High contrast optical film and devices including the same

Abstract

To provide a reflection type polarizer film that uses an optical film that includes a plurality of interference layers and that can be used in a liquid crystal display.SOLUTION: Each interference layer 102 reflects or transmits light primarily by optical interference. The total number of the interference layers is less than about 1000. For a substantially normally incident light 110 in a predetermined wavelength range, the plurality of interference layers has an average optical transmittance greater than about 85% for a first polarization state, an average optical reflectance greater than about 80% for an orthogonal second polarization state, and an average optical transmittance less than about 0.2% for the second polarization state.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This disclosure relates to a reflective polarizer film that may be used in liquid crystal displays. [Background technology]

[0002] Optical displays are widely used in laptop computers, handheld calculators, digital watches, and other devices. A well-known example of such an optical display is the liquid crystal display (LCD). In an LCD, a portion of the liquid crystal has an altered optical state due to the application of an electric field. This process generates the contrast necessary to display the "pixels" of information. In some examples, an LCD display may include a combination of various optical films, including reflective polarizers, to alter the optical properties of the display assembly.

[0003] LCD displays can be classified based on the type of lighting they use. "Reflective" displays are illuminated by ambient light entering the display from the "front." Typically, a matte aluminum reflector is positioned "behind" the LCD assembly. Another common example is incorporating a "backlit" assembly for reflective matte aluminum surfaces in applications where ambient light intensity is insufficient for viewing. A typical backlit assembly includes a light cavity and a lamp or other structure that generates light. Displays intended to be viewed under both ambient and backlit conditions are called "semi-transparent." One problem with semi-transparent displays is that a typical backlight is not as efficient a reflector as a conventional matte aluminum surface. Furthermore, backlights tend to randomize the polarization of light, further reducing the amount of light available to illuminate the LCD display. Therefore, adding a backlight to an LCD display generally results in lower brightness when viewed under ambient light. [Overview of the project]

[0004] In some examples, the Disclosure describes an optical film comprising a plurality of interference layers, each interference layer reflecting or transmitting light primarily by optical interference, the total number of interference layers being less than approximately 1000, and for substantially perpendicularly incident light within a given wavelength range, the plurality of interference layers have an average light transmittance of more than approximately 85% for a first polarization state, an average light reflectance of more than approximately 80% for a second orthogonal polarization state, and an average light transmittance of less than approximately 0.2% for the second polarization state.

[0005] In some examples, the disclosure describes an optical film comprising multiple interference layers, each interference layer reflecting or transmitting light primarily by optical interference, the total number of interference layers being less than approximately 1000, and for substantially normally incident light within a given wavelength range, the optical film has an average light transmittance (T) for a first polarization state (a). a ) and average light reflectance (R a ), the average light transmittance (T) for the orthogonal second polarization state (b) b ) and average light reflectance (R b ), T b / R b R is less than approximately 0.002. a / T a It is less than approximately 0.17.

[0006] In some examples, the disclosure describes an optical film comprising (N) sequentially numbered layers, where (N) is an integer greater than 200 and less than 1000, each layer having an average thickness of less than approximately 200 nm, the fit curve being a best fit regression applied to a layer thickness profile plotting the thickness of each layer as a function of the number of layers, the average slope of the fit curve in the region extending from the first layer to the (Nth)th layer being less than approximately 0.2 nm / layer, and for substantially perpendicularly incident light within a given wavelength range, the optical film having an average light transmittance of more than approximately 85% for a first polarization state and an average light reflectance of more than approximately 80% for a second orthogonal polarization state.

[0007] In some examples, the disclosure describes an optical film comprising (N) sequentially numbered layers, where (N) is an integer greater than 200, less than 10% of the layers having a thickness greater than approximately 200 nm, and the fit curve is a best fit regression applied to the layer thickness of the optical film as a function of the number of layers, with the mean slope of the fit curve in the region extending from the first layer to the (Nth)th layer being less than approximately 0.2 nm.

[0008] In some examples, the disclosure describes an optical film comprising a plurality of interference layers numbered sequentially from 1 to (N), where (N) is an integer greater than 50 and less than 1000, the optical film transmits at least 80% of light having a first polarization state within a given wavelength range and reflects at least 80% of light having a second polarization state orthogonal within a given wavelength range, the fit curve is a best fit regression applied to the layer thickness of the optical film as a function of the number of layers, the difference between the maximum and minimum slopes of the fit curve is less than approximately 0.70 nm / layer in the region extending from the first layer to the (N)th layer, and the maximum and minimum slopes are evaluated over any group of 25 to 50 adjacent layers.

[0009] In some examples, the disclosure describes an optical film that transmits at least 80% of light having a first polarization state within a given wavelength range and reflects at least 80% of light having a second polarization state orthogonal within a given wavelength range, the optical film comprising a laminate of (N) layers, where (N) is an integer greater than 50 and less than 1000, for multiple non-overlapping groups of continuously arranged layers in the (N) layer laminate, the layers in each group are numbered from 1 to (m), where (m) is greater than 25, for each non-overlapping group, the fit curve is a best fit regression applied to the layer thickness of the group as a function of the number of layers, and in the region extending from the first layer in the group to the (m)th layer in the group, the fit curve has an average slope such that the maximum difference between the average slopes of the fit curves in multiple non-overlapping groups is less than 0.70 nm / layer.

[0010] In some examples, the present disclosure describes an optical film including a plurality of alternating first and second layers, each of the first and second layers mainly reflects or transmits light by light interference, the total number of each of the first and second layers is less than 400 and greater than 100, and for each pair of adjacent first and second layers, in the plane of the first layer, the first layer has a maximum refractive index n1 along the x direction x and the second layer has a maximum refractive index n2 along the x direction x where the difference between n1 x and n2 x is greater than about 0.24, and the maximum angular range in the x direction of the first layer is less than about 2 degrees.

[0011] In some examples, the present disclosure describes an optical film including a plurality of alternating high-refractive-index and low-refractive-index interference layers, each interference layer mainly reflects or transmits light by light interference, the total number of interference layers is greater than 300, and the optical power of the optical film per interference layer is greater than about 0.7.

[0012] In some examples, the present disclosure describes an optical film including a plurality of alternating high-refractive-index and low-refractive-index interference layers, each interference layer mainly reflects or transmits light by light interference, and the optical power per interference layer of the plurality of interference layers exceeds (-0.0012 * N + 1.46), where (N) is the total number of alternating high-refractive-index and low-refractive-index interference layers, and (N) is greater than 100 and less than 1000.

[0013] In some examples, the disclosure describes an optical film comprising multiple interference layers that reflect and transmit light primarily by optical interference, wherein, for substantially normally incident light within a given wavelength range, the multiple interference layers transmit at least 80% of the light having a first polarization state and reflect at least 80% of the light having an orthogonal second polarization state, and have an average light density greater than about 2.5, wherein the multiple interference layers are divided into multiple optical stacks, and each pair of adjacent optical stacks is separated by one or more spacer layers that do not reflect or transmit light primarily by optical interference, and each light The optical laminate transmits at least 50% of light having a first polarization state within a predetermined wavelength range and reflects at least 50% of light having a second polarization state within a predetermined wavelength range, the interference layers in each optical laminate are numbered sequentially, each optical laminate has a best-fit linear equation relating the thickness of the optical laminate to the number of interference layers, the linear equation has an average slope within a region extending from the first interference layer in the laminate to the last interference layer in the laminate, and the maximum difference between the average slopes of the linear equations for multiple optical laminates is less than approximately 20%.

[0014] In some examples, the disclosure describes an optical film that transmits at least 80% of light having a first polarization state within a given wavelength range and reflects at least 80% of light having a second polarization state orthogonal within a given wavelength range, the optical film comprising 200 or more and 400 continuously arranged unit cells, each unit cell comprising a first layer of low refractive index and an adjacent second layer of high refractive index, the difference between the high and low refractive indices for each unit cell is greater than about 0.24, each unit cell has a total optical thickness equal to half the central wavelength in the given wavelength range, and for each of at least 80% of pairs of adjacent unit cells in the continuously arranged unit cells, the ratio of the difference between the central wavelengths of adjacent unit cells to the average of the central wavelengths of adjacent unit cells is less than about 2%.

[0015] In some examples, the disclosure describes an optical film comprising a plurality of interference layers that reflect or transmit light primarily by optical interference in a given wavelength range, where the maximum difference between the refractive indices of the interference layers is Δn, the fit curve is a best fit regression applied to the layer thickness of the optical film as a function of the number of layers, the fit curve has an average slope K in a region extending across the plurality of interference layers, and Δn / K is greater than approximately 1.2.

[0016] In some examples, the disclosure provides a system in which a series of first unit cells are arranged, each optimized to transmit or reflect light in a first predetermined wavelength range rather than a second predetermined wavelength range (M a The present invention describes an optical film comprising (M), where each of the first unit cells comprises a first high refractive index layer and a second low refractive index layer, b The continuously arranged second unit cells of (M) are optimized to transmit or reflect light in a second predetermined wavelength range, not in a first predetermined wavelength range, and each of the second unit cells comprises a third high refractive index layer and a fourth low refractive index layer, (M a For ) consecutively arranged first unit cells, the ratio of the average refractive index of the first high refractive index layer to the average refractive index of the second low refractive index layer × (M a ) exceeds approximately 300, (M b For ) consecutively arranged second unit cells, the ratio of the average refractive index of the third high refractive index layer to the average refractive index of the fourth low refractive index layer × (M b ) exceeds approximately 300, and light incident on the optical film at any incident angle from approximately 0 to approximately 30 degrees has any wavelength within a first predetermined wavelength range and a second predetermined wavelength range, and the average light transmittance (T) of the optical film for the first polarization state is greater than approximately 300. a ) versus the average light transmittance of the optical film for a second orthogonal polarization state (T b The ratio is approximately 1000:1 or greater.

[0017] In some examples, the disclosure describes a display assembly including a light source, a liquid crystal display assembly, and one of the optical films described in detail disposed between the liquid crystal display assembly and the light source.

[0018] In some examples, the disclosure describes a display assembly including a light source; a liquid crystal layer configured to be illuminated by the light source; one or more brightness-enhancing films disposed between the light source and the liquid crystal layer to increase brightness in the axial direction of the display assembly; a reflective polarizer disposed between the one or more brightness-enhancing films and the liquid crystal layer, configured to substantially transmit light having a first polarization state and substantially reflect light having a second orthogonal polarization state; and a reflective polarizer having an average light transmittance of less than about 0.2% for the second polarization state, wherein no absorbing polarizer is disposed between the light source and the liquid crystal layer, and the contrast ratio of the display assembly is at least twice that of a comparative display assembly having the same structure, except that the average transmittance of the reflective polarizer of the comparative display assembly for the second polarization state is greater than about 1.0%.

[0019] In some examples, the disclosure describes a display assembly including a light source, a liquid crystal layer configured to be illuminated by the light source, one or more brightness-enhancing films disposed between the light source and the liquid crystal layer to increase brightness in the axial direction of the display assembly, and a reflective polarizer disposed between the one or more brightness-enhancing films and the liquid crystal layer, comprising a plurality of interference layers that transmit or reflect light mainly by optical interference, wherein no absorbing polarizer is disposed between the light source and the liquid crystal layer such that, for substantially normally incident light within a given wavelength range, the plurality of interference layers transmit at least 80% of the light having a first polarization state and transmit less than about 0.2% of the light having an orthogonal second polarization state.

[0020] In some examples, the Disclosure describes an optical laminate comprising a reflective polarizer having a plurality of interference layers, each interference layer reflecting or transmitting light primarily by optical interference, wherein, for substantially normally incident light of a predetermined wavelength, the plurality of interference layers have an optical transmittance of more than about 85% for a first polarization state, an optical reflectance of more than 80% for an orthogonal second polarization state, and a light transmittance of less than about 0.1% for a second polarization state, coupled to the reflective polarizer and having substantially the same extent, wherein, for substantially normally incident light of a predetermined wavelength, the absorptive polarizer has a first optical transmittance for the first polarization state, a light absorptiveness of more than about 50% for a second polarization state, and a second light transmittance for a second polarization state, with the ratio of the second light transmittance to the first light transmittance being greater than about 0.001.

[0021] In some examples, the present disclosure describes an optical system for displaying an object to an observer centered on the optical axis, comprising: at least one optical lens having non-zero optical power; a reflective polarizer disposed on and conforming to the first principal surface of the optical lens, which substantially transmits light having a first polarization state and substantially reflects light having a second orthogonal polarization state; and a partial reflector disposed on and conforming to a different second principal surface of the optical lens, which has an average light reflectance of at least 30% over a given wavelength range, and the average light transmittance of the optical system to incident light along the optical axis having a second polarization state is less than about 0.1%.

[0022] In some examples, the Disclosure describes a polarizing beam splitter (PBS) comprising a first prism and a second prism, and a reflective polarizer disposed and bonded between the first and second prisms, wherein the reflective polarizer substantially reflects polarization having a first polarization state and substantially transmits polarization having a second polarization state which is orthogonal to the PBS, and incident light having a predetermined wavelength enters the PBS from the input side of the PBS, encounters the reflective polarizer at least once, and exits the PBS from the output side of the PBS, wherein the ratio of the average intensity of the exiting light to the average intensity of the incident light is greater than about 90% when the incident light has a first polarization state and less than about 0.2% when the incident light has a second polarization state.

[0023] Some examples describe liquid crystal display projection systems that include the optical films described herein.

[0024] In some examples, the present disclosure provides that a display assembly includes a light source, a liquid crystal layer configured to be illuminated by the light source, and a reflective polarizer comprising an optical film as described in any one of paragraphs 1 to 126, the reflective polarizer disposed adjacent to the liquid crystal layer.

[0025] Details of one or more examples are shown in the attached drawings and the following description. Other features, purposes, and advantages will become apparent from the description and drawings, as well as from the claims. [Brief explanation of the drawing]

[0026] [Figure 1] This is an exemplary optical film containing multiple interference layers numbered sequentially from 1 to (N).

[0027] [Figure 2] This is a schematic perspective view showing a segment of the optical film in Figure 1, which exhibits the alternating interference layer.

[0028] [Figure 3] Figure 1 shows an exemplary thickness profile plot of the optical film.

[0029] [Figure 4A] Another example of an optical film that can be formed to exhibit one or more optical properties described herein is shown.

[0030] [Figure 4B] Figure 4A shows a plot of the exemplary thickness profile of the optical film.

[0031] [Figure 4C] Figure 4A shows a pair of exemplary thickness profile plots of the optical film.

[0032] [Figure 5A] This is an exemplary transmission plot for a typical optical film according to the present disclosure. [Figure 5B] This is an exemplary transmission plot for a typical optical film according to the present disclosure.

[0033] [Figure 6] Another example of an optical film that can be formed to exhibit one or more optical properties described herein is shown.

[0034] [Figure 7] This is a diagram of an exemplary display assembly, including a reflective polarizer optical film, a liquid crystal display assembly, and a light source.

[0035] [Figure 8] Figure 7 shows an exemplary brightness profile of the display assembly.

[0036] [Figure 9] This plot shows the layer profile of Example 1.

[0037] [Figure 10] This is a schematic cross-sectional view of an exemplary optical system including an optical film in the form of a reflective polarizer.

[0038] [Figure 11] This is a schematic cross-sectional view of an exemplary polarizing beam splitter, which includes an optical film in the form of a reflective polarizer.

[0039] [Figure 12] This is a plot of exemplary thickness profiles (layer thickness versus number of layers) for exemplary reflective polarizer films described herein, compared to conventional reflective polarizer films.

[0040] [Figure 13] The layer thickness profiles of the optical film in Example 7 are plotted.

[0041] [Figure 14] The plot shows the block state transmission (Tb) for the film of Example 6 over the wavelength range of 375 to 850 nm.

[0042] [Figure 15] Table 6 shows the optical power per layer for a non-limiting number of layers of optical films prepared in accordance with the disclosure, compared with the comparative examples in Table 6. [Modes for carrying out the invention]

[0043] The optical films described herein are used in display assemblies to improve the brightness of the display when viewed under ambient light, reduce the overall thickness of the display assembly, or provide other useful advantages. In some examples, the optical films described herein can be used as reflective polarizers, which exhibit a relatively high contrast ratio of incident light within a desired wavelength range transmitted through the optical film in the transit polarization state compared to light transmitted through the film in the orthogonal reflective polarization state. In some examples, the described optical films can exhibit a contrast ratio of at least 1000:1 while using a relatively small number of total optical layers (e.g., 1000 or fewer total layers). In some examples, the properties and structure of the optical films described herein can provide reflective polarizers exhibiting a high contrast ratio while remaining remarkably thin in overall thickness (e.g., less than about 100 μm).

[0044] The optical films described herein may be characterized as multilayer optical films having a plurality of optical layers (e.g., interference layers) configured to selectively transmit and reflect light within a given wavelength range. In some such examples, the optical film may function as a reflective polarizer or a RP that selectively transmits and reflects light in different polarization states. For example, Figure 1 is a schematic perspective view showing an example of a multilayer optical film 100 having a total of (N) interference layers 102, including a plurality of interference layers 102 arranged along a central axis. The figure includes a coordinate system defining the X, Y, and Z directions referenced in perception of the optical film 100.

[0045] During use, light incident on the main surface (e.g., film surface 104) of the optical film 100, which is depicted as incident light 110, enters the first layer of the optical film 100, propagates through a plurality of interference layers 102, and undergoes selective reflection or transmission due to optical interference, depending on the polarization state of the incident light 110. The incident light 110 may include a first polarization state (a) and a second polarization state (b) that are orthogonal to each other. The first polarization state (a) can be considered a "pass-through" state, while the second polarization state (b) can be considered a "reflection" state. As the incident light 110 propagates through the plurality of interference layers 102, some of the light in the second polarization state (b) is reflected by the layer that is in focus in the second polarization state (b) and reflected by the optical film 100, while some of the light in the first polarization state (a) passes through the optical film 100 as a whole.

[0046] In some embodiments, the optical film 100 can be characterized in terms of the reflectance and transmittance of the first and second polarization states (a) and (b) of the incident light 110. For example, the amount of incident light 110 for a given wavelength that passes through the optical film 100 is T a Light transmittance (T) for the first polarization state (a) orthogonal to a ) the percentage of and the light transmittance (T) for the second polarization state (b). b ) can be expressed as a percentage. The amount of incident light 110 reflected by the optical film 100 for a predetermined wavelength range is T a The optical reflectance override (R) for the first polarization state (a) that is orthogonal to the first polarization state (a) a ), and the light reflectance (R) for the second polarization state (b). b ) can be expressed as a percentage. For a given optical film, for example, the sum of the transmittance, reflectance, and loss due to absorption is 100% for light within a given wavelength range. In this disclosure, the optical film 100 may have a relatively low absorbance for light within a given wavelength range. In some examples, the relatively low absorbance of incident light 110 by the optical film 100 can reduce the heat generated within the optical film 100, resulting in a more efficient reflective film overall.

[0047] The predetermined wavelength range may be any suitable wavelength range, including, for example, visible light (e.g., about 400 to about 700 nm), near-infrared light (e.g., about 800 to about 1300 nm), and a range based on the output of a liquid crystal display backlight (425 to 675 nm). In some examples, the optical film 100 may be configured to transmit and reflect light in different polarization states of two or more predetermined wavelength ranges, such as visible light and near-infrared light. For example, the predetermined wavelength range may include a first range of about 430 nm to about 465 nm, a second range of about 490 nm to about 555 nm, and a third range of about 600 nm to about 665 nm. In some such examples, the optical film 100 may include a number of laminates / packets, each containing multiple interference layers, as will be further described below with respect to Figure 4, and each laminate / packet may be oriented to a different predetermined wavelength range.

[0048] In some examples, the interference layer may be characterized as a series of two-layer unit cells, as will be further described below. The thickness of each unit cell may be configured to reflect target wavelengths within a given wavelength range. In some examples, the center wavelength of reflectance for a unit cell corresponds to twice the optical thickness of the two-layer unit cell. Thus, to reflect a given wavelength range (e.g., 400–1000 nm), the unit cells in the laminate / packet will have different thicknesses to cover wavelengths at the left band edge, the right band edge, and in between.

[0049] In some non-limiting examples, the optical film 100 may include fewer than approximately 1000(N) interference layers 102, each interference layer 102 reflecting or transmitting incident light 110 primarily by optical interference. For example, an optical film 100 is provided having fewer than 1000(N) total interference layers 102, but in some examples, the optical film 100 may include more than 1000 total interference layers 102, and some of the described optical properties can still be obtained. In other examples, it may be desirable to use fewer total layers to achieve the desired optical performance in order to reduce the overall thickness of the film, as it is desirable in many applications to reduce the overall thickness of the display assembly (e.g., LCD display). In addition, a smaller total number of interference layers 102 may reduce the complexity of the manufacturing process, reduce the possibility of variability (e.g., spectral variation in block or pass-through states), or reduce manufacturing errors in the final optical film (e.g., increased block-state transmittance due to depolarization between layers, decrease in pass-through state transmittance, etc.). In some examples, the optical film 100 may include other layers, with a total layer of less than 900(N) or less than 800(N).

[0050] In some such examples, by using a total of approximately 1000 (N) interference layers 102, the optical film achieves an average light transmittance (T) of more than approximately 85% for the first polarization state (a) for substantially normally incident light 110 within a given wavelength range. a ), the average light reflectance (R) is over 80% for the orthogonal second polarization state (b). b ), and an average light transmittance (T) of less than approximately 0.2% for the second polarization state (b). b ) may have.

[0051] In some examples, the optical film 100 may be characterized in terms of its light transmittance or reflectance. In some examples, the average light transmittance (T) of the first / pass-through polarization state (a) of the optical film 100 for incident light 110 (e.g., from air to the optical film 100) within a predetermined wavelength range is defined. a) may exceed approximately 85% when using a total (N) interference layer 102 of 1000 or less, may exceed 87% in some cases, and may exceed 89% in some cases. In some cases, the average light transmittance (T) of the second / reflected polarization state (b) of the optical film 100 for incident light 110 within a predetermined wavelength range is b When using a total (N) interference layer 102 of 1000 or less, the ratio can be less than approximately 0.15%, and in some cases, less than 0.10%.

[0052] In some examples, the optical film 100 may be characterized in terms of the light transmittance through the multiple interference layers 102 (for example, neglecting losses related to reflectance at the interface between air and the film). In some examples, the average light transmittance (T) of the first / pass-through polarization state (a) through the multiple interference layers 102 for incident light 110 within a given wavelength range is defined as the light transmittance through the multiple interference layers 102. a When using a total (N) interference layer 102 of less than 1000, the ratio may exceed approximately 90%, may exceed 95% in some cases, and may exceed 98% in some cases.

[0053] The properties and structure of the optical film 100 can provide a film with a relatively high contrast ratio. The contrast ratio can be defined as the ratio of the normal incident light 110 transmitted through the optical film 100 in a first polarization state (a) (e.g., the "passing" state) to the normal incident light 110 transmitted through the optical film 100 in a second orthogonal polarization state (b) (e.g., the "reflection" state) for a specific wavelength range.

[0054] In some examples, the transmittance and reflectance of the optical film 100 may be characterized by the ratio of transmittance to reflectance in a given polarization state. For example, the ratio of the percentage of light transmittance to the percentage of light reflectance in a first polarization state (a) is (R a / T a ) may be expressed as, and the ratio of the percentage of light transmittance to the percentage of light reflectance in the second polarization state (b) is (T b / Rb It can be expressed as ). In some examples, R a / T a The ratio can be relatively low, for example, less than approximately 0.17, T b / R b The ratio may be relatively low, for example, less than approximately 0.002.

[0055] In some non-limiting examples, an optical film 100 with a total (N) of fewer than approximately 1000 interference layers 102 reflects or transmits light primarily by optical interference, and for substantially perpendicular incident light 110 within a given wavelength range, the optical film 100 has a T b / R b The ratio is less than approximately 0.002 (for example, less than 0.001), and R a / T a It is less than approximately 0.017 (for example, less than 0.14), and T a and R a These are the average light transmittance and reflectance for each of the first polarization states (a) (e.g., the "pass" state) for incident light 110 within a predetermined wavelength range, and T b and R b These are the average light transmittance and reflectance for each of the second polarization states (b) (e.g., the "blocked" state).

[0056] In some examples, the optical film 100 is characterized by the ratio of the percentage of light transmittance for a first polarization state (a) to the percentage of light transmittance for a second polarization state (b). For example, the ratio T representing the light transmittance of the optical film 100 for the first polarization state (a) and the second polarization state (b) a / T b It can exceed approximately 425.

[0057] In addition, the optical film 100 is characterized in the ratio of the percentage of light reflectance for the second polarization state (b) and the first polarization state (a). For example, the ratio R representing the light transmittance of the optical film 100 for the second polarization state (b) and the first polarization state (a) b / R a It can exceed approximately 6.7.

[0058] In some examples, the transmittance and reflectance characteristics of the optical film 100 may be characterized by incident light within a predetermined wavelength range, where the incident angle on the surface 104 is within a set angle of less than approximately 30°, for example less than approximately 20°, or less than approximately 10°, and the incident angle measured from the normal to the surface 104 was 0°, representing the normal. For example, in some non-limiting examples, incident light on the surface 104 of the optical film 100, incident at an incident angle of less than approximately 10° within a predetermined wavelength range (e.g., visible light from approximately 400 nm to approximately 700 nm), has an average light transmittance (T) of more than approximately 85% for the first polarization state (a). a ), the average light reflectance (R) is over 80% for the second polarization state (b). b ), and an average light transmittance of less than approximately 0.2% for the second polarization state (b) (R b ) is possible.

[0059] In some examples, the interference layer 102 of the optical film 100 may consist of alternating layers (e.g., A and B) of two different polymer materials exhibiting different refractive index properties. For example, Figure 2 is a schematic perspective view of a segment of the optical film 100 showing the alternating interference layers 102a and 102b. Figure 2 includes a coordinate system that defines the X, Y and Z axes to help illustrate the optical properties of the optical film 100.

[0060] As shown in Figure 2, the optical film 100 comprises alternating layers of different optical materials, referred to as material "(A)" and material "(B)" (e.g., ABABA...), throughout the drawings and description. Furthermore, as described below, the various layers of the two different materials may be formed through an extrusion / lamination process in which the layers are extruded together to form a number of optical layers 102 (ABABA...) that are bonded together.

[0061] In some examples, during the extrusion process, the optical layer 102 may be stretched to impart various interference properties to the film. For example, the layers of optical materials A and B are stretched along one axis (e.g., the X-axis) (e.g., in a 5:1 or 6:1 ratio) but not significantly (1:1) along the orthogonal axis (e.g., the Y-axis). The X-axis is referred to as the “stretching” direction, while the Y-axis is referred to as the “transverse” direction.

[0062] The optical materials used to form layers A and B may be selected to impart specific optical properties to the film as a result of the stretching process. For example, the material (B) forming the optical layer 102b may have a nominal refractive index (e.g., n² = 1.64) that is not substantially altered by the stretching process. Thus, in the x and y directions (n² x and n2 y The refraction or refractive index of layer "B" 102b in both directions may be substantially the same in both directions after the stretching process. In contrast, the material (A) forming the optical layer 102a may have a refractive index that changes with the stretching process. For example, the uniaxially stretched layer 102a of material (A) may have a refractive index that changes in the X-axis or the stretching direction 120 (e.g., n1 x It has a higher refractive index in the Y-axis or non-stretching direction 122 (e.g., n1 = 1.88), and y The refractive indices may have different values ​​related to (=1.64). Since the refractive index is higher in the stretching direction, layer 102a containing material (A) may be considered a high refractive index (HIR) layer 102a, while layer 102b containing material (B) may be considered a low refractive index (LIR) layer 102b. In some examples, the refractive indices of the alternating A and B layers are controlled by appropriate material selection and processing conditions. In some examples, the optical properties of layer 102 may cause an optical film 100 to act as a reflective polarizer, substantially transmitting the first polarization state (a) component of incident light 110 within a predetermined wavelength range oriented with respect to the non-stretching axis 122. On the other hand, the stretching axis 120 would correspond to a reflective axis in which the component of incident light 110 in a second polarization state (b) within a predetermined wavelength range is substantially reflected through optical interference.

[0063] In some examples, the optical film 100 has a refractive index (i.e., Δn) between alternating HIR layers 102a and LIR layers 102b along the stretch axis 120. x =n1 x -n2 x The difference between them may be characteristic. In some such examples, the refractive index between the alternating HIR layer 102a and LIR layer 102b along the non-stretching axis 122 is such that the difference between them is Δn y =n1 y -n2 y The difference in refractive index between the HIR layer 102a and the LIR layer 102b may be substantially the same, such that the difference is approximately 0.0. In some examples, the Δn between the HIR layer 102a and the LIR layer 102b may be x By increasing the same light power, a lower Δn x Compared to optical films with a smaller total number of interference layers, polarization for a given wavelength range can be sufficiently transmitted / reflected.

[0064] Preferably, the direction of each stretch axis of the interference layer 102 is substantially aligned (e.g., aligned or nearly aligned) such that the X axis of each layer 102 represents the direction for obtaining the maximum refractive index in the XY plane (Figure 2) for each layer. However, depending on the mechanical tolerances and the number of interference layers 102, the stretch axis 120 for each interference layer (e.g., representing the direction for obtaining the maximum refractive index or maximum refraction for the layer) may be aligned within a variation of about ±2°.

[0065] In some non-limiting examples, the optical film 100 may include a first layer 102a and a second layer 102b, with a combined refractive index greater than 200 and less than 1000(N), which reflect or transmit light primarily by optical interference. For example, the optical film 100 may include a first layer 102a with a refractive index less than 400 and greater than 100, and a second layer 102b with a refractive index less than 400 and greater than 100. In some such examples, for each pair of adjacent first layers 102a and second layers 102b, the layers may define a stretching axis that represents the direction of the maximum refractive index obtained for each layer (e.g., refractive index n1 for the two layers). x and n2 x The corresponding X-axis / direction (120). Principal axis (e.g., Δnx =n1 x -n2 x The difference in refractive index between the first layer 102a and the second layer 102b with respect to ) may exceed about 0.24. In some such examples, the directions of the respective stretching axes for each of the first optical layer 102a and the second optical layer 102b may be substantially aligned, such that the interference layer 102 dictates that the maximum angular range of the directions of their respective stretching axes is less than about 2 degrees.

[0066] An optical film 100 containing multiple interference layers 102 can be formed using any preferred technique. For example, layers 102a and 102b containing optical materials A and B are each manufactured using co-extrusion, casting, and orientation processes to form a laminate / packet of tens to hundreds of interference layers 102, and then the extruded layers are stretched or oriented to form a laminate / packet of interference layers 102. Each laminate / packet may contain about 200 to about 1000 total interference layers, depending on the desired properties of the optical film 100. As used herein, “laminated / packet” is used to refer to a continuous set of alternating interference layers 102a, 102b, in which there are no spacers or non-interfering layers formed within the laminate / packet (e.g., continuously arranged). In some examples, spacers, non-interfering layers, or other layers may be added to the outside of a given laminate / packet, thereby forming an outer layer of the film without disrupting the alternating pattern of interference layers 102 within the laminate / packet.

[0067] In some examples, the optical film 100 may be manufactured by co-extrusion. This manufacturing method includes (a) providing at least first and second streams of resin corresponding to a first polymer and a second polymer to be used in the finished film, and (b) dividing the first stream and the second stream into a plurality of layers using a suitable feed block, the feed block having (i) a gradient plate including a first flow channel and a second flow channel, wherein the first channel has a cross-sectional area that changes along the flow channel from a first position to a second position, and (ii) a plurality of first conduits that are in fluid communication with the first flow channel and a plurality of second conduits that are in fluid communication with the second flow channel A supply pipe plate comprising a supply pipe plate in which each conduit supplies its respective slot die, each conduit having a first end and a second end, the first end of the conduit being in fluid communication with a flow channel and the second end of the conduit being in fluid communication with a slot die, and (iii) a supply pipe comprising an axial rod heater optionally disposed near the conduit, (c) passing a composite stream through an extrusion die to form a multilayer web in which each layer is substantially parallel to the main surface of the adjacent layer, and (d) casting the multilayer web onto a chill roll, sometimes called a casting wheel or casting drum, to form a cast multilayer film. The cast film may have the same number of layers as a finished film, but the layers of the cast film are typically much thicker than the layers of the finished film.

[0068] After cooling, the multilayer web can be reheated, stretched, or drawn to produce a near-finished multilayer optical film. Stretching or drawing serves two purposes: to thin the layers to a desired final thickness profile, and to orient the layers such that at least some of them are birefringent. Orientation or drawing can be achieved simultaneously or sequentially along the cross-web direction (e.g., via a tenter), along the down-web direction (e.g., via a length aligner), or in any combination thereof. When drawn in only one direction, the drawing is either "unconstrained" (the film is dimensionally relaxed in the in-plane direction perpendicular to the drawing direction) or "constrained" (the film is constrained and cannot be dimensionally relaxed in the in-plane direction perpendicular to the drawing direction). When drawn along the in-plane direction, the drawing is symmetrical, i.e., equal or asymmetrical along the orthogonal in-plane directions. Alternatively, the film may be drawn in a batch process. In either case, subsequent or simultaneous draw reduction, stress or strain equilibrium, heat setting, and other processing operations can also be applied to the film.

[0069] Preferably, the polymers of the various layers are selected to have similar rheological properties, such as melt viscosity, so that they can be co-extruded without significant obstruction to the flow. Extrusion conditions may be selected to ensure that each polymer is properly fed, dissolved, mixed, and pumped in a continuous and stable manner as the feed stream and melt stream. The temperature used to form and maintain each of the melt streams may be selected within a range that avoids freezing, crystallization, or excessive pressure drop at the lower end of the temperature range and avoids material degradation at the upper end of the temperature range.

[0070] Exemplary materials (A) suitable for the optical film 102 may include, for example, (a) polyethylene naphthalate (PEN), copolymers containing PEN and polyester (e.g., polyethylene terephthalate (PET) or dibenzoic acid), glycol-modified polyethylene terephthalate, etc. Exemplary materials (B) suitable for the optical film 102 may include, for example, PEN-based copolyester, PET-based copolyester, polycarbonate (PC), or blends of these three materials. To obtain high reflectivity with a suitable number of layers, adjacent microlayers should have a refractive index (Δn) of at least 0.2 for polarized light along the x-axis, in addition to the thickness profile described below. x The difference between these two can be shown.

[0071] In some examples, the stretching axes 122 (e.g., the Y-axis in Figure 2) of each of the HIR layers 102a and LIR layers 102b of the multiple interference layers 102 may be substantially aligned with each other (e.g., parallel or nearly parallel). In some examples, due to manufacturing tolerances, the alignment of the stretching axes 122 may include variations of up to 2°.

[0072] The optical film 100 may be described in some examples as having a total (N) of interference layers 102 of 1000 or less, but it will be understood that the lower limit of the total number of layers (N) can be any suitable amount configured to obtain the described optical properties. In some examples, there is a trade-off between the obtained optical properties and the total number of layers (N) / film thickness of the obtained film. For example, in some examples, the contrast ratio of the film may increase overall by increasing the total number of interference layers 102 contained in the optical film 100, without any of the manufacturing problems described above, but the film thickness will also increase as the number of layers increases. In some examples, as in modern thin optical display devices, the overall thickness of the film can be a limiting factor because the availability of space is limited in such optical display units. In some examples, the optical film 100 may have a significantly reduced film thickness (e.g., half) compared to other film structures (e.g., coupled absorbing polarizers and reflective polarizers used in some conventional display units), but may provide a significant increase in one or more optical properties (e.g., contrast ratio). Furthermore, excessive film thickness risks reducing the overall contrast ratio due to the depolarization of the transmitted light propagating through the film.

[0073] In some examples, the optical film 100 may have a total interference layer 102 of about 200 to about 1000 μm, with any film 100 having a total thickness of less than about 100 μm, including any non-interference or protective layer. In some examples, the optical film 100 may have a total thickness of less than about 100 μm (e.g., less than 60 μm) across the entire layer of the optical film 100.

[0074] In some examples, the thickness of individual interference layers 102 may be relatively thin, such that less than 30% of the interference layers 102 have a thickness of approximately 200 nm or more (e.g., less than 5% of the interference layers 102 have a thickness of approximately 200 nm or all interference layers 102 have a thickness of less than approximately 200 nm), but may vary depending on their location within the optical film 100. For example, the thickness of individual interference layers 102 changes as the overall thickness of the individual interference layers 102 moves from the first layer number to the Nth layer number (e.g., increases apart from local variations). In some examples, the optical film 100 may be distinctive with respect to the film thickness profile. For example, Figure 3 is a plot of an exemplary thickness profile of the optical film 100 showing the relative thickness of individual interference layers 102 according to the layer number (e.g., layers 1 to N are plotted so that the layer thickness increases overall from layer 1 to layer N). The fit curve 300 can be set to a region extending from the first to the Nth layer (excluding, for example, any non-interfering layers, spacer layers, or any other optical layers that do not form a laminate / packet), and the fit curve 300 represents the optimal fit regression applied to the layer thickness profile of the optical film 100. In some examples, the fit curve 300 may represent a quadratic, cubic, quartic, or quintic polynomial regression analysis, exponential regression analysis, etc.

[0075] As shown in Figure 3, the fitting curve 300 is represented as having an average slope that represents the layer thickness profile of the individual interference layers 102 of the optical film 100 according to the layer number. Specifically, the x-axis represents the layer number of the sequentially numbered interference layers 102, numbered 1 to N, and the y-axis represents the average thickness for a given layer number (e.g., the average thickness over the entire XY plane in Figure 1). As used herein, the term “sequentially numbered” interference layer 102 is used to refer to an interference layer 102 that is sequentially numbered in a particular direction (e.g., the direction moving along the Z-axis in Figure 1). In some examples, the interference layers 102 may be arranged sequentially to form a single laminate / packet, as shown in Figure 1. In other examples, the sequentially numbered interference layer 102 may include one or more spacer layers (e.g., a thicker non-interference layer, such as the non-interference layer 408 shown in Figure 4 below) that do not function by optical interference and are not numbered as part of the sequentially numbered interference layer 102. For example, in some cases, interference layers 102 numbered sequentially from 1 to N may represent two stacks / packets of interference layers, each containing a continuously arranged interference layer 102 separated by spacer layers (e.g., a first stack containing layers 1 to m and a second stack containing layers (m+1) to N). Thus, spacer layers are not counted as layers constituting the thickness profile shown in Figure 3.

[0076] In some non-restrictive examples, the slope of the fitting curve 300 is a positive slope (e.g., greater than 0), and the average thickness of the entire interference layer 102 of the optical film 100, numbered sequentially from 1 to N, may be less than approximately 0.2 nm per layer, N is greater than 200, and less than 30% of the interference layer 102 has a thickness greater than approximately 200 nm. For example, less than 10% of the interference layer 102 may have a thickness greater than approximately 200 nm, in some examples less than 5% of the interference layer 102 may have a thickness greater than approximately 200 nm, and in some examples all of the interference layers 102, numbered sequentially from 1 to N, may have a thickness of less than approximately 200 nm.

[0077] In some non-limiting examples, the optical film 100 may include interference layers 102 numbered sequentially by N, where N is an integer between 200 and 1000, and each layer 102 has an average thickness of less than approximately 200 nm. In some such examples, a fitted curve 300 representing the optimal regression applied to a thickness profile plotting the respective thicknesses of individual optical layers 102 according to the layer number may define an average slope measured from the first layer to the Nth layer, of approximately 0.2 nm / layer. In some such examples, for the thickness profile of the optical film 100, the film has an average light transmittance (T) of more than approximately 85% of the first polarization state (a) for perpendicularly incident light 110 within a given wavelength range. a ), the average light reflectance (T) of more than 80% of the orthogonal second polarization state (b) b ) can be defined.

[0078] In some examples, the gradient may be substantially the same throughout all interference layers 102, representing a continuous and constant change in thickness from layer to layer. In some such examples, the average gradient may be characterized as having an approximately constant step change in layer thickness between adjacent interference layers 202. For example, if the gradient is substantially constant at about 0.2 nm, then layer number x may have a thickness of t nm, while layer number (x+1) may have a thickness of (t+0.2 nm).

[0079] In some examples, the relative variation in layer thickness between adjacent interference layers 102 may vary depending on their location within the optical film 100, such that the slope of the fit curve 300 does not have to be substantially the same across all interference layers 102. In some such examples, the slope of the fit curve 300 may be characterized by a maximum and minimum slope. For example, the optical film 100 may contain interference layers 102 numbered sequentially by N, where N is an integer greater than 50 and less than 1000. The fit curve 300 representing the optimal fit regression can be applied to a thickness profile plotting the respective thicknesses of individual interference layers 102 according to their layer numbers, and both a maximum and minimum slope may be defined according to their layer numbers. In some such examples, the difference between the maximum and minimum slopes may be less than approximately 0.70 nm / layer (e.g., less than approximately 0.57 nm / layer), and the maximum and minimum slopes are evaluated, respectively, across any group of 25 to 50 adjacent interference layers 102. In some such examples, due to the thickness profile of the optical film 100, the film has an average light transmittance (T) of more than 80% of the first polarization state (a) for perpendicularly incident light 110 within a given wavelength range. a ), the average light reflectance (T) of more than 80% of the orthogonal second polarization state (b) b ) can be defined.

[0080] In some examples, the optical film 100 has an average slope (e.g., Δn) of the fitted curve 300. x The maximum difference between the refractive indices of multiple interference layers 102 (for example, the maximum Δn between interference layer 102a and interference layer 102b) is given by / K, where K represents the average slope of the fitting curve 300. x The ratio of ) may be characteristic. A lower average gradient may improve optical interference between optical films 100. In some examples, Δn x Designing a relatively large (e.g., greater than 1) optical film 100 to increase the / K ratio can result in a higher contrast ratio.

[0081] In some non-limiting examples, the optical film 100 has a Δn greater than approximately 1.2. x / K can be defined. In some such examples, the optical film may define an optical density greater than about 1.4, greater than 1.6, greater than 1.8, greater than 2.0, or greater than about 3.0 for a given wavelength range. As used herein, “optical density” is the -log(T) averaged over the entire wavelength range in question (e.g., 400 nm to 700 nm). b It is calculated as follows. In some examples, the higher the optical density, the higher the contrast ratio relative to the optical film.

[0082] In some such examples, the slope 302 of the fitting curve 300 may represent the average slope across subgroups of interference layers 102. For example, multiple interference layers 102 may be divided into multiple non-overlapping groups of continuously arranged interference layers 102 within the optical film 100. In the use of the present invention, "continuously arranged" interference layers 102 mean that the interference layers are directly adjacent to each other and do not include any spacer layers (e.g., non-interfering layers 408 described later in Figure 4) that are arranged between any two adjacent interference layers 102 within the continuously arranged layers. For each group of continuously arranged interference layers 102, the layers may be numbered sequentially from 1 to m, where m is greater than 25 and less than N, and N represents the total number of interference layers 102 in the optical film 100 (e.g., 50 to 1000 layers). The fitting curve 300 may be applied to the entire thickness profile of the interference layers 102 depending on the layer number. The resulting average gradient 302 (e.g., thickness change per m layers) can be determined for each subgroup of m layers. In some such examples, the maximum difference between the average gradients of all subgroups (e.g., the difference between the maximum gradient measured from one group and the minimum gradient measured from a different group) may be less than 0.70 nm / layer.

[0083] Considering the thickness profile of the optical film 100, it will be found that the relative thicknesses of at least some of the different interference layers 102 will differ throughout the entire lamination / packet of interference layers 102 within the optical film 100. In some examples, the difference in thickness of multiple interference layers 102 may be characterized by a difference in the average thickness of some of the interference layers 102. For example, the optical film 100 may contain at least one interference layer 102 that defines an average thickness of less than approximately 50 nm (e.g., layer number 1), and at least one other average thickness of interference layer 102 may be greater than approximately 100 nm (e.g., layer number N). In some examples, the optical film 100 may contain at least two interference layers 102 with an average thickness difference of at least less than approximately 30% (e.g., layer number 1 defines an average thickness of at least 30% less than the average thickness of layer number N).

[0084] In some examples, the relative thickness of the interference layer 102 can be described with respect to the optical thickness of unit cells 106a and 106b. As used, “unit cell” is used to mean a pair of continuously arranged HIR layers 102a and LIR layers 102b, collectively referred to as unit cell 106. In Figure 2, only two individual unit cells 106 are shown (e.g., unit cell 106a and unit cell 106b), but the optical film 100 may contain tens to hundreds of unit cells 106. In some examples, unit cells 106 may be continuously arranged or separated into different laminates / packets by one or more spacer layers.

[0085] The "optical thickness" (τ) of the unit cell 106 is given by each HIR layer 102a(d) of the unit cell. HIR ) thickness × stretching direction at the target wavelength (e.g., n1 x ) refractive index of the HIR layer + each LIR layer 102b(d LIR ) thickness × stretching direction at the same wavelength of the object (e.g., n2 x) can be defined as the refractive index of the LIR layer. Each unit cell 106 can be sized such that the unit cell defines an optical thickness equal to approximately half of each respective center wavelength within a predetermined wavelength range. For example, unit cell 106a may correspond to a center wavelength (λ a ), such that (τ a = λ a / 2 = d HIR * n1 x + d LIR * n2 x ) defines the optical thickness (τ a ). Each unit cell 106 within the optical film 100 can correspond to different center wavelengths within a predetermined wavelength range in order to provide desired transmission and reflection characteristics to the film within the predetermined wavelength range.

[0086] In some examples, the optical thickness (τ) of the unit cell 106 can be controlled such that the intrinsic bandwidth of a given unit cell overlaps the intrinsic bandwidth of an adjacent unit cell. By overlapping the intrinsic bandwidths of adjacent unit cells 106, the constructive interference obtained by the interference layer 102 remains high. One way to improve the constructive interference obtained in the optical film 100 is to maintain a relatively small difference in the optical thickness (τ) of adjacent unit cells 106 to generate a sufficient amount of intrinsic bandwidth overlap. In some examples, the optical thickness (τ) of the unit cell 106 can be controlled such that less than 10% of adjacent unit cells have an optical thickness (τ) difference greater than 1%. For example, the optical film of Example 1 further described below has less than 6% of adjacent unit cells having a difference in optical thickness (τ) greater than 1%, and less than 1.2% of adjacent unit cells have a difference in optical thickness (τ) greater than 1.5%.

[0087] In some examples, the change in optical thickness between adjacent unit cells (e.g., unit cell 106a and unit cell 106b) may be relatively small to obtain the desired optical properties. For example, in some non-limiting examples, the optical film 100 may contain continuously arranged unit cells 106 between approximately 100 and approximately 400, each having a refractive index of at least approximately 0.24 (e.g., Δn x It has one HIR layer 102a and one LIR layer 102b having a difference of ) ). Each unit cell 106 respectively defines an optical thickness (τ) equal to approximately half of a different central wavelength (e.g., λ / 2) within a given wavelength range. In some such examples, for at least 80% of adjacent pairs of unit cells (e.g., unit cell 106a and unit cell 106b form a pair of adjacent unit cells 108), the ratio of the difference in central wavelengths of adjacent unit cells 106a and unit cell 106b to the average of the central wavelengths of adjacent unit cells 106a and unit cell 106b is less than approximately 2% (e.g., abs([λ a(n) -λ a(n+1) ] / [(λ a(n) -λ a(n+1) ) / 2)<2%).

[0088] In some examples, the optical film 100 may be characterized with respect to the optical power of the interference layer 102. "Optical power" can be defined as the integral of the optical density in 1 / (wavelength) space over the region of interest for a blocked polarization state (b). In some examples, higher optical power may correspond to a higher contrast ratio in the region of interest. Depending on the intended application of the optical film 100, a specific amount of optical power may be desired for the optical film. However, the optical power per interference layer is inversely proportional to the total number of interference layers overall, such that the optical power per layer decreases as the total number of layers increases. Increasing the total number of interference layers can lead to an overall decrease in optical power per layer, while useful for obtaining other optical properties (e.g., a sufficient coverage range over a given wavelength range). The optical films described herein may provide higher optical power per layer for a given number of interference layers than those obtained using conventional reflective polarizer films.

[0089] In some non-limiting examples, the optical film 100 comprises about 100 to about 1000 alternating HIR 102a and LIR 102b layers, where each interference layer 102 reflects or transmits light primarily by optical interference. In some such examples, the optical film has about (-0.0012) interference layers 102. * The optical power of the optical film 100 can be defined to exceed N+1.46), where N represents the total number of interference layers 102 (for example, N is between approximately 100 and approximately 1000).

[0090] In addition, or in some non-limiting examples, the optical film 100 includes at least about 300 alternating HIR 102a and LIR 102b layers in total, where each interference layer 102 reflects or transmits light primarily by optical interference, and the optical film 100 specifies that the optical power per interference layer 102 exceeds about 0.7.

[0091] Furthermore, Figure 15, shown below, illustrates the optical power per layer for a non-limiting number of optical films of Example 1, prepared in accordance with the disclosure. Several comparative examples of conventional reflective polarizer films, either commercially available or described in the literature, are also included in the plot of Figure 15 (see Table 6). As shown in Figure 15 and Table 6, the optical film of Example 1 contains a total of 650 interference layers, defining approximately 0.74 optical powers per layer.

[0092] In some examples, the multiple interference layers 102 of the optical film 100 may be arranged in a continuous manner such that each interference layer 102 is directly adjacent to a nearby interference layer, forming an optical laminate / packet of up to 1000 individual layers. In other examples, the optical film 100 may be separated into two or more laminate / packet interference layers 102 separated by relatively thick non-interference layers that act as spacer layers (e.g., optical layers that do not reflect or transmit light primarily by optical interference). For example, Figure 4A shows another example of an optical film 400 that can be formed to exhibit one or more optical properties described above with respect to the optical film 100. As shown in Figure 4A, the optical film 400 includes multiple interference layers 402 separated into two optical laminates / packets 406a, 406b, each containing multiple interference layers 402. The optical laminates / packets 406a, 406b are separated by a relatively thick (e.g., thicker than the individual interference layers 402) spacer layer 408.

[0093] Similar to optical film 100, optical film 400 may include tens to hundreds of interference layers 402 divided between optical laminates / packets 406a, 406b. a +N b The first optical stack / packet 406a includes interference layers 402 that are numbered consecutively, totaling (N a The second stack / packet 406b includes the interference layer 402, and the total is (N b ) includes interference layer 402.

[0094] Each interference layer 402 may be substantially the same as the interference layer 102 described with respect to Figures 1 and 2. For example, the interference layer 402 may alternate between HIR layers (e.g., similar to HIR layer 102a) and LIR layers (e.g., similar to LIR layer 102a). Furthermore, as with the optical film 100, in some examples the total number (e.g., N) of interference layers 402 in the optical laminates / packets 406a and 406b of the optical film 400 may be less than 1000 or less than 800, as described above.

[0095] In some examples, optical stacks / packets 406a and 406b may contain substantially the same (e.g., the same or nearly the same) total number of interference layers 402. For example, optical stacks / packets 406a and 406b may each independently contain approximately 50 to approximately 400 interference layers 402, and the total number of interference layers 402 within each optical stack / packet 406a and 406b is the same (e.g., N a =N b ). In some examples, the total number of interference layers 402 within a single optical stack / packet 406a, 406b may be approximately 325 layers. In other examples, the optical stack / packet 406a, 406b may have a different total number (e.g., N a ≠N b ) may include an interference layer 402.

[0096] The spacer layer 408 may include any suitable optical material (e.g., an anti-interference layer) that does not reflect or transmit light primarily by optical interference. In some examples, the spacer layer 408 may include polyethylene naphthalate (PEN), a copolymer containing PEN and polyester (e.g., polyethylene terephthalate (PET) or dibenzoic acid), glycol-modified polyethylene terephthalate, polycarbonate (PC), or a blend of these four classes of materials. In some examples, the spacer layer 408 can be formed by co-extrusion or lamination, thereby thinning the optical laminates / packets 406a, 406b together with the spacer layer 408 between two laminates / packets. In addition, or alternatively, the spacer layer 408 may be optically bonded to the optical laminates / packets 406a, 406b (e.g., bonded to each laminate / packet 406a, 406b so that light passes through the spacer layer 408 without significant reflection or refraction).

[0097] The spacer layer 408 may be relatively thicker than the individual interference layers 402. For example, the spacer layer 408 may have an average thickness of more than approximately 500 nm. In addition, the spacer layer 408 may have an average thickness of at least 10 times the maximum wavelength in a given wavelength range. For example, if the given wavelength range includes visible light (e.g., approximately 400 to approximately 700 nm), the thickness of the spacer layer 408 may exceed 7000 nm. In some examples, the spacer layer 408 may have an average thickness of at least 50 times the maximum wavelength in a given wavelength range. In some examples, the spacer layer 408 can help reduce flow turbulence, otherwise the formation of multilayer optical laminates / packets 406a, 406b may occur during the co-extrusion process.

[0098] In some examples, the optical laminates / packets 406a and 406b may be independently optimized to transmit or reflect light in different predetermined wavelength ranges. Thus, the optical film 400 may be configured to transmit and reflect light depending on its polarization state across a number of distinct wavelength ranges. For example, the first optical laminate / packet 406a may be configured to transmit and reflect light in the visible spectrum (e.g., about 400 to about 700 nm), while the second optical laminate / packet 406b may be configured to transmit and reflect light in the near-infrared spectrum (e.g., about 800 to about 1300 nm).

[0099] In some examples, the two optical laminates / packets 406a and 406b may be configured such that the optical film 400 transmits and reflects light depending on its polarization state over a continuous predetermined wavelength range (e.g., about 400 to about 1300 nm). For example, the optical laminates / packets 406a and 406b may be configured such that the predetermined wavelength ranges of each laminate / packet 406a and 406b are in contact with or overlap each other with respect to a substantially continuous (e.g., continuous or nearly continuous) predetermined wavelength range.

[0100] In some examples, the first optical laminate / packet 406a is configured to transmit or reflect light in different polarization states within a first predetermined wavelength range, consisting of alternating HIR and LIR layers, 1 to (N a It may include interference layers 402 that are numbered up to and arranged continuously. A pair of directly adjacent HIR and LIR interference layers 402 is characterized by a unit cell 405, and the first optical stack / packet 406a totals approximately (M a =N a The second optical laminate / packet 406b may have 1 to 2) unit cells 405. Similarly, the second optical laminate / packet 406b is configured to transmit or reflect light in different polarization states within a second predetermined wavelength range, consisting of alternating HIR and LIR layers. b Interference layers 402 or approximately (M) are numbered and arranged in a continuous manner up to (M b =N b It may contain (n1) unit cells 405. Each HIR and LIR interference layer 402 forming each unit cell 405 has a ratio of the average refractive index of the HIR layer to the average refractive index of the LIR layer, for example (n1 x / n2 x ) may be characterized by the following.

[0101] In some examples, optical laminates / packets exhibit a relatively high contrast ratio (e.g., greater than 1000:1) to reflect and transmit light within a given wavelength range, using HIR (e.g., n1 x ) and LIR (e.g., n2 x The refractive index of the interference layer 402 and the total number of unit cells 405 in each optical stack / packet 406 (e.g., M) may be selected. In some examples, each optical stack / packet 406 is given by the following formula:[(n1 x / n2 x ) * It can be configured to satisfy [M>300].

[0102] In some non-limiting examples, the optical film 400 has first unit cells 405 of alternatingly arranged first HIR and second LIR interference layers 402 arranged in a continuous M a-This may include the first unit cell 405, which may be optimized to transmit or reflect light in a first predetermined wavelength range (e.g., about 400 to about 700 nm), but not in a second predetermined wavelength range (e.g., about 800 to about 1300 nm). In some such examples, the first HIR layer (n1 x The second LIR layer (n2) relative to the average refractive index of ) x ) Ratio of average refractive index × Total number of first unit cells 405 (M a The first HIR and second LIR interference layers 402, which are arranged alternately, are such that the number of (n1) is over 300. x ) and (n2 x The average refractive index of ) may be specified. Furthermore, the optical film has a second unit cell 405 of the alternately arranged third HIR and fourth LIR interference layers 402 arranged in a continuous M b The second unit cell 405 may be optimized to transmit or reflect light in a second predetermined wavelength range (e.g., about 400 to about 700 nm), but does not need to be optimized in a first predetermined wavelength range (e.g., about 800 to about 1300 nm). The third HIR layer (n3 x The fourth LIR layer (n4) relative to the average refractive index of ) x ) Ratio of average refractive index × second unit cell 405 (M b The alternating third HIR interference layer and fourth LIR interference layer 402 are such that the total number of (n3) is over 300. x ) and (n4 x The average refractive index of (T) may be defined. In some such examples, light incident on the optical film 400 at any incident angle of less than about 30 degrees, having any wavelength within the first and second predetermined wavelength ranges, is (T a ) vs (T b The ratio of ) to the first polarization state (a) is greater than approximately 1000:1, so the average light transmittance (e.g., T a ), and the average light transmittance for the second polarization state (b) (e.g., T b You may receive it.

[0103] In some such examples, the design of multiple laminates / packets 406 of the optical film 400 can provide a more efficient process for manufacturing the film compared to an optical film containing only a single packet of interference layers configured to reflect and transmit light within the same continuous range of predetermined wavelengths, for example, by reducing the total number of layers and the complexity of forming a large single laminate.

[0104] Similar to the case of optical film 100, in some examples, the degree of transmittance and reflectance of optical film 400 for substantially perpendicular incident light 110 (e.g., perpendicular or nearly perpendicular to surface 404) within a predetermined wavelength range (e.g., visible light or about 400 to about 700 nm) is the average light transmittance (T) for the first / pass-through polarization state (a). a ) and light reflectance (R a ) and the average light transmittance (T) for the second / reflected polarization state (b). b ) and light reflectance (R b The optical film 400 may be characterized by having the following: The light transmittance and reflectance values ​​of the optical film 400 may be substantially the same as the values ​​described above for the optical film 100. For example, the average light transmittance (T) of the optical film 400 a ) is fine if it is more than 80% of the first / pass-through polarization state (a), and the average light reflectance (R b ) is fine with approximately 80% or more for the orthogonal second / reflected polarization state (b), and the average light transmittance (T b ) may be less than approximately 0.2% with respect to the orthogonal second / reflected polarization state (b). In some examples, each optical laminate / packet 406a, 406b may have the characteristic of transmitting at least 50% of the normally incident light 110 having a first polarization state (a) within a predetermined wavelength range and reflecting at least 50% of the normally incident light 110 in a second polarization state (b) within a predetermined wavelength range.

[0105] Figure 4B is a plot of exemplary thickness profiles of the optical film 400, showing the thickness of individual interference layers 402 according to their layer numbers, where multiple interference layers 402 are numbered sequentially from 1 to N, and N is the total number of interference layers 402 in the optical film 400 (for example, N = N a +Nb This represents the spacer layer 408, which is excluded from the plot of the thickness profile of the optical film 400, as shown in Figure 4B.

[0106] The thickness profile of the optical film 400 may be characterized by two fit curves 410 and 412, each corresponding to the thickness profile of the respective optical laminates / packets 406a and 406b. Fit curves 410 and 412 represent optimal fit regression applied to the layer thickness profile of the optical film 400 with respect to the interference layer 402 within each laminate / packet. For example, fit curve 410 represents the thickness profile of the first laminate / packet 406a, which is 1~N a The sequentially numbered interference layer 402 is represented, and the fitting curve 412 represents the thickness profile of the second laminate / packet 406a, which is (N a +1)~(N a +N b ) represents interference layer 402 which is numbered sequentially (for example, 1 to N of the second stack / packet 406b). b (This corresponds to interference layer 402, which is numbered sequentially up to this point.)

[0107] As shown in Figure 4B, each optical laminate / packet 406a and 406b may include a layer thickness profile that defines its respective slope (e.g., plotting individual layer thicknesses against the number of layers). In some examples, the average slope of the fitting curves 410 and 412 may be less than 0.2 nm / number of layers for the interference layers 402 within each optical laminate / packet 406a and 406b. Each optical laminate / packet 406a and 406b of the optical film 400 may contain a total of less than approximately 400 interference layers 402, and the individual layer thickness of each interference layer 402 is relatively thin (e.g., having an average thickness of less than approximately 200 nm).

[0108] In some examples, the average slope of the fitting curves 410, 412 may represent the average slope of the entire subgroup of interference layers 402 within each optical stack / packet 406a, 406b. For example, the interference layers 402 within the first optical stack / packet 406a may be divided into multiple non-overlapping groups of continuously arranged interference layers 402. For each group of continuously arranged interference layers 402, the layers can be numbered sequentially from 1 to m, where m is N. a Although it is greater than / 10, N a Less than N a represents the total number of interference layers 402 in the first optical laminate / packet 406a. The fitting curve 410 may be applied to the thickness profile for each group of layers according to the layer number, and the resulting average slope for each group (e.g., thickness change per m layers) is determined for each group of layers. The maximum difference between the average slopes of all groups (e.g., the difference between the maximum slope measured from one group and the minimum slope measured from a different group) may be less than 0.70 nm / layer (e.g., less than 0.57 nm / layer), and the maximum and minimum slopes are evaluated across any group of 25 to 50 adjacent layers, respectively.

[0109] In some examples, the layer thickness profile of the optical film 400 may be characterized by an optimally fitted linear equation applied to the thickness profile of each optical laminate / packet 406a, 406b depending on the layer number. For example, Figure 4C is a pair of exemplary thickness profile plots of the optical film 400 showing the thicknesses of the first and second optical laminates / packets 406a, 406b depending on the interference layer number. As shown, the first optical laminate / packet 406a is 1~N a The second optical stack / packet 406b includes an interference layer 402 that is numbered sequentially, and the second optical stack / packet 406b is numbered 1 to N. bThis includes interference layers 402 that are sequentially numbered. Optimal linear regressions 420, 422 can be applied to each plot (e.g., linear least-squares regression) to provide their respective average slopes for the associated optimally fitted regression. In some examples, the maximum difference between the average slopes of the optimal linear regressions 420, 422 for all optical laminates / packets 406a, 406b within the optical film 400 may be less than approximately 20%. For example, relating to the optical film of the non-limiting Example 1 and Figure 9, the slopes of packets 1 and 2 forming the optical film of Example 1 show average slopes of 0.17 nm / layer and 0.18 nm / layer, respectively, resulting in a difference of approximately 6% in slope.

[0110] In some examples, the first and second optical stacks / packets 406a, 406b may include stitching within regions 424 and 426. Stitching describes an optical design in which at least two packets exist when there is only a small amount of overlap between the reflected bandwidths associated with each packet. This allows for the use of lower gradients in individual packets, which increases the optical power associated with each layer. Figure 13 shows an example of a stitched layer design. In such an example, the change in layer thickness relative to the layer of each optical stack / packet 406a, 406b adjacent to layer 408 (e.g., the first interference layer 402 adjacent to the spacer layer 408 having a given stack / packet) may increase proportionally to the change in thickness / layer relative to the other interference layer 402 within the optical stacks / packets 406a, 406b. This change is shown in regions 424 and 426 of Figure 4C as a layer thickness profile with a slight curl at the edges of the thickness profile of the optical laminates / packets 406a and 406b having adjacent sides to the spacer layer 408.

[0111] In some non-limiting examples, the optical film 400 has multiple interference layers 402 that, for substantially perpendicular incident light in a predetermined wavelength range, enter a first polarization state (e.g., T a It transmits at least 80% of the light having ) and a second polarization state that is orthogonal (e.g., T bThe optical laminates / packets may include a plurality of interference layers 402 that primarily reflect and transmit light by optical interference, such that they reflect at least 80% of the light having a first polarization state (a). The plurality of interference layers 402 may be divided into a plurality of optical laminates / packets 406a, 406b, each pair of adjacent optical laminates / packets 406a, 406b is separated by one or more spacer layers 408 that primarily reflect or transmit light by optical interference, and each optical laminate / packet 406a, 406b transmits at least 50% of the light having a first polarization state (a) within a predetermined wavelength range and reflects at least 50% of the light having a second polarization state (b) within a predetermined wavelength range. Within each optical laminate / packet 406a, 406b, the interference layers 402 may be numbered sequentially (e.g., N a or N b Each optical laminate / packet 406a, 406b has a best-fit linear equation (e.g., fitting lines 420, 422) relating the thickness of the optical laminate / packet 406a, 406b to the interference layer number, and the linear equation relates the first interference layer 402 in the laminate / packet to the last interference layer in the laminate / packet (e.g., layer numbers 1 to N of the first optical laminate / packet 406a). a The optical film 400 has an average gradient (e.g., laminate thickness / number of laminates) in the region extending to the line 420 to which it is applied, and the maximum difference between the average gradients of the best-fitting linear equations of the multiple optical laminates / packets 406a, 406b in the optical film 400 may be less than about 20%. In some such examples, the optical film 400 may have an average light density greater than about 2.5.

[0112] Figures 5A and 5B are exemplary transmission plots for a typical optical film according to this disclosure (e.g., optical film 400), showing transmittance for a first and second polarization state (e.g., pass and reflect polarization states, respectively) for perpendicularly incident light 110 in a specific wavelength range of 400–700 nm corresponding to the visible spectrum. Figure 5B shows a logarithmic plot of transmittance for the second polarization state (b) (e.g., reflect polarization state). The typical optical film 400 tested comprises two optical laminates (e.g., 406a, 406b), each having 325 interference layers 402, and comprises transmission spectra measured for the first and second polarization states, respectively, using a Lambda900 spectrometer (PerkinElmer). As shown, the transmission (e.g., reflection axis, T) in the entire second polarization state (b) across the visible spectral range is shown. b ) was significantly lower than 0.1%.

[0113] In some examples, the optical films 100, 400 may include one or more non-interference layers that can be used to isolate and / or protect one or more of the laminations / packets of interference layers 102, 402, or may be combined with non-interference layers. For example, Figure 6 shows another example of an optical film 600 that can be formed to exhibit one or more of the properties described above with respect to the optical films 100, 400. As shown in Figure 6, the optical film 600 includes multiple interference layers 602 divided into two optical laminations / packets 606a, 606b laminated between relatively thick non-interference layers 608. As shown in Figure 6, the first optical laminate / packet 606a is set between non-interference layers 608a and 608b, while the second optical laminate / packet 606b is set between non-interference layers 608c and 608d, such that non-interference layers 608b and 608c are directly adjacent to each other and act as spacer layers between the first and second optical laminates / packets 606a and 606b. In some examples, due to their relative thickness, the non-interference layers 608a and 608d outside the optical laminates / packets 606a and 606b may help protect each laminate / packet from unintended damage (e.g., scratches). In some examples, the non-interference layers 608a and 608b may define a reaction index of approximately 1.57.

[0114] In addition, one or more non-interference layers 608 may include coatings such as a hard coat (scratch-resistant coating), a diffuse coating, an anti-reflective coating, or an anti-glare coating.

[0115] Figure 7 shows an exemplary display assembly 700, which includes a reflective polarizer optical film 702, a liquid crystal display assembly (LCD) 710, and a light source 720. As shown herein, the LCD assembly 710 is illuminated by polarization provided by the optical film 702 and the light source 720. The LCD assembly 710 may include a multilayer structure having an outer absorbing polarizer film 712, one or more glass layers 714, and a liquid crystal layer 716.

[0116] Figure 7 shows two types of light delivered through the display assembly 700. Ambient light 730 represents the light incident on the display surface 711 passing through the LCD assembly 710, the optical film 702, and the diffuse reflective surface of the light source 720 reflected by the optical film 702. Light can also originate from the backlight assembly of the light source 720. For example, the light source 720 may include an edge-illuminated backlight containing a lamp 722 within a reflective lamp housing 724. Light from the lamp 722 is coupled to an optical guide 726, where it propagates until it collides with a diffuse reflective structure such as a spot 728 (e.g., a discontinuous layer of titanium oxide colored material). This discontinuous array of spots is arranged to take the lamp light and direct it toward the LCD assembly 710. Ambient light 730 entering the light source 720 may collide with the spots or leak out of the optical guide through the gap regions between the spots. A diffuse reflective layer 729 (for example, a layer of titanium oxide-colored material) is positioned beneath the optical guide 726 to block and reflect such light rays. Overall, all light rays emanating from the light source 720 toward the LCD assembly 710 are represented as a luminous flux 732. This luminous flux passes through an optical film 702 that transmits light having a first polarization state referred to as "(a)" and effectively reflects light having an orthogonal polarization state (b). The optical film 702 may correspond to any of the optical films 100, 400, or 600 described above.

[0117] In some examples, an LCD display assembly may include an absorbing polarizing film and a reflective polarizer film (AP / RP film) between the light source 720 and the LCD assembly 710. In such examples, the AP film may typically be used to generate sufficient contrast in the display assembly, while the inclusion of the RP film improves the brightness of the AP / RP film combination, particularly in high ambient light environments or high glare conditions, compared to a system with only the AP film. Surprisingly, it has been found that the AP / RP film can be substituted with the high-contrast reflective polarizer (RP) optical film 702 described herein without significantly reducing the brightness or contrast of the display assembly 700, even in high ambient light environments (e.g., external conditions). For example, it has been theorized that including only the optical film 702 in a display assembly 700 without a rear AP film results in a high level of glare due to undesirable reflection of ambient light from the optical film 702, while in practice, only a non-negligible or relatively small increase in glare is observed.

[0118] In some examples, the display assembly 700 including the optical film 702 can exhibit approximately 10% to 15% higher brightness compared to an equivalent display assembly including an AP / RP film.

[0119] In some examples, the display assembly 700 may include one or more brightness-enhancing films 740 disposed between the light source 720 and the optical film 702 to increase brightness in the axial direction of the display assembly 700. Examples of exemplary brightness-enhancing films 740 include, for example, a deflection film and a prism film.

[0120] In some non-limiting examples, the display assembly 700 may include a light source 720, an LCD assembly 710 configured to be illuminated by the light source 720, one or more brightness-enhancing films 740 disposed between the light source 720 and the LCD assembly 710 to increase the axial brightness of the display assembly 700, and an optical film 702 (e.g., RP) disposed between the one or more brightness-enhancing films 740 and the LCD assembly 710, configured to substantially transmit light having a first polarization state (a) and substantially reflect light having an orthogonal second polarization state (b). The optical film 702 may include a second polarization state (e.g., T) without an absorbing polarizer (AP) disposed between the light source 720 and the LCD assembly 710. b An average light transmittance of less than approximately 0.2% can be specified for the second polarization state (b). In some such examples, the display assembly 700 may specify a contrast ratio at least twice that of a comparative display assembly having the same structure, except that the average transmittance of the RP of the comparative display assembly for the second polarization state (b) is greater than approximately 1.0%.

[0121] In addition, or in some non-limiting examples, the display assembly 700 may include a light source 720, an LCD assembly 710 configured to be illuminated by the light source 720, one or more brightness-enhancing films 740 disposed between the light source 720 and the LCD assembly 710 to increase the axial brightness of the display assembly 700, and an optical film 702 disposed between the one or more brightness-enhancing films 740 and the LCD assembly 710. The optical film 702 may include a plurality of interference layers that transmit or reflect light mainly by optical interference, and as a result, for substantially normally incident light within a given wavelength range, in the absence of an absorbing polarizer (AP) disposed between the light source 720 and the LCD assembly 710, the plurality of interference layers are in a first polarization state (e.g., T a It transmits at least 80% of the light having ) and a second polarization state that is orthogonal (e.g., T b It transmits less than approximately 0.2% of the light that has )

[0122] Figure 8 shows exemplary luminance profiles for a display assembly 700 that includes an optical film 702 as a viewing angle feature, compared to a display assembly with an AP / RP film. Curve 800 represents the luminance profile of the optical film 702 for display assembly 700, while curve 802 represents the luminance profile for an equivalent display assembly that includes an AP / RP film (e.g., APCF, available from Nitto Denko Corporation (Tokyo)). As shown, the optical film 702 provides a slight improvement in the luminance profile for off-axis observation positions, while providing a comparative observation luminance profile for normal viewing angles (e.g., ±20°) (e.g., above 50°).

[0123] In some such examples, the use of optical film 702, in contrast to conventional AP / RP films, can significantly reduce the overall thickness of the LCD display assembly, as the high-contrast RP optical film described herein can be formed to approximately half the thickness of a conventional AP / RP film. While the use of optical film 702 alone in the display assembly 700, in contrast to AP / RP films, may yield benefits associated with a reduction in the thickness of the display assembly, in some examples, an absorbing polarizing film may be included between the LCD assembly 710 and the optical film 702 (not shown), if desired. In some such examples, the absorbing polarizer / optical film 702 combination may provide improved brightness and / or contrast ratio compared to conventional AP / RP films.

[0124] In some examples, the optical film 702 of the display assembly 700 can act as a high-contrast RP to substantially transmit light having a first polarization state (a) and substantially reflect light having an orthogonal second polarization state (b). In some examples, the optical film 702 specifies an average light transmittance of less than about 0.2% for the second polarization state (b), no absorbing polarizer is provided between the light source 720 and the liquid crystal layer 716, and the contrast ratio of the display assembly 700 is at least twice that of the comparative display assembly having the same structure, except that the average transmittance of the reflective polarizer of the comparative display assembly for the second polarization state is greater than about 1.0%.

[0125] In some examples, one or more of the optical films 100, 200, 400, and 600 described herein may be incorporated into an optical system designed to display an object to an observer centered on the optical axis (e.g., a virtual reality display system). Such an optical system may include one or more optical lenses having non-zero optical power and having a reflective polarizer (e.g., optical films 100, 200, 400, and 600) disposed on the first principal surface of one or more optical lenses and fitted thereto, and a fitted partial reflector disposed on the second principal surface of one or more optical lenses. In some examples, the lens and reflective polarizer may be convex around one or two orthogonal axes and may be positioned between the aperture plane (e.g., exit pupil or entrance pupil) and the image plane (e.g., the surface of a display panel or image recording device) to produce a system with a wide field of view, high contrast, low chromatic aberration, low distortion, and / or high efficiency in a compact configuration. This compact configuration is useful in various devices, such as head-mounted displays including virtual reality displays and cameras included in mobile phones.

[0126] Figure 10 is a schematic cross-sectional view of an exemplary optical system 1000 (e.g., a virtual reality display system) including an image plane 1030, an aperture plane 1035, and an optical laminate 1010 disposed between the image plane 1030 and the aperture plane 1035. The xyz coordinate system is shown in Figure 10. The image plane 1030 may be the output surface of an image forming device such as a display panel that emits polarized or unpolarized light, while the aperture plane 1035 may be the exit pupil of the optical system 1000, and may overlap with the entrance pupil of a second optical system, which may be, for example, an observer's eye or a camera.

[0127] In some examples, the optical laminate 1010 may include an optical lens 1012 having a first main surface 1014 and a second main surface 1016, a reflective polarizer 1027 (e.g., optical films 100, 200, 400, 600) disposed on the first main surface 1014, and a partial reflector 1017 disposed on the second main surface 1016 of the optical film 1012. In some examples, the optical laminate 1010 may also include one or more quarter-wavelength retarders 1015, 1025 disposed on the first main surface 1014 and the second main surface 1016, respectively.

[0128] As shown in Figure 10, the optical laminate 1010 may be convex toward the image plane 1030 so as to be perpendicular to the first axis and / or the second axis (e.g., the x-axis and the y-axis, respectively). The optical laminate 1010 can be manufactured by first forming the reflective polarizer 1027 with an arbitrary first quarter-wavelength retarder 1025 coated or laminated to the reflective polarizer 1027, and then thermoforming the resulting film into any shape corresponding to the optical lens 1012. The partial reflector 1017 and an optional second quarter-wavelength retarder 1015 can be manufactured by coating the quarter-wavelength retarder onto the partial reflector film, coating the partial reflector coating onto the quarter-wavelength retarder film, laminating the partial reflector film and the quarter-wavelength retarder film together, or by first forming the lens 1012 (which may be formed on a film containing the reflective polarizer 1027) in a film insert molding process and then coating the partial reflector 1017 onto the second main surface 1016. In some examples, the lens 1012 may be formed by injection molding the lens 1012 between the first and second films of the reflective polarizer 1027 and the partial reflector 1017. The first and second films may be thermoformed before the injection molding process.

[0129] The image source 1031 includes the image plane 1030, and the aperture plane 1035 is the exit pupil for the optical system 1000. In some examples, the image source 1031 may be a display panel. In other examples, the display panel may not be present, and instead, the image plane 1030 is an aperture that receives light reflected from an object outside the optical system 1000.

[0130] In some examples, a second optical system 1033 having an entrance pupil 1034 may be positioned in close proximity to an optical system 1000 having an aperture plane 1035 that overlaps with the entrance pupil 1034. The second optical system 1033 may be, for example, a camera that records an image transmitted through an image plane 637. In some examples, the second optical system 1033 is the viewer's eye, and the entrance pupil 1034 is the pupil of the viewer's eye. In such examples, the optical system 1000 may be used in a head-mounted display.

[0131] The reflective polarizer 1027 may be any one of the optical films 100, 200, 400, and 600 described herein. For example, the reflective polarizer may include at least 50 continuously numbered interference layers, each of which may be relatively thin (e.g., having an average thickness of less than about 200 nm), and the fit curve is a best fit regression applied to the layer thickness profile of the reflective polarizer 1027, where the average slope of the fit curve in the region extending from the first layer to the Nth layer is less than about 0.2 nm / layer, depending on the number of layers (e.g., curve 300 in Figure 3). The reflective polarizer 1027 substantially transmits light having a first polarization state (a) (e.g., linearly polarized in a first direction) and substantially reflects light having an orthogonal second polarization state (b) (e.g., linearly polarized in a second direction orthogonal to the first direction).

[0132] The partial reflector 1017 has an average light reflectance of at least 30% and a light transmittance of at least 30% in a given wavelength range, which may be any of the wavelength ranges described elsewhere in this specification. Any suitable partial reflector may be used. In some examples, the partial reflector 1017 may be, for example, a half mirror. In some examples, the partial reflector 1017 may be constructed by coating a thin layer of metal (e.g., silver or aluminum) on a transparent substrate. In addition, or alternatively, the partial reflector 1017 may be formed, for example, by depositing a thin film dielectric coating on the surface of a lens, or by depositing a combination of a metal coating and a dielectric coating on the surface of a lens. In some examples, the partial reflector 1017 may be a reflective polarizer itself.

[0133] The optional first quarter-wavelength retarder 1015 and second quarter-wavelength retarder 1025 may be a coating or film formed from any suitable material, including, for example, linear photopolymerizable polymer (LPP) materials and liquid crystal polymer (LCP) materials described in U.S. Patent Application Publication No. 2002 / 0180916 (Schadt et al.), No. 2003 / 028048 (Cherkaoui et al.), and No. 2005 / 0072959 (Moia et al.). Suitable LPP materials include ROP-131 EXP 306 LPP, and suitable LCP materials include ROF-5185 EXP 410 LCP, both of which are available from Rolic Technologies in Archeville, Switzerland. In some examples, the quarter-wavelength retarders 1015 and 1025 may be quarter-wavelength retarders at at least one wavelength within a given wavelength range.

[0134] During the operation of the optical system 1000, rays 1037 and 1038 are transmitted through the image plane 1030 and the aperture plane 1035, respectively. Rays 1037 and 1038 can be transmitted from the image plane 1030 to the aperture plane 1035 (for example in a head-mounted display application), or they can be transmitted from the aperture plane 1035 to the image plane 1030 (for example in a camera application). Ray 1038 is the central ray whose optical path defines the folded optical axis 1040 for the optical system 1000, which may be centered on the folded optical axis 1040. Ray 1038 can pass through the optical laminate 1010 without a large deviation from the optical axis 1040.

[0135] The path of the light ray 1037 can be deflected by the optical laminate 1010. The light ray 1037 passes through the partial reflector 1017 (including an optional second quarter-wavelength retarder 1015) and then through the lens 1012. After the first passage through the lens 1012, the light ray passes through an optional first quarter-wavelength retarder 1025 and is reflected from the reflective polarizer 1027. In an example where two quarter-wavelength retarders 1015, 1025 are incorporated into the optical laminate 1010, the quarter-wavelength retarders 1015, 1025 may be arranged on either side of the lens 1012 such that the quarter-wavelength retarders 1015, 1025 are located between the reflective polarizer 1027 and the image source 1031. In some such examples, the image source 1031 may emit light having polarization along the passing axis (a) of the reflective polarizer 1027, such that after passing through the quarter-wave retarders 1015 and 1025, the light is polarized along the blocking axis of the reflective polarizer 1027, and as a result, the light is reflected from the reflective polarizer 1027 when it is first incident on the film. The ray 1037 is first reflected from the reflective polarizer 1027, then returns after passing through the first quarter-wave retarder 1025, then reflected from the partial reflector 1017 (other rays not shown pass through the partial reflector 1017), then returns after passing through the lens 1012 and the first quarter-wave retarder 1025, and then incident on the reflective polarizer 1027 again. After passing through the first quarter-wavelength retarder 1025, being reflected from the partial reflector 1017, and passing back through the first quarter-wavelength retarder 1025, the ray 1037 has polarization along the passing axis (a) of the reflective polarizer 1027. Thus, the ray 1037 is transmitted through the reflective polarizer 1027 and then transmitted through the aperture surface 1035 into the second optical system 1033.

[0136] The design of a single integrated optical stack 1010 can provide a wide field of view in a compact system. The light ray 1037 transmitted through the outer edge of the image plane 1030 is the principal ray that intersects the aperture plane 1035 at the folded optical axis 1040 having a field of view angle θ, which may be, for example, at least 40 degrees, at least 45 degrees, or at least 50 degrees. The field of view at the aperture plane 1035 is, for example, 2θ, which may be at least 80 degrees, at least 90 degrees, or at least 100 degrees.

[0137] In some non-limiting examples, the optical system 1000 may include one or more optical lenses 1012 having a non-zero optical power, with a reflective polarizer 1027 disposed on a first principal surface 1014 of one or more optical lenses 1012 and fitted thereto, and one or more optical lenses 1012 having a partial reflector 1017 disposed on a different second principal surface 1016 of one or more optical lenses 1012 and fitted thereto. The reflective polarizer 1027 substantially transmits light 1037 having a first polarization state (a) along the optical axis 1040 having a second polarization state (b) such that the average light transmittance of the optical system 1000 for incident light 1037 having a second polarization state (b) is less than about 0.1%, and substantially reflects light having an orthogonal second polarization state (b) with the partial reflector 1017 having an average light reflectance of at least 30% over a given wavelength range.

[0138] Further examples of optical systems for displaying an object to an observer centered on the optical axis, including one or more reflective polarizers, are disclosed and described in U.S. Patent Application No. 14 / 865,017, which is incorporated herein by reference in its entirety. One or more of the optical films 100, 200, 400, and 600 described herein can be used in systems such as the reflective polarizers described herein.

[0139] In some examples, one or more of the optical films 100, 200, 400, and 600 described herein may be incorporated as reflective polarizers within a polarizing beam splitter (PBS). The PBS can be used to effectively split unpolarized light into two polarized states. A PBS system can be used in semiconductors, photonics equipment, or other optical systems to substantially reflect polarization in a second orthogonal polarization state (b) while substantially transmitting light in a first polarization state (a). In some examples, a PBS system may be designed to split an output polarized beam with a separation of about 90° while receiving light at an incident angle of 0° or 45°.

[0140] Figure 11 is a schematic cross-sectional view of an exemplary PBS 1100, including a first prism 1102, a second prism 1104, a reflective polarizer 1110, and a light source 1150. The first prism 1102 includes an input surface 1112 for receiving incident light from the light source 1150, an output surface 1114, and a first hypotenuse 1116. In some examples, the input surface 1112 and the output surface 114 may be further formed to have active regions for receiving and transmitting light passing through the first prism 1102. The second prism 1104 includes an output surface 1118 and a second hypotenuse 1120.

[0141] The reflective polarizer 1110 is positioned between the first hypotenuse 1116 and the second hypotenuse 1120 of the first prism 1102 and the second prism 1104, respectively. The reflective polarizer 1110 may be any of the optical films 100, 200, 400, and 600 described herein. For example, the reflective polarizer 1110 may include at least 50 continuously numbered interference layers, each of which may be relatively thin (e.g., having an average thickness of less than about 200 nm), and the fit curve is a best fit regression applied to the layer thickness profile reflective polarizer 1110 as a function of the number of layers (e.g., curve 300 in Figure 3), with an average slope of less than about 0.2 nm / layer in the region extending from the first to the Nth layer.

[0142] The first prism 1102 and the second prism 1104 may comprise glass or polymer material. Suitable polymer materials for the first prism 1102 and the second prism 1104 include, for example, transparent optical polymers such as acrylic polymers (e.g., polymethyl methacrylate), cyclic olefin copolymers, polycarbonates, and combinations thereof. In some examples, the first prism 1102 and the second prism 1104 may be formed by injection molding using a thermoplastic acrylic polymer, such as the acrylic polymer commercially available from Hitachi Chemical Co., Ltd. (Tokyo, Japan) under the trade designation "OPTOREZ OZ-1330" series polymer. In some examples, it is desirable to form the first prism 1102 and the second prism 1104 using the same polymer material to reduce the optical change between the two prisms; however, in other examples, the first prism 1102 and the second prism 1104 may be formed using different materials. In some examples, the first prism 1102 and the second prism 1104 may be of similar size, while in other examples, the first prism 1102 may have a smaller volume than the second prism 1104. In some examples, the volume of the first prism 1102 may be about half (or less than or equal to about 60%, or less than or equal to about 40%) the volume of the second prism 1104. The choice of which portion of the first prism 1102 may be removed depends in part on the optical paths of the incident, transmitted, and reflected light occurring within the envelope 1152.

[0143] During operation, the light source 1150 generates a light beam having an envelope 1152 containing a central ray 1154. The light from the light source 1150 may be unpolarized having a predetermined wavelength range. The central ray 1154 passes through the prism and then enters the first prism 1102 through the input surface 1112, which is incident on the reflective polarizer 1110 at an incident angle of about 45°. At that point, the central ray 1154 then passes through the reflective polarizer 1110 and reflects it, according to the polarization state of the light. For example, light corresponding to a first polarization state (a) (e.g., a pass-through state) passes through the reflective polarizer 1110 and travels through the second prism 1104 as a transmitted ray 1156 having the first polarization state (a), reaching the output surface 1118. Light corresponding to a second orthogonal polarization state (b) (e.g., block / reflection) is reflected from the reflective polarizer 1110 as a reflected ray 1158 having the second orthogonal polarization state (b). Depending on the angle of incidence between ray 1154 and the reflective polarizer 1110, the reflected ray 1158 is reflected by the reflective polarizer 1110 in the direction of the output surface 1114. In some examples, the transmitted ray 1156 and the reflected ray 1158 travel at a 90° angle to each other.

[0144] PBS1100 may include additional components (not shown) attached to one or more of the output or other faces of the first prism 1102 and the second prism 1104. In addition, PBS1100 may be incorporated into different optical systems. Various components or PBS1100 or those components coupled to PBS1100 may be in direct contact or attached via an optically transparent adhesive. In some examples, a reflective polarizer 1110 is attached to one or both of the first prism 1102 and the second prism 1104 using an optically transparent adhesive layer. Further examples of PBS designs and optical systems incorporating the PBS system are disclosed and described in U.S. Patent Application No. 14 / 865,017, which is incorporated herein by reference in its entirety.

[0145] In some non-limiting examples, the PBS 1100 may include a first prism 1102 and a second prism 1104, as well as a reflective polarizer 1110 disposed and bonded between the first prism 1102 and the second prism 1104 (for example, along the first hypotenuse 1116 and the second hypotenuse 1120). In such an example, when incident light having a predetermined wavelength (e.g., ray 1154) enters the PBS 1100 from the input surface 1112, strikes the reflective polarizer 1110 at least once, and then exits through the output surface (e.g., output surface 1118 or 1114) of the PBS 1110, the reflective polarizer 1110 can substantially reflect polarization having the first polarization state (a) and substantially transmit polarization having the orthogonal second polarization state (b), such that the ratio of the average intensity of the exiting light (e.g., transmitted ray 1156 or reflected ray 1158) to the average intensity of the incident light (e.g., ray 1154) is greater than about 90% when the incident light has a first polarization state (a) and less than about 0.2% when the incident light has a second polarization state (b). [Examples]

[0146] Example 1 - A birefringent reflective polarizer optical film was prepared as follows. Two multilayer optical packets were co-extruded with each packet consisting of 325 alternating layers of polyethylene naphthalate (PEN) and a low refractive index isotropic layer, which has a refractive index of approximately 1.57 and is manufactured using a blend of polycarbonate and copolyester (PC:coPET) to maintain substantially isotropy in the uniaxial direction, with a PC:coPET molar ratio of approximately 42.5 mol% PC and 57.5 mol% coPET, and a Tg of 105°C. This isotropic material was selected so that, after stretching the refractive index in two non-stretching directions, it would remain substantially matched with the refractive index of the birefringent material in the non-stretching direction, while in the stretching direction, there is a substantial mismatch in refractive index between the birefringent and non-birefringent layers. The PEN and PC / coPET polymers were fed from separate extruders into a multilayer co-extrusion feed block, which were then assembled into packets of 325 alternating optical layers ("packet 1" and "packet 2," respectively), with a thicker protective boundary layer of PC / coPET added to the outside of the stacked optical packets, for a total of 652 layers.

[0147] The layer profile for the high-contrast reflective polarizer (HCRP) optical film of Example 1 is shown in Figure 9 along with packet 1 and packet 2. Using least-squares linear regression, the average slope of packet 1 is approximately 0.17 nm / layer, and the average slope of packet 2 is approximately 0.18 nm / layer, showing a difference of approximately 6% in the slopes of the two packets. The film of Example 1 had the obtained total thickness as measured with a capacitance gauge of approximately 63.2 μm.

[0148] To evaluate the alignment of the multiple interference layers in Example 1, the optical axis of the film was determined for linearly polarized light incident on each principal surface of the film. The optical axis of the film corresponds to the orientation of the incident polarization in the plane of the film, which allows a minimum amount of linearly polarized light to pass through the film (e.g., aligned with the stretch axis 120 in Figure 2). In an ideal scenario, the optical axis of the film is identical regardless of the surface on which the polarized light is incident on the film. However, due to variations in the manufacturing process and misalignments of the individual optical axes of the multiple interference layers, the optical axis of the film may depend on which surface the polarized light is incident on. In some examples, the greater the degree of misalignment between the multiple layers, the greater the difference in the optical axis for the film. The difference between the optical axes of the film for two surfaces can, in some examples, be used as a criterion for evaluating the alignment between multiple interference layers. The two optical axes for the film in Example 1 were measured for two surfaces using linearly polarized light. The polarization was projected directly onto the first principal surface of the film, and the film was rotated until the minimum amount of polarization passing through the film was obtained. The optical axis of the first principal plane was marked as parallel to the polarization axis of the polarized light. This process was repeated for the second principal plane of the film. The difference between the optical axes of the first and second principal planes of the film in Example 1 was determined to be less than 0.1 degrees, indicating strong matching between multiple interference layers.

[0149] Example 2 - The birefringent reflective polarizer optical film was fabricated using the same process conditions as the film in Example 1, except that the optical film had a thickness of approximately 66.7 μm as measured by a capacitance gauge.

[0150] Example 3 - A birefringent reflective polarizer optical film was prepared as follows. Two multilayer optical packets were co-extruded with a low refractive index isotropic layer of PC / coPET described in Example 1, each optical packet comprising 325 alternating layers of 90 / 10coPEN (e.g., 90 mol% polyethylene naphthalate (PEN) and 10 mol% polyethylene terephthalate (PET)). The 90 / 10coPEN and PC / coPET polymers were fed from a separate extruder to a multilayer co-extrusion feed block, and a total of 652 layers were assembled, consisting of 325 alternating optical layer packets and a thicker protective boundary layer of coPEN on the outside of the laminated optical packets. The resulting film had the obtained total physical thickness, as measured with a capacitance gauge of approximately 63.2 μm.

[0151] Table 1 below provides the average transmission profiles for the optical films of Examples 1 to 3, comparing the first polarization state (a) and the second polarization state (b) (e.g., through axis and block axis) in the visible spectral range of 450 to 650 nm, and compares them with commercially available absorbing polarizers (AP) and reflective polarizers (RP), as well as those referenced in the literature. [Table 1]

[0152] Table 2 below shows the transmittance and reflectance values ​​for exemplary films 1 to 3 in a first polarization state (a) and an orthogonal second polarization state (b), calculated based on the values ​​in Table 1. These values ​​are calculated assuming negligible loss of light energy associated with absorption by the film layer. [Table 2]

[0153] Figure 12 is a plot of exemplary thickness profiles (layer thickness versus number of layers) for exemplary reflective polarizer films compared to conventional reflective polarizers described herein. The films are listed in Table 3 below. Films 1206 and 1208 represent commercially available multilayer reflective polarizer films available from 3M Corporation (St. Paul, Minnesota). Film 1210 is a typical conventional polarizer film with 275 layers, having a maximum thickness to minimum thickness ratio of 2.2, and the thickness varies continuously as described in its patent. Lines 1202 and 1204 correspond to the first and second optical laminates / packets in Example 1 of HCPR, respectively. Layer thickness profiles were measured using an atomic force microscope (AFM). [Table 3]

[0154] Table 4 below shows the calculated difference between the highest and lowest gradient regions for each of the films / packets 1202–1208 shown in Figure 12. The slope of each given region was determined using least-squares linear regression over a range of 25 layers. [Table 4]

[0155] Example 4 – Optical films were fabricated using the same manufacturing process as described for Examples 1, 2, and 3. A different layer thickness profile was implemented, utilizing a lower gradient / layer profile than that used in Examples 1, 2, and 3. In particular, two multilayer optical laminates / packets were co-extruded with each containing 325 alternating layers of polyethylene naphthalate (PEN) HIR layer and LIR isotropic layer. The LIR isotropic layer was manufactured from a blend of 20 wt% PETg (Eastman Chemicals, Knoxville, Tennessee) and 80 wt% Xylex (Sabic, Houston, Texas), which was a polycarbonate-copolyester alloy. The refractive index of the LIR layer was approximately 1.57 and it maintained substantially isotropy in the uniaxial direction. This isotropic material was selected so that, after stretching, its refractive index in the stretching direction remained substantially unchanged and was similar to that of the HIR layer in the unstretched direction, while the refractive index of the HIR layer in the stretching direction was substantially different from that of the LIR layer in the same direction. The materials for the HIR and LIR layers were supplied from a separate extruder that provided a multilayer co-extrusion feed block, which was assembled into two packets of 325 alternating optical layers, with a thick protective boundary layer made of isotropic LIR material added to each side of each packet, for a total of 653 layers, with spacer layers between the stacked optical packets considered to be optically and mechanically a single layer. The first packet (e.g., "packet 1") consisted of relatively thin alternating HIR / LIR layers, while the second packet (e.g., "packet 2") consisted of relatively thick alternating HIR / LIR layers, corresponding to predetermined wavelength ranges of approximately 390 nm to 620 nm and approximately 600 nm to 900 nm, respectively. The film is stretched in a parabolic tenter as described in U.S. Patent No. 6,916,440, the whole of which is incorporated herein by reference. The film is stretched at a temperature of about 316°F (e.g., 158°C). The film is stretched in the transverse direction at a ratio of about 6:1 and in the machine direction at a ratio of about 0.46:1, i.e., the film is relaxed in the machine direction.

[0156] Figure 13 shows a plot of the layer thickness profiles of the optical film of Example 4 obtained from AFM. Using least-squares linear regression, the mean slope of packet 1 was calculated to be approximately 0.104 nm / layer, and the mean slope of packet 2 was calculated to be approximately 0.141 nm / layer. The film of Example 4 had the obtained total thickness as measured with a capacitance gauge of approximately 65.7 μm. The average pass-through transmittance (T) evaluated over the wavelength range of 450 to 650 nm. a ) is approximately 89.1%, and the average block / reflection state transmittance (T b ) was approximately 0.057%.

[0157] Figure 14 shows the block state transmittance (T) for the film of Example 4. b The plot shows the values ​​over the wavelength range of 375 to 850 nm.

[0158] Example 5 - Table 5 below shows the Δn of the optical films of Examples 1 and 4 compared to commercially available RP2 and RP3 in the example. x This shows the / K ratio. As shown here, each packet of the optical film in Example 1 and Example 4 has a Δn greater than 1.2. x The / K ratio is shown, while the commercially available RP2 and RP3 in the examples have a Δn of less than 1. x This shows the / K ratio. [Table 5]

[0159] Example 6 - Table 5 below shows the optical density, optical power, and other optical properties of the optical film of Example 1. Table 5 also includes the results obtained for 24 comparative samples of conventional reflective polarizer films. The comparative samples correspond to various polarizer films that are commercially available or obtained using techniques disclosed in the literature. The optical power per layer relative to the total number of layers of the films listed in Table 6 is plotted in Figure 15. As shown in Figure 15, the optical films of Example 1 and Example 4 are (-0.0012 *The optical power per layer exceeds N+1.46 (illustrated by lines). [Table 6]

[0160] Example 7—The comparative display assembly investigation was carried out using the LCD display of an iPad 4 (Apple, Cupertino, California). Three reflective polarizers were tested in the display assembly as rear reflective polarizers (e.g., at the position of optical film 702 in display assembly 700). The reflective polarizers tested included the stock RP film of the iPad 4 laminated to a polyvinyl alcohol type adsorbent polarizer ("Comparative AP / RP Film"), the stock RP film of the iPad 4 without the RP ("Comparative RP Film"), and the high-contrast reflective polarizer optical film of Example 1. The adhesive used to bond the polarizer optical film to the LCD display was clear OCA8171, available from 3M, St. Paul, Minnesota. The light source used in the tests was the stock backlight with a brightness enhancement film (e.g., prism film / diffuser sheet) provided in the iPad 4 device.

[0161] The optical performance of three different display assemblies was tested using a commercially available conoscope, the ELDIM L80 (ELDIM SA, France, Elville Saint-Clair). The brightness and contrast results for the display assemblies are shown in Table 7, along with the normalized values ​​relative to the comparative AP / RP film. The results are as follows: The optical film of Example 1 showed superior brightness compared to both the comparative AP / RP film and the RP film. In addition, the optical film of Example 1 showed a much higher contrast ratio than the stock comparative RP film alone, which was comparable to the contrast ratio of the comparative AP / RP, despite the absence of a rear AP layer in the display assembly. [Table 7]

[0162] Paragraph 1: In one example, an optical film comprising a plurality of interference layers, each interference layer reflecting or transmitting light mainly by optical interference, the total number of interference layers being less than approximately 1000, and for substantially perpendicularly incident light within a predetermined wavelength range, the plurality of interference layers having an average light transmittance of more than approximately 85% for a first polarization state, an average light reflectance of more than approximately 80% for a second orthogonal polarization state, and an average light transmittance of less than approximately 0.2% for the second polarization state.

[0163] Section 2: In some examples of the optical films described in Section 1, the multiple interference layers have an average light transmittance of more than approximately 90% for a first polarization state in a given wavelength range.

[0164] Section 3: In some examples of the optical films described in Section 1, the multiple interference layers have an average light transmittance of more than approximately 95% for a first polarization state in a given wavelength range.

[0165] Section 4: In some examples of the optical films described in Section 1, the multiple interference layers have an average light transmittance of more than approximately 98% for a first polarization state in a given wavelength range.

[0166] Section 5: In some examples of optical films described in any of Sections 1 to 4, the multiple interference layers have an average light transmittance of less than approximately 0.15% for a second polarization state in a given wavelength range.

[0167] Section 6: In some examples of optical films described in any of Sections 1 to 5, the multiple interference layers have an average light transmittance of less than approximately 0.10% for a second polarization state in a given wavelength range.

[0168] Paragraph 7: In some examples of optical films described in any of paragraphs 1 to 6, with respect to light incident on the optical film at an incident angle of about 10 degrees in a predetermined wavelength range, the multiple interference layers have an average light transmittance of more than about 85% for a first polarization state, an average light reflectance of more than about 80% for a second polarization state, and an average light transmittance of less than about 0.2% for a second polarization state.

[0169] Paragraph 8: In some examples of optical films described in any of paragraphs 1 to 7, with respect to light incident on the optical film at an incident angle of about 20 degrees in a given wavelength range, the multiple interference layers have an average light transmittance of more than about 85% for a first polarization state, an average light reflectance of more than about 80% for a second polarization state, and an average light transmittance of less than about 0.2% for a second polarization state.

[0170] Section 9: In some examples of the optical films described in Section 1, with respect to light incident on the optical film at an incident angle of about 30 degrees in a given wavelength range, the multiple interference layers have an average light transmittance of more than about 85% for a first polarization state, an average light reflectance of more than about 80% for a second polarization state, and an average light transmittance of less than about 0.2% for a second polarization state.

[0171] Section 10: In one example, the optical film includes multiple interference layers, each interference layer reflecting or transmitting light mainly by optical interference, the total number of interference layers is less than approximately 1000, and for substantially normally incident light within a predetermined wavelength range, the optical film has an average light transmittance T for a first polarization state. a and average light reflectance R a For the second orthogonal polarization state, the average light transmittance T b and average light reflectance R b It has T b / R b R is less than approximately 0.002. a / T a It is less than approximately 0.17.

[0172] Section 11: In some examples of the optical films in Section 10, T a / T bThe number exceeds approximately 425.

[0173] Paragraph 12: In some examples of the optical films in paragraph 10 or 11, R b / R a It exceeds approximately 6.7.

[0174] Section 13: In some examples of optical films described in any of sections 10 to 12, the T of multiple interference layers a This exceeds approximately 90% within a given wavelength range.

[0175] Section 14: In some examples of optical films described in any of sections 10 to 13, the T of multiple interference layers a This exceeds approximately 95% within a given wavelength range.

[0176] Section 15: In some examples of optical films described in any of Sections 10 to 14, the T of multiple interference layers a This exceeds approximately 98% within the specified wavelength range.

[0177] Paragraph 16: In some examples of optical films described in any of paragraphs 10 to 15, T b It is less than approximately 0.15% within the given wavelength range.

[0178] Paragraph 17: In some examples of optical films described in any of paragraphs 10 to 16, T b It is less than approximately 0.10% within the given wavelength range.

[0179] Paragraph 18: In some examples of optical films described in any of paragraphs 10 to 17, with respect to light incident on the optical film at an incident angle of about 10 degrees in a given wavelength range, T a Over 85%, R b Over 80%, b The percentage is less than approximately 0.2%.

[0180] Item 19: In some examples of the optical film according to any one of Items 10 to 18, for light incident on the optical film at an incident angle of about 20 degrees within a predetermined wavelength range, T a exceeds about 85%, and R b exceeds about 80%, and T b is less than about 0.2%.

[0181] Item 20: In some examples of the optical film according to any one of Items 10 to 19, for light incident on the optical film at an incident angle of about 30 degrees within a predetermined wavelength range, T a exceeds about 85%, and R b exceeds about 80%, and T b is less than about 0.2%.

[0182] Item 21: In some examples of the optical film according to any one of Items 1 to 20, the optical film includes at least one non-interference layer disposed between two interference layers, and each of the at least one non-interference layer does not mainly reflect or transmit light by light interference.

[0183] Item 22: In some examples of the optical film according to Item 21, the average thickness of each of the at least one non-interference layer is at least 10 times the maximum wavelength within a predetermined wavelength range.

[0184] Item 23: In some examples of the optical film according to Item 21, the average thickness of each of the at least one non-interference layer is at least 50 times the maximum wavelength within a predetermined wavelength range.

[0185] Item 24: In some examples of the optical film according to any one of Items 1 to 23, the predetermined wavelength range is from about 400 nm to about 700 nm.

[0186] Item 25: In some examples of the optical film according to any one of Items 1 to 24, the predetermined wavelength ranges are from about 400 nm to about 700 nm and from about 800 nm to about 1300 nm.

[0187] Paragraph 26: In some examples of optical films described in any of paragraphs 1 through 25, the total number of interference layers is less than approximately 900.

[0188] Paragraph 27: In some examples of optical films described in any of paragraphs 1 through 26, the total number of interference layers is less than approximately 800.

[0189] Paragraph 28: In some examples of optical films described in any of paragraphs 1 through 27, the optical film has a thickness of less than approximately 60 μm.

[0190] Paragraph 29: In some examples of optical films described in any of paragraphs 1 to 28, the multiple interference layers include multiple alternating high refractive index first layers and low refractive index second layers.

[0191] Section 30: In one example, the optical film comprises N sequentially numbered layers, where N is an integer greater than 200 and less than 1000, each layer having an average thickness of less than approximately 200 nm, the fit curve is a best fit regression applied to a layer thickness profile plotting the thickness of each layer as a function of the number of layers, the average slope of the fit curve in the region extending from the first to the Nth layer is less than approximately 0.2 nm / layer, and for substantially normally incident light within a given wavelength range, the optical film has an average light transmittance of more than approximately 85% for a first polarization state and an average light reflectance of more than approximately 80% for a second orthogonal polarization state.

[0192] Section 31: In one example, the optical film contains N sequentially numbered layers, where N is an integer greater than 200, less than 10% of the layers have an average thickness greater than approximately 200 nanometers (nm), the fit curve is a best fit regression applied to the layer thickness of the optical film as a function of the number of layers, and the average slope of the fit curve in the region extending from the first layer to the Nth layer is less than approximately 0.2 nm.

[0193] Paragraph 32: In some examples of the optical films described in paragraph 31, the average thickness of at least one numbered layer in N consecutively numbered layers is at least 30% less than the average thickness of at least one other numbered layer in N consecutively numbered layers.

[0194] Paragraph 33: In some examples of optical films described in paragraph 30 or 32, the best-fit regression is one or more of the following: best-fit linear regression, best-fit nonlinear regression, best-fit polynomial regression, and best-fit exponential regression.

[0195] Paragraph 34: In some examples of optical films described in any one of paragraphs 30 to 33, the optical film includes at least one spacer layer disposed between two consecutively numbered layers in N consecutively numbered layers, each of the at least one spacer layer having an average thickness greater than approximately 500 nm.

[0196] Paragraph 35: In some examples of optical films described in any one of paragraphs 30 to 34, the optical film includes at least one spacer layer disposed between two consecutively numbered layers in N consecutively numbered layers, each of the at least one spacer layer having an average thickness of at least 10 times the longest wavelength in a given wavelength range.

[0197] Paragraph 36: In some examples of optical films described in any one of paragraphs 30 to 35, the optical film includes at least one spacer layer disposed between two consecutively numbered layers in N consecutively numbered layers, each of the at least one spacer layer having an average thickness of at least 50 times the longest wavelength in a given wavelength range.

[0198] Paragraph 37: In some examples of optical films described in any one of paragraphs 30 to 36, the average thickness of at least one layer in N consecutively numbered layers is less than approximately 50 nm, and the average thickness of at least one other layer in N consecutively numbered layers is greater than approximately 100 nm.

[0199] Paragraph 38: In some examples of optical films described in any one of paragraphs 30 to 37, N consecutively numbered layers are arranged in a continuous manner.

[0200] Paragraph 39: In some examples of optical films described in any one of paragraphs 30 through 38, the best-fit regression is one or more of the following: best-fit linear regression, best-fit nonlinear regression, best-fit polynomial regression, and best-fit exponential regression.

[0201] Paragraph 40: In some examples of optical films described in any one of paragraphs 30 to 39, the N sequentially numbered layers comprise a plurality of alternating high refractive index first layers and low refractive index second layers.

[0202] Section 41: In one example, the optical film comprises a plurality of layers numbered sequentially from 1 to N, where N is an integer greater than 50 and less than 1000, the optical film transmits at least 80% of light having a first polarization state within a given wavelength range and reflects at least 80% of light having a second polarization state orthogonal within a given wavelength range, the fit curve is a best fit regression applied to the layer thickness of the optical film as a function of the number of layers, the difference between the maximum and minimum slopes of the fit curve is less than approximately 0.70 nm / layer in the region extending from the first layer to the Nth layer, and the maximum and minimum slopes are each evaluated over any group of 25 to 50 adjacent layers.

[0203] Paragraph 42: In some examples of the optical films described in paragraph 41, each layer in the multiple layers has an average thickness of less than approximately 200 nm.

[0204] Item 43: In some examples of the optical film according to Item 41 or 42, the numbered layers in the plurality of layers are arranged continuously.

[0205] Item 44: In some examples of the optical film according to any one of Items 41 to 43, for substantially vertically incident light in a predetermined wavelength range, the average slope of the fitting curve in the region extending from the first layer to the Nth layer is less than about 0.2 nm.

[0206] Item 45: In some examples of the optical film according to any one of Items 41 to 44, the best-fit regression is one or more of the best-fit linear regression, the best-fit non-linear regression, the best-fit polynomial regression, and the best-fit exponential regression.

[0207] Item 46: In some examples of the optical film according to any one of Items 41 to 45, the optical film includes a spacer layer disposed between two successively numbered layers in one to N successively numbered layers of the plurality of layers, and the spacer layer has an average thickness that is at least 10 times the maximum wavelength in a predetermined wavelength range.

[0208] Item 47: In some examples of the optical film according to Item 46, the spacer layer has an average thickness that is at least 50 times the maximum wavelength in a predetermined wavelength range.

[0209] [[ID=2))Item 48: In some examples of the optical film according to any one of Items 41 to 47, the average thickness of at least one layer in one to N successively numbered layers is less than about 50 nm, and the average thickness of at least one layer in one to N successively numbered layers is greater than about 100 nm.

[0210] Item 49: In some examples of the optical film according to any one of Items 41 to 48, the N successively numbered layers include a plurality of alternating first layers with a high refractive index and second layers with a low refractive index.

[0211] Section 50: In one example, the optical film transmits at least 80% of light having a first polarization state within a given wavelength range and reflects at least 80% of light having a second polarization state orthogonal within a given wavelength range, the optical film comprises an N-layer laminate, where N is an integer greater than 50 and less than 1000, and for multiple non-overlapping groups of layers arranged continuously in the N-layer laminate, the layers in each group are numbered from 1 to m, where m is greater than 25, and for each non-overlapping group, the fit curve is a best fit regression applied to the layer thickness of the group as a function of the number of layers, and in the region extending from the first layer in the group to the m-th layer in the group, the fit curve has an average slope such that the maximum difference between the average slopes of the fit curves in multiple non-overlapping groups is less than 0.70 nm / layer.

[0212] Paragraph 51: In some examples of the optical films described in paragraph 51, the average thickness of at least one layer in the N-layer laminate is at least 30% less than the average thickness of at least one other layer in the N-layer laminate.

[0213] Paragraph 52: In some examples of optical films described in paragraph 51 or 52, the best-fit regression is one or more of the following: best-fit linear regression, best-fit nonlinear regression, best-fit polynomial regression, and best-fit exponential regression.

[0214] Paragraph 53: In some examples of optical films described in any of paragraphs 50 to 52, the average thickness of at least one layer in the N-layer laminate is less than about 50 nm, and the average thickness of at least one other layer in the N-layer laminate is greater than about 100 nm.

[0215] Paragraph 54: In one example, the optical film comprises a plurality of alternating first and second layers, each first and second layer reflecting or transmitting light primarily by optical interference, the total number of each of the first and second layers being less than 400 and greater than 100, and for each adjacent pair of first and second layers, the first layer has a maximum refractive index n1 along the x-direction in the plane of the first layer. x The second layer has a refractive index n2 along the x-direction. x It has n1 x and n2 x The difference is greater than approximately 0.24, and the maximum angular range in the x-direction of the first layer is less than approximately 2 degrees.

[0216] Paragraph 55: In some examples of the optical films described in paragraph 54, the multiple alternating first and second layers are arranged in a continuous manner.

[0217] Paragraph 56: In some examples of the optical films described in paragraph 54 or 55, the multiple alternating first and second layers comprise a total of N layers arranged in a continuous manner, the optical film transmits at least 80% of light having a first polarization state within a given wavelength range and reflects at least 80% of light having a second polarization state within a given wavelength range, the fit curve is a best fit regression applied to the layer thickness of the optical film as a function of the number of layers, and thus the region extending from the first layer to the Nth layer includes a slope of less than approximately 0.2 nm / number of layers.

[0218] Paragraph 57: In some examples of optical films described in any of paragraphs 54 through 56, the best-fit regression is one or more of the following: best-fit linear regression, best-fit nonlinear regression, best-fit polynomial regression, and best-fit exponential regression.

[0219] Paragraph 58: In some examples of optical films described in any of paragraphs 54 to 57, each of the multiple alternating first and second layers has an average thickness of less than approximately 200 nm per layer.

[0220] Paragraph 59: In some examples of optical films described in any of paragraphs 54 to 58, the plurality of alternating first and second layers comprises at least two laminates, each comprising a plurality of alternating first and second layers, the optical film further comprises a spacer layer disposed between the two laminates, the spacer layer having an average thickness of at least 10 times the longest wavelength in a given wavelength range.

[0221] Paragraph 60: In some examples of the optical films described in paragraph 59, the spacer layer has an average thickness of at least 50 times the longest wavelength in a given wavelength range.

[0222] Paragraph 61: In some examples of optical films described in any of paragraphs 54 to 60, the average thickness of at least one layer in a plurality of alternating first and second layers is less than about 50 nm, and the average thickness of at least one other layer in a plurality of alternating first and second layers is greater than about 100 nm.

[0223] Paragraph 62: In one example, the optical film includes multiple alternating high-refractive-index and low-refractive-index interference layers, each interference layer reflecting or transmitting light primarily by optical interference, the total number of interference layers is greater than 300, and the optical power per interference layer of the optical film is greater than approximately 0.7.

[0224] Paragraph 63: In some examples of the optical films described in paragraph 62, the total number of high-refractive-index interference layers and low-refractive-index interference layers is less than 1000.

[0225] Paragraph 64: In some examples of the optical films described in paragraph 62 or 63, the high refractive index interference layer and the low refractive index interference layer comprise at least two laminates, each comprising the high refractive index interference layer and the low refractive index interference layer, and the optical film further comprises a spacer layer disposed between the two laminates, the spacer layer having an average thickness of at least 10 times the longest wavelength in a given wavelength range.

[0226] Paragraph 65: In some examples of optical films described in any of paragraphs 62 to 64, the spacer layer has an average thickness of at least 50 times the longest wavelength in a given wavelength range.

[0227] Paragraph 66: In some examples of optical films described in any of paragraphs 62 to 65, the average thickness of at least one layer in a plurality of alternating high-refractive-index interference layers and low-refractive-index interference layers is less than approximately 50 nm, and the average thickness of at least one other layer in a plurality of alternating high-refractive-index interference layers and low-refractive-index interference layers is greater than approximately 100 nm.

[0228] Section 67: In one example, the optical film includes multiple alternating high-refractive-index and low-refractive-index interference layers, each interference layer reflecting or transmitting light primarily by optical interference, and the optical power per interference layer of the multiple interference layers is -0.0012 * N is greater than 1+1.46, where N is the total number of alternating high-refractive-index interference layers and low-refractive-index interference layers, and N is greater than 100 and less than 1000.

[0229] Paragraph 68: In some examples of optical films described in paragraph 67, the total number of high-refractive-index interference layers and low-refractive-index interference layers is less than 1000.

[0230] Paragraph 69: In some examples of the optical films described in paragraph 67 or 68, the high refractive index interference layer and the low refractive index interference layer comprise at least two laminates, each comprising the high refractive index interference layer and the low refractive index interference layer, and the optical film further comprises a spacer layer disposed between the two laminates, the spacer layer having an average thickness of at least 10 times the longest wavelength in a given wavelength range.

[0231] Paragraph 70: In some examples of the optical films described in paragraph 69, the spacer layer has an average thickness of at least 50 times the longest wavelength in a given wavelength range.

[0232] Paragraph 71: In some examples of optical films described in any of paragraphs 67 to 70, the average thickness of at least one layer in a plurality of alternating high-refractive-index interference layers and low-refractive-index interference layers is less than approximately 50 nm, and the average thickness of at least one other layer in a plurality of alternating high-refractive-index interference layers and low-refractive-index interference layers is greater than approximately 100 nm.

[0233] Paragraph 72: In one example, the optical film comprises a plurality of interference layers that reflect and transmit light mainly by optical interference, wherein, for substantially normally incident light within a given wavelength range, the plurality of interference layers transmit at least 80% of the light having a first polarization state and reflect at least 80% of the light having an orthogonal second polarization state, and have an average light density greater than about 2.5, the plurality of interference layers are divided into a plurality of optical laminates, and each pair of adjacent optical laminates is separated by one or more spacer layers that do not reflect or transmit light mainly by optical interference, and each optical The laminate transmits at least 50% of light having a first polarization state within a predetermined wavelength range and reflects at least 50% of light having a second polarization state within a predetermined wavelength range, the interference layers in each optical laminate are numbered sequentially, each optical laminate has a best-fit linear equation relating the thickness of the optical laminate to the number of interference layers, the linear equation has an average slope within a region extending from the first interference layer in the laminate to the last interference layer in the laminate, and the maximum difference between the average slopes of the linear equations for multiple optical laminates is less than approximately 20%.

[0234] Paragraph 73: In some examples of the optical films described in paragraph 72, each optical laminate includes at least 50 interference layers of multiple interference layers.

[0235] Paragraph 74: In some examples of optical films described in paragraph 72 or 73, the optical film comprises fewer than 1,000 layers of interference layers.

[0236] Paragraph 75: In some examples of optical films described in any of paragraphs 72 to 74, one or more spacer layers have an average thickness that is at least 10 times the longest wavelength in a given wavelength range.

[0237] Paragraph 76: In some examples of optical films described in any of paragraphs 72 to 75, one or more spacer layers have an average thickness of at least 50 times the longest wavelength in a given wavelength range.

[0238] Paragraph 77: In some examples of optical films described in any of paragraphs 72 to 76, the average thickness of at least one layer in the multiple interference layers is less than approximately 50 nm, and the average thickness of at least one other layer in the multiple interference layers is greater than approximately 100 nm.

[0239] Paragraph 78: In one example, an optical film transmits at least 80% of light having a first polarization state within a predetermined wavelength range and reflects at least 80% of light having a second polarization state that is orthogonal within a predetermined wavelength range, comprising 100 to 400 continuously arranged unit cells, each unit cell comprising a first layer of low refractive index and an adjacent second layer of high refractive index, the difference between the high and low refractive indices for each unit cell is greater than about 0.24, each unit cell has a total optical thickness equal to half of the different central wavelengths within the predetermined wavelength range, and for each of at least 80% of pairs of adjacent unit cells in the continuously arranged unit cells, the ratio of the difference between the central wavelengths of adjacent unit cells to the average of the central wavelengths of adjacent unit cells is less than about 2%.

[0240] Paragraph 79: In some examples of the optical films described in paragraph 78, the average thickness of at least one layer in a continuously arranged unit cell is at least 30% less than the average thickness of at least one other layer in a continuously arranged unit cell.

[0241] Paragraph 80: In some examples of optical films described in paragraph 78 or 79, a continuously arranged unit cell comprises a total of N continuously arranged layers, each of the N continuously arranged layers having an average thickness of less than approximately 200 nm, the fit curve is a best fit regression applied to the layer thickness of the optical film as a function of the number of layers, the average slope of the fit curve in the region extending from the first layer to the Nth layer is less than approximately 0.2 nm, and for substantially normally incident light within a given wavelength range, the optical film has an average light transmittance of more than approximately 80% for a first polarization state and an average light reflectance of more than approximately 80% for a second orthogonal polarization state.

[0242] Paragraph 81: In some examples of optical films described in any of paragraphs 78 through 80, the best-fit regression is one or more of the following: best-fit linear regression, best-fit nonlinear regression, best-fit polynomial regression, and best-fit exponential regression.

[0243] Paragraph 82: In some examples of optical films described in any of paragraphs 78 to 81, the average thickness of at least one layer in a laminate of N consecutively arranged layers is less than approximately 50 nm, and the average thickness of at least one other layer in the N consecutively arranged layers is less than approximately 100 nm.

[0244] Paragraph 83: In one example, the optical film comprises a plurality of interference layers that reflect or transmit light primarily by optical interference in a given wavelength range, the maximum difference between the refractive indices of the interference layers is Δn, the fit curve is a best fit regression applied to the layer thickness of the optical film as a function of the number of layers, the fit curve has an average slope K in a region extending across the plurality of interference layers, and Δn / K is greater than approximately 1.2.

[0245] Paragraph 84: In some examples of the optical films described in paragraph 83, Δn / K is greater than approximately 1.5.

[0246] Paragraph 85: Some examples of optical films described in paragraph 83 or 84 have an optical density greater than about 2.0 in a given wavelength range.

[0247] Paragraph 86: Some examples of optical films described in any of paragraphs 83 to 85 have an optical density greater than approximately 3.0 in a given wavelength range.

[0248] Paragraph 87: Some examples of optical films described in any of paragraphs 83 to 86 have an optical density greater than approximately 3.0 in a given wavelength range.

[0249] Paragraph 88: In some examples of optical films described in any of paragraphs 83 to 87, Δn is greater than approximately 0.24.

[0250] Paragraph 89: In some examples of optical films described in any of paragraphs 83 to 88, the multiple interference layers comprise a total of N consecutively arranged layers, where N is less than 1000, each of the N consecutively arranged layers having an average thickness of less than about 200 nm, the fit curve is a best fit regression applied to the layer thickness of the optical film as a function of the number of layers, the average slope of the fit curve in the region extending from the first to the Nth layer is less than about 0.2 nm, and for substantially normally incident light within a given wavelength range, the optical film has an average light transmittance of more than about 80% for a first polarization state and an average light reflectance of more than about 80% for a second orthogonal polarization state.

[0251] Paragraph 90: In some examples of optical films described in Paragraph 89, the best-fit regression is one or more of the following: best-fit linear regression, best-fit nonlinear regression, best-fit polynomial regression, and best-fit exponential regression.

[0252] Paragraph 91: In some examples of optical films described in paragraph 89 or 90, the average thickness of at least one layer in N consecutively arranged layers is less than about 50 nm, and the average thickness of at least one other layer in N consecutively arranged layers is greater than about 100 nm.

[0253] Paragraph 92: In some examples of optical films described in any of paragraphs 83 to 91, the optical film includes a spacer layer disposed between two of a plurality of interference layers, the spacer layer having an average thickness of at least 10 times the longest wavelength in a given wavelength range.

[0254] Paragraph 93: In some examples of the optical films described in paragraph 92, the spacer layer has an average thickness of at least 50 times the longest wavelength in a given wavelength range.

[0255] Paragraph 94: In one example, an optical film is optimized to transmit or reflect light in a first predetermined wavelength range rather than a second predetermined wavelength range. a A first unit cell consisting of a series of units, each unit cell comprising a first high refractive index layer and a second low refractive index layer, and an M optimized to transmit or reflect light in a second predetermined wavelength range rather than a first predetermined wavelength range. b A second unit cell arranged in a continuous manner, each of which includes a third high refractive index layer and a fourth low refractive index layer, and M a For a first unit cell arranged in a continuous sequence, the ratio of the average refractive index of the first high refractive index layer to the average refractive index of the second low refractive index layer × M a The number exceeds approximately 300, M b For a second unit cell arranged in a continuous sequence, the ratio of the average refractive index of the third high refractive index layer to the average refractive index of the fourth low refractive index layer × M b The light incident on the optical film at an incident angle exceeding approximately 300 degrees, and at any incident angle from approximately 0 degrees to approximately 30 degrees, has any wavelength within a first predetermined wavelength range and a second predetermined wavelength range, and the average light transmittance of the optical film for the first polarization state T a The average light transmittance T of the optical film for a second, orthogonal polarization state. b The ratio is approximately 1000:1 or greater.

[0256] Paragraph 95: In some examples of the optical films described in paragraph 94, the first predetermined wavelength range and the second predetermined wavelength range are within the visible and infrared ranges of the electromagnetic spectrum, respectively.

[0257] Paragraph 96: In some examples of the optical films described in paragraph 94 or 95, the first predetermined wavelength range is approximately 400 nm to approximately 700 nm.

[0258] Paragraph 97: In some examples of optical films described in any of paragraphs 94 to 96, the second predetermined wavelength range is approximately 800 nm to approximately 1300 nm.

[0259] Paragraph 98: In some examples of optical films described in any of paragraphs 94 to 97, M a The first unit cells and M are arranged in a continuous sequence. b Each of the continuously arranged second unit cells contains a total of less than 400 interference layers, and each interference layer has an average thickness of less than 200 nm, and the fit curve is M as a function of the number of layers. a This is a best fit regression applied to the layer thickness of a continuously arranged first unit cell, starting from the first interference layer (2 * The average slope of the fit curve in the region extending to the Ma) layer is less than approximately 0.2 nm / layer, and for substantially perpendicular incident light within a first predetermined wavelength range, the optical film has an average light transmittance of over 80% for a first polarization state and an average light reflectance of over 80% for a second orthogonal polarization state.

[0260] Paragraph 99: In some examples of optical films described in any of paragraphs 94 through 98, the best-fit regression is one or more of the following: best-fit linear regression, best-fit nonlinear regression, best-fit polynomial regression, and best-fit exponential regression.

[0261] Paragraph 100: In some examples of optical films described in any of paragraphs 94 to 99, M a The average thickness of at least one interference layer in the continuously arranged first unit cell is less than approximately 50 nm, Ma The average thickness of at least one other interference layer in the continuously arranged first unit cell exceeds approximately 100 nm.

[0262] Paragraph 101: In some examples of optical films described in any of paragraphs 94 to 100, the optical film is M a The first unit cell and M are arranged in a continuous sequence. b It includes a spacer layer disposed between a second unit cell and a second unit cell arranged in a continuous manner, the spacer layer having an average thickness of at least 10 times the longest wavelength in the first and second predetermined wavelength ranges.

[0263] Paragraph 102: In some examples of the optical films described in paragraph 101, the spacer layer has an average thickness of at least 50 times the longest wavelength in the first and second predetermined wavelength ranges.

[0264] Paragraph 103: In some examples of optical films described in any of paragraphs 30 to 100, for substantially normally incident light within a given wavelength range, the optical film has an average light transmittance T for a first polarization state. a and average light reflectance R a , and the average light transmittance T for a second orthogonal polarization state. b and average light reflectance R b It has T b / R b R is less than approximately 0.002. a / T a It is less than approximately 0.17.

[0265] Paragraph 104: In some examples of the optical films in paragraph 103, T a / T b The number exceeds approximately 425.

[0266] Paragraph 105: In some examples of the optical films of paragraph 103 or 104, R b / R a It exceeds approximately 6.7.

[0267] Paragraph 106: In some examples of optical films described in any of paragraphs 103 to 105, the given wavelength range is approximately 400 nm to approximately 700 nm.

[0268] Paragraph 107: In some examples of optical films described in any of paragraphs 103 to 106, the specified wavelength ranges are approximately 400 nm to approximately 700 nm and approximately 800 nm to approximately 1300 nm.

[0269] Paragraph 108: In some examples of optical films described in any of paragraphs 103 to 107, T for the layer a This exceeds approximately 90% within a given wavelength range.

[0270] Paragraph 109: In some examples of optical films described in any of paragraphs 103 to 108, T for the layer a This exceeds approximately 95% within a given wavelength range.

[0271] Paragraph 110: In some examples of optical films described in any of paragraphs 103 to 109, T for the layer a This exceeds approximately 98% within the specified wavelength range.

[0272] Paragraph 111: In some examples of optical films described in any of paragraphs 103 to 110, T b This is less than approximately 0.15% within the given wavelength range.

[0273] Paragraph 112: In some examples of optical films described in any of paragraphs 103 to 111, T b This is less than approximately 0.10% within the given wavelength range.

[0274] Paragraph 113: In some examples of optical films described in any of paragraphs 103 to 112, for light incident on the optical film at an incident angle of about 10 degrees in a given wavelength range, T a Over 85%, R b Over 80%, bThe percentage is less than approximately 0.2%.

[0275] Paragraph 114: In some examples of optical films described in any of paragraphs 103 to 113, for light incident on the optical film at an incident angle of about 20 degrees in a given wavelength range, T a Over 85%, R b Over 80%, b The percentage is less than approximately 0.2%.

[0276] Paragraph 115: In some examples of optical films described in any of paragraphs 103 to 114, with respect to light incident on the optical film at an incident angle of about 30 degrees in a given wavelength range, T a Over 85%, R b Over 80%, b The percentage is less than approximately 0.2%.

[0277] Paragraph 116: In some examples of optical films described in any of paragraphs 30 to 115, the optical film has a thickness of less than approximately 60 μm.

[0278] Paragraph 117: In some examples of optical films described in any of paragraphs 30 to 116, the layers include a plurality of alternating high refractive index first layers and low refractive index second layers.

[0279] Paragraph 118: In some examples of optical films described in any of paragraphs 30 through 117, the total number of layers is less than approximately 900.

[0280] Paragraph 119: In some examples of optical films described in any of paragraphs 30 through 118, the total number of layers is less than approximately 800.

[0281] Paragraph 120: In some examples of optical films described in any of paragraphs 1 through 119, the optical film has a contrast ratio greater than 1000:1.

[0282] Paragraph 121: In some examples of optical films described in any of paragraphs 1 to 120, the optical film has an optical density greater than approximately 2.0 in a given wavelength range.

[0283] Paragraph 122: In some examples of optical films described in any of paragraphs 1 through 121, the optical film has an optical power greater than approximately 0.7 per interference layer.

[0284] Paragraph 123: In some examples of optical films described in any of paragraphs 1 to 122, the predetermined wavelength range includes three predetermined wavelength ranges: about 430 nm to about 465 nm, 490 nm to about 555 nm, and about 600 nm to about 665 nm.

[0285] Paragraph 124: In some examples of optical films described in any of paragraphs 1 to 123, alternating high refractive index first layers and low refractive index second layers provide a refractive index difference greater than approximately 0.24 with respect to the axis corresponding to the first polarization state.

[0286] Paragraph 125: In some examples of optical films described in paragraph 124, the maximum difference in refractive index between alternating high-refractive-index first layers and low-refractive-index second layers is Δn, the fit curve is a best fit regression applied to the layer thickness of the optical film as a function of the number of layers, the fit curve has an average slope K in the region extending across multiple interference layers, and Δn / K is greater than approximately 1.2.

[0287] Paragraph 126: In some examples of the optical films described in paragraph 125, Δn / K is greater than approximately 1.5.

[0288] Paragraph 127: In one example, the display assembly comprises a light source, a liquid crystal display assembly, and an optical film as described in any of the preceding paragraphs, disposed between the liquid crystal display assembly and the light source.

[0289] Paragraph 128: In some examples of the display assemblies in paragraph 127, the light source includes an optical guide configured to direct light toward an optical film, and the liquid crystal display assembly includes a liquid crystal layer and an absorptive polarizer, the liquid crystal layer being disposed between the optical film and the absorptive polarizer.

[0290] Paragraph 129: In some examples of display assemblies described in paragraph 127 or 128, the display assembly does not include an absorbing polarizer film between the liquid crystal layer and the optical film.

[0291] Paragraph 130: In some examples of the display assemblies described in paragraph 127 or 128, the display assembly further includes an absorbing polarizer disposed between the liquid crystal layer and the optical film.

[0292] Paragraph 131: In one example, a display assembly includes a light source, a liquid crystal layer configured to be illuminated by the light source, one or more brightness-enhancing films disposed between the light source and the liquid crystal layer to increase brightness in the axial direction of the display assembly, and a reflective polarizer disposed between the one or more brightness-enhancing films and the liquid crystal layer, configured to substantially transmit light having a first polarization state and substantially reflect light having a second orthogonal polarization state, wherein the reflective polarizer has an average light transmittance of less than about 0.2% for the second polarization state, no absorptive polarizer is disposed between the light source and the liquid crystal layer, and the contrast ratio of the display assembly is at least twice that of a comparative display assembly having the same structure, except that the average transmittance of the reflective polarizer of a comparative display assembly for the second polarization state is greater than about 1.0%.

[0293] Paragraph 132: In some examples of the display assemblies of paragraph 131, the reflective polarizer includes an optical film as described in any one of paragraphs 1 through 126.

[0294] Paragraph 133: In one example, a display assembly includes a light source, a liquid crystal layer configured to be illuminated by the light source, one or more brightness-enhancing films disposed between the light source and the liquid crystal layer to increase brightness in the axial direction of the display assembly, and a reflective polarizer disposed between the one or more brightness-enhancing films and the liquid crystal layer, comprising a plurality of interference layers that transmit or reflect light mainly by optical interference, wherein, for substantially normally incident light within a given wavelength range, the plurality of interference layers transmit at least 80% of the light having a first polarization state and less than about 0.2% of the light having an orthogonal second polarization state, and no absorbing polarizer is disposed between the light source and the liquid crystal layer.

[0295] Paragraph 134: In some examples of the display assemblies described in paragraph 133, the reflective polarizer includes an optical film as described in any one of paragraphs 1 through 126.

[0296] Paragraph 135: In one example, an optical laminate is a reflective polarizer comprising a plurality of interference layers, each interference layer reflecting or transmitting light mainly by optical interference, wherein for substantially normally incident light having a predetermined wavelength, the plurality of interference layers comprise a reflective polarizer having an optical transmittance of more than 85% for a first polarization state, an optical reflectance of more than 80% for an orthogonal second polarization state, and a light transmittance of less than 0.1% for a second polarization state, and an absorptive polarizer coupled to the reflective polarizer and having substantially the same extent, wherein for substantially normally incident light having a predetermined wavelength, the absorptive polarizer has a first optical transmittance for the first polarization state, a light absorptiveness of more than 50% for the second polarization state, and a second light transmittance for the second polarization state, and the ratio of the second light transmittance to the first light transmittance is greater than 0.001.

[0297] Paragraph 136: In some examples of the optical laminates described in paragraph 135, the ratio of the second light transmittance to the first light transmittance is greater than approximately 0.01.

[0298] Paragraph 137: In some examples of optical laminates described in paragraph 135 or 136, the ratio of the second light transmittance to the first light transmittance is greater than approximately 0.1.

[0299] Paragraph 138: In some examples of optical laminates described in any one of paragraphs 135 to 137, the given wavelength is approximately 550 nm.

[0300] Paragraph 139: In some examples of optical laminates described in any one of paragraphs 135 to 138, the reflective polarizer includes an optical film described in any one of paragraphs 1 to 126.

[0301] Paragraph 140: In one example, an optical system for displaying an object to an observer centered on the optical axis, comprising: at least one optical lens having non-zero optical power; a reflective polarizer disposed on and conforming to the first principal surface of the optical lens, which substantially transmits light having a first polarization state and substantially reflects light having a second orthogonal polarization state; and a partial reflector disposed on and conforming to a different second principal surface of the optical lens, which has an average light reflectance of at least 30% over a given wavelength range, and the average light transmittance of the optical system for incident light along the optical axis having a second polarization state is less than about 0.1%.

[0302] Section 141: In some examples of the optical systems described in Section 140, the reflective polarizer includes N sequentially numbered interference layers, where N is an integer greater than 50, and each layer has an average thickness of less than approximately 200 nm, and the fit curve is a best fit regression applied to a layer thickness profile plotting the thickness of each layer as a function of the number of layers, with an average slope of less than approximately 0.2 nm / layer in the region extending from the first to the Nth layer.

[0303] Paragraph 142: In some examples of the optical systems described in paragraph 140 or 141, the reflective polarizer includes an optical film described in any one of paragraphs 1 through 126.

[0304] Paragraph 143: In some examples of optical systems described in any of paragraphs 140 to 142, the first principal surface of at least one optical lens is curved along at least a first direction.

[0305] Paragraph 144: In some examples of optical systems described in any of paragraphs 140 to 143, the second principal surface of at least one optical lens is curved along at least a first direction.

[0306] Paragraph 145: In some examples of optical systems described in any of paragraphs 140 to 144, each of the first principal plane and the second principal plane is curved along two mutually orthogonal directions.

[0307] Paragraph 146: In one example, a polarizing beam splitter (PBS) comprising first and second prisms and a reflective polarizer disposed and bonded between the first and second prisms, wherein the reflective polarizer substantially reflects polarized light having a first polarization state and substantially transmits light having a second polarization state which is orthogonal to the PBS, and incident light having a predetermined wavelength enters the PBS from the input side of the PBS, encounters the reflective polarizer at least once, and exits the PBS from the output side of the PBS, wherein the ratio of the average intensity of the exiting light to the average intensity of the incident light is greater than about 90% when the incident light has a first polarization state and less than about 0.2% when the incident light has a second polarization state.

[0308] Section 147: In some examples of PBS in Section 146, the reflective polarizer contains N sequentially numbered interference layers, where N is an integer greater than 50, each layer has an average thickness of less than approximately 200 nm, the fit curve is a best fit regression applied to a layer thickness profile plotting the thickness of each layer as a function of the number of layers, and the average slope of the fit curve in the region extending from the first to the Nth layer is less than approximately 0.2 nm / layer.

[0309] Paragraph 148: In some examples of PBS in paragraph 146 or 147, the reflective polarizer includes the optical film described in any one of paragraphs 1 through 126.

[0310] Paragraph 149: In some examples of PBS described in any one of paragraphs 146 to 148, at least one of the first prism and the second prism is a polymer.

[0311] Paragraph 150: In some examples of PBS described in any one of paragraphs 146 to 149, the given wavelengths are in the range of approximately 400 nm to approximately 700 nm.

[0312] Paragraph 151: In one example, the liquid crystal display projection system includes an optical film as described in any one of paragraphs 1 through 126.

[0313] Section 152: In some examples of the liquid crystal display projection systems described in Section 151, the system includes one or more optical retarder layers located adjacent to the optical film, the one or more optical retarder layers being configured to correct the polarization state of the incident light.

[0314] Paragraph 153: In some examples of the liquid crystal display projection systems described in paragraph 152, at least one light wave retarder layer is directly optically coupled to an optical film.

[0315] Paragraph 154: In some examples of the liquid crystal display projection systems of paragraph 152 or 153, at least one optical retarder layer is separated from the optical film.

[0316] Paragraph 155: In one example, a display assembly includes a light source, a liquid crystal layer configured to be illuminated by the light source, and a reflective polarizer comprising an optical film as described in any one of paragraphs 1 to 126, wherein the reflective polarizer is disposed adjacent to the reflective polarizer.

[0317] Paragraph 156: In one example, the optics comprises a plurality of interference layers, each primarily reflecting or transmitting light by optical interference; a total number of interference layers less than approximately 800 such that, for substantially normally incident light within a predetermined wavelength range, the plurality of interference layers have an average light transmittance of more than approximately 85% for a first polarization state; an average light reflectance of more than approximately 80% for a second orthogonal polarization state; and an average light transmittance of less than approximately 0.2% for the second polarization state.

[0318] Paragraph 157: In some examples of the optical films described in paragraph 156, the optical film further includes at least one non-interference layer disposed between two interference layers, each of which does not reflect or transmit light primarily by optical interference.

[0319] Paragraph 158: In some examples of the optical films described in paragraph 157, the average thickness of each of at least one non-interfering layer is at least 10 times the longest wavelength within a given wavelength range.

[0320] Paragraph 159: In some examples of the optical films described in paragraph 157, the average thickness of each of at least one non-interfering layer is at least 50 times the longest wavelength within a given wavelength range.

[0321] Paragraph 160: In some examples of optical films described in paragraph 156, the given wavelength range is approximately 400 nm to approximately 700 nm.

[0322] Paragraph 161: In some examples of the optical films described in paragraph 156, the given wavelength ranges are approximately 400 nm to approximately 700 nm and approximately 800 nm to approximately 1300 nm.

[0323] Paragraph 162: In some examples of the optical films described in paragraph 156, the interference layers comprise a plurality of alternating high refractive index first layers and low refractive index second layers.

[0324] Paragraph 163: In some examples of the optical films described in paragraph 156, the multiple interference layers have an average light transmittance of more than 90% for a first polarization state in a given wavelength range.

[0325] Paragraph 164: In some examples of the optical films described in paragraph 156, the multiple interference layers have an average light transmittance of more than approximately 95% for a first polarization state in a given wavelength range.

[0326] Paragraph 165: In some examples of the optical films described in paragraph 156, the multiple interference layers have an average light transmittance of more than approximately 98% for a first polarization state in a given wavelength range.

[0327] Paragraph 166: In some examples of the optical films described in paragraph 156, the multiple interference layers have an average light transmittance of less than about 0.15% for a second polarization state in a given wavelength range.

[0328] Paragraph 167: In some examples of the optical films described in paragraph 156, the multiple interference layers have an average light transmittance of less than about 0.10% for a second polarization state in a given wavelength range.

[0329] Paragraph 168: In some examples of the optical films described in paragraph 156, the optical film has multiple interference layers that, with respect to light incident on the optical film at an incident angle of about 10 degrees in a given wavelength range, have an average light transmittance of more than about 85% for a first polarization state, an average light reflectance of more than about 80% for a second polarization state, and an average light transmittance of less than about 0.2% for a second polarization state.

[0330] Paragraph 169: In some examples of the optical films described in paragraph 156, the optical film has multiple interference layers that, with respect to light incident on the optical film at an incident angle of about 20 degrees in a given wavelength range, have an average light transmittance of more than about 85% for a first polarization state, an average light reflectance of more than about 80% for a second polarization state, and an average light transmittance of less than about 0.2% for a second polarization state.

[0331] Paragraph 170: In some examples of optical films described in paragraph 156, the optical film has multiple interference layers that, with respect to light incident on the optical film at an incident angle of about 30 degrees in a given wavelength range, have an average light transmittance of more than about 85% for a first polarization state, an average light reflectance of more than about 80% for a second polarization state, and an average light transmittance of less than about 0.2% for a second polarization state.

[0332] Paragraph 171: In one example, the optical film comprises a plurality of interference layers, each interference layer reflecting or transmitting light mainly by optical interference, and for substantially normally incident light within a predetermined wavelength range, the optical film has an average light transmittance T for a first polarization state. a and average light reflectance R a For the second orthogonal polarization state, the average light transmittance T b and average light reflectance R b T less than approximately 0.002 b / R b , and R less than approximately 0.17 a / T a The total number of interference layers is less than approximately 800, so as to have this characteristic.

[0333] Paragraph 172: In some examples of the optical films described in paragraph 171, multiple interference layers are arranged in a continuous manner.

[0334] Paragraph 173: In some examples of the optical films described in paragraph 171, the optical film further includes at least one non-interfering layer disposed between two interfering layers in a plurality of interfering layers, each of which does not reflect or transmit light primarily by optical interference.

[0335] Paragraph 174: In some examples of the optical films in paragraph 171, T a / T b The number exceeds approximately 425.

[0336] Paragraph 175: In some examples of the optical films in paragraph 171, R b / R a It exceeds approximately 6.7.

[0337] Paragraph 176: In one example, an optical film comprises N consecutively numbered layers, where N is an integer greater than 200 and less than 800, and each layer having an average thickness of less than approximately 200 nm; and a fitting curve which is a best fit regression applied to the thickness of the optical film as a function of the number of layers, wherein the average slope of the fitting curve in the region extending from the first layer to the Nth layer is less than approximately 0.2 nm, such that for substantially normally incident light within a given wavelength range, the optical film has an average light transmittance of more than approximately 85% for a first polarization state and an average light reflectance of more than approximately 80% for a second orthogonal polarization state.

[0338] Paragraph 177: In some examples of the optical films described in paragraph 176, N consecutively numbered layers are arranged in a continuous sequence.

[0339] Paragraph 178: In some examples of optical films described in Paragraph 176, the best-fit regression is one or more of the following: best-fit linear regression, best-fit nonlinear regression, best-fit polynomial regression, and best-fit exponential regression.

[0340] Paragraph 179: In some examples of the optical films described in paragraph 176, the optical film further comprises spacer layers disposed between two consecutively numbered layers in N consecutively numbered layers, the spacer layers having an average thickness of at least 10 times the longest wavelength in a given wavelength range.

[0341] Paragraph 180: In some examples of the optical films described in paragraph 176, the average thickness of at least one layer in N consecutively numbered layers is less than approximately 50 nm, and the average thickness of at least one other layer in N consecutively numbered layers is greater than approximately 100 nm.

[0342] Paragraph 181: In one example, the optical film comprises N consecutively numbered layers, where N is an integer greater than 200, and each layer having an average thickness of less than approximately 200 nm, and a fitting curve which is a best-fit regression applied to the thickness of the optical film as a function of the number of layers, wherein the average slope of the fitting curve in the region extending from the first layer to the Nth layer is less than approximately 0.2 nm.

[0343] Paragraph 182: In some examples of the optical films described in paragraph 181, the optical film further comprises at least one spacer layer disposed between two consecutively numbered layers in N consecutively numbered layers, each of the at least one spacer layer having an average thickness greater than approximately 500 nm.

[0344] Paragraph 183: In some examples of the optical films described in paragraph 181, N consecutively numbered layers are arranged in a continuous sequence.

[0345] Paragraph 184: In some examples of the optical films described in paragraph 181, the average thickness of at least one numbered layer in N consecutively numbered layers is less than 30% of the average thickness of at least one other numbered layer in N consecutively numbered layers.

[0346] Paragraph 185: In one example, an optical film comprises a plurality of layers numbered sequentially from 1 to N, where N is an integer greater than 50 and less than 800, the optical film having a plurality of layers that transmit at least 80% of light having a first polarization state within a given wavelength range and reflect at least 80% of light having a second polarization state that is orthogonal within a given wavelength range, and a fit curve which is a best fit regression applied to the thickness of the optical film as a function of the number of layers, wherein the difference between the maximum and minimum slopes of the fit curve in the region extending from the first layer to the Nth layer is less than approximately 0.70 nm / layer.

[0347] Paragraph 186: In some examples of the optical films described in paragraph 185, each layer in the multiple layers has an average thickness of less than approximately 200 nm.

[0348] Paragraph 187: In some examples of the optical films described in paragraph 181, the numbered layers are arranged in a sequence.

[0349] Paragraph 188: In one example, the optical film transmits at least 80% of light having a first polarization state within a given wavelength range and reflects at least 80% of light having a second polarization state orthogonal within a given wavelength range, the optical film comprises an N-layer laminate, where N is an integer greater than 50 and less than 800, and for multiple non-overlapping groups of layers arranged continuously in the N-layer laminate, the layers in each group are numbered from 1 to m, where m is greater than N / 10, and for each group, the fit curve is a best fit regression applied to the thickness of the group as a function of the number of layers, and in the region extending from the first layer in the group to the m-th layer in the group, the fit curve has an average slope such that the maximum difference between the average slopes of the fit curves in multiple non-overlapping groups is less than 0.70 nm / layer.

[0350] Paragraph 189: In one example, the optical film comprises a plurality of alternating first and second layers, each first and second layer reflecting or transmitting light primarily by optical interference, the total number of first and second layers being less than 400 and greater than 100, and for each adjacent pair of first and second layers, the first layer has a maximum refractive index n1 along the x-direction in the plane of the first layer. x The second layer has a maximum refractive index n2 along the x-direction. x It has n1 x and n2 x The difference between the two is greater than approximately 0.24, and the maximum angular range in the x-direction of the first layer is less than approximately 2 degrees.

[0351] Paragraph 190: In some examples of the optical films described in paragraph 189, a plurality of alternating first and second layers are arranged in a continuous manner.

[0352] Paragraph 191: In one example, the optical film comprises several alternating high-refractive-index and low-refractive-index interference layers, each interference layer reflecting or transmitting light primarily by optical interference, the total number of layers being more than 300, and the optical power of each interference layer of the optical film being approximately more than 0.7.

[0353] Paragraph 192: In some examples of optical films described in paragraph 191, the total number of interference layers is less than 800.

[0354] Paragraph 193: In one example, the optical film comprises a plurality of alternating high-refractive-index and low-refractive-index interference layers, each interference layer reflecting or transmitting light primarily by optical interference, and the optical power per interference layer of the plurality of interference layers is -0.0012 * The value exceeds N+1.5, where N is the total number of interference layers, and N is an integer greater than 100 and less than 1000.

[0355] Paragraph 194: In one example, the optical film comprises a plurality of interference layers that reflect and transmit light mainly by optical interference, wherein for substantially normally incident light within a given wavelength range, the plurality of interference layers transmit at least 80% of the light having a first polarization state and reflect at least 80% of the light having an orthogonal second polarization state, and have an average light density greater than about 2.5, the plurality of interference layers are divided into a plurality of optical stacks, each pair of adjacent optical stacks is separated by one or more spacer layers that do not reflect or transmit light mainly by optical interference, and each optical product Each layer transmits at least 50% of light having a first polarization state within a predetermined wavelength range and reflects at least 50% of light having a second polarization state within a predetermined wavelength range. The interference layers in each optical laminate are numbered sequentially, and each optical laminate has a best-fit linear equation relating the thickness of the optical laminate to the number of interference layers. The linear equation has an average gradient within a region extending from the first interference layer to the last interference layer in the laminate, and the maximum difference between the average gradients of the linear equations for multiple optical laminates is less than approximately 20%.

[0356] Paragraph 195: In some examples of the optical films described in paragraph 194, each optical laminate includes at least 50 interference layers of multiple interference layers.

[0357] Paragraph 196: In one example, the display system comprises a light source, a liquid crystal layer configured to be illuminated by the light source, one or more brightness-enhancing films disposed between the light source and the liquid crystal layer to increase brightness in the axial direction of the display system, and a reflective polarizer disposed between one or more brightness-enhancing films and the liquid crystal layer, configured to substantially transmit light having a first polarization state and substantially reflect light having a second orthogonal polarization state, wherein the reflective polarizer has an average light transmittance of less than about 0.2% for the second polarization state, no absorptive polarizer is disposed between the light source and the liquid crystal layer, and the contrast ratio of the display system is at least twice that of a comparative display system having the same structure, except that the average transmittance of the reflective polarizer for the second polarization state is greater than about 1.0%.

[0358] Paragraph 197: In one example, the display system comprises a light source, a liquid crystal layer configured to be illuminated by the light source, one or more brightness-enhancing films disposed between the light source and the liquid crystal layer to increase brightness in the axial direction of the display system, and a reflective polarizer disposed between the one or more brightness-enhancing films and the liquid crystal layer, having a plurality of interference layers that transmit or reflect light mainly by optical interference, wherein, for substantially normally incident light within a predetermined wavelength range, the plurality of interference layers transmit at least 80% of the light having a first polarization state and transmit less than about 0.2% of the light having an orthogonal second polarization state, and no absorbing polarizer is disposed between the light source and the liquid crystal layer.

[0359] Paragraph 198: In one example, an optical film transmits at least 80% of light having a first polarization state within a predetermined wavelength range and reflects at least 80% of light having a second polarization state that is orthogonal within a predetermined wavelength range, comprising 200 to 400 continuously arranged unit cells, each unit cell comprising a first layer of low refractive index and an adjacent second layer of high refractive index, the difference between the high index and low index for each unit cell is greater than about 0.24, each unit cell has a total optical thickness equal to half of the different central wavelengths within the predetermined wavelength range, and for each of at least 80% of pairs of adjacent unit cells in the continuously arranged unit cells, the ratio of the difference in the central wavelength of the unit cells to the average central wavelength of the unit cells is less than about 2%.

[0360] Paragraph 199: In one example, an optical film comprises a plurality of interference layers that reflect or transmit light mainly by optical interference in a given wavelength range, wherein the maximum difference between the refractive indices of the interference layers is Δn, and a fit curve which is a best fit regression applied to the thickness of the optical film as a function of the number of layers, wherein the fit curve has an average slope K in a region extending across the plurality of interference layers, and Δn / K is greater than about 1.2.

[0361] Paragraph 200: In some examples of optical films described in paragraph 199, Δn / K is greater than approximately 1.5.

[0362] Paragraph 201: In some examples of optical films described in paragraph 199, the optical film has an optical density greater than about 2.0 in a given wavelength range.

[0363] Paragraph 202: In some examples of optical films described in paragraph 199, the optical film has an optical density greater than about 3.0 in a given wavelength range.

[0364] Paragraph 203: In one example, the optical film comprises a first unit cell M arranged in a continuous sequence, optimized to transmit or reflect light in a first predetermined wavelength range rather than a second predetermined wavelength range, and a second unit cell N arranged in a continuous sequence, optimized to transmit or reflect light in a second predetermined wavelength range rather than a first predetermined wavelength range, wherein the first and second unit cells comprise a low refractive index layer and an adjacent high refractive index layer, and for the first unit cell M arranged in a continuous sequence, the ratio of the average refractive index of the first layer to the average refractive index of the second layer × M is greater than approximately 300, and for the second unit cell N arranged in a continuous sequence, the ratio of the average refractive index of the first layer to the average refractive index of the second layer × N is greater than approximately 300, and for light incident on the optical film at any incident angle from about 0 to about 30 degrees, the optical film has any wavelength within the first predetermined wavelength range and the second predetermined wavelength range, and the average light transmittance T of the optical film for a first polarization state a The average light transmittance T of the optical film for a second, orthogonal polarization state. b The ratio is less than approximately 1000.

[0365] Paragraph 204: In some examples of the optical films described in paragraph 203, the first predetermined wavelength range and the second predetermined wavelength range are within the visible and infrared ranges of the electromagnetic spectrum, respectively.

[0366] Paragraph 205: In one example, a polarizing beam splitter (PBS) comprises a reflective polarizer disposed and bonded between a first prism and a second prism, wherein when incident light having a predetermined wavelength enters the PBS from the input side of the PBS, encounters the reflective polarizer at least once, and exits the PBS from the output side of the PBS, the reflective polarizer substantially reflects light having a first polarization state and substantially transmits light having an opposing second polarization state such that the ratio of the average intensity of the emitted light to the average intensity of the incident light is greater than about 90% when the incident light has a first polarization state and less than about 0.2% when the incident light has a second polarization state.

[0367] Paragraph 206: In some examples of PBS in paragraph 205, at least one of the first prism and the second prism is a polymer.

[0368] Paragraph 207: In some examples of PBS in Paragraph 205, the reflective polarizer comprises N sequentially numbered layers, where N is an integer greater than 50, each layer having an average thickness of less than approximately 200 nm, the fit curve is a best fit regression applied to the thickness of the optical film as a function of the number of layers, and the average slope of the fit curve in the region extending from the first to the Nth layer is less than approximately 0.2 nm.

[0369] Paragraph 208: In some examples of PBS in Paragraph 205, the given wavelengths are in the range of approximately 400 nm to approximately 700 nm.

[0370] Paragraph 209: In some examples of PBS in paragraph 205, the reflective polarizer includes an optical film as described in any of paragraphs 1 through 208.

[0371] Paragraph 210: In one example, an optical system for displaying an object to an observer centered on the optical axis includes one or more optical lenses having non-zero optical power; a reflective polarizer disposed on the first principal surface of one or more optical lenses and conforming to the first principal surface of the optical lens, which substantially transmits light having a first polarization state and substantially reflects light having a second orthogonal polarization state; and a partial reflector disposed on different second principal surfaces of one or more optical lenses and conforming to different second principal surfaces of the optical lens, which has an average light reflectance of at least 30% over a given wavelength range and the average light transmittance of the optical system to incident light along the optical axis having a second polarization state is less than about 0.1%.

[0372] Paragraph 211: In some examples of the optical systems described in Paragraph 210, the reflective polarizer comprises a number of N consecutively numbered layers, where N is an integer greater than 50, and each layer having an average thickness of less than approximately 200 nm, and a fit curve which is a best fit regression applied to the thickness of the optical film as a function of the number of layers, wherein the average slope of the fit curve in the region extending from the first to the Nth layer is less than approximately 0.2 nm.

[0373] Paragraph 212: In some examples of the optical systems described in paragraph 210, the first surface of at least one optical lens is curved along one or more first directions.

[0374] Paragraph 213: In some examples of the optical systems described in paragraph 210, the second surface of one or more optical lenses is curved along at least a first direction.

[0375] Section 214: In some examples of the optical systems described in Section 210, each of the first principal surface and the second surface is curved along two mutually orthogonal directions.

[0376] Paragraph 215: In some examples of the optical systems described in paragraph 210, the reflective polarizer includes an optical film described in any of paragraphs 1 through 214.

[0377] Paragraph 216: In one example, an optical laminate comprising a reflective polarizer including a plurality of interference layers, each interference layer reflecting or transmitting light mainly by optical interference, wherein for substantially normally incident light having a predetermined wavelength, the plurality of interference layers have an optical transmittance of more than 85% for a first polarization state, an optical reflectance of more than 80% for an orthogonal second polarization state, and a light transmittance of less than 0.1% for the second polarization state, and comprising an absorpturing polarizer coupled to the reflective polarizer and having substantially the same extent, wherein for substantially normally incident light having a predetermined wavelength, the absorpturing polarizer has a first optical transmittance for the first polarization state, a light absorptance of more than 50% for the second polarization state, and a second light transmittance for the second polarization state, and the ratio of the second light transmittance to the first light transmittance is greater than 0.001.

[0378] Paragraph 217: In some examples of optical laminates described in paragraph 216, the given wavelength is approximately 550 nm.

[0379] Paragraph 218: In some examples of optical films described in any one of paragraphs 1 through 217, the specified wavelength ranges of the optical film are approximately 430 nm to approximately 465 nm, 490 nm to approximately 555 nm, and approximately 600 nm to approximately 665 nm.

[0380] Paragraph 219: In some examples of optical films described in any one of paragraphs 1 through 218, the specified wavelength ranges of the optical film are approximately 400 nm to approximately 430 nm, 450 nm to approximately 500 nm, and approximately 550 nm to approximately 600 nm.

[0381] Various examples have been described. The other examples mentioned above are within the scope of the following claims.

Claims

1. An optical laminate comprising an absorptive polarizer and a reflective polarizer coupled to the absorptive polarizer and having substantially the same spread, wherein the reflective polarizer includes alternating layers of a first layer with a high refractive index and a second layer with a low refractive index, and each of the first layers includes a polymer of polyethylene naphthalate or a copolymer of polyethylene naphthalate and polyethylene terephthalate, and for substantially perpendicularly incident light in the wavelength range of visible light from 400 nm to 700 nm, the reflective polarizer has an average light transmittance Ta and an average light reflectance Ra for a first polarization state, and an average light transmittance Tb and an average light reflectance Rb for a second orthogonal polarization state, Tb / Rb is less than 0.002, and Ra / Ta is less than 0.17, the absorptive polarizer has a first average light transmittance for a first polarization state, an average light absorption rate exceeding 50% for a second polarization state, and a second average light transmittance for a second polarization state, and the ratio of the second average light transmittance to the first average light transmittance is greater than 0.01, for each pair of adjacent first and second layers, in the plane of the first layer, the first layer has a maximum refractive index n1x along the x direction, the second layer has a refractive index n2x along the x direction, and the difference between n1x and n2x is greater than 0.24, Optical laminate.

2. The ratio of the second average light transmittance to the first average light transmittance is greater than 0.1, The optical laminate according to claim 1.

3. The optical laminate according to claim 1, wherein the reflective polarizer has alternating layers of a plurality of different first and second polymer materials with a total number less than 800.

4. For incident light with an incident angle of 30 degrees, the reflective polarizer has an average light transmittance exceeding 85% for the first polarization state, an average light reflectance exceeding 80% for the second polarization state, and an average light transmittance less than 0.2% for the second polarization state. The optical laminate according to claim 1.

5. T ａ / T ｂ The optical laminate according to claim 1, wherein T / ａ is greater than 425

6. R ｂ / R ａ The optical laminate according to claim 1, wherein R / ｂ R ａ is greater than 6.7

7. The optical laminate according to claim 1, wherein the reflective polarizer has a thickness less than 60 μm.

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