KR102160081B1 - Transparent Substrate for Smart Window and Manufacturing Method Thereof - Google Patents

Abstract

The present invention is a transparent substrate for a smart window in which a polymer dispersed liquid crystal (PDLC) film is laminated on one side, and an adhesive layer is interposed between the polymer dispersed liquid crystal film and the transparent substrate for the smart window, The pressure-sensitive adhesive layer is characterized by forming a pattern, and even if the pressure-sensitive adhesive layer is interposed, it is possible to suppress a reduction in resolution due to scattering of an image or loss of transmittance, and pores are formed due to foreign matters generated when the pressure-sensitive adhesive layer is interposed. It relates to a transparent substrate for a smart window that can solve the problem and a manufacturing method thereof.

Description

Transparent Substrate for Smart Window and Manufacturing Method Thereof}

The present invention relates to a transparent substrate for a smart window and a method of manufacturing the same, and more particularly, to a transparent substrate for a smart window in which a patterned adhesive layer is interposed between a polymer dispersed liquid crystal film and a transparent substrate, and a method of manufacturing the same.

In recent years, the glass industry is developing various products that have changed the properties of existing glass based on the energy saving effect and the use of eco-friendly materials. In particular, smart windows are attracting attention as glass that can artificially control the transmittance of visible light.

The smart window was completed through research on liquid crystal materials along with the development of various thin film materials, and various products have been developed according to the type of material. In particular, a smart window is widely used to control the transmittance of light by using a polymer dispersed liquid crystal (PDLC) to increase the size.

This PDLC-type smart window consists of a structure in which a PDLC film is laminated on a transparent substrate such as glass. At this time, it is possible to implement a rear projection type smart window system by using the scattering characteristics of the liquid crystal polymer included in the PDLC film (refer to International Patent Publication No. 2016-010186, Korean Patent Publication No. 10-2009-0109927).

In this case, an adhesive layer is formed on one side of the film for bonding the PDLC film and the glass substrate, and when the image is diffused/transmitted, the image may be scattered while the transparent substrate and the PDLC film are bonded, and the transmittance decreases. There is a problem of lowering the resolution.

In addition, the pressure-sensitive adhesive layer is formed on the entire surface of one side of the film and is generally attached to the entire substrate. In this case, it is not easy to control the process because fine dust adheres to the film surface and forms pores during the process. In addition, there is a problem that the uniformity of the adhesion is low and the adhesion process takes time.

Regarding this problem, it is not a technology related to a smart window, but in Korean Patent Publication No. 10-1628551, a technology related to a surface protection film, the occurrence of bubbles and stains is prevented by forming an adhesive layer in a three-dimensional pattern on one side of the base film. Is getting the effect.

The above prior art solves the problem of the smart window transparent substrate that occurs during film bonding as described above if the technology for applying to the surface protection film for automobile interior materials or the technology for forming by patterning the adhesive layer is applied to the smart window transparent substrate. It is expected to be possible.

International Patent Publication No. 2016-010186 Korean Patent Application Publication No. 10-2009-0109927 Korean Patent Publication No. 10-1628551

The present invention was devised in view of the problems of the prior art as described above, and an object of the present invention is to provide a transparent substrate for a smart window capable of suppressing a reduction in resolution due to scattering of an image or loss of transmittance even if an adhesive layer is interposed therebetween. .

In addition, it is an object of the present invention to provide a transparent substrate for a smart window that solves the problem of forming pores due to foreign substances by interposing an adhesive layer.

In addition, it is an object of the present invention to provide heat insulating properties by patterning the pressure-sensitive adhesive layer to form a constant air layer.

In addition, it is an object of the present invention to provide a transparent substrate for a smart window capable of displaying a specific pattern or character on the smart window through patterning of an adhesive layer.

In addition, it is an object of the present invention to provide a method of manufacturing a transparent substrate for a smart window interposed between a polymer dispersed liquid crystal film and a glass substrate by patterning an adhesive layer.

The transparent substrate for a smart window of the present invention for solving the above problems is a transparent substrate for a smart window in which a polymer dispersed liquid crystal (PDLC) film is laminated on one side, and the polymer dispersed liquid crystal film and the smart window A pattern of a pressure-sensitive adhesive layer having a thickness of 5 to 2,000 μm is interposed between the transparent substrates for use, but the pattern has a distance between one pattern and a neighboring pattern of 10 to 100 mm, and the width of the pattern is 1 to It is characterized in that it is 20 mm.

The method of manufacturing a transparent substrate for a smart window of the present invention comprises: forming an adhesive layer on one surface of a polymer dispersed liquid crystal film; It may include; adhering the one surface on which the pressure-sensitive adhesive layer is formed to the surface of a transparent substrate for a smart window.

In addition, forming a pressure-sensitive adhesive layer on one side of the transparent substrate for smart windows; It may include a step of adhering the one surface on which the pressure-sensitive adhesive layer is formed to the surface of the polymer dispersed liquid crystal film.

The transparent substrate for a smart window according to the present invention exhibits an effect of suppressing a reduction in resolution due to image scattering or loss of transmittance even if an adhesive layer is interposed therebetween.

In addition, as the pressure-sensitive adhesive layer is patterned and interposed, it is possible to solve the problem of forming pores due to foreign matter.

In addition, by patterning the pressure-sensitive adhesive layer to form a constant air layer, it is possible to impart heat insulation properties.

In addition, since a specific pattern or letter can be displayed on the smart window through the patterning of the adhesive layer, various information can be displayed on the smart window according to the needs of the user.

In addition, it shows the effect of improving the process efficiency of the transparent substrate for smart windows through a method of manufacturing a transparent substrate for smart windows interposed between the polymer dispersed liquid crystal film and the transparent substrate by patterning the pressure-sensitive adhesive layer.

1 is a conceptual diagram showing a cross section of a smart window transparent substrate according to the present invention.
2 is a conceptual diagram showing a cross-sectional structure of a smart window according to an embodiment.
3 is a conceptual diagram showing a cross-sectional structure of a smart window according to another embodiment.
4 is a graph showing the luminance value measured in the horizontal direction according to each sample of the smart window.
5 is a graph showing the luminance value measured in the vertical direction according to each sample of the smart window.
6 is a conceptual diagram showing a model for measuring the heat transmission rate.
7 is a photograph of a prototype of a smart window glass substrate to which a polymer dispersed liquid crystal film according to the present invention is adhered before power is applied (a) and after power is applied (b).

The terms and words used in the specification and claims are not to be construed as being limited to a conventional or dictionary meaning, and the embodiments described in this specification and the configurations shown in the drawings are only the most preferred embodiments of the present invention. Since not all of the technical ideas of the present invention are represented, it should be understood that there may be various equivalents and modified examples that can replace them at the time of application.

Hereinafter, the present invention will be described in detail.

The transparent substrate for a smart window of the present invention forms a smart window by laminating a polymer dispersed liquid crystal (PDLC) film 300 on one surface of the transparent substrate 100, as shown in FIG. The pressure-sensitive adhesive layer 200 is interposed between the transparent substrate 100 and the polymer dispersed liquid crystal film 300, and the image data irradiated from the projector 400 is applied to the transparent substrate 100 and the polymer dispersed liquid crystal film 300. It is driven in such a way that it transmits and displays image information. That is, the technology applied to the smart window of the present invention uses a polymer dispersed liquid crystal.

In the case of a polymer dispersed liquid crystal, an external power supply for supplying power to the polymer dispersed liquid crystal film may be added or a power source may be stacked. In recent years, according to the trend of weight reduction, a power conversion unit that converts direct current power from a solar cell or a solar cell into a driving power source, a polymer dispersed liquid crystal unit whose light transmittance is changed depending on whether or not driving power is applied, and a power converter control the operation An input unit for generating an input signal for and a control unit for controlling a power conversion unit to apply driving power to the PDLC unit according to the input signal may be included, and examples of this may include Korean Patent Publication No. 10-1696724.

The smart window according to the present invention may have a stacked structure as shown in FIGS. 2 and 3.

In FIGS. 2 and 3, an adhesive layer 200 is formed on one surface of the smart window transparent substrate 100 and a polymer dispersed liquid crystal film 300 is laminated on the adhesive layer 200. In this case, the polymer dispersed liquid crystal film 300 has ITO PET films 330 stacked on both sides of the polymer dispersed liquid crystal mixture 340 as the center, as shown in FIG. 2, the adhesive layer 200 and the ITO PET film ( 330 is not directly bonded, but can be bonded through the PET film 310.

In addition, as shown in FIG. 3, the ITO PET film 330 is laminated on both sides of the polymer dispersed liquid crystal mixture 340, but the pressure-sensitive adhesive layer 200 and the ITO PET film 330 are directly adhered. It can also be composed of.

In this case, problems such as scattering of light, lowering transmittance, and generation of pores in the adhesive layer occur in the adhesive layer 200 to which the polymer dispersed liquid crystal film 200 and the transparent substrate 100 are bonded, and in the present invention, such a conventional polymer Its purpose is to secure the resolution of the smart window system and reduce the defect rate by solving the problem that occurs when bonding the film of the smart window to which the dispersed liquid crystal film is bonded.

To this end, in the present invention, unlike the conventional bonding structure in which the pressure-sensitive adhesive layer is interposed, the pressure-sensitive adhesive layer interposed between the polymer dispersed liquid crystal film and the transparent substrate is patterned.

This patterned pressure-sensitive adhesive layer has various advantages. First of all, it is possible to reduce the scattering of images and loss of transmittance when the glass substrate and the polymer dispersed liquid crystal film are bonded by the adhesive in the rear projection type smart window system. Can be mentioned.

Next, it is possible to block the generation of pores due to impurities generated in the process of adhering the polymer dispersed liquid crystal film to the transparent substrate, and can exhibit a greatly improved effect in terms of time and defect rate of the bonding process.

The transparent substrate may be made of glass or various polymer resins such as polyethylene, polypropylene, acrylonitrile-butadiene-styrene, and the like.In order to apply such a transparent substrate made of glass or polymer material, the composition of the pressure-sensitive adhesive is different depending on the type of the substrate. Or, there is a difficulty in optimizing the bonding process conditions, and this problem can be greatly improved through the patterning of the pressure-sensitive adhesive layer.

At this time, the patterned pressure-sensitive adhesive layer cannot be obtained by simply forming a pattern on the surface of a transparent substrate or film, and the characteristics of the pattern and the uniformity of the air layer formed by the pattern are characteristics when driving the smart window system. As it becomes an important factor to improve the value, optimization for this is indispensable.

In the present invention, the pattern constituting the patterned pressure-sensitive adhesive layer may be any one or more of circular, square, triangular, hexagonal, straight stripes, and curved stripes. The reason for diversifying the shape of the pattern is not simply to bond the transparent substrate and the film through the pressure-sensitive adhesive layer, but to impart thermal insulation properties by using the air layer generated through the pattern, and through the pattern of the pressure-sensitive adhesive layer. This is to achieve the purpose of displaying information such as certain characters, patterns, and logos on the smart window by light transmission.

In the present invention, it is preferable that the distance between one pattern and neighboring patterns is 10 to 100 mm, and the maximum width of the pattern is 1 to 20 mm.

In addition, it is preferable that the thickness of the pressure-sensitive adhesive layer formed through the pattern is 5 to 2,000 μm.

By satisfying these characteristics, even if the pressure-sensitive adhesive layer formed through the pattern is interposed between the transparent substrate and the polymer dispersed liquid crystal film, a phenomenon in which the optical properties of the smart window are reduced can be suppressed.

The method of manufacturing a transparent substrate for a smart window according to the present invention may be manufactured by bonding one substrate having an adhesive layer installed on one surface thereof to another substrate, in which case the adhesive layer may be installed on one surface of the polymer dispersed liquid crystal film. In addition, it may be installed on one side of the transparent substrate.

That is, it may be bonded through the step of forming the pressure-sensitive adhesive layer on one side of the polymer dispersed liquid crystal film and the step of bonding the one side on which the pressure-sensitive adhesive layer is formed to the surface of the transparent substrate for the smart window. It may be bonded through the step of forming the pressure-sensitive adhesive layer on one side of the transparent substrate and bonding the one side on which the pressure-sensitive adhesive layer is formed to the surface of the polymer dispersed liquid crystal film.

Patterning of the pressure-sensitive adhesive layer can be performed by applying the pressure-sensitive adhesive layer to the surface of the substrate and then irradiating a laser to a certain portion or forming a pattern using a punching process.Another method is to use the pressure-sensitive adhesive on the surface of the substrate through silk printing. You can also print the pattern yourself.

In addition, since the desired effect in the present invention can be achieved only by optimizing the width of the pattern and the spacing between the patterns when forming the pattern, a problem when the adhesive spreads and cannot maintain the width and pattern when forming the adhesive layer. Can be.

Accordingly, the pressure-sensitive adhesive used in the present invention can maintain a sufficient viscosity during pattern printing by adding a silane compound represented by the following formula (1) to a conventional acrylic pressure-sensitive adhesive including an acrylic resin and a crosslinking agent.

[Formula 1]

At this time, in Formula 1, n is 6 to 10, and R is any one of a methyl group, an ethyl group, and an isopropyl group.

The silane compound contains functional groups of urethane and pyridine, so that the initial adhesion to the surface of the glass is lowered, so that there is no problem in that the adhesive spreads or the pattern is deformed.After attachment, the time passes under high temperature or high temperature and high humidity conditions. Durability can be improved by increasing adhesion. In particular, by using a relatively long-chain alkyl group in which n is 6 to 10, the silane compound can have compatibility in the acrylic pressure-sensitive adhesive. In particular, when n is less than 6, the size of the molecule is relatively small, and even if there is compatibility in the acrylic pressure-sensitive adhesive, the initial adhesion is lowered too much, resulting in defects during the pattern formation process.

In order to confirm the effect of the patterned pressure-sensitive adhesive layer according to the present invention, various types of patterned pressure-sensitive adhesive layers were prepared and the characteristics of the smart window applied thereto were evaluated. As the pressure-sensitive adhesive, a conventional acrylic pressure-sensitive adhesive was used, and the pressure-sensitive adhesive layers of Samples 1 to 13 are shown in Table 1 below.

Distance between patterns (㎜) Maximum width of pattern (㎜) Adhesive layer thickness (㎛) Sample 1 20 10 0 Sample 2 20 10 10 Sample 3 20 10 50 Sample 4 20 10 100 Sample 5 20 10 500 Sample 6 20 10 1,000 Sample 7 20 10 2,000 Sample 8 5 10 1,000 Sample 9 80 10 1,000 Sample 10 110 10 1,000 Sample 11 20 0.5 1,000 Sample 12 20 15 1,000 Sample 13 20 25 1,000

The luminance (gain) was measured for each smart window sample.

In the present invention, luminance is a numerical characteristic value of intrinsic properties such as brightness and angle reflected when light is projected onto the screen fabric. Light is projected on the screen at a right angle, and the luminance meter is positioned at intervals of 5° left and right in a circle from the center. Measure the reflection value while changing At this time, the case of reflecting with the same brightness as the projected light is 10 gain, which is the brightest value that the screen can reflect, which is the peak gain (P.G.). In addition, the luminance value varies according to the measurement angle, and the angle of the half gain point of half the brightness from the peak gain is displayed as the viewing angle.

In the present invention, the luminance is defined by Equation 1 below.

[Equation 1]

G = I _s /I _laser

In the above equation, I _s is the intensity of the laser beam reflected on the screen, and I _laser is the intensity of the laser beam just before incident.

The viewing angle of the smart window can be defined using the luminance defined by the above equation. That is, the angle that satisfies the condition of G _S = 0.5G _F is defined as the half-viewing angle by comparing the luminance (G _S ) measured at each angle based on the luminance measured from the front (G _F ), and the viewing angle is the half-viewing angle. Decide to double. In the luminance measurement, a laser having a wavelength of 543.5 nm and 632.8 nm was used as a light source.

The luminance measured for each sample is shown in Table 2. In addition, the luminance measured in the horizontal direction and the luminance measured in the vertical direction are plotted in FIGS. 4 and 5.

Horizontal measurement luminance Vertical measurement luminance 543.5nm 632.8nm 543.5nm 632.8nm Sample 1 6 6 6 6.1 Sample 2 7.5 7.5 7.7 7.7 Sample 3 8.1 8.1 8.0 8 Sample 4 8.1 8.1 8.1 8.1 Sample 5 8.0 8.1 8 8 Sample 6 7.9 7.9 8 8 Sample 7 7.5 7.5 7.8 7.8 Sample 8 6.1 6.1 6.1 6.1 Sample 9 7.8 7.9 7.9 8 Sample 10 8 8.1 8 8.1 Sample 11 8 8.1 8.1 8.2 Sample 12 8 8 8 8.1 Sample 13 7.5 7.6 7.5 7.5

Looking at the results of Table 2, when the thickness of the pressure-sensitive adhesive layer starts to increase from 10 μm or more, the optimum brightness value can be obtained from 20 μm or more, and there is no difference in the thickness above that, but the brightness value is more than 2,000 μm. It can be seen that it decreases.

In addition, samples 8, 10, 11, and 13, which do not satisfy any one of 10 to 100 mm in distance and 1 to 20 mm in the maximum width of the patterns, decrease the luminance value even if the thickness of the adhesive layer is optimized. Appeared.

Comparing this with the graphs of FIGS. 4 and 5, it is easy to check the difference in measured luminance according to the thickness of the adhesive layer, the distance between patterns, and the width of the pattern.

From these experimental results, it can be seen that the pattern preferably has a distance between patterns of 10 to 100 mm, a maximum width of 1 to 20 mm, and a thickness of the pressure-sensitive adhesive layer formed through the pattern of 5 to 2,000 μm. .

In addition, the heat transmission rate was measured to evaluate the thermal insulation properties. In order to measure the heat transmission rate, it was calculated assuming that the transparent substrate was made of glass as shown in FIG. 6, and was calculated by the following equation. In Fig. 6, the measurement model represents a frame (1), a spacer (2), and a glass (3), respectively.

[Equation 2]

In the above formula, U _W is the heat transmission rate of the glass, A _g is the area of the glass (part 3 of Fig. 6), A _f is the area of the frame (parts 1 and 2 of Fig. 6), and U _g is the heat transmission rate of the glass (Fig. 3), U _f is the heat transmission rate of the frame (parts 1 and 2 in Fig. 6), l _g is the length of the edge of the glass (the length of the edge where 3 and 2 in Fig. 6 meet), Ψ _g is the glass, frame, and spacer. It is a complex linear heat transfer rate.

According to the above equation, the surface temperature of the smart window samples 1 to 7 was measured based on 38°C, and the results are shown in Table 3.

Heat transfer rate (W/㎡K) Temperature(℃) Sample 1 4 37 Sample 2 3.5 36.5 Sample 3 3.5 36.4 Sample 4 3.4 36.4 Sample 5 3.1 35.2 Sample 6 2.9 35 Sample 7 2.7 34

In the case of Sample 2 in Table 3 above, it can be seen that the heat transmittance and temperature decrease even if a slight air layer is provided, and the heat transmittance and temperature tend to decrease further as the air layer (thickness of the adhesive layer) increases. I can confirm.

The transparent substrate for smart windows to which such a patterned adhesive layer is applied increases the speed of the process of bonding the polymer dispersed liquid crystal film to the surface and significantly reduces the occurrence of bubbles or stains due to foreign substances, thereby reducing process defects. Represents.

7 shows an operating state of a smart window in which a polymer dispersed liquid crystal film and a transparent substrate are bonded according to the present invention. Referring to FIG. 7, it can be seen that bubbles or stains by foreign substances are not generated at all in a state in which the polymer dispersed liquid crystal film is adhered to the glass substrate.

In addition, before power is applied from an opaque state (Fig. 7 a) to a transparent state by power application, a pattern pattern by an adhesive pattern appears on the front of the smart window (Fig. 7 b), through this adhesive pattern. Since various characters, logos, patterns, and the like can be displayed on the smart window, the smart window to which the glass substrate of the present invention is applied can function as a smart window and simultaneously perform a function of displaying various information.

Therefore, in the present invention, by optimizing the patterning of the pressure-sensitive adhesive layer interposed between the polymer dispersed liquid crystal film and the transparent substrate and optimizing the spacing, size, and height of the pattern, the optical properties of the smart window are prevented from being reduced, while the thermal insulation effect and the occurrence of bubbles or stains are It is possible to provide a transparent substrate for smart windows that can solve the problem.

Although the present invention has been described as the above-mentioned embodiment, it is possible to make various modifications or variations without departing from the gist and scope of the invention. In addition, the appended claims include such modifications or variations that fall within the gist of the present invention.

100: transparent substrate 200: pressure-sensitive adhesive layer
300: polymer dispersed liquid crystal film
310: PET film 320: acrylic adhesive layer
330: ITO PET film 340: polymer dispersed liquid crystal mixture
400: projector

Claims (3)

In a transparent substrate for a smart window in which a polymer dispersed liquid crystal (PDLC) film is laminated on one side,
A pattern of a pressure-sensitive adhesive layer having a thickness of 5 to 2,000 μm is interposed between the polymer dispersed liquid crystal film and the transparent substrate for the smart window,
The pattern has a distance between one pattern and a neighboring pattern of 10 to 100 mm, and the width of the pattern is 1 to 20 mm,
The pressure-sensitive adhesive layer is a transparent substrate for a smart window, characterized in that formed by adding a silane compound represented by the following formula (1) to an acrylic pressure-sensitive adhesive.

[Formula 1]

In Formula 1, in Formula 1, n is 6 to 10, and R is any one of a methyl group, an ethyl group, and an isopropyl group.
In the method of manufacturing a transparent substrate for a smart window of claim 1,
Forming the pressure-sensitive adhesive layer on one surface of the polymer dispersed liquid crystal film;
Adhering the one side on which the pressure-sensitive adhesive layer is formed to the surface of the transparent substrate for the smart window;
Method of manufacturing a transparent substrate for a smart window, characterized in that it comprises a.
In the method of manufacturing a transparent substrate for a smart window of claim 1,
Forming the pressure-sensitive adhesive layer on one surface of the transparent substrate for the smart window;
Adhering the one surface on which the pressure-sensitive adhesive layer is formed to the surface of the polymer dispersed liquid crystal film;
Method of manufacturing a transparent substrate for a smart window, characterized in that it comprises a.

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