A flat beam-splitting polarizing film and its preparation method

Abstract

The present invention belongs to the field of precision optical technology, and specifically relates to a flat beam-splitting polarizing film and a method for preparing the same. The present invention uses film design software to perform film system design on the flat beam-splitting polarizing film, obtaining a film system design result for the flat beam-splitting polarizing film; the two bottom surfaces of the substrate are respectively plated according to the film system design result, and the flat beam-splitting polarizing films are respectively obtained on the two bottom surfaces of the substrate. The flat beam-splitting polarizing film prepared by the present invention has a high extinction ratio, with an extinction ratio (ER=Tp:Ts)>>10000:1, and can effectively separate the p component and s component of the incident light; and the actual adjustable wavelength range is wide (≥13nm), solving the technical problems of low extinction ratio and narrow actual adjustable wavelength range of optical films. At the same time, the reliability test results of the flat beam-splitting polarizing film prepared by the present invention are all OK; and the preparation method is convenient for mass production, maintenance, and batch preparation.

Description

Technical Field

[0001] The present invention belongs to the technical field of precision optics, and in particular relates to a flat beam-splitting polarization film and a preparation method thereof. Background Art

[0002] With the continuous development of society, the development of optical films has been rapid. Currently, the applications of optical films are not limited to simple anti-reflection and housing color decoration. In the field of precision optics, optical films are often required to achieve a high degree of separation between P and S light to achieve a high extinction ratio. At the same time, optical films must meet various stringent environmental tests (i.e., reliability tests).

[0003] However, the optical films disclosed in the prior art have the problems of low extinction ratio and narrow practical adjustable wavelength range. Summary of the Invention

[0004] The present invention aims to provide a flat beam-splitting polarizing film and a method for preparing the same. The flat beam-splitting polarizing film prepared by the present invention has a high extinction ratio (ER = Tp:Ts) of 10000:1 and a wide range of practically adjustable wavelengths, thereby solving the technical problems of low extinction ratio and narrow practically adjustable wavelength range in optical films.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] The present invention provides a method for preparing a flat beam-splitting polarizing film, comprising the following steps:

[0007] Film system design software is used to design a flat beam-splitting polarizing film. The flat beam-splitting polarizing film is formed by alternately stacking low-refractive index materials and high-refractive index materials. The film system design result of the flat beam-splitting polarizing film is obtained. The initial film stack used in the film system design is shown in Formula 1:

[0008] G0 / (0.5HL0.5H) S 0.5HLHL0.5H (0.5HL0.5H) S / AIR formula 1;

[0009] In formula 1, G0 represents the substrate, AIR represents the incident medium, H represents the high refractive index material, L represents the low refractive index material, S represents the repetition frequency of the "(0.5HL0.5H)" unit, and S ≥ 5;

[0010] The film system design results include the thickness of a single layer of high refractive index material, the thickness of a single layer of low refractive index material, the number of film layers of high refractive index material, the number of film layers of low refractive index material, the total number of layers and the total thickness;

[0011] The two bottom surfaces of the substrate are respectively plated according to the film system design result, and the flat beam-splitting polarization films are respectively obtained on the two bottom surfaces of the substrate.

[0012] Preferably, the high refractive index material is titanium pentoxide; and the low refractive index material is silicon dioxide.

[0013] Preferably, the material of the substrate is UV fused quartz;

[0014] The thickness of the substrate is 0.6-6 mm.

[0015] Preferably, the film system design software includes TFCalc optical thin film design software or Essential Macleod optical thin film design software.

[0016] Preferably, the film system design conditions include: the incident angle is 45°; the incident medium is air; the output medium is ultraviolet fused quartz; the p-polarized light transmittance of the flat beam splitting polarizing film in the target band is set to 100%, and the s-polarized light transmittance is set to 0.

[0017] Preferably, the plating conditions include: initial vacuum degree ≤ 3×10 -3 Pa; the substrate heating temperature is 150~200℃; the film forming rate of the high refractive index material is 0.2~0.3nm / s, and the film forming rate of the low refractive index material is 0.3~0.7nm / s.

[0018] Preferably, before the plating, the substrate is further subjected to ion source cleaning, and the vacuum degree of the ion source cleaning is ≤3×10 -3 Pa, the time is 2-5 min, and the heating temperature of the substrate during the ion source cleaning is 150-200°C.

[0019] Preferably, the target wavelength band of the flat beam-splitting polarizing film is the visible light and near-infrared wavelength band.

[0020] Preferably, the visible light and near-infrared bands are 400-2500 nm.

[0021] The present invention provides a flat beam-splitting polarizing film prepared by the preparation method described in the above technical solution, wherein the extinction ratio of the flat beam-splitting polarizing film is greater than 10000:1.

[0022] The present invention provides a method for preparing a flat beam-splitting polarizing film, comprising the following steps: using film system design software to perform film system design on the flat beam-splitting polarizing film, wherein the flat beam-splitting polarizing film is formed by alternately stacking low-refractive index materials and high-refractive index materials, and obtaining a film system design result of the flat beam-splitting polarizing film. The initial film stack used in the film system design is shown in Formula 1: G0 / (0.5HL0.5H)S 0.5HLHL0.5H (0.5HL0.5H) S / AIR Formula 1; in Formula 1: G0 represents the substrate, AIR represents the incident medium, H represents the high-refractive index material, L represents the low-refractive index material, S represents the repetition frequency of the "(0.5HL0.5H)" unit, and S ≥ 5; the film system design results include the single-layer film thickness of the high-refractive index material, the single-layer film thickness of the low-refractive index material, the number of film layers of the high-refractive index material, the number of film layers of the low-refractive index material, the total number of layers, and the total thickness; the two bottom surfaces of the substrate are respectively plated according to the film system design results, and the flat-plate beam-splitting polarizing film is obtained on the two bottom surfaces of the substrate. The present invention reasonably sets the initial film stack formula, uses film system design software to accurately optimize the film system design of the flat-plate beam-splitting polarizing film, and then plates it according to the film system design results. In addition, the present invention adopts a double-sided plating method on the substrate, and the resulting polarization beam-splitting film has an excellent polarization splitting effect. The flat-plate beam-splitting polarizing film prepared by the present invention exhibits a high extinction ratio (ER = Tp:Ts) of >> 10,000:1, effectively separating the p and s components of incident light. It also boasts a wide, practically adjustable wavelength range (≥13 nm), resolving the technical issues of low extinction ratios and narrow practically adjustable wavelength ranges often encountered in optical films. Furthermore, the flat-plate beam-splitting polarizing film prepared by the present invention has passed all reliability tests (including chemical stability, adhesion, friction testing, low-temperature testing, high-temperature testing, water boiling, constant humidity and heat, and temperature gradient testing). The preparation method also facilitates mass production, maintenance, and batch manufacturing.

[0023] Furthermore, in the present invention, the film system design conditions include: an incident angle of 45°. Unlike traditional flat-plate beam-splitting polarizing films, the flat-plate beam-splitting polarizing film prepared in the present invention has a light incident angle of 45°, which facilitates installation, commissioning, and use.

[0024] Furthermore, in the present invention, the substrate has a thickness of 0.6 to 6 mm. By optimizing the substrate thickness, the present invention can produce a flat-plate beam-splitting polarizing film with improved performance. When the substrate thickness is less than 0.6 mm, the substrate's compressive strength decreases after coating, and the risk of fragility increases. When the substrate thickness is greater than 6 mm, the excessive thickness of the substrate can affect light transmission. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is the design curve of the 532nm flat beam-splitting polarizing film in Example 1;

[0026] Figure 2 This is the test curve of the 532nm flat beam splitting polarizing film in Example 1;

[0027] Figure 3 This is the design curve for the 1310nm flat beam-splitting polarizing film in Example 2;

[0028] Figure 4 This is the test curve of the 1310nm flat beam-splitting polarizing film in Example 2. DETAILED DESCRIPTION

[0029] The present invention provides a method for preparing a flat beam-splitting polarizing film, comprising the following steps:

[0030] Film system design software is used to design a flat beam-splitting polarizing film. The flat beam-splitting polarizing film is formed by alternately stacking low-refractive index materials and high-refractive index materials. The film system design result of the flat beam-splitting polarizing film is obtained. The initial film stack used in the film system design is shown in Formula 1:

[0031] G0 / (0.5HL0.5H) S 0.5HLHL0.5H (0.5HL0.5H) S / AIR formula 1;

[0032] In formula 1, G0 represents the substrate, AIR represents the incident medium, H represents the high refractive index material, L represents the low refractive index material, S represents the repetition frequency of the "(0.5HL0.5H)" unit, and S ≥ 5;

[0033] The film system design results include the thickness of a single layer of high refractive index material, the thickness of a single layer of low refractive index material, the number of film layers of high refractive index material, the number of film layers of low refractive index material, the total number of layers and the total thickness;

[0034] The two bottom surfaces of the substrate are respectively plated according to the film system design result, and the flat beam-splitting polarization films are respectively obtained on the two bottom surfaces of the substrate.

[0035] In the present invention, unless otherwise specified, all preparation raw materials / components are commercially available products well known to those skilled in the art.

[0036] The present invention uses film system design software to design a film system for a flat beam-splitting polarizing film. The flat beam-splitting polarizing film is formed by alternately stacking low-refractive index materials and high-refractive index materials. The film system design result of the flat beam-splitting polarizing film is obtained. The initial film stack used in the film system design is shown in Formula 1:

[0037] G0 / (0.5HL0.5H) S 0.5HLHL0.5H (0.5HL0.5H) S / AIR formula 1;

[0038] In formula 1, G0 represents the substrate, AIR represents the incident medium, H represents the high refractive index material, L represents the low refractive index material, S represents the repetition frequency of the "(0.5HL0.5H)" unit, and S ≥ 5;

[0039] The film system design results include the single-layer film thickness of the high-refractive index material, the single-layer film thickness of the low-refractive index material, the number of film layers of the high-refractive index material, the number of film layers of the low-refractive index material, the total number of layers and the total thickness.

[0040] In the present invention, the high refractive index material is preferably titanium pentoxide. The low refractive index material is preferably silicon dioxide. The titanium pentoxide and silicon dioxide have the characteristics of high transmittance, low absorption, and high chemical stability.

[0041] In the present invention, it can be seen from the initial film stack formula 1 that a high refractive index material layer, a low refractive index material layer, a high refractive index material layer, a low refractive index material layer, ..., a high refractive index material layer, and a low refractive index material layer are sequentially arranged on the substrate.

[0042] In the present invention, the film system design software preferably includes TFCalc optical thin film design software or EssentialMacleod optical thin film design software, and in the embodiment, it can be TFCalc film system design software.

[0043] In the present invention, the conditions for the film system design preferably include: the incident angle is 45°; the incident medium is air; the output medium is ultraviolet fused quartz; the p-polarized light transmittance of the flat beam-splitting polarizing film in the target band is set to 100%, and the s-polarized light transmittance is set to 0.

[0044] In the present invention, the target wavelength of the flat beam-splitting polarizing film is preferably visible light and near-infrared wavelengths. The visible light and near-infrared wavelengths are preferably 400 to 2500 nm, and in embodiments, may be 405 nm, 532 nm, 780 nm, 808 nm, 1030 nm, 1064 nm, 1310 nm, or 1550 nm.

[0045] After obtaining the film system design result, the present invention performs coating on the two bottom surfaces of the substrate according to the film system design result, and obtains the flat beam-splitting polarization film on the two bottom surfaces of the substrate.

[0046] In the present invention, the coating is preferably performed using an evaporation light-controlled coating machine, which in the embodiment may be an Aluga series evaporation coating machine. The evaporation light-controlled coating machine can accurately monitor the film thickness.

[0047] In the present invention, the substrate is made of ultraviolet fused silica (UVFS). The substrate thickness is preferably 0.6 to 6 mm, more preferably 1 to 5 mm. The substrate is preferably cylindrical or prism-shaped. The two bottom surfaces (i.e., the coating surfaces) of the substrate can be circular or square. In one embodiment, the substrate can be a cylindrical UV fused silica glass with a diameter of 25.4 mm.

[0048] In the present invention, before the plating, the present invention preferably further comprises cleaning the substrate with an ion source. The present invention preferably places the substrate in a collar, and places the collar with the substrate on a hollow umbrella of the machine; and then performs ion source cleaning. The vacuum degree of the ion source cleaning is preferably ≤3×10 -3 Pa, the time is preferably 2-5 minutes, and the substrate heating temperature during ion source cleaning is preferably 150-200°C, and in embodiments, can be 180°C. By controlling the substrate heating temperature during ion source cleaning to 150-200°C, the present invention can reduce ion absorption by the substrate during the ion source cleaning process. In the present invention, the voltage for ion source cleaning is preferably 800-850V; the current is preferably 800-850mA. The gases used for ion source cleaning are preferably oxygen and argon, and the flow ratio of the oxygen and argon gases is preferably 60:8. The flow rate of the oxygen is preferably 60 sccm. The argon gases include a first argon gas and a second argon gas. The flow rate of the first argon gas (ion source argon gas) is preferably 0 sccm, and the flow rate of the second argon gas (neutralizer argon gas) is preferably 8 sccm.

[0049] In the present invention, the plating is performed after the ion source is cleaned. The plating preferably includes first plating a first flat-plate beam-splitting polarizing film on one bottom surface of the substrate (i.e., the first bottom surface); and then plating a second flat-plate beam-splitting polarizing film on the other bottom surface of the substrate (i.e., the second bottom surface). The first and second flat-plate beam-splitting polarizing films have the same film structure and composition.

[0050] In the present invention, during the plating, the present invention preferably places the substrate in the ring, and places the ring with the substrate on the hollow umbrella of the machine. The plating conditions preferably include: the initial vacuum degree is preferably ≤3×10 -3 The substrate heating temperature is preferably 150-200° C., and in the embodiment, it can be 180° C. The film forming rate of the high refractive index material is preferably 0.2-0.3 nm / s, and the film forming rate of the low refractive index material is preferably 0.3-0.7 nm / s.

[0051] In the present invention, the ion source coated with a high refractive index material is preferably Ti3O5; the voltage is preferably 800~850V; the current is preferably 800~850mA; the gases used are preferably oxygen and argon, and the flow ratio of oxygen and argon is preferably 75:16; the flow rate of oxygen is preferably 75sccm, and the argon includes a first argon and a second argon, the flow rate of the first argon (ion source argon) is preferably 8sccm, and the flow rate of the second argon (neutralizer argon) is preferably 8sccm.

[0052] In the present invention, the ion source coated with a low-refractive-index material is preferably SiO2; the voltage is preferably 800-850V; the current is preferably 800-850mA; and the gases used are preferably oxygen and argon, with the oxygen-to-argon flow ratio preferably being 60:8. The oxygen flow rate is preferably 60 sccm. The argon gas comprises a first argon gas and a second argon gas, with the first argon gas (ion source argon gas) preferably having a flow rate of 0 sccm and the second argon gas (neutralizer argon gas) preferably having a flow rate of 8 sccm.

[0053] In the present invention, the coating preferably includes: coating the surface of the substrate with a high refractive index material, a low refractive index material, a high refractive index material, a low refractive index material, ..., a high refractive index material, and a low refractive index material in sequence.

[0054] The present invention provides a flat beam-splitting polarizing film prepared by the preparation method described in the above technical solution, wherein the extinction ratio of the flat beam-splitting polarizing film is greater than 10000:1.

[0055] In the present invention, the flat beam-splitting polarizing film includes a first flat beam-splitting polarizing film located on the first bottom surface of the substrate and a second flat beam-splitting polarizing film located on the second bottom surface of the substrate. The first and second flat beam-splitting polarizing films have the same film structure and composition.

[0056] In the present invention, the extinction ratio (ER) of the first flat beam-splitting polarizing film or the second flat beam-splitting polarizing film is the ratio of the p-polarized light transmittance (Tp) to the s-polarized light transmittance (Ts).

[0057] The total extinction ratio of the first flat beam-splitting polarizing film and the second flat beam-splitting polarizing film is the product of the extinction ratio (ER1) of the first flat beam-splitting polarizing film and the extinction ratio (ER2) of the second flat beam-splitting polarizing film.

[0058] In the present invention, the actual adjustable wavelength range of the flat beam-splitting polarizing film is wide, and the actual adjustable wavelength range of the flat beam-splitting polarizing film is ≥13 nm, which is convenient for mass production, maintenance and batch preparation.

[0059] In the present invention, the flat beam-splitting polarizing film is a visible light and near-infrared single-point flat beam-splitting film, and the wavelength range of the flat beam-splitting polarizing film is 400~2500nm, and in the embodiment it can be 405nm, 532nm, 780nm, 808nm, 1030nm, 1064nm, 1310nm or 1550nm.

[0060] In order to further illustrate the present invention, the technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0061] Example 1

[0062] This embodiment provides a method for preparing a flat beam-splitting polarizing film. The specifications of the flat beam-splitting polarizing film prepared in this embodiment are as follows: a single point wavelength of 532 nm, p-polarized light transmittance: Tp>93%, s-polarized light transmittance Ts<0.5%, and an extinction ratio ER=Tp:Ts>10000:1.

[0063] The specific steps include:

[0064] 1. The coating materials are common silicon dioxide (SiO2) and titanium pentoxide (Ti3O5), due to their stable chemical properties in the visible light range. The substrate material is ultraviolet fused silica (UVFS), which has a transparent range of approximately 185-2100nm and stable performance.

[0065] 2. Design using TFC film system design software, with an incident angle set to 45°, air as the incident medium, and UVFS as the substrate and exit medium. Given the specification constraints: a. 525-550nm, p-polarized light transmittance Tp set to 100%, b. 525-550nm, s-polarized light transmittance Ts set to 0. This setting has a wider wavelength range and stricter transmittance specifications than the required specifications. The purpose is to obtain a better design, ensure a more stable film preparation solution, and have sufficient wavelength margin to facilitate mass production. The initial film stack uses: G0 / (0.5HL0.5H) S 0.5HLHL0.5H (0.5HL0.5H) S / AIR, where G0 represents the substrate, AIR represents the incident medium is air, H represents a high refractive index material, in this embodiment H is titanium pentoxide (Ti3O5), L represents a low refractive index material, in this embodiment L is silicon dioxide (SiO2), S represents the repetition frequency of the "(0.5HL0.5H)" unit, S=7. The optimized film structure is shown in Table 1, with a total of 58 layers and a total thickness of about 4μm. The first layer in contact with the substrate is titanium pentoxide, followed by the second layer: silicon dioxide, then the third layer: titanium pentoxide, followed by the fourth layer: silicon dioxide, ..., titanium pentoxide and silicon dioxide are repeated alternately, and finally end with the 58th layer: silicon dioxide. The design curve is as shown in Table 1. Figure 1 As shown, Figure 1 The angle in is 45.0° and the relevant wavelength is 550.0nm. Figure 1 The design curve shown is that Tp is about 99.95% and Ts is about 3.7×10 -4(%), or 0.00037%. A rough calculation of ER = 270135. This single-sided ER is already far greater than 10000:1. Therefore, the design evaluation of this embodiment meets the requirements.

[0066] Table 1 Designed membrane structure data for Example 1

[0067]

[0068] 3. Use Aluga vacuum evaporation light control coating machine to coat the designed film system. First, place the clean substrate (here is a cylindrical UV fused quartz glass with a diameter of 25.4mm and a height of 5mm) in the prepared ring. Place the ring on the hollow umbrella of the machine and prepare for coating (in this example, the two bottom surfaces of the cylindrical substrate need to be coated, and the sides do not need to be coated). Close the chamber door and evacuate. When the vacuum reaches the set value of 3.0×10 -3 Ion source cleaning was performed at 100 Pa for 3 minutes. Detailed ion source parameters are shown in Table 2. After cleaning, film deposition began. The first layer, titanium pentoxide (Ti3O5), was directly in contact with the substrate. This was followed by the second layer, silicon dioxide (SiO2). The third layer, titanium pentoxide (Ti3O5), was then deposited. The fourth layer, silicon dioxide (SiO2), was then deposited. This process was repeated in an overlapping fashion until the 58th layer of silicon dioxide was deposited, completing the first bottom surface coating and resulting in a flat beam-splitting polarizing film.

[0069] 4. Next, the second bottom film is prepared. The substrate coated with the first bottom surface is turned over, the chamber door is closed and vacuum is drawn. When the vacuum reaches the set value of 3.0×10 -3 The ion source is cleaned at Pa, and film formation is started on the second surface after cleaning. The film formation steps and parameters are the same as those for plating the first bottom surface, until it is completely completed, that is, the preparation of the flat beam splitting polarization film on the second bottom surface is completed.

[0070] In the preparation process of the flat beam-splitting polarizing film in this embodiment, heating + full-process ion source assisted coating is adopted, wherein the heating is 180°C, the film forming rate is 0.4nm / s for SiO2, and 0.25nm / s for Ti3O5. The detailed coating parameters are shown in Table 3.

[0071] Table 2 Ion source cleaning parameters in Example 1

[0072]

[0073] Table 3 Coating parameters in Example 1

[0074]

[0075] The transmittance of the substrate after coating is tested for p-polarized light and s-polarized light, and then the extinction ratio is calculated to check whether it meets the specifications. The transmission curves of the two surfaces are obtained using Hitachi UH4150 spectrophotometer. Figure 2 As shown in Figure 4, the first bottom surface polarization transmission is represented by Tp-1 and Ts-1, and the second bottom surface polarization transmission is represented by Tp-2 and Ts-2. Detailed extinction ratio data is shown in Table 4.

[0076] Table 4 Extinction ratio data table in Example 1

[0077]

[0078] From the analysis of Table 3 and Table 4, it can be seen that the total extinction ratio of the flat beam splitting polarizing film on the first and second surfaces of the substrate prepared in this embodiment at 532 nm is much greater than 10000:1; in Table 4, Tp min =94.7%>93%, Ts max =0.12%<0.5%, meaning the s-polarized light reflectivity (Rs) is >99.5%, meeting the specification. Although the specification only requires a single point at 532nm, this example actually meets the requirement from 527 to 540nm. This indicates that the film prepared in this example has a controllable range of 13nm, which is sufficient for industrial production.

[0079] The flat-plate beam-splitting polarizing film prepared in Example 1 was subjected to reliability tests, including adhesion, chemical stability, thermal shock, and high temperature and humidity. All tests were satisfactory, demonstrating that the method for preparing the flat-plate beam-splitting polarizing film provided in this example can withstand environmental testing. The test results are shown in Table 5. The test items in Table 5 are based on the standard GBT 26332.3-2015 Optics and Photonics - Optical Films - Part 3: Environmental Adaptability.

[0080] Table 5 Reliability results of the product of Example 1

[0081]

[0082] Example 2

[0083] This embodiment provides a method for preparing a flat beam-splitting polarizing film. The specifications of the flat beam-splitting polarizing film prepared in this embodiment are as follows: a single point wavelength of 1310 nm, p-polarized light transmittance: Tp>96%, s-polarized light transmittance Ts<0.5%, and an extinction ratio ER=Tp:Ts>10000:1.

[0084] The specific steps include:

[0085] 1. The coating materials are common silicon dioxide (SiO2) and titanium pentoxide (Ti3O5), due to their stable chemical properties in the visible light range. The substrate material is ultraviolet fused silica (UVFS), which has a transparent range of approximately 185-2100nm and stable performance.

[0086] 2. Designed using TFC film system design software, with an incident angle set to 45°, air as the incident medium, and UVFS as the substrate and exit medium. Given the specification constraints, a. 1290-1330nm, p-polarized light transmittance Tp is set to 100%, b. 1290-1330nm, s-polarized light transmittance Ts is set to 0. This setting has a wider wavelength range and stricter transmittance specifications than the required specifications. The purpose is to obtain a better design, ensure a more stable film preparation solution, and have sufficient wavelength margin to facilitate mass production. The initial film stack uses: G0 / (0.5HL0.5H) S 0.5HLHL0.5H (0.5HL0.5H) S / AIR, where G0 represents the substrate, AIR represents the incident medium is air, H represents a high refractive index material, in this embodiment H is titanium pentoxide (Ti3O5), L represents a low refractive index material, in this embodiment L is silicon dioxide (SiO2), S represents the repetition frequency of the "(0.5HL0.5H)" unit, S=7. The optimized film structure is shown in Table 6, with a total of 52 layers and a total thickness of about 9μm. The first layer in contact with the substrate is titanium pentoxide, followed by the second layer: silicon dioxide, then the third layer: titanium pentoxide, followed by the fourth layer: silicon dioxide, ..., titanium pentoxide and silicon dioxide are repeated alternately, and finally end with the 52nd layer: silicon dioxide. The design curve is as shown in Table 6. Figure 3 As shown, Figure 3 The angle in is 45.0° and the relevant wavelength is 1220.nm. Figure 3 The design curve shown shows a Tp of approximately 99.98% and a Ts of approximately 0.00214%. A rough calculation of the ER is 46719, and the single-sided ER is already far greater than 10000:1. Therefore, the design evaluation of this embodiment meets the requirements.

[0087] Table 6 Designed membrane structure data for Example 2

[0088]

[0089] 3. Use Aluga vacuum, evaporation light-controlled coating machine to coat the designed film system, and the coating parameters are the same as those in Example 1.

[0090] 4. Test the transmittance of the substrate after plating for p-polarized light and s-polarized light, and then calculate the extinction ratio to check whether it meets the specifications. Use Hitachi UH4150 spectrophotometer to test and get the transmittance curves of the two surfaces as shown below: Figure 4 The first bottom surface polarization transmission is represented by Tp-1 and Ts-1, and the second bottom surface polarization transmission is represented by Tp-2 and Ts-2. Detailed extinction ratio data is shown in Table 7.

[0091] Table 7 Extinction ratio data table in Example 2

[0092]

[0093] Depend on Figure 4 From the analysis of Table 7, it can be seen that the total extinction ratio of the flat beam splitting polarizing film on the first and second surfaces of the substrate prepared in this embodiment at 1310 nm is much greater than 10000:1; in Table 7, Tp min =97.52%>96%, Ts max =0.06335%<0.5%, meaning the s-polarized light reflectivity (Rs) is >99.5%, meeting the specification. Furthermore, the film curve can fluctuate within a range of approximately 15nm (1301-1316nm), meeting the requirements for industrial production.

[0094] The flat-plate beam-splitting polarizing film prepared in Example 2 was subjected to reliability testing. The same items were tested as in Example 1, and the results were all positive. This demonstrates that the method for preparing the flat-plate beam-splitting polarizing film provided in Example 2 can withstand environmental testing. The test results are shown in Table 8. The test items in Table 8 comply with the standards of GBT 26332.3-2015 Optics and Photonics - Optical Films - Part 3: Environmental Adaptability.

[0095] Table 8 Reliability results of the product of Example 2

[0096]

[0097] As can be seen from the above embodiments, the present invention reasonably sets the initial film stack formula, uses film system design software to accurately optimize the film system design of the flat beam-splitting polarizing film, and then coats it according to the film system design results. In addition, the present invention adopts a double-sided coating method on the substrate, and the polarization beam-splitting film obtained has excellent polarization splitting effect. The flat beam-splitting polarizing film prepared by the present invention has a high extinction ratio, and the extinction ratio (ER=Tp:Ts) is>>10000:1, which can effectively separate the p component and s component of the incident light; and the actual adjustable wavelength range is wide (≥13nm), which solves the technical problems of low extinction ratio and narrow actual adjustable wavelength range of optical films. At the same time, the reliability test results (including chemical stability, adhesion, friction test, low temperature test, high temperature test, boiling, constant humidity and heat, temperature gradient) of the flat beam-splitting polarizing film prepared by the present invention are all OK; and the preparation method is convenient for mass production maintenance and batch preparation.

[0098] Although the above embodiment provides a detailed description of the present invention, it is only a part of the embodiments of the present invention, not all of the embodiments. Other embodiments can be obtained based on this embodiment without creativity, and these embodiments all fall within the scope of protection of the present invention.

Claims

1. A method for preparing a flat beam splitting polarizing film, characterized in that: The following steps are involved: Film system design software is used to design a flat beam-splitting polarizing film. The flat beam-splitting polarizing film is formed by alternately stacking low-refractive index materials and high-refractive index materials. The film system design result of the flat beam-splitting polarizing film is obtained. The initial film stack used in the film system design is shown in Formula 1: G0 / (0.5HL0.5H) S 0.5HLHL0.5H (0.5HL0.5H) S / AIR Formula 1; In formula 1, G0 represents the substrate, AIR represents the incident medium, H represents the high refractive index material, L represents the low refractive index material, S represents the repetition frequency of the "(0.5HL0.5H)" unit, and S ≥ 5; The high refractive index material is titanium pentoxide; the low refractive index material is silicon dioxide; the film system design conditions include: an incident angle of 45°; the incident medium is air; the output medium is ultraviolet fused silica; the p-polarized light transmittance of the flat beam-splitting polarizing film is set to 100% and the s-polarized light transmittance is set to 0 within the target band, and the target band of the flat beam-splitting polarizing film is 400-2500nm; the film system design software includes TFCalc optical thin film design software or EssentialMacleod optical thin film design software; the film system design results include the single-layer film thickness of the high refractive index material, the single-layer film thickness of the low refractive index material, the number of film layers of the high refractive index material, the number of film layers of the low refractive index material, the total number of layers and the total thickness; The two bottom surfaces of the substrate are respectively plated according to the film system design result, and the flat beam-splitting polarization films are respectively obtained on the two bottom surfaces of the substrate.

2. The preparation method according to claim 1, characterized in that The material of the substrate is ultraviolet fused quartz; The thickness of the substrate is 0.6-6 mm.

3. The preparation method according to claim 1, characterized in that The plating conditions include: initial vacuum degree ≤ 3×10 -3 Pa; the substrate heating temperature is 150~200℃; the film forming rate of the high refractive index material is 0.2~0.3nm / s, and the film forming rate of the low refractive index material is 0.3~0.7nm / s.

4. The preparation method according to claim 1 or 3, characterized in that Before the plating, the substrate is further subjected to ion source cleaning, wherein the vacuum degree of the ion source cleaning is ≤3×10 -3 Pa, the time is 2-5 min, and the heating temperature of the substrate during the ion source cleaning is 150-200°C.

5. The flat beam-splitting polarizing film prepared by the preparation method according to any one of claims 1 to 4, characterized in that: The extinction ratio of the flat beam-splitting polarizing film is greater than 10000:1.

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