The present invention relates to an optical element used for filtering light, particularly to a grating-type color filter.
A conventional color filter (CF) is produced by preparing organic materials of three colors of R, G and B onto a transparent substrate by such methods as photolithography, printing, and deposition. The color filter of this type needs the three different organic materials to be formed successively on the substrate in the production, thus having such defects as uneven thickness and poor color purity; besides, because of complexity of the process steps, the production cost is extremely high, making the color filter particularly disadvantageous in its application to the large-sized panels. To overcome the above defects, some novel color filters have been proposed.
The color filter produced with the grating structure, because of its high light utilization efficiency and mature production process, has become the development direction of the color filter of the next generation. The currently known grating-type color filter includes a single layer metal grating structure, a multilayer medium grating structure, and a cascade grating structure of the medium grating and the metal grating. Wherein the color filter of the cascade grating structure both overcomes the low transmission efficiency of the medium grating, and reduces crosstalk of the metal grating, thus becoming a popular research direction of the grating-type color filter.
However, in this color filter of the grating structure, because the guided-mode resonance condition is strongly dependent on the incident angle of the incident light, i.e. the guided-mode resonance condition changes with the incident angle of the incident light, the transmission spectrum will move toward both sides to even disappear, which greatly limits application of the color filter in the actual production.
A purpose of the present invention is to provide a color filter of a cascade grating structure, and reduce the influence of the incident angle of light on the resonance conditions by improving its structure, so as to achieve the filtering effect within a relatively wide range of angle.
In order to achieve above purpose, the present invention adopts the following technical solution:
A color filter, comprising a substrate layer and a medium grating layer, wherein the medium grating layer, arranged on the substrate layer, has a grating structure of periodic arrangement and is provided with a metal profiling film, which covers the ridge portion of the grating structure, one or two sides of the lateral portion of the grating structure, and a part of the groove portion of the grating structure, with the area of the groove portion of the grating structure covered by the metal profiling film occupying 30%-95% of the total area of the lateral portion and the groove portion.
A further technical solution further includes a medium profiling film, which is arranged between the grating structure and the metal profiling film of the medium grating layer.
In the above technical solution, at least one of the media in the medium grating layer and the medium profiling film has a refractive index greater than 1.65, which is then a high refractive index medium.
The medium grating layer meets the guided-mode resonance condition, or the combination of the medium grating layer and the medium profiling film meets the guided-mode resonance condition.
In the above technical solution, the medium profiling film is arranged at the ridge portion, the single side and the groove portion of the grating structure, or at the ridge portion and the single side of the grating structure, or at the ridge portion and the groove portion of the grating structure, or at the ridge portion, the bilateral portion and the partial groove portion of the grating structure.
A further technical solution further includes a medium cover layer, which is arranged on the metal profiling film and covers and fills up the grating structure. In a preferred technical solution, an interval is left between the metal profiling film on the partial groove portion and at least one of the lateral portions on both sides of the groove. In the above technical solution, the metal profiling film is arranged at the ridge portion, the single lateral portion and the partial groove portion of the grating structure, wherein the metal profiling film on the partial groove portion is connected with that on the single lateral portion, and an interval is left between the metal profiling film on the partial groove portion and the other single lateral portion opposite the single lateral portion provided with the metal profiling film.
In the above technical solution, the period of the grating structure is less than the wavelength of the incident light.
With the above technical solutions, the present invention has the following advantages compared with the prior art:
The present invention provides a grating-type color filter, which has a cascade structure composed of a medium grating with the addition of a metal profiling film; meanwhile, a notch is provided in the metal layer covering the groove portion of the grating, making a part of the medium grating layer exposed, thus lowering the angle sensitivity of the resonant output, reducing influence of the incident angle of light on the resonance condition, thereby achieving the filtering effect within a relatively wide range of angle.
The present invention will further be described below with reference to drawings and examples:
In an application, the color filter 300 further includes a medium cover layer 340, which is arranged on the metal profiling film 330 and covers and fills up the grating structure of this medium grating layer 320.
The medium grating layer 320 and the substrate 310 may be of either the same or different materials. The size of the grating structure on this medium grating layer 320 is less than the wavelength of the incident light. Preferably, this medium grating layer 320 is a medium having a high refractive index, and the grating structure on the medium grating layer 320, i.e. the period and spatial frequency, meets the conditions under which the guided-mode resonance can be formed with the frequency of the incident light, thereby making the incident light have a higher transmittance. Taking the most common red light filter, green light filter and blue light filter as an example. Table 1 gives the grating structure under the filter of the three colors of light:
Wherein h1 is the thickness of the medium grating layer 320, h2 is the thickness of the metal profiling film 330, h3 is the thickness of the medium cover layer 340, P is the width of a single period of the medium grating, f is the spatial frequency of the grating structure, and A is the wavelength of the incident light.
It should be noticed that the structure of the metal profiling film 330 in this example is only a structure conducive to the production. In actual applications, this metal profiling film 330 can also have a variety of variant structures, e.g. the metal profiling film can be formed either on both of the two single lateral portions 323 or only on any one of the lateral portions. The metal profiling film 332 on the groove portion 322 can either form an interval with both of the two lateral portions intersected with each other, or form an interval with any one of them, with only a part of the medium grating needing to be exposed, so as to lower the angle sensitivity of the resonance.
Furthermore, the medium profiling film 420 can be arranged at various positions, e.g. at the ridge portion 421 of the medium grating layer 420, on the single lateral portion 423′ (or 423″) and the groove portion 422, on the ridge portion 421 and the single lateral portion 423′ (or 423″), on the ridge portion 421 and the groove portion 422, or on the ridge portion 421, the bilateral portion 423 and the groove portion 422.
While for the metal profiling film 430, its structure is the same with that in Example 1, and will thus not be described here in detail.
The light-transmitting properties of the color filter in this embodiment will be given below by taking the filter of the three colors of light, red, green and blue, as an example. Table 2 gives the grating structure under the filter of the three colors of light.
Wherein h4 is the thickness of the medium grating layer 420, h5 is the thickness of the medium profiling film 450, h6 is the thickness of the metal profiling film 430, h7 is the thickness of the medium cover layer 440, P′ is the width of a single period of the medium grating, f′ is the spatial frequency of the grating structure, and λ′ is the wavelength of the incident light.
For the green light filter in Example 1, the width ratio f2 of the metal film 332 to the groove portion 322 is defined, i.e. f2 refers to the coverage rate of the metal profiling film; for the coverage rate f2 of the metal film 332 in the groove portion 322 increased from 0.2 to 1, the corresponding transmission spectrum is as shown in
For the incident angle changing from 0 degree to 50 degrees, the transmission spectrum is as shown in
For the green light filter in Example 1, when the thickness h2 of the metal profiling film 330 changes in the range of 0.01-0.16 μm, the corresponding transmission spectrum is shown in
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/CN2010/079905 | 12/16/2010 | WO | 00 | 11/25/2013 |