JP2022154986A - Base film for hydraulic transfer printing and manufacturing method of base film for hydraulic transfer printing - Google Patents

Abstract

To provide base film for hydraulic transfer printing that does not cause warp and is excellent in printability and transfer property to the print layer of an object to be transferred to when printing a design to the base film.SOLUTION: The base film for hydraulic transfer printing is base film for hydraulic transfer printing mainly composed of polyvinyl alcohol resin (A), and the difference is 0.3 or less between the maximum value xmax and the minimum value xmin of the moisture percentage x(weight %) in the film width direction, and the average moisture percentage M in the film width direction is 2 to 5 weight %.SELECTED DRAWING: None

Description

The present invention has excellent printing characteristics that allow a high-definition design to be printed on the film surface, and excellent transfer characteristics that allow the high-definition design printed on the film surface to be accurately transferred to the surface of a transfer material. The present invention relates to a base film for hydraulic transfer printing.

Hydraulic transfer printing is used as a technique for applying designs to the surface of an object with unevenness. In this method, a design is printed on the surface of a film that serves as a base material, and the printed surface is floated on the surface of water. The design of the printed layer is transferred to the surface of the transfer-receiving material by pressing the transfer-receiving material in water from above. Conventionally, as a base film for hydraulic transfer printing, a polyvinyl alcohol-based resin film having a polyvinyl alcohol-based resin as a forming material has been used.

Since these polyvinyl alcohol-based resin films are water-soluble and have excellent swelling properties, they are suitable as base films for liquid pressure transfer printing. The film tends to sag under the influence of tension during film roll storage and humidity and temperature during film roll storage, which may cause problems when the film is unwound from the film roll and used.
In particular, when used for transfer printing, if the base film has slack, printing misalignment occurs when forming a printing layer on the film surface, making it difficult to form a high-definition printing layer, or during transfer. The film stretches unevenly on the surface of water, causing distortion in the printed layer, which causes problems such as the inability to perform high-definition transfer printing on the material to be transferred. .

As a base film with little slack, for example, by adjusting the peeling speed so that the peeling stress of the film is uniform during film formation, a film with a small deflection rate can be obtained (see, for example, Patent Document 1). , by setting the winding tension of the film to a specific range, it is possible to reduce the residual stress during storage even with a flexible and stretchable water-soluble PVA film,
A method for producing a water-soluble polyvinyl alcohol film that can prevent the film from being distorted or wrinkled has been disclosed (see, for example, Patent Document 2).

JP 2009-160922 A International publication WO2008/142835

However, even with the technique of the above-mentioned patent document, there were cases where the slackness-improving effect was not sufficiently obtained depending on the composition of the film and other manufacturing conditions.

Therefore, in view of this background, the present invention provides a base film for hydraulic transfer printing that does not cause slack and has excellent printability when printing a design on the base film and transfer characteristics of the printed layer to the transfer target. It is intended to provide

However, as a result of repeated studies by the inventors of the present invention to achieve the above object, a base for hydraulic transfer printing in which the occurrence of slackness is further suppressed by making the moisture content in the width direction of the film extremely uniform They found that a film can be obtained, and completed the present invention.

That is, the gist of the present invention is a base film for liquid pressure transfer printing containing a polyvinyl alcohol resin (A) as a main component, wherein the maximum value xmax and the minimum value x (% by weight) of the moisture content x (% by weight) in the width direction of the film The present invention relates to a base film for hydraulic transfer printing having a difference in xmin of 0.3 or less and an average moisture content M in the width direction of the film of 2 to 5% by weight.
Furthermore, the present invention also relates to a method for producing the base film for hydraulic transfer printing.

INDUSTRIAL APPLICABILITY The base film for hydraulic transfer printing of the present invention suppresses the occurrence of slack, and therefore has excellent design printability and transfer properties, and can be suitably used for hydraulic transfer printing of high-definition designs.

The present invention will be specifically described below.
The base film for hydraulic transfer printing of the present invention is a film containing a polyvinyl alcohol-based resin (A) as a main component, and the maximum moisture content x (% by weight) x _m in the width direction of the film
The difference between _ax and the minimum value x _min is 0.3 or less, and the average moisture content M in the width direction of the film is 2 to 5% by weight.
Hereinafter, the base film for liquid pressure transfer printing may be abbreviated as "base film", polyvinyl alcohol as "PVA", and polyvinyl alcohol resin as "PVA resin".

In the present invention, the maximum value x of the moisture content x (% by weight) in the width direction of the base film
If the difference between _max and the minimum value x _min is too large, slack is likely to occur when the film roll is unwound and used after being stored.
Maximum value x _max and minimum value x of moisture content x (% by weight) in the width direction of the base film
The difference in _min is particularly preferably 0.25 or less, more preferably 0.2 or less. The lower limit of the difference between the maximum value x _max and the minimum value x _min is usually zero.

Further, in the present invention, if the average moisture content M in the width direction of the base film is too low, slack is likely to occur, and the swelling speed of the base film decreases, resulting in curling and other deterioration in transfer characteristics. On the other hand, if the average moisture content is too high, the transfer characteristics such as misregistration will deteriorate.
The average moisture content M in the width direction of the base film is particularly preferably 3.0 to 4.8% by weight, more preferably 3.5 to 4.7% by weight, and most preferably 3.7 to 4.7% by weight. 4.6% by weight.

Furthermore, the minimum value x _min of the moisture content x (% by weight) in the width direction of the base film is preferably 3.7 or more, particularly preferably 3.7 to 4.2, and more preferably 3.
. 8 to 4.0. If the _minimum value xmin of the moisture content in the width direction of the base film is too large, the film tends to become loose when unwound and used.

A base film having a specific range of the difference between the maximum and minimum moisture content in the width direction and the average moisture content can be produced, for example, by drying under specific conditions in the film-forming process.

In the present invention, the difference between the _maximum value xmax and the _minimum value xmin of the moisture content x (% by weight) in the width direction of the base film is a value measured and calculated as follows.
5 from one end of the film to the other end at any position in the machine direction
A total of n pieces of 50 mm×50 mm size are cut out at intervals of 0 mm, and the moisture content xi (i=1, 2, 3, . . . , n) of each section is measured using a Karl Fischer moisture meter. Let x _{max be the maximum value and x min be the minimum value of the entire measured moisture content xi (i=1, 2, 3, . . . , n), and determine the difference between the maximum value x max and the} minimum value x _min .

Moreover, the average moisture content M of the moisture content (% by weight) in the width direction of the base film is a value calculated as follows.

ｎ： フィルム幅方向に沿って５０ｍｍ×ｉ区画ごとに測定した区画総数
ｘi： フィルム幅方向に沿って５０ｍｍ×ｉ区画ごとに測定したｉ区画目の水分率（重
量％）

n: Total number of sections measured for each 50 mm x i section along the film width direction xi: Moisture content (% by weight) of the i section measured for each 50 mm x i section along the film width direction

The base film of the present invention is formed into a film using a film-forming material containing a PVA-based resin (A) as a main component and preferably containing a plasticizer. In the present invention, "mainly composed of PVA-based resin" means that the PVA-based resin is contained in an amount of 50% by weight or more, preferably 60% by weight or more, particularly preferably 70% by weight or more, based on the entire base film. do.

<Film forming material>
First, the film-forming material will be described. The PVA-based resin (A) may be unmodified PVA in a range that does not impair the effects of the present invention (for example, 10 mol % or less, preferably 7 mol % or less), and other monomers modified PVA copolymerized
It's okay. A modified PVA-based resin obtained by chemically modifying hydroxyl groups after saponification can also be used.

Unmodified PVA can be produced by saponifying a vinyl ester polymer obtained by polymerizing a vinyl ester compound.
Examples of such vinyl ester compounds include vinyl formate, vinyl acetate, vinyl trifluoroacetate, vinyl propionate, vinyl butyrate, vinyl caprate, vinyl laurate, vinyl versatate, vinyl palmitate, and vinyl stearate. Among them, it is preferable to use vinyl acetate. The above vinyl ester compounds may be used alone or in combination of two or more.

The modified PVA-based resin can be produced by copolymerizing the vinyl ester-based compound and an unsaturated monomer copolymerizable with the vinyl ester-based compound, followed by saponification.
Examples of the unsaturated monomer copolymerizable with the vinyl ester compound include olefins such as ethylene, propylene, isobutylene, α-octene, α-dodecene and α-octadecene, 3-buten-1-ol, Hydroxy group-containing α-olefins such as 4-penten-1-ol and 5-hexene-1-ol and derivatives such as acylated products thereof; acrylic acid, methacrylic acid, crotonic acid, maleic acid, maleic anhydride, itaconic acid , unsaturated acids such as undecylenic acid, salts thereof, monoesters, or dialkyl esters; amides such as diacetone acrylamide, acrylamide, and methacrylamide; olefin sulfonic acids such as ethylenesulfonic acid, allylsulfonic acid, and methallylsulfonic acid; Its salt etc. are mentioned.

As the modified PVA-based resin, a polyvinyl alcohol-based resin having a 1,2-diol structure in a side chain can also be used. A polyvinyl alcohol resin having a 1,2-diol structure in the side chain can be produced by, for example, (i) a method of saponifying a copolymer of vinyl acetate and 3,4-diacetoxy-1-butene, (ii) acetic acid (iii) saponifying and decarboxylating a copolymer of vinyl and vinyl ethylene carbonate, (iii) saponifying and decarboxylating a copolymer of vinyl acetate and 2,2-dialkyl-4-vinyl-1,3-dioxolane (iv) a method of saponifying a copolymer of vinyl acetate and glycerin monoallyl ether;
etc.

In the present invention, the average viscosity at 20° C. of the 4% by weight aqueous solution of the PVA-based resin (A) is
It is preferably 10 to 70 mPa·s, particularly preferably 15 to 60 mPa·s. If the average viscosity of such a 4% by weight aqueous solution is too low, the design (pattern,
Patterns, etc.) tend to cause printing spots due to lack of film strength when printing. There is a tendency that the design printed on the film is not stable and the throwing power is lowered. On the other hand, if the average viscosity of the 4% by weight aqueous solution is too high, when the printed design is transferred to the transfer target, the transfer target and the base film of the present invention (the base film on which the design is printed)
The adhesiveness to the surface decreases, and there is a tendency for wrinkles and peeling to occur.Although it is possible to suppress the expansion of the film on the water surface, the transfer time is delayed and the viscosity is high, making it difficult to form the film. It tends to be difficult. In addition, the average viscosity at 20 ° C. of the 4 wt% aqueous solution, JIS K 672
6.

Furthermore, the average degree of saponification of the PVA-based resin (A) is generally preferably 70 to 98 mol%, particularly preferably 75 to 96 mol%. If the average degree of saponification of the PVA-based resin is too low, the dissolution of the base film after transfer tends to take a long time. Due to the high viscosity, creases tend to occur during transfer, and even if transfer is performed, film removal tends to be defective. The degree of saponification is measured according to JIS K 6726.

The above PVA-based resins may be used alone, or two or more of them may be used in combination. good too.

The base film of the present invention may further contain a plasticizer (B) in order to impart appropriate flexibility to the film and adjust the swelling speed.
As the plasticizer (B), polyhydric alcohol-based plasticizers are suitable. For example, glycerins such as glycerin, diglycerin and triglycerin; Examples include glycols and trimethylolpropane. Among them, glycerin and polyethylene glycol are preferable because they are easily available and a small amount thereof can provide a plasticizing effect. These may be used alone or in combination of two or more.

The content of the plasticizer (B) is preferably 0.05 to 5 parts by weight, particularly 0.1 to 4 parts by weight, and further 0.2 to 3 parts by weight with respect to 100 parts by weight of the PVA resin. parts by weight, especially 0.
It is preferably 3 to 2.5 parts by weight. If the content of the plasticizer is too high, slack is likely to occur, and dimensional stability is poor when a design is printed on the film surface, which tends to make high-definition printing difficult.

In addition to the PVA-based resin (A) and the plasticizer (B), various additives may be added to the film-forming material, if necessary.

For example, a surfactant is blended for the purpose of improving the releasability of the film from the metal surface of the cast surface drum or belt, such as the metal surface of the endless belt or drum roll that is the film forming apparatus for the base film. be able to. Examples of the above surfactants include polyoxyethylene nonylphenyl ether, polyoxyethylene octyl nonyl ether, polyoxyethylene dodecylphenyl ether, polyoxyethylene alkylallyl ether, polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monolaurate. Polyoxyethylene alkylamines such as palmitate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan monooleate, polyoxyalkylene alkyl ether phosphate ester monoethanolamine salt, polyoxyethylene laurylamine, polyoxyethylene stearylamine etc. These are used alone or in combination of two or more. Among them, polyoxyalkylene alkyl ether phosphate monoethanolamine salt, polyoxyethylene alkylamine, and polyoxyethylene sorbitan monolaurate are preferably used in terms of peelability.

The content of the surfactant is usually preferably 0.01 to 5 parts by weight, preferably 0.03 to 4.5 parts by weight, with respect to the total of 100 parts by weight of the PVA-based resin and the plasticizer. is more preferred. If the content of the surfactant is too low, the peelability between the metal surface of the drum or belt of the film-forming apparatus and the formed film tends to be low, making production difficult. It tends to bleed to the film surface and cause the design printed layer to come off.

Furthermore, within the range that does not interfere with the effects of the present invention, antioxidants (phenol, amine, etc.), stabilizers (phosphate esters, etc.), coloring agents, fragrances, bulking agents, antifoaming agents, antirust agents, UV absorber,
Inorganic powders (silicon dioxide, etc.), organic powders (starch, polymethyl methacrylate, etc.), and other water-soluble polymer compounds (sodium polyacrylate, polyethylene oxide, polyvinylpyrrolidone, dextrin, chitosan, chitin, methyl cellulose, hydroxyethyl cellulose etc.) may be added.

<Production of base film>
A PVA-based resin aqueous solution (film-forming raw material) is prepared by dissolving or dispersing the film-forming material containing the PVA-based resin, plasticizer, etc. in water.
The solid content concentration of the raw material for film formation thus obtained is preferably 10 to 50% by weight, particularly preferably 15 to 40% by weight, further preferably 20 to 35% by weight. If the concentration is too low, the drying load tends to increase and the productivity of the film tends to decrease.
If it is too high, the viscosity will be too high, and it will take time to defoam the raw material for film formation, and there will be a tendency for die lines to occur during film formation.

Next, the prepared film-forming raw material is shaped into a film and dried to produce a base film. In forming the film, for example, a method such as a melt extrusion method or a casting method can be employed, and the casting method is preferable in terms of film thickness accuracy.
When performing the casting method, for example, (i) a method in which the film-forming raw material is passed through a gap using an applicator, bar coater, or the like, and cast onto a casting surface such as a metal surface;
) A method of discharging from a slit such as a T-shaped slit die and casting it on a casting surface such as an endless belt or a metal surface of a drum roll, etc. Casting the raw material for film formation and drying it to form the base film of the present invention. can be manufactured.

The temperature of the film-forming raw material at the film-forming raw material discharge portion of a T-shaped slit die or the like is preferably 60 to 98°C, particularly preferably 70 to 95°C. If the temperature is too low, the viscosity of the raw material for film formation will increase, resulting in poor fluidity, which tends to reduce the productivity of the base film.

The surface temperature of the casting surface during casting of the raw material for film formation is preferably 50 to 150°C, particularly preferably 55 to 140°C, further preferably 60 to 95°C. If the surface temperature is too low, the moisture content of the film tends to be high due to insufficient drying, and blocking tends to occur. The moisture content deviation in the direction increases, and the film tends to become loose.

After casting, the film-forming material is dried on the casting surface.
Drying is performed by blowing hot air, heating the casting surface such as the metal surface of an endless belt or drum roll, drying by hot rolls, drying by blowing hot air on the film using a floating dryer, far-infrared equipment, dielectric heating. Drying by an apparatus or the like can also be used in combination.
In the present invention, it is preferable to dry by blowing hot air in a hot air dryer, and it is particularly preferable to perform drying in at least two hot air dryers.

In the present invention, the drying process is a process in which the film-forming raw material is discharged onto the casting surface (such as the metal surface of an endless belt or drum roll), dried to form a film, and peeled off from the casting surface. say.

The drying temperature in the drying step is preferably 50 to 150 ° C., more preferably 60
145° C., and the drying time is, for example, 1 to 20 minutes, more preferably 1 to 10 minutes. If the drying temperature is too high, it tends to be difficult to adjust the moisture content of the film, and if it is too low, drying tends to be insufficient and productivity tends to decrease. On the other hand, if the drying time is too long, productivity tends to decrease, and if it is too short, the drying tends to be insufficient and the average moisture content of the film tends to be too high.

A base film that satisfies the specified moisture content of the present invention can be produced by drying with hot air in the drying process and controlling the drying conditions to specified conditions.
In the present invention, in order to obtain a base film with very little variation in moisture content, the temperature distribution in the width direction of the cast surface when casting the raw material for film formation in the continuous casting method must be uniform, and the average temperature of the film must be The relationship between moisture content and drying speed is important, and by controlling the drying temperature in the drying process, the temperature distribution in the width direction of the cast surface and the average moisture content of the base film can be adjusted, resulting in a base film with little sagging. can be obtained.

In the present invention, it is preferable to dry by changing the drying temperature in stages. For example, the temperature is gradually increased from the start of drying until the film reaches a predetermined average moisture content. It is effective to reach the maximum drying temperature and then gradually lower the drying temperature to finally reach the desired moisture content.

Specifically, when adjusting the moisture content in the width direction of the base film uniformly, for example, in the drying process, 25 to 50% (preferably 30%) from the beginning of the entire drying process (distance)
~45%) can be adjusted by drying the average moisture content in the width direction of the film to 10% by weight or less.
The average moisture content is preferably 8% by weight or less, particularly preferably 6% by weight or less, particularly preferably 3.7 to 5% by weight. If the average moisture content in the width direction of the film from 25% to 50% in the entire drying process is too high, the moisture content distribution in the width direction of the obtained base film becomes uneven and slack is likely to occur.

At this time, with respect to the drying temperature (previous drying temperature) until the average moisture content in the width direction of the film is 10% by weight or less, the subsequent drying temperature (second drying temperature) is 95% or less (especially preferably is 80 to 95%, more preferably 80 to 90%).
If the drying temperature in the latter stage is too high, the temperature distribution in the width direction of the cast surface will become uneven, and the moisture content distribution in the width direction of the resulting base film will become uneven, making it easier for slack to occur. It has a high moisture content and tends to be difficult to peel off.

The drying temperature in the first stage is preferably 110 to 150° C., particularly 120° C.
~145°C is preferred. The drying temperature in the latter stage is preferably 60 to 130°C, more preferably 70 to 125°C.

Furthermore, the last 15-35% (preferably 20-30%) of the total drying process (distance) is
° C. or lower (particularly preferably 60 to 90° C., more preferably 70 to 85° C.).

In addition, in order to uniformly adjust the moisture content in the width direction of the film, it is also preferable to change the drying temperature in two or more stages for drying.
5%) at the distance (each drying temperature x drying distance at that temperature) / total film forming speed (drying amount at the previous stage) at the distance (55%) at the latter stage (each drying temperature x at that temperature It can be adjusted by drying under temperature conditions such that the sum of (drying distance)/film forming speed (drying amount in the latter stage) is 95% or less (preferably 80 to 90%).
For example, at a film forming speed of 12 m / min, drying temperature 120 ° C.-130 ° C.-115 ° C.-100
C. and the drying distance at each temperature is the same, the drying amount in the latter stage is 108% of the drying amount in the preceding stage.
Drying at multiple stages of drying temperatures can be carried out, for example, by passing the film through a plurality of hot air dryers set at respective temperatures.

In the present invention, after the drying step, the film may be heat-treated as necessary.
The heat treatment method is not particularly limited, and examples thereof include hot rolls (including calender rolls), hot air, far-infrared rays, and dielectric heating. The surface to be heat-treated is preferably the surface opposite to the surface in contact with the cast surface (the metal surface of endless belts, drum rolls, etc.), but there is no problem with nipping.

The heat treatment is usually preferably performed at 50 to 140 ° C., more preferably 60 to 13
0°C. If the temperature of the heat treatment is too low, the film surface in contact with the cast surface curls strongly, and problems tend to occur in the printing and transfer processes.
The resulting base film tends to be less water-soluble. Furthermore, the time for the above heat treatment is
Normally, it is preferable to set the time to 0.5 to 15 seconds.

<Base film>
Thus, the base film of the present invention is obtained, peeled from the cast surface, subjected to heat treatment as necessary, and then wound around a core tube to prepare a film roll.

The base film obtained by forming the film as described above, for example, is subjected to a conventionally known moisture-proof packaging treatment so as not to cause a change in the moisture content described above, and is suspended in an atmosphere of 10 to 25 ° C. Saving is preferred.

In the present invention, if necessary, before winding the film-formed base film, the end portion of the film is slit into the product size and then wound (on-line slitting), or once the base film is manufactured, it is wound. After winding the film after coating, it is preferable to slit the end of the film into the size of the unwound product again, wind it up (offline slitting), and store it suspended in the air as a film roll as described above.

The film width of the base film obtained above is appropriately selected depending on the size of the product, etc., but it is usually preferably 300 to 4000 mm, particularly 500 to 3 mm.
000 mm, more preferably 700 to 2000 mm. If the width is too narrow, the production efficiency tends to decrease, and if it is too wide, slack tends to occur and control of the film thickness tends to be difficult.
Furthermore, the film length of the entire film is preferably 500 m or longer, particularly 700 m or longer, and more preferably 1000 m or longer in view of the efficiency of using the film. Incidentally, the lower limit of the film length is usually 100 m.

In addition, the base film of the present invention usually has a thickness of 20 to 50 μm, preferably 2 μm.
5 to 47 μm, particularly preferably 30 to 45 μm, more preferably 35 to 42 μm.
If the film is too thin, the printed film will swell quickly and transfer problems will tend to occur. tends to increase.

The thus-obtained base film of the present invention is excellent in design printing aptitude and is useful for transferring a design to a transfer-receiving material having an uneven shape.

The base film of the present invention can be used for known general hydraulic transfer methods such as a continuous hydraulic transfer method and a batch hydraulic transfer method.
The material of the object to be transferred is not particularly limited, and for example, a plastic molded body, a metal molded body, a wooden molded body, an inorganic molded body such as glass, or the like can be used. Further, its shape is not particularly limited, and it may be flat or have various three-dimensional shapes.

EXAMPLES The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples as long as the gist thereof is not exceeded.
In addition, "parts" and "%" in the examples mean weight standards.

<Example 1>
[Preparation of base film]
4% aqueous solution viscosity 30 mPa s (20 ° C.), 100 parts of PVA with an average saponification degree of 88 mol%, 1.5 parts of glycerin as a plasticizer, 7 parts of starch, polyoxyalkylene alkyl ether phosphate ester mono Dissolve 1.0 part of ethanolamine salt in water and
. A 5% aqueous dispersion was obtained. Then, using the aqueous dispersion, a belt film-forming machine equipped with an endless belt made of stainless steel was used to form a film according to the casting film-forming method under the drying conditions shown in Table 1,
A base film was obtained (film width: 1000 mm, film length: 1000 m, film thickness: 40 µm).
Using the obtained base film, the moisture content, the presence or absence of slackness, and the printing properties were evaluated. Table 1 shows the results.

[Moisture content x in the width direction of the base film]
(Evaluation method)
From the obtained base film with a film width of 1000 mm, samples for moisture content measurement were cut out from one end to the other end in a size of 50 mm×50 mm at intervals of 50 mm in the width direction. After weighing the film weight (W) of each cut film sample with an electronic balance, the film sample was immersed in 15 ml (S) of dehydrated methanol having a moisture content of 0.03% or less, and the film was dried at room temperature for 1 hour. extract the water inside. 10 ml of extract (E
) was measured, and the film moisture content x (% by weight) was calculated from the following formula.

Ｆ： カールフィッシャー試薬の力価（ｍｇ／ｍｌ）
Ｖ： 抽出液１０ｍｌの滴定に用いたカールフィッシャー試薬量（ｍｌ）
Ｂ： 脱水メタノール１０ｍｌの滴定に用いたカールフィッシャー試薬量（ｍｌ）
Ｗ： ５０ｍｍ×５０ｍｍサイズにしたフィルム試料の重量（ｇ）
Ｅ： カールフィッシャー測定に使用した抽出液の量（ｍｌ）
Ｓ： フィルム試料の水分抽出に使用した脱水メタノールの量（ｍｌ）

F: Potency of Karl Fischer reagent (mg/ml)
V: Karl Fischer reagent amount (ml) used for titration of 10 ml of extract
B: Amount of Karl Fischer reagent used for titration of 10 ml of dehydrated methanol (ml)
W: Weight (g) of film sample with a size of 50 mm x 50 mm
E: Amount of extract used for Karl Fischer measurement (ml)
S: Amount (ml) of dehydrated methanol used to extract moisture from the film sample

〔slack〕
(Evaluation method)
In an environment of 23° C. and 50% RH, the film was unwound from the roll sample on which the base film was wound, and the unwound film was passed over two horizontal guide rolls placed at the same height 2 m apart. In the post-winding device, after unwinding the film, a tension of 50 to 80 N per 1 m of film width is applied to the film at an arbitrary length, and the film is temporarily stopped on two guide rolls. Based on the height through which the film passes, the difference in height between the guide rolls up to the hanging portion over the entire width of the film was measured and evaluated as follows.
In measuring the height difference, an ultrasonic displacement sensor (UD-300 manufactured by Keyence Corporation) is run horizontally on the film in the width direction for detection. In addition, the sensor installation position in the flow direction is set at the central portion, which is the same distance from the two guide rolls.
(Evaluation criteria)
〇・・・The difference in height from the reference height to the part that hangs the most is 10 mm or less ×…The difference in height from the reference height to the part that hangs down the most is greater than 10 mm

[Printability]
When a design for transfer was printed on the surface of the obtained base film for transfer printing, the appearance of the film was visually observed and evaluated as follows.
○・・・No appearance defects ×・・・Wrinkles

<Example 2, Comparative Examples 1 to 3>
A base film was produced and evaluated in the same manner as in Example 1, except that the drying conditions were changed as shown in Table 1. Table 1 shows the results.

From the results in Table 1 above, the base films of Examples 1 and 2 satisfy the specific conditions for the moisture content in the width direction of the film, so the film unwound from the roll sample does not slack, and printing is possible. No defects such as wrinkles from time were observed.
On the other hand, Comparative Examples 1 to 3 where the moisture content in the width direction of the film does not satisfy the specific condition
In this case, the film slacks, causing problems such as wrinkles during design printing, and cannot be put to practical use as a base film for hydraulic transfer printing.

The base film for hydraulic transfer printing of the present invention is excellent in printability, including the interior and exterior parts of automobiles, and is suitable for hydraulic transfer printing applications such as the exterior of mobile phones, various electrical appliances, building materials, and household and daily necessities. , can be widely applied.

Claims (4)

A base film for hydraulic transfer printing containing a polyvinyl alcohol-based resin (A) as a main component, wherein the maximum value x _max and the minimum value x _min of the moisture content x (% by weight) in the width direction of the film
difference is 0.3 or less, and the average moisture content M in the width direction of the film is 2 to 5% by weight. 2. The base film for hydraulic transfer printing according to claim 1, wherein the _minimum value xmin of moisture content x (% by weight) in the width direction of the film is 3.7 or more. 0.05 to 5 plasticizer (B) with respect to 100 parts by weight of polyvinyl alcohol resin (A)
3. The base film for hydraulic transfer printing according to claim 1, containing parts by weight. The base film for hydraulic transfer printing according to any one of claims 1 to 3, wherein the width is 300 to 4000 mm and the thickness is 20 to 50 µm.