KR102052843B1 - Polarizer-protecting polyester film and manufacturing method thereof and polarization plate using the same - Google Patents

Abstract

A polyester film for protecting a polarizer according to one embodiment of the present invention is a film which has excellent adhesion and optical and mechanical characteristics and can minimize a rainbow phenomenon after hard coating processing. The polyester film comprises a base film made of at least one axis elongated polyester, and a primer layer formed on at least one side of the base film and comprising at least one resin selected from a polyurethane resin and a polyester resin and a curing agent.

Description

A polarizer protective polyester film, a method of manufacturing the same and a polarizing plate having the same {POLARIZER-PROTECTING POLYESTER FILM AND MANUFACTURING METHOD THEREOF AND POLARIZATION PLATE USING THE SAME}

The present invention relates to a polyester film for polarizer protection, and more particularly, to a polarizer protection polyester film having excellent adhesion, excellent optical and mechanical properties, and minimizing interference mura after hard coating processing.

In general, polyester films are excellent in dimensional stability, thickness uniformity, and optical transparency, so that they are widely used not only for display devices but also for various industrial materials. In particular, as the interest in liquid crystal display devices, organic light emitting display devices, and electronic paper has recently increased, studies are being actively conducted to replace the substrates of these display devices with polyester films instead of conventional glass substrates. Replacing the glass base with a polyester film makes the overall weight of the display device lighter and gives flexibility in design. It is also resistant to impact and excellent moisture resistance, and can be manufactured in a continuous process. Compared with the productivity is high.

In particular, researches using such a polyester film as a polarizer protective film requiring high optical properties have been actively conducted. Basically, the polyester film has an orientation angle by crystal and bowing in the stretching process, and in the case of biaxial stretching, two optical axes are generated, thereby changing the polarization coming from the polarizer into an ellipse or circularly polarized light. This results in problems such as color changes or iridescent stains in the human eye.

Japanese Patent Laid-Open No. 2011-532061 and Korean Laid-open Patent No. 2017-0056027 disclose an invention using a polyester film as a polarizer protective film. However, when a polyester film is used as a polarizer protective film, the polarizer protective film which requires surface processing has become a problem, such as the fall of the visibility by the reflective rainbow, and has a low in-plane retardation, and the orientation angle of a main chain is changed. Since no attempt was made to lower, a problem such as a decrease in productivity occurred in obtaining the actual effective width, which hindered the use of the polyester film as a polarizer protective film.

Therefore, in addition to the optical properties of the polyester film itself, there is a need for a design of a suitable structure that can minimize the stress at the interface between the primer layer and AG or hard coating, and to solve the problem of poor adhesion and visibility between the coating layer. .

Japanese Patent Laid-Open No. 2011-532061 Korean Patent Publication No. 2017-0056027

The present invention is to solve the problems of the prior art as described above, the object of the present invention is to lower the draw ratio and orientation angle of the polyester film to ensure a low in-plane retardation (Re) and high thickness direction retardation (Rth), At the same time, by adjusting the main chain crystal angle of the film to reduce the main orientation angle as much as possible, to minimize the rainbow stain that may occur when oblique observation, and to add the appropriate particles to the primer layer to ensure the runability, the primer layer is the base film The present invention is to provide a polarizer-protective polyester film, a method of manufacturing the same, and a polarizing plate including the same, which not only have sufficient adhesiveness but also adjust the refractive index ratio between the primer layer and the base film. .

These and other objects and advantages of the present invention will become more apparent from the following description of preferred embodiments.

The object is formed on at least one surface of at least one uniaxially stretched polyester base film and the base film, comprising a primer layer comprising at least one resin and a curing agent selected from a polyurethane-based resin or polyester-based resin A polyester film for polarizer protection is achieved.

Preferably, the curing agent may be composed of at least one resin selected from the group consisting of oxazoline-based, carbodiimide-based and melamine-based.

Preferably, the polyurethane-based resin or polyester-based resin of the primer layer has a solid content of 4 to 7% in the total coating liquid, and the curing agent has a ratio of 100: 5 to 100: 50 relative to the polyurethane-based resin or polyester-based resin. Can be.

More preferably, the polyurethane-based resin or polyester-based resin may be 4.5 to 5.5% solids in the total coating liquid.

Preferably, the primer layer may have a reflectance of 4% or less in the wavelength band of 550 nm.

Preferably, the polyester base film may have an in-plane retardation (Re) of 500 nm or less, and a thickness direction retardation (Rth) of 8000 nm or more.

Preferably, the polyester base film may have a plane orientation coefficient (ΔP) of 0.164 or less.

Preferably, the orientation angle of the main chain of the crystalline region in the polyester base film may be 17 degrees or less.

Preferably, the refractive index ratio between the primer layer and the base film satisfies Equation 4 below.

[Equation 4]

0.958 <primer layer refractive index / refractive index of the base film <0.98.

Preferably, the primer layer may further include an anionic surfactant and particles having an average particle diameter of 10 to 500nm.

Preferably, the adhesion between the base film and the primer layer and the moisture resistance after 500 hours of high temperature and high humidity conditions at 60 ° C. and 90% humidity is 95% or more, and the adhesion between the primer layer and the post-processing resin may be 95% or more. .

In addition, the above object, in the first step of melt extrusion of the polyester resin to form an unstretched sheet, in the second step, the second stage of uniaxially stretching the unstretched sheet formed in the first step in the longitudinal direction (MD) The coating liquid is applied in the third and third steps of applying and drying the coating liquid in which at least one resin selected from the polyurethane resin or the polyester resin and the curing agent are mixed on at least one surface of the sheet uniaxially stretched in the longitudinal direction. In the method for producing a polarizer protective polyester film comprising a fourth step of biaxially stretching the sheet in the width direction (TD) and a fifth step of heat-setting the sheet stretched in the fourth step to form a polyester film for polarizer protection Can be achieved by

Preferably, the draw ratio in the longitudinal direction MD of the second step is 3.0 to 3.3 times, and the draw ratio in the width direction TD of the fourth step may be 3.0 to 3.6 times.

Preferably, the heat setting temperature in the fifth step may be 180 to 220 ° C.

In addition, the above object can be achieved by the polarizing plate is provided on the at least one surface of the polarizer protective polyester film according to the above polarizer.

As described above, according to the present invention, the productivity is improved during post-processing by minimizing the interference mura phenomenon, and has the effect of improving the visibility by suppressing the iridescent stain generated when observed obliquely in the case of lamination with the polarizer.

In addition, according to the present invention has the effect that the primer layer and the base film have sufficient adhesiveness and can ensure a high running.

In addition, according to the present invention is improved mechanical properties and moisture resistance of the material itself has the effect of having a high reliability even in harsh environments.

However, the effects of the present invention are not limited to the above-mentioned effects, and other effects not mentioned will be clearly understood by those skilled in the art from the following description.

1 is a cross-sectional view of a polyester film for polarizer protection according to an embodiment of the present invention.

Hereinafter, the present invention will be described in detail with reference to embodiments and drawings of the present invention. These examples are only presented by way of example only to more specifically describe the present invention, it will be apparent to those skilled in the art that the scope of the present invention is not limited by these examples. .

In the drawings, the thickness of layers, films, panels, regions, etc., are exaggerated for clarity. Like parts are designated by like reference numerals throughout the specification. When a part of a layer, film, region, plate, etc. is said to be "on" another part, this includes not only the other part being "right over" but also another part in the middle. On the contrary, when a part is "just above" another part, there is no other part in the middle.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. In case of conflict, the present specification, including definitions, will control. Also, although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, suitable methods and materials are described herein.

1 is a cross-sectional view of a polyester film for polarizer protection according to an embodiment of the present invention.

Referring to FIG. 1, a polarizer protective polyester film according to an embodiment of the present invention includes a base film 1 and a primer layer 2 formed on at least one surface of the base film 1.

The base film 1 is formed by melt-extruding a polyester resin. Preferably, the polyester forming the base film 1 may be selected from the group consisting of polyethylene terephthalate, polyethylene naphthalate, polyethylene isophthalate, and polycarbonate.

The base film 1 is processed by uniaxially stretching and / or biaxially stretching a film formed of polyester in the longitudinal direction (MD) and / or the width direction (TD). Biaxially stretching may be preferable because materials other than polycarbonate have no crystallinity in the unstretched state, and mechanical strength is weak, and difficulty in controlling after low is also caused.

The base film 1 may further include an ultraviolet absorber to absorb ultraviolet rays. In this case, the ultraviolet absorber may be at least one selected from the group consisting of benzotriazole-based, benzophenone-based, oxalic acid anilide-based, cyanoacrylate-based, and triazine-based. In addition, the base film 1 may further add an antioxidant to suppress the discoloration (browning) of the ultraviolet absorber contained in the base film (1).

It is preferable that the thickness of the base film 1 is 25-250um. If the thickness of the base film (1) is less than 25um there is a problem that the yield can be lowered because the wrinkles are easily mixed in the surface processing and the polarizing plate lamination process, if the thickness of the base film (1) exceeds 250um it is difficult to control the phase difference There is a problem in that the overall thickness of the display becomes thick.

Polyester base film according to an embodiment of the present invention preferably has the physical properties shown in Table 1 below.

Item Properties In-plane phase difference (Re) 500nm or less Thickness Direction Retardation (Rth) More than 8000nm Main orientation angle of film backbone 17 degrees or less Planar orientation coefficient (△ P) 0.164 or less

That is, when the base film 1 formed of the polyester resin is subjected to a biaxial stretching process in the longitudinal direction (MD) and the width direction (TD), distortion of polarization occurs according to the birefringence of the base film (1). Due to the distortion of the polarized light, rainbow spots may be generated when viewed obliquely (near Brewster's Angle). Therefore, the polyester base film according to an embodiment of the present invention preferably has physical properties as shown in Table 1 in order to remove the iridescent stain caused by the distortion.

In-plane retardation (Re) of the polyester base film may be defined as in Equation 1.

In Equation 1, Nx represents the refractive index in the direction perpendicular to the axis of light leakage when observing the refractive index of the film longitudinal direction or cross nicol of the polarizer. Ny represents the refractive index of the direction of the axis which light does not leak when observing the refractive index of the width direction of a film, or the cross nicol of a polarizer. And in formula (1) d represents the thickness of the polyester film for polarizer protection.

As defined in Equation 1, when the optical axis is 0 degrees, it can be seen that Nx coincides with the film length direction, and Ny coincides with the film width direction. In the polarizer protective polyester film, the optical axis is required to maintain the polarization degree of polarized light as much as possible, and since it is also associated with the occurrence of iridescent spots, the lower the in-plane retardation of the polarizer protective polyester film, the lower the glass (500 nm or less). The closer the optical axis is to 0 degrees, the better. That is, when the in-plane retardation of the polyester base film exceeds 500nm, it is difficult to maintain the polarization of the polarized light and rainbow color unevenness occurs.

Next, the thickness direction retardation (Rth) of the polyester base film may be defined as in Equation 2.

In Equation 2, Nx, Ny, and d are the same as those defined in Equation 1, and Nz represents a refractive index in the film thickness direction.

As defined in Equation 2, the thickness direction retardation is the average value of the in-plane refractive index components ((Nx + Ny) / 2) minus the refractive index (Nz) in the film thickness direction times the thickness of the film, which is the thickness As a formula for calculating the double refraction in the direction, it is preferable to have a value of 8000 nm or more in order to suppress the generation of iridescent light due to distortion. That is, when the thickness direction retardation of the polyester base film is less than 8000 nm, iridescent light may occur due to distortion.

The orientation angle of the main chain means the angle at which the crystals of the main chain are made relative to the width direction of the film. The orientation angle direction of a main chain direction is set by the crystallinity of a polyester-type material (polyester resin) with respect to a extending | stretching direction in the process of carrying out the heat setting process through a biaxial stretching process. First, the stretching in the longitudinal direction (MD) is finished and stretched in the width direction (TD) with respect to the unstretched film formed of polyester, in which the orientation angle of the main chain is usually 0 degrees at the stretching end in the width direction. And during the heat setting treatment, a bowing phenomenon occurs due to the residual stress after stretching, and the bowing phenomenon has a bow-shaped gradient in the opposite direction of the film traveling direction.

Since the orientation of the main chain crystal causes a change in the optical axis, iridescent spots may appear even if the phase difference is controlled. In order to suppress such an inorganic light generation phenomenon, it is necessary to suppress the bowing phenomenon so that the edge portion (edge portion of the film) can also be set as similar as possible to the physical properties of the width center of the film. In order to suppress the bowing phenomenon, it is necessary to process at a temperature lower than the normal heat setting treatment temperature to minimize the difference in stress between the stretching portion and the heat fixing portion. Therefore, for this purpose, the heat setting treatment temperature is preferably 180 to 220 ° C, and 180 It is more preferable that it is -200 degreeC. In this case, when the heat setting temperature is less than 180 ° C., the heat setting of the base film 1 and the primer layer 2 may not be performed properly, and when the heat setting temperature exceeds 220 ° C., a boeing phenomenon may occur.

The orientation angle of the main chain of the base film 1 is preferably 17 degrees or less, more preferably 10 degrees or less, and even more preferably 8 degrees or less. When the orientation angle of the main chain of the base film 1 exceeds 17 degrees, the optical axis identified by the polarizer cross nicol increases, resulting in a problem that the phase difference becomes large.

Next, the plane orientation coefficient (ΔP) of the polyester base film is defined as in Equation 3 by a numerical value for the degree of orientation of the film.

In Equation 3, Nx, Ny, and Nz are the same as the definitions of Equation 2 described above. It is preferable that the surface orientation coefficient of a polyester base film is 0.164 or less. If the surface orientation coefficient of the polyester base film exceeds 0.164, the film is over-stretched, excessive shrinkage stress occurs, causing a lot of heat shrinkage. More specifically, as shown in Equation 3, the larger the surface orientation coefficient at the same thickness, the greater the thickness direction retardation, so the larger the numerical value, the more advantageous it may be. However, the large surface orientation coefficient means that the refractive index Nx in the longitudinal direction of the film and the refractive index Ny in the width direction of the film are large, which means that the stretching ratio at the time of biaxial stretching is large. However, in order to control the orientation angle of the main chain, it is necessary to minimize the residual stress after stretching and minimize the stress difference between the stretched portion and the heat treated portion. However, when the draw ratio is high, the residual shrinkage stress increases, so that the orientation angle of the main chain is 17 degrees or less. It becomes difficult to control.

That is, it is important to have a minimum draw ratio in a line that biaxially stretches the base film 1 so that the in-plane retardation and thickness direction retardation can be maintained at the above-described numerical values. Accordingly, the draw ratio in the longitudinal direction of the base film 1 is preferably 3.0 to 3.3 times, and the draw ratio in the width direction is preferably 3.0 to 3.6 times. When the longitudinal stretching ratio of the base film 1 is less than 3.0, the film is difficult to control after the film is low and the strength is low, so that the film is torn in the longitudinal direction during lamination of the polarizing plate, and when the longitudinal stretching ratio exceeds 3.3, the remaining film Shrinkage stress becomes high, and it becomes difficult to adjust the orientation angle of main chain to 17 degrees or less. In addition, when the widthwise draw ratio of the base film 1 is less than 3.0, it is difficult to control the film after the film and the film is torn in the width direction in the polarizing plate lamination process, and when the widthwise draw ratio exceeds 3.6, the remaining shrinkage stress is increased. It becomes high, and it becomes difficult to adjust the orientation angle of a principal chain to 17 degrees or less. It is more advantageous to adjust the orientation angle of the main chain to adjust within the draw ratio in this range. In addition, the mechanical properties (strength and elongation) of the polyester film, moisture resistance, and the like can also be maintained at a low draw ratio as in the range of the draw ratio described above.

The primer layer 2 coated on at least one side of the base film 1 according to an embodiment of the present invention may be formed on one side of the base film 1, and if necessary, both sides of the base film 1 It can be formed on both. Since the polyester film for polarizer protection often processes using an adhesive and / or an adhesive agent, the primer layer 2 can be formed in one surface or both surfaces of the base film 1 as needed.

The primer layer 2 can suppress the iridescent phenomenon of the polyester film for polarizer protection. Even if the physical properties described in the above-described base film 1 are satisfied, since the iridescent light (reflection rainbow) that may occur in the post-processing process also becomes visible to the human eye, the primer layer 2 is placed on the base film 1. Coating can solve rainbow light phenomenon. Iridescent phenomenon (reflective rainbow) is a stain that becomes human to rainbows in human eyes depending on the refractive index and coating thickness of the base film (1), the primer layer (2), and the post-processing resin. If there is, it is a phenomenon you can see a lot. This is a phenomenon that occurs because light reflected at the interface between the post-processing resin and the primer layer 2 and the interface between the primer layer 2 and the base film 1 causes reinforcement and destructive interference, respectively.

In order to suppress such an iridescent phenomenon, the primer layer 2 according to an embodiment of the present invention preferably satisfies Equation 4 and Equation 5.

Since the occurrence of the rainbow light phenomenon (reflection rainbow) is the expression of the rainbow light due to the interference of light generated by the difference in reflectance at each interface, the primer layer 2 according to the embodiment of the present invention is represented by Equation 4 and By satisfying the condition of Equation 5, the rainbow light reflection can be eliminated and the visibility can be improved.

To this end, the primer layer 2 is formed on at least one surface of the base film 1. At this time, the primer layer 2 is an easily adhesive layer, and includes at least one or more main materials selected from a water-dispersible polyester copolymer resin or a polyurethane-based resin as a binder resin. The primer layer 2 may be formed of only one resin of the water-disperse polyester copolymer resin or the polyurethane-based resin, and may be formed of the polymer resin including the water-disperse polyester copolymer resin and the polyurethane-based resin.

In addition, the primer layer 2 may include organic or inorganic particles as particles to ensure runability. It is preferable that the particle | grains contained in the primer layer 2 are 10-500 nm in average particle diameter. If the average particle diameter of the particles exceeds 500nm, the haze is increased, and if the average particle diameter of the particles is less than 10nm, the surface roughness is lowered, causing blocking or problems in the film winding, deteriorate appearance. do.

In addition, the inorganic particles included in the primer layer 2 are preferably at least one of silica particles and silica-organic composites, and have a refractive index of 1.5 or more. If the refractive index of the inorganic particles is less than 1.5, the overall refractive index of the primer layer is lowered, resulting in a problem that a rainbow phenomenon occurs.

In addition, the primer layer 2 may include at least one or more selected from oxazoline, carbodiimide and melamine as a curing agent (crosslinking agent). In particular, the oxazoline-based curing agent inhibits or reacts with the moisture permeated to the polarizer protective polyester film, thereby preventing the blocking phenomenon that may occur during double-side coating. In addition, the melamine-based curing agent reacts with the main material, but improves the coating film strength through its own curing reaction between the melamine, thereby preventing the blocking phenomenon that can occur during double-side coating.

In addition, the primer layer 2 may further include an additive such as an anionic surfactant or an antifoaming agent, and may include various kinds of additives in addition to the surfactant.

As an example, the primer layer 2 may include a binder resin, a mixture of a polyester copolymer resin and a polyurethane resin, an aqueous solution of a curing agent, an aqueous dispersion of a surfactant, and an inorganic particle formed by mixing an oxazoline-based curing agent and an epoxy-based curing agent. It can be formed through a coating liquid consisting of a dispersion. The primer layer 2 may be formed by applying the above-described coating liquid on one side or both sides of the base film 1. At this time, the coating thickness of the primer layer 2 is preferably 80 to 150nm. When the coating thickness of the primer layer 2 is less than 80 nm, the reflective rainbow may be observed after the surface treatment, and when the thickness of the primer layer 2 exceeds the 150 nm, the problem of reflecting rainbow and blocking occurs.

The solid content of the polyurethane and / or polyester, which is the main material of the primer layer 2, is preferably 4 to 7% and more preferably 4.5 to 5.5% in the total coating liquid to ensure coating thickness and refractive index. If the solid content of the host material is less than 4%, it is difficult to secure the coating thickness of the primer layer (2), and if the solid content of the host material is more than 7% stains, transverse stains and longitudinal directions that may occur during coating of the primer layer (2) Staining may occur.

In addition, in consideration of the reactivity with the main material, the curing agent included in the primer layer 2 is preferably mixed in a ratio of 100: 5 to 100: 50 relative to the main material. When the curing agent is less than 100: 5 compared to the main body, the reactivity is easily lowered, and a blocking phenomenon is more likely to occur. When the curing agent exceeds 100: 50, coagulation tends to occur depending on the pH change of the coating liquid. In particular, when the curing agent is carbodiimide-based, the higher the ratio of the curing agent is, the higher the possibility of aggregation occurs due to the high reactivity with the polyurethane-based coating liquid.

Next, in the method of manufacturing a polarizer protective polyester film according to an embodiment of the present invention, the unstretched sheet formed in the first step and the first step of melt extruding a polyester resin to form an unstretched sheet in the longitudinal direction (MD) In the second step of uniaxial stretching in the step 1), at least one surface of the sheet uniaxially stretched in the longitudinal direction of the coating liquid mixed with any one selected from a polyurethane-based resin and a polyester-based resin or a combination of a polymer mixed resin and a curing agent A third step of coating and drying, a fourth step of biaxially stretching the sheet coated with the coating liquid in the width direction (TD), and a fifth step of heat-setting the stretched sheet to form a polyester film for polarizer protection.

In the manufacturing method of the polarizer protective polyester film according to an embodiment of the present invention, the description overlapped with the polarizer protective polyester film will be omitted.

The polarizer protective polyester film according to the embodiment of the present invention preferably has a total light transmittance of 90% or more, and more preferably 91% or more. If the total light transmittance is less than 90%, there is a problem that the brightness of the display material is lowered.

The polarizer protective polyester film according to the embodiment of the present invention preferably has a transmittance of 1.5% or less in the 370 nm wavelength band and a transmittance of 9% or less in the 380 nm wavelength band. When the transmittance exceeds 1.5% in the 370 nm wavelength band or the transmittance exceeds 9% in the 380 nm wavelength band, a problem arises in that a reflective rainbow is observed after surface processing.

Moreover, it is preferable that haze is 1.5% or less, and, as for the polyester film for polarizer protection which concerns on this invention, it is more preferable that it is 1% or less. If the haze exceeds 1.5%, the transparency becomes low, resulting in a problem of increasing contrast ratio.

In addition, the polarizer protective polyester film according to the present invention is the adhesion between the base film (1) and the primer layer (2) and the moisture resistance adhesion after the high temperature and high humidity conditions of 500 hours under 60 ℃, 90% humidity is 95% or more, It is preferable that the adhesive force of the primer layer 2 and the post-processing resin is also 95% or more.

Through the following Examples and Comparative Examples will be described in more detail the configuration and effects of the present invention. However, this embodiment is intended to specifically illustrate the present invention, the scope of the present invention is not limited to these examples.

EXAMPLE

[Production example]

The coating liquid constituting the primer layer was prepared in the configuration of Table 2 below.

The coating solution is binder resin consisting of 70% by weight of water and 30% by weight of polyurethane resin (H-15, manufactured by Cheil Industries) and 1% of 70% by weight of water and polyester resin (TR620K, Takamatsu Yuji Co., Ltd.). Preparation) was composed by mixing the main material 2 consisting of 30% by weight in the ratio shown in Table 2 below. 20.0% by weight of the aqueous resin resin dispersion and the oxazoline-based curing agent (WS500, manufactured by Nippon Carbide) for improving the moisture resistance, and the curing agent 1 and the melamine-based curing agent (PM80, DIC) composed of 40% by weight and 60% by weight of water. And 70% by weight and water 30% by weight of the curing agent 2 in the configuration shown in Table 2. 1.0 wt% of a surfactant aqueous dispersion consisting of 90 wt% of water and 10 wt% of anionic surfactant, 70 wt% of silica particles, and 30 wt% of water, and 0.5 wt% of the aqueous dispersion coating solution was prepared. The coating liquid was prepared using the water.

Coating liquid composition division Host 1: Host 2
(Weight ratio) Curing agent 1: Hardening agent 2
(Weight ratio) residence
Solid content (%) Main material: Curing agent
(Weight ratio) Coating liquid 1 1: 0 1: 0 4 100: 5 Coating solution 2 1: 0 1: 0 5.5 100: 5 Coating solution 3 1: 0 1: 0 7 100: 5 Coating liquid 4 1: 0 1: 0 4 100: 50 Coating solution 5 1: 0 1: 0 5.5 100: 50 Coating solution 6 1: 0 1: 0 7 100: 50 Coating liquid7 0: 1 1: 1 4 100: 5 Coating solution 8 0: 1 1: 1 5.5 100: 5 Coating solution 9 0: 1 1: 1 7 100: 5 Coating solution 10 0: 1 1: 1 4 100: 50 Coating liquid 11 0: 1 1: 1 5.5 100: 50 Coating solution 12 0: 1 1: 1 7 100: 50 Coating solution 13 1: 1 1: 1 4 100: 5 Coating liquid 14 1: 1 1: 1 5.5 100: 5 Coating solution 15 1: 1 1: 1 7 100: 5 Coating liquid 16 1: 1 1: 1 2 100: 1 Coating liquid 17 1: 1 1: 1 10 100: 75

[ Example  1-4]

Polyethylene terephthalate raw material chips are melt-extruded, the sheet is manufactured in an unstretched form in a casting roll, and the prepared unstretched sheet is subjected to a stretching process and a heat setting process according to Table 3 to prepare a base film, and Example 1 To 4 (films 1 to 4).

[ Example  5-19]

After preparing the unstretched sheet in the manufacturing process of the base film (film 3) of Example 3, uniaxially stretching in the longitudinal direction, and then using metal bar # 4 with the respective coating solutions (coating solutions 1 to 15) according to Table 2 above. After coating by using the coating and dried at 80 ℃ temperature biaxially stretched in the width direction to prepare a polyester film for protecting the polarizer it was set as Examples 5 to 19 as shown in Table 4.

[Comparative Example 1-4]

A base film was prepared in the same manner as in Example 1 except that the stretch conditions and the heat setting temperatures shown in Table 3 were used to prepare the base film, and Comparative Examples 1 to 4 (films 5 to 8) were used.

[Comparative Example 5-6]

After preparing the unstretched sheet in the manufacturing process of the base film (film 3) of Example 3, uniaxially stretching in the longitudinal direction, and then using metal bar # 4 with each of the coating liquids (coating solutions 16 to 17) according to Table 2 above. After coating by using the coating and dried at 80 ℃ temperature biaxially stretched in the width direction to prepare a polyester film for protecting the polarizer and to give Comparative Examples 5 to 6 as shown in Table 4.

Base film composition division MD draw ratio TD draw ratio Heat setting temperature
(℃) Film thickness
(um) Film 1 3.0 3.1 220 50 Film 2 3.1 3.3 210 50 Film 3 3.2 3.4 200 50 Film 4 3.3 3.6 180 50 Film 5 3.1 3.8 210 50 Film 6 3.1 4.0 190 50 Film 7 3.4 3.3 210 50 Film 8 3.4 3.6 190 50

Configuration of Examples and Comparative Examples division Sheet type Coating liquid type division Sheet type Coating liquid type Example 1 Film 1 - Example 14 Film 3 Coating liquid 10 Example 2 Film 2 - Example 15 Film 3 Coating liquid 11 Example 3 Film 3 - Example 16 Film 3 Coating liquid 12 Example 4 Film 4 - Example 17 Film 3 Coating liquid 13 Example 5 Film 3 Coating liquid 1 Example 18 Film 3 Coating liquids14 Example 6 Film 3 Coating liquid 2 Example 19 Film 3 Coating liquid 15 Example 7 Film 3 Coating liquid 3 Comparative Example 1 Film 5 - Example 8 Film 3 Coating liquid 4 Comparative Example 2 Film 6 - Example 9 Film 3 Coating solution 5 Comparative Example 3 Film 7 - Example 10 Film 3 Coating liquid 6 Comparative Example 4 Film 8 - Example 11 Film 3 Coating liquid7 Comparative Example 5 Film 3 Coating liquid16 Example 12 Film 3 Coating liquid 8 Comparative Example 6 Film 3 Coating liquid17 Example 13 Film 3 Coating liquid 9

Physical properties of the films according to Examples 1 to 19 and Comparative Examples 1 to 6 were measured by the following experimental examples, and the results are shown in Tables 5 and 6 below.

Experimental Example

(1) In-plane phase difference (Re) measurement

In-plane retardation is first placed biaxially stretched film between the two polarizing plates, observed with cross nicol, the angle with the film width direction in the vicinity of the light does not leak, and the direction of the angle Ny, perpendicular to the The phosphorus direction was defined as Nx, and the refractive index for each direction was measured. The refractive index was measured using an Abbe refractometer (ATAGO Co., NAR-3T), the eyepiece has a polarizing function, so that the refractive index can be measured by distinguishing in each direction. The phase difference was measured by multiplying the obtained refractive index by the thickness of the film thus prepared. The thickness of the protective film was measured using the micrometer (VL-50aS, Mitsudo Co., Ltd.).

(2) Thickness direction phase difference (Rth) measurement

The thickness direction retardation was measured by the same equipment and the same method as those measured in the in-plane retardation direction described above. The thickness direction refractive index Nz was computed from the average value of the thickness direction refractive index in Nx direction, and the thickness direction refractive index in Ny direction.

(3) Measurement of surface orientation coefficient (△ P)

The plane orientation coefficient was calculated by applying the measured value of the refractive index of the above Abe refractometer to Equation 3.

(4) main chain orientation angle measurement

After the main chain orientation angle was biaxially stretched, the sample was measured with an orientation angle measuring instrument (SST-4000, Shoji Nomura) to measure the crystal direction of the main chain with respect to the film width direction.

(5) transmission rainbow stain inspection

The prepared film was put in between two polarizing plates, and the presence or absence of the generation of the rainbow stain was confirmed. At this time, the observation angle was directly observed in the range of -90 ^o to 90 ^o with an angle of looking at the front side of the sample as 0 ^o .

(6) reflectance measurement

Reflectance in the visible range was measured using a UV-visible (UV-3600, Shimadzu Corporation). First, attach a colored tape (black insulation tape, etc.) on the opposite side of the surface to be measured, and measure the reflectance of 300nm to 800nm using the above equipment, and then measure the reflectance of 550nm wavelength. Confirmed.

(7) Primer layer refractive index and base film refractive index measurement

On the silicon substrate, the coating liquids prepared in Examples 5 to 19 and Comparative Examples 5 to 6 were applied, dried at 120 ° C, and applied using Ellipsometry (Elli-SE-aM12, Ellipso Tech Co., Ltd.). The refractive index of the layer only was measured. Based on this, the ratio of the refractive index (average value of Nx, Ny) of a primer layer and a base film was computed.

(8) reflected rainbow measurement

To the films made in Examples 1 to 19 and Comparative Examples 1 to 6, a hard coat coating liquid was applied and cured by UV. The cured film was visually checked for the presence of reflective rainbows.

(9) adhesion force measurement

The adhesion force makes a cutting line with the cutter, placing 2mm * 2mm squares in a 10 * 10 matrix. The cellophane tape (No. 405, width of NICHIBAN: 24 mm) is affixed to the film with a cutting line, and the tape is rubbed strongly with the film using a velvet, and then the tape is removed vertically. The area of the resin layer remaining in the primer layer was visually observed, and the adhesion was calculated by the above equation (6).

division Sheet
Kinds Re [nm] Rth [nm] Face orientation
Coefficient Main chain orientation angle [ ^o ]
(Width center / end) Penetration
Rainbow Example 1 Film 1 225 8352 0.159 0/8 ○ Example 2 Film 2 138 8264 0.161 0 / 9.7 ○ Example 3 Film 3 110 8123 0.163 0/12 ○ Example 4 Film 4 82 8050 0.164 0/17 ○ Comparative Example 1 Film 5 625 8290 0.168 0/7 Δ Comparative Example 2 Film 6 790 8325 0.175 0 / 5.5 X Comparative Example 3 Film 7 420 7950 0.172 0/22 X Comparative Example 4 Film 8 230 8005 0.169 0/19 Δ

(○: good, Δ: amblyopian, X: lecturer)

division Sheet
Kinds Coating liquid
Kinds reflectivity(%) Refractive index ratio reflect
Rainbow Adhesion Example 5 Film 3 Coating liquid 1 3.8 0.958 ○ 96 Example 6 Film 3 Coating liquid 2 3.7 0.958 ○ 97 Example 7 Film 3 Coating liquid 3 3.6 0.958 ○ 95 Example 8 Film 3 Coating liquid 4 3.9 0.976 ○ 96 Example 9 Film 3 Coating solution 5 3.7 0.976 ○ 98 Example 10 Film 3 Coating liquid 6 3.8 0.976 ○ 99 Example 11 Film 3 Coating liquid7 2.9 0.964 ○ 100 Example 12 Film 3 Coating liquid 8 3.1 0.964 ○ 100 Example 13 Film 3 Coating liquid 9 3.1 0.964 ○ 100 Example 14 Film 3 Coating liquid 10 3.0 0.968 ○ 100 Example 15 Film 3 Coating liquid 11 2.9 0.968 ○ 100 Example 16 Film 3 Coating liquid 12 2.8 0.968 ○ 100 Example 17 Film 3 Coating liquid 13 4.0 0.961 ○ 96 Example 18 Film 3 Coating liquids14 3.9 0.961 ○ 98 Example 19 Film 3 Coating liquid 15 3.8 0.961 ○ 96 Comparative Example 5 Film 3 Coating liquid16 5.8 0.914 X 85 Comparative Example 6 Film 3 Coating liquid17 2.9 0.99 △ 90

(○: microscopic, Δ: amblyopian, X: lecturer)

Examples 1 to 4 and Comparative Examples 1 to 4 described above are base films that do not form a primer layer, and Examples 1 to 4 form base films of Films 1 to 4 that satisfy the length and width direction draw ratio conditions. In Comparative Examples 1 to 4, base films of films 5 to 8 that do not satisfy the draw ratio conditions were formed.

As can be seen in Table 5, Examples 1 to 4 satisfy all of the in-plane retardation (Re) is less than 500nm, which is the physical property value of the in-plane retardation (Re) of Table 1, and do not generate a rainbow stain according to the transmission rainbow appear.

On the other hand, Comparative Examples 1 and 2 showed that the physical property value of the in-plane retardation (Re) exceeds 500 nm, the plane orientation coefficient exceeds 0.164, and rainbow staining occurs according to the transmission rainbow. In addition, Comparative Examples 3 and 4 also had a plane orientation coefficient of more than 0.164 and rainbow staining occurred according to the transmission rainbow.

Examples 5 to 19 and Comparative Examples 5 and 6 all used film 3 as a base film, but formed primer layers with different coating liquids.

As can be seen in Table 6 above, it is satisfied that the solid content ratio of the base material in the stretching ratio of the base film and the coating liquid is 4 to 7%, and the weight ratio of the base material to the hardener is 100: 5 to 100: 50. Examples 5 to 19 according to the present invention satisfies that the reflectance of Equation 5 is 4% or less, satisfies the refractive index ratio of Equation 4 is 0.958 to 0.98, satisfies that the adhesion is 95% or more, and the rainbow according to the reflective rainbow. No staining appeared.

On the other hand, Comparative Example 5, in which the solid content ratio of the base material in the coating liquid is 2% (less than 4%) and the weight ratio of the base material to the hardener is 100: 1, does not satisfy 100: 5 to 100: 50, has a reflectance of 5.8%. It is not satisfied that the reflectance of Equation 5 is 4% or less, the refractive index ratio is 0.914, does not satisfy the refractive index ratio of 0.958 to 0.98, the adhesion is 85%, does not satisfy the adhesion of 95% or more, and the reflection rainbow A rainbow stain was observed.

In addition, the comparative example 6 in which the solid content ratio of the base material in the coating liquid is 10% (more than 7%) and the weight ratio of the base material to the hardener is 100: 75 and does not satisfy 100: 5 to 100: 50 is represented by an equation of refractive index of 0.99. 4 did not satisfy the refractive index ratio of 0.958 to 0.98, the adhesion is 90%, does not satisfy the adhesion of more than 95%, it was shown that the rainbow spots occur according to the reflective rainbow.

In Comparative Examples 5 and 6, although the physical properties of the base film satisfy the required physical properties of the present invention, since the physical properties of the primer layer do not satisfy the requirements, it can be seen that a problem occurs in the finished polarizer-protective polyester film. have.

Unlike Examples 5 to 19, which are polyester films for polarizer protection satisfying the above-described various conditions as described above, Comparative Examples 5 to 6, which do not satisfy all of them, were found to have rainbow stains caused by transmission rainbow, and reflectance and refractive index ratio conditions were observed. It was confirmed that there was a problem in the adhesion force, not satisfied.

Polyester film for polarizer protection according to an embodiment of the present invention according to the above can minimize the rainbow phenomenon after the hard coating process to improve the productivity in post-processing, as the transmission rainbow is used as a protective purpose of the polarizer is improved This is possible. In addition, the polarizer protective polyester film according to an embodiment of the present invention according to the above-described excellent optical properties can be widely used as a protective film such as an antireflection film and a liquid crystal display device.

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 rights.

1: base film
2: primer layer

Claims (15)

At least uniaxially stretched polyester base film; And
A primer layer formed on at least one surface of the base film and including at least one resin and a curing agent selected from a polyurethane-based resin or a polyester-based resin;
Including;
The polyurethane-based resin or polyester-based resin of the primer layer has a solid content of 4 to 7% in the total coating solution, and the curing agent has a ratio of 100: 5 to 100: 50 relative to the polyurethane-based resin or polyester-based resin,
The draw ratio in the longitudinal direction of the polyester base film is 3.0 to 3.3 times, the draw ratio in the width direction is 3.0 to 3.6 times, the orientation angle of the main chain of the crystalline region (Crystalline Region) is 17 degrees or less, and the surface orientation according to the following formula 1 The coefficient ΔP is less than or equal to 0.164,
(Equation 1)

Nx is a refractive index of a film longitudinal direction, Ny is a refractive index of a film width direction, Nz is a refractive index of a film thickness direction, The polyester film for polarizer protection. The method of claim 1,
The curing agent is a polarizer protective polyester film of at least one resin selected from the group consisting of oxazoline-based, carbodiimide-based and melamine-based. delete The method of claim 1,
Polyurethane resin or polyester resin of the primer layer is a polarizer protective polyester film having a solid content of 4.5 to 5.5% in the total coating liquid. The method of claim 1,
The primer layer is a polarizer protective polyester film having a reflectance of 4% or less in the wavelength range of 550nm. The method of claim 1,
The said polyester base film is a polyester film for polarizer protection whose in-plane phase difference (Re) is 500 nm or less, and thickness direction phase difference (Rth) is 8000 nm or more. delete delete The method of claim 1,
The refractive index ratio between the primer layer and the base film satisfies Equation 4 below.
[Equation 4]
0.958 ≤ refractive index of the primer layer / refractive index of the base film ≤ 0.98
Polyester film for phosphorus polarizer protection. The method of claim 1,
The primer layer is a polarizer protective polyester film further comprises an anionic surfactant and particles having an average particle diameter of 10 to 500nm. The method of claim 1,
Adhesion between the base film and the primer layer and the moisture resistance adhesion after a high temperature and high humidity condition of 500 hours at 60 ℃, 90% humidity is more than 95%, the adhesion between the primer layer and the post-processing resin is 95% or more polyester for polarizer protection film. In the method for producing a polyester film comprising a polyester base film and a primer layer,
Melt extruding the polyester resin to form an unstretched sheet;
A second step of uniaxially stretching the unstretched sheet formed in the first step in the longitudinal direction (MD);
A third step of applying and drying a coating liquid in which at least one resin selected from a polyurethane resin or a polyester resin and a curing agent are mixed on at least one surface of the sheet uniaxially stretched in the length direction in the second step;
A fourth step of biaxially stretching the sheet coated with the coating liquid in the third step in the width direction (TD); And
Comprising a fifth step of forming a polarizer protective polyester film by heat-setting the sheet stretched in the fourth step,
The polyurethane-based resin or polyester-based resin has a solid content of 4 to 7% in the entire coating solution, the curing agent has a ratio of 100: 5 to 100: 50 compared to the polyurethane-based resin or polyester resin,
The draw ratio in the longitudinal direction is 3.0 to 3.3 times and the draw ratio in the width direction is 3.0 to 3.6 times,
In the polyester base film, the orientation angle of the main chain of the crystalline region is 17 degrees or less, and the plane orientation coefficient (ΔP) according to Equation 1 is 0.164 or less,
(Equation 1)

Nx is a refractive index of the longitudinal direction, Ny is a refractive index of the width direction, Nz is a refractive index of the thickness direction, the manufacturing method of the polarizer protective polyester film. delete The method of claim 12,
The heat setting temperature of the fifth step is 180 to 220 ℃ manufacturing method of the polarizer protective polyester film. The polarizing plate with which the polyester film for polarizer protection of any one of Claims 1, 2, 4-6, and 9-11 was provided in at least one surface of the polarizer.

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