JPS6198301A - Method for providing ultraviolet ray absorptive performance to cellulosic film - Google Patents

Abstract

PURPOSE:To form a UV absorbent-contg. layer only on the optional one surface side of a cellulosic film by sticking or impregnating a soln. prepd. by dissolving the UV absorbent in an org. solvent to one side of said film and adhering and coating further a synthetic resin barrier film thereto prior to evaporation. CONSTITUTION:The soln. prepd. by dissolving the UV absorbent in the org. solvent is stuck or impregnated to at least one side of the cellulosic film and thereafter the synthetic resin barrier film is adhered and coated thereto before the org. solvent evaporates by which the UV absorbent-contg. layer is formed on the surface of the cellulosic film. Since UV-absorptive performance is provided to the cellulosic film by the above-mentioned method, the treatment stage thereof, more specifically, the stage for dipping or coating the UV treating agent and the stage for adhering the barrier film are extremely simple the inexpensive manufacture of the cellulosic film having the required UV absorptive performance is made possible by such simple stage coupled with the simplicity of the treating stage.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is applicable to cellulose-based films widely used in applications requiring optical performance, such as eyeglasses and polarizing plates for liquid crystal display devices. In order to protect the properties and liquid crystal materials, we will go to methods of imparting ultraviolet absorption performance.

BACKGROUND ART Cellulose films have excellent optical properties and processability, and are therefore widely used as surface wave II materials for eyeglasses, polarizing plates, and the like. However, cellulose-based films suffer from the inherent drawback of yellowing when exposed to ultraviolet light for extended periods of time. For this reason, conventionally, a UV absorber is generally mixed into a cellulose-based plastic solution in advance, and a casting film made from this solution is supplied. However, the cell-O-su film produced in this way uniformly absorbs ultraviolet rays and contains a softener dispersed during the rest of the film, so it cannot be used alone for eyeglasses, etc. Although this is not a major problem in some cases, for example, when using a polarizing plate for a liquid crystal display device with lamination II-attached via an adhesive, the usage environment is particularly harsh, high temperature and high humidity. Under these conditions, the desired adhesive performance was significantly deteriorated due to the bleed staining of the ultraviolet absorber, causing problems such as peeling or the generation of turbidity or air bubbles between the adhesive surfaces, deteriorating the optical performance.

In addition, the ultraviolet absorption performance required of cellulose-based films differs depending on their use, but when using conventional manufacturing methods, small quantities and a wide variety of products with different added contents of ultraviolet absorbers are used to meet the above requirements. In practice, it is difficult to produce such products from a productivity standpoint, and as they are mass-produced as versatile products with relatively high ultraviolet absorption performance, they result in high costs. There were also some problems.

In view of the above-mentioned problems, this invention focuses on the fact that the problems are caused by the fact that the ultraviolet absorber is dispersed throughout the cellulose film. .

This product was completed as a result of intensive research with the aim of creating a film that could impart the required amount of ultraviolet absorption performance depending on its use to only one or both surfaces of a cellulose film. It is.

Means for solving the problem, that is, the present invention is based on the above technical problem,
After adhering to or impregnating at least one side of the cellulose film with a solution of an ultraviolet absorber dissolved in an organic solvent by coating or dipping, a synthetic resin barrier film is applied before the Ma-containing solvent evaporates. A layer containing an ultraviolet absorber is formed on the surface of the cellulose film by coating.
The gist of this paper is a method for imparting ultraviolet absorption performance to cellulose films.

In the above, the desired ultraviolet absorber-containing layer can be formed on the surface of the cellulose film by applying or dipping a solution containing an ultraviolet absorber in an organic solvent (hereinafter referred to as "UV treatment agent"). By being in contact for a predetermined time, and by maintaining this contact state for a predetermined time while suppressing external volatilization of the solvent by coating with a barrier film, the solution containing the ultraviolet absorber penetrates into the surface of the film and is absorbed. It is thought that this is because the Therefore, the contact time of the UV treatment agent with the surface of the cellulose film by coating or dipping is one of the factors that governs the UV absorption performance imparted to the film. Since the penetration and absorption of the UV treatment agent is supplemented by this, the above-mentioned contact time is sufficiently short, for example, about 1 to 60 seconds.

The ultraviolet absorber-containing layer is formed on one or both sides of the cellulose film depending on the use of the film. Moreover, its ultraviolet absorption performance is appropriately set in relation to the use of the film, and its control is based on the illumination of the ultraviolet absorber dissolved in the UV treatment agent. This is done by adjusting the temperature, the type of organic solvent, the contact treatment time, etc.

By the way, common examples of the cellulose film to be treated in the present invention include cellulose triacetate, cellulose diacetate, cellulose acetate butyrate, and cellulose propionate.

Further, the type of ultraviolet absorber used in the UV treatment agent of the present invention is not particularly limited, and various known ones may be arbitrarily selected and used, but preferably the relationship with the organic solvent used is One should select and use a material that has as high a solubility as possible for the layer agent, and generally, for example, 2-
21-dihydroxy-4methoxybenzophenone,
2-(2'-Hydroxy-5'-methyl-phenyl)-benzotriazole, 2゜2'4.4'tetrahydroxy-benzophenone,2-(2'-hydroxy-3'-5' deity amylph) enil)
Benzotriazole, 2-(2'-hydroxy-3'
=5'-D-butylphenyl)-5chlorobenzotriazole and the like are listed as preferred. In addition, examples of organic solvents that dissolve this include methyl alcohol, ethyl alcohol, methyl erketone, ethyl acetate,
Toluene and the like are preferably used. F! has the property of immediately dissolving cellulose films, such as methylene chloride and dimethylformamide. Although the use of J solvents is inappropriate, other solvents are not limited to those listed above.

Further, as the ultraviolet absorber and the organic solvent, each of the ones listed above may be used alone, but two or more types may be used in combination.

Rather, by using two or more types of ultraviolet absorbers in combination, it is sometimes possible to achieve -II excellent ultraviolet absorption effects with a relatively small amount used.

The treatment means for bringing the UV treatment agent into contact with and adhering to or impregnating the surface of the cellulose film may be either coating or dipping. Specifically, the coating means is a roll coater 17,0-]-9-・t'y''7y7:]
-9-.''11 Any coating means using an equalizer or the like can be used.

After the above treatment, a barrier film is attached to the treated surface of the cellulose-based film to tightly cover the surface. This is to allow the UV absorber to penetrate and absorb into the interior, and to prevent the UV absorber from bleeding afterward.The barrier film used for this purpose may be one that is not affected by the organic solvent of the UV treatment agent. Specifically, for example, a polyolefin film or a polyester film is preferably used.

Effects of the Invention Since the present invention imparts ultraviolet absorption performance to a cellulose film by the method described above, any of the treatment steps, that is, the step of dipping or coating the UV treatment agent and the step of attaching the barrier film, However, it is extremely easy to implement and there is no risk of disadvantageous increases in costs due to the complexity and difficulty of the treatment process.
(Of course, depending on the application, it is possible to form a UV absorber-containing layer on only one side of the cellulose film, so for example, this can be used as a surface protection film for a polarizing plate. case,
By forming the ultraviolet absorber-containing layer only on one side, which is the non-adhesive surface, it is possible to manufacture and provide a polarizing plate with even more excellent durability without causing deterioration of adhesive performance. In addition, if the product is to be used as a polarizing plate, an untreated cellulose film is attached to the polarizing film in advance, and then a layer containing an ultraviolet absorber is formed on the surface of the polarizing plate as a surface treatment. It can also be used to impart the required ultraviolet absorption performance, and can also be usefully employed as a treatment method used to improve the weather resistance of already manufactured polarizing plates.

Furthermore, since this invention is based on the method described above, the ultraviolet absorption performance imparted to the surface of the cellulose film can be determined by controlling the type of organic solvent of the UV treatment agent used, the concentration of the ultraviolet absorber, the contact time, etc. It can be freely set by adjusting.

Therefore, depending on the use of the film, the required ultraviolet absorption performance can be easily imparted in a variable manner,
It can also be conveniently adapted to the production of a wide variety of products in small quantities with different absorption properties.

Furthermore, the amount of expensive ultraviolet absorbers used can be easily adjusted to the necessary minimum according to the above-mentioned applications, which makes it possible to avoid cost increases due to the use of ultraviolet absorbers and reduce the processing process. Combined with the simplicity of this method, a cellulose film having the required ultraviolet absorption performance can be manufactured and provided at a low cost.

Examples Example 1 As an ultraviolet absorber, 2-(2'hydroxy-5'
-Methyl-phenyl)-benzotriazole and 1 part of the ultraviolet absorber 2Offiff was dissolved in 100 parts by weight of methanol as an organic solvent to prepare a UV treatment agent. A transparent cellulose triacetate film having a thickness of 80 μm was immersed in this UV treatment agent for 5 seconds. After that,
Immediately before the methanol evaporates, press rolls are applied to both sides of the film to form a polyethylene film (trade name: Zannytect Back 3) as a barrier film.
(manufactured by Sanei Chemical Co., Ltd.) was crimped.

The resulting cellulose film was obtained by peeling off the barrier film after several hours.
It had good transparency and excellent optical properties with no cloudy appearance. In addition, we investigated its ultraviolet absorption performance and found that it has an excellent ability to absorb all ultraviolet rays of 350 nm or less, and even in a weather resistance test using a Sunshine Weatherometer, there was no yellowing, cracking, etc. after 3000 hours. No appearance abnormalities were observed at all.

Example 2 A 50 μm thick cellulose triacetate film was used as a protective layer for a car on one side of a 20 μm thick polarizing film obtained by impregnating a polyvinyl alcohol film with a dye and stretching it for 11 days using a commonly used transparent adhesive. The object to be treated was a polarizing plate that had been bonded and integrated.

On the other hand, as an ultraviolet absorber, 20@■ parts of 2-2' dihydroxy-4methoxybenzophone was used, and this was mixed with methyl ethyl ketone and methanol in a 1:5 ratio as an organic solvent.
The solution dissolved in 100 parts by weight of the mixed solvent was used as a UV treatment agent.

Then, this UV treatment agent was applied to the cellulose film surface of the polarizing plate using a roll coater, and about 1 second later, while the solvent had not yet evaporated, a polyethylene film as a barrier film was applied and coated in the same manner as above. .

When the appearance of the polarizing plate thus obtained was visually inspected, it was found to be in good condition with no problems at all, as in the case of Example 1. In addition, the ultraviolet absorption performance of the cellulose film as the surface protective layer is such that it completely absorbs ultraviolet rays of 38Qr+m or less, and its weather resistance is similar to that of Example 1, with no harmful abnormalities occurring for a long period of time.
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Claims (1)

[Claims] A solution of an ultraviolet absorber dissolved in an organic solvent is attached or impregnated on at least one side of the cellulose film by coating or dipping, and then a synthetic resin barrier film is attached before the organic solvent evaporates. A method for imparting ultraviolet absorbing performance to a cellulose film, the method comprising forming a layer containing an ultraviolet absorber on the surface of the cellulose film by coating.