KR20070100506A - Polyester film having high transparency - Google Patents

Abstract

A polyester film of high transparency is provided to improve transparency with maintaining winding and running characteristics by forming a layer in an in-line coating method by using organic particles instead of an anti-blocking agent. A polyester film of high transparency has an anti-blocking layer formed by applying coating solution containing binder resin and organic particles, on at least one surface of a uniaxially oriented polyester base film by an in-line coating method. The organic particle produced in a spherical form has a refractive index different from that of the binder resin below 0.05. The 1~10wt.% of organic particle is added to the 100wt.% of binder resin. The anti-blocking layer has the thickness of 30~200nm after drying. The UV transmissivity of the polyester film measured by a UV transmissivity measuring instrument is over 80 and a surface roughness measured by a three-dimensional contactless surface roughness tester is below 10nm.

Description

Highly transparent polyester film {Polyester film having high transparency}

The present invention relates to a high-transparent polyester film, and more particularly, to a high-transparent polyester film useful in base films such as films for semiconductor materials because of excellent running properties and winding characteristics, and excellent transparency.

Polyester films, particularly PET films, which are used as base films for various films and the like, are particularly required to be thinned in accordance with the trend of high-resolution products required for films for semiconductor materials.

In accordance with the trend of such thinning, the adverse effects of the additives that are conventionally included in consideration of workability and the like during film manufacturing are highlighted. For example, in general, in manufacturing the PET base film, silica should be included as an antiblocking agent in consideration of running properties. Inclusion of the anti-blocking agent may be a method of injecting a particle size of 50 ~ 80㎛ in bulk in PET and a method of making an anti-blocking particle layer only on the surface layer by the coextrusion method. Without the use of an anti-blocking agent, there is a problem that the smell and running characteristics deteriorate. That is, the antiblocking agent serves to improve the slipperiness.

Although the anti-blocking agent is industrially used for this indispensable reason, the anti-blocking agent should be dispersed into fine particles in order not to impair the properties of the PET film, which is basically a thin film. However, in the case of the anti-blocking agent dispersed in fine particles, the dispersibility problem occurs in the PET polymerization step, and complex equipment improvement such as modification of the polymerization process is required for the pretreatment process to secure dispersibility. It has the effect of raising the cost, which causes the problem of impeding economic efficiency. In addition, the finer particles have a limit in securing transparency when the PET film is applied as a base film to a product requiring high transparency by dispersibility being lowered due to pH varying according to polymerization stages.

Accordingly, the present invention uniaxially stretches a coating liquid containing spherical organic particles in a binder resin while seeking ways to secure optical transparency while satisfying running characteristics and winding characteristics in the manufacture of PET films used as base films. As a result of producing base film by in-line coating method after coating on PET base film, it has excellent running characteristics and winding characteristics and does not generate voids between organic particles and binder layer. It was found that it can be secured to complete the present invention.

Accordingly, it is an object of the present invention to provide a highly transparent polyester film which is excellent in running characteristics and winding characteristics and which can secure transparency.

The high-transparent polyester film of the present invention for achieving the above object is coated with at least one surface of the uniaxially stretched polyester base film containing a binder resin and organic particles to the anti-blocking layer by an in-line coating method It is characterized by being formed.

In the present invention, the organic particles are spherical, and the refractive index difference from the binder resin is 0.05 or less.

In the present invention, the organic particles are methyl methacrylate, ethyl methacrylate, isobutyl methacrylate, normal butyl methacrylate, normal butyl methyl methacrylate, acrylic acid, copolymer of methacrylic acid or terpolymer Acrylic particles; Olefinic particles such as polyethylene, polystyrene and polypropylene; Copolymers of acryl and olefins; Or it is characterized in that it is selected from organic particles, such as multi-layer multi-component particles in which the homopolymer is formed on the layer and then coated with a different kind of monomer on the layer.

In the present invention, the binder resin is an unsaturated polyester, methyl methacrylate, ethyl methacrylate, isobutyl methacrylate, normal butyl methacrylate, normal butyl methyl methacrylate, acrylic acid, methacrylic acid copolymer or ternary Acrylic resins such as copolymers; Urethane-based resins; Epoxy resins; And melamine-based resins.

In the present invention, the organic particles are characterized in that it is included so as to add 1 to 10 parts by weight based on 100 parts by weight of the binder resin.

In the present invention, the anti-blocking layer is characterized in that it is formed so as to have a thickness of 30 to 200nm after drying.

In the present invention, the highly transparent polyester film has a UV transmittance measured by a UV transmittance meter of 80 or more, and the surface roughness measured by a method measured by a three-dimensional non-contact surface roughness meter is characterized in that less than 10nm.

The polyester film obtained by this invention is characterized by being a base film.

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

The present invention relates to a polyester film produced by the in-line coating method without the addition of conventional antiblocking agents.

The polyester film according to the present invention is generally selected in-line coating method instead of adding the anti-blocking agent has been added in consideration of the runability and winding characteristics during the manufacturing, using a substitute particle that does not impair transparency will be.

Herein, organic particles are used as particles that do not impair transparency while considering running characteristics and winding characteristics. Examples of representative particles include methyl methacrylate, ethyl methacrylate, isobutyl methacrylate, and normal butyl methacrylate. , Acrylic particles such as normal butyl methyl methacrylate, copolymer of acrylic acid, methacrylic acid or terpolymer; Olefinic particles such as polyethylene, polystyrene and polypropylene; Copolymers of acryl and olefins; Or organic particle | grains, such as a multilayer multicomponent type particle | grains which formed the particle | grains of a homopolymer, and coated the other kind of monomer on the layer, etc. are mentioned.

Such organic particles are specifically spherical or hexahedral and should have a difference in refractive index from that of the binder resin. Here, 'spherical' is the ratio of the minor axis (a) to the major axis (b) in the ellipse is 0.5 <a / b <2, and the relationship between the diagonal (d) in the rectangle is d ² ≤ a ² + b ² Is defined as In the cube, the relationship between the longest axis f between the vertices and the c axis other than the a and b axes is defined as f ² ≤ c ² + a ² + b ² . Preferably the organic particles are spherical.

On the other hand, organic particles preferably have an average particle diameter of about 0.5 μm to 5 μm, and when the particle size is smaller than this, the running characteristics and the winding characteristics are deteriorated. Can be.

As a binder resin which serves as an adhesive for applying such organic particles on a uniaxially stretched polyester film, those having good compatibility with organic particles may be used. Examples of such resins include unsaturated polyester and methyl methacryl. Acrylics such as latex, ethyl methacrylate, isobutyl methacrylate, normal butyl methacrylate, normal butyl methyl methacrylate, acrylic acid, copolymers of methacrylic acid or terpolymers; Urethane-based; Epoxy-based; Or a melamine resin, and the like, and preferably an acrylic resin.

The content of the organic particles is preferably 1 to 10 parts by weight based on 100 parts by weight based on the solid content of the binder resin. If the content of the organic particles is less than 1 part by weight based on 100 parts by weight of the binder resin, the anti-blocking effect is insufficient, and thus it is weak to scratches, and the winding and running characteristics are poor. There may be a problem.

Thus, the crude liquid containing organic particle | grains in binder resin is uniaxially stretched the unstretched polyester film obtained by carrying out the solvent extrusion of the PET pellet, and apply | coats on the uniaxially stretched film. The coating may be performed on at least one surface of the uniaxially stretched film, and the thickness thereof is preferably about 30 to 200 nm based on the thickness after the final drying. If the crude liquid containing the organic particles is applied thinner than 30 nm on the uniaxially stretched film, the organic particles may easily fall off, which is vulnerable to scratching, and the powder may occur. If the crude liquid containing the organic particles is thicker than 200 nm, the viscosity of the crude liquid may be increased. Due to the high in-line coating speed coating line occurs in the coating direction.

After applying the crude liquid containing the organic particles on the uniaxial stretched film, and then preheated and stretched to more than 150 ℃ uniaxial stretching temperature, the stretching conditions at this time is preferably a stretching ratio of 3.0 to 6.0. It is then subjected to a heat setting step, specifically, it is preferably carried out for 5 to 20 seconds at an oven temperature of 200 to 240 ℃. Then, when cooled to room temperature through a cooling roll can be obtained a polyester film having a thickness of 10 to 200㎛, the anti-blocking coating layer containing organic particles on at least one surface.

In this way, in-line coating method, when the coating using organic particles other than the general anti-blocking agent, while maintaining the winding characteristics and running characteristics due to the particle layer, the base film having excellent transparency due to the organic particles having excellent light transmittance You can get it.

The obtained base film can be usefully used as a base film of a semiconductor related product which requires transparency.

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

PET was produced by transesterification and polycondensation reaction from ethylene glycol and terephthalic acid.

The PET pellet was dried under reduced pressure at 120 ° C. for 8 hours, and then fed to an extruder and melted at 280 ° C.

This was wound around a casting drum having a surface temperature of 20 ° C. using an electrostatically applied cast method to cool and solidify, thereby forming an unstretched film. The discharge amount of the extruder was adjusted to adjust the thickness of the unstretched film to 250 μm.

On one surface of the unstretched film, a crude liquid obtained by mixing 0.1 g of polymethyl methacrylate as 4 g of acrylic resin as organic particles was applied to a thickness of 50 nm after final drying using gravure. The polymethyl methacrylate used herein is spherical, coated with polystyrene on the surface, and has a refractive index difference of 0.03 from an acrylic resin.

The longitudinal uniaxial stretched film to which the crude liquid containing organic particles was apply | coated was preheated at 120 degreeC, and it extended | stretched 4 times in the horizontal direction. The film was heat-set at a maximum temperature of 230 ° C. for 10 seconds under a predetermined length, and cooled to room temperature to obtain a polyester film having a total thickness of 16 μm and a thickness of 50 nm of a coating layer.

The winding properties, running characteristics and transparency of the polyester film were evaluated, and the results are shown in Table 2 below. Specific evaluation method is as follows.

(1) Winding characteristics

When slitting, compare the number of bone wrinkles at the winding length of 14000m and the slitting width of 1580mm. And the number of wrinkles shall be two or less good.

(2) UV transmittance

A UV transmittance meter (Agilent 8453, HP) is used to compare light transmittances on a 365 nm basis.

(3) surface roughness

It is measured by a three-dimensional non-contact surface roughness measuring instrument (NT 2000, WYKO).

Examples 2-5

A PET base film was prepared in the same manner as in Example 1, except that a crude liquid having a composition as shown in Table 1 was used as a crude liquid applied on an unstretched film.

Then, the winding properties, running characteristics and transparency of the obtained base film was evaluated in the same manner as in Example 1, and the results are shown in Table 2 below.

 Comparative Example 1

PET was produced by transesterification and polycondensation reaction from ethylene glycol and terephthalic acid. In this case, PET was prepared by including silica having a particle size of 1.0 to 2.0 μm in a resin composition of 0.03 to 0.07 wt%.

This was wound around a casting drum having a surface temperature of 20 ° C. using an electrostatically applied cast method to cool and solidify, thereby forming an unstretched film. By adjusting the discharge amount of the extruder, the thickness of the unstretched film was adjusted to 250um. Then, after preheating to a temperature of Tg or more, 4 times in the longitudinal direction was drawn and cooled to room temperature.

The film was then preheated at 120 ° C. and stretched 4 times laterally. The film was heat set at 230 ° C. for 10 seconds under a predetermined length, and cooled to room temperature to obtain a polyester base film having a total thickness of 16 μm.

About the obtained polyester base film, the winding characteristic, the running characteristic, and transparency were evaluated by the method similar to Example 1, and the result is shown as following Table 2.

Comparative Examples 2 to 4

A PET base film was prepared in the same manner as in Example 1, except that a crude liquid having a composition as shown in Table 1 was used as a crude liquid applied on an unstretched film.

Then, the winding properties, UV transmission characteristics and surface roughness characteristics of the obtained polyester base film in the same manner as in Example 1 was evaluated and the results are shown in Table 2 below.

Example Comparative example One 2 3 4 5 2 3 4 Binder the resin Acrylic resin 99 97.5 95 90 - 100 99 97.5 Polyester resin - - - - 97.5 - - -  particle Organic Particles (1.5㎛) One 2.5 5 10 2.5 - - - Colloidal Silica (80nm) - 0.16 - - - - One - Kaoline (200 nm) - - - - - - - 2.5 Characteristic Refractive Index Difference with Binder Resin 0.02 - - - 0.03 - - 0.07 shape rectangle rectangle rectangle rectangle rectangle - rectangle Plate

In description of the said Table 1, a unit is the weight% based on solid content.

Example Comparative example One 2 3 4 5 One 2 3 4 Winding characteristics ○ ○ ○ ○ ○ ○ X X X Transparency UV transmittance (@uvtransmitability) 87 86 84 82 84 75 88 86 82 Surface Roughness (nm) (Coated Surface) 4 5 8 12 7 28 One 3 7

From the results of Table 2, as in Examples 1 to 4, without using the silica used as an anti-blocking agent, the coating liquid containing the organic particles was applied on the film stretched in the longitudinal direction by the in-line coating method It can be seen that the film has a winding property similar to that of the conventional anti-blocking agent-based base film, but the UV transmittance and surface roughness properties are significantly improved. However, when the content of the organic particles in the anti-blocking layer forming crude liquid is excessive, as in Example 5, the transparency is slightly lowered as compared with Examples 1 to 4.

On the other hand, in the case of adding silica in the conventional bulk (Comparative Example 1), the winding characteristics are excellent, but the transparency is lowered, and by the in-line coating method including inorganic particles, not organic particles as in Comparative Examples 2 to 4 When the blocking layer is formed, it can be seen that the winding characteristics are inferior.

As described in detail above, the polyester film formed by the in-line coating method according to the present invention using a separate organic layer rather than a general anti-blocking agent, the winding properties and running characteristics due to the particles are maintained While being excellent in transparency due to organic particles having excellent light transmittance, it can be usefully used as a base film such as semiconductor-related products requiring transparency.

Claims (8)

A high transparency polyester film having an anti-blocking layer formed by in-line coating by applying a crude liquid containing a binder resin and organic particles to at least one surface of a uniaxially stretched polyester base film. The highly transparent polyester film according to claim 1, wherein the organic particles are spherical and have a refractive index difference of 0.05 or less. The copolymer of claim 1 or 2, wherein the organic particles are methyl methacrylate, ethyl methacrylate, isobutyl methacrylate, normal butyl methacrylate, normal butyl methyl methacrylate, acrylic acid or methacrylic acid. Or acrylic particles such as terpolymers; Olefinic particles such as polyethylene, polystyrene and polypropylene; Copolymers of acryl and olefins; Or organic particles, such as multi-layered multicomponent particles in which different types of monomers are coated on the layer after forming the particles of a homopolymer. The binder resin according to claim 1, wherein the binder resin is a copolymer of unsaturated polyester, methyl methacrylate, ethyl methacrylate, isobutyl methacrylate, normal butyl methacrylate, normal butyl methyl methacrylate, acrylic acid, methacrylic acid Or acrylic resins such as terpolymers; Urethane-based resins; Epoxy resins; And a melamine-based resin. The highly transparent polyester film according to claim 1 or 2, wherein the organic particles are contained in an amount of 1 to 10 parts by weight based on 100 parts by weight of the binder resin. The highly transparent polyester film of claim 1, wherein the antiblocking layer is formed to have a thickness of 30 to 200 nm after drying. The high transparency polyester film of claim 1, wherein the UV transmittance measured by a UV transmittance meter is 80 or more, and the surface roughness measured by a method measured by a three-dimensional non-contact surface roughness meter is 10 nm or less. The high transparency polyester film according to claim 1, wherein the polyester film is a base film.