JP4014554B2 - Method for producing ink jet recording material - Google Patents

Description

  The present invention relates to an inkjet recording medium manufacturing method in which a second coating is performed on a porous layer, and an inkjet recording that enables a uniform second coating without being affected by the gas contained in the lower layer. The present invention relates to a method for manufacturing a medium.

  As a recording material used in the ink jet recording method, a porous material composed of a water-soluble binder and a pigment such as a hydrophilic polymer ink receiving layer or amorphous silica on a support called ordinary paper or ink jet recording paper. Recording materials provided with an ink receiving layer are known.

  For example, as disclosed in JP-A-56-080489, JP-A-59-174381, JP-A-60-220750, JP-A-61-32788, JP-A-63-160875, JP-A-3-69388, etc. A recording material in which a hydrophilic polymer such as alcohol is coated on a support has been proposed.

  For example, JP-A Nos. 55-51583, 56-157, 57-107879, 57-107880, 59-230787, 62-160277, 62-184879, 62-183382 And a recording material obtained by coating a paper support with a silicon-containing pigment such as silica together with an aqueous binder, as disclosed in JP-A-64-11877 and the like.

  In addition, JP-B-3-56552, JP-A-2-188287, JP-A-10-81064, JP-A-10-119423, JP-A-10-175365, JP-A-10-193976, JP-A-10-203006, 10-217601, 11-20300, 11-20306, 11-34481, etc. use synthetic silica fine particles by a vapor phase method (hereinafter referred to as vapor phase silica). It is disclosed. JP-A-2-276671, JP-A-3-67684, JP-A-3-251488, JP-A-4-67986, JP-A-4-263833, JP-A-5-16517, etc. The use of Japanese products is disclosed. These vapor-phase method silica and alumina hydrate are ultrafine particles having an average primary particle diameter of several nm to several tens of nm, and are characterized by high glossiness and ink absorbability. In recent years, photo-like recording materials have been demanded, and the texture, texture and glossiness close to those of photographs have become increasingly important. The same polyolefin resin-coated paper as photographs (polyolefin resin such as polyethylene is coated on both sides of the base paper) Many recording materials have been proposed in which an ink-receiving layer mainly composed of these fine particles is coated on a water-resistant support such as the above.

  Further, in the method for producing an ink jet recording material using the porous layer mainly composed of these fine particles as the ink receiving layer, at the same time as or applying the first coating layer mainly composed of the fine particles. Before the first coating layer is reduced or after the first coating layer is dried to form a coating film, in any of these stages, a second agent containing a crosslinking agent, an ink dye fixing agent, a preservability improving agent, etc. There has been proposed a method for stably producing an inkjet recording material by coating. (For example, see Patent Document 1 etc.)

  However, according to the study by the present inventors, when the first coating layer and the second coating layer are applied at the same time, the coating liquids are in contact with each other, and in some cases, at the contact interface. In some cases, agglomerates are generated, and the agglomerates often cause failure of the coated surface, and it has been found that the agglomerates may be undesirable from the viewpoint of stable production. In addition, when the second coating layer is applied before the first coating layer exhibits the reduced rate of drying, the generation of the agglomerates is suppressed, but in the actual production process, At the stage where the second coating layer is applied, the drying state of one coating layer varies in the width direction of the coating, and the drying state changes depending on the elapsed time from the start of coating of the first coating layer. Since the dry state of the first coating layer is not uniform, the second coating by the dipping method disclosed in the example of Patent Document 1 is not uniformly penetrated into the first coating layer, and is actually It was found that there was a problem that the characteristics of the finished recording material were not constant. In the method in which the second coating is performed after the first coating layer is dried and a coating film is formed, air is present in the porous layer formed by drying the first coating layer. In the application by the dipping method as disclosed in the above, air existing in the porous layer remains as bubbles on the surface of the coating or inside, and the application of the second coating liquid becomes uneven, after drying It was found that the foam shape remained on the surface of the recording material, causing problems such as harming the appearance. In order to eliminate the influence of foam, it is necessary to have a means to scrape off the foam formed on the surface during immersion, and it is necessary to soak for a long time to replace the foam part, and the size of the immersion device is increased. It is not preferable.

  In addition, after the first application is performed, the second application is performed on the same application process, and the second application is performed after the decreasing rate drying unit where the void layer is formed in the coating layer by the first application, By using a method in which the total amount of the liquid used for the second coating and the water content of the void layer at the time of coating is limited to 1.5 times or less of the void volume of the void layer, it is used for the first coating. A method has been proposed in which an additive having a problem in addition such as cracking of the coated surface is applied to the recording material using the second coating to obtain a recording material free of failure. (See Patent Document 2)

  In this patent document, only a spray coater is described, and it is considered that the present invention is substantially implemented by a spray coater.

  The spray coater is literally a coater that sprays and applies a coating liquid as a large number of droplets, and is a method widely used for resist coating of a printed circuit board and powder production by drying the obtained droplets. Since ink jet printers record using droplets, it is easy to imagine using a spray coater that sprays similar droplets for the second application.

  However, when the present inventors examined a spray coater, when used for application to a porous layer, when the absorption capacity of the porous layer is less than or equal to, the droplets are rapidly absorbed, so that the droplets contact each other. As a result, it was found that the coating film itself was not formed, and the coating liquid distribution pattern had a shape in which the shape of the droplets adhered overlapped many times, resulting in non-uniform coating.

  Therefore, in this patent document, when an amount equal to or less than the absorption capacity of the porous layer is applied, the droplets applied by the spray coater cannot form a coating film, and thus are disclosed in Examples. " The “wet film thickness” should not exist in the first place, and if the wet film thickness exists, it means that the absorption capacity is exceeded, and it is also found that the content is different from the contents of the examples.

Furthermore, in this patent document, the void volume is described in J. It is defined by the amount of liquid transfer at a contact time of 2 seconds when measured by the liquid absorptivity test method (Bristow method) of paper and paperboard specified in TAPPI 51. It is known that the numerical value is considerably larger than the actual void volume due to the unevenness and lateral blurring, and the lateral blurring is particularly large in contact for a long time of 2 seconds. It is a numerical value greatly deviating from the capacity, and the void volume in the patent document is considered to be a value far from the actual void volume.
JP 2002-154269 A JP 2002-331745 A

  An object of the present invention is to perform a uniform overcoat without being affected by the gas present in the porous layer after the porous layer is formed after the first application for forming the porous layer is performed. Accordingly, an object of the present invention is to provide a method for producing an ink jet recording medium having high quality.

  As a result of researches to solve this problem, the present inventors have completed the present invention by the following method.

  (1) In the method for manufacturing an ink jet recording medium, in which the second coating is performed on the first coating for forming at least one porous layer comprising a pigment and a binder, After the porous layer by one application is formed, it is performed using a coating apparatus having a slit for flowing out uniformly in the width direction of the application, and the coating liquid used for the second application is the porous layer Inkjet recording characterized in that the liquid volume is pre-weighed so as not to exceed 90% of the void volume, and substantially the entire amount is absorbed by the porous layer within 1 second after contact with the porous layer A method for manufacturing a medium.

  (2) The coating liquid supply amount of the second coating does not exceed 90% of the void volume formed up to the second coating time point by drying after the first coating (1) The method for producing an ink jet recording medium according to (1).

  (3) The method for producing an ink jet recording medium according to (1) or (2), wherein the second coating is performed after completion of the reduction rate drying in the first coating.

  (4) The method for producing an inkjet recording medium according to any one of (1) to (3), wherein the second coating is performed after the first coating and before the coated material is wound up. .

  (5) The method for producing an ink jet recording medium according to any one of (1) to (4), wherein the porous layer comprises inorganic fine particles having an average primary particle size of 100 nm or less and a hydrophilic binder.

  (6) The method for producing an ink jet recording medium according to (5), wherein the inorganic fine particles are any one selected from alumina hydrate, gas phase method silica, and wet method silica or a mixture thereof.

  According to the production method of the present invention, when the second coating is performed on the porous layer formed by the first coating, there is no generation of bubbles due to gas such as air contained in the porous layer, which is uniform. It is possible to perform coating, and it is possible to obtain a high-quality ink jet recording medium without being limited to the types of additives and the like contained in the coating liquid used for the second coating.

  The present invention will be described in detail below. In the present invention, there is provided a production method for carrying out a uniform second coating (overcoat) on a porous layer. Conventionally, overcoating on a porous layer composed of a pigment and a binder is provided. Is considered to be very difficult due to the influence of gas such as air contained in the porous layer, but as a result of intensive studies, the present inventors have found that After the porous layer formed by the first application is formed in the second application, the application is performed using a coating apparatus having a slit for flowing out uniformly in the width direction of the application. The amount of liquid pre-weighed so as not to exceed 90% of the void volume of the porous layer, and substantially the entire amount is absorbed by the porous layer within 1 second after contact with the porous layer. And made it possible.

  In the present invention, the measurement position in the second application is important. In general, when coating is performed, it is necessary to determine the coating amount, which is generally referred to as metering, and can be broadly divided into post-measuring and pre-measuring.

  Application by post-metering is a method of applying a larger amount than the target application amount by an application device and then blowing off by using wind pressure such as an air knife, or scraping off by mechanical contact such as a doctor blade or a wire rod. Used to indicate that the target coating amount can be obtained by eliminating the surplus, and generally when applying a single layer such as an overcoat, a large amount of coating liquid is applied and scraped off. It is widely used because it is a method with excellent characteristics such as difficult to perform. However, in the present invention, the coating liquid used for the second coating is absorbed into the porous layer until it reaches the coating amount control part in the post-measurement such as an air knife or a wire rod. As a result, it has been found that not only post-measurement itself is difficult to be established but also non-uniformity of active ingredients and failure due to generation of bubbles.

  Application by pre-weighing is a method in which a pre-weighed coating liquid is supplied to the coating device to perform coating, and since the target coating amount is reached when it is pushed out from the coating device, the surplus is eliminated after coating. There is no process to do. Therefore, it has been found that a uniform coating amount can be obtained even on a highly absorbent substrate such as a porous layer, which is essential in the present invention.

  Moreover, it discovered that there existed an important factor also regarding the application quantity of the coating liquid with which 2nd application | coating is provided. When a coating liquid is applied in an amount exceeding 90% of the void volume, that is, 90% of the absorption capacity of the porous layer, the absorption into the porous layer is slow and the coating liquid remains on the surface of the porous layer. Since gas such as air inside is prevented from being exhausted, a gas having no escape space becomes bubbles on the surface, and the amount of the coating liquid used for the second application locally increases around the bubbles, which is not preferable. In addition, some of these coating liquids may associate and grow into small droplets, and undesirable phenomena such as local increase in coating amount were observed. Preferably it is 85% or less of the void volume, particularly preferably 75% or less.

  In addition, after applying the coating liquid to be used for the second coating, it is necessary that substantially all of the solvent contained in the coating liquid is absorbed by the porous layer within 1 second. In the case of absorption for more than 1 second, bubbles may be scattered in the coated material, which is not preferable.

  The reason why bubbles are not seen and the coated surface is good when it is 1 second or less is not clear, but it is thought to be related to the mutual bonding speed of gases such as air in the porous layer. In other words, when the applied coating liquid is 90% or less of the void volume of the porous layer, the surface of the gas such as air is sealed with the coating liquid as the coating liquid absorbs or penetrates into the porous layer. Cannot escape to the surface and therefore remains inside. In a stage where substantially the entire amount is absorbed in the porous material, it is considered that the gas such as air existing in the porous material is compressed into a relatively large gap portion which is scattered, and a short time of 1 second or less. When the coating liquid is absorbed in step 1, when there is no longer any coating liquid that seals the entire coating surface, it is released to the outside from the void not filled with the solvent inside the porous material, and the visible bubbles are Don't be. However, when it takes 1 second or more, the fine bubbles are bonded to each other, grow into large bubbles, break the liquid film of the coating liquid that seals the coating surface, and appear as bubbles. Yes. Of course, it is assumed that the fine bubbles are bonded to each other even in a region of 1 second or less, but it is assumed that they grow at an accelerated rate in about 1 second.

  The time required for the porous layer to absorb a substantial amount of the solvent contained in the coating solution after coating the coating solution to be used for the second coating is preferably 1 second or less, particularly preferably. It is preferably 0.8 seconds or less and is absorbed as soon as possible.

  When a water-soluble additive is contained in the coating liquid used for the second coating, it is absorbed and added into the porous layer together with the solvent. If it is a pigment or the like, it may remain on the surface.

  In the present invention, the fact that substantially all of the solvent contained in the coating solution is absorbed by the porous layer means that no wet film exists on the surface of the applied porous layer by absorbing the solvent. In other words, the time required for the substantial amount of the solvent to be absorbed by the porous layer is measured by measuring the surface reflectance after coating, or by making physical contact with the surface immediately after coating, and transfer of the wet film occurs. Measured with or without.

  When the measurement is performed by measuring the surface reflectance, the reflectance is greatly different between a region where the wet film is present on the surface and a region where substantially the entire amount of the solvent is absorbed. For example, when the time required for absorption is relatively long and about 1 second, the wet film is stable and the reflectance immediately after coating becomes high, and when the solvent is absorbed in the porous, the reflectance is relative. It becomes low. On the other hand, when the absorption is very fast in about 0.1 seconds, the surface of the wet film is unstable and wavy, so the reflectance is low, and when the solvent is absorbed porous, the reflectance is low. Relatively high. Therefore, when coating is performed at a constant coating speed, the time required for absorption can be obtained by measuring the distance from the coating apparatus and the change in reflectance.

  In addition, in the method of measuring by transferring a wet film by physical contact, a dye having an extremely high extinction coefficient is added to a model coating solution having the same composition, and PPC paper is brought into contact with the surface to facilitate discrimination. It can be measured by whether or not dye transfer occurs. When coating is performed at a constant coating speed, the time required for absorption can be obtained by measuring the distance from the coating apparatus and the presence or absence of transfer.

  The liquid property of the coating solution used for the second coating is not particularly specified as long as it is absorbed in the porous layer in 1 second or less, but the viscosity is 10 mPa · s or less, and the surface tension is 100 mN / m. The following is preferred.

  The void volume of the porous layer referred to in the present invention is an accumulation from a pore radius of 3 nm to 400 nm in a porous layer portion measured and processed using a mercury porosimeter (measuring instrument name: Autopore II 9220, manufacturer, micromeritics instrument corporation). By multiplying the pore volume (mL / g) by the coating solid content (g / square meter) of the porous layer, it can be obtained as a numerical value per unit area (square meter).

  In the coating apparatus used in the present invention, a known coating method can be used for the coating apparatus used for the first coating. For example, there are a slide bead method, a curtain method, an extrusion method, an air knife method, a roll coating method, a rod bar coating method, and the like.

Among the coating devices used in the present invention, the coating device used for the second coating is a coating device having a slit for uniformly flowing out in the width direction of the coating, for example, a slot coater system, an extension having a slit. A slide bead method, a curtain method, etc. can be used as a rugged method, but these are coating devices in which the coating liquid used for the second coating that has flowed out of the slit forms a liquid film and is applied in a liquid film state. Yes, and as mentioned above, it is essential to be pre-weighed.

  Conventionally, when coating on a porous layer containing a gas such as air, a coating method in which almost all of the coated surface is sealed with a coating liquid has not been attempted since the generation of bubbles is predicted or observed. In the invention, since the amount of coating was measured in advance and the coating liquid was absorbed into the porous layer promptly, it was possible to completely suppress the generation of bubbles, so these were excellent in uniformity of the coated surface for the first time. It became possible to adopt the coating method.

  For these coating apparatuses having slits for uniformly flowing out in the width direction, it is preferable that the distance between the coating apparatus and the porous layer to be coated is 100 microns or less. For example, there is a method of fixing the gap between the coating device and the porous layer using a roll, or a method of pressing the porous layer against the coating device and forming a gap with a liquid film formed by the coating liquid coming out of the coating device. Yes, various known methods can be used.

  After applying the second coating liquid, until the substantial amount of the solvent contained in the coating liquid is absorbed by the porous layer, that is, while the wet film remains on the surface, For example, it is preferable not to apply strong winds exceeding 20 m / sec. This is for allowing the coating liquid used for the second coating to stably penetrate and absorb into the porous layer.

  In the present invention, the void volume varies greatly depending on the dry state of the porous layer applied by the first application in the stage of performing the second application, and the application amount in the second application changes accordingly. .

  In the drying process, the wet coating applied on the substrate by the first application is continuously transported, and the drying is controlled to specific temperature and humidity conditions from the front, back, or both sides. Blow wind to dry.

  The drying process of the wet coating film can be classified mainly as follows. The initial stage of drying is called the constant rate drying section.Inkjet recording media with a large amount of water and solvent at the initial stage of drying evaporate while relatively free water and solvent take away the latent heat of vaporization of water and solvent. The surface temperature on the surface side having the quality layer is substantially constant. This period of constant temperature is called a constant rate drying section. In the case of a porous layer, even in the constant rate dry region, the porous layer is formed sequentially from the surface, but moisture is supplied to the surface from the lower wet coating through the pores of the porous layer to evaporate. The water movement in the coating and the water evaporation from the surface are constant. In this state, the inside of the pores of the formed porous layer is always filled with water and solvent. There are no voids.

  When the constant rate drying unit is completed, the process proceeds to the reduction rate drying unit. In the reduced rate drying section, the porous layer that has been formed sequentially from the surface reaches the surface of the substrate, the supply of water and solvent from the wet paint film is lost, the evaporation of water and solvent contained in the pores, and Water evaporates from the hydrophilic binder part in a swollen state, and water and solvent inside the pores disappear sequentially from the surface, and voids filled with gas such as air and water vapor begin to appear. As a result, the heat transfer efficiency of the drying air is reduced and the surface temperature is increased.

  Next, when the reduced rate drying is completed, the moisture and solvent to be evaporated disappear, and the temperature of the drying air and the surface temperature of the ink jet recording medium coincide with each other. This point is called the drying end point, and the gap in the ink jet recording medium is completed.

  The method for confirming the constant rate drying unit, the rate-decreasing drying unit, and the drying end point described above is not particularly limited. For example, the surface temperature of the surface coated with the porous layer is monitored, and the surface temperature is constant. It is possible to obtain the time when the constant area is the constant rate drying section and the area where the surface temperature is increased is the same as the decreasing rate drying section and the drying temperature as the drying end point.

  In the present invention, since the object is achieved by performing the second coating with a coating amount of 90% or less of the void volume of the porous layer, the coating should be applied after the reduced-rate drying region where voids begin to be formed. Is preferred. Because it is possible to use a coating device that performs uniform coating in the width direction, there is also a coating amount deviation caused by uneven drying in the width direction in the reduced rate drying area, as seen in the dipping method. Never do. When performing the second coating, the coating amount may be determined based on the portion having the smallest void volume in the width direction.

  Particularly preferred is application after the end of drying. By applying after the end point of drying where the voids of the porous layer are completely formed, it becomes possible to obtain the maximum application amount, and when it is desired to add a large amount of additives, it becomes a preferable form.

  In addition, when the second application is performed in the reduced rate drying region, it is naturally performed after the first application until the coated material is wound up, that is, the application is performed twice online. However, when applying after the end point of drying, not only the first application and the second application on-line in the same manner, but also after winding the application paper once after the first application, The second coating can be performed again, and an annealing treatment such as heating can be added before the second coating is performed. In particular, when the coated paper is taken up once and the second coating is performed again, there is an advantage that the same coating apparatus can be used.

  In the present invention, various solvents can be used as the solvent of the coating liquid used for the second coating depending on the purpose. In the present invention, the solvent is not particularly limited. Depending on the additive, water, an organic solvent such as methanol, ethanol, diethylene glycol and the like, and a mixture with water, or, if necessary, xylene, ether, etc. Can also be used.

  The additive provided to the ink jet recording medium by the second application of the present invention is not particularly limited, and can be widely used according to the purpose. For example, water-soluble natural polymers such as gelatin, carboxymethyl cellulose, starch and casein, surfactants, inorganic pigments such as silica, alumina and calcium carbonate, organic pigments such as polystyrene resin, acrylic resin and polyolefin resin, Metal salts, quaternary ammonium salts, various organic or inorganic matting agents, various latex emulsions, dyes or pigments for coloring, water-soluble resins such as polyvinyl alcohol and polyvinylpyrrolidone, polyvinyl butyral, polyvinyl formal Water-insoluble resins such as diethylene glycol and triethylene glycol, high boiling organic solvents such as diaminostilbene derivatives, brighteners such as diaminostilbene derivatives, preservatives such as isothyrazolinone, membrane surfaces such as sodium acetate and phosphate buffer Adjusting agents, ink dye fixing agent, a photocatalyst such as titanium oxide, very fine particles such various metals, various known additives alone or can be used suitably mixed.

  Thus, in the second coating according to the present invention, the coating amount is 90% or less of the void volume of the porous layer, and if the substantial amount of the solvent is absorbed by the porous layer within 1 second. Any substance can be uniformly applied to the inside or the surface of the porous layer.

  Moreover, in order to perform 2nd application | coating itself stably, a fluorine-type surfactant, acetylene diol type surfactant, acetylene alcohol, lower alcohols, etc. can be contained as needed. In the present invention, absorption to the porous layer has already started at the tip portion of the coating apparatus, and there is also an effect of improving the absorption to the porous layer. Preferred results can be obtained by adding surfactants and alcohols that lower the tension.

  The second application according to the present invention can be performed only once or in two or more times. That is, after performing the second application, drying is performed until a void volume necessary for the third application is ensured, and then the third application can be performed. By repeating the same steps, the necessary number of coatings can be repeated. However, since there is a problem that the manufacturing equipment becomes large and complicated, it is preferable to keep the number of times twice or three times.

The inorganic fine particles used for the first coating of the present invention have an average primary particle size of 100 nm or less, and include various known fine particles such as silica, alumina, alumina hydrate, calcium carbonate, magnesium carbonate, Silica and alumina hydrate are preferred. The ink-receiving layer, preferably contains inorganic fine particles 8 g / m ² or more, and more preferably employed in the range of 10 to 40 g / m ^2. If it is less than this range, the ink absorbency is inferior. A hydrophilic binder is 40 mass% or less with respect to inorganic fine particles, Preferably it is 35 mass% or less, and 10-25 mass% is especially preferable.

  These inorganic fine particles may be used alone or in combination, and the ink receiving layer may be composed of a plurality of layers, and the optimum inorganic fine particles may be appropriately used for each layer.

  In the present invention, the inorganic fine particles preferably contain 50% by mass or more, preferably 60% by mass or more, more preferably 65% by mass or more of the inorganic fine particles with respect to the main ratio in the ink absorption layer, that is, the total solid content. .

  There are two types of silica, one based on a wet method and the other based on a gas phase method, and both can be preferably used in the present invention. Wet silicas include (1) silica sol obtained through metathesis with sodium silicate acid and ion exchange resin layer, or (2) colloidal silica obtained by heating and aging this silica sol, and (3) gelation of silica sol. And by changing the production conditions, silica gel in which primary particles of several to 10 microns become three-dimensional secondary particles having siloxane bonds, and (4) silica sol, sodium silicate, sodium aluminate, etc. There are synthetic silicic acid compounds mainly composed of silicic acid, such as those obtained by heating to form a silicic acid.

  Vapor phase silica is also called a dry method as opposed to a wet method, and is generally made by a flame hydrolysis method. Specifically, a method of making silicon tetrachloride by burning with hydrogen and oxygen is generally known, but silanes such as methyltrichlorosilane and trichlorosilane can be used alone or silicon tetrachloride instead of silicon tetrachloride. Can be used in a mixed state. Vapor phase silica is commercially available from Nippon Aerosil Co., Ltd. as Aerosil, and from Tokuyama Co., Ltd. as QS type.

The average particle diameter of the primary particles of the vapor phase silica particularly preferably used in the present invention is preferably 5 to 30 nm, and is preferably 15 nm or less in order to obtain higher gloss. More preferably, the primary particles have an average particle diameter of 5 to 15 nm and a specific surface area by the BET method of 200 m ² / g or more. The BET method referred to in the present invention is one of powder surface area measurement methods by vapor phase adsorption, and is a method for determining the total surface area, that is, the specific surface area of a 1 g sample from the adsorption isotherm. Usually, nitrogen gas is often used as the adsorbed gas, and the method of measuring the adsorption amount from the change in pressure or volume of the gas to be adsorbed is most often used. The most prominent expression for expressing the isotherm of multimolecular adsorption is the Brunauer, Emmett, and Teller formula, called the BET formula, which is widely used for determining the surface area. The adsorption amount is obtained based on the BET equation, and the surface area is obtained by multiplying the area occupied by one adsorbed molecule on the surface.

  As the alumina of the present invention, γ-alumina, which is a γ-type crystal of aluminum oxide, is preferable, and δ group crystal is particularly preferable. γ-alumina can make primary particles as small as about 10 nm. Usually, secondary particles of several thousand to several tens of thousands nm are finely divided by ultrasonic waves, high-pressure homogenizers, counter-impact type jet crushers, etc. Those that have been crushed can be preferably used.

The alumina hydrate preferably used in the present invention is represented by a constitutional formula of Al ₂ O ₃ .nH ₂ O (n = 1 to 3). The case where n is 1 represents an alumina hydrate having a boehmite structure, and the case where n is greater than 1 and less than 3 represents an alumina hydrate having a pseudoboehmite structure. It can be obtained by a known production method such as hydrolysis of an aluminum alkoxide such as aluminum isopropoxide, neutralization of an aluminum salt with an alkali, or hydrolysis of an aluminate.

  The average particle diameter of primary particles of the alumina hydrate used in the present invention is preferably 5 to 50 nm. In order to obtain higher gloss, the average aspect ratio (ratio of average particle diameter to average thickness) is 5 to 30 nm. ) Is preferably a tabular grain having 2 or more.

  The average particle diameter of the inorganic fine particles of the present invention can be determined as the particle diameter of a circle equal to the projected area of each of 100 particles existing within a certain area by observing the dispersed particles with an electron microscope. The average particle diameter of the primary particles of the alumina hydrate of the present invention is measured in a planar state in the case of a flat plate shape. The average thickness of the plate-like alumina hydrate is obtained by observing the cut surface of the sheet coated with alumina hydrate on the film, and the aspect ratio of the alumina hydrate is obtained by the ratio of the average particle diameter to the average thickness. It is done.

  In the present invention, as the hydrophilic binder used together with the inorganic fine particles, various known binders can be used, and a hydrophilic binder that is highly transparent and can obtain higher ink permeability is preferably used. When using a hydrophilic binder, it is important that the hydrophilic binder does not swell during the initial penetration of the ink and block the voids. From this point of view, a hydrophilic binder having a relatively low swellability around room temperature is preferable. Used. Particularly preferred hydrophilic binders are fully or partially saponified polyvinyl alcohol or cation-modified polyvinyl alcohol.

  Particularly preferred among the polyvinyl alcohols are those having a degree of saponification of 80% or more or those completely saponified. Those having an average degree of polymerization of 200 to 5000 are preferred.

  The cation-modified polyvinyl alcohol has a primary to tertiary amino group or a quaternary ammonium group in the main chain or side chain of the polyvinyl alcohol as described in, for example, JP-A-61-10383. Polyvinyl alcohol.

  In the present invention, a hardener can be used together with the hydrophilic binder as necessary. Specific examples of the hardener include aldehyde compounds such as formaldehyde and glutaraldehyde, ketone compounds such as diacetyl and chloropentanedione, bis (2-chloroethylurea) -2-hydroxy-4,6-dichloro-1 , 3,5 triazine, a compound having a reactive halogen as described in US Pat. No. 3,288,775, divinyl sulfone, a compound having a reactive olefin as described in US Pat. No. 3,635,718, N-methylol compounds as described in Japanese Patent No. 2,732,316, isocyanates as described in US Pat. No. 3,103,437, US Pat. Nos. 3,017,280 and 2,983,611 described Aziridines such as carbodiimide compounds as described in US Pat. No. 3,100,704, Epoxy compounds as described in No. 3,091,537, halogen carboxaldehydes such as mucochloric acid, dioxane derivatives such as dihydroxydioxane, chromium alum, zirconium sulfate, boric acid and inorganic cross-linking agents such as borate, etc. Can be used alone or in combination of two or more.

  Hereinafter, the present invention will be described in more detail by way of examples. However, the present invention is not limited to these examples.

As a support, low-density polyethylene (70 parts), high-density polyethylene (20 parts) and titanium oxide (20 parts) were formed on the surface of a 120 g / m ² base paper composed of LBKP (50 parts) and LBSP (50 parts). 10 parts) is applied by 25 g / m ² by melt extrusion, the center line average roughness of the resin coating layer surface is 1.0 μm by cooling roll treatment, and high density polyethylene (50 parts) and low density are formed on the back surface. A resin composition made of polyethylene (50 parts) was melt-extruded to apply 25 g / m ² and treated with a cooling roll to prepare a resin-coated paper.

On the support of the resin-coated paper, a coating solution for a porous layer having the following composition was prepared and applied by a slide bead method so that the coating amount of the vapor phase method silica was 25 g / m ^{2 in} solid content. The solid content concentration of the coating liquid was 10%.

<Porous layer coating solution composition>
Gas phase method silica 100 parts (average primary particle size 7 nm)
Dimethyl diallylammonium chloride homopolymer 4 parts Boric acid 5 parts Polyvinyl alcohol 23 parts (saponification degree 88%, average polymerization degree 3500)

  After coating, the film was passed through a cooling zone at 0 ° C. for 30 seconds, the surface temperature was lowered to 5 ° C., and then dried while blowing air at the following temperatures and dew points for 45 seconds to prepare an ink jet recording medium.

Dryer 1 Temperature 30 ° C Dew point 0 ° C
Dryer 2 Temperature 50 ° C Dew point 0 ° C
Dryer 3 Temperature 50 ℃ Dew point 0 ℃
Dryer 4 Temperature 50 ℃ Dew point 0 ℃
Dryer 5 Temperature 50 ° C Dew point 0 ° C
Dryer 6 Temperature 50 ℃ Dew point 0 ℃
The transition from the constant rate dry state to the reduced rate dry state was performed in the middle of the dryer 4, and the drying end point was in the middle of the dryer 5. In other words, it is a constant rate drying region at the outlet of the dryer 3, the coating film is filled with moisture and there are no gaps, there is a gap at the outlet of the dryer 4, and the gap is completed at the outlet of the dryer 5. State.

Using a mercury porosimeter (measuring instrument name: Autopore II 9220 manufacturer, micromeritics instrument corporation), the sample collected from the outlet of the dryer 5 is used to determine the cumulative pore volume of the porous layer with a pore radius of 3 nm to 400 nm. The permeation void volume was determined to be 30 ml / m ² .

A sample was taken at the outlet of the dryer 4 and the water content was measured. As a result, it was found that 12 g / m ² of water was contained and the void volume was 18 ml / m ² . By the way, at the outlet of the dryer 3, it seems that a dry coating film is formed, but the lower part of the coating film is the coating liquid itself, and the yuba-like film is peeled off when contacting the surface, and there is no void. It was in a state.

  On the porous layer, a second coating layer coating solution-1 having the following composition was coated as a second coating. Inkjet recording media 1 to 9 were obtained by changing the coating position and coating device. Basic polyaluminum hydroxide is an additive that improves light resistance. The viscosity of the second coating layer coating solution-1 was 1.3 mPa · s (liquid temperature 25 ° C.) as a result of measurement using a BL type viscometer.

<Second coating layer coating solution-1>
Basic polyaluminum hydroxide (trade name: Purachem WT, manufactured by Riken Green Co., Ltd.) 2g
10g of water

<Inkjet recording medium 1>
The application was carried out at the outlet of the dryer 3 using a slot coater that applied by pressing a uniform slit-shaped opening in the width direction of the application. The coating solution was pre-weighed using a pump and applied at 12 g / m ² . The coating liquid was not absorbed by the lower porous layer, and a wet coating film was formed on the surface. The wet coating film was dried in the dryer, but the wet coating film was disturbed by the dry air in the dryer, resulting in coating unevenness.

<Inkjet recording medium 2>
Application was performed at the outlet of the dryer 4 using a slot coater. The coating solution was pre-weighed using a pump and applied at 12 g / m ² . The coating solution was rapidly absorbed in the lower porous layer in 0.1 seconds or less.

<Inkjet recording medium 3>
Application was performed at the outlet of the dryer 5 using a slot coater. The coating solution was pre-weighed using a pump and applied at 12 g / m ² . The coating solution was rapidly absorbed in the lower porous layer in 0.1 seconds or less.

<Inkjet recording medium 4>
Application was performed at the outlet of the dryer 5 using an extrusion die coater applied after the coating liquid pushed out from the uniform slit in the width direction of the application descended the slope. The coating solution was pre-weighed using a pump and applied at 12 g / m ² . The coating solution was rapidly absorbed in the lower porous layer in 0.1 seconds or less.

<Inkjet recording medium 5>
Application was performed at the outlet of the dryer 3 using a spray coater on which droplets were sprayed. The coating solution was pre-weighed using a pump and applied at 12.5 g / m ² . Since the sprayed coating liquid spreads around the periphery and a loss occurs, the compensation was increased by 0.5 g / m ² . The sprayed droplets were not absorbed by the lower porous layer, and the droplets provided by the spray coater were bonded to each other to form a wet coating film. The wet coating film was dried in the dryer, but the wet coating film was disturbed by the dry air in the dryer, resulting in coating unevenness.

<Inkjet recording medium 6>
Application was performed at the outlet of the dryer 4 using a spray coater. The coating solution was pre-weighed using a pump and applied at 12.5 g / m ² . Since the sprayed coating liquid spreads around the periphery and a loss occurs, the compensation was increased by 0.5 g / m ² . The sprayed droplets were absorbed rapidly and no wet film was formed on the surface.

<Inkjet recording medium 7>
Application was performed at the outlet of the dryer 5 using a spray coater. The coating solution was pre-weighed using a pump and applied at 12.5 g / m ² . Since the sprayed coating liquid spreads around the periphery and a loss occurs, the compensation was increased by 0.5 g / m ² . The sprayed droplets were absorbed rapidly and no wet film was formed on the surface.

<Inkjet recording medium 8>
Using an air knife coater, the air knife air volume was adjusted so that the coating amount was 12 g / m ^2, and coating was performed at the outlet of the dryer 3. A wet coating was formed after weighing with an air knife. The wet coating film was dried in the dryer, but the wet coating film was disturbed by the dry air in the dryer, resulting in coating unevenness.

<Inkjet recording medium 9>
Application was performed at the outlet of the dryer 5 using an air knife coater. Although an attempt was made to adjust the air knife air volume so that the coating amount was 12 g / m ² , the coating amount could not be 27 g / m ² or less, and the target coating amount could not be obtained. Also, coating unevenness was observed.

On the porous layer, a second coating layer coating solution-2 having the following composition was coated at a coating amount of 22 g / m ^{2 as a second} coating. The coating position and the coating apparatus were changed to obtain inkjet recording media 10-14. The viscosity of the second coating layer coating liquid-2 was 1.2 mPa · s (liquid temperature 25 ° C.) as a result of measurement using a BL type viscometer.

<Second coating layer coating solution-2>
Basic polyaluminum hydroxide (trade name: Purachem WT, manufactured by Riken Green Co., Ltd.) 2g
20g of water

<Inkjet recording medium 10>
Coating was performed at the outlet of the dryer 3 using a slot coater. The coating liquid was not absorbed by the lower porous layer, and a wet coating film was formed on the surface. The wet coating film was dried in the dryer, but the wet coating film was disturbed by the dry air in the dryer, resulting in coating unevenness.

<Inkjet recording medium 11>
Application was performed at the outlet of the dryer 4 using a slot coater. Most of the coating liquid was absorbed in the lower porous layer, but a part of the coating liquid remained on the surface as a wet coating film. The wet coating film was dried in the dryer, but the wet coating film was disturbed by the dry air in the dryer, resulting in coating unevenness.

<Inkjet recording medium 12>
Application was performed at the outlet of the dryer 5 using a slot coater. The coating solution was rapidly absorbed in the lower porous layer in about 0.5 seconds.

<Inkjet recording medium 13>
Application was performed at the outlet of the dryer 4 using a spray coater. The coating solution was pre-weighed using a pump and applied at 23 g / m ² . Since the sprayed coating liquid spreads around the periphery, the loss was added in advance, so that 1.0 g / m ^{2 was} increased as compensation. The sprayed droplets were mostly absorbed by the underlying porous layer, but a mottled and uneven wet coating film formed from the overflowing coating liquid. The wet coating film was dried in the dryer, but the wet coating film was disturbed by the dry air in the dryer, resulting in coating unevenness.

<Inkjet recording medium 14>
Application was performed at the outlet of the dryer 5 using a spray coater. The coating solution was pre-weighed using a pump and applied at 23 g / m ² . Since the sprayed coating liquid spreads around the periphery, the loss was added in advance, so that 1.0 g / m ^{2 was} increased as compensation. The sprayed droplets were absorbed into the underlying porous layer.

On the porous layer, a second coating layer coating solution-3 having the following composition was coated at a coating amount of 32 g / m ^{2 as a second} coating. Inkjet recording media 15 to 17 were obtained by changing the coating position and coating device. The viscosity of the second coating layer coating solution-3 was 1.1 mPa · s (liquid temperature 25 ° C.) as a result of measurement using a BL type viscometer.

<Second coating layer coating solution-3>
Basic polyaluminum hydroxide (trade name: Purachem WT, manufactured by Riken Green Co., Ltd.) 2g
30 g of water

<Inkjet recording medium 15>
Coating was performed at the outlet of the dryer 3 using a slot coater. The coating liquid was not absorbed by the lower porous layer, and a wet coating film was formed on the surface. The wet coating film was dried in the dryer, but the wet coating film was disturbed by the dry air in the dryer, resulting in coating unevenness.

<Inkjet recording medium 16>
Application was performed at the outlet of the dryer 4 using a slot coater. The coating liquid was absorbed to some extent by the lower porous layer, but most remained as a wet coating on the surface. The wet coating film was dried in the dryer, but the wet coating film was disturbed by the dry air in the dryer, resulting in coating unevenness.

<Inkjet recording medium 17>
Application was performed at the outlet of the dryer 5 using a slot coater. Most of the coating liquid was absorbed in the lower porous layer, but a part of the coating liquid remained on the surface as a wet coating film. The wet coating film was dried in the dryer, but the wet coating film was disturbed by the dry air in the dryer, resulting in coating unevenness.

On the porous layer, a second coating layer coating solution-4 having the following composition was coated at a coating amount of 27 g / m ^{2 as a second} coating. The coating apparatus was changed, and inkjet recording media 18 and 19 were obtained. The viscosity of the second coating layer coating solution-1 was 1.2 mPa · s (liquid temperature 25 ° C.) as a result of measurement using a BL type viscometer.

<Second coating layer coating solution-4>
Basic polyaluminum hydroxide (trade name: Purachem WT, manufactured by Riken Green Co., Ltd.) 2g
25 g of water

<Inkjet recording medium 18>
Application was performed at the outlet of the dryer 5 using a slot coater. The coating solution was rapidly absorbed in the lower porous layer in 0.8 seconds.

<Inkjet recording medium 19>
Using an air knife coater, the air knife air volume was adjusted so that the coating amount was 27 g / m ^2, and coating was performed at the outlet of the dryer 5.

The following evaluations were performed on the 19 types of ink jet recording media described above. Note that the ink jet recording, using P M -970C color printer manufactured by Seiko Epson Corporation, printing was performed under normal temperature and normal humidity. The results are shown in Table 1.

  <Ratio of coating amount with respect to void volume> The percentage of the coating amount with respect to the void volume at the time when the second coating is performed is shown. In the notation in the table, “∞” indicates that% cannot be displayed because there is no void volume at the application position. In the inkjet recording medium 9, the coating amount could not be controlled with an air knife, and 90% adhered even though the target coating amount was 40% of the void volume.

<Time required for absorption> In order to measure the time required for the second coating layer coating solution to be absorbed by the porous layer, the food dye Blue No. 2 is used for the second coating for measurement. An amount of 0.05 wt% of the liquid amount was added and the same coating was performed. The PPC paper was sequentially brought into contact with the porous layer from the position where the second coating layer coating solution was in contact with the porous layer by a coating device, and the presence or absence of dye transfer was examined. If there is a transfer, it indicates that the absorption has not been completed, and if there is no transfer, it indicates that the absorption has been completed. Thus, the distance from the position where the second coating layer coating solution was in contact with the porous layer (coating position) to the completion of absorption was measured, and the time required for absorption was calculated from the coating speed. At notation "-" in the table and, since the coating amount exceeds than the void volume does not absorb is completed indicates that the wet coating or wetting portion remains on the porous layer, " “Unmeasurable” indicates that measurement cannot be performed because the coating apparatus is a spray coater and the coating position is not clear, or measurement cannot be performed because the air knife coater is scraped off at the air knife position.

<White paper application unevenness> The white paper was observed obliquely, and it was evaluated whether application unevenness due to the second application was observed.
○: Application unevenness is not observed at all.
Δ: Some coating unevenness is scattered.
X: Coating unevenness is observed.

  <Light resistance> Magenta single-color solid printing was performed at the highest density, and the optical density of each color was measured with a reflection densitometer (SPECTROLINO, manufactured by GRETAG). The sample whose density was measured was left under a fluorescent lamp (illuminance 30,000 lx) for 10 days, the optical density was measured again, and the residual ratio was expressed as a percentage. The larger the remaining rate, the better the fading due to light, that is, the better the light resistance. For example, when it is 100%, no fading occurs.

<Light resistance unevenness> The density unevenness of the magenta and cyan print areas of the sample left for 10 days under a fluorescent lamp (illuminance of 30,000 lx) was visually determined. This is due to the distribution of polyaluminum hydroxide that provides light resistance, and if the coating is uniform, no density unevenness is observed at all, but if the coating is uneven due to various factors, Since a difference in light resistance occurs every time, it is observed as density unevenness.
○: No density unevenness is observed.
Δ: Some density unevenness is observed.
X: Density unevenness is large.

  As is apparent from the results in Table 1, the inkjet recording medium according to the present invention has no blank paper application unevenness due to the second application, and since the second application is uniformly performed, no light resistance unevenness is observed. Light resistance is also good. If absorption into the porous layer is not performed completely regardless of the coating method, the coating liquid remaining on the surface of the porous layer is affected by the dry air in the dryer, resulting in coating unevenness.

  A spray coater that does not have slits for evenly flowing in the width direction of the coating will appear to be applied uniformly at first glance, but since the droplets are absorbed, it is even on the coating surface due to the leveling of the droplets. Therefore, there is uneven distribution of the additive provided by the second application, which leads to uneven light resistance.

  In addition, the application by post-weighing with an air knife is not only possible to control the application amount to less than 90% of the absorption capacity of the porous layer, but also when it is controlled to 90% of the absorption capacity of the porous layer. However, a large amount of coating unevenness is observed on the surface, which is not suitable.

  As in Example 1, as a second application on the porous layer, the second application layer coating liquids-5 to 7 having the following composition with different coating liquid viscosities were applied at the outlet of the dryer 5, and Sample 1 ~ 3 was obtained.

<Second coating layer coating solution-5>
Carboxymethyl cellulose (trade name: Serogen WS-A, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) 0.1 g
Blue No. 2 0.01g
19.89g of water

  The viscosity of the second coating layer coating solution-5 was 17.5 mPa · s with a BL type viscometer.

<Second coating layer coating solution-6>
Carboxymethylcellulose (trade name: Cellogen WS-A, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) 0.04 g
Blue No. 2 0.01g
19.95g of water

  The viscosity of the second coating layer coating solution-6 was 7.2 mPa · s with a BL type viscometer.

<Second coating layer coating solution-7>
Carboxymethylcellulose (trade name: Cellogen WS-A, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) 0.01 g
Blue No. 2 0.01g
19.98 g of water

  The viscosity of the second coating layer coating solution-5 was 3.5 mPa · s with a BL type viscometer.

  The following evaluation was performed on the three types of samples described above. The results are shown in Table 2. The contents of each item are the same as those in the first embodiment.

  As is clear from the results in Table 2, the sample according to the present invention has no white paper coating unevenness due to the second coating. In the sample having a time required for absorption of the coating liquid of 2 seconds, foam marks were observed as uneven coating, which was not preferable.

Claims (1)

In the method for manufacturing an ink jet recording medium, wherein the second coating is performed on the first coating for forming at least one porous layer composed of a pigment and a binder, and the second coating is the first coating. by after the porous layer is formed, coated in the state of Chi lifting slit for uniformly flow out in the width direction of the coating, the coating liquid to be subjected to a second coating which has flowed from the slit to form a liquid film the liquid film The amount of liquid pre-weighed to 40% or more of the void volume so that the coating liquid used for the second coating does not exceed 90% of the void volume of the porous layer. A method for producing an ink jet recording medium, wherein substantially the entire amount is absorbed by the porous layer within 1 second after contact with the porous layer.