KR102316335B1 - Pdlc composition and pdlc film using thereof - Google Patents

Abstract

The present invention relates to a polymer dispersed liquid crystal composition and a polymer dispersed liquid crystal film using the same, and more particularly, PETA (pentaerythritol triacrylate) or DPHA (dipentaerythritol hexaacrylate) Polymer dispersed liquid crystal that can exhibit sufficient performance even when bent to a curved surface while securing functions such as turbidity, transmittance, and wide viewing angle in the state, and can reduce the dropout phenomenon of liquid crystal in a high temperature state or in a curved state It relates to a composition and a polymer dispersed liquid crystal film using the same.
The polymer dispersed liquid crystal composition according to the present invention is a polymer dispersed liquid crystal composition comprising a polymer, a nematic liquid crystal mixture, and a photoinitiator, wherein the polymer includes PETA (pentaerythritol triacrylate) or DPHA (dipentaerythritol hexa acrylate) is mixed.

Description

Polymer dispersed liquid crystal composition and polymer dispersed liquid crystal film using same {PDLC COMPOSITION AND PDLC FILM USING THEREOF}

The present invention relates to a polymer dispersed liquid crystal composition and a polymer dispersed liquid crystal film using the same, and more particularly, PETA (pentaerythritol triacrylate) or DPHA (dipentaerythritol hexaacrylate) Polymer dispersed liquid crystal that can exhibit sufficient performance even when bent to a curved surface while securing functions such as turbidity, transmittance, and wide viewing angle in the state, and can reduce the dropout phenomenon of liquid crystal in a high temperature state or in a curved state It relates to a composition and a polymer dispersed liquid crystal film using the same.

In general, a PDLC composite film, which is a PDLC display device, is a display device in which fine liquid crystal droplets dispersed in a matrix of a polymer material respond to an externally applied voltage to display information in the form of scattering or transmission.

The polymer dispersed liquid crystal composite film having the above functions can exhibit the liquid crystal function in a flexible film compared to the conventional liquid crystal display device, and can not only dramatically improve the light utilization efficiency but also increase the area, which is impossible with liquid crystal alone. It is attracting attention as a new display material because it is possible to develop the function that has been previously used.

The liquid crystal molecules and the polymer in the polymer dispersed liquid crystal composite film device cause phase separation to form small liquid crystal droplets between the polymer matrix. A difference occurs between the refractive index of the drop and the refractive index of the polymer, and as a result, the incident light is scattered opaquely, and when a voltage is applied, the liquid crystal molecules in the liquid crystal drop align in one direction and become equal to the refractive index of the polymer. As a result, incident light is transparently transmitted through the specimen. In the polymer dispersed liquid crystal composite film, the display is driven in two states, the light transmitting state and the scattered light state depending on the presence or absence of voltage.

A polymer dispersed liquid crystal (PDLC, hereinafter referred to as 'PDLC') composition having the above properties generally consists of a liquid crystal, a monomer, a photoinitiator, and an oligomer, and a PDLC film using this composition is a transparent electrode ( Indium Tin). Oxide, ITO) is formed between two coated transparent films. When the substrate on which the transparent electrode is formed is irradiated with ultraviolet rays and heat, the oligomer and the monomer undergo a curing reaction by the photoinitiator, thereby forming a polymer matrix, and the liquid crystal is separated to form liquid crystal droplets.

A film product manufactured in the form of a film using the PDLC composition having the above characteristics is attached to glass or used as a blind film. There is a problem in that performance such as transmittance is significantly lowered.

In addition, when a film product manufactured in the form of a film using the PDLC composition is repeatedly or continuously placed or bent in a high temperature state, the liquid crystal of the liquid crystal composite film is separated and dislodged or moved, so that the performance of turbidity or transmittance for each part is reduced. It has different disadvantages.

Republic of Korea Patent Publication No. 10-2004-0043230 Republic of Korea Patent Publication No. 10-0812276

The present invention has been devised in recognition of the above points, and by mixing PETA (pentaerythritol triacrylate) or DPHA (dipentaerythritol hexaacrylate) with a polymer, turbidity, transmittance, wide viewing angle, etc. A polymer dispersed liquid crystal composition and a polymer dispersed liquid crystal film using the same, which can exhibit sufficient performance even in a curved state while ensuring the function of is to provide

In order to achieve the above object, the polymer dispersed liquid crystal composition according to the present invention is a polymer dispersed liquid crystal composition comprising a polymer, a nematic liquid crystal mixture, and a photoinitiator, wherein the polymer contains PETA (pentaerythritol triacrylate) Or DPHA (dipentaerythritol hexaacrylate) is characterized in that it is mixed.

In addition, the polymer dispersed liquid crystal composition according to the present invention includes NOA65 (urethane oligomer), EB230 (acrylate oligomer), EB264 (acrylate oligomer), IBOA (isobornyl acrylate), EHA (ethylhexyl acrylate), ) is included.

On the other hand, the polymer dispersed liquid crystal film using the polymer dispersed liquid crystal composition according to the present invention includes a conductive film lower plate, a polymer dispersed liquid crystal composite film coated with the polymer dispersed liquid crystal composition on the conductive film lower plate, and the polymer It is characterized in that it comprises a conductive film upper plate laminated to the dispersion type liquid crystal composite film.

The polymer dispersed liquid crystal film using the same relates to a polymer dispersed liquid crystal composition and a polymer dispersed liquid crystal film using the same, and more particularly, PETA (pentaerythritol triacrylate) or DPHA (dipentaerythritol hexaacrylate) to the polymer. ), while securing functions such as turbidity, transmittance, and wide viewing angle in a flat state, it can exhibit sufficient performance even when bent to a curved surface, as well as reduce liquid crystal dropout in a high temperature state or in a curved state. has an advantage

1 is a graph showing a change in transmittance according to a driving voltage for a polymer dispersed liquid crystal film using a polymer dispersed liquid crystal composition according to an embodiment of the present invention;
2 is a diagram conceptually illustrating a transmittance test method in a curved state for a polymer dispersed liquid crystal film using a polymer dispersed liquid crystal composition according to an embodiment of the present invention; FIG.
3 is a graph showing the difference in transmittance in a curved state with different diameters and transmittance in an OFF state for a polymer dispersed liquid crystal film using a polymer dispersed liquid crystal composition according to an embodiment of the present invention;
4 is a view conceptually illustrating a state of a specimen for measuring liquid crystal loss of a polymer dispersed liquid crystal film using a polymer dispersed liquid crystal composition according to an embodiment of the present invention; FIG.

Hereinafter, a polymer dispersed liquid crystal composition according to the present invention and a polymer dispersed liquid crystal film using the same will be described in more detail with reference to the drawings and examples.

1 is a graph showing a change in transmittance according to a driving voltage for a polymer dispersed liquid crystal film using a polymer dispersed liquid crystal composition according to an embodiment of the present invention, and FIG. 2 is a polymer dispersed liquid crystal film according to an embodiment of the present invention. It is a diagram conceptually showing a transmittance test method in a curved state for a polymer dispersed liquid crystal film using a liquid crystal composition, and FIG. 3 is a polymer dispersed liquid crystal film using a polymer dispersed liquid crystal composition according to an embodiment of the present invention. It is a graph showing the difference in transmittance in a curved surface state running a diameter for that and in an OFF state, and FIG. 4 is a measurement of liquid crystal loss of a polymer dispersed liquid crystal film using a polymer dispersed liquid crystal composition according to an embodiment of the present invention. It is a diagram conceptually showing the state of the specimen for

The polymer dispersed liquid crystal composition according to the present invention is a mixture containing a polymer, a nematic liquid crystal mixture, and a photoinitiator. In particular, the polymer dispersed liquid crystal composition according to the present invention is a polymer dispersed liquid crystal composition comprising a monomer having many functional groups in the polymer, PETA (pentaerythritol triacrylic rate) or DPHA (dipentaerythritol hexaacrylate) is characterized in that it is mixed.

More specifically, the polymer is NOA65 (urethane oligomer), EB230 (acrylate oligomer), EB264 (acrylate oligomer), IBOA (isobornyl acrylate), EHA (ethylhexyl acrylate), HDDA (hexanediol diacrylate). ), TPGDA (tripropylene glycol diacrylate), PETA (pentaerythritol triacrylate), or DPHA (dipentaerythritol hexaacrylate) is characterized in that part or all of it is mixed.

In addition, in the polymer mixture, 1 part by weight of a photoinitiator is mixed with respect to 100 parts by weight of the polymer mixture in which the material is mixed, and the nematic liquid crystal mixture is (polymer): (nematic liquid crystal mixture) = (4 to 6): (6 ~ 4) It is characterized in that it is mixed in a weight ratio.

The polymer dispersed liquid crystal film using the polymer dispersed liquid crystal composition composed as described above includes a conductive film lower plate, a polymer dispersed liquid crystal composite film coated with the polymer dispersed liquid crystal composition of claim 4 on the conductive film lower plate, and the polymer dispersed It is characterized in that it comprises a conductive film upper plate laminated to the type liquid crystal composite film.

<Example 1: Blending of polymer and polymer dispersed liquid crystal composition>

Polymer formulations constituting the polymer dispersed liquid crystal composition are shown in Table 1 below.

polymer NOA65
wt% EB230
wt% EB264
wt% IBOA
wt% EHA
wt% HDDA
wt% TPGDA
wt% PETA
wt% DPHA
wt% control 20 20 20 20 20 test group 20 20 20 15 15 10 test group 2 20 20 20 15 15 10 Test group 3 20 20 20 15 15 10 test group 4 20 20 20 15 15 10 test group 5 20 20 20 15 15 5 5 test group 6 20 20 20 15 15 5 5 test group 7 20 20 20 15 15 5 5

1 part by weight of a photoinitiator (irgaqure 184) was mixed with the polymer obtained in Test Groups 1 to 7 and the control group with respect to 100 weight of the polymer, and nematic liquid crystal E7 (E7 nematic liquid crystal from Merk) was added in a mixing ratio (polymer: nematic liquid crystal) = (4:6) was mixed in a weight ratio to blend a polymer dispersed liquid crystal composition.

<Example 2: Preparation of polymer dispersed liquid crystal film specimen>

A 20 cm ball spacer was added to the polymer dispersed liquid crystal composition mixture formulated in Example 1, coated on the 188 ITO film as a conductive film lower plate, and then the ITO film on the conductive film upper plate was laminated, and UV rays were irradiated. A polymer dispersed liquid crystal composite film was prepared by a PIPS (polymerization induced phase separation) method.

A specimen having a size of 5 cm × 10 cm was cured under low pressure UV with a light quantity of 100 W/cm 2 to prepare a specimen.

<Example 3: Transmittance, turbidity and curved transmittance and liquid crystal dropout test>

For each specimen prepared as described above, haze at 110V driving voltage ON/OFF was measured with COH-400 manufactured by Nippon Denshoku and summarized in Table 2 below.

Optical Characteristics OFF Haze ON Haze control 80.59 3.19 test group 1 83.14 4.57 test group 2 86.62 6.25 Test group 3 72.86 8.98 test group 4 70.55 10.18 test group 5 76.95 7.12 test group 6 74.29 6.24 test group 7 72.42 8.17

According to Table 2, the test group showed similar or slightly inferior performance on ON/OFF turbidity change compared to the control group. In the case of Test Group 4, the turbidity in the ON state was measured to be 10.18%, and it was confirmed that the transmittance was slightly lowered to less than 90%.

For each of the specimens prepared as described above, transmittance according to the driving voltage was measured using an Avaspec-2048L spectrophotometer manufactured by Avantes, and summarized in Table 3 below, and FIG. 1 is a graph showing this.

drive voltage 0V 10V 20V 30V 40V 50V 60V 110V control 4.41 9.88 54.58 77.49 81.75 81.81 81.81 86.81 test group 1 1.86 5.68 44.15 69.03 80.2 80.39 80.43 85.43 test group 2 0.95 6.25 16.49 48.12 66.05 77.58 78.74 83.75 Test group 3 12.14 14.9 16.71 25.65 41.11 56.24 74.08 81.02 test group 4 14.45 15.15 16.9 24.22 39.29 56.85 64.44 79.82 test group 5 8.05 8.06 19.73 39.06 54.76 65.12 75.49 82.88 test group 6 10.71 10.71 16.71 25.65 41.11 56.24 68.75 83.76 test group 7 12.58 12.6 15.8 24.5 32.22 48.73 60.15 81.83

According to Table 2 and FIG. 1, in the case of Test Group 1 and Test Group 2, the transmittance was confirmed to be 50% or more when a driving voltage of 30V was applied, and it was evaluated that the function was secured even at a low voltage driving voltage, and that of Test Groups 4 to 7 In this case, it was confirmed that the transmittance exceeded 50% when the driving voltage was 50 to 60V or higher.

However, it was confirmed that both the test group and the comparison group had a transmittance of 80% or more at 110V, which is a normal driving voltage, to ensure sufficient performance.

Next, a change in transmittance performance when deformed to a curved surface was measured for each specimen prepared as described above.

In order to measure the transmittance according to the curved surface, a specimen obtained by cutting a flat polymer-modified liquid crystal film was attached to a cylindrical bottle with diameters of 14Cm, 12Cm, 10Cm, 8Cm, and 6Cm. The transmittance was measured by setting the pressure and curvature applied to the film. 2 is a conceptual diagram illustrating a state of measuring transmittance according to a curved surface. The transmittance was measured at the center of the film attached to the cylinder using an Avaspec-2048L spectrophotometer manufactured by Avantes. Table 4 is a summary by measuring transmittance according to the curved surface.

Optical Characteristics OFF state
transmittance 16cm 14cm 12cm 10cm 8cm 6cm control 4.41 4.86 6.85 10.75 24.73 29.82 31.05 test group 1 1.86 1.9 3.13 8.45 16.08 19.26 19.79 test group 2 0.95 1.42 2.94 3.19 11.86 14.66 16.04 Test group 3 12.14 12.14 12.14 13.76 14.85 15.43 15.43 test group 4 14.45 14.45 14.45 14.76 14.99 16.23 16.55 test group 5 8.05 8.15 10.74 11.02 11.3 12.46 13.85 test group 6 10.71 10.72 11.13 11.55 13.41 14.86 14.94 test group 7 12.58 12.6 13.76 13.82 14.12 16.86 17.01

Referring to Table 3, it was confirmed that the smaller the diameter of the circle, the higher the transmittance because the film had more pressure and high curvature.

On the other hand, the small difference between the transmittance in each curved surface and the transmittance in the OFF state (transmittance in the curved state - transmittance in the OFF state) means that the performance of the film is small even if it is deformed into a curved surface. In order to evaluate this, the difference between the transmittance in each curved surface and the transmittance in the OFF state was calculated and shown in FIG. 3 . According to FIG. 3 , in Test Groups 4 to 7, it was confirmed that the transmittance difference at the diameter of 6 cm with the greatest curvature of the curved surface was formed within 5% or about 5%.

For each of the specimens prepared as described above, the degree of liquid crystal loss, which is a disadvantage of the PDLC film, which is generated when the PDLC film is placed at a high temperature or is bent to a curved surface, was tested.

In the test, liquid crystal loss was observed for each specimen after 240 hours at a temperature of 120 °C. Since the liquid crystal moves from the central part to the cut section due to the flow of the liquid crystal, the liquid crystal dropout was measured using the size of the part that became transparent at the cut edge as a measure. 4 is a conceptual diagram illustrating a state in which liquid crystal is removed from the edge of the specimen. Table 5 summarizes the measured sizes.

missing characteristic t(cm) control -3.2 test group 1 -2.5 test group 2 -2 Test group 3 -0.4 test group 4 -0.1 test group 5 -One test group 6 -0.7 test group 7 -0.6

In the test results, in Test Groups 4 to 7, the size of the edge was measured to be remarkably small, and it is seen that the liquid crystal does not come off.

From the above-described embodiment, as the content of PETA or DPHA, which is a monomer having many functional groups in the compounding ratio, increases, the difference in transmittance of the off-state according to the curvature tends to decrease, but the driving voltage tends to increase.

The polymer dispersed liquid crystal composition and the polymer dispersed liquid crystal film using the same as described above and shown in the drawings are only examples for carrying out the present invention, and should not be construed as limiting the technical spirit of the present invention. The protection scope of the present invention is defined only by the matters described in the claims below, and improved and changed embodiments without departing from the gist of the present invention are obvious to those of ordinary skill in the art to which the present invention belongs. It will be said that it falls within the protection scope of the present invention.

Claims (3)

In the polymer dispersion type liquid crystal composition comprising a polymer composition blend, a nematic liquid crystal mixture, and a photoinitiator,
The polymer composition formulation contains NOA65 (urethane oligomer) 20 wt%, EB230 (acrylate oligomer) 20 wt%, EB264 (acrylate oligomer) 20 wt%, IBOA (isobornyl acrylate) 15 wt%, EHA (ethylhexyl acrylate) 15 wt% , DPHA (dipentaerythritol hexaacrylate) 10wt% is mixed,
1 part by weight of the photoinitiator is mixed with respect to 100 weight of the polymer composition formulation,
The polymer composition mixture and the nematic liquid crystal mixture are mixed in a weight ratio of 4:6, a polymer dispersed liquid crystal composition. In the polymer dispersion type liquid crystal composition comprising a polymer composition blend, a nematic liquid crystal mixture, and a photoinitiator,
The polymer composition formulation contains NOA65 (urethane oligomer) 20 wt%, EB230 (acrylate oligomer) 20 wt%, EB264 (acrylate oligomer) 20 wt%, IBOA (isobornyl acrylate) 15 wt%, EHA (ethylhexyl acrylate) 15 wt% , DPHA (dipentaerythritol hexaacrylate) 5wt%, HDDA (hexanediol diacrylate), TPGDA (tripropylene glycol diacrylate), PETA (pentaerythritol triacrylate) any one selected from 5wt% is mixed,
1 part by weight of the photoinitiator is mixed with respect to 100 weight of the polymer composition formulation,
The polymer composition mixture and the nematic liquid crystal mixture are mixed in a weight ratio of 4:6, a polymer dispersed liquid crystal composition. a conductive film lower plate;
A polymer dispersed liquid crystal composite film coated with the polymer dispersed liquid crystal composition of claim 1 or 2 on the lower plate of the conductive film;
A polymer dispersed liquid crystal film comprising a conductive film upper plate laminated to the polymer dispersed liquid crystal composite film.

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