KR100457696B1 - Transparent film for inkjet printing having excellent ink absorbency and good transparency, durability and water resistance - Google Patents

Abstract

PURPOSE: A transparent film for inkjet printing is provided to have an excellent ink absorbency, a good transparency, durability and water resistance and not to discolor even though storing for a long time. CONSTITUTION: The transparent film for an inkjet printing comprises an ink absorbing layer on at least one side of a substrate. The ink absorbing layer has a glass transition temperature of 40 to 90 deg.C and is composed of 40 to 80 wt.% of an acrylic copolymer having a hydroxyl value of 10 to 80 mgKOH/g and an acid value of 40 to 100 mgKOH/g and 20 to 60 wt.% of a hydrophilic resin. The ink absorbing layer is applied in a thickness of 5 to 15 micrometers.

Description

Inkjet Transparency Film

The present invention relates to a transparent film for inkjet, and more particularly to a transparent film useful as an inkjet output device, an OHP film, an advertising design and a transparent film for photomasks.

Inkjet printing is being used in a variety of industries and offices due to its low cost, near-laser printing performance, and printing speed.

In addition, the inkjet printing method is popular in the office printer market with various colors and high quality color reproduction.

However, until now, the printer device and related software markets have been led by several companies, and therefore, inkjet films have been released to suit the characteristics of each manufacturer.

On the other hand, up to now, the electro-transfer OHP film is composed of a hydrophobic coating layer, and the hydrophobic coating layer is thermally compressed with the toner to form a desired image, so that the ink of the aqueous or aqueous / high boiling organic solvent used in the inkjet method can be absorbed well. There was a disadvantage.

Therefore, the coating layer of the transparent film used in the inkjet method is designed by adding a hydrophilic natural or synthetic water-soluble resin to design a surface layer suitable for the aqueous or aqueous / high boiling point organic solvent used in the inkjet method.

However, simply adding a hydrophilic water-soluble resin to the hydrophobic resin cannot improve the ink absorbency of the coating layer. Therefore, it is necessary to design a hydrophobic resin suitable for inkjet applications.

In addition, addition of the hydrophilic water-soluble resin lowers the water resistance of the ink absorbing layer, and therefore, it is required to balance ink absorption and water resistance. In addition, since the hydrophilic water-soluble resin lowers the adhesion to the base film, in order to compensate for this, hydrophobic resins having excellent adhesion are added.

On the other hand, the vertical diffusion and the side diffusion of the ink are closely related to the absorbency, drying time, and resolution of the ink. To some extent, ink diffusion forms a uniform image and accelerates surface drying, but excessive ink diffusion There was a problem of reducing the resolution of the image.

In order to solve this problem, U.S. Patent No. 4,956,230 discloses hydrophobic resins such as cellulose acetate, polyvinyl foam, and polysulfone, and hydrophilic aqueous solutions such as polyvinylpyrrolidone, poly (N, N-dimethylacrylamide), and polyethyloxazoline. An inkjet transparent film having an ink absorbing layer mixed with a resin is provided.

In addition, US Pat. No. 5,206,071 introduces an ink absorbing layer composed of a hydrogel and a high molecular weight ammonium salt. US Pat. No. 5,521,002 introduces a coating layer composed of a hydrophilic water-soluble resin, ethyl cellulose, polyalkyl alcohol and a filler. Disclosed are a transparent film for an inkjet and a method for manufacturing the same.

However, such a variety of inkjet transparent film research has not solved the problems of ink absorbency and water resistance limitation and resolution.

An object of the present invention is to add a hydrophilic water-soluble resin to the ink absorbing layer and to design a hydrophobic resin suitable for the ink-absorbing layer to be suitable for the inkjet transparent film, excellent ink absorption in the ink-jet output device is suitable for high-speed output, excellent transparency on the OHP The transparent image is not only useful as a film for OHP, but also excellent in durability and durability, and color does not change even when stored for a long time, thereby providing an inkjet transparent film that can be used for advertisement design or photomask.

The inkjet transparent film of the present invention for achieving the above object has an ink absorbing layer on at least one side of the substrate, wherein the ink absorbing layer has a glass transition temperature of 40 ~ 90 ℃, a hydroxyl value of 10 ~ 80mgKOH / g, acid value It is characterized by consisting of 40 to 80% by weight of hydrophobic polymer resin of 40 to 100mgKOH / g and 20 to 60% by weight of hydrophilic water-soluble resin.

The present invention will be described in more detail as follows.

The hydrophobic polymer resin constituting the ink absorbing layer of the present invention is an acrylic copolymer, which not only binds the hydrophilic water-soluble resin and silica after applying and drying the ink absorbing layer to the substrate, but also provides adhesion and water resistance to the substrate, Prevents stickiness of the resin and gives a dry surface property.

In this case, the acrylic copolymer has a glass transition temperature (Tg) of 40 to 90 ° C, a hydroxyl value of 10 to 80 mgKOH / g, and an acid value of 40 to 100 mgKOH / g, and when it is satisfied, the range does not inhibit the effect of the invention. There are no restrictions on the constituents or other physical properties such as molecular weight and solubility factor.

Here, the glass transition temperature of the acrylic copolymer is 40 ~ 90 ℃, preferably 45 ~ 80 ℃, if it is lower than 40 ℃ the ink strength of the ink absorbing layer after the ink absorbing layer is applied on the substrate and there is a sticky and wet touch It is not preferable because the surface scratches caused by the friction of the injection nozzle is weakened, and if it is higher than 90 ° C., the adhesion with the plastic film as the base material becomes poor.

In addition, the hydroxyl value of the acrylic copolymer is 10 to 80 mgKOH / g, preferably 15 to 70 mgKOH / g. If the hydroxyl value is less than 10 mgKOH / g, adhesion with the substrate is insufficient and ink diffusion is lowered. The absorption and drying performance of the resin are not deteriorated, and when the hydroxyl value exceeds 80 mgKOH / g, the dryness of the surface after the ink absorption is deteriorated, the surface hardness is lowered, and durability and storage properties are poor.

The acid value of the acrylic copolymer is 40 to 100 mgKOH / g, preferably 45 to 90 mgKOH / g. If the acid value is less than 40 mgKOH / g, the adhesion to the substrate is insufficient and the water absorption and drying performance of the ink are deteriorated. If it does not exceed 100mgKOH / g, the water resistance is extremely degraded, there is a problem that the durability and storage after the output is poor.

In the entire ink absorbing layer applied on the substrate of the inkjet transparent film of the present invention, the content of the acrylic copolymer is preferably 40 to 80% by weight. If the content is less than 40% by weight, adhesion to the substrate is rapidly increased. Deterioration, water resistance is lowered, poor durability after output is not good, and if it exceeds 60% by weight, the ink is not absorbed well, so that the drying time is slow and the ink is smeared from the surface, the resolution is reduced.

On the other hand, the copolymerization component constituting the acrylic copolymer is a copolymer composed of acrylic acid or methacrylic acid, and alkyl esters thereof, wherein the copolymerizable component is as follows.

First, alkyl acrylates include methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, butyl acrylate, ethylhexyl acrylate, 2-phenoxyethyl acrylate, and the like. Hydroxypropyl acrylate, methyldiaminoethyl acrylate, ethyldiaminoethyl acrylate and the corresponding methacrylate, and acrylamide, diacetoacrylamide, acrylonitrile, vinyl acetate, styrene, vinyltoluene, vinyl ether Vinyl monomers in which a dicarboxylic acid component and a bisphenol A component are combined with vinyl alcohol, maleic anhydride, and the like.

In addition, the acrylic copolymer is prepared by a solution polymerization method, and the polymerization method thereof is a 1,000 ml polymerization reactor equipped with a cooler, a thermometer and an inlet is installed in a temperature control tank, the inside of the reactor is replaced with nitrogen, and then 120 parts by weight of ethanol. After the addition, the temperature was raised to 80 ° C., 200 parts by weight of the prepared monomer mixture and 1.0 part by weight of AIBN (azobis (isobutyronitrile)) were added thereto. Then, the mixture was reacted for 3 hours with stirring at 200 rpm at the same temperature, and then a mixed solution of 3.0 parts by weight of AIBN and 30 parts by weight of methyl ethyl ketone was prepared, added only 1/3 of it, and aged for 1 hour, and then the mixed solution. One-third of the total amount was added, and finally, after one hour of aging, the final one-third was added and the post-reaction was carried out for three hours. The solid content was adjusted to 50% with 50 parts by weight of ethanol, and then cooled and discharged. Obtain a copolymer.

On the other hand, the hydrophilic water-soluble resin constituting the ink-absorbing layer of the inkjet transparent film of the present invention is not limited, polyvinylpyrrolidone resin or its copolymer, polyvinyl alcohol or its copolymer having excellent water adsorption properties can be used. .

Here, as the polyvinylpyrrolidone resin, a copolymer of polyvinylpyrrolidone resin alone, polyvinylpyrrolidone and one compound selected from polyvinylacetate, styrene, dimethylaminoethyl methacrylate and polyacrylic acid, etc. There is this.

The content of such hydrophilic water-soluble resin is 20 to 60% by weight, preferably 25 to 50% by weight based on the dried ink absorbing layer.

If the content is less than 20% by weight, the ink absorbency is lowered, the ink drying speed and the resolution is lowered, which is poor. If the content exceeds 60% by weight, the water resistance is lowered, resulting in problems in durability and storage after printing.

In addition, in the transparent film of the present invention, the ink absorbing layer is a slip agent such as an olefin wax or a silicone wax, an inorganic particle such as silica or calcium carbonate, or an organic material for the purpose of improving the running property of the film within a range that does not impair the effect of the invention. A small amount of particles may be mixed, and a small amount of an additive for adjusting the viscosity of the coating liquid may be used in combination, and there is no limitation on these components or constitutions.

The method for producing a transparent film having such an ink absorbing layer comprises diluting ketone-based, acetone-based, alcohol-based, acetate-based solvents, tetrahydrofuran, toluene, monomethyl ethers of alcohols, etc. alone or in a mixed solvent. A coating liquid prepared by sufficiently stirring and mixing the acrylic copolymer and the hydrophilic water-soluble resin solution is controlled to a desired viscosity, and then applied and dried on a substrate.

There is no restriction on the method of dispersion and filtration of the coating liquid in the present invention, but it is preferable that the mixture is sufficiently stirred and mixed using a mixer, and it is preferable to filter the coating liquid immediately before coating.

At this time, the thickness of the applied ink absorbing layer is 5 ~ 15㎛, if the thickness is less than 5㎛ because it does not absorb all the ejected ink and the ink drying speed is slow, it is not suitable for high-speed output, diffusion to the side It's not good because it gets worse and the resolution goes down.

In addition, if the thickness exceeds 15 μm, there is a problem in that the perfect penetration into the inside and the diffusion to the side are insufficient, and thus, the printing is impossible and the sharpness of the image projected on the OHP is lowered and the price is increased as the thickness is increased.

On the other hand, as the base film in the present invention, a polyester having excellent dimensional stability, heat resistance and weather resistance is preferable. Specifically, as a biaxially stretched polyethylene terephthalate film, the thickness varies depending on the purpose of use, but preferably about 15 to 200 μm. .

More preferably, in order to improve the adhesive force with an ink absorption layer, the polyester film which pre-treated the corona treatment or the polyester copolymer or the acrylic copolymer to the surface is used as a base material.

Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited by the Examples.

Example 1

16.4 parts by weight of polyvinylpyrrolidone and a solution obtained by diluting an acryl-based copolymer having a glass transition temperature, a hydroxyl value, and an acid value as shown in Table 1 at 50% concentration to 78.6 parts by weight of a mixed solvent of methanol and methylcellolsolve (ISP, PVP K-90) 4.9 parts by weight and 0.16 parts by weight of silica (Mizukasil P-50) were added, followed by mixing at 2,500 rpm for 30 minutes to obtain an ink odd layer coating solution.

The coating solution was applied to a biaxially stretched polyester film having a thickness of 100 μm using a Meyer bar # 30 so as to have a thickness of 9 μm, and dried at 150 ° C. for 2 minutes to prepare an inkjet transparent film.

On the other hand, the glass transition temperature of the acrylic copolymer was measured by using a DSC (differential scanning calorimeter, Perkin Elmer, DSC7 series) after completely drying the acrylic copolymer in a 100 ℃ vacuum oven.

The hydroxyl value of the acrylic copolymer was dissolved in 0.5 ml of a 1: 3 mixed solution of acetic anhydride and pyridine at 100 ° C. for 60 minutes, and then 50 ml of pure water and 50 ml of pyridine were added to proceed with acetylation. After titration with 0.5N KOH, it was calculated by the following Equation 1.

Equation 1

In addition, the acid value is a value calculated by dissolving 0.5 g of the acrylic copolymer in acetone 80 ml and neutralizing titration with 0.1 N KOH according to the following formula (2).

Equation 2

Example 2

Next, 15.8 parts by weight of a solution obtained by diluting an acryl-based copolymer having a glass transition temperature, a hydroxyl value, and an acid value as shown in Table 1 to 50 parts by weight to 39 parts by weight of a mixed solvent of methanol and methylcellolsolve for 20 minutes at 2,500 rpm. After mixing, 45 parts by weight of a 10% dilution solution of polyvinyl alcohol (Dongyang Chemical Co., Ltd., Polynol P-24) was gradually added and mixed again to obtain an ink absorbing layer coating solution.

The coating solution was applied to a biaxially stretched polyester film having a thickness of 100 μm using a Meyer bar # 30 so as to have a thickness of 9 μm, and dried at 150 ° C. for 2 minutes to prepare an inkjet transparent film.

Comparative Example 1

An inkjet transparent film was manufactured in the same manner as in Example 1, except that the ink absorbing layer coating liquid had a thickness of 3 μm.

Comparative Example 2

A transparent film for inkjet was prepared in the same manner as in Example 1, except that the compound of Table 1 (C) was used as the acrylic copolymer.

Comparative Example 3

A transparent film for inkjet was prepared in the same manner as in Example 1, except that the compound of Table 1 (D) was used as the acrylic copolymer.

Comparative Example 4

A transparent film for inkjet was prepared in the same manner as in Example 1, except that the compound of Table 1 (e) was used as the acrylic copolymer.

Comparative Example 5

A transparent film for inkjet was prepared in the same manner as in Example 1, except that the compound of Table 1 (bar) was used as the acrylic copolymer.

Comparative Example 6

A transparent film for inkjet was prepared in the same manner as in Example 1, except that the compound of Table 1 (g) was used as the acrylic copolymer.

TABLE 1

Experimental Example

For the transparent films prepared according to Examples 1 to 2 and Comparative Examples 1 to 6, the adhesion between the ink absorbing layer and the substrate, the initial ink absorption, the ink drying speed, the resolution, and the water resistance were measured. Indicated.

Here, the adhesion between the ink absorbing layer and the substrate was evaluated by the number of hatches peeled off after making 100 square hatches in a sample portion of 4 cm in width and length, 180 ° peeled with Scotch tape.

In addition, the initial ink absorbency of the ink may be applied to an inkjet printer (Canon, BJC-4300) immediately after printing the evaluation drawing, covering the clean A4 paper, rubbing it evenly, and then evaluating the degree of staining. Grade 2 and the case where the ink is slightly smeared on A4 paper Grade 2, the case where the ink is much on A4 paper grade 3, and when the ink almost on the A4 paper grade 4.

The ink drying speed was measured by the inkjet printer (Canon, BJC-4300) and the time required for the ink to dry completely after printing the picture for evaluation.

The resolution was printed with an inkjet printer (Canon, BJC-4300) for evaluation and after the ink was completely dried, the bleeding portion of the interface was measured under a microscope (× 200).

Then, the water resistance was printed by an inkjet printer (Canon, BJC-4300) and the ink was completely dried, then wet the cotton swab in water and then pushed the output at a 45 ° angle to measure the surface strength.

As a result, the case of not being pushed at all was rated as 1 grade, the case where the surface layer was slightly pushed out as 2 grade, the case where the surface layer was pushed out a lot, and the grade was 4 grade.

TABLE 2

From the results in Table 2, the transparent film having an ink absorbing layer using an acrylic copolymer satisfying glass transition temperature, hydroxyl value and acid value as a hydrophobic polymer resin, as in the present invention, has excellent ink absorption, high resolution, and It can be seen that not only the adhesion but also the water resistance is excellent.

On the other hand, when the glass transition temperature, the hydroxyl value and the acid value is out of the range, the adhesion with the substrate is poor, the initial ink absorption is poor, the resolution is poor, and the water resistance is poor.

As described in detail above, the acrylic copolymer and the hydrophilic water-soluble in which the glass transition temperature is 40-90 ° C., the hydroxyl value is 10-80 mgKOH / g, and the acid value is 40-100 mgKOH on at least one side of the substrate as in the present invention. An inkjet transparent film having an ink absorbing layer made of resin is excellent in ink absorption and capable of high speed printing using an inkjet output device, and is excellent in adhesion to a support and excellent in water resistance and thus useful as an inkjet film.

Claims (2)

In an inkjet transparent film having an ink absorbing layer on at least one side of a substrate, the ink absorbing layer has a glass transition temperature of 40 to 90 ° C., an acrylic copolymer having a hydroxyl value of 10 to 80 mgKOH / g, and an acid value of 40 to 100 mgKOH / g. An inkjet transparent film comprising 80% by weight and 20 to 60% by weight of a hydrophilic water-soluble resin. The inkjet transparent film of claim 1, wherein the ink odd layer is coated to have a thickness of 5 to 15 μm.