WO2020052455A1

WO2020052455A1 - Selectively erasing device and writing-erasing pen for liquid crystal writing board

Info

Publication number: WO2020052455A1
Application number: PCT/CN2019/103924
Authority: WO
Inventors: Jiuzhi Xue; Ran AN; Shuzhen CUI
Original assignee: Smart Liquid Crystal Technologies Co., Ltd.
Priority date: 2018-09-10
Filing date: 2019-09-02
Publication date: 2020-03-19
Also published as: CN110888248A; CN110888248B

Abstract

A selectively erasing device and a writing-erasing pen for a liquid crystal writing board. The selectively erasing device comprises a power source, a driving circuitry and an ultrasonic generating assembly (10), wherein the power source and the ultrasonic generating assembly (10) are electrically connected to the driving circuitry, the ultrasonic generating assembly (10) comprises a matching layer (11), an ultrasonic generator (12) and a backing layer (13) stacked in sequence, and the matching layer (11) is positioned on the side contacting with the liquid crystal writing board. The selectively erasing device and the writing-erasing pen apply an ultrasonic technology to fulfill the selectively erasing, resulting in energy-saving and environmental protection, as well as safe and convenient to use.

Description

[Title established by the ISA under Rule 37.2] SELECTIVELY ERASING DEVICE AND WRITING-ERASING PEN FOR LIQUID CRYSTAL WRITING BOARD

Technical Field

The present invention relates to the liquid crystal display application field, and more particularly relates to a selectively erasing device and a writing-erasing pen for a liquid crystal writing board.

Background of the Invention

At present, in the field of liquid crystal writing boards, the main erasing mode of liquid crystal writing boards is only used for entirely erasing, which leads to poor customer experiences and becomes the biggest obstruction for market penetration of liquid crystal writing boards especially in the education. The external elements affecting the arrangement and structure of liquid crystals mainly include acoustic field, light, electric field, heat and magnetic field. Among them, light, electric field and heat are currently used for selectively erasing, but light and heat will accelerate the aging of liquid crystal writing boards, while using electric field will make the manufacturing process of writing boards more complex and cost extremely high. On the other side, the influence of magnetic field on liquid crystal materials is weak, causing direct application of magnetic field on liquid crystal writing boards to realize selectively erasing not practical.

The selectively erasing of liquid crystal writing boards is an outstanding problem in the field. CN Utility Patent No. 206057726U to WICUE Inc. disclosed a semiconductor thermal erasing technology which uses a semiconductor element heat liquid crystals to the isotropic state and the liquid crystals stay in a scattering multi-domain structure after cooling, realizing the conversion from the reflective planar state to the scattering focal conic state and further the selectively erasing of writing boards. However the thermal transfer rate of the semiconductor is low, causing the problems of scalding dangers and high energy consumption. Moreover, the selectively erasing method limits the actual working temperature range of liquid crystal writing boards, accelerates the aging of thin film materials and liquid crystal materials of writing boards, and severely affects the service lifetime of liquid crystal writing boards.

Summary of the Invention

In order to overcome the above mentioned issues, one objective of the present invention is to provide a selectively erasing device for a liquid crystal writing board. The selectively erasing device comprises a power source, a driving circuitry and an ultrasonic generating assembly, wherein the power source and the ultrasonic generating assembly are electrically connected to the driving circuitry, and the ultrasonic generating assembly comprises a matching layer, an ultrasonic generator and a backing layer stacked in sequence, wherein the matching layer is positioned on the side contacting with the liquid crystal writing board.

In a preferred embodiment, the ultrasonic generator for emitting ultrasonic waves is one or a combination of a piezoelectric transducer, a magnetostrictive transducer and an electrostatic transducer.

In a preferred embodiment, the matching layer is composed of a single-layer or multi-layer medium.

In an embodiment, the acoustic impedance value of the single-layer medium gradually decreases along the direction away from the ultrasonic generator. In a preferred embodiment, the surface of the matching layer in contact with the liquid crystal writing board is a flat surface or a rough surface with micro-structured protrusions. In a more preferred embodiment, the micro-structured protrusions have a tetrahedral structure.

In another embodiment, the acoustic impedance value of the multi-layer medium gradually decreases along the direction away from the ultrasonic generator.

In an embodiment, the material of the matching layer is one or more selected from the group of metals, metallic oxides, inorganic nonmetals and polymers. In more preferred embodiments, the metal is tungsten or aluminum, the metallic oxide is tungsten oxide or aluminum oxide, and the inorganic nonmetal is silicon dioxide. In another preferred embodiment, the polymer is one or more selected from the group of epoxy resin, polyester resin, polyvinyl chloride, and their combination with fillers. In a more preferred embodiment, the filler is an inert metal powder or a non-metal powder.

In some embodiments, the ultrasonic generator is a single ultrasonic generator or an array of ultrasonic generators which are connected to each other in series or in parallel. In a preferred embodiment, the cross section of the ultrasonic generator has a shape of round, square, rectangle or their combinations.

In some embodiments, the selectively erasing device further comprises a gel layer or an elastic polymer layer located on the side of the matching layer away from the ultrasonic generator, the gel layer or the elastic polymer layer is tightly attached to the upper substrate of the liquid crystal writing board when the liquid crystal writing boards is selectively erased.

In some embodiments, the backing layer comprises a solid filler made of metallic oxides or non-metallic oxides and one or more polymers selected from epoxy resins, polyester resins and polyvinyl chloride, and the backing layer is used for absorbing the reflected ultrasonic waves at the interface between the matching layer and ultrasonic generator.

Another objective of the present invention is to provide a writing-erasing pen for a liquid crystal writing board, which comprises a pen body, a writing end and an erasing end, wherein the erasing end comprises the selectively erasing device for a liquid crystal writing board mentioned above.

In some embodiments, the writing end and the erasing end are located at the two ends of the pen body respectively. In a preferred embodiment, the erasing end is detachably connected to the pen body.

In a preferred embodiment, the writing-erasing pen further comprises a charging device connecting to the power source.

The present invention provides a selectively erasing device and a writing-erasing pen for a liquid crystal writing board, which apply an ultrasonic technology to fulfill the selectively erasing, resulting in energy-saving and environmental protection, as well as safe and convenient to use.

Brief Description of the drawings

The present invention will become more apparent by the description of embodiments thereof with reference to the attached drawings in which:

FIG. 1 is a schematic view illustrating the structure of the ultrasonic generating assembly where the matching layer is composed of a single-layer medium according to an embodiment of the present invention;

FIG. 2 is a schematic view illustrating the structure of the matching layer with multiple tetrahedral micro-structured protrusions and the ultrasonic generator;

FIG. 3 is a schematic view illustrating the structure of the ultrasonic generating assembly where the matching layer is composed of a multi-layer medium according to an embodiment of the present invention;

FIG. 4 is a schematic view illustrating the structure of the ultrasonic generating assembly where the matching layer is wedge-shaped according to an embodiment of the present invention;

FIG. 5 is a schematic view illustrating the structure of the ultrasonic generating assembly with an additional gel layer or elastic polymer layer according to an embodiment of the present invention;

FIG. 6 is a schematic view illustrating the structure of the writing-erasing pen according to an embodiment of the present invention;

FIG. 7 is a schematic view illustrating the writing process of the writing-erasing pen on a liquid crystal writing board;

FIG. 8 is a schematic view illustrating the texture structure of liquid crystals in the liquid crystal writing board in FIG. 7;

FIG. 9 is a schematic view illustrating the selectively erasing process of the writing-erasing pen on a liquid crystal writing board;

FIG. 10 is a schematic view illustrating the texture structure of liquid crystals in the liquid crystal writing board in FIG. 9.

Detailed Description of the Invention

In the following description, for the purpose of explanation so as to have a comprehensive understanding of the invention, numerous specific details are disclosed, however, it is obvious to those skilled in the art, that the invention can be implemented without these specific details. In other embodiments, well-know structures and devices are shown in block diagrams in the invention. The exemplary embodiments are merely illustrative of the invention, rather than limiting the scope of the present invention being defined by appended claims thereof.

The selectively erasing device and the writing-erasing pen will be described in detail below with reference to the drawings.

FIG. 1 is a schematic view illustrating the structure of the ultrasonic generating assembly where the matching layer is composed of a single-layer medium, FIG. 2 is a schematic view illustrating the structure of the matching layer with multiple tetrahedral micro-structured protrusions and the ultrasonic generator, FIG. 3 is a schematic view illustrating the structure of the ultrasonic generating assembly where the matching layer is composed of a multi-layer medium and FIG. 4 is a schematic view illustrating the structure of the ultrasonic generating assembly where the matching layer is wedge-shaped. By combining with FIG. 1 to FIG. 4, the selectively erasing device for a liquid crystal writing board according to an embodiment of the present invention comprises a power source (not shown) , a driving circuitry (not shown) and an ultrasonic generating assembly 10, where the power source and the ultrasonic generating assembly 10 are electrically connected to the driving circuitry. The ultrasonic generating assembly 10 includes a matching layer 11, an ultrasonic generator 12 and a backing layer 13 stacked in sequence, where the matching layer 11 is positioned on the side contacting with the liquid crystal writing board.

The ultrasonic generator 12 is one of a piezoelectric transducer, a magnetostrictive transducer and an electrostatic transducer or their combination, which is used for emitting ultrasonic waves. For example, the ultrasonic generator 12 can be a piezoelectric ceramic transducer (PZT) , which is composed of piezoelectric crystals with an axial and longitudinal expansion and generate ultrasonic wave of a certain frequency to realize electromechanical convention. The rough materials of the piezoelectric ceramic transducer can be lead zirconate-titanate or barium titanate. The ultrasonic generator 12 has an axial resonance direction (perpendicular to the plane of the ultrasonic generator 12) and a longitudinal resonance direction (parallel to the plane of the ultrasonic generator 12) , which can be switched by adjusting the voltage. In another word, the ultrasonic generator 12 can generate an axial vibration or a longitudinal vibration depending on the applied voltage. For the structures in FIG 1 and FIG 3, the longitudinal vibration has a better erasing effect, whereas for the structures in FIG 2 and FIG 4, the axial vibration has a better erasing effect. In the embodiments of the present invention, for the structures in FIG 1, 3 and 4, the ultrasonic waves directly go through the upper substrate of the liquid crystal writing board into the liquid crystal layer to change the alignment of liquid crystals, while for the structure in FIG 2, the ultrasonic generator 12 makes the upper substrate oscillation to change the alignment of liquid crystals. However, the present invention is not limited thereto, and other shapes and structures of the ultrasonic generating assembly 10 may be set in accordance with the idea of the present invention.

In some embodiments, the ultrasonic generator 12 can be a single ultrasonic generator, or an array of multiply ultrasonic generators connected to each other in series or in parallel. The cross section of the ultrasonic generator has a shape of round, square, rectangle or their combinations, which can be adjusted according to the detailed applicant.

In some embodiments, the material of the matching layer 11 is one or more selected from the group of metals, metallic oxides, inorganic nonmetals and polymers. For example, the metal is tungsten or aluminum, the metallic oxide is tungsten oxide or aluminum oxide, the inorganic nonmetal is silicon dioxide, and the polymer is one or more selected from the group of epoxy resin, polyester resin, polyvinyl chloride, and their combination with fillers. The filler is an inert metal powder or a non-metal powder.

The matching layer 11 is composed of a single-layer or multi-layer medium, which is normally selected from compact, dense and small-damping insulator materials that have low absorbing and attenuating to the ultrasonic waves. As shown in FIG. 1, the matching layer 11 is composed of a single-layer medium whose acoustic impedance value gradually decreases along the direction away from the ultrasonic generator 12. In some embodiments, the lower surface of the matching layer 11 can be a flat surface (as shown in FIG. 1) or a rough surface with micro-structured protrusions. The shape of the micro-structured protrusions can be cylinder, quadrilateral, cone, tetrahedron or other polyhedrons. Preferably, the micro-structured protrusions have a tetrahedral structure as shown in FIG. 2. The matching layer 11 also can be composed of a multi-layer medium whose acoustic impedance value gradually decreases along the direction away from the ultrasonic generator 12. As shown in FIG. 3, the matching layer 11 is a double-layer medium including the first matching layer 111 and the second matching layer 112, where the first matching layer 111 is close to the ultrasonic generator 12. The acoustic impedance value of the first matching layer 111 is larger than that of the second matching layer 112. For example, the acoustic impedance value of the first matching layer 111 is 15～20 MRayl, while the acoustic impedance value of the second matching layer 112 is 3～5 MRayl. In some embodiments, the first matching layer 111 contains composite materials of polymers and solid powders. The polymer can be epoxy resin, polyester resin or polyvinyl chloride, and the solid powder contains lead zirconate-titanate, tungsten oxide, iron oxide, titanium dioxide or silicon dioxide. The second matching layer 112 contains elastic and self-adhesive materials, such as gelatinous substances or elastic polymer. The second matching layer 112 will cause the selectively erasing device contact tightly to the liquid crystal writing board, which reduces the air between the selectively erasing device and the upper substrate of the liquid crystal writing board, reduces the attenuation of ultrasonic waves and improves the propagating efficiency of ultrasonic waves. Meanwhile, it will prevent appearing of writing traces caused by the stress of the second matching layer 112 during the erasing process. The material of second matching layer 112 includes but not limited to low acoustic impedance organic polymers such as silicone gels or silicone resins. The first matching layer 111 and the second matching layer 112 are bonded through adhesive agents bonding, chemical bonding after surface modification or after doping modification, physical adsorption after surface tension modification and so on.

In some embodiments, the thickness of the matching layer 11 is uniform, as shown in FIG. 1 and FIG. 2. Also, the thickness of the matching layer 11 is not even, as shown in FIG. 4, where the matching layer 11 is wedge-shaped. In another word, the cross section of the matching layer has a shape of triangle. However, the present invention is not limited thereto, and the cross section of the matching layer 11 can be trapezoidal, circular arc, wavy or other irregular polygons.

FIG. 5 is a schematic view illustrating the structure of the ultrasonic generating assembly with an additional gel layer or elastic polymer layer. As shown in FIG. 5, the selectively erasing device comprises a gel layer or an elastic polymer layer 14 located on the side of the matching layer 11 away from the ultrasonic generator 12. When in the selectively erasing process, the gel layer or elastic polymer layer is tightly attached to the upper substrate of the liquid crystal writing board, in order to push out the air between the selectively erasing device and the upper substrate and make the entry of ultrasonic waves into the liquid crystal layer more efficient, which reduces the attenuation of ultrasonic waves, improves the propagating efficiency of ultrasonic waves and prevents appearing of writing traces caused by the stress of the matching layer 11 during the erasing process.

In some embodiments, the backing layer 13 contains solid fillers made of metallic oxides or non-metallic oxides and one or more polymers selected from epoxy resins, polyester resins, and polyvinyl chloride. The backing layer is used for absorbing the reflected ultrasonic waves at the interface between the matching layer and the ultrasonic generator, which reduces the effect of surface reflection, suppresses interference and improves the utilization of the ultrasonic waves entering into the liquid crystal writing board.

In embodiments of the present invention, the matching layer 11 and the ultrasonic generator 12 or the ultrasonic generator 12 and the backing layer 13 are bonded through adhesive agents bonding, chemical bonding after surface modification or after doping modification, physical adsorption after surface tension modification and so on.

FIG. 6 is a schematic view illustrating the whole structure of the writing-erasing pen according to an embodiment of the present invention. As shown in FIG. 6, the writing-erasing pen includes a pen body 300, a writing end 200 and an erasing end 100, where the erasing end 100 includes the selectively erasing device as mentioned above. In some embodiments, the writing end 200 and the erasing end 100 are located at the two ends of the pen body 300. The writing end 200 has a writing tip to directly contact with a liquid crystal writing board during a writing process. The power source and the driving circuitry of the selectively erasing device can be set inside the pen body 300 or the connection part between the pen body 300 and the writing end 200 or the erasing end 100. However, the present invention is not limited thereto, and the power source and the driving circuitry may be installed in other parts of the writing-erasing pen or connected to the writing-erasing pen through wireless method. As shown in FIG. 6, the ultrasonic generating assembly 10 is located in the erasing end 100, where the backing layer 13, the ultrasonic generator 12 and the matching layer 11 is disposed in sequence from the pen body 300 to the erasing end 100. Moreover, a gel layer or elastic polymer layer (not shown) is included outside of the matching layer 11.

In some embodiments, the erasing end 100 is detachably connected to the pen body 300, such as through a removable connection by thread, snap or magnetic materials. In the above embodiment, the erasing end 100 is located on one side of the pen body 300. However, the present invention is not limited thereto, and the erasing end 100 may be located on other part of the pen body 300, such as the lateral side of the pen body. In some embodiments, the writing-erasing pen comprises a charging device connecting the power source. The charging device may be set inside the pen body 300, outside the pen body 300 or between the pen body 300 and the erasing end 100 or the writing end 200. The power source charged by the charging device can provide enough power to the ultrasonic generating assembly 10 for easily carrying and using of the entire writing-erasing pen. In addition, the writing-erasing pen can include a power switch to control the power source. For example, the power switch is an elastic switch which is turned on through a long-time push. When the elastic switch is turned on, the ultrasonic generating assembly 10 continues working; while the elastic switch is turned off, the ultrasonic generating assembly 10 stop working. The ultrasonic generating assembly 10 is in the off state when the writing-erasing pen is put still or the elastic switch is free from external forces.

FIG. 7 is a schematic view illustrating the writing process of the writing-erasing pen on a liquid crystal writing board and FIG. 8 is a schematic view illustrating the texture structure of liquid crystals in the liquid crystal writing board in FIG. 7. As shown in FIG. 7 and FIG. 8, the liquid crystal writing board used in the present invention includes bistable polymer stabilized cholesteric liquid crystal. When the liquid crystal writing board is pushed by the pen tip of the writing-erasing pen, the liquid crystals around the pushing position will switch from a scattering state to a reflective state, therefore the incident light of a certain wavelength is reflected back to eyes and the liquid crystal writing board will show the writing words with a certain color.

FIG. 9 is a schematic view illustrating the selectively erasing process of the writing-erasing pen on a liquid crystal writing board and FIG. 10 is a schematic view illustrating the texture structure of liquid crystals in the liquid crystal writing board in FIG. 9. As shown in FIG. 9 and FIG. 10, during the selectively erasing process, the erasing end of the writing-erasing pen is pointed to the erasing party and the ultrasonic generating assembly 10 emits ultrasonic waves by turn on the power switch. In detail, when applied high frequency AC, the ultrasonic generator 12 will generate ultrasonic waves of same frequency and a certain vibration direction. After going through the matching layer 11, the ultrasonic waves pass the upper substrate of the liquid crystal writing board and enter into the liquid crystal layer. Affected by the ultrasonic waves, the liquid crystals in the liquid crystal layer switch from the reflective state to the scattering state. Therefore the reflection and the writing words are disappeared, but other parts that do not contact to the erasing end will stay unaffected.

The external field used in the present invention is ultrasonic waves, where the orientation of the liquid crystals is adjusted by ultrasonic waves and the selectively erasing is realized by directly changing from the reflective state to the scattering state. In theory, the acoustic field does not transfer heat or light in the orientation of liquid crystals, which eliminates the phenomenon of accelerated aging. Moreover, this selectively erasing method will not increase the manufacturing cost, and it is harmless to the human body. The selectively erasing device and the writing-erasing pen for a liquid crystal writing board apply an ultrasonic technology to fulfill the selectively erasing, resulting in energy-saving and environmental protection, as well as safe and convenient to use.

While several particular exemplary embodiments have been described above in detail, the disclosed embodiments are considered illustrative rather than limiting. Those skilled in the art will readily realize that alternatives, modifications, variations, improvements, and substantial equivalents are possible without substantially departing from the novelty spirits or scope of the present disclosure. Thus, all such alternatives, modifications, variations, improvements, and substantial equivalents are intended to be embraced within the scope of the present disclosure as defined by the appended claims.

Claims

A selectively erasing device for a liquid crystal writing board, comprising: a power source, a driving circuitry and an ultrasonic generating assembly, wherein the power source and the ultrasonic generating assembly are electrically connected to the driving circuitry, and the ultrasonic generating assembly comprises a matching layer, an ultrasonic generator and a backing layer stacked in sequence, wherein the matching layer is positioned on the side contacting with the liquid crystal writing board.
The selectively erasing device for a liquid crystal writing board according to claim 1, wherein the ultrasonic generator for emitting ultrasonic waves is one or a combination of a piezoelectric transducer, a magnetostrictive transducer and an electrostatic transducer.
The selectively erasing device for a liquid crystal writing board according to claim 1, wherein the matching layer is composed of a single-layer or multi-layer medium.
The selectively erasing device for a liquid crystal writing board according to claim 3, wherein the acoustic impedance value of the single-layer medium gradually decreases along the direction away from the ultrasonic generator.
The selectively erasing device for a liquid crystal writing board according to claim 4, wherein the surface of the matching layer in contact with the liquid crystal writing board is a flat surface or a rough surface with micro-structured protrusions.
The selectively erasing device for a liquid crystal writing board according to claim 5, wherein the micro-structured protrusions have a tetrahedral structure.
The selectively erasing device for a liquid crystal writing board according to claim 3, wherein the acoustic impedance value of the multi-layer medium gradually decreases along the direction away from the ultrasonic generator.
The selectively erasing device for a liquid crystal writing board according to claim 1, wherein the material of the matching layer is one or more selected from the group of metals, metallic oxides, inorganic nonmetals and polymers.
The selectively erasing device for a liquid crystal writing board according to claim 8, wherein the metal is tungsten or aluminum, the metallic oxide is tungsten oxide or aluminum oxide, and the inorganic nonmetal is silicon dioxide.
The selectively erasing device for a liquid crystal writing board according to claim 8, wherein the polymer is one or more selected from the group of epoxy resin, polyester resin, polyvinyl chloride, and their combination with fillers.
The selectively erasing device for a liquid crystal writing board according to claim 10, wherein the filler is an inert metal powder or a non-metal powder.
The selectively erasing device for a liquid crystal writing board according to claim 1, wherein the ultrasonic generator is a single ultrasonic generator or an array of ultrasonic generators which are connected to each other in series or in parallel.
The selectively erasing device for a liquid crystal writing board according to claim 12, wherein the cross section of the ultrasonic generator has a shape of round, square, rectangle or their combinations.
The selectively erasing device for a liquid crystal writing board according to claim 1, further comprising a gel layer or an elastic polymer layer located on the side of the matching layer away from the ultrasonic generator, and the gel layer or the elastic polymer layer is tightly attached to the upper substrate of the liquid crystal writing board when the liquid crystal writing board is selectively erased.
The selectively erasing device for a liquid crystal writing board according to claim 1, wherein the backing layer comprises a solid filler made of metallic oxides or non-metallic oxides and one or more polymers selected from epoxy resins, polyester resins and polyvinyl chloride, and the backing layer is used for absorbing the reflected ultrasonic waves at the interface between the matching layer and the ultrasonic generator.
A writing-erasing pen for a liquid crystal writing board, comprising a pen body, a writing end and an erasing end, wherein the erasing end comprises the selectively erasing device for a liquid crystal writing board according to any one of claims 1-15.
The writing-erasing pen for a liquid crystal writing board according to claim 16, wherein the writing end and the erasing end are located at the two ends of the pen body respectively.
The writing-erasing pen for a liquid crystal writing board according to claim 17, wherein the erasing end is detachably connected to the pen body.
The writing-erasing pen for a liquid crystal writing board according to claim 16, further comprising a charging device connecting to the power source.