Dual-factor certified membrane

Abstract

An optical film (100) includes a plurality of polymer layers (40) disposed between opposing first outer layers (11) and second outer layers (12), wherein the thinnest polymer layer is disposed closer to the first outer layer (11) and the thickest polymer layer is disposed closer to the second outer layer (12). The thickness gradient of the optical film (100) includes a first portion (43) and a second portion (45) connected by stepped portions (20), the thickness variation across the stepped portions (20) being at least 5 times the thickness variation across each of the first portion (43) and the second portion (45), wherein the optical film (100) has a first average transmittance percentage TA1 in a first wavelength range and a peak transmittance percentage Tp in different second wavelength ranges. The first wavelength range and the second wavelength range are separated by a third wavelength range having a third average transmittance percentage TA3, such that TA1 > Tp > 30 (TA3).

Description

Summary of the Invention

[0001] In some aspects of this specification, an optical film is provided comprising a plurality of polymer layers, the plurality of polymer layers being at least 200 in total, disposed between opposing first and second outer layers, and co-extruded and co-stretched with the first and second outer layers. Each of these polymer layers has an average thickness of less than about 150 nm. The thinnest polymer layer among the plurality of polymer layers is disposed closer to the first outer layer, and the thickest polymer layer among the plurality of polymer layers is disposed closer to the second outer layer. The thickness gradient of the optical film comprises a first portion and a second portion connected by stepped portions, wherein each of the first portion and the second portion extends across at least 30 of these polymer layers, and the stepped portions extend across less than about 10 of these polymer layers. The thickness variation across the stepped portions is at least 5 times greater than the thickness variation across each of the first portion and the second portion. The optical film has a first average transmittance percentage TA1 in a first wavelength range (e.g., near-infrared range), a peak transmittance percentage Tp in different second wavelength ranges (e.g., human visible range), and the first and second wavelength ranges are separated by a third wavelength range having a third average transmittance percentage TA3, such that each of the first and third wavelength ranges is at least about 100 nm wide, the second wavelength range is less than about 50 nm wide, and TA1 > Tp > 30 (TA3).

[0002] In some aspects of this specification, a light-reflecting film is provided, comprising a plurality of polymer layers, the total count of which is at least 200. A graph of the average layer thickness relative to the number of polymer layers includes stepped portions separating a left portion where the polymer layers have a smaller number of layers from a right portion where the polymer layers have a larger number of layers, each of the left and right portions extending across at least 30 sequentially arranged polymer layers. The optical transmittance of the light-reflecting film relative to wavelength includes a peak at a peak wavelength having a corresponding full width at half maximum (FWHM) in the visible wavelength range, the peak separating a lower wavelength range from a higher wavelength range extending across M1 nanometers, such that the ratio M1 / FWHM ≥ 1.5. For substantially normally incident light, the plurality of polymer layers have an average transmittance TA2 across each of the lower and higher wavelength ranges, and a transmittance Tp at the peak wavelength, such that the ratio of Tp / TA2 is greater than or equal to 30.

[0003] In some aspects of this specification, an optical system is provided, comprising a display configured to display an image to a viewer; a light source configured to emit light having a blue emission spectrum, a green emission spectrum, a red emission spectrum, and a near-infrared emission spectrum, the blue, green, red, and near-infrared emission spectra having their respective blue full width at half maximum (FWHM), green FWHM, red FWHM, and near-infrared FWHM; and an optical film disposed between the light source and the display. The optical film has a first average transmittance percentage TA1 in a first wavelength range and a peak transmittance percentage Tp in different second wavelength ranges. The first and second wavelength ranges are separated by a third wavelength range having a third average transmittance percentage TA3. Each of the first and third wavelength ranges is at least about 100 nm wide, and the second wavelength range is less than about 50 nm wide, such that TA1 > Tp > 30 (TA3). The FWHM corresponding to the peak transmittance in the second wavelength range is less than at least each of the green FWHM, red FWHM, and near-infrared FWHM.

[0004] In some aspects of this specification, an optical reflector is provided comprising a plurality of polymer layers, the total number of which is at least 200. Each of these polymer layers has an average thickness of less than about 500 nm. The layer thickness gradient of these polymer layers includes a first portion and a second portion connected by a stepped portion. Each of the first and second portions extends across at least 30 of these polymer layers, and the stepped portion extends across less than about 10 of these polymer layers. The thickness variation across the stepped portion is at least 5 times greater than the thickness variation across each of the first and second portions. For substantially normally incident light, the plurality of polymer layers have an average optical reflectivity greater than about 80% over a visible wavelength range extending from about 420 nm to about 700 nm; and an optical transmittance relative to wavelength, the optical transmittance including a bandpass segment having a global peak transmittance between about 2% and about 80% at a global peak wavelength in the visible wavelength range, and a corresponding full width at half maximum (FWHM) between about 10 nm and about 50 nm.

[0005] In some aspects of this specification, an optical reflector is provided comprising a plurality of polymer layers, the total number of which is at least 200. Each of these polymer layers has an average thickness of less than about 500 nm. For substantially normally incident light, the plurality of polymer layers have an average optical reflectivity greater than about 80% over a visible wavelength range extending from about 420 nm to about 700 nm; and an optical transmittance relative to wavelength, including a bandpass segment having a global peak transmittance greater than about 2% at a global peak wavelength in the visible wavelength range, and a corresponding full width at half maximum (FWHM) of at least 5 nm. When substantially white Lambertian light having first color coordinates a1* and b1* in the CIE Lab color space illuminates the optical reflector, the optical reflector reflects the illuminated white light. The reflected light has corresponding second color coordinates a2* and b2*, averaged over all reflection angles. The color difference ΔE*(ab) between the first and second color coordinates is less than about 10.

[0006] In some aspects of this specification, an optical reflector is provided comprising a plurality of polymer layers, the total number of which is at least 200. Each of these polymer layers has an average thickness of less than about 500 nm. For substantially normally incident light, the plurality of polymer layers have an average optical reflectivity greater than about 80% over a visible wavelength range extending from about 420 nm to about 700 nm; and an optical transmittance relative to wavelength, the optical transmittance including a bandpass segment having a global peak transmittance at a global peak wavelength in the visible wavelength range, and a corresponding full width at half maximum (FWHM). When substantially white Lambertian light is incident on the optical reflector, the optical reflector reflects the incident white light, wherein the difference ΔE*(ab) between the color coordinates (a1*, b1*) of the incident light in the CIE Lab color space and the color coordinates (a2*, b2*) of the reflected light in the CIE Lab color space, averaged over all reflection angles, is between about 0.01 and about 0.5. Attached Figure Description

[0007] Figure 1A and Figure 1B A side view of an optical system including a dual-factor certified optical film according to an embodiment of this specification is shown;

[0008] Figure 2 The layers of a two-factor certified optical film according to an embodiment of this specification are shown;

[0009] Figure 3 A graph of the percentage of transmittance versus wavelength for a two-factor certified optical film according to an embodiment of this specification is provided;

[0010] Figure 4A and Figure 4B Different embodiments of the two-factor certified optical film according to the embodiments of this specification are shown;

[0011] Figure 5 The layer thickness distribution of the optical film is a two-factor certified embodiment according to the present specification.

[0012] Figures 6A to 6C A graph of an alternative layer thickness distribution for a two-factor certified optical film according to an embodiment of this specification is provided;

[0013] Figures 7A to 7C According to one embodiment of this specification, the transmittance performance of a dual-factor certified optical film was compared with the emission spectra of various light sources.

[0014] Figure 8 A graph showing the optical transmittance of several variants of the two-factor certified optical film according to the embodiments of this specification is provided.

[0015] Figure 9 Graphs and data regarding the color difference between emitted light and light reflected by the optical film, according to embodiments of this specification, are provided; and

[0016] Figure 10 This is a side view of an optical system including a transceiver and an optical film according to an embodiment of this specification. Detailed Implementation

[0017] Reference is made in the following description to the accompanying drawings, which form part of the invention and illustrate various embodiments by way of example. The drawings are not necessarily drawn to scale. It should be understood that other embodiments may be conceived and practiced without departing from the scope or spirit of this specification. Therefore, the following detailed description should not be considered limiting.

[0018] Increasingly, mobile devices are being manufactured with additional security features, such as biometric identification. These methods can be as simple as fingerprints on the skin's surface, or combinations of two or more biometric factors, including but not limited to fingerprint or handprint recognition, recognition of subsurface features (such as vein patterns), heart rate, blood oxygen levels, or any other suitable biometric factor. There is also a growing desire to avoid security issues such as “spoofing,” for example, when someone uses a forged or raised fingerprint to deceive a fingerprint sensor. It is also desirable to perform “activity” detection on subjects attempting to access the device to prevent someone from using a non-physical number, such as to gain access to a system protected by a fingerprint system. One way to do this is by creating photoplethysmography (PPG), an optical trajectory that can be used to detect changes in blood volume in the microvascular bed of a subject's tissue. This type of measurement typically determines the different absorption characteristics of oxygenated and deoxygenated blood and often uses two different wavelengths of light for comparison. For example, different measurements can be performed at approximately 620 nm (visible to humans) and approximately 940 nm (near-infrared).

[0019] According to some aspects of this specification, an optical film is provided that can be used to perform a two-factor authentication on a consumer electronic device. In some embodiments, the optical film may be a multilayer optical film with a discontinuous layer distribution, such that for a target wavelength, there is no layer with an optical thickness close to a quarter wavelength of the target wavelength (i.e., the multilayer optical film is not strongly reflective to the target wavelength because none of the layers resonate at the target wavelength). This can be used to generate an optical film with high transmittance in infrared wavelengths (e.g., approximately 940 nm, allowing for fingerprint recognition using infrared, or for measuring the absorption characteristics of blood in infrared) and also a narrow band of high transmittance in human visible wavelengths (e.g., approximately 620 nm, allowing for the measurement of the absorption characteristics of blood in human visible wavelengths). In some embodiments, this narrow band of transmittance in visible light may be a high (e.g., transmittance exceeding 80%) but narrow (e.g., full width at half maximum or FWHM less than 20 nm) transmittance spike, such that the visible transmittance is sufficient for biometric measurements without significantly altering the display's color. In other embodiments, the transmittance band in the visible light can be wider (e.g., greater than 40 nm FWHM) but shorter (e.g., less than 30% transmittance), which can be sufficient visible energy to perform biometric measurements, but low enough transmittance percentage to avoid significantly altering the display color.

[0020] In some embodiments, the optical film may be part of an optical system. In some embodiments, the optical system may include a transceiver and an optical film disposed between the transceiver and a measuring subject, the transceiver being configured to emit emitted light toward the measuring subject (e.g., a user's finger or face) and receive reflected light reflected by the measuring subject. In some embodiments, the emitted light from the transceiver may include at least one of wavelengths within a first wavelength range and wavelengths within a second wavelength range. For example, a smartwatch may include a transceiver that emits light from the back of the watch (i.e., the side closer to the user's skin) and receives light reflected from the measuring subject (i.e., light reflected from the user's skin) to perform certain biometric functions.

[0021] According to some aspects of this specification, the optical film comprises a plurality of polymer layers, totaling at least 200, at least 300, or at least 500, disposed between opposing first and second outer layers, and co-extruded and co-stretched with the first and second outer layers. In some embodiments, each of the polymer layers has an average thickness that may be less than about 150 nm. In some embodiments, the thinnest polymer layer among the plurality of polymer layers may be disposed closer to the first outer layer, and the thickest polymer layer may be disposed closer to the second outer layer.

[0022] In some embodiments, the thickness gradient of the optical film may include a first portion and a second portion connected by a stepped portion, wherein each of the first and second portions extends across at least 30 layers of the polymer layer, and the stepped portion extends across fewer than about 10 layers of the polymer layer. In some embodiments, the first and second portions may be substantially linear. That is, in some embodiments, the best linear fit for each of the first and second portions may have an R-squared value greater than or equal to about 0.8, or about 0.85, or about 0.90. In some embodiments, the thickness change across the stepped portion may be at least 5 times the thickness change across each of the first and second portions.

[0023] In some embodiments, the optical film may have a first average transmittance percentage TA1 in a first wavelength range (e.g., the near-infrared range) and a peak transmittance percentage Tp in different second wavelength ranges (e.g., the human visible or visible range). In some embodiments, the first wavelength range and the second wavelength range may be separated by a third wavelength range having a third average transmittance percentage TA3. In some embodiments, each of the first and third wavelength ranges may be at least about 100 nm wide, and the second wavelength range may be less than about 50 nm wide, or less than about 40 nm wide, or less than about 30 nm wide. In some embodiments, the first average transmittance percentage TA1 may be greater than the peak transmittance percentage Tp, and Tp may be significantly greater than the third average transmittance percentage TA3 (e.g., Tp may be 30 times, 40 times, 50 times, or 60 times TA3). In some embodiments, TA1 may be greater than about 80%, or greater than about 85%, or greater than about 90%. In some implementations, Tp may be greater than about 30%, or greater than about 40%, or greater than about 50%.

[0024] In some embodiments, the first wavelength range may be a near-infrared wavelength range extending from about 800 nm to about 2000 nm, and the second wavelength range may be a human-visible wavelength range extending from about 550 nm to about 700 nm. In some embodiments, the first wavelength range may be one of the visible wavelength range and the near-infrared wavelength range, and the second wavelength range may be the other of the visible wavelength range and the near-infrared wavelength range. In other words, there may be applications where the peak transmittance percentage is the peak value within the near-infrared wavelength range, and the first wavelength range may be the visible wavelength range. It should be noted that, for the purposes of this specification, the term "near-infrared" (NIR) should be defined as including wavelengths of light in the range from about 680 nm to about 2000 nm. Furthermore, for the purposes of this specification, the terms "human-visible" and "visible" should be considered synonymous.

[0025] In some implementations, the optical film described herein may have multiple embodiments and represent multiple system functions. For example, the optical film may be a reflector, a reflective polarizer, an absorptive polarizer, a partial reflector, and a diffuser.

[0026] In some embodiments, the optical stack may include two or more optical films as described herein. In some embodiments, at least one optical property (e.g., optical transmittance or optical reflectance) of at least one of the two or more optical films may vary by at least 10% for two orthogonal polarization states, wherein the same optical property of another optical film is substantially the same for the two orthogonal polarization states. For example, the first film of the optical stack may substantially reflect light of a first polarization state (e.g., light of the p-pol polarization type) and substantially transmit light of a second orthogonal polarization type (e.g., light of the s-pol polarization type), while the second film of the optical stack may substantially transmit light of both polarization types.

[0027] In some embodiments, the optical system may include a display configured to emit light having blue, green, red, and near-infrared emission spectra, as well as any optical films described herein. Each emission spectrum of the display may have a respective blue full width at half maximum (FWHM), green FWHM, red FWHM, and near-infrared FWHM, and the optical film may exhibit an FWHM value corresponding to the peak transmittance in a second wavelength range, which is less than at least each of the green FWHM, red FWHM, and near-infrared FWHM values. In some embodiments, the FWHM of the peak transmittance in the second wavelength range may also be less than the blue FWHM value. In other words, in some embodiments, the peak transmittance may be represented by a narrow “spik” of the transmittance value that is smaller (narrower) than the width of the corresponding light source emission spectrum curve, thereby minimizing any negative effects on the display’s visual quality (but allowing for peak transmittance in a narrow wavelength range to enable sensing of optical properties for authentication and other purposes).

[0028] According to some aspects of this specification, the light-reflecting film comprises a plurality of polymer layers, the total count of which is at least 200. A graph of the average layer thickness relative to the number of polymer layers includes stepped portions separating a left portion (where the polymer layers have a smaller number of layers) from a right portion (where the polymer layers have a larger number of layers), each of the left and right portions extending across at least 30 sequentially arranged polymer layers. In some embodiments, the optical transmittance of the light-reflecting film relative to wavelength may include a peak value at a peak wavelength having a corresponding full width at half maximum (FWHM) within the visible wavelength range (i.e., the human visible wavelength range), the peak value separating a lower wavelength range from a higher wavelength range extending across M1 nanometers, such that the ratio M1 / FWHM is greater than or equal to about 1.5, or greater than about 2.0, or greater than about 3.0. In some embodiments, for substantially normal incident light, the plurality of polymer layers may have an average transmittance TA2 across each of the lower and higher wavelength ranges, and a transmittance Tp at the peak wavelength, such that the ratio of Tp / TA2 is greater than or equal to about 30, or about 40, or about 50. In some embodiments, Tp may be greater than about 70%, or about 80%, or about 90%.

[0029] In some embodiments, each of the left and right portions of the graph of average layer thickness versus number of layers may be substantially linear. In such embodiments, the best linear fit of each of the first substantially linear portion and the second substantially linear portion may have an R-squared value greater than or equal to about 0.8, or about 0.85, or about 0.90.

[0030] In some embodiments, for substantially normally incident light, the plurality of polymer layers may have an average transmittance TA1 in the infrared wavelength range such that TA1 is greater than or equal to Tp, and wherein each of the visible wavelength range and the infrared wavelength range is at least about 200 nm wide.

[0031] According to some aspects of this specification, the optical system includes a display configured to display an image to a viewer; a light source configured to emit light having a blue emission spectrum, a green emission spectrum, a red emission spectrum, and a near-infrared emission spectrum, the blue, green, red, and near-infrared emission spectra having their respective blue full width at half maximum (FWHM), green FWHM, red FWHM, and near-infrared FWHM; and an optical film disposed between the light source and the display. In some embodiments, the optical film may have a first average transmittance percentage TA1 in a first wavelength range (e.g., the near-infrared wavelength range) and a peak transmittance percentage Tp in different second wavelength ranges (e.g., the visible wavelength range). In some embodiments, the first and second wavelength ranges may be separated by a third wavelength range having a third average transmittance percentage TA3. In some embodiments, each of the first and third wavelength ranges may be at least about 100 nm wide, and the second wavelength range may be less than about 50 nm wide, such that TA1 is greater than Tp, and Tp is 30 times, or 40 times, or 50 times TA3. In some embodiments, the FWHM corresponding to the peak transmittance in the second wavelength range may be less than at least each of the green FWHM, red FWHM, and near-infrared FWHM. In some embodiments, the FWHM of the peak transmittance in the second wavelength range may also be less than the blue FWHM value. In some embodiments, the light source may include one or more of a display backlight and a light source external to the display backlight (e.g., the light source may include a display backlight emitting blue, green, and red emission spectra, and a separate LED emitting infrared emission spectra).

[0032] According to some aspects of this specification, the optical reflector includes a plurality of polymer layers, the total number of which is at least 200. In some embodiments, each of the polymer layers has an average thickness of less than about 500 nm. In some embodiments, the layer thickness gradient of the polymer layers may include a first portion and a second portion connected by a stepped portion. In some embodiments, each of the first and second portions may extend across at least 30 layers of the polymer layers, and the stepped portion may extend across less than about 10 layers of the polymer layers. In some embodiments, the thickness change across the stepped portion may be at least 5 times the thickness change across each of the first and second portions. In some embodiments, the stepped portion may have a negative slope. In some embodiments, the stepped portion may have a positive slope. In some embodiments, the stepped portion may be substantially vertical.

[0033] In some embodiments, for substantially normally incident light, the plurality of polymer layers may have an average optical reflectance greater than about 80%, or greater than about 85%, or greater than about 90% in a visible wavelength range extending from about 420 nm to about 700 nm, and may have an optical transmittance relative to wavelength including a bandpass segment comprising a global peak transmittance at a global peak wavelength in the visible wavelength range between about 2% and about 80%, or between about 2% and about 60%, or between about 2% and about 40%, and a corresponding full width at half maximum (FWHM) between about 10 nm and about 50 nm, or between about 10 nm and about 40 nm, or between about 10 nm and about 30 nm, or between about 10 nm and about 20 nm.

[0034] In some implementations, for each of the mutually orthogonal polarization states, the optical reflector may have an average optical reflectivity greater than about 80%, or greater than about 85%, or greater than about 90% in the visible wavelength range.

[0035] In some embodiments, the optical reflector may be part of an optical system. In some embodiments, the optical system may include a light source and an optical reflector. In some embodiments, the light source may be configured to emit emitted light toward a measuring subject (e.g., a user's finger) and receive reflected light reflected by the measuring subject. In some embodiments, the optical reflector may be positioned between the light source and the measuring subject.

[0036] According to some aspects of this specification, the optical reflector includes a plurality of polymer layers, the total number of which is at least 200. In some embodiments, each of the polymer layers has an average thickness that may be less than about 500 nm. In some embodiments, for substantially normal incident light, the plurality of polymer layers may have an average optical reflectivity greater than about 80%, or greater than about 85%, or greater than about 90% over a visible wavelength range extending from about 420 nm to about 700 nm, and an optical transmittance relative to wavelength including a bandpass segment having a global peak transmittance greater than about 2% at the global peak wavelength in the visible wavelength range, and a corresponding full width at half maximum (FWHM) of at least 5 nm. In some implementations, when a substantially white Lambertian light having first color coordinates a1* and b1* in the CIE Lab color space illuminates an optical reflector, the optical reflector reflects the illuminated white light, the reflected light having respective second color coordinates a2* and b2* averaged over all reflection angles, wherein the color difference ΔE*(ab) between the first color coordinates and the second color coordinates is less than about 10.

[0037] In some implementations, for each of the mutually orthogonal polarization states, the optical reflector may have an average optical reflectivity greater than about 80%, or greater than about 85%, or greater than about 90% in the visible wavelength range.

[0038] In some embodiments, the optical reflector may be part of an optical system. In some embodiments, the optical system may include a light source and an optical reflector. In some embodiments, the light source may be configured to emit substantially white Lambertian light toward the measuring subject (e.g., a user's finger or skin) and receive the reflected light. In some embodiments, the optical reflector may be positioned between the light source and the measuring subject.

[0039] According to some aspects of this specification, the optical reflector includes a plurality of polymer layers, the total number of which is at least 200. In some embodiments, each of the polymer layers has an average thickness that may be less than about 500 nm. In some embodiments, for substantially normal incident light, the plurality of polymer layers may have an average optical reflectivity greater than about 80%, or greater than about 85%, or greater than about 90% in a visible wavelength range extending from about 420 nm to about 700 nm; and may have an optical transmittance relative to wavelength, the optical transmittance including a bandpass segment having a global peak transmittance at a global peak wavelength in the visible wavelength range, and a corresponding full width at half maximum (FWHM). In some implementations, when substantially white Lambertian light is incident on an optical reflector, the optical reflector reflects the incident white light, wherein the difference ΔE*(ab) between the color coordinates (a1*, b1*) of the incident light in the CIE Lab color space and the color coordinates (a2*, b2*) of the reflected light in the CIE Lab color space, averaged over all reflection angles, is between about 0.01 and about 0.5.

[0040] In some implementations, for each of the mutually orthogonal polarization states, the optical reflector may have an average optical reflectivity greater than about 80%, or greater than about 85%, or greater than about 90% in the visible wavelength range.

[0041] In some embodiments, the optical reflector may be part of an optical system. In some embodiments, the optical system may include a light source and an optical reflector. In some embodiments, the light source may be configured to emit substantially white Lambertian light toward the measuring subject (e.g., a user's finger or skin) and receive the reflected light. In some embodiments, the optical reflector may be positioned between the light source and the measuring subject.

[0042] Now turn to the attached image. Figure 1A and Figure 1B A side view of an optical system including a dual-factor certified optical film, according to this specification, is shown. Figure 1A and Figure 1B The embodiments shown in each figure are similar and share many components with similar numbers. Unless otherwise specifically stated, the functions of components with similar numbers in each figure should be considered the same, and therefore the descriptions of these components need not be repeated for each figure. Figure 1A Initially, the optical system 200 includes a display 50, a backlight 60 including a plurality of light sources 65 (e.g., light-emitting diodes), and an optical film 100 disposed between the display 50 and the backlight 60. In some embodiments, the backlight 60 (via the light sources 65) is configured to emit light 30 having a blue emission spectrum, a green emission spectrum, a red emission spectrum, and a near-infrared emission spectrum.

[0043] Temporarily transferred to Figure 6A and Figure 6B These accompanying figures provide additional details of the emission spectrum emitted by the light source 65. Figure 6A The typical emission spectrum of a backlight source, such as a light-emitting diode, is shown. Figure 6A The emission spectra of blue light 90b, green light 90g, and red light 90r are shown. (Example) Figure 6A As shown, each of spectra 90b, 90g, and 90r has a corresponding full width at half maximum (FWHM) value. In this example, the FWHM of the blue spectrum 90b is approximately 25 nm, the FWHM of the green spectrum 90g is approximately 40 nm, and the FWHM of the red spectrum 90r is approximately 25 nm. Figure 6B The typical emission spectrum of an infrared LED 90ir is shown. The infrared spectrum of 90ir has a corresponding FWHM value of approximately 45 nm. Figure 6A and Figure 6B The shape (including height and width) of each of the spectral curves is related to the functional performance of the optical film 100, which will be discussed elsewhere in this paper.

[0044] Back Figure 1AThe optical film 100 may include a plurality of polymer layers, totaling at least 200, 300, 400, 500, or 600, disposed between opposing first and second outer layers, and co-extruded and co-stretched with the first and second outer layers. In some embodiments, each of the polymer layers has an average thickness of less than about 150 nm and may be arranged with a thickness gradient, wherein the thinnest polymer layer is disposed closer to the first outer layer and the thickest polymer layer is disposed closer to the second outer layer. In some embodiments, the thickness gradient of the optical film 100 may be configured such that the optical film has a first average transmittance percentage in a first wavelength range (e.g., the near-infrared wavelength range) and a peak transmittance percentage (e.g., a narrow transmittance “spike” or notch peak in the visible wavelength range) in different second wavelength ranges. In other words, the optical film 100 may be configured to substantially allow wavelength transmittance in at least two different wavelength ranges, enabling the film to be used in applications requiring biometric authentication using two different wavelengths of light. Additional details regarding the construction and performance of the optical film 100 are provided elsewhere in this document.

[0045] Figure 1B It shows something similar to Figure 1A The optical system 200B of the optical system 200, except that the optical stack 150 replaces... Figure 1A The embodiment includes a single optical stack 100. The optical stack 150 comprises two or more optical films 100a and 101, both of which are substantially similar to... Figure 1A Optical film 100. At least one of optical films 100a and 101 can be configured to exhibit different optical properties based on the polarization type of light passing through the film. For example, optical film 101 can be substantially similar to... Figure 1A The optical film 100 is identical to the optical film 100, except that it substantially transmits light 30 of one polarization type (e.g., light with linear p-pol polarization) and substantially (or partially) blocks light 30 of a second orthogonal polarization type (e.g., light with linear s-pol polarization). In some embodiments, another optical film 100a may be used with... Figure 1AThe optical films 100 are substantially identical and can transmit light of substantially two orthogonal polarization types. In some embodiments, at least one of films 100a and 101 may be configured to transmit or reflect light based on the polarization type of light 30. The use of linear S-pol and linear P-pol polarization types in this specification is merely illustrative, and other polarization types (e.g., linear to circular polarization types) may also be appropriate and within the scope of this specification. Furthermore, it should be noted that other configurations of the optical stack are possible, and the optical films 100 (or 100a, 101) can be used to implement optical films with additional functions, including but not limited to films such as reflectors, reflective polarizers, absorptive polarizers, partial reflectors, and diffusers.

[0046] Figure 2 Provided according to this specification Figure 1A Additional details regarding the construction of the optical film 100 are provided below. In some embodiments, the optical film 100 comprises a plurality of polymer layers 40 (including layers 40a-40d and 40w-40z) totaling at least 200, disposed between a first outer layer 11 and an opposite second outer layer 12, and co-extruded and co-stretched with the first outer layer and the opposite second outer layer. In some embodiments, each of the polymer layers 40 has an average thickness that may be less than about 150 nm. In some embodiments, the thinnest polymer layer 40a among the plurality of polymer layers may be disposed closer to the first outer layer 11, and the thickest polymer layer 40z may be disposed closer to the second outer layer 12.

[0047] Multiple polymer layers 40 may be divided into two or more segments 43 and 45. Within each of segments 43 and 45, the layer thickness gradient of each segment may be substantially linear. In some embodiments, a discontinuity 20 may exist between segments 43 and 45 (e.g., a non-linear step in the layer width between layers 40d and 40w). This step in the width of the discontinuity 20 may be at least about 5 times the corresponding step change in thickness of each segment in segments 43 and 45. Additional details regarding the layer thickness gradient of the optical film 100 may be discussed elsewhere herein. Figure 5 I saw it in the middle.

[0048] Figure 3 Figure 90 provides a percentage of transmittance as a function of wavelength for a two-factor certified optical film according to this specification. Figure 90 is an exemplary diagram of one embodiment of the optical film 100 (see, for example, Figure 1AOther embodiments consistent with or variants thereof are also possible. Figure 90 can be divided into three main wavelength ranges of interest. A first wavelength range 71 represents the first average transmittance percentage TA1, a second wavelength range 72 represents the peak transmittance percentage Tp, and a third wavelength range 73 represents the third average transmittance percentage TA3. Figure 3 In one embodiment, the first wavelength range 71 is the near-infrared wavelength range, and the second wavelength range 72 is a narrow notch transmittance set within the visible wavelength range. However, other embodiments may be configured such that the first wavelength range 71 and the second wavelength range 72 are substantially interchanged (i.e., the first wavelength range 71 extends across the visible wavelength range, and the narrow notch of the second wavelength range 72 is set within the near-infrared wavelength range).

[0049] In some embodiments, the first average transmittance percentage TA1 may be greater than the peak transmittance percentage Tp. In some embodiments, the peak transmittance percentage Tp may be greater than the third average transmittance percentage TA3. In some embodiments, the peak transmittance percentage Tp may be 30 times, 40 times, or 50 times TA3.

[0050] In some embodiments, the optical film 100, as shown in FIG. 90, can substantially transmit light in the near-infrared wavelength range. In some embodiments, this near-infrared wavelength range (i.e., the first wavelength range 71) can extend from about 700 nm to about 2000 nm, or from about 800 nm to about 1500 nm, or from about 840 nm to about 1300 nm. In some embodiments, the optical film 100, as shown in FIG. 90, can also substantially transmit light in a narrow visible wavelength range. In some embodiments, this visible wavelength range (i.e., the second wavelength range 72) can extend from about 550 nm to about 700 nm, or from about 600 nm to about 700 nm, or from about 610 nm to about 680 nm.

[0051] In some embodiments, Figure 90 may have a peak Tp at the peak wavelength of the corresponding full width at half maximum (FWHM) in the visible wavelength range. The peak Tp can separate the lower wavelength range from the higher wavelength range. In some embodiments, such as Figure 3 For example, the lower and higher wavelength ranges can extend across M1 nanometers, such that the M1 / FWHM ratio is greater than or equal to about 1.5, or about 2.0, or about 2.5, or about 3.0. In other words, the FWHM associated with the peak Tp can be configured to be relatively narrow in order to minimize the amount of light transmitted in the visible wavelength range, which can negatively affect the quality of the displayed image. In some embodiments, the range extends across both the lower and higher wavelength ranges (such as...) Figure 3Those shown exhibit a second average transmittance percentage TA2 over the wavelength range. In some embodiments, the optical film 100 (see, for example, Figure 1A It can be configured such that the ratio Tp / TA2 is greater than or equal to about 30, or about 40, or about 50.

[0052] As described herein, optical films can be configured to allow the transmission of light in two separate wavelength ranges for dual-factor authentication, namely the near-infrared range and the visible range. Therefore, it is crucial to ensure that any light transmitted within the visible wavelength range does not have a significant (negative) effect on the image quality seen on the display. That is, if visible wavelengths (e.g., approximately 620 nm light used to determine information related to the absorption characteristics of blood) are used in the authentication scheme, visible light can produce visible effects that are perceptible on the display. To mitigate this negative drawback, visible wavelengths can be limited to either the wavelength range (e.g., a very narrow transmittance spike) or the percentage of transmittance (e.g., a shorter spike with a lower transmittance "power"). Figure 4A and Figure 4B Exemplary graphs of transmittance percentage versus wavelength for two different embodiments of the optical film are provided. Figure 4A In this design, the optical film is configured to exhibit a single, narrow "peak" of transmittance 75a, which is relatively high (i.e., has nearly 70% transmittance at the peak wavelength) but very narrow (i.e., extends across only a small wavelength range from approximately 615 nm to approximately 640 nm). Figure 4B In this design, the optical film is configured to exhibit a relatively short and wide transmittance region 75b, which is relatively short (i.e., a transmittance peak of approximately 28%) but extends across a large wavelength range (i.e., extending from approximately 590 nm to approximately 660 nm). The transmittance profile and peak value of the optical film can be configured to meet the needs of a specific application. For example, in some applications, depending on the performance of the sensor used, a transmittance peak of approximately 30% may be sufficient to be detected for authentication procedures. Figure 4A and Figure 4B All implementation schemes provide methods for limiting the impact of visible light transmission on the visual appearance of the display.

[0053] Figure 5This is a graph illustrating the layer thickness distribution of an embodiment of the optical film described herein. The layer thickness gradient 80 is a graph of layer thickness in nanometers (nm) on the y-axis versus the number of layers on the x-axis. The layer thickness gradient 80 includes a first portion 82 and a second portion 88. In some embodiments, each of the first portion 82 and the second portion 88 is a substantially linear portion. In some embodiments, for example, the best linear fit of each of the first portion 82 and the second portion 88 may have an R-squared value greater than or equal to about 0.8, or about 0.85, or about 0.90. In some embodiments, each of the first portion 82 and the second portion 88 may extend across at least 30 polymer layers, or at least 40 polymer layers, or at least 50 polymer layers, or at least 100 polymer layers, or at least 200 polymer layers. In some embodiments, the first portion 82 and the second portion 88 are separated by a stepped portion 85 that may extend across less than about 10 polymer layers. The thickness variation across the step portion 85 can be at least five times greater than the thickness variation across each of the first portion 82 and the second portion 88. In some embodiments, the step portion 85 can be configured such that, for the target wavelength, there is no layer with an optical thickness close to a quarter wavelength of the target wavelength (i.e., the multilayer optical film is not strongly reflective for the target wavelength because none of the layers resonate at the target wavelength). In other words, by positioning the step portion 85 such that certain layer thicknesses are avoided throughout the thickness gradient, the optical film will not block or reflect (i.e., it will essentially transmit) wavelengths of light that would normally resonate with the omitted layers.

[0054] Figures 6A to 6C An alternative layer thickness profile is provided for the dual-factor certified optical film. Similar to... Figure 5 The diagram shown, Figures 6A to 6C Each graph in the diagram represents a layer thickness gradient 80a, 80b, 80c, which is a graph of the layer thickness in nanometers (nm) on the y-axis relative to the number of layers on the x-axis. Each of the layer thickness gradients 80a, 80b, 80c includes a first portion 82a, 82b, 82c and a second portion 88a, 88b, 88c, which is substantially linear and separated by stepped portions 85a, 85b, 85c. In the embodiment 80a, Figure 6A In the diagram, the first part 82a shows a gradual decrease in layer thickness as the number of layers increases, the stepped part 85a shows a steeper decrease in layer thickness, and the second part 88a shows a gradual increase in layer thickness. Embodiment 80b is shown. Figure 6BIn the embodiments shown, the first portion 82b illustrates a gradual increase in layer thickness with increasing layer number, the stepped portion 85b illustrates a steep decrease in layer thickness, and the second portion 88b illustrates a gradual decrease in layer thickness. In each of embodiments 80a and 80b, the stepped portions 85a and 85b can be configured such that, for the target wavelength, there are no layers with an optical thickness close to a quarter wavelength of the target wavelength, similar to... Figure 5 The embodiment 80 described herein (i.e., the multilayer optical film does not strongly reflect the target wavelength because none of the layers resonate at the target wavelength). In some embodiments, the stepped portions may have a negative slope (“reduced”, as in stepped portions 85a, 85b), while in other embodiments, the stepped portions may have a positive slope (“increased”, as in...) Figure 5 Step section 85 or step section 85c).

[0055] However, Figure 6C Implementation scheme 80c achieves the same effect by changing the "optical thickness" of the layers across the gradient, rather than the physical layer thickness gradient. That is, the layers in each of the first portion 82c and the second portion 88c exhibit a refractive index difference between alternating layers, and the stepped portion 85c may have layers that do not exhibit a refractive index difference between consecutive layers, or alternatively, exhibit a refractive index difference different from that exhibited by the first portion 82c and the second portion 88c. In other words, even if the layer thickness gradient across Figure 80c is continuous, the stepped portion 85c can be configured such that, for the target wavelength, there is no layer with an optical thickness close to a quarter wavelength of the target wavelength. In implementation scheme 80( Figure 5 In embodiments 80a and 80b, the optical thickness is controlled by a physical layer thickness gradient, and in embodiment 80c, the optical thickness is controlled by changing the refractive index in the layer to achieve a similar optical thickness difference. Figures 6A to 6C The embodiments shown are merely examples and are not intended to be limiting. Other layer thickness gradients are also possible within the scope of this disclosure.

[0056] Figure 7A and Figure 7B The typical emission spectra of LED light sources are discussed elsewhere in this article, including blue emission spectrum 90b, green emission spectrum 90g, red emission spectrum 90r and near-infrared emission spectrum 90ir, and the corresponding FWHM value for each spectral curve in the spectral curves. Figure 7C Similar to Figure 3 The curve is provided here to compare Figure 90 with... Figure 7A and Figure 7B The emission spectra were compared. From... Figure 7C It can be seen that the FWHM in the second wavelength range of 72 is smaller than that in the following cases. Figure 7A and Figure 7B The FWHM of each of the emission spectra shown are 90b, 90g, 90r, and 90ir.

[0057] Figure 8 A graph showing the optical transmittance of several variants of the dual-factor certified optical film is presented. Figure 9 This specification provides graphs and data regarding the color difference between the emitted light and the light reflected by the optical film. It should also be viewed... Figure 8 and Figure 9 The following discussion will take place. Figure 8 It shows something similar to Figure 3 and Figure 7C Several variations (a) to (f) of the optical transmittance plot in Figure 90 are shown. In each variation, the peak transmittance percentage Tp and the amplitude or height of the FWHM of the plot are different, both gradually increasing from variation (a) to variation (f). These variations can be achieved by adjusting the optical film (e.g., optical film 100) as described above. Figure 1A The desired Tp and FWHM values ​​are achieved through the layer thickness distribution. In some embodiments, it is desirable to limit both the height of Tp and the FWHM such that the color coordinates measured from the light reflected (or transmitted) from the optical film are not significantly different from the light emitted by the light source. That is, at wavelengths close to the peak transmittance Tp, sufficient light must "leak through" the film to enable the use of said wavelength (e.g., red wavelengths for biometric authentication via optical sensors) without significantly affecting the color perceived by the operator on a display using the optical film. In some embodiments, for example, Figure 8 (b) or Figure 8 The implementation shown in (c) can have a sufficiently high Tp to achieve the desired functionality, while still having a sufficiently low Tp amplitude and a narrow FWHM to avoid perceptible color shift on the associated display.

[0058] Figure 9 Indicates for Figure 8 (a) to Figure 8 Figure 120 shows the chromatic difference between the emitted light (signal) and the recirculated light (light reflected by the optical film) for each embodiment of the film shown in (f). At the top of the figure, the table shows the measured percentage of transmittance (shown as Tnotch, indicating...). Figure 8 The peak transmittance (Tp) on the corresponding graph and the chromatic difference between emitted and reflected light (labeled JND, or "the only easily visible difference"). The formula for the JND value is in... Figure 9The graph shown below represents the δ (variation) of the values ​​between the first set of color coordinates (a1, b1) and the second set of color coordinates (a2, b2), or ΔE*(ab), measured using the CIE Lab color space. The gray box on the graph represents the region 122 of the graph that occurs before the sharp knee 124 in Figure 120. As shown in Figure 120, the lower the peak transmittance Tp value, the lower the chromatic aberration JND value, and after the knee 124, the JND value rises sharply after approximately 90% of Tp. The associated width of the FWHM will also vary, as a larger FWHM affects a greater number of wavelengths of light.

[0059] In some implementations, optical films (e.g., Figure 1A The optical film 100 may be configured such that the optical transmittance of the optical film relative to wavelength includes a bandpass segment having a corresponding full width at half maximum (FWHM) between about 2% and about 80%, or between about 2% and about 60%, or between about 2% and about 40%, and between about 10 nm and about 50 nm, or between about 10 nm and about 40 nm, or between about 10 nm and about 30 nm, or between about 10 nm and about 20 nm.

[0060] The optical films according to this specification can be used in various optical systems and implementations, in addition to the examples contained herein. For example, Figure 10 One embodiment of an optical system 400 (e.g., a smartwatch) is provided, which includes a transceiver 67 and an optical film 100 (or any embodiment of the optical film according to this specification). In some embodiments, the transceiver 67 is configured to emit emitted light 420 toward a measuring body 410 (e.g., skin on a user's wrist) and receive reflected light 422 reflected by the measuring body 410. In some embodiments, the optical film 100 is disposed between the transceiver 67 and the measuring body 410. In some embodiments, the emitted light 420 includes at least one of light wavelengths in the human visible wavelength range and light wavelengths in the infrared wavelength range.

[0061] Terms such as “about” will be understood in the context in which they are used and described by those skilled in the art. If it is unclear to those skilled in the art in the context of their use and description of “about” to express quantities of characteristic size, quantity, and physical properties, then “about” will be understood to mean within 10% of a specified value. A quantity given a specified value as “about” can be precisely the specified value. For example, if it is unclear to those skilled in the art in the context of their use and description of this specification, a quantity having a value of about 1 means that the quantity has a value between 0.9 and 1.1, and that the value can be 1.

[0062] The term "substantially" will be understood by those skilled in the art in the context of its use and description herein. If the use of "substantially equal" is unclear to those skilled in the art in the context of its use and description herein, "substantially equal" will refer to approximately as described above. If the use of "substantially parallel" is unclear to those skilled in the art in the context of its use and description herein, "substantially parallel" will refer to being within 30 degrees of parallelism. In some embodiments, directions or surfaces described as substantially parallel to each other may be within 20 degrees or 10 degrees of parallelism, or may be parallel or nominally parallel. If the use of "substantially aligned" is unclear to those skilled in the art in the context of its use and description herein, "substantially aligned" will refer to alignment within 20% of the width of the aligned objects. In some embodiments, objects described as substantially aligned may be aligned within 10% or 5% of the width of the aligned objects.

[0063] All cited references, patents, and patent applications are incorporated herein by reference in their entirety in a consistent manner. In the event of any inconsistency or contradiction between the incorporated references and this application, the information in the foregoing description shall prevail.

[0064] Unless otherwise stated, the description of elements in the accompanying drawings should be understood to apply equally to corresponding elements in the other drawings. While specific embodiments have been illustrated and described herein, those skilled in the art will recognize that various alternative and / or equivalent embodiments may be used instead of the illustrated and described embodiments without departing from the scope of this disclosure. This application is intended to cover any modifications or variations of the specific embodiments discussed herein. Therefore, this disclosure is intended to be limited only by the claims and their equivalents.

Claims

1. An optical film, comprising: A plurality of polymer layers, the total number of which is at least 200, are disposed between and co-extruded and co-stretched with opposite first and second outer layers. Each of the polymer layers has an average thickness of less than 150 nm. The thickness gradient of the optical film comprises a first portion and a second portion connected by stepped portions. Each of the first and second portions extends across at least 30 layers of the polymer layers. The stepped portions extend across less than 10 layers of the polymer layers. The thickness change across the stepped portions is at least 5 times greater than the thickness change across each of the first and second portions. Within the stepped portions, consecutive layers exhibit a refractive index difference of 0 relative to alternating layers in the first and second portions. The optical film has a first average transmittance percentage TA1 in a first wavelength range, a peak transmittance percentage Tp in different second wavelength ranges, and the first wavelength range and the second wavelength range are separated by a third wavelength range having a third average transmittance percentage TA3, each of the first wavelength range and the third wavelength range being at least 100 nm wide, the second wavelength range being less than 50 nm wide, TA1 > Tp > 30TA3, and wherein the stepped portion is configured such that, for the target wavelength in the second wavelength range, there is no polymer layer with an optical thickness of one-quarter of the target wavelength.

2. The optical film according to claim 1, wherein each of the first portion and the second portion is a linear portion.

3. The optical film of claim 2, wherein the best linear fit of each of the linear first portion and the second portion has an R-squared value greater than or equal to 0.

8.

4. The optical film according to claim 1, wherein the stepped portion has a negative slope.

5. The optical film according to claim 1, wherein the stepped portion has a positive slope.

6. The optical film according to claim 1, wherein the optical film is selected from the group consisting of reflectors, reflective polarizers, absorptive polarizers, partial reflectors, and diffusers.

7. The optical film according to claim 1, wherein the wavelength in the first wavelength range is in the range of 800nm ​​to 2000nm, and the wavelength in the second wavelength range is in the range of 550nm to 700nm.

8. The optical film according to claim 1, wherein the first wavelength range is one of the visible wavelength range and the near-infrared wavelength range, and the second wavelength range is the other of the visible wavelength range and the near-infrared wavelength range.

9. An optical system, comprising: A transceiver configured to emit emitted light toward a measuring body and receive reflected light reflected by the measuring body; and According to claim 1, the optical film is disposed between the transceiver and the measuring body, and the emitted light includes at least one of light wavelengths in the first wavelength range and light wavelengths in the second wavelength range.

10. A light-reflecting film comprising a plurality of polymer layers totaling at least 200, wherein a graph of the average layer thickness relative to the number of polymer layers includes a stepped portion separating a left portion of the polymer layers having a smaller number of layers from a right portion of the polymer layers having a larger number of layers, each of the left and right portions extending across at least 30 sequentially arranged polymer layers, and wherein... Within the stepped portion, the continuous layers exhibit a refractive index difference of 0 relative to the alternating layers in the left and right portions, such that the optical transmittance of the light-reflecting film relative to wavelength includes a peak at the peak wavelength of a corresponding full width at half maximum (FWHM) in the visible wavelength range, the peak separating the lower wavelength range from the higher wavelength range, the lower wavelength range and the higher wavelength range extending across M1 nanometers, M1 / FWHM ≥ 1.5, such that for normally incident light, the plurality of polymer layers have: The average transmittance TA2 across each of the lower and higher wavelength ranges, and The transmittance Tp at the peak wavelength is Tp, Tp / TA2 ≥ 30, and the stepped portion is configured such that, for the target wavelength, there is no polymer layer with an optical thickness of one-quarter of the target wavelength.

11. The light-reflecting film of claim 10, wherein each of the left portion and the right portion is a linear portion.

12. The light-reflecting film of claim 11, wherein the best linear fit of each of the left portion and the right portion has an R-squared value greater than or equal to 0.

8.

13. The light-reflecting film of claim 11, wherein the best linear fit of each of the left portion and the right portion has an R-squared value greater than or equal to 0.

85.

14. The light-reflecting film of claim 11, wherein the best linear fit of each of the left portion and the right portion has an R-squared value greater than or equal to 0.

90.

15. The light-reflecting film of claim 10, wherein for normally incident light, the plurality of polymer layers have an average transmittance TA1 in the infrared wavelength range, TA1 ≥ Tp, wherein each of the visible wavelength range and the infrared wavelength range is at least 200 nm wide.

16. The light-reflecting film according to claim 11, wherein Tp is greater than 70%.

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