JP2000158814A - Method for forming coating film, coating film, its heat treatment method, heat-sensitive recording medium and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for forming a coating film formed of a plurality of laminates of resin-containing film applied on a base, from which a residual solvent can be removed by a quick and simple process, and provide a heat- sensitive recording medium, by removing quickly the amount of the residual solvent in the heat-sensitive recording medium to the level of allowable amount so as to provide the stable coloring density. SOLUTION: In a method for forming a coating film comprising a laminate of a plurality of films containing a resin, one of the two coating fluids used for forming two optional adjacent films A and B out of a plurality films contains at least a solvent X and the resin A (quoted as a coating fluid A), while the other is a coating fluid (quoted as a coating fluid B) having molar molecular volume smaller than that of the solvent X, and containing a solvent Y melting the resin A, and after the film A is formed by using the coating fluid A, the film B is formed by using the coating fluid B, and also a manufacturing method of the heat-sensitive recording medium using the above method is provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a coating film, a coating film and a heat treatment method thereof, and a heat-sensitive recording medium and a method for manufacturing the same. A method for forming a coating film by applying and drying a coating solution containing a solvent and a coating film, a heat treatment method using the coating film and a heat treatment method thereof, and a color-forming reaction between an electron-donating color-forming compound and an electron-accepting compound. It relates to the manufacturing method.

[0002]

2. Description of the Related Art Various processes are known in various product fields in which various materials are blended, a polymer resin is used as a binder, a coating is formed using an organic solvent, and a base material is coated and dried to form a coating film. For example, a recording medium such as a magnetic recording medium and a heat-sensitive recording medium, an electrophotographic photosensitive member, and the like are examples. Such coating films having various functions often have a multilayer structure including a plurality of layers having different functions. These individual layers are formed by repeatedly applying and drying a coating liquid on the layer once formed. In each of these film formations, the composition of the organic solvent used in the coating solution is selected from various reasons such as the solubility of the material, the dispersibility of the material, the fluidity of the coating solution, and the evaporation characteristics during the drying film formation process. Is done.

For example, in order to apply a particle-dispersed coating liquid, it is necessary to select a solvent that balances the solubility of a polymer resin as a binder and the dispersibility of dispersed particles. Further, in order to obtain a coating film having excellent surface properties without coating film defects, it is important to control the evaporation characteristics in the process of dry film formation. In particular, in the process of drying a coating liquid film having a relatively large coating amount, rapid drying causes generation of Benard cells and reticulation. In such a case, control by conditions such as temperature and wind speed in the drying process is possible, but control is generally also performed by the organic solvent composition of the coating liquid. The control of the organic solvent composition of the coating liquid is adjusted by using a substance that evaporates slowly from the coating liquid film, that is, a solvent having a high boiling point. Accordingly, the solvent composition of the coating liquid is selected for various reasons, and in some cases, the coating liquid may contain an organic solvent that is difficult to evaporate. This tendency is particularly strong when the coating amount is relatively large.

[0004] Such a solvent which is difficult to evaporate has many substances having a low diffusion rate in the resin at the same time, and it is sometimes very difficult to remove the solvent. Ease of removing the residual solvent from the coating film has a strong correlation with the residual solvent concentration. When the residual solvent concentration is high, the solvent removal rate shows a relatively large value, but sharply decreases as the residual solvent concentration decreases. The concentration at which the solvent removal rate sharply decreases is referred to as the critical solvent content, and the subsequent solvent removal phenomenon is considered to be internal diffusion-controlled. The only method for promoting the internal diffusion-controlled solvent removal process is the solvent removal operation at a high temperature. Therefore, in order to process the internal diffusion controlled process at a relatively low temperature, the solvent removal rate is very low, and a long time treatment is required for the removal.

[0005] The residual solvent concentration in the coating film must be controlled to a small level for odor and safety reasons, but it may be extremely difficult industrially to completely remove it. Thus, some residual solvent is often tolerated. In some cases, the residual solvent concentration must be controlled within a certain range in relation to the function of the product. As a typical example, a thermosensitive recording medium will be described. Since the heat-sensitive recording medium develops color once it is heated to a certain temperature or higher, it is impossible to process the coating film at a high temperature in the manufacturing process. Therefore, the drying process after the application of the coating liquid in the manufacturing process and the solvent removing process performed simultaneously with or subsequent to the coating process must be performed at a relatively low temperature. Such restrictions make it extremely difficult to efficiently remove the residual solvent from the heat-sensitive recording medium, require a long drying time, and deteriorate the productivity.

Japanese Unexamined Patent Publication No. 7-223364 specifies the solvent physical properties and the residual solvent concentration of the residual solvent in the heat-sensitive recording medium. Also, Japanese Patent Application Laid-Open No. 9-2489
In Japanese Patent No. 64, the residual solvent in the heat-sensitive recording medium is specified to be controlled to a certain amount or less, and further, the physical properties of the material relating to color development contained so as to be processed at as high a temperature as possible are specified. A reduction in the time required for residual solvent removal has been achieved. However, even when such a material is selected, the coating film thickness tends to increase due to a demand for improving the quality of the thermosensitive recording medium.
For this reason, removal of the residual solvent has become more difficult, and further improvement has been required.

[0007] The drying step after applying the coating liquid to the substrate,
It is usually carried out by continuously transporting in a tunnel type drying furnace.
Various studies have been made on the types, shapes and operating conditions of these drying ovens. For example, Japanese Patent Publication No. 51-2136,
JP-A-165658 and JP-A-3-123664 disclose the shape of a drying oven.
627, JP-B-6-94985, JP-A-2-380
No. 48, JP-A-6-26764 and the like disclose a hot air nozzle in a drying furnace.
No. 73 and Japanese Unexamined Patent Publication No. Hei 8-240387 disclose operating conditions of a drying furnace. These inventions are effective in transporting the coated substrate, suppressing the occurrence of film defects, improving thermal efficiency, and drying the coating liquid film at the initial stage. However, there is no effective method for removing the residual solvent in the internal diffusion control process after the drying of the coating liquid film has progressed to some extent. In particular, when the temperature during drying cannot be set high for some reason, the time required for removing the residual solvent has become extremely long. In such a case, in order to secure a sufficient drying time in a tunnel-type drying furnace, the processing speed becomes extremely low, and productivity is extremely impaired.

In order to improve such extremely poor productivity in a tunnel type drying furnace, it is also effective to perform a heat treatment at a subsequent stage. If the continuous base material is processed into a wound roll shape and heat-treated, the space and heat efficiency can be improved. However, in this method, since there is no gap between the wound substrates, the effect of removing the residual solvent is small. Therefore, as one of the effective means for such heat treatment, there is a method of performing a knurling treatment on the edge of the base material. The purpose of such a knurling treatment is not necessarily to remove the residual solvent from the coating film, but since there is a space between the base materials wound around the roll, blocking is prevented and there is a contribution to the removal of the residual solvent. The invention relating to such a knurling process is disclosed in the specification of US Pat. No. 1,615,744, and the edge processing method is improved in Japanese Patent Publication No. 47-161744, Japanese Patent Publication No. 58-54007, and Japanese Patent Publication No. 5-19899. It has been disclosed. However, even in such a heat treatment method or when heat treatment is performed on a knurling wound film, it is very difficult at present to remove a solvent which is difficult to diffuse among residual solvents in the coating film.

As an effective method for removing residual solvent from a coating film, a method proposed by Vrentas et al. Based on theoretical analysis [J. Appl. Polym. Sci. , 30,449
9 (1985)]. This method will be briefly described. Have proposed a method of introducing a second solvent in order to promote the removal of the solvent from the coating film. This method is intended for removing a small amount of a high-boiling solvent remaining in a polymer resin at a relatively low temperature. Factors that make it difficult to remove the high-boiling solvent remaining in the polymer resin are mainly the following two points. As the amount of solvent remaining in the polymer resin decreases, the diffusion coefficient of the solvent in the polymer resin sharply decreases. The diffusion coefficient of the solvent in the polymer resin decreases as the size (molar molecular volume) of the solvent molecule itself increases (the high-boiling point solvent has a small diffusion coefficient because the specific molecule is large). Vren
The method of tas et al. performs the following treatment on a polymer resin film in which a very small amount of a high boiling point solvent (first solvent) remains. The substrate is exposed to and heated in a second solvent vapor having a smaller molar molecular volume than the high boiling point solvent. Remove from the second solvent vapor atmosphere and heat.

In the operation, a second solvent is introduced into the system. Thus, the diffusion coefficient of the solvent (both the first solvent and the second solvent) in the resin film is increased, and the first solvent that is difficult to remove is removed. The operation of removing the second solvent remaining in the resin film. According to Vrentas et al., The removal time of the solvent is shorter than the time required for simply removing the first solvent remaining in the polymer resin by simply heating the first solvent. Things. Therefore, the method of Vrentas is an operation of heating substantially in a solvent vapor.

In order to apply this method to an actual process, it is necessary to expose the coating film to a solvent vapor having a relatively high concentration. If it is within the range, an inert environment for preventing explosion such as nitrogen purge is required. The apparatus for achieving the inert environment is also applied to a tunnel type drying furnace for treating a continuous substrate, but the apparatus is complicated and expensive, and the cost for operation is high at present. Also,
The introduction of the second substance from the solvent vapor, which is based on the method of Vrentas, is achieved by using the difference between the solvent concentration on the surface of the coating film and the saturation concentration of the solvent on the surface of the coating film in a solvent vapor environment as a driving force. . Usually, it is difficult to increase the driving force, and the time for introducing the second substance into the coating film is relatively long, which is disadvantageous for substantially shortening the time for removing the solvent. Was.

[0012] Removal of organic solvents from resin materials is found in processes in various product areas. Obtained in the synthesis process, etc.
A method of removing a solvent by treating a resin dissolved in an organic solvent or a resin containing impurities such as a solvent with a non-solvent of the resin has been used for a long time. Japanese Patent Publication No. 8-16165 and Japanese Patent Application Laid-Open No. 6-9772 disclose a method of removing residual solvent by subjecting polycarbonate particles to a treatment using a non-solvent to remove the residual solvent. Also, in other fields, a method using a non-solvent for a resin is applied, and JP-A-2-22336 describes that
In a method for producing a polyamide-imide resin prepreg,
A method for promoting removal of residual solvent by washing the resin with water / methanol as a non-solvent is disclosed. However, when this non-solvent treatment is applied to the removal of the residual solvent from the coating film containing the resin, the non-solvent has a low penetrating power into the coating film. Time was needed to improve productivity.

[0013]

SUMMARY OF THE INVENTION Accordingly, a first object of the present invention is to provide a method for removing a residual solvent from a resin-containing film applied to a substrate, particularly when the treatment at a high temperature cannot be performed. Another object of the present invention is to provide a method for removing a residual solvent by a quick and simple method. Further, a second object of the present invention is to provide a thermosensitive recording medium capable of quickly removing an amount of a residual solvent in the thermosensitive recording medium to an allowable amount and obtaining a stable color density.

[0014]

Means for Solving the Problems As a result of intensive studies, the present inventors have made the first layer a coating film containing a resin and a solvent which is difficult to diffuse in the film, dissolve the resin, and dissolve the residual resin. The present inventors have found that the object of the present invention can be achieved by adopting a method of introducing a solvent having a smaller molar molecular volume than a solvent and easily diffusing in a film with a coating liquid for layer coating on the first layer. Reached the present invention.

That is, according to the present invention, first, in a method for forming a coating film formed by laminating a plurality of films containing a resin, any two adjacent films A and B of the plurality of films are formed. One of the two coating liquids used for the coating contains at least the solvent X and the resin A (referred to as coating liquid A), and the other is the solvent X
A coating liquid having a smaller molar molecular volume and containing a solvent Y that dissolves the resin A (referred to as coating liquid B). After the film A is formed using the coating liquid A, the film B is formed using the coating liquid B. A method for forming a coating film is provided.
Secondly, in the method for forming the first coating film, the content of the solvent Y in all volatile components in the coating liquid B is 95% by weight or more. Is provided. Third, in the method of forming the first coating film, the solvent X has a molar molecular volume of 100 cc / mol or more and the content of all volatile components in the coating liquid A is 5% by weight.
That is, the solvent Y has a molar molecular volume of 100 cc / mol.
The method for forming a coating film is characterized in that the content is less than 95% by weight in the total volatile components in the coating liquid B. Fourth, in the method of forming the first coating film, the thickness of the film A formed using the coating solution A is 5
μm or more, and a coating amount of the solvent Y contained in the coating liquid B is 30 g / m ² or less. Fifth, there is provided a method for forming a coating film, wherein the nonvolatile component in the coating solution B is 1% by weight or less in the method for forming the first coating film. Sixth, in the method for forming the first coating film, the resin component contained in the coating liquid A may be used in the form of 5
0% by weight or more is selected from those having a structure having a vinyl group, and a single or plural solvents selected from ethyl acetate, tetrahydrofuran and methyl ethyl ketone are used as the solvent Y in the coating liquid B. There is provided a method for forming a coating film, wherein the content of these solvents in a volatile component is 95% by weight or more. Seventh, in the method for forming the first coating film, the amount of the residual solvent in the coating film A immediately before the coating liquid B is applied is 1% by weight.
A method for forming a coating film characterized by the above is provided. Eighthly, there is provided a method for forming a coating film, wherein a die coating method is used as a coating method for the coating liquid B in the method for forming the first coating film. Ninth, in a film formed by sequentially coating a plurality of layers containing at least a resin on a base material, the composition of the solvent remaining in the plurality of films indicates that the solvent group having a molar molecular volume of 100 cc / mol or more remains. A coating film formed on a substrate is provided, wherein the latter is larger than the former in the ratio of the amount to the residual amount of the solvent group having a molar molecular volume of less than 100 cc / mol. Tenthly, there is provided a method for producing a formed coating film, wherein the method for forming the first coating film is used in producing the ninth film. Eleventh, a heat treatment method for a coating film, characterized in that the coating film formed on the ninth substrate is a long continuous body, which is processed into a rolled shape and heat-treated. Is provided.
Twelfth, in the eleventh heat treatment method for a coating film,
A heat treatment method for a coating film, characterized in that an edge of a substrate is subjected to a knurling treatment. Thirteenth, in a recording medium in which a plurality of layers containing at least a resin are provided on a base material, the composition of a solvent contained in the plurality of films has a molar molecular volume
There is provided a recording medium characterized in that the ratio of the content of the solvent group of 00 cc / mol or more to the content of the solvent group having a molar molecular volume of less than 100 cc / mol is larger in the latter than in the former. Fourteenthly, there is provided a method for manufacturing a recording medium, wherein the method for forming the first coating film is used in manufacturing the thirteenth recording medium.
Fifteenth, on a plastic film, a thermosensitive coloring layer containing a leuco dye, a developer for coloring the leuco dye by heating and a binder resin as a binder as a main component, and a protective layer further provided thereon. In the thermosensitive recording medium, the ratio of the residual amount of the solvent group having a molar molecular volume of 100 cc / mol or more to the residual amount of the solvent group having a molar molecular volume of less than 100 cc / mol in the composition of the solvent remaining in the thermosensitive coloring layer and the protective layer film. In the above, there is provided a sensible recording medium characterized in that the latter is larger than the former. Sixteenthly, there is provided a method for manufacturing a thermosensitive recording medium, characterized by using the method for forming the first coating film in manufacturing the fifteenth thermosensitive recording medium. Seventeenth, in producing the above fifteenth thermosensitive recording medium, a single or plural solvents selected from ethyl acetate, tetrahydrofuran and methyl ethyl ketone are used as a solvent for the protective layer coating liquid, A method for producing a thermosensitive recording medium is provided, wherein the content of these solvents in the total volatile components of the liquid is 95% by weight or more.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. The method for forming a coating film according to the present invention is a method for forming a coating film formed by laminating a plurality of films containing a resin, wherein any two adjacent films A among the plurality of films are formed.
One of the two coating liquids used to form B contains at least solvent X and resin A (referred to as coating liquid A), and the other contains a solvent Y having a smaller molar molecular volume than solvent X and dissolving resin A. (Referred to as coating liquid B) and coating liquid A
The method is characterized in that after forming the film A by using the coating liquid B, the film B is formed by using the coating liquid B. In particular, in the method, the content of the solvent Y in all the volatile components in the coating liquid B is 95% by weight.
It is desirable that this is the case. That is, the basic configuration of the present invention is as follows. The content of the solvent Y in the coating liquid B ... volatile component is 95% by weight.
Preferably, the solvent Y dissolves the resin A well and has a smaller molecular volume than the solvent X. Film A: coating liquid A containing at least resin A and solvent X
A film coated and formed with.

In the present invention, the value of the molar molecular volume to be contained in the coating liquid for laminating coating (that is, coating liquid B) is 10
Preferably, it is less than 0 cc / g. Examples of the solvent species having a molar molecular volume value of less than 100 cc / g include, but are not limited to, methyl alcohol,
Ethyl alcohol, isopropyl alcohol, acetone, tetrahydrofuran, ethyl acetate, methyl ethyl ketone, acetonitrile, dichloromethane, dichloroethane, ethyl chloride, chloroform, methylamine,
Dichloroethylene, 1,4-dioxane, carbon disulfide,
Examples include methylformide, benzene, and carbon disulfide. However, by using a solvent selected from these, the intended effect is not necessarily obtained, and the correlation with the resin contained in the first layer is important.

These laminated solvents may be used by mixing solvent types selected from them. However, it is particularly preferable that the lamination solvent satisfying the above conditions is 95% by weight or more, more preferably 98% by weight or more. In addition, as a substance other than the solvent contained in the coating liquid to be laminated, a resin, an organic filler,
An inorganic filler, a UV resin, an initiator thereof, and the like may be contained, but only a solvent may be used.

As an example of the method of forming a coating film of the present invention as an effective layer configuration, a main function layer that performs a main function is set as a first layer, and a first function layer for protecting the main function layer is formed thereon. There is a configuration in which a layer is provided. For such a purpose, generally, the main functional layer has a large film thickness and a thin protective film. Examples of the recording medium having such a configuration include a display medium such as a thermosensitive recording material and a reversible thermosensitive recording material, and a magnetic recording material.

Applying the method for forming a coating film of the present invention;
Although the resin contained in the first layer is not limited to this, for example, Po1y (vinyl ace)
state), Po1y (vinyl butyra)
l), Po1y (vinyl chloride), P
olyacetal, Polyacrylamide,
Poly (acrylic acid), Po1ybu
tadiene, Po1y (ethyl acryla
te), Poly (ethylene oxide),
Poly (methacrylic acid), Po
ly (methylacrylate), Poly (m
Ethyl methacrylate) and modified products thereof, and copolymers containing them.

In the method of forming a coating film of the present invention, as described above, the mutual relationship between the resin contained in the first layer and the solvent contained in the coating liquid applied on this layer is important. There is an appropriately selected combination of the resin of the layer and the solvent to be laminated. Although not limited thereto, for example, Poly (vinyl chloride) is used as the resin of the first layer.
And modified products thereof, copolymers, and solvents for lamination such as methyl ethyl ketone, ethyl acetate, and tetrahydrofuran. Poly (viny) as the resin of the first layer
l butyral) and modified products thereof, copolymers, as a solvent for lamination, methyl ethyl ketone, ethyl acetate, tetrahydrofuran, acetone and the like. Poly (vinyl acetate) as the first layer resin
And modified products thereof, copolymers, acetone, tetrahydrofuran, methyl ethyl ketone, methanol, ethanol and the like as a solvent for lamination. Poly (acrylic acid) and modified denatured resin as the first layer resin, copolymer, methanol, ethanol, etc. as the solvent to be laminated. Polyb as the first layer resin
Utadiene and its modified products, copolymers, methyl ethyl ketone, tetrahydrofuran, etc. as a solvent for lamination. Poly (eth
(yelene oxide) and its metamorphosis,
Copolymers, such as tetrahydrofuran as a solvent for lamination. Poly (methyl me) as the resin of the first layer
acrylate, a modified product thereof, a copolymer, methyl ethyl ketone as a solvent for lamination,
Tetrahydrofuran and the like. Such a combination is appropriate.

In the method of forming a coating film of the present invention, the application of the selected layered coating liquid to the first layer may be repeated a plurality of times. If the solvent of the layered coating solution is appropriately selected, by repeating a plurality of times, it is possible to remove more of the hardly diffusible solvent contained in the first layer, that is, the hardly removable solvent. However, since the initial drying operation is required for the number of times of application, the process required for removing the remaining hardly diffusible solvent and the process required for the laminating operation must be compared and set appropriately.

In the method of forming a coating film according to the present invention, a solvent that dissolves the resin contained in the first layer is coated on the first layer formed in advance by coating. May impair the existing first layer internal structure and surface properties. In addition, when the coating liquid to be laminated contains non-volatile components and they are formed into a film and perform some function, coating with only the solvent selected under the conditions of the present invention makes it possible to form a coating film. Easy to generate defects. For example, when a coating liquid containing a large amount of solvent is applied on the first layer having a relatively small thickness, the first layer completely dissolves. This is the same phenomenon as applying. In this case, since the lamination solvent is composed of a solvent having a relatively high evaporation rate, coating defects such as Benard cells and reticulation are caused. Furthermore,
When the first layer contains a substance other than resin that has a relatively low molecular weight as a substance that is well dissolved in the lamination solvent, a bleeding phenomenon or the like that precipitates on the surface after lamination may occur. In addition, phenomena such as brushing may occur.

In order to avoid these problems, the application conditions of the coating liquid to be laminated must be set appropriately. In other words, it is necessary to avoid the conditions of the lamination coating that completely dissolves the film formed in advance by coating, but under the conditions of the lamination coating that hardly dissolves, the intended effect cannot be obtained. . These problems can be avoided as follows. That is, 1
The film of the layer has a thickness of 5 μm or more, and the coating amount of the solvent in the coating liquid for laminating coating (hereinafter may be abbreviated as the solvent WET coating amount) is 30 g / m ² or less. Thus, this problem can be solved. Preferably, the first layer is 1
0 μm or more, and the solvent WET coating amount is 30 g /
m ² or less is desired. The above problem can be solved by such conditions.

The method of forming a coating film according to the present invention can substantially reduce the time for removing the residual solvent from the coating film, but this effect is achieved by coating and drying at least the first layer and laminating and coating. It must be evaluated both in the drying process. The relationship between the amount of residual solvent in the first layer and the amount of residual solvent after coating and drying on this layer is relatively small. That is, 1
Regardless of whether the residual solvent amount of the layer is large or small, there is no significant change in the residual solvent amount after laminating. Therefore, in the step of coating and drying the first layer, it is not necessary to remove the residual solvent amount more than necessary, and it is sufficient that the residual solvent amount can be removed to an extent that does not cause a problem under other conditions such as blocking. By doing so, the time required for the first-layer coating and drying step can be reduced, and the total time for removing the residual solvent including the subsequent steps of laminating and drying can be reduced. Therefore, it is desired that the amount of the residual solvent in the first layer is 1% or more. More preferably, it is desired to be 2% or more.

A method for measuring the residual solvent will be described. From the film formed by coating, a sample having a size of about 2.5 mm × 15 mm is cut out. The coating film around the cut sample is peeled off from the substrate, and the thickness of both the substrate and the coating film is measured with a contact-type film thickness meter (manufactured by Anritsu Corporation). From this measurement, the thickness of the substrate and the thickness of the sample are calculated. The cut sample is measured to the nearest 0.1 mg using a precision balance. Next, the sample was wrapped in Pyrofoil f358 (manufactured by Nippon Kagaku Kogyo Co., Ltd.) and pressed on the whole to prepare a measurement sample for gas chromatography. The measurement sample was heated for 10 seconds with a pyrolyzer (JHP-3 manufactured by Nippon Kagaku Kogyo Co., Ltd.), and the pyrolyzed gas was introduced into a gas chromatograph (HP5890SERIESII manufactured by Yokogawa Hewlett-Packard Co.). Using a capillary (DB-WAX manufactured by J & WSCIENTIFIC) as a column of the gas chromatograph, a sample was introduced at a split ratio of about 15: 1 to obtain a gas chromatograph.

Next, a method of analyzing the gas chromatograph will be described. First, a calibration curve of the component of interest was created. The calibration curve is obtained by dissolving the solvent of interest and adjusting the concentration in a solvent whose retention time is distant from the solvent of interest, introducing the liquid into a gas chromatograph with a gas-tight syringe, and measuring the relationship between the introduced amount and the detected area value. Obtained by asking. The area value of the target component of the gas chromatograph obtained by the method described above was determined, and the amount of the solvent (unit: mg) detected by the calibration curve was determined. From this value, the residual solvent concentration was calculated from the following equation.

[Formula 1] Residual solvent concentration (%) = ｛(amount of detected solvent)
× 100｝ / [(weight of base material and coating film) × ｛(thickness of coating film × density of coating film) / (thickness of base material × density of base material + thickness of coating film × density of coating film)｝ ]

In the method of forming a coating film according to the present invention,
A pre-metering type coating method is suitable as a coating method for laminating and coating the first layer which has been previously coated and formed into a film. For example, the coating method of the pre-measurement type is not limited thereto, but includes various die coating methods, curtain coating methods, spray coating methods, roll transfer methods, gravure coating methods, and the like. Die coating is suitable. This is because, according to the die coating method, the first layer can be laminated and applied without contact, so that the structure and surface of the first layer are not roughened. Another reason is that the coating amount range of the die coating is good at the coating amount range suitable for the present invention. Further, even in the post-metering type, one in which the time from application of the coating liquid to liquid measurement is short is appropriate. For example, among the post-weighing types, a short dwell wire bar, various blades, and a knife-edge type are also suitable.

Further, the method for forming a coating film according to the present invention comprises:
It may be combined with the above-mentioned Vrentas method. The basic configuration is that, after laminating on the first layer, in the drying step and / or the medium removing step, it is exposed to the vapor of the solvent contained in the laminating coating liquid and treated. Become. By adopting such a configuration, it is possible to remove more of the solvent that hardly diffuses and remains in the first layer.

As a post-step of the method for forming a coating film of the present invention, some heat treatment may be performed. The method of forming a coating film according to the present invention can efficiently remove a solvent which is hardly diffused and remains in the first layer, but after a multilayer coating, a drying process in a short time still does not reach a target residual solvent. There is. In such a case, the residual solvent can be efficiently removed by performing a heat treatment in a thermostat controlled at a predetermined temperature. According to the present invention, the residual solvent in the coating film has a large ratio of the solvent which is easily diffused, and thus, such as this heat treatment,
Even when the dry strength is relatively low, it is possible to efficiently remove the residual solvent. Further, in the case of a coating film applied to a continuous base material, a method of heat-treating the base material wound up in a roll shape is efficient in space.

When the continuous substrate on which the coating film is formed is wound into a roll and heat-treated, it is effective to knurl the edge of the substrate. The knurling process is
It is intended to increase the thickness of the edge of the base material, but by performing such processing, in portions other than the edge of the base material, a gap is provided between the coating film and the back surface of the base material. Can be. Residual solvent diffuses through this gap and is discharged from the end face of the roll, so that efficient solvent removal can be performed. Further, this knurling treatment is also effective in preventing blocking. Various methods have been proposed for the knurling treatment. The larger the gap is, the greater the effect of removing the residual solvent is.

The method for forming a coating film according to the present invention enables efficient removal of a residual solvent which is hardly diffused and remains in the first layer. The composition of the residual solvent in the thus-obtained multi-layered film is the composition of the solvent remaining in the plurality of films, and the residual amount of the solvent group having a molar molecular volume of 100 cc / mol or more and the molar molecular volume of 100 cc / mol. In the ratio of the residual amount of the solvent group of less than mol, the latter is larger than the former.
In the coating film having such a composition of the residual solvent, a large amount of the solvent that is substantially easily diffused remains, and the amount of the solvent that is hardly diffused is small, so that the residual solvent is easily removed.

The ease of removing the residual solvent from the coating film has a strong correlation with the residual solvent concentration. When the residual solvent concentration is high, the solvent removal rate shows a relatively large value, but sharply decreases as the residual solvent concentration decreases. The concentration at which the solvent removal rate sharply decreases is referred to as the critical solvent content, and the subsequent solvent removal phenomenon is considered to be internal diffusion-controlled. In the process of internal diffusion control, the removal rate of the solvent is very low, so that a long-time treatment is required for removal. In the solvent removal process controlled by internal diffusion, the ease of solvent diffusion is important as it affects the solvent removal rate. The value of the critical solvent content slightly varies depending on the type of the non-volatile component, the type of the solvent, the coating film thickness, the drying conditions, and the like, but does not largely differ. In order to efficiently remove the residual solvent by internal diffusion control, the residual solvent composition at this critical solvent content is very important. At this time, if a large amount of the solvent that does not easily diffuse remains, a very long time is required to remove the total residual amount. Conversely, if a large amount of the solvent that easily diffuses remains, the total residual amount can be reduced quickly. The solvent composition remaining in the coating film is such that the latter contains 70% or more in the ratio of the residual amount of the solvent group having a molar molecular volume of 100 cc / mol or more to the residual amount of the solvent group having a molar molecular volume of less than 100 cc / mol. Is more desirable.

In the case where a liquid containing a solvent having a molar molecular volume of 100 cc / mol or more in a coating liquid is applied to any one of the plural layers of the coating film and dried, the residual solvent composition of the present invention is obtained. In order to obtain a coating film having the following formula, the method for forming a coating film of the present invention is preferably applied. It is extremely difficult to achieve the residual solvent composition of the present invention by other methods.

To prepare the heat-sensitive recording material of the present invention, on a transparent or translucent support, a leuco dye, a head coloring agent for coloring the leuco dye by heating and a binder resin as a binder are mainly used. Heat-sensitive recording layer, and a protective layer thereon. Further, a back layer mainly composed of an ultraviolet absorbent and a polyester resin may be provided on the back surface.

The leuco dye used in the present invention is a compound having an electron donating property, and may be used alone or as a mixture of two or more kinds. However, the leuco dye itself is a colorless or light-colored dye precursor, and is not particularly limited. Known ones, for example, triphenylmethanephthalide, triallylmethane, fluoran, phenothidiane, thiofluoran, xanthene, indophthalyl, spiropyran, azaphthalide, chromenopyrazole, methine, rhodamine anilino Leuco compounds such as lactams, rhodamine lactams, quinazolines, diazaxanthenes and bislactones are preferably used.

Next, the color developer used in the present invention is an electron-accepting compound, and various conventionally known electron-accepting color developers can be used. It is an electron-accepting developer containing a long-chain alkyl group in the molecule disclosed in Japanese Unexamined Patent Publication No. 3-355078.
For example, an organic phosphoric acid compound, an aliphatic carboxylic acid compound or a phenol compound having an aliphatic group having 12 or more carbon atoms, a metal salt of mercaptoacetic acid having an aliphatic group having 10 to 18 carbon atoms, or a metal salt of 5 to 8 carbon atoms And alkyl phosphates of caffeic acid having an alkyl group, and acidic phosphate esters having an aliphatic group having 16 or more carbon atoms. Aliphatic groups include linear or branched alkyl and alkenyl groups,
It may have a substituent such as a halogen, an alkoxy group and an ester. In the present invention, the color developer is not limited to the compounds described above, and various other electron-accepting compounds can be used.

In the heat-sensitive recording medium of the present invention, the developer is used in an amount of 1 to 20 parts, preferably 2 to 10 parts, per part of the color former. The color developer can be applied alone or in combination of two or more, and the color former can also be applied alone or in combination of two or more.

Next, various known resins can be used as the binder resin in the thermosensitive coloring layer used in the present invention.
For example, polyacrylamide, maleic acid copolymer, polyacrylate, polymethacrylate,
Vinyl chloride / vinyl acetate copolymer, styrene copolymer,
Polyester, polyurethane, polyvinyl butyral,
Ethyl cellulose, polyvinyl acetal, polyvinyl acetoacetal, polycarbonate, epoxy resin,
Polyamide and the like.

The specific examples of the leuco dye, the developer and the binder resin which are the main components in the thermosensitive coloring layer of the thermosensitive recording material of the present invention have been described above, but the present invention is not limited thereto. Also,
If necessary, known fillers, pigments, surfactants, and heat-fusible substances can be added.

The heat-sensitive recording layer of the present invention is prepared by uniformly dispersing or dissolving a color former and a developer together with a binder resin in an organic solvent, applying the resultant on a support and drying it. Is not particularly limited. In the case of using a dispersion in which a developer is dispersed in the coating liquid for the recording layer, the particle size of the developer is 0.1% because the particle size of the developer greatly affects the surface roughness of the protective layer and, consequently, the dot reproducibility during printing. 5 μm or less is preferable. The thickness of the recording layer is about 1 to 50 μm, preferably about 5 to 20 μm, although it depends on the composition of the recording layer and the use of the thermosensitive recording medium. In addition, various additives such as a surfactant can be added to the recording layer coating liquid, if necessary, for the purpose of improving coatability or recording characteristics.

In the present invention, a layer containing a pigment, a binder, a heat-fusible substance or the like is provided as an intermediate layer between the support and the thermosensitive coloring layer, if necessary, for example, to improve smoothness. I can do it.

In the present invention, a protective layer is provided on the heat-sensitive coloring layer in order to improve chemical resistance, water resistance, rub resistance, light resistance and head matching with a thermal head. Examples of the resin used for the protective layer include a hydrophobic resin, an ultraviolet ray, and an electron beam curable resin. Specific examples of the resin include poly (meth) acrylate resin,
Polyvinyl butyral resin, polyvinyl acetoacetal resin, cellulose acetate propionate, polyurethane resin, polyester grease, polyvinyl acetate resin, styrene acrylate resin, polyolefin resin, polystyrene resin, polyvinyl chloride resin, poly Examples include ether-based resins, polyamide-based resins, polycarbonate-based resins, polyethylene resins, polypropylene resins, and polyacrylamide resins. Further, a crosslinking agent can be added as needed. As the crosslinking agent used together with such a resin, a conventionally known compound can be used. Further, from the viewpoint of transparency, the protective layer resin in the present invention has a refractive index ratio of 0.8 to the transparent support.
It is preferred to use a resin that is between 1.2.

Fillers, waxes and oils can be added to the protective layer for the purpose of improving head matching. Examples of the filler include phosphate fiber, potassium titanate, acicular magnesium hydroxide, whisker, talc, mica, glass flake, calcium carbonate, plate-like char, aluminum hydroxide, plate-like aluminum hydroxide, silica, and clay. , Kaolin, talc, calcined clay, inorganic fillers such as hydrotalcite, cross-linked polystyrene resin, urea-formalin resin,
Organic fillers such as silicone resin, cross-linked polymethyl methacrylate resin, and melamine-formaldehyde resin are exemplified, but the present invention is not limited thereto.

Specific examples of the waxes include stearic acid amide, palmitic acid amide, oleic acid amide, lauric acid amide, ethylenebisstearamide, methylenebisstearamide, methylol stearoamide, paraffin wax, polyethylene, carnauba Wax, paraffin oxide, zinc stearate and the like. As the oil, a general silicone oil or the like can be used.

As a method for producing the thermosensitive recording medium of the present invention,
Applying the method of forming a coating film according to the present invention can quickly remove the amount of the residual solvent in the thermosensitive recording medium to an allowable amount, and has an effect of obtaining a stable color density. In order to be applied as a method for manufacturing a thermosensitive recording medium, the first layer containing a residual solvent corresponds to the thermosensitive recording layer,
It is appropriate that the layer laminated thereon be a protective layer. Therefore, a solvent that satisfies the conditions of claim 1 may be selected as a coating solvent for the protective layer. However, the layer to be laminated does not necessarily need to be a protective layer, and it is also possible to apply only a solvent as described above. In the case where the above-described intermediate layer is provided, it may be applied in forming the intermediate layer.

In the case of the method for producing a thermosensitive recording medium, the solvent of the coating solution to be laminated must be selected in consideration of the solubility of the color developer in addition to the solubility of the resin of the first layer. No. In the heat-sensitive recording medium of the present invention, when the developer is dissolved in the solvent, it reacts with the leuco dye to form a colored state. Therefore, a solvent that does not dissolve the developer must be used.
For example, a solvent selected from methyl acetate, tetrahydrofuran, methyl ethyl ketone and the like satisfies this condition. Therefore, it is preferable that the solvent selected from these solvents contained in the protective layer coating liquid has a content of 95% or more. More preferably, this content is 9
8% or more.

[0048]

The present invention will be described below with reference to examples. In the following, all parts and percentages are based on weight.

Example A1 The following composition [Solution A] was used as a first layer coating solution. [Solution A] PVC acetate resin VYNS3 (manufactured by Union Carbide Co., Ltd.) 20 parts Methyl ethyl ketone (reagent special grade purity 99.0% or more) 48 parts Toluene (reagent special grade purity 99.5% or more) 32 parts The above [A liquid] is transparent. It was applied on a PET film (thickness: 50 μm) using an applicator. Quick surface temperature 8
The coated back surface of the film was pressed against a hot plate made of stainless steel at 5 ° C. and dried by heating for 15 seconds to form a first coated film. At this time, the coating gap of the applicator was adjusted so that the film thickness after drying was 14 μm. By the way, the molar molecular volume of methyl ethyl ketone is 90.2 cm ³ / mol,
The molar molecular volume of toluene is 106.6 cm ³ / mol.

Next, the following composition [Solution B] was used as a second layer coating solution. [Solution B] 8 parts of polyvinyl butyral resin (# 512 manufactured by General Science Corporation) Methyl ethyl ketone (special grade of reagent: 99.0% or more) 92 parts The above [Solution B] was applied on the film coated with the first layer. Coating was performed using a heater, followed by heating and drying at 60 ° C. on the back side with hot air for 1 minute to obtain a coating film. The gap of the applicator was adjusted so that the coating thickness of the second layer was 3 μm. The solvent coating amount at this time was about 25 g / m ² . By the way, the molar molecular volume of methyl ethyl ketone is 90.2 cm
³ / mol.

Example A2 [Solution C] 8 parts of polyvinyl butyral resin (# 512 manufactured by General Science Corporation) Tetrahydrofuran (special grade of reagent: 99.5% or more) 92 parts The above [Solution C] is a second layer coating solution. A coating film was obtained in the same manner as in Example A1, except that the above conditions were satisfied. Incidentally, the molar molecular volume of tetrahydrofuran is 81.9 cm ³ / mol.

Comparative Example A1 [Solution E] Polyvinyl butyral resin 8 parts (# 512, manufactured by General Science Corporation) Methyl ethyl ketone (special grade of reagent: 99.0% or more) 74 parts Toluene (special grade of reagent: 99.5% or more) 18 parts A coating film was obtained in the same manner as in Example A1, except that [E solution] was used as the second layer coating solution.

Comparative Example A2 [Solution F] 8 parts of polyvinyl butyral resin (# 512 manufactured by General Science Corporation) methyl ethyl ketone (special grade of reagent: 99.0% or more) 83 parts Toluene (special grade of reagent: 99.5% or more) 9 parts A coating film was obtained in the same manner as in Example A1, except that the [F liquid] was used as a second coating liquid.

Comparative Example A3 [Solution G] Polyvinyl butyral resin 8 parts (# 512, manufactured by General Science Corporation) Methanol (special grade of reagent: 99.8% or more) 92 parts The above [Solution G] is a second layer coating solution. A coating film was obtained in the same manner as in Example A1, except that the above conditions were satisfied. Incidentally, the molar molecular volume of methanol is 40.7 cm ³ / mol.

Comparative Example A4 [Solution H] Polyvinyl butyral resin 8 parts (# 512, manufactured by General Science Corporation) Ethanol (special grade of reagent: 99.5% or more) 92 parts The above [Solution H] was coated in a second layer. A coating film was obtained in the same manner as in Example A1, except that the above conditions were satisfied. Incidentally, the molar molecular volume of ethanol is 58.5 cm ³ / mol.

Example A3 [Solution I] Polyvinyl butyral resin 16 parts (# 512 manufactured by General Science Corporation) Tetrahydrofuran (special grade of the reagent, purity 99.5% or more) 59 parts Toluene (special grade of the reagent, purity 99.5% or more) 25 parts [Solution I] was used as a first layer coating solution. This is transparent PE
It was applied on a T film (thickness: 50 μm) using an applicator. The coated back surface of the film was quickly pressed against a hot plate made of stainless steel having a surface temperature of 85 ° C. and dried by heating for 20 seconds to form a first coated film. At this time, the film thickness after drying is 1
The coating gap of the applicator was adjusted to be 0 μm.

Methyl ethyl ketone (special grade reagent, purity 9)
(9.0% or more) alone as a second-layer coating solution, and applied on the film coated with the first layer using an applicator at 60 ° C.
It was heated and dried for 1 minute by hot air drying on the back side to obtain a coating film. The gap of the applicator was adjusted to 50 μm, and the coating amount of methyl ethyl ketone was about 25 g / m ² .

Example A4 A first-layer coating film was formed in the same manner as in Example A3.
Next, methyl ethyl ketone (special grade reagent, 99.0% purity)
Above) is used as a second layer coating solution, an application is performed using an applicator on the film on which the first layer has been coated, and heating and drying is performed for 1 minute at 60 ° C. on the back side with hot air. The process was repeated twice to obtain a coating film. In each coating, the gap of the applicator was adjusted to 50 μm, and the coating amount of methyl ethyl ketone was about 25 g / m ² .

Example A5 A coating film was obtained in the same manner as in Example A3, except that [Solution B] of Example A1 was used as a second layer coating liquid.

Comparative Example A5 The same procedure as in Example A3 was carried out except that the gap of the applicator was adjusted to 80 μm and the coating amount of methyl ethyl ketone was set to about 40 g / m ^{2 in} the coating of the second layer of Example A3. Thus, a coating film was obtained.

Comparative Example A6 A coating film was obtained in the same manner as in Example A3, except that [solution E] in Comparative example A1 was used as a second layer coating liquid.

Example A6 [Solution J] 16 parts of polyvinyl acetate (# 347 manufactured by General Science Corporation) Tetrahydrofuran (special grade of reagent, purity: 99.5% or more) 59 parts Toluene (special grade of reagent, purity: 99.5% or more) 25 parts J solution] was used as the first layer coating solution. This is transparent PE
It was applied on a T film (thickness: 50 μm) using an applicator. The coated back surface of the film was quickly pressed against a hot plate made of stainless steel having a surface temperature of 70 ° C. and dried by heating for 20 seconds to form a first coated film. At this time, the coating gap of the applicator was adjusted so that the film thickness after drying was 13 μm. Example A2 was formed on the first layer obtained as described above.
[Liquid C] was laminated in the same manner as described above to obtain a coating film.

Example A7 A coating film was obtained in the same manner as in Example A6, except that [Solution G] of Comparative Example A3 was used as the second layer coating solution.

Comparative Example A7 A coating film was obtained in the same manner as in Example A6, except that [solution E] in Comparative example A1 was used as the second layer coating liquid.

Example B1 The following composition was pulverized and dispersed by a ball mill to a particle size of 0.3 μm to prepare a recording layer coating solution. [K Solution] 3-Diethylamino-6-methyl-7-anilinofluoran 4 parts Octadecylphosphonic acid 12 parts Polyvinyl butyral 4 parts (Denka Butyral # 3000-2 manufactured by Denki Kagaku Kogyo Co., Ltd.) Polyvinyl acetoacetal (Sekisui Chemical Co., Ltd., KS-1) 12 parts Toluene 90 parts Methyl ethyl ketone 90 parts After applying the coating solution prepared as described above on a 75 μm-thick polyester film, apply [H solution] to a temperature of 60 ° C.
Was supplied from both sides at a wind speed of 10 m / s, and dried for 2 minutes to form a thermosensitive recording layer having a thickness of 10 μm.

Further, the following composition was sufficiently stirred to prepare a protective layer coating solution [L solution]. [Liquid L] Polyvinylacetoacetal resin 2.5 parts (Sekisui Chemical Co., Ltd., KS-1) Melamine formaldehyde copolymer filler 7.5 parts (Nippon Shokubai Co., Ltd., Eposter S) Methyl ethyl ketone 90 parts Adjusted as above The protective layer coating solution [Liquid L] was applied onto the previously obtained heat-sensitive recording layer, and hot air at a temperature of 60 ° C. was supplied from both sides at an air velocity of 10 m / s, dried for 3 minutes and dried to a thickness of 1 mm. A protective layer of 0.5 μm was provided. The solvent coating amount at this time was about 13 g / m ² . Thus, a heat-sensitive recording layer was obtained.

Example B2 The heat-sensitive recording medium obtained in Example B1 was heat-treated in a 40 ° C. hot air circulating dryer for 24 hours.

Example B3 [M Liquid] Polyvinylacetoacetal resin 2.5 parts (KS-1 manufactured by Sekisui Chemical Co., Ltd.) Melamine formaldehyde copolymer filler 7.5 parts (Nippon Shokubai Co., Ltd., Eposter S) Ethyl acetate 90 Part The protective layer coating solution [M solution] prepared as described above was applied on the heat-sensitive recording layer obtained in the same manner as in Example B1,
Hot air at a temperature of 60 ° C is supplied from both sides at a wind speed of 10 m / s,
After drying for 3 minutes, a protective layer having a thickness of 1.5 μm was provided. The solvent coating amount at this time was about 13 g / m ² . Incidentally, the molar molecular volume of ethyl acetate is 98.2 cm ³ / mo.
l. Thus, a heat-sensitive recording layer was obtained.

Comparative Example B1 The following composition was sufficiently stirred to prepare a protective layer coating solution [N solution]. [N Liquid] Polyvinylacetoacetal resin 2.5 parts (KS-1 manufactured by Sekisui Chemical Co., Ltd.) Melamine formaldehyde copolymer filler 7.5 parts (Nippon Shokubai Co., Ltd., Eposter S) 72 parts methyl ethyl ketone 18 parts toluene 18 parts or more A thermosensitive recording medium was obtained in the same manner as in Example B1, except that the protective layer coating solution [N solution] prepared in the manner described above was applied onto the thermosensitive recording layer obtained in the same manner as in Example B1.

Comparative Example B2 The heat-sensitive recording medium obtained in Comparative Example B1 was subjected to a heat treatment in a hot air circulating drier at 40 ° C. for 24 hours.

Example B4 The following composition was pulverized and dispersed in a ball mill to a particle diameter of 3 μm to prepare a recording layer coating liquid [O liquid]. [O Solution] 3-Diethylamino-6-methyl-7-anilinofluoran 4 parts Octadecylphosphonic acid 12 parts Polyvinyl butyral 2 parts (Denka Butyral # 3000-2, manufactured by Denki Kagaku Kogyo KK) Polyvinyl acetoacetal (Sekisui Chemical 6 parts Toluene 16 parts Methyl ethyl ketone 105 parts [O Solution] prepared as described above was dried on a continuous polyester film having a width of 600 mm and a thickness of 100 µm to a dry film thickness of 12 µm by die coating. Coated as follows. This was dried for 1 minute and 30 seconds with a floating dryer at a drying temperature of 75 ° C., wound up in a roll form, and a thermosensitive recording layer applied to a continuous film was obtained.

Next, the protective layer coating solution [L solution] of Example B1
Was applied on the heat-sensitive recording layer by die coating so as to have a dry film thickness of 2 μm. The solvent coating amount at this time was about 17 g / m ² . This was dried with a floating dryer at a drying temperature of 65 ° C. for 2 minutes and 20 seconds, wound up in a roll form, and a thermosensitive recording medium coated on a continuous film was obtained.

Example B5 Obtained in Example B4. The heat-sensitive recording medium wound in a roll shape is re-wound so that a gap between the base material and the base material is opened.
In a hot air circulation type drier for 4 days to obtain a heat-sensitive recording medium.

Comparative Example B3 In Example B4, [N] of Comparative Example B1 was used as the coating liquid for the protective layer.
Liquid] was used to obtain a thermosensitive recording medium in the same manner as in Example B4.

Comparative Example B4 The heat-sensitive recording medium obtained in Comparative Example B3 and wound into a roll was re-wound so that the gap between the base materials was opened, and was heated at 40 ° C.
In a hot air circulation type drier for 4 days to obtain a heat-sensitive recording medium.

[Evaluation] With respect to the heat-sensitive recording medium produced as described above, the process of reducing the amount of residual solvent in the coating film was measured and evaluated, and the heat-sensitive recording medium was evaluated as follows. The results are shown in Tables 1 to 5 and FIGS.

<Measurement of Residual Solvent Loss Process> In the process of reducing the residual solvent, a hot air circulation type constant temperature bath was set at a predetermined temperature, the coating film was heated therein, and the coating film was heated at predetermined time intervals. Residual solvent was measured as described above.

<Evaluation of Thermosensitive Recording Medium> The thermosensitive recording medium was evaluated as follows. Dynamic sensitivity curve and image density
It was determined by printing a solid image of 17 gradations according to the printing energy in the table below. Note that the image density is 31 by X-Rite.
The transmission density was measured at 0TR. Gradation energy (mj / mm ² ) 1 3.9 2 4.7 3 5.5 4 6.2 5 7.0 6 7.7 7 8.5 8 9.3 9 10.1 10 10.9 11 11.6 12 12.4 13 13.2 14 14.0 15 14.8 16 15.5 17 16.3

[0079]

[Table 1]

[0080]

[Table 2]

[0081]

[Table 3]

[0082]

[Table 4]

[0083]

[Table 5]

Reduction process of residual solvent after heat treatment at 85 ° C. in Example 1 (relationship between residual solvent amount and drying time)
Is shown in FIG. The total residual solvent in Comparative Example A5 was 4.4%, and the heat treatment time at 85 ° C. required to reach this value required 1 hour after the first layer coating. However, in Example A1,
This value is reached if the heat treatment is performed for about 1 minute after the second layer coating.

FIG. 2 shows the gradation (the relationship between optical density and gradation) of the thermosensitive recording media of Example B4, Comparative Example B3, Example B5, and Comparative Example B4. From FIG. 2, it can be seen that Example B4 has better gradation than Comparative Example B3, and Example B5 has better gradation than Comparative Example B4.

[0086]

According to the method for forming a coating film according to the first aspect, a coating film containing a resin and a solvent which is hardly diffused in the film is used as a first layer, the resin is dissolved, and a mole of the resin is larger than that of the residual solvent. By introducing a solvent having a small molecular volume and easily diffusing in the film from a coating solution for layer coating on the first layer, 1
Solvents that are difficult to diffuse and remain in the layer can be efficiently removed.

According to the method for forming a coating film according to the second aspect, since most of the solvent of the coating solution to be layer-coated is a solvent that rapidly diffuses in the film, a solvent that is difficult to diffuse in the first layer is used. It can be removed more effectively.

According to the method for forming a coating film of the third aspect, the coating film containing a resin and a solvent which is hardly diffused in the film is used as the first layer, and most of the solvent of the coating solution applied thereon is
Since the solvent diffuses quickly in the film, the solvent that is difficult to diffuse in the first layer can be more effectively removed.

According to the method for forming a coating film of the present invention, the coating film containing a resin and a solvent which is hardly diffused in the film is used as the first layer, and the coating amount of the coating liquid to be laminated and coated thereon is reduced. Since it is not excessively large, no film defects occur during the drying process after the lamination coating.

According to the method for forming a coating film according to the fifth aspect, the coating film containing a resin and a solvent which is hardly diffused in the film is used as the first layer, and a coating solution to be laminated thereon is applied to the coating liquid. Since only the solvent that diffuses fast is included, the solvent that is difficult to diffuse in the first layer can be effectively removed.

According to the method for forming a coating film according to the sixth aspect, a coating film containing a resin having a vinyl group in the structure and a solvent which is hardly diffused in the film is used as the first layer, and the coating film is formed on the first layer. Since a solvent selected from among ethyl acetate, tetrahydrofuran, and methyl ethyl ketone is used as a main component, the solvent remaining in the first layer and difficult to diffuse can be efficiently removed.

According to the method for forming a coating film of the present invention, the coating film containing the resin and the solvent which is hardly diffused in the film is used as the first layer, and the solvent is not excessively removed in the drying step of the first layer. By applying the method of forming a coating film according to the present invention, the total processing time of the first layer and the step of laminating thereon can be reduced.

According to the method for forming a coating film of the present invention, the first coating film containing a resin and a solvent which is hardly diffused in the film is used as the first coating film, and the first coating film is formed thereon. In addition, since the coating can be performed in a non-contact manner, the effect of preventing the first layer coating surface from being roughened is added.

According to the ninth aspect of the present invention, in the composition of the residual solvent applied to the substrate and substantially dried, the amount of the solvent that is easy to dry in the applied film is larger than the amount of the solvent that is difficult to diffuse. In the subsequent process, the total amount of the residual solvent in the coating film tends to decrease.

According to the method for producing a coated film according to the tenth aspect, since the method for forming the coated film according to the first aspect is used, the residual solvent in a substantially dried state after being applied to the substrate is obtained. In the composition, the total amount of the residual solvent can be easily reduced by a simple method.

According to the method for heat-treating a coating film according to the eleventh aspect, the coating film applied to a long continuous body is in a state where the total amount of the residual solvent tends to decrease. The residual solvent can be removed with good productivity.

According to the heat treatment method for a coating film of claim 12, the coating film applied to the long continuous body is in a state in which the total amount of the residual solvent is easily reduced, and this forms a gap between the base materials. By performing the heat treatment in the wound state, the residual solvent can be removed with higher productivity.

The recording medium according to the thirteenth aspect is a recording material formed by coating and drying on a base material. In the composition of the residual solvent in a substantially dried state, the amount of the solvent which can be easily dried in the coating film is small. Since the amount of the solvent is less than that of the hardly diffusible solvent, the total amount of the residual solvent in the coating film in the subsequent process is easily reduced.

According to the method of manufacturing a recording medium of claim 14, since the method of forming a coating film of claim 1 is used, the recording material is coated on a substrate and dried, and substantially dried with a recording material to be formed. In the composition of the residual solvent in the heated state, the total amount of the residual solvent can be easily reduced by a simple method, and the productivity can be improved.

The heat-sensitive recording medium according to claim 15 is a heat-sensitive recording material formed by coating and drying on a base material, wherein the solvent is easily dried in the coating film in the composition of the residual solvent in a substantially dried state. Since the amount thereof is larger than that of the solvent which is hardly diffused, the total amount of the residual solvent in the coating film in the subsequent process is easily reduced, and as a result, excellent coloring characteristics can be achieved.

According to the method of manufacturing a thermosensitive recording medium of the sixteenth aspect, since the method of forming a coating film of the first aspect is used, the thermosensitive recording material formed by coating and drying on a base material can be used. In the composition of the residual solvent in the dried state,
With a simple method, the total amount of the residual solvent can be easily reduced, and the productivity can be improved.

According to the method for producing a thermosensitive recording medium of the present invention, as a protective layer solvent applied on the thermosensitive recording layer applied on the base material, the resin of the thermosensitive recording layer is well dissolved and the molecular weight is high. Since ethyl acetate, tetrahydrofuran, and methyl ethyl ketone, which are small, were used as most components, the residual solvent could be rapidly removed, and the productivity could be improved.

[Brief description of the drawings]

FIG. 1 is a view showing a relationship between a residual solvent and a drying time in a heat treatment of Example A1.

FIG. 2 is a diagram illustrating a relationship between optical density and gradation in Example B4, Comparative Example B3, Example B5, and Comparative Example B4.

Continued on the front page (72) Inventor Hideo Aihara 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Company (72) Inventor Hideo Su ▲ saki ▼ 1-3-6 Nakamagome, Ota-ku, Tokyo Stock In Ricoh Company (72) Inventor Shinji Hirata 1-3-6 Nakamagome, Ota-ku, Tokyo Stock Company Ricoh F-term (reference) 2H026 AA07 BB02 BB21 DD55 FF11 HH05 HH07 4D075 AC02 AE03 DC27 EB19 EB56 EC17 EC30 EC54

Claims (17)

[Claims] In a method for forming a coating film formed by laminating a plurality of films containing a resin, one of two coating liquids used for forming any two adjacent films A and B among the plurality of films. Contains at least solvent X and resin A (coating solution A
A coating solution containing a solvent Y having a smaller molar molecular volume than the solvent X and dissolving the resin A (hereinafter referred to as a coating solution B).
After forming the film A using the coating liquid A, the coating liquid B
A method for forming a coating film, comprising forming a film B by using the method. 2. The method for forming a coating film according to claim 1, wherein the content of the solvent Y in all volatile components in the coating solution B is 9%.
A method for forming a coating film characterized by being at least 5% by weight. 3. The method for forming a coating film according to claim 1, wherein the solvent X has a molar molecular volume of 100 cc / mol or more.
The content in the total volatile components in the coating solution A is 5% by weight or more, the solvent Y has a molar molecular volume of less than 100 cc / mol, and the content in the total volatile components in the coating solution B is 95% by weight.
A method for forming a coating film characterized by the above. 4. The method for forming a coating film according to claim 1, wherein the thickness of the film A formed using the coating solution A is 5 μm or more, and the coating amount of the solvent Y contained in the coating solution B is 30 g /
A method of forming a coating film which is characterized in that m ^{2 or} less. 5. The method for forming a coating film according to claim 1, wherein the nonvolatile component in the coating solution B is 1% by weight or less. 6. The method for forming a coating film according to claim 1, wherein 50% by weight of a resin component contained in the coating liquid A is used.
The above is selected from those having a structure having a vinyl group,
As the solvent Y in the coating liquid B, one or more solvents selected from ethyl acetate, tetrahydrofuran and methyl ethyl ketone are used, and the content of these solvents in the total volatile components of the coating liquid is 95% by weight or more. A method for forming a coating film, characterized in that: 7. The method for forming a coating film according to claim 1, wherein the amount of the residual solvent in the coating film A immediately before applying the coating liquid B is 1% by weight or more. how to. 8. The method for forming a coating film according to claim 1, wherein a die coating method is used as a coating method of the coating liquid B. 9. In a film formed by sequentially coating a plurality of layers containing at least a resin on a substrate, a solvent group having a molar molecular volume of 100 cc / mol or more in a composition of a solvent remaining in the plurality of films. Residual amount and molar molecular volume 100 cc / mol
A coating film formed on a substrate, wherein the latter is larger than the former in a ratio of the residual amount of the solvent group of less than. 10. A method for manufacturing a coated film, wherein the method for forming a coated film according to claim 1 is used in manufacturing the film-formed product according to claim 9. 11. The coating film formed on the base material according to claim 9 is a long continuous body, which is processed into a wound shape,
A heat treatment method for a coating film, wherein the heat treatment is performed. 12. The heat treatment method for a coating film according to claim 11, wherein the edge portion of the base material is subjected to a knurling process. 13. A recording medium in which a plurality of layers containing at least a resin are provided on a base material, the content of a solvent group having a molar molecular volume of 100 cc / mol or more, and A recording medium characterized in that the latter is larger than the former in the ratio of the content of the solvent group having a molecular volume of less than 100 cc / mol. 14. A method for manufacturing a recording medium according to claim 13, wherein the method for forming a coating film according to claim 1 is used in manufacturing the recording medium according to claim 13. 15. A thermosensitive coloring layer mainly comprising a leuco dye, a developer for causing the leuco dye to be heated and a binder resin as a binder, and a protective layer provided thereon. In thermal recording media,
In the composition of the solvent remaining in the thermosensitive coloring layer and the protective layer film, the latter is the former in the ratio of the residual amount of the solvent group having a molar molecular volume of 100 cc / mol or more to the residual amount of the solvent group having a molar molecular volume of less than 100 cc / mol. Sensation recording medium characterized by being larger than. 16. A method for manufacturing a thermosensitive recording medium according to claim 15, wherein the method for forming a coating film according to claim 1 is used in manufacturing the thermosensitive recording medium according to claim 15. 17. The method for producing a thermosensitive recording medium according to claim 15, wherein a single or plural solvents selected from ethyl acetate, tetrahydrofuran and methyl ethyl ketone are used as a solvent for the coating liquid for the protective layer. Wherein the content of these solvents in the total volatile components is 95% by weight or more.