Patent Application
20060176422
1. Field of the Invention
The present invention relates to a brightness-enhancing integral polarizer and optical film structure and a manufacturing method for the same, and more particularly to a brightness-enhancing integral polarizer and optical film structure, and a manufacturing method for the same, that use a non-linear optical design to coat a brightness-enhancing integral polarizer and optical film with a different dye onto at least one substrate. The brightness-enhancing integral polarizer and optical film include two kinds of polarizers, an absorptive polarizer and a reflective polarizer, and the reflective polarizer provides a reflective light source and concurrently features enhanced reflective brightness, high degree of polarization, high transmittance, wide viewing angle and high contrast.
2. Description of Related Art
A liquid crystal display mainly uses a linear polarization produced by two polarizers to achieve its display effect and a backlight module as its main light source. The light produced by the backlight module passes through a first polarizer to produce a linear polarization, and then a second polarizer produces a change of brightness according to twisted nematic liquid crystal molecules to provide the display effect for a viewer's eyes.
A light source usually can maintain less than 5% of its brightness perceived by a viewer after the light passes through several layers of materials and goes through the processes of reflections, refractions or absorptions. The absorption and light transmission of a dichroic polarizer in a display are the main factors that affect brightness, and thus increasing the intensity of a light source and its light transmittance level is a main issue for displays.
At present, there are two main methods for increasing the overall light transmittance level: (1) by increasing the transmitting effect of an incident light; and (2) by increasing the light intensity of a backlight module. The first method is to improve the transmittance of a polarizer, or change the polarization mode of an incident light before the incident light enters the polarizer, so that the polarization mode of the incident light is parallel to the polarization of the polarizer, thus enhancing the transmissive effect of the incident light. At present, the transmittance of the current iodine polarizers is up to 44% to 46%, and has approached a level that makes a further improvement of the light transmittance level difficult. The way of changing the polarization mode of an incident light to make the polarization parallel to the polarization of the polarizer and achieve a high light transmittance goes with an enhanced brightness film produced by a DBEF (by the 3M Company) and the reflective polarizer of a cholesterol liquid crystal. The second method is to increase the intensity of the incident light of a backlight source or achieve a 100% polarized light transmitting effect by a direct polarization of the backlight source. In summation of the description above, the contrast, viewing angle and light transmittance level of the display are determined by the polarizer. Increasing the light transmittance level of polarizers is an important development trend for polarizers in the future.
The present major polarizer is the O-type iodine polarizer. Its main advantages include (1) a high degree of polarization (99.9%); (2) a high light transmittance level (44%-46%), and its main disadvantages include (1) a large viewing angle that gives a strong leakage of light, thus requiring a wide viewing angle film to achieve a high contrast effect; (2) poor climate resistance; (3) low mechanical characteristic, thus requiring a protective film to enhance the mechanical characteristic thereof, and (4) a requirement of being used and attached on the exterior of the display. At present, an E-type liquid crystal polarizer is the latest polarizer, and the body of the polarizer primarily adopts absorptive disc-shaped liquid crystals, so that if light passes through the disk-shaped liquid crystal, the O-type polarized light will be absorbed and the E-type polarized light passes through, so as to achieve a linear polarization effect. The best optical effect for the polarizer of this kind has a polarization level of approximately 95% and a light transmittance level of approximately 40%-44%. The E-type polarizer has the disadvantages of (1) having insufficient polarization level and light transmittance level for the TFT-LCD and (2) having a small viewing angle that will cause a light leak. On the other hand, the E-type polarizer has the advantages of (1) providing a lightweight and thin polarizer (approximately 0.3-0.8 μm) and (2) being produced in the display cell (refer to
Another research area for a coated polarizer is the dye series polarizer. A polarizer of this type primarily absorbs dyes as its carriers. The parameters affecting the absorbability of a polarizer includes (1) the coefficient of absorption of dye molecules, (2) the dye concentration, and (3) the thickness of the polarizer. The main advantages of the dye series polarizer include (1) stronger climate resistance, (2) more choices for the coating method, including spin coating, die coating and dip coating, and (3) being manufactured in a display cell. The dye series polarizer has the disadvantages of (1) having difficulties of obtaining a dye with a high absorption level, (2) a high level of polarization requires a dye with a high concentration, and thus results in high costs, and (3) a thick film (approximately 3 μm) causes a decrease of light transmittance and thus limits the applications of the dye series polarizer.
An enhanced brightness film is mainly divided into a cholesterol liquid crystal reflective-type polarizer and a reflective-type DBEF multilayer film. The main principle of the optical device of a cholesterol liquid crystal reflective polarizer adopts the separation characteristics of the left-hand rotated and the right-hand rotated cholesterol polarized lights to separate a non-polarized white incident light into left-rotated and right-rotated polarized lights. The circularly polarized light with an opposite optical rotation can pass through, and the circularly polarized light in the same optical rotation is reflected. The passing circularly polarized light is reflected for a second time to increase the light transmittance level. To cope with a ¼ wavelength delay film, the passing circularly polarized light is converted into a linear polarized light and then enters the polarizer. As a result, the light source is fully converted into a polarization mode for passing all polarized lights through the polarizer to achieve the brightness enhancement effect. The principle of a dual brightness enhancement film (DBEF) mainly uses two different materials with different refraction indexes to form a multilayer film. A white light passes through the multilayer film to divide the non-polarized white light into a light P parallel to an incident surface and a light S perpendicular to the incident surface. After the white light passes through the dual brightness enhancement film, the wave P penetrates and the wave S is reflected. The wave S reflected by an interface penetrates after being converted into the wave P, and the final objective is to pass a plurality of light sources through the polarizer, so as to achieve the brightness enhancement effect.
Referring to
As to the polarization, the iodine polarizer has a polarization of approximately 99.5%, and thus the contribution of the brightness-enhancing film to the overall polarization is negligible. In summation of the description above, the brightness enhancement effect produced by the brightness-enhancing film accompanied with the polarizer is used to lower the light transmittance level first, and then the second light transmittance level of the reflective light is used again to increase the light transmittance level. Therefore, the multilayer film does not have a good optical effect, but has a large loss of light transmittance level. Even if a light-enhancing film is added, the whole light enhancement effect of the light-enhancing film cannot be shown. If a cell is manufactured in the future, then a common light-enhancing film sold in the market usually comes with a thickness exceeding 100 mm (over 100 mm for the DBEF), and such thickness will cause a shift of drive voltage in the cell that makes the manufacture difficult. Thus, only external cells can be manufactured to go with the common polarizer sold in the market.
At present, the mainstream of iodine polarizers as disclosed by U.S. Pat. No. 4,591,512 entitled “Method of making light polarizer” uses a polyvinyl alcohol (PVA) for its substrate. After immersing a uniaxially stretched film of the PVA in an iodine solution to produce a light polarizer, qualities such as the mechanical characteristic, climate resistance, and heat resistance of the film layer are poor. Besides the body of the iodine polarizer, the upper and lower surfaces require a TAC film as a protective film. Therefore, the thickness of the current iodine polarizers is approximately 200 μm. In the E-type polarizers as disclosed in U.S. Pat. Nos. 6,583,284, 6,563,640, 6,174,394, 6,049,428 and 5,739,296, the polarizer is produced by a coating process to coat supermolecules with an absorption effect on the surface of the substrate, so as to complete the manufacture of the E-type polarizer. After a light passes through the polarizer, the polarization status is exactly opposite that of the traditional 0-type polarizers, which is known as E-type polarization. In another method of coating the O-type polarizer, a dye is coated onto the surface of the substrate to produce a polarizer. U.S. Pat. Nos. 5,812,264, 6,007,745, 5,601,884 and 5,743,980 are patents related to the dye coating of polarizers. The main principle of the light-enhancing film is to divide a non-polarized visible light into two perpendicular polarized lights, such that a polarized light is passed, and another perpendicular polarized light is reflected and converted into a parallel polarization, and then passed for a second time.
The prior art reflective type polarized light-enhancing films are disclosed in U.S. Pat. Nos. 5,828,488, 6,101,032 and 6,124,971. The cholesterol liquid crystal reflective-type polarizer is disclosed in U.S. Pat. Nos. 5,999,243, 6,016,177 and 6,025,958, and the fully coated cholesterol liquid crystal reflective brightness-enhancing device is disclosed in U.S. patent application Ser. No. 20040130672_A1, and the objective of this patent is change the color shift only.
In summation of the description above, the polarizer for producing a polarization in the present LCDs does not itself come with a brightness enhancement effect; rather, the brightness enhancement effect is provided by the brightness-enhancing film. Most of the systems adopt a brightness-enhancing film attached with a polarizer, but the systems do not combine with a polarizer to produce the overall performance.
In view of the foregoing shortcomings of the prior art polarizers, the present invention provides a brightness-enhancing integral polarizer and optical film structure, and a manufacturing method for the same, to overcome the foregoing shortcomings.
Therefore, it is a primary objective of the present invention to provide a brightness-enhancing integral polarizer and optical film structure, and a manufacturing method for the same, that primarily adopt a system assembly model to overcome the overall poor match of optical effect of the traditional polarizer and brightness-enhancing film, causing an overall decrease of the light transmittance and having its polarization contributed by the polarizer only. The present invention rearranges the polarization and light transmittance level of different films to produce an overall polarization and light transmittance level higher than those of the polarizer accompanied with the brightness-enhancing film. The invention also has the effect of a reflective light, and thus the brightness-enhancing integral polarizer together with the optical film in accordance with the present invention can fully obtain a light transmittance effect for the first and second times, without incurring an optical loss.
To achieve the foregoing objective, the present invention provides a method for manufacturing a brightness-enhancing integral polarizer and optical film structure, which is used as a polarizer for displays, a brightness-enhancing film, a wide viewing angle film, or a general optical film. The manufacturing method comprises the steps of providing at least one substrate and coating at least one layer of a brightness-enhancing integral polarizer and optical film made of a material different from that of the substrate onto the substrate. Such material includes two portions, a reflective type polarized brightness-enhancing film and an absorptive polarizer.
The present invention also provides a brightness-enhancing integral polarizer and optical film structure, which is coated with at least one layer of material different from that of the brightness-enhancing integral polarizer and optical film. Such material includes two portions, a reflective type polarized brightness-enhancing film and an absorptive polarizer.
The foregoing aspects and many of the attendant advantages of this invention will be more readily appreciated as the same becomes better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein:
The above and other objects, features, and advantages of the present invention will become apparent from the following detailed description taken with the accompanying drawings. However, the drawings are provided for reference and illustration, and are not intended to limit the present invention.
If light passes through two polarizers stacked with each other, the total thickness of the polarizers is greater than the thickness of a single polarizer, thus increasing the light transmitting thickness. Although such an arrangement increases absorbability and polarization, it suffers a significant loss of light transmission. In addition to the basic film problems, the two stacked polarizers also have an optic axis alignment problem. If the polarized light produced by a first polarizer enters a second polarizer, some portion of the light intensity is absorbed due to the deviation angle of the optic axis alignment. The light transmission level will thus drop. Although the two combined polarizers can increase the degree of polarization, the precious light transmission level is sacrificed as a tradeoff, and such a tradeoff is undoubtedly a major disadvantage for the display industry.
The present invention uses a non-linear nonlinear optical design to carry out a system model integration and combines two low-efficiency polarizers into a polarizer of high polarization and high transmittance. The invention carries out an optical system integration for two different polarizers to produce a brightness-enhancing integral polarizer and optical film. The levels of polarization and transmittance of the brightness-enhancing integral polarizer and optical film are rearranged for each film, and thus the overall level of polarization and light transmittance of the polarizer are determined by the entire film. Although the level of polarization and transmittance of the entire film is a constant, the combination of the films may vary, and thus may be rearranged and combined according to different environmental conditions and different compositions of materials. Since the level of polarization and light transmittance varies in different films, the stacked film will not lose the required light transmittance, but it will enhance the degree of polarization.
Reference is made to
Reference is made to
As illustrated in the figure, two brightness-enhancing integral polarizers and optical films are stacked with each other and constructed on the same side of a substrate 10. The substrate 10 is a transmissive substrate or a non-transmissive substrate. The brightness-enhancing integral polarizer and optical film made of a different material combines a reflective polarizer and an absorptive polarizer. The design of the brightness-enhancing integral polarizer and optical film made of a different material adopts the combination of several dye brightness-enhancing polarizers and optical films. The types of these polarizers include the O-type, E-type, P-type, S-type, right-handed rotary type, left-handed rotary type, and their combinations.
If the brightness-enhancing integral polarizer and optical film made of a different material are produced outside a display cell, the absorptive polarizer is a dye polarizer or an E-type polarizer, and the reflective polarizer is a reflective type polarized brightness-enhancing film or a cholesterol liquid crystal brightness-enhancing film.
If the reflective polarizer is produced outside a display cell, the reflective polarizer can be a reflective type polarized brightness-enhancing film or a cholesterol liquid crystal reflective-type polarizer brightness-enhancing film. The absorptive polarizer can be constructed inside or outside a display cell. If the absorptive polarizer is an E-type polarizer and the reflective polarizer is a cholesterol liquid crystal reflective-type polarizer brightness-enhancing film, then a λ/4 wavelength sheet is installed between the E-type polarizer and a cholesterol liquid crystal layer. If the absorptive polarizer is an E-type polarizer and the reflective polarizer is a cholesterol liquid crystal reflective-type polarizer brightness-enhancing film, then the degree of polarization of the brightness-enhancing integral polarizer and optical film is over 70% and the light transmittance is over 40%. If the absorptive polarizer is constructed outside the display cell, then the reflective polarizer will be attached. The absorptive polarizer is coated onto the reflective polarizer first and then attached onto the display cell.
Unlike the foregoing coating method, the reflective polarizer and the absorptive polarizer as shown in
Reference is made to
If the brightness-enhancing integral polarizer and optical film is constructed outside a display cell, the absorptive polarizer is a dye polarizer or an E-type polarizer, and the reflective polarizer is a reflective type polarized brightness-enhancing film or a cholesterol liquid crystal reflective-type polarizer brightness-enhancing film. If the absorptive polarizer is an E-type polarizer and the reflective polarizer is a cholesterol liquid crystal reflective-type polarizer brightness-enhancing film, then a λ/4 wavelength sheet is installed between the E-type polarizer and a cholesterol liquid crystal layer. If the absorptive polarizer is an E-type polarizer and the reflective polarizer is a cholesterol liquid crystal reflective-type polarizer brightness-enhancing film, then the degree of the polarization brightness-enhancing integral polarizer and optical film is over 70% and the light transmittance is over 40%.
Reference is made to
The present invention also provides a method for manufacturing brightness-enhancing integral polarizer and optical film used as a polarizer of displays, a brightness-enhancing film, a wide viewing angle film or a general polarizer/optical film. The brightness-enhancing integral polarizer and optical film adopt an optical design of wide viewing angle, thin film, high contrast, high degree of polarization and high light transmittance, and the brightness-enhancing integral polarizer and optical film further comprise at least one substrate made of a transmissive material, a non-transmissive material, or polymers. The brightness-enhancing integral polarizer and optical film have at least one layer of a different material coated onto the substrate and include two portions, a reflective polarizer 12 and an absorptive polarizer 14.
The coating method can be a slot-die coating, an extrusion coating, a Mayer rod coating or a blade coating. The brightness-enhancing integral polarizer and optical film adopt a coating method to be coated onto a thin film transistor inside a display. If the brightness-enhancing integral polarizer and optical film is constructed outside a display cell, then the absorptive polarizer is a dye polarizer or an E-type polarizer and the reflective polarizer is a reflective type polarized brightness-enhancing film or a cholesterol liquid crystal reflective-type polarizer brightness-enhancing film. The reflective polarizer can be constructed inside or outside a display cell. If the reflective polarizer is constructed outside the display cell, then the reflective polarizer is a reflective type polarized brightness-enhancing film or a cholesterol liquid crystal reflective-type polarizer brightness-enhancing film. The absorptive polarizer can be constructed inside or outside a display cell. If the absorptive polarizer is constructed outside the display cell, then the reflective polarizer is attached to a reflective type polarized brightness-enhancing film or a cholesterol liquid crystal reflective-type polarizer brightness-enhancing film. The absorptive polarizer is coated onto the reflective polarizer first and then attached to the display cell (which is attached to the reflective type polarized brightness-enhancing film or the cholesterol liquid crystal reflective-type polarizer brightness-enhancing film).
Unlike the prior arts, the present invention has the following technical characteristics: (1) The present invention employs a full coating method or a half-coating half-attaching method, and the whole polarizer includes two portions, a reflective polarizer and an absorptive polarizer, and both the reflective and absorptive polarizers have contributions to the overall degree of polarization and light transmittance. (2) The present invention designs its polarization and light transmittance such that the combination of the polarizer and the brightness-enhancing film will not just improve the polarization while losing light transmittance. (3) The present invention integrates the polarizers while maintaining the advantages of high polarization, high light transmission, and a wide viewing angle effect. The brightness-enhancing integral polarizer and optical film of the invention primarily adopts a system assembly model to overcome the overall poor match of optical effect of the traditional polarizer and brightness-enhancing film, causing an overall decrease of the light transmittance and having its polarization contributed by the polarizer, only. The present invention rearranges the polarization and light transmittance level of different films to produce high polarization and light transmittance levels accompanied with a brightness enhancement effect. The invention also has the effect of a reflective light, and thus the brightness-enhancing integral polarizer together with the optical film in accordance with the present invention can fully obtain a light transmitting effect for the first and second times without suffering an optical loss.
Overall speaking, the brightness-enhancing integral polarizer and optical film of the present invention includes a reflective polarizer and an absorptive polarizer, in which the reflective polarizer can produce a reflective light source effect. Therefore, the brightness-enhancing integral polarizer and optical film will improve the polarization and light transmittance while having the reflective brightness enhancement effect. The overall transmittance will not drop due to the multiple of films. Compared with the similar brightness-enhancing intensity provided by the brightness-enhancing film, the brightness-enhancing integral polarizer and optical film will produce a better light transmitting effect.
The brightness-enhancing integral polarizer and optical film of the invention shows the required polarization and light transmission by means of a non-linear optical design to rearrange each film, and thus the overall polarization and light transmittance of the brightness-enhancing integral polarizer and optical film are actually determined by the entire film. In addition, although the polarization and light transmittance of the entire film are designed to be constant, there are a variety of combinations for the films and thus can be adjusted according to different environmental conditions and composition of materials. Since the degree of polarization and light transmittance of the brightness-enhancing integral polarizer and optical film are scattered and combined according to the non-linear optical design, the films are stacked with each other. Such arrangement not only prevents a loss of light transmittance, but also improves the overall polarization.
The brightness-enhancing integral polarizer and optical film of the invention comes with a good reflectivity and features a better reflective brightness enhancement effect than that of general iodine polarizers. With the same or better degree of polarization as general iodine polarizers, the light transmittance for both narrow viewing angle range and wide viewing angle range is higher than that of the iodine polarizer. Therefore, the brightness-enhancing integral polarizer and optical film of the invention concurrently has the inflective brightness enhancement and the wide viewing angle features.
While the invention has been described in terms of what is presently considered to be the most practical and preferred embodiments, it is to be understood that the invention needs not be limited to the disclosed embodiment. On the contrary, it is intended to cover various modifications and similar arrangements included within the spirit and scope of the appended claims which are to be accorded with the broadest interpretation so as to encompass all such modifications and similar structures.
| Number | Date | Country | Kind |
|---|---|---|---|
| 94103676 | Feb 2005 | TW | national |
