JP4797416B2 - 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 the same, and more specifically, a recording paper called a plain paper that does not have a coating layer containing a pigment on the surface, and an electrophotographic system using the recording paper And an ink jet image recording method.

  Electrophotographic equipment, such as laser printers and copiers, now permeates most offices. Therefore, a recording paper that is mainly used is a recording paper that does not have a coating layer containing a pigment on a surface called a so-called plain paper.

On the other hand, the ink-jet recording method is easy to colorize, has low energy consumption, low noise during recording, and can reduce the manufacturing cost of the printer. .
Therefore, as a function required for so-called plain paper in the office, it can be used without any problem in both the electrophotographic recording method and the ink jet recording method.

  However, in the electrophotographic recording system, when the toner image transferred onto the paper is heat-fixed, the paper is curled by dehumidification from the heating surface because it is heated from one side of the paper. For this reason, there are problems such as paper jams at the paper discharge unit and poor storage capacity of the paper discharge tray.

  Various studies have been made to improve the problem of curling after printing. For example, paying attention to the distortion inherent in the paper, a method of performing tension drying at the time of papermaking and drying of the transfer paper (for example, refer to Patent Document 1), or by adjusting the moisture at the time of packaging to reduce the moisture, There has been proposed a method for reducing the elongation due to. For example, a method (for example, see Patent Documents 2 and 3) that defines the moisture content immediately after calendar finishing of coated paper is disclosed.

  Moreover, although the method of making the front-back difference of fiber orientation small and prescribing the moisture content at the time of opening is disclosed (for example, refer patent document 4), the front-back difference of expansion / contraction behavior is made small by making the front-back difference of fiber orientation small. It is thought that it will decrease. However, in the electrophotographic thermal fixing unit, the most common method is to fix the toner by sandwiching between the heating unit and the pressure unit, and the temperature differs between the heating unit and the pressure unit. The expansion and contraction behaviors of the front and back surfaces are different, and it seems difficult to reduce curling after heat fixing. In addition, when the moisture content at the time of opening is lowered, the paper absorbs moisture in an environment where the paper is left after opening, and therefore contributes less to curling after heat fixing.

  Furthermore, although a method for defining the moisture content at the time of opening of a paper having a pigment coating layer including a void portion is disclosed (for example, refer to Patent Document 5), it is possible to improve the image quality by providing the pigment coating layer with a void. This is the purpose and has no effect on curling after heat fixing. Further, reducing the moisture content at the time of opening is insufficient for reducing the post-heat-fixing curl of the paper that has absorbed moisture in the left environment.

  A method in which the underwater elongation and the moisture content at the time of opening are specified is also disclosed (for example, see Patent Document 6). However, curling after heat fixing is a change in paper dimensions at the time of dehumidification, and it is impossible to control curling after heat fixing by controlling the elongation in water, which is a dimensional change at the time of moisture absorption. As described above, by reducing the moisture content at the time of opening, the effect of reducing the heat fixing curl after moisture absorption is insufficient.

  Moreover, in addition to the moisture adjustment at the time of packaging, a method for regulating the moisture content in a 28 ° C. and 85% RH environment is also disclosed (for example, see Patent Document 7). This method stipulates the difference between the equilibrium moisture in a high humidity environment and the moisture content at the time of opening, but this method is also based on the ease of moisture absorption of the paper. The effect is insufficient as a control factor. A method for regulating the moisture content at 20 ° C. and 65% RH and the moisture content at the time of opening has also been proposed (see, for example, Patent Documents 8 and 9), but the effect of reducing heat fixing curl after moisture absorption is insufficient. It is.

  In addition, a method of defining only the moisture content at 20 ° C. and 65% RH for waste paper-containing paper has also been proposed (see, for example, Patent Document 10). However, this method is also based on the ease of moisture absorption of the paper, and is not sufficiently effective as a control factor for post-heat-fixing curl that occurs during dehumidification. In addition, in this method, means for using low beating pulp or increasing the internal filler have been proposed, but it is an electrophotographic method to use pulp with low beating degree or excessively increasing the internal filling amount. In the ink jet method, paper dust is generated, and transportability and print quality are hindered. Therefore, it is not preferable as plain paper used in the office.

  Recent copiers and printers are becoming smaller and more complex, such as automatic double-sided copying and automatic bookbinding, and the mechanism and paper path of the device are becoming more complex, and the diameter and complexity of the heat-fixing roll are also increasing. Therefore, even if only the difference between the front and back of the dimensional change is reduced, when using paper with the above technology under high humidity conditions, especially for small printers that heat more from one side, the curl after heat fixing becomes large, and the edge of the paper However, it has become clear that paper jams or the like are likely to occur due to contact with members in the machine, and the above-described prior art cannot sufficiently reduce curling after heat fixing.

  On the other hand, in the inkjet method, when an image with a high image density is printed, curling to the opposite side of the printing surface is noticeable immediately after printing, and the ink surface is greatly curled after drying the ink. It has become. In electrophotography, there is still a problem that the curl after fixing becomes large on a sheet with high moisture.

  In the inkjet method, as a method of improving curling and undulation after printing, for example, a method of reducing curling and undulation by once humidifying a paper sheet and reducing the stress of the paper (see, for example, Patent Document 11) , A method for reducing the underwater elongation in the CD direction of the paper to reduce curling and undulations (see, for example, Patent Document 12), and the underwater elongation rate in the MD direction and the CD direction of the paper is 1.3 times or less. To reduce curling and undulation (for example, see Patent Document 13), and to reduce curling and undulation by reducing the underwater elongation in the operation direction of the ink ejecting portion to 2.0% or less (for example, Patent Document 14), a method of reducing curling and undulation by setting the underwater elongation in the CD direction to 1.8% or less (for example, see Patent Document 15) and the like have been proposed.

However, it has been reported that these methods have a certain effect on curling and undulation. However, with these methods, curling occurs when ink that has high permeability to the inside of the recording paper is used, and when the amount of ink discharged is large or when the printing speed is high and the amount of ink discharged per unit time is large. It grows up and cannot be used as a document.
In addition, a method has been proposed for reducing waviness after printing by keeping the internal bond strength of a recording sheet provided with an ink receiving layer within a certain range (see, for example, Patent Document 16). However, it is not possible to obtain a sufficient effect on curling, undulation and undulation simply by defining the internal bond strength. 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, a method has been proposed for reducing curling and undulation that occurs after drying by leaving the irreversible shrinkage rate in the MD direction and the CD direction within a certain range when the relative humidity of the leaving environment is changed ( For example, see Patent Document 17). 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.

Further, in an ink jet recording sheet having a base material and an ink receiving layer, the ink receiving layer comprising a cationic polymer and porous inorganic fine particles contains a maleic anhydride-containing polymer to improve the water resistance of the ink receiving layer. Paper has been proposed (see, for example, Patent Document 18). This is obtained by improving water resistance by reacting maleic anhydride with a cationic polymer, and cannot improve curl.
JP-A-5-341554 JP-A-5-241366 Japanese Patent Laid-Open No. 7-219262 JP-A-6-138688 JP-A-8-123066 JP 11-282193 A JP-A-6-202371 JP-A-6-295087 JP 11-338181 A JP-A-3-287894 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 JP 2001-334744 A

  The present invention suppresses curling that occurs after fixing when an image is formed by an electrophotographic method, and curls and waviness that occur immediately after printing when printed by an ink jet recording method, and curls that occur after standing drying and It is an object of the present invention to provide a recording sheet capable of suppressing undulations and an image recording method using the same.

As a result of intensive investigations on curling reduction of recording paper used for image recording in electrophotographic and ink jet recording systems, the present inventors have found that the following invention solves the above-described problems, and complete the present invention. It came.
That is, the present invention is,

< 1 > A recording paper containing pulp fibers and fillers as main components, and containing an acid anhydride composed of an organic acid having 1 or 2 carboxyl groups and a molecular weight of 160 or less. is there.
< 2 > The acid anhydride is at least one selected from the group consisting of itaconic anhydride, glutaconic anhydride, glutaric anhydride, succinic anhydride, maleic anhydride, phthalic anhydride, malonic anhydride, and butyric anhydride. The recording paper according to < 1 >, which is characterized by the above.

< 3 > The recording paper according to < 1 >, further comprising a nonionic water-soluble polymer.
< 4 > The recording paper according to < 3 >, wherein the nonionic water-soluble polymer is polyvinyl alcohol.

< 5 > A charging step for uniformly 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 on the surface of the electrostatic latent image carrier. The formed electrostatic latent image is developed using an electrostatic charge image developer to form a toner image, a transfer step for transferring the toner image onto a recording paper, and a transfer onto the recording paper An image recording method of an electrophotographic recording system including a fixing step of fixing a toner image, wherein the recording paper is the recording paper described in < 1 >.

< 6 > Inkjet image recording method in which droplets of ink containing water and / or a water-soluble organic solvent and a color material are ejected onto the surface of a recording paper to form an image on the surface of the recording paper The image recording method is characterized in that the recording sheet is the recording sheet described in < 1 >.

  According to the present invention, curling that occurs after fixing when an image is formed by an electrophotographic method is suppressed, and curling and undulation that occurs immediately after printing when an image is printed by an inkjet recording method, and that occurs after being left to dry. It is possible to provide a recording sheet capable of suppressing curling and undulation, and an image recording method using the recording sheet.

<Recording paper>
The recording paper of the first aspect of the present invention is a recording paper produced through a step of applying a size press treatment liquid on the surface of a base paper containing pulp fibers and fillers as main components, and the size press treatment liquid Difference between the moisture content when the sample contains at least starch and is conditioned in a 23 ° C. and 50% RH environment and the moisture content when conditioned in a 23 ° C. and 50% RH environment and then conditioned in a 23 ° C. and 25% RH environment Is 1.2% or less. Here, “containing pulp fiber and filler as main components” means that the total content of pulp fiber and filler is 80% by mass or more.

  In the recording paper of the first aspect of the present invention, the moisture content when adjusted to a humidity of 23 ° C. and 50% RH is JIS-P-8127, except that the humidity is adjusted for 12 hours or more in a 23 ° C. and 50% RH environment. : It is the value measured by the method based on 1998. The moisture content when humidity is adjusted in a 23 ° C. and 25% RH environment after conditioning in a 23 ° C. and 50% RH environment is 23 ° C. and 50% RH in an environment of 23 ° C. and 25% RH. The value is measured by a method based on JIS-P-8127: 1998 except that the humidity is adjusted for 12 hours or more.

The recording paper of the first invention is a so-called plain paper that does not have a coating layer containing a pigment. The size press treatment liquid is preferably substantially free of pigment. However, “substantially free of pigment” means that the blending amount of the pigment in the size press treatment liquid is 10% by mass or less.
Hereinafter, the recording paper of the first aspect of the present invention will be described.

  The difference between the moisture content when the humidity is adjusted in the 23 ° C. and 50% RH environment and the moisture content when the humidity is adjusted in the 23 ° C. and 25% RH environment after conditioning in the 23 ° C. and 50% RH environment (hereinafter referred to as “the present invention”). The difference in the moisture content in the case of “is sometimes referred to as a“ moisture percentage difference ”” is essential to be 1.2% or less as described above, preferably 1.1% or less, and more preferably 1.0% or less. preferable. If the moisture content difference in the present invention exceeds 1.2%, the effect of the present invention of suppressing curling and undulation cannot be obtained.

  The recording paper of the first invention preferably has a moisture content of 6.6% or less, more preferably 6.4% or less when the humidity is adjusted in the 23 ° C. and 50% RH environment. More preferably, it is 6.0% or less. When the moisture content when the humidity is adjusted in the 23 ° C. and 50% RH environment is 6.6% or less, the effect of the present invention of suppressing curling and undulation becomes more remarkable.

  The recording paper of the first aspect of the present invention has a moisture content difference in the present invention of 1.2% or less by passing through a step of applying a size press treatment liquid containing at least starch. It is possible to reduce the moisture content to 6.6% or less when humidity is adjusted in an RH environment.

Examples of the starch used in the recording paper of the first present invention include starch that is processed to a certain degree of low molecular weight by processing starch in addition to the starch itself obtained by extraction from plants, and has improved workability. Examples thereof include enzyme-modified starch in which a glucoside bond has been cleaved by enzyme treatment, and oxidized starch that has been decomposed and reduced in molecular weight using an oxidizing agent.
In general, oxidized starch is often used as a surface sizing agent for papermaking. Not only processed starch oxidized with sodium hypochlorite but also oxidized with other oxidizing agents, such as periodate. Self-modified starch obtained by thermochemically treating a treated dialdehyde starch or raw starch with an oxidizing agent such as persulfate immediately before use is used.

In the recording paper according to the first aspect of the present invention, the size press treatment liquid preferably contains a saccharide together with the starch. When the size press treatment liquid contains saccharide, the effect of the present invention of suppressing curling and undulation becomes more remarkable.
Sugars are generally highly hygroscopic substances, but when mixed with starch, the hygroscopicity of the mixture is low, and even when subjected to size press treatment on the surface of recording paper, the effect of suppressing moisture fluctuations appears and dehumidifies. Water fluctuation due to is small. As the saccharides, oligosaccharides are particularly preferable because of their high affinity with starch.

  In addition, by using these sugars together, even when oxidized starch is used, the phenomenon (white spots), which is an ink-jet image quality defect and that is not dyed as if it were white-repelled in a solid part, is suppressed. Can do. This is because the carboxyl groups of oxidized starch have repulsive force against ink color materials having the same anionic property, whereas substances that are easily soluble in water, such as oligosaccharides, form large aggregates with the color material. I guess it is less affected. This is particularly effective for dye inks that have a small colorant size and are easily affected by the repulsive force of oxidized starch.

The recording paper of the first aspect of the present invention preferably contains a large amount of components that are easily eluted when hot water extraction is performed on a paper coated with a size press solution containing starch and saccharide components. In this case, the saccharide is preferably contained in an amount of 10 to 90% by mass, and more preferably 10 to 50% by mass in the solid content obtained when the size press-treated paper is extracted with hot water. When the saccharide in the solid content is 10% by mass or more, curling after heat fixing in the electrophotographic recording method is further suppressed, and generation of white spots can be sufficiently suppressed in the ink jet recording method. On the other hand, if it is 90% by mass or less, curling and white spots after heat fixing can be suppressed, and the surface of the paper is reinforced by a polymer film, so that the surface strength is increased. As a result, in both the electrophotographic recording method and the ink jet recording method, the generation of paper dust when contacting the conveying member or the like is suppressed, and the conveyance property and the image quality are improved.
Here, the characteristics of the hot water extract were measured as follows. Each recording paper 0.06 m ^{2 was} subjected to Soxhlet extraction at 100 ° C. for 8 hours using pure water as a solvent. Then, it was once dried and solidified, and the mass of the solid content and the ratio of the oligosaccharide contained were confirmed. The ratio of saccharides was measured using high performance liquid chromatography.

In the recording paper of the first aspect of the invention, the size press treatment liquid contains a cationic polyvalent metal salt, and the surface electrical resistivity A at 23 ° C. and 50% RH is 1.0 × 10 ^9. To 1.0 × 10 ¹¹ [Ω / □], the volume resistivity B is 5.0 × 10 ⁹ to 5.0 × 10 ¹¹ [Ω · cm], and the surface resistivity A is The value (A / B) [1 / □ · cm] divided by the volume resistivity B is preferably 0.1-1. The surface resistance value A and the volume resistivity B are measured by a method based on JIS-K-6911 under the condition of 23 ° C. and 50% RH.

The recording paper of the first aspect of the present invention improves the color developability in the ink jet recording system by further containing a cationic polyvalent metal salt in the size press treatment liquid.
The surface electrical resistivity A is set to 1.0 × 10 ^{9 to} 1.0 × 10 ¹¹ [Ω / □], and the volume electrical resistivity B is set to 5.0 × 10 ⁹ to 5.0 × 10 ¹¹ [ By setting the (A / B) to 0.1-1 [1 / □ · cm] in Ω · cm], toner transferability is not impaired. This is because the cationic polyvalent metal salt remains in the vicinity of the surface of the recording paper by controlling the surface electrical resistivity A, the volume electrical resistivity B, and (A / B) to the above values. .

  The (A / B) is preferably 0.1 to 1 [1 / □ · cm], more preferably 0.1 to 0.5 [1 / □ · cm]. When the (A / B) is less than 0.1 [1 / □ · cm], when the electrophotographic printing is performed, the charge is excessively accumulated on the sheet, and the discharge is generated when the sheet is peeled off from the transfer member. An image quality defect may occur. On the other hand, when the above (A / B) exceeds 1 [1 / □ · cm], the cationic polyvalent metal salt permeates into the inside of the paper in a large amount and remains in the vicinity of the surface of the cationic polyvalent metal salt. As a result, there is a case where the color development is hardly improved when an image is recorded by the ink jet method. In addition, even when an image is recorded by the electrophotographic method, a transfer defect may occur due to the charge remaining on the sheet and flowing to the back surface.

The surface electrical resistivity A is preferably 1.0 × 10 ^{9 to} 1.0 × 10 ¹¹ [Ω / □], and is 5.0 × 10 ^{9 to} 7.0 × 10 ¹⁰ [Ω / □]. More preferably, it is 5.0 × 10 ^{9 to} 2.0 × 10 ¹⁰ [Ω / □]. The surface electrical resistivity A is the surface electrical resistivity of the surface (printing surface) coated with the size press treatment liquid of the base paper.

The volume electrical resistivity B is preferably 5.0 × 10 ^{9 to} 5.0 × 10 ¹¹ [Ω · cm], and more preferably 1.0 × 10 ^{10 to} 1.6 × 10 ^11. 1.3 × 10 ^{10 to} 4.3 × 10 ¹⁰ are more preferable.

-Starch-
Next, the starch used for this invention is demonstrated.
As starch used for the recording paper of the first invention, raw starch such as corn starch, potato starch, tapioca starch, enzyme modified starch, oxidized starch, etc. can be used. As oxidized starch, not only processed starch oxidized with sodium hypochlorite but also dialdehyde starch or raw starch oxidized with periodate is heated with an oxidizing agent such as persulfate just before size press. Includes self-modified starch that has been chemically treated. As a raw material starch, corn starch, potato starch, tapioca starch, waxy starch, sweet potato starch and the like can be used. As the starch used for the recording paper of the first invention, oxidized starch and enzyme-modified starch are preferable.

-Sugar-
As the saccharide used in the recording paper of the first invention, those having a glucose unit of 10 or less are preferable. If the glucose unit exceeds 10, the dehydrating inhibitory effect may not be obtained. Specific examples of the saccharide include glucose, maltose, saccharose, isomaltooligosaccharide, gentiooligosaccharide, fructooligosaccharide, trehalose, and lastose. Among them, glucose, maltose, isomaltoligosaccharide, etc. obtained by enzymatic degradation of starch are preferable because of their high affinity with starch, and isomaltoligosaccharide, gentio-oligosaccharide, fructo-oligosaccharide is an ink jet method for capturing a coloring material. This is preferable. That is, isomaltooligosaccharides having both advantages are most effective in combining with oxidized starch.

  The recording paper of the first aspect of the present invention is obtained by applying a size press treatment liquid containing at least starch and optionally containing sugars, polyvalent metal salts, and the like to the surface of the base paper described above. The method for applying the size press treatment liquid to the surface of the base paper is not particularly limited. Usually, however, the size press treatment liquid is used as a coating liquid (size press liquid), and the method of applying the size press treatment to the base paper surface is utilized. It is preferable.

  Note that the size press treatment liquid does not substantially contain a pigment as described above (the amount of the pigment in the treatment liquid is 10% by mass or less). That is, the recording paper of the first aspect of the present invention is a plain paper in which the surface-treated recording paper of the present invention does not have a coating layer containing a pigment on the surface, such as so-called coated paper. Coated paper having a coating layer containing a pigment on the surface of the recording paper is not preferable for electrophotographic and ink jet recording paper in general offices due to cost, scratches on the conveying member, and influence of paper dust.

  In addition to the size press treatment, the coating liquid is applied to the surface of the base paper by commonly used coating means such as shim size, gate roll, roll coater, bar coater, air knife coater, rod blade coater, blade coater. Can be applied. The recording paper of the present invention can be obtained through a drying process on a base paper coated with a cationic substance, a heterocarboxylic acid, and a water-soluble polymer.

When the recording paper of the first aspect of the present invention contains saccharides, the blending ratio (starch: saccharides) in the coating solution of starch and saccharides is preferably 1: 9 to 9: 1. Preferably it is 3: 7-9: 1. In addition, when processing starch and saccharides on the surface of the base paper, the processing amount per side of the base paper is preferably in the range of 0.5 to 6 g / m ² in terms of solid content (solid content), A range of 0.5 to 3 g / m ² is more preferable.

  If the blending ratio of starch and saccharide in the coating solution is less than 1: 9 (the starch content is less than 1/9 of the saccharide content), the surface strength of the paper is not sufficient, and there is a problem with paper dust and the like. May occur. On the other hand, when the blending ratio of the starch and saccharide in the coating solution is larger than 1: 9, the characteristics of the starch will be strong, and white spots in the ink jet recording method may not be reduced.

Moreover, when the recording paper of 1st this invention contains saccharides, it is preferable that the quantity apply | coated to the paper surface of each starch and saccharides is 0.1 g / m < ² > or more. When the amount of starch and saccharide applied to the paper surface is less than 0.1 g / m ² , the paper surface coating may be insufficient. In addition, in the inkjet method, since both the saccharide that is eluted when ink lands and captures the color material and the starch component that retains the captured color material on the paper surface are small, the image quality is lowered, specifically, the concentration is lowered, and feathering Deterioration, ICB deterioration, and color reproducibility deterioration may occur.
On the other hand, when the starch and saccharides are applied to the surface of each paper, but exceeding 5 g / m ² , the texture as a so-called plain paper may be impaired. Therefore, the total amount of starch and saccharide solids applied on the surface is preferably in the range of 0.6 to 5 g / m ² .

  In the step of applying the treatment liquid containing starch and saccharide to the surface of the base paper, as a technique for controlling the penetration of the treatment liquid into the base paper, the base paper before application is subjected to a calendar process, etc. It is preferable to adjust the air permeability to 10 to 30 seconds. This is because by increasing the air permeability of the base paper, the penetration of the treatment liquid into the inside can be suppressed. However, if the air permeability of the base paper is increased too much, the bonded area between the fibers of the pulp inside the paper is increased, the amount of dimensional change with respect to the change in the moisture content is increased, and the curl is likely to increase. It is preferable to adjust the air permeability of the base paper in consideration.

  There is also a technique for reducing the penetration of the coating liquid into the base paper by separately passing the size press process on the dried base paper without passing through the size press process after papermaking.

  The recording paper of the second aspect of the present invention is plain paper containing pulp fibers and fillers as main components, and contains an acid anhydride composed of an organic acid having one or two carboxyl groups and a molecular weight of 160 or less. It is characterized by. The recording paper of the second invention is so-called plain paper which does not have a coating layer substantially containing a pigment, like the recording paper of the first invention. Further, in the recording paper of the second aspect of the present invention, containing pulp fibers and fillers as main components means that the total content of pulp fibers and fillers is 80% by mass or more.

  The recording paper of the second invention contains an acid anhydride composed of an organic acid having one or two carboxyl groups and a molecular weight of 160 or less (hereinafter sometimes referred to as “acid anhydride in the invention”). This suppresses curling and undulation that occurs immediately after printing when printing is performed by the ink jet recording method, and curling and undulation that occurs after standing drying, and curl that occurs after fixing when an image is formed by the electrophotographic method. Can also be suppressed.

The present inventors, on recording papers used in electrophotographic systems and ink jet systems, generate curls after thermal fixing in electrophotographic systems, curls and undulations that occur immediately after printing in ink jet systems, and after standing and drying. A method for suppressing curling and waving was studied.
As a result, it was confirmed that curling and undulation that occurred immediately after printing in the ink jet method was caused by rapid elongation of the cellulose (pulp) fiber layer of the recording paper that absorbed the water in the ink. In addition, curling and undulation that occurs after standing drying occurs due to shrinkage due to dehumidification of the cellulose fiber layer that has absorbed the ink, and further, ink permeation in a minute time in the thickness direction of the recording paper is fast, and ink permeation It was confirmed that the larger the depth, the larger.
In addition, it was confirmed that the electrophotographic method was caused by a difference in shrinkage between the front and back surfaces due to moisture dehumidification after heat fixing.

  From these results, the present inventors have eagerly investigated the stretching and transmission properties of the cellulose fiber layer that has absorbed ink or absorbed moisture due to water absorption and desorption. As a result, it can be seen that the stretch transmission due to moisture absorption and desorption is deeply related to the stretch rate of the recording paper. By reducing the stretch rate, the stretch stretch is weakened. The present inventors have found that curling and undulation after standing drying and curling after heat fixing can be reduced.

  In order to weaken the stretch transferability due to water absorption and desorption of the cellulose fiber layer, in the ink jet method, when ink penetrates from the surface of the recording paper to the inside during printing, the hydroxyl groups of the cellulose fibers constituting the cellulose fiber layer, etc. It is necessary to prevent the water in the ink from approaching the hydrophilic group and making it incompatible. In the electrophotographic system, it is necessary that hydrophilic groups such as hydroxyl groups of cellulose fibers constituting the cellulose fiber layer hardly absorb moisture in the air.

  For this reason, the present inventors consider that it is necessary to hydrophobize the hydrophilic group of the cellulose fiber in both the ink jet system and the electrophotographic system, and have a carboxyl group as a hydrophobizing method to produce an acid anhydride. The use of the substance was studied earnestly. As a result, it was confirmed that an acid anhydride composed of an organic acid having 1 or 2 carboxyl groups and having a molecular weight of 160 or less was highly effective.

As the acid anhydride in the present invention, any known substance can be used as long as it has a molecular weight of 160 or less and maintains a stable liquid or solid state at room temperature, and may be composed of an organic acid having a molecular weight of 140 or less. Preferably, it consists of an organic acid having a molecular weight of 120 or less. When the molecular weight exceeds 160, the effect of the present invention of suppressing curling cannot be obtained.
The acid anhydride in the present invention is at least one selected from the group consisting of itaconic anhydride, glutaconic anhydride, glutaric anhydride, succinic anhydride, maleic anhydride, phthalic anhydride, malonic anhydride, and butyric anhydride. Among these, at least one selected from itaconic anhydride and phthalic anhydride is more preferable.

  The acid anhydride in the present invention can be applied or impregnated on recording paper by using it as a processing liquid blended in water without adding a binder component together with a metal salt used in combination as necessary. It is. The treatment liquid can also be used as a sizing liquid to which a water-soluble resin, a surface sizing agent, and the like are further added.

Examples of the water-soluble resin in this case include carboxymethyl cellulose, hydroxypropyl cellulose, hydroxyethyl cellulose, curdlan, polyvinyl alcohol (PVA), modified cationized polyvinyl alcohol, cationized starch, oxidized starch, anionized starch, and nonionic starch. , Enzyme-modified starch, etherified starch and the like. However, in order to further reduce curling and undulation, it is preferable to use a nonionic water-soluble resin (water-soluble polymer). Further, the nonionic water-soluble resin may be used alone, but may be further used by mixing with a cationic or anionic water-soluble polymer.
Nonionic water-soluble resins include nonionic polyvinyl alcohol, enzyme-modified starch, hydroxypropylcellulose, hydroxyethylcellulose and the like. Among these, nonionic polyvinyl alcohol is preferable.

  The treatment liquid is applied to the surface of the base paper by a commonly used coating means such as shim size, gate roll, roll coater, bar coater, air knife coater, rod blade coater, blade coater in addition to size press treatment. can do.

The content of the acid anhydride in the present invention is preferably in the range of 0.005 to 0.5 / m ^2, more preferably in the range of 0.01~0.2g / m ^2, 0. More preferably, it is in the range of 02 to 0.1 g / m ² . When the content of the acid anhydride in the present invention is 0.005 g / m ² or more, the reaction effect on hydrophilic groups such as hydroxyl groups of pulp fibers is enhanced, and the effect of reducing the dimensional change of the recording paper is also enhanced. In addition, the effect of suppressing curling and undulation becomes more remarkable. Further, if it is 0.5 g / m ² or less, the pH of the paper is lowered, and the storage stability is not deteriorated due to acidification of the paper. The content of acid anhydride in the present invention is determined by pyrolysis gas chromatography (GC) -mass spectrometer (MS), after decomposing paper with cellulase, derivatizing and analyzing / identifying with GC-MS. This can be confirmed by the presence of an ester bond of cellulose by a spectroscopic device (IR).

The recording paper according to the second aspect of the present invention has a surface electrical resistivity of 1.0 × 10 ⁹ at 23 ° C. and 50% RH in order to provide sufficient toner transferability during image formation by electrophotography. it is preferably ~1.0 × 10 ¹² Ω / □ range, more preferably ^{5.0 × 10 9 ~1.0 × 10 12} Ω / □ range, 1.0 × 10 ¹⁰ ~ More preferably, it is in the range of 1.0 × 10 ¹¹ Ω / □.

Further, from the same viewpoint, the volume electrical resistivity of the recording paper of the present invention is preferably in the range of 1.0 × 10 ^{10 to} 1.0 × 10 ¹² Ω · cm, and 1.3 × 10 ¹⁰ to 1 more preferably in the range of .6 × 10 ¹¹ Ω · cm, more preferably in the range of ^{1.3 × 10 10 ~4.3 × 10 10} Ω · cm. The surface electrical resistivity and volume electrical resistivity of the recording paper of the second invention are measured by the same method as the surface electrical resistivity A and volume electrical resistivity B of the recording paper of the first invention. It is a thing.

-Base paper-
Next, the base paper used for the recording paper of the first invention and the recording paper of the first invention (hereinafter collectively referred to as “recording paper of the invention”) will be described.
The base paper used for the recording paper of the present invention contains pulp fibers and a filling amount as main components.
Pulp fibers include chemical pulp, specifically hardwood bleached kraft pulp, hardwood unbleached kraft pulp, softwood bleached kraft pulp, softwood unbleached kraft pulp, hardwood bleached sulfite pulp, hardwood unbleached sulfite pulp, softwood bleached sulfite pulp, Preference is given to pulp produced by chemically treating wood and fiber raw materials such as cotton, hemp, and hulls in addition to softwood unbleached sulfite pulp and the like.

  In addition, ground wood pulp that mechanically pulps wood and chips, chemimechanical pulp mechanically pulped after chemicals are soaked into wood and chips, and pulping with refiner after chips are softened slightly Thermomechanical pulp, especially chemithermomechanical pulp, which is characterized by high yield, can also be used. These may be used only with virgin pulp, or waste paper pulp may be added as necessary.

  In particular, the virgin pulp is bleached mainly using ozone / hydrogen peroxide or the like without using chlorine gas and using chlorine dioxide (Elementary Chlorine Free: ECF) or without using any chlorine compound. It is preferably one that has been bleached by the method (Total Chlorine Free: TCF).

  In addition, as raw materials of the waste paper pulp, unprinted waste paper such as cuts, damaged paper, widened white, special white, medium white, white loss, etc. generated in bookbinding, printing factories, cutting offices, etc .; printing and copying High-quality printed paper such as high-quality paper, high-quality coated paper, etc .; water-based ink, oil-based ink, old paper written with a pencil, etc .; printed high-quality paper, high-quality coated paper, medium-quality paper, medium-quality coated paper, etc. Newspaper waste paper including flyers; waste paper such as medium-quality paper, medium-quality coated paper, and reprint paper can be blended.

  The waste paper pulp used in the base paper used for the recording paper of the present invention is preferably obtained by treating the raw paper pulp raw material with at least one of ozone bleaching treatment and hydrogen peroxide bleaching treatment. Further, from the viewpoint of obtaining a recording paper having a higher whiteness, it is preferable that the blending ratio of the used paper pulp obtained by the bleaching treatment is in the range of 50 to 100% by mass. Further, from the viewpoint of resource reuse, it is more preferable that the ratio of the waste paper pulp is in the range of 70 to 100% by mass.

The ozone bleaching treatment has an action of decomposing fluorescent dyes or the like normally contained in high-quality paper, and the hydrogen peroxide bleaching treatment has an action of preventing yellowing due to alkali used during deinking treatment.
By combining two treatments, ozone bleaching treatment or hydrogen peroxide bleaching treatment, the waste paper pulp not only facilitates deinking of the waste paper, but also improves the whiteness of the pulp. In addition, since there is also an action of decomposing and removing residual chlorine compounds in the pulp, a great effect can be obtained in reducing the content of organic halogen compounds in waste paper using chlorine bleached pulp.

In addition to pulp fibers, a filler is added to the base paper used in the present invention in order to adjust opacity, whiteness, and surface properties. In order to reduce the amount of halogen in the recording paper, it is preferable to use a filler that does not contain halogen.
As the filler, 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, Synthetic silica, aluminum hydroxide, alumina, sericite, white carbon, saponite, calcium montmorillonite, sodium montmorillonite, bentonite and other inorganic pigments, acrylic plastic pigments, polyethylene, chitosan particles, cellulose particles, polyamino acid particles, urea Examples thereof include organic pigments such as resins.

In addition, when used paper pulp is blended with the base paper, it is necessary to estimate the ash contained in the used paper pulp raw material in advance and adjust the addition amount.
The blending amount of the filling amount is not particularly limited, but is preferably in the range of 1 to 80 parts by mass, more preferably in the range of 1 to 50 parts by mass, with respect to 100 parts by mass of the pulp fiber. More preferably, it is the range of 1-30 mass parts.

  When making the pulp fiber to obtain a base paper, the fiber orientation ratio of the obtained base paper is preferably in the range of 1.0 to 1.55, and preferably in the range of 1.0 to 1.45. Is more preferable, and the range of 1.0 to 1.35 is still more preferable. When the fiber orientation ratio is in the range of 1.0 to 1.55, not only the curling after printing by the electrophotographic method is made smaller, but also the curling of the recording paper after printing is performed when printing by the ink jet method. Can be reduced.

The fiber orientation ratio is a fiber orientation ratio determined by an ultrasonic propagation velocity method, and the ultrasonic propagation velocity in the MD direction of the recording paper (traveling direction of the paper machine) is defined as the CD direction of the recording paper (progress of the paper machine). The value divided by the ultrasonic propagation velocity in the direction perpendicular to the direction) is represented by the following formula (1).
Formula (1) Fiber orientation ratio (T / Y ratio) of the base paper by the ultrasonic propagation velocity method = MD direction ultrasonic propagation velocity / CD direction ultrasonic propagation velocity The fiber orientation ratio by this ultrasonic propagation velocity method is It can be measured using SonicSheetTester (manufactured by Nomura Corporation).

  The sizing degree of the recording paper of the present invention can be adjusted to a required value only by the amount and type of the binder. However, if the adjustment of the sizing degree is not sufficient by itself, a surface sizing agent may be further used. As such a surface sizing agent, rosin sizing agents, synthetic sizing agents, petroleum resin sizing agents, neutral sizing agents, starch, polyvinyl alcohol and the like can be used.

Further, an internal sizing agent may be blended at the slurry preparation stage in the papermaking process, and the sizing degree may be adjusted in advance. In order to reduce the amount of halogen in the recording paper, it is preferable to use an internal sizing agent or a surface sizing agent that does not contain halogen. Specifically, rosin sizing agents, synthetic sizing agents, petroleum resin sizing agents, neutral sizing agents, and the like can be used.
Further, a sizing agent and a fiber fixing agent can be used in combination. In this case, aluminum sulfate, cationized starch or the like can be used as a fixing agent. Further, from the viewpoint of improving the storage stability of the recording paper, it is preferable to use a neutral sizing agent. The sizing degree is adjusted by the amount of sizing agent added.

  In addition, by containing the acid anhydride in the present invention, the moisture content when the humidity is adjusted in a 23 ° C. and 50% RH environment, which is the regulation of the recording paper of the first invention, and the adjustment in the 23 ° C. and 50% RH environment. It becomes easier for the difference from the moisture content when the humidity is adjusted at 23 ° C. and 25% RH after the humidity to be 1.2% or less. For this reason, in the recording paper of the present invention, the size press treatment liquid preferably contains at least starch and the acid anhydride of the present invention.

The recording paper of the present invention preferably contains a cationic polyvalent metal salt. Here, the polyvalent metal salt means a metal salt containing a divalent or higher metal ion, and a known metal salt can be used. In addition, as a bivalent or more metal ion, aluminum, beryllium, calcium, magnesium, strontium, barium, and radium are preferable, and calcium and magnesium are more preferable.
Specific examples of the polyvalent metal salt include zinc chloride, zinc bromide, calcium nitrate, copper nitrate, calcium bromide, calcium chloride, calcium thiocyanate, calcium iodide, zinc nitrate, iron chloride, magnesium chloride, copper chloride. , Magnesium bromide, iron bromide, iron chloride, iron nitrate, magnesium chromate, aluminum nitrate, iron nitrate, zinc sulfate, barium bromide, calcium acetate, magnesium sulfate, magnesium carbonate, iron sulfate, barium chloride, copper sulfate, Examples thereof include aluminum sulfate, barium hydroxide, calcium chromate and the like.

These polyvalent metal salts can serve as a conductive agent in recording paper. Furthermore, when printing by the ink jet method, these metal ions have a low molecular weight and are likely to elute into the ink that has landed on the recording paper. A certain color material can be quickly insolubilized and / or agglomerated.
In particular, inkjet printers that perform high-speed printing use highly penetrating inks to improve the drying properties of the inks, and if the insolubilization and / or aggregation of the coloring material is not performed more quickly, the image quality can be improved. Absent. However, even in such a case, if a metal salt containing a divalent or higher metal ion is used, it is possible to cope with further improvement in image quality.

The content of the polyvalent metal salt is preferably in the range of 0.1 to 3 g / m ² by dry mass, and more preferably in the range of 0.5 to ² g / m ² . When the processing amount is less than 0.1 g / m ² , the reaction with the ink component is weakened, which may cause deterioration in color developability and deterioration in feathering. On the other hand, if the coating amount exceeds 3 g / m ² , the texture as so-called plain paper may be impaired.

The recording paper of the present invention preferably has a Steecht sizing degree in the range of 10 to 40 seconds, and more preferably in the range of 15 to 30 seconds. If the Steecht sizing degree is less than 10 seconds, when printing by an ink jet recording method, feathering deteriorates and fine characters become indistinguishable, or when a bar code or the like is printed, reading is impossible. May impair the practicality.
On the other hand, if the Steecht sizing degree exceeds 40 seconds, the fixing property of the toner when printed by the electrophotographic method is impaired, and when ink is printed by the ink jet method, the penetration of the ink is slowed down, so that bleeding between colors occurs. However, the color image quality deteriorates, and at the same time, the ink drying property deteriorates, and the back surface of the paper may be stained during high-speed printing.

  The above-mentioned squeecht sizing degree is that described in JIS P8122: 1976 measured in a standard environment (temperature 23 ° C., relative humidity 50% RH) defined in JIS P8111: 1998.

  Further, from the viewpoint of improving toner transferability and improving graininess, the smoothness of the recording paper is preferably 20 to 100 seconds or less, and more preferably 70 to 100 seconds. If the smoothness is less than 20 seconds, the graininess may deteriorate. Also, if the smoothness exceeds 100 seconds, high-pressure pressing is performed in the wet state during production in order to obtain high smoothness. As a result, the opacity of the paper decreases, or after printing in ink jet printing. The curl may become large. In addition, the said smoothness means what was measured based on JIS-P-8119: 1998.

  In addition, when forming an image by the electrophotographic recording method, the texture index is preferably 20 or more, and more preferably 30 or more, from the viewpoint of improving cloudiness as a picture quality. When the texture index is less than 20, when the toner is heat-fused in the electrophotographic recording method, the penetration of the toner into the paper becomes non-uniform, and a mottle is generated, which may impair the image quality.

  Here, the texture index is M / K Systems, Inc. A 3D sheet analyzer (M / K950) manufactured by (MKS) was used, the aperture of the analyzer was 1.5 mm in diameter, and measurement was performed using a micro formation tester (MFT). That is, a sample is mounted on a rotating drum in a 3D sheet analyzer, and a local basis weight difference in the sample is detected by a light source attached to the drum shaft and a photodetector attached to the outside of the drum corresponding to the light source. Measure as 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, 1000000 data are taken in one scan, and the histogram frequency for the data is obtained. obtain. 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.

When the recording paper of the present invention is used as an electrophotographic system, an inkjet system, a thermal transfer, and a recording medium that also combines them, a conductive agent is further blended (when a cationic polyvalent metal salt is contained) In combination with the cationic polyvalent metal salt, the surface electrical resistivity of the recording paper is preferably adjusted. However, it is preferable to use a conductive agent that does not contain halogen in order to reduce the amount of halogen in the recording paper.
Examples of such conductive agents include inorganic electrolytes such as sodium sulfate, sodium carbonate, lithium carbonate, sodium metasilicate, sodium tripolyphosphate, sodium metaphosphate; sulfonates, sulfate esters, carboxylates, phosphates, etc. Anionic surfactants; cationic surfactants, nonionic surfactants such as polyethylene glycol, glycerin and sorbit and amphoteric surfactants; conductive agents such as polymer electrolytes can be used.

<Electrophotographic image recording method>
The electrophotographic image recording method of the present invention comprises a charging step for uniformly 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, A developing step of developing the electrostatic latent image formed on the surface of the electrostatic latent image carrier using an electrostatic charge image developer to form a toner image; and a transferring step of transferring the toner image onto a recording sheet. And a fixing step of fixing the toner image transferred onto the recording paper, wherein the recording paper is the recording paper of the present invention described above.

  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 distribution is used. A toner containing a binder resin having a low melting point that can be fixed can be used.

  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 fixing.

<Image recording method of ink jet recording system>
Next, the ink jet recording type image recording method of the present invention (hereinafter sometimes referred to as “ink jet recording method”) will be described.
In the inkjet recording method of the present invention, an ink droplet containing water and / or a water-soluble organic solvent and a color material is ejected onto the surface of a recording paper to form an image on the surface of the recording paper. In the recording method, the recording sheet of the present invention described above is used as the recording sheet.

  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 , BlackPearlsL, Monarch7 0, Monarch 800, Monarch 880, Monarch 900, Monarch 1000, Monarch 1100, Monarch 1300, Monarch 1400 (above made by Cabot), Color Black FW1, Color Black FW2, Color Black FW2, Color Black FW2, Color Black FW2 , Color Black S160, Color Black S170, Pritex35, PritexU, Pritex Vrintex140U, Printex140V, Special Black6, Special Black5, Special, Black 4A, Black 4A, Black 4A , 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 recording head tip tends to occur, and if it is less than 0.1% by mass, 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-
When a pigment is used as the color material contained in the ink, a pigment dispersant can be used to ensure the dispersibility of the pigment. 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 mass average molecular weight (Mw) of 2000 to 15000, and particularly preferably 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.

For example, the ink using the self-dispersing pigment is subjected to a surface modification treatment on the pigment, and the resulting pigment is added to water and sufficiently stirred, and then dispersed by a disperser similar to the above as necessary. After removing coarse particles by centrifugation or the like, a predetermined solvent, additive, etc. 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 by the ink jet method using the ink as described above, the ink drop amount ejected from the nozzle of the recording head is preferably in the range of 1 to 20 pl. More preferably, it is in the range of 3-18 pl.

In addition, printing is performed by 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 recording head, and stable ejection properties may not 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 recording 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. Further, a heating system such as recording paper is provided during printing or before and after printing, and the recording paper and ink are heated at a temperature of 50 ° C. to 200 ° C., and a system having a function of promoting ink absorption and fixing is also used. be able to.

  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 energized 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.

An ink tank that stores inks of cyan, magenta, yellow, and black is integrally attached to each recording head above the recording head. 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 of the present invention is conveyed onto the platen at a predetermined timing by a conveyance roller for paper feeding. 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, an example in which four recording heads corresponding to cyan, magenta, yellow, and black are provided has been described. However, the range in which the inkjet recording method of the present invention can be applied to the multi-pass method is not limited to this example. Two recording heads, a black recording head and a color recording head, are provided. Of these, the color recording head divides the nozzles in the arrangement direction and assigns a predetermined color to each of the divided areas. It may be something like that.

In addition, 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 recording head scanning speed is 25 cm / sec or more. Depending on the case, the interval at which the two different colors of ink are printed becomes narrow, and inter-color bleeding (ICB) may easily occur.
The recording head scanning speed is a recording speed when the recording head performs printing by scanning the recording paper surface a plurality of times in the so-called multi-pass method in which the recording head travels perpendicularly to the recording paper discharge direction. The moving speed of the head.

Also, in order to support high-speed printing, it is necessary to use ink with low surface tension in order to improve the drying property of the ink, which causes feathering and image density reduction, and such low surface tension. Since ink has high penetrability into paper, printed characters and images are easily seen through from the back side, which may impair double-sided printability.
Therefore, in order to cope with such a problem, it is preferable to adopt the following one-pass method.

  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, and this one-pass method has a recording head having a width substantially equal to the width of the recording paper, and the 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, in addition to the occurrence of curling and undulation immediately after printing, the curling and undulation after standing drying has occurred.

  However, in the inkjet recording method of the present invention, the recording head scanning speed in the multipass method is high-speed printing with a recording head scanning speed of 250 mm / second or more, and the recording paper conveyance speed in a state where the recording head in the multipass 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 undulations immediately after printing and after standing and drying can be suppressed by using the recording paper of the present invention described above.

  The recording head scanning speed is preferably 500 mm / second or more, 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, the ink ejection amount is preferably in the range of 7~20ml / m ^2, and more preferably in the range of 7.5~10ml / m ^2.

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples.
< Reference Example 1>
Hardwood kraft pulp was bleached by an ECF multi-stage bleaching method comprising an oxygen bleaching step, an alkali extraction step, and a gas phase chlorine dioxide treatment step. The obtained pulp was beaten and adjusted to a freeness of 450 ml. With respect to 100 parts by mass of the pulp, 3 parts by mass of bentonite filler, 3 parts by mass of light calcium carbonate filler, alkyl ketene dimer (AKD) internal size A base paper was manufactured by blending 0.1 parts by weight of the agent.
Further, 88 parts by mass of water as a surface sizing agent, 10 parts by mass of oxidized starch A (Ace A manufactured by Oji Cornstarch), 2 parts by mass of fructooligosaccharide (manufactured by Wako Pure Chemical Industries, Ltd.), and 1 part by mass of sodium sulfate as a conductive agent A coating liquid (size press treatment liquid) is prepared, and the coating liquid is size-pressed on the manufactured base paper with a size press machine for testing by Kumagaya Riiki, and then at 100 ° C., 0 with a KRK rotary dryer made by Kumagai Riki. and dried at .4m / min condition, per side oxidized starch 0.9 g / m ² on the surface, fructooligosaccharide 0.2 g / m ^2, the recording of reference example 1 sodium 0.1 g / m ² sulfate were coated Got the paper. For reference, if a polyvalent metal salt is used, there is no need to apply a further conductive agent. The same applies to the following reference examples and comparative examples.

< Reference Example 2>
Papermaking was performed in the same manner as in Reference Example 1 to produce a base paper. Furthermore, it consists of 88 parts by mass of water as a surface sizing agent, 10 parts by mass of oxidized starch A (Ace A manufactured by Oji Cornstarch Co., Ltd.) used in Reference Example 1, 2 parts by mass of gentio-oligosaccharide, and 1 part by mass of sodium sulfate as a conductive agent. A coating solution is prepared, and the coating solution is size-pressed on the manufactured base paper using a size press for testing by Kumagai Riiki, and then dried at 100 ° C. and 0.4 m / min using a KRK rotary dryer made by Kumagai Riiki. to, per side oxidized starch 0.9 g / m ² on the surface, gentiooligosaccharides 0.2 g / m ^2, to obtain a recording paper of example 2 sodium 0.1 g / m ² sulfate were applied.

< Reference Example 3>
Hardwood kraft pulp was bleached by a TCF multi-stage bleaching method comprising a xylanase treatment step, an alkali extraction step, a hydrogen peroxide treatment step, and an ozone treatment step. The obtained pulp was beaten and adjusted to have a freeness of 450 ml, and 3 parts by weight of kaolin filler, 6 parts by weight of light calcium carbonate filler and alkenyl succinic anhydride (ASA) in 100 parts by weight of the pulp. A paper was made by adding 0.2 part by mass of an additive sizing agent.
Furthermore, as a surface sizing agent, a coating liquid comprising 86 parts by mass of water, 2 parts by mass of oxidized starch B (Ace B manufactured by Oji Cornstarch), 10 parts by mass of the same fructooligosaccharide as in Reference Example 1, and 2 parts by mass of calcium chloride was prepared. The coated liquid is size-pressed on the manufactured base paper using a size press for testing by Kumagai Riki, and then dried at 100 ° C. and 0.4 m / min using a KRK rotary dryer made by Kumagai Riki. per oxidized starch 0.2 g / m ^2, fructooligosaccharide 0.9 g / m ^2, calcium chloride 0.2 g / m ² was obtained recording paper of example 3 was coated.

< Reference Example 4>
Papermaking was performed in the same manner as in Reference Example 3 to produce a base paper. Further, a coating comprising 86 parts by weight of water as a surface sizing agent, 10 parts by weight of isomaltoligosaccharide, 2 parts by weight of oxidized starch B (Ace B manufactured by Oji Cornstarch Co., Ltd.) used in Reference Example 3, and 2 parts by weight of calcium chloride. After adjusting the liquid and size-pressing the coating liquid on the manufactured base paper with a size press for testing by Kumagai Riki, the coating liquid was dried at 100 ° C. and 0.4 m / min on a KRK rotary dryer manufactured by Kumagai Riki. , per side of oxidized starch 0.2 g / m ² on the surface, isomalto-oligosaccharides 0.9 g / m ^2, calcium chloride 0.2 g / m ² was obtained recording paper of example 4 was coated.

< Reference Example 5>
Bleaching softwood mechanical pulp with hydrosulfite and adjusting the beating so that the freeness becomes 450 ml. 8 parts by weight of light calcium carbonate filler and 100 parts by weight of alkenyl succinic anhydride (ASA) A base paper was manufactured by blending 0.02 parts by mass of the internal sizing agent.
Furthermore, as a surface sizing agent, a coating comprising 88 parts by mass of water, 1 part by mass of oxidized starch C (Ace C manufactured by Oji Cornstarch), 9 parts by mass of isomaltoligosaccharide (manufactured by Wako Pure Chemical Industries, Ltd.), and 2 parts by mass of magnesium nitrate. After preparing the working liquid and size-pressing the coating liquid on the manufactured base paper with a size press for testing by Kumagai Riki, it was dried at 100 ° C. and 0.4 m / min using a KRK rotary dryer manufactured by Ryu Kumagai. Te, per side oxidized starch is 0.1 g / m ² on the surface, isomalto oligosaccharide 0.9 g / m ^2, magnesium nitrate to obtain a recording paper of 0.2 g / m ² coated been reference example 5.

< Reference Example 6>
Hardwood kraft pulp was bleached by a TCF multi-stage bleaching method comprising a xylanase treatment step, an alkali extraction step, a hydrogen peroxide treatment step, and an ozone treatment step. The obtained pulp was beaten and adjusted to a freeness of 450 ml, and 3 parts by weight of light calcium carbonate filler, 3 parts by weight of saponite filler and 2 parts by weight of neutral rosin sizing agent with respect to 100 parts by weight of the pulp. Part of the paper was mixed to produce a base paper.
Furthermore, 89 parts by mass of water as a surface sizing agent, 5 parts by mass of the same oxidized starch C (Ace C manufactured by Oji Cornstarch Co., Ltd.) as used in Reference Example 5, 5 parts by mass of the same isomaltoligosaccharide used in Reference Example 3, A coating solution consisting of 1 part by weight of sodium chloride was prepared, and the coating solution was size-pressed on the manufactured base paper with a size press for testing by Kumagai Riiki, and then at 100 ° C., 0 with a KRK rotary dryer made by Kumagaya Riiki. and dried at .4m / min conditions, reference example per one surface oxidized starch on the surface 0.5 g / m ^2, isomalto oligosaccharide 0.5 g / m ^2, sodium chloride was 0.1 g / m ² coated 6 recording sheets were obtained.

< Reference Example 7>
Papermaking was performed in the same manner as in Reference Example 1 to produce a base paper.
Water 40 parts by further surface sizing agent, Reference Examples same oxidized starch A (manufactured by Ace A Oji Cornstarch Co., Ltd.) as that used in the 1 30 parts by weight, same fructooligosaccharides 25 parts by weight as that used in Reference Example 1, chloride A coating solution consisting of 5 parts by weight of sodium was prepared, and the coating solution was size-pressed on the manufactured base paper with a size press for testing by Kumagai Riki Co., Ltd. and dried at 4m / min conditions, reference example per side oxidized starch a is 6.0 g / m ^2, fructooligosaccharide is 5.0 g / m ^2, sodium chloride was 1.0 g / m ² applied to the surface 7 Obtained recording paper.

<Comparative Example 1>
Hardwood sulfite pulp was bleached by an ECF multi-stage bleaching method comprising an oxygen bleaching step, an alkali extraction step, and a vapor phase chlorine dioxide treatment step. The obtained pulp was beaten and adjusted to a freeness of 450 ml, and 15 parts by weight of light calcium carbonate filler and 0.1 part by weight of alkenyl succinic anhydride (ASA) internal sizing agent were added to 100 parts by weight of the pulp. Paper was prepared and blended to produce a base paper.
Furthermore, 82 parts by mass of water as a surface sizing agent, 15 parts by mass of the same oxidized starch B (Ace B manufactured by Oji Cornstarch Co., Ltd.) as used in Reference Example 3, 1 part by mass of fructooligosaccharides as used in Reference Example 2, and chloride A coating solution consisting of 2 parts by mass of calcium was prepared, and the coating solution was size-pressed on the manufactured base paper with a size press for testing by Kumagai Riki Co., Ltd. and dried at 4m / min condition, per side oxidized starch B on the surface of 2.0 g / m ^2, fructooligosaccharide is 0.1 g / m ^2, compared calcium chloride is 0.2 g / m ² coated example 1 Obtained recording paper.

<Comparative example 2>
Hardwood sulfite pulp was bleached by an ECF multi-stage bleaching method comprising an oxygen bleaching step, an alkali extraction step, and a vapor phase chlorine dioxide treatment step. The obtained pulp was beaten and adjusted to a freeness of 450 ml, and 20 parts by mass of kaolin filler and 0.05 part by mass of an alkyl ketene dimer (AKD) internal sizing agent were blended with respect to 100 parts by mass of the pulp. Paper was made to produce a base paper.
Furthermore, a coating liquid comprising 92 parts by mass of water as a surface sizing agent, 10 parts by mass of oxidized starch A (Ace A manufactured by Oji Cornstarch Co., Ltd.) same as that used in Reference Example 1, and 1 part by mass of calcium thiocyanate was prepared and manufactured. The coated liquid is size-pressed with a test size press machine manufactured by Kumagai Riki Co., Ltd., then dried with a KRK rotary dryer manufactured by Kumagai Riki Co., Ltd. under the conditions of 100 ° C. and 0.4 m / min. starch A2.0g / m ^2, to obtain a recording paper of Comparative example 2 calcium thiocyanate is 0.1 g / m ² coating.

<Comparative Example 3>
Hardwood sulfite pulp was bleached by an ECF multi-stage bleaching method comprising an oxygen bleaching step, an alkali extraction step, and a vapor phase chlorine dioxide treatment step. The obtained pulp was beaten and adjusted to a freeness of 450 ml, and 20 parts by mass of kaolin filler and 0.05 part by mass of an alkyl ketene dimer (AKD) internal sizing agent were blended with respect to 100 parts by mass of the pulp. Paper was made to produce a base paper.
Furthermore, a coating liquid consisting of 79 parts by weight of water, 20 parts by weight of maltose and 20 parts by weight of calcium formate was prepared as a surface sizing agent, and the coating liquid was size-pressed on a manufactured base paper using a size press for testing by Kumagai Riki. after, 100 ° C. in Kumagaya Riki made KRK rotary dryer and dried at 0.4 m / min condition, maltose per side 2.5 g / m ² on the surface, calcium formate is 2.5 g / m ² coated The recording paper of Comparative Example 3 was obtained.

<Comparative example 4>
Papermaking was performed in the same manner as in Reference Example 1 to produce a base paper.
Furthermore, from 95 parts by mass of water as a surface sizing agent, 1 part by mass of oxidized starch A (Ace A manufactured by Oji Cornstarch Co., Ltd.) used in Reference Example 1, 0.5 parts by mass of fructooligosaccharide, and 3.5 parts by mass of sodium chloride A coating liquid is prepared, and the coating liquid is size-pressed on the manufactured base paper with a size press for testing by Kumagai Riki, and then at 100 ° C. and 0.4 m / min on a KRK rotary dryer manufactured by Kumagai Riki. dried, per side oxidized starch a is 0.1 g / m ² on the surface, the glucose was obtained recording paper to 0.05 g / m ^2, Comparative example 4 sodium chloride was 0.5 g / m ² coated .

<Comparative Example 5>
P paper (Fuji Xerox Office Supply Co., Ltd.), which is a commercially available PPC paper, was used as the recording paper of Comparative Example 5.

<Comparative Example 6>
Green 100 paper (manufactured by Fuji Xerox Office Supply Co., Ltd.), which is a commercially available PPC paper, was used as the recording paper of Comparative Example 6.

<Comparative Example 7>
A multi-use paper manufactured by Sharp Corporation, which is a commercially available inkjet recording paper, was used as the recording paper of Comparative Example 7.

−Measurement of physical properties of recording paper−
The following items were measured on the recording papers of Reference Examples 1-7 and Comparative Examples 1-7.
The Steecht sizing degree was measured in a standard environment (temperature 23 ° C., relative humidity 50% RH) in accordance with JIS-P-8122: 1976.
The smoothness was measured according to JIS-P-8119: 1998, using an Oken type digital display type air permeability smoothness measuring instrument EY type (manufactured by Asahi Seiko Co., Ltd.). The texture index is M / K Systems, Inc. A 3D sheet analyzer (M / K950) manufactured by (MKS) was used, the diameter of the analyzer was 1.5 mm, and measurement was performed using a micro formation tester (MFT).

The surface electrical resistivity and volume electrical resistivity were measured by a method according to JIS-K-6911 after leaving the recording paper in an environment of 23 ° C. and 50% RH for 8 hours or more to adjust the humidity. As a measuring instrument, a digital ultrahigh resistance meter R8340 and a resiliency chamber R12704 manufactured by Advantest were used, and the applied voltage was measured at 100V.
The texture index is M / K Systems, Inc. A 3D sheet analyzer (M / K950) manufactured by (MKS) was used, the diameter of the analyzer was 1.5 mm, and measurement was 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 difference in the sample is detected by a light source attached to the drum shaft and a photodetector attached to the outside of the drum corresponding to the light source. It was measured as a light intensity difference.

Further, the moisture content in the environment of 23 ° C. and 50% RH was measured by the same method as in JIS-P-8127: 1998, except that the paper was conditioned for 12 hours or more in the environment. Humidity control at 23 ° C and 25% RH is JIS-P except that the paper is conditioned at 23 ° C and 50% RH for 12 hours or more and then conditioned at 23 ° C and 25% RH for 12 hours or more. -8127: measured by the same method as in 1998.
The hot water extract was Soxhlet extracted for 8 hours at 100 ° C. using pure water as a solvent for each recording paper 0.06 m ² . Then, it was once dried and solidified, and the weight of the solid content and the ratio of saccharides containing 10 or less glucose units were confirmed. The ratio of saccharides was measured using high performance liquid chromatography.
The measurement results of the above physical property values are shown in Table 1 together with the composition components of the treatment liquid used for producing the recording paper.

[Evaluation by electrophotographic method]
Using the DocuPrint 260 manufactured by Fuji Xerox Co., Ltd. as an electrophotographic recording apparatus for the recording papers of Reference Examples 1 to 7 and Comparative Examples 1 to 7, the evaluation of curling, image density, and transferability after printing is as follows. It was done in. The results are shown in Table 2.

-Curling evaluation after printing-
A document with an image density of 5% is printed in a single black color using the recording papers of the reference example and the comparative example that have been conditioned at 23 ° C. and 50% RH for 12 hours or more. At this time, 10 sheets of each recording sheet are continuously printed. Immediately after printing, place it on a flat measuring table and measure the distance from the measuring table to the bottom of the recording paper. At this time, the four corners were measured, and the place with the longest distance was evaluated according to the following criteria. The size of the paper is A4 size.
A: 20 mm or less B: 20 mm to 25 mm
Δ: 26 mm to 35 mm
×: 36 mm or more

-Evaluation of transferability-
About the image printed by image density evaluation, the generation level of the image spot by a transfer defect was confirmed. Judgment criteria were as follows.
A: The density unevenness of the image cannot be distinguished at all.
(Triangle | delta): The spot of an image can be confirmed with the naked eye although it is slight.
X: The whole image is full of spots.

[Evaluation by inkjet method]
Using a WorkCenter B900 manufactured by Fuji Xerox Co., Ltd. as an ink jet recording apparatus, evaluation of curling immediately after printing, undulation, curling after standing drying, undulation, and image density (generation of white spots) was performed according to the following criteria. The results are shown in Table 2.

For the printing test, WorkCenter B900 was used. The black ink is a pigment ink, and other dye inks such as Cyan, Magenta, and Yellow are used. Printing was performed in an environment of 23 ° C. and 50% RH. The nozzle pitch was 800 dpi, 256 nozzles, the drop amount was about 15 pl, the maximum ink / pretreatment liquid ejection amount was about 15 ml / m ² , the print mode was one-sided batch printing, and the head scan speed was about 1100 mm / second. Hereinafter, various evaluations will be described.

-Curling evaluation immediately after printing-
Leave the recording paper in a 23 ° C, 50% RH environment for 8 hours or more to adjust the humidity, and print a magenta 100% solid image of the dye ink on a sample cut to a postcard size (100 x 148 mm) with a 5 mm margin. Then, the amount of hanging curl generated opposite to the printed surface generated immediately after being discharged from the apparatus after printing was measured with calipers. The obtained measured value was converted into a curl 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 100% solid image of a secondary color of 2cm x 2cm dye ink is printed on the recording paper cut to postcard size (100 x 148mm) at the center of the postcard, and the maximum height of the undulation that occurs immediately after printing is laser The displacement was measured with a displacement meter (manufactured by Keyence Corporation, model number: LK085). The evaluation criteria are as follows, where ○ is an acceptable level.
◎: Less than 1.5 mm ○: 1.5 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-
Remove 5 mm of white space on a postcard-sized recording paper that has been conditioned for 8 hours or more in an environment of 23 ° C. and 50% RH, and print a magenta 100% solid image of dye ink, and print the printing surface in an environment of 23 ° C. and 50% RH. The amount of hanging curl generated after standing on a flat surface and leaving it for 50 hours after printing was measured in the same manner as the curl evaluation immediately after printing. The obtained measured value was converted into a curl 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

-Wavy evaluation after leaving to dry-
Using the above printer, print a magenta 100% solid image of dye ink on recording paper cut to A4 size (210 x 297 mm) and leave the printing surface flat on an environment of 23 ° C and 50% RH. The wavy state generated after 50 hours from standing was visually evaluated. The evaluation criteria are as follows, and ◎ and ○ are acceptable levels.
◎: No wavy ○: Slightly wavy, but acceptable △: Worried about the occurrence of wavy ×: Large wavy

-Image optical density-
The image optical density of the solid patch portion one day after printing was measured using X-Rite 369 (manufactured by X-Rite). Judgment criteria were as follows, and ◎ and ○ were acceptable.
◎: 1.5 or more ○: 1.0 or more and less than 1.5 ×: less than 1.0

From Table 2, when printing is performed with an electrophotographic recording apparatus using the recording papers of Reference Examples 1 to 7, curling after printing is reduced, and when printing is performed with an inkjet recording apparatus, it is left to dry immediately after printing. It can be seen that curl and undulation are reduced in each of the latter.

<Example 8>
10 parts by weight of light calcium carbonate filler, 0.1 part by weight of alkyl ketene dimer (AKD) as an internal sizing agent, 100 parts by weight of hardwood kraft pulp adjusted to a freeness of 420 ml, cationized starch (NCAT Co., Ltd. Cato-304) 0
. 4 parts by mass was blended to make a paper to produce a base paper having a basis weight of 75 g / m ² .
Furthermore, it contains 94.25 parts by mass of water as a surface sizing agent, 5 parts by mass of oxidized starch A (Ace A manufactured by Oji Cornstarch), 0.25 parts by mass of itaconic anhydride, and 0.5 parts by mass of metal salt (Na ₂ SO ₄ ). The treatment liquid was prepared, size-pressed on the manufactured base paper with a size press for testing by Kumagai Riki, and then dried at 100 ° C. and 0.4 m / min on a KRK rotary dryer made by Kumagai Riki. Got the paper. In addition, the application amount of the treatment liquid treated on the base paper is 1.0 g / m ² per one side in terms of dry mass.

<Example 9>
A treatment solution containing 92.75 parts by mass of water, 5 parts by mass of oxidized starch A (Ace A manufactured by Oji Cornstarch), 0.25 parts by mass of butyric anhydride, and 2 parts by mass of a metal salt (Ca (SCN) ₂ ) as a surface sizing agent After adjusting and size-pressing the base paper produced in Example 8 with a size press for testing by Kumagai Riki, the paper was dried in a KRK rotary dryer made by Kumagai Riki under the conditions of 100 ° C. and 0.4 m / min. A record sheet was obtained. In addition, the application amount of the treatment liquid treated on the base paper is 1.0 g / m ² per one side in terms of dry mass.

<Example 10>
A treatment liquid containing 94.25 parts by mass of water, 5 parts by mass of oxidized starch A (Ace A manufactured by Oji Cornstarch), 0.25 parts by mass of phthalic anhydride, and 0.5 parts by mass of metal salt (Na ₂ SO ₄ ) was prepared. The base paper produced in Example 8 was size-pressed with a size press for testing by Kumagai Riki, and then dried at 100 ° C. and 0.4 m / min in a KRK rotary dryer made by Kumagai Riki. Got. In addition, the application amount of the treatment liquid treated on the base paper is 1.0 g / m ² per one side in terms of dry mass.

<Example 11>
Example 8 A treatment solution containing 94.25 parts by mass of water, 5 parts by mass of PVA (PVA110 manufactured by Kuraray), 0.25 parts by mass of itaconic anhydride, and 0.5 parts by mass of metal salt (Na ₂ SO ₄ ) was prepared. The base paper produced in Step 1 was size-pressed with a size press for testing by Kumagai Riki, and then dried at 100 ° C. and 0.4 m / min with a KRK rotary dryer made by Kumagai Riki to obtain the recording paper of Example 11.
In addition, the application amount of the treatment liquid treated on the base paper is 1.0 g / m ² per one side in terms of dry mass.

<Comparative Example 8>
The base paper manufactured in Example 8 was manufactured by changing the internal sizing agent alkyl ketene dimer (AKD) from 0.1 parts by mass to 0.05 parts by mass of alkenyl succinic anhydride. On the other hand, a treatment liquid containing 94.5 parts by mass of water, 5 parts by mass of oxidized starch A (Ace A manufactured by Oji Cornstarch), and 0.5 parts by mass of metal salt (Na ₂ SO ₄ ) was prepared, and this was produced first. The base paper was size-pressed with a test size press manufactured by Rikuma Kumagai, and then dried at 100 ° C. and 0.4 m / min using a KRK rotary dryer manufactured by Rikuma Kumagai to obtain a recording paper of Comparative Example 8. In addition, the application amount of the treatment liquid treated on the base paper is 1.0 g / m ² per one side in terms of dry mass.

<Comparative Example 9>
The base paper produced in Example 8 was prepared by preparing a treatment liquid containing 94.5 parts by mass of water, 5 parts by mass of oxidized starch A (Ace A manufactured by Oji Cornstarch), and 0.5 parts by mass of metal salt (Na ₂ SO ₄ ). After performing size pressing with a test size press manufactured by Kumagai Riki, the paper was dried with a KRK rotary dryer manufactured by Rum Kumagai under the conditions of 100 ° C. and 0.4 m / min to obtain a recording paper of Comparative Example 9. In addition, the application amount of the treatment liquid treated on the base paper is 1.0 g / m ² per one side in terms of dry mass.

−Measurement of physical properties of recording paper−
The measurement of the following item was implemented about Examples 8-11 and Comparative Examples 8-9.
The smoothness was measured according to JIS-P-8119: 1998, using an Oken type digital display type air permeability smoothness measuring instrument EY type (manufactured by Asahi Seiko Co., Ltd.). The texture index is M / K Systems, Inc. A 3D sheet analyzer (M / K950) manufactured by (MKS) was used, the diameter of the analyzer was 1.5 mm, and measurement was performed using a micro formation tester (MFT).
The surface electrical resistivity and volume electrical resistivity were measured by a method according to JIS-K-6911 after leaving the recording paper in an environment of 23 ° C. and 50% RH for 8 hours or more to adjust the humidity. As a measuring instrument, a digital ultrahigh resistance meter R8340 and a resiliency chamber R12704 manufactured by Advantest were used, and the applied voltage was measured at 100V.
The fiber orientation ratio was measured by an ultrasonic propagation velocity method using SonicSheetTester (manufactured by Nomura Corporation).
The measurement results of the above physical properties are shown in Table 3 together with the constituent materials of the recording paper.

First, an ink used for image recording evaluation by an inkjet method was prepared.
[Preparation of ink]
The ink used for the evaluation by the inkjet method was adjusted as follows.
-Magenta ink-
Surface treatment pigment (IJX-266 Cabot Corporation): 5 parts by mass Styrene-maleic acid-sodium maleate copolymer: 0.5 parts by mass Diethylene glycol: 20 parts by mass Surfactant (Surfinol 465: day) (Shinsei Co., Ltd.): 0.5 part by mass, urea: 5 parts by mass, ion-exchanged water: 70 parts by mass The above composition was stirred to prepare Magenta ink. This ink had a surface tension of 33 mN / m and a viscosity of 2.7 mPa · s.

-Cyan ink-
Surface treatment pigment (IJX-253 manufactured by Cabot Corporation): 5 parts by mass Styrene-maleic acid-sodium maleate copolymer: 0.5 parts by mass Diethylene glycol: 20 parts by mass Surfactant (Surfinol 465: day) (Shinsei Co., Ltd.): 0.5 part by mass, urea: 5 parts by mass, ion-exchanged water: 70 parts by mass The above composition was stirred to prepare Cyan ink. This ink had a surface tension of 32 mN / m and a viscosity of 2.5 mPa · s.

-Yellow ink-
Surface treatment pigment (IJX-273 Cabot Corporation): 5 parts by mass Styrene-maleic acid-sodium maleate copolymer: 0.5 parts by mass Diethylene glycol: 20 parts by mass Surfactant (Surfinol 465: day) (Shinsei Co., Ltd.): 0.5 part by mass, urea: 5 parts by mass, ion-exchanged water: 70 parts by mass The above composition was stirred to prepare Yellow ink. This ink had a surface tension of 33 mN / m and a viscosity of 2.7 mPa · s.

  Various evaluations using a thermal ink jet recording apparatus were performed by combining the inks produced as described above and the recording papers of Examples 8 to 11 and Comparative Examples 8 to 9. The results are shown in Table 3.

  Note that the print evaluation is a thermal ink jet recording apparatus for evaluation of multi-pass printing (Fuji Xerox Co., Ltd.) equipped with four recording heads corresponding to cyan, magenta, yellow, and black in an environment of 23 ° C. and 50% RH. Manufactured, model number: model printer prototype). The ink discharge nozzle pitch of the recording head of this apparatus was 800 dpi, the number of ink discharge nozzles was 256 nozzles, the discharge amount was about 15 pl, the printing was performed by one-sided batch printing, and the head scan speed was about 28 cm / sec. Moreover, various evaluation shown in Table 3 was performed as follows.

-Curling evaluation immediately after printing-
Leave the recording paper in a 23 ° C, 50% RH environment for 8 hours or more to adjust the humidity, and print a magenta 100% solid image of the dye ink on a sample cut to a postcard size (100 x 148 mm) with a 5 mm margin. Then, the amount of hanging curl generated opposite to the printed surface generated immediately after being discharged from the apparatus after printing was measured with calipers. The obtained measured value was converted into a curl 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 100% solid image of a secondary color of 2cm x 2cm dye ink is printed on the recording paper cut to postcard size (100 x 148mm) at the center of the postcard, and the maximum height of the undulation that occurs immediately after printing is laser The displacement was measured with a displacement meter (manufactured by Keyence Corporation, model number: LK085). The evaluation criteria are as follows, where ○ is an acceptable level.
◎: Less than 1.5 mm ○: 1.5 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-
Remove 5 mm of white space on a postcard-sized recording paper that has been conditioned for 8 hours or more in an environment of 23 ° C. and 50% RH, and print a magenta 100% solid image of dye ink, and print the printing surface in an environment of 23 ° C. and 50% RH. The amount of hanging curl generated after standing on a flat surface and leaving it for 50 hours after printing was measured in the same manner as the curl evaluation immediately after printing. The obtained measured value was converted into a curl 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

-Wavy evaluation after leaving to dry-
Using the above printer, print a magenta 100% solid image of dye ink on recording paper cut to A4 size (210 x 297 mm) and leave the printing surface flat on an environment of 23 ° C and 50% RH. The wavy state generated after 50 hours from standing was visually evaluated. The evaluation criteria are as follows, and ◎ and ○ are acceptable levels.
◎: No wavy ○: Slightly wavy, but acceptable △: Worried about the occurrence of wavy ×: Large wavy

-Feathering evaluation-
8-point characters were printed with Magenta ink. A visual test was performed on the print quality. The evaluation criteria are as follows.
A: No bleeding is observed in all kanji and hiragana.
○: Bleeding is observed in a small part of kanji and hiragana. There is no practical problem.
Δ: Bleeding is observed in some kanji and hiragana. There are practical problems.
X: Bleeding is observed in kanji and hiragana.

-Color development evaluation-
L ^* a ^* b ^* (L ^* a ^* b ^* color system specified in JISZ8729) for the density of color solid patches of cyan, mageta, and yellow one day after printing in a 2-degree field of view of the X-Rite D50 light source Measured and calculated and evaluated the color reproduction area. The evaluation criteria are as follows.
A: Color reproduction area is 8000 or more.
○: Color reproduction region is 7000 or more and less than 8000 Δ: Color reproduction region is 6000 or more and less than 7000 ×: Color reproduction region is less than 6000

Further, various evaluations were performed on the recording papers of Examples 8 to 11 and Comparative Examples 8 to 9 by an electrophotographic recording apparatus. The results are shown in Table 3.
-Electrophotographic evaluation-
Using DocuCentreColor500CP manufactured by Fuji Xerox Co., Ltd. as an electrophotographic recording apparatus, the evaluation paper was conditioned at 23 ° C. and 50% RH for 12 hours to evaluate toner transfer and curl immediately after printing.

-Toner transferability evaluation-
There are blue secondary colors and tertiary colors consisting of yellow, magenta and cyan, and a chart capable of outputting in 10% increments from 0 to 100% of the halftone dot area ratio is used to record the recording papers (1) to ( 11) was output by the printer, and toner transfer unevenness was visually evaluated according to the following evaluation criteria.
A: There is no toner transfer unevenness and it is extremely excellent. There is no problem in practical use.
○: Although toner transfer unevenness is confirmed in a very small part, there is no practical problem.
Δ: Toner transfer unevenness is conspicuous and there is a problem in practical use.
X: Toner transfer unevenness occurs on the entire surface, and there is a problem in practical use.

-Curling evaluation immediately after printing-
An image was not formed on an A4 size (210 × 297 mm) recording paper, but was printed on white paper, and the amount of hanging curl generated 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

  From Table 3, when printing is performed with an electrophotographic recording apparatus using the recording papers of Examples 8 to 11, curling after printing is reduced, and when printing is performed with an inkjet recording apparatus, it is left to dry immediately after printing. It can be seen that curl and undulation are reduced in each of the latter.

Claims (6)

  A recording paper, which is a plain paper containing pulp fibers and fillers as main components and containing an acid anhydride composed of an organic acid having 1 or 2 carboxyl groups and a molecular weight of 160 or less. The acid anhydride is at least one selected from the group consisting of itaconic anhydride, glutaconic anhydride, glutaric anhydride, succinic anhydride, maleic anhydride, phthalic anhydride, malonic anhydride, and butyric anhydride. The recording paper according to claim 1 . The recording paper according to claim 1 , further comprising a nonionic water-soluble polymer. The recording paper according to claim 3 , wherein the nonionic water-soluble polymer is polyvinyl alcohol. A charging step for uniformly 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 The electrostatic latent image is developed using an electrostatic charge image developer to form a toner image, the transfer step of transferring the toner image onto a recording paper, and the toner image transferred onto the recording paper An image recording method of an electrophotographic recording system including a fixing step for fixing,
An image recording method according to claim 1 , wherein the recording sheet is the recording sheet according to claim 1 . An ink jet image recording method in which droplets of ink containing water and / or a water-soluble organic solvent and a color material are ejected onto the surface of a recording paper to form 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 claim 1 .