TWI429966B - Polarizer - Google Patents

Description

Polarizer

The present invention relates to a polarizing plate, and more particularly to a polarizing plate which utilizes a nanowire to produce a polarizing effect.

Polarizers are widely used in many optoelectronic products because they allow the light to pass through to have a specific polarization state. Polarizers can be classified into the following types according to their principle of action. The first is to use a multilayer film interferometry to penetrate a particular linearly polarized light and reflect light that is orthogonal to the direction of linear polarization. The second type is a wire-grid polarizer, which mainly screens light with a linear strip of parallel strips arranged in parallel, and the light having the direction of linear polarization and the direction of alignment of the metal lines can pass, and vice versa. The third type is a film made of a cholesteric liquid crystal material, which is reflected when the circular polarization state of the light is aligned with the cholesteric liquid crystal, and vice versa. Represented by the patents of Nitto, Philips and MRL. Both the first and second polarizers are required to have a nanometer-scale process capability, and the fabrication process is complicated and it is difficult to produce a large-area polarizer. The optical performance of the third polarizing plate is excellent, but the liquid crystal material is expensive and the alignment direction of the liquid crystal molecules is not easily controlled.

In 1969, Corning Corporation of the United States first disclosed the patent number GB 1276548 A, which used a deuterated glass substrate doped with an alkali metal oxide and added silver halide silver particles to the substrate. Producing an ellipsoidal shape (length to short axis ratio of 2:1 to 5:1) by heating and stretching a glass substrate The non-isotropic light absorption rate is achieved for the purpose of polarization. Since the particles of the metal halide absorb light having a polarization direction parallel to the long axis direction thereof, it belongs to an absorption type polarizing plate, and the extinction ratio is about 100.

In U.S. Patent No. 7,570,424, the disclosure of U.S. Patent No. 7,570,424 discloses a nanowire grid polarizer having a two-layer structure having an extinction ratio of about 4,000. However, the patented nanowire grid is formed by a microlithography process, which is extremely costly and difficult to fabricate large-sized polarizers.

U.S. Patent No. 3,610,729 issued to U.S. Patent No. 3,610,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, The light. Wherein the thickness and refractive index product of each film is a quarter wavelength of the reflected light. However, the structure of the multilayer film is not only costly but also low in yield.

The present invention provides a polarizing plate which can solve the problem that the conventional polarizing plate is expensive and the size is not easily increased.

The polarizing plate of the present invention comprises a polymer substrate and a plurality of nanowires. The molecules of the polymer substrate have a main alignment direction. Alternatively, the surface of the polymer substrate has a plurality of microchannels substantially parallel to the main array direction. The nanowires are arranged on the surface of the polymer substrate in a direction substantially parallel to the main alignment.

In an embodiment of the invention, the polymer substrate is made of polyvinyl alcohol (PVA), polyester (PET) or Polyimine (PI).

In one embodiment of the present invention, the polymer substrate described above is stretched during the production process so that the molecules of the polymer substrate have a main alignment direction.

In an embodiment of the invention, the surface of the polymer substrate described above has micro grooves formed by friction.

In an embodiment of the invention, the material of the nanowire is silver.

In an embodiment of the invention, the nanowires comprise from 50% to 100% of the surface area of the polymeric substrate.

In one embodiment of the invention, the nanowires comprise from 85% to 95% of the surface area of the polymeric substrate.

In an embodiment of the invention, the angle between the ith nanowire and the main alignment direction is θ _i , where n is the number of nanowires. And S 0.5.

In an embodiment of the invention, the polarizing plate has a suitable wavelength, and the line width of each of the nanowires is less than or equal to a suitable wavelength.

In an embodiment of the invention, the polarizing plate has a suitable wavelength, and the length of each of the nanowires is greater than or equal to ten times the applicable wavelength.

In an embodiment of the invention, the polarizing plate further includes a transparent layer disposed on the polymer substrate and covering the nanowire.

Based on the above, the polarizing plate of the present invention can be produced by a simple and inexpensive process, and is easy to enlarge.

The above described features and advantages of the present invention will be more apparent from the following description.

1 is a schematic view of a polarizing plate according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view of the polarizing plate of FIG. 1. Referring to FIG. 1 and FIG. 2 , the polarizing plate 100 of the embodiment includes a polymer substrate 110 and a plurality of nanowires 120 . The molecules of the polymer substrate 110 have a main alignment direction D10. The nanowire 120 is disposed on the surface of the polymer substrate 110 substantially in parallel with the main array direction D10. Since most of the nanowires 120 are arranged in parallel with the main alignment direction D10, light having a linear polarization direction perpendicular to the main alignment direction D10 can pass through the polarizing plate 100, and light having a linear polarization direction parallel to the main alignment direction D10 will Reflected by the polarizing plate 100.

In the polarizing plate 100 of the present embodiment, since the molecules of the polymer base material 110 originally have the main array direction D10, the nanowires 120 are naturally aligned along the main array direction D10. As a result, the manufacturing cost of the polarizing plate 100 of the present embodiment can be reduced, and the polarizing plate 100 of the present embodiment can be easily applied to a large-sized product because it is easy to achieve an increase in size.

The material of the polymer substrate 110 of the present embodiment may be polyvinyl alcohol, polyester, polyimine or other polymer materials. In order to allow the molecules of the polymer substrate 110 to be along the main alignment direction D10 as much as possible, the polymer substrate 110 can be stretched during the production process of the polymer substrate 110. In addition, the material of the nanowire 120 of the present embodiment is silver or other metal. The nanowire 120 is formed on the polymer substrate 110 by chemical reaction or physical deposition.

The quality of the polarizer can be expressed by the extinction ratio. The extinction ratio = T _⊥ /T _∥ , where T _⊥ is the transmittance of light indicating that the direction of linear polarization is perpendicular to the direction in which the nanowires are arranged, and T _∥ is that the direction of linear polarization is parallel to the direction of alignment of the nanowires The penetration rate of light. In order to obtain a preferable extinction ratio, the nanowire 120 preferably accounts for 50% to 100% of the surface area of the polymer substrate 110, and the nanowire 120 accounts for 85% to 95% of the surface area of the polymer substrate 110. good. In other words, the more the nanowire 120 is distributed on the surface of the polymer substrate 110, the more the polarizing plate 100 will have the better extinction ratio.

In addition, whether or not the nanowire 120 is parallel to the main alignment direction D10 also affects the extinction ratio of the polarizing plate 100. Here, an index S is provided to indicate the extent to which the nanowire 120 of the polarizing plate 100 is parallel to the main array direction D10. Assuming that the number of nanowires 120 is n and the angle between the i-th nanowire 120 and the main alignment direction D10 is θ _i , then

When S=1, it means that all the nanowires 120 are parallel to the main arrangement direction D10, and at S In the case of 0.5, the extinction ratio of the polarizing plate 100 can be made usable.

The purpose of the "nano" in the name of the nanowire 120 of the present embodiment is that the line width of each of the nanowires 120 is nanometer. The polarizing plate 100 of the present embodiment has a suitable wavelength, and the line width of each of the nanowires 120 is less than or equal to the applicable wavelength, and the length of each of the nanowires 120 is greater than or equal to ten times the applicable wavelength.

Figure 3 is a cross-sectional view showing a polarizing plate according to another embodiment of the present invention. Referring to FIG. 3, the polarizing plate 200 of the present embodiment is similar to the polarizing plate 100 of FIG. 2, except that the polarizing plate 200 of the present embodiment further includes a transparent layer 210. The transparent layer 210 is disposed on the polymer substrate 110 and covers the nanowire 120. The refractive index of the transparent layer 210 affects the extinction ratio of the polarizing plate 200. Figure 4 is the refractive index of the transparent layer, the distribution density of the nanowires, and the polarizer The relationship between the extinction ratio and the three. The horizontal axis of FIG. 4 is the distribution density of the nanowire 120, that is, the ratio of the nanowire 120 to the surface area of the polymer substrate 110. The vertical axis of Fig. 4 is the refractive index of the transparent layer. The extinction ratio of the polarizing plate is shown in Fig. 4 in different shades, and the relationship between the depth of the line and the extinction ratio of the polarizing plate is shown on the right side of Fig. 4. As can be seen from FIG. 4, after the design of optimizing the refractive index of the transparent layer 210 and the distribution density of the nanowire 120, the extinction ratio of the polarizing plate 200 can be improved. For example, when the simulation is performed with green light having a wavelength of 0.55 μm, if the ratio of the surface area of the nano metal wire 120 to the surface area of the polymer substrate 110 is 93%, and the refractive index of the transparent layer 210 is 1.43, a polarizing plate can be obtained. The extinction ratio of 200 is 100.

Figure 5 is a cross-sectional view showing a polarizing plate according to another embodiment of the present invention. Referring to FIG. 5, the polarizing plate 300 of the present embodiment is similar to the polarizing plate 100 of FIG. 2, except that the surface of the polymer substrate 310 of the polarizing plate 300 of the present embodiment has a substantially parallel main alignment direction (similar to FIG. 1). A plurality of micro-grooves 312 are arranged in the main direction D10). The nanowire 320 of the polarizing plate 300 of the present embodiment is formed in the microgroove 312, so that the nanowire 320 is substantially parallel to the direction of the microgroove 312, that is, the main alignment direction. There are many methods for forming the microgrooves 312 on the surface of the polymer substrate 310, and a simple method is to rub the surface of the polymer substrate 310.

In the production of the polarizing plate of each of the above embodiments, the molecules of the polymer substrate are first arranged in the main alignment direction, and in the embodiment, for example, the polymer substrate is stretched in the production process of the polymer substrate. Alternatively, a plurality of microchannels substantially parallel to the main array direction are formed on the surface of the polymer substrate. Next, a nanowire in a substantially parallel main alignment direction is formed on the surface of the polymer substrate by chemical reaction or physical deposition. The method of forming the nanowire is, for example, first immersing the treated polymer substrate in a mixed solution of 20 ml of water and 2.2 g of ammonium persulfate ((NH ₄ ) ₂ S ₂ O ₈ , ammonium persulfate). After 30 seconds, the polymer substrate was taken out from the mixed solution and dried at 60 ° C for 10 minutes, and then the dried polymer substrate was mixed with 20 ml of water and 0.8 ml of pyrrole. After soaking for 30 seconds, the polymer substrate was taken out from the mixed solution and dried at 60 ° C for 24 hours, and then the dried polymer substrate was immersed in silver nitrate (AgNO ₃ ) having an equivalent concentration of 0.1 N. It takes 30 seconds to complete.

As described above, in the polarizing plate of the present invention, the nano-metal formed on the surface of the polymer substrate can be obtained by using the molecular arrangement direction of the polymer substrate itself or the micro-groove on the surface of the polymer substrate. The lines are substantially parallel to one main alignment direction. Thereby, the polarizing plate has an anisotropy dielectric constant, which allows light of a specific linear polarization direction to penetrate, and reflects light whose linear polarization direction is perpendicular to a specific linear polarization direction. Since the polarizing plate of the present invention can be formed by a simple process, the cost can be reduced. Moreover, the polarizing plate of the present invention is easy to increase in size and can be used in an application field.

Although the present invention has been disclosed in the above embodiments, it is not intended to limit the invention, and any one of ordinary skill in the art can make some modifications and refinements without departing from the spirit and scope of the invention. The scope of the invention is defined by the scope of the appended claims.

100, 200, 300‧‧‧ polarizers

110, 310‧‧‧ polymer substrate

120, 320‧‧‧Nan metal wire

D10‧‧‧Main arrangement direction

210‧‧‧ transparent layer

312‧‧‧Microgroove

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a schematic view of a polarizing plate according to an embodiment of the present invention.

Figure 2 is a cross-sectional view of the polarizing plate of Figure 1.

Figure 3 is a cross-sectional view showing a polarizing plate according to another embodiment of the present invention.

4 is a graph showing the relationship between the refractive index of the transparent layer, the distribution density of the nanowires, and the extinction ratio of the polarizing plate.

Figure 5 is a cross-sectional view showing a polarizing plate according to another embodiment of the present invention.

100‧‧‧Polarizer

110‧‧‧ polymer substrate

120‧‧‧Nano wire

D10‧‧‧Main arrangement direction

Claims (11)

A polarizing plate comprising: a polymer substrate, wherein molecules of the polymer substrate have a main alignment direction, or a surface of the polymer substrate has a plurality of microchannels substantially parallel to the main alignment direction; The nanowires are arranged on the surface of the polymer substrate substantially parallel to the main alignment direction. The polarizing plate according to claim 1, wherein the polymer substrate is made of polyvinyl alcohol (PVA), polyester (PET) or polyimide (PI). The polarizing plate according to claim 1, wherein the polymer substrate is stretched during the production process so that the molecules of the polymer substrate have the main alignment direction. The polarizing plate of claim 1, wherein the surface of the polymer substrate has the micro grooves by friction. The polarizing plate of claim 1, wherein the nanowires are made of silver. The polarizing plate of claim 1, wherein the nanowires comprise from 50% to 100% of the surface area of the polymer substrate. The polarizing plate of claim 1, wherein the nanowires comprise 85% to 95% of the surface area of the polymer substrate. The polarizing plate of claim 1, wherein an angle between the i-th nanowires and the main alignment direction is θ _i , where n is the number of the nano metal wires, And S 0.5. The polarizing plate of claim 1, which has a suitable wavelength, and the line width of each of the nanowires is less than or equal to the applicable wavelength. The polarizing plate according to claim 1 has a suitable wavelength, and the length of each of the nanowires is greater than or equal to ten times the applicable wavelength. The polarizing plate of claim 1, further comprising a transparent layer disposed on the polymer substrate and covering the nanowires.