TWI459021B - Method for forming optical film - Google Patents

Description

Method for forming optical film

The present invention relates to a film material having a hardened layer and a method of forming the same, and more particularly to a method of forming an optical film having a hardened layer having a skin hardness greater than an internal hardness.

The photocurable composition undergoes a hardening reaction upon exposure to light. In order to increase the hardening rate and degree of hardening of the photocurable composition, a photosensitizer and a photoinitiator are generally added to the photocurable composition. Since the photosensitizer and the photoinitiator are uniformly mixed in the photocurable composition, the hardness of the hardened material or the hardened layer obtained by the conventional method is uniform.

In order to attach a film material, for example, a polarizing plate, to another optical element, for example, a phase retardation film having a multilayer structure or a liquid crystal cell, a pressure-sensitive adhesive layer is formed on the surface of the polarizing plate and then attached to the film. On the film. When the hardness of the entire pressure-sensitive adhesive layer is large, although the pressure-sensitive adhesive layer can provide support for the polarizing plate, has high stability and surface pressure resistance, the pressure-sensitive adhesive layer cannot be used with the polarizing plate. The shape of the shrinkage or expansion caused by the change in the temperature environment changes correspondingly, and the stress generated by the change of the size of the polarizing plate cannot be absorbed by the pressure-sensitive adhesive layer having a large hardness, that is, the stress relieving ability for high temperature and high humidity is insufficient. Therefore, it is difficult to apply to a device that may be deformed. Further, the residual stress in the polarizing plate is not uniform, which causes a problem of "light leakage" or "color unevenness" in the liquid crystal cell. When the hardness of the entire pressure-sensitive adhesive layer is small, although the stress generated by the change of the size of the polarizing plate can be alleviated, the stability of the pressure-sensitive adhesive layer and the ability of the surface pressure-resistant point are lowered.

According to an aspect of the invention, a method of forming a film having a hardened layer is provided. The method includes the following steps. A substrate is provided. A photoinitiating layer is applied to the substrate. A photocurable colloid layer is applied to the photoinitiating layer. The surface of the photocurable colloid layer contacts the photoinitiator layer. The light-curable colloid layer and the photo-initiating layer are caused to harden the photocurable colloid layer and the photo-initiating layer to form the hardened layer. The hardness of the surface layer of the hardened layer is greater than the hardness of the inner layer.

According to another aspect of the present invention, a method of forming an optical film is provided. The method includes the following steps. A release film is provided. A photoinitiating layer is applied to the release film. A photocurable colloid layer is applied to the photoinitiating layer. The surface of the photocurable colloid layer contacts the photoinitiator layer. A polarizing plate is disposed on the photocurable colloid layer. The light-curable colloid layer and the photo-initiating layer are caused to cure the photo-curable colloid layer and the photo-initiating layer to form an adhesive layer. The surface layer of the adhesive layer has a hardness greater than the internal hardness.

According to still another aspect of the present invention, a film material having a hardened layer is provided. The hardened layer is a single film, and the hardness of the surface layer of the hardened layer is greater than the internal hardness.

Embodiments of the present invention provide a method of forming an optical film, wherein the optical film has a hardened layer having a skin hardness greater than an internal hardness. 1 to 4 show the process of an optical film according to an embodiment of the present invention. Referring to FIG. 1, the photoinitiator layer 2 is coated on the substrate 1. In one embodiment, the substrate 1 is a release film. The photoinitiating layer 2 may include a photoinitiator or a photosensitizer or both. The photosensitizer may, for example, include benzophenone, diacetyl, acetophenone, anthracene, phenanthrene or anthracene. The photoinitiator may, for example, comprise tertiary amine acrylate, 9-phenylacridine (9-PHA), tetraethyl benzophenone (4,4-Bis(diethylamino)benzophenone). ; EAB) or Trimethylolpropane tris (3-mercaptopropionate; TMPX). Referring to FIG. 2, the photocurable colloid layer 3 is coated on the photoinitiator layer 2. One surface of the photocurable colloid layer 3, for example, the surface shown in Fig. 2, is in contact with the photoinitiator layer 2. The photocurable colloid layer 3 may, for example, include a photocurable monomer, an oligomer or a resin, and a photoinitiator. The photocurable colloid layer 3 may further include a photosensitizer. The photosensitizer can transfer the absorbed energy to other materials, such as a photoinitiator or photocurable colloidal layer 3 photocurable monomer, oligomer or resin; and the photoinitiator itself will occur after absorbing energy. The chemical change is decomposed into radicals or cations to initiate polymerization of the photocurable monomer, oligomer or resin in the photocurable colloid layer 3. The photocurable monomer, oligomer or resin may be an ultraviolet curable monomer, oligomer or resin. For example, the photocurable colloid layer 3 may include an acrylic monomer such as trimethylolpropane triacrylate (TMPTA), or an acrylic resin such as an acrylic copolymer or a polyvinyl alcohol. Molecular or polyurethane resin. In one embodiment, the photocurable colloid layer 3 is an ultraviolet (UV) curable colloid layer. The photocurable colloid layer 3 may also include an antistatic substance such as an amine compound, a phosphate ester, an ethoxylated gum esters of fatty acid, a fatty amine derivative, and other alcohols. Chemical substances such as derivatives, metal salts. The cation of the metal salt contains lithium ions, sodium ions, potassium ions, cesium ions or a combination thereof. The anion of the metal salt includes a perchlorate ion, a hexafluoroarsenate ion, a hexafluorophosphate ion, a tetrafluoroborate ion, or a combination thereof.

Referring to FIG. 3, another substrate 4 is disposed on the photocurable colloid layer 3. In a specific embodiment, the substrate 4 is a polarizing plate. Then, the photocurable colloid layer 3 and the photoinitiator layer 2 are subjected to an illuminating step to cause the photocurable colloid layer 3 and the photoinitiating layer 2 to undergo a curing reaction to become the hardened layer 5, as shown in FIG. In one embodiment, the illuminating step is carried out using ultraviolet light having a wavelength in the range of 200 nm to 400 nm.

Referring to FIG. 4, the hardened layer 5 (which includes the surface layer 5 ' ) is a single film, that is, a completely inseparable film, and the hardness of the surface layer 5 ' of the hardened layer 5 is greater than the hardness of the inside of the hardened layer 5. This is because a surface of the photocurable colloid layer 3 (Fig. 3) is in contact with the photoinitiating layer 2 to have the highest content of the photoinitiator or photosensitizer or both, or even the light having the highest concentration. The initiator or the photosensitizer or both, the photoinitiator or photosensitizer of the surface layer at the contact end of the photocurable colloid layer 3 and the photoinitiating layer 2 or both are larger than the interior of the photocurable colloid layer 3 The content of the photoinitiator or photosensitizer or both, so that the surface of the photocurable colloid layer 3 hardens faster than the internal hardening rate during curing by light, in other words, the degree of hardening of the surface It is larger than the internal hardening degree, and thus the hardness of the surface layer 5 ' (Fig. 4) of the hardened layer 5 formed is larger than the internal hardness.

Further, in order to promote the degree of hardening of the surface of the photocurable colloid layer 3 (Fig. 3) to be higher than the degree of internal hardening, it is also possible to control the direction of the illumination from the bottom to the top, that is, from the photoinitiator layer 2 to the photocuring layer. The direction of the colloidal layer 3 is irradiated so that the surface of the photoinitiating layer 2 or the photocurable colloid layer 3 adjacent to the photoinitiating layer 2 absorbs a large amount of light energy. However, the invention is not limited to the direction of illumination. In some embodiments, the content of the photoinitiator or the photosensitizer or both of the photoinitiating layer 2 and the photocurable colloid layer 3 is appropriately adjusted to obtain a surface layer 5 ' (Fig. 4) having a hardness greater than that of the interior. Hardened layer 5 of hardness. According to the above, the method of forming the hardened layer of the embodiment of the present invention is simple and economical.

Referring to Fig. 4, in the application example in which the substrate 1 is a release film and the other substrate 4 is a polarizing plate, the hardened layer 5 can serve as an adhesive layer or a pressure-sensitive adhesive layer. Since the hardened layer of the surface layer 55 'hardness greater than the hardness of the interior, thus the hardened layer of the surface layer 55' to provide protection for the substrate (or polarizer) 4 and 5 while the inner layer can be hardened with the substrate ( Or the thermal expansion and contraction of the polarizing plate 4 is changed, or the stress generated by the substrate (or the polarizing plate) 4 due to the shape change is alleviated.

In order to make the above content of the present invention more apparent, the following specific embodiments are described in detail below:

<Preparation of optical film>

The preparation step of the optical film of Example 1 comprises coating a photoinitiator layer on the release film, coating a photocurable colloid layer on the photoinitiator layer (about 25 μm), and then illuminating the photoinitiator layer and the photocurable colloid layer. To form an adhesive layer (molecular weight of about 800,000 to 850,000). The preparation steps of the optical films of Comparative Example 2 to Comparative Example 4 included coating a photocurable colloid layer (about 25 μm) on the release film, and then irradiating the photocurable colloid layer to form an adhesive layer (molecular weight of about 800,000~ 850,000). The illumination step was performed using a high pressure mercury-vapor lamp with an intensity of 30 mW/cm and an illumination time of 20 seconds.

Table 1 shows the composition weight ratios of the optical films of Example 1 and Comparative Example 2 to Comparative Example 4. The curable colloid layer of Example 1 and Comparative Example 2 to Comparative Example 4 includes an acrylic polymer of n-butyl acrylate (BA) and n-methyl acrylate (MA); trimethylol a monomer of trimethylol propane triacrylate (TMPTA); a polyisocyanate compound of 4,4'-diphenylmethane diisocyanate (MDI); benzophenone ( A photoinitiator of benzophenone; and an antistatic agent of chlorate (LiClO ₄ ). The photoinitiator layer of Example 1 includes a photosensitizer of tertiary amine acrylate (supplier: Hengqiao Industry Co., Ltd., product name: Chemcure-NPG).

<Property Analysis>

Table 2 shows the results obtained by analyzing the optical film of Example 1 and Comparative Example 2 to Comparative Example 4 after bonding with a polarizing plate.

1. Durability

The polarizing plate bonded to the optical film was cut into 10 cm*10 cm, and attached to the glass using a laminating machine at a bonding pressure of 2.8 kg/cm ² and an overpressure depth (pitting depth of the sample and the glass) of -0.7 mm. Above, then pressurization defoaming (50 ° C, 5 kg, 20 minutes). The sample was then placed in a reliability tester for analysis at 60 ° C / 90% RH 1000 hr and 80 ° C / 1000 hr. The method of reliability assessment is as follows:

○: no peeling and foaming

△: peeling <2mm (distance between the adhesive layer and the glass), no more than 5 small bubbles in the unit of 10cm*10cm

X: Exfoliated ≧ 2mm, more than 5 small bubbles in a unit of 10cm*10cm

2. Cutability (Cuttability)

A polarizing plate that is bonded to the optical film is cut using a hydraulic cutter. The method of reliability assessment is as follows:

○: Debonding of the edge of the polarizing plate (the distance the adhesive layer is taken away by the cutter when cutting) <0.1mm

△: Debonding of the edge of the polarizing plate 0.1~0.5mm

X: Debonding of polarizing plate edge>0.5mm

3. Residual (Residual)

The polarizing plate bonded to the optical film was cut into 10 cm * 10 cm, and attached to the glass using a laminating machine at a bonding pressure of 2.8 kg/cm ² and an overpressure depth of -0.7 mm, and then subjected to pressure defoaming (50). °C, 5kg, 20 minutes). The sample was then placed in a reliability tester at 80 ° C for 3 hr. Then use a Polarizer Remover to remove the tear. The method of evaluating the residual glue is as follows:

○: Glass residual rubber <1% (area percentage)

△: glass residual glue 1% ~ 5%

X: glass residual glue >5%

4. Pressure point (Dent)

30 to 50 particles having a particle diameter of 300 μm to 500 μm were uniformly dispersed on a release film of an optical film bonded to a polarizing plate, and then pressed with 800 g of glass for 5 minutes, followed by removing the glass and observing the pressure point. Form the quantity. The method of pressure point evaluation is as follows:

○: Number of pressure points <3

△: Number of pressure points 3~7

X: number of pressure points >7

The smaller the number of pressure points, the higher the hardness of the optical film. Therefore, according to the results shown in Table 2, the hardness of the optical film of Example 1 was higher than that of the optical films of Comparative Examples 2 to 4.

5. Light leakage (Mura)

The polarizing plate bonded to the optical film was cut into 10 cm*10 cm, and attached to a glass of 150 mm*150 mm by a bonding machine at a bonding pressure of 2.8 kg/cm ² and an overpressure depth of -0.7 mm. The film is made straight and the backlight module is used in the dark room for light leakage testing. The method of light leakage assessment is as follows:

○: no light leakage

△: slight light leakage

X: Severe light leakage

6. Impedance (Anti-Static Electirc)

After confirming the range of the standard side sheet from 4.95 to 5.0×10 ⁸ , the adhesive layer of A4 size was placed on the glass base, tested three times with an impedance meter, and the values were recorded and averaged. The over in Table 2 indicates that the impedance value is greater than 10 ¹⁵ and therefore cannot be measured. In order to prevent the liquid crystal from being electrostatically driven when the polarizing plate is reworked, the impedance value of the adhesive layer is generally less than 10E11.

While the present invention has been described in its preferred embodiments, the present invention is not intended to limit the invention, and the present invention may be modified and modified without departing from the spirit and scope of the invention. The scope of protection is subject to the definition of the scope of the patent application.

1. . . Substrate

2. . . Photoinitiating layer

3. . . Photocurable colloid layer

4. . . Substrate

5. . . Hardened layer

5 ' . . . Surface layer of hardened layer

1 to 4 show the process of an optical film according to an embodiment of the present invention.

1. . . Substrate

4. . . Substrate

5. . . Hardened layer

5 ' . . . Surface layer of hardened layer

Claims (7)

A method for forming an optical film, comprising the steps of: providing a release film; coating a photoinitiating layer on the release film; and coating a photocurable colloid layer on the photoinitiating layer, wherein the photocuring property a surface of the colloid layer contacts the photoinitiating layer; a polarizing plate is disposed on the photocurable colloid layer; and the photocurable colloid layer and the photoinitiating layer are illuminated to cause the photocurable colloid layer and the photoinitiator The layer undergoes a curing reaction to form an adhesive layer, wherein the surface layer of the adhesive layer has a hardness greater than the internal hardness. The method of forming an optical film according to claim 1, wherein the adhesive layer is a single film. The method of forming an optical film according to claim 1, wherein the photoinitiating layer comprises a first photoinitiator or a first photosensitizer. The method for forming an optical film according to claim 1, wherein the photocurable colloid layer comprises a second photoinitiator or a second photosensitizer. The method of forming an optical film according to claim 1, wherein the photocurable colloid layer comprises an ultraviolet curable monomer, an oligomer or a resin. The method of forming an optical film according to claim 1, wherein the illuminating step irradiates the photocurable colloid layer with the photoinitiating layer with an ultraviolet ray (UV). The method for forming an optical film according to claim 1, wherein the photocurable colloid layer comprises trimethylolpropane triacrylate (TMPTA), an acrylic copolymer, and a polyvinyl alcohol polymer. Or polyurethane resin.