KR101945844B1 - Polyester film for optical - Google Patents

Abstract

The present invention relates to an optical hard coat polyester film having no interference fringe phenomenon, high transmittance and low haze.

Description

POLYESTER FILM FOR OPTICAL

The present invention relates to an optical hard coat polyester film having no interference fringe phenomenon, high transmittance and low haze.

The optical film is used as an optical member for a display, and is used as an optical material of an LCD BLU or an optical member for surface protection of various displays such as an LCD, a PDP, and a touch panel.

Such an optical film is required to have excellent transparency and visibility, and a biaxially stretched polyester film excellent in mechanical properties and electrical characteristics is used as a base film.

Since the biaxially stretched polyester film has low surface hardness and lacks abrasion resistance or scratch resistance, when used as an optical member for various displays, surface damage is easily caused by friction with or contact with an object. In order to prevent this, A primer coating layer is formed as an intermediate layer in order to improve the adhesion between the polyester film as a substrate and the hard coat layer.

Acrylic resin, urethane resin or the like is usually used as an intermediate layer in order to remove the light interference phenomenon (rainbow phenomenon) due to the improvement of the adhesion between the base layer and the hard coating layer and the difference in the high refractive index between the hard coating layer and the polyester film. When the same resin is used alone, since the refractive index is about 1.5 in the case of forming the primer coating layer, the refractive index of the hard coat layer is shifted to the refractive index of 1.64 which is the surface refractive index of the biaxially stretched polyester film and the refractive index of the ordinary hard coating layer is 1.52, The optical interference phenomenon due to the difference in the refractive index between the coating layer and the polyester film can not be removed and the optical interference phenomenon is deteriorated in view of eye fatigue and screen visibility when applied to the display member.

In order to improve such eye fatigue, the applicant of the present invention disclosed in Korean Patent Publication No. 10-2011-0034784 that a polyurethane coating composition comprising a polyurethane binder having a refractive index of 1.54 to 1.59 is coated on one surface of a substrate film, Discloses an optical film coated with an acrylic coating composition including an acrylic binder having a refractive index of 1.4 to 1.5 on a surface thereof. In the above-mentioned prior art, the refractive index was controlled by changing the structure of the isocyanate used in the polyurethane coating composition, and it was confirmed that the rainbow phenomenon was improved.

Also, as a prior art for improving the rainbow phenomenon, Korean Patent No. 10-0994051 includes a hard coating layer coated with a hard coating composition containing particles having an average particle diameter of 1 to 30 占 퐉, wherein the hard coating front layer is composed of 500 A hard coating film having a reflectance minimum wavelength band of 占 퐉 占 50 占 퐉 and a refractive index of 1.58 占 0.1 is disclosed. In the above-mentioned prior art, the organic beads selected from the silicone resin and acrylic resin beads are added to the hard coat layer to control the refractive index. However, when organic beads are used for the hard coat layer, the transparency of the hard coat layer itself may decrease, resulting in a problem that visibility is deteriorated.

In order to improve the rainbow phenomenon of the hard coating film, various techniques for controlling the refractive index by controlling the coating composition and the organic or inorganic particles constituting the hard coating layer have been developed, and the refractive index varies depending on the combination of the coating composition and the particles Therefore, studies are being conducted to find a combination for obtaining a desired refractive index.

Korean Patent Laid-Open No. 10-2011-0034784 (April, 2011) Korean Patent No. 10-0994051 (2010.11.05)

An object of the present invention is to provide a primer coating composition having a refractive index intermediate with that of a polyester film and a hard coat layer, the refractive index of which is a combination of a polyester resin and an inorganic particle. The primer coating composition is applied to one side or both sides of a polyester base film And to provide a polyester film for optical use in which rainbow phenomenon is improved by forming a primer coating layer.

The present invention relates to an optical film for hard coating, and more particularly to a polyester film comprising a polyester base film, a polyester resin having a refractive index of 1.4 to 1.6 on one or both sides thereof, and inorganic particles having a refractive index of 1.8 to 2.2, A primer coating layer applied with a coating composition of 1.56 to 1.6, wherein the primer coating layer has a dry coating thickness of 50 to 150 nm.

In the present invention, the inorganic particles preferably have an average particle diameter of 1 to 50 nm.

In the present invention, it is preferable to use surface-modified zirconia as the inorganic particles.

Further, in the present invention, the surface-modified zirconia preferably has an acyl group or an alkylate group on its surface, and Na ⁺ is preferably used as a counter ion.

In addition, the present invention may further include an acrylic resin coating layer having a refractive index of 1.51 to 1.53 on one or both sides of the primer coating layer.

In the present invention, the thickness of the acrylic resin coating layer is preferably 1 to 10 탆.

In the present invention, when the acrylic resin coating layer is formed on one surface, the haze is 1.0 or less, the total light transmittance is 91% or more, and when the acrylic resin coating layer is formed on both surfaces, the haze is 0.5% or less and the total light transmittance is 92% Can be satisfied.

The optical film according to the present invention has an adhesive strength suitable for use as a hard coat film and has a rainbow-improving effect.

Further, when the hard coating layer is further included, the present invention can satisfy excellent optical properties because the total light transmittance is as high as 91% or more and the haze is as low as 1% or less.

1 is a sectional view showing a first embodiment of the present invention.
2 is a sectional view showing a second embodiment of the present invention.
3 is a cross-sectional view showing a third embodiment of the present invention.
4 is a cross-sectional view showing a fourth embodiment of the present invention.

The present inventors have found that an organic binder having a refractive index of 1.4 to 1.6 and a refractive index of 1.8 are required to have an intermediate value between a refractive index of a primer coating layer of an optical film and a refractive index of a refractive index of a hard coating layer of 1.64 To 2.2, and the total refractive index of the coating composition is adjusted to be 1.56 to 1.6, more preferably 1.58, the refractive index of the primer coating layer exhibits a refractive index range similar to that of the base film, thereby improving the rainbow phenomenon And thus the present invention has been completed.

When the average particle size of the inorganic particles is 50 nm or less, specifically 1 to 50 nm, when the hard coat layer is formed on one side of the polyester film, the total light transmittance is 91% or more and the haze is 1% Or less, and when the hard coat layer is formed on both sides, the total light transmittance is 92% or more, and the haze is 0.5% or less, satisfying the physical properties, and the optical property is further improved, thereby completing the present invention.

More specifically, the present invention uses a polyester resin as the organic binder, a zirconia sol as the inorganic particles, and the surface modified zirconia is used to improve the coagulation phenomenon with the binder, The present inventors have completed the present invention by discovering that the pot life of the coating composition is improved.

As shown in FIG. 1, the first embodiment of the present invention is a polyester base film 10, a polyester resin having a refractive index of 1.4 to 1.6 on one side thereof, And a primer coating layer (20) coated with a composition including an inorganic particle having a total refractive index of 1.56 to 1.6.

As shown in Fig. 2, the second embodiment of the present invention is a polyester film comprising a polyester base film 10, a polyester resin having a refractive index of 1.4 to 1.6 and inorganic particles having a refractive index of 1.8 to 2.2 on both sides thereof, And a primer coating layer (20a, 20b) coated with a composition of 1.56 to 1.6.

3, the third embodiment of the present invention comprises a base film 10, a polyester resin having a refractive index of 1.4 to 1.6 and inorganic particles having a refractive index of 1.8 to 2.2 on one side thereof, and having an overall refractive index of 1.56 To 1.6, and an acrylic resin coating layer (30). The present invention also relates to an optical polyester film comprising the primer coating layer (20) and the acrylic resin coating layer (30).

A fourth aspect of the present invention is a polyester resin composition comprising a polyester base film 10, a polyester resin having a refractive index of 1.4 to 1.6 and inorganic particles having a refractive index of 1.8 to 2.2 on both sides thereof, A primer coating layer 20a, 20b coated with a composition of 1.56 to 1.6, and an acrylic resin coating layer 30a, 30b.

However, these embodiments are only intended to explain the present invention more specifically, but are not limited thereto.

Hereinafter, the present invention will be described more specifically.

Base film

The base film used in the present invention is preferably a polyester film, more specifically, a polyethylene terephthalate film because of its excellent light transmittance. Such a polyethylene terephthalate film is preferably a stretched film, and a uniaxially or biaxially stretched film can be used.

The base film may have a thickness of 25 to 250 탆, but is not limited thereto.

Primer coating layer

In the present invention, the primer coating layer comprises a polyester resin having a refractive index of 1.4 to 1.6 and an inorganic particle having a refractive index of 1.8 to 2.2, and has a total refractive index of 1.56 to 1.6. Dispersible emulsion having a refractive index similar to that of the polyester base film can be prepared by the other additives added in the preparation of the aqueous dispersion emulsion in the range of the refractive index of 1.56 to 1.6.

More specifically, the polyester resin preferably has a refractive index in the range of 1.4 to 1.6. By using a polyester resin, it is possible to increase the adhesive force with the base film, and as the refractive index value is higher than that of the other resin composition, the amount of inorganic particles to be used decreases and the cost can be reduced. There is an effect that the cost of the film is reduced because the color change and the physical property deterioration of the chip are reduced when reclaiming the film again.

The inorganic particles are preferably inorganic particles having a refractive index of from 1.8 to 2.2, and are not specifically limited. For example, one or more of ZnO, TiO ₂ , CeO ₂ , SnO ₂ , and ZrO ₂ Can be used. More preferably, zirconia (ZrO ₂ ) is used. More preferably, the use of the surface-modified zirconia is preferable because the coagulation phenomenon with the polyester resin as the binder resin can be improved and the liquid stability can be enhanced. The surface-modified zirconia preferably has an acyl group or an alkylate group on its surface, and Na < ⁺ > is preferably used as a counter ion. The acyl group includes an acetyl group, a propionyl group, a malonyl group, a benzoyl group and the like.

The surface-modified zirconia is produced by reacting a zirconium salt (such as zirconium oxychloride) with an alkali such as sodium hydroxide, potassium hydroxide or ammonia at 10 to 50 ° C to obtain a slurry of zirconium oxide particles Then, the slurry is filtered and washed, and 1 moles of organic acid such as carboxylic acid, hardoxycarboxylic acid, formic acid, and acetic acid is added to 1 mole of zirconium, and the surface treatment can be performed by heat treatment at a water temperature of 170 ° C or higher.

Na + is not limited to being used as a counter ion, and it is preferable to use Na + ions in order to prevent the ion balance from being broken because the ionizer of the polyester binder used as the main binder is NaSO ₃ . When other ionizers are introduced, aggregation of the polyester binder may occur.

By using surface-modified zirconia particles, stability of the liquid solution is enhanced and ILC coating films with stable properties can be obtained in the PET film production process which is a continuous process. It is also preferable to use one having an average particle diameter of 1 to 50 nm. It is more preferable to use an average particle diameter of 1 to 10 nm. When the particle size is less than 1 nm, the particle agglomeration phenomenon is further accelerated to deteriorate the pot life of the composition. When the inorganic particle size exceeds 50 nm, the optical characteristics of the optical film, especially haze, may increase.

More preferably, the inorganic particles may be used in the form of a water-dispersed sol having a solid content of 5 to 40% by weight, wherein the pH is 7 to 9, more preferably 8 to 8.5. When the solid content is 5 wt% or less, it is difficult to add a sufficient amount of inorganic particles, and when the solid content is 40 wt% or more, coagulation phenomenon may occur in the inorganic particle raw material itself.

The present invention is characterized by using a coating composition having a total refractive index of 1.56 to 1.6 including the polyester resin and the inorganic particles. When the refractive index is less than 1.56, a difference in refractive index from the substrate film is large, thereby raising the rainbow phenomenon. The content of the high-refractive-index particles must be higher than the range of the present invention in order to raise the stain of the coating appearance during the production of the film, and the commerciality is deteriorated due to the increase of the cost. When the refractive index exceeds 1.6, the light interference phenomenon (rainbow phenomenon) may increase as the refractive index difference from the hard coat layer increases.

In the present invention, the coating composition for forming the primer coating layer is preferably a polyester resin, a wetting agent, silica having an average particle size of 100 to 200 nm and water-dispersed inorganic particles having a solid content of 5 to 40 wt% Composition.

More preferably, the coating composition for primer coating comprises 5 to 30 wt% of a polyester resin having a refractive index of 1.4 to 1.6, 0.1 to 0.4 wt% of a wetting agent, 0.1 to 0.5 wt% of silica having an average particle diameter of 100 to 200 nm, It is preferable to use a water-dispersible or water-soluble composition containing 0.5 to 30% by weight of water-dispersed inorganic particles of 5 to 40% by weight and having a total solid content of 2 to 10% by weight.

The method of applying the coating composition for forming the primer coating layer may be applied to an in-line coating to be applied to the surface during the stretching process of the polyester film, an off-line coating after the film is formed It is possible. It is also possible to use both of them in parallel.

Preferably, in-line coating is applied simultaneously with the film formation, so that the manufacturing cost is reduced, and the thickness of the coating layer can be changed by the extension magnification.

Acrylic resin coating layer

The present invention may further include an acrylic resin coating layer having a refractive index of 1.50 to 1.54, more preferably 1.51 to 1.53 on one side or both sides of the primer coating layer. The thickness of the acrylic resin coating layer is preferably 1 to 10 mu m.

The acrylic resin coating layer can be used without limitation as long as it is a component for forming a hard coat layer. Specifically, a commercialized product such as AIKA Z-711 product can be used, but the present invention is not limited thereto.

In the present invention, when the acrylic resin coating layer is formed on one surface, the refractive index and the thickness of the primer coating layer are satisfied, and the haze is 1.0 or less and the total light transmittance is 91% or more when the acrylic resin coating layer is formed on both surfaces. , It is possible to satisfy the property that the haze is 0.5% or less and the total light transmittance is 92% or more.

Hereinafter, the present invention will be described in detail with reference to the following examples. However, the present invention is not limited to the following examples.

Methods for measuring the physical properties shown in the following examples and comparative examples are as follows.

1) Total light transmittance measurement

The total light transmittance of the entire film was measured using a total light transmittance meter (Nippon Denshoku 300A).

2) Measurement of refractive index

2-1) Measurement of refractive index of polyester resin for primer coating

The water-dispersed polyester resin composition was coated on a polycarbonate film, dried, and measured at room temperature using a refractometer ABBE refractometer (ATAGO, DR-M2, @ 550).

2-2) Measurement of refractive index of inorganic material

The liquid inorganic fine particles were applied to a polycarbonate film in an amount of 10 to 50% by weight in an aqueous resin solution having a refractive index of 1.52, and then dried. The resultant was dried with a refractometer ABBE refractometer (ATAGO, DR-M2, 550) at room temperature.

Plotting the measurement results, we regarded the particle content and the refractive index as a proportional relation, and predicted the refractive index when the inorganic particles were 100%.

3) Measurement of rainbow phenomenon-1: After the production of optical films according to Examples and Comparative Examples, one side thereof was hard coated (refractive index: 1.52), and the other side was blackened to see if rainbow occurred visually. Visual evaluation was carried out in a dark room under a three-wavelength lamp.

The evaluation criteria are as follows.

Image: Rainbow is not visible and uniform color is seen.

Medium: Rainbow phenomenon appears soft and uniform color

H: The rainbow looks strong and shows a strong color

4) Measurement of rainbow phenomenon-2: After the production of optical films according to Examples and Comparative Examples, one surface thereof was hard coated (refractive index: 1.52), the other surface was blackened, and a visible ray region The reflection pattern was measured.

Phase: Ripple amplitude decreases from 500 to 600 nm compared to ripple amplitude at other wavelengths. Ripple amplitude is less than 1%.

Medium: Ripple amplitude decreases from 500 to 600 nm compared to ripple amplitude at other wavelengths, ripple amplitude is less than 3%

Bottom: When the wavelength range in which the ripple amplitude is reduced is not 500 to 600 nm, or when the wavelength in which the amplitude is decreased is not seen

5) Adhesion measurement with hard coat layer (ASTM B905)

After the production of the optical films according to Examples and Comparative Examples, the adhesive strength between the hard coat layer and the adhesive layer was evaluated after adhesive treatment at room temperature and high-temperature hot water treatment (100 캜, 10 min)

5, 95%, 4, 95, 85%, 3, 85% and 65%, respectively, of the remaining 100% Was set at zero.

6) Dry coating thickness measurement

The cross section of the film was measured with a SEM (Hitachi S-4300) by measuring the full width of the film in the vertical direction of the machine direction (TD) at an interval of 1 m and measuring 30 points within the section, Respectively.

7) Particle Size Measurement

The UPa-UT151 manufactured by Nikkiso Co., Ltd. was charged with 1% of a liquid sample and expressed as an average value.

[Example 1]

Preparation of coating composition (1)

(Zirconia sol having a refractive index of 2.1 and a solid content of 30 wt.%) Having an average particle diameter of 6 nm and an average particle diameter of 6 nm, a silicone-based wetting agent (Dow Corning, polyester siloxane copolymer) %, Surface treatment using Soduim Citrate) and 0.3 wt% of colloidal silica particles having an average particle diameter of 140 nm were added to water, followed by stirring for 3 hours to prepare a polyester coating composition having a total solid content of 5.5 wt% Respectively. The refractive index of the composition was 1.58.

Manufacture of double-coated polyester film

The moisture-removed polyethylene terephthalate chip was placed in an extruder, melt extruded, and then quenched and solidified by a casting drum having a surface temperature of 20 캜 to prepare a polyethylene terephthalate sheet having a thickness of 2000 탆. The prepared polyethylene terephthalate sheet was stretched 3.5 times at 80 DEG C in the machine direction (MD), and then cooled to room temperature. Then, the coating composition (1) was coated on both sides by a bar coating method, heated to 110 to 150 ° C at a rate of 1 ° C per second, preheated and dried, and then drawn 3.5 times in the transverse direction (TD). Thereafter, heat treatment was carried out at 235 ° C in a 5-stage tenter, and the film was relaxed by 10% in longitudinal and transverse directions at 200 ° C to be thermally fixed, thereby preparing a 188 μm biaxially oriented film having a primer coating layer on both sides as shown in FIG.

The thickness of the primer coating layer was 90 nm for the first coating layer and 90 nm for the second coating layer, and their refractive indexes were 1.58.

The physical properties of the obtained optical film are shown in Table 1 below.

[Example 2]

Preparation of Coating Composition (2)

(Zirconia sol having a refractive index of 2.1 and a solid content of 30 wt.%) Having an average particle size of 6 nm and 0.3 wt% of a silicone based wetting agent (Dow Corning, polyester siloxane copolymer), 17 wt% %, Surface treatment using Soduim Citrate), 0.3 wt% of colloidal silica particles having an average particle diameter of 140 nm were added to water and stirred for 3 hours to prepare a polyester coating composition having a total solid content of 5 wt% Respectively. The refractive index of the composition was 1.59.

A double-coated polyester film was prepared in the same manner as in Example 1, and the thickness of the primer coating layer was 80 nm for the first coating layer and 80 nm for the second coating layer, and their refractive indexes were 1.59.

The physical properties of the obtained optical film are shown in Table 1 below.

[Example 3]

Preparation of Coating Composition (3)

(Zirconia sol having a refractive index of 2.1 and a solids content of 30 wt.%) Having an average particle size of 6 nm and an average particle size of 6 nm, a silicone-based wetting agent (Dow Corning, polyester siloxane copolymer) %, Surface treatment using Soduim Citrate) and 0.3 wt% of colloidal silica particles having an average particle diameter of 140 nm were added to water, followed by stirring for 3 hours to prepare a polyester coating composition having a total solid content of 6 wt% Respectively. The refractive index of the composition was 1.57.

Side coated polyester film was prepared in the same manner as in Example 1. The thickness of the primer coating layer was 104 nm for the first coating layer and 104 nm for the second coating layer, and their refractive indexes were 1.57. The physical properties of the obtained optical film are shown in Table 1 below.

[Example 4]

Preparation of coating composition (4)

(Zirconia sol having a solid content of 30 wt%) having a refractive index of 2.1 and an average particle diameter of 6 nm, 0.3 wt% of a silicone based wetting agent (Dow Corning, polyester siloxane copolymer), 10 wt% of an aqueous polyester binder %, Surface treatment using Soduim Citrate) 0.3% by weight of colloidal silica particles having an average particle size of 140 nm were added to water and stirred for 3 hours to prepare a polyester coating composition having a total solid content of 3% by weight Respectively. The refractive index of the composition was 1.6.

Side coated polyester film was prepared in the same manner as in Example 1. The thickness of the primer coating layer was 62 nm for the first coating layer and 62 nm for the second coating layer and their refractive index was 1.6. The physical properties of the obtained optical film are shown in Table 1 below.

[Example 5]

Manufacture of one side coated polyester film

The moisture-removed polyethylene terephthalate chip was placed in an extruder, melt extruded, and then quenched and solidified by a casting drum having a surface temperature of 20 캜 to prepare a polyethylene terephthalate sheet having a thickness of 2000 탆. The prepared polyethylene terephthalate sheet was stretched 3.5 times at 80 DEG C in the machine direction (MD), and then cooled to room temperature. Thereafter, the coating composition (1) prepared in Example 1 was coated on one side by a bar coating method and then heated to 110 to 150 ° C at a rate of 1 ° C / To 3.5 times. Thereafter, the film was heat-treated at 235 ° C in a 5-stage tenter, relaxed by 10% in longitudinal and transverse directions at 200 ° C, and heat set to prepare a 188 μm biaxially oriented film coated on one surface. The thickness of the primer coating layer was 92 nm, and the refractive index was 1.58.

The physical properties of the obtained optical film are shown in Table 1 below.

[Example 6]

Manufacture of one side coated polyester film

The moisture-removed polyethylene terephthalate chip was placed in an extruder, melt extruded, and then quenched and solidified by a casting drum having a surface temperature of 20 캜 to prepare a polyethylene terephthalate sheet having a thickness of 2000 탆. The prepared polyethylene terephthalate sheet was stretched 3.5 times at 80 DEG C in the machine direction (MD), and then cooled to room temperature. Thereafter, the coating composition (2) prepared in Example 2 was coated on one side by a bar coating method, heated to 110 to 150 ° C at a rate of 1 ° C per second, preheated and dried, To 3.5 times. Thereafter, the film was heat-treated at 235 ° C in a 5-stage tenter, relaxed by 10% in longitudinal and transverse directions at 200 ° C, and heat set to prepare a 188 μm biaxially oriented film coated on one surface. The thickness of the primer coating layer was 85 nm, and the refractive index was 1.59.

The physical properties of the obtained optical film are shown in Table 1 below.

[Example 7]

Preparation of coating composition (5)

(Zirconia Sol, CIK) having an average particle diameter of 65 nm and a refractive index of 2.1, 0.3 wt% of a silicone based wetting agent (Dow Corning, polyester siloxane copolymer), 20 wt% of an aqueous polyester binder (refractive index: 1.54) 8 weight% of ZRW E-15) and 0.3 weight% of colloidal silica particles having an average particle diameter of 140 nm were added to water and stirred for 3 hours to prepare a polyester coating composition having a total solid content of 5.5 weight%. The refractive index of the composition was 1.58.

Side coated polyester film was prepared in the same manner as in Example 1. The thickness of the primer coating layer was 89 nm for the first coating layer and 89 nm for the second coating layer, and their refractive indexes were 1.58. The physical properties of the obtained optical film are shown in Table 1 below.

[Example 8]

Preparation of Coating Composition (6)

(Zirconia sol having a refractive index of 2.1 and a solid content of 30 wt.%) Having an average particle diameter of 50 nm and 0.3 wt% of a silicone based wetting agent (Dow Corning, polyester siloxane copolymer), 20 wt% %, Surface treatment using Soduim Citrate) and 0.3 wt% of colloidal silica particles having an average particle diameter of 140 nm were added to water, followed by stirring for 3 hours to prepare a polyester coating composition having a total solid content of 5.5 wt% Respectively. The refractive index of the composition was 1.58.

Side coated polyester film was prepared in the same manner as in Example 1. The thickness of the primer coating layer was 89 nm for the first coating layer and 89 nm for the second coating layer, and their refractive indexes were 1.58. The physical properties of the obtained optical film are shown in Table 1 below.

[Example 9]

Preparation of Coating Composition (6)

(Zirconia sol having a refractive index of 2.1 and a solids content of 30 wt.%) Having an average particle size of 6 nm and an average particle size of 6 nm, a silicone-based wetting agent (Dow Corning, polyester siloxane copolymer) %, Surface treatment using Soduim Citrate), 0.3 wt% of colloidal silica particles having an average particle diameter of 140 nm were added to water, and the mixture was stirred for 3 hours to prepare a polyester coating composition having a total solid content of 6 wt% Respectively. The refractive index of the composition was 1.56.

Side coated polyester film was prepared in the same manner as in Example 1. The thickness of the primer coating layer was 95 nm for the first coating layer and 95 nm for the second coating layer, and their refractive indexes were 1.56. The physical properties of the obtained optical film are shown in Table 1 below.

[Example 10]

A two-side coated polyester film was prepared in the same manner as in Example 1 using the coating composition (1) prepared in Example 1. The thickness of the primer coating layer was 50 nm for the first coating layer and 50 nm for the second coating layer. Their refractive index was 1.58. The physical properties of the obtained optical film are shown in Table 1 below.

[Example 11]

A two-side coated polyester film was prepared in the same manner as in Example 1 using the coating composition (1) prepared in Example 1. The thickness of the primer coating layer was 70 nm for the first coating layer and 70 nm for the second coating layer, Their refractive index was 1.58. The physical properties of the obtained optical film are shown in Table 1 below.

[Example 12]

A two-side coated polyester film was produced in the same manner as in Example 1 using the coating composition (1) prepared in Example 1. The thickness of the primer coating layer was 120 nm for the first coating layer and 120 nm for the second coating layer, Their refractive index was 1.58. The physical properties of the obtained optical film are shown in Table 1 below.

[Example 13]

A two-side coated polyester film was prepared in the same manner as in Example 1 except that the coating composition (1) prepared in Example 1 was used. The thickness of the primer coating layer was 150 nm for the first coating layer and 150 nm for the second coating layer, Their refractive index was 1.58. The physical properties of the obtained optical film are shown in Table 1 below.

[Comparative Example 1]

Preparation of coating composition (7)

(Zirconia sol having a solid content of 30% by weight) having an average particle diameter of 6 nm and a refractive index of 2.1 was prepared by mixing 8% by weight of an aqueous acrylic binder (refractive index 1.44), 0.3% by weight of a silicone based wetting agent (Dow Corning, polyester siloxane copolymer) , Surface treatment using Soduim Citrate) and 0.3 wt% of colloidal silica particles having an average particle diameter of 140 nm were added to water, followed by stirring for 3 hours to prepare an acrylic coating composition having a total solid content of 5 wt%. The refractive index of the composition was 1.53.

The physical properties of the obtained optical film are shown in Table 1 below.

[Comparative Example 2]

Preparation of coating composition (8)

(Zirconia sol having a refractive index of 2.1 and a solid content of 30 wt.%) Having an average particle size of 6 nm and an average particle size of 6 nm, a water-based polyester binder (refractive index: 1.54) %, Surface treatment using Soduim Citrate) and 0.3 wt% of colloidal silica particles having an average particle diameter of 140 nm were added to water, followed by stirring for 3 hours to prepare a polyester coating composition having a total solid content of 2 wt% Respectively. The refractive index of the composition was 1.57.

The physical properties of the obtained optical film are shown in Table 1 below.

[Comparative Example 3]

Preparation of coating composition (9)

(Zirconia sol having a refractive index of 2.1 and a solid content of 30 wt.%) Having an average particle diameter of 6 nm and an average particle diameter of 6 nm, a silicone-based wetting agent (Dow Corning, polyester siloxane copolymer) %, Surface treatment using Soduim Citrate) and 0.3 wt% of colloidal silica particles having an average particle size of 140 nm were added to water, followed by stirring for 3 hours to prepare a polyester coating composition having a total solid content of 6.5 wt% Respectively. The refractive index of the composition was 1.62.

[Table 1]

As shown in Table 1, the polyester film coated with the primer coating composition of the present invention had a total light transmittance (TT) of 90.1 to 91.7% and a haze of 0.73 to 1.74. When the particle size of 65 mu m was used as in Example 7, it was found that the haze was somewhat higher.

[Examples 14 to 22]

A hard coat layer was formed on the primer coating layer of the films prepared in Examples 1 to 8 above.

At this time, acrylic resin (AIKA, Z-711) was used as the hard coating layer, and the refractive index and thickness were adjusted as shown in Table 2 below.

The physical properties of the obtained optical film are shown in Table 2 below.

[Comparative Examples 4 to 6]

A hard coating layer was formed on the primer coating layer of the films prepared in Comparative Examples 1 to 3.

At this time, acrylic resin (AIKA, KY-11) was used as the hard coating layer, and the refractive index and thickness were adjusted as shown in Table 2 below.

The physical properties of the obtained optical film are shown in Table 2 below.

[Table 2]

As shown in Table 2, ripple convergence was observed at 300 nm for Comparative Example 4 (Comparative Example 1) in which the refractive index was out of the range of the present invention, and ripple convergence was observed for Comparative Example 6 (Comparative Example 3) It was found that the optical characteristics were degraded at 800 nm and rainbow phenomenon occurred. In addition, in the case of Comparative Example 5 (Comparative Example 2) in which the coating thickness of the primer coating layer is outside the scope of the present invention, ripple convergence was observed at 300 nm.

10: Polyester base film
20, 20a, 20b: primer coating layer
30, 30a, 30b: Hard coating layer

Claims (8)

A polyester resin having a refractive index of 1.4 to 1.6 on one or both sides thereof, a zirconia sol having a refractive index of 1.8 to 2.2, an average particle diameter of 1 to 50 nm, an organic acid-modified surface and an average particle diameter of 100 to 200 nm And a primer coating layer applied with a coating composition having a total refractive index of 1.56 to 1.6,
Wherein the primer coating layer has a dry coating thickness of 50 to 150 nm. delete delete The method according to claim 1,
The zirconia sol surface-modified with the organic acid has an acyl group or an alkylate group on its surface, and Na ⁺ is used as a counter ion. The method according to claim 1,
Wherein the coating composition comprises 5 to 30% by weight of a polyester resin having a refractive index of 1.4 to 1.6, 0.1 to 0.4% by weight of a wetting agent, 0.1 to 0.5% by weight of silica having an average particle diameter of 100 to 200 nm, and a solid content of 5 to 40% 0.5 to 30% by weight of a zirconia sol surface-modified with an organic acid, and a total solid content of 2 to 10% by weight. 6. A compound according to any one of claims 1, 4 and 5,
Further comprising an acrylic resin coating layer having a refractive index of 1.51 to 1.53 on one side or both sides of the primer coating layer. The method according to claim 6,
Wherein the acrylic resin coating layer has a dry coating thickness of 1 to 10 占 퐉. 8. The method of claim 7,
Wherein the acrylic resin coating layer has a haze of 1.0 or less, a total light transmittance of 91% or more, and a haze of 0.5% or less and a total light transmittance of 92% or more when the acrylic resin coating layer is formed on both surfaces .

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