KR101137970B1 - Biaxially stretched polyester film for flexo-printing plate - Google Patents

Abstract

The present invention relates to a biaxially stretched polyester film for flexographic printing plates, and more particularly, to a biaxially stretched polyester film for flexographic printing plates having excellent adhesiveness with photosensitive resins, excellent antistatic properties and transparency, and excellent running properties. It is about. To this end, the biaxially stretched polyester film for flexographic printing plate according to the present invention has a coating layer having excellent adhesion properties with the photosensitive resin layer on one side of the polyester base layer even after ultraviolet exposure, and the other side including an antistatic layer. It is characterized by.

Polyester film, photosensitive resin, flexographic printing plate, antistatic, adhesive, coating

Description

Biaxially oriented polyester film for flexographic printing plate {BIAXIALLY STRETCHED POLYESTER FILM FOR FLEXO-PRINTING PLATE}

The present invention relates to a biaxially stretched polyester film for flexographic printing plates, and more particularly, to a biaxially stretched polyester film for flexographic printing plates having excellent adhesiveness with photosensitive resins, excellent antistatic properties and transparency, and excellent running properties. It is about.

In general, polyesters, especially polyethylene terephthalate, have excellent structural stability, excellent chemical properties, physical properties, thermal properties, mechanical properties, solvent resistance, durability, chemical resistance, and electrical insulation, and thus are suitable for magnetic recording media, capacitors, and electronics. In addition to parts, packaging and photographic materials, it is widely used in all kinds of industries such as medical, industrial, etc.

Despite these many advantages, however, the problem of static electricity, which is a disadvantage of all polymer films, is not an exception. Polyester is a big problem not only for quality but also for safety due to foreign matter adhesion, sparks, electrical shock, etc. during manufacturing or processing. There is a situation.

In order to solve these electrostatic problems, various methods such as metal deposition, coating on the film surface, and incorporation into the film have been proposed to have electroconductivity or antistatic properties. Considering transparency, economic efficiency, processing processability, and ease of use, It is a well-known fact that the method of applying to is the most useful method.

Functionality impart adhesiveness, antistatic property, slip resistance, light resistance, scratch resistance, antifouling property, antibacterial property or mold release property to the film surface by using inline or offline coating method. There is a problem such as a performance degradation.

The present invention has been made to solve the above problems, an object of the present invention is to provide a biaxially stretched polyester film for flexographic printing plate excellent in antistatic properties and transparency and excellent running properties while excellent adhesiveness with the photosensitive resin. I would like to.

The polyester film for flexographic printing plate according to the present invention for achieving the above object is provided on one side of the polyester base layer, the coating layer excellent in adhesive properties with the photosensitive resin layer even after ultraviolet exposure, the other side is an antistatic layer It is characterized by including.

In addition, the substrate layer is characterized in that it comprises at least one ultraviolet absorber.

In addition, the base layer preferably comprises at least one sunscreen, characterized in that it comprises a sunscreen of 50ppm to 220ppm based on the polyester film.

In addition, the coating layer is characterized in that the water-soluble or water-dispersible resin, the antistatic layer is characterized in that the coating with a resin binder on the film before and after the stretching process using inorganic particles, such as layered silicate mineral.

Hereinafter, the present invention will be described in detail with reference to embodiments and drawings of the present invention. It is to be understood by those skilled in the art that these embodiments are only for describing the present invention in more detail and that the scope of the present invention is not limited by these embodiments in accordance with the gist of the present invention .

According to the present invention, in the production of a polyester film, a surface layer for excellent adhesive properties with a photosensitive resin layer on one side of a polyester base layer and a surface having a low humidity dependence and an antistatic property on the opposite side are composed of at least Provided is a method for producing a polyester film for flexographic printing plate having excellent transparency, UV blocking property, adhesiveness and antistatic property, containing at least one sunscreen agent in one layer.

In the manufacture of flexographic printing plates, a photosensitive resin is coated or extruded on one side of a polyester substrate, and then a protective film is laminated to protect the photosensitive resin, followed by aging, followed by exposure to ultraviolet light (white exposure) on the polyester substrate. It strengthens the bonding force of the ester base material and the photosensitive resin layer. After the white exposure, peel off the protective film, apply UV light (hereinafter referred to as "main exposure") on the photosensitive resin as a mask, develop using solvent or heat, and finally post-exposure Eliminate flutter and at the same time make it resistant to fire. The manufactured rubber printing plate is able to perform flexo printing by installing on a flexographic printing roll by using a super strong double-sided tape on the polyester side.

The main required properties of the polyester film used as the base material in this process should be excellent adhesiveness with the photosensitive resin, and especially good adhesion with the photosensitive resin layer at the end of the white and after exposure. The film must be transparent during the processing process so that the progress of light is not refracted during exposure, so that the resolution can be increased, and the antistatic property is also a major feature that can minimize defects caused by foreign matter adhesion.

The stabilization mechanism of UV stabilizer is expressed in two ways. First, a method of blocking ultraviolet energy, selectively absorbing ultraviolet energy and releasing it as other forms of energy that are not harmful to the polymer material, or suppressing the photolysis initiation reaction by suppressing chromophore of the activated polymer material. Light blocking agents, ultraviolet absorbers, etc. belong to this. Second, radical scavengers, peroxide decomposers, hindered amine stabilizers, etc. are included as a method of inhibiting photolytic growth reactions by reacting with free radicals or hydrogen peroxide to stop free radicals and decomposing peroxides during photodegradation.

UV stabilizers generally used include hydroxy benzophenone series and hydroxyphenyl benzotriazole series. Although benzophenone UV stabilizers have excellent compatibility with resins and are used in various ways, UV absorption ability of 340 nm or more is inferior to benzotriazole UV stabilizers. Benzotriazole-based UV stabilizers have the ability to absorb over a wide range and are mainly used for colorless and high-end products. In addition, there are ultraviolet absorbers such as resorcinol monobenzoate, salicylate, hydroxy benzoate and formamidine. In addition, free radical capture captures free radicals, which are the mediators of oxidation, unlike the previously described methods of eliminating energy sources. Representative ultraviolet stabilizers by free radical capture include hindered amines (HALS), which are easily oxidized to be converted into nitrooxy radicals and react with polymeric radicals to form hydroxyamine ethers. Unlike UV absorbers, hindered amine UV stabilizers have excellent surface protection and can be applied to products with thin cross-sections. In addition, a cyclic imino ester compound having two carbon atoms constituting an aromatic nucleus and an imino ester ring as disclosed in US Pat. No. 4,446,262 may be used as an ultraviolet stabilizer. Imino ester UV stabilizers have been reported to have excellent thermal and oxidative stability.

The reason for using the sunscreen in the present invention is that when the ultraviolet ray passing through the photosensitive resin layer is reflected at the opposite boundary when the photosensitive resin is laminated with UV after the photosensitive resin is laminated, it is hardened to cause a decrease in resolution. . Appropriate UV protection properties are preferably 0.2 to 1.2 on the basis of OD, more preferably 0.3 to 1.0. If the OD is less than 0.2, it is difficult to block the ultraviolet light, causing a decrease in resolution. If the OD is more than 1.2, the manufacturing cost rises as well as a long exposure time takes time.

The film must be transparent during the processing process so that the progress of light is not refracted during exposure, so that the resolution can be increased, and the antistatic property is also a major feature that can minimize defects caused by foreign matter adhesion.

Conventionally known methods for imparting antistatic properties include internal addition using organic sulfonates or organic phosphates, methods for depositing metal compounds, methods for applying conductive inorganic particles, methods for applying anionic or cationic compounds. Internal addition method using an organic sulfonate or organophosphate compound has the advantage of excellent change over time or stability, but has the disadvantage of inhibiting the inherent characteristics of the film support and the antistatic effect, and the method of depositing a metal compound The method of coating the conductive inorganic particles is excellent in antistatic properties and has been widely used for transparent conductive film in recent years, but the manufacturing cost is so high that it is used only for specific purposes. On the other hand, the coating method using an anionic or cationic compound has been applied very widely because the antistatic effect is relatively good and advantageous in terms of manufacturing cost, but has a disadvantage of high humidity dependence.

In the present invention, the imparting antistatic property is characterized by having excellent antistatic properties at a wide range of humidity levels by coating with a resin binder and the like on the film before and after the stretching process using inorganic particles having antistatic properties. As an example of the inorganic particle which has such a characteristic, a layered silicate mineral may be included and you may use 2 or more types together. The mesoporous silicate minerals that can be used include natural and synthetic minerals, which are mesoporous silicate mineral compounds consisting of silica tetrahedral sheets and alumina or magnesium octahedral sheets, typically selected from the group Smectite or Montmorillonite, etc. At least species of mineral compound. Examples of synthetic minerals or synthetic phyllosilicates include LAPONITE® manufactured by Laporte Industries, Ltd. of Charlotte, North Carolina, Megadite and Fluorohectorite, KUNIPIA® manufactured by Kunimine Industries, Ltd. and SUMECTON (registered trademark) and the like can be included, and preferred among them are LAPONITE (registered trademark) and KUNIPIA (registered trademark). These one or more minerals may typically have at least one naturally occurring cation or primary cation such as potassium, calcium, or sodium present in the gallery attracted to the net negative charge on the clay surface and may contain a small amount of water. As a result, the static electricity that accumulates on the surface by external or friction can be challenged. The natural moisture content and internal charge of about 10% has the characteristics to maintain excellent antistatic properties even at a wide range of humidity levels.

The polyester film of the present invention melt-extruded polyester resin having an intrinsic viscosity of 0.4 to 1.0 dl / g and electrostatically applied on a cooling roll at 15 to 35 ° C. to form an unstretched sheet, and then in the longitudinal direction at 70 to 130 ° C. Stretching to 2 to 5 times, preferably 3 to 4.5 times, then to 2 to 5 times, preferably 3 to 4.5 times, transversely at 100 to 140 ° C., followed by 180 to 260 ° C., preferably 210 to After the longitudinal stretching of the biaxially stretched sheet at 240 DEG C to obtain a polyester film, the coating liquid is applied to one or both sides in the step before the transverse stretching to bond or / and charge It becomes possible to manufacture a polyester film having a prevention function.

Although not particularly limited, it is preferable to perform a corona discharge treatment on the surface of the film in order to easily wet the coating liquid or to improve adhesion with the base substrate before applying the coating liquid.

The coating layer for improving the adhesiveness to the photosensitive resin is a water-soluble or water-dispersible resin, the type of resin is suitable for ester, urethane, acrylic, melamine, epoxy, etc. It is common to use it in coalescing form. In addition, surfactants, organic particles, inorganic particles, crosslinking agents, antistatic agents, antioxidants, antifoaming agents, sunscreens, waxes, silicone oils, flame retardants, pigments, dyes, various solvents, and the like can be used in these coating solutions. have.

In order to secure the transparency of the film in the present invention, even if no particles are added or added to the polyester base substrate layer at 50 ppm or less, the particles used at this time are 0.1 to 10.0 μm in size, and silica and carbonate Inorganic particles such as calcium, alumina, aluminum silicate, titanium dioxide, barium sulfate, zirconia and organic particles such as PMMA and melamine can be used in the form of sphere, porosity, plate shape, amorphous form, etc. The coating or co-extrusion to include inorganic particles or organic particles improves runability, and the other side can be coated with a resin to have easy adhesion to photosensitive resins or various coatings.                     

Features and other advantages of the present invention as described above will become more apparent from the following examples. Of course, the present invention is not limited to the following examples.

[Example]

Preparation of Polyester Resin A

80 parts by weight of polyethylene terephthalate pellets prepared by a conventional method and 20 parts by weight of an imino ester sunscreen (Cytec) are dried and melt-extruded in a vacuum twin extruder to prepare a sunscreen master batch chip. .

Preparation of Polyester Resin B

80 parts by weight of polyethylene terephthalate pellets prepared by a conventional method and 20 parts by weight of a benzotriazine-based sunscreen (manufactured by Ciba-Geigyi Co., Ltd.) were dried and melt-extruded in a vacuum twin extruder to prepare a sunscreen masterbatch chip. do.

Example 1

Preparation of Coating Liquid C

A surfactant, a water-dispersible acrylic resin, and a melamine-based crosslinking agent are added to the pure water passed through the ion exchange resin and stirred to prepare a coating solution. The mixture is 100 parts by weight of a water-dispersible acrylic copolymer resin (manufactured by Rohm & Haas), 20 parts by weight of melamine crosslinking agent (manufactured by Cytec), and polyoxyethylene nonylphenyl ether (used as a surfactant) based on non-evaporable components. 2.5 parts by weight of a total solid content of 5.0% of the composition was prepared.

Preparation of Coating Liquid D

Into the pure water passed through the ion exchange resin, laponite, an inorganic fine particle having surfactant and antistatic properties, was added and stirred well to form a nanosol, and then a water-dispersible acrylic resin and a melamine-based crosslinking agent were added and stirred again. A coating solution is prepared. The mixture was 100 parts by weight of acrylic resin, 100 parts by weight of laponite, 10 parts by weight of melamine-based crosslinking agent, and 2.5 parts by weight of polyoxyethylene nonylphenyl ether as a surfactant to prepare a composition having a total solid content of 3.0%.

Preparation of Polyester Film Substrate

Polyurethane terephthalate pellets with an intrinsic viscosity of 0.625㎗ / g containing 20ppm of porous amorphous spherical silica particles with an average particle diameter of 3.0 µm and UV blocking agent content based on the film of the UV-blocking master batch chip (polyester resin A) After mixing to 150ppm and vacuum-dried and melt-extruded in a conventional manner, and then adhered to the cooling drum by electrostatic application method to form an amorphous non-stretched sheet, it is heated again and stretched 3.3 times in the film traveling direction at 105 ℃ to polyester A film substrate is produced.

Production of polyester film for flexographic printing plate

Next, after the corona discharge treatment on both sides of the film, the coating liquid C is applied to the surface layer, and the coating liquid D is applied to the opposite surface by using the Maever bar coating method. The coated film is dried and preheated in a stenter and stretched 3.5 times in the direction perpendicular to the direction of the film in a section of 100 to 140 ° C., followed by heat treatment at 240 ° C. for 14 seconds to provide a 125 μm polyester for flexographic printing plate. A film was obtained. Surface resistance was excellent as 1.2 E + 10.

[Example 2]

100 parts by weight of a water-dispersible copolymerized urethane resin (manufactured by Nippon-Ink Co., Ltd.) instead of acryl of the coating solution C was used, and the solids were coated in the same manner as in Example 1 except that the coating was made using a 5.0% composition.

EXAMPLES 3-4

The polyester resin A, which is a sunscreen master batch chip, was used in the same manner as in Example 1 except that the film-based sunscreens were used to have 50 ppm and 220 ppm, respectively.

[Example 5]

The polyester resin B, which is a sunscreen master batch chip, was used in the same manner as in Example 1 except that the film-based sunscreen agent was used to have a content of 220 ppm.

[Example 6]

The polyester resin A and the polyester resin B, which are UV blocking master batch chips, were used in the same manner as in Example 1, except that the film-based sunscreens were used to be 80 ppm and 220 ppm, respectively.

Comparative Example 1

The same procedure as in Example 1 was carried out except that polyester resin A or polyester resin B, which was a sunscreen master batch chip, was not used.

Comparative Example 2

Polyester resin A, a UV blocking master batch chip, was used in the same manner as in Example 1 except that the film-based sunscreen was used so that the content of the sunscreen was 10 ppm.

Comparative Example 3

A polyester resin A, a sunscreen master batch chip, was used in the same manner as in Example 1 except that the film-based sunscreen agent was used to have a content of 750 ppm.

After evaluating the items shown in Table 1 using the film according to Examples 1 to 6 and Comparative Examples 1 to 3, the results are shown in Table 1 below.

[Table 1]

Transparency OD Adhesion Printing plate precision
[Line / 25mm] White exposure
Time ratio [%] Before exposure After exposure Example 1 ◎ 0.60 ◎ ◎ 250 140 Example 2 ◎ 0.60 ○ ○ 250 140 Example 3 ◎ 0.41 ◎ ○ 180 110 Example 4 ○ 0.69 ◎ ◎ 250 165 Example 5 ○ 0.46 ◎ ◎ 230 130 Example 6 ○ 0.84 ◎ ◎ 250 180 Comparative Example 1 ◎ 0.02 ◎ Ⅹ 150 100 Comparative Example 2 ◎ 0.17 ◎ Ⅹ 150 100 Comparative Example 3 △ 1.50 ◎ ◎ 250 300

As can be seen in Table 1, when the OD is 0.2 to 1.2 as in Examples 1 to 5, the transparency and adhesiveness before and after exposure were excellent, and the resolution of the printed plate was also equivalent to the gravure 250 line printing level. However, when containing too little sunscreen as in Comparative Examples 1 to 3, the transparency is excellent, but the adhesiveness after exposure is reduced, and when too much is contained, the adhesion is excellent but the transparency is poor and the white exposure It can be seen that it takes a lot of time.                     

Various evaluation of the film manufactured in the Example and the comparative example was performed according to the following method.

Adhesive evaluation

After laminating the UV-curable photoresist to the adhesive coating layer of the polyester film, the UV-curable photosensitive resin layer and the polyester film layer are placed on the instron to measure the load applied during peeling. . The result of this evaluation is shown as follows.

◎: not peeled off between two layers

○: 2.5kg / 25mm or more at peeling

Δ: 1.0 or more and less than 2.5 kg / 25 mm at the time of peeling

Ⅹ: less than 0.5kg / 25mm

Transparency rating [%]

The haze value in which the ratio of the scattered light to incident light in% value was measured using a C-light source with a model NDH-1001DP type haze meter of Densoku Kogyo Co., Ltd. The difference in haze is shown by the following criteria. The smaller the deviation of the haze, the better the transparency of the film.

◎: less than 0.1%

○: 0.1% or more but less than 0.5%

Δ: 0.5% or more but less than 1.0%

Ⅹ: 1.0% or more                     

Optical Density (OD) Measurement

OD was measured using a Kodak wratten 18A filter on a Dupont Mcbeth TD 904 Densitometer instrument. Higher OD means higher UV blocking rate.

White exposure time ratio [%] measurement

The time taken to form a floor by exposing the photoresist-coated film on the film side, which means the ratio [%] of the exposure time to the general transparent film, and the lower the ratio, the faster the white exposure time when the floor is formed. . 200% means it takes twice as long.

Print plate precision [line / 25㎜] measurement

The printing plate precision was evaluated by the number of gravure coaters which is equivalent to that when printed on the manufactured printing plate. That is, 180 of the printing plate precision means that the printed matter printed on the flexographic printing plate is of the same quality as that printed using the 180 lines / 25 mm roll of gravure. Higher numbers mean more precise printing.

In the present specification, only a few examples of various manufacturing and analysis experiments performed by the present inventors are described, but the technical idea of the present invention is not limited thereto, but may be variously modified and implemented by those skilled in the art.

As described above, according to the biaxially stretched polyester film for flexographic printing plate according to the present invention, it is excellent in adhesiveness with the photosensitive resin and may have effects such as excellent antistatic property and transparency and excellent running performance.

Claims (5)

Polyester base layer; An adhesive coating layer coated on one surface of the polyester base layer for adhesion with the photosensitive resin layer; And Including an antistatic layer applied to the other surface of the polyester base layer, The polyester base layer comprises at least one sunscreen, and comprises a 50ppm to 220ppm sunscreen based on the polyester film, The adhesive coating layer is formed from a composition comprising a water dispersible acrylic copolymer resin or a water dispersible copolymer urethane resin, a melamine crosslinking agent and a surfactant, The antistatic layer is formed from a composition comprising an acrylic resin, laponite, melamine-based crosslinking agent and a surfactant, polyester film for flexographic printing plate. delete delete The method of claim 1, The adhesive coating layer is a polyester film for flexographic printing, characterized in that the water-soluble or water-dispersible resin. 5. The method of claim 4, The antistatic layer is formed by coating with a resin binder on the film before and after the stretching step by using inorganic particles such as layered silicate mineral, polyester film for flexographic printing plate.