JP2004025855A - Inkjet recording sheet and manufacturing method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a recording sheet which imparts a texture and high gloss, similar to those of a silver halide photograph, to a formed image, and exerts good curl characteristics even under environments from low humidity to high humidity. <P>SOLUTION: This inkjet recording sheet includes a base which is composed of a base material and polyolefin covering layers formed on both the sides of the base material by covering each of the sides thereof with polyolefin, and an ink receiving layer which is predominantly composed of hydrated alumina and formed on one of the polyolefin covering layers. The inkjet recording sheet is characterized in that the base is curled in the direction of the other polyolefin covering layer by heat treatment at 60°C and a relative humidity of 45% or less, so as to present a concave surface on the side of the the other polyolefin covering layer and present a convex surface on the side of one polyolefin covering layer. <P>COPYRIGHT: (C)2004,JPO

Description

【００５５】
表１の結果から、熱処理後にバックカールする被覆紙にインク受容層を塗工した記録シートは、良好なカール特性を示していることがわかる。また実施例１と４の結果から表面のポリエチレン密度が、バック面側のポリエチレン密度よりも低くすることにより、より高い効果を得ていることがわかる。
【００５６】
【発明の効果】
以上の如き本発明によれば、両面がポリオレフィンで被覆され、かつ相対温度４５％以下、６０℃で熱処理したときに一方の面にカールする支持体（例えば、被覆紙）を用い、他方の面にアルミナ水和物を主成分とするインク受容層を形成することで、形成された画像が銀塩写真に近い質感および高光沢を持ち、かつ低湿から高湿の環境下でもカール特性が良好な記録シートとすることができた。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an ink jet recording sheet (hereinafter abbreviated as “recording sheet”) suitable for recording by an ink jet recording method and a method for producing the same, and more specifically, an image having a texture and high gloss close to a silver halide photograph can be formed, The present invention also relates to a recording sheet exhibiting good curl characteristics even in a low humidity to high humidity environment and a method for producing the same.
[0002]
[Prior art]
The ink jet recording method is characterized in that it is excellent in high-speed printability, low noise, flexibility in recording patterns, and can easily perform multicolor printing. Furthermore, recent technological innovations have made it possible to make image quality comparable to silver halide photography, and thus have become widespread in a wide range of fields.
[0003]
Accordingly, recording sheets have been required to have higher properties. In other words, not only does the printer respond to multicolor and higher image quality of the printer, but also the importance of silver halide photographic surface gloss and texture is becoming very important in ink jet images.
[0004]
Various proposals have hitherto been made to meet these requirements, and among them, ink receiving on a support (hereinafter sometimes referred to as “coated paper”) having both sides of the paper coated with a resin such as polyolefin. A recording sheet having a layer formed thereon has high gloss and texture, and has recently been rapidly spreading as a silver halide photographic recording sheet.
[0005]
As the ink receiving layer provided on the coated paper, a large number of ink receiving layers containing inorganic fine particles have been proposed (Patent Documents 1 and 2, etc.). These have high ink absorption speed, and have good handleability because they have no stickiness.
[0006]
Among them, a recording sheet in which an alumina hydrate is applied as an inorganic fine particle to an ink receiving layer has a feature that the glossiness is higher and the image density is higher as proposed in Patent Document 3 and the like. Among the recording sheets using the coated paper, a silver halide photographic image can be obtained.
[0007]
However, on the other hand, the recording sheet having the ink receiving layer formed on the coated paper also has a drawback that curl fluctuation is remarkable due to a change in humidity. Generally, the curl of a recording sheet is uncurled or slightly curled from the aspect of appearance when the recording sheet is placed on a flat surface or when affixed to a wall or the like, and from the viewpoint of printability. It is preferable that the curl on the side opposite to the ink receiving layer (hereinafter referred to as “back surface side”) has a concave curved surface on the back surface side.
[0008]
Various methods have been known as means for controlling the curl of the coated paper with respect to the above problems. An example is shown below.
1. Adjust the curl of the substrate (eg, uncoated paper) itself.
2. Change the thickness of the front and back polyolefin.
3. Change the composition of the front and back polyolefin resin.
4. Change the density of the front and back polyolefin.
Actually, curl control is performed by combining these plural methods.
[0009]
However, the curl of the recording sheet after the formation of the ink receiving layer is due to the interaction between the paper, the covering polyolefin, and the ink receiving layer. In particular, since the curl behavior greatly differs depending on the type and properties of the ink receiving layer, the effect is not sufficiently exhibited only by controlling the curl of the support.
[0010]
On the other hand, Patent Document 4 discloses a method for suppressing curling of a recording sheet in which an ink receiving layer is provided on a support in which both surfaces of a paper are coated with a polyolefin resin. However, the effect of the ink receiving layer on the curl according to the present invention is hardly considered, and the curl is substantially controlled only by the physical properties of the base material, and it cannot be said that the effect is sufficiently exhibited. .
[0011]
[Patent Document 1]
Japanese Patent Application Laid-Open No. 8-1744992 [Patent Document 2]
JP 10-175365 A [Patent Document 3]
Japanese Patent Application Laid-Open No. 2000-301829 [Patent Document 4]
JP 2001-10203 A
[Problems to be solved by the invention]
The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to form a formed image having a texture and high gloss close to that of a silver halide photograph, and a curl characteristic even in an environment of low humidity to high humidity. Is to provide a good recording sheet.
Another object of the present invention is to provide a method for manufacturing such a recording sheet.
[0013]
[Means for Solving the Problems]
The present inventors have conducted intensive studies and found that the curl when heat-treating the coated paper affected the curl of the recording sheet after forming the ink receiving layer, and further contained alumina hydrate as a main component. The present invention has been completed by finding a coated paper suitable for forming the formed ink receiving layer.
[0014]
That is, the present invention provides a support comprising a base material and a polyolefin coating layer formed on both surfaces by coating both surfaces thereof with polyolefin, and alumina hydrate as a main component. Wherein the support is heat-treated at a relative humidity of 45% or less at 60 ° C. and the other polyolefin-coated layer of the polyolefin-coated layer is coated with an ink-receiving layer formed on one of the polyolefin-coated layers. An ink jet recording sheet is characterized in that it curls in the direction of the layer and shows a concave curved surface on the other polyolefin coating layer side and a convex curved surface on the one polyolefin coating layer side. In the recording sheet, the polyolefin is polyethylene, the polyethylene comprises a first type polyethylene and a lower density second type polyethylene, and the other polyolefin coating layer is the first type polyethylene. Wherein the one polyolefin coating layer is made of the second type polyethylene, or the ink receiving layer applies a coating liquid of 0.5 to 60 g / m ^{2 in} terms of solid content. It is preferable that it is formed by the above.
[0015]
Further, the present invention provides a support comprising a substrate and a polyolefin coating layer formed on both surfaces thereof by coating both surfaces thereof with polyolefin, and alumina hydrate as a main component. Wherein the support is heat-treated at 60 ° C. at a relative humidity of 45% or less, and the other one of the polyolefin-coated layers is formed. Curl in the direction of the polyolefin coating layer of the other polyolefin coating layer side to show a concave curved surface, the one polyolefin coating layer side shows a convex curved surface, and the ink receiving layer coating liquid Coating on said one polyolefin coating layer and heating the resulting ink receiving layer to a surface temperature of at least 80 ° C Providing coated inkjet manufacturing method of the recording sheet, characterized in that the drying of the coating liquid as.
[0016]
With the above configuration and manufacturing method, the recording sheet of the present invention has an image formed thereon having a texture and high gloss close to that of a silver halide photograph, and has good curl characteristics even in an environment of low to high humidity.
[0017]
In the study of the present inventors, the curl of a recording sheet in which an ink receiving layer containing alumina hydrate as a main component was formed on coated paper was less than 45% relative humidity, rather than the curl characteristics of the coated paper in a normal state. It was found that the curling characteristics after heat treatment at 60 ° C. had a stronger effect. Here, the heat treatment means that the substrate is left for 10 minutes under the above humidity and temperature conditions.
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, the present invention will be described in more detail with reference to preferred embodiments.
The substrate used for the support in the recording sheet of the present invention can be a commonly used paper, and is not particularly limited. The wood pulp is not particularly limited, and examples thereof include chemical pulp and mechanical pulp. Preferably, chemical pulp is used. Further, in order to improve the texture (formation) after coating, it is more preferable to mainly use LBKP or the like having a large amount of short fibers. Into the substrate, commonly used papermaking additives such as a paper strength enhancer, a filler, a binder, and a fluorescent whitening agent can be appropriately added.
[0019]
The thickness of the substrate is not particularly limited, but is preferably 50 to 300 μm. If it is less than 50 μm, the rigidity and texture of the recording sheet will be quite different from that of silver halide photography. On the other hand, if the thickness exceeds 300 μm, there is a high possibility that a problem occurs in the transportability of the recording sheet during printing. In addition, various calendering treatments can be performed after the paper making process to adjust the thickness and simultaneously increase the surface smoothness.
[0020]
Examples of the polyolefin used in the present invention include polymers and copolymers such as ethylene and propylene.In consideration of the combination with the substrate, the polyolefin is suitable for the curl characteristics of the support used in the present invention. It is necessary to select a suitable polyolefin material. In addition, opacity and whiteness can be increased by adding a white pigment such as titanium dioxide and zinc oxide to the polyolefin. As other additives, a fluorescent whitening agent, an antioxidant, a dye, a dispersant, and the like can be appropriately used.
[0021]
Among the above polyolefin materials, it is preferable to use polyethylene from the viewpoint of processability and cost. In that case, the polyethylene coated on both sides of the substrate is made of one kind of polyethylene, and the polyethylene coated on one side of the substrate and the polyethylene coated on the other side have the same density. The support may be made of two types of polyethylene having different densities, and the density of the polyethylene coated on one side of the support may be different from the density of the polyethylene coated on the other side. When one kind of polyethylene is used, the thickness may be changed so that the other side of the support on which the ink receiving layer is formed is curled convexly, and two kinds of polyethylene having different densities may be used. When used, polyethylene having a lower density may be used on the other surface of the substrate on which the ink receiving layer is formed, and polyethylene having a higher density may be used on one side of the substrate. By using one kind of polyethylene or two kinds of polyethylene as described above, the effects of the present invention can be more easily obtained.
[0022]
Polyethylene is crystallized by heating and contracts as a result. In addition, the higher the density, the more easily the crystallization proceeds, and therefore, the higher the density, the higher the tendency to shrink. Therefore, when the substrate is coated with polyethylene having different densities on the front and back sides, the obtained support is considered to curl in the surface direction using polyethylene having higher density.
[0023]
Each polyolefin coating layer is formed by melt-extrusion coating a polyolefin on a running substrate. Thereafter, the coated paper is obtained as a support by being pressed between the pressure roll and the cooling roll and then peeled off from the cooling roll. At that time, by selecting a desired cooling roll, one or both of the coated surfaces can be subjected to a glossy or mat-like or embossed treatment.
[0024]
Further, the thickness of the coating layer is not particularly limited, but is preferably in the range of 5 to 50 μm, more preferably 8 to 40 μm. However, since the curl characteristics of the coated paper change depending on the thickness of the coating layer on the front and back surfaces, it is necessary to select a thickness that matches the curl characteristics of the present invention. Further, the surface of the polyolefin coating layer can be subjected to a corona discharge treatment, a flame treatment, an undercoat treatment, or the like.
[0025]
In the present invention, alumina hydrate is used as a main component of the ink receiving layer. As described above, by using alumina hydrate, a recording sheet having high gloss and high density of an image to be formed can be obtained.
[0026]
Examples of the alumina hydrate used in the present invention include those represented by the following general formula (1).
Al ₂ O _3-n (OH) _2n · mH ₂ O (1)
(In the formula, n represents any one of the integers of 0, 1, 2, or 3, and m represents a value of 0 to 10, preferably 0 to 5.)
In the above formula, mH ₂ O often represents a detachable aqueous phase that does not participate in the formation of a crystal lattice, and thus m can take a non-integer value. Also, when this type of alumina hydrate is calcined, m can reach a value of zero.
[0027]
In general, alumina hydrate having a boehmite structure is a layered compound whose (020) crystal plane forms a giant plane, and shows a diffraction peak specific to an X-ray diffraction pattern. As the boehmite structure, in addition to complete boehmite, a structure called excessive boehmite, which contains excess water between layers on the (020) plane, can also be employed. Although the X-ray diffraction pattern of this pseudo-boehmite shows a broader diffraction peak than that of complete boehmite, complete boehmite and pseudo-boehmite are not clearly distinguishable from each other. It is called alumina hydrate.
[0028]
The form of the alumina hydrate in the present invention is preferably in the range of 150 nm to 250 nm, more preferably in the range of 160 nm to 230 nm, in order to obtain an ink receiving layer having high gloss and high transparency. When the average particle size of the alumina hydrate is smaller than 150 nm, the ink absorbency decreases, and bleeding or beading (which can absorb ink) when printing with a printer that discharges a large amount of ink or a printer that outputs at high speed is performed. Phenomena which result in granular density unevenness). On the other hand, if the average particle size is larger than 250 nm, the transparency and strength of the ink receiving layer may be reduced.
[0029]
The alumina hydrate used in the present invention preferably has a BET specific surface area of 40 to 500 m ² / g. When the BET specific surface area is less than 40 m ² / g, the transparency of the ink receiving layer is impaired due to the large size of the alumina hydrate particles, the image density is reduced, and an image such as a printed matter having a white and hazy appearance is obtained. Prone. If the BET specific surface area exceeds 500 m ² / g, a large amount of acid is required to peptize the alumina hydrate. A more preferred range is 50 to 250 m ² / g (particularly 50 to 150 m ² / g), and the ink receiving layer is excellent in ink absorption, beading resistance, smoothness, and the like.
[0030]
An aqueous resin may be added as a binder to the coating liquid containing alumina hydrate used in the present invention. Examples of the aqueous resin include a water-soluble or water-dispersible polymer compound, for example, starch, gelatin, casein and modified products thereof, methylcellulose, carboxymethylcellulose, cellulose derivatives such as hydroxyethylcellulose, and fully or partially saponified polyvinyl. Alcohol or modified products thereof (cation-modified, anion-modified, silanol-modified, etc.), urea resin, melamine resin, epoxy resin, epichlorohydrin resin, polyurethane resin, polyethyleneimine resin, polyamide resin, polyvinylpyrrolidone resin , Polyvinyl butyral resin, poly (meth) acrylic acid or copolymer thereof, acrylamide resin, maleic anhydride copolymer, polyester resin, SBR latex, NBR latex, methyl meta Acrylate-based polymer latex such as acrylate-butadiene copolymer latex, acrylate ester copolymer, vinyl-based polymer latex such as ethylene-vinyl acetate copolymer, and a cationic group or anion Functional group-modified polymer latexes having a functional group. Among them, polyvinyl alcohol having an average degree of polymerization of 300 to 5,000 is preferred. The saponification degree is preferably from 70 to less than 100%, particularly preferably from 80 to 99.5%. These water-soluble or water-dispersible resins can be used alone or as a mixture of two or more.
[0031]
The amount of the aqueous resin used is preferably in the range of 1/30 to 1/1, more preferably in the range of 1/20 to 1/3 in terms of the mixing mass ratio with respect to the alumina hydrate. When the amount of the aqueous resin is within these ranges, the formed ink receiving layer is less likely to crack or fall off, and has good ink absorbency.
[0032]
Further, in the ink receiving layer of the recording sheet of the present invention, a hardener, a dye fixing agent, a coloring dye, a coloring pigment, a dispersing agent, a thickener, a pH adjuster, as long as the performance as the recording sheet is not impaired. Lubricants, flow modifiers, surfactants, antistatic agents, antifoaming agents, penetrants, optical brighteners, ultraviolet absorbers, antioxidants and the like can also be added.
[0033]
The solid content concentration in the coating liquid for forming the ink receiving layer used in the present invention is not particularly limited as long as the viscosity is such that the ink receiving layer can be formed on the coated paper. Is preferably 5 to 50% by mass. When the solid content concentration is less than 5% by mass, it is necessary to increase the coating amount to increase the thickness of the ink receiving layer, and it becomes uneconomical because much time and energy are required for drying. There are cases. On the other hand, when the solid content exceeds 50% by mass, the viscosity of the coating liquid is increased, and the coating property may be reduced.
[0034]
Examples of the method for applying such a coating liquid on a support include a spin coating method, a roll coating method, a blade coating method, an air knife coating method, a gate roll coating method, a bar coating method, a size press method, and a spray coating method. Conventionally known coating methods such as a gravure coating method, a curtain coating method, a rod blade coating method, a lip coating method, and a slit die coating method can be used. If necessary, the surface smoothness of the ink receiving layer can be improved by using a calender roll or the like after coating.
[0035]
The coating amount of the ink receiving layer may be appropriately selected depending on the amount of ink absorption required for the ink receiving layer, but care must be taken because the effect on the curl increases as the coating amount increases. A preferable range of the coating amount is 0.5 to 60 g / m ² in terms of solid content, and a more preferable range is 5 to 50 g / m ² . When the coating amount is less than 0.5 g / m ² , when the ink is applied to the formed ink receiving layer, the water in the ink cannot be sufficiently absorbed, and the ink flows or the image bleeds. When the coating amount exceeds 60 g / m ² , a remarkable effect may not be exhibited as expected in the ink absorption performance.
[0036]
The recording sheet of the present invention can be obtained by applying the above-mentioned coating solution to a support and then drying it using a drying device such as a hot-air dryer, a hot drum, or a far-infrared dryer. In this case, by setting the surface temperature of the ink receiving layer to 80 ° C. or higher, preferably 80 to 120 ° C., the effects of the present invention can be more reliably exhibited and preferable results can be obtained. By increasing the drying time or increasing the surface temperature of the ink receiving layer, the back curl of the coated paper tends to increase. However, care must be taken because if the amount of heat applied is too large, defects occur on the front and back surfaces. Here, the surface temperature means the maximum temperature of the surface of the ink receiving layer in the drying step.
[0037]
According to the present invention, the support is curled on one of the two surfaces of the support by a heat treatment at 60 ° C. at a relative humidity of 45% or less. When the substrate is subjected to a heat treatment for 10 minutes, the support preferably shows a curl of −40 mm to −3 mm on the side opposite to the surface on which the ink receiving layer is formed, and more preferably −30 mm to −10 mm. When an ink receiving layer is formed on a support exhibiting a curl exceeding −40 mm, the curl after storage in a low-temperature and low-humidity environment becomes strong, and when the ink receiving layer is formed on a support exhibiting a curl of less than −3 mm, a high temperature occurs. Curling after storage in a high-humidity environment tends to be strong, resulting in poor appearance and poor printability.
[0038]
Depending on the constituent material, the ink receiving layer tends to expand by a moisture absorbing action in a high humidity state and conversely contract in a low humidity state. However, the ink receiving layer containing alumina hydrate as a main component used in the present invention, on the contrary, tends to shrink in a high-humidity state and expand in a low-humidity state, and particularly tends to shrink in a high-humidity state. Was more prominent.
[0039]
As described above, it is desirable that the recording sheet is not curled or slightly curled toward the back surface side. Therefore, when the ink receiving layer mainly containing the alumina hydrate of the present invention is formed. The coated paper must be curled toward the back surface. However, since the curl of the coated paper changes greatly after the heating and drying step after the formation of the ink receiving layer, use a coated paper that curls to one side by heat treatment and shows a concave curl. By forming an ink receiving layer on the opposite surface, a recording sheet having good curl characteristics can be obtained even in an environment of low to high humidity. When such a coated paper is used and the surface temperature of the ink receiving layer is set to 80 ° C. or higher in the drying step, curling can be more effectively controlled.
[0040]
The ink used for recording on the recording sheet of the present invention is not particularly limited, but a dye or pigment is used as a coloring material, a mixture of water and a water-soluble organic solvent is used as a medium, and the dye is used as the medium. Alternatively, it is preferable to use a general aqueous ink for inkjet recording in which a pigment is dissolved or dispersed.
[0041]
【Example】
Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples. In the following description, “parts” and “%” are based on mass unless otherwise specified.
[0042]
Example 1
<Manufacture of coated paper>
A low-density polyethylene (LDPE, density 0.914 g / cm ³ ) is applied to the surface (the surface on which an ink receiving layer is to be formed) of a high-quality paper (160 g / m ² ) made of LBKP as a main material and calendered (base A). Was applied by a melt extrusion coating method so as to have a thickness of 30 μm, and then subjected to a gloss treatment. On the other side, high-density polyethylene (HDPE, density: 0.945 g / cm ³ ) was applied by a melt extrusion coating method so as to have a thickness of 30 μm, and a mat treatment was performed. Further, the surface of the low-density polyethylene coating layer was subjected to a corona discharge treatment to produce a coated paper. The coated paper was placed in an oven at a relative humidity of 45% or less at 60 ° C. for 10 minutes to perform a heat treatment, and the curl was measured in the following manner.
[0043]
<Preparation of alumina hydrate dispersion>
Aluminum dodexide was prepared by the method described in U.S. Pat. No. 4,242,271. Next, the aluminum dodexide was hydrolyzed to produce an alumina slurry by the method described in U.S. Pat. No. 4,202,870. Water was added to the alumina slurry until the alumina hydrate having a boehmite structure had a solid content of 7.7%. At this time, the pH of the alumina slurry was 9.4, and a 3.9% nitric acid solution was added thereto to adjust the pH.
[0044]
Next, using an autoclave, aging was performed at pH before aging: 6.0, aging temperature: 150 ° C, and aging time: 6 hours to obtain a colloidal sol. The colloidal sol was spray-dried at an inlet temperature of 120 ° C. to obtain an alumina hydrate powder. The obtained powder was an alumina hydrate having a flat particle shape and a boehmite crystal structure. The BET specific surface area of the obtained powder was measured using a specific surface area / pore distribution measuring device (Micromeritex ASAP2400, manufactured by Shimadzu Corporation). As a result, it was 140.2 m ² / g. Further, an alumina hydrate dispersion was prepared by mixing the alumina hydrate powder having the boehmite structure in ion-exchanged water so that the concentration became 19.0%. When the obtained alumina hydrate dispersion was measured using a laser particle size analyzer PAIII (manufactured by Otsuka Electronics Co., Ltd.), the average particle size of the alumina hydrate particles was 178.3 nm.
[0045]
<Preparation and coating of coating liquid for forming ink receiving layer>
The alumina hydrate dispersion was mixed with 12.7 parts of a 3% boric acid aqueous solution (2% based on alumina hydrate), and 45 parts of ion-exchanged water was mixed with polyvinyl alcohol (PVA-224, Kuraray Co., Ltd.). 5 parts) was added to prepare a coating liquid for forming an ink receiving layer. Next, the surface of the coated paper (the surface to be coated with the ink-receiving layer) was coated with the above-mentioned coating solution with a wire bar so as to have a dry coating amount of 30 g / m ² . The recording sheet was obtained by drying with hot air for 15 minutes. At that time, the surface temperature of the ink receiving layer immediately before being taken out of the oven was measured.
[0046]
Example 2
A recording sheet was prepared in the same manner as in Example 1 except that the dry coating amount of the ink receiving layer in Example 1 was changed to 15 g / m ^2, and the surface temperature of the ink receiving layer was measured immediately before the recording sheet was taken out of the oven. .
[0047]
Example 3
A recording sheet was prepared in the same manner as in Example 1 except that the dry coating amount of the ink receiving layer in Example 1 was changed to 50 g / m ^2, and the surface temperature of the ink receiving layer was measured immediately before the recording sheet was taken out of the oven. .
[0048]
Example 4
Example 1 A recording sheet was prepared in the same manner as in Example 1 except that the drying conditions for forming the ink receiving layer were 90 ° C. and 20 minutes, and the surface temperature of the ink receiving layer immediately before the recording sheet was taken out of the oven was measured. It was measured.
[0049]
Example 5
A support and a recording sheet were prepared in the same manner as in Example 1 except that the surface of the coating layer of Example 1 was 20 μm of HDPE and the opposite surface was 40 μm of HDPE, and the ink receiving layer immediately before removing the recording sheet from the oven was prepared. The surface temperature was measured.
[0050]
Comparative Example 1
A support and a recording sheet were produced in the same manner as in Example 1 except that the surface of the coating layer of Example 1 was 30 μm for HDPE and the opposite surface was 30 μm for LDPE, and the ink immediately before the recording sheet was taken out of the oven was prepared. The surface temperature of the receiving layer was measured.
[0051]
Comparative Example 2
A support and a recording sheet were prepared in the same manner as in Example 1 except that the surface of the coating layer of Example 1 was 30 μm of HDPE and the opposite surface was 30 μm of HDPE, and the ink immediately before the recording sheet was taken out of the oven was prepared. The surface temperature of the receiving layer was measured.
[0052]
<Measurement method of curl of support>
After the heat-treated support is cut into A4 as described above, it is left in a sealed state in a plastic bag for 5 hours at 20 ° C. and 65%, and then taken out of the bag and the low-density polyethylene-coated surface is turned up. After being placed on a horizontal desk for one hour, the lifting at the four corners was measured. Further, the support was turned upside down and the lifting amount at the four corners was measured, and the maximum value among the eight points was defined as the curl value. The results are shown in Table 1. The curl in the front direction (the surface on which the ink receiving layer was formed) was +, and the opposite direction was-.
[0053]
<Recording sheet curl measurement>
In two environments of 30 ° C. and 80% RH (H / H) and 15 ° C. and 10% RH (L / L), the curl of the support was measured according to the above-described method of measuring curl. The results are shown in Table 1. In the size of the recording sheet prepared in the present embodiment, if the curl is −15 to +10 mm, it is unlikely to cause a problem in practical use. Conversely, if the curl is larger than −20 mm and +15 mm, the appearance and printability are serious. Problems easily occur.
[0054]

[0055]
From the results shown in Table 1, it can be seen that the recording sheet obtained by applying the ink receiving layer to the coated paper that is back-curled after the heat treatment exhibits good curling characteristics. Further, from the results of Examples 1 and 4, it can be seen that a higher effect is obtained by making the surface polyethylene density lower than the back surface side polyethylene density.
[0056]
【The invention's effect】
According to the present invention as described above, a support (for example, coated paper) that is curled on one surface when heat-treated at 60 ° C. at a relative temperature of 45% or less using polyolefin on both surfaces and the other surface is used By forming an ink receiving layer containing alumina hydrate as a main component, the formed image has a texture and high gloss close to that of a silver salt photograph, and has a good curl characteristic even in an environment of low to high humidity. It could be a recording sheet.

Claims (4)

A support comprising a base material and a polyolefin coating layer formed on both surfaces by coating both surfaces thereof with polyolefin, and a polyolefin coating layer comprising one of the polyolefin coating layers containing alumina hydrate as a main component; In the ink jet recording sheet including the ink receiving layer formed thereon, the support curls in the direction of the other polyolefin coating layer of the polyolefin coating layer by a heat treatment at 60 ° C. at a relative humidity of 45% or less. Wherein the other polyolefin coating layer has a concave curved surface and the one polyolefin coating layer has a convex curved surface. The polyolefin is polyethylene, the polyethylene comprises a first type of polyethylene and a lower density second type of polyethylene, and the other polyolefin coating layer comprises the first type of polyethylene; 2. The ink jet recording sheet according to claim 1, wherein one of the polyolefin coating layers is made of the second type of polyethylene. Wherein the ink receiving layer, an ink jet recording sheet according to claim 1 and is formed by 0.5~60g / m ² coating a coating liquid on a solid basis. A support comprising a base material and a polyolefin coating layer formed on both surfaces by coating both surfaces thereof with polyolefin, and a polyolefin coating layer comprising one of the polyolefin coating layers containing alumina hydrate as a main component; A method for producing an ink jet recording sheet including an ink receiving layer formed thereon, wherein the support is subjected to a heat treatment at 60 ° C. at a relative humidity of 45% or less in a direction of the other polyolefin coating layer of the polyolefin coating layers. Curving to show a concave curved surface on the other polyolefin coating layer side, showing a convex curved surface on the one polyolefin coating layer side, and applying the ink receiving layer coating liquid to the one polyolefin coating layer. Coating on top so that the resulting ink receiving layer is heated to a surface temperature of at least 80 ° C Ink-jet recording sheet manufacturing method which is characterized in that the drying of the coating liquid was.