JP2003335052A - Surface coating agent for inkjet recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface coating agent for an inkjet recording medium capable of providing an excellent carrying characteristics on a recording apparatus and obtaining a recording image with a high gloss and a high resolution. <P>SOLUTION: A monomer composition (A) and another monomer composition (B) are composed by compounding (c) an α,β-unsaturated carboxylic acid and/or its salt into at least one of two monomer compositions comprising (a) α- methylstyrene and/or (b) an alkyl (meth)acrylate of formula (1) (wherein R<SP>1</SP>is a hydrogen atom or the like, and R<SP>2</SP>is a 1-22C aliphatic hydrocarbon group). The surface coating agent is prepared by polymerizing the monomer composition (A) and then, copolymerizing the monomer composition (B), and comprises a copolymer emulsion in which the difference between glass transition temperatures of a polymer prepared of the monomer composition (A) and a polymer prepared of the monomer composition (B) is ≥5°C. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface coating agent for an inkjet recording medium, and more specifically, it can impart excellent transportability to a recording medium in a recording apparatus and also provides a high gloss and high resolution recorded image. The present invention relates to a surface coating agent for an inkjet recording medium.

[0002]

2. Description of the Related Art Ink jet recording systems are rapidly spreading because they are low in noise, high-speed recording, multi-color recording, and compact apparatus are possible. With the recent increase in speed of inkjet recording devices, higher definition of recorded images, and full-color printing,
The quality requirements for recording media are becoming more and more stringent, and there is a strong demand for recording media that can provide recorded images with high gloss and high resolution comparable to that of color photographs.

In particular, recently, since high-speed printing and multi-color printing that are not comparable to those before are performed, the conventional recording medium has a glossy feeling, ink absorbency, and a plurality of inks adhered to the same place. However, there was a problem in that the color development property, the color clarity, the definition, and the like were insufficient, and a high-resolution recorded image satisfying the currently required quality could not be obtained.

As a method for solving the above-mentioned problems, the present inventors applied a copolymer emulsion having a monomer unit having a specific structure to a recording medium (JP-A-10-12).
No. 9108), a method of applying a polymer emulsion having a specific particle size and an anionic colloidal silica (Japanese Patent Laid-Open No. HEI 2).
000-238418) has already been proposed. However, these methods have a problem that although they have a glossy feeling to some extent and a high-resolution recorded image can be obtained, the transportability in the recording apparatus is deteriorated. That is, in order to obtain a high-resolution recorded image, the coating layer is made porous by using a polymer emulsion or colloidal silica having a high glass transition temperature, and as a result, the slipperiness of the recording medium surface is increased, and in a recording device such as a printer. There is a problem that the transportability of the recording medium is reduced.

Generally, as a means for improving the transportability in a recording apparatus, a method using a polymer emulsion having a low glass transition temperature and a water-soluble binder such as polyvinyl alcohol are added in order to suppress the slipperiness of the recording medium surface. It is known how to do it. However,
In these methods, the absorptivity of ink is lowered, and another problem that a high-resolution recorded image cannot be obtained occurs. As described above, it is extremely difficult to simultaneously satisfy the transportability of the recording apparatus and the high-resolution recorded image.

The present invention has been made in view of the above circumstances, and is for an ink jet recording medium capable of imparting excellent transportability in a recording apparatus to a recording medium and obtaining a recorded image of high gloss and high resolution. It is intended to provide a surface coating agent.

[0007]

Means for Solving the Problems and Embodiments of the Invention
As a result of intensive studies to achieve the above object, the present inventors have found that a polymer obtained from two monomer compositions containing a specific monomer has a glass transition temperature difference of 5 degrees or more. By applying a surface coating agent for an inkjet recording medium containing a copolymer emulsion obtained by stepwise copolymerization to the surface of the recording medium such as paper, pigment coated paper, resin film in the inkjet recording system. The inventors have found that a recording medium can be provided with excellent transportability in a recording apparatus and that a recorded image with high gloss and high resolution can be obtained, and the present invention has been completed.

That is, the present invention is as follows: (A) Monomer composition and (B) monomer constituted by blending at least one of two monomer compositions containing the following monomer (a) and / or monomer (b) with the monomer (c) below A surface coating agent for an inkjet recording medium, comprising a copolymer emulsion obtained by copolymerizing the composition, wherein the copolymer emulsion is obtained by polymerizing the monomer composition (A) in the first step. A copolymer obtained by copolymerizing the monomer composition (B) in the second step, and having a glass transition temperature Tg _A of the polymer of the monomer composition (A) and a polymer of the monomer composition (B). surface coating agent for ink jet recording medium, wherein a difference between the glass transition temperature Tg _B of is 5 ° C. or more, (a) styrene and / or α- methylstyrene (b) the following formula (1) Acrylic acid alkyl ester and / or methacrylic acid alkyl ester represented

[Chemical 2] (In the formula, R ¹ represents a hydrogen atom or a methyl group, and R ² represents a saturated or unsaturated linear or branched aliphatic hydrocarbon group having 1 to 22 carbon atoms.) (C) α, β-unsaturated carboxylic acid and / or its salt 2. The surface coating agent for an inkjet recording medium according to (1), wherein the (A) monomer composition and / or the (B) monomer composition further contains the following monomer (d): 2. Monomers capable of polymerizing with the monomers (c) to 3. The average particle size of the copolymer emulsion is 0.02.
3. The surface coating agent for an inkjet recording medium according to 1 or 2, characterized in that The surface coating agent for an inkjet recording medium according to any one of 1 to 3, which contains an anionic colloidal silica. 5. Provided is a surface coating agent for an inkjet recording medium according to 4, wherein the anionic colloidal silica has an average particle size of 0.01 to 0.15 μm.

The present invention will be described in more detail below. In the present invention, the copolymerization ratio of the monomers (a) to (d) constituting the copolymer emulsion contained in the surface coating agent for an inkjet recording medium is not particularly limited, but the obtained surface It is determined in due consideration of the performance of the coating agent. The monomer (a) is styrene and / or α-methylstyrene, and the copolymerization ratio of these monomers is based on the total mass of the monomer composition (A) and the monomer composition (B). 5-9
It is preferably 5% by mass, particularly 30 to 90% by mass. If this copolymerization ratio is less than 5% by mass, the gloss of the recording medium after printing may be insufficient, while 95% by mass
When it exceeds, there is a possibility that the light resistance is lowered.

The monomer (b) is an alkyl acrylate represented by the above formula (1) and /
Alternatively, although it is an alkyl methacrylate, it is preferable that the monomer (b) contains an acrylic ester from the viewpoint of improving the transportability of the recording medium in the recording apparatus and the resolution of the recorded image in a well-balanced manner. In this case, the alkyl group constituting the ester is, as described above, a saturated or unsaturated linear or branched aliphatic hydrocarbon group having 1 to 22 carbon atoms, for example,
Examples thereof include methyl, ethyl, n-butyl, s-butyl, t-butyl, pentyl, 2-ethylhexyl, lauryl and stearyl groups.

Specific (meth) acrylic acid esters include methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, and (meth) acrylic acid. Lauryl,
Stearyl (meth) acrylate and the like can be mentioned, and these can be used alone or in combination of two or more. Further, the copolymerization ratio of the above-mentioned monomer (b) is
Although not particularly limited, with respect to the total mass of the (A) monomer composition and the (B) monomer composition,
It is preferably 0.5 to 95% by mass, particularly preferably 1 to 85% by mass. If the copolymerization ratio is less than 0.5% by mass, the vividness of the color development of the recorded image may decrease, while if it exceeds 95% by mass, the resolution of the recorded image may decrease.

Examples of the α and β unsaturated carboxylic acids and / or salts thereof in (c) above include acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, crotonic acid and their sodium salts, potassium salts, ammonium salts. Examples thereof include salts, and these can be used alone or in combination of two or more. Among these, it is preferable to use sodium salt or ammonium salt of acrylic acid or methacrylic acid from the viewpoints of cost reduction and improvement of adhesion strength to the substrate. In addition, the copolymerization ratio of the above-mentioned (c) monomer is 0.5 to 0.5 with respect to the total amount of the (A) monomer composition and the (B) monomer composition.
It is preferably 30% by mass, particularly preferably 1 to 20% by mass. If the copolymerization ratio is less than 0.5% by mass, the resolution of the recorded image may be reduced, while if it exceeds 30% by mass, the water resistance may be reduced.

The above-mentioned monomer (d) is the above-mentioned monomer (a).
To (c) are monomers that can be polymerized with the monomers, and are components that can be used within a range that does not impair the effects of the present invention. Examples of the monomer (d) include acrylamide, methacrylamide, N-hydroxymethyl acrylamide, 2-hydroxyethyl acrylate, methoxy polyethylene glycol methacrylate, vinyl acetate, acrylonitrile, methylene bis acrylamide, polyethylene glycol diacrylate, and the like.
Examples thereof include divinylbenzene, trimethylolpropane triacrylate, styrenesulfonic acid and its salts, 2-acrylamido-2-methylpropanesulfonic acid and its salts, and the like.

Further, the copolymerization ratio of the monomer (d) is 20% by mass or less, particularly 0.1 to 15% by mass, based on the total amount of the (A) monomer composition and the (B) monomer composition. It is preferably in the range of. This copolymerization ratio is 20
If the content is more than mass%, the effect of the present invention, particularly the gloss of the recording medium may be deteriorated.

The monomer composition (A) in the present invention and
And (B) the monomer composition is a mono-component of the above (a) to (c).
And optionally the monomer of (d)
Which is a mixture of (A) monomer composition
Glass transition temperature Tg of polymer _AAnd (B) monomer composition
Transition temperature Tg of polymer_BAnd the difference is more than 5 ℃
It is necessary to make such a composition. Where glass transition temperature
When the difference in degree is less than 5 ° C, the coating agent of the present invention is used for surface treatment.
Conveyance of the used recording paper in the recording device will decrease.
It Points to further enhance the transportability of this recording device
Therefore, the difference in glass transition temperature is preferably 10 ° C or more.
Good

In this case, in order to set the difference in glass transition temperature to the above range, the copolymerization ratio of the monomer (c) in the monomer composition (A) and the above in the monomer composition (B). The difference from the copolymerization ratio of the monomer (c) needs to be at least 1 mass% or more, preferably 2 mass% or more. Either of the glass transition temperature Tg _A and the glass transition temperature Tg _B may be higher, but in order to further enhance the vividness of the color development of the recorded image, Tg _A <
It is preferably Tg _B. Each glass transition temperature is a value calculated from the following Fox (FOX) formula.

[0017]

[Formula 1]

In the above formula 1, Tg _a ~Tg _d shows the (a) ~ the glass transition temperature of the homopolymer of each monomer (d) (K), a~d, the above (a) ~ ( The copolymerization mass ratio of each monomer of d) is shown, and a + b + c + d = 1
Is.

Further, the glass transition temperature Tg _A of the polymer of the monomer composition (A) and the glass transition temperature Tg _B of the polymer of the monomer composition (B) are both 0 to 200.
The range of ° C is preferable, and more preferably 20 to 180 ° C. If the glass transition temperature is lower than 0 ° C, the thermal stability of the coating layer (coating film) may be insufficient, and problems such as fusion may occur when the coated surfaces are superposed.
If the temperature exceeds ° C, a homogeneous coating layer (coating film) may not be formed.

As described above, the (A) monomer composition and the (B) monomer composition, which are the raw materials of the copolymer emulsion in the present invention, respectively, when the total amount of each monomer composition is 100% by mass, The monomers (a) to (d) are preferably contained in the ratios shown in Table 1 below, but the present invention is not limited thereto.

[0021]

[Table 1]

In the present invention, the ratio of the monomer composition (A) and the monomer composition (B) used in preparing the copolymer emulsion is determined by the total amount of the monomer composition constituting the copolymer emulsion. Is 100 mass%, the (A) monomer composition is 10 to 90 mass%, in particular,
20 to 60% by mass, 90 to 10 of (B) monomer composition
It is preferably in the range of% by mass, particularly 80 to 40% by mass. Here, if the ratio of the (A) monomer composition or the (B) monomer composition is less than 10% by mass or more than 90% by mass, the effects of the present invention, in particular, the transportability in the recording apparatus is not sufficiently exhibited. There is a risk.

In the present invention, the copolymer emulsion is prepared by polymerizing the monomer composition (A) in the first step and then copolymerizing the monomer composition (B) in the second step as described above. It was obtained by letting me do it. In this case, the polymerization method for obtaining the copolymer emulsion, the polymerization conditions and the like are not particularly limited, and, for example, a commonly used emulsion polymerization method or the like can be used, but in particular, the solid content of the copolymer emulsion is 20 to 50% by mass, average particle size 0.02-0.1
It is preferable to select a manufacturing condition of 5 μm, particularly 0.03 to 0.10 μm. Here, the average particle size is 0.0
If it is less than 2 μm, the printing gloss may decrease, while if it exceeds 0.15 μm, the sharpness of the recorded image may decrease.

As a specific polymerization method, for example, an emulsifier or the like is dissolved in water, a part of the above (A) monomer composition is added and emulsified, and then the remaining (A) monomer composition and radical polymerization are carried out. Emulsion polymerization is carried out by continuously dropping an initiator, and then (B) a monomer composition and a radical polymerization initiator are continuously dripped to obtain a copolymer emulsion, a monomer composition and a radical polymerization initiator. When (A) the monomer composition is polymerized, it is polymerized by adding it all at once, and when the (B) monomer composition is polymerized, these are also collectively added and polymerized (simultaneous reaction) to carry out emulsion polymerization. Examples of the method include a method of performing stepwise supply of each of the above-mentioned monomer compositions to the reaction system by divided charging, etc. Dropping method is preferable. In each of the above methods, a method of supplying the monomer composition to the reaction system in an emulsified state with an emulsifier can also be used. The polymerization temperature is preferably 40 to 95 ° C. The copolymer particles in the copolymer emulsion obtained by these methods often have a hetero-phase structure such as a core-shell structure or a sea-island structure.

When the above emulsion polymerization is adopted, the emulsifier used is not particularly limited, and known emulsifiers can be used, but it is said that the average particle size of the copolymer emulsion is efficiently controlled. From the viewpoint, it is preferable to use an anionic emulsifier. Examples of such anionic emulsifiers include higher alcohol sulfuric acid ester salts, alkylbenzene sulfonates, aliphatic sulfonates, dialkylsulfosuccinates, alkylnaphthalene sulfonates, alkyldiphenyl ether disulfonates, polyoxyethylene alkyl ethers. Emulsifiers such as sulfuric acid ester salts, polyoxyethylene alkylphenyl ether sulfuric acid ester salts, allyl alkylphenyl polyethylene oxide sulfuric acid ester salts, and allyl alkyl sulfosuccinic acid diester salts can be used. In addition, a nonionic emulsifier such as polyoxyethylene alkylphenyl ether, polyoxyethylene alkyl ether, polyoxyethylene alkyl ester, or a polymeric emulsifier such as sodium polystyrene sulfonate or sulfonated polyvinyl alcohol is used in combination with the anionic emulsifier. It doesn't matter.

On the other hand, the radical polymerization initiator used in the emulsion polymerization is not particularly limited, and examples thereof include peroxides such as hydrogen peroxide, ammonium persulfate, sodium persulfate, potassium persulfate, and the like. Various redox initiators usually used in combination with oxides, and azo initiators such as 2,2-azobis (aminodipropane) hydrochloride can be used. Further, if necessary, a molecular weight modifier such as dodecyl mercaptan, dialkylamine or allyl alcohol may be used.

The surface coating agent for an ink jet recording medium described above may contain anionic colloidal silica having an average particle diameter of 0.01 to 0.15 μm in addition to the above copolymer emulsion. In this case, the composition ratio of the copolymer emulsion and the anionic colloidal silica is
The solid content ratio is preferably in the range of 6/4 to 0.3 / 9.7, more preferably in the range of 5/5 to 0.5 / 9.5, and further preferably in the range of 4/6 to 0. The range is 7 / 9.3. Here, if the proportion of the copolymer emulsion exceeds 60% by mass, the sharpness of the recorded image may decrease, while if it is less than 0.3% by mass, the glossiness may decrease.

The average particle size of the anionic colloidal silica is not particularly limited, but is 0.01 to
It is preferably 0.15 μm, more preferably 0.015 to 0.12 μm, still more preferably 0.02.
Is about 0.10 μm. Here, the average particle size is 0.01
If it is less than μm, the ink absorptivity may decrease, while if it exceeds 0.15 μm, the sharpness of a recorded image may decrease.

The above-mentioned anionic colloidal silica is a colloidal solution in which spherical silica is dispersed in water, and the silanol groups on the particle surface are negatively charged, and bases such as sodium hydroxide, sodium silicate, and organic amines are used. It is anionic by being neutralized with. As such anionic colloidal silica, commercially available ones can be used, such as Silicadol (manufactured by Nippon Kagaku Kogyo Co., Ltd.) and Adelite AT (Asahi Denka Kogyo Co., Ltd.).
(Manufactured by Japan Chemical Industry Co., Ltd.), Cataloid (manufactured by Catalysts & Chemicals Industry Co., Ltd.), Snowtex (manufactured by Nissan Chemical Industries, Ltd.) and the like can be used.
It is preferable to use the sol-like water dispersion liquid in view of compatibility stability with the copolymer emulsion.

Further, the ratio (X) / the average particle diameter (X) of the polymer emulsion constituting the surface coating agent of the present invention to the average particle diameter (Y) of the anionic colloidal silica.
(Y) is not particularly limited, but from the viewpoint of enhancing the sharpness and glossiness of the recorded image, it is preferably 0.5 to 5.
It is in the range of 0, more preferably in the range of 0.6 to 4.0, and further preferably in the range of 0.7 to 3.5. In the present invention, the average particle size of the copolymer emulsion and the anionic colloidal silica is a value measured by an electrophoretic light scattering photometer (ELS-800, Otsuka Electronics Co., Ltd.).

As described above, the surface coating agent for an ink jet recording medium of the present invention contains a copolymer emulsion, or a copolymer emulsion and an anionic colloidal silica. The proportion of the entire coating agent is usually 10 to 100% by mass,
It is preferably 30 to 100% by mass. The surface coating agent for an inkjet recording medium of the present invention includes, in addition to the above copolymer emulsion and anionic colloidal silica, a binder, a paper strength enhancer, a surface sizing agent, and a charge that are commonly used in paper processing and the like. An inhibitor, a viscosity modifier, a dye, an ultraviolet absorber, an antioxidant, an antifoaming agent, an antifungal agent, an antislip agent, a film-forming auxiliary agent, etc. may be used in combination. In this case, the mixing ratio of these additives is not particularly limited as long as it does not impair the functions of the copolymer emulsion and the anionic colloidal silica, but is usually 0.1 to the entire surface coating agent. -50% by mass, preferably 1
Is about 30% by mass.

The substrate (ink jet recording medium) to which the surface coating agent of the present invention is applied is not particularly limited as long as it is suitable for ink jet recording, and examples thereof include natural pulp paper, pigment coated paper, and synthetic paper. In addition, a cloth or a plastic film sheet such as polyethylene terephthalate can be used. When the above-mentioned surface coating agent is applied to the substrate, the coating amount is not particularly limited, but it is 0.
If it is less than 1 g / m ² , the thickness of the coating film is insufficient and the gloss of the recording medium is insufficient, and if it exceeds 40 g / m ² , the cost becomes high. Therefore, 0.1-40 g / m ² , particularly 1-30 g. / M ² is preferable. Further, the coating method is also not particularly limited, conventionally used methods, for example, air doctor coater, air knife coater, blade coater,
A method of coating with a roll coater, curtain coater, gravure coater, spray or the like can be adopted. When using paper as the substrate, silica or alumina, or a mixture thereof with a polymer latex binder, is applied to the base paper prior to the application, and the surface coating agent of the present invention is applied thereon. You may work.

[0033]

EXAMPLES The present invention will be described in more detail with reference to examples and comparative examples, but the present invention is not limited to the following examples. In the following explanation,
Unless otherwise specified, "% by mass" and "parts by mass"
Are abbreviated as “%” and “part”, respectively.

[1] Production of Copolymer Emulsion [Production Example 1] Deionized water 641 was placed in an apparatus equipped with a stirrer, a thermometer, a reflux condenser, a dropping funnel and a nitrogen introducing tube.
Parts, 9 parts of sodium salt of polyoxyethylene (n = 5) lauryl ether sulfate (emulsifier), and 10 parts of the monomer composition (A) shown in Table 2 below were charged, and the mixture was heated to 75 ° C. under a nitrogen stream. After heating 75 under stirring
While maintaining at 0 ° C., 10 parts of a deionized aqueous solution in which 1.5 parts of ammonium persulfate was dissolved was added to start the polymerization reaction. While maintaining the temperature at 75 ° C., 110 parts of the remaining (A) monomer composition was added dropwise over 40 minutes, and this was added at the same temperature for 30 minutes.
After keeping the temperature for a minute to allow the polymerization reaction to proceed, 180 parts of the monomer composition (B) shown in Table 2 below was added dropwise over 1 hour. Further, this was kept at the same temperature for 1 hour to complete the polymerization reaction. After cooling, the pH was adjusted to 8 with 10% ammonia water.
Adjusted to 0 and diluted with deionized water to obtain a solid concentration of 30%,
Copolymer emulsion with an average particle size of 0.055 μm (S
-1) was obtained. The glass transition temperature Tg _A of the polymer of the monomer composition (A) was 70 ° C., and the glass transition temperature Tg _B of the polymer of the monomer composition (B) was 101 ° C.

[0035]

[Table 2]

[Production Example 2] Monomer compositions are shown in Table 3 below.
Except for changing the composition shown, the same operation as in Production Example 1 was performed.
Conducted with a solid content of 30% and an average particle diameter of 0.075 μm
A combined emulsion (S-2) was obtained. (A) Mono
Glass transition temperature Tg of polymer of mer composition _A80 ℃,
(B) Glass transition temperature Tg of polymer of monomer composition_B
Was 97 ° C.

[0037]

[Table 3]

[Production Example 3] Monomer compositions are shown in Table 4 below.
Except for changing the composition shown, the same operation as in Production Example 1 was performed.
Conducted with a solid content of 30% and an average particle size of 0.090 μm
A combined emulsion (S-3) was obtained. (A) Mono
Glass transition temperature Tg of polymer of mer composition _AIs 40 ℃,
(B) Glass transition temperature Tg of polymer of monomer composition_B
Was 120 ° C.

[0039]

[Table 4]

[Production Example 4] The same procedure as in Production Example 1 was repeated except that the sodium salt of allyllaurylsulfosuccinic acid diester was used as an emulsifier and the monomer composition was changed to the composition shown in Table 5 below. 30%, average particle size 0.035 μm copolymer emulsion (S-
4) was obtained. The glass transition temperature Tg _A of the polymer of the monomer composition (A) was 65 ° C, and the glass transition temperature Tg _B of the polymer of the monomer composition (B) was 101 ° C.

[0041]

[Table 5]

[Production Example 5] 490 parts of deionized water and 10 parts of the emulsion of the monomer composition (A) shown in Table 6 below were charged in the same reactor as in Production Example 1, and the mixture was placed under a nitrogen stream. Heated to 70 ° C. While maintaining the temperature at 70 ° C. under stirring, 10 parts of a deionized aqueous solution in which 2.3 parts of ammonium persulfate was dissolved was added to initiate a polymerization reaction. While maintaining the temperature at 70 ° C., 250 parts of the rest of the emulsion of the monomer composition (A) was added to 1 part.
The mixture was added dropwise over a period of time and kept at the same temperature for 30 minutes to allow the polymerization reaction to proceed. Then, 390 parts of an emulsion of the monomer composition (B) shown in Table 6 below was added dropwise over 1 hour 30 minutes. . Further, this was kept at the same temperature for 1 hour to complete the polymerization reaction. After cooling, the pH was adjusted to 7.0 with 10% sodium hydroxide and diluted with deionized water to obtain a solid content concentration of 40.
%, And a copolymer emulsion (S-5) having an average particle diameter of 0.130 μm was obtained. The glass transition temperature Tg _A of the polymer of the monomer composition (A) was 85 ° C., and the glass transition temperature Tg _B of the polymer of the monomer composition (B) was 112 ° C.

[0043]

[Table 6]

[Production Example 6] Monomer compositions are shown in Table 7 below.
Except for changing the composition shown, the same operation as in Production Example 1 was performed.
Conducted with a solid content of 30% and an average particle size of 0.095 μm
A combined emulsion (S-6) was obtained. (A) Mono
Glass transition temperature Tg of polymer of mer composition _AIs 101
° C, glass transition temperature T of the polymer of the monomer composition (B)
g_BWas 70 ° C.

[0045]

[Table 7]

[Comparative Production Example 1] The same reactor as in Production Example 1 was charged with 641 parts of deionized water and polyoxyethylene (n =
5) Charge 9 parts of sodium salt of lauryl ether sulfate (emulsifier) and 10 parts of the monomer composition shown in Table 8 below, and after heating to 75 ° C. under a nitrogen stream,
While maintaining the temperature at 75 ° C. under stirring, ammonium persulfate 1.
The polymerization reaction was started by adding 10 parts of deionized water in which 5 parts were dissolved. Remaining monomer composition 2 while maintaining at 75 ° C
90 parts was added dropwise over 1 hour and 40 minutes. This was kept at the same temperature for 1 hour to complete the polymerization reaction. After cooling 10
Copolymer emulsion (H-1) having a solid content of 30%, a glass transition temperature of 88 ° C., and an average particle size of 0.050 μm, which is diluted with deionized water to adjust pH to 8.0.
Got

[0047]

[Table 8]

[Comparative Production Example 2] The same operation as in Production Example 1 was carried out except that the composition of the monomer composition was changed to that shown in Table 9 below, and the solid content concentration was 30% and the average particle diameter was 0.060 μm.
m copolymer emulsion (H-2) was obtained. In addition,
(A) Glass transition temperature Tg _A of polymer of monomer composition
Was 85 ° C., and the glass transition temperature Tg _B of the polymer of the monomer composition (B) was 89 ° C.

[0049]

[Table 9]

[Comparative Production Example 3]
The same operation as in Production Example 1 was carried out except that the composition was changed to that shown in 0 to obtain a solid content concentration of 30% and an average particle diameter of 0.055 μm.
m copolymer emulsion (H-3) was obtained. In addition,
(A) Glass transition temperature Tg _A of polymer of monomer composition
Was 89 ° C., and the glass transition temperature Tg _B of the polymer of the monomer composition (B) was 85 ° C.

[0051]

[Table 10]

Table 11 below shows the monomer composition, glass transition temperature and average particle size of the copolymer emulsions obtained in each of the above Production Examples and Comparative Production Examples. The average particle size is measured by an electrophoretic light scattering photometer (EL
S-800, a value measured by Otsuka Electronics Co., Ltd.

[0053]

[Table 11]

In Table 11, the abbreviations of the components (a) to (d) have the following meanings. St: styrene, n-BA: n-butyl acrylate, E
A: ethyl acrylate MMA: methyl methacrylate, 2-EHA: 2-ethylhexyl acrylate MAA: methacrylic acid, AA: acrylic acid, AAm: acrylamide

[2] Evaluation of surface coating agent for ink jet recording medium [Example 1] The copolymer emulsion (S-1) synthesized in Production Example 1 was used in a basis weight of 85 g / m ² and a Steckigt sizing degree of 6 After applying each surface coating agent to the second paper using an applicator bar # 4 so that the dry solid content becomes 5 g / m ² , it is dried at 100 ° C. for 40 seconds to give a test paper. Obtained.

[Examples 2 to 6] A coating agent was prepared and coated in the same manner as in Example 1 except that (S-2) to (S-6) were used as the copolymer emulsion. Then, it was dried to obtain a test paper.

[Comparative Examples 1 to 3] A coating agent was prepared and coated in the same manner as in Example 1 except that (H-1) to (H-3) were used as the copolymer emulsion. Then, it was dried to obtain a test paper.

Each of the test papers obtained in Examples 1 to 6 and Comparative Examples 1 to 3 was used as an ink jet printer (PM-82).
0C, Seiko Epson Co., Ltd. full-color printing was performed, and the sharpness of color development, the resolution of the recorded image, the glossiness, and the transportability in the recording apparatus were evaluated. The results are shown in Table 1.
2 shows.

[0059]

[Table 12]

In Table 12, each item was evaluated according to the following criteria. (1) Vividness of color development The color and vividness of color development of a recorded image were visually evaluated according to the following criteria. ⊚: The colors and colors are excellent in vividness and there is no color blurring ○: There is a slight color fading, but there is no problem in practical use △: A little inferior in color and coloring vividness ×: Color fading , The vividness of colors and colors is inferior

(2) Resolution of recorded image The degree of bleeding of the recorded image was visually determined according to the following criteria. ◎: No bleeding ○: Slightly bleeding, but no problem in practical use △: Some bleeding is recognized ×: Large bleeding

(3) Glossiness The glossiness of the printed test paper was visually evaluated according to the following criteria. ⊚: Very glossy and excellent ○: Highly glossy Δ: Very little glossy and slightly inferior ×: No glossy and inferior

(4) Conveyability in the recording apparatus 10 sheets of test paper were stacked and set in the printer, and the conveyance state of them was evaluated according to the following criteria. ◎: Smooth transfer ○: Slightly lacking in smoothness, but can be transferred practically △: Can not be transferred once every several times ×: Can not be transferred almost every time

As shown in Table 12, the test papers coated with the specific copolymer emulsions of the present invention of Examples 1 to 6 had a sharpness of color development, a resolution of recorded images, as compared with Comparative Examples.
It can be seen that the gloss feeling and the transportability in the recording apparatus are excellent.

Example 7 The copolymer emulsion (S-1) synthesized in Production Example 1 above and an average particle size of 0.035.
μm, pH = 9.0, solid content 40% anionic colloidal silica (Sample A) were mixed so that the solid content ratio of the copolymer emulsion and the anionic colloidal silica was 1/9, and purified. A surface coating agent diluted with water to a solid content of 30% was applied to a paper having a basis weight of 85 g / m ² and a Steckigt sizing degree of 6 seconds using an applicator bar # 4 to obtain a dry solid content of 5 g / m ^2. After coating to 100, 100
A test paper was obtained by drying at 40 ° C. for 40 seconds.

[Examples 8 to 11] The solid content ratio of the copolymer emulsion to the anionic colloidal silica was 3/7,
A surface coating agent was prepared and coated in the same manner as in Example 7, except that the coating compositions were changed to 5/5, 7/2, and 9/1, respectively.
A test paper was obtained by drying.

[Examples 12 to 16] Average particle size 0.06
A surface coating agent was prepared, coated and dried in the same manner as in Example 7, except that anionic colloidal silica (Sample B) having a thickness of 5 μm, a pH of 9.5 and a solid content of 40% was used. A test paper was obtained.

[Comparative Examples 4 and 5] A surface coating agent was prepared with a composition of anionic colloidal silica alone, coated and dried to obtain a test paper. The test papers of Examples 7 to 16 and Comparative Examples 4 and 5 were printed in the same manner using the above printer,
Performance evaluation was performed. The results are shown in Table 13.

[0069]

[Table 13]

As shown in Table 13, Examples 7 to 16
The test paper coated with a coating agent containing the copolymer emulsion of the present invention and colloidal silica has a sharpness of color development, a resolution of a recorded image, a glossy feeling, and a recording apparatus as compared with a comparative example coated with only colloidal silica. It can be seen that the transportability is excellent. Further, it can be seen that the evaluation items are better than those of Examples 1 to 6 in which colloidal silica is not added.

Examples 17 to 21 (S-2) to (S-6) were used as the copolymer emulsion, and the solid content ratio of the copolymer emulsion to the anionic colloidal silica was 3/7. A surface coating agent was prepared, coated and dried in the same manner as in Example 7 except that the test paper was obtained.

[Examples 22 to 26] A surface coating agent was prepared, coated and dried in the same manner as in Example 7 except that Sample B was used as the anionic colloidal silica to obtain test papers. It was

Example 27 Average particle size 0.007 μm
m, pH = 9.5, anionic colloidal silica having a solid content of 30% (Sample C) was used, and the solid content ratio of the copolymer emulsion to the anionic colloidal silica was 3/7.
A surface coating agent was prepared, coated and dried in the same manner as in Example 7 except that the test paper was obtained.

Example 28 Average particle size 0.35 μm,
A surface coating agent was prepared, coated and dried in the same manner as in Example 7 except that anionic colloidal silica having a pH of 9.3 and a solid content of 40% (Sample D) was used. Got

[Comparative Examples 6 to 8] A surface coating agent was prepared and applied in the same manner as in Example 7, except that (H-1) to (H-3) were used as the copolymer emulsion. It was worked and dried to obtain a test paper. Examples 17-28, Comparative Examples 6-8
The test paper of No. 1 was printed in the same manner using the above-mentioned printer, and the performance was evaluated. The results are shown in Table 14.

[0076]

[Table 14]

As shown in Table 14, Examples 17-2
The test paper coated with the coating agent containing the copolymer emulsion of the present invention of 4 and colloidal silica had a clearer color than the comparative example coated with the coating agent containing the copolymer emulsion of the present invention and colloidal silica. It is understood that the degree, the resolution of the recorded image, the glossiness, and the transportability in the recording apparatus are excellent.

[0078]

As described above, since the surface coating agent for an ink jet recording medium of the present invention contains a specific copolymer emulsion, the recording medium coated with the surface coating agent can be used in a recording device. It is possible to enhance the transportability during recording and to improve the sharpness of color development, resolution, and glossiness in the obtained image and the like.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Minoru Kamiya             1-3-7 Honjo, Sumida-ku, Tokyo Rio             Within the corporation F-term (reference) 2H086 BA15 BA33 BA34 BA41 BA45                 4J011 AA05 BA04 BB07 KB13 KB14                       KB19 PA65 PC06                 4J100 AB02P AB02Q AB03P AB03Q                       AJ01P AJ01Q AJ02P AJ02Q                       AJ08P AJ08Q AJ09P AJ09Q                       AK01P AK01Q AK07P AK07Q                       AK18P AK18Q AK20P AK20Q                       AL02P AL02Q AL03P AL03Q                       AL04P AL04Q AL05P AL05Q                       CA03 JA01 JA13

Claims (5)

[Claims] 1. A monomer composition (A) constituted by blending at least one of two monomer compositions containing the monomer (a) and / or the monomer (b) with the monomer (c) below. And (B) a surface coating agent for an inkjet recording medium, which comprises a copolymer emulsion obtained by copolymerizing the monomer composition, wherein the copolymer emulsion is used in the first step as the (A) monomer composition. Obtained by copolymerizing the monomer composition (B) in the second step after the polymerization of the polymer (A) and the glass transition temperature T of the polymer of the monomer composition (A).
_A surface coating agent for an inkjet recording medium, wherein the difference between g _A and the glass transition temperature Tg _B of the polymer of the monomer composition (B) is 5 ° C. or more. (A) Styrene and / or α-methylstyrene (b) Acrylic acid alkyl ester and / or methacrylic acid alkyl ester represented by the following formula (1): (In the formula, R ¹ represents a hydrogen atom or a methyl group, and R ² represents a saturated or unsaturated linear or branched aliphatic hydrocarbon group having 1 to 22 carbon atoms.) (C) α, β-unsaturated carboxylic acid and / or its salt 2. The surface coating agent for an inkjet recording medium according to claim 1, wherein the monomer composition (A) and / or the monomer composition (B) further contains a monomer (d) below. . (D) Monomer polymerizable with the monomers (a) to (c) 3. The surface coating agent for an inkjet recording medium according to claim 1, wherein the average particle diameter of the copolymer emulsion is 0.02 to 0.15 μm. 4. The surface coating agent for an ink jet recording medium according to claim 1, which contains an anionic colloidal silica. 5. The surface coating agent for an inkjet recording medium according to claim 4, wherein the anionic colloidal silica has an average particle size of 0.01 to 0.15 μm.