Polymer dispersed liquid crystal display with improved angular haze for sunroofs

Abstract

The invention relates to a polymer dispersed liquid crystal display with improved angular haze for sunroofs. Specifically, one embodiment of the present application provides a polymer dispersed liquid crystal display including a first electrode, a second electrode on the first electrode, and a PDLC layer disposed between the first electrode and the second electrode, the PDLC layer including liquid crystal droplets having a size in a range of 0.8 to 1.5 [mu] m, and the thickness of the PDLC layer is in the range of 15 to 25 [mu] m.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of priority to Korean Patent Application No. 10-2023-0104609, filed on August 10, 2023, which is incorporated herein by reference as if fully set forth herein. Technical Field

[0003] The present application relates to a smart window, a polymer dispersed liquid crystal display (PDLCD), and more specifically, a polymer dispersed liquid crystal display (PDLCD) with improved angle haze in an electro-transmittive state. Background Art

[0004] Polymer dispersed liquid crystal (PDLC) displays have the advantages of simple manufacturing and low power consumption. PDLC displays are one of the most widely used smart windows.

[0005] Generally, liquid crystals are dispersed in the polymer system of a polymer dispersed liquid crystal display (PDLCD), and in the absence of an initial potential difference, the scattering state of incident light can be controlled, and by applying a potential difference to the film and aligning the liquid crystal molecules in the same direction as the light direction, the transparent state of incident light passing through without scattering can be controlled.

[0006] In the case of a polymer dispersed liquid crystal display (PDLCD), a difference in haze occurs between the front and the side, and the haze on the side is high, and a clearer image than the front cannot be obtained. The reason why the side haze is important is that when the polymer dispersed liquid crystal display (PDLCD) is applied to the sunroof, the occupant mostly views the polymer dispersed liquid crystal display (PDLCD) from the side rather than the front. Specifically, when the polar angle at which the occupant views from the front is 0°, the occupant views the polymer dispersed liquid crystal display (PDLCD) from an angle of 60° to 70°, so it is very important to improve the side haze.

[0007] Therefore, research is being continuously conducted to improve the haze on the side of a polymer dispersed liquid crystal display (PDLCD). Summary of the invention

[0008] One embodiment of the present application is to provide a polymer dispersed liquid crystal display with improved side haze.

[0009] One embodiment of the present application is to provide a smart window manufactured using a polymer dispersed liquid crystal display.

[0010] In addition to the above-mentioned objects of the present disclosure, other objects and features of the present disclosure will be clearly understood by those skilled in the art from the following description of the present disclosure.

[0011] An embodiment of the present application for achieving the above technical problem provides a polymer dispersed liquid crystal display, which includes a first electrode, a second electrode on the first electrode, and a PDLC layer disposed between the first electrode and the second electrode, the PDLC layer including liquid crystal droplets having a size in the range of 0.8 to 1.5 μm, and a thickness of the PDLC layer in the range of 15 to 25 μm.

[0012] The refractive index anisotropy of the liquid crystal droplets may be in the range of 0.20 to 0.25.

[0013] The clearing point of the liquid crystal droplets may be 90° C. or higher.

[0014] The liquid crystal droplet may include the first compound represented by Chemical Formula 1.

[0015] The first compound may be 3 to 20 wt % based on the total content of the liquid crystal droplets.

[0016] The liquid crystal droplet may further include a second compound represented by Formula 2.

[0017] The concentration of the second compound may be in the range of 50 to 1000 ppm.

[0018] The PDLC layer may further include a polymer, and the polymer may be formed of a polymer precursor including the third compound represented by Chemical Formula 3.

[0019] The liquid crystal droplet may not contain the fourth compound represented by Chemical Formula 4.

[0020] The first electrode and the second electrode may include a transparent conductive material.

[0021] The transparent conductive material may include at least one of indium tin oxide (ITO) and indium zinc oxide (IZO).

[0022] Another embodiment of the present application provides a smart window manufactured using the polymer dispersed liquid crystal display. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The above and other objects, features and other advantages of the present disclosure will be more clearly understood from the following detailed description in conjunction with the accompanying drawings, in which:

[0024] Figure 1 is a cross-sectional view of a polymer dispersed liquid crystal display according to an embodiment of the present application.

[0025] Figure 2 It is the image according to the viewing angle when viewed from the front and side through the polymer dispersed liquid crystal display in the turned-on state.

[0026] Figure 3is a schematic diagram illustrating a haze measurement method.

[0027] Figures 4A to 4C is a diagram showing a manufacturing process of a polymer dispersed liquid crystal display.

[0028] Figure 5 is an image showing the liquid crystal alignment and refractive index of a liquid crystal droplet in a polymer dispersed liquid crystal display. DETAILED DESCRIPTION

[0029] The advantages and features of the present disclosure and their implementation methods will be explained by the following embodiments described with reference to the accompanying drawings. However, the present disclosure can be implemented in different forms and should not be interpreted as being limited to the embodiments described herein. On the contrary, these embodiments are provided to make the present disclosure comprehensive and complete, and to fully convey the scope of the present disclosure to those skilled in the art. In addition, the present disclosure is limited only by the scope of the claims.

[0030] The shapes, sizes, ratios, angles, and quantities disclosed in the drawings used to describe the embodiments of the present disclosure are merely examples, and therefore, the present disclosure is not limited to the details shown. Throughout the specification, the same reference numerals represent the same elements. In the following description, when the detailed description of the relevant known function or configuration is determined to be unnecessarily obscure the main points of the present disclosure, the detailed description will be omitted.

[0031] In case of using “including,” “having,” and “comprising” described in the present disclosure, another part may be added unless “only to” is used. Terms in the singular form may include plural forms unless otherwise specified.

[0032] When explaining an element, the element is interpreted as including an error range although not explicitly described.

[0033] In describing a positional relationship, for example, when the positional relationship is described as “on”, “above”, “below”, and “immediately adjacent to”, more than one part may be disposed between two other parts unless “just” or “directly” is used.

[0034] As shown in the figures, spatially relative terms such as "below," "beneath," "lower," "above," and "upper" may be used herein to easily describe the relationship of one or more elements to another one or more elements. It should be understood that these terms are intended to cover different orientations of the device as well as the orientations shown in the accompanying drawings. For example, if the device shown in the figure is reversed, a device described as being arranged "below" or "below" another device may be arranged "above" the other device. Thus, the exemplary term "below or below" may include both "below or below" and "above" orientations. Similarly, the exemplary term "above" or "upper" may include both "above" and "below or below" orientations.

[0035] When describing a time relationship, for example, when a time sequence is described as "after," "afterwards," "next," and "before," discontinuous cases may be included unless "directly" or "directly" is used.

[0036] It should be understood that although the terms "first", "second", etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another element. For example, a first element may be referred to as a second element, and similarly, a second element may be referred to as a first element without departing from the scope of the present disclosure.

[0037] It should be understood that the term "at least one" includes all combinations associated with any one item. For example, "at least one of a first element, a second element, and a third element" may include all combinations of two or more elements selected from the first, second, and third elements and each element of the first, second, and third elements.

[0038] As can be fully understood by those skilled in the art, the features of the various embodiments of the present disclosure can be partially or completely combined or combined with each other, and can interoperate and drive technology differently from each other. The embodiments of the present disclosure can be performed independently of each other, or can be performed together in a mutually dependent relationship.

[0039] When adding reference numerals to components of each of the drawings describing embodiments of the present disclosure, the same components may have the same symbols as may be displayed on other drawings.

[0040] Figure 1 is a cross-sectional view of a polymer dispersed liquid crystal display 100 according to an embodiment of the present application.

[0041] refer to Figure 1 , the polymer dispersed liquid crystal display 100 may include a first electrode 121 and a second electrode 122 .

[0042] The first electrode 121 and the second electrode 122 may each include a transparent conductive material. For example, the first electrode 121 and the second electrode 122 may each include at least one of indium tin oxide (ITO) and indium zinc oxide (IZO). Preferably, the first electrode 121 and the second electrode 122 may be indium tin oxide (ITO).

[0043] refer to Figure 1 The polymer dispersed liquid crystal display 100 may include a PDLC layer 110. Specifically, the PDLC layer 110 may be disposed between the first electrode 121 and the second electrode 122.

[0044] Although not shown in the figure, the polymer dispersed liquid crystal display 100 may include a first substrate and a second substrate. Specifically, the first substrate and the second substrate may each include a transparent material. For example, the first substrate and the second substrate may include at least one of a single glass layer and a transparent plastic film.

[0045] According to an embodiment of the present application, the PDLC layer 110 may include liquid crystal droplets 111. Specifically, a plurality of liquid crystal droplets 111 may be distributed in the PDLC layer 110.

[0046] According to an embodiment of the present application, the PDLC layer 110 may include a polymer 112. Specifically, the PDLC layer 110 includes a liquid crystal droplet 111 and a polymer 112, and the polymer 112 surrounds the liquid crystal droplet 111.

[0047] The liquid crystal droplets 111 are phase-separated from the polymer 112. Specifically, when the polymer liquid crystal mixture 113 is cured, the PDLC layer 110 is formed, and the dispersibility of the liquid crystal droplets 111 and the polymer 112 in the PDLC layer 110 can be increased (see Figure 4A and 4B ). In this process, the polymer 112 is phase-separated from the liquid crystal droplet 111 and can be distinguished from the liquid crystal droplet 111.

[0048] Figure 5 is an image showing the arrangement and refractive index of liquid crystal of a polymer dispersed liquid crystal display. Specifically, Figure 5 is an enlarged view of a liquid crystal droplet, and shows changes in the refractive index n(θ) according to the alignment state of the liquid crystal in the liquid crystal droplet and the incident angle of vertical polarization in an environment where an electric field is applied.

[0049] Figure 5 The left image of is an image showing the actual liquid crystal alignment state in the liquid crystal droplet.

[0050] Figure 5 The right image of is an image showing an ideal liquid crystal alignment state in a liquid crystal droplet.

[0051] When the LCD Figure 5 When arranged in a liquid crystal droplet, the refractive index ne(θideal) according to the incident angle of vertical polarization can be expressed as a function of the refractive index ne of the ideal light of the liquid crystal and the refractive index (no) of the normal light as shown in the right image of . Considering the above ideal situation, the smaller the refractive index ne(θideal) according to the incident angle of vertical polarization, that is, the smaller the difference between the refractive index ne of the ideal light and the refractive index of the normal light, the lower the side haze of the transmission mode, but the haze characteristics of the scattering mode will also be reduced.

[0052] However, if Figure 5As shown in the left image, even when an electric field is applied to the polymer dispersed liquid crystal display, the liquid crystal aligns along the curved surface on the polymer surface, and the liquid crystal becomes parallel to the electric field toward the center of the liquid crystal droplet. In this case, the refractive index (n∥(θreal)) according to the incident angle of the vertical polarization of the liquid crystal droplet can be expressed as a function of the refractive index (n∥) parallel to the electric field and the refractive index (n⊥) perpendicular to the electric field in the liquid crystal droplet. In this case, the relationship between ne > n∥ and no < n⊥ is established by the alignment of the liquid crystal in the actual liquid crystal droplet, and the difference between the two relationships increases as the size of the liquid crystal droplet decreases. That is, when manufacturing a polymer dispersed liquid crystal display using liquid crystal with the same refractive index anisotropy (ne - no), the smaller the size of the liquid crystal droplet, the smaller the actual refractive index anisotropy (n⊥) in the liquid crystal droplet, resulting in a reduction in side haze in the transmission mode. However, since the refractive index anisotropy inherent in the liquid crystal is maintained, the haze does not decrease in the scattering mode.

[0053] As described above, according to an embodiment of the present application, the size of the liquid crystal droplet 111 can be in the range of 0.8 μm to 1.5 μm. When the size of the liquid crystal droplet 111 is in the range of 0.8 μm to 1.5 μm, when the polymer dispersed liquid crystal display 100 is used for a sunroof or the like, the visibility with respect to the side view is improved.

[0054] On the other hand, when the size of the liquid crystal droplet 111 is less than 0.8 μm, the red wavelength is not scattered in the polymer dispersed liquid crystal display 100. As a result, the polymer dispersed liquid crystal display 100 generally appears red.

[0055] Moreover, when the size of the liquid crystal droplet 111 is greater than 1.5 μm, the liquid crystal droplets 111 in the PDLC layer 110 become too large, and the side haze becomes large. As a result, when the polymer dispersed liquid crystal display 100 is used for a sunroof or the like, there is a problem that the visibility with respect to the side view cannot be improved. Therefore, in order to improve the side haze, the liquid crystal droplet 111 is adjusted to be in the range of 0.8 μm to 1.5 μm. More preferably, the liquid crystal droplet can be adjusted in the range of 0.8 μm to 1.3 μm.

[0056] According to an embodiment of the present application, the liquid crystal droplets 111 in the PDLC layer 110 are controlled by the curing conditions in the process. Specifically, the curing conditions are that the intensity of ultraviolet light is 2 to 6 mW / cm 2 , and the temperature during curing is 25 to 45 °C. As a result, the size of the liquid crystal droplets 111 can be adjusted to be in the range of 0.8 to 1.5 μm.

[0057] According to an embodiment of the present application, the transparent point of the liquid crystal droplet 111 may be 90° C. or above. The polymer dispersed liquid crystal display 100 is used for a vehicle sunroof or a smart window, and, for example, the outer surface temperature of the vehicle sunroof in summer may be 90° C. or above. Therefore, in order to use the polymer dispersed liquid crystal display 100 as a vehicle sunroof, the transparent point of the liquid crystal droplet 111 needs to be 90° C. or above. Preferably, the transparent point of the liquid crystal droplet 111 may be 100° C. or above. More preferably, it may be 110° C. or above.

[0058] According to an embodiment of the present application, the liquid crystal droplet 111 may include the first compound represented by Chemical Formula 1.

[0059] [Chemical formula 1]

[0060]

[0061] In Chemical Formula 1, R 11 is at least one of a C2-C10 alkyl group, a vinyl group and an alkoxy group, ring A is a phenyl group or a cyclohexyl group, (F) is a fluorine group or a hydrogen group, and R 22 It refers to C2-C10 alkyl, fluorine or cyano.

[0062] According to an embodiment of the present application, Chemical Formula 1 may be any group selected from Chemical Formulas 1-1 to 1-11,

[0063] [Chemical formula 1-1]

[0064]

[0065] [Chemical formula 1-2]

[0066]

[0067] [Chemical formula 1-3]

[0068]

[0069] [Chemical formula 1-4]

[0070]

[0071] [Chemical formula 1-5]

[0072]

[0073] [Chemical formula 1-6]

[0074]

[0075] [Chemical formula 1-7]

[0076]

[0077] [Chemical formula 1-8]

[0078]

[0079] [Chemical formula 1-9]

[0080]

[0081] [Chemical formula 1-10]

[0082]

[0083] [Chemical formula 1-11]

[0084]

[0085] The first compound is a material necessary to maintain the clearing point of the liquid crystal droplet 111 at 100° C. or higher.

[0086] According to an embodiment of the present application, the first compound represented by Chemical Formula 1 may be 3 to 20 wt%. Specifically, wt% refers to 3 to 20 wt% based on the total content of the liquid crystal droplet 111. In order to keep the liquid crystal droplet 111 at a transparent point above 100°C, the first compound needs to be maintained at 3 to 20 wt%.

[0087] On the other hand, when the first compound is less than 3 wt %, it may be difficult to maintain the clearing point of the liquid crystal droplet 111 at 90° C. or more.

[0088] In addition, when the first compound exceeds 20% by weight, the possibility of crystallization at low temperature increases, resulting in a problem of crystal precipitation.

[0089] According to an embodiment of the present application, the liquid crystal droplet 111 may further include a second compound represented by Chemical Formula 2.

[0090] [Chemical formula 2]

[0091]

[0092] The second compound represented by Chemical Formula 2 serves to prevent a chain reaction during a radical reaction caused by heat in the PDLC layer 110 .

[0093] According to an embodiment of the present application, the concentration of the second compound may be in the range of 50 to 1000 ppm. In order to ensure the thermal stability of the PDLC layer 110, the concentration of the second compound needs to be maintained in the range of 50 to 1000 ppm.

[0094] On the other hand, when the concentration of the second compound is less than 50 ppm, there is a problem that the effect of preventing a radical reaction due to heat in the PDLC layer 110 is reduced, and as a result, thermal stability in the PDLC layer 110 is reduced.

[0095] In addition, when the concentration of the second compound exceeds 1000 ppm, the transparent point of the liquid crystal droplet 111 decreases, resulting in a problem that the electro-optical characteristics of the polymer dispersed liquid crystal display 100 are deteriorated.

[0096] According to an embodiment of the present application, the polymer 112 may be formed of a polymer precursor including the third compound represented by Chemical Formula 3.

[0097] In this case, the polymer precursor can be said to be before the polymer 112 is cured. Specifically, the polymer precursor includes the third compound represented by Chemical Formula 3, and the polymer 112 can be formed by curing. The polymer or monomer having the structure shown in Chemical Formula 3 is an acrylate-based photocurable polymerizable material, and R 33 represents methyl or hydrogen.

[0098] [Chemical formula 3]

[0099]

[0100] Moreover, according to an embodiment of the present application, when the liquid crystal droplet 111 does not contain the fourth compound represented by the following chemical formula 4, the size of the liquid crystal droplet 111 can be adjusted within the range of 0.8 to 1.5 μm. Specifically, according to an embodiment of the present application, when the liquid crystal droplet 111 includes the fourth compound, it is not easy to manufacture the size of the liquid crystal droplet 111 within the range of 0.8 to 1.5 μm.

[0101] [Chemical formula 4]

[0102]

[0103] In chemical formula 4, R 44 refers to any one of an alkyl group and a vinyl group, Y refers to a vinyl group (-CH2=CH2), and ring B and ring C refer to a cyclohexyl group. When the above-mentioned vinyl group (-CH2=CH2) and cyclohexyl group are present, the absorption wavelength of the acrylate monomer of the third compound represented by Chemical Formula 3 is absorbed by the vinyl group (-CH2=CH2) and the cyclohexyl group instead. As a result, when the polymer 112 is cured, there is a problem that the liquid crystal droplet 111 becomes too large.

[0104] Therefore, in order to manufacture the size of the liquid crystal droplet 111 within the range of 0.8 to 1.5 μm, the liquid crystal droplet 111 should not contain the fourth compound represented by Chemical Formula 4.

[0105] According to an embodiment of the present application, the thickness of the PDLC layer 110 may be in the range of 15 μm to 25 μm. Specifically, in order to scatter the liquid crystal droplets 111 and stabilize the manufacturing process of the polymer dispersed liquid crystal display 100, the thickness of the PDLC layer 110 is preferably in the range of 15 μm to 25 μm.

[0106] According to an embodiment of the present application, the liquid crystal droplet 111 may include a plurality of liquid crystals. According to an embodiment of the present application, the refractive index anisotropy of the liquid crystal may be in the range of 0.20 to 0.25. Specifically, when the refractive index anisotropy of the liquid crystal is in the range of 0.20 to 0.25, a shielding effect may be generated even in a scattering mode at a high temperature.

[0107] However, if the refractive index anisotropy of the liquid crystal in the liquid crystal droplet 111 is less than 0.20, the side haze according to the viewing angle is improved in the transmission mode, thereby improving the viewing angle, but the haze is reduced in the high temperature scattering mode, resulting in a problem of reduced shielding function.

[0108] In addition, when the refractive index anisotropy of the liquid crystal in the liquid crystal droplet 111 exceeds 0.25, the side haze according to the viewing angle in the transmission mode increases, resulting in a decrease in the viewing angle.

[0109] According to an embodiment of the present application, the polymer dispersed liquid crystal display 100 may be provided with a power source 130 capable of applying a driving voltage to the first electrode 121 and the second electrode 122 .

[0110] refer to Figure 4C , in a state where no driving voltage is applied to the first electrode 121 and the second electrode 122, i.e., in an open circuit state, an electric field may not be generated between the first electrode 121 and the second electrode 122. In this case, the liquid crystal droplet 111 is arranged not to have a certain directionality, and the incident light is scattered, resulting in an opaque scattering state.

[0111] Moreover, reference Figure 4C , the first electrode 121, the second electrode 122, and the power source 130 may be electrically connected to each other, so that an electric field may be generated between the first electrode 121 and the second electrode 122 in a closed circuit state. The direction of the electric field may be perpendicular to the first electrode 121 and the second electrode 122. The liquid crystal droplet 111 may be aligned in a direction parallel to the electric field. That is, the long axis of the liquid crystal droplet 111 is arranged parallel to the direction of the electric field, and the incident light passes through without scattering, becoming a transparent transmission state.

[0112] Figure 2 It is the image according to the viewing angle when viewed from the front and side through the polymer dispersed liquid crystal display in the turned-on state.

[0113] Specifically, Figure 2The left image is the image viewed from the front (0° polar angle) through the PDLC. Figure 2 The right image is viewed through the PDLC from the side (70° polar angle).

[0114] Generally, when electricity is applied to the polymer dispersed liquid crystal display 100 , a difference in haze occurs between the front and side surfaces due to the refractive index anisotropy of liquid crystal.

[0115] Specifically, refer to Figure 2 , since the haze on the sides is higher than that on the front, it is impossible to get a clear image.

[0116] The reason why the side haze is important is that when the polymer dispersed liquid crystal display 100 is applied to a sunroof, the occupants mostly view the polymer dispersed liquid crystal display 100 from the side rather than from the front. When the polar angle when the occupants view from the front is 0°, the occupants mostly view at a polar angle of 60° to 70°, so it is important to improve the haze.

[0117] Figure 3 is a schematic diagram illustrating a haze measurement method.

[0118] Specifically, Figure 3 2 is a schematic diagram showing a method for measuring the haze of a polymer dispersed liquid crystal (PDLC). Here, the polymer dispersed liquid crystal (PDLC) may correspond to the PDLC layer 110 of the present application.

[0119] refer to Figure 3 , the light incident on the polymer dispersed liquid crystal (PDLC) is defined as I0, the light transmitted head-on within an error range of ±2.5° of the incident light (I0) is defined as Ir, and when Is is the light in the transmitted light excluding the light transmitted head-on (Ir), the haze is defined as Is / (Ir+Is).

[0120] in this case, Figure 3 The left image is an image showing the measured front haze. Figure 3 The right image of is an image showing the measured side haze.

[0121] Figures 4A to 4C is a diagram showing a manufacturing process of the polymer dispersed liquid crystal display 100 .

[0122] Specifically, refer to Figure 4A In the manufacturing process of the polymer dispersed liquid crystal display 100 , the polymer liquid crystal mixture 113 is applied to one surface of the first electrode 121 , and then the second electrode 122 is bonded thereon using a roller, thereby manufacturing the polymer dispersed liquid crystal unit 101 .

[0123] Then, refer to Figure 4B, the first electrode 121 including the polymer liquid crystal mixture 113 is irradiated with ultraviolet rays (UV) to cure the polymer liquid crystal mixture 113, thereby manufacturing the polymer dispersed liquid crystal display 100.

[0124] Next, refer to Figure 4C A power source 130 connecting the first electrode 121 and the second electrode 122 may be provided.

[0125] In this case, in a state where no driving voltage is applied to the first and second electrodes 121 and 122, ie, in an open state, an electric field may not be generated between the first and second electrodes 121 and 122. In this case, the liquid crystal droplet 111 may be arranged not to have certain directionality.

[0126] Moreover, the first electrode 121, the second electrode 122, and the power source 130 may be electrically connected to each other so that an electric field may be generated between the first electrode 121 and the second electrode 122 in a closed circuit state. The direction of the electric field may be perpendicular to the first electrode 121 and the second electrode 122. The liquid crystal droplet 111 may be aligned in a direction parallel to the electric field. That is, the long axis of the liquid crystal droplet 111 may be parallel to the direction of the electric field.

[0127] Hereinafter, the present application will be described in detail with reference to Examples and Comparative Examples. However, the following Examples are only for helping to understand the present application, and the scope of the present application is not limited to these Examples.

[0128] Examples 1-5 and Comparative Examples 1-4

[0129] In order to improve the present application, polymer dispersed liquid crystal displays were prepared using various polymer liquid crystal mixtures. The contents of the polymer liquid crystal mixtures are shown in Table 1 below.

[0130] [Example 1]

[0131] BP008 (Bayi Co., Ltd.) was used as a polymer liquid crystal mixture, and in BP008, 8 wt% of (Chemical Formula 1-5) and 7 wt% of (Chemical Formula 1-9) were present in the liquid crystal droplets, and 250 ppm of an antioxidant (4-sec-butyl-2,6-di-tert-butylphenol; Chemical Formula 2) was mixed. The first electrode and the second electrode were used by sputtering ITO onto a PET product of A4165 PET product of Toyobosa Co., Ltd., and the polymer liquid crystal mixture was coated with a slot die, using a 3 mW / cm2 wave with a wavelength of 365 nm. 2 The UV lamp was applied at a cumulative dose of 1 J. During the process, the temperature was 25°C, and a PDLC layer of 17 μm was obtained after preparation.

[0132] [Example 2]

[0133] The polymer liquid crystal mixture is the same as that in Example 1, except that 200 ppm of an antioxidant (Chemical Formula 2) is added in Example 1, and the PDLC manufacturing method is the same as that in Example 1, except that the curing temperature is 30°C.

[0134] [Example 3]

[0135] The polymer liquid crystal mixture is the same as that in Example 1, except that 300 ppm of an antioxidant (Chemical Formula 2) is added in Example 1, and the PDLC manufacturing method is the same as that in Example 1, except that the curing temperature is 40°C.

[0136] [Example 4]

[0137] BP015 (Bayi Co.) was used as a polymer liquid crystal mixture, and 5 wt % of Chemical Formula 1-5 and 250 ppm of an antioxidant (4-sec-butyl-2,6-di-tert-butylphenol; Chemical Formula 2) were mixed in BP015.

[0138] The PDLC film was manufactured at a curing temperature of 35° C., and the rest of the manufacturing method was manufactured in the same manner as in Example 1.

[0139] [Example 5]

[0140] BP016 (Bayi Co.) was used as a polymer liquid crystal mixture, and 5 wt % of Chemical Formula 1-4 and 5 wt % of Chemical Formula 1-5 and 250 ppm of an antioxidant (4-sec-butyl-2,6-di-tert-butylphenol; Chemical Formula 2) were mixed in BP016.

[0141] The PDLC film was manufactured at a curing temperature of 35° C., and the rest of the manufacturing method was manufactured in the same manner as in Example 1.

[0142] [Comparative Example 1]

[0143] The polymer liquid crystal mixture was a mixture of 49 wt % of polymer precursor NOA65 (Edmond Optics Korea), 50 wt % of liquid crystal E7 (Merck Co., not containing Chemical Formula 1), and 1 wt % of argacure 651 (Shibasa).

[0144] The PDLC film was manufactured at a curing temperature of 30° C., and the rest of the manufacturing method was manufactured in the same manner as in Example 1.

[0145] [Comparative Example 2]

[0146] The polymer liquid crystal mixture is the same as that in Example 1, except that 15 ppm of an antioxidant (Chemical Formula 2) is added in Example 1, and the PDLC manufacturing method is the same as that in Example 1, except that the curing temperature is 20°C.

[0147] [Comparative Example 3]

[0148] The polymer liquid crystal mixture is the same as that in Example 1, except that 0 ppm of an antioxidant (Chemical Formula 2) is added in Example 1, and the PDLC manufacturing method is the same as that in Example 1, except that the curing temperature is 50°C.

[0149] [Comparative Example 4]

[0150] BP013 (Bayi Co.) was used as a polymer liquid crystal mixture. 10 wt % of chemical formula 1-5, 10 wt % of R 44 The chemical formula 4 is propyl (-C3H7) and 10 ppm of an antioxidant (4-sec-butyl-2,6-di-tert-butylphenol; chemical formula 2).

[0151] The PDLC film was manufactured at a curing temperature of 40° C., and the rest of the manufacturing method was manufactured in the same manner as in Example 1.

[0152] [Table 1]

[0153]

[0154] [Table 2]

[0155]

[0156] For the polymer dispersed liquid crystal displays of Examples 1-5 and Comparative Examples 1-4 prepared in this way, i) the size of the liquid crystal droplets, ii) the room temperature side ON haze, iii) the high temperature front OFF haze, iv) the presence or absence of red shift, and v) the amount of haze change after heating were confirmed.

[0157] i) Liquid crystal droplet size

[0158] The measurement was performed using a scanning electron microscope (PE-300SEM) manufactured by Youngin Science. Specifically, 20 liquid crystal droplet sizes were measured by magnification at 10,000 times, and the liquid crystal droplet size in Table 1 represents the average value of the 20 liquid crystal droplets.

[0159] ii) Measurement of side ON haze at room temperature

[0160] The light incident on the polymer dispersed liquid crystal (PDLC) is defined as I0, the light transmitted head-on within an error range of ±2.5° of the incident light (I0) is defined as Ir, and when Is is the light in the transmitted light excluding the light transmitted head-on (Ir), the haze is defined as Is / (Ir+Is).

[0161] When the side haze was measured, the voltage was 48 V, the viewing angle (θ) was 70°, and the temperature was 25°C.

[0162] As a haze measuring instrument, NDH 7000II from Nippon Denshoku was used, and as a measurement standard, ASTM D1003 was used.

[0163] iii) Measurement of high temperature front-side off haze

[0164] The light incident on the polymer dispersed liquid crystal (PDLC) is defined as I0, the light transmitted head-on within an error range of ±2.5° of the incident light (I0) is defined as Ir, and when Is is the light in the transmitted light excluding the light transmitted head-on (Ir), the haze is defined as Is / (Ir+Is).

[0165] When the front haze is measured, the voltage is 0 V, the viewing angle (θ) is 0°, and the temperature is 90°C.

[0166] As a haze measuring instrument, NDH 7000II from Nippon Denshoku was used, and as a measurement standard, ASTM D1003 was used.

[0167] iv) Check redshift

[0168] The presence or absence of red shift in the prepared polymer dispersed liquid crystal display was determined by naked eyes.

[0169] v) Measure the change in haze after heating

[0170] The amount of haze change after heating was calculated by preparing a 17 μm PDLC layer, placing it in an oven at a temperature of 80° C., heating it for 168 hours, and then measuring the amount of haze change at room temperature.

[0171] Referring to Tables 1 and 2, in Examples 1 to 5, when the liquid crystal droplet size was 0.7 to 1.50 μm, the values ​​of the side haze in the open state at room temperature were 9 to 12%. In the case of Comparative Example 3 in which the liquid crystal droplet size was 0.7 μm or less, red shift occurred, and in the cases of Comparative Examples 1, 2, and 4 in which the liquid crystal droplet size was 1.5 μm or more, the side haze had a high value of 15% or more.

[0172] Comparative Example 1 without (Chemical Formula 1) has a front haze of 20% in the off state at high temperature, which is very low compared with other comparative examples and embodiments. Therefore, (Chemical Formula 1) is a key factor in maintaining the shielding state of PDLC at high temperature.

[0173] Compared with the comparative examples containing no or a trace amount of (chemical formula 2) and the examples having 100 ppm or more, the "haze change after heating" was 2.0 to 3.0% in the comparative examples, but was a good level of 1.0% or less in the examples.

[0174] The curing temperature of Comparative Example 4 including (Chemical Formula 4) is 40° C., which is higher or similar to that of the embodiment, but the liquid crystal droplet size is 1.51 μm, which is larger than 1.50 μm. Therefore, the side haze is very high, which is 18%.

[0175] According to the present disclosure, the following advantageous effects can be obtained.

[0176] The polymer dispersed liquid crystal display according to the embodiment of the present application can improve the side haze in the transmission state where electricity is applied.

[0177] The polymer dispersed liquid crystal display according to the embodiment of the present application can increase the haze in a scattering state without applying electricity at high temperature to achieve complete shielding.

[0178] In addition to the above-mentioned effects, other features and advantages of the present application can be described below or can be clearly understood from these techniques and descriptions by ordinary technicians in the field to which the present application belongs.

[0179] In addition to the above-mentioned effects, other features and advantages of the present invention may be described below or may be clearly understood from these techniques and descriptions by those having ordinary skill in the art to which the present invention pertains.

[0180] In addition to the above-mentioned effects, other features and advantages of the present invention will be described below or will be clearly understood from these techniques and descriptions by those having ordinary skill in the art to which the present invention pertains.

[0181] It will be apparent to those skilled in the art that the above disclosure is not limited by the above embodiments and drawings, and that various substitutions, modifications and variations may be made to the disclosure without departing from the spirit or scope of the disclosure. Therefore, the scope of the disclosure is defined by the appended claims, and all variations or modifications derived from the meaning, scope and equivalent concepts of the claims are intended to fall within the scope of the disclosure.

Claims

1. A polymer dispersed liquid crystal display, comprising: a first electrode; a second electrode on the first electrode; as well as a PDLC layer disposed between the first electrode and the second electrode; wherein the PDLC layer comprises liquid crystal droplets having a size ranging from 0.8 μm to 1.5 μm and containing a plurality of liquid crystals, and The thickness of the PDLC layer is in the range of 15 μm to 25 μm.

2. The polymer dispersed liquid crystal display according to claim 1, wherein the refractive index anisotropy of the liquid crystal droplets is in the range of 0.20 to 0.

25.

3. The polymer dispersed liquid crystal display according to claim 1, wherein the clearing point of the liquid crystal droplets is 90°C or higher.

4. The polymer dispersed liquid crystal display according to claim 1, wherein the liquid crystal droplet comprises a first compound represented by Chemical Formula 1: [Chemical formula 1] R 11 It refers to at least one of C2-C10 alkyl, vinyl and alkoxy, (F) means fluorine or hydrogen, Ring A is phenyl or cyclohexyl, and R 22 It refers to C2-C10 alkyl, fluorine or cyano. 5 . The polymer dispersed liquid crystal display according to claim 4 , wherein the first compound is 3 wt % to 20 wt % based on the total content of the liquid crystal droplets.

6. The polymer dispersed liquid crystal display according to claim 1, wherein the liquid crystal droplet further comprises a second compound represented by Chemical Formula 2: [Chemical formula 2] 7 . The polymer dispersed liquid crystal display according to claim 6 , wherein a concentration of the second compound is in the range of 50 ppm to 1000 ppm.

8. The polymer dispersed liquid crystal display according to claim 1, wherein the PDLC layer further comprises a polymer, and the polymer is formed of a polymer precursor comprising a third compound represented by Chemical Formula 3: [Chemical formula 3] R 33 It refers to methyl or hydrogen.

9. The polymer dispersed liquid crystal display according to claim 1, wherein the liquid crystal droplets do not contain a fourth compound represented by Chemical Formula 4: [Chemical formula 4] R 44 It refers to any one of an alkyl group and a vinyl group, Y refers to vinyl (-CH2=CH2), and Ring B and Ring C refer to cyclohexyl groups.

10. The polymer dispersed liquid crystal display of claim 1, wherein the first electrode and the second electrode comprise a transparent conductive material. 11 . The polymer dispersed liquid crystal display of claim 10 , wherein the transparent conductive material comprises at least one of indium tin oxide (ITO) and indium zinc oxide (IZO).

12. A smart window comprising the polymer dispersed liquid crystal display according to any one of claims 1 to 11.

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