KR102231814B1 - Polarizing film by extruding method - Google Patents

Abstract

The present invention provides a polarizing film in which a resin containing a dichroic dye is dispersed in a thermoplastic resin through a melt extrusion process, the dichroic dye is oriented through a dry drawing process, and the resin containing the oriented dichroic dye is continuously/discontinuously and randomly dispersed, in a needle form, in the thermoplastic resin in a predetermined direction, and a method for manufacturing the polarizing film. The present invention allows a resin composition including a polarizing function to be present in another resin, and thus does not require attachment of an additional protective film to a skin layer of a polarizing film, and enables the manufacture of the polarizing film through melt extrusion. Since the polarizing function is uniformly dispersed in the resin, the present invention is advantageous in reducing stains and the like on a polarizing film. In addition, a melt-extrusion-type manufacturing method can remarkably reduce environmental pollution and the like.

Description

Melt extrusion polarizing film {Polarizing film by extruding method}

The present invention relates to a resin composition of a melt extrusion type dispersed polarizing film, a polarizing filler using the same, and a method of manufacturing the polarizing film. More specifically, through a melt extrusion process, the skin layer of the thermoplastic resin (A) and the resin (C) containing a plasticizer and a dichroic dye (B) are dispersed inside the thermoplastic resin (A) to form a core layer. The dichroic dye (B) is oriented through a dry stretching process, and the resin (C) containing the oriented dichroic dye (B) is continuously or fired in the interior of the thermoplastic resin (A) in a needle-shaped needle shape. It relates to a resin composition of a polarizing film and a method of manufacturing a polarizing film, which is a polarizing film, which is continuously randomly dispersed in a predetermined direction, and is produced through melt extrusion and uniaxial to biaxial stretching processes.

The display technology of the modern society has continued to develop into a CRT, a projector, a plasma display (PDP), a liquid crystal display (LCD), and an organic light emitting diode (OLED). Among them, liquid crystal displays must use two polarizing films in principle, and organic light emitting diodes also use one polarizing film to increase the contrast ratio.
Polarizing films can be largely divided into dye-type polarizing films and polarizing films using dichroic dyes. In recent years, polarizing films using dichroic dyes, that is, iodine, have become mainstream. The manufacturing method of a wet dichroic dye polarizing film is to prepare a non-stretched film using a polyvinyl alcohol resin, and iodine, potassium iodide, or zinc iodide is dissolved in a water bath at a temperature of 30 to 60°C. It is manufactured by making it act as a polarizer, and wastewater is also generated during this process. In addition, a protective film and a retardation film are attached to protect the polarizer. As a protective film, TAC film, PMMA film, COP film, PET film, etc. are typically used. The protective film is manufactured through a separate process. Depending on the characteristics of the film, a separate adhesive or adhesive may be used. This multi-step manufacturing process requires not only high manufacturing costs, but also the quality of each film.

Therefore, as a method to solve these problems, the inventors of the present invention have melt-extruded the skin layer of the thermoplastic resin (A) and the resin (C) containing a plasticizer and a dichroic dye (B) to the inside of the thermoplastic resin (A). The core layer is formed by dispersing in, and the dichroic dye (B) is oriented through a dry stretching process, and the resin (C) containing the oriented dichroic dye (B) is formed into a needle-shaped needle-shaped thermoplastic resin (A ), it was possible to invent the invention in a form in which the resin (C) was dispersed in a certain direction continuously or discontinuously in a certain direction. As the resin (C) was dispersed in the thermoplastic resin (A), the thermoplastic resin (A) was used as a dichroic dye ( In addition to serving as a carrier for the resin (C) containing B), it was possible to invent an integrated polarizing film by making the components of the skin layer the same as or similar to the resin.

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The present invention is a polarizing film having a skin layer of a thermoplastic resin (A) and a core layer in which a resin (C) containing a dichroic dye (B) is continuously or discontinuously dispersed in the thermoplastic resin (A). By inventing the invention, it is to provide a polarizing film having excellent quality such as epoch-making cost reduction and staining through a single melt extrusion process and dry stretching process without the need for dyeing of dichroic dyes and a separate protective film manufacturing process.

In order to solve the above problems, the physical properties of the thermoplastic resin (A), especially optical properties, must have a transmittance and a refractive index suitable for a polarizing film. Resins that can be used as materials for polarizing films include polymethyl methacrylate (PMMA), triacetylcellulose (TAC), polypropylene (PP), cycloolefin polymer (COP), polyethylene terephthalate (PET), and polycarbonate ( PC), Amorphopolyethylene terephthalate (APET), Polypropylene terephthalate (PPT), Polybutylene terephthalate (PBT), Polyethylene naphthalate (PEN), Polyethylene terephthalate glycerol (PETG), Polycyclohexylene dimethylene Terephthalate (PCTG), cycloolefin copolymer (COC), polyacrylate (PA), polystyrene (PS), polyester sulfone (PES), polyethylene (PE), silicone resin, modified epoxy resin, etc. As a dye, iodine, potassium iodide, zinc iodide, etc. can be used as a certified material. The component of the resin (C) containing the dichroic dye is preferably an olefin-based resin that can facilitate the orientation of the dichroic dye, and in particular, polyvinyl alcohol (PVA), which is used in conventional polarizing films, is the best. In the case of PVA), there is little difference between the melting point and the thermal decomposition temperature, so by using a plasticizer such as glycerin, diglycerin, and triglycerin, the melt processing temperature can be lowered to prevent pyrolysis.

In the polarizing film, it is necessary to minimize the refraction of light. In general, when two or more types of resins are blended, an interface is formed between the resin and the resin, and when the difference in refractive index of each resin is large, some light is reflected at the interface, which appears as a loss of light. In order to reduce this, it is better to eliminate or minimize the difference in refractive index of each resin. Therefore, assuming that the resin containing the dichroic dye is polyvinyl alcohol (PVA), the refractive index of polyvinyl alcohol is about 1.50, so triacetylcellulose (TAC, refractive index 1.50) and polymethyl methacrylate ( It is recommended to select one or more resins from PMMA, refractive index 1.49), polypropylene (PP, refractive index 1.47), and cycloolefin polymer (COP, refractive index 1.50).

In order to minimize the thermal decomposition of polyvinyl alcohol in the melt extrusion process, a resin capable of melt extrusion at a temperature lower than the thermal decomposition temperature of polyvinyl alcohol 220°C is preferable. These include polymethyl methacrylate (PMMA), polypropylene (PP), cycloolefin polymer (COP), and amorphous polyethylene terephthalate (APET). Considering the optical and thermal properties of the polarizing film mentioned above, polymethyl methacrylate (PMMA) is optimal as the thermoplastic resin (A), and as a dichroic dye, one or more of iodine, potassium iodide, and zinc iodide can be selected and used. When using a dichroic dye, it is better to dissolve it in glycerin, diglycerin, triglycerin, etc. When dissolving, it is necessary to adjust the mixing ratio of iodine, potassium iodide, and zinc iodide in order to increase the dissolved concentration.

Hereinafter, the present invention will be described in more detail.
Although the polymethyl methacrylate (PMMA) resin used in the present invention is a representative resin, since polymethyl methacrylate (PMMA) is also a part of the acrylic resin, the acrylic resin will be described in detail.
Acrylic
The acrylic resin used in the present invention refers to a resin prepared by polymerizing an acrylate-based monomer, and is characterized in that it does not contain a ring structure in the main chain.
As an acrylate-based monomer, there is no ring structure in the main chain, and it is composed of methyl methacrylate, methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl methacrylate, lauryl methacrylate, and benzyl methacrylate. Any one or more selected from the group consisting of may be used.
In addition, if necessary, the acrylic resin may further include a styrene-based monomer. The glass transition temperature of the acrylic resin is 90 to 120°C. When the glass transition temperature is less than 90°C, the thermal stability of the film is deteriorated. The weight average molecular weight of the acrylic resin is 90,000 to 160,000 g/mole. If the weight average molecular weight is less than 90,000 g/mole, fractures frequently occur during the film manufacturing process, resulting in a problem in establishing process conditions as well as poor mechanical properties. When the weight average molecular weight exceeds 160,000 g/mole, extrusion processing becomes difficult.

Polyvinyl alcohol (PVA) resin
Polyvinyl alcohol (PVA) resins are used as raw materials for various moldings such as films and sheets, and various plasticizers are used in these moldings for the purpose of softening polyvinyl alcohol resins. The plasticizer's performance is (1) to make PVA resin flexible and to prevent thermal decomposition by lowering the processing temperature during extrusion (2) to have low volatility and long-term function (3) to have similar compatibility with PVA and optical refractive index characteristics. And keeping the optical properties good. As the plasticizer of PVA, glycerin satisfies the above functions relatively well, but diglycerin, triglycerin, etc. can also be used. As other plasticizers, triacetin, dibutyl sebacate (DBS), diethyl phthalate (DEP), di phthalate It consists of butyl (DBP), ethyl phthalate, methyl phthalate, dipropyl phthalate, triethyl citrate (TEC), and combinations thereof, and is present in the range of 5 to 20 parts by weight of the composition, more preferably 8 to 15 parts by weight. good.
As for the content of glycerin, it is preferable to contain 8 parts by weight or more of glycerin based on 100 parts by weight of the PVA resin. Glycerin and diglycerin can be used alone or in combination of two or more.
The degree of polymerization of PVA is not particularly limited, but a degree of polymerization of 100 or more and 10,000 or less is preferable. In particular, since it is used for dispersion, it is also possible to use a PVA resin having a lower polymerization degree than a general PVA film.
The degree of saponification is preferably 90 mole% or more, but 99.0 mole% or more is good for the degree of polarization, and more preferably 99.9 mole% or more.

Dichroic dye
In a general polarizing film manufacturing method, a method of swelling and dyeing an unstretched film made of a PVA material in a hot water state in which dichroic dyes such as iodine and potassium iodine are dissolved. Therefore, it is used by dissolving iodine and potassium iodide in water. Since water cannot be used in the melt extrusion method, it is used by dissolving in one or more substances such as glycerin, diglycerin, triglycerin, etc. instead of water. At this time, in order to improve the solubility, the method of raising the temperature of the plasticizer and the mixing ratio of iodine, potassium iodide, and zinc iodide can be adjusted to be used. The ratio (B/A) of iodine (A) and potassium iodine (B) is preferably 1.0 to 100 or less.

Layer structure of polarizing film
The layer structure of the polarizing film is composed of a core layer constituting the polarizer in the case of the lower polarizing plate of the LCD panel, the retardation film layer on the upper polarizer protective layer, and the core layer in the case of the upper polarizing plate, and the upper retardation film in the lower part. It consists of a protective film layer. Depending on the optical characteristics of the polarizing film, the upper and lower protective films and the retardation film may be made of the same material, or different types of films may be used. In the present invention, the design was made of PMMA material. In the case of coextrusion, when the core layer is present and the skin layer is present above and below the skin layer, production is stabilized when the top and bottom thicknesses of the skin layer are the same. If the thickness of the upper and lower skin layers is different, curls are generated when passing through the film manufacturing process, so that the process cannot be stabilized. In recent years, even when the thickness of the polarizer is reduced to 5 to 7 μm, the degree of polarization can be sufficiently achieved. The thickness of the skin layer may be 1 μm or less in the case of coextrusion. The thickness of the skin layer can be varied depending on the conditions of the LCD to be used. In other words, it is also possible to make the thickness thinner in mobiles and tablet PCs. For monitors and TVs, there are relatively few restrictions on the thickness. The total thickness of the polarizing film, that is, the combined thickness of the skin layer and the core layer is 7 to 300 μm.

Resin containing dichroic dye (C) and thermoplastic resin (A)
Resin (C) containing dichroic dyes such as iodine, potassium iodide, and zinc iodide is a resin that has been tested for polyvinyl alcohol (PVA). Iodine or the like is impregnated in PVA and extruded through a melt extruder with PMMA resin. At this time, the PMMA resin of the skin layer is also coextruded, so if the content of the PVA resin is too high, peeling occurs at the interface due to the effect of heterogeneous resins between the core layer and the skin layer. In order to solve this problem, the content of the PVA resin is preferably 50% or less based on the volume of the total resin present in the core layer. In other words, if PMMA is used as the sea and PVA is present in the form of an island, the delamination phenomenon can be eliminated. That is, it should be less than 50% by volume, more preferably less than 45%.
In addition, during melt extrusion, the dichroic dye-containing resin PVA is blended with PMMA. As it goes through a dry uniaxial or biaxial stretching process and is fixed by cooling, it exists in the form of a needle-shaped needle inside the polarizing film. The length varies depending on the conditions of the melt extruder and is also affected by the draw ratio. It is 2.0 µm or more as confirmed by the present inventors.

Lamination with retardation film
The polarizing film may be subjected to various surface treatment processes depending on the purpose of use. The first is lamination with retardation film. Due to the difference in optical properties, the polarizing film may or may not be laminated with other retardation films. Types of retardation film include PMMA film, TAC film, COP film, and PET film.

Surface treatment of polarizing film
On the surface of the polarizing film, anti-reflection (ANTI-REFLECTION) to prevent the reduction of the contrast ratio (CONTRAST RATIO) due to reflection (ANTI-REFLECTION), low It can be treated such as LOW-REFLECTION treatment, ANTI-STASTIC treatment to prevent dust generation to protect the liquid crystal array, and hard coating to protect the surface of the polarizing film.
To prevent see-through, dissolve acrylic or polycarbonate resin in a solvent such as water, alcohol, methyl ethyl ketone, etc., then mix silica gel or organic spherical particles such as acrylic, silicone, styrene, etc., and coat the film surface and dry. Thus, it is possible to prevent reflection by diffusely reflecting light by protruding some of the particles to the surface of the resin. In this case, an ultraviolet (UV) curing agent may be used depending on the surface treatment conditions and may be subjected to an ultraviolet treatment process.
As a method for preventing reflection, it is possible to achieve a low reflection function by interfering with light due to the difference in multilayer refractive index and internal extinction by repeatedly coating a high-refractive resin and a low-refractive resin on the surface of the film treated with hard coating or anti-reflection treatment. have. As a method for low reflection, by coating a low refractive index resin on the surface of the hard-coated film, it is possible to achieve a low reflection function due to the interference effect of light. A wet coating method of metal mixed resin is also possible.
Amorphous inorganic particles are sometimes used when particles are mixed with a solvent and a binder for surface treatment of the film, but organic particles are preferably used for accurate refractive index control. Among organic particles, the more uniform the particle size distribution, the easier it is to design a binder and a solvent. The spherical type of particles is good, and acrylic, silicone, and polystyrene are typical. In the present invention, in consideration of the refractive index of the skin layer resin, an acrylic series is more preferable. The size of the particles varies depending on the required physical properties of the polarizing film, but the diameter is preferably 0.1 to 20 μm.
The polarizing film of the present invention can be used for LCD panels and OLED panels, and can be used for final products such as LCD products and OLED products.

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The polarizing film manufactured through the present invention can achieve superior manufacturing cost reduction compared to the conventional manufacturing method by coextruding the core layer serving as a polarizing function and the skin layer serving as a polarizer protection function at the same time. In addition, when the polarizing film is manufactured by co-extrusion, the thickness increases, so that the manufacturing processability is improved and the overall thickness of the polarizing film can be drastically reduced. In addition, it is easy to control the quality of the polarizing film by simultaneously extruding the core layer and the skin layer.
In addition, since it is not manufactured by dyeing method and produced through melt extrusion, the production environment is improved and there is no pollution due to wastewater generation. Since it is possible to control the thickness of the entire polarizing film, it is advantageous in lamination with the retardation film, and the surface treatment of the film can be easily performed.

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The representative drawing (Fig. 1) shows a state in which a dichroic dye, especially 3 ③ or 5 ④ of iodine molecules is oriented in a thermoplastic resin ①, and is contained in a separate resin ②, and a skin layer is arranged on the upper layer ⑤ lower layer ⑥. .
FIG. 2 shows that the dispersed polarizing film ⑦ and the retardation film ⑧ are laminated to be laminated up and down on a glass liquid crystal ⑨.
FIG. 3 is a result of laminating a dispersion-type polarizing film ⑦ and a reflective polarizing film ⑩ using an adhesive or adhesive ⑪.
4 is a hard coating ⑫ on the dispersed polarizing film⑦.
FIG. 5 shows a non-penetrating coating ⑬ using particles ⑭ on a dispersed polarizing film ⑦.

이하이다.

< 하드코팅 >
편광필름은 액정디스플레이에서 최외각에 위치한다. 따라서 고선명도,내마모성,내스크래치성이 필요하다. 이를 위해 편광필름의 상면에 하드코팅을 실시한다.
하드코팅에 대한 내용을 도 4에 나타냈다.

< 내스크래치 코팅>
LCD 패널의 하부 편광필름은 백라이트유닛과 접하게 되다. 이 때 백라이트유닛의 최상부 필름과의 마찰이 발생하고 편광필름이나 백라이트유닛 필름에 스크래치가 발생할 수 있다. 이를 방지하기 위해 내스크래치 코팅을 한다. 내스크래치코팅은 아크릴 수지를 메틸에틸케톤 등의 용매에 용해하고 여기에 20㎛ 이하의 입자를 코팅하고 건조 그리고 자외선 경화를 한다. 입자는 20㎛ 이하가 좋지만 2.0㎛ 이하의 입자를 사용할 수도 있다. 입자는 아크릴 계통,폴리스티렌 계통 혹은 폴리실리콘 등의 구형 형상이 좋다.
내스크래치 코팅에 대한 내용을 도 4와 5에 나타냈다.

< 반사편광필름 합지>
LCD 패널의 하부 편광필름에 반사편광필름을 합지함으로써 LCD의 휘도를 더욱 향상시킬 수 있다. 반사편광필름은 다층일 수도 있고, 분산형 반사편광필름을 사용할 수도 있다.
반사편광필름 합지에 대한 내용을 도 3에 나타냈다.

< 위상차필름과의 합지>
위상차필름은 PMMA필름,TAC필름,COP필름,PET필름 등이 있으며 사용 용도에 따라 상기의 필름과 합지하여 사용하는 것도 가능하다.

< 실시예 1>
<코어용 편광자>
PMMA(LG MMA, IF850)수지를 건조 온도 80℃에서 15시간 건조하여 수운율 50 ppm의 건조 수지를 준비하였다.
PVA(Kuraray, JC-25,검화도 99.98몰%, 중합도 2400)수지를 건조 온도 70℃에서 20시간 건조하여 수분율 50 ppm의 건조 수지를 준비하였다.
글리세린 100 중량부에 요오드 1.7 중량부,요오드화칼륨 15.0 중량부,붕산 2.0 중량부를 50℃에서 용해시켜 혼합 용액을 제조하였다.
상기의 건조된 PMMA수지와 건조 PVA수지 그리고 혼합 용액을 PMMA 100 중량부 기준으로 건조 PVA수지 70 중량부,혼합 용액 20 중량부를 싱글 용융 압출기에 투입하여 170℃로 용융시켰다.

< 보호용 스킨층>
상기의 건조된 PMMA수지를 180℃의 온도로 싱글 용융 압출기를 통해 용융시켰다.

< 공압출>
상기의 코어용 폴리머와 스킨용 폴리머를 층비가 30 : 40 : 30이 되도록 피드블록과 T-Die을 통해 압출시켰다. 이 때 T-Die의 폭은 2.0 미터로 하였다.

< 카렌더링>
상기 공압출된 폴리머를 3개의 수평 카렌더롤( 폭 2.3 미터 ,지름 450mm)에 냉각시켰다. 이 때 카렌더 롤의 온도는 80℃로 유지시켰다.
카렌더링 공정에서의 미연된 필름의 두께는 360㎛으로 제어하였다.
카렌더링 공정의 라인속도는 분당 5.0 미터로 제어하였다.

< 종방향 연신>
상기의 미연신필름을 직경 300㎜ 예열롤 10개를 120 내지 125℃ 범위로 조절하면서 예열하였다. 예열된 필름을 직경 200㎜인 연신롤 두 개를 거쳐 연신하였다. 연신롤 사이의 거리는 15㎜로 하였으며 필름은 연신 전단롤의 상부에서 연신 후단롤의 하부를 지나도록 하였다.이 때 연신롤 사이에 적외선 히터를 통해 가열하면서 6배 연신을 하였다. 그 뒤에 8개의 냉각롤을 통해 연신된 필름을 냉각시켰다. 이 때 롤의 온도는 30 내지 90℃로 제어하였다.

< 열고정>
상기의 연신필름을 텐터를 통해 열고정하였다. 텐터의 온도는 30℃ 내지 160℃로 제어하였다.

< 엣지 컷팅 및 권취>
상기의 필름을 엣지 컷팅(Edge cutting)하고 6인치 플라스틱 지관에 권취하고 샘플을 채취하여 물성을 평가 하였다.생산된 편광필름의 두께는 60㎛이었다 물성의 결과는 표에서 나타냈다.

<실시예 2>
실시예 1에서 스킨(skin)층과 코어(core)층의 비율을 1:8:1로 하고 미연신필름의 두께를 180㎛으로 생산하였다.나머지 조건은 동일하게 하고 연신후의 필름 두께는 30㎛으로 하였다.

<실시예 3>
실시예 2에서 스킨(skin)층과 코어의 비율을 3:4:3으로 하고 미연신필름의 두께를 180㎛으로 생산하였다. 나머지는 실시예 2과 동일하게 하고 연신후의 필름 두께는 30㎛으로 하였다.

<실시예 4>
실시예 3에서 스킨층과 코어층의 비율을 4:2:4로 하고 미연신필름의 두께를 150㎛, 연신후의 필름 두께를 25㎛으로 하였다.

<실시예 5>
실시예 1에서 글리세린 100 중량부에 요오드 3.4 중량부,요오드화칼륨 30.0 중량부,붕산 2.0 중량부를 50℃에서 용해시킨 혼합 용액을 제조하였다. 나머지는 동일한 조건에서 필름을 제조하였다.

<실시예 6>
실시예 5에서 미연신필름의 두께를 180㎛으로 하고 연신후의 필름 두께를 30㎛으로 하였다.

<비교예 1>
실시예 3에서 스킨층과 코어층의 비율을 11:3:11로 하고 미연신필름 두께를 150㎛,연신후의 필름 두께를 25㎛으로 하였다.

<비교예 2>
실시예 1에서스킨층과 코어층의 두께비율을 1:8:1로 하고 미연신필름 두께를 360um으로 하고 연신후의 필름두께를 60㎛으로 하였다.Hereinafter, the present invention will be described in detail.
As described above, in the conventional polarizing film, iodine particles are dispersed in the PVA resin in the form of 3 atom continuous orientation (I3) or 5 atom continuous orientation (I5) for polarization. In order to achieve polarization, iodine must be uniformly oriented in one axis direction. As a method to achieve this, the polymer molecules and iodine molecules inside the PVA are oriented through the stretching process. PVA resin is hydrophilic and easily swells in water and is also easy to draw. In the swollen state, iodine particles also enter the molecular chain; however, depending on the molecular weight of PVA, it may dissolve when swelling in water, and the density of iodine particles varies from site to site, causing stains in many cases.
In the present invention, a thermoplastic resin is used as a method by a melt extrusion method. There are many types of thermoplastic resins, but the resins that can be used for polarizing films are acrylic resins, polymethyl methacrylate (PMMA), triacetyl cellulose (TAC), polypropylene (PP), cycloolefin polymer (COP), and polyethylene terephthalate. (PET), Polycarbonate (PC), Amorphous Polyethylene terephthalate (APET), Polypropylene terephthalate (PPT), Polybutylene terephthalate (PBT), Polyethylene naphthalate (PEN), Polyethylene terephthalate glycerol (PETG) ,Polycyclohexylenedimethylene terephthalate (PCTG), cycloolefin copolymer (COC), polyacrylate (PA), polystyrene (PS), polyester sulfone (PES), polyethylene (PE), silicone resin, modified epoxy Suzy and the like. The polarizing function resin used in the present invention is a resin whose polyvinyl alcohol has been tested.

<Refractive index of resin related to polarizing film>
If the refractive index difference of the resin used in the polarizing film is large, light reflection occurs at the interface between the resin and the resin, which leads to a decrease in transmittance and a decrease in polarization rate, thereby deteriorating the value as a polarizing film. In order to solve this problem, it is good to minimize the difference in refractive index of the resin used.
Since the refractive index of the PVA resin is 1.50, a resin having a refractive index of 1.50 or a similar refractive index is preferable. The corresponding resin is TAC resin. TAC resin has a refractive index of 1.50, which is excellent optically as it is consistent with PVA resin. However, TAC resin has the disadvantage of being hydrophilic and very expensive, and is not suitable for melt extrusion process. not. The resin that approaches this with another resin is an acrylic-based PMMA resin. PMMA resin has a refractive index of 1.49, almost similar to PVA resin, and has a light transmittance of 94%, which is a very good material for optics. For this reason, PMMA resin is widely used as a material for light guide plates and diffusion plates. PMMA resin is a thermoplastic resin and is very suitable for use in melt extrusion. PMMA resin has a glass transition temperature of 99°C and is excellent in heat resistance.

<Polyvinyl alcohol (PVA) resin>
PVA resin is a material that has been certified as a polarizer functional resin for a polarizing film. In particular, resins with a degree of saponification of 99.9 mole% or more have excellent performance in polarization function. For a polarizing film, a polymerization degree of 500 to 5000 is usually preferred. In particular, the degree of polymerization is 1700 to 3000, more preferably 2100 to 2700.
The higher the degree of saponification of the PVA resin, the better. This is because the higher the degree of saponification, the more advantageous the molecular arrangement of iodine is uniformly oriented along one axis. In general, a saponification degree of 85 mole% or higher is recommended, but the recent saponification degree of PVA resin for polarizing films is 99.8 mole% or higher.
PVA resin is not suitable for melt extrusion process because its melting temperature and pyrolysis temperature are similar. However, it is possible to lower the temperature of the melt extruder by using a plasticizer, and it is advantageous in terms of retention in the process by dispersing it inside the PMMA resin.

<plasticizer>
Polyhydric alcohol ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, sorbitol, ethylene oxide, glycerin, diglycerin, triglycerin, and the like are used as plasticizers of the PVA resin. Among them, glycerin is the best. One glycerin can be used, but more than two can be used. Glycerin may be used in an amount of 2 to 100 parts by weight based on 100 parts by weight of the PVA resin, but 5 to 30 parts by weight, more preferably, 15 to 25 parts by weight. Other plasticizers include triacetin, dibutyl sebacate (DBS), diethyl phthalate (DEP), dibutyl phthalate (DBP), ethyl phthalate, methyl phthalate, dipropyl phthalate, triethyl citrate (TEC), and combinations thereof. The composition is preferably in the range of 5 to 20 parts by weight, and more preferably in the range of 8 to 15 parts by weight. In order to increase the plasticity of the PVA resin, 100 parts by weight or more may be used in some cases. In this case, a dysfunction may appear in the post process. In the present invention, it is possible to use a lot of plasticizers by using the PVA resin in a continuous or discontinuous dispersion type. In the case of glycerin, the refractive index is 1.47, which is similar to that of PVA resin, so light loss is relatively small. Glycerin has a boiling point of 290° C., and thus has a relatively small bubble problem during the extrusion process.
Glycerin is a substance having three -OH groups, which are hydrophilic groups, and plays a good role as a solvent that dissolves iodine, potassium iodine, and zinc iodide instead of water.

<Iodine, potassium iodine, zinc iodine>
Iodine is the most important material that performs a polarizing function in a polarizing film using a dichroic dye. Iodine is a trimolecular iodine (I3), a 5-molecular iodine (I5), etc., and is present between the PVA molecules. Since iodine is a single substance and has a limited concentration in water or glycerin, the dissolution rate of iodine can be increased by mixing iodine with potassium iodide or zinc iodide. The mixing ratio of iodine and potassium iodide is about 1.0 to 500 potassium iodide/iodine by weight. In order to improve the polarization function, it is most important to uniformly orient iodine molecules in one axis direction.
In a polarizing film, it is very important to maintain the orientation of the stretched PVA resin and iodine. Therefore, by crosslinking the PVA resin using boric acid as a crosslinking agent, the orientation stability of the PVA resin and iodine molecules can be improved.

<Mixed solution of glycerin, iodine and boric acid>
In order to increase the physical properties of the polarizing film, that is, high polarization degree and light transmittance, it is very important to uniformly disperse the mixed solution of glycerin iodine boric acid inside the PVA resin. In the present invention, the weight of iodine is 1 to 3 parts by weight based on 100 parts by weight of glycerin. Preferably 1.5 to 2.0 parts by weight, potassium iodide is preferably 9 to 27 parts by weight, more preferably 10 to 20 parts by weight. Boric acid is preferably 1.0 to 3.0 parts by weight, and even more preferably 1.5 to 2.5 parts by weight. In order to increase the solubility of iodine, potassium iodide, zinc iodide and boric acid, the temperature of the mixed solution is dispersed at 30 to 70°C.

<Contents of glycerin, iodine and boric acid inside the PVA resin>
For the plasticity of the PVA resin, 5 to 50 parts by weight of glycerin, more preferably 10 to 40 parts by weight and even more preferably 15 to 25 parts by weight of 100 parts by weight of the PVA resin. Potassium iodide is preferably 2 to 4 parts by weight. 0.22 to 0.44 parts by weight is good The boric acid is preferably 0.25 to 0.55 parts by weight.

<drying>
Since the PMMA resin and PVA resin are melt-extruded at a high temperature of 170 to 180°C, if there is moisture, breakage due to bubbles may occur, and the quality of the polarizing film is also problematic. To eliminate this, the PMMA resin and PVA resin are dried and moisture is dried. It is better to set it to 50 ppm or less. The drying temperature is preferably 15 hours or more at 80℃ for PMMA resin and 20 hours or more at 70℃ for PVA resin.

<Dispersion of iodine-containing PVA resin inside the core layer PMMA>
The core of the present invention is whether or not the iodine-containing PVA resin is uniformly dispersed inside the PMMA resin, depending on whether it is successful or not. As a method of dispersing, it is very important to make the viscosity of the two types of resins similar. In particular, the viscosity similarity with PMMA resin is important below 180℃, which is the thermal stability temperature of PVA resin. If the difference in polymer viscosity is large, the dispersibility of iodine-containing PVA in the PMMA may become uneven. In order to improve the dispersibility, the content of the iodine-containing resin is preferably 45% or less based on the volume of the core layer. In order to increase the dispersibility, it is relatively advantageous to increase the viscosity of these polymers. The weight average molecular weight of PMMA for melt extrusion is preferably 100,000 to 150,000.
In melt extrusion, the iodine-containing PVA polymer is dispersed during the melting process. At this time, since the skin polymer is PMMA, the core layer must have PMMA as the sea and iodine-containing PVA in the form of islands to eliminate the peeling phenomenon from the skin layer.

<Skin layer PMMA melt extrusion>
The melting temperature of the PMMA resin used for skin may be melt-extruded at 180 to 190°C.

<Feed block, T-Die>
In the feed block, the core layer polymer and the skin layer polymer are combined. Depending on the application, the thickness of the core layer and the thickness of the skin layer can be adjusted. The thickness of the core layer is about 5 to 20 μm, as it functions as a polarizing function. In the case of the skin layer, it may be 2 µm to 50 µm for mobile and tablic PCs, and 80 to 200 µm or more for large TVs.

<Calendar process>
There are a casting method and a calendar method in the film forming process. A pinning wire, etc., should be used for the casting method, which has an advantage in controlling the thickness.
However, it is possible to use a separate additive to improve the pinning property inside the polymer. On the other hand, the calendar method controls the thickness of the unstretched film by the interval between the two rolls. The thickness uniformity is lower than that of the casting method, but the optical properties are improved because there is no additional additive. Through this process, the iodine-containing PVA resin serving as a polarizer becomes an amorphous shape.
In the case of the calendar method, the temperature condition of the calendar roll is important. In the case of an amorphous polymer, it is operated at a glass transition temperature of 10 to 30°C.
In the case of PMMA, it is operated at 70 to 90°C, which is lower than the glass transition temperature of 99°C.

<MDO (species) stretching>
MDO (species) stretching is the most important process in which molecules such as iodine, a polarizing function, are aligned, and consists of a preheating roll, a drawing roll, and a cooling roll. The temperature of the preheating roll can be increased from the glass transition temperature to +30°C.
In the present invention, since the PMMA resin is the main process control resin, the preheating roll temperature is maintained at about 99 to 140°C.
Stretching takes place between rolls and rolls, and it is preferable that the stretching rolls have a diameter of about 100 to 300 mm for uniformity of stretching. The smaller the roll diameter is, the more advantageous it is to increase the stretching uniformity.
Cooling is operated below the glass transition temperature. In the present invention, it is operated at 99 to 30°C.

<Fixed heat>
Heat setting is done using a tenter. The temperature is set at 120 to 150°C, which is about 20°C higher than the glass transition temperature.

<Edge slitting, winding>
The thick part of the edge is removed by slitting and wound around a 6-inch plastic paper tube.
In addition, the surface treatment of the film of the present invention and lamination with other types of films will be described.

<Prevention of see-through>
In order to prevent penetration of an acrylic resin, an acrylic resin is dissolved in a methyl ethyl ketone solvent, and amorphous silica gel having an average particle diameter of 5 μm or more is mixed to coat the upper surface of a polarizing film, which is then dried and cured with ultraviolet rays.
In high-end products, amorphous silica gel with an average particle diameter of 5㎛ or less is mixed, and in high-resolution products, spherical organic particles of 5.0㎛ or less with excellent particle size distribution are used.
It is shown in Figure 5 the content on the prevention of see-through.

<Anti-reflection, low reflection>
Anti-reflective coating is applied to the upper surface of the polarizing film of the present invention by hard coating or non-infiltrating coating. If a multilayer coating of three or more layers of a high-refractive resin and a low-refractive resin is applied thereon, a reflectance of 0.1 to 0.3% can be achieved. Preferably, about 5 layers of high-refractive-index resin and low-refractive-index resin are recommended. If the multilayer coating is made into 6 or more layers, the reflectance is further lowered, but there is a problem that the coating cost increases. Low-reflective anti-reflective or hard coating is applied to the top of the polarizing film of the present invention, and then a low-refractive mixed resin is coated and UV cured. The reflectance is generally 0.7 to 1.7%.

<Antistatic prevention>
Surface treatment is performed to prevent damage to the module by static electricity. Generally, nickel or gold is plated, and conductive particles are put therein to coat. The surface resistance of the film for antistatic is

Below.

<Hard coating>
The polarizing film is located at the outermost part of the liquid crystal display. Therefore, high definition, abrasion resistance, and scratch resistance are required. For this, hard coating is applied to the upper surface of the polarizing film.
The contents of the hard coating are shown in FIG. 4.

<Scratch resistant coating>
The lower polarizing film of the LCD panel comes into contact with the backlight unit. At this time, friction with the uppermost film of the backlight unit may occur, and scratches may occur on the polarizing film or the backlight unit film. To prevent this, apply a scratch-resistant coating. In the scratch-resistant coating, an acrylic resin is dissolved in a solvent such as methyl ethyl ketone, coated with particles of 20 μm or less, dried, and cured with ultraviolet rays. Particles of 20 μm or less are good, but particles of 2.0 μm or less may be used. The particles have a spherical shape such as acrylic, polystyrene, or polysilicon.
The contents of the scratch-resistant coating are shown in FIGS. 4 and 5.

<Reflective polarization film laminate>
By laminating the reflective polarizing film to the lower polarizing film of the LCD panel, the brightness of the LCD can be further improved. The reflective polarizing film may be multilayered or a distributed reflective polarizing film may be used.
The contents of the reflective polarizing film laminate are shown in FIG. 3.

<Lamination with retardation film>
The retardation film includes a PMMA film, a TAC film, a COP film, a PET film, and the like, and may be used in combination with the above film according to the intended use.

<Example 1>
<Core polarizer>
PMMA (LG MMA, IF850) resin was dried at a drying temperature of 80° C. for 15 hours to prepare a dry resin having a water transport rate of 50 ppm.
PVA (Kuraray, JC-25, saponification degree 99.98 mol%, polymerization degree 2400) resin was dried at a drying temperature of 70° C. for 20 hours to prepare a dry resin having a moisture content of 50 ppm.
A mixed solution was prepared by dissolving 1.7 parts by weight of iodine, 15.0 parts by weight of potassium iodide, and 2.0 parts by weight of boric acid at 50°C in 100 parts by weight of glycerin.
The dried PMMA resin, the dried PVA resin, and the mixed solution were melted at 170° C. by putting 70 parts by weight of the dry PVA resin and 20 parts by weight of the mixed solution into a single melt extruder based on 100 parts by weight of PMMA.

<Protective skin layer>
The dried PMMA resin was melted through a single melt extruder at a temperature of 180°C.

<Coextrusion>
The core polymer and the skin polymer were extruded through a feed block and a T-Die so that the layer ratio was 30:40:30. At this time, the width of the T-Die was set to 2.0 meters.

<Car rendering>
The coextruded polymer was cooled on three horizontal calender rolls (2.3 meters in width, 450 mm in diameter). At this time, the temperature of the calendar roll was maintained at 80°C.
The thickness of the unrolled film in the calendering process was controlled to 360 μm.
The line speed of the calendaring process was controlled at 5.0 meters per minute.

<longitudinal stretching>
The unstretched film was preheated while controlling 10 preheating rolls of 300 mm in diameter in the range of 120 to 125°C. The preheated film was stretched through two stretching rolls having a diameter of 200 mm. The distance between the stretching rolls was 15 mm, and the film was passed from the top of the stretching front roll to the lower portion of the stretching rear end roll. At this time, stretching was performed 6 times while heating between the stretching rolls through an infrared heater. After that, the stretched film was cooled through eight cooling rolls. At this time, the temperature of the roll was controlled at 30 to 90°C.

<Passion>
The stretched film was heat-set through a tenter. The temperature of the tenter was controlled at 30°C to 160°C.

<Edge cutting and winding>
The film was edge-cut, wound on a 6-inch plastic paper tube, and sample was collected to evaluate the physical properties. The thickness of the produced polarizing film was 60 μm. The results of the physical properties are shown in the table.

<Example 2>
In Example 1, the ratio of the skin layer and the core layer was 1:8:1 and the thickness of the unstretched film was 180 µm. The remaining conditions were the same, and the film thickness after stretching was 30 µm. I did it.

<Example 3>
In Example 2, the ratio of the skin layer and the core was 3:4:3, and the thickness of the unstretched film was 180㎛. The rest were the same as in Example 2, and the film thickness after stretching was 30 μm.

<Example 4>
In Example 3, the ratio of the skin layer and the core layer was 4:2:4, the thickness of the unstretched film was 150 µm, and the film thickness after stretching was 25 µm.

<Example 5>
In Example 1, a mixed solution was prepared by dissolving 3.4 parts by weight of iodine, 30.0 parts by weight of potassium iodide, and 2.0 parts by weight of boric acid at 50° C. in 100 parts by weight of glycerin. The rest of the films were prepared under the same conditions.

<Example 6>
In Example 5, the thickness of the unstretched film was set to 180 µm and the film thickness after stretching was set to 30 µm.

<Comparative Example 1>
In Example 3, the ratio of the skin layer and the core layer was 11:3:11, the unstretched film thickness was 150 µm, and the film thickness after stretching was 25 µm.

<Comparative Example 2>
In Example 1, the thickness ratio of the skin layer and the core layer was 1:8:1, the unstretched film thickness was 360um, and the film thickness after stretching was 60㎛.

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division Film thickness Skin layer core layer thickness ratio I+KI content in mixed solution Polarization degree Transmittance unit ㎛ Wt% % % Example 1 60 3:4:3 1.7+15.0 99.9 43.1 Example 2 30 1:8:1 1.7+15.0 99.9 43.0 Example 3 30 3:4:3 1.7+15.0 99.7 44.1 Example 4 25 4:2:4 1.7+15.0 97.9 45.2 Example 5 60 3:4:3 3.4+30.0 99.9 40.3 Example 6 30 3:4:3 3.4+30.0 99.9 43.1 Comparative Example 1 25 11:3:11 1.7+15.0 96.9 47.4 Comparative Example 2 60 1:8:1 1.7+15.0 99.9 35.1

Polarization degree and transmittance measurement method; Japan Spectroscopic Co., Ltd. (JASCO) product V-7100, model name; VAP-7070(SP) used
Polarization degree and transmittance are based on the wavelength of light of 550 nm.

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Claims (33)

(1) Through the melt extrusion process, the skin layer of the thermoplastic resin (A) and the resin (C) containing a plasticizer and a dichroic dye (B) are dispersed inside the thermoplastic resin (A) to form a core layer. , (2) The dichroic dye (B) is oriented through a dry uniaxial or biaxial stretching process, and the resin (C) containing the oriented dichroic dye (B) is in the shape of a needle-shaped needle in the core layer. A polarizing film, characterized in that continuously or discontinuously dispersed in a uniaxial direction randomly in the inside of the thermoplastic resin (A) of.
In claim 1, the thermoplastic resin (A) of the skin layer and the thermoplastic resin (A) of the core layer are polymethyl methacrylate (PMMA), triacetyl cellulose (TAC), polypropylene (PP), cyclo Olefin polymer (COP), polyethylene terephthalate (PET), polycarbonate (PC), amorphous polyethylene terephthalate (APET), polypropylene terephthalate (PPT), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN) ), polyethylene terephthalate glycerol (PETG), polycyclohexylenedimethylene terephthalate (PCTG), cycloolefin copolymer (COC), polyacrylate (PA), polystyrene (PS), polyester sulfone (PES), polyethylene (PE), a silicone resin, a polarizing film, characterized in that a mixture of one or more resins selected from a modified epoxy resin.
The polarizing film of claim 1, wherein the dichroic dye (B) is one or two or more dichroic dye compositions selected from iodine, potassium iodide, and zinc iodide.
The polarizing film of claim 1, wherein the resin (C) is polyvinyl alcohol (PVA).
The polarizing film of claim 2, wherein the polymethyl methacrylate (PMMA) has a weight average molecular weight of 100,000 to 150,000.
In claim 2, the glass transition temperature of the polymethyl methacrylate (PMMA) is a polarizing film, characterized in that the 90 to 120 ℃.
In claim 2, the polymethyl methacrylate (PMMA) is methyl methacrylate, methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl methacrylate, lauryl methacrylate, benzyl methacrylate Polarizing film, characterized in that at least one selected resin is mixed.
The polarizing film according to claim 1, wherein the dichroic dye (B) is dissolved in the plasticizer and used.
The polarizing film of claim 3, wherein a weight-based mixing ratio (potassium iodide/iodine) of the iodine and the potassium iodide is 1.0 to 100.
The polarizing film according to claim 1, wherein a ratio (B/C) of the sum of the weights of the dichroic dye (B) and the weight of the resin (C) is 0.0222 to 0.0444.
The polarizing film according to claim 1, wherein the weight ratio (D/C) of the sum (D) of the resin (C) and the plasticizer is 0.05 to 0.6.
The polarizing film according to claim 1, wherein the resin (C) is polyvinyl alcohol and has a polymerization degree of 100 to 10,000.
The polarizing film of claim 12, wherein the saponification degree of the polyvinyl alcohol is 85 mole% or more.
In claim 1, the plasticizer is glycerin, diglycerin, triglycerin, triacetin, dibutyl sebacate, ethyl phthalate, dibutyl phthalate, methyl phthalate, dipropyl phthalate, polarized light, characterized in that one or more contained in triethyl citrate film.
The polarizing film of claim 1, wherein a sum of the thicknesses of the skin layer and the core layer is 7 to 300 μm.
The polarizing film of claim 15, wherein the core layer has a thickness of 5 to 200 μm.
The polarizing film according to claim 1, wherein the ratio (C/E) of the volume of the resin (C) to the volume (E) of the sum of the skin layer and the core layer is 0.01 to 0.4.
The polarizing film of claim 1, wherein the length of the needle-shaped acicular shape is 2.0 μm or more.
The polarizing film of claim 15, wherein the polarizing film is uniaxially or biaxially stretched in a machine direction (MDO) or a tenter direction (TDO).
[16] The polarizing film of claim 15, wherein a reflective polarizing film is adhered or adhered to one surface of the polarizing film.
The polarizing film according to claim 15, wherein a retardation film is adhered or adhered to one surface of the polarizing film.
In claim 21, the retardation film is one or more selected from polymethyl methacrylate (PMMA), triacetyl cellulose (TAC), polypropylene (PP), cycloolefin polymer (COP), polyethylene terephthalate (PET) material. Polarizing film characterized by.
[16] The polarizing film of claim 15, wherein one surface of the skin layer is treated with anti-glare (ANTI-GLARE).
[16] The polarizing film of claim 15, wherein one surface of the skin layer is treated with antistatic (ANTI-STATIC) treatment.
[16] The polarizing film of claim 15, wherein one surface of the skin layer is hard coated.
[16] The polarizing film of claim 15, wherein one surface of the skin layer is treated with antireflection (ANTI-REFLECTION) or low reflection (LOW-REFLECTION).
[16] The polarizing film of claim 15, wherein at least one surface of the polarizing film is coated with particles to prevent scratches.
The polarizing film of claim 27, wherein the component of the particles contains at least one of acrylic, polystyrene, and silicone materials.
The polarizing film of claim 27, wherein the particles are spherical particles and have a size of 0.1 to 20 μm.
An LCD panel having the polarizing film of claim 15.
An LCD product having the LCD panel of claim 30
An OLED panel having the polarizing film of claim 15.
An OLED product having the OLED panel of claim 32

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