WO2015046936A1

WO2015046936A1 - Optical film and method for manufacturing same

Info

Publication number: WO2015046936A1
Application number: PCT/KR2014/008997
Authority: WO
Inventors: 김종훈; 박기호; 이정규
Original assignee: 삼성에스디아이 주식회사
Priority date: 2013-09-27
Filing date: 2014-09-26
Publication date: 2015-04-02

Abstract

An optical film comprising: a polarizer; a first adhesive layer and a second adhesive layer respectively formed on two surfaces of the polarizer; and a first protective film and a second protective film formed by being adhered to the first adhesive layer and the second adhesive layer, wherein at least a portion of the first adhesive layer and/or the second adhesive layer has alignment properties, and a method for manufacturing an optical film allowing an adhesive inside a laminated film to have alignment properties, by laminating a polyvinyl alcohol-based film on at least one surface of the optical film while an adhesive is interposed, and laminating same.

Description

Optical film and manufacturing method thereof

The present invention relates to an optical film and a method of manufacturing the same.

Polarizing plates are used inside and outside the liquid crystal cell for the purpose of controlling the vibration direction of light in order to visualize the display pattern of the liquid crystal display device. Applications of liquid crystal display devices range from small devices in the early stages of development to notebook computers, liquid crystal monitors, liquid crystal color projectors, liquid crystal televisions, in-vehicle navigation systems, personal phones, and measuring devices used indoors and outdoors. It is shown. In particular, among the field of application of the liquid crystal display device, a liquid crystal monitor, a liquid crystal television, etc. often use a high brightness backlight.

Recently, as the display devices become thinner, internal parts are also required to be thinner. Therefore, the polarizing film used for a polarizing plate also came to require thickness reduction more than a conventional product.

Therefore, there is a need for an optical film including a polarizing film that is thin and excellent in optical characteristics, and a method of manufacturing the same.

Accordingly, the technical problem to be solved by the present invention is to provide an optical film including a polarizer having excellent optical characteristics as described above. In addition, to provide a manufacturing method for easily manufacturing the optical film.

The objects of the present invention are not limited to the above-mentioned technical problem, and other technical problems not mentioned will be clearly understood by those skilled in the art from the following description.

The optical film according to an embodiment of the present invention for achieving the above object is a polarizer, a first adhesive layer and a second adhesive layer formed on both sides of the polarizer, respectively, and a first adhesive layer formed in contact with the first adhesive layer and the second adhesive layer It includes a protective film and a second protective film, at least one of the first adhesive layer and the second adhesive layer may have an orientation.

The polarizer may have a thickness in the range of 0.5 μm to 15 μm.

The polarizer may include a polyvinyl alcohol-based resin containing a dichroic material.

The polarizer may be a uniaxially stretched film or a biaxially stretched film.

An orientation of at least one of the first adhesive layer and the second adhesive layer having at least a portion of the alignment may be the same as that of the polarizer.

The surface roughness of the polarizer may be Rz of 3 μm or less.

At least one of the first adhesive layer and the second adhesive layer may have at least one absolute value of a ratio of the maximum absorbance to the minimum absorbance greater than 1.

The optical film according to another embodiment of the present invention for achieving the above object includes a polarizer, a third adhesive layer and a fourth adhesive layer formed on both sides of the polarizer, and a third protective film formed in contact with the third adhesive layer. At least a portion of the fourth adhesive layer may have an orientation.

The optical film according to another embodiment of the present invention for achieving the above object comprises a polarizer, a fifth adhesive layer formed on one surface of the polarizer, and a fourth protective film formed in contact with the fifth adhesive layer, the fifth At least a portion of the adhesive layer may have an orientation.

The optical film manufacturing method according to an embodiment of the present invention for achieving the above object is a step of laminating a polyvinyl alcohol-based film on the at least one surface of the base film via an adhesive, dyeing the laminated film with a dichroic dye May include stretching the laminated film, removing the base film to obtain a polarizer, and laminating a protective film to the polarizer.

The stretching ratio of the stretching step may range from 2.0: 1 to 10: 1.

The step of laminating the polyvinyl alcohol-based film on the base film may be laminating the polyvinyl alcohol-based film on both sides of the base film.

After the stretching step, the first protective film is laminated on the opposite side of the base film of the polyvinyl alcohol-based film of the laminated film, and after removing the base film, the second protective film is a substrate of the polyvinyl alcohol-based film It can laminate on a film bonding surface.

In the stretching step, the adhesive inside the laminated film may have an orientation.

Specific details of other embodiments are included in the detailed description and the drawings.

According to embodiments of the present invention has at least the following effects.

That is, the optical film of the present invention includes a polarizing film having excellent optical properties while being a thin film, and the optical film manufacturing method of the present invention can produce an optical film including a polarizer having easy and excellent optical properties in the process.

The effects according to the present invention are not limited by the contents exemplified above, and more various effects are included in the present specification.

1 is a cross-sectional view schematically showing an optical film according to an embodiment of the present invention.

2 is a cross-sectional view schematically showing an optical film according to another embodiment of the present invention.

3 is a cross-sectional view schematically showing an optical film according to another embodiment of the present invention.

4 is a schematic process flowchart of an optical film manufacturing method according to an embodiment of the present invention.

Advantages and features of the present invention and methods for achieving them will be apparent with reference to the embodiments described below in detail with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but will be implemented in various forms, and only the present embodiments are intended to complete the disclosure of the present invention, and the general knowledge in the art to which the present invention pertains. It is provided to fully convey the scope of the invention to those skilled in the art, and the present invention is defined only by the scope of the claims.

References to elements or layers "on" other elements or layers include all instances where another layer or other element is directly over or in the middle of another element. Like reference numerals refer to like elements throughout.

Although the first, second, etc. are used to describe various components, these components are of course not limited by these terms. These terms are only used to distinguish one component from another. Therefore, of course, the first component mentioned below may be a second component within the technical spirit of the present invention.

In addition, unless the steps constituting the manufacturing method described herein are sequential or sequential, or unless otherwise indicated, one step and another step constituting one manufacturing method in the order described in the specification. It is limited and not interpreted. Therefore, the order of construction steps of the manufacturing method can be changed within a range that can be easily understood by those skilled in the art, in which case the obvious changes to those skilled in the art will be included within the scope of the present invention.

Optical film

Hereinafter, an optical film according to embodiments of the present invention will be described with reference to FIGS. 1 to 3. 1 to 3 are cross-sectional views schematically showing an optical film according to embodiments of the present invention.

First, referring to FIG. 1, an optical film according to an embodiment of the present invention may include a polarizer 110, a first adhesive layer 131 and a second adhesive layer 132 formed on both surfaces of the polarizer 110, and a first adhesive layer 132. A first protective film 121 and a second protective film 122 formed in contact with the first adhesive layer 131 and the second adhesive layer 132 and positioned on both surfaces in the thickness direction, and including the first adhesive layer 131 and At least one of the second adhesive layers 132 may be at least partially aligned.

The thickness of the polarizer 110 may be appropriately adjusted depending on the conditions of the device to be applied, but is not limited thereto, and may be in the range of 0.5 μm to 15 μm. When the thickness of the polarizer 110 is 0.5 μm or more, the process may be thinner, and when it is 15 μm or less, it may be applied to a thin film device or the like.

The polarizer 110 may be used without limitation as long as it is a material having a polarizing function. For example, the polarizer 110 may include a polyvinyl alcohol (PVA) -based resin containing a dichroic material. In addition, it may further contain a suitable additive. Examples of the additives include a surfactant and an antioxidant, but are not limited thereto.

The polarizer 110 may be a uniaxially or biaxially stretched film. The stretched polarizer may realize retardation characteristics when adhered to the liquid crystal cell.

Examples of such dichroic materials include, but are not limited to, iodine, dyes, pigments and mixtures thereof.

The polyvinyl alcohol-based resin can generally be obtained by saponifying a polyvinyl acetate-based resin. The polyvinyl alcohol-based resin generally may have a saponification degree in a range of 85 mol% to 100 mol%, and a polymerization degree in a range of 1,000 to 10,000, but is not limited thereto. Non-limiting examples of the polyvinyl alcohol-based resins include polyvinyl alcohol or ethylene-vinyl alcohol copolymers.

The optical film 100 may be used as a polarizing plate by itself, but may be used after removing at least one of the first protective film 121 and the second protective film 122. When the first protective film 121 and the second protective film 122 are used in the polarizing plate, it may be a transparent material to suit the purpose.

The first protective film 121 and the second protective film 122 are not particularly limited as long as they are suitable materials for each application, but are not limited to triacetyl cellulose, cellulose such as diacetyl cellulose, polyethylene terephthalate, polyethylene naphthalate, and polybutylene. Polyesters such as terephthalate, cyclic polyolefins, polycarbonates, polyethers, polysulfones, polyamides, polyimides, polyolefins, polyarylates, polyvinyl alcohols, polyvinyl chlorides The film may be made of a material selected from the group consisting of polyvinylidene chloride, acrylic, or a mixture thereof, but is not limited thereto.

The first protective film 121 and the second protective film 122 may each have a thickness in the range of 5 μm to 200 μm. In the above range, it can be used as a polarizing plate when laminated on the polarizing element. In some exemplary embodiments, the first protective film 121 and the second protective film 122 may have a thickness in the range of 5 μm to 100 μm, respectively, for the purpose of thinning.

The alignment of at least one of the first adhesive layer 131 and the second adhesive layer 132 having at least a portion of the alignment may be the same as the alignment direction of the polarizer 110. For this reason, more excellent optical characteristics can be exhibited.

The orientation can be confirmed by the ratio of the maximum absorbance to the minimum absorbance. For example, the minimum absorbance can be obtained when the polarization perpendicular to the alignment direction is incident, and the maximum absorbance can be obtained when the polarization parallel to the orientation direction is incident. If not oriented at all, the ratio of the maximum absorbance to the minimum absorbance will be one. In addition, when the orientation is perfect, the ratio of the maximum absorbance to the minimum absorbance may be infinite, so the upper limit of the ratio of the maximum absorbance to the minimum absorbance is meaningless. In addition, since the positive direction and the negative direction may be defined according to the direction, the ratio may be determined as an absolute value.

For example, when analyzing the degree of alignment of the carbon chain, which is the main chain, through IR analysis, it may be determined that the absolute value of the ratio of the maximum absorbance to the minimum absorbance is greater than one.

The polarizer 110 may have a surface roughness of Rz of 3 μm or less, but is not limited thereto. When having a relatively low surface roughness as described above, it is possible to reduce the haze problem and the like, and to exhibit high optical properties in some cases.

Referring to FIG. 2, the optical film according to another embodiment of the present invention may include a polarizer 210, a third adhesive layer 231 and a fourth adhesive layer 232, and a third adhesive layer formed on both surfaces of the polarizer 210, respectively. A third protective film 220 formed in contact with 231, and at least a portion of the fourth adhesive layer 232 may have an orientation.

In the case of the fourth adhesive layer 232, it may face the display substrate, or may contact a separate film for protecting the optical film itself.

Other descriptions corresponding to or identical to those of FIG. 1 will be omitted to avoid duplication.

Referring to FIG. 3, an optical film according to another embodiment of the present invention is formed in contact with the polarizer 310, the fifth adhesive layer 330 formed on one surface of the polarizer 310, and the fifth adhesive layer 330. Including the fourth protective film 320, at least a portion of the fifth adhesive layer 330 may have an orientation.

Liquid crystal display

Although not separately illustrated, the liquid crystal display according to the exemplary embodiment of the present invention may include the optical film. A description with reference to reference numerals of FIG. 1 is as follows.

The liquid crystal display device may include a liquid crystal cell and a backlight unit.

The liquid crystal cell usually includes two substrates and a liquid crystal layer interposed between the substrates. In general, one of the substrates may include a color filter, an opposite electrode, and an alignment layer, and the other substrate may include a liquid crystal driving electrode, a wiring pattern, a thin film transistor element, and an alignment layer.

Examples of the operation mode of the liquid crystal cell include a twisted nematic mode or an electrically controlled birefrigence mode. Examples of the electrically controlled birefrigence mode include a vertical alignment method, an OCB (Optically Compensated) method, an IPS (In-Plane Switching) method, and the like.

The backlight unit may generally include a light source, a light guide plate, a reflective film, and the like. According to the configuration of the backlight can be arbitrarily divided into a direct method, a side light method, a planar light source method.

The optical film 100 may be interposed between the backlight unit and the liquid crystal cell. In this case, the polarizer 110 of the optical film 100 may transmit only light that vibrates in a specific direction among the light incident from the light source of the backlight unit.

In addition, the optical film 100 may be included at a position opposite to the backlight of the liquid crystal cell. In this case, it may be a form interposed between the other components of the liquid crystal display device, it may be located on the surface of the liquid crystal display device. In addition, when two optical films 100 are positioned with the liquid crystal cell interposed therebetween, the transmission axes of the polarizers 110 of each optical film 100 may be orthogonal or parallel.

Optical film manufacturing method

Referring to FIG. 4 together with FIG. 1, in the method of manufacturing an optical film, a step of laminating a polyvinyl alcohol-based film on at least one surface of a base film with an adhesive (S10), and dyeing the laminated film with a dichroic dye. The step (S20), the step of stretching the laminated film (S30), the step of removing the base film to obtain a polarizer (S40) and the step of laminating a protective film to the polarizer (S50).

The base film is not particularly limited as long as it can be stretched in a temperature range suitable for stretching the polyvinyl alcohol-based film. For example, the polymer film may have a transmittance of 90% or more, but is not limited thereto.

In the step of laminating (S10), a polyvinyl alcohol-based film having a thickness of 30 μm or less is laminated to the base film using an adhesive. In an exemplary embodiment, after the lamination step S10, the drying process may be performed. The drying temperature may be a temperature below the melting point and / or glass transition temperature of the base film and the polyvinyl alcohol-based film.

The dyeing step (S20) is a process of introducing iodine, a dye, a pigment, or a mixture thereof, which is a dichroic substance, into the polyvinyl alcohol-based film of the laminated film to adsorb them into the film. The iodine, dye, or pigment molecules absorb light oscillating in the stretching direction of the polarizing film and transmit light oscillating in the vertical direction, thereby obtaining polarized light having a specific vibration direction.

The dyeing process can be achieved by impregnating the dichroic film in a dichroic material solution. For example, when the dichroic substance is iodine, the temperature of the iodine solution may range from 20 ° C. to 50 ° C., and the impregnation time may range from 10 to 300 seconds. When the iodine solution is used as the iodine solution, an aqueous solution containing iodine (I ₂ ) and iodine ions, for example, potassium iodide (KI) used as a dissolution aid, may be used. In an exemplary embodiment, the concentration of iodine (I ₂ ) may range from 0.01 to 0.5 weight percent based on the total weight of the aqueous solution, and the concentration of potassium iodide (KI) may range from 0.01 to 12 weight percent based on the total weight of the aqueous solution. have.

In an exemplary embodiment, the swelling step may be further included before performing the dyeing step (S20). The swelling step may serve to soften the molecular chain of the polyvinyl alcohol-based film and relax the molecular chain, so that the dichroic material is homogeneously dyed into the polyvinyl alcohol-based film during the dyeing process so that staining does not occur. .

The swelling ratio can be 110% to 600%. In this swelling process, the polyvinyl alcohol-based film can be stretched to have an elongation of 1.0 to 6.0 times. When satisfying the swelling ratio and the elongation as described above, it is possible to achieve high permeability while preventing the occurrence of staining during the dyeing process without inhibiting the physical properties of the polarizing film and to improve the uniformity of the optical properties. The swelling step can be performed by a dry method or a wet method. In an exemplary embodiment, it may be carried out by a wet method in a swelling bath containing swelling liquid. In addition, the swelling temperature may vary depending on the film thickness, for example, may be in the range of 0 ℃ to 100 ℃. Of course, in the case of the dry method can proceed at a higher temperature than the wet method.

In another exemplary embodiment, a crosslinking process may be further included after the dyeing step (S20).

When the dichroic substance molecules are dyed to the polyvinyl alcohol-based film in the dyeing step (S20), the dichroic molecules are adsorbed onto the polymer matrix of the polyvinyl alcohol-based film using boric acid, borate, or the like. Examples of the crosslinking method include a deposition method in which a polyvinyl alcohol-based film is deposited by dipping a boric acid solution or the like, but is not limited thereto, and may be performed by a coating method or a spraying method for applying or spraying a solution to a film. It may be.

Stretching step (S30) may use a wet stretching method and / or dry stretching method common in the art.

Non-limiting examples of the dry stretching method include an inter-roll stretching method, a heating roll stretching method, a compression stretching method, a tenter stretching method, and the like. Non-limiting examples include a tenter stretching method, an inter-roll stretching method, and the like.

In the case of the wet stretching method, stretching may be performed in alcohols, water or boric acid aqueous solution, and for example, a solvent such as methyl alcohol or propyl alcohol may be used, but is not limited thereto.

Stretching temperature and time can be suitably selected and used according to the material of a film, desired elongation rate, a usage method, etc. In addition, the stretching step S30 may be uniaxial stretching or biaxial stretching. However, biaxial stretching may be performed to manufacture a polarizing film adhered to a liquid crystal cell so as to realize retardation characteristics.

In an exemplary embodiment, the stretching ratio of the stretching step S30 may range from 2.0: 1 to 10: 1.

In the stretching step (S20) while the adhesive layer between the base film and the polyvinyl alcohol-based film of the laminated film is stretched together, it may have the same orientation as the polyvinyl alcohol-based film.

The dyeing step (S20) and the stretching step (S30) does not always have to be the same order, and can be appropriately selected by the order according to the process equipment and equipment, in some cases, the stretching step (S30) is a dyeing process (S20) or may be performed simultaneously with the crosslinking process. When the stretching step S30 proceeds simultaneously with the dyeing step S20, the stretching step S30 may be performed in the iodine solution. On the other hand, when the stretching step (S30) is carried out simultaneously with the crosslinking process, the stretching step (S30) may be carried out in an aqueous boric acid solution.

In another exemplary embodiment, the step of laminating (S10) may be laminating a polyvinyl alcohol-based film on both sides of the base film. When the polyvinyl alcohol-based film is laminated and stretched on one surface of the base film, end curling and curling may be caused by shrinkage of the polyvinyl alcohol-based film due to the difference in coefficient of thermal expansion between the base film and the polyvinyl alcohol-based film. curl) may occur. When the polyvinyl alcohol-based film is laminated and dyed on both sides of the base film, shrinkage forces act in opposite directions to cancel the force to control end curling and curling. In addition, since two optical films can be produced per one process, the process efficiency is excellent.

Removing the base film to obtain a polarizer (S40) and the step of laminating the protective film (S50) can be proceeded by appropriately placing the order in some cases, in some cases may proceed at the same time, the first protective film The base film may be removed between the paper of the 121 and the second protective film 122.

In an exemplary embodiment, after the stretching step S30, the first protective film 121 is laminated on the opposite side of the base film of the polyvinyl alcohol-based film (polarizer 110) of the laminated film, and the base film After removal, the second protective film 122 may be laminated on the base film bonding surface of the polyvinyl alcohol-based film.

Preparation Example 1

After the polyvinyl alcohol (PVA) film having a thickness of 30 μm is corona treated on one surface of the polypropylene (PP) film, a PVA adhesive is applied and laminated, and then dried at 70 ° C. for 4 minutes to obtain a laminated film. The laminated film is stretched 2.5 times at room temperature for 95 seconds to undergo a swelling process. The laminated film that passed through the swelling process is immersed by immersion at room temperature for 163 seconds in an aqueous solution in which the amount of use is adjusted to meet a target transmittance at a ratio of iodine: KI = 1:23. The dyed laminated film is crosslinked by immersing at room temperature for 63 seconds in an aqueous solution containing 3% by weight of boric acid. Thereafter, the laminated film is stretched so that the final stretching ratio is 5.6 times at 60 ° C. for about 105 seconds in an aqueous solution containing 3 wt% boric acid and 3 wt% KI. The stretched laminated film is dried at 70 ° C. for 4 minutes to obtain a laminated film including a polarizer. The base film was removed from the laminated film, and a transparent protective film (Fujita, FUJITAC 80 μm) was coated on both sides of the polarizer by applying a PVA adhesive, and then laminated at 70 ° C. for 4 minutes to prepare an optical film.

Preparation Example 2

An optical film was manufactured in the same manner as in Preparation Example 1, except that the PVA film was laminated on both surfaces of the base film.

Comparative Production Example 1

An optical film was prepared in the same manner as in Preparation Example 1, except that a 60 μm thick PVA film alone was used without a separate base film.

Comparative Production Example 2

An optical film was manufactured in the same manner as in Preparation Example 1, except that the PVA solution was coated on one surface of the base film.

Experimental Example 1

For the optical films produced in Preparation Example 1, Preparation Example 2 and Comparative Preparation Example 1, the transmittance, polarization degree, and roughness of the polarizing film inside the optical film were measured, and the results are shown in Table 1 below.

Table 1

division	Transmittance (%)	% Polarization	Polarizing Film Number / Process	Roughness (Rz)	Remarks
Preparation Example 1	42.379	99.993	One	<3.0 μm
Preparation Example 2	42.232	99.996	2	<3.0 μm	Upper side
Preparation Example 2	42.326	99.995	2	<3.0 μm	Lower side
Comparative Production Example 1	42.312	99.996	One	-
Comparative Production Example 2	42.369	99.970	One	> 3.0 μm	Coated

Referring to Table 1, it can be seen that the optical films produced in Preparation Examples 1 and 2 exhibited transmittance and polarization degree equivalent to or higher than those of the conventional optical films prepared in Comparative Preparation Examples 1 and 2 in optical properties. In addition, the optical films prepared in Preparation Examples 1 and 2 including polarizers having a surface roughness Rz of less than 3.0 μm have a polarization degree higher than that of the optical film manufactured in Comparative Preparation Example 1 including a polarizer having a surface roughness Rz of 3.0 μm or more. It can be confirmed that is excellent.

The embodiments described above are all exemplary, and different embodiments may be applied in combination.

Claims

Polarizer;

First and second adhesive layers respectively formed on both surfaces of the polarizer; And

A first protective film and a second protective film formed in contact with the first adhesive layer and the second adhesive layer,

At least one of the first adhesive layer and the second adhesive layer is at least partly an optical film.
According to claim 1,

The polarizer has an optical film having a thickness in the range of 0.5 μm to 15 μm.
According to claim 1,

The polarizer comprises a polyvinyl alcohol-based resin containing a dichroic substance.
According to claim 1,

The polarizer is an uniaxially oriented film or biaxially oriented film.
According to claim 1,

The at least one of the first adhesive layer and the second adhesive layer having at least a portion of the alignment is the same as the optical film.
According to claim 1,

The surface roughness of the said polarizer is an optical film with Rz of 3 micrometers or less.
According to claim 1,

At least one of the first adhesive layer and the second adhesive layer has at least a portion of the absolute value of the ratio of the maximum absorbance to the minimum absorbance is greater than one.
Polarizer;

Third and fourth adhesive layers formed on both surfaces of the polarizer, respectively; And

It includes a third protective film formed in contact with the third adhesive layer,

At least a part of the fourth adhesive layer has an optical film.
Polarizer;

A fifth adhesive layer formed on one surface of the polarizer; And

A fourth protective film formed in contact with the fifth adhesive layer,

At least a part of the fifth adhesive layer has an orientation.
Laminating a polyvinyl alcohol-based film on at least one surface of the base film with an adhesive interposed therebetween;

Dyeing the laminated film with a dichroic dye;

Stretching the laminated film;

Removing the base film to obtain a polarizer; And

Laminating a protective film on the polarizer.
The method of claim 10,

The stretching ratio of the stretching step is a method for producing an optical film in the range of 2.0: 1 to 10: 1.
The method of claim 10,

The step of laminating a polyvinyl alcohol-based film to the base film is a method for producing an optical film of laminating the polyvinyl alcohol-based film on both sides of the base film.
The method of claim 10,

After the stretching step, the first protective film is laminated on the opposite side of the base film of the polyvinyl alcohol-based film of the laminated film, and after removing the base film, the second protective film is a substrate of the polyvinyl alcohol-based film The manufacturing method of the optical film laminated | stacked on the film bonding surface.
The method of claim 10,

In the stretching step, the adhesive inside the laminated film is a manufacturing method of a polarizing film having an orientation.