KR20130126783A

KR20130126783A - Color particle for electrophoretic display device and electrophoretic display device including the same

Info

Publication number: KR20130126783A
Application number: KR1020120038985A
Authority: KR
Inventors: 엄성용; 김진욱; 김영주; 이화열
Original assignee: 엘지디스플레이 주식회사
Priority date: 2012-04-16
Filing date: 2012-04-16
Publication date: 2013-11-21
Also published as: KR101971068B1

Abstract

The present invention relates to an optical element comprising: a core having a reflection characteristic; And a color enhancing agent, wherein the color enhancing agent is represented by the following chemical formula.

Description

Technical Field [0001] The present invention relates to color particles for electrophoretic display devices and electrophoretic display devices including the same,

The present invention relates to an electrophoretic display device, and more particularly, to an electrophoretic display device which includes a coloring agent for coloring a polymer resin layer constituting a shell in a core / shell type particle and a coloring enhancer for improving reflection characteristics, And an electrophoretic display device including the colored particles.

2. Description of the Related Art In general, a liquid crystal display, a plasma display, and an organic electric field display have become mainstream in display devices. However, recently, various types of display devices have been introduced to meet the rapidly diversifying consumer needs.

Especially, it is accelerating the implementation of lightweight, thin, high efficiency, and full color video by enhancing the information utilization environment and portability. As a result, studies on electrophoretic display devices that merely combine the merits of paper and conventional display devices have been actively conducted.

The electrophoretic display device is attracting attention as a next generation display device which has advantages of excellent contrast ratio, visibility, fast response speed, and ease of portability.

In addition, the electrophoretic display device does not require a polarizing plate, a backlight unit, a liquid crystal layer, and the like, unlike the liquid crystal display device.

Hereinafter, a conventional electrophoretic display device will be described with reference to the accompanying drawings.

1 is a diagram schematically showing the structure of the electrophoretic display device for explaining the driving principle thereof.

1, the conventional electrophoretic display device 1 includes first and second substrates 11 and 36 and an ink layer 57 interposed between the first and second substrates 11 and 36 . The ink layer 57 includes a plurality of capsules 63 filled with a plurality of charged white particles 59 and black particles 61 through a condensation polymerization reaction.

A plurality of pixel electrodes 28 connected to a plurality of thin film transistors (not shown) are formed on the first substrate 11 for each pixel region (not shown). That is, the plurality of pixel electrodes 28 are selectively supplied with a positive voltage or a negative voltage.

When a voltage having a positive polarity or a negative polarity is applied to the ink layer 57, the charged white and black particles 59 and 61 in the capsule 63 are attracted toward the opposite polarity. That is, when the black particles 61 move upward, black is displayed, and when the white pigment 59 moves upward, white is displayed.

This electrophoretic display device 1 uses white particles 59 and black particles 61 and requires a color filter layer for color display.

2, which is a cross-sectional view schematically showing a conventional electrophoretic display device, a conventional electrophoretic display device 1 includes first and second substrates 11 and 36 which are opposed to each other, And an ink layer 57 interposed between the second substrates 11 and 36. The ink layer 57 includes first and second adhesive layers 51 and 53 made of a transparent material corresponding to the facing surfaces, , A common electrode 55 made of a transparent conductive material therebetween, and a plurality of capsules 63 filled with charged black particles 61 and white particles 59 are attached in a film form. Further, the black pigment 82 is charged with (+) polarity and the white pigment 84 is charged with (-) polarity, respectively.

The second substrate 36 is made of a transparent plastic material or glass. The first substrate 11 is made of an opaque stainless material. If necessary, a transparent plastic material or a transparent glass material is used .

At this time, a color filter layer 40 composed of red, green, and blue color filter patterns is formed on the lower front surface of the second substrate 36.

On the other hand, a gate wiring (not shown) and a data wiring (not shown) are formed on the first substrate 10 to define a pixel region P perpendicularly intersecting each other in a matrix form. A thin film transistor Tr, which is a switching element, is formed for each pixel region P at the intersection of wirings (not shown).

The thin film transistor Tr includes a gate electrode 14 extending from a gate wiring (not shown), a gate insulating film 16 covering the gate electrode 14, and an active layer A source electrode 20 which is in contact with the semiconductor layer 18 and extends in a data line (not shown), a source electrode 20 which is in contact with the semiconductor layer 18, And a drain electrode 22 spaced apart.

A protective layer 26 including a drain contact hole 27 exposing the drain electrode 22 is formed on the entire surface of the thin film transistor Tr.

A pixel electrode 28 connected to the drain electrode 22 through the drain contact hole 27 is formed on the passivation layer 26 to correspond to each pixel region P. [ The pixel electrode 28 is mainly composed of a transparent conductive material such as indium-tin-oxide (ITO) and indium-zinc-oxide (IZO).

The electrophoretic display device 1 having the above-described configuration uses external light including natural light or room light as a light source and applies a voltage to the pixels (not shown) selectively applied with (+) polarity or The electrode 28 induces a change in the position of the plurality of white pigments 59 and the black pigment 61 filled in the capsule 63 and the reflected light passes through the color filter layer 40 to realize a color image .

The electrophoretic display device described above requires a color filter layer for realizing color images, thereby increasing the thickness and weight of the electrophoretic display device.

In addition, there arises a problem that the production cost increases and the manufacturing process becomes complicated due to the formation of the color filter layer.

In the present invention, an electrophoretic display device capable of displaying a color image without a color filter layer is provided.

In order to solve the above-mentioned problems, the present invention provides a semiconductor device comprising: a core having a reflection characteristic; And a color enhancing agent, wherein the color enhancing agent is represented by the following chemical formula.

Wherein R 1 and R 2 are independently selected from the group consisting of hydrogen, an alkyl group having 1 to 16 carbon atoms, an alkenyl group having 2 to 21 carbon atoms, an aryl group having 6 to 21 carbon atoms, and an aralkyl group having 7 to 21 carbon atoms, Is selected from the group consisting of hydrogen, an alkyl group having 1 to 8 carbon atoms and an alkenyl group having 2 to 8 carbon atoms, and "B-" is any one of SO3-, NO2-, Cl-, Br-, PO3- and CN-.

Wherein the core is made of any one of titanium oxide, calcium carbonate, silicon oxide, zinc oxide, zirconia, manganese oxide, magnesium oxide, barium oxide and aluminum oxide.

Wherein the polymer resin layer is formed of any one of polyester, acrylic, polyamide, polyamic acid, alkyd and polyurethane.

In another aspect, the present invention provides a liquid crystal display comprising first and second substrates facing each other; A first electrode located on the first substrate; A second electrode located on the second substrate; And an ink layer disposed between the first and second substrates and including color particles charged with one of (+) or (-) polarity and black particles charged with another one of (+) or And the color particles include a core having a reflection characteristic, a core resin surrounding the core, a polymer resin, a colorant, and a color enhancing agent, wherein the color enhancing agent is represented by the following formula.

And the black particles have a larger size than the color particles.

The black particles have a diameter of 500 to 800 nm and the color particles have a diameter of 200 to 400 nm.

And barrier ribs formed on any one of the first and second substrates to provide a closed space.

In the present invention, the electrophoretic display device includes charged color particles, so that a color image can be realized without a color filter layer. Therefore, problems such as increase in thickness and weight due to the color filter layer, increase in manufacturing cost, complication of the manufacturing process, and the like can be prevented.

Further, the reflection characteristic is improved by the color enhancing agent contained in the polymer resin layer of the color particles, thereby realizing a high-brightness image.

In addition, high image quality can be achieved with improved image stability.

1 is a view for explaining a driving principle of an electrophoretic display device;
2 is a cross-sectional view schematically showing a conventional electrophoretic display device.
3 is a cross-sectional view schematically showing an electrophoretic display device according to an embodiment of the present invention.
4 is a graph showing the characteristics of color particles according to an embodiment of the present invention.

Hereinafter, an electrophoretic display device according to the present invention will be described with reference to the accompanying drawings.

3 is a cross-sectional view schematically showing an electrophoretic display device according to an embodiment of the present invention.

1, the electrophoretic display device 100 includes a first substrate 110, a second substrate 120 facing the first substrate 110, and a second substrate 110 formed on the first substrate 110. The electrophoretic display device 100 includes a first substrate 110, A first electrode 130 formed on the second substrate 120 and a second electrode 140 formed on the second substrate 120 and an ink layer 150 disposed between the first and second electrodes 130 and 140.

Although not shown, a gate line and a data line are defined in the first substrate 110 so as to define a pixel region perpendicularly intersecting each other in the form of a matrix, and at the intersection of the gate line and the data line, .

For example, the thin film transistor includes a gate electrode extending in a gate wiring, a gate insulating film covering the gate electrode, a semiconductor layer overlapping the gate electrode and composed of an active layer and an ohmic contact layer, A source electrode extending in the data line, and a drain electrode spaced apart from the source electrode. The active layer is made of pure amorphous silicon, and the ohmic contact layer is made of impurity amorphous silicon.

The first electrode 130 is connected to the thin film transistor and is located in each pixel region. The first electrode 130 may be in direct contact with the drain electrode of the thin film transistor. Meanwhile, a protective layer having a contact hole for exposing the drain electrode may be formed to cover the TFT, and the first electrode 130 may be formed on the protective layer. In this case, the first electrode 130 is connected to the drain electrode through the contact hole.

The first electrode 130 may be formed of a transparent conductive material such as indium-tin-oxide (ITO) or indium-zinc-oxide (IZO). Meanwhile, since the electrophoretic display device 100 uses external light such as natural light or indoor light as a light source, the first electrode 130 may include an opaque metal material.

The second electrode 140 faces the first electrode 130 and is located on the second substrate 120. Since the external light is reflected by the ink layer 150 and passes through the second electrode 140 to be displayed outside, the second electrode 130 is made of a transparent conductive material. For example, any one of indium-tin-oxide (ITO) and indium-zinc-oxide (IZO).

A partition wall 160 is formed at the boundary of the pixel region to separate the ink layer 150 for each pixel region.

That is, a plurality of pixel regions are defined on the first substrate 110, and the first electrodes 130 are independently formed in each pixel region, so that each pixel region is independently driven. At this time, the barrier ribs 160 are formed on one of the first and second substrates 110 and 120 to seal the respective pixel regions.

Since the electrophoretic display device 100 of the present invention includes the color particles 154, the color particles 154 of neighboring pixel regions should not be mixed with each other. For this purpose, To be sealed. The barrier ribs 160 may be formed of an organic insulating material.

The ink layer 150 is positioned between the first and second electrodes 130 and 140 and includes the color particles 154 and the black particles 156 in the electrophoretic medium 152 and the electrophoretic medium 152, . The ink layer 150 may be formed by any one of a screen printing method, a gravure printing method, an offset printing method, and a flexographic printing method.

For example, the color particles 154 may be charged with (+) polarity, and the black particles 156 may be charged with (-) polarity. Alternatively, the color particles 154 may be charged with (-) polarity, and the black particles 156 may be charged with (+) polarity. That is, the color particles 154 and the black particles 158 have different polarities.

The black particles 156 are charged with positive polarity and the black particles 156 are charged with positive polarity and the positive electrode 154 is charged with negative polarity as shown in FIG. Voltage is applied to the second electrode 140 and the black particles 156 are attracted toward the first electrode 130 and the color particles 154 are attracted to the second electrode 140. [ 140). Therefore, the external light is reflected by the color particles 154, so that the electrophoretic display device 100 implements a color image.

When a negative voltage is applied to the first electrode 130 and a positive voltage is applied to the second electrode 140, the black particles 156 are attracted toward the second electrode 140 The color particles 154 are attracted toward the first electrode 140. Therefore, the electrophoretic display device 100 implements a black image.

Accordingly, the electrophoretic display device 100 of the present invention has an advantage that a color image can be realized without a color filter layer.

The color particles 154 are in the form of a core and a shell enclosing the core. The core has reflective properties. For example, the core may be made of any one of titanium oxide, calcium carbonate, silicon oxide, zinc oxide, zirconia, manganese oxide, magnesium oxide, barium oxide and aluminum oxide.

The shell comprises a polymer resin layer, a colorant in the polymer resin layer, and a coloring enhancer. The shell may further comprise a charge control agent.

The polymer resin layer is formed of any one of a polymer resin such as polyester, acrylic, polyamide, polyamic acid, alkyd, and polyurethane.

In addition, the colorant may be an anthraquinone, diketopyrolopyrole, isoindolidone, axopyridone, azopyrolidone, diazodiarylide, A substance having a chromophore such as triarylmethane, phthalocyanine, quinophthalone, thioindigoid, thioxanthene or xanthene is used.

In addition, the color enhancing agent has about 10 to 300 weight percent, preferably 50 to 200 weight percent, based on the colorant. When the color enhancing agent is smaller than 10 weight percent, the reflectance is significantly lowered. When the color enhancing agent is larger than 300 weight percent, it is difficult to exhibit the color intended to be realized.

The color enhancing agent is characterized by being represented by the following general formula (1).

Formula 1

R 1 and R 2 are independently selected from the group consisting of hydrogen, an alkyl group having 1 to 16 carbon atoms, an alkenyl group having 2 to 21 carbon atoms, an aryl group having 6 to 21 carbon atoms, and an aralkyl group having 7 to 21 carbon atoms, Independently selected from the group consisting of hydrogen, an alkyl group having 1 to 8 carbon atoms, and an alkenyl group having 2 to 8 carbon atoms. "B-" is a complex salt having a negative sign and is any of SO ³ ^- , NO ² ^- , Cl ^- , Br ^- , PO ³ ^- , and CN ^- .

The black particles 156 include black, for example, carbon black. At this time, the black particles 158 have a larger size than the color particles 154. For example, the black particles 158 have a diameter of about 500 to 800 nm, and the color particles 154 have a diameter of about 200 to 400 nm. As such, since the size of the black particles 158 is larger than that of the color particles 154, it is possible to realize a high-quality image with improved bistability, i.e., image stability.

That is, the color particles 154 have a diameter of about 200 to 400 nm in order to reflect light of a visible light region wavelength (about 400 to 700 nm). At this time, if the size of the black particles 158 is equal to or smaller than the color particles 154, the bistability is degraded. Here, the bistability means that the first and second electrodes 130 and 140 have a voltage difference and the brightness is measured. Thereafter, the voltage difference between the first and second electrodes 130 and 140 is removed, When the brightness is measured, the brightness also means the difference. That is, when the lightness difference is small, the electrophoretic display device 100 has a stable driving state with excellent high bistability.

The color enhancing agent of the color particles 154 described above exhibits fluorescence properties, whereby the color particles 154 have a high reflectance. Therefore, a high-luminance image can be realized. Further, the effect of improving the bistability due to the size of the color particles 154 and the black particles 156 is obtained.

Hereinafter, color particles and black particles are prepared and their properties are evaluated.

1. Experimental Example 1

2.0 grams of polyester was dissolved in 45.0 grams of methylene chloride and 3.0 grams of titanium oxide was mixed with the binder resin. Then, the mixture was placed in a glass bottle filled with 60 volume percent of 0.5 mm zirconia beads and dispersed for 12 hours to obtain an average particle size A white pigment dispersion having a diameter of 200 nm was prepared.

After separating the zirconia beads from the white pigment dispersion thus prepared, 0.24 grams of the yellow colorant shown in the following chemical formula 2, 0.06 grams of the color enhancing agent shown in the following chemical formula 3, 0.01 grams of cetyltrimethylammonium bromide as the charge control agent, and methylene chloride 280.0 Gram was added to prepare a solution of the internal phase.

The inner solution thus prepared was added dropwise to 600.0 grams of an isoparaffin-based solvent (isopar G) to prepare electrophoretic particles. Thereafter, methylene chloride and isoparaffinic solvent were distilled at 70 ° C., concentrated, and then centrifuged and washed with an isoparaffinic solvent to prepare a yellow electrophoretic particle suspension so that the concentration was 36 weight percent.

(2)

(3)

2. Experimental Example 2

After separating the zirconia beads in the white pigment dispersion thus prepared, 0.04 g of the blue colorant represented by the following chemical formula 4, 0.06 g of the color enhancing agent shown in the chemical formula 3, 0.01 g of cetyltrimethylammonium bromide as the charge control agent and methylene chloride 280.0 Gram was added to prepare a solution of the internal phase.

The inner solution thus prepared was added dropwise to 600.0 grams of an isoparaffin-based solvent (isopar G) to prepare electrophoretic particles. After that, methylene chloride and isoparaffinic solvent were distilled at 70 ° C. and concentrated. The concentrate was washed by centrifugation, and a green electrophoretic particle suspension was prepared so as to have a concentration of 36 wt% by using an isoparaffin solvent. Because the color enhancer has a weak yellow color, it becomes green with the blue colorant.

Formula 4

3. Comparative Example 1

After separating the zirconia beads from the white pigment dispersion thus prepared, 0.24 grams of the yellow coloring agent represented by the above formula (2), 0.01 grams of cetyltrimethylammonium bromide as a charge control agent, and 280.0 grams of methylene chloride as a solvent were added to form an internal phase Solution. (The color enhancing agent of Experimental Example 1 was not added)

4. Comparative Example 2

After separating the zirconia beads from the white pigment dispersion thus prepared, 0.04 g of the blue colorant shown in the formula (4), 0.01 g of cetyltrimethylammonium bromide as a charge control agent, and 280.0 g of methylene chloride as a solvent were added to form an internal phase Solution. (The color enhancing agent of Experimental Example 2 was not added)

The inner solution thus prepared was added dropwise to 600.0 grams of an isoparaffin-based solvent (isopar G) to prepare electrophoretic particles. After that, methylene chloride and isoparaffinic solvent were distilled at 70 ° C. and concentrated. The concentrate was washed by centrifugation, and a green electrophoretic particle suspension was prepared so as to have a concentration of 36 wt% by using an isoparaffin solvent.

5. Preparation of black particles

As the binder resin, polyester 16.0 ram and zinc salicylic acid 4.0 ram as a charge control agent were dissolved in 260.0 grams of methylene chloride, and 4.0 grams of carbon black was mixed. Then, 0.8 mm zirconia beads were filled in a 60% Followed by dispersion to prepare a black pigment dispersion having an average particle size of 150 nm. 1200 g of methylene chloride was mixed with the black pigment dispersion, stirred, and added dropwise to 1800 g of an isoparaffin-based solvent to prepare electrophoretic particles. Thereafter, methylene chloride was distilled off at 60 ° C., and the mixture was washed by centrifugation. A black electrophoretic particle dispersion was prepared using an isoparaffinic solvent so as to have a concentration of 36 wt%.

The dispersion liquid and the black particle dispersion prepared in Experimental Examples 1 and 2 and Comparative Examples 1 and 2 were injected between a first substrate and a second substrate (2 inches × 2 inch) each having a partition and an ITO electrode, The color coordinates and the light reflectance were measured using a spectroscopic colorimeter (CM-5, Konica Minolta) set to a D65 light source continuously for 10 minutes while the pause was 2 seconds. In Table 1 below, ΔL represents the brightness difference between the initial brightness and 10 minutes, and shows the stability of the image, that is, the stability of the image.

Color state Black state reflectivity CIE (x) CIE (y) ΔL reflectivity CIE (x) CIE (y) ΔL Experimental Example 1 48.37 0.3777 0.5062 -1.1 3.6 0.2891 0.3033 0.3 Experimental Example 2 37.73 0.2813 0.3958 -1.3 3.8 0.2785 0.3054 0.8 Comparative Example 1 40.41 0.3708 0.4487 -1.6 4.5 0.2854 0.2968 1.1 Comparative Example 2 33.65 0.2832 0.4001 -1.8 4.9 0.2805 0.2995 2.5

4 is a graph showing the characteristics of color particles. In FIG. 4, A is the color particle of Experimental Example 1, C is the color particle of Experimental Example 2, B is the color particle of Comparative Example 1, and D is the characteristic graph of Comparative Example 2.

Referring to Table 1 together with FIG. 4, the color particles of Experimental Example 1 and Experimental Example 2 have high reflectance and can realize an image of brightness. That is, from the graphs of Experimental Example 1 and Comparative Example 1, in Experimental Example 1 including the color enhancing agent, the reflectance rapidly increases at a wavelength of about 500 nm. Also in Experimental Example 2 including a color enhancing agent, it has a higher reflectance than Comparative Example 2.

In addition, in the case of Experimental Example 1 and Experimental Example 2, it has a high color purity because it has a higher CIE (y) value than Comparative Example 1 and Comparative Example 2, respectively.

In addition, Experimental Example 1 and Experimental Example 2 have a lower DELTA L value than Comparative Examples 1 and 2. That is, it can be seen that, in the case of Experimental Example 1 and Experimental Example 2 including the color enhancing agent, the brightness of the voltage applied state (ON) is maintained even after the voltage is removed (OFF). A stable image can be provided since the voltage applied state (ON) is maintained for a predetermined time even when the voltage is removed (OFF).

When the color particles containing the color enhancing agent of the present invention are used, the bistability is improved, and in particular, the size of the color particles can be made smaller than that of the black particles to further improve the bistability.

As described above, the color particles of the present invention are composed of a core having a reflection characteristic and a shell surrounding the core, wherein the shell is made of a colorant and a color enhancing agent. Particularly, the color enhancing agent is represented by the above formula (1), and the reflection characteristic can be improved to realize a high brightness image.

In addition, it is possible to realize a high-quality image by improving the bistability due to the color enhancing agent, and by making the size of the color particles smaller than that of the black particles, the bistability is further improved.

The electrophoretic display device of the present invention using color particles including a color enhancing agent can realize a color image even without a color filter layer. Therefore, the thickness and weight of the electrophoretic display device can be prevented from increasing by the color filter layer. Further, since the step for forming the color filter layer is omitted, the manufacturing cost can be reduced and the manufacturing process can be simplified.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention as defined in the appended claims. It can be understood that

100: electrophoretic display device 101: first substrate
120: second substrate 130: first electrode
140: second electrode 150: ink layer
152: electrophoresis medium 154: colored particles
156: black particles 160: partition wall

Claims

A core having reflection characteristics;
A core, and a polymeric resin, a colorant, and a color enhancing agent,
Wherein the color enhancing agent is represented by the following formula.

The method according to claim 1,
Wherein the core is made of any one of titanium oxide, calcium carbonate, silicon oxide, zinc oxide, zirconia, manganese oxide, magnesium oxide, barium oxide and aluminum oxide.

The method according to claim 1,
Wherein the polymer resin layer is made of any one of polyester, acrylic, polyamide, polyamic acid, alkyd, and polyurethane.

A first substrate and a second substrate facing each other;
A first electrode located on the first substrate;
A second electrode located on the second substrate;
And an ink layer disposed between the first and second substrates and including color particles charged with one of (+) or (-) polarity and black particles charged with another one of (+) or and,
Wherein the color particles include a core having a reflection characteristic, a core resin surrounding the core, a polymer resin, a colorant, and a color enhancing agent, wherein the color enhancing agent is represented by the following formula.

5. The method of claim 4,
Wherein the core is made of any one of titanium oxide, calcium carbonate, silicon oxide, zinc oxide, zirconia, manganese oxide, magnesium oxide, barium oxide and aluminum oxide.

5. The method of claim 4,
Wherein the polymer resin layer is made of any one of polyester, acrylic, polyamide, polyamic acid, alkyd, and polyurethane.

5. The method of claim 4,
Wherein the black particles have a larger size than the color particles.

5. The method of claim 4,
Wherein the black particles have a diameter of 500 to 800 nm and the color particles have a diameter of 200 to 400 nm.

5. The method of claim 4,
And a barrier provided on one of the first and second substrates to provide a closed space.