KR101377202B1 - Optical film exhibiting excellent blocking property for ultraviolet rays and polarizing plate comprising the same - Google Patents

Abstract

A second peak having a maximum extinction coefficient of 0.07 to 0.10 phr ⁻¹ μm ⁻¹ in the 290 to 320 nm wavelength band, and a second having a maximum extinction coefficient of 0.11 to 0.16 phr-1 μm ⁻¹ in the 330 to 400 nm wavelength band The present invention relates to an optical film including a UV absorber having a peak, an acrylic resin, and a piperidine-based light stabilizer (HALS, Hindered Amine Light Stabilizer), and a polarizing plate including the same.

Description

OPTICAL FILM EXHIBITING EXCELLENT BLOCKING PROPERTY FOR ULTRAVIOLET RAYS AND POLARIZING PLATE COMPRISING THE SAME}

The present invention relates to an optical film having excellent UV blocking function and a polarizing plate including the same, and more particularly, even a small amount of ultraviolet absorber can effectively block ultraviolet rays of a wide wavelength band, and even if exposed to ultraviolet rays for a long time, the light spectrum It relates to a stable optical film and a polarizing plate using the same.

Currently, a polarizing plate used in an image display device such as a liquid crystal display device generally uses a triacetyl cellulose film (hereinafter, TAC film) as a protective film for protecting a polyvinyl alcohol polarizer. However, the TAC film does not have sufficient heat and moisture resistance, and when used under high temperature or high humidity, the TAC film has a problem in that polarization plate characteristics such as polarization degree and color are degraded due to film deformation. Therefore, a method of using a transparent acrylic resin film having excellent moisture and heat resistance instead of a TAC film has recently been proposed as a material for a polarizer protective film.

On the other hand, in recent years, in order to protect a polyvinyl alcohol polarizer from ultraviolet rays, the technique of adding a ultraviolet absorber to a protective film is proposed. The solar ultraviolet rays call the wavelength band of 320 to 400 nm as the UVA region and the wavelength band of 290 to 320 nm to the UVB region. The UVA region is not absorbed by the ozone layer, and the intensity is also high, so it must be blocked. Most of the UVB region is absorbed by the ozone layer, but since the energy is strong as the wavelength is short, it needs to be blocked even if the amount reaching the surface is small. However, in the case of the protective films including the ultraviolet absorber proposed up to now, there is a problem that the ultraviolet blocking region is limited to the wavelength range of 320 to 400nm.

In addition, in the case of the acrylic optical film including the ultraviolet absorber proposed up to now, a significant amount of ultraviolet absorber should be added in order to obtain a significant UV blocking effect, but in the case of adding a large amount of ultraviolet absorber in this way, the extruder When the acrylic resin melted under high temperature and pressure is suddenly cooled in the process of passing through the T-die and passing through the casting roll, the UV absorber decomposes and comes out of the film and gets on the casting roll. The migration, which is a phenomenon, was severe, and as a result, the ultraviolet absorber to be thermally decomposed is also buried in the film, thereby deteriorating the appearance of the film. In addition, since the ultraviolet absorber has a low molecular weight and a glass transition temperature, when the content of the ultraviolet absorbent is increased, the molecular weight and glass transition temperature of the acrylic film including the same may be lowered, thereby reducing heat resistance.

In addition, in the case of the acrylic optical film including the ultraviolet absorber proposed up to now, when exposed to ultraviolet light for a long time, a part of the ultraviolet absorber is broken by the ultraviolet rays to generate radicals, thus absorbing other regions deviating from the area that was initially absorbed. As a result, light transmittance in some wavelength bands is greatly reduced, resulting in a yellowing phenomenon in which the film becomes yellow.

Therefore, even when a small amount of the ultraviolet absorber is included, it is possible to effectively block both the ultraviolet ray (UVA region) in the 320-400 nm wavelength band and the ultraviolet ray (UVB region) in the 290-320 nm wavelength band, and furthermore, long-term exposure to ultraviolet rays. Even if it is, the acrylic optical film with stable light spectrum is calculated | required such that there is little change of light transmittance.

The present invention has been made to solve the above problems, including a small amount of the ultraviolet absorber, can effectively block both the ultraviolet rays of the UVA region and UVB region, stable optical spectrum even when exposed to ultraviolet rays for a long time, acrylic optical film And to provide a polarizing plate comprising the same.

In one aspect, the present invention is 290 to 320㎚ a maximum extinction coefficient in the wavelength range 0.07 to 0.10 phr ^-1 ㎛ ^{- 1} which has a first peak, a maximum extinction coefficient in the wavelength band 330 to 400㎚ 0.11 to 0.16 phr ^- An optical film including a UV absorber having a second peak of ¹ μm ^{− 1} , an acrylic resin, and a piperidine-based light stabilizer (HALS, Hindered Amine Light Stabilizer) is provided.

In another aspect, the present invention provides a polarizer and a polarizer including the optical film on one side or both sides of the polarizer.

In another aspect, the present invention provides an image display device including the polarizing plate.

The optical film of the present invention has excellent ultraviolet absorption performance and excellent effect of lowering both the light transmittance in the 290 nm wavelength band and the light transmittance in the 380 nm wavelength band to 5.5% or less, measured in terms of thickness of 50 μm. It is simple in composition and low in content, so that the amount of heat loss caused by pyrolysis in the extrusion process is low, and the price is competitive.

In addition, the optical film according to the present invention is stable even if exposed to ultraviolet light for a long time, such as the light spectrum is stable bar, yellowing phenomenon can be prevented.

1 is an absorption spectrum showing the absorption coefficient according to the wavelength of the ultraviolet absorbent NST5 of DKSH.
FIG. 2 is a light spectrum showing light transmittance according to ultraviolet light exposure time of an optical film including an ultraviolet absorbent NST5 of DKSH and piperidine-based light stabilizer (HALS) SABOSTAB UV62 of Songwon Industries.
FIG. 3 is a light spectrum showing light transmittance according to ultraviolet light exposure time of an optical film including an ultraviolet absorbent NST5 of DKSH and piperidine light stabilizer (HALS) SABOSTAB UV94 of Songwon Industries.
FIG. 4 is a light spectrum showing light transmittance with respect to ultraviolet light exposure time of an optical film including ultraviolet absorbent NST5 manufactured by DKSH, but not including piperidine-based light stabilizer (HALS).

Hereinafter, preferred embodiments of the present invention will be described. However, the embodiments of the present invention can be modified into various other forms, and the scope of the present invention is not limited to the embodiments described below. Further, the embodiments of the present invention are provided to more fully explain the present invention to those skilled in the art.

The optical film of the present invention has a first peak having a maximum extinction coefficient of 0.07 to 0.10 phr ⁻¹ μm ⁻¹ in the wavelength band of 290 to 320 nm, and a maximum extinction coefficient of 0.11 to 0.16 phr ⁻¹ in the wavelength band of 330 to 400 nm. Ultraviolet light absorber having a second peak of μm ⁻¹ , acrylic resin and piperidine-based light stabilizer (HALS, Hindered Amine Light Stabilizer) is characterized in that it comprises a.

In the absorption spectrum showing the absorption coefficient according to the wavelength calculated using the following formulas (1) to (2), the ultraviolet absorber of the present invention has a maximum absorption coefficient of 0.07 to 0.10 phr ⁻ in the wavelength band of 290 to 320 nm. Having a first peak of ¹ μm ⁻¹ , having a second peak with a maximum extinction coefficient of 0.11 to 0.16 phr ⁻¹ μm ⁻¹ in the 330 to 400 nm wavelength band, and more preferably in the 290 to 320 nm wavelength band ¹ has a second ^peak-to-peak with the first maximum, the extinction coefficient of 0.075 to 0.085 phr ^-1 ㎛ ^-1, 330 to a maximum absorption coefficient of 0.125 to 0.155 phr ^-1 ㎛ in 400㎚ wavelength band.

Equation (1) A = -Log T

(2) A = εbc

In the above formulas (1) to (2), A denotes absorbance, T denotes transmittance, ε denotes an absorption coefficient, b denotes a film thickness (μm), and c denotes a concentration (weight part) of an ultraviolet absorber. The value is obtained by calculating after adding the ultraviolet absorber to the film, the unit is phr ⁻¹ μm ⁻¹ , and for reference, there is no unit of absorbance (dimensionless).

In this case, the ultraviolet absorbent can effectively absorb ultraviolet rays even in a wide wavelength band of 290 to 400 nm. In more detail, the solar ultraviolet rays are called UVA regions of 320 to 400 nm and UVB regions of 290 to 320 nm, but the UVA regions are not absorbed by the ozone layer and have high intensity. It is necessary to block, and most of the UVB region is absorbed by the ozone layer, but because the energy is strong as the wavelength is short, it needs to be blocked even if the amount reaching the surface is small. When the ultraviolet absorbent satisfies the above conditions, the ultraviolet absorber effectively absorbs both the ultraviolet rays of the UVA region and the UVB region, thereby preventing the ultraviolet rays from adversely affecting the optical properties of the polarizer.

In addition, the ultraviolet absorber of the present invention is not limited thereto, but preferably includes at least one compound selected from the group consisting of a compound represented by the following formula (1) and a compound represented by the formula (2). That is, an ultraviolet absorber including the compound represented by the following Chemical Formula 1, or an ultraviolet absorber including the compound represented by the following Chemical Formula 2, or the ultraviolet absorber including both the compound represented by the following Chemical Formula 1 and the compound represented by the Chemical Formula 2 Is preferably.

[Formula 1]

(In Formula 1, R1 ~ R3 each independently represent a substituted or unsubstituted alkyl group having 18 or less carbon atoms)

(2)

(In Formula 2, R4 ~ R5 each independently represent a hydrogen or substituted or unsubstituted alkyl group having 18 or less carbon atoms)

In Chemical Formula 1, examples of the substituted or unsubstituted C18 or less alkyl group represented by R1 to R3 include, but are not limited to, methyl, ethyl, propyl, isopropyl, butyl, second butyl, third butyl, Isobutyl, amyl, isoamyl, tertiary amyl, hexyl, heptyl, 2-methylhexyl, isoheptyl, tertiary heptyl, n-octyl, isooctyl, tertiary octyl, 2-ethylhexyl, nonyl, isononyl, decyl , Dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, cyclopentyl, cyclohexyl, cycloheptyl, chloromethyl, dichloromethyl, trichloromethyl, 2-hydroxyethyl, 2-hydroxy Hydroxypropyl, 3-hydroxypropyl, 2-methoxyethyl, 2-ethoxyethyl, 2-butoxyethyl, 2-methoxypropyl, 3-methoxypropyl, and the like.

In Chemical Formula 2, examples of the substituted or unsubstituted C18 or less alkyl group represented by R4 to R5 include, but are not limited to, methyl, ethyl, propyl, isopropyl, butyl, second butyl, third butyl, Isobutyl, amyl, isoamyl, tertiary amyl, hexyl, heptyl, 2-methylhexyl, isoheptyl, tertiary heptyl, n-octyl, isooctyl, tertiary octyl, 2-ethylhexyl, nonyl, isononyl, decyl , Dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, cyclopentyl, cyclohexyl, cycloheptyl, chloromethyl, dichloromethyl, trichloromethyl, 2-hydroxyethyl, 2-hydroxy Hydroxypropyl, 3-hydroxypropyl, 2-methoxyethyl, 2-ethoxyethyl, 2-butoxyethyl, 2-methoxypropyl, 3-methoxypropyl, and the like.

On the other hand, it is more preferred that R1 to R3 of Formula 1 are each independently unsubstituted alkyl group of 1 to 6 carbon atoms, R 4 to R5 of Formula 2 are each independently hydrogen or an unsubstituted alkyl group of 1 to 6 carbon atoms It is more preferable that is.

In Chemical Formula 1, examples of the unsubstituted alkyl group having 1 to 6 carbon atoms represented by R 1 to R 3 include, but are not limited to, methyl, propyl, isopropyl, butyl, second butyl, third butyl, isobutyl, Amyl, isoamyl, tertiary amyl, hexyl, etc. are mentioned as an example.

In Chemical Formula 2, examples of the unsubstituted alkyl group having 1 to 6 carbon atoms represented by R 4 to R 5 include, but are not limited to, methyl, propyl, isopropyl, butyl, second butyl, third butyl, isobutyl, Amyl, isoamyl, tertiary amyl, hexyl, etc. are mentioned as an example.

In addition, the ultraviolet absorber of the present invention is not limited thereto, but more preferably includes at least one compound selected from the group consisting of a compound represented by the following formula (1-1) and a compound represented by the formula (2-1).

[Formula 1-1]

[Formula 2-1]

In addition, the content of the ultraviolet absorber of the present invention is preferably 0.3 to 1.0 parts by weight based on 100 parts by weight of the acrylic resin. If the UV absorber is less than 0.3 parts by weight, it does not have sufficient UV blocking effect. If the UV absorber exceeds 1.0 part by weight, the acrylic resin melted under high temperature and pressure in the extruder during the acrylic film manufacturing process is tee-die. When it cools abruptly in the process of passing through the T-die and passing through the casting roll, the UV absorber decomposes and escapes from the film, which causes the migration roll to become more severe. This is because the ultraviolet absorbents are also deposited on the film, which eventually leads to poor appearance of the film.

In addition, in consideration of processability and productivity, the ultraviolet absorber of the present invention preferably has a molecular weight of 400 to 600 g / mol, more preferably 500 to 600 g / mol.

Next, in the present invention, the acrylic resin includes a resin containing an acrylate unit and / or a methacrylate unit as a main component, and not only a homopolymer resin composed of an acrylate unit or a methacrylate unit. The concept also includes a copolymer resin in which other monomer units are copolymerized in addition to the acrylate units and / or methacrylate units, and blend resins in which other resins are blended with the acrylic resin as described above.

The acrylic resin usable in the present invention is, for example, but not limited to, copolymer resins comprising alkyl (meth) acrylate-based units and N-cycloalkyl maleimide-based units; A copolymer resin comprising an alkyl (meth) acrylate-based unit and a styrene-based unit; It may be a copolymer resin including an alkyl (meth) acrylate unit, an N-cycloalkyl maleimide unit and a styrene unit. In addition, it may be a blend resin containing such a copolymer resin and an aromatic resin having a carbonate portion in the main chain.

On the other hand, the alkyl (meth) acrylate-based unit means both alkyl acrylate-based unit and alkyl methacrylate-based unit, the alkyl group of the alkyl (meth) acrylate-based unit is preferably 1 to 10 carbon atoms, It is more preferable that it is C1-C4. In addition, the N-cycloalkyl group of the N-cycloalkyl maleimide-based unit is preferably 4 to 12 carbon atoms, and more preferably 5 to 8 carbon atoms. In addition, the styrene-based unit is not limited thereto, for example, styrene, α-methylstyrene, 3-methylstyrene, 4-methylstyrene, 2,4-dimethylstyrene, 2,5-dimethylstyrene, 2- Methyl-4-chlorostyrene, 2,4,6-trimethylstyrene, cis-β-methylstyrene, trans-β-methylstyrene, 4-methyl-α-methylstyrene, 4-fluor-α-methylstyrene, 4- Chloro-α-methylstyrene, 4-bromo-α-methylstyrene, 4-t-butylstyrene, 2-fluorostyrene, 3-fluorostyrene, 4-fluorostyrene, 2,4-difluorostyrene, 2 , 3,4,5,6-pentafluorostyrene, 2-chlorostyrene, 3-talloworostyrene, 4-tallowostyrene, 2,4-dichlorostyrene, 2,6-dichlorostyrene, octachlorostyrene, 2 With bromostyrene, 3-bromostyrene, 4-bromostyrene, 2,4-dibromostyrene, α-bromostyrene, β-bromostyrene, 2-hydroxystyrene and 4-hydroxystyrene 1 selected from the group consisting of It may be a species or more, and more preferably styrene or α-methylstyrene.

The acrylic resin may be a (meth) acrylate resin having an aromatic ring, and as the (meth) acrylate resin having an aromatic ring, (a) one or more kinds of (A) described in Korean Patent Application Laid-Open No. 10-2009-0115040 (Meth) acrylate type units containing a meth) acrylate derivative; (b) an aromatic unit having a chain having an hydroxy group-containing portion and an aromatic moiety; (c) styrenic units comprising at least one styrene derivative; And (d) a ring-based unit having a ring portion. Each of the (a) to (d) units may be included in the resin composition in the form of a separate copolymer, and two or more units of the (a) to (d) units may be included in the resin composition in the form of one copolymer. have.

As a specific example, a copolymer comprising (a) units such as methyl (meth) acrylate and (d) units such as N-cyclohexylmaleimide, that is, poly (N-cyclohexylmaleimide-co-methyl (meth) ) Acrylate) can be used. In addition, a copolymer containing (c) units such as styrene and (d) units such as maleic anhydride can be used. Moreover, the copolymer containing methyl methacrylate as (a) unit, styrene and (alpha) -methylstyrene as (c) unit, and N-cyclohexyl maleimide as (d) unit can be used. Moreover, the copolymer containing methyl methacrylate as (a) unit, styrene or (alpha) -methylstyrene as (c) unit, and N-cyclohexyl maleimide and maleic anhydride as (d) unit can be used. However, the above examples are for illustrating the present invention, and the scope of the present invention is not limited to the above examples.

Next, in the present invention, the piperidine-based light stabilizer (HALS) is included so that there is almost no change in light transmittance even when the optical film is exposed to ultraviolet light for a long time. More specifically, when the optical film is exposed to ultraviolet light for a long time, a part of the ultraviolet absorber included in the optical film is broken by the ultraviolet light, and radicals are generated. As a result, light transmittance in a specific wavelength band (for example, around 400 nm) of the optical film is greatly reduced. However, when the piperidine-based light stabilizer (HALS) is included in the optical film, piperidine-based light stabilizer (HALS) prevents this phenomenon, so that there is almost no change in the light transmittance, and as a result, the optical spectrum is stable Allows you to provide film.

In particular, the present invention has a first peak having a maximum extinction coefficient of 0.07 to 0.10 phr ⁻¹ μm ⁻¹ in the wavelength band of 290 to 320 nm used in the present invention, and a maximum extinction coefficient of 0.11 to 0.16 phr ⁻ in the wavelength band of 330 to 400 nm. ^In the case of the acrylic optical film including the ultraviolet absorber having the second peak of ¹ μm ⁻¹ , the optical transmittance may be greatly reduced in the vicinity of the 400 nm wavelength band when the piperidine-based light stabilizer (HALS) is not included. As a result, a lot of light is absorbed in the vicinity of the 400 nm wavelength band, the light of a relatively red series is more strong, yellowing phenomenon that the film may turn yellow. Therefore, the piperidine-based light stabilizer (HALS) is included to prevent this.

In the present invention, the piperidine-based light stabilizer (HALS) is not particularly limited as long as it contains at least one of the structures represented by the following formulas (A) to (D).

(A)

[Formula B]

≪ RTI ID = 0.0 &

[Chemical Formula D]

Formula A is connected to the nitrogen and 4-position carbon of the piperidine ring and other atoms in the piperidine-based light stabilizer (HALS), the formula B is connected to nitrogen and 4-position carbon of the piperidine ring The oxygen present is connected to another atom in the piperidine-based light stabilizer (HALS), wherein the 4-position carbon of the piperidine ring is connected to another atom in the piperidine-based light stabilizer (HALS), In Formula (D), oxygen connected to the 4-position carbon of the piperidine ring is connected to another atom in the piperidine-based light stabilizer (HALS).

As a piperidine-based light stabilizer (HALS) containing at least one of the above formulas (A) to (D) in a molecule, for example, but not limited thereto, it has one structure selected from the group consisting of structures represented by the following formulas And the like.

(I)

(In the formula (I), n is an integer of 3 to 6)

[Formula II]

(In Formula II, m is an integer of 3 to 6)

[Formula (III)

(In Formula III, l is an integer of 9 to 13)

[Formula IV]

(In Formula IV, o is an integer of 3 to 8)

[Formula V]

(In Formula V, p is an integer of 9 to 18)

(VI)

(In the above formula (VI), q is an integer of 3 to 8)

[Formula Ⅶ]

(In the formula (VII), r is an integer of 3 to 8)

(VIII)

(In the formula (VII), s is an integer of 3 to 8)

[Formula IX]

(In the formula (VII), t is an integer of 5 to 15)

[Formula Ⅹ]

(In the formula (VII), u is an integer of 3 to 8)

[Formula VIIⅠ]

(In the formula (XI), v is an integer of 6 to 16)

[Formula XII]

(In the formula (XII), w is an integer of 4 to 13)

[Formula XIII]

(In the formula (XIII), x is an integer of 4 to 12)

[Chemical Formula XIV]

(In the formula (XIV), y is an integer of 6 to 8)

[Formula XV]

이다)
(In Chemical Formula XV,

to be)

Meanwhile, in the present invention, the piperidine light stabilizer (HALS) preferably has a molecular weight of 1500 to 6000 g / mol, more preferably 1800 to 5000 g / mol or 2000 to 4500 g / mol. This is because the thermal stability is excellent when the molecular weight of the piperidine light stabilizer (HALS) is within the above range. In the case of the present invention, the piperidine-based light stabilizer (HALS) is mixed with an ultraviolet absorber in an acrylic resin and made into pellet form through high-temperature processing, and then the film is extruded at a high temperature close to 300 ° C. In the case of poor thermal stability, a large amount of fume occurs in the T-die, resulting in a poor working environment, and a migration phenomenon that is transferred to the casting rolls. On the other hand, when the molecular weight is large enough to be out of the above range, the number of moles of piperidine-based light stabilizer (HALS) participating in the reaction may decrease, which may cause a problem of poor reactivity.

In the present invention, the piperidine-based light stabilizer (HALS) is 1% pyrolysis temperature measured by a thermogravimetric analyzer (TGA) is preferably 250 to 500 ℃, 250 to 400 ℃ or 250 to 350 ℃ More preferred. If the 1% pyrolysis temperature measured by the thermogravimetric analyzer (TGA) is lower than the above range because the piperidine-based light stabilizer (HALS) is decomposed during film extrusion may cause a migration phenomenon that the casting roll is contaminated.

On the other hand, the optical film of the present invention as described above may be prepared using a resin composition prepared by mixing the ultraviolet absorber and piperidine-based light stabilizer (HALS) to the acrylic resin. More specifically, the optical film of the present invention is prepared by producing an acrylic resin in which the ultraviolet absorber and piperidine-based light stabilizer (HALS) are mixed in a film form according to a method well known in the art, such as a solution caster method or an extrusion method. Can be prepared. In view of economics, it is more preferable to use an extrusion method. In some cases, during the film production process, an additive such as a modifier may be further added within a range that does not impair the physical properties of the film, and a uniaxial or biaxial stretching step may be further performed.

The stretching process may perform longitudinal (MD) stretching, transverse (TD) stretching, or both. In the case of performing both the longitudinal drawing and the transverse drawing, either one of them may be stretched in the other direction, or the two directions may be stretched at the same time. In addition, the stretching may be performed in one step or may be performed in multiple steps. In the case of longitudinal stretching, stretching by the speed difference between rolls can be performed, and in the case of transverse stretching, tenter can be used. The time of railing of the tenter is usually within 10 degrees, thereby suppressing the bowing phenomenon occurring in the transverse direction drawing and controlling the angle of the optical axis regularly. Even when the transverse stretching is performed in multiple stages, the effect of inhibiting the bowing can be obtained.

On the other hand, the stretching may be carried out in a temperature range of (Tg-20) ℃ ~ (Tg + 30) ℃. The temperature range refers to a range from the temperature at which the storage modulus of the resin composition begins to decrease, and thus the loss modulus becomes larger than the storage modulus, to a temperature at which the orientation of the polymer chain is relaxed and lost. Alternatively, the temperature during the stretching process may be a glass transition temperature of the resin composition. The glass transition temperature of the resin composition can be measured by a differential scanning calorimeter (DSC). For example, when using a differential scanning calorimeter (DSC), the endothermic and calorific value of the material according to the phase change occurs when the sample is sealed in a dedicated pan and heated to a constant temperature condition. The transition temperature can be measured.

The stretching speed is preferably in the range of 1 to 100 mm / min for the universal testing machine (Zwick Z010) and within the range of 0.1 to 2 m / min for the pilot stretching equipment. The drawing ratio is preferably about 5 to 300%.

It is preferable that the optical film of this invention manufactured by the above method has the light transmittance in 290 nm wavelength and the light transmittance in 380 nm wavelength measured in conversion of 50 micrometers in thickness of 5.5% or less. In addition, the light transmittance in the visible light region is preferably 92% or more. When the light transmittance at the wavelength of 290 nm and the light transmittance at the wavelength of 380 nm are both 5.5% or less, the ultraviolet rays of the UVA and UVB regions can be effectively blocked, and the transparency of the film when the light transmittance in the visible region is 92% or more. And because the color is excellent.

It is preferable that it is 5-80 micrometers in thickness, and, as for the optical film of this invention manufactured by the above method, it is more preferable that it is 5-50 micrometers. As can be seen from the above formulas (1) to (2), the absorbance increases as the b-value related to the thickness increases, so the absorbance increases as the thickness of the film increases, but the thickness is too large due to the characteristics of the modern industry in pursuit of thinning. It is not desirable to thicken. On the other hand, if the thickness is thin, the ultraviolet ray blocking effect is reduced, so the content of the ultraviolet absorber should be increased, in which case there may be various problems accompanying this, such as an increase in cost. Therefore, it is desirable to be able to absorb ultraviolet rays efficiently by using an economical amount of ultraviolet absorber having an appropriate thickness range.

The optical film of the present invention is attached to one or both sides of the polarizer can be usefully used as a polarizing plate protective film. At this time, the polarizer and the optical film of the present invention is coated with an adhesive on the surface of the film or polarizer using a roll coater, gravure coater, bar coater, knife coater or capillary coater, etc. It may be carried out by a method of laminating by heating or pressing at room temperature. As the adhesive, adhesives used in the related art, for example, a polyvinyl alcohol adhesive, a polyurethane adhesive, an acrylic adhesive and the like may be used without limitation.

In addition, the optical film of the present invention can be applied to various image display devices such as liquid crystal display devices, plasma displays, and electroluminescent devices.

Hereinafter, the present invention will be described in more detail with reference to specific examples.

Ultraviolet absorber

For the experiment, the absorption coefficient according to the component and wavelength of the commercial ultraviolet absorber NST5 of DKSH was measured. At this time, the extinction coefficient of the ultraviolet absorber was calculated using the following equations (1) to (2), and the measurement results are shown in FIG. 1.

Equation (1) A = -Log T

(2) A = εbc

In the above formulas (1) to (2), A denotes absorbance, T denotes transmittance, ε denotes an absorption coefficient, b denotes a film thickness (μm), and c denotes a concentration (part by weight) of an ultraviolet absorber. The value is obtained by calculating after adding the ultraviolet absorber to the film, the unit is phr ⁻¹ μm ⁻¹ , and for reference, there is no unit of absorbance (dimensionless).

As can be seen in Figure 1, DKSH UV absorber NST5 has a first peak having a maximum extinction coefficient of 0.073 to 0.074 phr ^-1 μm ^-1 in the 290 to 320 nm wavelength band, the maximum absorption in the 330 to 400 nm wavelength band The coefficient was found to have a second peak with 0.130 to 0.131 phr ⁻¹ μm ⁻¹ .

Piperidine light stabilizer ( HALS )

Each piperidine-based light stabilizer (HALS) used for the experiment is shown in Table 1 below.

product name Molecular Weight constitutional formula
Songwon Industry
SABOSTAB
UV62
3100-4000
g / mol

Songwon Industry
SABOSTAB UV94
2000-3100
g / mol

Example  One

0.7 parts by weight of UV absorber NST5 from DKSH, Switzerland, and 100% by weight of poly (N-cyclohexylmaleimide-co-methylmethacrylate-co-αmethyl-styrene) having a glass transition temperature of 120 ° C. A ferridine light stabilizer (HALS) SABOSTAB UV62 0.4 parts by weight of a uniformly mixed resin composition was supplied to an extruder of 24 φ which was nitrogen-substituted from the raw material hopper to the extruder, and melted at 250 ° C. to prepare a raw material pellet. . The poly (N-cyclohexylmaleimide-co-methylmethacrylate-co-αmethyl-styrene) resin has N-cyclohexylmarimide content of 6.0 wt% and αmethyl-styrene content of 2.0 wt% according to NMR analysis. Was%.

The raw material pellets prepared above were vacuum dried and melted with an extruder at 250 ° C., and then passed through a coat hanger type T-die, and a film having a thickness of 160 μm was passed through a chrome plating casting roll and a drying roll. Prepared.

The film was stretched at twice the ratio in the MD and TD directions at 130 to 135 ° C. using an experimental film stretching equipment to prepare a biaxially stretched film having a thickness of 50 μm.

Example  2

0.7 parts by weight of UV absorber NST5 from DKSH, Switzerland, and 100% by weight of poly (N-cyclohexylmaleimide-co-methylmethacrylate-co-αmethyl-styrene) having a glass transition temperature of 120 ° C. A resin composition obtained by uniformly mixing 0.4 parts by weight of ferridine-based light stabilizer (SALS) SABOSTAB UV94 was supplied to an extruder of 24 φ which was nitrogen-substituted from a raw material hopper to an extruder, and melted at 250 ° C. to prepare a raw material pellet. . The poly (N-cyclohexylmaleimide-co-methylmethacrylate-co-αmethyl-styrene) resin has N-cyclohexylmarimide content of 6.0 wt% and αmethyl-styrene content of 2.0 wt% according to NMR analysis. Was%.

The raw material pellets prepared above were vacuum dried and melted with an extruder at 250 ° C., and then passed through a coat hanger type T-die, and a film having a thickness of 160 μm was passed through a chrome plating casting roll and a drying roll. Prepared.

The film was stretched at twice the ratio in the MD and TD directions at 130 to 135 ° C. using an experimental film stretching equipment to prepare a biaxially stretched film having a thickness of 50 μm.

Comparative Example

A resin composition obtained by uniformly mixing 0.7 parts by weight of ultraviolet absorbent NST5 of DKSH of Switzerland with 100 parts by weight of poly (N-cyclohexylmaleimide-co-methylmethacrylate-co-αmethyl-styrene) having a glass transition temperature of 120 ° C A raw material hopper was fed from a raw material hopper to an extruder of 24φ substituted with nitrogen and melted at 250 ° C. to prepare raw material pellets. The poly (N-cyclohexylmaleimide-co-methylmethacrylate-co-αmethyl-styrene) resin has N-cyclohexylmarimide content of 6.0 wt% and αmethyl-styrene content of 2.0 wt% according to NMR analysis. Was%.

The raw material pellets prepared above were vacuum dried and melted with an extruder at 250 ° C., and then passed through a coat hanger type T-die, and a film having a thickness of 160 μm was passed through a chrome plating casting roll and a drying roll. Prepared.

The film was stretched at twice the ratio in the MD and TD directions at 130 to 135 ° C. using an experimental film stretching equipment to prepare a biaxially stretched film having a thickness of 50 μm.

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Next, the light transmittance (initial and 100 hours later) and the yellowing phenomenon occurrence rate according to ultraviolet light exposure time in the wavelength bands of 290 nm, 380 nm, and 400 nm of the optical films of Examples 1 to 2 and Comparative Examples were measured. Table 3 shows. In addition, the spectrum showing the light transmittance (initial and 100 hours later) according to the ultraviolet light exposure time in the 400 nm wavelength band of the optical film of Examples 1 to 2 and Comparative Examples are shown in Figures 2 to 4 below. The measuring method is as follows.

1. Ultraviolet exposure: It exposed at 100 degreeC in 60 degreeC and 0.6W / m <2> conditions in UV2000 of Atlas.

2. Light transmittance: Measured using Hitachi U-3310 spectrometer.

3. The degree of yellowing phenomenon: The optical film is red when the value of a is large, green when the value of a is small, yellow when the value of b is large, and blue when the value of b is small. The smaller the value of b, the smaller the occurrence of yellowing. A and b are calculated using the following formulas (3) to (8), respectively.

Equation (3)

Equation (4)

Equation (5)

Equation (6)

Equation (7)

Equation (8)

In the above formula, S (λ), x (λ), y (λ), z (λ) is the light source spectrum of the spectrometer to measure, using a value corresponding to Hitachi U-3310 spectrometer , R (λ) is the light transmittance spectrum of the sample measured by placing the film sample in a spectrometer (spectrometer), the light transmittance spectrum value measured by putting the film sample in the Hitachi U-3310 spectrometer.

division Ultraviolet absorber Light stabilizer Light transmittance Yellowing phenomenon Kinds content Kinds content division % T_290nm % T_380nm % T_400nm a b Example 1 NST5 0.7
Weight portion SABOS
TAB
UV62 0.4
Weight portion Early 4.4 3.5 72.4 -0.3 0.5 After 100 hours 4.5 3.4 70.4 -0.4 0.7 Example 2 NST5 0.7
Weight portion SABOS
TAB
UV94 0.4
Weight portion Early 3.9 3.2 70.1 -0.5 0.9 After 100 hours 4.0 3.1 68.9 -0.5 0.9 Comparative Example NST5 0.7
Weight portion - - Early 4.9 3.7 72.8 -0.4 0.6 After 100 hours 5.0 3.3 62.1 -0.7 1.1

As shown in Table 3 and FIGS. 2 to 4 below, in the case of the optical film containing piperidine-based light stabilizers (HALS) as in Examples 1 to 2, the amount of change in light transmittance in the vicinity of the 400 nm wavelength band is very high. It can be seen that the yellowing phenomenon hardly occurs. However, in the case of the optical film containing no piperidine-based light stabilizer (HALS) as in the comparative example, it can be seen that the amount of change in light transmittance in the vicinity of the 400 nm wavelength band is very large and yellowing phenomenon occurs severely.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, It will be obvious to those of ordinary skill in the art.

Claims (16)

A second peak having a maximum extinction coefficient of 0.07 to 0.10 phr ⁻¹ μm ⁻¹ in the wavelength band of 290 to 320 nm, and a second having a maximum extinction coefficient of 0.11 to 0.16 phr ⁻¹ μm ⁻¹ in the wavelength band of 330 to 400 nm Ultraviolet absorbers having peaks;
Acrylic resin; And
Optical film comprising a piperidine-based light stabilizer (HALS, Hindered Amine Light Stabilizer) containing at least one of the structures represented by the formulas A to D in the molecule.
(A)

[Chemical Formula B]

&Lt; RTI ID = 0.0 &

[Chemical Formula D]

(Formula A is connected to the nitrogen and 4-position carbon of the piperidine ring is connected to other atoms in the piperidine-based light stabilizer (HALS), the formula B is connected to nitrogen and 4-position carbon of the piperidine ring Oxygen is connected to another atom in the piperidine-based light stabilizer (HALS), wherein the carbon at the 4-position of the piperidine ring is connected to another atom in the piperidine-based light stabilizer (HALS) In Formula D, the oxygen connected to the 4-position carbon of the piperidine ring is connected to another atom in the piperidine-based light stabilizer (HALS)
delete The method of claim 1,
The piperidine-based light stabilizer (HALS, Hindered Amine Light Stabilizer) is an optical film having a structure selected from the group consisting of structures represented by the following formula (I) to (VV).
(I)

(In Formula I, n is an integer of 3 to 6)
[Formula II]

(In Formula II, m is an integer of 3 to 6)
[Formula (III)

(In Formula III, l is an integer of 9 to 13)
[Formula IV]

(In Formula IV, o is an integer of 3 to 8)
[Formula V]

(In Formula V, p is an integer of 9 to 18)
[Formula VI]

(In Formula VI, q is an integer of 3 to 8)
[Formula VII]

(In the formula (VII), r is an integer of 3 to 8)
(VIII)

(In the formula (VII), s is an integer of 3 to 8)
[Formula IX]

(In the formula (VII), t is an integer of 5 to 15)
[Formula Ⅹ]

(In the formula (VII), u is an integer of 3 to 8)
[Formula VIIⅠ]

(In the formula (XI), v is an integer of 6 to 16)
[Formula XII]

(In Chemical Formula XII, w is an integer of 4 to 13)
[Formula XIII]

(In Chemical Formula XIII, x is an integer of 4 to 12)
[Formula IV]

(In Formula (IV), y is an integer of 6 to 8)
[Formula XV]

(In Chemical Formula XV,

being)
The method of claim 1,
The piperidine-based light stabilizer (HALS, Hindered Amine Light Stabilizer) has a molecular weight (molecular weight) of 1500 to 6000 g / mol.
The method of claim 1,
The piperidine optical stabilizer (HALS, Hindered Amine Light Stabilizer) is an optical film having a 1% pyrolysis temperature of 250 to 500 ℃ measured by a thermogravimetric analyzer (TGA)
The method of claim 1,
The ultraviolet absorber is an optical film comprising at least one compound selected from the group consisting of compounds represented by the formula (1) and (2).
[Chemical Formula 1]

(In Formula 1, R1 ~ R3 each independently represent a substituted or unsubstituted alkyl group having 18 or less carbon atoms)
(2)

(In Formula 2, R4 ~ R5 each independently represent a hydrogen or substituted or unsubstituted alkyl group having 18 or less carbon atoms)
The method according to claim 6,
R 1 to R 3 of Formula 1 are each independently an unsubstituted alkyl group having 1 to 6 carbon atoms, and R 4 to R 5 are each independently hydrogen or an unsubstituted alkyl group having 1 to 6 carbon atoms.
The method according to claim 6,
The ultraviolet absorber is an optical film comprising at least one compound selected from the group consisting of compounds represented by the formula 1-1 and 2-1.
[Formula 1-1]

[Formula 2-1]

The method of claim 1,
The content of the ultraviolet absorber is 0.3 to 1.0 parts by weight based on 100 parts by weight of the acrylic resin.
The method of claim 1,
The optical film has an optical transmittance at a wavelength of 290 nm and a transmittance at a wavelength of 380 nm of 5.5% or less, measured in terms of a thickness of 50 μm.
The method of claim 1,
The optical film has an optical transmittance of 92% or more in the visible light region.
The method of claim 1,
The optical film has a thickness of 5 μm to 80 μm.
The method of claim 1,
The acrylic resin is an optical film which is a copolymer comprising an alkyl (meth) acrylate unit, an N-cycloalkyl maleimide unit and a styrene unit.
The method of claim 1,
The ultraviolet absorber is an optical film having a molecular weight of 400 to 600g / mol.
A polarizer; And
Claim 1 and claim 3 to claim 14 wherein the polarizing plate comprising the optical film of any one of the polarizer.
An image display device comprising the polarizing plate of claim 15.

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