A privacy film for display screens and a method of making and using the same

Abstract

The present application belongs to the technical field of optical film materials, and relates to a display screen privacy protection film, a preparation method and application thereof. The privacy protection film comprises, in sequence, an upper support protection layer, a privacy protection layer and a lower support protection layer; wherein the privacy protection layer comprises, in sequence from top to bottom, a polarizing film layer, one or two hybrid orientation liquid crystal network polymer film layers and at most one twisted orientation liquid crystal network polymer film layer. The technical scheme has the following beneficial effects: the privacy protection film provided by the present application has excellent privacy protection effect, which can realize privacy protection in left and right directions, and can realize privacy protection in front, back, left and right directions by using two hybrid orientation liquid crystal network polymer film layers in the privacy protection layer; the privacy protection film provided by the present application has a high front light transmittance of nearly 80%, which maximally avoids the loss of display backlight and greatly improves the visual experience of users.

Description

Technical Field

[0001] This invention belongs to the field of optical film material technology, specifically relating to a privacy film for display screens, its preparation method, and its application. Background Technology

[0002] In today's digital information age, people's demands for display devices are becoming increasingly diversified. Especially in recent years, the rapid rise of technologies such as liquid crystal displays (LCDs) and organic light-emitting diode (OLEDs) displays has led to the widespread use of electronic products such as smartphones, tablets, and smartwatches in various settings. However, because current displays typically have wide viewing angles, users browsing information on electronic screens in public places are easily exposed to others, potentially causing unnecessary damage to their reputation and property.

[0003] Traditional optical grating privacy films utilize a microstructure similar to venetian blinds to block side light. However, several problems remain to be solved. Besides their relatively thick thickness and high cost, the internal black light-absorbing units inevitably result in poor front light transmission, further increasing device power consumption and user eye fatigue, thus affecting the user experience.

[0004] Therefore, there is an urgent need to develop a privacy film that is different from micro blinds, and features high front light transmittance, thinness, and low cost. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a privacy screen protector, its preparation method, and its application. The privacy screen protector provided by this invention has high front light transmittance, minimizing backlight loss in the display while also providing excellent privacy protection.

[0006] To achieve the above objectives, a first aspect of the present invention provides a privacy film for a display screen, the privacy film comprising, in sequence, an upper support protective layer, a privacy layer, and a lower support protective layer;

[0007] The privacy screen layer comprises, from top to bottom, the following layers arranged sequentially: a polarizing film layer, one or two hybrid-oriented liquid crystal network polymer film layers, and at most one twisted-oriented liquid crystal network polymer film layer.

[0008] When the hybrid-oriented liquid crystal network polymer film is a single layer, the parallel orientation direction in the hybrid-oriented liquid crystal network polymer film is parallel or orthogonal to the polarization axis of the polarizing film; when the hybrid-oriented liquid crystal network polymer film is a double layer, the parallel orientation directions in the two hybrid-oriented liquid crystal network polymer film layers are orthogonal to each other, and the parallel orientation direction in one of the hybrid-oriented liquid crystal network polymer film layers is parallel to the polarization axis of the polarizing film.

[0009] When the twisted-oriented liquid crystal network polymer film layer is present, the upper orientation direction of the twisted-oriented liquid crystal network polymer film layer is parallel to the polarization axis of the polarizing film layer, and the lower orientation direction is parallel to the polarization direction of the display panel.

[0010] In this invention, during the use of the privacy film, the polarization axis of the polarizing film is parallel to the polarization direction of the display backlight.

[0011] In this invention, when the privacy layer contains a hybrid-oriented liquid crystal network polymer film layer, the privacy film can exhibit a privacy effect on the display screen in two directions in one dimension, wherein the parallel orientation direction in the liquid crystal network polymer film layer is parallel or orthogonal to the polarization axis of the polarizing film layer; when the privacy layer contains two hybrid-oriented liquid crystal network polymer film layers, the privacy film can exhibit a privacy effect on the display screen in four directions on orthogonal axes, wherein the parallel orientation directions in the two liquid crystal network polymer film layers are orthogonal to each other, and the parallel orientation direction in one of the hybrid-oriented liquid crystal network polymer film layers is parallel to the polarization axis of the polarizing film layer.

[0012] According to one embodiment of the present invention, the privacy layer further includes a twisted-oriented liquid crystal network polymer film layer, wherein when the layer is disposed, the twisted-oriented liquid crystal network polymer film layer is located at the bottom layer of the privacy layer.

[0013] In this invention, the twist angle of the twisted-oriented liquid crystal network polymer film is set to 45 degrees, which changes the polarization direction of the display backlight, thereby meeting the privacy requirements of display panels with a current mainstream polarization direction of 45 degrees. For privacy requirements of display panels with other polarization directions, such as 0 degrees or 90 degrees, the twisted-oriented liquid crystal network polymer film in the privacy layer can be removed.

[0014] In this invention, when the twisted-oriented liquid crystal network polymer film is needed, it is located at the bottom of the privacy layer, while its upper orientation direction is parallel to the polarization axis of the top polarizing film of the privacy layer, and its lower orientation direction is parallel to the polarization direction of the display panel.

[0015] According to the present invention, preferably, the hybrid-oriented liquid crystal network polymer film and the twisted-oriented liquid crystal network polymer film are prepared by photopolymerization reaction of polymerizable liquid crystal monomers and photoinitiators.

[0016] In this invention, the composition and polymerization method of the twisted-oriented liquid crystal network polymer film are the same as those of the hybrid-oriented liquid crystal network polymer film. The only difference is that the former is obtained by polymerization in a 45-degree twisted-oriented liquid crystal cell.

[0017] According to the present invention, preferably, the method for preparing the hybrid-oriented liquid crystal network polymer film layer includes the following steps:

[0018] (1) The vertical alignment agent solution and the parallel alignment agent solution are spin-coated onto two glass substrates respectively, and dried and cured to obtain a glass substrate coated with parallel alignment agent and a glass substrate coated with vertical alignment agent. The glass substrate coated with parallel alignment agent is rubbed in one direction with a cloth. Then the two glass substrates are assembled to obtain a liquid crystal cell with one end parallel alignment and the other end vertical alignment. Preferably, one of the glass substrates is replaced with a polarizing film.

[0019] (2) Mix the polymerizable liquid crystal monomer with the photoinitiator, heat and melt it, and then stir and mix it evenly to obtain a liquid crystal mixture, which is then poured into a liquid crystal cell.

[0020] (3) Cool the liquid crystal cell into which the liquid crystal mixture was poured in step (2) to below the clearing point of the liquid crystal mixture, and then carry out the photopolymerization reaction;

[0021] (4) After the polymerization reaction is completed, the liquid crystal cell is opened and the hybrid oriented liquid crystal network polymer film is obtained by peeling.

[0022] According to a preferred embodiment of the present invention, in the preparation step of the hybrid-oriented liquid crystal network polymer film liquid crystal cell, a polarizing film can be used as a parallel or vertically oriented substrate, that is, one of the substrates is a polarizing film, thereby directly obtaining a hybrid-oriented liquid crystal network polymer film with an integrated polarizing film.

[0023] According to the present invention, preferably, the method for preparing the twisted-oriented liquid crystal network polymer film layer includes the following steps:

[0024] (1) Spin-coat the parallel alignment agent solution onto two glass substrates, dry and cure them to obtain two glass substrates coated with parallel alignment agent. First, rub one glass substrate in one direction with a cloth, then rub the other glass substrate with a cloth at a 45-degree angle to the former. Then assemble the two glass substrates to obtain a liquid crystal cell with the upper and lower substrates aligned at a 45-degree angle.

[0025] (2) Mix the polymerizable liquid crystal monomer with the photoinitiator, heat and melt it, and then stir and mix it evenly to obtain a liquid crystal mixture, which is then poured into a liquid crystal cell.

[0026] (3) Cool the liquid crystal cell into which the liquid crystal mixture was poured in step (2) to below the clearing point of the liquid crystal mixture, and then carry out the photopolymerization reaction;

[0027] (4) After the polymerization reaction is completed, the liquid crystal cell is opened and the twisted-oriented liquid crystal network polymer film is peeled off.

[0028] According to the present invention, preferably, the conditions for the photopolymerization reaction include: the light source is ultraviolet or visible light with a wavelength of 200nm-600nm, preferably 300-400nm, and the light intensity is 0.01-10mW / cm². 2 The preferred value is 0.01-2 mW / cm 2 The polymerization time is 5-120 min, preferably 15-90 min.

[0029] According to the present invention, preferably, the thickness of the liquid crystal cell is 5μm-100μm, more preferably 20μm-50μm.

[0030] According to the present invention, preferably, the conditions for the photopolymerization reaction include: the light source is ultraviolet or visible light with a wavelength of 200nm-600nm, preferably 300-400nm, and the light intensity is 0.01-10mW / cm². 2 The preferred value is 0.01-2 mW / cm 2 The polymerization time is 5-120 min, preferably 15-90 min;

[0031] The thickness of the liquid crystal cell is 5μm-100μm, preferably 20μm-50μm;

[0032] The parallel orientation agent is a PVA solution or a PI solution, and the vertical orientation agent is a DMOAP solution or a PI solution.

[0033] According to the present invention, preferably, the polymerizable liquid crystal monomer is a monoacrylate group liquid crystal monomer and / or a diacrylate group liquid crystal monomer.

[0034] Preferably, the monoacrylate-based liquid crystal monomer is selected from at least one of the monoacrylate-based liquid crystal monomers shown in general formulas 1-6.

[0035]

[0036] In each expression, n is an integer from 3 to 12, and m is an integer from 3 to 6.

[0037] Preferably, the diacrylate-based liquid crystal monomer is selected from at least one of the diacrylate-based liquid crystal monomers represented by general formulas I-IX.

[0038]

[0039] In each expression, n is an integer from 3 to 12, m is an integer from 3 to 6, and p is an integer from 3 to 8.

[0040] According to the present invention, preferably, the photoinitiator is a free radical photoinitiator, and is preferably selected from at least one of Irgacure 651, Irgacure 819, Irgacure DEAP, Irgacure 1173, Irgacure 184, Irgacure 2959, Irgacure 907, Irgacure 369, Irgacure 819, Irgacure MBF, Irgacure TPO, Irgacure TPO-L, Irgacure BMS, Irgacure BP, Irgacure ITX, Irgacure DETX and Irgacure 2-EA.

[0041] Preferably, the content of the photoinitiator is 0.1 to 3 wt%, based on the total weight of the liquid crystal mixture.

[0042] According to the present invention, preferably, the polarizing film layer is a polarizing film with anisotropic light-absorbing material as the polarizing substance, preferably an iodine-based PVA polarizing film, a dichroic dye polarizing film, a polyethylene polarizing film, a metal nanoparticle polarizing film, a carbon nanotube or nanowire / chain polarizing film; preferably, the thickness of the polarizing film layer is 5 to 500 μm.

[0043] According to the present invention, preferably, the upper support protective layer and the lower support protective layer are each independently selected from at least one film selected from PET, TAC, COP, PI, PEN, PC, PBT, PMMA, PS, PEI, PE, PP, LDPE, LLDPE, POE, ES, EP, EH, ABS, PU, ​​PVA, EVA, EAA, PA, PVC, PDMS, PPS, PES and PVDF; the thickness of the upper support protective layer and the lower support protective layer is preferably 0.005 to 1 mm.

[0044] Preferably, the film layers in the upper support protective layer, the lower support protective layer, and the privacy layer are connected by an optically transparent adhesive layer.

[0045] A second aspect of the present invention provides a method for preparing the privacy film for a display screen, comprising the following steps:

[0046] The privacy film for the display screen is obtained by combining the upper support protective layer, the lower support protective layer, and the privacy layer.

[0047] A third aspect of the present invention provides the application of the privacy film for a display screen or the privacy film for a display screen prepared by the preparation method described herein in a display screen.

[0048] Preferably, the display screen is a display screen with an internal polarizer; wherein, during the use of the privacy film, the polarization axis of the polarizing film is parallel to the polarization direction of the display backlight.

[0049] The beneficial effects of the technical solution of the present invention are as follows:

[0050] 1) The privacy film provided by the present invention exhibits excellent privacy protection effect. It can not only achieve privacy protection in the left and right directions, but also achieve privacy protection in the front, back, left and right directions by using two hybrid-oriented liquid crystal network polymer films in the privacy layer.

[0051] 2) The privacy film provided by this invention has a high front light transmittance of nearly 80%, which minimizes the loss of backlight on the display and greatly improves the user's visual experience.

[0052] 3) The privacy film provided by this invention has a wide range of applications, including all display screens with internal polarizers.

[0053] 4) The privacy film provided by the present invention has a simple and easy preparation method, low cost, and small film thickness, which is conducive to commercialization.

[0054] Other features and advantages of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0055] The above and other objects, features and advantages of the present invention will become more apparent from the more detailed description of exemplary embodiments of the invention in conjunction with the accompanying drawings, wherein the same reference numerals generally represent the same components in the exemplary embodiments of the invention.

[0056] Figure 1 The diagram shows a three-layer structure of the privacy film provided by the present invention, as well as a privacy layer structure with different privacy directional characteristics.

[0057] Figure 2 The average transmittance distribution curves of polarized visible light at different angles are shown for the privacy film prepared in Example 1 of the present invention.

[0058] Figure 3 The images shown are photographs of the privacy film prepared in Embodiment 1 of the present invention displayed from different angles when used for privacy protection of a display.

[0059] Figure 4 A comparison diagram of the privacy film prepared in Example 2 and the privacy film prepared in Example 1 is shown, showing the privacy direction during use.

[0060] Figure 5The images shown are photographs of the privacy film prepared in Embodiment 3 of the present invention used for privacy protection of a display screen, and are displayed from different angles. Detailed Implementation

[0061] Preferred embodiments of the invention will now be described in more detail. While preferred embodiments of the invention are described below, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein.

[0062] The directional terms used in this invention, such as [up], [down], [front], [back], [left], [right], [diagonal], [diagonal], etc., are merely for illustrating and understanding the invention, and not for limiting it.

[0063] The privacy films described in the embodiments of this invention all satisfy the following conditions: Figure 1 The three-layer structure shown indicates the polarization axis direction of the polarizing film (upper layer) and the parallel alignment direction of the hybrid-aligned liquid crystal network polymer film (lower layer). Furthermore, the privacy protection principle of the privacy layer described in this invention is based on the hybrid-aligned liquid crystal network polymer film and the polarizing film, utilizing their anisotropic transmittance for linearly polarized backlight in a specific direction to achieve narrow viewing angle performance. The privacy layers described in the following embodiments are differentiated, and the details will be explained specifically in the embodiments.

[0064] Example 1

[0065] This embodiment provides a method for preparing a privacy film, including the following steps:

[0066] Step 1: Fabrication of hybrid-oriented liquid crystal cells

[0067] 1) Clean and dry both glass substrates. Then, spin-coat the PI solution for vertical and parallel alignment onto the two glass substrates respectively. The spin-coating operation is performed in two stages, with no interval between the first and second stages. The specific operation is as follows:

[0068] In the first stage, the spin coating speed is set to 500-800 rpm, and the duration is 5-10 seconds.

[0069] In the second stage, the spin coating speed is set to 2000-3000 rpm and the duration is 30-60 seconds.

[0070] 2) After spin coating, both glass substrates are dried and cured. The drying parameters are as follows:

[0071] For glass substrates coated with parallel-oriented polyimide: first heat at 80℃ for 3-5 minutes, then heat to 240℃ and cure for 20-30 minutes.

[0072] For glass substrates coated with vertically oriented polyimide: first heat at 110℃ for 30-60 minutes, then heat to 220℃ and cure for 90 minutes.

[0073] 3) A glass substrate coated with parallel-oriented polyimide is rubbed unidirectionally using a cloth, while the glass substrate coated with vertically oriented polyimide is left untreated. The two treated glass substrates are then assembled with adhesive to fabricate a liquid crystal cell with one end parallel-oriented and the other end vertically oriented. The cell thickness is controlled at 30 μm.

[0074] Step 2: Preparation of hybrid-oriented liquid crystal network polymer film

[0075] 1) Mix 65 wt% of diacrylate liquid crystal monomer RM82 (1,4-bis-[4-(6-acryloyloxyhexyloxy)benzoyloxy]-2-methylbenzene), 34 wt% of monoacrylate liquid crystal monomer RM105 (4-[[6-[(1-oxo-2-propenyl)oxy]hexyl]oxy]benzoic acid 4-methoxyphenyl ester), and 1 wt% of photoinitiator 651. Heat and melt the mixture, then shake and stir to obtain a uniform liquid crystal monomer mixture. Pour the mixture into the liquid crystal cell prepared in step 1.

[0076] 2) Cool the liquid crystal cell below the clearing point of the liquid crystal mixture, then place it under 365nm ultraviolet light (intensity 0.1mW / cm²). 2 Polymerize for 50 minutes.

[0077] 3) After polymerization is complete, open the liquid crystal cell and peel off the liquid crystal network polymer film.

[0078] Step 3: Composite the various film layers into a privacy film.

[0079] The upper support PET protective layer, the lower support PET protective layer, a polarizing film and a hybrid oriented liquid crystal network polymer film in the privacy layer are connected to each other by an optically transparent adhesive layer, thereby obtaining the privacy film prepared in Example 1.

[0080] Figure 2 The diagram shows the average transmittance distribution curves of polarized visible light at different angles in one dimension for the privacy film prepared in Embodiment 1 of the present invention. The polarization axis of the input light is aligned with the polarizing film in the privacy layer and is used to simulate the backlight emitted by a display. The average transmittance decreases non-linearly from 78% to nearly 3%, while the transmittance curves on both sides of the normal are relatively symmetrical.

[0081] Using the technical solution of this embodiment, when the privacy film is applied to the display screen, the background image can be clearly seen when viewed from the front. However, as the viewing angle increases from left to right, the image contrast decreases significantly, and the screen brightness becomes darker. Figure 3 As shown, the arrows and dashed lines represent the polarization direction of the backlight and the parallel alignment direction in the hybrid-aligned liquid crystal network polymer film, respectively. The background image is barely discernible at a 50-degree viewing angle, demonstrating that the privacy film provides good privacy protection for users.

[0082] In this embodiment, the backlight polarization direction of the display used for demonstration is 90 degrees. The privacy protection direction is orthogonal to the parallel orientation direction in the hybrid-oriented liquid crystal network polymer film within the privacy protection layer.

[0083] Example 2

[0084] This embodiment provides a method for preparing a privacy film, including the following steps:

[0085] Step 1: Fabrication of hybrid-oriented liquid crystal cells

[0086] The method is the same as step one described in Example 1.

[0087] Step 2: Preparation of hybrid-oriented liquid crystal network polymer film

[0088] 1) Mix 25 wt% of diacrylate liquid crystal monomer RM257 (4-(3-acryloyloxypropoxy)benzoic acid 2-methyl-1,4-phenyl ester), 37 wt% of monoacrylate liquid crystal monomer RM105 (4-[[6-[(1-oxo-2-propenyl)oxy]hexyl]oxy]benzoic acid 4-methoxyphenyl ester), 37 wt% of monoacrylate liquid crystal monomer RM23 (4-cyanophenyl 4-((6-(acryloyloxy)hexyl)oxy)benzoate), and 1 wt% of photoinitiator 651, heat to melt, and then shake and stir evenly to obtain a liquid crystal monomer mixture, and pour it into the liquid crystal cell prepared in step 1;

[0089] 2) Cool the liquid crystal cell below the clearing point of the liquid crystal mixture, then place it under 365nm ultraviolet light (intensity 2mW / cm²). 2 Polymerize for 20 minutes.

[0090] 3) After polymerization is complete, open the liquid crystal cell and peel off the liquid crystal network polymer film.

[0091] Step 3: Fabrication of a liquid crystal cell with a 45-degree twisted orientation

[0092] 1) Clean and dry both glass substrates. Then, spin-coat the PI parallel alignment agent onto the two glass substrates. The spin-coating operation is performed in two stages, with no interval between the first and second stages. The specific operation is as follows:

[0093] In the first stage, the spin coating speed is set to 500-800 rpm, and the duration is 5-10 seconds.

[0094] In the second stage, the spin coating speed is set to 2000-3000 rpm and the duration is 30-60 seconds.

[0095] 2) After spin coating, heat the two glass substrates at 80℃ for 3-5 minutes, then raise the temperature to 240℃ and cure for 20-30 minutes. After curing, cool to room temperature for later use.

[0096] 3) First, rub one glass substrate in one direction with a soft cloth. Then, rub the other glass substrate with the soft cloth at a 45-degree angle to the orientation of the first substrate. Finally, assemble the two glass substrates with glue to prepare a liquid crystal cell with the upper and lower substrates oriented at a 45-degree angle. The cell thickness is controlled at 30μm.

[0097] Step 4: Prepare a liquid crystal network polymer film with a 45-degree twisted orientation.

[0098] The only difference between this step and step two in this embodiment is that the liquid crystal cell used is a liquid crystal cell with a 45-degree twist orientation.

[0099] Step 5: Composite the various film layers into a privacy film.

[0100] The upper supporting PET protective layer, the lower supporting PET protective layer, and the privacy layer (including a polarizing film, a hybrid-oriented liquid crystal network polymer film, and a 45-degree twisted liquid crystal network polymer film) are connected to each other by an optically transparent adhesive layer, thereby obtaining the privacy film prepared in Example 2. The layout and structure of the privacy layer are as follows: Figure 1 As shown in the upper right corner.

[0101] In Embodiment 1 above, the twisted-aligned liquid crystal network polymer layer was removed from the privacy shield, making it suitable for display panels with polarizers oriented at 0 degrees or 90 degrees. However, for display panels where the current mainstream polarization direction is 45 degrees, the absence of a twisted-aligned liquid crystal network polymer layer would result in the privacy shield acting as a diagonal privacy shield instead of a left-right or front-back privacy shield, leading to poor performance. In this embodiment, the twisted-aligned liquid crystal network polymer film is retained. Utilizing the optical rotation of twisted liquid crystal molecules, the 45-degree twisted-aligned liquid crystal network polymer film can correspondingly rotate the polarization direction of incident polarized light by 45 degrees. Therefore, when this liquid crystal film is superimposed on the display panel, it is equivalent to the polarization direction of the display backlight also being rotated by 45 degrees.

[0102] like Figure 4As shown, the privacy film prepared in this embodiment was attached to a mobile phone screen with a polarization direction of 45 degrees, and the privacy film prepared in Example 1 was used as a control group. It can be seen that when using a liquid crystal network polymer film with a 45-degree twisted orientation, the privacy direction changes from the original diagonal to the left and right direction, thereby meeting the privacy requirements of different types of display panels.

[0103] Example 3

[0104] This embodiment provides a method for preparing a privacy film, including the following steps:

[0105] Step 1: Fabrication of hybrid-oriented liquid crystal cells

[0106] The method is the same as step one described in Example 1.

[0107] Step 2: Preparation of hybrid-oriented liquid crystal network polymer film

[0108] 1) Mix 29 wt% of diacrylate liquid crystal monomer RM82 (1,4-bis-[4-(6-acryloyloxyhexyloxy)benzoyloxy]-2-methylbenzene), 35 wt% of monoacrylate liquid crystal monomer RM105 (4-[[6-[(1-oxo-2-propenyl)oxy]hexyl]oxy]benzoic acid 4-methoxyphenyl ester), 35 wt% of monoacrylate liquid crystal monomer RM23 (4-cyanophenyl 4-((6-(acryloyloxy)hexyl)oxy)benzoate), and 0.5 wt% of photoinitiator 651, heat to melt, and then shake and stir evenly to obtain a liquid crystal monomer mixture. Pour the mixture into the liquid crystal cell prepared in step 1.

[0109] 2) Cool the liquid crystal cell below the clearing point of the liquid crystal mixture, then place it under 365nm ultraviolet light (intensity 0.5mW / cm²). 2 Polymerize for 30 minutes.

[0110] 3) After polymerization is complete, open the liquid crystal cell and peel off the liquid crystal network polymer film.

[0111] Step 3: Fabrication of a liquid crystal cell with a 45-degree twisted orientation

[0112] The method is the same as step three described in Example 2.

[0113] Step 4: Prepare a liquid crystal network polymer film with a 45-degree twisted orientation.

[0114] The only difference between this step and step two in this embodiment is that the liquid crystal cell used is a liquid crystal cell with a 45-degree twist orientation.

[0115] Step 5: Composite the various film layers into a privacy film.

[0116] The upper supporting PET protective layer, the lower supporting PET protective layer, a polarizing film in the privacy layer, two hybrid-oriented liquid crystal network polymer films, and a 45-degree twisted liquid crystal network polymer film are connected to each other by an optically transparent adhesive layer, thereby obtaining the privacy film prepared in Example 3. The layout and structure of the privacy layer are as follows: Figure 1 As shown in the lower right corner.

[0117] Using the technical solution of this embodiment, when the privacy film is applied to the mobile phone screen, it maintains high transparency in the front direction, allowing clear observation of the background image. However, when viewed at a 45-degree angle in the left-right or front-back directions, the image becomes very blurry, as... Figure 5 As shown. In other words, the privacy film prepared in this embodiment can prevent peeping in four directions: front, back, left, and right, thereby meeting people's needs for privacy protection in specific situations.

[0118] In this embodiment, the backlight polarization direction of the mobile phone display used for demonstration is 45 degrees. The privacy protection direction is parallel to and orthogonal to the polarization axis of the polarizing film in the privacy film.

[0119] Example 4

[0120] This embodiment provides a method for preparing a privacy screen protector. The only difference between this method and Example 2 is that in steps two and four, the monoacrylate liquid crystal monomer RM105 (4-[[6-[(1-oxo-2-propenyl)oxy]hexyl]oxy]benzoic acid 4-methoxyphenyl ester) is not added, and the amount of diacrylate liquid crystal monomer RM257 (4-(3-acryloyloxypropoxy)benzoic acid 2-methyl-1,4-phenyl ester) added is 99 wt%. The rest is the same as in Example 2.

[0121] Using the technical solution of this embodiment, when the privacy film is applied to a display screen with a 45-degree polarization direction, its light transmittance in the screen normal direction is close to 80%, resulting in high image clarity and color contrast. As the left and right viewing angles increase, the image contrast decreases significantly, and the light transmittance is less than 10% at a 45-degree side viewing angle. Furthermore, the light transmittance reaches approximately 78% across the entire viewing angle range from 0 to 60 degrees.

[0122] Example 5

[0123] This embodiment provides a method for preparing a privacy screen protector. The only difference between this embodiment and Example 2 is that, in steps two and four, the diacrylate liquid crystal monomer RM257 (4-(3-acryloyloxypropoxy)benzoic acid 2-methyl-1,4-phenyl ester) is not added, and the amount of monoacrylate liquid crystal monomer RM105 (4-[[6-[(1-oxo-2-propenyl)oxy]hexyl]oxy]benzoic acid 4-methoxyphenyl ester) added is 99wt%. The rest is the same as in Example 2.

[0124] Using the technical solution of this embodiment, when the privacy film is applied to a display screen with a 45-degree polarization direction, its light transmittance in the screen's normal direction is close to 82%, and its light transmittance is greater than 70% within a 20-degree viewing angle range. This allows users to clearly observe the screen image within the acceptable viewing angle. As the left and right viewing angles increase to over 30 degrees, the image contrast decreases significantly, and at a 50-degree side viewing angle, the light transmittance is close to 2%, making the background image on the screen difficult to discern. Furthermore, the light transmittance reaches approximately 80% across the entire viewing angle range from 0 to 60 degrees, enabling the privacy film to provide users with a good user experience.

[0125] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A privacy screen protector for a display screen, characterized in that, The privacy film comprises, in sequence, an upper support protective layer, a privacy layer, and a lower support protective layer; The privacy screen layer comprises, from top to bottom, the following layers arranged sequentially: a polarizing film layer, one or two hybrid-oriented liquid crystal network polymer film layers, and at most one twisted-oriented liquid crystal network polymer film layer. When the hybrid-oriented liquid crystal network polymer film is a single layer, the parallel orientation direction in the hybrid-oriented liquid crystal network polymer film is parallel or orthogonal to the polarization axis of the polarizing film; when the hybrid-oriented liquid crystal network polymer film is a double layer, the parallel orientation directions in the two hybrid-oriented liquid crystal network polymer film layers are orthogonal to each other, and the parallel orientation direction in one of the hybrid-oriented liquid crystal network polymer film layers is parallel to the polarization axis of the polarizing film. When the twisted-oriented liquid crystal network polymer film layer is present, the upper orientation direction of the twisted-oriented liquid crystal network polymer film layer is parallel to the polarization axis of the polarizing film layer, and the lower orientation direction is parallel to the polarization direction of the display panel. The method for preparing the hybrid-oriented liquid crystal network polymer film includes the following steps: (1) Spin-coat the vertical alignment agent solution and the parallel alignment agent solution onto two glass substrates respectively, and dry and cure them to obtain a glass substrate coated with parallel alignment agent and a glass substrate coated with vertical alignment agent. Use a cloth to rub the glass substrate coated with parallel alignment agent in one direction, and then assemble the two glass substrates to obtain a liquid crystal cell with one end parallel alignment and the other end vertical alignment. (2) Mix polymerizable liquid crystal monomers with photoinitiators, heat to melt, and then shake and stir to obtain a liquid crystal mixture, which is then poured into a liquid crystal cell; (3) Cool the liquid crystal cell into which the liquid crystal mixture was poured in step (2) to below the clearing point of the liquid crystal mixture, and then carry out the photopolymerization reaction; (4) After the polymerization reaction is completed, the liquid crystal cell is opened and the hybrid oriented liquid crystal network polymer film is peeled off.

2. The privacy film for a display screen according to claim 1, wherein, The twisted-oriented liquid crystal network polymer film is prepared by photopolymerization of polymerizable liquid crystal monomers and photoinitiators.

3. The privacy film for a display screen according to claim 1, wherein, One of the glass substrates was replaced with a polarizing film.

4. The privacy film for a display screen according to claim 2, wherein, The method for preparing the twisted-oriented liquid crystal network polymer film includes the following steps: (1) Spin-coat the parallel alignment agent solution onto two glass substrates, dry and cure them to obtain two glass substrates coated with parallel alignment agent. First, rub one glass substrate in one direction with a cloth, and then rub the other glass substrate with a cloth at a 45-degree angle to the former. Then assemble the two glass substrates to obtain a liquid crystal cell with the upper and lower substrates aligned at a 45-degree angle. (2) Mix polymerizable liquid crystal monomers with photoinitiators, heat to melt, and then shake and stir to obtain a liquid crystal mixture, which is then poured into a liquid crystal cell; (3) Cool the liquid crystal cell into which the liquid crystal mixture was poured in step (2) to below the clearing point of the liquid crystal mixture, and then carry out the photopolymerization reaction; (4) After the polymerization reaction is completed, the liquid crystal cell is opened and the twisted-oriented liquid crystal network polymer film is peeled off.

5. The privacy film for a display screen according to claim 1 or 4, wherein, The conditions for the photopolymerization reaction include: the light source is ultraviolet or visible light, the wavelength is 200nm-600nm, and the light intensity is 0.01-10mW / cm². 2 The polymerization time is 5-120 min; The thickness of the liquid crystal cell is 5μm-100μm; The parallel orientation agent is a PVA solution or a PI solution, and the vertical orientation agent is a DMOAP solution or a PI solution.

6. The privacy film for a display screen according to claim 5, wherein, The wavelength is 300-400nm, and the light intensity is 0.01-2mW / cm². 2 The polymerization time is 15-90 min.

7. The privacy film for a display screen according to claim 5, wherein, The thickness of the liquid crystal cell is 20μm-50μm.

8. The privacy film for a display screen according to any one of claims 1-4, wherein, The polymerizable liquid crystal monomer is a monoacrylate group liquid crystal monomer and / or a diacrylate group liquid crystal monomer.

9. The privacy film for a display screen according to claim 8, wherein, The monoacrylate group liquid crystal monomer is selected from at least one of the monoacrylate group liquid crystal monomers shown in general formulas 1-6. In each expression, n is an integer from 3 to 12, and m is an integer from 3 to 6.

10. The privacy film for a display screen according to claim 8, wherein, The diacrylate-based liquid crystal monomer is selected from at least one of the diacrylate-based liquid crystal monomers represented by general formulas I-IX. In each expression, n is an integer from 3 to 12, m is an integer from 3 to 6, and p is an integer from 3 to 8.

11. The privacy film for a display screen according to any one of claims 1-4, wherein, The photoinitiator is a free radical type photoinitiator.

12. The privacy film for a display screen according to claim 11, wherein, The photoinitiator is selected from at least one of Irgacure 651, Irgacure 819, Irgacure DEAP, Irgacure 1173, Irgacure 184, Irgacure 2959, Irgacure 907, Irgacure 369, Irgacure 819, Irgacure MBF, Irgacure TPO, Irgacure TPO-L, Irgacure BMS, Irgacure BP, Irgacure ITX, Irgacure DETX, and Irgacure 2-EA.

13. The privacy film for a display screen according to claim 11, wherein, Based on the total weight of the liquid crystal mixture, the content of the photoinitiator is 0.1~3wt%.

14. The privacy film for a display screen according to claim 1, wherein, The polarizing film layer is a polarizing film with anisotropic light-absorbing material as the polarizing agent; The upper and lower support protective layers are each independently selected from at least one film selected from PET, TAC, COP, PI, PEN, PC, PBT, PMMA, PS, PEI, PE, PP, LDPE, LLDPE, POE, ES, EP, EH, ABS, PU, ​​PVA, EVA, EAA, PA, PVC, PDMS, PPS, PES, and PVDF.

15. The privacy film for a display screen according to claim 14, wherein, The polarizing film layer is an iodine-based PVA polarizing film, a dichroic dye polarizing film, a polyethylene polarizing film, a metal nanoparticle polarizing film, or a carbon nanotube or nanowire / chain polarizing film.

16. The privacy film for a display screen according to claim 14, wherein, The thickness of the polarizing film is 5~500μm.

17. The privacy film for a display screen according to claim 14, wherein, The thickness of the upper support protective layer and the lower support protective layer are each independently 0.005~1mm.

18. The privacy film for a display screen according to claim 14, wherein, The upper support protective layer, the lower support protective layer, and the privacy layer are connected by an optically transparent adhesive layer.

19. The method for preparing a privacy screen protector according to any one of claims 1-18, characterized in that, Includes the following steps: The privacy film for the display screen is obtained by combining the upper support protective layer, the lower support protective layer, and the privacy layer.

20. The use of the privacy film for a display screen according to any one of claims 1-18 or the privacy film for a display screen prepared by the preparation method according to claim 19 in a display screen.

21. The application according to claim 20, wherein, The display screen is a display screen with an internal polarizer; wherein, during the use of the privacy film, the polarization axis of the polarizing film is parallel to the polarization direction of the display backlight.

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