JPS5841752B2 - Transfer printing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for applying transfer printing to an object by floating a water-soluble polymer thin film, particularly a thin film mainly composed of polyvinyl alcohol resin, on the surface of water. The present invention relates to a method for achieving beautiful transfer printing by effectively preventing the occurrence of curling in the copy.

A pattern is printed on a thin film, and this film is floated on the liquid surface with the printed side facing up.Then, the object to be transferred is submerged in the liquid while contacting this film, and the liquid pressure at that time causes the above-mentioned The so-called transfer printing method in which a pattern is transferred to the surface of an object and then the film is dissolved and removed from the surface of the object is disclosed in Japanese Patent Application Laid-Open No. 51-219.
No. 11, JP-A No. 51-21914.

However, when transfer printing is performed by floating a water-soluble polymer thin film on water, water permeates through the water surface only from the bottom of the thin film, and the top surface of the thin film has a printing ink layer on top. It was inevitable that the peripheral edge of the thin membrane would curl upwards due to factors such as the fundamental difference in elasticity on the bottom surface.

When curling occurs, it becomes difficult for stress and strain to escape freely, resulting in wrinkles 2 in addition to curls 1 at the peripheral edge as shown in Figure 1.
As shown in the figure, wrinkles occur, and if they are severe, wrinkles also occur in the center, which may make it difficult to perform uniform transfer printing.

This phenomenon tends to occur particularly when the film thickness is relatively large because the difference between the front and back sides of the film becomes large.

Therefore, giving the membrane a curl in the opposite direction in advance by changing the balance of the surface layer structure on the front and back surfaces or changing the thermal history during the membrane manufacturing process may be a solution, but the above-mentioned difficulties arise. It does not reach the point where it is resolved.

Due to the above reasons, the product rate is improved due to the occurrence of curls,
The transfer surface is not fully utilized, and transfer to objects with complex curved surfaces, vertically elongated objects, and objects with recesses does not proceed smoothly, which limits the field of application of transfer printing.

The present invention completely solves the above-mentioned conventional problems, and is characterized by using a thin film whose edges are heat-treated to make it narrower. When a thin polymer film is floated on the water surface, no curling occurs at the peripheral edge.

■ Wrinkles as shown in Figure 1 do not occur.

■ Therefore, the entire area of the membrane can be used effectively, and there is no complication or failure rate, such as pressing objects while avoiding wrinkles or overestimating the membrane area.

■ Beautiful printing can be performed even if the object has complex unevenness.

This produces a remarkable effect.

Water-soluble polymers that make up the thin film include polyvinyl alcohol, sodium polyacrylate, polyacrylic acid amide, polyvinylpyrrolidone, polyethylene oxide,
Synthetic polymers such as methylcellulose and carboxymethylcellulose, vegetable polymers such as starch, modified starch, dextrin, cellulose, albumin, soybean protein, and gum arabic, animal polymers such as glue, gelatin, casein, and polypeptide, french, and agar. Water-soluble polymers such as seaweed polymers such as sodium alginate can be used, but they have the film strength and elongation that enable multicolor printing, have good swelling ability on the water surface, and are flexible. The most suitable polymer is polyvinyl alcohol resin, which has excellent softening properties and allows a thin film to stretch and develop on the uneven surface of an object while adhering closely to the uneven surface.

Such polyvinyl alcohol resins have various average degrees of polymerization and degrees of saponification, particularly those having an average degree of polymerization of 300 to 3000 and an average degree of saponification of 65 to 97.
Mol% is preferred.

If the average degree of polymerization is too small, the film strength, especially the underwater film strength, will be extremely low, and the film will rupture and the printed pattern will be disturbed when it is transferred to an object using water pressure. On the other hand, if the average degree of polymerization is too high, the strength will be too high. This results in poor tracking of objects and lack of throwing power.

When the average degree of saponification is too low, the elongation, flexibility, and throwing power of the thin film are poor, while when the average degree of saponification is too high, when printing and (especially) when floating on the water surface. It has a large curling property, lacks elongation and flexibility on the water surface, and has poor throwing power during transfer operations.
Furthermore, it tends to be difficult to wash and remove the thin film after transfer.

In addition, when using two or more types of polyvinyl alcohol resins together, even if the average degree of polymerization or average saponification degree of one of them is outside the above range, the average degree of polymerization or average saponification degree of the entire mixture is within the above range. It should be within the range.

In addition, unsaturated carboxylic acids or esters or salts thereof, unsaturated sulfonic acids or salts thereof, α-olefins having 2 to 20 carbon atoms, unsaturated amides, and Saturated nitrile, vinyl ether,
It may be copolymerized with vinyl chloride or the like, or it may be post-modified by means such as acetalization, urethanization, esterification, cyanoethylation, and grafting.

Note that thin films made of polyvinyl alcohol resin alone tend to have an excessively high elongation rate when floating on water.
It is desirable to adjust the extension rate by using other water-soluble polymers such as starch, modified starch, starches such as dextrin, polyacrylic acid amide, polyethylene oxide, methyl cellulose, etc. in combination.

However, it is desirable that the amount of these other water-soluble polymers is 50% by weight or less of the total (that is, the polyvinyl alcohol resin accounts for 50% by weight or more of the total).

When a small amount of boric acid or borax is added to the polymer component that makes up the film, the expansion rate of the film during transfer is moderately suppressed, resulting in good reproducibility of the printed pattern and further improving the ability to throw around objects. .

In addition, by applying an aqueous solution, solvent solution, or dispersion of boric acid or its salt to one or both sides of a thin film and drying it, the same effect can be obtained as when boric acid or its salt is added to the stock solution during film formation. It is possible to suppress the elongation rate and improve the throwing power.

Thin membranes are usually manufactured by casting an aqueous solution containing the above-mentioned components into a membrane, but membranes can also be formed by a hydrous extrusion method.

The thin film preferably has a smooth surface in order to be printed, but if necessary, surface treatments such as satin finish and various embossing treatments may be applied to one or both sides of the thin film.

The thickness of the thin film is desirably selected from a range of 0.01 to 0.1%.

If the film thickness is less than 0.01%, not only the strength of the film will decrease and printability will be impaired, but also the time required for dissolution in the transfer process will be too short, narrowing the transferable range.
Membrane rupture is likely to occur.

On the other hand, if it exceeds 0.1'X, the difference in water content between the front and back surfaces at the water surface during transfer becomes too large, and the curling property at the water surface increases, making it impossible to put it to practical use.

A particularly preferred range is 0.020 to 0.070%.

In the present invention, a thin film whose ends are heat-treated to have a narrow width is used as the thin film.

The heat treatment is performed using a heating bar, a mold, a heating roll, etc. formed into a predetermined frame shape.

The heat treatment temperature depends on the type of water-soluble polymer used8
The temperature is selected from the range of about 0 to 250°C, and the heat treatment time is about a fraction of a second to several tens of seconds.

It is desirable that the heat treatment width be within about 10% from the edge of the membrane.

However, in the case of a large thin film with a size exceeding 0.5, the ratio may be set within about 15%.

Setting the width of the heat treatment at the peripheral edge too large is meaningless in terms of effectiveness, but if the width of the heat treatment is too small, sufficient curl prevention cannot be expected, so at least 1%
Before and after are required.

The heat treatment may be applied not only to the entire area around the edges, but also to only the edges in the long side direction of the film.

Further, heat treatment may be applied to a portion slightly inside the end portion.

It goes without saying that any known printing method can be applied to pattern printing on the thin film.

When floating a printed film on the water surface, depending on the properties of the ink film, it may not be possible to perform the transfer operation as is, but if the ink film is hard, it may be necessary to
The transfer operation can also be performed after applying a solvent or the like to the surface.

When a thin film with heat-treated edges is floated on the surface of water with the printed side facing up, the film stretches uniformly in the vertical and horizontal directions, swells, and
soften.

When an object is pressed against it and submerged in water at an appropriate stretching rate, the membrane wraps around the uneven surface of the object due to hydraulic pressure.

As a simple measuring method to evaluate this performance, the following test is conducted.

Now, a truncated conical shaped grooved cup with a bottom (bottom diameter 65 φ, head diameter 90% φ, height 250%, 50% from the bottom)
A cup with a slit of 2% width and 1% depth) was adopted as a standard object, and from the point when the thin film on the water surface had expanded to a certain extent, the cup was heated 20 crr from the bottom.
A test in which the membrane is pressed down and allowed to settle in water at a speed of Vn Yu is referred to as a throwing power test.

Membranes with poor throwing power tend to break when the cup is submerged in water, or form wrinkles, folds, and polymerization. It was found that the transfer performance of a thin film can be evaluated by the vertical distance from the surface.

In addition, suitability for transfer to curved surfaces with severe irregularities or small curvature, and narrow grooves can be evaluated based on the direction along the above-mentioned slit.

Normally, the water used to float the membrane is just water, but
If the stretching rate of the membrane is large and the printed pattern becomes enlarged and the print becomes unclear, the stretching of the membrane can be appropriately suppressed by appropriately dissolving boric acid, its salts, or phenols in water.

In order to remove the printed thin film after it has been transferred to the object, it may be washed with water by immersing the object in water or running water, spraying it with water, or the like.

If necessary, enzymes may be added to the washing water, acids or bases may be added, and the washing water may be lightly brushed during or after washing.

By such a water washing operation, the film is easily dissolved and removed, leaving only the printed pattern on the surface of the object, completing the desired transfer printing.

A top coat is usually applied over the printed pattern to protect the printed layer.

Next, the method of the present invention will be further explained with reference to Examples.

Hereinafter, "parts" and "%" are expressed on a weight basis unless otherwise specified, except for elongation percentage (%).

The three-component mixtures of Examples 1 and 2 and Comparative Example 1 were dissolved in water to make a 20% aqueous solution, and the mixture was formed into a 20% aqueous solution using a drum casting method at a drum temperature of 95°C to a thickness of 0.
A thin film of 0.035% was produced.

A wood grain pattern was printed on this thin film using a known printing device.

Next, cut this film into a size of 250% x 350%,
The four peripheral edges were heat-treated using a heat sealer under the following conditions.

Floating the thin film with the peripheral edge heat-treated on the surface of water at a temperature of 30°C with the printed side facing up for 55 seconds, the curling at the edge of the membrane was measured when the stretching rate reached 30%. In addition to observing the presence or absence of wrinkles on the membrane surface, from that point on, the cup (bottom diameter 65 mm, head diameter 90%, height 2
A throwing power test was conducted by pressing a 50% slit-bottomed truncated conical cup from the bottom against the membrane at a speed of No. 20 and allowing it to settle in water.

After the throwing power test, the cup was showered with water at room temperature to dissolve and remove the film, and only the wood grain pattern was applied to the sides and bottom of the cup.

The results are shown in Table 1.

Each component was dissolved in water to make a 20% aqueous solution, and a thin film having a thickness of 0.035% was produced in the same manner as in Example 1.

A wood grain pattern was printed on this thin film using a known printing device.

Next, cut this film into a size of 250% x 350%,
The four peripheral edges were heat-treated using a heat roller under the following conditions.

Example 3 Heat treatment temperature: 200°C A thin film subjected to such heat treatment was floated on a water surface at a temperature of 30°C with the printed side facing up, and after 40 seconds, the elongation rate reached 3.
The presence or absence of curls at the ends of the membrane and the presence or absence of wrinkles on the membrane surface were observed at the time when the temperature reached 0%, and from that point on, a cup was pressed against the membrane to perform a throwing power test.

The results are shown in Table 2.

Examples 5 to 8, Comparative Examples 3 to 6 A mixed aqueous solution with the following composition (6% dipropylene glycol (based on the resin) as a commonly used softener and modifier, and 0.4% nonionic surfactant (based on the resin) ) was added.

) was used to produce a thin film with a thickness of 0.035%.

A marble pattern is printed on one side of the thin film, and this is 250%
I cut it to 350% size.

Next, the four peripheral edges of this membrane were heated to a temperature of 180 5% from the edge.
Heat treatment was carried out using a bar sealer at 1 second at 0.degree.

Next, a certain amount of a solvent having affinity with the ink was applied thinly to the printed surface to activate the ink, and then the film was immediately floated on the surface of water at a temperature of 30° C. to perform transfer printing onto the cup.

Note that all of the following comparative examples use membranes that were not subjected to heat treatment.

The results are shown in Table 3.

Example 7, Control Example 5 Enzyme-treated starch membrane (but does not contain propylene glycol) Example 8, Control Example 6 Polyvinylpyrrolidone membrane (but does not contain propylene glycol) Examples 9 to io, Control Example 7 Average A wood grain pattern was printed on a polyvinyl alcohol thin film having a degree of polymerization of 1400, an average degree of saponification of 86.5 mol%, and a thickness of 0.045%.

This film was cut into a size of 250% x 350%, and its four peripheral edges were heat-treated using a heat sealer under the following conditions.

Next, the ink is activated by applying a thin layer of a solvent that is compatible with the ink to the entire printed surface, and then the film is placed, printed side up, on a 0.02% borax aqueous solution at a temperature of 25°C. After 130 seconds had elapsed and the elongation rate reached 45%, transfer printing onto the cup was performed.

The results are shown in Table 4.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing the curling and wrinkling of a thin film floating on the water surface.

Claims (1)

[Claims] 1. Transfer printing in which a water-soluble polymer thin film is floated on the surface of water with its printed side facing up, and then an object is pressed from above and allowed to settle, thereby transferring a printed pattern onto the surface of the object. A transfer printing method, characterized in that the thin film is a thin film whose edges are heat-treated to make it narrower. 2. The method according to claim 1, wherein the water-soluble polymer thin film is a thin film containing polyvinyl alcohol resin as a main component.