracted in hot air at 80 ° C. for 10 seconds. More preferably, it is about 30 to 60%.

Example 1
An ink receiving layer was provided by applying and drying an aqueous solution having the following composition to a dry film thickness of 20 μm on one side of a heat-shrinkable PET film (Toyobo Space Clean) having a thickness of 50 μm as a substrate.
<Ink-receiving layer forming composition>
Polyether urethane resin (Daiichi Kogyo Seiyaku Co., Ltd. Superflex 600, solid content 25%) 72 parts by mass Acrylic / styrene copolymer resin (Chuo Rika Kogyo Co., Ltd. Rikabond FK-820 solid content 39%) 24 parts by mass Oxazoline group Water-soluble polymer (solid content 40%) 0.5 part by mass As a water-soluble acrylic self-emulsifying epoxy curing agent, a grafted product of methacrylic acid / butyl acrylate / methyl methacrylate / styrene copolymer and polyethyleneimine Hydrogen chloride neutralized product (solid content 49%) 3.5 parts by mass

  Next, an aqueous solution obtained by adding 4 parts by mass of alumina particles (average particle size 6.0 μm) to the ink receiving layer forming composition is coated and dried on the surface opposite to the side having the ink receiving layer so as to have a dry film thickness of 20 μm. An ink jet recording medium was prepared by providing a high moisture transpiration resin layer.

Example 2
The surface of a PET substrate having a thickness of 100 μm was roughened so that the surface roughness was 7 μm in terms of Ra value (see JIS B 0601-2001), and the ink receiving layer forming composition used in Example 1 was further formed thereon. A transfer medium having a resin layer on the surface was prepared by applying and drying the following adhesive layer coating solution so that the dry thickness was 20 μm, and applying and drying the following adhesive layer coating solution to a dry thickness of 5 μm.
<Coating liquid for adhesive layer>
Acrylic resin (SK Dyne 1502A70: Soken Chemical Co., Ltd.) (solid content 40%) 30 parts by mass IPA 75 parts by mass

Separately, the ink-receiving layer is coated on one side of a 50 μm-thick heat-shrinkable PET film (Toyobo Space Clean) as a substrate and dried to a dry film thickness of 20 μm. A heat shrinkable film was prepared.
The surface of the adhesive layer of the transfer medium is bonded to the surface of the heat-shrinkable film that does not have an ink-receiving layer, and then the PET substrate that is the transfer substrate is peeled off, and one surface of the heat-shrinkable film is removed. An ink jet recording medium having an ink receiving layer and a resin layer having irregularities on the other surface was prepared.

Comparative Example Inkjet recording of a comparative example in which a 50 μm thick heat-shrinkable PET film (Toyobo Space Clean) 2 as a substrate was coated and dried with an aqueous solution of the ink-receiving layer forming composition to a dry film thickness of 20 μm. Created media.

Evaluation test The flat surface of each corner of the curled amount cut into A3 single sheets after placing it in an atmosphere of 18 ° C. and 65% close to the environment in the packaging of the recording medium to a temperature equivalent to outside air of 18 ° C. and humidity of 35% The average height from was taken. A positive value means the curl amount of the curl with the ink receiving layer inside.
The curl amount is measured only when the surface of the recording medium having the ink receiving layer (the upper surface of the recording medium) is exposed to the atmosphere corresponding to the outside air for 30 seconds, and is also measured after the both surfaces are exposed to the atmosphere corresponding to the outside air for 30 seconds. did.

The results are shown in Table 1.

In Example 1, the alumina particles cause irregularities on the surface of the base material lower surface layer, and the surface area is larger than that of the base material upper surface layer. In Example 1 and Example 2 having irregularities on the surface, the surface area is large and the moisture transpiration is larger than that of the upper surface layer.
The first 30 seconds when only the upper surface is exposed to the outside air corresponds to the last one round before leaving the roll when being wound from the roll, and the next 30 seconds is the double side to the print head after the recording medium is separated from the roll. It corresponds to the situation where is exposed to the outside air.
It can be seen that in Example 1 and Example 2 in which the moisture transpiration property of the lower surface layer is larger than that of the upper surface layer, the curl once generated is suppressed in a state where both surfaces of the latter half are exposed to the outside air.
In the comparative example, it can be seen that the curl generated in the first 30 seconds is not corrected in the next 30 seconds.

  1. 1. inkjet recording medium 2. a surface of the ink jet recording medium on which an ink receiving layer 21 (layer not shown) is provided; 3. The surface of the ink jet recording medium on which the resin layer 31 (the layer is not shown) is provided. An ink head, a. A point where the ink jet recording medium leaves the roll; b. The direction in which the recording medium is pulled out.

Claims (4)

  An ink jet recording medium having an ink receiving layer provided on a surface of a base material, wherein the ink receiving layer has a resin layer having a higher water vaporization capacity than the ink receiving layer on a surface opposite to the surface having the ink receiving layer. Medium.   The inkjet recording medium according to claim 1, wherein the substrate is a heat shrinkable substrate.   The inkjet recording medium according to claim 1 or 2, wherein the substrate has a thickness of 60 µm or less.   The ink jet according to any one of claims 1 to 3, wherein a resin layer having a higher water transpiration capacity than the ink receiving layer is prepared by transferring a resin layer prepared in advance on the surface of another substrate. recoding media.

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