KR102086923B1 - Composite sheet for display device, display device comprising the same and manufacturing method for the same - Google Patents

Abstract

The present invention relates to a composite sheet for a display device, which comprises: a polyester base film with UV durability of 85% or more; and a UV curable visibility improving layer located on one side of the base film and including a colored layer on at least a portion. The composite sheet maintains excellent physical properties even when the composite sheet is manufactured by an ultraviolet curing method, and has improved manufacturing efficiency.

Description

COMPOSITE SHEET FOR DISPLAY DEVICE, DISPLAY DEVICE COMPRISING THE SAME AND MANUFACTURING METHOD FOR THE SAME}

The present invention relates to a composite sheet for a display device, a display device including the same, and a manufacturing method thereof.

As the information society enters, various displays such as liquid crystal display (LCD), plasma display panel (PDP), and electrophoretic display (ELD) are being developed or commercialized. Increasingly and thinning displays for indoor exhibitions are becoming increasingly smaller and lighter. In order to further improve the function of such a display, various optical films are used.

Colored sheets of the optical film may be variously applied depending on the type and / or use of the display. The colored sheet includes a base layer and a pattern layer provided on the base layer. The pattern layer is formed through UV curing, and thus the base layer requires durability against UV irradiation. However, the plastic film used in the conventional substrate layer is poor in durability due to UV irradiation, there is a problem that the reliability in the process of forming a pattern layer.

Japanese Patent No. 5737231 Republic of Korea Patent Publication No. 10-2015-0079054

An object of the present invention is to provide a composite sheet for a display device to which a polyester base film with excellent durability is applied, a display device including the same, and a manufacturing method thereof.

In order to achieve the above object, the composite sheet for a display device according to an embodiment of the present invention, the polyester base film having a UV durability of 80% or more evaluated by Equation 1 below; And an ultraviolet curable visibility improvement layer positioned on one surface of the base film and including a colored layer at least in part.

Equation 1:

In Equation 1, D _uv is ultraviolet durability (%), TS _in is initial tensile strength, and TS _fn is tensile strength measured after exposure to ultraviolet light for 48 hours at an output of 0.68 W / m ² . .

The base film may be 82% or more of MD direction ultraviolet durability.

The base film may have a TD direction UV durability of 86% or more.

A protective film may be further included on the other surface of the base film.

The optical adhesive layer may be further included on the visibility improvement layer.

The base film may have a light transmittance of 80% or more with respect to light having a wavelength of 380 nm.

The base film may have an in-plane retardation value (Ro, 550 nm) of 6,500 nm or more.

The base film may have a thickness variation within 2.5% based on the thickness of the base film.

The visibility improvement layer may include an ultraviolet curable first refractive layer positioned on the base film; And an ultraviolet curable second refractive layer positioned on the first refractive layer and having a refractive index larger or smaller than the refractive index of the first refractive layer.

The display device according to another exemplary embodiment of the present invention includes the composite sheet for display device described above.

According to another aspect of the present invention, there is provided a method of manufacturing a composite sheet for a display device, comprising a polyester base film having a UV durability of 85% or more, a composition for a first refractive layer, and a composition for a second refractive layer, which is evaluated by Equation 1 below. Preparatory step; And forming a first pattern layer on the base film with a composition for a first refractive layer and irradiating ultraviolet rays to form a cured first refractive layer, and forming a second refractive layer on the first refractive layer. And a visibility improvement layer forming step including forming a second pattern layer using the composition for the refractive layer to form a second refractive layer by irradiating ultraviolet rays to form a second refractive layer.

Equation 1:

In Equation 1, D _uv is ultraviolet durability (%), TS _in is initial tensile strength, and TS _fn is tensile strength measured after exposure to ultraviolet light for 48 hours at an output of 0.68 W / m ² . .

The manufacturing method of the composite sheet for a display device further includes a base film manufacturing step before the preparing step.

The base film manufacturing step, the stretching process for forming a polyester film in a composition for producing a polyester film, and stretched by 1.0 to 1.3 times in the MD direction and 3.0 to 5.0 times in the TD direction; And a heat-setting process for producing a base film by heat-setting the stretched film to a temperature of 160 to 230 ℃; includes.

The composite sheet for a display device of the present invention, a display device including the same, and a manufacturing method thereof according to the present invention maintain the durability or minimize the drop in the process of forming a visibility improvement layer by applying an ultraviolet ray curing method and excellent optical properties. A composite sheet including a polyester-based substrate film may be provided.

1 to 4 is a conceptual diagram illustrating a cross section of the composite sheet according to an embodiment of the present invention, respectively.
5 is a conceptual diagram illustrating a process of manufacturing a composite sheet in cross section according to an embodiment of the present invention.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. Like parts are designated by like reference numerals throughout the specification.

Throughout this specification, the term "combination of these" included in the expression of the makushi form means one or more mixtures or combinations selected from the group consisting of constituents described in the expression of the makushi form, wherein the constituents It means to include one or more selected from the group consisting of.

Throughout this specification, terms such as “first”, “second” or “A”, “B” are used to distinguish the same terms from each other.

In the present specification, the "~" system may mean to include a compound corresponding to "~" or a derivative of "~" in the compound. “Derivative” means a compound that has been changed as long as it does not change the structure and properties of the parent such as introduction of a specific compound, oxidation, reduction, substitution of atoms, etc. as a parent.

As used herein, B on A means that B is on direct contact with A, or B on A, with another layer in between, and B on a surface. It is limited to what does and is not interpreted.

In the present specification, the singular forms “a,” “an” and “the” are intended to be interpreted in the context of the singular or plural, unless the context describes otherwise.

1 to 4 are conceptual views illustrating a cross section of a composite sheet according to an embodiment of the present invention, respectively, and FIG. 5 is a conceptual view illustrating a process of manufacturing a composite sheet according to an embodiment of the present invention in cross section. Hereinafter, the present invention will be described in more detail with reference to FIGS. 1 to 5.

In order to achieve the above object, the composite sheet for display device 10 according to an embodiment of the present invention, the ultraviolet-based durability of more than 80% polyester-based base film (100); And an ultraviolet curable visibility improvement layer 200 positioned on one surface of the base film and including at least a portion of a colored layer.

Since the composite sheet 10 for a display device is applied for a display device, excellent optical characteristics are required. Therefore, in addition to the visibility improvement layer 200 applied for the purpose of improving visibility, the composite sheet should also have excellent optical properties over a certain level.

In particular, when the display sheet composite sheet 10 is manufactured by a method such as curing by virtue of ultraviolet irradiation in the manufacturing process described later, the visibility improvement layer 200 itself has a multi-layer structure. Since there are many, the durability of the base film 100 itself should be maintained even in one or two or more repeated curing processes.

The ultraviolet durability of the base film 100 is evaluated by the following Equation 1.

Equation 1:

In Equation 1, D _uv is ultraviolet durability (%), TS _in is initial tensile strength, and TS _fn is tensile strength measured after exposure to ultraviolet light for 48 hours at an output of 0.68 W / m ² . .

The base film 100 may be 80% or more, 80 to 100%, 85% to 95% UV durability is evaluated by Equation 1 above.

The ultraviolet durability is evaluated based on tensile strength, and because the base film 100 is a stretched film, it may have different ultraviolet durability depending on the direction. The ultraviolet durability is evaluated based on a lower value among the values of ultraviolet durability measured in the MD direction and ultraviolet durability measured in the TD direction.

The base film 100 may have a MD direction of UV durability of 82% or more, 85% or more, and 85 to 95%.

The base film 100 may have a TD direction UV durability of 86% or more, 88% or more, and 88 to 94%.

When the base film 100 has such ultraviolet durability, it is possible to maintain excellent durability even in repeated strong ultraviolet rays, in particular, to provide a base sheet that maintains sufficient strength even if repeated ultraviolet irradiation in the process of manufacturing a composite sheet can do.

The base film 100 may have a light transmittance of 80% or more, 80 to 99%, and 85 to 95% of light having a wavelength of 380 nm. When the polyester film having such excellent light transmittance is applied to the base film 100, the UV curing system can be operated by the light transmitted through the base film 100 so that the composite sheet for display device can be operated more efficiently. (10) can be manufactured.

In the case of forming a cured layer by applying an ultraviolet curing system, a cured layer is formed by directly irradiating ultraviolet rays on the coating layer after forming a coating layer on the base layer. In addition, in the case of the coating layer having a flat surface, it is common and efficient to proceed with ultraviolet curing by forming a coating layer by a conventional coating method and then irradiating the coating layer with ultraviolet light directly on the coating layer.

However, in the present invention, a method of curing the coating layer by ultraviolet rays passing through the substrate layer is applied. Specifically, in the visibility improvement layer 200 applied in the present invention, a plurality of layers having different densities from each other in the visibility improvement layer are laminated while repeatedly having a fine pattern on the interface, and the shape of the pattern applied at this time The angle is also finely controlled. That is, like the general coating layer (composition layer), the visibility improvement layer 200 forms an uncured coating layer, forms a pattern using a mold, and then removes the mold and directly irradiates ultraviolet rays on the surface of the uncured coating layer to attempt ultraviolet curing. In this case, the shape or angle of the fine pattern is easily deformed before curing, and may be cured in a deformed state, and the process is difficult in terms of control of the viscosity of the coating liquid, and the defect rate may be considerably large.

Accordingly, in the present invention, ultraviolet rays are generated by the ultraviolet irradiator 300 positioned under the other surface of the base film 100 without removing the mold for pattern formation, and the ultraviolet rays pass through the base film 100 for visibility. It acts on the composition layer for forming the improvement layer and forms the visibility improvement layer 200. In this case, since UV curing can be performed without removing the mold, it is possible to form the visibility improvement layer 200 in which the shape or angle of the pattern is precisely controlled.

A polyester film often applies a ultraviolet absorber in the composition for polyester film formation in order to improve the durability of a polyester film. The base film 100 of the present invention is a polyester film, but contains substantially no ultraviolet absorber in the base film. Specifically, the base film 100 may include 0.1 wt% or less of the ultraviolet absorber based on the entire base film, may include 0.01 wt% or less, and may not substantially include the base film.

When the ultraviolet absorbent is applied to the base film 100 of the present invention, since the ultraviolet ray required for the operation of the ultraviolet curing system may be blocked in the process of forming the visibility improvement layer 200, its use is refrained.

In particular, the ultraviolet absorbent may be an ultraviolet absorbent having a maximum absorption wavelength in a wavelength band of 320 to 380 nm, which is a wavelength band required for operating the ultraviolet curing system. The ultraviolet absorbent having such a maximum absorption wavelength based on the entire polyester film may be included in an amount of 0.1 wt% or less, 0.01 wt% or less, and may not be substantially included.

The in-plane retardation value Ro is a parameter defined by the product of anisotropy (ANxy = | nx-ny |) of the biaxial refractive index orthogonal in the plane of the film and the film thickness d (nm) (ANxy X d). Or a measure of anisotropy (see Equation 2 below).

Equation 2: Ro = (nx-ny) * d

In Equation 2, Ro is an in-plane retardation value, d is a film thickness, nx is a refractive index in the in-plane slow axis direction, and ny is a refractive index in the in-plane fast axis direction. The retardation value is positive in absolute value.

The base film 100 may have an in-plane retardation value (Ro, 550 nm) of 6,500 nm or more, a phase difference deviation (Ro) of 7,000 nm or more, and may be 7,000 to 300,000 nm. Applying the base film having such an in-plane retardation value, it is possible to provide a composite sheet substantially generating rainbow stains and improved visibility.

The base film 100 may have a value of in-plane phase angle deviation of -5% to + 5% based on the in-plane retardation value. When applying a polyester film having such a phase difference deviation value to the base film 100, it is possible to provide a composite sheet for a display device 10 that color distortion is more prevented.

Thickness direction retardation (Rth) means film thickness in two birefringences [Delta] Nxz (= | Nx-Nz |) and [Delta] Nyz (= | Ny-Nz |), respectively, as seen from the cross section of the film thickness direction. It is calculated as the average of the phase differences obtained by multiplying d (see equation 3 below).

Equation 3: Rth = (nx-nz) * d

In the above Equation 3, Rth is the retardation in the thickness direction, d is the thickness of the film, nx is the refractive index in the in-plane slow axis direction, and nz is the refractive index in the thickness direction. The retardation value may be defined as a positive value as an absolute value.

The base film 100 may have a thickness direction retardation Rth of about 7,000 nm or more, for example, about 7,000 nm to about 30,000 nm, for example, about 11,000 to about 13,000 nm. When the polyester film having such a thickness direction retardation is applied to the base film, it is possible to provide a composite film having more clear and excellent visibility.

The base film 100 may have a water vapor transmission rate smaller than that of the protective film described later.

The base film 100 may have a water vapor transmission rate of 16 g / m ² .day or less, 0.1 to 15 g / m ² .day, 0.1 to 10 g / m ² .day, and 5 to 9.5 g / m ² .day The base film 100 having such a moisture permeability has remarkably excellent moisture permeability characteristics compared to a TAC film applied as a protective film, and when the protective film and the base film are applied together in one composite sheet, the moisture permeability characteristics that the protective film lacks Complementary to this, it is possible to provide a composite sheet 10 for a display device having excellent physical properties.

The base film 100 may have a thickness of 30 to 150 um and 50 to 120 um. When the base film 100 has the above-mentioned thickness, it can be applied as a base film to maintain the appropriate durability and ultraviolet transmittance.

The base film 100 may have a thickness variation within -2.5% to + 2.5% based on the thickness of the base film. When the base film 100 having such a thickness variation is applied to the composite sheet for display device 10, the composite sheet for display device 10 having excellent characteristics may be provided even when applied to a large area display device. have.

The base film 100 may have a visible light transmittance of 80% or more, and may be 85 to 98%.

The visibility improvement layer 200 may include an ultraviolet curable first refractive layer 210 positioned on one surface of the base film 100; And a UV curable second refractive layer 220 positioned on one surface of the first refractive layer 210 and having a refractive index greater than or less than that of the first refractive layer 210.

One surface of the first refractive layer 210 may have a patterned surface 213 on which two or more repetitive intaglio or embossed patterns are formed. The patterned surface 213 may change the movement path of the light passing through the first refractive layer to improve visibility of the light passing through the composite sheet 10 for the display device.

The patterned surface 213 may have an intaglio or embossed pattern according to the design of the entire visibility improvement layer 200, but will be described based on the intaglio pattern.

The pattern 213 has a top surface (a) at the top and a bottom (b) is formed at the bottom, and the inclined surface connecting the same is a flat or curved surface with a single pattern 215 having a substantially trapezoidal cross section side by side at regular intervals. It may be formed.

The upper surface (a) is positioned above the single pattern 215 and serves to increase the viewing angle and brightness by allowing more light reaching the first refractive layer 210 to diffuse.

The height h of the single pattern 215 may be 25 μm or less, and may be 5 to 18 um. The single pattern 215 may have a base angle θ of 70 to 89.9 ° and 80 to 89 °. When the single pattern 215 having the above range is applied to the first refraction layer 210, a luminance film may be minimized and a viewing angle may be increased to provide a composite film having improved visibility.

The ratio of the height h of the width a of the upper surface of the single pattern 215 to the length of the lower surface of the single pattern 215 may be 0.2 to 1.1, and may be 0.4 to 0.85. In this case, an effect of improving the contrast ratio and the viewing angle at the side can be obtained.

The single pattern 215 is formed repeatedly, and the distance p between the neighboring single patterns 215 may be 10 to 40 um, and may be 10 to 30 um.

When the first refraction layer 210 having the pattern 213 in which the single patterns 215 having such a feature are arranged side by side is applied, the upper surface of the single pattern 215 or between the adjacent single patterns 215 is positioned. The light reaching the flat surface is totally reflected by the pattern and emitted to diffuse the light. Also, when the space c between the single patterns except for the bottom b of the single pattern is greater than or equal to the bottom b of the single pattern at a distance between neighboring single patterns 215, the viewing angle is It is possible to provide a composite sheet that is more excellent and does not cause moiré phenomenon.

The first refractive layer 210 and the second refractive layer 220 may be applied to the difference in the refractive index. In detail, the refractive index of the first refractive layer 210 may be larger or smaller than the refractive index of the second refractive layer 220 by 0.05 to 0.28, and may be larger or smaller by 0.1 to 0.25. Specifically, the refractive index of the one having the large refractive index among the first refractive layer 210 and the second refractive layer 220 may be 1.51 to 1.80. In addition, the refractive index of the one having the small refractive index among the first refractive layer 210 and the second refractive layer 220 may be 1.40 to 1.50. If the refractive index and the refractive index difference in this range, it is possible to obtain a more excellent light diffusion effect.

Specifically, acrylic, polyethylene, polycarbonate, epoxy resin, etc. may be applied to the first refractive layer 210 and the second refractive layer 220, and metal particles, ceramic particles, etc. may be used as necessary to control refractive index. It can be incorporated and applied.

The visibility improvement layer 200 may further include a black layer 230 on the second refractive layer or under the first refractive layer.

In this configuration, the visibility improvement layer 200 can increase the brightness by diffusing the incident light, and can improve the visibility by widening the viewing angle.

In the composite sheet for display device 10, the visibility improvement layer 200 is positioned on one surface of the base film 100.

The visibility improvement layer 200 may be matched such that a direction in which the TD direction or the MD direction of the base film 100 and the single pattern 215 are formed to be parallel to each other. In this case, the composite sheet for display device 10 may have better visibility.

The composite sheet for display device 10 may further include a protective film 700 positioned on the other surface of the base film 100. It is preferable that an isotropic film is applied as the protective film 700, and an anti-reflective film having excellent surface strength may be applied. Specifically, the protective film 700 may be applied to a polyester film, TAC film and the like.

An adhesive layer 600 may be further included between the other surface of the base film 100 and the protective film 700. Pressure sensitive adhesive (PSA) may be applied as the adhesive layer, but is not limited thereto.

The composite sheet for display device 10 may further include an optical adhesive layer 400 on the visibility layer improvement layer 200.

The composite sheet for display device 10 may be applied to the base film 100 having a better light transmittance of 380 nm wavelength than that of the protective film 700. In detail, the base film 100 may have an excellent light transmittance of 5 times or more, more than 10 times, and may be 10 to 20 times better than the protective film 700. In this case, the structure of the visibility improvement layer 200 and the like through the base film 100 while minimizing the aging process due to the ultraviolet light as a whole of the composite sheet 10 for the display device by the protective film 700, such as UV curing Can be applied efficiently.

The composite sheet for display device 10 may be applied to the substrate film 100 having a moisture permeability smaller than that of the protective film 700. In such a case, the base film 100 may further improve the overall moisture resistance of the composite sheet 10 for a display device by supplementing the protective film 700.

The release film or the polarizer 500 may be positioned on the optical adhesive layer 400. Specifically, on the optical adhesive layer 400, the release film 500 is applied to the display device until the composite sheet 10 for the display device is applied to a display device (not shown). This can be located.

The display device (not shown) according to another exemplary embodiment of the present invention includes the composite sheet 10 for a display device described above. Specifically, the composite sheet for display device 10 may be applied in a manner that is attached to one surface of the polarizing plate of the display device.

The display device may be an LCD display device, an LED display device, an OLED display device, or a QLED display device. Specifically, the display device may be a QD-LED or QD-LCD display device using a quantum dot and a light source such as an LCD or an LED. The display device may be a quantum dot film applied to a light guide plate.

Detailed description of the structure and characteristics of the composite sheet is duplicated with the description above, so the detailed description thereof will be omitted.

According to another embodiment of the present invention, a method of manufacturing a composite sheet for display device 10 includes: preparing a step; And a visibility improvement layer forming step.

The preparation step is a step of preparing a polyester-based base film, a composition for the first refractive layer and a composition for the second refractive layer having a UV durability of 85% or more, which is evaluated by Equation 1 below.

Equation 1:

In Equation 1, D _uv is ultraviolet durability (%), TS _in is initial tensile strength, and TS _fn is tensile strength measured after exposure to ultraviolet light for 48 hours at an output of 0.68 W / m ² . .

The description of the polyester-based substrate film 100 is duplicated with the description above, so the description thereof is omitted. In addition, the manufacturing process of the base film 100 will be described later.

The visibility improvement layer forming step may include providing a visibility improvement layer 200 including a first refractive layer and a second refractive layer having different refractive indices, including forming a first refractive layer and forming a second refractive layer. do.

The first refractive layer forming process is to form a first pattern layer 211 as a composition for the first refractive layer on the base film 100 and to form a cured first refractive layer 210 by irradiating UV light. to be. As the composition for the first refractive layer, an acrylic resin composition, a polyethylene resin composition, etc. to which an ultraviolet curing system is applied may be applied. In addition, the composition may further include a refractive index adjusting material, such as metal particles or ceramic particles, if necessary.

Specifically, the first pattern layer 211 is formed by applying a composition for the first refractive layer on the base film 100. The first pattern layer 211 has a suitable light diffusion characteristic and forms a pattern 213 for the purpose of improving visibility. The pattern 213 is a structure in which the single pattern 215 described above is formed repeatedly. When the pattern is an intaglio pattern, a pattern is formed by applying a pattern frame 250 having a corresponding relief pattern. However, when the pattern frame 250 is removed before the curing of the composition for the first refractive layer is higher than a predetermined level, it is difficult to obtain an elaborate pattern having the intended characteristics. In the state positioned on the 211, the composition for the first refractive layer included in the first pattern layer 211 is cured by ultraviolet rays transmitted in one direction from the other surface of the base film 100.

That is, in the process of forming the first refractive layer, the first pattern layer 211 is formed on the base film 100 using the composition for the first refractive layer and passes through the base film 100 to pass the first pattern layer ( The first refractive layer composition is cured by ultraviolet rays irradiated 211 to form a first refractive layer 210 having a pattern on the surface thereof.

After the first refractive layer 210 is formed, the pattern frame 250 may be removed to proceed to the next step.

In the process of forming the second refractive layer, the second pattern layer 221 is formed on the first refractive layer 210 with the composition for the second refractive layer to irradiate ultraviolet rays to form the second refractive layer 220. It is a process. As the composition for the second refractive layer, an acrylic resin composition, a polyethylene resin composition, etc. to which an ultraviolet curing system is applied may be applied. In addition, the composition may further include a refractive index adjusting material, such as metal particles or ceramic particles, if necessary.

One surface of the second refractive layer 220 may be formed flat, and the other surface of the second refractive layer 220 may have an embossed pattern corresponding to the first refractive layer 210. In addition, the second refractive layer 220 may have a pattern layer (not shown) that is similar to the pattern of the first refractive layer 210 described above on one surface thereof but has a predetermined angle with the pattern of the first refractive layer. .

The second refractive layer 220 may be formed by irradiating the second pattern layer 221 with ultraviolet rays to harden the composition for the second refractive layer. In this case, ultraviolet irradiation may be performed on one surface of the second refractive layer 220 or may be performed under the other surface of the second refractive layer 220, and in particular, the ultraviolet irradiation under the other surface of the second refractive layer 220. When is progressed, UV curing of the composition may proceed by the ultraviolet light passing through the base film 100 and the first refractive layer 210.

The visibility improvement layer forming step may further include a black layer forming process. The black layer forming process may be performed before the first refractive layer forming process and may be performed after the second refractive layer forming process.

The process of forming the black layer may be performed by forming an uncured black layer 231 using the composition for the black layer and then curing the black layer. The composition for the black layer may be a composition in which a colored material such as carbon black and an acrylic resin composition or a polyethylene resin composition are mixed, and an ultraviolet curing system may be applied.

The forming of the black layer may be performed in a manner of forming a cured black layer 230 by irradiating ultraviolet light to the uncured black layer 231 formed of the composition for the black layer. In addition, as described above, the ultraviolet radiation applied in the process of forming the black layer may be irradiated on one surface of the black layer 230, the ultraviolet light passing through the base film 100 under the other surface of the black layer 230 It may proceed in a manner applied to the uncured black layer.

The manufacturing method may further include a base film manufacturing step before the preparation step.

The base film manufacturing step includes an stretching process and a heat setting process.

The stretching process is a process of forming a polyester sheet with a composition for producing a polyester film and stretching in the MD direction and the TD direction to produce a stretched film.

Specifically, an unstretched polyester sheet is prepared by melt-extrusion of a resin composition capable of producing a polyester film, and the unstretched sheet is transverse direction (tenter direction, TD) and longitudinal direction (LD). , mechanical direction, MD) to prepare a stretched film.

The MD direction stretching may be performed at 1.0 to 1.3 times to produce a base film having excellent ultraviolet durability and excellent ultraviolet transmittance. TD direction stretching may proceed 3.0-5.0 times, proceed 3.5-5.0, and proceed 4.0-4.8 times. When the stretching is performed in such a ratio, it is possible to produce a polyester film having excellent utilization as a base film due to excellent ultraviolet transmittance, light transmittance, ultraviolet durability, and the like.

The stretching speed may be 2 times / minute to 8 times / minute, 2.5 times / minute to 6 times / minute, or 2.5 times / minute to 3 times / minute.

The stretching temperature may proceed at a temperature of 75 to 120 ° C. When the stretching temperature is low, the stretchability is excellent but breakage of the film may occur. In addition, when the stretching temperature is too high, breakage may occur due to the occurrence of a cloudy phenomenon during stretching of the film. Specifically, the stretching temperature in the longitudinal direction is 75 to 85 ℃, the stretching temperature in the width direction may be applied to 80 to 120 ℃.

The heat setting process is a process of manufacturing the base film by heat-setting the stretched film to a temperature of 160 to 230 ℃, specifically 175 to 215 ℃. If the heat setting temperature is too low, the film shrinkage may be high, and if too high, breakage may occur, resulting in poor manufacturability.

The heat setting may be performed for 0.5 to 10 minutes, specifically, for 0.5 to 5 minutes, and then the substrate film 100 may be prepared by lowering the temperature step by step.

Hereinafter, the present invention will be described in more detail with reference to specific examples. The following examples are merely examples to help understanding of the present invention, but the scope of the present invention is not limited thereto.

One. Manufacture of samples

Example 1

Polyethylene terephthalate resin (manufactured by SKC Co., Ltd.) applying ethylene glycol and terephthalic acid in a 1: 1 molar ratio, respectively, was melt extruded through an extruder at about 280 ° C., and then cooled in a casting roll at about 25 ° C. to unstretched polyester film. Was prepared. The unstretched polyester film was stretched in the longitudinal direction and the width direction at the magnification shown in Table 1 at the temperatures shown in Table 1 below, and the stretched film was heat-set at the temperatures shown in Table 1 to form a base film. .

On one surface of the base film, a visibility improvement layer was formed by UV curing. Specifically, the visibility improvement layer includes a low refractive index pattern layer having an intaglio pattern, a high refractive index pattern layer positioned on the low refractive index pattern layer, and a colored layer containing black ink (see FIG. 3). The release film was placed on the colored layer after forming an optically transparent adhesive layer.

In addition, the composite film of Example 1 was prepared by placing an adhesive layer on the other surface of the base film, and a TAC layer serving as a protective layer under the adhesive layer.

Examples 2 to 3

A substrate film was prepared in the same manner as in Example 1 except that the substrate layer was formed at a draw ratio, a stretching temperature, and a heat setting temperature shown in Table 1 below. The composite film was manufactured by forming a visibility improvement layer, a protective layer, and the like on the one side and the other side of the base film as described above.

Comparative Examples 1 and 2

It carried out similarly to Example 1 except having formed the base material layer in the draw ratio, draw temperature, heat setting temperature, and thickness shown in Table 1 below.

Comparative Example 3

A TAC film (triacetylcellulose film) was purchased and evaluated under the same conditions as in Example below to make Comparative Example 3.

Sample name Base Film Process Condition Draw ratio Stretching temperature
(℃) Heat setting temperature
(℃) thickness
(Μm) MD TD Elongation Product Example 1 1.1 4.3 4.73 95 180 81 Example 2 1.1 4.3 4.73 95 200 80 Example 3 One 4.3 4.3 95 180 80 Comparative Example 1 1.1 4.3 4.73 95 180 60 Comparative Example 2 3.2 3.8 12.16 140 240 75 Comparative Example 3 One One One - - 60

One. Evaluation of physical properties

1) Tensile strength and UV durability evaluation

The base film was measured in the MD direction and the TD direction by using a universal measuring instrument (initial tensile strength, TS _in , unit: kg / mm ² ). Specifically, the tensile strength was measured by dividing the maximum load by the original cross-sectional area of the film at a value that increases by applying a load to the film according to KS B 5521.

After 48 hours of exposure to ultraviolet light of 0.68 W / m ² output on the same film using QLab's QUV model, the tensile strength was measured again using the same instrument as above (tensile strength after exposure, TS _fn , unit: kg / mm). ² ).

The measured value was applied to Equation 1 below to evaluate UV durability (D _uv , unit%). The results are shown in Table 2 below.

Equation 1:

2) Measurement of UV transmittance

Ultraviolet transmittance was measured by applying Shimatsu's UV2600 instrument, and the measurement wavelength was 380 nm.

3) moisture permeability measurement

Moisture permeability was measured by applying Morcon's PERMATRAN_W model.

4) Thickness, thickness deviation, in-plane phase difference evaluation

In-plane retardation (Ro) is a parameter defined as the product of anisotropy (ANxy = nx-ny |) of the refractive index of orthogonal biaxial in the plane of the film and the product of film thickness d (nm) (ANxy X d). ， It is a measure indicating optical isotropy or anisotropy.

Specifically, orthogonal biaxial refractive indices (nx, ny) and the refractive index (nz) in the thickness direction are measured using an Otsuka refractive index meter (RETS, measurement wavelength 550 nm), and the film thickness d (nm) is measured by an electric micrometer. (Measured using (Millitron 1245D, Fineryuf), the unit was converted to nm. The difference between each of the measured biaxial indices of refraction is determined as an absolute value (| nx-ny |), and the in-plane retardation (Ro) is obtained by multiplying the thickness d (nm) of the film (nxy × d). Indicated.

Thickness direction retardation (Rth) means film thickness in two birefringences [Delta] Nxz (= | Nx-Nz |) and [Delta] Nyz (= | Ny-Nz |), respectively, as seen from the cross section of the film thickness direction. It is calculated as the average of the phase difference obtained by multiplying d.

5) visibility evaluation

Visual observation was observed from the front and inclined directions of the base film to determine whether or not a rainbow color stain occurred. When the rainbow stain was not generated in any direction or observed in the inclined direction, when very light rainbow stain was observed, it was evaluated as Pass or when the rainbow stain was clearly observed when observed in the tilt direction.

MD tensile strength
(kg / mm ² ) TD tensile strength
(kg / mm ² ) UV durability
(%) Visibility I'm after I'm after MD TD Pass Example 1 9.1 7.8 29.6 26.8 85.4 90.5 Pass Example 2 9.1 7.9 29.1 27 86.8 92.8 Pass Example 3 8.8 7.8 30 26.7 88.6 89 Pass Comparative Example 1 9 8.1 25.8 24.2 89.9 93.8 Pass Comparative Example 2 17.9 10.5 24.6 17.1 58.7 69.5 Fail Comparative Example 3 17 12.1 15.3 11.4 71.3 74.7 Pass

thickness
(Μm) Thickness difference
(Μm) Thickness deviation * Ro
(Nm) Ro
Deviation** Rth
(Nm) UV transmittance
(%, 380nm) Breathable
(g / m ² .day) Example 1 81 1.5 Pass 8370 Pass 11700 88.9 8.6 Example 2 80 1.6 Pass 8490 Pass 12100 89.3 9.1 Example 3 80 1.2 Pass 8660 Pass 11500 90.1 9.2 Comparative Example 1 60 0.6 Pass 6050 Fail 8520 1.8 17.8 Comparative Example 2 75 2.5 Fail 3600 Fail 10940 88.6 9.1 Comparative Example 3 60 1.4 Pass 1.4 Pass 59 6.7 660 or more

* The thickness deviation was evaluated as Pass when the difference in thickness was equal to or smaller than the value corresponding to 2.5% of the measured thickness, and as Fail when the thickness was larger.

** Ro deviation was evaluated by measuring the in-plane phase difference at 100mm intervals over the full width and evaluating the deviation. If the deviation was within 5% based on the average in-plane phase difference value, it was evaluated as Pass.

Referring to the results of Tables 2 and 3, the polyester base film of Examples 1 to 3 showed excellent results in both the MD direction and the TD direction in terms of UV durability, which was superior to the TAC film. . This is a particularly excellent result compared to Comparative Example 2, which is a biaxially stretched polyester film, which is a composite film of the present invention in the environment of use that can be repeatedly exposed to a large amount of ultraviolet light for the purpose of ultraviolet curing, etc. in the composite film manufacturing process. This is a necessary characteristic.

In addition, by using a UV curable resin to form a visibility improvement layer on the base film, the visibility improvement layer also has a multi-layered structure as described above, since it is formed by a process of several ultraviolet light, in the case of ultraviolet transmittance It becomes an important factor whether or not the base film can serve as a base film, all of the embodiments of the present invention showed an excellent UV transmittance of more than 85%. On the other hand, the film of Comparative Example 1 is a polyester film, but the in-plane retardation (Ro) value has a value of approximately 6000 nm, it was shown that the ultraviolet ray is hardly transmitted.

The base film shows a very good result in terms of moisture permeability, which is a property necessary to protect the display to which the composite film is applied and to improve the water resistance of the film. In Comparative Example 2, the base film has a moisture permeability within the required range, but Comparative Example 1 In the case of the moisture permeability falls, in the case of Comparative Example 3 was found to be vulnerable to moisture. This showed that the base film of the present invention also serves to complement the TAC film vulnerable to moisture.

Although the preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements of those skilled in the art using the basic concepts of the present invention defined in the following claims are also provided. It belongs to the scope of right.

10: composite sheet for display device 100: base film
200: visibility improvement layer
210: first refractive layer 211: first pattern layer
213: pattern, patterned surface 215: single pattern
220: second refractive layer 221: second pattern layer
230: black layer 231: uncured black layer
250: pattern frame
300: ultraviolet irradiator 400: optical adhesive layer
500: release film or polarizing plate 600: adhesive layer
700: protective film
a: width of top, top b: width of bottom, bottom
c: space between single patterns p: distance between single patterns
h: height of single pattern θ: angle of single pattern

Claims (10)

Polyester base film; And an ultraviolet curable visibility improvement layer located on one surface of the base film and including a colored layer at least in part.
The visibility improvement layer may include an ultraviolet curable first refractive layer; And an ultraviolet curable second refractive layer positioned on the first refractive layer and having a refractive index larger or smaller than the refractive index of the first refractive layer.
One surface of the first refractive layer has a patterned surface on which at least two repetitive intaglio or embossed patterns are formed,
The polyester base film has a light transmittance of 80% or more with respect to light having a wavelength of 380 nm,
The polyester base film has a UV durability of 80% or more, which is evaluated by Equation 1 below, a composite sheet for a display device;
Equation 1:

In Equation 1, D _uv is ultraviolet durability (%), TS _in is initial tensile strength, and TS _fn is tensile strength measured after exposure to ultraviolet light for 48 hours at an output of 0.68 W / m ² . . The method of claim 1,
Further comprising a protective film located on the other surface of the base film,
The base film is a composite sheet for a display device excellent in light transmittance of more than five times the wavelength of 380 nm compared to the protective film. The method of claim 1,
The composite sheet for a display device further comprises an optical adhesive layer located on the visibility improvement layer. The method of claim 1,
The base film has a light transmittance of 85 to 98% for light of a wavelength of 380 nm, composite sheet for a display device. The method of claim 1,
The base film has a thickness direction retardation (Rth) of 11,000 to 13,000 nm, composite sheet for a display device. The method of claim 1,
The base film has a thickness variation of less than 2.5% based on the thickness of the base film, the composite sheet for a display device. delete A display device comprising the composite sheet for display device according to claim 1. Preparing a polyester base film, a composition for a first refractive layer, and a composition for a second refractive layer; And
Forming a first pattern layer with a composition for a first refractive layer on the base film and irradiating UV light to form a first cured UV curable layer, and the first refractive layer formed on the first refractive layer And a second refractive layer forming process of forming a second pattern layer using the composition for a second refractive layer and irradiating ultraviolet rays to form an ultraviolet curable second refractive layer.
The ultraviolet curable second refractive layer has a refractive index that is greater than or less than the refractive index of the ultraviolet curable first refractive layer,
One surface of the first refractive layer has a patterned surface on which at least two repetitive intaglio or embossed patterns are formed,
The polyester base film has a light transmittance of 80% or more with respect to light having a wavelength of 380 nm,
The polyester base film has a UV durability of 80% or more, which is evaluated by Equation 1 below, a manufacturing method of a composite sheet for a display device;
Equation 1:

In Equation 1, D _uv is ultraviolet durability (%), TS _in is initial tensile strength, and TS _fn is tensile strength measured after exposure to ultraviolet light for 48 hours at an output of 0.68 W / m ² . . The method of claim 9,
The manufacturing method further comprises a base film manufacturing step before the preparation step,
The base film manufacturing step
A stretching process of forming a polyester film with a composition for preparing a polyester film and stretching the film by 1.0 to 1.3 times in the MD direction and 3.0 to 5.0 times in the TD direction; And
A heat setting process of heat-setting the stretched film to a temperature of 160 to 230 ° C. to produce a base film;
A manufacturing method of a composite sheet for a display device comprising a.

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