JP4742530B2 - Recording paper and image recording method using the same - Google Patents

Description

  The present invention relates to a recording paper and an image recording method using an ink jet recording method or an electrophotographic recording method using the recording paper.

  The ink jet recording system has been attracting widespread attention because it is easy to color, has low energy consumption, low noise during recording, and can reduce the manufacturing cost of the printer. Furthermore, in recent years, high image quality, high speed, and high reliability have progressed, but there are many opportunities to print on plain paper, and it is extremely important to improve the printability of plain paper.

  In order to improve black character image quality and mixed color bleeding, conventional ink-jet printers use black ink, ink that has low permeability to recording paper that uses pigment as a color material (hereinafter sometimes simply referred to as “paper”). The mainstream is one that uses ink that has a high permeability to recording paper using a dye as a coloring material.

  Therefore, in particular, when printing images with high recording density using color inks that have increased permeability to the paper, curl and undulation occur greatly on the recording paper immediately after printing, and paper jams and images in the printer The rubbing of the part will occur. In addition, when performing double-sided printing, the time required for the curling generated on the recording paper immediately after printing to be relaxed and the time for the ink to dry are required, resulting in a drastic decrease in print productivity. Further, when an image having a high recording density is printed, there is a problem that curling and waviness that occur after standing and drying are large, and high image quality, curling suppression, and wavy suppression cannot be achieved at a high level.

  In order to improve the curling and undulation after the printing, a method of reducing the curling and undulation by humidifying the paper sheet once and reducing the stress of the paper (for example, refer to Patent Document 1), and the CD direction of the paper A method of reducing curling and undulation by regulating the underwater elongation of the paper (for example, see Patent Document 2), curling the underwater elongation rate in the MD direction and CD direction of the paper by 1.3 times or less, A method for reducing undulation (for example, see Patent Document 3), a method for reducing curling and undulation by setting the underwater elongation in the operation direction of the ink ejection portion to 2.0% or less (for example, see Patent Document 4), A method of reducing curling and undulation by reducing the elongation in water in the CD direction to 1.8% or less (see, for example, Patent Document 5), the pigment contained in the support is 5 to 35% by mass, and a recording sheet ( The internal bond strength of the recording paper is 1 How to reduce the waviness of the coat type ink jet recording sheet by the 0~455g / cm (e.g., see Patent Document 6) have been proposed.

  In the methods described in Patent Documents 1 to 5, it has been reported that curling and undulation are reduced. However, ink that has a high permeability to the inside of the recording paper is used, and the amount of ink discharged is large or the printing speed. However, when the amount of ink ejected per unit time increases rapidly, curling increases, and the document cannot be used.

  In the method described in Patent Document 6, an attempt is made to reduce waviness after printing by keeping the internal bond strength of a recording sheet provided with an ink receiving layer within a certain range. It is not possible to obtain a sufficient effect on curling, undulations, and undulations simply by prescribing. In particular, when ink that has high penetration into the recording paper is used and the amount of ink discharged is large, that is, when the printing speed is high and the amount of ink discharged per unit time is large, the wave is large and used as a document. I can't stand it.

  In addition, in order to improve curling and undulation after standing drying, the irreversible shrinkage rate between the MD direction and the CD direction when the relative humidity of the leaving environment is changed is within a certain range, and thus occurs after standing drying. A method for reducing curling and undulation has been proposed (see, for example, Patent Document 7). However, if the ink penetration of the recording paper is not suppressed, the fiber that penetrates into the recording paper and shrinks after drying as a whole when the ink having a high permeability is used and the ink discharge amount is large. The absolute amount of is increased and the curl after drying is increased, so that a sufficient effect cannot be obtained.

On the other hand, in order to improve the image quality, a method has been proposed in which an ester nonionic surfactant having an HLB of 11 or more is included in the ink receiving layer (see, for example, Patent Document 8), but an ester nonionic surfactant having an HLB of 11 or more is proposed. Since the agent is highly hydrophilic, the hydrophilic group of the base material (base paper) cannot be covered with the hydrophobic group of the surfactant, and when the amount of ink is large, the recording paper is easily deformed, so the curl is large and used as a document I can't stand it.
In addition, a method has been proposed in which a surface active agent having an HLB in the range of 3 to 12 is included in the ink receiving layer on the film surface in order to improve the image quality (see, for example, Patent Document 9). Even if it is applied, the amount added is as low as less than 0.1% by mass, the hydrophilic group of the base material cannot be covered with the hydrophobic group of the surfactant, and the amount of ink discharged is particularly quick to penetrate into the recording paper When there is a large amount of ink, that is, when the printing speed is fast and the amount of ink ejected per unit time is large, the wave is so large that it cannot be used as a document.

In order to prevent curling, a method of size-pressing dry oxidized starch has been proposed (see, for example, Patent Document 10). However, when a large amount of ink is printed, this technique alone can prevent water in the ink. The base material stretches greatly, curls increase, and it cannot be used as a document.
Furthermore, an ink receiving layer containing silanol-modified polyvinyl alcohol (PVA), 11 to 20% by mass of a nonionic surfactant, and synthetic amorphous silica as a filler has been proposed to improve image quality in the ink jet recording system. (For example, refer to Patent Document 11) In this method, there is no description of the HLB of the surfactant, and since the HLB of the surfactant used in the examples is 14, the hydrophilicity of the surfactant is low. When applied to paper made of cellulose pulp as a raw material, the hydrophilic group of the base material cannot be increased by the hydrophobic group of the surfactant. Is large, curl is large, can not be used as a document.

In addition, in printing paper, a method including a bulk softener of HLB 6 or less has been proposed for improving bulk bulk and flexibility. However, surfactants of HLB 6 or less, particularly HLB 4 or less, have poor dispersibility, and are not contained in the substrate. The hydrophilic group cannot be covered with the hydrophobic group of the surfactant, and the absolute amount of the fiber that expands and contracts increases, so that the curl becomes large and a sufficient effect cannot be obtained (see, for example, Patent Document 12).
JP-A-3-38375 JP-A-3-38376 Japanese Patent Laid-Open No. 3-199081 JP 7-276786 A Japanese Patent Laid-Open No. 10-46498 Japanese Patent No. 3172298 Japanese Patent No. 3127114 Japanese Patent Laid-Open No. 10-278409 Japanese Patent Laid-Open No. 62-144986 JP 2002-348798 A Japanese Patent Laid-Open No. 11-115304 JP 2002-155494 A

The object of the present invention is to solve the above-mentioned problems of the prior art.
That is, the present invention is capable of double-sided printing by suppressing curling and undulation that occurs immediately after printing when printing by an inkjet recording method, and can suppress curling and undulation that occurs after standing drying, In addition, the unevenness of the image is improved, and even when printing is performed by an electrophotographic method, there is no transfer failure, and double-sided printing is possible by suppressing curling and undulation that occurs immediately after printing. It is an object of the present invention to provide a recording paper that can be used for both an ink jet recording method and an electrophotographic recording method, and an image recording method using the same, which can suppress curling and undulation.

The inventors of the present invention have intensively studied a method of suppressing curling that occurs immediately after printing on plain paper, imparts double-sided printing suitability by improving waviness, and further suppresses curling that occurs after standing drying.
As a result, the present inventors have confirmed that the curl and undulation that occurs immediately after printing is caused by the rapid elongation of the fiber layer that has absorbed water in the water-based ink. In addition, curling and undulation that occurs after standing drying occurs due to shrinkage due to dehumidification of the fiber layer that has absorbed the ink, and further, ink permeation in a minute time in the thickness direction of the paper is quick and ink permeation deepens. As a result, it was confirmed that curling and undulation after standing drying increased.

  Based on these results, the present inventors have eagerly studied the stretching / transmitting property of the fiber layer that has absorbed the ink due to water absorption and desorption. As a result, it can be seen that the stretch and transmission properties due to moisture absorption and desorption are closely related to the expansion and contraction rate of the paper. It has been found that curling and undulation that occurs later can be reduced. In order to reduce the stretch rate, the presence of a surfactant having a certain range of HLB in the paper inhibits the formation of hydrogen bonds, thereby reducing the stretch rate, thereby reducing the curl and wave. I found.

  Furthermore, when the surface sizing agent, which is an essential component of the paper, is treated, the dimensional change of the surfactant is particularly increased by containing 5% by mass or more of a hydrophobic surface sizing agent having a contact angle with water of a certain level or more. It has been found that the surface sizing agent is less likely to inhibit the reduction effect, and as a result, it is possible to further reduce curling that occurs immediately after printing, ripples and curls that occur after standing drying, and ripples.

  Also, sincerity studies were made on the applicability of electrophotographic recording and inkjet recording, and when a surfactant was treated to reduce curl on a base paper with a certain degree of size, depending on the type of surfactant, an electrophotographic method It was confirmed that image transfer failure may occur in

  From the above, the present inventors have paid attention to the structure of the surfactant and have intensively studied the transferability of various surfactants and electrophotography. As a result, it is clear that there is a deep relationship between the intramolecular arrangement of hydrophilic groups in the surfactant and poor image transfer in electrophotography, and the hydrophilic groups of the surfactant are present dispersed in the molecule. By using a nonionic surfactant, image transfer failure does not occur in the electrophotographic method, and curling can be reduced even when recording by the ink jet method, and the compatibility of the electrophotographic method and the ink jet method has been confirmed. . In particular, when the surfactant and the surface sizing agent are combined, the dispersion of the surfactant in the paper becomes uniform, and the image transfer effect in the electrophotographic system due to the structure of the surfactant is further improved. The inventors have found that the present invention has an unprecedented effect and have completed the present invention.

  Furthermore, by using polyvinyl alcohol as a surface sizing agent having a contact angle with water in the range of 40 to 75 degrees, and further reducing the polymerization degree, the dispersibility of the surfactant is improved, and the electrophotographic system It was found that the image transfer effect in the image and the image unevenness in the ink jet method can be further improved. In this case, by defining the degree of saponification of the polyvinyl alcohol and making it more hydrophobic, it is possible to significantly reduce the curl in the inkjet while improving the image transfer effect in the electrophotographic system.

  In addition, the penetrability of the surface sizing liquid was also examined, and intensive studies were conducted on the degree of squeecht sizing of the paper to which the surface sizing liquid containing a nonionic surfactant was applied. As a result, it has been found that the degree of size and the problems in various image output methods are closely related. If the Steecht sizing degree exceeds 30 seconds, the surfactant is not uniformly present on the paper, the curling reduction effect is lowered, and the electrical characteristics are locally changed, resulting in uneven image transfer. Further, if the Steecht sizing degree is less than 1 second, the sizing property is low, and in the ink jet recording method, bleeding, feathering, and back-slip are extremely deteriorated. Therefore, curling can be reduced in the ink jet method by setting the steecht sizing degree to 1 to 30 seconds, and image quality problems such as feathering and back-slip do not occur, and further, image transfer defects in the electrophotographic method do not occur. It was confirmed.

  In addition, the formation, which is an indicator of the unevenness of the presence of fibers on the paper, was also examined, and the relationship between the range of the formation index, the occurrence of curl in the ink jet system, and the image transfer in the electrophotographic system was investigated. As a result, it was found that the formation index and the problems in various image output methods are closely related. Specifically, when the formation index is less than 10, uneven presence of the surfactant is likely to occur from uneven formation, and uneven image transfer in the electrophotographic system is likely to occur. In addition, when the formation index exceeds 50, it may be necessary to strengthen the beating of the paper in order to ensure its homogeneity. When this method is used, the curl in the ink jet system will increase. confirmed.

  In addition, in the ink jet recording method, a nonionic surface activity added for curling reduction can be obtained by allowing a cationic material (polyvalent metal salt, cationic resin) that is ionic opposite to the ink or ink dispersant to be present on the paper. It has been found that the color developability which is lowered by the agent can be improved. Further, in order to ensure image transferability in the electrophotographic system, the electrical resistance characteristic of the paper is important. In particular, in the present invention, since a surfactant or a cationic material that may change electrical characteristics is added, the range for securing image transferability in an electrophotographic system is studied, and a stable image can be obtained. As a result, the inventors have found a range in which the image can be transferred, and have completed a recording paper that can be used for both the electrophotographic system and the inkjet system.

That is, the present invention
<1> At least the surface of the base material made from cellulose pulp contains an ester nonionic surfactant as a surface sizing agent and a nonionic surfactant having an HLB in the range of 6 to 13, and the ester nonionic surfactant Is a range of 1 to 100 parts by mass with respect to 100 parts by mass of the surface sizing agent, and the surface sizing agent having a contact angle with water of 40 to 75 degrees has a saponification degree of 98 or more, or by a polyvinyl alcohol is less than 35 or more 80 surface sizing solution containing 5 wt% or more of the total surface size of the polyvinyl alcohol, Ri Na is surface treated, the layer of ink absorption on the surface-treated said surface This is a recording paper on which an image is recorded on the surface .

<2> The HLB of the ester nonionic surfactant is 6 or more and less than 11 , and the applied amount of the ester nonionic surfactant after the surface treatment is in the range of 0.02 to 1.0 g / m ² . The recording paper according to <1>, wherein the Steecht sizing degree is in a range of 1 to 30 seconds in terms of basis weight of 70 g / m ² .

<3> The concentration of a component containing the surface sizing agent and the ester nonionic surfactant in the surface sizing liquid is in the range of 3 to 7% by mass, according to <1> or <2> Recording paper.
<4> The recording paper according to any one of < 1 > to <3>, wherein the polymerization degree of the polyvinyl alcohol is in a range of 100 to 1500.

<5> An ink jet recording image recording method for discharging ink droplets onto a recording paper and recording an image on the surface of the recording paper,
An image recording method according to claim 1, wherein the recording sheet is the recording sheet according to any one of <1> to <4> .

<6> A charging step for charging the surface of the electrostatic latent image carrier, an exposure step for exposing the surface of the electrostatic latent image carrier to form an electrostatic latent image, and a surface formed on the surface of the electrostatic latent image carrier. Developing the electrostatic latent image using an electrostatic latent image developer to form a toner image, transferring the toner image to the surface of the recording paper, and fixing the toner image on the surface of the recording paper An image recording method according to any one of <1> to <4> , wherein the recording paper is a recording paper according to any one of <1> to <4>. It is.

  According to the present invention, when printing is performed by an ink jet recording system, double-sided printing is possible by improving the image quality of a document and suppressing curling and undulation that occurs immediately after printing. To provide a recording paper that does not cause image transfer failure even when an image is formed by an electrophotographic method and can be used for both an ink jet recording method and an electrophotographic method, and an image recording method using the same. Can do.

Hereinafter, the present invention will be described in detail by roughly dividing it into a recording sheet and an image recording method.
<Recording paper>
Recording paper of the invention, and at least a cellulose pulp surface of the substrate as a raw material, a surface sizing agent and HLB ester nonionic surfactant as nonionic surfactant in the range of 6 to 13, the ester The content of the nonionic surfactant is in the range of 1 to 100 parts by mass with respect to 100 parts by mass of the surface sizing agent, and the surface sizing agent having a contact angle with water of 40 to 75 degrees has a saponification degree of 98 or more. Or a surface treatment with a surface sizing liquid containing at least 5% by mass of the polyvinyl alcohol , wherein the surface treatment is performed. The surface does not have an ink absorbing layer, and an image is recorded on the surface-treated surface .

  When the recording paper of the present invention is printed by the ink jet recording system using this, (1) double-sided printing is possible by suppressing curling and undulation that occurs immediately after printing, and (2) after leaving to dry The generated curling and undulation can be suppressed. Further, (3) it is possible to suppress unevenness in the image portion and improve the density.

  In addition, when printing is performed by an electrophotographic method, (4) curling and undulation after standing drying can be suppressed, and (5) image transfer unevenness can be prevented during image transfer.

On the other hand, the recording paper used in the conventional ink jet recording method and electrophotographic method is not subjected to surface treatment with a surfactant, and even if it has been subjected to surface treatment, an HLB exceeding 13 is used. Since the amount was generally 0.01 g / m ² or less, the curl could not be reduced as in the recording paper of the present invention.

  As described above, in order to reduce curling and undulation of the recording paper after ink printing, it is effective to cover the hydrophilic group in the base material (base paper) with the hydrophobic group of the surfactant. On the other hand, when manufacturing paper, in order to improve the whiteness of the paper, a pigment such as calcium carbonate and a surface sizing agent are often used to keep it on the substrate. When the sizing agent is used at the same time, the surface sizing agent hinders the cellulose coating in the base material of the surfactant, and the sufficient effect of reducing the dimensional change by the surfactant cannot be obtained. There wasn't.

  As a result of intensive studies by the present inventors, the nonionic surfactant having a certain hydrophobicity in the HLB range of 6 to 13 is treated on the paper surface as a surface sizing liquid together with the surface sizing agent instead of alone. It was found that the nonionic surfactant can be surface-treated on the paper uniformly and stably.

  In particular, the surface sizing agent has a higher hydrophobicity than a normal surface sizing agent, a surface sizing agent having a contact angle with water of 40 to 75 degrees, and a nonionic surfactant having a HLB of 6 to 13 In combination with the surface active agent, penetration of the surfactant into the base material is carried out without being hindered by the surface sizing agent, which is more excellent for curling after printing and for curling after standing drying. It has been found that the inhibitory effect is exerted.

  The surface sizing agent needs to have a contact angle with water in the range of 40 to 75 degrees, preferably in the range of 45 to 60 degrees, and more preferably in the range of 50 to 60 degrees.

  When the contact angle with water is less than 40 degrees, the hydrophilicity of the surface sizing agent is increased, the cellulose coating in the base material of the surfactant is inhibited, and a sufficient dimensional change reduction effect by the surfactant cannot be obtained. For this reason, curling and undulation immediately after printing, curling and undulation after standing drying increase. On the other hand, if the contact angle with water exceeds 75 degrees, the water repellency of the paper is increased, the ink permeation becomes slow, and image quality problems such as inter-color bleeding occur in ink jet recording.

A method for measuring the contact angle of the surface sizing agent with water in the present invention will be described with reference to FIG.
FIG. 1 is a schematic diagram showing a state in which a contact angle with water is being measured. As a measurement sample, first, 1 ml of an aqueous solution adjusted so that the surface sizing agent is 10% by mass is dropped on the surface of the preparation 10 and dried in a dryer at 105 ° C. until the water is evaporated. A surface sizing film layer 20 is formed on the surface.

  Next, about 2 μl of distilled water is dropped on the surface sizing film layer 20 on the surface of the preparation 10 by the microsyringe 30, and the contact angle a of the distilled water droplet 40 with the surface sizing film layer 20 after 10 seconds is set. The “contact angle with water” was obtained from the image taken with the CCD camera 50.

  More specifically, the measurement was performed in an environment of 23 ° C. and 50% RH, and the contact angle was measured using a contact angle meter CA-X type manufactured by Kyowa Interface Science Co., Ltd. As a characteristic, when the contact angle increases, the hydrophilicity of the surface sizing agent decreases, and when the contact angle decreases, the hydrophilicity increases.

  In order to obtain a surface sizing agent having a contact angle with water of a certain level or more in the present invention, it is necessary to increase the hydrophobicity of the surface sizing agent. For that purpose, the hydroxyl group which is a hydrophilic group of the surface sizing agent is acetylated. There is a method of chemical modification by substitution, phosphoric esterification, etc., and substitution with a hydrophobic group. There is also a method of improving the crystallization degree of the surface sizing agent, forming a structure in which water is difficult to enter, and improving hydrophobicity.

Specifically, as the surface sizing agent in the present invention, among the surface sizing agents, not the oxidized starch usually used as the surface sizing agent, but acetylated starch having improved hydrophobicity, phosphate esterified starch and the like may be used. preferable. Also, polyvinyl alcohol having a very low saponification degree to leave a hydrophobic group or a very high saponification degree to improve the crystallinity and improve the hydrophobicity is preferably used. Furthermore, a silanol-modified surface sizing agent with improved hydrophobicity may be used.
These may be mixed or used alone, and are not limited to these as long as the “contact angle with water” is in the preferred range.

  On the other hand, the HLB of the nonionic surfactant in the present invention (hereinafter sometimes simply referred to as “surfactant”) needs to be in the range of 6 to 13, and preferably in the range of 6 to 11, More preferably, it is in the range of 7-9.

  When the HLB exceeds 13, the hydrophilicity is high, the cellulose coating effect of the surfactant in the base material is low, and the effect of reducing the dimensional change of the recording paper by the surfactant is low. Later curls and undulations increase. If the HLB is less than 6, the surfactant dispersibility is low, the surfactant cannot be uniformly present on the paper, and the effect of reducing the dimensional change by the surfactant is low. , Curling and undulation after standing and drying increase.

Nonionic surfactants used in the present invention include, for example, polyoxyethylene nonyl phenyl ether, polyoxyethylene octyl phenyl ether, polyoxyethylene dodecyl phenyl ether, polyoxyethylene alkyl ether, polyoxyethylene fatty acid ester, sorbitan fatty acid ester Acetylene glycol ethylene oxide adduct, polyoxyethylene sorbitan fatty acid ester, fatty acid alkylolamide, polyethylene glycol polypropylene glycol block copolymer, glycerin ester polyoxyethylene ether, sorbitol ester polyoxyethylene ether, and the like can be used.
Of these, acetylene glycol ethylene oxide adducts and ester compounds are preferably used.

  Further, the content of the surfactant in the surface sizing solution in the present invention needs to be in the range of 1 to 100 parts by mass with respect to 100 parts by mass of the surface sizing agent. The content of the surfactant is preferably 1 to 20 parts by mass, and more preferably 5 to 10 parts by mass.

  If the amount of the surfactant is less than 1 part by mass, the amount of the surfactant is small, so the cellulose coating effect of the surfactant in the substrate is low, and the effect of reducing the dimensional change of the recording paper by the surfactant is low. The curl and the undulation become larger. On the other hand, when the amount exceeds 100 parts by mass, the amount of the surfactant is too large, and problems such as bleeding between colors may occur.

As described above, when the surfactant is used together with the surface sizing agent, the curling cannot be reduced because the dimensional change reduction effect by the surfactant cannot be obtained unless the surfactant is present in a certain amount or more. In particular, in the conventional ink jet / electrophotographic system paper, even if the surfactant is not added or not, the HLB exceeds 11, and the processing amount is 0.01 g / m ² or less. Since it was general, curl could not be reduced.
In addition, when a surfactant is added, depending on the combination of the type of surfactant and the degree of sizing of the surface, unevenness may occur during image transfer in the electrophotographic method.

As a result of intensive studies by the present inventors, nonionic surfactants having a certain hydrophobicity with an HLB range limited to 6 or more and less than 11 more than the preferred HLB range surfactants are 0.02-1. It has been found that curling can be further reduced by treating the paper so that it is applied in the range of 0.0 g / m ² . Furthermore, by making the surfactant an ester-based nonionic surfactant and setting the paper sizing degree in the range of 1 to 30 seconds, curl is small and unevenness occurs during electrophotographic image transfer. I found out that I would not.

Specifically, a surface size containing 5% by mass or more of a surface sizing agent having a contact angle with water of 40 to 75 degrees using a nonionic surfactant having a certain hydrophobicity HLB of 6 or more and less than 11 Surface treatment is performed with a surface sizing solution combined with an agent such that the surfactant is applied in the range of 0.02 to 1.0 g / m ² .
Here, the term “applied to paper” means that a material having the above characteristics is included in the surface of the recording paper and / or the pulp fiber inside the recording paper when the recording paper is produced.・ It means to combine. Thus, by providing a specific surfactant, it is possible to inhibit bonding between fibers as described above.

Since the surfactant has particularly hydrophobicity by using a nonionic surfactant having an HLB of 6 or more and less than 11, a surface sizing agent having a contact angle with water outside the range of 40 to 75 degrees is used as a mixture. be able to. For this reason, the hydrophobicity of the paper after the surface treatment can be improved.
As described above, when the surface sizing agent having a contact angle with water in the range of 40 to 75 degrees and other mixture is used, the contact angle with water is in the range of 40 to 75 degrees. The surface sizing agent is preferably contained in an amount of 5% by mass or more, more preferably 20% by mass or more.

  Furthermore, in this case, the nonionic surfactant is preferably an ester type. If the surfactant is other than an ester-based nonionic surfactant, the hydroxyl group of the paper can be coated with the surfactant to reduce curling, but the hydrophobic group of the surfactant is exposed on the paper surface and locally. The electrical characteristics may change and image transfer unevenness may occur. On the other hand, in the ester-based nonionic surfactant, since hydrophilic groups are dispersed in the molecule, even when the hydroxyl group of the paper is covered with the surfactant, the hydrophilic group of the surfactant exists on the paper surface, Local electrical characteristics do not change and image transfer unevenness does not occur.

Examples of the ester nonionic surfactant include sorbitan fatty acid ester, mono fatty acid glycerin, polyoxyethylene hydrogenated castor oil fatty acid ester, polyglycerin fatty acid ester, and the like, but are not limited thereto.
Of these, sorbitan fatty acid esters and polyglycerol fatty acid esters are particularly preferred.

The excellent effect of the specific ester-based nonionic surfactant is that the amount of surfactant applied after the treatment is 0.02 to 1.0 g / m ² due to the surface sizing liquid containing the surface sizing agent and the surfactant. It can obtain by making it become the range of. Application amount of the surfactant is more preferably in the range of 0.02~0.8g / m ^2, more preferably in the range of 0.05 to 0.4 g / m ^2.
If the applied amount of the surfactant is less than 0.02 g / m ² , the amount of the surfactant is small, so the cellulose coating effect of the surfactant in the substrate is low, and the dimensional change of the recording paper by the surfactant The reduction effect is reduced, and curling and undulation may be increased. On the other hand, if it exceeds 1.0 g / m ² , the amount of the surfactant may be too large, causing intercolor bleed and causing image quality problems such as back-faced.

Further, as described above, the sizing degree of the paper is preferably in the range of 1 to 30 seconds, more preferably in the range of 2 to 25 seconds, and further preferably in the range of 2 to 20 seconds.
If the Steecht sizing degree exceeds 30 seconds, the surfactant is not uniformly present on the paper, and the curling reduction effect is lowered, and the electrical characteristics are locally changed, and uneven image transfer may occur. is there. If the Steecht sizing degree is less than 1 second, the sizing property is low, and bleeding, feathering, and back-slip may be extremely deteriorated in the ink jet recording method.

In the present invention, the term “steechit sizing” refers to the degree of steecht sizing measured according to JIS P8122, and the basis weight of 70 g / m ² is used as a reference, and for papers having different basis weights, the Lucas-Washburn equation is used. , Steecht sizing degree (seconds) = measured sizing degree sizing x (70 / basis weight of measured paper) The value converted to ² was defined as the schiecht sizing degree in the present invention.

The surface sizing agent having a contact angle with water in the range of 40 to 75 degrees used when the ester-based nonionic surfactant is used is preferably polyvinyl alcohol.
In this case, by reducing the degree of polymerization of the polyvinyl alcohol used, the surfactant can uniformly act on the paper, curling can be reduced, and image transferability in electrophotography can be improved. Further, since the surface of the paper is made uniform, the unevenness of the image in the ink jet can be improved, and the density can be improved.

  Specifically, the polymerization degree of polyvinyl alcohol is preferably in the range of 100 to 1500, more preferably in the range of 200 to 1000, and even more preferably in the range of 200 to 500. When the degree of polymerization is greater than 1500, the film properties of polyvinyl alcohol are improved, and the surfactant may be difficult to disperse uniformly. In addition, when the degree of polymerization is less than 100, the film property of polyvinyl alcohol is extremely lowered, and when paper is output by an electrophotographic printer or the like, paper dust is likely to be generated, and the trouble in the machine accompanying it may occur. is there.

  Further, as the polyvinyl alcohol, those having a very low saponification and leaving a hydrophobic group, or a very high saponification and improving the crystallinity to improve the hydrophobicity are preferable. Specifically, when the degree of saponification is 98 or more, or 35 or more and less than 80, hydrophobicity is improved, curling in the ink jet recording system is reduced, and image transferability in the electrophotographic system can be secured. it can. If the degree of saponification is 80 or more and less than 98, the hydrophilicity of polyvinyl alcohol increases, and curling is less effective in reducing the image transferability in the electrophotographic system in some cases. If the degree of saponification is less than 35, the surface size liquid may not be adjusted because the hydrophobicity is too high to disperse or dissolve in water.

  The recording paper of the present invention uses at least cellulose pulp as a raw material, and the following substrate is surface-treated with a surface sizing liquid containing the surface sizing agent and the nonionic surfactant.

The base material is made of at least cellulose pulp, and may be the following base paper, or plain paper obtained by treating the base paper surface with a pigment or a binder.
The base paper contains cellulose pulp, but known cellulose pulp can be used, specifically, chemical pulp, specifically hardwood bleached kraft pulp, hardwood unbleached kraft pulp, conifer bleached kraft. Pulp, softwood unbleached kraft pulp, hardwood bleached sulfite pulp, hardwood unbleached sulfite pulp, softwood bleached sulfite pulp, softwood unbleached sulfite pulp, wood, and fiber raw materials such as cotton, hemp, and leather The produced pulp can be used.

  In addition, ground wood pulp that mechanically pulped wood and chips, chemimechanical pulp mechanically pulped after soaking chemicals into wood and chips, and pulp with a refiner after digesting the chips until they become slightly soft Thermomechanical pulp that has been made into a material can also be used. These may be used only with virgin pulp, or waste paper pulp may be added as necessary.

  In particular, pulp used in virgin is bleached mainly using ozone / hydrogen peroxide without using chlorine gas and without using chlorine dioxide (Elementary Chlorine Free; ECF) or chlorine compounds. It is preferably one that has been bleached by a method (Total Chlorine Free; TCF).

  In addition, as a raw material of the waste paper pulp, there are unprinted waste paper such as cuts, damaged paper, widened white, special white, medium white, white loss generated in bookbinding, printing factories, cutting offices, etc .; Used high-quality paper, high-quality coated paper, etc .; high-quality printed old paper; water-based ink, oil-based ink, old paper written with pencils, etc .; printed high-quality paper, high-quality coated paper, medium-quality paper, medium-quality coated paper, etc. Newspaper waste paper containing medium; waste paper such as medium-quality paper, medium-quality coated paper, and reprint paper;

  The waste paper pulp used for the base paper used in the present invention is preferably one obtained by treating the waste paper raw material with at least one of ozone bleaching treatment and hydrogen peroxide bleaching treatment. Moreover, in order to obtain a base paper with higher whiteness, it is desirable that the ratio of the used paper pulp obtained by the bleaching treatment is 50% by mass or more and 100% by mass or less. Furthermore, from the viewpoint of resource reuse, it is more preferable that the ratio of the used paper pulp is 70% by mass or more and 100% by mass or less.

  The ozone treatment has an action of decomposing a fluorescent dye or the like usually contained in fine paper, and the hydrogen peroxide treatment has an action of preventing yellowing due to alkali used during deinking treatment. In particular, it is known that the combination of the two not only facilitates deinking of waste paper, but also improves the whiteness of the pulp. Moreover, since it also has an action of decomposing and removing residual chlorine compounds in the pulp, it has a great effect in reducing the content of organic halogen compounds in the waste paper using chlorine bleached pulp.

  Moreover, in order to adjust opacity, whiteness, and surface property, it is preferable to add a filler to the base paper used for this invention. In particular, when it is desired to reduce the amount of halogen in the paper, it is preferable to use a filler that does not contain halogen. Usable fillers are heavy calcium carbonate, light calcium carbonate, chalk, kaolin, calcined clay, talc, calcium sulfate, barium sulfate, titanium dioxide, zinc oxide, zinc sulfide, zinc carbonate, aluminum silicate, calcium silicate, magnesium silicate And white inorganic pigments such as synthetic silica, aluminum hydroxide, alumina, sericite, white carbon, saponite, calcium montmorillonite, sodium montmorillonite, bentonite, and organic pigments such as acrylic plastic pigment, polyethylene, urea resin, etc. Can do. Moreover, when mix | blending waste paper, it is necessary to estimate the ash content contained in a waste paper raw material previously, and to adjust addition amount.

  Furthermore, it is preferable to add an internal sizing agent to the base paper used in the present invention. As the internal sizing agent, a neutral rosin-based sizing agent used for neutral papermaking, alkenyl succinic anhydride (ASA). Alkyl ketene dimer (AKD) and petroleum resin sizing agent can be used.

  In addition, when the surface of the recording paper is adjusted to be cationic, for example, a hydrophilic cationic resin can be treated on the surface as the cationic substance. In order to suppress this, it is preferable that the paper size before applying the cationic resin is 10 seconds or more and less than 60 seconds.

The recording paper of the present invention can be obtained by subjecting the base paper as described above to surface treatment with a surface sizing liquid containing the surface sizing agent and the nonionic surfactant.
The surface sizing liquid is mainly composed of a solvent such as water, and the concentrations of the surface sizing agent and nonionic surfactant contained therein are preferably in the range of 1 to 10% by mass, and 3 to 7% by mass. % Is more preferable.

The amount of treatment with the surface size liquid is preferably in the range of 0.1 to 2.0 g / m ² , more preferably in the range of 1.0 to 2.0 g / m ² per one side of the recording paper. .
When the treatment amount exceeds ² g / m ² , the absolute amount of the surface sizing agent is large, the curling reduction effect of the surfactant is inhibited, and curling and undulation may be increased. If the amount is less than 0.1 g / m ² , the absolute amount of the surface sizing agent is small, and the pigment applied together with the surface sizing agent cannot be fixed on the paper surface. In some cases, a large amount of paper dust is generated, causing trouble to the machine.

  The surface treatment is carried out by applying the surface sizing liquid to the paper by a commonly used application means such as a size press, shim size, gate roll, roll coater, bar coater, air knife coater, rod blade coater, blade coater. be able to. Thereafter, the recording paper of the present invention can be obtained through a drying process.

The basis weight of the recording paper of the present invention is not particularly limited, preferably in a range of 60~128g / m ^2, more preferably in the range of 60 to 100 g / m ^2, of 60 to 90 g / m ² Within the range is more preferable. A higher basis weight is more advantageous for curling and waving, but if the basis weight exceeds 128 g / m ² , the paper becomes too stiff and the paper runnability of the printer may be reduced. On the other hand, if it is lower than 60 g / m ² , it may be difficult to suppress the occurrence of curling and undulation, and it is not preferable from the viewpoint of set-off.

Further, it is preferable to adjust the fiber orientation ratio in the range of 1.0 to 1.55, preferably in the range of 1.0 to 1.45, more preferably in the range of 1.0 to 1.35 during papermaking. . By adjusting in this way, curling of the paper (recording paper) after printing by the inkjet method can be reduced. The fiber orientation ratio is the fiber orientation ratio determined by the ultrasonic propagation velocity method, and the ultrasonic propagation velocity in the MD direction of the paper (traveling direction of the paper machine) is defined as the CD direction of the paper (perpendicular to the traveling direction of the paper machine). ) Divided by the ultrasonic wave propagation velocity, and is represented by the following equation.
Fiber orientation ratio (T / Y ratio) = (MD direction ultrasonic propagation speed) / (CD direction ultrasonic propagation speed)
In addition, the fiber orientation ratio by this ultrasonic propagation velocity method is measured using SonicSheetTester (manufactured by Nomura Corporation).

  The recording paper of the present invention preferably contains a cationic resin and / or a polyvalent metal salt on its surface. When the surface of the recording paper contains a cationic resin or a polyvalent metal salt, when the ink for ink jet contains an anionic polymer, cross-linking the ink enables extremely quick aggregation of the coloring material and is excellent. Printing image quality and suppressing the penetration of the ink solvent into the paper, it is possible to further improve the occurrence of curling and undulation immediately after printing, and further curling and undulation after standing drying. it can.

  Examples of the polyvalent metal salts include potassium, barium, calcium, magnesium, zinc, tin, manganese, aluminum and other polyvalent metal chlorides, sulfates, nitrates, formates, acetates, and the like. Barium chloride, calcium chloride, calcium acetate, calcium nitrate, calcium formate, magnesium chloride, magnesium sulfate, magnesium nitrate, magnesium acetate, magnesium formate, zinc chloride, zinc sulfate, zinc nitrate, zinc formate, tin chloride, tin nitrate Manganese chloride, manganese sulfate, manganese nitrate, manganese formate, aluminum sulfate, aluminum nitrate, aluminum chloride, aluminum acetate and the like can be exemplified, and these can be used alone or in combination of two or more. Of these polyvalent metal salts, metal salts having high solubility in water and high valence are preferable. Further, when the counter ion of the polyvalent metal salt is a strong acid, paper yellowing after coating occurs, and therefore, calcium chloride, calcium formate, magnesium chloride, magnesium formate, and the like are preferable.

  Examples of the cationic resin include, but are not limited to, cationized cellulose, cationized starch, and cationized starch.

  The cationic resins and polyvalent metal salts listed above can be placed on the surface of the recording paper by mixing them in the surface size liquid or by applying a separately prepared coating liquid on the surface of the paper. In the latter case, the coating solution obtained by dissolving in water may be directly applied to the recording paper (or paper), but it is generally used by mixing with a binder.

Cationic resin contained in the recording paper surface, the content of the polyvalent metal salt, more to be in the range of 0.1-2 g / m ² is in the range of preferably 0.5 to 1 g / m ² preferable.
If the content is less than 0.1 g / m ² , the reaction with the pigment or anionic polymer in the ink is weakened, resulting in a decrease in image quality, curling immediately after printing, undulation, curling after standing drying, and undulation. There is a case. When the content exceeds 2 g / m ² , the ink permeability deteriorates, and the ink drying property may deteriorate in high-speed printing.

  In the recording paper of the present invention, the formation index is preferably in the range of 10-50, more preferably in the range of 20-40. If the formation index is less than 10, the presence of the surfactant is likely to occur from the formation unevenness, and the image transfer unevenness in the electrophotographic system is likely to occur. Further, if the formation index exceeds 50, it is necessary to strengthen the beating of the paper in order to ensure the homogeneity, and the curling in the ink jet system becomes large.

Here, the texture index is M / K Systems, Inc. A 3D sheet analyzer (M / K950) manufactured by (MKS) is used, the diameter of the analyzer is 1.5 mm, and measurement is performed using a micro formation tester (MFT).
Specifically, a sample is mounted on a rotating drum in a 3D sheet analyzer, and a local basis weight of the sample is measured by a light source attached to the drum shaft and a photodetector attached to the outside of the drum corresponding to the light source. The difference is measured as the light intensity difference. The measurement target range at this time is set by the diameter of the diaphragm attached to the light incident part of the photodetector. Next, the light intensity difference (deviation) is amplified, A / D converted, classified into 64 photometric basis weight classes, and 1000000 data are taken in one scan, and the histogram frequency for that data is taken. Get. Then, the highest frequency (peak value) of the histogram is divided by the number of classes having a frequency of 100 or more out of those classified into classes corresponding to a micro basis weight of 64, and the value obtained by dividing it by 1/100 is the ground index. Calculated. This texture index indicates that the greater the value, the better the texture.

In addition, when recording paper is used for electrophotographic image recording, the electrical characteristics of the paper are important. Particularly, in the present invention, surfactants and cationized materials that can change the electrical characteristics of the paper are frequently used. Depending on the combination and content, uneven image transfer may occur in the electrophotographic system.
In the present invention, the surface resistance value of at least the printing surface of the recording paper is preferably in the range of 1.0 × 10 ^{9 to} 1.0 × 10 ¹¹ Ω / □, and the volume resistivity is 1.0 × 10. It is preferable to set in the range of ^{10 to} 1.0 × 10 ¹² Ω · cm. If the surface resistance value and volume resistivity are not within the above ranges, image transfer unevenness may occur in the electrophotographic system.

The surface resistance value is more preferably in the range of 5.0 × 10 ^{9 to} 7.0 × 10 ¹⁰ Ω / □, and in the range of 5.0 × 10 ^{9 to} 2.0 × 10 ¹⁰ Ω / □. More preferably. The surface resistance value indicates the resistance of the surface formed by applying the polyvalent metal salt and / or the cationic resin. The volume resistivity is more preferably in the range of 1.3 × 10 ^{10 to} 1.6 × 10 ¹¹ Ω · cm, and 1.3 × 10 ^{10 to} 4.3 × 10 ¹⁰ Ω · cm. More preferably, it is in the range.
The surface resistance value and the volume resistivity are measured by a method based on JIS-K-6911 after storing for 24 hours under conditions of 23 ° C. and 50% RH and adjusting the humidity. .

<Image recording method>
Next, the image recording method of the present invention will be described.
The image recording method of the present invention can be applied to recording using an inkjet ink (hereinafter sometimes abbreviated as “ink”) or an electrophotographic toner (hereinafter sometimes abbreviated as “toner”). The recording paper is not particularly limited as long as the recording paper is used. However, the image recording method of the present invention is more preferably an ink jet recording method using ink in order to obtain a high-quality document.

(Inkjet recording type image recording method)
First, the ink jet recording type image recording method of the present invention (hereinafter sometimes referred to as “ink jet recording method”) will be described.
The ink jet recording method of the present invention is an ink jet recording type image recording method in which ink droplets are ejected onto a recording paper and an image is recorded on the surface of the recording paper.

  The ink is not particularly limited as long as it is a known ink containing at least a color material, but preferably contains a color material, an anionic compound, a water-soluble organic solvent and water as essential components. , Surfactants, various additives, and the like. Hereinafter, each component will be described.

-Color material-
Examples of the color material used in the ink include water-soluble dyes, organic pigments, and inorganic pigments.
In the case of black ink, those mainly composed of pigments are common, and examples of black pigments include carbon black pigments such as furnace black, lamp black, acetylene black, channel black, and the like. Raven7000, Raven5750, Raven5250, Raven5000 ULTRA II, Raven3500, Raven2000, Raven1500, Raven1250, Raven1200, Raven1190 ULTRAII, Raven1170, Raven1170, Raven1170, Raven1170 , Mogu L, BlackPearls L, Monarch 700, Monarch 800, Monarch 880, Monarch 900, Monarch 1000, Monarch 1100, Monarch 1300, Monarch 1400 (manufactured by Cabot Corporation), Color Black FW1, Color Black FW2, Color Black FW2, Color Black FW, Color Black FW2, Color Black FW2, Color Black FW2, Color Black FW2, Color Black FW Black S150, ColorBlack S160, Color Black S170, Pritex35, PritexU, Pritex Vrintex140U, Printex140V, Special Black6, Special Black5, Special4, Black4, Special4, Black4 No.) 25, no. 33, no. 40, no. 47, no. 52, no. 900, no. 2300, MCF-88, MA600, MA7, MA8, MA100 (manufactured by Mitsubishi Chemical Corporation) and the like.

Although it is difficult to uniformly discuss a suitable structure of carbon black, the average primary particle size is 15 to 30 nm, the BET surface area is 70 to 300 m ² / g, and the DBP oil absorption is 0.5 to 1.0 × 10. ^-3 L / g, volatile content is preferably 0.5 to 10% by mass, and ash content is preferably 0.01 to 1.00% by mass. If carbon black outside the above range is used, the dispersed particle size in the ink may increase.

Color materials used in cyan, magenta, and yellow inks are not limited to dyes, and pigments made hydrophilic by adding a dispersant containing a hydrophilic group to hydrophobic pigments and self-dispersing pigments should also be used. Can do.
As the water-soluble dye, known ones or newly synthesized ones can be used. Among these, a direct dye or an acid dye that can obtain a vivid color is preferable. Specifically, C.I. I. Direct Blue-1, -2, -6, -8, -22, -34, -70, -71, -76, -78, -86, -142, -199, -200, -201, -202, -203, -207, -218, -236 and 287, C.I. I. Direct Red-1, -2, -4, -8, -9, -11, -13, -20, -28, -31, -33, -37, -39, -51, -59, -62, -63, -73, -75, -80, -81, -83, -87, -90, -94, -95, -99, -101, -110 and 189, C.I. I. Direct Yellow-1, -2, -4, -8, -11, -12, -26, -27, -28, -33, -34, -41, -44, -48, -86, -87, -88, -135, -142 and 144, C.I. I. Acid Blue-1, -7, -9, -15, -22, -23, -27, -29, -40, -43, -55, -59, -62, -78, -80, -81, -90, -102, -104, -111, -185 and 254, C.I. I. Acid Red-1, -4, -8, -13, -14, -15, -18, -21, -26, -35, -37, -249 and 257, C.I. I. Acid Yellow-1, -3, -4, -7, -11, -12, -13, -14, -19, -23, -25, -34, -38, -41, -42, -44, -53, -55, -61, -71, -76 and 79 are used. These may be used alone or in admixture of two or more.

  Examples of the cationic dye include C.I. I. Basic yellow-1, -11, -13, -19, -25, -33, -36; I. B. basic red-1, -2, -9, -12, -13, -38, -39, -92; I. Basic Blue-1, -3, -5, -9, -19, -24, -25, -26, -28 and the like.

  Specific examples of cyan pigments include C.I. I. Pigment Blue-1, C.I. I. Pigment Blue-2, C.I. I. Pigment Blue-3, C.I. I. Pigment Blue-15, C.I. I. Pigment Blue-15: 1, C.I. I. Pigment Blue-15: 3, C.I. I. PigmentBlue-15: 34, C.I. I. Pigment Blue-16, C.I. I. Pigment Blue-22, C.I. I. Pigment Blue-60 and the like.

  Specific examples of magenta pigments include C.I. I. Pigment Red-5, C.I. I. Pigment Red-7, C.I. I. Pigment Red-12, C.I. I. Pigment Red-48, C.I. I. Pigment Red-48: 1, C.I. I. Pigment Red-57, C.I. I. Pigment Red-112, C.I. I. Pigment Red-122, C.I. I. PigmentRed-123, C.I. I. Pigment Red-146, C.I. I. Pigment Red-168, C.I. I. Pigment Red-184, C.I. I. Pigment Red-202 and the like.

  Specific examples of yellow pigments include C.I. I. Pigment Yellow-1, C.I. I. Pigment Yellow-2, C.I. I. Pigment Yellow-3, C.I. I. Pigment Yellow-12, C.I. I. Pigment Yellow-13, C.I. I. Pigment Yellow-14, C.I. I. Pigment Yellow-16, C.I. I. Pigment Yellow-17, C.I. I. Pigment Yellow-73, C.I. I. Pigment Yellow-74, C.I. I. Pigment Yellow-75, C.I. I. Pigment Yellow-83, C.I. I. Pigment Yellow-93, C.I. I. Pigment Yellow-95, C.I. I. Pigment Yellow-97, C.I. I. Pigment Yellow-98, C.I. I. Pigment Yellow-114, C.I. I. Pigment Yellow-128, C.I. I. Pigment Yellow-129, C.I. I. Pigment Yellow-151, C.I. I. Pigment Yellow-154 and the like.

  The pigment that can be used in the present invention may be a pigment that can be self-dispersed in water (self-dispersing pigment). The self-dispersing pigment is a pigment that has many water-solubilizing groups on the pigment surface and can be stably dispersed without the presence of a pigment dispersant. Specifically, a self-dispersing pigment is obtained by subjecting a normal so-called pigment to surface modification treatment such as acid / base treatment, coupling agent treatment, polymer graft treatment, plasma treatment, oxidation / reduction treatment, etc. Obtainable. In addition to the pigment subjected to such surface modification treatment, as a self-dispersing pigment, cab-o-jet-200, cab-o-jet-300, IJJ-55, IJJ-253, manufactured by Cabot Corporation, Commercially available products such as IJX266, IJX-273 Orientjet Chemical Company's Microjet Black CW-1, and pigments sold by Nippon Shokubai Co., Ltd. may be used.

  The water-solubilizing group present on the surface of the self-dispersing pigment may be any of nonionic, cationic or anionic, and sulfonic acid, carboxylic acid, hydroxyl group and phosphoric acid are particularly desirable. In the case of sulfonic acid, carboxylic acid and phosphoric acid, they can be used as they are in the free acid state, but are preferably used in the form of a salt with a basic compound in order to increase water solubility.

  In this case, basic compounds include alkali metals such as sodium, potassium and lithium, aliphatic amines such as monomethylamine, dimethylamine and triethylamine, monomethanolamine, monoethanolamine, diethanolamine, triethanolamine and diisopropanol. Alcohol amines such as amines and basic compounds such as ammonia can be used. Among these, basic compounds of alkali metals such as sodium, potassium and lithium can be particularly preferably used. This is presumably because the alkali metal basic compound is a strong electrolyte and has a large effect of promoting dissociation of acidic groups.

  When a pigment is contained as a coloring material in the ink, the content of the pigment is preferably in the range of 0.5 to 20% by mass, particularly in the range of 2 to 10% by mass. When the pigment content is less than 0.5% by mass, the optical density may be lowered. On the other hand, if it exceeds 20% by mass, the image fixability may deteriorate.

  When the ink contains a dye as a coloring material, the dye content is in the range of 0.1 to 10% by mass, preferably 0.5 to 8% by mass, more preferably 0.8 to 6% by mass. It is a range. If it is contained in an amount of more than 10% by mass, clogging at the front end of the print head is likely to occur, and if it is less than 0.1% by mass, a sufficient image density may not be obtained.

-Anionic compounds-
Examples of the anionic compound used in the ink include acids such as carboxylic acids and sulfonic acids and derivatives thereof, anionic water-soluble polymers, anionic polymer emulsions, and the like. It may be a dispersant.
Specific examples of the carboxylic acid include formic acid, acetic acid, propionic acid, butyric acid, valeric acid, lactic acid, tartaric acid, benzoic acid, acrylic acid, crotonic acid, butenoic acid, methacrylic acid, tiglic acid, allylic acid, 2- Examples thereof include carboxylic acids such as ethyl-2-butenoic acid, succinic acid, malonic acid, succinic acid, glutaric acid, maleic acid, fumaric acid, methylmaleic acid and glyceric acid, and polymers and derivatives thereof. In addition, alkali metal salts, alkaline earth metal salts, ammonium salts, and the like of these compounds can also be used.

  Specific examples of the sulfonic acid include benzenesulfonic acid, toluenesulfonic acid, xylenesulfonic acid, benzenedisulfonic acid, benzenetrisulfonic acid, hydroxybenzenesulfonic acid, chlorobenzenesulfonic acid, bromobenzenesulfonic acid, 4-hydroxy-1 , 3-benzenedisulfonic acid, 4,5-dihydroxybenzene-1,3-disulfonic acid sodium salt, o-aminobenzenesulfonic acid and other sulfonic acids, and derivatives thereof, and alkali metal salts and alkaline earth metals thereof Examples thereof include salts and ammonium salts.

These compounds are preferably used in the form of a salt with a basic compound in order to enhance water solubility. The compounds that form salts with these compounds include alkali metals such as sodium, potassium and lithium, aliphatic amines such as monomethylamine, dimethylamine and triethylamine, monomethanolamine, monoethanolamine, diethanolamine and triethanolamine. Alcohol amines such as diisopropanolamine, ammonia and the like can be used.
More preferable specific examples of the anionic water-soluble polymer include acrylic acid alkyl ester-acrylic acid copolymer, styrene-methacrylic acid alkyl ester-methacrylic acid copolymer, styrene-maleic acid copolymer, styrene-methacrylic acid. Acid copolymer, styrene-acrylic acid copolymer, methacrylic acid alkyl ester-methacrylic acid copolymer, styrene-acrylic acid alkyl ester-acrylic acid copolymer, styrene-methacrylic acid phenyl ester-methacrylic acid copolymer, Examples thereof include styrene-methacrylic acid cyclohexyl ester-methacrylic acid copolymers, and salts and derivatives of these copolymers.

The anionic water-soluble polymer contained in the ink preferably has a structure composed of a hydrophilic part and a hydrophobic part. Further, a carboxylic acid or a carboxylic acid salt is used as a functional group constituting the hydrophilic part. It is preferable to include.
Specifically, as the anionic water-soluble polymer, the monomer constituting the hydrophilic portion is preferably at least one selected from acrylic acid, methacrylic acid and (anhydrous) maleic acid.

  On the other hand, as monomers constituting the hydrophobic part of the anionic water-soluble polymer, styrene derivatives such as styrene, α-methylstyrene, vinyltoluene, vinylcyclohexane, vinylnaphthalene, vinylnaphthalene derivatives, alkyl acrylate esters, Examples include methacrylic acid alkyl ester, methacrylic acid phenyl ester, methacrylic acid cycloalkyl ester, crotonic acid alkyl ester, itaconic acid dialkyl ester, maleic acid dialkyl ester, among them, styrene, alkyl of (meth) acrylic acid, It is preferably at least one selected from aryl and alkylaryl esters.

  These anionic water-soluble polymers may be used alone or in combination of two or more. The content of the anionic water-soluble polymer in the ink is preferably in the range of 0.1 to 10% by mass, particularly in the range of 0.3 to 5% by mass. If the amount is less than 0.1% by mass, the long-term storage stability may be inferior, or the optical density may be decreased. If the amount exceeds 10% by mass, normal ejection may not be performed, or the optical density may be decreased.

-Water-soluble organic solvent-
Examples of the water-soluble organic solvent used in the ink include polyhydric alcohols such as ethylene glycol, diethylene glycol, propylene glycol, butylene glycol, triethylene glycol, 1,5-pentanediol, 1,2,6-hexanetriol, glycerin, Polyethylene alcohol derivatives such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, propylene glycol monobutyl ether, dipropylene glycol monobutyl ether, pyrrolidone, N- Methyl-2-pyrrolidone, cyclohexyl pyrrolidone, triethanolamine Nitrogen-containing solvents, alcohols such as ethanol and isopropyl alcohol, butyl alcohol, benzyl alcohol, thiodiethanol, thiodiglycerol, sulfolane, sulfur-containing solvents such as dimethyl sulfoxide, propylene carbonate, ethylene and the like carbonates. The water-soluble organic solvent may be used alone or in combination of two or more.

  The content of the water-soluble organic solvent contained in the ink is preferably in the range of 1 to 60% by mass, particularly in the range of 5 to 40% by mass. If the content of the water-soluble organic solvent is less than 1% by mass, the long-term storage stability may be inferior. Moreover, when it exceeds 60 mass%, discharge stability may fall and it may not discharge normally.

-Water-
As the water used in the ink, ion exchange water, distilled water, pure water, ultrapure water, or the like can be used.
The content of water contained in the ink is preferably in the range of 15 to 98% by mass, particularly in the range of 45 to 90% by mass. If it is less than 15% by mass, the ejection stability may be lowered, and the ejection may not be performed normally. Moreover, when it exceeds 98 mass%, it may be inferior in long-term storage stability.

-Other ingredients-
A pigment dispersant can be used for dispersing the pigment contained in the ink. Specific examples of the pigment dispersant include a polymer dispersant, an anionic surfactant, a cationic surfactant, an amphoteric surfactant nonionic surfactant, and the like.
Among these pigment dispersants, a pigment dispersant that becomes an organic anion when ionized in water is referred to as an anionic pigment dispersant in the present invention. As the anionic pigment dispersant, the anionic water-soluble polymer described above can be used.

As the polymer dispersant, any polymer having a hydrophilic structure portion and a hydrophobic structure portion can be used effectively. Examples of the polymer having a hydrophilic structure portion and a hydrophobic structure portion include a condensation polymer and an addition polymer.
Examples of the condensation polymer include known polyester dispersants. Examples of the addition polymer include addition polymers of monomers having an α, β-ethylenically unsaturated group. By subjecting a monomer having an α, β-ethylenically unsaturated group having a hydrophilic group and a monomer having an α, β-ethylenically unsaturated group having a hydrophobic group to appropriate copolymerization, a desired polymer dispersant is obtained. Can be obtained. A homopolymer of a monomer having an α, β-ethylenically unsaturated group having a hydrophilic group can also be used.

  Examples of the monomer having an α, β-ethylenically unsaturated group having a hydrophilic group include monomers having a carboxyl group, a sulfonic acid group, a hydroxyl group, a phosphoric acid group, such as acrylic acid, methacrylic acid, crotonic acid, Itaconic acid, itaconic acid monoester, maleic acid, maleic acid monoester, fumaric acid, fumaric acid monoester, vinyl sulfonic acid, styrene sulfonic acid, sulfonated vinyl naphthalene, vinyl alcohol, acrylamide, methacryloxyethyl phosphate, bismethacryloxy Examples thereof include ethyl phosphate, methacrylooxyethyl phenyl acid phosphate, ethylene glycol dimethacrylate, and diethylene glycol dimethacrylate.

  On the other hand, examples of monomers having an α, β-ethylenically unsaturated group having a hydrophobic group include styrene derivatives such as styrene, α-methylstyrene, vinyltoluene, vinylcyclohexane, vinylnaphthalene, vinylnaphthalene derivatives, alkyl acrylates. Examples include esters, acrylic acid phenyl esters, methacrylic acid alkyl esters, methacrylic acid phenyl esters, methacrylic acid cycloalkyl esters, crotonic acid alkyl esters, itaconic acid dialkyl esters, and maleic acid dialkyl esters.

  Examples of preferred copolymers of these monomers include styrene-styrene sulfonic acid copolymer, styrene-maleic acid copolymer, styrene-methacrylic acid copolymer, styrene-acrylic acid copolymer, vinyl naphthalene-maleic acid. Acid copolymer, vinyl naphthalene-methacrylic acid copolymer, vinyl naphthalene-acrylic acid copolymer, acrylic acid alkyl ester-acrylic acid copolymer, methacrylic acid alkyl ester-methacrylic acid, styrene-methacrylic acid alkyl ester-methacrylic Examples thereof include an acid copolymer, a styrene-acrylic acid alkyl ester-acrylic acid copolymer, a styrene-methacrylic acid phenyl ester-methacrylic acid copolymer, and a styrene-methacrylic acid cyclohexyl ester-methacrylic acid copolymer.

  These polymers can also be used by appropriately copolymerizing monomers having a polyoxyethylene group and a hydroxyl group. Furthermore, in order to increase the affinity with the pigment having an acidic functional group on the surface and improve the dispersion stability, a monomer having a cationic functional group, such as N, N-dimethylaminoethyl methacrylate, N, N-dimethyl, etc. Aminoethyl acrylate, N, N-dimethylaminomethacrylamide, N, N-dimethylaminoacrylamide, N-vinylpyrrole, N-vinylpyridine, N-vinylpyrrolidone, N-vinylimidazole, and the like may be appropriately copolymerized and used. it can.

These copolymers may have any structure such as random, block, and graft copolymers. Polystyrene sulfonic acid, polyacrylic acid, polymethacrylic acid, polyvinyl sulfonic acid, polyalginic acid, polyoxyethylene-polyoxypropylene-polyoxyethylene block copolymer, formalin condensate of naphthalene sulfonic acid, polyvinyl pyrrolidone, polyethyleneimine, polyamine , Polyamides, polyvinyl imidazoline, aminoalkyl acrylate D acrylamide copolymer, chitosan, polyoxyethylene fatty acid amide, polyvinyl alcohol, polyacrylamide, carboxymethylcellulose, carboxyethylcellulose and other cellulose derivatives, polysaccharides and their derivatives are also used can do.
Although not particularly limited, the hydrophilic group of the pigment dispersant is preferably a carboxylic acid or a carboxylic acid salt.

The neutralizing amount of the pigment dispersant is preferably 50% or more, and particularly preferably 80% or more, with respect to the acid value of the copolymer. The pigment dispersant has a weight average molecular weight (Mw) of 2000 to 15000, particularly 3500 to 10,000. Moreover, the structure and composition rate of a hydrophobic part and a hydrophilic part can use a preferable thing from the combination of a pigment and a solvent.
These pigment dispersants may be used alone or in combination of two or more. The amount of pigment dispersant added varies greatly depending on the pigment, so it cannot be said unconditionally. However, it is generally in the range of 0.1 to 100% by weight, preferably in the range of 1 to 70% by weight, based on the pigment. Preferably it is the quantity of the range of 3-50 mass%.

The ink may contain a surfactant. This is because the pigment dispersant of the pigment ink and the surface tension and wettability of the ink are adjusted, or the organic impurities are solubilized and the reliability when ejected from the ink nozzle is improved.
As the type of the surfactant, nonionic and anionic surfactants that do not easily affect the dispersion state of the water-insoluble colorant or the dissolved state of the water-soluble dye are preferable. Nonionic surfactants include, for example, polyoxyethylene nonyl phenyl ether, polyoxyethylene octyl phenyl ether, polyoxyethylene dodecyl phenyl ether, polyoxyethylene alkyl ether, polyoxyethylene fatty acid ester, sorbitan fatty acid ester, polyoxyethylene sorbitan Fatty acid esters, fatty acid alkylolamides, acetylene alcohol ethylene oxide adducts, polyethylene glycol polypropylene glycol block copolymers, glycerin ester polyoxyethylene ethers, sorbitol ester polyoxyethylene ethers, and the like can be used.

  Examples of anionic surfactants include alkylbenzene sulfonates, alkylphenyl sulfonates, alkylnaphthalene sulfonates, higher fatty acid salts, sulfates and sulfonates of higher fatty acid esters, and higher alkyl sulfosuccinates. Can be used.

  Further, as the amphoteric surfactant, betaine, sulfobetaine, sulfate betaine, imidazoline and the like can be used. In addition, silicone surfactants such as polysiloxane polyoxyethylene adducts, fluorine surfactants such as oxyethylene perfluoroalkyl ether, biosurfactants such as splicrisporic acid, rhamnolipid, and lysolecithin can also be used. The surfactant used in the ink may be used alone or in combination of two or more. What is necessary is just to adjust the addition amount by target characteristics, such as surface tension.

  Further, the ink may include a pH buffer, an antioxidant, an antifungal agent, a viscosity modifier, a conductive agent, an ultraviolet absorber, a chelating agent, a water-soluble dye, a disperse dye, an oil-soluble dye, etc. Can also be added. The content of these additives in the ink is preferably 20% by mass or less.

The ink as described above is obtained by adding a predetermined amount of a coloring material to an aqueous solution, stirring sufficiently, then dispersing using a disperser, removing coarse particles by centrifugation or the like, It can be obtained by adding an additive or the like and stirring and mixing, followed by filtration.
A commercially available dispersing machine can be used. For example, colloid mill, flow jet mill, slasher mill, high speed disperser, ball mill, attritor, sand mill, sand grinder, ultra fine mill, Eiger motor mill, dyno mill, pearl mill, agitator mill, cobol mill, 3 rolls, 2 rolls Examples thereof include a roll, an extruder, a kneader, a microfluidizer, a laboratory homogenizer, and an ultrasonic homogenizer. These may be used alone or in combination of two or more. In order to prevent mixing of inorganic impurities, it is preferable to use a dispersion method that does not use a dispersion medium. In that case, it is preferable to use a microfluidizer, an ultrasonic homogenizer, or the like.

  The ink using the self-dispersing pigment is obtained by, for example, subjecting the pigment to a surface modification treatment, adding the obtained pigment to water, stirring sufficiently, and using a disperser similar to the above as necessary. After dispersing and removing coarse particles by centrifugation or the like, a predetermined solvent, additives and the like are added, followed by stirring, mixing, and filtration.

  The pH of the ink is preferably in the range of 3 to 11, and particularly preferably in the range of 4.5 to 9.5. In addition, in an ink having an anionic free radical on the pigment surface, the pH of the ink is preferably in the range of 6 to 11, more preferably in the range of 6 to 9.5, and 7.5 to 9. A range of 0 is more preferable. On the other hand, in the ink having a cationic free radical on the pigment surface, the pH of the ink is preferably in the range of 4.5 to 8.0, and more preferably in the range of 4.5 to 7.0.

  The viscosity of the ink is preferably in the range of 1.5 to 5.0 mPa · s, and more preferably in the range of 1.5 to 4.0 mPa · s. When the viscosity of the ink is larger than 5.0 mPa · s, since the permeability to the recording paper is slow, mixed color bleeding may occur. On the other hand, when the viscosity of the ink is smaller than 1.5 mPa · s, the permeability to the recording paper is too fast, the ink pigment and the anionic compound cannot be aggregated, and the ink penetrates into the recording paper. Therefore, there is a case where the density is reduced and the characters are blurred.

  The surface tension of the ink can be adjusted mainly by the amount of the surfactant added, and is preferably adjusted in the range of 25 to 37 mN / m. When the surface tension is less than 25 mN / m, the ink permeability to the recording paper is too fast, the ink coloring material and the anionic water-soluble polymer cannot be aggregated, and the ink penetrates into the recording paper. , A decrease in density and bleeding of characters may occur. On the other hand, if it is larger than 37 mN / m, the ink permeability to the recording paper becomes slow, and the drying property may be deteriorated.

When printing on the recording paper of the present invention using the ink as described above by the ink jet method, the ink drop amount ejected from the nozzle is preferably in the range of 1 to 20 pl, and 3 to 18 pl. More preferably, it is in the range.
In addition, printing is performed by a so-called thermal ink jet method in which droplets are formed by applying thermal energy, and the ink drop amount is in the range of 1 to 20 pl, preferably in the range of 3 to 18 pl as described above. In this case, it is preferable that the dispersed particle diameter of the pigment in the ink is in the range of 20 to 120 nm in terms of volume average particle diameter, and the number of coarse particles of 500 nm or more is 5 × 10 ⁵ or less in 2 μl of ink. . If the volume average particle diameter is less than 20 nm, sufficient image density may not be obtained. On the other hand, if the volume average particle size is larger than 120 nm, clogging is likely to occur in the print head, and stable ejection properties cannot be ensured. Further, if the number of coarse particles having a volume average particle size of 500 nm or more exceeds 5 × 10 ^{5 in} 2 μl of ink, clogging is likely to occur in the print head, and ink may not be ejected stably. The number of coarse particles is more preferably 3 × 10 ⁵ or less, and further preferably 2 × 10 ⁵ or less.

Further, the storage elastic modulus of the ink at 24 ° C. is particularly preferably in the range of 5 × 10 ⁻⁴ to 1 × 10 ⁻² Pa. This is because by having appropriate elasticity in this region, the behavior on the surface of the recording paper becomes preferable. In addition, the said storage elastic modulus is a value when it measures in the low shear rate area | region in the range whose angular velocity is 1-10 rad / s. This value can be easily measured by using an apparatus capable of measuring viscoelasticity in the low shear rate region. Examples of the measuring device include a VE type viscoelasticity analyzer (manufactured by VILASTIC SCIENTIFIC INC.), A DCR very low viscosity viscoelasticity measuring device (manufactured by Paar Physica), and the like.

  As long as the inkjet recording method in the present invention is a known inkjet apparatus, good print quality can be obtained regardless of which inkjet recording method is used. Furthermore, for a system having a function of promoting the absorption and fixing of ink by providing heating means such as recording paper during printing or before and after printing, and heating the recording paper and ink at a temperature of 50 ° C. to 200 ° C. Also, the ink jet recording method of the present invention can be applied.

  Next, an example of an ink jet recording apparatus suitable for carrying out the ink jet recording method of the present invention will be described. This example is a so-called multi-pass method, in which an image is formed by a recording head scanning the surface of a recording sheet a plurality of times.

  As a method for ejecting ink from a nozzle, there is a so-called thermal ink jet method in which ink in a nozzle is foamed by energizing and heating a heater provided in the nozzle, and the ink is ejected by the pressure. There is also a method in which a piezoelectric element is electrically deformed to physically deform the element, and ink is ejected from the nozzles using a force generated by the deformation. In this system, a piezoelectric element using a piezo element is typical. In the ink jet recording apparatus used in the ink jet recording method of the present invention, the method for ejecting ink from the nozzles may be any of the above methods, and is not limited to these methods. This is the same in the following.

  The nozzles are arranged in a direction substantially perpendicular to the main scanning direction of the head carriage. Specifically, they can be arranged in a row at a density of 800 per inch. The number and density of the nozzles are arbitrary. Moreover, it can arrange not only in a line but also in a staggered pattern.

  On the upper part of the recording head, ink tanks containing inks of the present invention for cyan, magenta, yellow and black are integrally attached to the respective recording heads. The ink stored in the ink tank is supplied to the recording head corresponding to each color. The ink tank and the head may be formed integrally. However, the present invention is not limited to this method. For example, an ink tank may be disposed separately from the recording head and ink may be supplied to the recording head via an ink supply tube.

  Further, a signal cable is connected to each of these recording heads. This signal cable transmits image information after being processed by the pixel processing unit to each recording head for each color of cyan, magenta, yellow, and black.

  The recording head is fixed to a head carriage. The head carriage is slidably attached in the main scanning direction along the guide rod and the carriage guide. By rotating the drive motor at a predetermined timing, the head carriage can be driven to reciprocate along the main scanning direction via the timing belt.

  A platen is fixed below the head carriage, and the recording paper used in the present invention is conveyed onto the platen at a predetermined timing by a paper feed conveyance roller. The platen can be made of, for example, a plastic molding material.

  In this way, it is possible to print on the recording paper of the present invention using the ink as described above. In the example of the multi-pass method, the example in which five heads including the pretreatment liquid are provided has been described. However, the range in which the ink jet recording method of the present invention can be applied to the multi-pass method is not limited to this example. There are a total of two heads, a black head and a color head. Of these, the color head is such that the nozzles are divided in the arrangement direction and a predetermined color is assigned to each divided area. Good.

  In the so-called multi-pass method in which the print head travels perpendicularly to the recording paper discharge direction, the print head scanning speed is the speed of the recording head when the recording head performs printing by scanning the surface of the recording paper a plurality of times. Refers to moving speed.

  When performing high-speed printing with a printing speed of 10 ppm (10 sheets / min) or more, comparable to a laser printer in the office, it is inevitable that the scanning speed of the print head is 25 cm / second or more. Therefore, the interval at which two different colors of ink are printed is also narrowed, and intercolor bleeding (ICB) is likely to occur. In addition, it is necessary to use an ink having a low surface tension in order to improve the drying property of the ink, which causes the occurrence of feathering and a decrease in image density. Such an ink having a low surface tension has a high permeability to paper. Therefore, printed characters and images are easily seen through from the back side, and the double-sided printing property is impaired.

  Next, a second example of an ink jet recording apparatus suitable for carrying out the ink jet recording method of the present invention will be described. This example is called a one-pass method. This one-pass method has a recording head having a width substantially equal to the width of the recording paper, and printing is terminated when the recording paper passes under the head. Since high productivity can be obtained at the same scanning speed as compared with the multi-pass method, high-speed printing more than the laser recording method is possible.

  Since the one-pass method does not need to scan the recording head a plurality of times unlike the multi-pass method, even at a recording paper conveyance speed of 60 mm / second or more (speed at which the recording paper passes below the recording head) corresponding to 10 ppm or more, High-speed printing can be easily performed. However, since division printing cannot be performed, it is necessary to eject a large amount of ink at a time. For this reason, in the conventional inkjet recording method that does not use the recording paper of the present invention, curling and undulation immediately after printing, and further, curling and undulation after standing drying occurred.

  However, in the ink jet recording method of the present invention, the print head scanning speed in the multi-pass method is high-speed printing of 250 mm / sec or more, and the recording paper conveyance speed in a state where the print head in the multi-pass method is fixed is 60 mm. Even when high-speed printing at a speed of at least / sec is performed, the occurrence of curling and undulation of the recording paper can be suppressed by using the recording paper of the present invention described above.

  The scanning speed of the print head is preferably 500 mm / second or more, and more preferably 1000 mm / second or more, from the viewpoint of “productivity comparable to a laser printer”. Further, the conveyance speed of the recording paper is preferably 100 mm / second or more, and more preferably 210 mm / second or more.

Furthermore, in the ink jet recording method of the present invention, it is preferable that the ink shot amount is in the range of 6 to 30 ml / m ² .
The ink ejection amount is the amount of ink per unit area ejected in one scan when a solid image is formed using one or more colors of ink.

In any of the above-described methods, since ink sufficient to form a solid image with a small number of scans is applied to the recording paper, the ink ejection amount becomes as large as 6 ml / m ² or more. However, even with high-speed printing that requires such a large amount of ink, the use of the ink jet recording method of the present invention can suppress the occurrence of curling and undulations on the recording paper after printing.
Incidentally, it is preferable that the ink ejection amount is in the range of 7~20ml / m ^2, and particularly preferably more preferably within a range of 7.5~10ml / m ^2, is less than 10 ml / m ^2.

(Electrophotographic image recording method)
The electrophotographic image recording method of the present invention comprises a charging step for charging the surface of the electrostatic latent image carrier, an exposure step for exposing the surface of the electrostatic latent image carrier to form an electrostatic latent image, and the static step. The electrostatic latent image formed on the surface of the electrostatic latent image carrier is developed using an electrostatic charge image developer to form a toner image, the transfer step of transferring the toner image to the recording paper surface, And a fixing step of fixing the toner image on the surface of the recording paper, wherein the recording paper is the recording paper of the present invention described above.
The electrophotographic image recording method of the present invention can obtain a high-quality image as in the conventional case and can suppress curling that occurs immediately after printing.

  The image forming apparatus used in the electrophotographic image recording method of the present invention is not particularly limited as long as it uses an electrophotographic system having the charging step, the exposure step, the development step, the transfer step, and the fixing step. . For example, when four color toners of cyan, magenta, yellow, and black are used, a four-cycle development system in which a developer containing each color toner is sequentially applied to one photoreceptor to form a toner image. Or a color image forming apparatus (so-called tandem machine) provided with four developing units corresponding to each color can be used.

  The toner used for image formation is not particularly limited as long as it is a known toner. For example, in order to obtain a highly accurate image, a spherical toner having a small particle size and particle size distribution is used, and energy saving is supported. In addition, a toner containing a binder resin having a low melting point that can be fixed at a low temperature can be used.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated more concretely, of course, this invention is not limited to these Examples. First, after describing the ink and recording paper used in the examples and comparative examples, various evaluation results when these are combined and printed are described.

(1) Preparation of ink As ink, dye-based ink set 1 and pigment-based ink set 2 were prepared. The physical properties of the following ink were measured under the following conditions. The surface tension was measured using a Wilhelmy type surface tension meter in an environment of 23 ° C. and 55% RH. The viscosity was measured under the conditions of measurement temperature: 23 ° C. and shear rate: 1400 s ⁻¹ by placing the ink to be measured in a measurement container and mounting it on Neomat 115 (manufactured by Contraves).

<Ink set 1 (color dye ink)>
-Magenta ink-
Direct Red 227 (10% by mass aqueous solution): 20 parts by mass Ethylene glycol: 25 parts by mass Urea: 5 parts by mass Surfactant (Surfinol 465, manufactured by Nissin Chemical Co., Ltd.): 2 parts by mass Deionized water was added to bring the total amount to 100 parts by mass, and the mixture was stirred for 30 minutes. Thereafter, it was passed through a membrane filter having an opening of 1 μm. This ink had a surface tension of 31 mN / m and a viscosity of 2.0 mPa · s.

-Cyan ink-
Direct Blue 142 (10% by mass aqueous solution): 20 parts by mass Ethylene glycol: 25 parts by mass Urea: 5 parts by mass Surfactant (Surfinol 465, manufactured by Nissin Chemical Co., Ltd.): 2 parts by mass Deionized water was added to bring the total amount to 100 parts by mass and stirred for 30 minutes. Thereafter, it was passed through a membrane filter having an opening of 1 μm. This ink had a surface tension of 31 mN / m and a viscosity of 2.0 mPa · s.

-Yellow ink-
Direct yellow 144 (10% by mass aqueous solution): 20 parts by mass Ethylene glycol: 25 parts by mass Urea: 5 parts by mass Surfactant (Surfinol 465, manufactured by Nissin Chemical Co., Ltd.): 2 parts by mass Deionized water was added to bring the total amount to 100 parts by mass, and the mixture was stirred for 30 minutes. Thereafter, it was passed through a membrane filter having an opening of 1 μm. This ink had a surface tension of 31 mN / m and a viscosity of 2.0 mPa · s.

<Ink set 2 (pigment ink)>
-Black ink-
-Surface treatment pigment (Cab-o-jet-300, manufactured by Cabot Corporation): 4 parts by mass-Styrene-maleic acid-sodium maleate copolymer: 0.5 parts by mass-Diethylene glycol: 20 parts by mass-Surfactant ( Surfinol 465, manufactured by Nissin Chemical Co., Ltd.): 0.5 part by mass, urea: 5 parts by mass, ion-exchanged water: 70 parts by mass The above composition was stirred for 30 minutes. Thereafter, it was passed through a membrane filter having an opening of 1 μm. This ink had a surface tension of 32 mN / m and a viscosity of 2.8 mPa · s.

-Cyan ink-
Surface treatment pigment (IJX-253, manufactured by Cabot Corporation): 4 parts by mass Styrene-maleic acid-sodium maleate copolymer: 0.5 parts by mass Diethylene glycol: 20 parts by mass Surfactant (Surfinol 465, Nissin Chemical Co., Ltd.): 0.5 part by mass, urea: 5 parts by mass, ion-exchanged water: 70 parts by mass The above composition was stirred for 30 minutes. Thereafter, it was passed through a membrane filter having an opening of 1 μm. This ink had a surface tension of 32 mN / m and a viscosity of 2.5 mPa · s.

-Magenta ink-
Surface treatment pigment (IJX-266, manufactured by Cabot Corporation): 4 parts by mass Styrene-maleic acid-sodium maleate copolymer: 0.5 parts by mass Diethylene glycol: 20 parts by mass Surfactant (Surfinol 465, Nissin Chemical Co., Ltd.): 0.5 part by mass, urea: 5 parts by mass, ion-exchanged water: 70 parts by mass The above composition was stirred for 30 minutes. Thereafter, it was passed through a membrane filter having an opening of 1 μm. This ink had a surface tension of 33 mN / m and a viscosity of 2.7 mPa · s.

-Yellow ink-
Surface treatment pigment (IJX-273, manufactured by Cabot Corporation): 4 parts by mass Styrene-maleic acid-sodium maleate copolymer: 0.5 parts by mass Diethylene glycol: 20 parts by mass Surfactant (Surfinol 465, Nissin Chemical Co., Ltd.): 0.5 part by mass, urea: 5 parts by mass, ion-exchanged water: 70 parts by mass The above composition was stirred for 30 minutes. Thereafter, it was passed through a membrane filter having an opening of 1 μm. This ink had a surface tension of 33 mN / m and a viscosity of 2.7 mPa · s.

(2) Production of recording paper The following recording papers (1) to (28) were produced as the recording paper.
<Recording paper (1)>
100 parts by mass of Green 100 paper (medium recycled paper) manufactured by Fuji Xerox Office Supply, which has a contact angle with water of 49 degrees (phosphorylated starch, manufactured by Nippon Food Processing Co., Ltd., Solar Eclipse MS # 4600) And 16.6 parts by mass of an ether-based nonionic surfactant (manufactured by Nissin Chemical Industry Co., Ltd., Surfynol 440, HLB: 8). Size-pressed with a size press for testing by Kumagai Riki so that the treatment amount is 1 g / m ² in terms of dry mass (surfactant applied amount is 0.14 g / m ² ), and then with a KRK rotary dryer made by Kumagaya Riki It dried on 110 degreeC and 0.5 m / min conditions, and obtained the recording paper (1) whose basic weight is 69 g / m < ² >.

<Recording paper (2)>
100 parts by mass of surface sizing agent (dialdehyde starch, dry oxidised starch produced by Oji Cornstarch) having a contact angle with water of 100 degrees by Green100 paper (medium recycled paper) manufactured by Fuji Xerox Office Supply, and 16.6 parts by mass 1 g of an aqueous solution (surface sizing liquid) having a concentration of 5% by weight containing an ether-based nonionic surfactant (manufactured by Nissin Chemical Industry Co., Ltd., Surfynol 465, HLB: 13) in a dry weight of 1 g. / M ² (surfactant applied amount is 0.14 g / m ² ) After size pressing with a Kumagaya Riki test size press, 110 ° C., 0.5 m / min with a KRK rotary dryer manufactured by Kumagaya Riki The recording paper (2) having a basis weight of 69 g / m ² was obtained by drying under the min condition.

<Recording paper (3)>
100 parts by mass of Green 100 paper (medium recycled paper) manufactured by Fuji Xerox Office Supply, which has a contact angle with water of 49 degrees (phosphorylated starch, manufactured by Nippon Food Processing Co., Ltd., Solar Eclipse MS # 4600) 5 mass% aqueous solution (surface sizing liquid) containing 5.0 parts by mass of an ether-based nonionic surfactant (manufactured by Nissin Chemical Industry Co., Ltd., Surfynol 440, HLB: 8). After the size press with a size press for testing by Kumagaya Riki so that the treatment amount is 2 g / m ² in terms of dry mass (surfactant applied amount is 0.10 g / m ² ), with a KRK rotary dryer manufactured by Kumagaya Riki It dried on 110 degreeC and 0.5 m / min conditions, and obtained the recording paper (3) whose basic weight is 70 g / m < ² >.

<Recording paper (4)>
100 parts by mass of Green 100 paper (medium recycled paper) manufactured by Fuji Xerox Office Supply, which has a contact angle with water of 49 degrees (phosphorylated starch, manufactured by Nippon Food Processing Co., Ltd., Solar Eclipse MS # 4600) And 5 mass% aqueous solution (surface size liquid) containing 1.0 part by mass of an ether-based nonionic surfactant (manufactured by Nissin Chemical Industry Co., Ltd., Surfynol 440, HLB: 8) Size-pressed with a size press for testing by Kumagai Riki so that the treatment amount is 1 g / m ² in terms of dry mass (surfactant applied amount is 0.02 g / m ² ), then with a KRK rotary dryer manufactured by Kumagaya Riki It dried on 110 degreeC and 0.5 m / min conditions, and obtained the recording paper (4) whose basic weight is 69 g / m < ² >.

<Recording paper (5)>
100 parts by mass of a surface sizing agent (high saponification degree polyvinyl alcohol, Kuraray PVA124) whose contact angle with water is 47 degrees on Green 100 paper (medium recycled paper) manufactured by Fuji Xerox Office Supply, and 16.6 parts by mass A 5% by weight aqueous solution (surface sizing liquid) containing an ether-based nonionic surfactant (manufactured by Nissin Chemical Industry Co., Ltd., Surfynol 440, HLB: 8) is treated with a dry mass of 0. After size-pressing with a size press for testing manufactured by Kumagai Riki so as to be 5 g / m ² (surfactant applied amount is 0.11 g / m ² ), 110 ° C., 0.5 m using a KRK rotary dryer manufactured by Kumagai Riki The recording paper (5) having a basis weight of 69 g / m ² was obtained by drying under a / min condition.

<Recording paper (6)>
100 parts by mass of surface sizing agent (oxidized starch, manufactured by Oji Cornstarch Co., Ltd., Ace A) whose contact angle with water is 29 degrees on Green 100 paper (medium recycled paper) manufactured by Fuji Xerox Office Supply, and 16.6 parts by mass 1 g of an aqueous non-ionic surfactant (Shinfin Chemical Co., Ltd., Surfynol 440, HLB: 8) containing 5% by weight of an aqueous solution (surface sizing liquid) with a dry weight of 1 g. / M ² (surfactant applied amount is 0.14 g / m ² ) After size pressing with a Kumagaya Riki test size press, 110 ° C., 0.5 m / min with a KRK rotary dryer manufactured by Kumagaya Riki It dried on min conditions and obtained the recording paper (6) whose basic weight is 69 g / m < ² >.

<Recording paper (7)>
100 parts by mass of Green 100 paper (medium recycled paper) manufactured by Fuji Xerox Office Supply, which has a contact angle with water of 49 degrees (phosphorylated starch, manufactured by Nippon Food Processing Co., Ltd., Solar Eclipse MS # 4600) And 16.6 parts by mass of an ether-based nonionic surfactant (manufactured by Nissin Chemical Industry Co., Ltd., Surfynol 485, HLB: 17). Size-pressed with a size press for testing by Kumagai Riki so that the treatment amount is 1 g / m ² in terms of dry mass (surfactant applied amount is 0.14 g / m ² ), and then with a KRK rotary dryer made by Kumagaya Riki It dried on 110 degreeC and 0.5 m / min conditions, and obtained the recording paper (7) with a basic weight of 69 g / m < ² >.

<Recording paper (8)>
100 parts by mass of Green 100 paper (medium recycled paper) manufactured by Fuji Xerox Office Supply, which has a contact angle with water of 49 degrees (phosphorylated starch, manufactured by Nippon Food Processing Co., Ltd., Solar Eclipse MS # 4600) And 16.6 parts by mass of an ether-based nonionic surfactant (manufactured by Nissin Chemical Industry Co., Ltd., Surfynol 420, HLB: 4). Size-pressed with a size press for testing by Kumagai Riki so that the treatment amount is 1 g / m ² in terms of dry mass (surfactant applied amount is 0.14 g / m ² ), and then with a KRK rotary dryer made by Kumagaya Riki It dried on 110 degreeC and 0.5 m / min conditions, and obtained the recording paper (8) with a basic weight of 69 g / m < ² >.

<Recording paper (9)>
100 parts by mass of Green 100 paper (medium recycled paper) manufactured by Fuji Xerox Office Supply, which has a contact angle with water of 49 degrees (phosphorylated starch, manufactured by Nippon Food Processing Co., Ltd., Solar Eclipse MS # 4600) 5 mass% aqueous solution (surface sizing liquid) containing 0.05 part by mass of an ether-based nonionic surfactant (manufactured by Nissin Chemical Industry Co., Ltd., Surfynol 440, HLB: 8) Size-pressed with a size press for testing by Kumagaya Riki so that the treatment amount is 1 g / m ² in terms of dry mass (surfactant applied amount is 0.005 g / m ² ), and then with a KRK rotary dryer made by Kumagaya Riki It dried on 110 degreeC and 0.5 m / min conditions, and obtained the recording paper (9) whose basic weight is 69 g / m < ² >.

<Recording paper (10)>
100 parts by mass of a surface sizing agent (oxidized starch, manufactured by Oji Cornstarch Co., Ltd., Ace B) having a contact angle with water of Green 100 paper (medium recycled paper) manufactured by Fuji Xerox Office Supply, and 16.6 parts by mass 1 g of an aqueous non-ionic surfactant (Shinfin Chemical Co., Ltd., Surfynol 440, HLB: 8) containing 5% by weight of an aqueous solution (surface sizing liquid) with a dry weight of 1 g. / M ² (surfactant applied amount is 0.14 g / m ² ) After size pressing with a Kumagaya Riki test size press, 110 ° C., 0.5 m / min with a KRK rotary dryer manufactured by Kumagaya Riki It dried on min conditions and obtained the recording paper (10) with a basic weight of 69 g / m < ² >.

<Recording paper (11)>
Dry pulp composed of hardwood kraft pulp, which was beaten and adjusted to a freeness of 420 ml, was disaggregated to prepare a pulp dispersion so that the pulp solid content was 0.3% by mass.
In this pulp dispersion, 0.3 part by mass of succinic anhydride (ASA) internal sizing agent (Fibran-81 manufactured by Nippon SC Co., Ltd.) with respect to 100 parts by mass of pulp solids contained in the pulp dispersion And 0.5 parts by mass of cationized starch (NCS Co., Ltd. Cato-304), and using an 80-mesh wire with an orientation paper machine for experiments made by Kumagai Riki, paper making speed of 1000 m / min, paper Paper making was performed under the condition of a material discharge pressure of 1.5 kg / cm ² . Thereafter, the set was squeezed for 3 minutes at 10 kg / cm ² with a press for a square sheet machine made by Kumagai Riki, and then dried at 110 ° C. and 0.5 m / min on a KRK rotary dryer made by Kumagai Riki. A base paper having an amount of 69 g / m ² was obtained.

On this base paper, 50 parts by mass of oxidized starch as a surface sizing agent (Oji Cornstarch Co., Ltd., Ace A, contact angle with water: 39 degrees) and polyvinyl alcohol (Kuraray Co., Ltd., PVA102, degree of saponification: 99, polymerization) Degree: 200, contact angle with water: 64 degrees) 50 parts by weight, 10 parts by weight of sodium nitrate, 50 parts by weight of an ester-based nonionic surfactant (manufactured by Nippon Emulsion Co., Ltd., EMALEX TSG-10, HLB: 8) A test size manufactured by Kumagai Riki Co., Ltd. so that the processing amount of the 5% by weight aqueous solution (surface size solution) containing 1 g / m ² on the base paper is 1 g / m ² (surfactant applied amount is 0.3 g / m ² ). After size-pressing with a press, the paper was dried with a KRK rotary dryer manufactured by Kumagai Riki under conditions of 110 ° C. and 0.5 m / min to obtain a recording paper (11) having a basis weight of 70 g / m ² .

<Recording paper (12)>
A base paper having a basis weight of 69 g / m ² obtained in the same manner as the recording paper (11), oxidized starch as a surface sizing agent (Ace A, manufactured by Oji Cornstarch Co., Ltd., contact angle with water: 39 degrees), 50 mass Parts and polyvinyl alcohol (manufactured by Kuraray Co., Ltd., PVA102, degree of saponification: 99, degree of polymerization: 200, contact angle with water: 64 degrees), 10 parts by weight of sodium nitrate, ester-based nonionic surfactant (Japan) Emulsion Co., Ltd., EMALEX SPIS-100, HLB: 10) 5% by weight aqueous solution (surface sizing liquid) containing 50 parts by mass so that the processing amount to the base paper is 1 g / m ² (surface active) agent application amount is 0.3 g / m ^2), after size press in Kumagaya size press Riki made tests, 110 ° C. in Kumagaya Riki made KRK rotary dryer and dried at 0.5 m / min conditions, basis There was obtained a recording paper of 70g / m ² (12).

<Recording paper (13)>
A base paper having a basis weight of 69 g / m ² obtained in the same manner as the recording paper (11), oxidized starch as a surface sizing agent (Ace A, manufactured by Oji Cornstarch Co., Ltd., contact angle with water: 39 degrees), 50 mass Parts and polyvinyl alcohol (manufactured by Kuraray Co., Ltd., PVA102, degree of saponification: 99, degree of polymerization: 200, contact angle with water: 64 degrees), 10 parts by weight of sodium nitrate, ester-based nonionic surfactant (Japan) Emulsion Co., Ltd., EMALEX GMS-B, HLB: 6) A 5% by weight aqueous solution (surface sizing liquid) containing 50 parts by mass so that the processing amount to the base paper is 1 g / m ² (surface active) The amount of agent applied was 0.3 g / m ² ), size pressed with a size press for testing by Kumagaya Riki, and then dried at 110 ° C. and 0.5 m / min on a KRK rotary dryer manufactured by Rum Kumagai. 70 / Yield m ² of the recording sheet (13).

<Recording paper (14)>
A base paper having a basis weight of 69 g / m ² obtained in the same manner as the recording paper (11), oxidized starch as a surface sizing agent (Ace A, manufactured by Oji Cornstarch Co., Ltd., contact angle with water: 39 degrees), 50 mass Parts and polyvinyl alcohol (manufactured by Kuraray Co., Ltd., PVA102, degree of saponification: 99, degree of polymerization: 200, contact angle with water: 64 degrees), 10 parts by weight of sodium nitrate, ester-based nonionic surfactant (Japan) Emulsion Co., Ltd., EMALEX TSG-10, HLB: 8) A 5% strength by weight aqueous solution (surface sizing liquid) containing 50 parts by mass so that the processing amount to the base paper is 1 g / m ² (surface active) The amount of the applied agent is 0.1 g / m ² ), size pressed with a size press for testing by Kumagai Riki, and then dried at 110 ° C. and 0.5 m / min with a KRK rotary dryer manufactured by Rum Kumagai. 7 to obtain a recording paper g / m ² (14).

<Recording paper (15)>
A base paper having a basis weight of 69 g / m ² obtained in the same manner as the recording paper (11), oxidized starch as a surface sizing agent (Ace A, manufactured by Oji Cornstarch Co., Ltd., contact angle with water: 39 degrees), 50 mass Parts and polyvinyl alcohol (manufactured by Kuraray Co., Ltd., PVA102, degree of saponification: 99, degree of polymerization: 200, contact angle with water: 64 degrees), 10 parts by weight of sodium nitrate, ester-based nonionic surfactant (Japan) Emulsion Co., Ltd., EMALEX TSG-10, HLB: 8) 5% by weight aqueous solution (surface sizing liquid) containing 100 parts by mass so that the processing amount to the base paper is 2 g / m ² (surface active) agent application amount is 1.0 g / m ^2), after size press in Kumagaya size press Riki made tests, 110 ° C. in Kumagaya Riki made KRK rotary dryer and dried at 0.5 m / min conditions, basis weight To obtain a recording paper of 1g / m ² (15).

<Recording paper (16)>
In the papermaking on the recording paper (11), except that the amount of the internally added sizing agent was changed to 0.4 parts by mass, a base paper having a basis weight of 69 g / m ² obtained in the same manner was coated with oxidized starch (Oji corn starch) as a surface sizing agent. 50 parts by mass, polyvinyl alcohol (manufactured by Kuraray Co., Ltd., PVA102, saponification degree: 99, polymerization degree: 200, contact angle with water: 64 degrees) 11 A 5% by weight aqueous solution (surface sizing liquid) containing 10 parts by weight of sodium hydroxide and 50 parts by weight of ester nonionic surfactant (manufactured by Nippon Emulsion Co., Ltd., EMALEX TSG-10, HLB: 8). , so that the processing amount to the base paper becomes 1 g / m ² (surface active agent deposition amount 0.1 g / m ^2), after size press in Kumagaya size press Riki made tests, Kumagai Riki made KRK times 110 ° C. in a type drier, and dried at 0.5 m / min conditions, basis weight was obtained recording paper 70g / m ² (16).

<Recording paper (17)>
In the papermaking on the recording paper (11), except that the amount of the internally added sizing agent was changed to 0.1 parts by mass, a base paper having a basis weight of 69 g / m ² obtained in the same manner was coated with oxidized starch (Oji corn starch) as a surface sizing agent. 50 parts by mass, polyvinyl alcohol (manufactured by Kuraray Co., Ltd., PVA102, saponification degree: 99, polymerization degree: 200, contact angle with water: 64 degrees) 50 A 5% by weight aqueous solution (surface sizing liquid) containing 10 parts by weight of sodium hydroxide and 50 parts by weight of ester nonionic surfactant (manufactured by Nippon Emulsion Co., Ltd., EMALEX TSG-10, HLB: 8). , so that the processing amount to the base paper becomes 1 g / m ² (surface active agent deposition amount 0.3 g / m ^2), after size press in Kumagaya size press Riki made tests, Kumagai Riki made KRK times 110 ° C. in a type drier, and dried at 0.5 m / min conditions, basis weight was obtained recording paper 70g / m ² (17).

<Recording paper (18)>
10 mass of oxidized starch (Ace A, manufactured by Oji Cornstarch Co., Ltd., contact angle with water: 39 degrees) as a surface sizing agent on a base paper having a basis weight of 69 g / m ² obtained in the same manner as the recording paper (11) Part and polyvinyl alcohol (manufactured by Kuraray Co., Ltd., PVA102, degree of saponification: 99, degree of polymerization: 200, contact angle with water: 64 degree), 10 parts by weight of sodium nitrate, ester-based nonionic surfactant (Japan) Emulsion Co., Ltd., EMALEX TSG-10, HLB: 8) A 5% strength by weight aqueous solution (surface sizing liquid) containing 50 parts by mass so that the processing amount to the base paper is 1 g / m ² (surface active) The amount of agent applied was 0.3 g / m ² ), size pressed with a size press for testing by Kumagaya Riki, and then dried at 110 ° C. and 0.5 m / min on a KRK rotary dryer manufactured by Rum Kumagai. 7 to obtain a recording paper g / m ² (18).

<Recording paper (19)>
A base paper having a basis weight of 69 g / m ² obtained in the same manner as the recording paper (11), oxidized starch as a surface sizing agent (Ace A, manufactured by Oji Cornstarch Co., Ltd., contact angle with water: 39 degrees), 50 mass Parts and polyvinyl alcohol (manufactured by Nippon Shokuhin Kako Co., Ltd., phosphoric esterified starch # 4600, contact angle with water: 56 degrees), 10 parts by weight of sodium nitrate, an ester-based nonionic surfactant (Nippon Emulsion Co., Ltd.) Manufactured, EMALEX TSG-10, HLB: 8) 5% by weight aqueous solution (surface sizing liquid) containing 50 parts by mass so that the amount of processing to the base paper is 1 g / m ² (surfactant applied amount) Is 0.3 g / m ² ), size-pressed with a size press for testing by Kumagai Riki, and then dried at 110 ° C. and 0.5 m / min with a KRK rotary dryer made by Kumagai Riki, with a basis weight of 70 g / m. ² Recording paper (19) was obtained.

<Recording paper (20)>
A base paper having a basis weight of 69 g / m ² obtained in the same manner as the recording paper (11), oxidized starch as a surface sizing agent (Ace A, manufactured by Oji Cornstarch Co., Ltd., contact angle with water: 39 degrees), 50 mass Parts and polyvinyl alcohol (manufactured by Kuraray Co., Ltd., PVA110, degree of saponification: 99, degree of polymerization: 1000, contact angle with water: 68 degrees), 10 parts by weight of sodium nitrate, ester-based nonionic surfactant (Japan) Emulsion Co., Ltd., EMALEX TSG-10, HLB: 8) A 5% strength by weight aqueous solution (surface sizing liquid) containing 50 parts by mass so that the processing amount to the base paper is 1 g / m ² (surface active) agent application amount is 0.3 g / m ^2), after size press in Kumagaya size press Riki made tests, 110 ° C. in Kumagaya Riki made KRK rotary dryer and dried at 0.5 m / min conditions, basis weight To obtain a recording paper of 0g / m ² (20).

<Recording paper (21)>
A base paper having a basis weight of 69 g / m ² obtained in the same manner as the recording paper (11), oxidized starch as a surface sizing agent (Ace A, manufactured by Oji Cornstarch Co., Ltd., contact angle with water: 39 degrees), 50 mass Parts and polyvinyl alcohol (manufactured by Kuraray Co., Ltd., PVA505, degree of saponification: 73, degree of polymerization: 500, contact angle with water: 55 degrees), 10 parts by weight of sodium nitrate, an ester-based nonionic surfactant (Japan) Emulsion Co., Ltd., EMALEX TSG-10, HLB: 8) A 5% strength by weight aqueous solution (surface sizing liquid) containing 50 parts by mass so that the processing amount to the base paper is 1 g / m ² (surface active) The amount of agent applied was 0.3 g / m ² ), size pressed with a size press for testing by Kumagaya Riki, and then dried at 110 ° C. and 0.5 m / min on a KRK rotary dryer manufactured by Rum Kumagai. 7 to obtain a recording paper g / m ² (21).

<Recording paper (22)>
A base paper having a basis weight of 69 g / m ² obtained in the same manner as the recording paper (11), oxidized starch as a surface sizing agent (Ace A, manufactured by Oji Cornstarch Co., Ltd., contact angle with water: 39 degrees), 50 mass Parts and polyvinyl alcohol (manufactured by Kuraray Co., Ltd., PVA102, degree of saponification: 99, degree of polymerization: 200, contact angle with water: 64 degrees), 10 parts by weight of sodium nitrate, ester-based nonionic surfactant (Japan) Emulex TSG-10 manufactured by Emulsion Co., Ltd., HLB: 8) A processing amount of a 5% by weight aqueous solution (surface sizing liquid) containing 50 parts by mass and 75 parts by mass of calcium chloride as a polyvalent metal salt to base paper in so it becomes 1.5 g / m ² (surface active agent deposition amount 0.4 g / m ^2), after size press in Kumagaya size press Riki made tests, Kumagai Riki made KRK rotary dryer 10 ° C., and dried at 0.5 m / min conditions, basis weight was obtained recording paper 71g / m ² (22).

<Recording paper (23)>
The basis weight is 70 g / m ² and the formation index is 15 in the same manner as the recording paper (21) except that the base paper obtained by setting the freeness in the recording paper (11) to 500 ml is used. Recording paper (23) was obtained.

<Recording paper (24)>
A base paper having a basis weight of 69 g / m ² obtained in the same manner as in the recording paper (11), oxidized starch as a surface sizing agent (Ace A, manufactured by Oji Cornstarch Co., Ltd., contact angle with water: 39 degrees), 25 mass Parts and polyvinyl alcohol (manufactured by Kuraray Co., Ltd., PVA102, degree of saponification: 99, degree of polymerization: 200, contact angle with water of 64 degrees) and an ester nonionic surfactant (manufactured by Nippon Emulsion Co., Ltd., EMALEX TSG) -10, HLB: 8) A 5% strength by weight aqueous solution (surface sizing solution) containing 100 parts by mass so that the amount of treatment to the base paper is 3 g / m ² (surfactant applied amount is 2.0 g) / M ² ), size-pressed using a test size press manufactured by Kumagai Riki Co., Ltd., then dried at 110 ° C. and 0.5 m / min using a KRK rotary dryer manufactured by Kumagai Riki Co., Ltd., with a basis weight of 72 g / m ² (24) was obtained.

<Recording paper (25)>
A base paper having a basis weight of 69 g / m ² obtained in the same manner as the recording paper (11), oxidized starch as a surface sizing agent (Ace A, manufactured by Oji Cornstarch Co., Ltd., contact angle with water: 39 degrees), 50 mass Parts and polyvinyl alcohol (manufactured by Kuraray Co., Ltd., PVA102, degree of saponification: 99, degree of polymerization: 200, contact angle with water of 64 degrees), ether ester nonionic surfactant (manufactured by Nippon Emulsion Co., Ltd., EMALEX TPM-320, HLB: 9) A 5% strength by weight aqueous solution (surface sizing solution) containing 50 parts by mass is applied to the base paper so that the treatment amount becomes 1 g / m ² (surfactant applied amount is 0). 3 g / m ² ), size pressed with a size press for testing by Kumagaya Riki, and then dried at 110 ° C. and 0.5 m / min with a KRK rotary dryer manufactured by Rum Kumagai, and the basis weight is 70 g / m ^2. Recording paper (25) was obtained.

<Recording paper (26)>
100 mass of oxidized starch (Oji Cornstarch Co., Ltd., Ace A, contact angle with water: 39 degrees) as a surface sizing agent on a base paper having a basis weight of 69 g / m ² obtained in the same manner as the recording paper (11) Part and an ester-based nonionic surfactant (manufactured by Nippon Emulsion Co., Ltd., EMALEX TSG-10, HLB: 8) in an amount of 5% by weight aqueous solution (surface size liquid), After size-pressing with a test size press manufactured by Kumagai Riiki so that the amount is 1 g / m ² (surfactant applied amount is 0.3 g / m ² ), 110 ° C., 0. The recording paper (26) having a basis weight of 70 g / m ² was obtained by drying under the condition of 5 m / min.

<Recording paper (27)>
A base paper having a basis weight of 69 g / m ² obtained in the same manner as the recording paper (11), oxidized starch as a surface sizing agent (Ace A, manufactured by Oji Cornstarch Co., Ltd., contact angle with water: 39 degrees), 50 mass Parts and polyvinyl alcohol (manufactured by Kuraray Co., Ltd., PVA102, degree of saponification: 99, degree of polymerization: 200, contact angle with water of 64 degrees), ester nonionic surfactant (manufactured by Nippon Emulsion Co., Ltd., EMALEX INTD) -139, HLB: 2) A 5% strength by weight aqueous solution (surface sizing solution) containing 50 parts by mass so that the processing amount to the base paper is 1 g / m ² (surfactant applied amount is 0.3 g) / M ² ), size-pressed with Kumagaya Riki test size press, then dried with KRK rotary type KRK rotary dryer at 110 ° C. and 0.5 m / min for recording with basis weight of 70 g / m ² Paper (27) was obtained.

<Recording paper (28)>
A base paper having a basis weight of 69 g / m ² obtained in the same manner as the recording paper (11), oxidized starch as a surface sizing agent (Ace A, manufactured by Oji Cornstarch Co., Ltd., contact angle with water: 39 degrees), 50 mass Parts and polyvinyl alcohol (made by Kuraray Co., Ltd., PVA102, degree of saponification: 99, degree of polymerization: 200, contact angle with water: 64 degrees) Size press with a size press for testing made by Kumagai Riki so that the amount of processing becomes 1 g / m ^2, and then dried at 110 ° C. and 0.5 m / min on a KRK rotary dryer made by Kumagai Riki. A recording paper (28) having an amount of 70 g / m ² was obtained.
Table 1 summarizes the configuration and characteristic values of each recording sheet.

(Examples 6 to 19, Comparative Examples 1 to 15 )
Using the recording paper, image recording was performed by an ink jet recording method and an electrophotographic method, and the recording paper performance was confirmed as follows. Table 2 summarizes the recording paper used in each example and comparative example, the conditions of inkjet recording, and the like.

(1) Evaluation by inkjet recording method Printing evaluation is performed in an environment of 23 ° C. and 50% RH, and printing is performed using a thermal inkjet recording apparatus for evaluation of multi-pass printing including four recording heads. ink ejection nozzle pitch is 800 dpi, the ink discharge nozzles 256 nozzles, the discharge amount of about 15 pl, ink ejection amount is the standard and 10 ml / m ^2, and the two levels of 7.5 ml / m ^2. Printing was performed by single-sided batch printing at a head scan speed of about 28 cm / sec.

Various evaluations after printing were performed as follows.
-Curling evaluation immediately after printing-
A margin of 5 mm was taken on a postcard-sized recording paper, a 100% solid Magenta image was printed, and the amount of hanging curl generated immediately after printing on the surface opposite to the printed surface was measured. The measured value was converted into curvature and evaluated. The evaluation criteria are as follows, and ◎ and ○ are acceptable levels.
◎: Less than 20 m ^-1 ○: 20 m ^-1 or more and less than 35 m ^-1 Δ: 35 m ^-1 or more and less than 50 m ^-1 ×: 50 m ^-1 or more

−Wave evaluation immediately after printing−
A 2 cm × 2 cm secondary color 100% solid (Blue) image was printed on a postcard-sized recording paper at the center of the postcard, and the maximum height of the corrugation generated immediately after printing was measured with a laser displacement meter. The evaluation criteria are as follows, and ◎ and ○ are acceptable levels.
◎: Less than 1 mm ○: 1 mm or more and less than 2 mm Δ: 2 mm or more and less than 3 mm x: 3 mm or more

-Curling evaluation after leaving to dry-
5mm margin on a postcard size recording paper, printing a 100% Magenta solid image, leaving the printing surface flat on an environment of 23 ° C and 50% RH, and hanging after leaving for 100 hours after printing The amount of curling was measured. The measured value was converted into a curl curvature and evaluated. The evaluation criteria are as follows, and ◎ and ○ are acceptable levels.
◎: Less than 30 m ^-1 ○: 30 m ^-1 or more and less than 75 m ^-1 ×: 75 m ^-1 or more

-Image quality evaluation-
An image in which Yellow 100% and Black 100% are adjacent to each other was printed on a postcard-sized recording paper, and the boundary was evaluated according to the following criteria. ○ is an acceptable level.
○: No blurring occurs in the mixed colors of the image, and the back surface is small.
Δ: Slight blurring of mixed colors in the image or slight offset
X: The image has mixed color bleeding or a large setback.
The above results are summarized in Table 2.

(2) Evaluation in electrophotographic system The recording papers (1) to (10) were evaluated as follows using DocuCenterColor400CP manufactured by Fuji Xerox Co., Ltd. as an electrophotographic recording apparatus.
A margin of 5 mm was taken on a postcard-sized recording paper, a Magenta 100% solid image was printed, and the amount of hanging curl immediately after printing was measured. The measured value was converted into curvature and evaluated. The evaluation criteria are as follows, and ◎ and ○ are acceptable levels.
◎: Less than 10 m ^-1 ○: 10 m ^-1 or more and less than 20 m ^-1 Δ: 20 m ^-1 or more and less than 35 m ^-1 ×: 35 m ^-1 or more

For the recording sheets (11) to (28), the following evaluation was performed using DocuPrint C3530 manufactured by Fuji Xerox Printing Systems Co., Ltd. as an electrophotographic recording apparatus.
Using a chart capable of outputting a monochrome black with a dot area ratio of 100%, printer output was performed using the recording paper, and toner transfer unevenness was visually evaluated according to the following evaluation criteria. ○ and ○-are acceptable levels.
○: Excellent toner transfer unevenness. There is no problem in practical use.
○-: Toner transfer unevenness is very slight. There is no problem in practical use.
Δ: Toner transfer unevenness and slightly inferior. There are practical problems.
X: Toner transfer unevenness is large and inferior. There are practical problems.
The results are summarized in Table 2.

  As shown in Table 2, the recording paper of the present invention used in the examples was excellent in image quality without causing curling or undulation after printing in both the ink jet recording method and the electrophotographic method. On the other hand, in the recording paper of the comparative example, some problems such as curling after printing, image quality deterioration, and in-machine running failure occurred.

It is a schematic diagram which shows the state which measures the contact angle with water in this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Preparation 20 Surface sizing agent film layer 30 Micro syringe 40 Drop of distilled water 50 CCD camera

Claims (5)

At least the surface of the substrate made of cellulose pulp as a raw material contains a surface sizing agent and an ester nonionic surfactant as a nonionic surfactant having an HLB in the range of 6 to 13, and the content of the ester nonionic surfactant Is in the range of 1 to 100 parts by mass with respect to 100 parts by mass of the surface sizing agent, and the surface sizing agent having a contact angle with water of 40 to 75 degrees has a saponification degree of 98 or more, or 35 or more. by a polyvinyl alcohol is less than 80 surface sizing solution containing 5 wt% or more of the total surface size of the polyvinyl alcohol, Ri Na been surface treated, have a layer ink absorbed by the surface-treated said surface A recording paper on which an image is recorded on the surface . The ester nonionic surfactant has an HLB of 6 or more and less than 11 , and the applied amount of the ester nonionic surfactant after the surface treatment is in the range of 0.02 to 1.0 g / m ^2. the recording sheet according to claim 1 degree is equal to or in the range of 1 to 30 seconds at a basis weight 70 g / m ² basis. The recording paper according to claim 1 or 2, wherein a concentration of a component containing the surface sizing agent and the ester nonionic surfactant in the surface sizing liquid is in a range of 3 to 7% by mass. . An inkjet recording type image recording method for discharging ink droplets onto a recording sheet and recording an image on the surface of the recording sheet,
The image recording method according to claim 1, wherein the recording sheet is the recording sheet according to claim 1 . A charging step for charging the surface of the electrostatic latent image carrier; an exposure step for exposing the surface of the electrostatic latent image carrier to form an electrostatic latent image; and an electrostatic process formed on the surface of the electrostatic latent image carrier. A latent image is developed using an electrostatic latent image developer to form a toner image, a transfer step for transferring the toner image to the surface of the recording paper, and a fixing step for fixing the toner image on the surface of the recording paper An electrophotographic image recording method including:
The image recording method according to claim 1, wherein the recording sheet is the recording sheet according to claim 1 .