JPH07172037A - Ink-jet recording sheet - Google Patents

Abstract

PURPOSE:To cope with far higher resolution printing since strike-through is hard to occur as ink absorption per unit capacity on a surface part is increasing in the quantity, by a method wherein the sheet is allowed to contain porous resin particles. CONSTITUTION:An ink-jet recording sheet is allowed to contain porous resin particles. Although the porous resin particles are obtained by various polymerizing methods, emulsion polymerization is preferable. In a resin component, a sheet base which is allowed to contain the porous resin particles, for example, polyester resin, methacrylate resin or polycarbonate resin possesses pulp or paper possessing the pulp as its row materials or polyolefin or polyester as their row materials. Although there are various methods which allow a printed body sheet to contain porous resin particles, it is most preferable to apply to a sheet base along with a binder. The quantity of porous particles which are allowed to contain in the sheet base are taken preferably as 10-50wt.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention has little blurring of characters during printing, enables clear and high-resolution printing, has little change in printing density and sharpness with time, and can dry ink in a printing portion quickly. The present invention relates to a recording sheet for inkjet printing, which is less likely to be stained by undried ink.

[0002]

2. Description of the Related Art In recent years, various techniques for printing and printing characters and images on a substrate such as paper and OHP film have been proposed. Although these techniques are diverse, there are not many printing / printing techniques that are widely used without requiring specialized knowledge and techniques in offices and homes. Examples of popular printing / printing technology include dot impact method used in voucher printers, thermal transfer method used in personal word processors, thermal printing method used in facsimiles, and copy machines. Although there are electrophotographic methods and the like used, the inkjet method has become widespread in most homes and offices in recent years.

The ink jet system is basically a system in which water, oil, or solvent ink droplets are ejected from fine nozzles and adhered to a printing surface such as paper to obtain information as characters or images. Is. As for this inkjet method, various methods that can be classified by the method of generating ink droplets, the method of attaching ink droplets, the type of ink, etc. have been proposed, and many inkjet printers that apply these technologies have been commercialized. Has been done.

The advantages of the ink jet system are (1) there are few restrictions on the shape and type of the printing medium, and no special paper such as thermal paper is required. Further, the consumption of the printing medium (ink) is limited to the printing section, and the printing medium can be replenished only by replenishing the ink, and the printing cost is low. (2) Quiet with almost no noise during printing, and high-speed printing is possible because the printing surface and the printing device do not mechanically contact each other. (3) The printing device is not large and can be downsized, and the power consumption of the device is small. That is, the method is widely used because of its low cost, quietness, and small size.

However, the disadvantages of the ink jet system are that ink in a liquid state is adhered to a printing medium, and the principle of the system is as follows: (1) Depending on the surface state of the printing medium, bleeding of printing and unevenness of contrast may occur. Likely to happen. (2) When the printed surface is touched immediately after printing, or when printed sheets are overlaid, undried ink adheres and stains the surrounding area. Due to market demands in recent years, the system is also required to have higher speed and higher resolution. In addition, in many cases, such as color printing, inks of a plurality of colors are overlaid and printed.

When the ink jet printing has a higher resolution, the dot size which is the minimum unit of the printing size becomes smaller. This also means that the minimum unit of the amount of ejected ink becomes small. Therefore, when the ink adhering to the printing medium penetrates deep into the printing medium, the amount of pigment / dye in the effective ink near the surface layer of the printing medium decreases, and the printing contrast decreases significantly. Further, when the adhered ink spreads in the lateral direction near the surface layer of the printing medium, it causes bleeding of the printing and lowers the resolution.

In order to prevent the deterioration of contrast and bleeding, there is a method of smoothing the surface of the printing medium and reducing the pores in the vicinity of the surface layer. However, this method slows the absorption of ink into the printing medium. However, it takes a long time to dry the ink, and an object that touches the printed portion immediately after printing may be soiled or the obtained printing or image information may be damaged. Further, in the case of the inkjet method, it is essential that the viscosity of the ink is low. Therefore, when the absorption of the ink to the printing medium is slow, the ejected ink may splash or the undried ink may flow down. However, this may cause blurring of printing. These things also hinder the speeding up of printing.

Further, in the case of color printing by the ink jet system, a plurality of types of inks are ejected in order, so if the ink absorption amount of the printing object is small, the previously ejected color ink is absorbed by the adhesion object, What is injected later is not absorbed and remains near the surface. Therefore, the color ejected later may be more intensely colored, and the final color may not be as set.

There is also a method of improving the drying property by improving the ink itself, but the drying property tends to decrease rather by making the ink non-solvent and water-based. As a means for solving such contradictory factors relating to speeding up and high resolution of the ink jet system, there is a method of making the surface layer of the printing object porous and improving the water absorption and oil absorption properties near the surface layer.
That is, if there is sufficient ink absorption capacity in the vicinity of the surface layer, all the ink is promptly absorbed in the vicinity of the surface layer regardless of the absorption capacity of the entire print object, and stays at that location. Will be resolved. As a means for making the surface of the printing medium near the surface layer porous, there is a method of incorporating or coating inorganic porous particles such as colloidal silica into the printing medium. However, the inorganic particles are generally hard and have a problem that the running system of the printing apparatus is easily damaged. In addition, since the weight of the inorganic particles is much larger than that of the resin particles, the weight of the object to be printed using the inorganic particles becomes large, and
If the same weight as that of the printing object using the resin particles is used, the amount of the inorganic particles used is decreased, and the effect is reduced.

[0010]

SUMMARY OF THE INVENTION An object of the present invention is to provide an ink jet recording sheet which can be applied to an ink jet system of higher resolution and higher speed.

[0011]

[Means for Solving the Problems] As a result of extensive studies to solve the above problems, the porous resin particles are excellent in water absorption and oil absorption, and are lighter and softer than the inorganic porous particles. The present invention has been completed. That is,
The present invention is an ink jet recording sheet characterized by containing porous resin particles.

The present invention will be described in detail below. The porous resin particles used in the present invention may be those obtained by an emulsion polymerization method, a suspension polymerization method, a dispersion polymerization method, or another polymerization method, or may be a pulverized lump of porous resin. . The resin component is not particularly limited, for example, polyester resin, methacrylic resin, polycarbonate resin, styrene copolymer resin, vinyl chloride resin, polypropylene resin and blends thereof. Also,
The means for making the resin particles porous or for obtaining the resin made porous is not particularly limited. Among them, porous resin particles obtained by emulsion polymerization are preferable, and for example, fine particle aggregate emulsion particles disclosed in JP-A-2-70741 are preferable. Further, the structure described in Japanese Patent Laid-Open No. 5-222108 by the present inventors has one or more through-holes connecting the surface layer of the particles to the inside thereof, and the particle diameter is 0.1 to 5.0 μm. It is more preferable that the emulsion particles have a multilayer structure.

The particle size of the porous resin particles is from 0.05 to
It is 100μ, preferably 0.1 to 50μ, and more preferably 0.2 to 20μ. If the particle size is less than 0.05 μ, it is difficult to make the particles porous. On the other hand, when it is 100 μm or more, the unevenness of the surface of the printing object becomes large, and the smoothness of the printing surface is significantly impaired, which is contrary to the object of the present invention.

Whether or not the porous resin particles have been made porous can be externally known by using an electron microscope or the like. The degree of porosity can be determined by measuring the specific surface area with a mercury porosimeter. You can check. See J
It can also be confirmed by measuring the oil absorption amount described in IS K-5101. This utilizes the fact that it absorbs more oil than non-porous particles of the same component and the same particle size due to the capillarity of the pores existing on the surface and inside the particles.

By containing such a porous resin particle in the sheet to be printed or coating it on the surface of the sheet, the surface portion of the sheet is made more finely porous.
When the surface portion is made finely porous, the amount of water absorption / oil absorption per unit volume in the vicinity of the surface of the sheet increases. If the ink ejected from the nozzle adheres to the surface portion with improved absorption capacity, it is immediately absorbed, but since it has sufficient absorption capacity, the ink does not penetrate deeply and dries near the surface of the sheet. It will be fixed. on the other hand,
Even if it does not contain porous resin particles, for example, uncoated paper base paper is also porous. But in this case, the "hole"
Is the gap between the fibers of the paper, and the shape and size are different from the “pores” of the porous resin particles. Also, the absorption capacity per unit volume of the fibers themselves is Low compared to quality particles. Therefore, in the case of paper base paper or the like, the adhered ink permeates through the gaps between the fibers, which causes the above-described decrease in contrast and bleeding.

In addition, when inorganic porous particles such as colloidal silica are used, they are generally hard and therefore easily damage the running system of the printing device, which causes problems in high-speed printing and long-term use. In addition, since the weight of the inorganic particles is much larger than that of the resin particles, the weight of the sheet to be printed using the inorganic particles becomes large, and if the weight of the sheet to be printed using the resin particles is the same as that of the sheet to be printed. , The amount of inorganic particles used is reduced, and the effect is reduced. In addition, the components that fix the pigments and dyes of the ink have less affinity with the inorganic particles than the resin particles, so even if the ink is once absorbed by the inorganic particles, the capillary phenomenon occurs before the ink is dried and fixed. Diffuses and causes a decrease in contrast and bleeding.

As described above, when the porous resin particles are contained in the sheet to be printed, the ink absorbing ability of the sheet is remarkably improved, and the effect is superior to the inorganic particles. Examples of the sheet base material containing the porous resin particles include, but are not particularly limited to, pulp and pulp-based paper, recycled paper, synthetic paper, and films based on polyolefin and polyester. In addition, if necessary, latex may be impregnated into these sheets, a waterproofing agent or a paper strengthening agent may be internally added, size press may be performed, and a fluorescent agent or a white pigment may be added to the sheet. Processing similar to
There is no particular limitation as long as the added value is increased.

The method for incorporating the porous resin particles into the sheet to be printed is to coat the sheet base material with a binder, add it internally to the sheet base material, or form / film with the molten sheet base material. Although it is not particularly limited, it is preferable to coat paper with a binder as a sheet base material on the surface thereof. When the sheet base material is coated, the type and amount of the binder and other additives such as other pigments to be used and the coating method may be the same as those for general coated paper, and there is no particular limitation. When it is contained in the sheet base material by internal addition or molding, it may be the same as the conventional method of containing the resin particles, and the additive or the like used in combination may be similarly used.

The larger the amount of the porous particles contained in the sheet base material, the greater the effect of oil absorption. However,
It is preferable to add 5 to 80 parts by weight, preferably 10 to 50 parts by weight, based on 100 parts by weight of the entire sheet substrate. If the content is less than 5 parts by weight, the effect is small, and if the content is 80 parts by weight or more, the strength of the base material is extremely lowered, which is not practical. However, when coating on a sheet substrate, since the particles are present only in the coating layer, it is not necessary to consider the strength of the substrate, and the number of effective particles existing near the sheet surface increases. So it is more effective. Therefore, in the case of coating, it may be contained in an amount of 1 to 95 parts by weight, preferably 5 to 60 parts by weight, based on the total weight of the coating layer. If the content is less than 1 part by weight, the effect is small, and if the content is 95 parts by weight or more, the strength of the coating layer is extremely reduced, which is not practical. The amount of the coating layer component with respect to the base material to be coated may be the same as that of general coated paper. It is also effective to subject the sheet to be printed containing these porous resin particles to post-treatment such as calendering for improving the smoothness of the surface portion, which is preferable.

[0020]

[Preparation of inkjet recording sheet]

Example-1 Porous resin particles were prepared according to the method disclosed in Polymerization Example-1 of JP-A-5-222108. Water in a separable flask equipped with a stirrer, thermometer and reflux condenser.
500 parts are charged, and the temperature is raised to 80 ° C. while substituting nitrogen for stirring. Keeping the internal temperature at 80 ℃, as a polymerization initiator,
After adding 1.5 parts of potassium persulfate and dissolving, water 7
Parts, styrene 16 to 0.2 parts sodium lauryl sulfate
, 0.3 parts of methacrylic acid, and 0.2 parts of divinylbenzene were added with stirring to prepare an emulsion, which was charged in a separable flask and polymerized for 1 hour to prepare a seed particle emulsion. Next, an emulsion prepared by previously adding 40 parts of water, 0.3 part of sodium lauryl sulfate to 55 parts of methyl methacrylate, 5 parts of butyl acrylate, and 40 parts of methacrylic acid was continuously added over 1 hour. The reaction was carried out, and aging was carried out for 1 hour after the addition was completed.

Subsequently, as a polymerization initiator, an aqueous solution prepared by dissolving 3 parts of ammonium persulfate in 30 parts of water was added, and further 240 parts of water, 1.2 parts of sodium lauryl sulfate, 468 parts of methyl methacrylate, and 120 parts of butyl acrylate. ,
An emulsion prepared by adding 12 parts of methacrylic acid with stirring was continuously added over 1 hour to cause a reaction, and aging was continued for 2 hours after the addition was completed.

After completion of the polymerization, 490 parts of the above emulsion and 78 parts of water were charged into another separable flask equipped with a stirrer, a thermometer, and a reflux condenser, and 8.5 parts of 28% ammonia water was added with stirring. . Next, the internal temperature is raised to 85 ° C., and stirring is continued for 30 minutes as it is. Then, an aqueous solution in which 0.5 part of ammonium persulfate is dissolved in 5 parts of water is added as a polymerization initiator, and further 120 parts of water and lauryl are preliminarily added. An emulsion prepared by adding 297 parts of styrene and 3 parts of acrylonitrile to 0.6 part of sodium sulfate with stirring is continuously added over 90 minutes to react, and aging is continued for 90 minutes after the addition is completed. went.

The obtained emulsion has a nonvolatile content of 40%.
And was a particle having a through hole and a diameter of 0.50 μm. Regarding the produced particle powder, JIS K-5
The oil absorption was measured according to 101. The sample powder was dried at 50 ° C. for 24 hours and then pulverized in a mortar.
A filter cloth of # 150 mesh was used. The result was 84 oil absorption. An inkjet recording sheet was produced using the porous resin particle emulsion. First, a coating liquid was prepared which was an aqueous solution / dispersion liquid having a solid content of 40%, which was composed of the following components. Porous resin particle emulsion 125 parts (solid amount 50 parts) UW-90 (kaolin clay) 50 parts [EMC Co., Ltd., trade name] Poise 530 (sodium polyacrylate pigment dispersant) [Kao Co., Ltd.] , Trade name] 1 part (solid content 0.4 part) MS-3600 (phosphoric acid esterified starch) [Nippon Shokuhin Kogyo Co., Ltd., trade name] 5 parts Polylac 780A-2 (SBR latex) [Mitsui Toatsu Chemicals Co., Ltd., trade name] 24 parts (solid amount 12 parts) The coating liquid is prepared by adding a sodium polyacrylate pigment dispersant (Poise 530 having a solid content of 40%) to water and using a Cowles mixer. Kaolin clay UW-90 is well dispersed,
The above emulsion is added to this as porous resin particles. As the binder, phosphoric acid esterified starch MS-3
600 and polylac 780A-2 having a solid content of 50% were added to obtain a coating liquid. Commercially available high-quality paper (basis weight approximately 5
0 g / m ² ) with an applicator so that the dry coating amount is about 15 g / m ² , and the drying conditions are 120 ° C. and 2
What was dried in 0 seconds was rolled with a calender roll at a roll temperature of 60 ° C., a linear pressure of 70 kg / cm, and a speed of 10 m / min.
Under the conditions of 2 times to obtain an inkjet recording sheet,
Performance evaluation was performed as Example-1.

Example-2 Porous resin particles were prepared according to the method disclosed in Example-1 of JP-A-2-70741. Water 1 in a separable flask equipped with stirrer, thermometer and reflux condenser.
00 parts, 0.05 parts of sodium lauryl sulfate were charged,
The temperature is raised to 70 ° C. while substituting nitrogen for stirring. The internal temperature was kept at 70 ° C., and potassium persulfate of 0.
After 8 parts were added and dissolved, a mixed monomer of 4 parts of methyl methacrylate, 4 parts of butyl acrylate and 2 parts of methacrylic acid was charged and reacted for 2 hours. After the completion of the reaction, 1.6 parts (about 1.1 molar equivalent) of 28% ammonia water is added to the obtained copolymer emulsion, and well stirred to neutralize and swell to obtain seed particles.

Then, an aqueous solution prepared by dissolving 0.5 parts of ammonium persulfate in 5 parts of water was added as a polymerization initiator, and further 50 parts of water, 0.5 parts of sodium lauryl sulfate and 85 parts of styrene and 5 parts of divinylbenzene were previously added. The emulsion prepared by adding under stirring was continuously added and reacted for 4 hours, and aging was carried out for 3 hours after completion of the addition. The obtained emulsion has a solid content of 40% and 0.1 to 0.3 μ.
Average particle diameter of 0.9μ
A fine particle aggregate particle emulsion of was obtained. The oil absorption measured in the same manner as in Example-1 was 82. An ink jet recording sheet produced in the same manner as in Example-1 using this porous resin particle emulsion was evaluated as Example-2.

Comparative Example-1 Muticle SPMM-47BF (manufactured by Mitsui Toatsu Chemicals, Inc., trade name; solid content 47%; particle size 0.5 μ; oil absorption 60) was used as a non-porous polystyrene resin particle emulsion. An inkjet recording sheet produced in the same manner as in Example-1 was used as Comparative Example-1 for performance evaluation.

Comparative Example-2 As the porous inorganic particles, fine powder Mizukasil silicate P-5 was used.
27 (manufactured by Mizusawa Chemical Industry Co., Ltd., trade name; particle size 1.6)
μ; oil absorption 168) was used, and an ink jet recording sheet produced in the same manner as in Example-1 was used as Comparative Example-2 for performance evaluation. Comparative Example-3 An inkjet recording sheet, which was not subjected to coating on the high-quality paper used as the base material and only subjected to the calender treatment, was evaluated as Comparative Example-3.

[Evaluation of Inkjet Recording Sheet] The inkjet recording sheet prepared by the above method was printed with a commercially available inkjet printer (manufactured by Canon Inc., ink is black for the printer), and the following items were evaluated in 5 grades. . Color density was measured with a Macbeth densitometer. The sharpness of the image was visually evaluated by sensory evaluation. Immediately after printing, stack the paper used as the substrate on the print surface immediately after printing, put a weight equivalent to 10 g / cm ² for 1 minute, remove the weight and the paper, and visually check the transfer of the print to the stacked paper. It was sensory evaluated. The color density and the sharpness were evaluated 5 minutes and 1 hour after printing the same sample. The evaluation results are shown in Table 1. It was divided into five stages: excellent "◎", good "○", ordinary "△", "×" that causes problems in use, and "XX" that has serious defects.

[0029]

[Table 1]

[0030]

INDUSTRIAL APPLICABILITY The ink jet recording sheet of the present invention has a higher ink absorption amount per unit volume in the surface portion than conventional ones (paper, film, etc.), so that ink jet printing with higher resolution and higher speed can be achieved. Can handle. Further, as compared with the case where inorganic porous particles are contained, it is possible to provide an ink jet recording sheet that has less change in printing density and sharpness with time, is lightweight, and does not damage a printing device at high speed and long term printing.

[Procedure amendment]

[Submission date] February 15, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be amended] Detailed explanation of the invention

[Correction method] Change

[Correction content]

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention has little blurring or strike-through of characters at the time of printing, enables clear and high-resolution printing, has little change in printing density and sharpness with time, and is capable of printing ink in a printing portion. The present invention relates to a recording sheet for inkjet printing, which dries quickly and is less likely to be stained by undried ink.

[0002]

2. Description of the Related Art In recent years, various techniques for printing and printing characters and images on a substrate such as paper and OHP film have been proposed. Although these techniques are diverse, there are not many printing / printing techniques that are widely used without requiring specialized knowledge and techniques in offices and homes. Examples of popular printing / printing technology include dot impact method used in voucher printers, thermal transfer method used in personal word processors, thermal printing method used in facsimiles, and copy machines. Although there are electrophotographic methods and the like used, the inkjet method has become widespread in most homes and offices in recent years.

The ink jet system is basically a system in which water, oil, or solvent ink droplets are ejected from fine nozzles and adhered to a printing surface such as paper to obtain information as characters or images. Is. As for this inkjet method, various methods that can be classified by the method of generating ink droplets, the method of attaching ink droplets, the type of ink, etc. have been proposed, and many inkjet printers that apply these technologies have been commercialized. Has been done.

The advantages of the ink jet system are (1) there are few restrictions on the shape and type of the printing medium, and no special paper such as thermal paper is required. Further, the consumption of the print medium (ink) is limited to the print section, and the print medium is normally replenished only with the ink, and double-sided printing is possible without using special paper or a device. , Printing cost is low. (2) Quiet with almost no noise during printing, and high-speed printing is possible because the printing surface and the printing device do not mechanically contact each other. (3) The printing device is not large and can be downsized, and the power consumption of the device is small. That is, the method is widely used because of its low cost, quietness, and small size.

However, the disadvantages of the ink jet system are that ink in a liquid state is adhered to a printing medium, and the principle of the system is as follows: (1) Depending on the surface state of the printing medium, bleeding of printing and unevenness of contrast may occur. Likely to happen. (2) When the printed surface is touched immediately after printing, or when printed sheets are overlaid, undried ink adheres and stains the surrounding area. Due to market demands in recent years, the system is also required to have higher speed and higher resolution. In addition, in many cases, such as color printing, inks of a plurality of colors are overlaid and printed.

When the ink jet printing has a higher resolution, the dot size which is the minimum unit of the printing size becomes smaller. This also means that the minimum unit of the amount of ejected ink becomes small. Therefore, when the ink adhering to the printing medium penetrates deep into the printing medium, the amount of pigment / dye in the effective ink near the surface layer of the printing medium decreases, and the printing contrast decreases significantly. Further, when the adhered ink spreads in the lateral direction near the surface layer of the printing medium, it causes bleeding of the printing and lowers the resolution. Furthermore, if the printing target is thin or if the ink penetrates deep into the printing target, the print tends to come out on the back side of the printing target, so-called strike-through easily occurs. Is greatly impaired.

In order to prevent the deterioration of contrast and bleeding, there is a method of smoothing the surface of the printing medium and reducing the pores in the vicinity of the surface layer. However, this method slows the absorption of ink into the printing medium. However, it takes a long time to dry the ink, and an object that touches the printed portion immediately after printing may be soiled or the obtained printing or image information may be damaged. Further, in the case of the inkjet method, it is essential that the viscosity of the ink is low. Therefore, when the absorption of the ink to the printing medium is slow, the ejected ink may splash or the undried ink may flow down. However, this may cause blurring of printing. These things also hinder the speeding up of printing.

Further, in the case of color printing by the ink jet system, a plurality of types of inks are ejected in order, so if the ink absorption amount of the printing object is small, the previously ejected color ink is absorbed by the adhesion object, What is injected later is not absorbed and remains near the surface. Therefore, the color ejected later may be more intensely colored, and the final color may not be as set.

As a means for making the surface of the material to be printed near the surface layer porous, there is a method of incorporating or coating inorganic porous particles such as colloidal silica into the material to be printed. However, the inorganic particles are generally hard and have a problem that the running system of the printing apparatus is easily damaged. Moreover, since the weight of the inorganic particles is much larger than that of the resin particles, the weight of the printing object using the inorganic particles becomes large, and if the same weight as the printing object using the resin particles is used, the inorganic particles are There is a problem that the amount of particles used decreases and the effect decreases.

[0010]

SUMMARY OF THE INVENTION An object of the present invention is to provide an ink jet recording sheet which can be applied to an ink jet system of higher resolution and higher speed.

[0011]

[Means for Solving the Problems] As a result of extensive studies to solve the above problems, the porous resin particles are excellent in water absorption and oil absorption, and are lighter and softer than the inorganic porous particles. The present invention has been completed. That is,
The present invention is an ink jet recording sheet characterized by containing porous resin particles.

In the present invention, the porous resin particles may be those obtained by an emulsion polymerization method, a suspension polymerization method, a dispersion polymerization method or another polymerization method, and a lumpy porous resin is pulverized. Anything is fine. The resin component is not particularly limited, for example, polyester resin, methacrylic resin, polycarbonate resin, styrene copolymer resin, vinyl chloride resin, polypropylene resin and blends thereof. Further, the means for making the resin particles porous or for obtaining the resin made porous is not particularly limited. Among them, porous resin particles obtained by emulsion polymerization are preferable, and for example, fine particle aggregate emulsion particles disclosed in JP-A-2-70741 are preferable. Further, the structure described in Japanese Patent Laid-Open No. 5-222108 by the inventors of the present invention has one or more through holes connecting the surface layer of the particles to the inside thereof, and the particle diameter is 0.1 to 5.0 μm. It is more preferable that the emulsion particles have a multilayer structure.

The particle size of the porous resin particles is from 0.05 to
It is 100μ, preferably 0.1 to 50μ, and more preferably 0.2 to 20μ. If the particle size is less than 0.05 μ, it is difficult to make the particles porous. On the other hand, when it is 100 μm or more, the unevenness of the surface of the printing object becomes large, and the smoothness of the printing surface is significantly impaired, which is contrary to the object of the present invention.

Whether or not the porous resin particles have been made porous can be externally known by using an electron microscope or the like. The degree of porosity can be determined by measuring the specific surface area with a mercury porosimeter. You can check. See J
It can also be confirmed by measuring the oil absorption amount described in IS K-5101. This utilizes the fact that it absorbs more oil than non-porous particles of the same component and the same particle size due to the capillarity of the pores existing on the surface and inside the particles.

On the other hand, even if the porous resin particles are not contained,
For example, uncoated paper base paper is also porous. However, in this case, the "pores" are the gaps between the fibers of the paper, and the shape and size are different from the "pores" of the porous resin particles, and the absorption capacity per unit volume of the fibers themselves is , Lower than porous resin particles and inorganic porous particles.
Therefore, in the case of paper base paper or the like, the adhered ink permeates through the gaps between the fibers, which causes the above-described decrease in contrast, bleeding, and strikethrough.

In addition, when inorganic porous particles such as colloidal silica are used, they are generally hard and therefore easily damage the running system of the printing device, which causes problems in high-speed printing and long-term use. In addition, since the specific gravity of the inorganic particles is much larger than that of the resin particles, the weight of the printing object sheet using the inorganic particles becomes large, and if the same weight as the printing object sheet using the resin particles is used, , The amount of inorganic particles used is reduced, and the effect is reduced. In addition, the components that fix the pigments and dyes of the ink have less affinity with the inorganic particles than the resin particles, so even if the ink is once absorbed by the inorganic particles, the capillary phenomenon occurs before the ink is dried and fixed. Diffuses and causes contrast deterioration, bleeding, and strikethrough.

As described above, when the porous resin particles are contained in the sheet to be printed, the ink absorbing ability of the sheet is remarkably improved, and the effect is superior to the inorganic particles. Examples of the sheet base material containing the porous resin particles include, but are not particularly limited to, pulp and pulp-based paper, recycled paper, synthetic paper, and films based on polyolefin and polyester. In addition, if necessary, latex may be impregnated into these sheets, a waterproofing agent or a paper strengthening agent may be internally added, size press may be performed, and a fluorescent agent or a white pigment may be added to the sheet. Processing similar to
There is no particular limitation as long as the added value is increased.

The method for incorporating the porous resin particles into the sheet to be printed is to coat the sheet base material with a binder, add it internally to the sheet base material, or form / film with the molten sheet base material. Although it is not particularly limited, it is preferable to coat paper with a binder as a sheet base material on the surface thereof. When the sheet base material is coated, the type and amount of the binder and other additives such as other pigments to be used and the coating method may be the same as those for general coated paper, and there is no particular limitation. When it is contained in the sheet base material by internal addition or molding, it may be the same as the conventional method of containing the resin particles, and the additive or the like used in combination may be similarly used. The thickness of the sheet base material is not particularly limited as long as it conforms to the specifications of the printing device, but is 1 mm to 1
μm is preferable, and 0.1 to 10 μm is more preferable.

The larger the amount of the porous particles contained in the sheet base material, the greater the effect of oil absorption. However,
It is preferable to add 5 to 80 parts by weight, preferably 10 to 50 parts by weight, based on 100 parts of the entire sheet base material. If the content is less than 5 parts by weight, the effect is small, and if the content is 80 parts by weight or more, the strength of the base material is extremely lowered, which is not practical. However,
When coating on a sheet substrate, since the particles are present only in the coating layer, it is not necessary to consider the strength of the substrate,
It is more effective because the number of effective particles existing near the sheet surface is increased. Therefore, in the case of coating, 1 to 95 parts by weight, preferably 5 to 6 parts by weight based on 100 parts by weight of the entire coating layer is applied.
It may be contained in an amount of 0 parts by weight. If the content is less than 1 part by weight, the effect is small, and if the content is 95 parts by weight or more, the strength of the coating layer is extremely reduced, which is not practical. The thickness or coating weight of the coating layer may be the same as that of general coated paper, but
100 μ or 1 to 50 g / m ² is preferable.

[0020]

EXAMPLES Specific examples of the present invention will be described below. All parts and% are parts by weight and% by weight. [Preparation of Inkjet Recording Sheet] Example-1 Porous resin particles were prepared according to the method disclosed in Polymerization Example-1 of JP-A-5-222108. Water in a separable flask equipped with a stirrer, thermometer and reflux condenser.
500 parts are charged, and the temperature is raised to 80 ° C. while substituting nitrogen for stirring. Keeping the internal temperature at 80 ℃, as a polymerization initiator,
After adding 1.5 parts of potassium persulfate and dissolving, water 7
Parts, styrene 16 to 0.2 parts sodium lauryl sulfate
Parts, 0.3 parts of methacrylic acid, and 0.2 parts of divinylbenzene were added with stirring to prepare an emulsion, which was charged in a separable flask and polymerized for 1 hour to prepare a seed particle emulsion. Next, an emulsion prepared by previously adding 40 parts of water, 0.3 part of sodium lauryl sulfate to 55 parts of methyl methacrylate, 5 parts of butyl acrylate, and 40 parts of methacrylic acid was continuously added over 1 hour. The reaction was carried out, and aging was carried out for 1 hour after the addition was completed.

Subsequently, as a polymerization initiator, an aqueous solution prepared by dissolving 3 parts of ammonium persulfate in 30 parts of water was added, and further 240 parts of water, 1.2 parts of sodium lauryl sulfate, 468 parts of methyl methacrylate, and 120 parts of butyl acrylate. ,
An emulsion prepared by adding 12 parts of methacrylic acid with stirring was continuously added over 1 hour to cause a reaction, and aging was continued for 2 hours after the addition was completed.

After completion of the polymerization, 490 parts of the above emulsion and 78 parts of water were charged into another separable flask equipped with a stirrer, a thermometer, and a reflux condenser, and 8.5 parts of 28% ammonia water was added with stirring. . Next, the internal temperature is raised to 85 ° C., and stirring is continued for 30 minutes as it is. Then, an aqueous solution in which 0.5 part of ammonium persulfate is dissolved in 5 parts of water is added as a polymerization initiator, and further 120 parts of water and lauryl are preliminarily added. An emulsion prepared by adding 297 parts of styrene and 3 parts of acrylonitrile to 0.6 part of sodium sulfate with stirring is continuously added over 90 minutes to react, and aging is continued for 90 minutes after the addition is completed. went.

Example-2 2500 parts of water was charged into a separable flask equipped with a stirrer, a thermometer and a reflux condenser, and the temperature was raised to 80 ° C. while substituting nitrogen for stirring. Keep the internal temperature at 80 ° C, add 1.5 parts of potassium persulfate as a polymerization initiator, and after dissolution,
An emulsion prepared by previously adding 7 parts of water, 0.2 part of sodium lauryl sulfate to 16 parts of styrene, 0.3 part of methacrylic acid and 0.2 part of divinylbenzene was charged in a separable flask and polymerized for 1 hour. Then, a seed particle emulsion was prepared. Next, an emulsion prepared by previously adding 45 parts of methyl methacrylate, 5 parts of butyl acrylate, and 50 parts of methacrylic acid to 40 parts of water and 0.3 part of sodium lauryl sulfate under stirring was continuously added over 1 hour. To react,
After completion of the addition, aging was carried out for 1 hour. Subsequently, an aqueous solution in which 1.5 parts of ammonium persulfate was dissolved in 15 parts of water was added as a polymerization initiator, and further 160 parts of water, 0.8 parts of sodium lauryl sulfate, 312 parts of methyl methacrylate, 80 parts of butyl acrylate, An emulsion prepared by adding 8 parts of methacrylic acid with stirring was continuously added over 2 hours to cause a reaction, and aging was continued for 2 hours after the addition was completed.

After completion of the polymerization, 625 parts of the above emulsion (equivalent to 100 parts of solid content) and 279 parts of water were charged into another separable flask equipped with a stirrer, a thermometer and a reflux condenser, and 7 parts of 28% ammonia water was added. Add with stirring.
Next, the internal temperature is raised to 85 ° C., and stirring is continued for 30 minutes as it is. Then, an aqueous solution in which 0.5 part of ammonium persulfate is dissolved in 5 parts of water as a polymerization initiator is added, and water 120
Parts, 0.6 parts of sodium lauryl sulfate and styrene 297
And acrylonitrile (3 parts) were added under stirring, and the emulsion prepared was continuously added over 90 minutes to cause a reaction, and after the addition was completed, aging was performed for 90 minutes. The obtained emulsion had a nonvolatile content of 30% and was a particle having a through hole and a diameter of 0.7 μm. The oil absorption measured in the same manner as in Example-1 was 150. Using this porous resin particle emulsion, an inkjet recording sheet produced in the same manner as in Example-1 was evaluated as Example-2 for performance evaluation.

Example-3 Porous resin particles were prepared according to the method disclosed in Example-1 of JP-A-2-70741. Water 1 in a separable flask equipped with stirrer, thermometer and reflux condenser.
00 parts, 0.05 parts of sodium lauryl sulfate were charged,
The temperature is raised to 70 ° C. while substituting nitrogen for stirring. The internal temperature was kept at 70 ° C., and potassium persulfate of 0.
After 8 parts were added and dissolved, a mixed monomer of 4 parts of methyl methacrylate, 4 parts of butyl acrylate and 2 parts of methacrylic acid was charged and reacted for 2 hours. After the completion of the reaction, 1.6 parts (about 1.1 molar equivalent) of 28% ammonia water is added to the obtained copolymer emulsion, and well stirred to neutralize and swell to obtain seed particles. An ink jet recording sheet produced in the same manner as in Example-1 using this porous resin particle emulsion was evaluated as Example-2.

Comparative Example-1 Muticle PP100P (Mitsui Toatsu Chemicals, Inc.) was used as a non-porous polystyrene resin particle emulsion.
Product name: Solid content 43%; Particle size 0.6μ; Oil absorption 4
Using 5), the ink jet recording sheet produced in the same manner as in Example-1 was evaluated as Comparative Example-1.

Comparative Example-2 As the porous inorganic particles, fine powder Mizukasil silicate P-5 was used.
27 (manufactured by Mizusawa Chemical Industry Co., Ltd., trade name; particle size 1.6)
μ; oil absorption 168) was used, and an ink jet recording sheet produced in the same manner as in Example-1 was used as Comparative Example-2 for performance evaluation. Comparative Example-3 An inkjet recording sheet, which was not subjected to coating on the high-quality paper used as the base material and only subjected to the calender treatment, was evaluated as Comparative Example-3.

Color density was measured with a Macbeth densitometer. The strike-through was evaluated by measuring the color density on the back side of the printed paper. The sharpness of the image was visually evaluated by sensory evaluation. Immediately after printing, stack the paper used as the substrate on the printed surface immediately after printing, 10 g /
After applying a weight corresponding to cm ² for 1 minute, the weight and the paper were removed, and the transfer of the print to the overlapped paper was visually sensory evaluated. The color density and the sharpness were evaluated 5 minutes and 1 hour after printing the same sample. The evaluation results are shown in Table 1. It was divided into five stages: excellent "◎", good "○", ordinary "△", "×" that causes problems in use, and "XX" that has serious defects.

[0029]

[Table 1]

[0030]

EFFECTS OF THE INVENTION The ink jet recording sheet of the present invention has a higher ink absorption amount per unit volume in the surface portion than conventional ones (paper, film, etc.). It can be used for high-speed inkjet printing. Further, as compared with the case where inorganic porous particles are contained, it is possible to provide an ink jet recording sheet that has less change in printing density and sharpness with time, is lightweight, and does not damage a printing device at high speed and long term printing.

Claims (3)

[Claims] 1. An ink jet recording sheet containing porous resin particles. 2. A coating layer containing porous resin particles,
The inkjet recording sheet according to claim 1, wherein the inkjet recording sheet is formed of a base material that supports the coating layer. 3. The structure when dried has at least one through hole connecting the surface layer of the particle to the inside thereof, and the particle diameter is 0.15 to 0.15.
The inkjet recording sheet according to claim 1, wherein the coating layer contains multi-layered emulsion particles having a size of 5.0 μm.