Patent Application
20060102205
1. Field of Invention
The present invention relates to a TAC film pre-processing method. More particularly, the present invention relates to a TAC film pre-processing method for reducing the contact angle of water on a TAC film.
2. Description of Related Art
LCD displays are one of the most rapidly developed display technologies in the world. In the field of computer industry, computers having LCD displays occupy a very large market share. Moreover, in the market of home televisions, the ratio of televisions with LCD displays (LCDTV) is growing rapidly. Therefore, LCD displays will play a very important role in the future.
An LCD display includes, for example, a back light module, polarizers, a liquid crystal layer and color filters. A polarizer allows a light that is linearly polarized in a specific direction to pass. When the LCD display is controlled by an external voltage, the LCD display is capable of generating a white mode and a black mode. Thus, the LCD display can be controlled to show images.
Therefore, a polarizer plays an important role in an LCD display. Generally speaking, the structure of a polarizer is made by sandwiching a PVA (polyvinyl alcohol) film between two TAC (cellulose tri-acetate) films. The interface between the PVA film and the TAC film is a hydrophilic interface, so that a more hydrophilic TAC film attaches to the PVA film more easily. Therefore, before the TAC film is attached to the PVA film, the TAC film needs to be pre-processed to obtain a smaller contact angle of water, i.e. a better hydrophilic character.
It is therefore an aspect of the present invention to provide a TAC film pre-processing method that is capable of reducing the contact angle of water on a TAC film.
It is another aspect of the present invention to provide a TAC film pre-processing method for reducing the contact angle of water on a TAC film, which method is simple, fast, and greatly reduces the contact angle.
It is still another aspect of the present invention to provide a TAC film pre-processing method for reducing the contact angle of water on a TAC film, which method is cheap.
In accordance with the foregoing and other aspects of the present invention, a TAC film pre-processing method for reducing the contact angle of water on a TAC film is provided. The method includes the following steps. The TAC film is sequentially cleaned by a base solution, water, and an acid solution. Then, the TAC film is cleaned by an aqueous solution of an alcohol without arising any solvolysis reaction of the TAC film.
According to a preferred embodiment of this invention, the concentration of the alcohol is preferably about 2-100% by volume, and more preferably 4-6% by volume. The alcohol is, for example, methanol, ethanol, or propanol, and preferably isopropanol (IPA).
The invention has at least the following advantages. The TAC film pre-processing method can effectively reduce the contact angle of water on the TAC film. The method is simple, fast and cheap, and is achieved by adding an alcohol to the second rinse tank.
It is to be understood that both the foregoing general description and the following detailed description are examples, and are intended to provide further explanation of the invention as claimed.
The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. In the drawings,
Reference will now be made in detail to the present preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers are used in the drawings and the description to refer to the same or like parts.
Before the TAC film 102, the PVA film 104, and the TAC film 106 are attached together, the TAC film 102 and the TAC film 106 have to be pre-processed, so that the contact angle of water on the TAC film 102 or the TAC film 106 is smaller than 20 degrees. Because the interface between the PVA film 104 and the TAC film 106 is a hydrophilic interface, the contact angle of water on the TAC film 102 or the TAC film 106 should be smaller than 20 degrees for tight cohesion.
First, a base cleaning process is performed by immersing the TAC film in a base tank (step 302). The base tank contains KOH and the concentration of KOH is about 1.6 N. The temperature is about 50° C. The process time of the base cleaning is about 100 seconds.
Then, a first water cleaning process is performed by immersing the TAC film in a first rinse tank (step 304). The temperature is about 25° C. The process time of the first water cleaning process is about 4 seconds.
Next, a first acid cleaning process is performed by immersing the TAC film in a first acid tank (step 306). Following that, a second acid cleaning process is performed by immersing the TAC film in a second acid tank (step 308). The first acid cleaning process combined with the second acid cleaning process is called an acid cleaning process (step 307). The first acid tank and the second acid tank both contain, for example, H2SO4. The concentration of H2SO4 is about 0.1 N in both the first acid tank and the second acid tank. The total acid cleaning process time is about 4 seconds and the temperature is about 25° C.
Then, a second water cleaning process is performed by immersing the TAC film in a second rinse tank (step 310) without solvolysis of the TAC film. An alcohol is added at a predetermined concentration to the second rinse tank. For example, the alcohol can be methanol, ethanol, or propanol. A preferred alcohol is isopropanol (IPA). For example, in the second rinse tank, the predetermined concentration of the alcohol is about 2-100% by volume, and preferably about 4-6% by volume.
Subsequently, a drying process (step 312) is performed by putting the TAC film into an oven. The temperature is about 100° C. and the drying process time is about 10 minutes. Then, a pre-processing process is completed.
An experimental test was held, and the results are listed in Table 1. From the Table 1, it shows that once the IPA was added to the second rinse tank to perform the second water cleaning step 310, the contact angle of water on the TAC film was reduced from 17.6 degrees to smaller than 14 degrees. The contact angle is far smaller than the 20-degree requirement. Therefore, the method mentioned above can effectively reduce the contact angle of water on the TAC film.
Although the present invention has been described in considerable detail with reference to certain preferred embodiments thereof, other embodiments are possible. Therefore, their spirit and scope of the appended claims should not be limited to the description of the preferred embodiments contained herein.
It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the present invention without departing from the scope or spirit of the invention. In view of the foregoing, it is intended that the present invention cover modifications and variations of this invention provided they fall within the scope of the following claims and their equivalents.
| Number | Date | Country | Kind |
|---|---|---|---|
| 93104361 | Feb 2004 | TW | national |
This application is a continuation-in-part of U.S. application Ser. No. 10/949,188, filed Sep. 27, 2004, which claims priority to Taiwan application 93104361, filed Feb. 20, 2004, now pending.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 10949188 | Sep 2004 | US |
| Child | 11319654 | Dec 2005 | US |
