JP2014048324A - Hard coat film manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method that obtains a hard coat film preventing occurrence of a wrinkle in a hardening step by ultraviolet light irradiation after applying an ultraviolet light hardening resin composition to one surface of a film base material such as a cellulose triacetate (TAC) film, and having high flatness.SOLUTION: A hard coat film manufacturing method is configured to comprise the steps of: applying ultraviolet light hardening resin to one surface of a film base material; drying the ultraviolet light hardening resin; heating the ultraviolet light hardening resin; bringing the ultraviolet light hardening resin into contact with the other surface side so as to hold a backup roll; and irradiating the ultraviolet light hardening resin of the one surface thereof with ultraviolet light in the state of being brought into contact with the other surface side. A heating temperature in the step of heating the film base material is 5 to 50°C higher with respect to a temperature of the backup roll.

Description

  The present invention relates to a method for producing a hard coat film having excellent flatness.

  The surface of the polarizing plate for liquid crystal displays is provided with a hard coat layer for improving the surface hardness on the surface of a cellulose triacetate (TAC) film which is a kind of resin film substrate constituting the polarizing plate. In order to form the hard coat layer, a method is used in which a resin that is cured by ultraviolet rays or electron beams is applied onto a TAC film and cured by ultraviolet rays or electron beams. In this curing step, there are problems that wrinkles occur in the film and that flatness is impaired.

  In order to solve the above problem, Patent Document 1 discloses a method of applying a tension of 30 to 300 N / m in the transport direction of the resin film base material when irradiating ultraviolet rays to form a hard coat layer on the resin film base material. Is marked.

  From the same viewpoint, in Patent Document 2, when a hard coat layer is formed by irradiating ultraviolet rays while hugging a resin film base material on a backup roll, the resin film base material is held on a back roll at a surface pressure of 250 to 3000 Pa. A method is disclosed.

  In addition, in Patent Document 3, an entrained air layer formed between a resin film substrate and a back roll is formed when a hard coat layer is formed by irradiating ultraviolet rays while holding the resin film substrate on a backup roll. A method of 0.5 to 10 μm is disclosed.

  Although the method described in Patent Document 1 seems to be effective at first glance, when transporting a resin film substrate, tension is applied in the transport direction, and a tension of 30 to 300 N / m is special. Since this is not a necessary condition, it is insufficient as a method for solving wrinkles.

  In the technique described in Patent Document 2, as means for applying surface pressure, means for blowing compressed air on the surface of a resin film substrate and means for applying reduced pressure to the back surface of the film substrate are disclosed. However, it is difficult to apply a uniform surface pressure with these means.

  In Patent Document 3, although the advantage of reducing the thickness of the air layer is shown, the presented condition range is not necessarily a special condition in transporting the resin film base material, so as a means for solving wrinkles It is insufficient.

JP-A-2005-47936 WO2010 / 041520 WO2010 / 044316

  The present invention has been made in consideration of such a situation, and after applying an ultraviolet curable resin composition to one surface of a film substrate such as a cellulose triacetate (TAC) film, wrinkles are caused in a curing step by ultraviolet irradiation. It aims at providing the manufacturing method which prevents generation | occurrence | production of this and obtains a hard coat film with high flatness.

The invention according to claim 1 of the present invention embraces a backup roll on the other surface side, a step of applying an ultraviolet curable resin material on one side of the film substrate, a step of drying, a step of heating, and the other side. A method for producing a hard coat film, which is sequentially subjected to a step of contacting the surface and a step of irradiating the ultraviolet curable resin layer on one side with ultraviolet rays in the state,
In the method for producing a hard coat film, the heating temperature in the step of heating the film base is 5 to 50 ° C. higher than the temperature of the backup roll.

  The invention according to claim 2 of the present invention is the method for producing a hard coat film according to claim 1, wherein the temperature of the backup roll is 15 to 70 ° C.

  The invention according to claim 3 of the present invention is the method for producing a hard coat film according to claim 1 or 2, wherein the heating temperature in the step of heating the film substrate is 30 to 70 ° C. is there.

  According to the first aspect of the present invention, after the ultraviolet curable resin composition is applied to one surface of the film substrate, it is further heated after being dried, so that the backup roll is held on the other surface side. In a series of steps of irradiating the ultraviolet curable resin layer on one side with ultraviolet rays in a state where the film is heated, the heating temperature of the step of heating the film base is 5 to 50 ° C. higher than the temperature of the backup roll. By doing so, generation | occurrence | production of the wrinkle at the time of hardening by ultraviolet irradiation can be suppressed remarkably, and it becomes possible to obtain a hard coat film with high planarity as a result.

  Moreover, according to Claim 2 of this invention, the damage by the heat | fever of the said film base material can be prevented by making the temperature of the said backup roll into 15-70 degreeC.

  Moreover, according to Claim 3 of this invention, the damage by the heat | fever of the said film base material can be prevented similarly to the above by making the heating temperature of the process of heating the said film base material into 30-70 degreeC. it can.

  The present invention can provide a production method for preventing wrinkles and obtaining a hard coat film having high flatness by the above-described actions and effects.

It is the schematic of the manufacturing process which shows one Embodiment of this invention.

  Hereinafter, the present invention will be described in detail with reference to the drawings.

  FIG. 1: has shown the process schematic of one Embodiment which concerns on the manufacturing method of the hard coat film of this invention. In the present invention, the step 10 of applying the ultraviolet curable resin composition to one surface of the film substrate 1, the step 20 of drying, the step 30 of heating, and the other surface come into contact with each other so as to embrace the backup roll. It is a manufacturing method of the hard coat film characterized by sequentially passing through the process 40 and the process 40 which irradiates an ultraviolet-ray.

  That is, by increasing the heating temperature of the step 30 of heating the film substrate 1 by 5 to 50 ° C. with respect to the backup roll temperature, it is possible to remarkably suppress the generation of wrinkles during curing by ultraviolet irradiation, As a result, it is a manufacturing method which can obtain a hard coat film with high flatness.

  If the heating temperature of the step 30 of heating the film substrate 1 is a height (temperature difference) of less than 5 ° C. with respect to the backup roll temperature, wrinkles generated by curing during ultraviolet irradiation cannot be suppressed. . Further, when the height (temperature difference) exceeds 50 ° C., the temperature applied to the film base material 1 becomes high, so that the film base material 1 itself is damaged by heat, and the film base material 1 before ultraviolet irradiation. Will lose its flatness.

  Moreover, in the said manufacturing method, the temperature of a backup roll has preferable 15-70 degreeC. If the temperature of the backup roll is less than 15 ° C, there is a risk that the surface of the backup roll will dew, and if it exceeds 70 ° C, the film substrate 1 may be damaged by the heat of the backup roll and the flatness may be lost. is there.

  Moreover, as for the heating temperature of the film base material 1 in the said manufacturing method, 30-70 degreeC is preferable. If the heating temperature is less than 30 ° C., the effect of flattening due to a temperature difference from the backup roll in the next step cannot be obtained. On the other hand, if the heating temperature exceeds 70 ° C., further heating of the backup roll in the next step causes a large thermal damage to the film substrate 1, and a flattening effect cannot be obtained.

  The ultraviolet curable resin composition according to the present invention is composed of an ultraviolet curable resin, a photopolymerization initiator, a solvent, and the like, and the composition can be appropriately adjusted according to the hard coat characteristics and is not particularly limited.

  Moreover, in the process 10 which apply | coats the said ultraviolet curable resin composition, as the coating method, according to the viscosity of the said ultraviolet curable resin composition, or a required film thickness, a roll coat method, a gravure coat method, a die coat method etc. A general-purpose coating method can be used and is not particularly limited.

  Further, in the drying step 20 after the application of the ultraviolet curable resin composition, various drying methods such as general hot air drying are appropriately selected depending on the properties (boiling point, etc.) of the solvent contained in the ultraviolet curable resin composition. can do.

  Moreover, in the heating process 30 performed after the said drying process 20, the heating apparatus provided with the infrared heater, the heating apparatus by a hot air, etc. can be used, It does not specifically limit.

  As a heating method of the backup roll in the process of contacting after being held in the backup roll, which is performed after the heating process, a heat medium such as oil filled in the backup roll may be heated (indirectly). The heater provided in the backup roll may be heated (directly). In addition, cooling is necessary in an environment of room temperature (room temperature) or less. An indirect heating method using a heat medium is preferable from the viewpoint of easy temperature control of the backup roll.

  It is important for the heating method in the heating step 30 and the heating method of the backup roll to accurately control the temperature difference between the two according to the present invention, thereby preventing generation of wrinkles during curing due to ultraviolet irradiation. And a smooth hard coat film can be produced.

  In addition, as an ultraviolet irradiation method in the ultraviolet irradiation step according to the present invention, an irradiation method using a commonly used electrode type lamp such as a high pressure mercury lamp or a metal halide lamp, or an irradiation method using an electrodeless lamp is used. can do. The irradiation energy at that time needs to be appropriately adjusted depending on the reactivity (curability), film thickness, line speed, etc. of the ultraviolet curable resin used.

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

Example 1
A cellulose triacetate (TAC) film having a thickness of 40 μm was used as a film substrate, and an ultraviolet curable resin composition having the following composition was applied to one surface thereof by a slot die method.
<Ultraviolet curable resin composition>
50 parts by weight of UV curable resin (pentaerythritol triacrylate)
Photopolymerization initiator: 2 parts by weight of Irgacure 184 (Ciba Specialty Chemicals)
Solvent: 50 parts by weight of methyl ethyl ketone

  After the application, it was dried in a drying oven at 50 ° C. Then, it heated to 40 degreeC in the heating process, and also, the ultraviolet irradiation was performed in the state which made it contact so that the other surface might be included in the backup roll set to 20 degreeC after that. In the ultraviolet irradiation, an electrodeless lamp (H bulb manufactured by FUSION UV SYSTEM) was used as a light source, and the output was 240 W / cm. Moreover, the conveyance speed of the resin film base material was 20 m / min. By the above method, a hard coat film having a hard coat layer thickness of 7 μm was obtained.

(Comparative Example 1)
The ultraviolet curable resin composition was applied in the same manner as in Example 1.

  After the application, it was dried in a drying oven at 50 ° C. Thereafter, without passing through the heating step, ultraviolet irradiation was performed in a state where the other surface was brought into contact with the backup roll set at 20 ° C. In the ultraviolet irradiation, an electrodeless lamp (H bulb manufactured by FUSION UV SYSTEM) was used as a light source, and the output was 240 W / cm. Moreover, the conveyance speed of the resin film base material was 20 m / min. By the above method, a hard coat film having a hard coat layer thickness of 7 μm was obtained.

(Comparative Example 2)
The ultraviolet curable resin composition was applied in the same manner as in Example 1.

  After the application, it was dried in a drying oven at 50 ° C. Then, it heated at 30 degreeC in the heating process, and also, the ultraviolet irradiation was performed in the state which made it contact so that the other surface might be included in the backup roll set as 30 degreeC after that. In the ultraviolet irradiation, an electrodeless lamp (H bulb manufactured by FUSION UV SYSTEM) was used as a light source, and the output was 240 W / cm. Moreover, the conveyance speed of the resin film base material was 20 m / min. By the above method, a hard coat film having a hard coat layer thickness of 7 μm was obtained.

(Comparative Example 3)
The ultraviolet curable resin composition was applied in the same manner as in Example 1.

  After the application, it was dried in a drying oven at 50 ° C. Then, it heated at 100 degreeC in the heating process, and also, the ultraviolet irradiation was performed in the state which made it contact so that the other surface might be included in the backup roll set to 20 degreeC after that. In the ultraviolet irradiation, an electrodeless lamp (H bulb manufactured by FUSION UV SYSTEM) was used as a light source, and the output was 240 W / cm. Moreover, the conveyance speed of the resin film base material was 20 m / min. By the above method, a hard coat film having a hard coat layer thickness of 7 μm was obtained.

(Evaluation)
About the hard coat film obtained in Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 3, the appearance by ultraviolet curing was visually evaluated. It was. The results are shown in Table 1 below.

(Comparison result)
In Example 1, that is, the method for producing a hard coat film of the present invention, a good hard coat film having no appearance abnormality such as generation of wrinkles could be produced in curing by ultraviolet irradiation.
On the other hand, the comparative example 1 which does not heat a TAC film (film base material) and the backup roll temperature is 20 ° C., the comparative example where the heating temperature of the TAC film is 30 ° C. and the backup roll temperature is 30 ° C. 2 and Comparative Example 3 in which the heating temperature of the TAC film is 100 ° C. and the backup roll temperature is 20 ° C., all of the abnormalities in appearance such as the generation of wrinkles were confirmed in the curing by ultraviolet irradiation. Did not come.

DESCRIPTION OF SYMBOLS 1 Film base material 10 Application | coating process 20 Drying process 30 Heating process 40 The process 50 which contacts a backup roll 50 Ultraviolet irradiation process

Claims (3)

One surface of the film base, a step of applying an ultraviolet curable resin to one side of the film substrate, a step of drying, a step of heating, a step of bringing the backup roll into the other surface side, A method of producing a hard coat film through a step of irradiating ultraviolet ray curable resin with ultraviolet rays,
The method for producing a hard coat film, wherein the heating temperature in the step of heating the film base is 5 to 50 ° C. higher than the temperature of the backup roll.   The temperature of the said backup roll is 15-70 degreeC, The manufacturing method of the hard coat film of Claim 1 characterized by the above-mentioned.   The method for producing a hard coat film according to claim 1 or 2, wherein the heating temperature in the step of heating the film substrate is 30 to 70 ° C.

Images