Protective film, method and device for cutting protective film

Abstract

A protective film, a method (200) and a device (300, 400) for cutting the protective film, which can improve user experience. The protective film has a birefringence effect and is used to be attached to the screen of an electronic device; wherein the fast axis direction of the protective film is parallel to the polarization direction of a first polarizer in the display screen of the electronic device, and the slow axis direction of the protective film is perpendicular to the polarization direction of the first polarizer, or the slow axis direction of the protective film is parallel to the polarization direction of the first polarizer, and the fast axis direction of the protective film is perpendicular to the polarization direction of the first polarizer, or the polarization direction of the first polarizer forms an angle of 45 degrees with the fast axis direction and the slow axis direction of the protective film.

Description

[0001] This application claims priority to the Chinese patent application filed with the State Intellectual Property Office of China on February 13, 2018, with application number 201810150575.X and application name “PROTECTIVE FILM, METHOD AND APPARATUS FOR CUTTING PROTECTIVE FILM”, and the Chinese patent application filed with the State Intellectual Property Office of China on March 1, 2018, with application number 201810170848.7 and application name “PROTECTIVE FILM, METHOD AND APPARATUS FOR CUTTING PROTECTIVE FILM”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application relates to the field of terminals, and more specifically, to a protective film, a method and a device for cutting the protective film in the field of terminals. Background Art

[0003] In recent years, with the development of electronic devices, users have the habit of applying films to protect the screens of electronic devices, such as applying protective films to the screens of electronic devices. However, some protective films have a birefringence effect. When light passes through the protective film, the polarization characteristics of the light will change. For example, during the production process of polyethylene terephthalate (PET) film, the film is formed by extrusion, calendaring, and biaxial stretching. However, biaxial stretching will lead to anisotropy and crystallization, which will produce a birefringence effect. When light passes through the PET film, the polarization characteristics of the light will change, which will affect the operation of the optical sensor in the electronic device to recognize the user, for example, it will affect the optical sensor to recognize the user's fingerprint. Therefore, there is an urgent need for a protective film that has less impact on the electronic device when the protective film is attached to the screen of the electronic device. Summary of the invention

[0004] The embodiments of the present application provide a protective film, a method and a device for cutting the protective film, which can reduce the impact on electronic equipment.

[0005] In a first aspect, a protective film is provided, wherein the protective film has a birefringence effect and is used for being attached to a screen of an electronic device;

[0006] Among them, the fast axis direction of the protective film is parallel to the polarization direction of the first polarizer in the display screen of the electronic device, and the slow axis direction of the protective film is perpendicular to the polarization direction of the first polarizer; or, the slow axis direction of the protective film is parallel to the polarization direction of the first polarizer, and the fast axis direction of the protective film is perpendicular to the polarization direction of the first polarizer; or, the polarization direction of the first polarizer forms an angle of 45 degrees with the fast axis direction and the slow axis direction of the protective film.

[0007] In the embodiment of the present application, if the fast axis direction of the protective film is parallel to the polarization direction of the first polarizer in the display screen, and the slow axis direction of the protective film is perpendicular to the polarization direction of the first polarizer, the slow axis direction of the protective film will not change the polarization direction of the transmitted light, and the polarization direction of the incident light is parallel to the fast axis direction of the protective film. In this way, the polarization state of the incident light will not change when passing through the protective film, thereby reducing the impact of the protective film on the electronic device, which helps to improve the user experience. If the fast axis direction of the protective film is perpendicular to the polarization direction of the first polarizer in the display screen, and the slow axis direction of the protective film is parallel to the polarization direction of the first polarizer, the fast axis direction of the protective film will not change the polarization direction of the incident light, and the polarization direction of the transmitted light is parallel to the slow axis direction of the protective film. In this way, the polarization state of the incident light will not change when passing through the protective film, thereby reducing the impact of the protective film on the electronic device, which helps to improve the user experience. If the polarization direction of the first polarizer is at an angle of 45 degrees to the fast axis direction and slow axis direction of the protective film, the fast axis direction and slow axis direction of the protective film will not change the amplitude of the incident light, thereby reducing the impact of the protective film on the electronic device.

[0008] Optionally, the first polarizer is the polarizer closest to the protective film in the electronic device, or in other words, the first polarizer is the last polarizer that light passes through in the process of reaching the protective film from the light-emitting element of the electronic device.

[0009] Optionally, the protective film may be any protective film having a birefringence effect.

[0010] In some implementations, if the polarization direction of the first polarizer forms an angle of 45 degrees with the fast axis direction and the slow axis direction of the protective film, the thickness of the protective film satisfies the following formula:

[0011] (n fast -n slow )*T=1 / 2*m*λ

[0012] Among them, n fast is the refractive index of the protective film in the fast axis direction, n slow is the refractive index of the protective film in the slow axis direction, T is the thickness of the protective film, m is a positive integer, and λ is the operating wavelength of the optical sensor.

[0013] In some implementations, the electronic device supports under-screen fingerprint recognition.

[0014] In certain implementations, the protective film is a PET film.

[0015] In some implementations, the protective film may be a composite film having a birefringence effect, for example, the composite film may be a composite material film composed of a PET film and a TPU film.

[0016] In a second aspect, a method for cutting a protective film is provided, comprising: detecting the power of the transmitted light which sequentially passes through a second polarizer and a protective film rotating parallel to the second polarizer to reach a third polarizer and passes through the third polarizer, the second polarizer and the third polarizer having the same polarization direction, and the protective film having a birefringence effect; determining a first fast axis direction or a first slow axis direction of the protective film according to the power of the transmitted light; and cutting the protective film according to the first fast axis direction or the first slow axis direction to obtain the cut protective film.

[0017] Therefore, in the embodiment of the present application, the incident light passes through two polarizers with the same polarization direction, and the power of the transmitted light is taken into consideration during the process of cutting the protective film. In this way, when determining the first fast axis direction and the first slow axis direction of the protective film, the directions that have the least impact on the transmitted light can be selected as the fast axis direction and the slow axis direction of the protective film as much as possible, and the protective film can be cut in the first fast axis direction and the first slow axis direction according to the size requirements of the protective film, thereby helping to reduce the impact of the protective film on electronic equipment.

[0018] Optionally, the polarization direction of the second polarizer is the same as the polarization direction of the first polarizer of the electronic device.

[0019] Optionally, the second polarizer is parallel to the third polarizer, and the second polarizer can be projected onto the third polarizer.

[0020] In some implementations, determining the first fast axis direction or the first slow axis direction of the protective film according to the power of the transmitted light includes: determining the fast axis direction of the protective film corresponding to the maximum power of the transmitted light as the first fast axis direction; or determining the slow axis direction of the protective film corresponding to the maximum power of the transmitted light as the first slow axis direction.

[0021] In this way, when determining the cutting direction of the protective film, the fast axis direction of the protective film with the largest transmitted light power is selected as the first fast axis direction, and the slow axis direction of the protective film with the largest transmitted light power is selected as the first slow axis direction. That is, cutting the protective film according to the size requirements of the protective film and the first fast axis direction or the first slow axis direction has the least impact on the electronic device.

[0022] Optionally, the fast axis direction of the protective film corresponding to the larger transmitted light power may be determined as the first fast axis direction of the protective film. Optionally, the slow axis direction of the protective film corresponding to the larger transmitted light power may be determined as the first slow axis direction of the protective film, which is not limited in the present embodiment.

[0023] Optionally, the rotation direction of the protective film can be determined according to the change of the transmitted light power. For example, when the protective film is rotated clockwise, the transmitted light power gradually changes from large to small, and the rotation direction of the protective film can be changed to counterclockwise.

[0024] In some implementations, after determining the first fast axis direction or the first slow axis direction of the protective film, the first fast axis direction is parallel to the polarization direction of the second polarizer, and the first slow axis direction is perpendicular to the polarization direction of the second polarizer, or, the first fast axis direction is perpendicular to the polarization direction of the second polarizer, and the first slow axis direction is parallel to the polarization direction of the second polarizer.

[0025] In some implementations, after determining the first fast axis direction or the first slow axis direction of the protective film,

[0026] The polarization direction of the second polarizer forms an angle of 45 degrees with the first fast axis direction and the first slow axis direction, and the thickness of the cut protective film satisfies the following formula:

[0027] (n fast -n slow )*T=1 / 2*m*λ

[0028] Among them, n fast is the refractive index of the protective film in the fast axis direction, n slow is the refractive index of the protective film in the slow axis direction, T is the thickness of the protective film, m is a positive integer, and λ is the operating wavelength of the optical sensor.

[0029] In some implementations, the cut protective film is used to be affixed to the screen of an electronic device that supports under-screen fingerprint recognition, wherein the polarization direction of the first polarizer and the second polarizer of the display screen in the electronic device is the same.

[0030] In an embodiment of the present application, when the cut protective film is attached to the screen of an electronic device that supports under-screen fingerprint recognition, and the polarization directions of the first polarizer and the second polarizer in the display screen are the same, when the cut protective film is attached to the electronic device, the cut protective film will not affect the fingerprint recognition effect, or the influence of the protective film on the fingerprint recognition effect can be reduced.

[0031] In certain implementations, the protective film is a PET film.

[0032] In some implementations, the protective film may be a composite film having a birefringence effect, for example, the composite film may be a composite material film composed of a PET film and a TPU film.

[0033] According to a third aspect, an electronic device is provided, the electronic device supporting under-screen fingerprint recognition, the screen of the electronic device being adhered with a protective film according to the second aspect or any possible implementation of the second aspect.

[0034] In a fourth aspect, a device for cutting a protective film is provided, comprising: a detection unit, for detecting the power of the transmitted light which passes through the second polarizer and the protective film rotating parallel to the second polarizer to reach the third polarizer, and passes through the third polarizer, the second polarizer and the third polarizer have the same polarization direction, and the protective film has a birefringence effect; a determination unit, for determining the first fast axis direction or the first slow axis direction of the protective film according to the power of the transmitted light; and a cutting unit, for cutting the protective film according to the first fast axis direction or the first slow axis direction to obtain the cut protective film.

[0035] In some implementations, the determination unit is specifically used to: determine the fast axis direction of the protective film corresponding to the maximum transmitted light power as the first fast axis direction; or determine the slow axis direction of the protective film corresponding to the maximum transmitted light power as the first slow axis direction.

[0036] In some implementations, after determining the first fast axis direction or the first slow axis direction of the protective film, the first fast axis direction is parallel to the polarization direction of the second polarizer, and the first slow axis direction is perpendicular to the polarization direction of the second polarizer, or, the first fast axis direction is perpendicular to the polarization direction of the second polarizer, and the first slow axis direction is parallel to the polarization direction of the second polarizer.

[0037] In some implementations, after determining the first fast axis direction or the first slow axis direction of the protective film, the polarization direction of the second polarizer forms an angle of 45 degrees with the first fast axis direction and the first slow axis direction, and the thickness of the protective film after cutting satisfies the following formula:

[0038] (n fast -n slow )*T=1 / 2*m*λ

[0039] Among them, n fast is the refractive index of the protective film in the fast axis direction, n slow is the refractive index of the protective film in the slow axis direction, T is the thickness of the protective film, m is a positive integer, and λ is the operating wavelength of the optical sensor.

[0040] In some implementations, the cut protective film is used to be affixed to the screen of an electronic device that supports under-screen fingerprint recognition, wherein the polarization direction of the first polarizer and the second polarizer of the display screen in the electronic device is the same.

[0041] In certain implementations, the protective film is a PET film.

[0042] In a fifth aspect, a computer-readable storage medium is provided, wherein instructions are stored in the computer-readable storage medium, and when the computer-readable storage medium is executed on a computer, the computer executes the method in the first aspect or any possible implementation manner of the first aspect.

[0043] In a sixth aspect, a computer program product comprising instructions is provided, which, when executed on a computer, enables the computer to execute the method in the first aspect or any possible implementation of the first aspect.

[0044] In a seventh aspect, an electronic device is provided, the electronic device supporting under-screen fingerprint recognition, the touch screen of the electronic device being affixed with a protective film, the protective film comprising a first axis and a second axis, the first axis being perpendicular to the second axis, wherein:

[0045] The first axis of the protective film is parallel to the polarization direction of the first polarizer of the touch display screen of the electronic device, and the second axis of the protective film is perpendicular to the polarization direction of the first polarizer of the display screen of the electronic device, or,

[0046] The second axis of the protective film is parallel to the polarization direction of the first polarizer of the touch display screen of the electronic device, and the first axis of the protective film is perpendicular to the polarization direction of the first polarizer of the touch display screen of the electronic device, or,

[0047] The polarization direction of the first polarizer forms an angle of 45 degrees with the first axis and the second axis of the protective film.

[0048] In some implementations, if the polarization direction of the first polarizer forms an angle of 45 degrees with the first axis and the second axis of the protective film, the thickness of the protective film satisfies the following formula:

[0049] (n fast -n slow )*T=1 / 2*m*λ

[0050] Among them, n fast is the refractive index of the protective film in the fast axis direction, n slow is the refractive index of the protective film in the slow axis direction, T is the thickness of the protective film, m is a positive integer, and λ is the operating wavelength of the optical sensor.

[0051] In certain implementations, the protective film is a polyethylene terephthalate resin PET film.

[0052] In some implementations, the first axis is a fast axis and the second axis is a slow axis.

[0053] In some implementations, the first polarizer of the touch display screen is the last polarizer that the light emitted by the light-emitting element of the electronic device passes through when reaching the protective film.

[0054] In the above implementation, the electronic device may be a mobile phone, a watch or glasses. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Figure 1 It is a schematic diagram of the principle of the under-screen fingerprint recognition technology provided in an embodiment of the present application.

[0056] Figure 2 It is a schematic diagram of an electronic device supporting under-screen fingerprint recognition technology provided by an embodiment of the present application.

[0057] Figure 3 It is a schematic diagram of the polarization direction of the polarizer provided in the embodiment of the present application.

[0058] Figure 4 It is a schematic diagram of a method for cutting a protective film provided in an embodiment of the present application.

[0059] Figure 5 It is a schematic diagram of detecting the power of transmitted light provided in an embodiment of the present application.

[0060] Figure 6 It is a schematic diagram of the protective film provided in an embodiment of the present application being attached to the screen of an electronic device.

[0061] Figure 7 It is a schematic diagram of the optical path when the existing protective film is attached to the mobile phone.

[0062] Figure 8 It is a schematic diagram of the optical path when the protective film provided in an embodiment of the present application is attached to a mobile phone.

[0063] Fig. 9 It is a schematic block diagram of a device for cutting a protective film provided in an embodiment of the present application.

[0064] Fig.10 It is a schematic block diagram of another device for cutting a protective film provided in an embodiment of the present application. DETAILED DESCRIPTION

[0065] The technical solutions in the embodiments of the present application will be described below in conjunction with the accompanying drawings.

[0066] In one possible application scenario, the cut protective film in the embodiment of the present application is used to adhere to the screen of an electronic device that can support under-screen fingerprint recognition technology.

[0067] The principle of under-screen fingerprint recognition technology is described below.

[0068] like Figure 1As shown, the under-screen fingerprint recognition technology includes the following steps: light emitted by the display screen 120 is irradiated to the finger 110; the fingerprint on the finger 110 reflects light; the light 125 reflected by the fingerprint on the finger 110 passes through the light-transmitting gap on the display screen 120, and is projected onto the sensor array 140 under the convergence effect of the lens 130; the sensor 141 of the sensor array 140 converts the optical signal projected onto the sensor 141 into an electrical signal, thereby generating fingerprint data.

[0069] The following describes electronic devices that support under-screen fingerprint recognition technology.

[0070] like Figure 2 As shown, an electronic device supporting under-screen fingerprint recognition technology includes a touch display screen (also called a screen) and an optical sensor module, wherein the optical sensor module is arranged below the touch display screen. Specifically, the touch display screen is parallel or approximately parallel to the plane of the optical sensor. The projection of the optical sensor module on the touch display screen is located in a first area, which is a partial or entire area of ​​the touch display screen. Among them, the touch display screen includes a touch sensing screen module having a touch sensing layer on the top, and a display screen module located under the touch sensing module. The optical sensor module may include: a lens and a sensor array. The optical sensor module is coupled to the display touch display module and is located below it to receive and capture the returned light from the top surface of the touch sensing screen module, and image the returned light onto an optical sensor array of optical sensing pixels or photodetectors. The optical sensor module can convert the optical image in the returned light into a pixel signal for further processing.

[0071] Generally, the display screen module is usually divided into a liquid crystal display (LCD) screen and an organic light-emitting diode (OLED) display screen (also known as an organic laser display (OLED) screen) according to the light emitting principle. In order to control the polarization direction of the light, the LCD screen and the OLED screen will add a polarizer, so the outgoing light of the display screen module has polarization characteristics. With the development of electronic devices, in order to prevent the screen of the electronic device from being contaminated or damaged, the user usually puts a protective film on the screen of the electronic device to protect the screen of the electronic device. For example, a tempered film, a thermoplastic polyurethane elastomer rubber (TPU) film or a PET film can be pasted. However, in the process of making the PET film, the film is formed by extrusion, calendaring and bidirectional stretching, but the bidirectional stretching film formation will cause anisotropy and crystallization, which will produce a birefringence effect. When the light from the display screen passes through the PET film, the polarization characteristics will change. When the light reflected back by the finger passes through the polarizer again, part of the light will be blocked, resulting in a weakened light signal, which will affect the electronic device's recognition of the user's operation. For example, PET film has a 1 / 4 wave plate effect. When the light passes through the protective film of the polarizer to reach the surface of the finger and then reflects back, the polarization direction of the light is just rotated 90 degrees. At this time, the light is completely resisted by the polarizer and cannot pass through. The serious consequence of this is that the optical sensor cannot obtain any fingerprint data, thereby limiting the application of under-screen fingerprint recognition technology.

[0072] In the embodiment of the present application, the polarizer has the function of shielding and transmitting the incident light. For example, for a transverse wave, the polarization direction and the propagation direction are perpendicular, such as Figure 3 As shown, the propagation direction of the incident light passing through the polarizer is K, and the polarization direction is E.

[0073] In the embodiment of the present application, the protective film will have a fast axis direction and a slow axis direction after production, wherein the direction of the light vector (Light vector) with a slow propagation speed in the protective film is the slow axis, and the direction of the light vector with a fast propagation speed in the protective film is the fast axis.

[0074] In response to the above problems, the method for cutting a protective film provided in an embodiment of the present application determines the first fast axis direction and the first slow axis direction of the protective film by the power of the transmitted light passing through two polarizers with the same polarization direction and the protective film between the two polarizers. For example, the fast axis direction of the protective film corresponding to the larger or maximum power of the projected light can be used as the first fast axis direction, or the slow axis direction of the protective film corresponding to the larger or maximum power of the projected light can be used as the first slow axis direction. In this way, on the premise of knowing the size requirement of the protective film after cutting, the protective film is cut according to the first fast axis direction or the first slow axis direction, which is equivalent to cutting according to the first fast axis direction or the first slow axis direction that makes the projected light power larger or maximum. In other words, during the rotation of the protective film, after the incident light passes through the protective film, the direction with the least impact on the incident light is the first fast axis direction or the first slow axis direction of the protective film. The polarization direction of the polarizer in the display screen of the electronic device is the same as the polarization direction of the two polarizers during the cutting process. In this way, when the cut protective film is attached to the electronic device, the impact on the fingerprint data is reduced.

[0075] Combine the following Figure 4 The method 200 for cutting a protective film provided in an embodiment of the present application is described. The method 200 includes:

[0076] S210, detecting the power of the transmitted light that reaches the third polarizer via the second polarizer and the protective film rotating parallel to the second polarizer, wherein the second polarizer and the third polarizer have the same polarization direction, and the protective film has a birefringence effect.

[0077] Optionally, the protective film can be any protective film with a birefringence effect. For example, the protective film can be a PET film, or a composite film with a birefringence effect, for example, the composite film can be a composite film composed of a PET film and a TPU film. The birefringence effect is caused by the characteristics of the material of the protective film. The birefringence effect can be generated by a first fast axis and a second slow axis.

[0078] Alternatively, the second polarizer and the third polarizer may be linear polarizers.

[0079] Optionally, the polarization directions of the second polarizer and the third polarizer are the same, and the propagation directions of the incident light passing through the second polarizer and the third polarizer are also the same.

[0080] Wherein, the second polarizer, the protective film and the third polarizer are parallel to each other.

[0081] S220 , determining a first fast axis direction or a first slow axis direction of the protective film according to the power of the transmitted light.

[0082] In the embodiment of the present application, the fast axis direction and the slow axis direction of the protective film are constantly changing during the process of the protective film rotating parallel to the second polarizer. In S220, it is necessary to determine the first fast axis direction and the first slow axis direction in the constantly changing fast axis direction and slow axis direction of the protective film.

[0083] As an optional embodiment, S220 includes: determining the fast axis direction of the protective film corresponding to the maximum transmitted light power as the first fast axis direction; or determining the slow axis direction of the protective film corresponding to the maximum transmitted light power as the first slow axis direction. Optionally, determining the fast axis direction of the protective film corresponding to the larger transmitted light power as the first fast axis direction; or determining the slow axis direction of the protective film corresponding to the larger transmitted light power as the first slow axis direction.

[0084] Optionally, the power of the maximum transmitted light can be determined only after the protective film is rotated 180 degrees. Optionally, when the power of the transmitted light changes gradually from small to large and then changes gradually from large to small, the fast axis direction of the protective film corresponding to the power of the maximum transmitted light during this change can be determined as the first fast axis direction, or the slow axis direction of the protective film corresponding to the power of the maximum transmitted light during this change can be determined as the first slow axis direction.

[0085] For example, Figure 5 As shown, the incident light passes through the second polarizer, then passes through the rotating protective film, and finally passes through the third polarizer. The power of the transmitted light that finally passes through the third polarizer is detected, and the first fast axis direction or the first slow axis direction of the protective film is determined according to the power of the transmitted light. For example, the fast axis direction of the protective film corresponding to the maximum projection light power can be used as the first fast axis direction, or the slow axis direction of the protective film corresponding to the maximum transmission light power can be used as the first slow axis direction. Figure 5 In the figure, K is the propagation direction of the incident light passing through the second polarizer and the second polarized light, and E is the polarization direction of the incident light passing through the second polarizer and the third polarizer.

[0086] As an optional embodiment, the method further includes: determining the rotation direction of the protective film according to the power of the transmitted light, for example, when the power of the transmitted light gradually changes from high to low, the rotation direction of the protective film can be changed, and when the power of the transmitted light gradually changes from low to high, the rotation direction of the protective film can be unchanged. For example, when the protective film is rotated clockwise in a plane parallel to the second polarizer, when it is detected that the power of the transmitted light gradually changes from high to low, the protective film is rotated counterclockwise in a plane parallel to the second polarizer.

[0087] When the fast axis direction of the protective film corresponding to the maximum transmitted light power is determined as the first fast axis direction, or the slow axis direction of the protective film corresponding to the maximum transmitted light power is determined as the first slow axis direction, the relationship between the first fast axis direction or the first slow axis direction and the polarization direction of the second polarizer may be as follows.

[0088] In the first case, the first fast axis direction is parallel to the polarization direction of the second polarizer, and the first slow axis direction is perpendicular to the polarization direction of the second polarizer, wherein the first fast axis direction is perpendicular to the first slow axis direction. In this case, when the incident light passes through the second polarizer and then through the protective film, the first slow axis direction will not change the polarization direction of the transmitted light, and the polarization direction of the transmitted light is parallel to the first fast axis direction. In this way, the polarization state of the incident light will not change when passing through the protective film.

[0089] In the second case, the first fast axis direction is perpendicular to the polarization direction of the second polarizer, and the first slow axis direction is parallel to the polarization direction of the second polarizer, wherein the first fast axis direction is perpendicular to the first slow axis direction. In this case, when the incident light passes through the second polarizer and then through the protective film, the first fast axis direction will not change the polarization direction of the transmitted light, and the polarization direction of the transmitted light is parallel to the first slow axis direction. In this way, the polarization state of the incident light will not change when passing through the protective film.

[0090] In the third case, the polarization direction of the second polarizer forms an angle of 45 degrees with the first fast axis direction and the first slow axis direction, and the thickness of the protective film after cutting satisfies the following formula:

[0091] (n fast -n slow )*T=1 / 2*m*λ

[0092] Among them, n fast is the refractive index of the protective film in the fast axis direction, n slow is the refractive index of the protective film in the slow axis direction, T is the thickness of the protective film, m is a positive integer, λ is the working wavelength of the optical sensor, wherein the fast axis direction of the protective film is perpendicular to the slow axis direction of the protective film.

[0093] S230, cutting the protective film according to the first fast axis direction or the first slow axis direction to obtain a cut protective film.

[0094] Specifically, after the first fast axis direction or the first slow axis direction is determined, the protective film can be cut according to the cutting size of the protective film. For example, the screen size of the electronic device is fixed, and after the first fast axis direction or the first slow axis direction is fixed, the cutting size is also fixed, and then the cut protective film is obtained according to the first fast axis direction or the first slow axis direction and the cutting size of the protective film sample, and the cut protective film is used to be attached to the screen of the electronic device.

[0095] Optionally, the protective film is a PET film. Of course, the protective film can also be a composite film with a birefringence effect, for example, the composite film can be a composite material film composed of a PET film and a TPU film.

[0096] The following description will be made taking the protective film as a PET film as an example.

[0097] The polarization direction of the polarizer on the electronic device display is perpendicular to the direction of the outgoing light from the screen, such as Figure 6 As shown, the screen of the electronic device in the upper half of the left picture has no PET film, and it can be seen that there is almost no transmitted light. The screen of the electronic device in the lower half of the left picture has a randomly cut PET film, and it can be seen that the PET film changes the polarization state of the transmitted light, causing some light to be transmitted. Figure 6 On the right, the PET film in the right picture is cut in a specific fast axis direction or slow axis direction and then pasted on the screen of an electronic device. You can see the positions on the screen where the film is pasted and where it is not pasted. There is no obvious change in the transmitted light, which is equivalent to that the PET film cut according to the transmitted light power does not affect the polarization state of the light emitted from the screen. In this way, in the under-screen fingerprint recognition technology, the light reflected by the finger can pass through the display screen well to reach the optical sensor module.

[0098] For example, Figure 7 The diagram shows the optical path when the existing protective film is attached to the mobile phone in the fingerprint recognition technology. The protective film has a birefringence effect. The polarization direction of the polarizer is parallel to the horizontal direction of the paper surface. When the light (including the horizontal light parallel to the paper surface and the vertical light perpendicular to the paper surface) passes through the polarizer, only the horizontal light can pass through, and the vertical light cannot pass through. Since the protective film is cut arbitrarily, when the horizontal light reaches the existing PET protective film, the linear polarized light becomes circular polarized light due to the birefringence effect of the PET film. After being reflected by the finger, when it passes through the linear polarizer again, the vertical light cannot pass through, resulting in energy loss of the light reflected back from the finger, thereby causing inaccurate fingerprint data. Figure 8The optical path diagram when the protective film in the embodiment of the present application is attached to the mobile phone in the fingerprint recognition technology is shown. The protective film is cut according to the method in the embodiment of the present application. When the light passes through the polarizer, only the horizontal light can pass through, and the vertical light cannot pass through. Since the fast axis direction of the protective film is parallel or perpendicular to the polarization direction of the polarizer or at a 45-degree angle, or the slow axis direction of the protective film is parallel or perpendicular to the polarization direction of the polarizer or at a 45-degree angle, when the horizontal direction passes through the protective film, the protective film does not change the polarization state of the light, and the light reflected back by the finger is still horizontal light. Therefore, the protective film has little effect on the fingerprint data or even no effect on the fingerprint data. It can be understood that for LCD screens, the light is the light emitted by the backlight module; for OLED screens, the light is the light emitted by the light-emitting layer.

[0099] Table 1 shows four types of PET films, A, B, C, and D. The first column represents the four types of PET films. The second column represents the extinction ratio of the electronic device without any protective film. The third column represents the extinction ratio of the electronic device when the four protective films are directly attached to the screen of the electronic device according to the factory orientation of the protective film. The fourth column represents the protective film rotated a certain angle according to the factory orientation (rotated along the central axis of the protective film). The fifth column represents the extinction ratio of the protective film after it is rotated a certain angle and then cut and attached to the screen of the electronic device. It can be seen that the extinction ratios of the four different films are improved after being rotated a certain angle.

[0100] Table 1

[0101]

[0102] Optionally, the cut protective film is used to be affixed to the screen of an electronic device that supports under-screen fingerprint recognition technology, and the polarization directions of the first polarizer and the second polarizer of the display screen in the electronic device are the same. In other words, the second polarizer and the third polarizer used in the process of cutting the protective film have the same polarization direction as the first polarizer of the display screen in the electronic device. In this way, when the cut protective film is affixed to the electronic device, it will not affect the polarization direction of the polarizer in the electronic device, thereby reducing the impact of the protective film on the fingerprint recognition effect. Optionally, when the polarization directions of the polarizers of different electronic devices are different, the cutting directions of the protective films on the screens of different electronic devices may also be different. For example, if the polarization direction of the first polarizer of the first electronic device is the first polarization direction, then the polarization directions of the second polarizer and the third polarizer are also the first polarization direction, and the fast axis direction of the protective film can be determined to be fast axis direction 1, or the slow axis direction of the protective film can be determined to be slow axis direction 1; if the polarization direction of the first polarizer of the second electronic device is the second polarization direction, then the polarization directions of the second polarizer and the third polarizer are also the second polarization direction, and the fast axis direction of the protective film can be determined to be fast axis direction 2, or the slow axis direction of the protective film can be determined to be slow axis direction 2.

[0103] Combination of the above Figures 3 to 8 A method for cutting a protective film provided in an embodiment of the present application is described, and the protective film is described below.

[0104] The embodiment of the present application provides a protective film, wherein the protective film has a birefringence effect, and the protective film is used to be attached to the screen of an electronic device, and the relationship between the fast axis direction or the slow axis direction of the protective film and the polarization direction of the first polarizer of the display screen of the electronic device has the following situations. It should be understood that the display screen of the electronic device may have one or more polarizers, wherein the first polarizer is a polarizer close to the screen of the electronic device, or the first polarizer may be the last polarizer that the light emitted by the light-emitting element of the electronic device passes through in the process of reaching the protective film. For electronic devices with LCD screens, the light-emitting element may be the light emitted by the backlight module; for electronic devices with OLED screens, the light-emitting element may be the light emitted by the light-emitting layer.

[0105] Optionally, the electronic device may support various optical recognition technologies on the screen, for example, support under-screen fingerprint recognition technology. Among them, under-screen fingerprint recognition technology is also called invisible fingerprint technology, which is a technology that completes the fingerprint recognition and unlocking process under the screen glass. It mainly uses ultrasonic, optical and other penetration technologies, which can penetrate various materials to achieve the purpose of fingerprint recognition.

[0106] In the first case, the fast axis direction of the protective film is parallel to the polarization direction of the first polarizer in the display screen of the electronic device, and the slow axis direction of the protective film is perpendicular to the polarization direction of the first polarizer in the display screen of the electronic device, wherein the fast axis direction of the protective film is perpendicular to the slow axis direction of the protective film.

[0107] In the second case, the slow axis direction of the protective film is parallel to the polarization direction of the first polarizer in the display screen of the electronic device, and the fast axis direction of the protective film is perpendicular to the polarization direction of the first polarizer in the display screen of the electronic device, wherein the fast axis direction of the protective film is perpendicular to the slow axis direction of the protective film.

[0108] In a third case, the polarization direction of the first polarizer in the display screen of the electronic device forms an angle of 45 degrees with the fast axis direction and the slow axis direction of the protective film.

[0109] In the third case, the thickness of the protective film satisfies the following formula:

[0110] (n fast -n slow )*T=1 / 2*m*λ

[0111] Among them, n fast is the refractive index of the protective film in the fast axis direction, n slow is the refractive index of the protective film in the slow axis direction, T is the thickness of the protective film, m is a positive integer, and λ is the operating wavelength of the optical sensor.

[0112] In one possible implementation, an embodiment of the present application provides an electronic device that supports under-screen fingerprint recognition technology, and the screen of the electronic device is attached with the aforementioned protective film.

[0113] It should be understood that in the embodiment of the present application, perpendicularity is not absolutely perpendicular. A and B are perpendicular, and the angle between A and B can be in the range of [90-a, 90+a]. Parallelism is not absolutely parallel. A and B are parallel, and the angle between A and B can be in the range of [0, b]. A and B are at an angle of 45 degrees, which is not absolutely a 45-degree angle. A and B are at an angle of 45 degrees, and the angle between A and B can be in the range of [45-c, 45+c]. For example, a can be 5, b can be 4, and c can be 3; a, b, and c can be 5; a can be 6, b can be 3, and c can be 6; a, b, and c can also be 15, and so on.

[0114] The following example takes a as 5, b as 4, and c as 3 as an example:

[0115] For example, the fast axis direction of the protective film is parallel to the polarization direction of the first polarizer in the display screen of the electronic device, which can be: the angle range between the fast axis direction of the protective film and the polarization direction of the first polarizer is [0, b], where b can be 4. For example, if the angle between the fast axis direction of the protective film and the polarization direction of the first polarizer is 0 degrees, 2 degrees, or 4 degrees, it should be understood that the fast axis direction of the protective film in the embodiment of the present application is parallel to the polarization direction of the first polarizer in the display screen of the electronic device.

[0116] For another example, the slow axis direction of the protective film is perpendicular to the polarization direction of the first polarizer, which can be: the angle between the fast axis direction of the protective film and the polarization direction of the first polarizer is in the range of [90-a, 90+a], where a can be 5. For example, the angle between the fast axis direction of the protective film and the polarization direction of the first polarizer is 85 degrees, 88 degrees, 90 degrees, 93 degrees or 95 degrees, which should be understood as the slow axis direction of the protective film mentioned in the embodiments of the present application being perpendicular to the polarization direction of the first polarizer.

[0117] For another example, the polarization direction of the first polarizer forms an angle of 45 degrees with the fast axis direction and the slow axis direction of the protective film. The angle range between the first polarizer and the fast axis direction of the protective film may be [45-c, 45], and the angle range between the first polarizer and the slow axis direction of the protective film may be [45, 45+c], where c may be 3. For example, the angle between the first polarizer and the fast axis direction of the protective film is 42 degrees, and the angle between the first polarizer and the slow axis direction of the protective film is 48 degrees; or the angle between the first polarizer and the fast axis direction of the protective film is 44 degrees, and the angle between the first polarizer and the slow axis direction of the protective film is 46 degrees. In these cases, it should be understood that the polarization direction of the first polarizer mentioned in the embodiments of the present application forms an angle of 45 degrees with the fast axis direction and the slow axis direction of the protective film. Fig. 9 As shown, the embodiment of the present application provides a device 400 for cutting a protective film, comprising:

[0118] A detection unit 310, for detecting the power of the incident light that reaches the third polarizer via the second polarizer and the protective film rotating parallel to the second polarizer and passes through the third polarizer, wherein the second polarizer and the third polarizer have the same polarization direction, and the protective film has a birefringence effect;

[0119] A determination unit 320, which determines a first fast axis direction or a first slow axis direction of the protective film according to the power of the transmitted light;

[0120] The cutting unit 330 is used to cut the protective film according to the first fast axis direction or the first slow axis direction to obtain a cut protective film.

[0121] As an optional embodiment, the determination unit 420 is specifically used to: determine the fast axis direction of the protective film corresponding to the maximum transmitted light power as the first fast axis direction; or determine the slow axis direction of the protective film corresponding to the maximum transmitted light power as the first slow axis direction.

[0122] As an optional embodiment, after determining the first fast axis direction or the first slow axis direction of the protective film, the first fast axis direction is parallel to the polarization direction of the second polarizer, and the first slow axis direction is perpendicular to the polarization direction of the second polarizer, or, the first fast axis direction is perpendicular to the polarization direction of the second polarizer, and the first slow axis direction is parallel to the polarization direction of the second polarizer.

[0123] As an optional embodiment, after determining the first fast axis direction or the first slow axis direction of the protective film, the polarization direction of the second polarizer forms an angle of 45 degrees with the first fast axis direction and the first slow axis direction, and the thickness of the protective film after cutting satisfies the following formula:

[0124] (n fast -n slow )*T=1 / 2*m*λ

[0125] Among them, n fast is the refractive index of the protective film in the fast axis direction, n slow is the refractive index of the protective film in the slow axis direction, T is the thickness of the protective film, m is a positive integer, and λ is the operating wavelength of the optical sensor.

[0126] As an optional embodiment, the cut protective film is used to be affixed to the screen of an electronic device that supports under-screen fingerprint recognition technology, wherein the polarization direction of the first polarizer and the second polarizer of the display screen in the electronic device is the same.

[0127] As an optional embodiment, the protective film is a polyethylene terephthalate resin PET film.

[0128] As an optional embodiment, the protective film may be a composite film having a birefringence effect, for example, the composite film may be a composite material film composed of a PET film and a TPU film.

[0129] like Fig.10 As shown, an embodiment of the present application provides a device for cutting a protective film, comprising:

[0130] The power detector 410 is used to detect the power of the incident light that reaches the third polarizer via the second polarizer and the protective film rotating parallel to the second polarizer, and passes through the third polarizer. The second polarizer and the third polarizer have the same polarization direction, and the protective film has a birefringence effect.

[0131] The processor 420 determines a first fast axis direction or a first slow axis direction of the protective film according to the power of the transmitted light.

[0132] The cutter 430 is used to cut the protective film according to the first fast axis direction or the first slow axis direction to obtain a cut protective film.

[0133] As an optional embodiment, the processor 420 is specifically used to: determine the fast axis direction of the protective film corresponding to the maximum transmitted light power as the first fast axis direction; or determine the slow axis direction of the protective film corresponding to the maximum transmitted light power as the first slow axis direction.

[0134] As an optional embodiment, after determining the first fast axis direction or the first slow axis direction of the protective film, the first fast axis direction is parallel to the polarization direction of the second polarizer, and the first slow axis direction is perpendicular to the polarization direction of the second polarizer, or, the first fast axis direction is perpendicular to the polarization direction of the second polarizer, and the first slow axis direction is parallel to the polarization direction of the second polarizer.

[0135] As an optional embodiment, after determining the first fast axis direction or the first slow axis direction of the protective film, the polarization direction of the second polarizer forms an angle of 45 degrees with the first fast axis direction and the first slow axis direction, and the thickness of the protective film after cutting satisfies the following formula:

[0136] (n fast -n slow )*T=1 / 2*m*λ

[0137] Among them, n fast is the refractive index of the protective film in the fast axis direction, n slow is the refractive index of the protective film in the slow axis direction, T is the thickness of the protective film, m is a positive integer, and λ is the operating wavelength of the optical sensor.

[0138] As an optional embodiment, the cut protective film is used to be affixed to the screen of an electronic device that supports under-screen fingerprint recognition, wherein the polarization direction of the first polarizer and the second polarizer of the display screen in the electronic device is the same.

[0139] As an optional embodiment, the protective film is a polyethylene terephthalate resin PET film.

[0140] It can be understood that, for the above embodiment, the first fast axis can be the first axis, and the first slow axis can be the second axis. The first axis can be perpendicular to the second axis.

[0141] It can be understood that the parallelism mentioned in the above embodiments can be absolute parallelism or parallelism with errors. For example, A and B are parallel, and the angle between A and B can be in the range of [0, b]. The specific value of b varies according to different products. For example, b can be 4, where A can be the first axis (first fast axis) of the protective film, or the second axis (first slow axis) of the protective film, and B can be the polarization direction of the polarizer (for example, the first polarizer) of the display screen (for example, a touch display screen) of the electronic device. For specific descriptions, please refer to the description in the above embodiments.

[0142] It can be understood that the vertical mentioned in the above embodiments can be absolutely vertical or vertical with error, for example, A and B are perpendicular, and the angle between A and B can be in the range of [90-a, 90+a]. The specific value of a varies according to different products. For example, a can be 5, where A can be the first axis of the protective film (for example, the first fast axis) or the second axis of the protective film (for example, the first slow axis), and B can be the polarization direction of the polarizer (for example, the first polarizer) of the display screen (for example, the touch display screen) of the electronic device. For specific descriptions, please refer to the description in the above embodiments.

[0143] It can be understood that the polarization direction of the first polarizer mentioned in the above embodiment forms an angle of 45 degrees with the fast axis direction (first axis direction) and the slow axis direction (second axis direction) of the protective film, or the polarization direction of the first polarizer forms an angle range of [45-c, 45+c] with the fast axis direction (first axis direction) and the slow axis direction (second axis direction) of the protective film, and the specific value of c varies according to different products, for example, c can be 3. For specific description, please refer to the description in the above embodiment.

[0144] It can be understood that the fast axis direction of the protective film mentioned in the above embodiment is parallel or perpendicular to the polarization direction of the first polarizer, which can be: the fast axis of the protective film is parallel or perpendicular to the polarization direction of the first polarizer. The slow axis direction of the protective film mentioned in the above embodiment is parallel or perpendicular to the polarization direction of the first polarizer, which can be: the slow axis of the protective film is parallel or perpendicular to the polarization direction of the first polarizer. The polarization direction of the first polarizer mentioned in the above embodiment forms an angle of 45 degrees with the fast axis direction and the slow axis direction of the protective film, which can be: the polarization direction of the first polarizer forms an angle of 45 degrees with the fast axis and the slow axis of the protective film.

[0145] Those of ordinary skill in the art will appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art may use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of this application.

[0146] In the several embodiments provided in the present application, it should be understood that the disclosed devices and methods can be implemented in other ways. For example, the device embodiments described above are only schematic. For example, the division of the units is only a logical function division. There may be other division methods in actual implementation, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of devices or units, which can be electrical, mechanical or other forms.

[0147] In addition, each functional unit in each embodiment of the present application may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit.

[0148] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art who is familiar with the present technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. An electronic device, characterized in that: The electronic device supports under-screen fingerprint recognition, and the electronic device includes a touch display screen and an optical sensor, wherein the optical sensor is arranged below the touch display screen, and a protective film is attached to the surface of the touch display screen. Light from the touch display screen passes through the protective film to reach the finger, and after being reflected by the finger, passes through the protective film and the touch display screen in sequence and is projected to the optical sensor to generate fingerprint data; The protective film has a birefringence effect, and the protective film includes a fast axis and a slow axis, wherein the fast axis is perpendicular to the slow axis, The fast axis of the protective film is parallel to the polarization direction of the first polarizer of the touch display screen of the electronic device, and the slow axis of the protective film is perpendicular to the polarization direction of the first polarizer of the touch display screen of the electronic device, or, The slow axis of the protective film is parallel to the polarization direction of the first polarizer of the touch display screen of the electronic device, and the fast axis of the protective film is perpendicular to the polarization direction of the first polarizer of the touch display screen of the electronic device, or, The polarization direction of the first polarizer forms an angle of 45 degrees with the fast axis and the slow axis of the protective film.

2. The electronic device according to claim 1, characterized in that: If the polarization direction of the first polarizer forms an angle of 45 degrees with the fast axis and the slow axis of the protective film, the thickness of the protective film satisfies the following formula: (n fast -n slow )*T=1 / 2*m*λ Among them, n fast is the refractive index of the protective film in the fast axis direction, n slow is the refractive index of the protective film in the slow axis direction, T is the thickness of the protective film, m is a positive integer, and λ is the operating wavelength of the optical sensor.

3. The electronic device according to claim 1 or 2, characterized in that: The protective film is a polyethylene terephthalate resin PET film.

4. The electronic device according to claim 1 or 2, characterized in that: The first polarizer of the touch display screen is the polarizer that the light emitted by the light-emitting element of the electronic device passes through last when reaching the protective film.

5. The electronic device according to claim 1 or 2, characterized in that: The electronic device is a mobile phone, a watch or glasses.

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