KR20130047026A - Electrophoretic medium, electrophoretic dispaly device using the same and method for fabricating the electrophoretic dispaly device - Google Patents
Electrophoretic medium, electrophoretic dispaly device using the same and method for fabricating the electrophoretic dispaly device Download PDFInfo
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- KR20130047026A KR20130047026A KR1020110111784A KR20110111784A KR20130047026A KR 20130047026 A KR20130047026 A KR 20130047026A KR 1020110111784 A KR1020110111784 A KR 1020110111784A KR 20110111784 A KR20110111784 A KR 20110111784A KR 20130047026 A KR20130047026 A KR 20130047026A
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- electrophoretic
- fluid
- electrophoretic medium
- liquid crystal
- insulating fluid
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- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour
- G02F1/165—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour based on translational movement of particles in a fluid under the influence of an applied field
- G02F1/166—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour based on translational movement of particles in a fluid under the influence of an applied field characterised by the electro-optical or magneto-optical effect
- G02F1/167—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour based on translational movement of particles in a fluid under the influence of an applied field characterised by the electro-optical or magneto-optical effect by electrophoresis
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D57/00—Separation, other than separation of solids, not fully covered by a single other group or subclass, e.g. B03C
- B01D57/02—Separation, other than separation of solids, not fully covered by a single other group or subclass, e.g. B03C by electrophoresis
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- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour
- G02F1/165—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour based on translational movement of particles in a fluid under the influence of an applied field
- G02F1/1675—Constructional details
- G02F2001/1678—Constructional details characterised by the composition or particle type
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- Nonlinear Science (AREA)
- Health & Medical Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- Molecular Biology (AREA)
- General Physics & Mathematics (AREA)
- Optics & Photonics (AREA)
- Electrochromic Elements, Electrophoresis, Or Variable Reflection Or Absorption Elements (AREA)
Abstract
Description
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophoretic display, and more particularly, to an electrophoretic medium having low volatility and low viscosity, an electrophoretic display using the same, and a manufacturing method thereof.
In the electrophoretic display (EPD), charged particles dispersed in an insulating fluid induce electrophoresis on the display surface according to the action of an electric field, and display using the optical properties of the insulating fluid and the charged particles. The electrophoretic display applies a voltage to a pair of opposing electrodes to display white when the white particles collect on the display surface and black when the black particles collect. Unlike liquid crystal displays, electrophoretic displays do not use a backlight light source, have low power consumption, and have memory characteristics capable of maintaining a display state without power supply.
Conventional electrophoretic display devices have a problem that the response speed is about 300 ms to 700 ms due to the viscous resistance of the insulating fluid because the electrophoretic particles are moved in the insulating fluid.
In addition, a conventional electrophoretic display device mainly uses a screen printing process or an ink get printing process to inject an electrophoretic medium including electrophoretic particles in an insulating fluid into a partition wall. However, since the volatility of the insulating fluid is high in the conventional electrophoretic medium, there is a problem that a viscosity deviation occurs for each location due to a local increase in viscosity during the screen printing process or the ink jet printing process. Accordingly, there is a problem that the conventional electrophoretic medium is difficult to apply to the large-area model due to unfilling and change in specific gravity of the ink.
The present invention has been made to solve the conventional problems, the problem to be solved by the present invention is an electrophoretic medium having low volatility and low viscosity characteristics using a self-assembled liquid crystal, an electrophoretic display device using the same and manufacturing To provide a way.
In order to solve the above problems, the electrophoretic medium according to the present invention and the insulating fluid; Electrophoretic particles dispersed in the insulating fluid; The insulating fluid includes a dispersion fluid and a self-assembled liquid crystal; It is characterized in that the content ratio of the liquid crystal to the insulating fluid is in the range of 2.5wt% to 30wt% so as to have a low volatility and low viscosity characteristics than when not containing the liquid crystal.
The self-assembled liquid crystal has a structure in which a cyano group and a flexible spacer are bonded to both sides based on mesogen, as shown in Formula 1 below.
≪ Formula 1 >
In the flexible spacer, it is characterized in that it is even in the range of n = 4 ~ 12.
The dispersion fluid may be a fluorine-based single fluid or a mixed fluid in which the fluorine-based fluid and the saturated hydrocarbon-based fluid are mixed.
The electrophoretic medium has a low viscosity in the range of 2.1 cP to 3.6 cP at room temperature, has a response time in the range of 20 ms to 120 ms, and has a volatility range of 30% to 58% in the screen printing process.
An electrophoretic display device according to the present invention comprises: a plurality of pixels into which the electrophoretic medium is injected; First and second electrodes formed to apply an electric field to each of the plurality of pixels; The electrophoretic particles include white or color electrophoretic particles having a first charge and black electrophoretic particles having a second charge.
A method of manufacturing an electrophoretic display device according to the present invention includes the steps of manufacturing the electrophoretic medium; Forming a partition on the lower substrate on which the first electrode is formed to form respective pixel spaces; Injecting the electrophoretic medium into the pixel space to form each pixel; Bonding the upper substrate on which the second electrode is formed on the lower substrate on which each pixel is formed;
The electrophoretic medium is injected using spin coating, slit coating, dip coating, inkjet, roll-to-roll coating, or screen printing process.
The electrophoretic medium according to the present invention has low volatility and low viscosity by containing a liquid crystal in a halocarbon-based single dispersion fluid, or by containing a liquid crystal in a halocarbon-based fluid and isoparaffin-based mixed dispersion fluid. Accordingly, by controlling the low volatility and low viscosity of the electrophoretic medium at the same time, the local viscosity increase that can occur in the processing process including the printing process, the viscosity deviation by position within the process time, the fluid not filled and specific gravity change, the fluid refill, The process margin can be widely operated by solving the conventional problem of large area application. In addition, since the printing process margin can be controlled by adjusting the even number of flexible spacers contained in the liquid crystal in the range of 4 to 12, the process efficiency can be increased in terms of manufacturing process, and it can be applied to a large-area model.
In addition, as the viscosity of the electrophoretic medium according to the present invention decreases, the response time of the electrophoretic display may be reduced to about 30 to 120 ms. Therefore, the electrophoretic medium and the electrophoretic display apparatus using the same according to the present invention not only can display a video through a quick response speed, but also provide a quick response speed even when a touch panel is mounted on the electrophoretic display device. Respond quickly to commands.
1 is a view showing the structure of a liquid crystal applied to an electrophoretic medium according to the present invention.
FIG. 2 is a graph showing the thermal characteristics of liquid crystals versus the number of flexible spacers in the liquid crystal shown in FIG. 1.
3 is a view showing a printing process of the electrophoretic medium according to the present invention.
Figure 4 is a graph showing the viscosity relationship for the shear rate of the electrophoretic medium according to the present invention.
5 is a cross-sectional view illustrating a structure of a monoelectrophoretic display device to which an electrophoretic medium according to the present invention is applied.
6 is a cross-sectional view illustrating a structure of a color electrophoretic display device to which an electrophoretic medium according to the present invention is applied.
The electrophoretic medium according to the present invention includes an insulating fluid having low volatility and low viscosity characteristics, white electrophoretic particles or color electrophoretic particles dispersed in the insulating fluid, and black electrophoretic particles.
The insulating fluid uses a fluoro-based fluid, for example, a halocarbon-based single dispersion fluid. Alternatively, the insulating fluid uses a mixed dispersion fluid in which a halocarbon series fluid and a saturated hydrocarbon series isoparaffin series fluid are mixed. The fluorine-based dispersion fluid has a low dielectric constant and low viscosity in the range of 2 to 30, and has a specific gravity of 1.75 g / ml or more to prevent sedimentation of high specific gravity white electrophoretic particles. There is no chemical interaction with the polyester resin used to minimize the deformation of the electrophoretic particles.
In particular, the insulating fluid includes a self-assembled liquid crystal having the structure shown in FIG. 1 in order to solve the conventional high volatility and thereby the viscosity increase problem.
The liquid crystal shown in FIG. 1 includes a cyano group bonded to the left side of the mesogen and a flexible spacer coupled to the right side of the mesogen based on mesogen which is a basic unit. . In the flexible spacer, n is determined as an even number having good physical properties in the range of 4 to 12. The smaller the number of n, the lower the molecular weight, the lower the viscosity.
FIG. 2 is a graph illustrating the thermal characteristics of the liquid crystal shown in FIG. 1 and showing a transition temperature according to the number n of flexible spacers.
In FIG. 2, T Ni represents a temperature transitioned from a solid to nematic, and Ti represents a temperature transitioned from an nematic to anisotropic. Referring to FIG. 2, it can be seen that the transition temperature (T Ni , Ti) decreases as the number of flexible spacers increases.
In the liquid crystal, as shown in FIG. 3, mesogen is present on a surface having low free energy under anisotropic conditions to form a kind of protective layer (barrier). Accordingly, the mesogen not only volatilizes the solvent easily on the surface but also increases the residence time to suppress the volatilization of the solvent as much as possible, thereby making the insulating fluid have low volatility.
In addition, when shear force is applied to the insulating fluid during the screen printing process or the ink jet printing process, as shown in FIG. 3, the mesogen becomes anisotropic state in which the mesogen is oriented in the shear direction, which is a kind of chain slippage. Since the viscosity of the insulating fluid is drastically reduced by the occurrence of the serves to increase the printability.
In addition, the viscosity of the insulating fluid decreases as the shear rate increases during the printing process. Referring to FIG. 4 which shows the relationship of the viscosity η of the insulating fluid to the shear rate γ during the printing process, it can be seen that the viscosity η of the insulating fluid decreases as the shear rate γ increases.
The insulating fluid preferably has a liquid crystal content in the range of 2.5 wt% to 30 wt% for low volatility and low viscosity. Here, if the liquid crystal content is less than 2.5wt%, there is no meaning to contain the liquid crystal, so it should be 2.5wt% or more, and if it exceeds 30wt%, the viscosity increase of the system according to the increase of the concentration of the liquid crystal is the Since there is a problem that the viscosity increases larger than the viscosity decrease has a critical significance that should be less than 30wt%.
As described above, the electrophoretic medium according to the present invention has low volatility and low viscosity by containing a liquid crystal in a halocarbon-based single fluid or a liquid crystal in a halocarbon-based fluid and an isoparaffin-based mixed fluid. Accordingly, by controlling the low volatility and low viscosity of the electrophoretic medium at the same time, the local viscosity increase that can occur in the processing process including the printing process, the viscosity deviation by position within the process time, the fluid not filled and specific gravity change, the fluid refill, The process margin can be widely operated by solving the conventional problem of large area application. In addition, since the printing process margin can be controlled by adjusting the even number of flexible spacers contained in the liquid crystal in the range of 4 to 12, process efficiency can be increased in terms of manufacturing process.
In addition, as the viscosity of the electrophoretic medium according to the present invention decreases, the response time of the electrophoretic display may be reduced to about 30 to 120 ms.
5 illustrates a cross-sectional structure of one pixel in a monoelectrophoretic display device to which an electrophoretic medium according to the present invention is applied.
The monoelectrophoretic display illustrated in FIG. 5 includes a
The
A glass substrate is mainly used as the
In each pixel space provided by the first and
As described above, the insulating
The white
In response to the voltages applied to the first and
A method of manufacturing the electrophoretic display device illustrated in FIG. 5 is as follows.
On the
The electrophoretic display device is manufactured by bonding and sealing the
6 illustrates a cross-sectional structure of one pixel in a color electrophoretic display device to which an electrophoretic medium according to the present invention is applied.
The color electrophoretic display device shown in FIG. 6 is identical to the monoelectrophoretic display device shown in FIG. 5 except that it includes
Each pixel provided by the upper and
In response to voltages applied to the first and
Table 1 below shows a comparison of the characteristics of the conventional electrophoretic display device containing no liquid crystal and the electrophoretic display device containing the liquid crystal according to the present invention.
In Table 1, WT represents white particles, BK represents black particles, and CR represents contrast ratio. Comparative Example 1 shows volatilization and driving characteristics of a conventional electrophoretic display using an insulating fluid containing no liquid crystal. Example 1-3 shows the volatilization characteristics and driving characteristics of the electrophoretic display device of the present invention using an insulating fluid containing a liquid crystal of 5wt% content according to the present invention. Example 1 shows the case where the number of flexible spacers in the liquid crystal shown in FIG. 1 is n = 8, Example 2 shows the case where n = 6, and Example 3 shows the volatilization characteristics and the driving characteristics when n = 4. . Referring to Table 1, it can be seen that the volatilization degree (30% to 58%) of Examples 1-3 of the present invention is lower than that of the conventional Comparative Example 1 (75%). In addition, it can be seen that the driving speed (20 ~ 120ms) of Example 1-3 of the present invention is faster than the driving speed (280ms) of Comparative Example 1. Moreover, it turns out that the fluid viscosity (2.1-3.6 cP) of Example 1-3 of this invention is lower than the fluid viscosity (4.5cp) at normal temperature (25 degreeC) of the comparative example 1. In addition, it can be seen that in Examples 1-3 of the present invention, the reflectivity, the contrast ratio (CR), and the bistable stability, which exhibit driving characteristics, are similarly good even if they contain liquid crystal.
As described above, the electrophoretic medium according to the present invention has low volatility and low viscosity by containing a liquid crystal in a halocarbon-based single fluid or a liquid crystal in a halocarbon-based fluid and an isoparaffin-based mixed fluid. Accordingly, by controlling the low volatility and low viscosity of the electrophoretic medium at the same time, the local viscosity increase that can occur in the processing process including the printing process, the viscosity deviation by position within the process time, the fluid not filled and specific gravity change, the fluid refill, The process margin can be widely operated by solving the conventional problem of large area application. In addition, since the printing process margin can be controlled by adjusting the even number of flexible spacers contained in the liquid crystal in the range of 4 to 12, the process efficiency can be increased in terms of manufacturing process, and it can be applied to a large area model.
In addition, as the viscosity of the electrophoretic medium according to the present invention decreases, the response time of the electrophoretic display may be reduced to about 30 to 120 ms. Therefore, the electrophoretic medium and the electrophoretic display apparatus using the same according to the present invention not only can display a video through a quick response speed, but also provide a quick response speed even when a touch panel is mounted on the electrophoretic display device. Respond quickly to commands.
10: first substrate 12: first electrode
20: second substrate 22: second electrode
24: partition 30: insulating fluid
32: white particles 34: black particles
42: color particles
Claims (9)
Electrophoretic particles dispersed in the insulating fluid;
The insulating fluid includes a dispersion fluid and a self-assembled liquid crystal;
Electrophoretic medium, characterized in that the content ratio of the liquid crystal to the insulating fluid is in the range of 2.5wt% to 30wt% so as to have a lower volatility and a lower viscosity than the case without the liquid crystal.
The self-assembled liquid crystal has a structure in which a cyano group and a flexible spacer are bonded to both sides based on mesogen, as shown in Formula 1 below.
≪ Formula 1 >
Electrophoretic medium, characterized in that even in the range of n = 4 ~ 12 in the flexible spacer.
The dispersion fluid is
Electrophoretic medium, characterized in that the use of a single fluorine-based fluid, or a mixed fluid of a mixture of the fluorine-based fluid and a saturated hydrocarbon-based fluid.
An electrophoretic medium characterized by having a low viscosity in the range of 2.1 cP to 3.6 cP at room temperature.
An electrophoretic medium characterized by a response time in the range of 20 ms to 120 ms.
Electrophoretic medium, characterized in that the volatilization in the screen printing process ranges from 30% to 58%.
First and second electrodes formed to apply an electric field to each of the plurality of pixels;
The electrophoretic particles include white or color electrophoretic particles having a first charge and black electrophoretic particles having a second charge.
Forming a partition on the lower substrate on which the first electrode is formed to form respective pixel spaces;
Forming each pixel by injecting the electrophoretic medium into the pixel space;
And attaching and sealing an upper substrate on which the second electrode is formed on the lower substrate on which each pixel is formed.
The electrophoretic medium is a spin coating, slit coating, dip coating, inkjet, roll-to-roll coating, or a screen printing process for manufacturing an electrophoretic display device characterized in that the injection.
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Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
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CN109507841A (en) * | 2018-12-24 | 2019-03-22 | 中山大学 | The electric ink and its device architecture of quick response |
CN109521622A (en) * | 2018-12-24 | 2019-03-26 | 中山大学 | A kind of the micropackaging structure and Electronic Paper of the electric ink of quick response |
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Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
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CN109507841A (en) * | 2018-12-24 | 2019-03-22 | 中山大学 | The electric ink and its device architecture of quick response |
CN109521622A (en) * | 2018-12-24 | 2019-03-26 | 中山大学 | A kind of the micropackaging structure and Electronic Paper of the electric ink of quick response |
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