JP7294928B2 - Pressure-bonded postcard, its manufacturing method, and method for suppressing blocking in a pressure-bonded postcard in which an information recording surface provided with a pseudo-pressure-bonded layer on the surface is folded inward and pressure-bonded - Google Patents

Description

The present invention relates to a pressure-bonded postcard, a method for manufacturing the same, and a method for suppressing blocking in a pressure-bonded postcard in which an information recording surface provided with a pseudo pressure-bonded layer is folded inward and pressure-bonded.

Conventionally, a removable adhesive layer (pseudo-adhesive layer) that is easy to peel but difficult to re-adhere has been provided in order to more easily transmit confidential or confidential information only to the recipient. A pressure-bonded postcard in which an information recording surface is hidden with a sheet is known. Such pressure-bonded postcards are produced by printing information on a base sheet by means of various inks, electrophotography, etc., overlapping the information-recording surfaces, providing a pseudo-adhesive layer on the overlapping surfaces, and pressing the postcards. By adhering the information by means of (1), it is possible to immediately recognize whether or not it has been peeled off before it is handed over to the recipient, thereby preventing anyone other than the recipient from knowing the information. In addition to the purpose of concealing information as described above, such pressure-bonded postcards record a large amount of information such as advertisement information on a sheet larger than the postcard size, and the sheet is postcard-sized at a low postage rate. It is also used for direct mail by folding to the size of a sealed letter. Crimped postcards can be classified into several forms, depending on the type of folding (ie, how they are folded) and the type of pseudo-adhesive layer that is formed.

Folding types mainly include two-folding (also called V-folding) and Z-folding. Folding in two is a method in which a pseudo-adhesive layer is formed on the inner surface on which information is recorded, and the entire inner surface is folded in two and pasted together. In the case of folding in half, four information recording surfaces are provided including the exposed front and back surfaces. In Z-folding, a rectangular sheet is folded in three in a Z shape, a pseudo-adhesive layer is formed on both the front and back sides of the central surface, and the surfaces on both sides are attached to the pseudo-adhesive layers on the front and back respectively. It is. In this case, both the front and back surfaces can be peeled off, providing six information recording surfaces including the exposed front and back surfaces.

The types of pseudo-adhesive layers mainly include PP (polypropylene) thermal compression method, active energy ray-curable varnish compression method, and glue compression method. is mentioned. In the active energy ray-curable varnish press method, after applying a varnish that hardens when exposed to active energy rays such as ultraviolet rays and electron beams, the coated surface is irradiated with active energy rays to form a pseudo-adhesive layer. An example of such a varnish is the one described in Patent Document 1, for example. The glue pressing method forms a pseudo-adhesive layer by applying a pressure-sensitive glue mainly composed of water-based emulsion or latex. can.

JP 2007-145907 A JP-A-2001-146584

As described above, pressure-bonded postcards printed on re-peelable sheets have various advantages. may occur. If you try to forcibly peel off the pseudo-adhesive surface of a pressure-bonded postcard with such blocking, the sheet may be torn, or a part of the sheet that was not partially peeled may remain on the inner information recording surface, resulting in information loss. The readability of the recording surface is adversely affected. Such a phenomenon is considered to be caused by the fact that the strength of the sheet is lowered by wetting with water, and the strength becomes weaker than the strength of pseudo-adhesion. In particular, pressure-bonded postcards tend to get wet due to delivery in rainy weather, flooding of mailboxes, and the like. Such pressure-bonded postcards generally have instructions to dry them before peeling off if they get wet, but you need to wait for them to dry naturally, and even if you dry them with a dryer, etc. requires time and effort.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a pressure-bonded postcard in the form of a re-peelable sheet that can suppress the occurrence of blocking even when in contact with water. do.

As a result of extensive studies to solve the above-described problems, the present inventors have found that a pressure-bonded postcard, in which the information recording surface provided with the pseudo-adhesive layer as described above is folded inward and pressure-bonded, is folded. All of the above problems can be solved by providing a water-resistant layer formed of an alkali-soluble water-soluble resin, a styrene-based film-forming emulsion, and an aqueous coating agent containing water on the surface exposed to the outside in a folded state. The discovery led to the completion of the present invention. Specifically, the present invention provides the following.

The present invention is a pressure-bonded postcard having an information recording surface provided with a pseudo-adhesive layer on the surface folded inward and having a water-resistant layer on the surface exposed to the outside in the folded state, wherein the water-resistant layer is , an alkali-soluble water-soluble resin, a styrene-based film-forming emulsion , silica and an aqueous coating agent containing water.

The styrene-based film-forming emulsion is at least one selected from the group consisting of styrene-acrylic polymers, styrene-maleic acid-based polymers, and styrene-maleic acid half-ester-based polymers having a glass transition temperature (Tg) of 0 to 20°C. is preferred.

The alkali-soluble water-soluble resin is preferably a styrene-acrylic and/or styrene-maleic acid-based alkali-soluble resin.

The ratio of the alkali-soluble water-soluble resin to the styrene-based film-forming emulsion contained in the water-based coating agent is 10/90 to 30/70 in solid content mass ratio of alkali-soluble water-soluble resin/styrene-based film-forming emulsion. Preferably.

The present invention also relates to a method for producing a pressure-bonded postcard in which an information recording surface provided with a pseudo pressure-bonded layer on the surface is folded inward and pressure-bonded, wherein the surface exposed to the outside in the folded state is coated with an alkali-soluble water-soluble A press-bonded postcard manufacturing method comprising a step of forming a matte waterproof layer by applying an aqueous coating agent containing a curable resin , a styrene-based film-forming emulsion, silica and water.

The styrene-based film-forming emulsion is at least one selected from the group consisting of styrene-acrylic polymers, styrene-maleic acid-based polymers, and styrene-maleic acid half-ester-based polymers having a glass transition temperature (Tg) of 0 to 20°C. is preferred.

The alkali-soluble water-soluble resin is preferably a styrene-acrylic and/or styrene-maleic acid-based alkali-soluble resin.

The ratio of the alkali-soluble water-soluble resin to the styrene-based film-forming emulsion in the water-based coating agent is preferably 10/90 to 30/70 in solid content mass ratio of alkali-soluble water-soluble resin/styrene-based resin.

In the present invention, a water-based coating agent containing an alkali-soluble water-soluble resin, a styrene-based film-forming emulsion , silica and water is applied to the portion exposed to the outside in the folded state to form a matte waterproof layer. It is also a method for suppressing blocking in a pressure-bonded postcard in which an information recording surface provided with a pseudo pressure-bonded layer on the surface is folded inward and pressure-bonded.

ADVANTAGE OF THE INVENTION According to the present invention, there is provided a pressure-bonded postcard in the form of a re-peelable sheet that can suppress the occurrence of blocking even when in contact with water.

FIG. 1 is a schematic diagram showing a crimped postcard 1 of the present invention. The left side of FIG. 1 shows the state before crimping, and the right side of FIG. 1 shows the state after crimping. FIG. 2 is a schematic diagram showing the XX' section in FIG.

Hereinafter, an embodiment of the press-bonded postcard of the present invention, an embodiment of the method for producing a printed matter of the present invention, and suppression of blocking in printed matter press-bonded by folding an information recording surface having a pseudo-pressed layer on the surface inward. An embodiment of a method for doing so will be described. It should be noted that the present invention is not limited to the following embodiments or modes, and can be implemented with appropriate modifications within the scope of the present invention.

<Pressed postcard>
First, an embodiment of the press-bonded postcard of the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram showing a crimped postcard 1 of the present invention. The left side of FIG. 1 shows the state before crimping, and the right side of FIG. 1 shows the state after crimping. FIG. 2 is a schematic diagram showing the XX' section in FIG. The pressure-bonded postcard 1 of the present invention is a printed matter in which an information recording surface 3 having a pseudo-adhesive layer 5 on its surface is folded inward and pressure-bonded. It is characterized by having a water-resistant layer 6 made of a water-soluble coating agent containing a soluble water-soluble resin, a styrene-based film-forming emulsion, and water. The size of the pressure-bonded postcard of the present invention is not limited to the size of a postcard, and may be, for example, the size of a sealed letter or larger.

In the pressure-bonded postcard 1, an information recording surface 3 is formed by recording information on a sheet-like printing medium 2 by means of printing or the like, and a pseudo-adhesive layer 5 is formed on the surface of the information recording surface 3. Thus, the information recording surface 3 can be folded inward along the fold line 11 extending along the length direction L at substantially the center in the width direction W and crimped. The pressure-bonded postcard 1 has an exposed portion 31 formed at the end of the information recording surface 3, and the exposed portion 31 is used as a clue to form a pseudo-adhesive layer 5 positioned between the pseudo-adhesive layers 5, 5 facing each other in the folded state. By peeling along the surface A, the information recording surface 3 is exposed.

The printing medium 2 is made of paper and can be printed on both sides. For example, on the pressure-bonded postcard 1, necessary information can be printed on the inner surface when folded, and information such as an address can be printed on the outer surface when folded.

The pseudo-adhesive layer 5 is formed by applying an active energy ray-curable varnish or pressure-sensitive glue for crimping, or by attaching a PP film, etc., and crimping is performed with the pseudo-adhesive layers 5 facing each other. Then, a quasi-adhered state that can be peeled off is obtained. Various varnishes and pressure-sensitive glues for forming the pseudo-adhesive layer 5 are commercially available, and such materials can be used as appropriate.

A waterproof layer 6 is formed on the surface of the outer surface 4 . The water-resistant layer 6 prevents the water from penetrating into the printing medium 2, which is paper, when the folded pressure-bonded postcard 1 comes into contact with water. Suppresses blocking due to adhesion of water.

The water-resistant layer 6 is formed by forming a film from an alkali-soluble water-soluble resin and a styrene-based film-forming emulsion. Specifically, an aqueous coating agent containing an alkali-soluble water-soluble resin, a styrene-based film-forming emulsion, and water is applied to the surface to be the outer surface 4 and dried to form a resin thin film. serves as the waterproof layer 6 . From the viewpoint that the alkali-soluble water-soluble resin and the styrene-based film-forming emulsion form a film and form a resin thin film with good water resistance, the glass transition temperature (Tg) of the styrene-based film-forming emulsion is 0 to 20°C. is preferred. When the Tg is 0°C or higher, stickiness of the resin thin film formed on the surface of the outer surface 4 can be suppressed, which is preferable. It is preferable because the film formation becomes good and a resin thin film having good water resistance is formed.

Styrene-based film-forming emulsions contained in water-based coating agents have a core-shell structure consisting of a shell that is a highly hydrophilic polymer that functions as a macromolecular emulsifier and a core that is made of a resin that is more hydrophobic than the shell. is preferred. Polymers constituting the shell and core include styrene-acrylic polymers that are copolymers of styrene and acrylic acid, styrene-maleic acid-based polymers that are copolymers of styrene and maleic acid, and styrene-maleic acid half ester-based polymers. etc. are preferably mentioned. Among these, in particular, a water-soluble acrylic resin is used as a polymer emulsifier to copolymerize monomers such as styrene monomers, alkyl esters of (meth)acrylic acid such as 2-ethylhexyl (meth)acrylate and butyl acrylate. can preferably be mentioned. The shell part and the core part may be of the same type of polymer, or may be of different types of polymer. As for the structure of the shell portion and the core portion, assuming that both are made of a styrene-acrylic polymer, for example, a polymer having a high acrylic acid ratio and a high acid value is preferably selected as the polymer constituting the shell. It is preferred that a polymer having a high styrene ratio and a low acid value be selected as the core-constituting polymer. An emulsion containing such resin fine particles is prepared by performing emulsion polymerization in an aqueous solvent. Known methods can be used for the preparation, and such emulsions are commercially available and may be used. In this specification, (meth)acrylic acid represents acrylic acid and/or methacrylic acid, and (meth)acrylate represents acrylate and/or methacrylate.

As described above, there is a preferable range for the Tg of the fine resin particles that constitute the emulsion contained in the aqueous coating agent. , the theoretical glass transition temperature determined by the following Wood's formula can be employed. The resin fine particles are prepared by emulsion polymerization as described above. It represents the glass transition temperature of the copolymer obtained when copolymerized at once without

Wood's formula: 1/Tg= _W1 /Tg1+ _W2 / _Tg2 + _{W3 / Tg3} +...+ _Wx / _Tgx
(In the above _formula , Tg ₁ to Tg _x are the glass transition temperatures of the respective homopolymers of monomers ₁ , 2, 3, . The mass fraction of each of the bodies 1, 2, 3, ..., x, Tg represents the theoretical glass transition temperature.The glass transition temperature in Wood's formula is the absolute temperature.)

The acid value of the styrene-based film-forming emulsion is preferably about 30 to 100 mgKOH/g from the viewpoint of water resistance. The acid value here means the theoretical amount of neutralization of KOH for the amount of each ethylenically unsaturated monomer theoretically required to obtain 1 g of the copolymer, and the amount of neutralization. It is obtained by regarding the total mg number as the acid value (theoretical acid value) of the copolymer. In addition, the acid value is derived from the polymer emulsifier that constitutes the shell. is 10 mgKOH/g. The acid value of the fine resin particles is more preferably about 30 to 70 mgKOH/g.

In the water-based coating agent, the solid content of the styrene-based film-forming emulsion may be about 5 to 10% by mass, but is not particularly limited.

The water-based coating agent contains, in addition to the styrene-based film-forming emulsion, an alkali-soluble water-soluble resin from the aspect of coatability. The alkali-soluble water-soluble resin is added to the aqueous coating agent as a varnish dissolved in an alkaline aqueous solution. The inclusion of such varnishes in water-based coating agents imparts viscosity to enhance their spreadability. The alkali-soluble water-soluble resin is preferably at least one selected from the group consisting of styrene-acrylic polymers and styrene-maleic acid-based polymers. is preferably used after neutralization with an alkali of The weight average molecular weight of the water-soluble resin is preferably about 5,000 to 20,000. Further, the acid value of the water-soluble resin is about 100 to 300 mgKOH/g.

The ratio of the alkali-soluble water-soluble resin to the styrene-based film-forming emulsion contained in the aqueous coating agent is about 10/90 to 30/70 in solid content mass ratio of alkali-soluble water-soluble resin/styrene-based film-forming emulsion. are preferably mentioned.

The water-based coating agent may contain various components in addition to the styrene-based film-forming emulsion and alkali-soluble water-soluble resin described above. Such components include waxes, silica particles, antifoaming agents, and the like.

Wax is added mainly to improve the abrasion resistance of the waterproof layer. Examples of wax include polyethylene wax and polytetrafluoroethylene wax. The average particle size of the wax is preferably about 1 to 10 μm, more preferably about 4 to 8 μm, as calculated by the call counter method. The amount of wax added to the water-based coating agent is preferably about 3 to 10% by mass.

Silica is added mainly to lower the gloss of the waterproof layer and improve the matte feeling. The amount of silica added to the aqueous coating agent is preferably about 1 to 5% by mass.

Antifoaming agents suppress the generation of air bubbles in water-based coating agents and improve the leveling properties of water-based coating agents. It is added to suppress voids and improve coatability. Defoamers include commercially available acetylenic dialcohol compositions. The amount of antifoaming agent added to the aqueous coating agent is preferably about 0.5 to 3% by mass.

When the water-based coating agent is applied to the surface to be the outer surface 4 to form the waterproof layer 6, a known application method can be used without particular limitation. Examples of such a coating method include coating using a gravure coater and coating using a spray. Among these, coating using a gravure coater is preferred.

As the water-based coating agent applied to the outer surface 4 dries, the particles of the styrene-based film-forming emulsion contained therein and the acrylic-soluble water-soluble resin form a film to form a resin thin film. As a result, the water-resistant layer contains the resin derived from the styrene-based film-forming emulsion and the alkali-soluble water-soluble resin. When drying the applied water-based coating agent, known means such as natural drying and hot air drying can be used without particular limitation.

In the present invention, as described above, a water-resistant resin thin film is formed by applying an aqueous coating agent containing particles of a styrene-based film-forming emulsion and an alkali-soluble water-soluble resin. From the viewpoint of forming a water-resistant and gap-free film, a means of applying UV varnish or the like and curing it is also conceivable. However, when UV varnish is used, a certain amount of film thickness is required to form a gap-free, water-resistant film, and when this is applied to pressure-bonded postcards, the weight of the thick water-resistant layer may result in excessive weight. There is In this respect, it is preferable to form a resin thin film using the water-based coating agent as described above, since a thin and light waterproof layer can be formed.

As described above, an embodiment of the pressure-bonded postcard of the present invention has been described by taking a double-folded (V-folded) pressure-bonded printed matter as an example, but it goes without saying that the present invention may be a Z-folded pressure-bonded postcard. .

<Manufacturing method of printed matter>
Next, one embodiment of the method for producing a pressure-bonded postcard of the present invention will be described. This manufacturing method is a method for manufacturing the pressure-bonded postcard of the present invention, and the content of the description has many points in common with the already-described pressure-bonded postcard of the present invention. Therefore, in the following description, the description of the parts common to the pressure-bonded postcard of the present invention will be omitted, and the different parts will be mainly described.

The manufacturing method of the present invention is a method for manufacturing a pressure-bonded postcard in which an information recording surface provided with a pseudo pressure-bonded layer on the surface is folded inward and pressure-bonded, and the surface exposed to the outside in the folded state is coated with an alkali. It is characterized by comprising a step of forming a water-resistant layer by applying an aqueous coating agent containing a soluble water-soluble resin, a styrene-based film-forming emulsion, and water. This step may be performed before or after the pressure-bonded postcard is folded. The structure of the pressure-bonded postcard manufactured in this way is the same as the pressure-bonded postcard 1 of the present invention. Also, the alkali-soluble water-soluble resin and the styrene-based film-forming emulsion are the same as those of the water-based coating agent. That is, the manufacturing method of the present invention is characterized by comprising a step of forming the water-resistant layer 6 on the outer surface 4 of the crimped postcard 1 . The method of applying the water-based coating agent to the outer surface 4 has already been explained.

When the outer surface 4 is printed, the above step of forming the waterproof layer 6 is preferably performed after the printing. In the case of a pressure-bonded postcard, the address is printed on one of the two outer surfaces 4, and the above process is preferably performed after the address is printed.

The styrene-based film-forming emulsion contained in the aqueous coating agent is selected from the group consisting of styrene-acrylic polymers, styrene-maleic acid-based polymers, and styrene-maleic acid half ester-based polymers having a glass transition temperature (Tg) of 0 to 20°C. At least one kind is preferable. This has already been described in the description of the crimped postcard 1 above.

Also, the alkali-soluble water-soluble resin contained in the water-based coating agent is preferably a styrene-acrylic and/or styrene-maleic acid-based alkali-soluble resin. This has already been described in the description of the crimped postcard 1 above.

Further, the ratio of the alkali-soluble water-soluble resin and the styrene-based film-forming emulsion in the aqueous coating agent is preferably 10/90 to 30/70 in solid content mass ratio of alkali-soluble water-soluble resin/styrene-based resin. . This has already been described in the description of the crimped postcard 1 above.

<Method for Suppressing Blocking in Printed Matter Pressed by Folding the Information Recording Surface Having a Pseudo-Pressed Layer on the Surface>
Next, an embodiment of a method for suppressing blocking in a printed material pressed by folding the information recording surface provided with the pseudo pressure layer on the surface thereof according to the present invention will be described. In this method, an aqueous coating agent containing an alkali-soluble water-soluble resin, a styrene-based film-forming emulsion, and water is applied to the portion exposed to the outside in the folded state to form a water-resistant layer on the portion. It is characterized by maintaining the peelability of the pseudo-adhesive surface even when the printed matter comes into contact with water by applying the aqueous coating agent to the outer surface like the pressure-bonded postcard 1 of the present invention. blocking. Since this has already been explained, the explanation here is omitted. In addition, the “outer surface” is the surface that is arranged on the outside when it is folded into a crimped postcard shape, and the timing at which the waterproof layer is formed on this “outer surface” is It may be before it is folded into a crimped postcard shape, or after it is folded into a crimped postcard shape.

EXAMPLES Hereinafter, the present invention will be described in more detail by showing examples, but the present invention is not limited to the following examples.

[Preparation of varnish]
BASF Corp. product name JONRYL6610 (weight average molecular weight 8500, acid value 215 mgKOH/g) was used as a styrene-acrylic alkali-soluble water-soluble resin varnish. This varnish contains an alkali-soluble water-soluble resin.

[Preparation of aqueous coating agent]
70 parts by mass of styrene acrylic emulsion (manufactured by BASF Corporation, product name JONRYL7741), 20 parts by mass of the above styrene acrylic alkali-soluble water-soluble resin varnish, 7 parts by mass of polyethylene wax, 3 parts by mass of silica powder, and acetylenic dialcohol 1.5 parts by mass of the composition (manufactured by Air Products Japan Co., Ltd., product name SURFYNOL104E) was mixed to prepare an aqueous coating agent.

On the surface of the coated paper, a commercially available UV varnish for pressure-bonded postcards (Cure Star XUV-K3AP, manufactured by Sakata Inx Co., Ltd.) is applied with a 200-line hand proofer and irradiated with ultraviolet rays to harden to provide a pseudo-adhesive layer. I got a new sheet. Then, this sheet was cut into a size of 5 cm×21 cm and folded in half so that the pseudo-adhesive layers overlapped on the inside. The sheet folded in two was crimped by a 4-stage press stacker with a 15 mm seam tightening to obtain a crimped sample. This procedure was repeated to produce a total of 6 crimped samples.

The water-based coating agent was applied in a wet state to thicknesses of 4 μm, 9 μm, 14 μm, and 18 μm on four press-bonded samples, respectively, and dried naturally at room temperature for 24 hours to form a water-resistant layer on the outer surface. . In addition, a commercially available UVOP varnish was applied to a thickness of 2 to 3 μm on one press-bonded sample, and this was cured by ultraviolet rays to form a water-resistant layer on the outer surface. The remaining one pressed sample did not form a water-resistant layer.

A drop of water was dropped on the outer surface of each of the six pressure-bonded samples using a dropper, and the sample was allowed to stand as it was. The pseudo-adhesive surface of the pressure-bonded sample was peeled off, and the presence or absence of blocking at the location where water was dripped was checked, and the time required for blocking was recorded. Table 1 shows the results.

As shown in Table 1, it can be seen that it takes a considerable amount of time for blocking to occur in any of the pressure-bonded samples (corresponding to the pressure-bonded postcards of the present invention) on which a water-based coating agent is applied to form a water-resistant layer. On the other hand, in the press-bonded sample with UVOP varnish forming a water-resistant layer with a practical thickness of 2 to 3 μm for a press-bonded postcard, blocking occurred overwhelmingly less than the one using the water-based coating agent. It turns out that time is short. In the case of UVOP varnish, there is not much difference between the wet film thickness and the film thickness after curing, but with water-based coating agents, the film thickness after drying is significantly thinner than the wet film thickness due to the evaporation of water. Taking this into consideration, the superiority of the water-resistant layer in the present invention formed from the water-based coating agent can be understood.

REFERENCE SIGNS LIST 1 crimped postcard 2 printed material 3 information recording surface 4 outer surface 5 pseudo-adhesive layer 6 waterproof layer A pseudo-adhesive surface

Claims (9)

A pressure-bonded postcard having an information recording surface provided with a pseudo-adhesive layer on the surface folded inward and having a water-resistant layer on the surface exposed to the outside in the folded state, wherein the water-resistant layer comprises an alkali-soluble water-soluble 1. A pressure-bonded postcard characterized by being a matte coat formed of an aqueous coating agent containing a curable resin , a styrene-based film-forming emulsion, silica and water. The styrene-based film-forming emulsion is at least one selected from the group consisting of styrene-acrylic polymers, styrene-maleic acid-based polymers, and styrene-maleic acid half-ester-based polymers having a glass transition temperature (Tg) of 0 to 20°C. Item 1. A pressure-bonded postcard according to item 1. 3. The press-bonded postcard according to claim 1, wherein said alkali-soluble water-soluble resin is a styrene-acrylic and/or styrene-maleic acid-based alkali-soluble resin. The ratio of the alkali-soluble water-soluble resin and the styrene-based film-forming emulsion contained in the aqueous coating agent is 10/90 to 30/70 in solid content mass ratio of alkali-soluble water-soluble resin/styrene-based film-forming emulsion. The pressure-bonded postcard according to any one of claims 1 to 3, characterized in that there is a A method for producing pressure-bonded postcards in which an information recording surface provided with a pseudo pressure-bonded layer on the surface is folded inward and pressure-bonded, wherein the surface exposed to the outside in the folded state is coated with an alkali-soluble water-soluble resin, a styrene-based A press-bonded postcard manufacturing method comprising a step of forming a matte waterproof layer by applying an aqueous coating agent containing a film-forming emulsion , silica and water. The styrene-based film-forming emulsion is at least one selected from the group consisting of styrene-acrylic polymers, styrene-maleic acid-based polymers, and styrene-maleic acid half-ester-based polymers having a glass transition temperature (Tg) of 0 to 20°C. Item 6. A method for producing a pressure-bonded postcard according to item 5. 7. The method for producing a press-bonded postcard according to claim 5, wherein said alkali-soluble water-soluble resin is a styrene-acrylic and/or styrene-maleic acid-based alkali-soluble resin. The ratio of the alkali-soluble water-soluble resin and the styrene-based film-forming emulsion in the aqueous coating agent is 10/90 to 30/70 in solid content mass ratio of alkali-soluble water-soluble resin/styrene-based resin. The method for manufacturing a pressure-bonded postcard according to any one of claims 5 to 7. A water-based coating agent containing an alkali-soluble water-soluble resin, a styrene-based film-forming emulsion , silica and water is applied to the part exposed to the outside in the folded state to form a matte waterproof layer. A method for suppressing blocking in a pressure-bonded postcard in which an information recording surface having a pseudo pressure-bonded layer on the surface thereof is folded inward and pressure-bonded.

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