JP2007313838A - Oily inkjet recording sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an oily inkjet recording sheet with no offset of ink in material printed by oily inkjet. <P>SOLUTION: In the oily inkjet recording sheet, on the front side of a base material of which at least an oily inkjet image accepting layer is provided, while on its opposite side, a back layer is provided, the back layer is a cross-liked layer made of a silicone acrylic resin. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

The present invention relates to an oil-based inkjet recording sheet. Furthermore, the present invention relates to an oil-based ink jet recording sheet having no ink transfer.

An oil-based ink jet recording method has been widely used in recent years and provides a wide variety of printed matter. In color oil-based ink jets, printing is performed on large-sized recording sheets such as AO size using a large oil-based ink jet printer, and the use of posters, sign displays, and the like has become widespread. The image-receiving layer of the oil-based ink jet has a mechanism for fixing the ink by absorbing oil-based ink (also called solvent ink) while the binder of the image-receiving layer swells. Therefore, the ink absorption speed is much slower than that of the water-based ink jet, and the printer has to take a process of leaving the product printed with the oil-based ink jet usually for one day and then shipping it to the customer.

  There is a problem that the ink floating on the surface of the image receiving layer is turned over when the printed matter is placed without considering the fixing time of the ink. If the printed matter can be stored in layers before the ink is completely fixed, the storage space is reduced. Further, it is not necessary to perform the printing work while paying attention to the ink set-off, and the workability is improved.

Even though patent literature and the like were investigated for this problem, no one has yet found a solution because the technical field is narrow.

The inventor of the present invention provides an oil-based ink jet recording sheet having no ink set-off in the case of oil-based ink jet printing to solve the above problems.

The present invention is an oil-based inkjet recording sheet in which at least an oil-based inkjet image-receiving layer is provided on a substrate and a back layer is provided on the opposite surface, and the back layer is an oil-based inkjet recording sheet having a crosslinked layer of a silicone acrylic resin.

In the printing by the oil-based ink jet using the oil-based ink jet recording sheet of the present invention, the ink does not show off. As a result, the printed matter after printing can be stored in an overlapping manner, and the storage space can be reduced. In the printing operation, it is not necessary to pay attention to the ink setback, and the workability is improved.

As the substrate used in the present invention, a resin film or a polyolefin resin-coated paper is preferably used from the viewpoints of good image quality, gloss, smoothness and the like. Examples of the resin film include a polyester film, a polyimide film, a polycarbonate film, a polyamide film, and a polyolefin film. Among these resin films, a polyester film can be preferably used in terms of strength and cost.

  The polyolefin resin-coated paper is produced by a melt extrusion coating method in which a polyolefin resin heated and melted on a base paper is cast or an emulsion coating method in which a polyolefin resin emulsion is applied.

In order to obtain a high-quality, high-gloss printed matter, the substrate preferably has a surface with a center line average roughness of 0.4 μm or less according to JIS-B0601. The substrate has a thickness of about 10 to 300 μm.

  The back layer is obtained by crosslinking a silicone acrylic resin. Examples of the silicone acrylic resin include a block polymer or a graft polymer prepared by reacting an acrylic acid polymer with an organopolysiloxane. As this organopolysiloxane, a linear polymer having an OH functional group is preferable, and examples thereof include compounds represented by the following chemical formula.

HO-Si (R) _2- O- [Si (R) _2- O] n-Si (R) _2- OH
(In the formula, R is a methyl group, a mixture of a hydrogen element and a methyl group, or a part of those methyl groups is substituted with an ethyl group, a vinyl group or a phenyl group, n is an integer of 10 to 5,000). In the above chemical formula, an organopolysiloxane in which 50 to 100 mol% of R is a methyl group and 0 to 50 mol% is a hydrogen element is preferred, and up to 80 mol% of the methyl group is an ethyl group, vinyl group or phenyl group. It may be replaced with.

  The acrylic acid polymer is a polymer or copolymer having a molecular weight of 500 to 80,000, preferably 1,000 to 15,000 obtained by polymerization reaction of monomers such as α, β-unsaturated acid or ester thereof. It is a coalescence. Examples of the α, β-unsaturated acid or ester thereof include acrylic acid, methacrylic acid, and methyl ester, ethyl ester, butyl ester, stearyl ester, 2-ethylhexyl ester, 2-hydroxyethyl ester, and 3-hydroxypropyl. Examples include esters.

Examples of the comonomer that can be copolymerized with the α, β-unsaturated acid or ester thereof include maleic acid, itaconic acid, fumaric acid, styrene, α-methylstyrene, vinyl acetate, and vinyl propionate. it can. In addition, when said acrylic acid or an acrylate-type polymer is a copolymer, the ratio of acrylic acid, methacrylic acid or its ester in the entire copolymer is usually 10 to 75 mol%. , Preferably 25 to 60 mol%.

  The back layer contains a curing agent in order to crosslink the silicone acrylic resin. The curing agent can react and crosslink with the crosslinkable functional group derived from the acrylic monomer contained in the silicone acrylic resin to form a strong layer, and can maintain the layer's ink transfer resistance. it can.

Since the curing agent reacts with the silicone acrylic resin, it has a crosslinkable functional group such as a hydroxyl group, an epoxy group, a carboxyl group, an amino group, an active methylene group, and an alkoxysilyl group.

It does not specifically limit as a hardening | curing agent, For example, melamine resin (Cymel-211), block isocyanate (MEK oxime block HMDI nurate), polyisocyanate crosslinking agent (IPDI nurate; Takenate D-140N, HMDI nurate; Coronate HX, MDI; Coronate 2041).

As the curing agent, for example, when the silicone acrylic resin has a hydroxyl group, a melamine resin or a polyisocyanate crosslinking agent can be used as the curing agent. When the silicone acrylic resin has an epoxy group, a curing agent having a carboxyl group or an amino group can be used. Conversely, when the silicone acrylic resin has a carboxyl group, the curing agent has an epoxy group. Things can be used. When the silicone acrylic resin has an alkoxysilyl group, a curing agent having a hydroxyl group or a melamine resin can be used. When the silicone acrylic resin has an active methylene group, the curing agent may be a compound having an α, β-unsaturated carbonyl group, for example, a Michael addition reaction product of a poly (meth) acrylate of an aliphatic polyhydric alcohol. it can. Curing agents can be used alone or in combination of two or more.

As a compounding quantity of a hardening | curing agent, 5-100 weight part etc. can be mentioned by solid content with respect to 100 weight part of solid content of a silicone acrylic resin. If it is less than 5 parts by weight, crosslinking may be insufficient. If it exceeds 100 parts by weight, the ink back-off eliminability of the resulting back layer may be lowered due to the reduction in the amount of silicone acrylic resin.

In addition to the silicone acrylic resin and the curing agent, the back layer may contain other binders for the purpose of increasing the adhesion to the substrate. Examples of other binders include silicone urethane resins, cellulose resins, polyester resins, acrylic resins, epoxy resins, and acrylic polyols. The blending of the other binder is less than 40 parts by weight when the total of the silicone acrylic resin and the curing agent is 100 parts by weight.

The back layer may contain particles in order to prevent blocking with the image receiving layer before printing. The particles are preferably spherical particles. Further, the spherical particles are preferably spherical. The effect of this invention is stably acquired as it is a spherical shape. The spherical particles include organic particles and inorganic particles, but either particle can be used.

  The organic particles are made of polyethylene, polypropylene, polymethylpentene, polystyrene, polymethyl acrylate, polyethyl acrylate, polymethyl methacrylate, polyethyl methacrylate, polyvinyl acetate, polyvinyl chloride, ethylene vinyl acetate copolymer Resins, epoxy resins, urea-formalin resins, benzoguanamine resins, melamine-formalin resins and the like can be mentioned. The organic particles include cross-linked particles and non-cross-linked particles, but any particles that are cross-linked or non-cross-linked can be used as long as they do not dissolve in the solvent of the back surface coating solution. Examples of the inorganic particles include silica particles.

The spherical particles desirably have the following three requirements.
(1) The average particle diameter D of spherical particles is in the range of 1 to 15 μm.
(2) The monodisperse particles have a variation in the particle diameter of the spherical particles within a range of D ± 0.4 D μm.
(3) The relationship between the thickness T of the back layer and the average particle diameter D of the spherical particles is DT = 0.9-14 μm.

The spherical particles need to be larger than the thickness T of the back layer in FIG. 1, and the requirement (1) is that the average particle diameter D is in the range of 1 to 15 μm. If it is less than the above range, the effect on blocking becomes low. If the above range is exceeded, spherical particles can be taken and easily fall off.

  In general, the size distribution of such fine particles has a variation close to a normal distribution as shown in FIG. Therefore, particles that are actually effective for blocking act as particles having a particle size larger than the average particle size. It is not working. Therefore, when the particles are contained in the back layer, it is unavoidable to use a method of containing a large average particle diameter or a method of increasing the amount of large particles by increasing the content of particles. In the former method, particles having a larger particle size than necessary are present, and the particles fall off. In the latter method, when the cost of the back layer is increased, or when transparency is required as a recording sheet, it becomes opaque and cannot be practically used.

  The spherical particles used in the present invention are monodisperse particles having a particle size variation defined by the requirement (2) within a range of D ± 0.4 D μm. Monodisperse particles refer to particles having a uniform particle size as shown in FIG. In general, such monodisperse particles are used as spacers between liquid crystal panels. As described above, the ultrafine particles of less than submicron have no effect on the particle size effective for blocking, and there is a problem that spherical particles can be taken when the size is excessive. However, if the monodisperse particles of the present invention are used, only particles having an appropriate particle size can be used, and therefore the effect can be exhibited in a small amount compared to the conventional case. That is, blocking resistance can be obtained with a small amount.

  Monodisperse particles are commercially available mainly for spacers of liquid crystal panels by Soken Chemical, Nippon Shokubai, Sekisui Chemical, etc. Any manufacturer can use any average particle size within the range of requirement (2).

  In addition to the spherical monodisperse particles, spherical particles and non-spherical particles having the general particle size distribution shown in FIG. 2 may be included for other purposes within a range not impeding the effects of the present invention. The content is less than 30% by weight with respect to the total amount of particles. Other purposes mean, for example, the inclusion of colored pigment particles to color the back layer.

  The content of the spherical particles in the back layer is in the range of 1 to 30% by weight. When it is less than the above range, the blocking resistance is lowered. When the above range is exceeded, the anti-blocking effect does not increase more than a certain level and becomes uneconomical.

  If the size of the protruding spherical particles is not sufficient as compared with the thickness T of the back surface layer in FIG. Specifically, it is necessary to set the protrusion length of DT = 0.9 to 14 μm of requirement (3). When it is less than the above range, the blocking resistance is lowered. If the above range is exceeded, spherical particles can be taken and easily fall off.

  The thickness T of the back layer is about 0.05 to 5 μm. If it is less than the above range, the spherical particles cannot be retained and the particles fall off. Exceeding the above range results in increased costs and is uneconomical. Since the spherical particles used in the present invention are monodisperse particles, the thickness of the back layer can be made extremely thin relative to the thickness of a general back layer holding the particles. Specifically, the thickness T of the back layer can be in the range of 0.1 to 0.5 μm. More preferably, it is the range of 0.2-0.4 micrometer. When the particle size distribution of the spherical particles varies as shown in FIG. 2, such a thin thickness makes it impossible to hold large particles.

For example, when a spherical particle having an average particle diameter of 10 μm having a distribution as shown in FIG. 2 is used with respect to the thickness of the back layer of 0.3 μm, the maximum particle diameter is about 20 to 30 μm. . Then, the large particles close to the maximum diameter are not held in the back layer, and the particles fall off. However, in the case of the monodisperse particles used in the present invention, the dispersion of monodisperse particles having an average particle diameter of 10 μm is in the range of 6 to 14 μm. The maximum particle size is 14 μm and is sufficiently retained by the back layer. Thus, by using monodisperse particles, the content of spherical particles can be reduced, and the thickness of the back layer can be reduced, so that the cost can be reduced. When it is desired to make the entire recording sheet transparent, the back layer of the present invention is thin and has a small amount of spherical particles, and becomes a transparent back layer, which is preferable.

The image-receiving layer for oil-based inkjet is a recording sheet that is easy to block because it is formed mainly of an organic solvent-absorbing resin such as polyvinyl chloride vinyl acetate copolymer resin, vinyl chloride resin, urethane resin, polyester resin, and acrylic resin. The image receiving layer often does not contain porous particles. The surface of the image receiving layer which is composed of only the binder and does not contain porous particles is an ultra-smooth surface where no fine cracks are seen compared to the image receiving layer subjected to the calendar treatment. In addition, since the binder itself having an adhesiveness on the smooth opposite surface of the substrate is used, it is easy to block. The back layer containing the spherical particles can provide a sufficient effect in blocking resistance in the oil-based inkjet recording sheet.

  For the back layer, a silicone acrylic resin, a curing agent, and if necessary, spherical particles are dissolved or dispersed in an appropriate solvent to prepare a back layer forming ink. Can be formed by coating and drying with various devices such as knife coaters, curtain coaters, die coaters, lip coaters, blade coaters, gate roll coaters, bar coaters, rod coaters, roll coaters, bill blade coaters, short dwell blade coaters, etc. . The image receiving layer can be formed in the same manner as the back layer forming method.

  Some oil-based ink jet recording sheets have a structure in which an adhesive layer, a weak adhesive layer, or an adhesive layer such as silicone is provided on the opposite surface of the image receiving layer having the structure shown in FIG. When a smooth separator such as the base material of the recording sheet of the present invention is used as the separator, the problem of ink transfer occurs. Even in such a recording sheet, the effect of the present invention can be obtained by providing the back layer of the present invention and the back layer of the separator as shown in FIG.

On a white polyester film having a thickness of 50 μm as a substrate, the following oil-based inkjet image-receiving layer coating solution was applied and dried to form an image-receiving layer having a thickness of 20 μm. The back side coating solution shown in Table 1 was applied to the opposite side of the image-receiving layer and dried to form a back layer having a thickness of 0.2 μm to produce oil-based inkjet recording sheets of Examples 1-2 and Comparative Examples 1-3. did.

Oil-based inkjet image-receiving layer coating solution PVC vinyl acetate copolymer resin 15 parts by weight (Solvine CN, manufactured by Nissin Chemical)
MEK 50 parts by weight MC acetate 5 parts by weight

Table 1 (parts by weight)

Evaluation method It evaluated by the following evaluation method. The evaluation results are shown in Table 1.
1. Ink set-off A recording sheet sample printed with a large oil-based (solvent) oil-based ink jet printer manufactured by Mimaki Engineering is cut into A4 size. Three hours after printing, the cut sheets are overlaid. A load of 400 g is applied to the entire sheet. (400 g / A4) Load treatment is performed for 10 minutes. Visually check if the ink is set off.
○: No setback is seen.
X: Set-off has occurred.

2. Blocking resistance A recording sheet sample having a width of 1 m wound on a 3-inch paper tube was stored at 45 ° C. for 96 hours, and then the sheet was unwound to check for blocking.
○: No blocking is observed.
X: Blocking has occurred.

An example of a schematic cross-sectional view of the oil-based inkjet recording sheet of the present invention General particle size distribution chart Size distribution chart of monodisperse particles used in the present invention Other examples of schematic cross-sectional views of the oil-based inkjet recording sheet of the present invention

Explanation of symbols

1: Back layer 2: Substrate 3: Image receiving layer 4: Spherical particles 5: Adhesive layer, weak adhesive layer, or adhesive layer 6: Separator

Claims (1)

An oil-based ink jet recording sheet comprising a base material and at least an oil-based ink jet image-receiving layer and a back layer on the opposite surface, wherein the back layer is a crosslinked layer of a silicone acrylic resin.

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