JP2005154705A - Negatively charged fine particle having electron trap caused by irradiation of radiation - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize the production of negatively charged fine particles necessary for the constitution of a system capable of eliminating, or the like, secondary coagulation, precipitation and past record images in a transmission electrophoresis device and reflection electrophoresis device by utilizing the electrophoresis of the negatively charged fine particles. <P>SOLUTION: The negatively charged fine particles are formed by adding a resin having an electron trap into a polymeric fine particle material, also making a real spherical fine particle structure in its synthesis, irradiating 10-300 kGy electron beam to form electlet type negatively charged fine particles. Also, by irradiating 5-10 kGy gamma ray to make zero ζ potential, and by overlapping 10-300 kGy electron beam irradiation, it is possible to produce the negatively charged particles having ≥(-)60 mV ζ potential. These particles repulse each other by coulomb force among the fine particles to enable the prevention of the secondary coagulation and precipitation, and a high speed response and the elimination of the past record displaying images. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

Detailed Description of the Invention

  The present invention relates to electrophoretic particles in a transmissive electrophoretic display device and a reflective electrophoretic display device using an electrophoretic phenomenon using a transparent insulating liquid such as petroleum or silicone oil as a medium. More specifically, an electron trap material is added to a polymer fine particle material such as styrene, propylene, polymide, methacrylic ester, etc., and this is used as a core resin to irradiate the spherical ultrafine particles produced by the polymerization method. The present invention also relates to negatively charged fine particles for transmissive electrophoretic display devices and reflective electrophoretic display devices, which trap carriers (electrons) in an electron trap and charge an electret negative charge.

Generally, the display device starts from a cathode ray tube (CRT), and is a fluorescent display tube (VFD), an electroluminescence (EL) display device, a light emitter diode (LED) display device, a liquid crystal display device (LCD), and a plasma display. -Panel (PDP) etc. are marketed. However, since all commercially available display devices use luminescent color and transmitted light and see the color of the substance itself with a display device for viewing (transmitted light type), they do not endure long-term staring.
With the recent progress in IT, the development of a display device (reflected light type) for reading that has display characteristics such as printed materials, is easy on the eyes, and can withstand long-time fixations is active. In particular, the progress of computerization technology for newspapers is remarkable. Distribution by satellite is expected to contribute to conservation of forest resources and the global environment as well as major reforms of printing, transportation and delivery, and reduction of paper consumption. The e-book business has also entered an era of practical use.

  In order to satisfy such demands, display devices have many demands such as large size, low price, high definition, energy saving, high speed response, and full color. For this reason, many systems such as particle system, liquid crystal system, rewritable marking system, etc. have been developed, but for large size and high definition, the display method using electrophoretic phenomenon by spherical charged fine particles is ideal. Think of it as the most advanced display device for reading. There are electrophoretic display devices, such as those based on the movement of particles in microcapsules in the thickness direction and the movement of charged fine particles in a transparent insulating liquid in the medium plane. In addition, for a demand for high definition of 300 dpi or more, a transmission type electrophoretic display device and a reflection type electrophoretic display device using spherically charged fine particles are optimal.

  The idea of using charged fine particles for electrophoresis and display or storage devices has been proposed for a long time (Ota: Patent Publication No. 50-15115). However, the shape of charged fine particles, the small charge potential (ζ potential), There were many technical problems such as secondary agglomeration and precipitation of particles, erasure of previous display images, and response speed, which could not be realized.

  As a full-scale electrophoretic display method, there is a proposal of a horizontal movement type electrophoretic display method and apparatus. (Gouda: Japanese Patent Laid-Open No. 2001-56373) However, although it is a display device capable of performing simple matrix driving while suppressing the occurrence of crosstalk using electrophoresis of charged particles dispersed in a transparent insulating liquid, In order to provide a barrier, a large-sized display device has a complicated configuration, and there is no solution such as secondary aggregation, precipitation, and erasure of previous history display images.

Problems to be solved by the invention

The charging mechanism of the organic material is complicated. In the case of electrophotography, charged fine particles (developer: toner, particle size 5 to 20 μm) by triboelectric charging produced by a charge train of an organic fine particle material and a charge control agent are used, and 300 It has a resolution of ~ 500 dpi. In a transmissive electrophoretic display device, a reflective electrophoretic display device, and the like, charged fine particles are dispersed in a transparent insulating liquid, and an electric field is applied to display an image using the electrophoretic phenomenon of the charged particles.
For this reason, spherical charged fine particles of 1 to 10 μm can be used, and an extremely high-definition electrophoretic image display device can be realized. Transmission type electrophoretic display on electronic newspapers, books and the like received by satellite distribution in the future. This suggests the possibility of the device and the reflection type electrophoretic display device. However, the electrophoretic particles in the transparent insulating liquid cannot be charged by friction or the like, and it is necessary to maintain a strong physical charge.

In order to secure the response of the display image in the transparent insulating liquid, it is necessary to increase the electrophoresis speed υ in the medium of charged fine particles. In general, the electrophoretic velocity υ of the migrating particles in the transparent insulating liquid is expressed by the following equation from the relationship between the Coulomb force and the viscous resistance of the transparent insulating liquid.
υ = qE / 6πrθη
Where q is the amount of charge on the effective surface of the particle, r is the effective radius of the particle, θ is the shape of the migrating particle, a constant related to the surface state, η is the viscosity of the dispersion medium acting on the migrating particle, and E is acting on the migrating particle. Electric field strength. For this reason, the migrating particles used in the electrophoretic display device are first charged fine particles having a large ζ potential. The shape must be regular spherical ultrafine particles in order to obtain a high-density display image by regularly moving at high speed in a transparent insulating liquid. Further, in order to apply an external force (for example, an AC electric field) for secondary aggregation, precipitation, erasure of the previous history display image, etc., it is important that the migrating particles maintain a high charged charge semipermanently. Therefore, there is a need for means for electret charging by changing basic physical properties.

Means for solving the problem

  In the first aspect of the present invention, a resin that serves as an electron trap is added to a core resin of true spherical ultrafine particles having a particle diameter of 1 to 10 μm produced by polymerizing a polymer fine particle material, and an electron beam of 10 to 300 kGy is added thereto. Irradiation is performed to capture carriers (electrons) in an electron trap, and the electrification negatively charged fine particles are manufactured by changing the charging mechanism in terms of physical properties. Further, negatively charged fine particles used for monochrome and color display devices are manufactured by coloring the core resin material in a desired color.

  According to the second aspect of the present invention, a fluorine resin serving as an electron trap is added to the polymer fine particle material to form a core resin, which is colored black, white, magenta, yellow, cyan, etc. Fine particles are used. If a transparent material is selected as the electron trap resin material, there is no problem in color tone.

  In the invention of claim 3, the spherical ultrafine particles having an electron trap are irradiated with an electron beam at 10 to 300 kGy at room temperature, subjected to heat treatment at 100 to 150 ° C. for several tens of minutes, and gradually cooled, and a ζ potential of −60 mV is obtained. Produces electret negatively charged fine particles.

  According to the invention of claim 4, when the spherical ultrafine particles having an electron trap are irradiated with an electron beam at 10 to 300 kGy at 100 to 150 ° C. and slowly cooled to room temperature, electret negatively charged fine particles having a ζ potential of −80 mV are produced. To do.

  In the invention of claim 5, the spherical ultrafine particles having electron traps are irradiated with 5 to 10 kGy of radiation, the ζ potential of the spherical ultrafine particles is set to around 0 mV, and then irradiated with an electron beam of 10 to 300 kGy. When heat treatment is performed at 100 to 150 ° C. for several tens of minutes and then cooled slowly, electret negatively charged fine particles having a ζ potential of −00 mV can be produced. The effect of superposition is significant.

  The invention of claim 6 irradiates the spherical ultrafine particles having electron traps with a radiation of 5 to 10 kGy, then irradiates with an electron beam of 10 to 300 kGy at 100 to 150 ° C., and slowly cools to room temperature. It is possible to produce electret negatively charged fine particles having a high ζ potential. The superimposing effect is very remarkable.

  According to the invention of claim 7, the negatively charged fine particles are transparent because they have a high negative ζ potential and true spherical ultrafine particles when a positive DC electric field is applied in a transparent insulating liquid such as petroleum or silicone oil. It is a negatively charged fine particle for a transmissive electrophoretic display device or a reflective electrophoretic display device that can regularly move at high speed in an insulating liquid and can display an image with high density and high image quality.

  In the invention of claim 8, the spherical ultrafine particles repel each other by the Coulomb force in the insulating liquid by maintaining a ζ potential of −20 mV or more, and serve to prevent secondary aggregation and precipitation.

  According to the ninth aspect of the present invention, when the radiation is irradiated by 10 kGy or more, the ζ potential of the organic fine particle material is discharged and settles to near zero regardless of the positive or negative relation. Therefore, by utilizing this property, the ζ potential of the charged fine particles can be freely controlled to a desired potential depending on the radiation dose.

  According to the invention of claim 10, the negatively charged fine particles are dispersed in a transparent insulating liquid and can be used for a transmission type electrophoretic display device, a reflection type electrophoretic display device or the like utilizing an electrophoretic phenomenon.

  According to the eleventh aspect of the present invention, negatively charged fine particles can be mixed with positively charged fine particles, non-charged magnetic fine particles, non-charged nanomagnetic fine particles, etc., and electrophoretic display and magnetophoretic display can be driven simultaneously. It is possible to produce negatively charged fine particles to be used for transmission / electrophoresis display devices for monochrome / color display or for reflection / electrophoresis display devices.

  The present inventors have studied the fine particle material for electrophoresis in a spherical ultrafine particle obtained by polymerizing polymer fine particle material such as styrene, propylene, polymide, methacrylic ester, etc. at room temperature. It has been found that electret negatively charged fine particles of −60 to −70 mV are produced when irradiation with an electron beam of 300 kGy and heat treatment at 100 to 150 ° C. are performed for several tens of minutes. It was also found that when an electron beam irradiation of 5 to 10 kGy and an electron beam irradiation of 10 to 300 kGy were applied, an even higher electret negative charge of −100 to 140 mV was charged. This is based on the basic physical properties of electrons being trapped in the electron trap. Unlike frictional charging, it is highly reliable and does not disappear due to external force such as application of an alternating electric field.

Hereinafter, embodiments of negatively charged fine particles by radiation irradiation according to the present invention will be described with reference to the drawings.
FIG. 1 is a production flowchart of negatively charged particles. As a polymer fine particle material, an electron trap material fluorine resin is added to a resin such as styrene, acrylic, polymide, or propylene methacrylate, resulting in black, white, magenta, yellow, cyan, etc. After coloring, spherical ultrafine particles having a particle diameter of 1 to 10 μm were prepared by a solution polymerization method, an emulsion polymerization method, and a suspension polymerization method.
This is charged by irradiation and heat treatment.
i. A 10-300 kGy electron beam is irradiated at normal temperature, and heat processing is performed for several tens of minutes at 100-150 degreeC.
ii. In a 100 to 150 ° C. atmosphere, an electron beam of 10 to 300 kGy is irradiated and gradually cooled.
iii. In advance, the gamma rays emitted from ⁶⁰ Co are irradiated with 5 to 10 kGy, irradiated with an electron beam of 10 to 300 kGy at room temperature, and then heat-treated at 100 to 150 ° C. for several tens of minutes.
iv. Gamma rays previously emitted from ⁶⁰ Co are irradiated with 5 to 10 kGy in an atmosphere of 100 to 150 ° C. and irradiated with an electron beam of 10 to 300 kGy and gradually cooled.
Next, particle size, particle size distribution, measurement of ζ potential, electrophoretic characteristics, display characteristics, and the like were observed, and negatively charged fine particles for transmission type electrophoretic display devices and reflection type electrophoretic display devices were evaluated.
The charged fine particles are measured by measuring the ζ potential, particle size, particle size distribution, and the like by a laser method. In addition, the electrophoresis and display characteristics of particles in the horizontal and vertical directions are observed. Black, white, magenta, yellow, and cyan negatively charged fine particles are produced by coloring the core resin.

FIG. 2 is a schematic view of a cross section of the prototype negatively charged fine particles. Inside the outermost shell resin 1 is added core resin 2 such as acrylic resin, polyester resin, and styrene polymer resin, and fluorine resin as an electron trap. 1 to 10 μm true spherical ultrafine particles were produced.
Developers (toners) used in electrophotography have a softening point of 160 ° C. or lower due to thermal fixing, but in the case of negatively charged fine particles, there are no restrictions on the softening point, and there are no restrictions on the softening point. The electronic trapping material and the coloring method can be selected.

FIG. 3 shows the relationship between the electron beam dose and the ζ potential when ultrafine particles made spherical by suspension polymerization are irradiated to a styrene resin to which an electron trap with a particle size of 5 to 10 μm is added. .
i. The characteristics marked with ○ are the characteristics of the negatively charged fine powder particles when irradiated with an electron beam of 10 to 300 kGy at room temperature, and heat-treated at 130 ° C. for 20 minutes and gradually cooled. The saturation of ζ potential by electron beam irradiation occurs in the vicinity of −70 mV.
ii. The characteristics marked with ◎ are the characteristics of negatively charged fine particles when gamma rays emitted from ⁶⁰ Co are irradiated with 8 kGy in advance, irradiated with electron beams of 10 to 300 kGy at room temperature, heat-treated at 130 ° C. for 20 minutes, and gradually cooled. . Saturation of ζ potential due to electron beam irradiation occurs in the vicinity of −100 mV.
iii. The characteristics marked with ● are the characteristics of negatively charged fine particles when gamma rays emitted from ⁶⁰ Co are irradiated with 8 kGy in advance, irradiated with an electron beam of 10 to 300 kGy in an atmosphere of 120 ° C., and gradually cooled. The superposition effect is noticeable with a high ζ potential saturation value of −140 mV.
However, in any case, irradiation with an electron beam of 250 kGy or more causes the electron trap to collapse, and the ζ potential decreases rapidly. 150-250 kGy is optimal for the electron beam dose.

FIG. 4 shows electrophoretic characteristics between parallel electrodes in which negatively charged fine particles are dispersed in silicon-oil having a viscosity of 2.3 poise and insulated with a polycarbonate resin film having a thickness of 20 μm. The electrode interval is 200 μm, and the negatively charged fine particles have ζ potentials of −20 mV, −60 mV, and −100 mV. With negatively charged particles having a ζ potential of −60 mV, a response of 5 msec can be obtained by applying a voltage of +100 V (electric field strength 2 × 10 ⁵ V / m). With negatively charged particles having a ζ potential of −100 mV, a response of 5 msec was obtained when a voltage of 50 V (electric field strength 1 × 10 ⁵ V / m) was applied. If a transparent insulating liquid having a low viscosity is used, the response is further improved.

  The present invention is not limited to the above-described embodiments, and it goes without saying that various modifications, design changes, and the like within the technical scope of the present invention are included in the technical scope.

The invention's effect

  According to claim 1, the spherical ultrafine particles produced by various polymerization methods such as suspension polymerization, dissolution suspension, emulsion aggregation, and dispersion polymerization of the polymer fine particle material can be easily reduced in size, and the particle size distribution. Narrow and easy to spheroidize. In particular, suspension polymerization is excellent in reducing the particle size and spheroidizing, and is the most suitable technique for producing the negatively charged fine particles in this case. When a resin to be an electron trap is added and irradiated with an electron beam of 10 to 250 kGy, spherical ultrafine particles charged with an electret negative charge having a high ζ potential are obtained and colored to a desired color. A negatively charged fine particle for a color electro-transmissive electrophoretic display device and a reflective electrophoretic display device is realized.

  According to the second aspect of the present invention, the resin that becomes an electron trap is a fluorine-based resin, which is added in a small amount to the polymer fine particle material of the core resin during the polymerization of the spherical ultrafine particles, and these are added to black, white, magenta, yellow Colored to a desired color such as color or cyan, a monochromatic, color, etc. transmission type electrophoretic display device and a negatively charged fine particle for a reflection type electrophoretic display device are realized.

  According to claim 3, when the spherical ultrafine particles having an electron trap are irradiated with an electron beam of 200 kGy at room temperature, subjected to heat treatment for several tens of minutes at 100 to 150 ° C., and slowly cooled, electret property of −70 mV ζ potential Negatively charged fine particles with charging characteristics can be manufactured.

  According to the fourth aspect, when a spherical ultrafine particle having an electron trap is irradiated with an electron beam of 10 to 300 kGy in an atmosphere of 100 to 150 ° C., carriers (electrons) are trapped in a deep electron trap level and gradually. When cooled, negatively charged fine particles having electret charging characteristics with a ζ potential of −100 mV are realized.

  According to claim 5, the spherical ultrafine particles having an electron trap are preliminarily irradiated with 8 kGy of radiation, the ζ potential is set to around 0 mV, the electron beam of 200 kGy is irradiated at room temperature, and a few tens of minutes at 100 to 150 ° C. When subjected to heat treatment and slow cooling, negatively charged fine particles having electret charging characteristics with a ζ potential of −140 mV are realized.

  According to claim 6, when the spherical ultrafine particles having an electron trap are preliminarily irradiated with 8 kGy of radiation, then irradiated with 200 kGy of electron beam at 150 ° C., and slowly cooled, an electret having a −140 mV ζ potential is obtained. Negatively charged microparticles with negative charge characteristics.

  According to the seventh aspect, when spherical negatively charged fine particles are dispersed in a petroleum-based or silicone oil-based transparent insulating liquid and a positive DC electric field is applied, the particles move regularly due to the true spherical ultrafine particles. The time is short, the response is several milliseconds, and the display image quality is high definition, high density, and high image quality.

  According to the eighth aspect, when the negatively charged fine particles have a ζ potential of −20 mV or more, the negatively charged fine particles repel each other due to Coulomb force, which is the greatest drawback of the electrophoretic display device. , Can be a puzzling solution to precipitation.

  According to the ninth aspect, the ζ potential of the negatively charged fine particles can be controlled to a desired potential depending on the radiation dose.

  According to the tenth aspect, the negatively charged fine particles can be used in electrophoretic particles such as a transmissive electrophoretic display device and a reflective electrophoretic display device using the electrophoretic phenomenon by being dispersed in a transparent insulating solution. A high-definition electrophoretic display device of 300 dpi or more can be realized.

  According to the eleventh aspect of the invention, the negatively charged fine particles are mixed with uncharged magnetic fine particles, uncharged nanomagnetic fine particles, and the like, and drive electrophoresis and magnetophoresis simultaneously. An electrophoretic display device is realized.

  It is a manufacture flowchart of negatively charged fine particles.   It is sectional drawing of a negatively charged fine particle.   It is the relationship between the electron beam irradiation amount of negatively charged fine particles and the ζ potential.   It is the relationship between the electric field strength and response time in the transparent insulating liquid of negatively charged fine particles.

Explanation of symbols

1. Shell resin 2. Core resin

Claims (11)

  A resin that serves as an electron trap is added to a core resin of a spherical ultrafine particle having a particle diameter of 1 to 10 μm produced by polymerizing a polymer fine particle material, and an electron beam of 10 to 300 kGy is irradiated to the resin. Negatively charged fine particles obtained by coloring a core resin in a desired color with fine particles charged with a negative charge.   The resin that serves as the electron trap is a fluorine-based resin, which is added to the polymer fine particle material during polymerization to form a core resin. The core resin is formed into a desired color such as black, white, magenta, yellow, and cyan. The negatively charged fine particles according to claim 1, wherein the negatively charged fine particles are colored.   When irradiating a spherical ultrafine particle having an electron trap with an electron beam, it is irradiated with an electron beam of 10 to 300 kGy at room temperature, then heated at 100 to 150 ° C. for several tens of minutes, and gradually cooled to room temperature to be an electret. Negatively charged fine particles characterized by charging a negative charge.   When irradiating the spherical ultrafine particles having the electron trap with an electron beam, the electron beam is irradiated with an electron beam of 10 to 300 kGy at 100 to 150 ° C., and gradually cooled to room temperature to charge an electret negative charge. Negatively charged particles.   The spherical ultrafine particles having electron traps are irradiated with 5 to 10 kGy of radiation, and further irradiated with an electron beam of 10 to 300 kGy at room temperature, and then heated at 100 to 150 ° C. for several tens of minutes and gradually brought to room temperature. A negatively charged fine particle characterized by being cooled and charged with an electret negative charge.   The spherical ultrafine particles having electron traps are irradiated with 5 to 10 kGy of radiation, and further irradiated with an electron beam of 10 to 300 kGy at a temperature of 100 to 150 ° C. Negatively charged fine particles characterized by charging   The negatively charged fine particles are composed of spherical ultrafine particles, and when a positive electric field is applied in a transparent insulating liquid such as petroleum-based or silicone oil-based, regular high-speed electrophoresis in the thickness direction in a short time, 7. The negatively charged fine particles according to claim 1, wherein the density of the display image is increased.   The negatively charged fine particles according to claim 1, wherein the negatively charged fine particles have a ζ potential of −20 mV or more, and the fine particles are repelled by Coulomb force to prevent secondary aggregation and precipitation. .   The negatively charged fine particles according to any one of claims 1 to 8, wherein the negatively charged fine particles freely control a ζ potential value according to a dose of radiation. 10. The negatively charged fine particles are dispersed in a transparent insulating solution, and can be used in a transmission type electrophoretic display device, a reflection type electrophoretic display device using an electrophoretic phenomenon, or the like. Negatively charged fine particles.   Transmission electrophoretic and magnetophoresis, wherein the negatively charged fine particles are mixed with positively charged fine particles, non-charged magnetic fine particles, non-charged nanomagnetic fine particles, and the like, and electrophoretic display and magnetophoretic display are simultaneously driven. 10. The negatively charged fine particles according to claim 1, which can be used in a display device, a reflection type electrophoretic display device and the like.

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