KR102558814B1 - Optical Film and Polarizing Plate Comprising the Same - Google Patents

Abstract

The present invention provides an optical film that can be easily cut with an IR laser cutter having a wavelength of 9.4 μm, including an infrared absorbing cyclic olefin-based resin having a wavelength of 9.4 μm, and a polarizing plate including the same.

Description

Optical film and polarizing plate containing the same {Optical Film and Polarizing Plate Comprising the Same}

The present invention relates to an optical film and a polarizing plate including the same, and more particularly, to an optical film including an infrared absorbing cyclic olefin-based resin having a wavelength of 9.4 μm and easily cut with an IR laser cutter having a wavelength of 9.4 μm, and a polarizing plate including the same.

A liquid crystal display (LCD) is widely used as a popular image display device. However, despite its many excellent characteristics, a narrow viewing angle has been pointed out as a representative disadvantage. Accordingly, a technology for securing a wide viewing angle by applying a functional optical film such as a retardation film is being used.

A liquid crystal display device requires a polarizing plate for polarizing light on both sides of the liquid crystal cell, and generally, a polarizing plate has a protective film on both sides centered on the polarizer, and a functional film such as a retardation film is additionally used to compensate for the viewing angle on the liquid crystal cell side. Recently, the retardation film is common in that it serves not only to compensate for a viewing angle, but also to a protective film.

Such a retardation film is mainly formed from a cyclic olefin resin (Cyclo Olefin Polymer, COP resin). For example, Korean Patent Publication No. 2008-0059243 discloses a retardation film formed from a norbornene compound addition polymer, which is a type of COP resin. However, it is not easy to cut this COP resin with an IR laser cutter having a wavelength of 9.4 μm. Therefore, when cutting a laminate including a retardation film containing a COP resin, an IR laser must be applied for a long time, and thus other layers except for the retardation film containing the COP resin are melted.

Therefore, development of an optical film containing a COP resin, which can be easily cut with an IR laser cutter having a wavelength of 9.4 μm, is required.

Republic of Korea Patent Publication No. 2008-0059243

The present invention is to solve the above problems, and one object of the present invention is to provide an optical film containing a COP resin, which can be easily cut with an IR laser cutter having a wavelength of 9.4 μm.

On the other hand, the present invention provides an optical film including a cyclic olefin-based resin including a repeating unit represented by Formula 1 below.

[Formula 1]

In the above formula,

R is a C ₁ -C ₈ alkoxy group, C ₁ -C ₈ alkoxycarbonyl group or C ₁ -C ₈ alkylcarboxylate group,

는 단일결합 또는 이중결합이다.

is a single bond or a double bond.

In one embodiment of the present invention, the cyclic olefin-based resin is a monomer represented by the following formula (2); It may be a copolymer obtained by subjecting one or more of the monomers represented by Chemical Formulas 3 to 5 to ring-opening polymerization and selectively hydrogenating them.

[Formula 2]

[Formula 3]

[Formula 4]

[Formula 5]

In the above formula,

R is a C ₁ -C ₈ alkoxy group, a C ₁ -C ₈ alkoxycarbonyl group or a C ₁ -C ₈ alkylcarboxylate group.

On the other hand, the present invention provides a polarizing plate including a polarizer and the optical film laminated on at least one side of the polarizer.

On the other hand, the present invention provides a liquid crystal display device equipped with the polarizing plate.

The optical film according to the present invention includes a COP resin formed from a monomer having a functional group capable of absorbing IR of a 9.4 μm wavelength, and is easily cut with an IR laser cutter having a wavelength of 9.4 μm.

Hereinafter, the present invention will be described in more detail.

One embodiment of the present invention relates to an optical film including a cyclic olefin-based resin (Cyclo Olefin Polymer, COP resin) including a repeating unit represented by Formula 1 below.

[Formula 1]

In the above formula,

R is a C ₁ -C ₈ alkoxy group, C ₁ -C ₈ alkoxycarbonyl group or C ₁ -C ₈ alkylcarboxylate group,

는 단일결합 또는 이중결합이다.

is a single bond or a double bond.

As used herein, the C ₁ -C ₈ alkoxy group refers to a straight-chain or branched alkoxy group having 1 to 8 carbon atoms, and includes, but is not limited to, methoxy, ethoxy, n-propanoxy, and the like.

As used herein, the C ₁ -C ₈ alkoxycarbonyl group refers to a carbonyl group substituted with a straight-chain or branched alkoxy group having 1 to 8 carbon atoms, and includes methoxycarbonyl, ethoxycarbonyl, n-propaneoxycarbonyl, etc., but is not limited thereto.

As used herein, the C ₁ -C ₈ alkylcarboxylate group refers to a carboxylate group substituted with a straight-chain or branched alkyl group having 1 to 8 carbon atoms, and includes acetate, ethyl carboxylate, n-propyl carboxylate, etc., but is not limited thereto.

In one embodiment of the invention, R is methoxycarbonyl, acetate or ethoxy.

는 단일결합이다.
In one embodiment of the present invention,

is a single bond.

In one embodiment of the present invention, the COP resin is a monomer represented by Formula 2; It may be a copolymer obtained by selectively hydrogenating one or more of the monomers represented by Chemical Formulas 3 to 5 through ring-opening metathesis polymerization.

[Formula 2]

[Formula 3]

[Formula 4]

[Formula 5]

In the above formula,

R is a C ₁ -C ₈ alkoxy group, a C ₁ -C ₈ alkoxycarbonyl group or a C ₁ -C ₈ alkylcarboxylate group.

The content of the monomer represented by Formula 2 may be 5 to 50% by weight based on 100% by weight of the total monomers forming the COP resin. If the content of the monomer represented by Formula 2 is less than 5% by weight, the optical film may not be easily cut with an IR laser cutter having a wavelength of 9.4 μm, and if the content of the monomer represented by Formula 2 is greater than 50% by weight, the light transmittance is lowered or the moisture permeability is increased, which may cause a decrease in transmittance and durability during manufacture of a polarizing plate.

a monomer represented by Chemical Formula 2; A process of preparing a COP resin from ring opening polymerization of one or more of the monomers represented by Chemical Formulas 3 to 5 can be easily performed according to a conventional method.

For example, palladium (II) acetylacetonate [Pd(acac) ₂ ] and tricyclohexylphosphine are used as polymerization catalysts, and dimethylanilinium tetrakiss (pentafluorophenyl) borate is used as a cocatalyst. The polymerization process can be carried out using.

가 이중결합으로부터 단일결합으로 전환될 수 있다. 상기 수소화는 당해 기술분야에 공지된 방법에 따라 수소화 촉매의 존재 하에 수소 기체와 반응시켜 수행될 수 있다. 수소화율은 바람직하게는 90% 이상, 보다 바람직하게는 95% 이상, 보다 더 바람직하게 99% 이상이다. 상기 범위 내의 수소화율은 우수한 내열 열화성(heat degradation resistance), 내광 열화성(light degradation resistance) 등을 제공할 수 있다.
The COP resin may be additionally hydrogenated after ring opening polymerization. In Formula 1 through the hydrogenation

can be converted from a double bond to a single bond. The hydrogenation may be performed by reacting with hydrogen gas in the presence of a hydrogenation catalyst according to a method known in the art. The hydrogenation rate is preferably 90% or higher, more preferably 95% or higher, still more preferably 99% or higher. A hydrogenation rate within the above range may provide excellent heat degradation resistance, light degradation resistance, and the like.

The number average molecular weight (Mn) of the COP resin may be measured through gel permeation chromatography (GPC) using a toluene solvent, and may be preferably 25,000 to 200,000, more preferably 30,000 to 100,000. A number average molecular weight within the above range can provide a resin having excellent mechanical strength, good solubility, moldability and casting operability.

As a method of forming the optical film according to the present invention from the COP resin, any suitable molding method may be employed. Specific examples thereof include a compression molding method, a transfer molding method, an injection molding method, an extrusion molding method, a blow molding method, a powder molding method, an FRP molding method, and a casting method. The extrusion molding method and the casting method are preferred because the obtained film can have improved smoothness and good optical uniformity. Molding conditions may be appropriately set depending on the composition or type of resin used, desired properties of the optical film, and the like.

The optical film may have a thickness of 20 to 110 μm, preferably 30 to 100 μm.

The optical film according to the present invention may be stretched as needed. As the stretching method, any suitable method may be adopted depending on desired optical properties (eg, refractive index distribution, Nz coefficient). Specific examples of the stretching method include transverse uniaxial stretching, free-end uniaxial stretching, fixed-end biaxial stretching, fixed-end uniaxial stretching, and sequential biaxial stretching. Specific examples of the fixed-end biaxial stretching include a method of stretching the film in one direction (transverse direction) while conveying the film in the longitudinal direction. This method may apparently be transverse monoaxial stretching. These stretching methods may be applied singly or in combination. For example, there is a method of performing fixed-end uniaxial stretching after performing free-end uniaxial stretching.

The optical film according to the present invention can be used for various purposes such as a retardation film or a protective film. When the optical film according to the present invention is used as a retardation film, the retardation film may be, for example, a single layer of a film formed of the COP resin or a laminate of a plurality of films having predetermined optical characteristics. For example, a retardation film having a flat wavelength dispersion characteristic may be formed by laminating an optical film having a relationship of Δnd(380) > Δnd(550) > Δnd(780) (so-called positive wavelength dispersion property) and an optical film having a relationship of Δnd(380) < Δnd(550) < Δnd(780) (so-called reverse wavelength dispersion property). In this case, other optical properties (in-plane retardation, thickness direction retardation, Nz coefficient, photoelastic coefficient, etc.) can be adjusted to desired values by adjusting the material, thickness, manufacturing conditions, etc. of the optical film used.

One embodiment of the present invention relates to a polarizing plate including a polarizer and the optical film laminated on at least one surface of the polarizer.

In one embodiment of the present invention, a protective film may be laminated on the other side of the polarizer on which the optical film is laminated.

In one embodiment of the present invention, the polarizer is a hydrophilic polymer film such as a polyvinyl alcohol-based film, a partially formalized polyvinyl alcohol-based film, or an ethylene/vinyl acetate copolymer-based partially saponified film. A film prepared by adsorbing a dichroic material such as iodine or a dichroic dye and uniaxially stretching the film; and a polyene-based oriented film such as a dehydrated product of a polyvinyl alcohol-based film or a dechlorinated product of a polyvinyl chloride-based film. Among these, a polarizer produced by adsorbing a dichroic substance such as iodine to a polyvinyl alcohol-based film and uniaxially stretching the film is particularly preferable from the viewpoint of high polarization dichroism. The thickness of the polarizer is not particularly limited, but is generally about 5 to 80 μm.

A polarizer manufactured by adsorbing iodine on a polyvinyl alcohol-based film and uniaxially stretching the film, for example, immersing the polyvinyl alcohol-based film in an iodine aqueous solution for coloring, and stretching the film to a length 3 to 7 times the original length. It can be prepared by. The aqueous solution may contain boric acid, zinc sulfate, zinc chloride, etc. as needed, or the polyvinyl alcohol-based film may be immersed in an aqueous solution such as potassium iodide. In addition, the polyvinyl alcohol-based film may be immersed in water and washed with water before coloring, if necessary. Water washing of the polyvinyl alcohol-based film not only removes contaminants on the surface of the film or removes the antiblocking agent, but also prevents non-uniformity such as uneven coloring by swelling the polyvinyl alcohol-based film. Stretching of the film may be performed after coloring the film with iodine, during coloring of the film, or prior to coloring the film with iodine. Stretching can be carried out in boric acid or potassium iodide aqueous solution, or in a water bath.

In one embodiment of the present invention, any suitable protective film can be used as the protective film as long as it can protect the polarizer without interfering with the effect of the present invention.

As the material of the polarizer protective film, specifically, acrylic, cellulose, polyolefin, polyester, or polycarbonate may be used.

For example, acrylic resins such as polymethyl (meth)acrylate and polyethyl (meth)acrylate; polyester resins such as polyethylene terephthalate, polyethylene isophthalate, polyethylene naphthalate, and polybutylene terephthalate; cellulosic resins such as diacetyl cellulose and triacetyl cellulose; polyolefin-based resins such as polyethylene, polypropylene, polyolefins having a cyclo-based or norbornene structure, and ethylene-propylene copolymers; Polycarbonate-type resin etc. are included.

The thickness of the polarizer protective film is usually 10 to 200 μm, preferably 10 to 150 μm.

In one embodiment of the present invention, the polarizer and the optical film and / or protective film according to the present invention may be bonded using an adhesive.

Any suitable adhesive may be used as the adhesive, and a material having excellent transparency, thermal stability, low birefringence, and the like is preferable. Specific examples include water-based adhesives, thermoplastic adhesives, hot-melt adhesives, rubber-based adhesives, thermosetting adhesives, monomer reactive adhesives, inorganic adhesives, and natural adhesives. Preferable examples include monomer reactive adhesive "Takenate 631" (trade name, manufactured by Mitsui Takeda Chemicals) containing an aliphatic isocyanate as a main component, from the viewpoint of excellent optical transparency, weather resistance, and heat resistance; and water-based adhesive "GOHSEFIMER Z series" (trade name, manufactured by Nippon Synthetic Chemical Industry) containing, as a main component, denatured polyvinyl alcohol having an acetoacetyl group.

The thickness of the adhesive layer may be appropriately determined depending on the type of resin serving as the adhesive, adhesive strength, and the environment in which the adhesive is used. The adhesive layer may preferably have a thickness of 0.01 μm to 50 μm, more preferably 0.1 μm to 10 μm.

The bonding method may use a conventional method in the art, for example, a polarizer, a protective film, or a method of applying an adhesive composition to the bonding surface of the optical film according to the present invention using a casting method, a Meyer bar coating method, a gravure coating method, a die coating method, a dip coating method, a spray coating method, and the like, and then bonding them. The casting method is a method of applying an adhesive composition to a bonding surface while moving a polarizer, a protective film, or an optical film according to the present invention in a generally vertical direction, a horizontal direction, or an inclined direction between the two. After applying the adhesive composition, a polarizer, a protective film, or an optical film according to the present invention is sandwiched and bonded to a niprol or the like.

After bonding, a drying treatment may be performed. The drying treatment is carried out, for example, by spraying hot air, and the drying temperature is appropriately selected from the range of 40 to 100°C, preferably 60 to 100°C. The drying time may be about 20 to 1,200 seconds. After drying, it is preferable to cure for about 12 to 600 hours at room temperature or a temperature slightly higher than that, for example, at a temperature of 20 to 50 ° C.

The polarizing plate according to the present invention can be applied to all conventional liquid crystal display devices. Accordingly, one embodiment of the present invention relates to a liquid crystal display device including the polarizing plate.

Hereinafter, the present invention will be described in more detail by Examples, Comparative Examples and Experimental Examples. These Examples, Comparative Examples and Experimental Examples are only for explaining the present invention, and it is obvious to those skilled in the art that the scope of the present invention is not limited thereto.

Example 1 to 6 and comparative example 1 to 3: COP Resin synthesis and optical film manufacturing

In a polymerization reactor, the monomer composition shown in Table 1 below and a cyclohexane solvent were added at a weight ratio of 1:2, and 0.01 mol% of palladium(II) acetylacetonate [Pd(acac) ₂ ] as a catalyst and 0.01 mol% of tricyclohexylphosphine relative to the monomer as catalysts, and 0.02 mol% of dimethylaniline based on the monomer dissolved in CH ₂ Cl ₂ as a cocatalyst. After adding dimethylanilinium tetrakiss (pentafluorophenyl) borate, the mixture was reacted with stirring at 60°C for 48 hours.

After the reaction, the reactant was added to an excess of acetone to obtain a white copolymer precipitate. The copolymer recovered by filtering the precipitate through a glass funnel was dried in a vacuum oven at 50° C. for 48 hours to obtain each COP resin.

After dissolving the COP resin in tetrahydrofuran, it was put into an autoclave equipped with a stirrer, and then a hydrogenation catalyst solution of bis(tricyclohexylphosphine)benzylidene ruthenium dichloride and ethyl vinyl ether dissolved in tetrahydrofuran was added, and hydrogenation was performed at 100° C. for 6 hours at a hydrogen pressure of 1 MPa to obtain a hydrogenated COP resin.

Each of the hydrogenated COP resins was dissolved in a cyclohexane solvent to a solid content of 20% by weight, coated on a silicone release-treated PET film to a dry film thickness of 40 μm, dried in a hot air dryer at 80 ° C. for 3 minutes, and then the film was peeled from the release film to obtain an optical film containing the hydrogenated COP resin.

Copolymer monomer composition (% by weight) Example 1

Example 2

Example 3

Example 4

Example 5

Example 6

Comparative Example 1

Comparative Example 2

Comparative Example 3

Experimental example 1: of optical film cutability evaluation

The optical films obtained in Examples and Comparative Examples were respectively cut using a CO ₂ RF IR laser cutting machine (product name: SLC-LC+, manufacturer: LP-tech) while applying a laser having a wavelength of 9.4 μm at an output intensity of 2 W, and cutting at a cutting speed of 40 cm / sec to evaluate the cutability, and the evaluation criteria are as follows.

<Evaluation Criteria for Cutability>

○: The cut end is cleanly cut

×: not cut

The evaluation results are shown in Table 2 below.

cutability evaluation Example 1 ○ Example 2 ○ Example 3 ○ Example 4 ○ Example 5 ○ Example 6 ○ Comparative Example 1 × Comparative Example 2 × Comparative Example 3 ×

As shown in Table 2, the optical films of Examples 1 to 6 were able to be cut cleanly at a high speed even under low power (2W), but it was confirmed that the optical films of Comparative Examples 1 to 3 were not cut.

As above, specific parts of the present invention have been described in detail, and for those skilled in the art, these specific techniques are only preferred embodiments, and the scope of the present invention is not limited thereto. It is clear. Those skilled in the art to which the present invention pertains will be able to make various applications and modifications within the scope of the present invention based on the above information.

Accordingly, the substantial scope of the present invention will be defined by the appended claims and equivalents thereof.

Claims (7)

An optical film comprising a cyclic olefin-based resin including a repeating unit represented by Formula 1 below,
The cyclic olefin-based resin is a monomer represented by the following formula (2); An optical film that is a copolymer obtained by subjecting one or more of the monomers represented by Formulas 3 to 5 to ring-opening polymerization and hydrogenation:
[Formula 1]

[Formula 2]

[Formula 3]

[Formula 4]

[Formula 5]

In the above formula,
R is a C ₁ -C ₈ alkoxy group, C ₁ -C ₈ alkoxycarbonyl group or C ₁ -C ₈ alkylcarboxylate group,

is a single bond or a double bond. According to claim 1,

is a single bond optical film. delete The optical film of claim 1, wherein the content of the monomer represented by Chemical Formula 2 is 5 to 50% by weight based on 100% by weight of the total monomers forming the cyclic olefin-based resin. The optical film according to claim 1, wherein the number average molecular weight of the cyclic olefin-based resin is 25,000 to 200,000. A polarizing plate comprising a polarizer and the optical film according to any one of claims 1, 2, 4, and 5 laminated on at least one surface of the polarizer. A liquid crystal display device having the polarizing plate according to claim 6 on at least one side of a liquid crystal cell.