TWI629542B - Optical film - Google Patents

Abstract

The invention relates to an optical film including a first diffraction structure layer, a second diffraction structure layer and a cover layer. A surface of the first diffraction structure layer has a plurality of first diffraction gratings arranged in the same direction, the second diffraction structure layer fills the gaps of the first diffraction gratings of the first diffraction structure layer, and A second diffraction grating having a plurality of co-directional arrangements is formed on the first diffraction structure layer, the arrangement directions of the first diffraction grating and the second diffraction grating are parallel to each other, and the cover layer is filled and flat By optimizing the second diffraction gratings of the second diffractive structure layer, the optical film can reduce the light leakage defect of the conventional liquid crystal display at a large viewing angle, so that the liquid crystal display has a uniform dark state picture and color image quality at each viewing angle.

Description

Optical film

The invention relates to an optical film used for a liquid crystal display, which has the effects of reducing the large-vision role deviation and dark state light leakage, and increasing the color of each viewing angle and the uniformity of the dark state picture.

The current liquid crystal display (LCD) is a non-self-luminous display, and the backlight is easily affected by the asymmetry of liquid crystal molecules after passing through the liquid crystal panel, so that the image quality of the positive viewing angle and the large viewing angle has a large drop.

Especially when displaying a black screen, the backlight of the conventional LCD display cannot be turned off, and only the dark state is switched by the liquid crystal panel. Therefore, there are different levels of light leakage at various viewing angles, which makes the screen contrast and The color varies with the viewing angle, which may cause color shift or unevenness. Please refer to Figure 1, which is a distribution diagram of the dark state brightness of the conventional liquid crystal display with the horizontal viewing angle. The degree is the smallest. Therefore, when viewing the LCD at different angles, the user can easily feel the drop in image quality, which affects the visual experience.

Therefore, the inventor of the present invention proposes an optical film, which can improve the light leakage of a large viewing angle of a liquid crystal display, improve the uniformity of dark images at different viewing angles, and reduce the color shift phenomenon.

In view of the above-mentioned problems of the prior art, the object of the present invention is to provide an optical film with patent requirements such as novelty, progress, and industrial applicability, in order to overcome the difficulties of existing products.

To achieve the above object, the present invention provides an optical film. In a preferred embodiment, the optical film includes a first diffractive structure layer having opposite upper and lower surfaces, and the upper surface has a plurality of same directions An array of first diffraction gratings; a second diffraction structure layer, the second diffraction structure layer filling the gaps of the first diffraction gratings of the first diffraction structure layer, and in the first diffraction A second diffraction grating having a plurality of co-directional arrangements is formed on the structural layer, wherein the arrangement directions of the first diffraction grating and the second diffraction grating are parallel to each other; and a cover layer is filled and flat The second diffraction gratings of the second diffraction structure layer.

In an optical film of an embodiment, the first diffraction structure layer has a first refractive index n1, the second diffraction structure layer has a second refractive index n2, and the cover layer has a third refractive index n3, And the range of n1, n2, n3 is between 1.4 and 1.7.

In the optical film of another embodiment, the second refractive index n2 is greater than the first refractive index n1 and the third refractive index n3.

In the optical film of another embodiment, the first refractive index n1 and the third refractive index n3 are the same or different.

In the optical film of another embodiment, each grating width w1 of the first diffraction grating and each grating width w2 of the second diffraction grating are each between 0.3 μm and 1.5 μm.

In the optical film of another embodiment, each grating depth d1 of the first diffraction grating and each grating depth d2 of the second diffraction grating are each between 0.5 μm and 1.5 μm.

In the optical film of another embodiment, the grating pitch g1 of the first diffraction grating and the grating pitch g2 of the second diffraction grating are each between 0.3 μm and 1.5 μm.

In the optical film of another embodiment, the grating width, the grating depth, and the grating pitch of the first diffraction grating and the second diffraction grating are the same or different.

In an optical film of another embodiment, the optical film further includes a functional layer disposed on the lower surface of the first diffractive structure layer of the optical film, wherein the functional layer is selected from a polarizing layer, a hard coating layer, Low reflection layer, anti-reflection layer, anti-glare layer, protective layer or a combination thereof. .

1.11‧‧‧Optical film

2‧‧‧The first diffraction structure layer

2a‧‧‧First diffraction grating

3‧‧‧Second diffraction structure layer

3a‧‧‧Second diffraction grating

4‧‧‧overlay

6‧‧‧Functional layer

w1, w2‧‧‧ grating width

d1, d2‧‧‧ grating depth

g1, g2‧‧‧ grating pitch

Figure 1: It is a distribution diagram of the dark state brightness of the conventional liquid crystal display with the horizontal viewing angle.

FIG. 2A is a perspective perspective view of an optical film according to an embodiment of the invention.

Figure 2B is a schematic cross-sectional view of the optical film shown in Figure 2A.

FIG. 3 is a schematic cross-sectional view of a first diffraction structure layer and a second diffraction structure layer of an optical film according to an embodiment of the invention.

Fig. 4 is a perspective perspective view of an optical film according to another embodiment of the invention.

In order to make the invention features, contents, advantages and achievable effects easier to understand, the present invention is described in detail in conjunction with the drawings and in the form of expressions of the embodiments, and the drawings used therein have the main purpose It is only for illustration and auxiliary description, and may not be the true scale and precise configuration after the implementation of the present invention, so it should not be interpreted and limited to the relationship between the scale and configuration of the attached drawings, and the scope of the present invention in practical implementation is limited. First clarify.

The embodiments of the optical film according to the present invention will be described below with reference to related drawings, For ease of understanding, the same elements in the following embodiments are described with the same symbols.

Please refer to FIG. 2A and FIG. 2B. The present invention provides an optical film 1. In a preferred embodiment, the optical film 1 includes a first diffractive structure layer 2 having opposite upper, A lower surface (not shown), and the upper surface has a plurality of first diffraction gratings 2a arranged in the same direction; a second diffraction structure layer 3, the second diffraction structure layer 3 is filled in the first diffraction structure layer 2 the gaps of the first diffraction gratings 2a, and a second diffraction grating 3a having a plurality of co-directional arrangements is formed on the first diffraction structure layer 2, wherein the first diffraction gratings 2a and The arrangement directions of the second diffraction gratings 3a are parallel to each other; and a cover layer 4 fills and planarizes the second diffraction gratings 3a of the second diffraction structure layer 3.

In the optical film of another embodiment, the first diffraction structure layer 2 has a first refractive index n1, the second diffraction structure layer 3 has a second refractive index n2, and the cover layer 4 has a third refractive index n2 The refractive index n3, and the range of n1, n2, n3 is between 1.4 and 1.7. The materials used for the first diffractive structure layer 2, the second diffractive structure layer 3 and the cover layer 4 can be selected from thermosetting or photocuring resins, such as acrylic resin, silicone resin, polyurethane resin (polyurethane resin), epoxy resin (epoxy resin) or a combination thereof.

In the optical film of another embodiment, the second refractive index n2 is greater than the first refractive index n1 and the third refractive index n3, the first refractive index n1 and the third refractive index n3 are the same or different, therefore, The adjacent two sides of the interface between the first diffraction structure layer 2, the second diffraction structure layer 3 and the cover layer 4 may have different refractive indexes, wherein the second diffraction structure layer 3 and the first diffraction structure layer 2 or The difference in refractive index of the cover layer 4 is preferably between 0.1 and 0.3.

The microstructure sizes of the first diffraction structure layer 2 and the second diffraction structure layer 3 can be adjusted according to the pixel size of the display. Please refer to FIG. 3, which is the first winding A schematic cross-sectional view of the diffractive structure layer 2 and the second diffractive structure layer 3. In the optical film of another embodiment, each grating width w1 of the first diffraction grating 2a and each grating width of the second diffraction grating 3a w2 is each between 0.3 μm and 1.5 μm; each grating depth d1 of the first diffraction grating 2 a and each grating depth d2 of the second diffraction grating 3 a are each between 0.5 μm and 1.5 μm; the first winding The grating pitch g1 of the radiating grating and the grating pitch g2 of the second diffractive grating are each between 0.3 μm and 1.5 μm.

In the optical film of another embodiment, the grating width w1, the grating depth d1, the grating pitch g1 of the first diffraction grating 2a and the grating width w2, the grating depth d2, and the grating pitch g2 of the second diffraction grating 3a are mutually The lines are the same or different.

Please refer to FIG. 4. In the optical film 14 of another embodiment, the optical film 14 further includes a functional layer 6 disposed on the lower surface of the first diffraction structure layer 2 of the optical film 14, wherein the function The layer 6 is selected from one or a combination of a polarizing layer, a hard coat layer, a low reflection layer, an anti-reflection layer, an anti-glare layer, and a protective layer.

Next, through various embodiments of the present invention, the effect of the optical film of the present invention to improve the dark state and image quality of a liquid crystal display at a large viewing angle is improved. Table 1 is the size setting 1 of the grating structure used in the optical film of the present invention; Table 2 is the size setting 2 of the grating structure used in the optical film of the present invention, and these size structures are continuously filled with repeating units and formed in the first The diffraction structure layer or the second diffraction structure layer. The refractive index of the resin material used in the second diffraction structure layer is 1.6, and the refractive index of the resin material used in the first diffraction structure layer and the cover layer is 1.5.

Please refer to Table 3 again, which is the optical test data conducted by using a liquid crystal display (model: BenQ GW2270). The comparative example is the liquid crystal display to which the optical film of the present invention is not attached. Examples 1 and 2 are different examples of the optical film to which the liquid crystal display is attached. Among them, the optical film used in the first embodiment has the first The first diffraction grating of the diffractive structure layer adopts a size setting of one, and the second diffraction grating of the second diffractive structure layer adopts a size setting of two. The optical film used in the second embodiment has the first diffraction structure layer The first diffraction grating adopts size setting two, and the second diffraction grating of the second diffraction structure layer adopts size setting two.

It can be seen from Table 3 that in the dark state brightness maximum (L0 _max ) test item when the tone is zero, both the first embodiment and the second embodiment are smaller than the test value of the comparative example 0.703nits, which means that the invention is attached After the optical film, it can effectively reduce the dark state light leakage of the conventional liquid crystal display at a large viewing angle, so that the dark state picture presented at different angles is more consistent, and the maximum value of the dark state brightness at zero order occurs the viewing angle (L0 _max angle ) In the test project, Example 1 and Example 2 are 46 degrees and 65 degrees, respectively. Compared with the comparative example, the maximum dark state brightness occurs at a viewing angle of 44 degrees. It can be seen that the optical film of the present invention not only reduces dark light leakage at large viewing angles, It can also delay the angle of view of the occurrence of large light leakage in the dark state. For large viewing angles, such as color saturation, contrast, and color accuracy, GDI (Gamma Distortion Index) and P-value can be used as evaluation indicators in LCD monitors. GDI is the actual measurement of all levels. The distortion value of the gamma curve adjusted from L0 to L255 compared with the standard gamma curve (such as gamma 2.2). Therefore, the lower the value, the less the amount of distortion, and the better the quality of the large viewing angle; and P-value is for LCD monitors are generally prone to defects. The difference between the measured value and the standard gamma curve value L96 is different. The lower the value, the less the deviation. Therefore, you can quickly see whether the viewing angle is poor. It can also be seen from Table 3 that the average GDI value (GDI _avg. ) In the horizontal viewing angle 60 ° to 80 °, the average P-value (P-value _avg. ) In the horizontal viewing angle 60 ° to 80 °, and a single horizontal direction In the test items of P-value _(0,60) with a viewing angle of 60 ° and P-value _{(0,80 )} with a single horizontal viewing angle of 80 °, the test values of Example 1 and Example 2 are both smaller than the comparative examples, which represent the invention The examples have obvious improvement effect.

The above-mentioned embodiments are only to illustrate the technical ideas and features of the present invention, and its purpose is to enable those skilled in the art to understand the content of the present invention and implement it accordingly, but cannot limit the patent scope of the present invention, That is to say, any equivalent changes or modifications made according to the spirit disclosed by the present invention should still be covered by the patent scope of the present invention. .

Claims (9)

An optical film comprising: a first diffraction structure layer having opposite upper and lower surfaces, and the upper surface having a plurality of first diffraction gratings arranged in the same direction; a second diffraction structure layer, the second The diffractive structure layer fills the gap of the first diffractive structure layer, and a second diffractive grating having a plurality of co-directional arrangements is formed on the first diffractive gratings of the first diffractive structure layer, wherein, the The alignment directions of the first diffraction grating and the second diffraction grating are parallel to each other; and a cover layer that fills and planarizes the second diffraction gratings of the second diffraction structure layer. The optical film as described in item 1 of the patent application range, wherein the first diffraction structure layer has a first refractive index n1, the second diffraction structure layer has a second refractive index n2, and the cover layer has a first The triple refractive index n3, and the range of n1, n2, n3 is between 1.4 and 1.7. The optical film as described in item 2 of the patent application range, wherein the second refractive index n2 is greater than the first refractive index n1 and the third refractive index n3. The optical film as described in item 2 of the patent application range, wherein the first refractive index n1 and the third refractive index n3 are the same or different. The optical film as described in item 1 of the patent application range, wherein the grating width, the grating depth, and the grating pitch of the first diffraction grating and the second diffraction grating are the same or different. The optical film as described in item 5 of the patent application range, wherein the grating width w1 of each of the first diffraction gratings and the grating width w2 of the each of the second diffraction gratings are each between 0.3 μm and 1.5 μm. The optical film as described in item 5 of the patent application range, wherein the grating depth d1 of each of the first diffraction gratings and the grating depth d2 of each of the second diffraction gratings are each between 0.5 μm and 1.5 μm . The optical film as described in item 5 of the patent application range, wherein the grating pitch g1 between two adjacent first diffraction gratings and the grating pitch g2 between two adjacent second diffraction gratings are each between 0.3 μm to 1.5μm. The optical film as described in item 1 of the patent application scope further includes a functional layer disposed on the lower surface of the first diffractive structure layer of the optical film, wherein the functional layer is selected from the group consisting of polarizing layer and hard coating Layer, low reflection layer, anti-reflection layer, anti-glare layer and protective layer constitute one or a combination thereof.