CN114019598A

CN114019598A - Optical filter, preparation method thereof and camera module

Info

Publication number: CN114019598A
Application number: CN202111240236.9A
Authority: CN
Inventors: 李俊峰; 高晶
Original assignee: Kunshan Q Technology Co Ltd
Current assignee: Kunshan Q Technology Co Ltd
Priority date: 2021-10-25
Filing date: 2021-10-25
Publication date: 2022-02-08
Anticipated expiration: 2041-10-25
Also published as: CN114019598B

Abstract

The application discloses optical filter and preparation method, module of making a video recording thereof, this optical filter includes: the filter comprises a filter body and a black film. The black film is distributed on the infrared cut-off surface of the optical filter body and used for absorbing large-angle incident light rays incident to the edge of the lens, the black film comprises an antireflection layer and a light absorption layer which are stacked, and the light absorption layer is made of black solid materials. Therefore, the reflectivity of the light shielding layer can be effectively reduced, the problem of flare caused by reflected light of the light shielding layer is solved, and the imaging quality of the camera module is improved.

Description

Optical filter, preparation method thereof and camera module

Technical Field

The application relates to the technical field of camera shooting, in particular to an optical filter, a manufacturing method thereof and a camera shooting module.

Background

At present, intelligent equipment with a camera shooting function, such as a smart phone, has become an indispensable electronic product in people's life, and the imaging requirement on a camera shooting module is higher and higher. The optical filter is an indispensable component in the camera module. In order to reduce the influence of stray light and improve the imaging quality, a light shielding layer is usually silk-screened in the peripheral edge region of the optical filter to absorb the large-angle incident light incident to the edge of the lens.

However, with the advent of high-pixel and large-size image sensing chips, the Flare (Flare) phenomenon still easily occurs in high-pixel image pickup modules, and the imaging quality of such image pickup modules is difficult to improve.

Disclosure of Invention

The embodiment of the application provides the optical filter, the preparation method of the optical filter and the camera module, and is beneficial to improving the flare problem of the high-pixel camera module, so that the imaging quality of the camera module is improved.

In a first aspect, an embodiment of the present application provides an optical filter, which is applied to a camera module, where the optical filter includes:

a filter body, and

the black film, the black film distribute in the infrared cut-off face of light filter body for absorb the wide-angle incident ray of incidenting the camera lens edge, the black film is including range upon range of antireflection layer and the light absorption layer that sets up, the light absorption layer is black solid material.

Further, the black solid material is a metal material and/or a metal oxide which presents black, and the transmittance of the light absorption layer is more than 95%.

Further, the antireflection layer with the light absorption layer is provided with the multilayer respectively, the antireflection layer with the light absorption layer is the setting of piling up in turn.

Further, the antireflection layer is formed by alternately stacking high-refractive-index material layers and low-refractive-index material layers.

Further, the high-refractive-index material is titanium dioxide or titanium pentoxide, and the low-refractive-index material is silicon dioxide.

In a second aspect, an application embodiment provides a method for manufacturing an optical filter, the method including:

forming a filter body;

and forming a black film on the infrared cut-off surface of the optical filter body, wherein the black film is used for absorbing large-angle incident light rays incident to the edge of the lens, the black film comprises an antireflection layer and a black light absorption layer which are stacked, and the light absorption layer is a black solid material.

Further, the forming of the black film on the infrared cut surface of the filter body includes:

forming a photoresist layer on the infrared cut-off surface of the optical filter body;

exposing and developing the photoresist layer;

and alternately forming the stacked antireflection layer and the light absorption layer on the surface of the developed photoresist layer, and carrying out photoresist removing treatment to form the black film.

Further, the antireflection layer is formed by alternately stacking high-refractive-index material layers and low-refractive-index material layers, wherein the high-refractive-index material is titanium dioxide or titanium pentoxide, and the low-refractive-index material is silicon dioxide.

In a third aspect, an embodiment of the present application provides a camera module, including the optical filter of the first aspect.

One or more technical solutions provided in the embodiments of the present application have at least the following technical effects or advantages:

because the black membrane that sets up on the infrared cut-off face (IR face) on the light filter body is including the antireflection layer of range upon range of setting and the light-absorbing layer that has the visible light absorption characteristic to this black membrane is as the light shield layer, can reach the shading effect, absorbs the wide-angle incident light that incides the lens edge promptly, compares in traditional silk screen printing scheme, can also reduce the reflectivity of light shield layer self effectively, thereby improve the flare problem that brings because light shield layer self reverberation, be favorable to improving the imaging quality of the module of making a video recording.

In addition, because the light absorption layer is a black solid material, the antireflection layer and the light absorption layer can be processed by the same coating process, such as a sputtering coating process, so that the preparation efficiency of the black film is improved, and the processing efficiency of the optical filter is improved.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on the drawings without creative efforts.

Fig. 1 is a schematic structural diagram of a camera module according to an embodiment of the present disclosure;

fig. 2 is an exemplary cross-sectional view of an optical filter provided in a first aspect of an embodiment of the present disclosure;

fig. 3 is an exemplary top view of an optical filter provided in a first aspect of an embodiment of the present disclosure;

fig. 4 is a flowchart illustrating steps of a method for manufacturing an optical filter according to a second aspect of an embodiment of the present disclosure;

fig. 5 is a schematic view of a paste application in a method for manufacturing an optical filter according to a second aspect of the embodiment of the present application;

fig. 6 is a schematic diagram of development in a method for manufacturing an optical filter according to a second aspect of the embodiments of the present application;

FIG. 7 is a schematic diagram of a black coating film in a method for manufacturing an optical filter according to a second aspect of the embodiment of the present application;

FIG. 8 is a schematic diagram of the real-time photographing effect of the camera module assembled before the improvement of the optical filter;

fig. 9 is a schematic diagram of the real-time shooting effect of the camera module assembled after the filter is improved.

Detailed Description

Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. It should be understood that the description is illustrative only and is not intended to limit the scope of the present disclosure. Moreover, in the following description, descriptions of well-known structures and techniques are omitted so as to not unnecessarily obscure the concepts of the present disclosure.

Various structural schematics according to embodiments of the present disclosure are shown in the figures. The figures are not drawn to scale, wherein certain details are exaggerated and possibly omitted for clarity of presentation. The shapes of various regions, layers, and relative sizes and positional relationships therebetween shown in the drawings are merely exemplary, and deviations may occur in practice due to manufacturing tolerances or technical limitations, and a person skilled in the art may additionally design regions/layers having different shapes, sizes, relative positions, as actually required.

In the context of the present disclosure, when a layer/element is referred to as being "on" another layer/element, it can be directly on the other layer/element or intervening layers/elements may be present. In addition, if a layer/element is "on" another layer/element in one orientation, then that layer/element may be "under" the other layer/element when the orientation is reversed.

Aiming at the problem that the imaging quality of the high-pixel camera module is difficult to improve due to the fact that the high-pixel camera module still easily has a Flare (Flare) phenomenon, the inventor conducts long-term research and finds that the reflectivity of the silk screen also influences the generation of stray light. The traditional screen printing scheme usually adopts an ink printing mode, the shading layer is made of ink, the average reflectivity is usually 2% -3%, and the screen printing method can be suitable for camera modules with lower pixels such as 4800 ten thousand pixels. However, with the appearance of higher pixels and large-size image sensing chips, the size of the optical filter is also larger and larger, the area of a light shielding layer in the optical filter also needs to be correspondingly increased, so that reflected light of the silk screen cannot be ignored, even the Flare problem can be caused, and the imaging quality of the camera module is not guaranteed.

Based on the discovery, the embodiment of the application provides an optical filter, a manufacturing method thereof and a camera module, wherein a black film arranged on an infrared cut-off surface (IR surface) of an optical filter body comprises an anti-reflection layer and a light absorption layer with visible light absorption characteristics, which are arranged in a stacked manner, and the black film is used as a light shielding layer, so that the light shielding effect can be achieved, namely, large-angle incident light rays incident to the edge of a lens are absorbed, and compared with the traditional silk-screen scheme, the reflectivity of the light shielding layer can be effectively reduced, the problem of flare caused by reflected light of the light shielding layer is solved, and the imaging quality of the camera module is improved.

In addition, in order to facilitate understanding of the technical solutions provided in the embodiments of the present application, a basic structure of the camera module is briefly introduced first. As shown in fig. 1, the camera module 1 includes a lens 20, an optical filter 10, an image sensing chip 30, a chip driving circuit board 40, and a holder 50 for holding the lens. The optical filter 10 is disposed between the lens 20 and the image sensing chip 30, and light incident from the lens 20 enters the image sensing chip 30 through the optical filter 10. The filter 10 is an infrared cut filter, an infrared cut surface (i.e., an IR surface) of the filter 10 faces the lens 20, and an anti-reflection surface (i.e., an AR surface) of the filter 10 faces the image sensor chip 30.

The following respectively describes the optical filter, the optical filter manufacturing method, and the camera module provided in the embodiments of the present application in detail. It should be understood that the specific features in the embodiments and examples of the present application are detailed description of the technical solutions in the embodiments of the present application, and are not limited to the technical solutions in the present application, and the technical features in the embodiments and examples of the present application may be combined with each other without conflict.

In a first aspect, an embodiment of the present application provides an optical filter, which is applied to a camera module. As shown in fig. 2, the optical filter 10 includes: a filter body 100 and a black film 110.

The filter body 100 includes a substrate 101 and an infrared cut film 102 disposed on a first surface of the substrate 101. Further, an antireflection film 103 disposed on the second surface of the substrate 101 may be further included. In particular implementations, the substrate 101 may be Blue Glass (BG) or other glass.

The black film 110 is used as a light shielding layer of the optical filter 10 and is distributed on the IR surface of the optical filter body 100 to prevent large-angle light from being incident on the surface of a gold wire connecting the image sensing chip and the circuit board or on the inner wall of the bracket to generate stray light. As shown in fig. 3, the black film 110 may be distributed in a ring shape, for example, a square ring (such as the diagonal filled area in fig. 3) or may be distributed in other shapes in the edge area of the IR surface. Therefore, the large-angle incident light rays incident to the edge of the lens can be incident to the black film 110 to be absorbed, and the small-angle incident light rays incident to the middle area 120 of the optical filter 10 can normally pass through the optical filter 10 to be imaged on the image sensor.

Specifically, as shown in fig. 2, the black film 110 includes an antireflection layer 111 and a light absorbing layer 112, which are stacked, and the light absorbing layer 112 is a black solid material. It should be noted that the number of layers and the lamination relationship of the antireflection layer 111 and the light absorbing layer 112 in the black film 110 shown in fig. 2 are only illustrative, and the lamination order may be determined according to different spectral specifications.

In an alternative embodiment, the anti-reflection layer 111 and the light absorbing layer 112 are respectively provided with a plurality of layers, and the plurality of anti-reflection layers 111 and the plurality of light absorbing layers 112 are alternately stacked. For example, an antireflection layer a1, a light absorbing layer B1, an antireflection layer a2, light absorbing layers B2, … …, a light absorbing layer B may be alternately laminated in this order on the IR surface of the filter body 100_mAnd an antireflection layer A_n. In specific implementation, the number of layers of the antireflection layer 111 and the light absorption layer 112 can be determined according to different spectral specifications, with the aim of achieving a better light absorption effect and a lower reflectivity of the finally formed black film 110.

The antireflection layer 111 is also called an antireflection layer, and may be made of a material with a low refractive index or may be made of multiple materials to achieve an antireflection effect. In an alternative embodiment, the anti-reflection layer 111 may be formed by alternately stacking high refractive index material layers and low refractive index material layers. For example, titanium oxide such as titanium dioxide or titanium pentoxide may be used as the high refractive index material, and silicon dioxide may be used as the low refractive index material. In view of better bonding to the surface of the substrate 101, a silicon oxide layer may be formed on the IR surface and then a titanium oxide layer may be formed on the silicon oxide layer. Compared with a single-layer film, the antireflection layer 111 formed by combining the silicon dioxide layer and the titanium oxide layer can achieve a better antireflection effect, and the thickness of each specific material layer can be set according to multiple tests. Of course, in other embodiments of the present application, other suitable materials may be used to form the antireflection layer 111, which is not limited herein.

In an alternative embodiment, the black solid material used for the light absorbing layer 112 may be a metal material and/or a metal oxide that exhibits black color, and the transmittance may be greater than 95%, which is advantageous for reducing the reflectance from the light absorbing layer 112 itself from the material level. And because the light absorbing layer 112 is a black solid material, the antireflection layer 111 and the light absorbing layer 112 can be processed by the same coating process, such as a sputtering coating process, which is beneficial to improving the preparation efficiency of the black film 110, thereby improving the processing efficiency of the optical filter 10. For example, a metal material that is processed to have a black color may be used as the black solid material. For example, it may be an electrophoretic process treatment or an oxidation treatment. For example, magnesium is black after oxidation.

Because the anti-reflection layer 111 and the black light absorption layer 112 enable the whole black film 110 to be black, the black film 110 has a visible light absorption characteristic and can achieve a low reflectivity, the problem of flare caused by the reflected light of the light shielding layer is solved, and the imaging quality of the camera module is improved.

In a second aspect, an embodiment of the present application further provides a method for manufacturing an optical filter 10, which is used to manufacture the optical filter 10 according to the first aspect. As shown in fig. 4, the method includes:

step S401, forming a filter body;

step S402, forming a black film on the infrared cut-off surface of the optical filter body, wherein the black film is used for absorbing large-angle incident light rays incident to the edge of the lens, the black film comprises an antireflection layer and a black light absorption layer which are arranged in a stacked mode, and the light absorption layer is made of black solid materials.

It is understood that in the specific production of the optical filter 10, the large-sized optical filter 10 is generally formed and then cut. Therefore, after step S402 is completed, the filter body 100, i.e., the middle sheet, which has been coated with the black coating film 110, needs to be cut into small pieces and then assembled for use.

Specifically, the filter body 100 having the infrared cut function may be formed by polishing a substrate 101 such as Blue Glass (BG) or other glass, then plating an infrared cut film 102 on a first surface of the polished substrate 101 and plating an anti-reflection film 103 on a second surface of the substrate 101 through a plating process. In specific implementation, the working band specification of the filter body 100 may be determined according to an actual application scenario.

Further, in an alternative embodiment, a mask may be formed on the IR surface of the filter body 100 through a photolithography process, so as to implement the black coating 110 on the IR surface of the filter body 100 in an area that needs to cover the light shielding layer. Of course, in other embodiments of the present application, other manufacturing processes may be used, for example, a nano-imprinting process may also be used, and is not limited herein.

Specifically, as shown in fig. 5, a photoresist layer 400 may be formed on the IR surface of the filter body 100; the photoresist layer 400 is then exposed and developed to form a patterned mask 401, as shown in fig. 6. The mask 401 pattern is set according to the shape and size of the light shielding layer coverage area of the optical filter 10 in the actual application scenario. For example, the light-shielding layer covers the region in a ring shape, and the mask 401 exhibits a corresponding pattern. As shown in fig. 6, after development, the region of the IR surface of the filter body 100 that needs to be covered with the light shielding layer is exposed, and the region that needs to be transparent is covered with the mask 401. Further, as shown in fig. 7, the stacked antireflection layer 111 and light absorbing layer 112 are alternately formed on the IR surface covered with the mask 401, and then a photoresist removing process is performed, so that the patterned black film 110 can be formed on the IR surface of the filter body 100, as shown in fig. 2. It should be noted that the number of film layers and the lamination relationship of the antireflection layer 111 and the light absorbing layer 112 shown in fig. 7 are merely illustrative, and the number and the sequence of lamination may be determined according to different spectral specifications.

For example, the stacked antireflection layer 111 and light absorbing layer 112 may be alternately formed on the IR surface covered with the mask 401 by a spin coating process. The spin coating process is simple to realize, and the thickness of the film layer is uniform.

Alternatively, the stacked antireflection layer 111 and light absorbing layer 112 may be alternately formed on the IR surface covered with the mask 401 by a sputtering coating process. For example, a target related to the anti-reflection layer 111 and a target related to the light absorption layer 112 may be placed in a sputtering coating apparatus, and corresponding film layers may be formed on the IR surface covered with the mask 401 alternately as needed.

The antireflection layer 111 and the light absorption layer 112 are processed by the same coating process, which is beneficial to improving the preparation efficiency of the black film 110, thereby improving the processing efficiency of the optical filter 10.

In an alternative embodiment, the anti-reflection layer 111 may be formed by alternately stacking high refractive index material layers and low refractive index material layers. For example, titanium oxide such as titanium dioxide or titanium pentoxide may be used as the high refractive index material, and silicon dioxide may be used as the low refractive index material, and in this case, if a sputtering coating process is used, the target material of the anti-reflection layer 111 includes a titanium oxide target material and a silicon dioxide target material. In view of better bonding to the surface of the substrate 101, a silicon oxide layer may be formed on the IR surface and then a titanium oxide layer may be formed on the silicon oxide layer. Compared with a single-layer film, the antireflection layer 111 formed by combining the silicon dioxide layer and the titanium oxide layer can achieve a better antireflection effect, and the thickness of each specific material layer can be set according to multiple tests. Of course, in other embodiments of the present application, other suitable materials may be used to form the antireflection layer 111, which is not limited herein.

In an alternative embodiment, the black solid material used for the light absorbing layer 112 may be a metal and/or metal oxide that exhibits black color, and the transmittance may be greater than 95%, which is advantageous for reducing the reflectance from the light absorbing layer 112 itself from the material level. For example, magnesium may be used as the black solid material, and it is understood that magnesium is oxidized in air to be black, and in this case, if a sputtering coating process is used, the target material of the light absorbing layer 112 is a black magnesium target material.

In an alternative embodiment, in the step of plating the black film 110, the plurality of anti-reflection layers 111 and the plurality of light absorption layers 112 may be alternately plated to form the black film 110. For example, an anti-reflection layer a1, a light absorbing layer B1, an anti-reflection layer a2, light absorbing layers B2, … …, and a light absorbing layer B may be alternately laminated in this order on the IR surface of the filter body 100_mAnd an antireflection layer A_n. In specific implementation, the number of layers of the antireflection layer 111 and the light absorption layer 112 can be determined according to different spectral specifications, with the aim of achieving a better light absorption effect and a lower reflectivity of the finally formed black film 110.

For example, in an application scenario, the antireflection layer 111 includes a silicon dioxide layer and a titanium oxide layer, and the light absorption layer 112 is a black metal material layer, and if a sputtering coating process is adopted for coating, a total of 10 silicon dioxide layers, 12 to 18 titanium oxide layers, and 5 black metal material layers may be coated, so as to finally form the black film 110.

In addition, in order to verify the flare improvement effect of the optical filter 10 formed in the embodiment of the present application, the black film 110 formed by the photolithography process was compared with each parameter of the ink light-shielding layer formed by the screen printing process. The comparison results are shown in table 1, and the pattern accuracy, minimum line width, and alignment accuracy of the photolithography process are superior to those of the screen printing process. It is worth noting that compared with the traditional silk-screen printing ink shading layer, the black film 110 formed by the embodiment of the application is used as the shading layer, and the maximum reflectivity R is achieved under the wave band of 380-780 nm_maxUpper limit value and average reflectance R of_aveThe upper limit value of (2) is significantly reduced, so that the intensity of reflected light from the light-shielding layer itself can be effectively reduced, thereby improving the problem of flare due to reflected light from the light-shielding layer itself.

TABLE 1

In addition, the inventors also performed comparative experiments. The following two sets of samples were prepared separately: the first set of test samples: preparing an optical filter by using screen printing ink as a shading layer, and assembling the optical filter to a camera module; second set of test samples: the optical filter 10 is prepared and assembled to the camera module by using the black film 110 prepared through the processes of gluing → exposing → developing → black film plating → photoresist stripping as a light shielding layer. It should be noted that the other components and manufacturing processes of the two sets of test samples are the same except that the material and manufacturing process of the light shielding layer on the optical filter are different. The two groups of test samples were photographed in a dark room, respectively. The first set of test specimens was taken as shown in fig. 8, and the second set of test specimens was taken as shown in fig. 9. By contrast, it can be seen that there is significant flare in the oval dashed box mark portion in the image shown in fig. 8. Whereas the flare at the corresponding position in fig. 9 is significantly improved.

In a third aspect, based on the same inventive concept, an embodiment of the present application further provides a camera module, where the camera module includes the optical filter 10 according to the first aspect. The specific structure and effect of the optical filter 10 can refer to the corresponding content in the embodiments provided in the foregoing first aspect, and are not described herein again.

Of course, as shown in fig. 1, the camera module includes, in addition to the filter 10 described in the above first aspect, other components, such as a lens 20, an image sensing chip 30, a chip driving circuit board 40, and a bracket 50 for supporting the lens 20, and specifically, reference may be made to the structure of the existing camera module, which is not described in detail herein.

Since the optical filter 10 included in the image capturing module described in the embodiment of the present application is described above, all image capturing modules including the optical filter 10 in the embodiment of the present application belong to the protection scope of the present application.

The technical scheme in the embodiment of the application at least has the following technical effects or advantages:

because the black film 110 arranged on the infrared cut-off surface (IR surface) of the optical filter body 100 comprises the anti-reflection layer 111 and the light absorption layer 112 with visible light absorption characteristics, and the black film 110 is used as a light shielding layer, the black film can achieve the light shielding effect, namely, the black film can absorb the incident light rays with large angles at the edge of the lens, and compared with the traditional silk-screen scheme, the black film can also effectively reduce the reflectivity of the light shielding layer, thereby improving the flare problem caused by the reflected light of the light shielding layer and being beneficial to improving the imaging quality of the camera module.

In the above description, technical details such as patterning of each layer are not described in detail. It will be appreciated by those skilled in the art that layers, regions, etc. of the desired shape may be formed by various technical means. In addition, in order to form the same structure, those skilled in the art can also design a method which is not exactly the same as the method described above. In addition, although the embodiments are described separately above, this does not mean that the measures in the embodiments cannot be used in advantageous combination. Moreover, the same and similar parts between the various embodiments can be referred to each other.

While the preferred embodiments of the present application have been described, additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. Therefore, it is intended that the appended claims be interpreted as including preferred embodiments and all alterations and modifications as fall within the scope of the application.

It will be apparent to those skilled in the art that various changes and modifications may be made in the present application without departing from the spirit and scope of the application. Thus, if such modifications and variations of the present application fall within the scope of the claims of the present application and their equivalents, the present application is intended to include such modifications and variations as well.

Claims

1. The utility model provides an optical filter, its characterized in that is applied to the module of making a video recording, the optical filter includes:

a filter body, and

2. The optical filter according to claim 1, wherein the black solid material is a metal material and/or a metal oxide exhibiting a black color, and the light absorbing layer has a transmittance of more than 95%.

3. The optical filter according to claim 1, wherein the anti-reflection layer and the light absorption layer are respectively provided with a plurality of layers, and the anti-reflection layer and the light absorption layer are alternately stacked.

4. The filter of claim 1, wherein the anti-reflection layer is formed by alternately stacking high refractive index material layers and low refractive index material layers.

5. The filter according to claim 4, wherein the high refractive index material is titanium dioxide or titanium pentoxide, and the low refractive index material is silicon dioxide.

6. A method of manufacturing an optical filter, the method comprising:

forming a filter body;

7. The method of claim 6, wherein forming a black film on an infrared cut surface of the filter body comprises:

exposing and developing the photoresist layer;

8. The method of claim 6, wherein the antireflection layer is formed by alternately stacking high refractive index material layers and low refractive index material layers, the high refractive index material is titanium dioxide or titanium pentoxide, and the low refractive index material is silicon dioxide.

9. The method of claim 6, wherein the black solid material is a metal material and/or a metal oxide exhibiting a black color, and the light absorbing layer has a transmittance of more than 95%.

10. A camera module, characterized in that it comprises the optical filter according to any one of claims 1 to 5.