Cellulose ester film having excellent ultraviolet-blocking performance, polarizing plate, and image display device

Abstract

The present invention relates to a cellulose ester film comprising, in a cellulose ester substrate, a sesamolbenzotriazole-based first ultraviolet absorber and at least one second ultraviolet absorber selected from benzotriazole-based, malonate-based, triazine-based and benzophenone-based ultraviolet absorbers, and the cellulose ester film of the present invention uses both a long-wavelength first ultraviolet absorber containing an alkyl chain to ensure sufficient solubility and a second ultraviolet absorber for ensuring light resistance, and thus ensures both long-wavelength region absorption performance and light resistance reliability while having significantly low ultraviolet transmittance.

Description

Cellulose ester film, polarizing plate and image display device with excellent UV blocking performance

[0001] The present invention relates to a cellulose ester film having excellent ultraviolet ray blocking performance and a polarizing plate and an image display device including the same, and more specifically, to a cellulose ester film having excellent ultraviolet ray blocking performance and excellent light resistance obtained by including two types of ultraviolet ray absorbers in the substrate of the cellulose ester film, and a polarizing plate and an image display device using the same.

[0002] Display device development is focused on liquid crystal displays (LCDs) and organic light-emitting diodes (OLEDs). The demand for high resolution in OLED displays is driving a growing demand for high brightness. One way to achieve high brightness in OLEDs is to increase the light transmittance of polarizers, enabling them to operate at lower power levels. However, increasing the transmittance of polarizers also increases UV transmittance, degrading the performance of OLED devices and shortening their lifespan.

[0003] To protect the polarizing plate, a cellulose ester film, such as triacetyl cellulose, is attached to one side of the polarizing plate. This cellulose ester film typically contains a benzophenone-based compound or a benzotriazole-based UV absorber to block UV rays around 380 nm, thereby protecting the display device by blocking UV rays incident on the display device from the outside. However, to prevent deterioration of OLED elements, UV blocking performance in the long-wavelength range of 400 nm or longer is required, and this level is insufficient. To solve this problem, the UV transmittance in the range of 400 nm or longer is lowered by additionally including a long-wavelength UV absorber in a coating layer or adhesive layer on the substrate. For example, Japanese Patent Application Laid-Open No. 2020-129107 discloses an optical film in which at least one of the first functional layer and the second functional layer on a light-transmitting substrate includes a benzotriazole-based UV absorber. However, this coating method has the disadvantage of containing excessive amounts of UV absorbers in thin layers of less than 10㎛. This leads to UV radiation being concentrated in specific areas, accelerating deterioration and ultimately reducing long-term light resistance reliability. When manufacturing display devices using polarizing plate protective films with poor light resistance, changes in the film's properties can cause problems with the operation or appearance of internal components.

[0004] The present invention is intended to overcome the problems of the prior art described above, and one object of the present invention is to provide a cellulose ester film that uses a long-wavelength ultraviolet absorber to significantly reduce ultraviolet transmittance at a wavelength of 380 nm in the UVA region and ultraviolet transmittance at a wavelength of 400 nm near the visible light region, thereby preventing deterioration of OLED elements, particularly blue light-emitting elements and internal elements of OLEDs, and at the same time improving light resistance.

[0005] In addition, the present invention aims to provide a polarizing plate using a polarizing protective film.

[0006] In addition, the present invention aims to provide an optical film using the polarizing plate.

[0007] In addition, the present invention aims to provide an image display device using the polarizing plate or optical film.

[0008] One aspect of the present invention to achieve the above-described purpose is:

[0009] The present invention relates to a cellulose ester film comprising a first ultraviolet absorber of the sesamol benzotriazole type represented by the following chemical formula 1 and at least one second ultraviolet absorber selected from among benzotriazole type, malonate type, triazine type, and benzophenone type ultraviolet absorbers within a cellulose ester substrate.

[0010]

[0011] In the above formula, R is hydrogen and a C1 to C8 ketone, aldehyde, ether, ester, alkene, alcohol, carbonyl group, or carboxyl group.

[0012] In the present invention, the polymer film serving as the support is preferably a cellulose ester film. Commonly used cellulose esters are preferably lower fatty acid esters of cellulose. The lower fatty acid used in the production of lower fatty acid esters of cellulose refers to a fatty acid having 6 or fewer carbon atoms. Examples of lower fatty acid esters include cellulose acetate, cellulose propionate, cellulose butyrate, and mixed fatty acid esters of cellulose, such as cellulose acetate propionate or cellulose acetate butyrate. Among the lower fatty acid esters of cellulose, cellulose triacetate or cellulose acetate propionate is particularly preferred.

[0013] The molecular weight range of the cellulose ester is not limited, but a weight average molecular weight of 150,000 to 300,000 is preferred. By setting the molecular weight above a certain level, the strength of the film can be effectively prevented from deteriorating. In addition, by setting the molecular weight below a certain level, the viscosity of the cellulose ester solution (main dope solution) can be maintained below a certain level, making film production using the solvent casting method easier.

[0014] In the present invention, the total thickness of the cellulose ester film is within the range of 20 to 100 ㎛.

[0015] For the entire cellulose ester film, the total content of the ultraviolet absorber may be 0.2 to 10 wt%, the content of the first ultraviolet absorber may be 0.1 to 5.0 wt%, and the content of the second ultraviolet absorber may be 0.1 to 5.0 wt%.

[0016] The above first ultraviolet absorber may be at least one selected from among ultraviolet absorbers represented by the following chemical formulas 2 to 10.

[0017]

[0018]

[0019]

[0020]

[0021]

[0022]

[0023]

[0024]

[0025]

[0026]

[0027] The above-described cellulose ester film can be a protective film for a polarizing plate.

[0028] Another aspect of the present invention relates to a polarizing plate or surface-treated film comprising the above-described cellulose ester film.

[0029] Another aspect of the present invention relates to an image display device including the above-described polarizing plate.

[0030] The cellulose ester film of the present invention uses a first long-wavelength ultraviolet absorber containing an alkyl chain to ensure sufficient solubility and a second ultraviolet absorber to ensure light resistance, thereby ensuring both long-wavelength (400 nm or more) region absorption performance and light resistance reliability while having significantly low ultraviolet transmittance.

[0031] The polarizing plate protective film and surface treatment film using the cellulose ester film of the present invention have excellent ultraviolet absorption performance, can prevent yellowing even when exposed to ultraviolet rays for a long time, and can provide the advantages of stable optical properties and no decrease in durability.

[0032] The optical film of the present invention can improve the deterioration of organic light-emitting devices (OLEDs) that are vulnerable to ultraviolet rays by eliminating ultraviolet transmittance in the wavelength range near visible light, thereby extending their lifespan.

[0033] Hereinafter, the present specification will be described in detail.

[0034] In this specification, when a part is said to 'include' a certain component, this does not mean that other components are excluded, but rather that other components may be included, unless otherwise specifically stated.

[0035] In this specification, when it is said that a member is located 'on' another member, this includes not only cases where a member is in contact with another member, but also cases where another member exists between the two members.

[0036] One aspect of the present invention relates to a cellulose ester film comprising a first ultraviolet absorber of the sesamol benzotriazole type represented by the following chemical formula 1 and at least one second ultraviolet absorber selected from among benzotriazole type, malonate type, triazine type, and benzophenone type ultraviolet absorbers in a cellulose ester substrate.

[0037] [Chemical Formula 1]

[0038]

[0039] In the above formula, R is hydrogen and a C1 to C8 ketone, aldehyde, ether, ester, alkene, alcohol, carbonyl group, or carboxyl group.

[0040] In the present invention, in order to prevent deterioration of an organic light-emitting device, one of the sesamol benzotriazole-based UV absorbers, such as chemical formula 1, is used to have high transparency and effectively absorb ultraviolet rays up to a wavelength of 405 nm, and in order to secure light resistance reliability, at least one second UV absorber is used from among benzotriazole-based, malonate-based, triazine-based, and benzophenone-based. When only one of the first and second UV absorbers is used alone, the transmittance and color required for protecting the OLED device can be satisfied, but when exposed to sunlight for a long time, there is a concern that the ultraviolet absorption performance may deteriorate due to insufficient light resistance reliability of the film.

[0041] The first sesamol benzotriazole-based ultraviolet absorbent of chemical formula 1 of the present invention is a compound having a benzotriazole structure, has a maximum absorption wavelength (λmax) of 365 nm or more, an absorbance (ε) at that time of about 20,000 or more, and has a particularly high ultraviolet absorption ability in the long wavelength region.

[0042] The first UV absorber can be represented by Chemical Formula 1, and the R position contains a ketone, aldehyde, ether, ester, alkene, alcohol, carbonyl group, carboxyl group, etc. containing hydrogen and an alkyl chain of 1 to 8 carbon atoms. In the structure of the UV absorber, the solubility varies depending on the terminal substituent, and the solubility tends to be proportional to the length of the substituent, that is, the molecular weight. The longer the terminal substituent, the higher the solubility due to the attractive force between the solvent and the additive, whereas the longer the substituent, the higher the color b value, and the more the content must be increased to achieve the same UV blocking performance. As the content of the UV absorber increases, there is a concern that the mechanical performance of the film may deteriorate, dimensional change may increase in high temperature and high humidity environments, and the price may increase. On the other hand, when the substituent is short, the solubility may decrease, causing the UV absorber to bleed out from the film during the process, which may cause process contamination, foreign matter generation, and decreased UV absorption performance. Therefore, it is necessary to optimize the substituent to an appropriate length.

[0043] Examples of the first ultraviolet absorber usable in the present invention include, but are not necessarily limited to, the sesamol benzotriazole-based ultraviolet absorbers of the following chemical formulas 2 to 10.

[0044] [Chemical Formula 2]

[0045]

[0046] [Chemical Formula 3]

[0047]

[0048] [Chemical Formula 4]

[0049]

[0050] [Chemical Formula 5]

[0051]

[0052] [Chemical Formula 6]

[0053]

[0054] [Chemical Formula 7]

[0055]

[0056] [Chemical Formula 8]

[0057]

[0058] [Chemical Formula 9]

[0059]

[0060] [Chemical Formula 10]

[0061]

[0062] In the present invention, by using a second ultraviolet absorber in addition to the first ultraviolet absorber described above, light resistance reliability can be improved, thereby stably protecting the OLED element even in an external environment for a long time. In order to secure the durability of the cellulose ester film, for example, at least one second ultraviolet absorber selected from among benzotriazole-based, malonate-based, triazine-based, and benzophenone-based ultraviolet absorbers having a maximum absorption wavelength (λmax) of 330 to 380 nm, preferably 330 to 370 nm, and more preferably 347 to 360 nm is used.

[0063] Specific examples of the second ultraviolet absorber include 2-(2H-benzotriazol-2-yl)-6-(1-methyl-1-phenylethyl)-4-(1,1,3,3-tetramethylbutyl)phenol, 2-(2H-benzotriazol-2-yl)-4,6-bis(1-methyl-1-phenylethyl)phenol, 2-[2-hydroxy-3,5-di(1,1-dimethylbenzyl)phenyl] 2H-benzotriazole, 2,2'-methylenebis[6-(2H-benzotriazol-2-yl)-4-(1,1,3,3-tetramethylbutyl) phenol], 2-(4,6-diphenyl-1,3,5-triazin-2-yl)-5-[(hexyl)oxy]-phenol, At least one selected from the group consisting of 1,3-bis-[2'-cyano-3',3-diphenylacrylonyl]oxy]-2,2-bis-{[2-cyano-3',3'-phenylacrylonyl]oxy}methyl}propane, edyl 2-cyano-3,3-diphenylacrylate, malonic acid 2-[[4-(dimethylamino)phenyl]methylene]1,3-dimethyl ester, tetra-ethyl-2,2'-(1,4-phenylene-dimethylidene)-bismalonate, dimethyl 4-methoxybenzylidene malonate, 2-tert-butyl-6-(5-chloro-2H-benzotriazol-2-yl)-4-methylphenol and 3-(diaryl)[1,3,5]triazin-2-yl)-5-(alkoxy substrate)-phenol, but not necessarily these It is not limited.

[0064] In the present invention, the total content of the ultraviolet absorber is preferably about 0.2 wt% to about 10 wt%, more preferably about 0.5 wt% to about 7 wt%, based on the solid content. The content of the first ultraviolet absorber is 0.1 to 5.0 wt%, more preferably 0.5 to 4.0 wt%. If the total content of the first ultraviolet absorber is less than 0.1%, the transmittance in the 405 nm wavelength range may be high, so that the protective function of the organic light-emitting element may not be properly performed. In addition, if the total content of the first ultraviolet absorber exceeds 5%, the yellowish tint of the film color may be strengthened (the color b value may increase), which may affect the color reproducibility of the OLED panel. The content of the second ultraviolet absorber is 0.1 to 5.0 wt%, preferably 0.5 to 3.0 wt%. If the content of the second ultraviolet absorber is too small, there is a risk that the durability of the film may be reduced, and if it is too large, there is a risk that bleed out may occur due to the total content of additives in the film being excessive.

[0065] The cellulose ester film of the present invention has a light transmittance of 0.01 to 1.0% at a wavelength of 380 nm, a light transmittance of 0.1 to 5% at a wavelength of 405 nm, and a light transmittance of 90 to 95% at a wavelength of 550 nm. When the above light transmittance conditions are satisfied, the polarizing plate can be prevented from being deformed by ultraviolet rays, particularly ultraviolet rays in the UVA region, and thus, ultraviolet rays in the UVA region can be prevented from having a negative effect on the optical properties of the polarizer.

[0066] The color b value of the cellulose ester film of the present invention is 7 or less, and the difference between the transmittance at 425 nm and the transmittance at 415 nm is 30 to 50%. As a result, compared to the case where a single type of conventional ultraviolet absorbent is used, a superior ultraviolet ray blocking effect is obtained while suppressing yellowing of the film color, thereby improving the color reproducibility of the organic light-emitting device.

[0067] Another aspect of the present invention relates to an optical film, such as a polarizing plate protective film or surface treatment film, using the cellulose ester film of the present invention. The polarizing plate protective film of the present invention can be manufactured using a resin composition manufactured by mixing the cellulose ester resin as the substrate with a first ultraviolet absorber and a second ultraviolet absorber. More specifically, the polarizing plate protective film of the present invention can be manufactured by manufacturing a cellulose ester resin mixed with the ultraviolet absorber into a film form using a method well known in the art, such as a solvent casting method or an extrusion method. In some cases, a uniaxial or biaxial stretching process may be additionally performed in the film manufacturing process.

[0068] The solvent casting method is a method of manufacturing dope by dissolving cellulose resin in a mixer with additives such as plasticizers, ultraviolet absorbers, and slip agents, and a mixed solvent such as methylene chloride and methanol, and then filtering it using a filter.

[0069] When producing films using the solvent casting method, the solvent used to prepare the cellulose solution is preferably an organic solvent. Halogenated hydrocarbons are preferred, and examples of such organic solvents include chlorinated hydrocarbons, methylene chloride, and chloroform, with methylene chloride being the most preferred. Furthermore, organic solvents other than halogenated hydrocarbons may be mixed and used, if necessary. Examples of such organic solvents include esters, ketones, ethers, and alcohols. As esters, methyl formate, ethyl formate, propyl formate, pentyl formate, methyl acylate, ethyl acylate, pentyl acetate, etc. can be used; as ketones, acetone, methyl ethyl ketone, diethyl ketone, diisobutyl ketone, cyclopentanone, cyclohexanone, methylcyclohexanone, etc. can be used; as ethers, diisopropyl ether, dimethoxymethane, dimethoxyethane, 1,4-dioxane, 1,3-dioxolane, tetrahydrofuran, anisole, phenetole, etc. can be used; as alcohols, methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, t-butanol, 1-pentanol, 2-methyl-2-butanol, cyclohexanol, 2-fluoroethanol, 2,2,2-trifluoroethanol, 2,2,3,3-Tetrafluoro-1-propanol, etc. are used. More preferably, methylene chloride is used as the main solvent, and alcohol can be used as the secondary solvent. Specifically, methylene chloride and alcohol can be mixed and used in a weight ratio of 70:30 to 95:5. Most suitably, methyl chloride and methanol are preferably used in a mixing ratio of 90:10.

[0070] In the production of the cellulose ester film of the present invention, various additives may be added to the dope used in the solvent casting method according to the intended use, such as plasticizers, anti-aging agents, slipping agent fine particles, release agents, ultraviolet stabilizers, infrared absorbers, wavelength dispersion modifiers, optical anisotropy modifiers, etc. The specific types of these additives are not limited as long as they are commonly used in the relevant field, and it is preferable to use the content within a range that does not deteriorate the physical properties of the film. The timing of adding the additive is determined depending on the type of the additive.

[0071] Meanwhile, the cellulose ester film contains a plasticizer to improve mechanical strength, impart good castability and water absorption resistance, and reduce moisture permeability. Any plasticizer commonly used may be used without limitation, and examples thereof include carboxylic acid esters selected from phosphoric acid esters, phthalic acid esters, and citric acid esters. It is also possible to use terminal asymmetric aromatic compounds and terminal symmetric aliphatic compounds. It is also preferable to use polyhydric alcohol ester plasticizers, polyester plasticizers, and polyhydric carboxylic acid plasticizers.

[0072] When the above plasticizer is contained, the content is preferably about 2 wt% to about 15 wt% based on the cellulose resin, taking into account dimensional stability and processability. If the content of the plasticizer is too low, the effect of reducing the moisture permeability of the film is small, and when slitting or punching is performed, a smooth cut surface cannot be obtained, and the generation of cutting debris tends to increase. In other words, the effect of containing the plasticizer cannot be fully exerted. In addition, if the content is too high, there is a problem that the plasticizer bleeds out from the resin film, deteriorating the physical properties of the film and contaminating the surface.

[0073] The solvent casting method of the present invention can produce a film having superior physical properties, such as optical properties, compared to other manufacturing methods. In the solvent casting method, after preparing a dope, the dope is discharged from a T-die onto a support (belt), and the solvent volatilizes to form a flexible acetyl cellulose sheet, which then acquires self-supporting properties and is peeled off from the belt and returned to a stretching process. The stretching process is generally performed in a temperature range of glass transition temperature (Tg) to glass transition temperature (Tg) -50°C to glass transition temperature (Tg) +50°C, and the stretching ratio is set to 100 to 150% in the width direction or length direction. However, as the stretching ratio increases, the phase difference value becomes uneven due to stretching unevenness between the edges and the center, so no stretching is preferable.

[0074] The cellulose ester film formed in this way is dried inside a dryer below the glass transition temperature (Tg), which simultaneously obtains the heat fixing effect of the dryer, thereby controlling the appearance of the film, such as wrinkles, and increasing the dimensional stability, such as heat shrinkage and wet heat expansion rate.

[0075] The cellulose ester film manufactured by the present invention has a film thickness of about 20 ㎛ to about 100 ㎛. In the present invention, when the thickness of the acetyl cellulose film is less than 20 ㎛, the physical properties are poor, and when it exceeds 100 ㎛, the industrial applicability is poor. For example, the thickness of the cellulose ester film of the present invention may be 25 ㎛, 40 ㎛, 60 ㎛, 80 ㎛, or 100 ㎛, and the content of the ultraviolet absorber may be adjusted for each thickness, so that the physical properties may be adjusted so that the light transmittance at a wavelength of 380 nm is 0.5% or less, the light transmittance at a wavelength of 405 nm is 4% or less, and the light transmittance at a wavelength of 550 nm is 90% or more.

[0076] The cellulose ester film of the present invention is particularly preferably applied to a polarizing plate or a polarizing plate protective film. The polarizing plate can be manufactured according to a conventional method. For example, the stretched cellulose ester film of the present invention is alkali-saponified, and the resulting film is bonded to both sides of a polarizing film manufactured by immersing a polyvinyl alcohol (PVA) film in an iodine solution and stretching the film using a fully saponified polyvinyl alcohol aqueous solution. Alkali saponification refers to a treatment in which a cellulose ester film is immersed in a high-temperature strong alkaline solution to improve the wettability of the film for a water-based adhesive and to provide good adhesion to the film.

[0077] Another aspect of the present invention relates to a polarizing plate comprising a polarizer and a protective film for a polarizing plate formed on one or both sides of the polarizer. The protective film for a polarizing plate can be attached to one or both sides of the polarizer and usefully used as a protective film for a polarizing plate. In this case, the attachment of the polarizer and the optical film of the present invention can be performed by coating an adhesive composition on the surface of the film or polarizer using a roll coater, a gravure coater, a bar coater, a knife coater, a capillary coater, or the like, and then heating and bonding the protective film and the polarizer with a bonding roll or bonding them by compressing at room temperature.

[0078] Another aspect of the present invention is a film that uses the film of the present invention as a substrate and has a surface treatment such as anti-reflection or hard coating applied to the top, which can be applied to a display.

[0079] Another aspect of the present invention provides an image display device including the polarizing plate described above. The protective film for the polarizing plate described above can be applied to various image display devices such as liquid crystal displays, plasma displays, and electroluminescent devices.

[0080] Hereinafter, the present specification will be described in more detail through examples. However, the following examples are intended to illustrate the present specification and are not intended to limit the scope of the present specification.

[0081] Example

[0082] Example 1

[0083] Cellulose triacetate (TAC) resin was dissolved at 17 wt% in a mixed solvent of methylene chloride and methanol at a ratio of 9:1, and 2.0 wt% of 2-[2-(6-hydroxybenzo[1,3]dioxol-5-yl)-2H-benzotriazol-5-yl]ethyl 2-methylpentanoate (Shipro Kasei, S91) of the chemical formula 10 was included as a first ultraviolet absorber, 1.0 wt% of 2-(2H-benzotriazol-2-yl)-6-(1-methyl-1-phenylethyl)-4-(1,1,3,3-tetramethylbutyl) phenol (BASF, Tinuvin-928) was included as a second ultraviolet absorber, 8 wt% of a polyester plasticizer was included as a plasticizer, and 0.1 wt% of silica was included as a matting agent. Dope was manufactured.

[0084] Next, the dope was cast in the form of a sheet with a width of 800 mm on the surface of a stainless steel band support. While rotating the stainless steel band support, the solvent of the dope was evaporated, and through a stretching and drying process, an acetylcellulose film with a thickness of 40 μm was manufactured.

[0085]

[0086] Example 2

[0087] An acetylcellulose film was manufactured in the same manner as in Example 1, except that the content of the first ultraviolet absorber in Example 1 was changed to 0.6 wt%.

[0088]

[0089] Example 3

[0090] An acetylcellulose film was manufactured in the same manner as in Example 1, except that the content of the first ultraviolet absorber in Example 1 was changed to 3.0 wt%.

[0091]

[0092] Example 4

[0093] An acetylcellulose film was manufactured in the same manner as in Example 1, except that the first ultraviolet absorbent was changed to a compound of chemical formula 2.

[0094]

[0095] Example 5

[0096] An acetylcellulose film was manufactured in the same manner as in Example 1, except that the first ultraviolet absorbent was changed to a compound of chemical formula 3.

[0097]

[0098] Example 6

[0099] An acetylcellulose film was manufactured in the same manner as in Example 1, except that the first ultraviolet absorbent was changed to a compound of chemical formula 4.

[0100]

[0101] Example 7

[0102] An acetylcellulose film was manufactured in the same manner as in Example 1, except that the first ultraviolet absorbent was changed to a compound of chemical formula 5.

[0103]

[0104] Example 8

[0105] An acetylcellulose film was manufactured in the same manner as in Example 1, except that the first ultraviolet absorbent was changed to a compound of chemical formula 6.

[0106]

[0107] Example 9

[0108] An acetylcellulose film was manufactured in the same manner as in Example 1, except that the first ultraviolet absorbent was changed to a compound of chemical formula 7.

[0109]

[0110] Example 10

[0111] An acetylcellulose film was manufactured in the same manner as in Example 1, except that the first ultraviolet absorbent was changed to a compound of chemical formula 8.

[0112]

[0113] Example 11

[0114] An acetylcellulose film was manufactured in the same manner as in Example 1, except that the first ultraviolet absorbent was changed to a compound of chemical formula 9.

[0115]

[0116] Comparative Example 1

[0117] An acetylcellulose film was manufactured in the same manner as in Example 1, except that only 3.0 wt% of the second UV absorber, benzotriazole-based 2-(2H-benzotriazol-2-yl)-6-(1-methyl-1-phenylethyl)-4-(1,1,3,3-tetramethylbutyl) phenol (BASF, Tinuvin-928), was used instead of the first UV absorber, sesamol benzotriazole.

[0118]

[0119] Comparative Example 2

[0120] An acetylcellulose film was manufactured in the same manner as in Example 1, except that the first UV absorber was changed from sesamol benzotriazole to an indole-based UV absorber (Orient chemical, Bonasorb UA3912) (0.6 wt%).

[0121]

[0122] Comparative Example 3

[0123] An acetylcellulose film was manufactured in the same manner as in Example 1, except that the content of the first ultraviolet absorber in Example 1 was changed to 0.1 wt%.

[0124]

[0125] Comparative Example 4

[0126] An acetylcellulose film was manufactured in the same manner as in Example 1, except that the content of the first ultraviolet absorber in Example 1 was changed to 5.5 wt%.

[0127]

[0128] Comparative Example 5

[0129] An acetylcellulose film was manufactured in the same manner as in Example 1, except that the first ultraviolet absorbent was changed to a compound of the following chemical formula 11.

[0130]

[0131]

[0132] Comparative Example 6

[0133] An acetylcellulose film was manufactured in the same manner as in Example 1, except that the first ultraviolet absorbent was changed to a compound of the following chemical formula 12.

[0134]

[0135]

[0136] Comparative Example 7

[0137] An acetylcellulose film was manufactured in the same manner as in Example 1, except that the second UV absorber, benzotriazole (BASF, Tinuvin-928), was not used in the dope of Example 1.

[0138]

[0139] Comparative Example 8

[0140] To compare the performance differences between UV blocking implementation methods, a coating film was manufactured by incorporating a UV absorber into the coating film. The substrate and coating film were composed as follows.

[0141] A dope containing 17 wt% of cellulose triacetate (TAC) resin dissolved in a mixed solvent of methylene chloride and methanol in a ratio of 9:1, 2.2 wt% of benzotriazole-based 2-(2H-benzotriazol-2-yl)-6-(1-methyl-1-phenylethyl)-4-(1,1,3,3-tetramethylbutyl) phenol (BASF, Tinuvin-928), 8 wt% of a polyester-based plasticizer, and 0.1 wt% of silica as a matting agent was prepared. The dope was cast in the form of a sheet having a width of 800 mm on the surface of a stainless steel band support. The solvent of the dope was evaporated while rotating the stainless steel band support, and through an unstretching and drying process, an acetylcellulose film having a thickness of 40 ㎛ was prepared as a substrate.

[0142] A coating solution was prepared containing 30 wt% of an acrylate resin containing a sesamol benzotriazole-based UV absorber of the following chemical formula 13, 0.5 wt% of 1-hydroxy-cyclohexyl-phenyl-ketone (Ciba, IRGACURE 184) as a photoinitiator, 0.2 wt% of a leveling agent (BYK 307), 40 wt% of methyl ethyl ketone, and 29.3 wt% of methyl isobutyl ketone.

[0143] The coating solution was applied onto the above substrate using a Meyer bar, and then dried and UV cured to produce a coating film with a thickness of approximately 6 ㎛.

[0144]

[0145]

[0146] Exam example

[0147] The solubility of the ultraviolet absorber used in the examples and comparative examples and the properties of the manufactured acetylcellulose film were evaluated using the following methods, and the results are shown in Table 1 below.

[0148] [Method of evaluating physical properties]

[0149] 1. Solubility and precipitation by UV absorber structure

[0150] The solubility of the UV absorber was evaluated by adding the UV absorber in an amount of mass according to concentration to a mixed solvent of methylene chloride (90%) / methanol (10%) at a temperature of 22-25℃ / humidity of 30-60%, and then using a general stirring method to determine the concentration at which it could be dissolved within 30 minutes. To ensure the stability of the additive, the solubility in the solvent must be secured at least 5%. If the solubility is insufficient, a precipitation phenomenon is observed on the film surface after film formation.

[0151] - Solubility

[0152] ◎: Solubility 20% or more

[0153] ○: Solubility 10~20%

[0154] △: Solubility 5-10% or less

[0155] X: Solubility 5% or less

[0156] - Presence or absence of precipitation

[0157] ○: Confirmation of full-scale precipitation phenomenon on the film surface

[0158] △: Confirmation of local precipitation on the film surface

[0159] X: No precipitation observed on the film surface

[0160]

[0161] 2. UV light transmittance

[0162] -Equipment: JASCO V-650 UV spectrometer

[0163] -Measurement conditions

[0164] - Measurement environment: 20~25℃, humidity 30~60%

[0165] -Measurement wavelength: 200~780nm, scan speed: high speed, measurement interval: 0.5nm or 1nm

[0166] -Light source: Deuterium lamp / Halogen lamp

[0167] -Measurement method: Prepare a sample measuring 30 mm x 30 mm, place it in the measuring section of the measuring device, and measure the overall transmittance in the 200-780 nm range. After completing the measurement, check the light transmittance values ​​in the 380 nm / 405 nm / 410 nm / 430 nm / 550 nm wavelength ranges in the results window. Measure three times and take the average value as the result.

[0168]

[0169] 3. Colorimeter measurement (color b value)

[0170] -Equipment: Konica Minolta CM-3700

[0171] -Measurement conditions

[0172] - Measurement environment: 20~25℃, humidity 30~60%, measurement wavelength: 360~740nm, light source: pulsed xenon lamp

[0173] -Measurement method: Prepare a 40mm x 40mm sample and secure it in the measuring position inside the measuring device. Measure the L, a*, and b* values ​​of the sample in transmission mode. Measure three times and take the average value as the result.

[0174]

[0175] 4. Evaluation of light resistance by UV absorber composition

[0176] The light fastness of the cellulose ester films manufactured in the examples and comparative examples was evaluated according to the conditions and measurement methods below, and the results are shown in the table below. The samples were prepared in a size of 70 mm x 50 mm, and the UV transmittance and color b value before the light fastness evaluation were checked. The sample was mounted on the light fastness evaluation equipment, with the upper surface of the film facing the light source, and the distance between the light source and the sample was kept the same. After leaving it under the above measurement conditions for 120 hours, the sample was taken out, and the light transmittance was measured in the same manner as before, and the degree of change was calculated as the difference from the initial value.

[0177] -Equipment: Fademeter SUGA U48AU

[0178] -Measurement conditions: Temperature 50±10℃, humidity 50%, 120 hours,

[0179] - Light source: Carbon Arc

[0180] - ◎: ​​Change in standard light transmittance is less than 5%

[0181] ○: Change in standard light transmittance is 5% or more and less than 10%

[0182] △: Change in standard light transmittance of 10% or more

[0183] X: Change in standard light transmittance is 20% or more

[0184]

[0185] Classification 1st UV absorber 2nd UV absorber Solubility Precipitation UV transmittance (%) Color b Light resistance 380 nm 405 nm Example 1 Chemical formula 10 benzotriazole ◎ X 0.05 3.4 5.5 ◎ Example 2 Chemical formula 10 benzotriazole - X 1.0 5.0 4.5 ◎ Example 3 Chemical formula 10 benzotriazole - X 0.02 1.26.7 ◎ Example 4 Chemical formula 2 benzotriazole △ △ 0.04 3.25.1 ◎ Example 5 Chemical formula 3 benzotriazole △ △ 0.04 3.35.4 ◎ Example 6 Chemical formula 4 benzotriazole ○ X 0.05 3.4 5.7 ◎ Example 7 Chemical formula 5 benzotriazole ◎ X 0.04 3.35.8 ◎ Example 8 Chemical formula 6 Benzotriazole◎X0.053.35.7◎Example 9 Chemical formula 7 Benzotriazole◎X0.043.45.6◎Example 10 Chemical formula 8 Benzotriazole○X0.053.45.8◎Example 11 Chemical formula 9 Benzotriazole◎X0.033.36.4◎Comparative example 1 - Benzotriazole -X3.482.80.4◎Comparative example 2 Indole benzotriazole -X0.052.09.3XComparative example 3 Chemical formula 10 Benzotriazole -X2.975.91.8◎Comparative example 4 Chemical formula 10 Benzotriazole -X0.00.0127.3◎Comparative example 5 Chemical formula 11 Benzotriazole X○0.043.04.4◎Comparative example 6 Chemical formula 12 Benzotriazole ◎ X 0.04 4.0 7.5 ◎ Comparative Example 7 Chemical Formula 10 -- X 0.05 3.4 5.4 ○ Comparative Example 8 Chemical Formula 13 Coated Product --- 0.03.5 5.8 △

[0186]

[0187] As shown in Table 1 above, the acetyl cellulose film of the present invention exhibited excellent light transmittance and light resistance in the long wavelength region (405 nm).

Claims

1. A cellulose ester film comprising a first ultraviolet absorber of the sesamol benzotriazole series represented by the following chemical formula 1 and at least one second ultraviolet absorber selected from among benzotriazole series, malonate series, triazine series, and benzophenone series ultraviolet absorbers in a cellulose ester substrate. [Chemical Formula 1] In the above formula, R is hydrogen and a C1 to C8 ketone, aldehyde, ether, ester, alkene, alcohol, carbonyl group, or carboxyl group.

2. A cellulose ester film according to claim 1, characterized in that the total thickness of the cellulose ester film is 20 to 100 ㎛.

3. A cellulose ester film, characterized in that in the first paragraph, the total content of the ultraviolet absorber is 0.2% to 10% by weight for the entire cellulose ester film, the content of the first ultraviolet absorber is 0.1% to 5.0% by weight, and the content of the second ultraviolet absorber is 0.1 to 5.0% by weight.

4. A cellulose ester film, characterized in that in the first paragraph, the first ultraviolet absorbent is any one of the ultraviolet absorbents represented by the following chemical formulas 2 to 10. [Chemical Formula 2] [Chemical Formula 3] [Chemical Formula 4] [Chemical Formula 5] [Chemical Formula 6] [Chemical Formula 7] [Chemical Formula 8] [Chemical Formula 9] [Chemical Formula 10] 5. In the first paragraph, the cellulose ester film is characterized in that the light transmittance at a wavelength of 380 nm is 0.01 to 1.0% or less, the light transmittance at a wavelength of 405 nm is 0.1 to 5.0% or less, and the light transmittance at a wavelength of 550 nm is 90 to 95% or more.

6. A cellulose ester film according to claim 5, characterized in that the color b value of the cellulose ester film is 7 or less, and the difference between the transmittance at 425 nm and the transmittance at 415 nm is 30 to 50%.

7. A cellulose ester film according to claim 1, characterized in that the cellulose ester film is a protective film for a polarizing plate.

8. A polarizing plate comprising a cellulose ester film according to any one of claims 1 to 7.

9. A surface-treated film comprising a cellulose ester film according to any one of claims 1 to 7.

10. An image display device including a polarizing plate of Article 8.

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